rocam 2015 abstract book

Transcription

THE 8th INTERNATIONAL CONFERENCE ON
ADVANCED MATERIALS,
ROCAM 2015
7-10 JULY 2015, BUCHAREST, ROMANIA
Held under the auspices of
ACADEMY OF ROMANIAN SCIENTISTS
An International Conference on Advanced Materials with Special
Topics on Nano, Multifunctional and Photovoltaic Materials
ABSTRACT BOOK
EDITURA GRANADA
2015
THE 8th INTERNATIONAL CONFERENCE ON
ADVANCED MATERIALS,
ROCAM 2015
7-10 JULY 2015,
BUCHAREST, ROMANIA
Held under the auspices of
An International Conference on Advanced Materials with Special
Topics on Nano, Multifunctional and Photovoltaic Materials
ABSTRACT BOOK
EDITURA GRANADA, 2015
ROCAM 2015 ORGANIZERS:
ROMANIAN MATERIALS SCIENCE - CRYSTAL GROWTH SOCIETY
UNIVERSITY OF BUCHAREST, FACULTY OF PHYSICS, ROMANIA
NATIONAL INSTITUTE OF MATERIALS PHYSICS (NIMP), ROMANIA
UNIVERSITY POLITEHNICA OF BUCHAREST
TRANSILVANIA UNIVERSITY OF BRASOV, ROMANIA
NATIONAL INSTITUTE FOR R&D IN ELECTRICAL ENGINEERING ICPE-CA, ROMANIA
CULTURE AND PHYSICS AT MAGURELE" FOUNDATION, ROMANIA
Abstract Book Editors:
Florin STANCULESCU
Claudia NASTASE
ISSN 1842-3574
SPONSORS
CULTURE AND PHYSICS AT
MAGURELE" FOUNDATION
ROMANIAN MATERIALS SCIENCE CRYSTAL GROWTH SOCIETY
THE 8th INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS: ROCAM 2015
ORGANIZING COMMITTEE
Chairmen:
Program Chair:
Treasurer:
Members:
Technical
Committee:
Horia Alexandru, University of Bucharest
Joseph Greene, University of Illinois, Urbana, Illinois
Thomas Kuech, Univ of Wisconsin – Madison, USA
Stefan Antohe, University of Bucharest
Lucian Pintilie, NIMP, Bucharest - Magurele
Florin Stanculescu, University of Bucharest
Marcela Socol, NIMP, Bucharest
Emil Barna, University of Bucharest
Anca Dumitru, University of Bucharest
Daniel Munteanu, Transilvania University of Brasov
Mihai Popescu, NIMP, Bucharest - Magurele
Daniel Vizman, University of Timisoara
Lucian Ion, University of Bucharest
Sorin Jinga, University Politehnica of Bucharest, Romania
Mihai Alexandru Grumezescu, University Politehnica of Bucharest
Daniela Dragoman, University of Bucharest, Romania
Florin Nastase, National Institute for Research and Development in
Microtechnologies, Bucharest - Romania
Ionut Marius Enculescu, NIMP, Bucharest – Magurele
Sorina Iftimie, University of Bucharest
Liviu Nedelcu, NIMP, Bucharest – Magurele
Lucian Gheorghe, INFLPR, Bucharest - Magurele
Anca Stanculescu, NIMP, Bucharest - Magurele
Marius Volmer, Transilvania University of Brasov
Stefania Mazilu, “Carol I” Central University Library, Bucharest
Claudia Nastase, University of Bucharest
Adrian Radu, University of Bucharest
Silviu Vulpe, University of Bucharest
Oana Rasoga, NIMP, Bucharest - Magurele
Valentin Barna, University of Bucharest
Catalin Manu, NIMP, Bucharest - Magurele
Florin Ion, University of Bucharest
Carmen Breazu, NIMP, Bucharest - Magurele
III
INTERNATIONAL ADVISORY COMMITTEE
Jean-Louis Bobet
Institut de Chimie de la Matière Condensée de Bordeaux, Université
Bordeaux 1, France
Gabriel Caruntu
Alexander
Chernov
Colege of Science and Technology, Central Michigan University
Lawrence Livermore National Laboratory, USA, Former president of the
International Organization for Crystal Growth
Floriana Craciun
Istituto dei Sistemi Complessi, CNR, Roma
Hanna Dabkowska McMaster University, Hamilton, Canada; Executive Comm. of
International Organization for Crystal Growth
James De Yoreo
Lawrence Berkeley National Laboratory & Department of Energy of
USA, Executive Comm: International Organization for Crystal Growth,
Emmanuel Defay
Centre de Recherche Public Gabriel Lippmann, Belvaux, Luxembourg
Wolfgang Diehl
Thierry Duffar
Fraunhofer Institute for Surface Engineering and Thin Films
President of The Society of Vacuum Coaters
l’Université de Grenoble, Grenoble, France
Klaus Ellmer
Institute Solar Fuels, Helmholtz Zentrum - Berlin
Claude Estourne
Interuniversity Center for Materials Research and Engineering
(CIRIMAT), Institut Carnot, Université Toulouse III - Paul Sabatier,
France
José Maria da
Fonte Ferreira
Department of Materials and Ceramic Engineering, Centre for Research
in Ceramics and Composite Materials ( CICECO), University of Aveiro,
Portugal
Roberto Fornari
President: “International Organization for Crystal Growth”
Elvira Fortunato
Materials Science Department, New University of Lisbon, Portugal,
Associate Editor of Rapid Research Letters Physica Status Solidi and
Co-Editor of Europhysics Letters
Mihaela Girtan
LPHIA: Laboratoire de Photonique d’Angers, Université d’Angers,
France
Pedro GómezRomero
Institut Catala de Nanociencia I Nanotecnologia, ICN2 (CSIC-CERCA),
Barcelona, Spain
Grzegorz
Greczynski
Linköping University Sweden
Joseph Greene
Duncan Gregory
University of Illinois at Urbana-Champaign, USA,
Editor-in-Chief: Thin Solid Films
School of Chemistry, University of Glasgow
Maryline GuillouxViry
Elizabeth von
Hauff
Institut des Sciences Chimiques de Rennes, Université de Rennes 1,
France
Department of Physics and Astronomy, Vrije Universiteit Amsterdam,
The Netherlands
John Irvine
School of Chemistry, University of St Andrews, Scotland, United
IV
Koichi Kakimoto
Kingdom
Kyushu University, Japan
Yoji Koike
Tohoku University, Department of Applied Physics, Japan
Thomas Kuech
University of Wisconsin – Madison, USA,
Ed-in-Chief J.Crystal Growth.
Rodrigo Martins
New University of Lisbon, Institute of New Technologies
Wolfram Miller
Xavier Moya
Leibniz Institute of Crystal Growth (IKZ), Germany
Department of Materials Science & Metallurgy, University of Cambridge
Tatau Nishinaga
University of Tokyo, Japan, Assoc. Editor J.Crystal Growth, Former
President of the International Organization for Crystal Growth
Aleksander
Ostrogorsky
Illinois Institute of Technology, USA
Deepak Pant
Flemish Institute for Technological Research, Belgium
Editorial broad member for the Journals: ‘ISRN Biotechnology’, ‘The
Scientific World Journal’ and ‘Sustainability’
Fabio Di
Pietrantonio
Theo Rasing
Institute of Acoustic and Sensors "Orso Mario Corbino", Italy
Kevin Roberts
University of Strathclyde, Glasgow, UK, Assoc. Editor J.Crystal Growth
Peter Rudolph
Liliana Stan
Crystal Technology Consulting (CTC), Berlin, Germany
Argonne National Laboratory, USA
Marius Stan
Argonne National Laboratory and Department of Energy Office of
Nuclear Energy (DOE-NE).
Member of the Editorial Boards of the Journal of Nuclear Materials,
Journal of Phase Diagrams,
Hendrik Swart
Masahiko Tani
Department of Physics, University of the Free State, South Africa
Univ of Fukui. Research Center for dev. Far-Infrared region.. Japan
Institute of Molecules and Materials, Radboud University Nijmegen,
Netherlands
Magdalena Titirici School of Eng.and Mater. Science Queen Mary University of London
Associate editor for J. Mater. Chem. A.
Editorial board member of ChemSusChem (Wiley) and J. Mater. Chem.
A (RSC)
Peter Vekilov
University of Houston, USA
Elias Vlieg
Radboud University Nijmegen, The Netherlands
V
ROMANIAN SCIENTIFIC COMMITTEE
A. Aldea, National Institute of Materials Physics, Bucharest
M. Baibarac, National Institute of Materials Physics, Bucharest
E. Barna, Vice-Rector, University of Bucharest
V. Ciupina, "Ovidius" University, Constanta
M. Ciurea, National Institute of Materials Physics, Bucharest
D.S. Delion, "Horia Hulubei" National Institute of Physics and Nuclear Engineering,
Bucharest
M. Dinescu, National Institute for Laser, Plasma and Radiation Physics, Bucharest
D. Dragoman, Physics Faculty, University of Bucharest
A. Duta, Transilvania University of Brasov
V. Filip, Physics Faculty, University of Bucharest
M. Gartu, "Ovidius" University, Constanta
L. Gheorghe, National Institute for Laser, Plasma and Radiation Physics, Bucharest
C. Ghica, National Institute of Materials Physics
V. Grecu, Physics Faculty, University of Bucharest
F.Iacomi, Faculty of Physics, Alexandru Ioan Cuza University of Iasi
L. Ion, Vice-Dean, Faculty of Physics, University of Bucharest
W. Kappel, Director, ICPE - Adv.Res., Bucharest
D. Munteanu, Vice-Rector,Transilvania University of Brasov
M. Pavelescu, Academy of Romanian Scientists, Bucharest
M. Popescu, National Institute of Materials Physics, Bucharest
R. Savastru, Director, National Institute for Optoelectronics, Bucharest
F. Vasiliu, National Institute of Materials Physics, Bucharest
D. Vizman, West University of Timisoara
V. Vlad, President of Romanian Academy
M. Volmer, Transilvania University of Brasov
M. Zaharescu, Romanian Academy
VI
EXHIBITORS
Agilrom Scientific SRL
AMS 2000 Trading Impex
SRL
Analytik Jena
Comtest
HISTERESIS SRL
VII
VIII
FOREWARD
The 8th International Conference on Advanced Materials, ROCAM 2015 will be held at
the RIN Grand Hotel, Bucharest, July 7-10, 2015, under the auspices of the ACADEMY OF
ROMANIAN SCIENTISTS. The International Summer School on Materials for Energy
Conversion will be a parallel event, July 6 - 11, 2015, at the same location.
The main organizer of ROCAM events is the Romanian Materials Science - Crystal Growth
Society, a non-profit association. Other important co-organizer institutions of ROCAM 2015 are
University of Bucharest - Faculty of Physics and National Institute of Materials Physics, Bucharest
ROCAM 2015 Conference covers four days in three parallel sections, including eight topics:
S1:
Advanced Materials for Solar Energy Conversion
S2:
Carbon-based Nanomaterials and Applications
S3:
Thin Films and Nanostructures of Functional Materials
S4:
Advanced Biomaterials, Biodevices and Biotechnology
S5:
Advances in Surface Science and Engineering
S6:
Advanced Ceramics: Synthesis, Properties, and Applications
S7:
Ferroelectrics, Nonlinear Optical and Luminescent Materials, Prop.and Applications
S8:
Advanced Materials Characterization and Modeling
There are six plenary lectures delivered by the following distinguished personalities:
Joseph Greene: University of Illinois, USA, Ed-in-Chief Thin Solid Film; Wolfgang Diehl:
Fraunhofer Institute for Surface Engineering and Thin Films, President of The Society of Vacuum
Coaters, Germany; Tatau Nishinaga: The University of Tokyo, former President of the International
Organization for Crystal Growth; Elvira Fortunato: Centre for Materials Research New University
of Lisbon, Portugal, Associate Editor of Physica Status Solidi -Rapid Research Letters;
Thomas Kuech University of Wisconsin- Madison, Editor-in-Chief Journal of Crystal Growth USA,
Marius Stan: Argonne Nat. Laboratory, Department of Energy of the USA and Rodrigo Martins,
New University of Lisbon and Institute of New Technologies, President of E-MRS.
Organizing Committee of the Conference gratefully acknowledge the active contribution of
the following personalities: Prof. Joseph GREENE, Prof. Thierry DUFFAR, Grenoble Institute of
Technology, France, Prof. Tatau NISHINAGA, Professor Emeritus, The University of Tokyo,
Prof. Stefan ANTOHE, the Dean of the Faculty of Physics, University of Bucharest, Romania,
Prof. Lucian PINTILIE, the Institute of Materials Physics, Bucharest-Magurele, Romania.
More than 180 participants from all over the world will attend the Conference. In the
Abstract Book, almost 285 abstracts were included. There are 43 invited, 82 oral and 154 poster
contributions. The title of “Honorary Member of the Romanian Materials Science - Crystal Growth
Society” and the diploma, will be awarded to some distinguished participants. Full paper
contributions presented in the conference will be published in some international journals (Thin
Solids Films, J. Crystal Growth, International Journal of Pharmaceutics, Journal of Optoelectronics
and Advanced Materials, Optoelectronics and Advanced Materials - Rapid Communications).
We are indebted to our colleagues from the University of Bucharest, Faculty of Physics,
from the National Institute of Materials Physics (NIMP) Bucharest, members of the organizing team
of the conference, who accomplished difficult technical, logistic and administrative tasks.
Bucharest, June 2015
Prof. Horia ALEXANDRU
University of Bucharest, Faculty of Physics,
Chairman of ROCAM 2015
E-mail: [email protected]
Dr. Florin STANCULESCU
University of Bucharest, Faculty of Physics,
Program Chair, ROCAM 2015
E-mail: [email protected]
IX
CONTENT
Plenary Contributions
1
S1: Advanced Materials for Solar Energy Conversion
7
S2: Carbon-based Nanomaterials and Applications
29
S3: Thin Films and Nanostructures of Functional Materials
43
S4: Advanced Biomaterials, Biodevices and Biotechnology
73
S5: Advances in Surface Science and Engineering
99
S6: Advanced Ceramics: Synthesis, Properties, and Applications
113
S7: Ferroelectrics, Nonlinear Optical and Luminescent Materials, Properties and Applications
133
S8: Advanced Materials Characterization and Modeling
149
LATE NEWS
177
x
Plenary Lectures
1
2
THE 14-BILLION YEAR HISTORY OF THE UNIVERSE LEADING TO MODERN THIN FILM SCIENCE
Joe Greene
D.B. Willett Professor of Materials Science and Physics, University of Illinois; Tage Erlander Professor of Physics,
Linköping University, Sweden; University Professor of Materials Science, National Taiwan Univ. of Science and
Technology
The story begins approximately 13.8 billion years ago with the Big Bang. A brief introduction will trace the evolution
of the universe to what we observe today. Many of the formative events occurred in the first tiny fractions of a second
(e.g., from a quark/gluon plasma, protons, neutrons, and electrons appeared) to a few tens of thousands of years
(elementary particles react to form the first elements which leads, in turn, to the development of stars due to local
density fluctuations). Planet Earth nucleated and began to accrete interstellar debris ~4.5 billion years ago. While the
lighter metal elements on earth formed primarily due to stellar supernovae explosions, the primary mechanism leading
to the formation of the heavier elements has only recently been demonstrated. The first known stone tools used by
huminids, found in northern Ethiopia, date to 2.6 million years ago
Gold is likely the first metal discovered by man, more than 11,000 years ago. However, unlike copper (Mesopotamia,
~9000 BC), bronze (Iran, ~5000 BC), and cast iron (China, ~600 BC), it was too soft for fabrication of tools and
weapons. Instead, gold was used for decoration, religious artifacts, and commerce. The earliest documented thin films
were gold layers, < 3000 Å, produced chemi-mechanically by Egyptians approximately 5000 years ago. Examples,
gilded on statues and artifacts (requiring interfacial adhesion layers), were found in early stone pyramids dating to
~2650 BC in Saqqara; gold brazing ~3400 BC in Sumaria. Spectacular samples of embossed Au sheets date to at least
2600 BC. Electroless plating was developed by the Moche Indians of Peru in ~100 BC.
The earliest published electroplating experiments were ~1800 AD following the invention of the dc electrochemical
battery by Volta. Chemical vapor deposition (CVD) of metal films was reported in 1649, atmospheric arc deposition of
oxides (Priestley) in the mid-1760s, and atmospheric plasmas (Siemens) in 1857. Sols were produced in the mid-1850s
(Faraday) and sol-gel films synthesized in 1885.
Vapor phase film growth including sputter deposition (Grove, 1852), arc deposition ("deflagration," Faraday, 1857),
plasma-enhanced CVD (Berthelot, 1869), and evaporation (Stefan, Hertz, and Knudsen, 1873-1915) all had to wait for
the invention of vacuum pumps, ~1650 for mechanical pumps through ~1865 for mercury pumps producing ballistic
pressures in small systems. The development of crystallography (Plato, 360 BC, to Haüy, 1780s) led to Miller indices
(1839) for describing thin film orientation and epitaxial relationships. The starting point for the development of
heterogeneous thin film nucleation theory was provided by Young in 1805.
While an historical road map tracing the progress of thin film technology is interesting in itself, the stories behind these
developments are even more fascinating and provide insight into the evolution of scientific reasoning.
2014 NOBEL PRIZE IN PHYSICS FOR THE INVENTION OF EFFICIENT BLUE LED - HISTORICAL
BACKGROUND TO THE PRIZE
Tatau Nishinaga
The University of Tokyo (Professor Emeritus)
The Nobel Prize in Physics is given for an "invention" or a "discovery." The citation of the last year's prize was “for the
invention of efficient blue light-emitting diodes”. This great invention made a white light source possible and helped
realize a large amount of energy conservation. Dr. Akasaki and Dr. Amano received the prize for the invention of the pn junction blue light-emitting diode in 1969, which was a first in history. The fundamentals of this invention are due to
the successful hetero-epitaxial growth of high-quality gallium nitride using a low-temperature buffer layer and the
success in getting p-type gallium nitride, which was only possible by using such high-quality crystal. It was 1986 when
the first high-quality gallium nitride using a low-temperature buffer layer was reported, and 6 years later in 1992, Dr.
Nakamura utilized the low-temperature buffer layer invented by Dr. Akasaki, etc., and developed a new method to
create p-type gallium nitride, which employed a thermal annealing after the growth, thus successfully allowing the mass
production of a nitride semiconductor light-emitting diode.
The key technology that made p-GaN possible was to grow high quality GaN on sapphire between which there is a
large lattice mismatch. The technology to grow high quality film on a mismatched substrate is called HM2 (Highly
lattice MisMached heteroepitaxy). So far there are three technologies in HM2, (1) growth with low-temperature buffer
layer, (2) that with supper lattice and (3) microchannel epitaxy. In this presentation, historical review for (1) to (3) will
be given especially focusing on that of (1).
3
PLASMA TECHNOLOGIES – FUNCTIONAL COATINGS FOR AUTOMOTIVE APPLICATIONS
W. Diehl, R. Bandorf, S. Biehl, J. Brand, T. Jung, C.-P. Klages, M.Keunecke M. Thomas, M. Vergöhl, G. Bräuer
Fraunhofer Institute for Surface Engineering and Thin Films IST, Bienroder Weg 54E, 38108 Braunschweig, Germany
Thin functional coatings are the key to new and superior products in almost all industrial branches. The most flexible
and widely used technology for deposition of thin films are plasma processes. These technologies are the first choice for
an enormous bandwidth of materials and functions to be realized.
A well-established class of hard coatings for automotive applications, mechanical engineering and tools are Diamond
Like Carbon Coatings (DLC) and their metal containing derivatives. They are prepared by plasma processes such as
PACVD, DC magnetron sputtering, and plasma activated evaporation. A new approach for the production of multilayer
hard coatings for the protection against erosion under severe conditions is the hollow cathode gas flow sputtering
technique (GFS).
A sensor technology based on carbon films with high wear resistance and piezoresisitive properties has been developed
for applications in force and load measurements and can be performed by PACVD. The application can be realised
either as strain gauges on parts experiencing mechanical deformation or as direct contact in force closure. Hence, force
and load measurement without significantly modifying the dimensions of technical parts are accessible as additional
information.
TCOs – Transparent Conductive Oxides are of major importance for automobile display applications e.g. head-up
displays, sun-protection/photovoltaic coatings etc. and can be deposited by reactive magnetron sputtering.
HIPIMS – High Power Impulse Magnetron Sputtering Technology has been used to develop a stable coat and bend
process for the deposition of TCO films with a defined nanocrystalline structure. After annealing and bending excellent
electrical properties can be realised.
For interior applications (e.g. remove of unpleasant smell) photocatalytic technologies can be used.
Photo induced hydrophilicity and photocatalytic decomposition of organic material can be achieved by coatings with
crystalline TiO2. These coatings can be deposited by plasma based processes even on temperature sensitive surfaces,
for example on polycarbonate. In order to improve the activity in visible light TiO 2 can be doped with different
elements.
To improve adhesion of coatings, glues, paint etc. targeted surface functionalization can be achieved by means of
atmospheric pressure plasma processes. Handheld devices for cleaning and treatment of wood/fabrics will be presented.
CONTROLLING SURFACE PROCESSES TO CREATE NEW SEMICONDUCTING ALLOYS
T. F. Kuech1, S.E. Babcock2, A.S. Brown4, L. Mawst3, and D. Morgan2
Department of Chemical and Biological Engineering; 2Department of Materials Science and Engineering; 4Department
of Electrical and Computer Engineering University of Wisconsin – Madison, Madison, WI 53706 USA; 3Department of
Electrical and Computer Engineering Duke University, Durham, NC, 22708 USA
1
The optical and electronic devices that form the basis of almost all of our advanced technologies rely on a limited class
of materials which can be produced on commercially-available substrates from the range of thermodynamically stable
elemental, compound and alloy semiconductors. The range of potential materials or material compositions which could
be used is vast. Despite the freedom afforded in materials design by the use of multicomponent semiconductors, very
few have been extensively developed and commercially employed. This is due, in part, to the difficulties in the
formation of many of these materials since they exhibit large regions of immiscibility with composition. When
synthesized using modern low temperature, epitaxial techniques, these materials can be formed through the control of
those surface processes which lead to phase separation. Phase separation from the uniform flux of reactants to the
surface is accomplished through those kinetic processes allowing for mass transport on the surface, enabling lateral
variations in composition, and the processes associated with incorporation into the growing surface. This talk will look
at the means to control these surfaces processes enabling the formation a broader class of semiconductor alloy
materials. A model system, GaAs1-yBiy, will be used to explore these processes and develop new insights into the
formation of highly immiscible systems.
4
MATERIALS DESIGN FOR ENERGY APPLICATIONS
Marius Stan
Argonne National Laboratory, Department of Energy, U.S.A.
Modern society has increasing energy needs that require new materials with significantly improved properties.
Advanced mathematical modelling and high performance computer simulation, coupled with experimental validation,
contribute to enhancing the understanding of the complex phenomena that occur in materials at multiple time and length
scales. In USA, national laboratories and universities partner in providing validation data of particular importance in
ensuring that computer simulations represent reality. This presentation reviews recent computational materials science
results, with an emphasis on the design of innovative materials for energy production (fuels) and storage (batteries).
MATERIALS FOR A NEW WINDOW OF THE ICT AGE
Elvira Fortunato, R. Branquinho, Lidia Santos, Daniela Salgueiro, Pedro Barquinha, Luís Pereira and Rodrigo Martins
Departamento de Ciência dos Materiais, CENIMAT/i3N, Faculdade de Ciências e Tecnologia - Universidade Nova de
Lisboa and CEMOP/Uninova, 2829-516 Caparica, Portugal, [email protected]
Before starting this presentation I just like to remind you that 10 years ago
it was IMPOSSIBLE to use a metal oxide as a semiconductor. NOW we
have companies selling products, especially in the display and ICT areas
facing the needs to new generation of devices. But science is dynamic, and
as a researcher we are always unsatisfied and we need to discover new
solutions not only for existing problems but also for predicting the future.
This is the big challenge where MATERIALS SCIENCE in conjunction
with NANOTECHNOLOGY is pushed to the limit.
To decrease costs associated to electronic devices a strategy is using cheap
and abundant materials in conjunction with low cost fabrication methods,
associated to an overall increase of electrical performance. Metal oxides
(MO) are chemically stable, mostly non-toxic and abundant materials,
often manufactured by low cost methods, under ambient conditions.
Consequently, devices made of MO are inexpensive, very stable and
environmentally safe, the 3 most important requirements for electronics.
In many ways, oxides are unique materials. Despite being explored for
more than a century for electronic applications, from the initial works of
Badeker in 1907 with CdO to the cutting edge IGZO available these days
in active matrix backplanes of flat panel displays, oxides still present an
exceptional and innovative combination of properties not achievable by
any other material class. In fact, they are true multifunctional materials,
being able to exhibit optical transparency, conducting / semiconducting /
insulating behaviour, piezoelectricity and catalytic or self-cleaning
properties among many others.
In this presentation we will review some of the most promising new
technologies based on oxide conductors, semiconductors, dielectrics as
well as electrochromic devices either in the form of nano-films or
nanoparticles, and we will summarize the major milestones already achieved with this emerging and very promising
technology focused on the work developed in our laboratory.
By using these materials and technologies we are contributing to the evolution of environmentally conscious electronics
that is able to add new electronic functionalities onto surfaces, which currently are not used in this manner.
E. Fortunato, P. Barquinha, and R. Martins, "Oxide Semiconductor Thin-Film Transistors: A Review of Recent
Advances," Advanced Materials, vol. 24, pp. 2945-2986, Jun 12 2012.
P. Barquinha, R. Martins, L. Pereira and E. Fortunato, Transparent Oxide Electronics: From Materials to Devices. West
Sussex: Wiley & Sons (March 2012). ISBN 9780470683736.
5
6
S1
Advanced Materials for solar energy conversion
Invited Papers
7
8
LARGE-AREA MAGNETRON SPUTTERING OF SOLAR CELLS AND ELECTRODES FOR WATER
SPLITTING FOR OUR FUTURE RENEWABLE ENERGY SUPPLY
Klaus Ellmer
Helmholtz-Zentrum für Materialien und Energie, dept. solar fuels, Hahn-Meitner-Platz 1, 14109 Berlin, Germany, email [email protected]
Magnetron sputtering, invented by the renowned plasma physicist Penning already in 1939, is today a widely used
large-area, plasma-assisted deposition method for many industrial applications like
•
architectural and low emissivity glass coatings,
•
hard coatings,
•
optical and protective films,
•
magnetic layers for hard disk drives,
•
transparent electrodes
•
thin film solar cells, to name only a few.
In this lecture the potential distribution and energetic species in a magnetron discharge are explained and related to
electronic properties of Al-doped zinc oxide, a transparent conductive oxide (TCO), used for instance in thin film solar
cells.
The energies of the species contributing and assisting the film growth are significantly higher compared to thermal
or plasma-enhanced chemical vapour (PECVD) deposition processes. The sputtered species, forming the deposited film,
exhibit energies in the range of some to tens of electron volts. Since in typical magnetron sputtering systems the
discharge voltages can reach hundreds of volts, some species, especially negative ions (O-, S-, F- etc.), can even reach
energies of hundreds of eV. This is one of the reasons, why magnetron sputtering is not yet used on an industrial scale
for the deposition of active semiconducting films, for instance in thin film solar cells.
By using energy-resolved mass spectrometry we have shown that the detrimental high-energy flux of negative ions
is strongly reduced when the discharge frequency is increased from d.c. up to 27 MHz. On the other hand, the often
beneficial low-energy ion flux that the positive ions provide is enhanced for r.f. discharges. Thus, these quantitative ion
energy and flux measurements explain the empirical fact, that for TCOs and other semiconductors often r.f. magnetron
sputtering leads to better films.
This was demonstrated for ZnO:Al films, deposited as a function of the substrate temperature for 3 discharge
frequencies: d.c., 13.56 and 27.12 MHz.
The effects of the plasma excitation energy on the electronic properties of the active layers in thin film solar cells
and photoelectrodes are demonstrated for the materials Cu(In,Ga)Se 2 and BiVO4.
THE INFLUENCE OF VARYING GROWTH PARAMETERS ON THE QUALITY OF MULTICRYSTALLINE SILICON GROWN BY A BRIDGMAN TECHNIQUE
Radu Andrei Negrila, Vasile Pupazan, Alexandra Popescu and Daniel Vizman
Physics Faculty, West University of Timisoara, Bd. V. Parvan 4, 300223 Timisoara, Romania, corresponding author:
[email protected]
In the race to improve the price of solar energy by lowering the costs for silicon solar panel production, one of the
important production segments to be addressed are the purification and crystallization of photovoltaic grade silicon. It
stands for almost 1/3 of the total production cost. Currently, directionally solidified multi-crystalline silicon is
predominant in the market of photovoltaic silicon (2015: 60%) and is expected to stay so during the following decade.
Because of its low costs and its similarities with directional solidification, Bridgman growth of small diameter (max.
3cm) multi-crystalline silicon is a suitable technique for a fundamental study of the influence of growth parameters (like
growth rate and process time, temperature gradients, crucible coating) on the interface shape, grains size and impurity
distribution and precipitation, which are important parameters for the photovoltaic applications. As silicon is
crystallized in non-reusable silica crucibles with anti-sticking silicon nitride coatings, experimental investigations have
been performed on new different crucible-coating combinations for the identification of cheaper and maybe even
reusable crucible materials. Even though an electronic grade quality (very high purity) Silicon feedstock was employed
a large distribution of impurity precipitates (especially of SiC, which is highly undesirable because it induces damage
during wafering of silicon ingots) was found in most growth experiments. A very high neutral impurity (C and O)
concentration has been found. These impurities have largely entered the molten silicon through diffusion into the liquid
phase, aided by convective transport. Therefore the impurity concentration in the melt is strongly related with the time
duration in which the silicon was in the molten phase, but also to the different coating materials that were employed.
These observations are discussed in the interest of discerning the influence of the different growth conditions on the
accumulation and precipitation of impurities and crystalline structure. This understanding is a key aspect in improving
the quality of the photovoltaic material by tailoring the different growth parameters.
9
TOWARDS HIGH EFFICIENCY STABLE ORGANIC PHOTOVOLTAICS
Elizabeth von Hauff
Department of Physics and Astronomy, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
Organic semiconductors offer vast potential to realise low cost, large scale photovoltaic applications. Modification
to the chemical structure of the organic semiconductor allows for enormous flexibility to tune the opto-electronic
response of the molecule. The development of new absorber materials has led to rapid increases in power conversion
efficiency, and record efficiencies for organic solar cells have exceeded 10 %. This is generally considered a benchmark
value for the market entry of low cost photovoltaics. In addition to efficiency, the lifetime and reliability of a
photovoltaic technology is very critical for determining feasibility. Recent research efforts in the field have been
focussed on understanding the fundamental mechanisms which lead to performance loss in organic photovoltaic
devices. The challenge is to identify and localise microscopic loss processes in such complex device architectures. In
this talk I will discuss the opto-electronic properties of high performance organic solar cells. Frequency-resolved
techniques such as intensity modulated photocurrent spectroscopy and impedance spectroscopy are very powerful for
extracting highly detailed information related to electronic structure of materials and interfaces, as well as transport and
trapping phenomena which influence the current-voltage characteristic. This allows us to reconstruct the density of
electronic states, and monitor how the transport properties of the devices change over time.
ORGANIC AND HYBRID BIOLOGIC/ORGANIC STRUCTURES FOR PHOTOVOLTAIC APPLICATIONS
1
Ştefan Antohe1,2
University of Bucharest, Faculty of Physics, P.O.Box: MG-11, Bucharest-Magurele, 077125 ROMANIA, E-mail:
[email protected] , 2Academy of Romanian Scientists-Physics
In the last decades the second and third generations of photovoltaic cells based organic thin films have attracted a
great deal of interest among scientists involved in the research efforts to produce efficient and low-cost solar cells.
More recently, the biological materials were tested successfully in electronic and optoelectronic applications. Among
the organic semiconductors envisaged to be used in such structures, small molecules like metal-doped phthalocyanines
(MePc, with Me=Cu, Mg, Zn, etc.) and polymers are the most studied, due to their peculiar optical properties. As
biologic semiconductor, the Chlorophyll-a is a potential candidate for photovoltaic structures. For these materials, the
optical absorption in the visible range of the solar spectrum is strong, but based on an excitonic mechanism. A typical
value for the diffusion length of the exciton in organic semiconductors is of 30-80 nm, while in order to achieve the
required efficiency in light absorption, the absorber layer has to be at least 100 nm thick. This inconvenient could be
avoid, by the preparation of the multilayered structures containing different organic and biologic absorbers, or creating
a large number of Donor/Acceptor Interfaces, spread in the whole volume of the composite absorber, leading to so call
,,Bulkheterojunction”cells.
In this work are summarized the electrical and photoelectrical properties of the photovoltaic cells based on the
organic (small molecules and polymers) and biologic thin films. In the case of second generation of photovoltaic cells,
first the single-layer structures (ITO/CuPc/Al and ITO/TPyP/Al) were been prepared and characterized. The doublelayer photovoltaic structures based on the p-n heterojunction present at the interface between two organic layers, like,
ITO/CuPc/TPyP/Al and ITO/Chl a/TPyP/Al, exhibits stronger spectral sensitivity and better spectral matching to a solar
spectrum than Schottky cells using either CuPc or TPyP layer, having a power conversion efficiency with about two
orders of magnitude, higher than those of single-layer structures. Three-layered organic solar cells with an interlayer of
co-deposited dyes of p-type CuPc and n-type TPyP, between the respective dye layers were also prepared and
characterized, showing an increased power conversion efficiency, with respect of double–layer structures.
In the case of third generation of solar cells, the polymeric photovoltaic cells were produced by spin-coating
technique. The structures based on the P3HT: PCBM (1:1) blend and the hybrid structures of Chl/:P3HT:PCBM(1:1)
shows a promising photovoltaic response, with a power conversion efficiency increased of about two order of degree,
with respect of those measured in the case of structures based on single P3HT and PCBM or Chl-a thin films. Different
design of structures were prepared and characterized trying permanently to improve the performances and the stability
of the photovoltaic cells.
Keywords: organic thin films, chlorophyll-a, ”Bulkheterojunction” photovoltaic cells
10
TRENDS IN THE NEW GENERATION SOLAR CELLS RESEARCH
Mihaela Girtan
LPHIA – Photonics Laboratory, LUNAM - Angers University, 2 Bd. Lavoisier, 49045, Angers, France,
[email protected]
Since the 50’s when the concept of the first semiconducting photovoltaic cell was practically proved, different
materials and technologies were tested in order to increase the conversion efficiencies and to reduce the fabrication
costs. Today world records conversion efficiencies for single junctions solar cells without concentrators are of 28,8%
for thin film GaAs[1], of 25% for single crystal monocrystalline Si [2], 21.7% for CIGS thin films [3], 19.3.% for
perovskites cells [4], 13.4% for amorphous silicon thin films solar cells [5], 11.9% for dye –sensitized cells [6] and of
11.1 % for organic solar cells [7].
For the industrial development of different technologies many aspects should be taken into account: i) the
efficiency, ii) the materials cost and iii) the life time of materials and solar energy devices.
Due to the discrete band structure of semiconductors, only photons with energies equal or greater than the bandgap
energy (Eg) will be absorbed and contribute to the electrical photovoltaic solar cell output. Photons having higher
energies than Eg, even they are absorbed, their energies are underutilized due to the thermalization of charge carriers. In
order to reduce these spectral losses and increase the energy conversion efficacy, many strategies were considered, such
as: multi-junction cells (multiple semiconductors stacked cells, intermediate band semiconductors solar cell, up and
down converters. Up and down converters are based on rare earth doped materials which may modify the photons
energies in order to adapt them to the corresponding value of the band gap of the active material. Hence, the advantage
of this concept is that one that it could be applied to all types of solar cells.
Another important aspect represent the solar cells cost. A lot of work was done for all kind of photovoltaics devices
in order to reduce the fabrication costs, by looking for less expensive materials for transparent electrodes and active
layers and also less expensive technologies such as: spray, ink jet or roll to roll deposition methods.
Finally, but not less important is the life duration of materials and devices involved in solar cells and solar cells
panels fabrication. Silicon has the advantage to be a very stable material, but recent studies shows that also some
conducting polymers such as PEDOT-PSS, P3HT and PCDTBT usually used in the fabrication of organic solar cells
are enough stable too to be developed at industrial scale.
In this talk we present the state of art and the new trends in solar cells research.
References
[1] B.M. Kayes, L. Zhang, I.K. Ding, G.S. Higashi, Flexible Thin-Film Tandem Solar Cells With > 30%
Efficiency, Ieee J. Photovolt. 4 (2014) 729–733. doi:10.1109/jphotov.2014.2299395.
[2] K. Masuko, M. Shigematsu, T. Hashiguchi, D. Fujishima, M. Kai, N. Yoshimura, et al., Achievement of More
Than 25% Conversion Efficiency With Crystalline Silicon Heterojunction Solar Cell, Ieee J. Photovolt. 4 (2014) 1433–
1435. doi:10.1109/jphotov.2014.2352151.
[3] P. Jackson, D. Hariskos, R. Wuerz, O. Kiowski, A. Bauer, T.M. Friedlmeier, et al., Properties of Cu(In,Ga)Se2
solar cells with new record efficiencies up to 21.7%, Phys. Status Solidi RRL – Rapid Res. Lett. 9999 (2014) n/a–n/a.
doi:10.1002/pssr.201409520.
[4] H.S. Jung, N.-G. Park, Perovskite solar cells: from materials to devices., Small Weinh. Bergstr. Ger. 11 (2015).
doi:10.1002/smll.201402767.
[5] O. Isabella, A.H.M. Smets, M. Zeman, Thin-film silicon-based quadruple junction solar cells approaching 20%
conversion efficiency, Sol. Energy Mater. Sol. Cells. 129 (2014) 82–89. doi:10.1016/j.solmat.2014.03.021.
[6] M.K. Panda, K. Ladomenou, A.G. Coutsolelos, Porphyrins in bio-inspired transformations: Light-harvesting to
solar cell, Coord. Chem. Rev. 256 (2012) 2601–2627. doi:10.1016/j.ccr.2012.04.041.
[7] O. Adebanjo, P.P. Maharjan, P. Adhikary, M. Wang, S. Yang, Q. Qiao, Triple junction polymer solar cells,
Energy Environ. Sci. 6 (2013) 3150–3170. doi:10.1039/c3ee42257g.
11
SOLAR CELLS ON CELLULOSE PAPER TO BACK UP SMART PAPER ELECTRONICS
Rodrigo Martins, L. Pereira, A. Vicente, H. Águas, D. Gaspar, T. Mateus, A. Araújo, Elvira Fortunato
CENIMAT/I3N, Departamento de Ciência dos Materiais, Faculdade de Ciências e Tecnologia, FCT, Universidade
Nova de Lisboa and CEMOP-UNINOVA, 2829-516 Caparica, Portugal.
Nowadays there is a strong demand for smart packaging to provide comfort, welfare and security to owners, vendors
and consumers, by allowing them to know the contents and interact with the goods. This is of particular relevance for
low cost, fully disposable and recyclable products like identification tags, medical diagnostic tests and devices for
analysis and/or quality control in food and pharmaceutical industry1-3, most of them requiring continuous power which
can be addressed by a combined use of a small disposable solid state battery4, charged by a disposable solar cells5, able
to work under indoor lighting. Presently, the development of non-wafer-based photovoltaics allows supporting thin film
solar cells on a wide variety of low-cost recyclable and flexible substrates such as paper; thereby extending PV
solutions to a broad range of consumer-oriented indoor disposable applications where autonomous energy harvesting is
today a bottleneck issue. Here, we show a proof-of-concept of the pioneering production of thin-film amorphous silicon
(a-Si:H) photovoltaic cells with efficiencies of 4%5, by plasma enhanced chemical vapor deposition (PECVD), on
packaging cardboard (LPC)6 commonly used in the food and beverage industry. Such accomplishment put us one step
closer to this revolution, by providing a flexible, renewable and extremely cheap autonomous energy packaging system.
Moreover, such Si thin films take advantage of their good performance at low-light levels, which also makes them
highly desirable for cheap mobile indoor applications. We also process solar cells on paper coated with a layer of a
hydrophilic mesoporous (HM) material, where, as a proof f concept we produce solar cells with a 3.4% efficiency.
The way how cells were produced, the existing challenges and the plethora of electronics 7-10 that they can serve will
be presented and discussed in this presentation.
References
[1] R. Martins, L. Pereira, E. Fortunato, SID 2014Frontline Technology: The Future Is Paper Based, p20-24Vol 52
(2014), pp. 50-55
[2] R. Martins, I. Ferreira and E. Fortunato, “Electronics with and on paper”. Physica Status Solidi- RapidResearch
Letters, 5 (9) (2011), pp. 332-335.
[3] D. Tobjork, R. & Osterbacka, Paper Electronics. Advanced Materials 23, (2011), pp.1935-1961.
[4] I. Ferreira, B. Bras, J.I. Martins, N. Correia, P. Barquinha, E. Fortunato, R. Martins, “Solid-state paper batteries
for controlling paper transistors”. Electrochimica Acta 56 (2011) 1099–1105
[5] A. Vicente, H. Águas, T. Mateus, A. Araújo, A. Lyubchyk, S. Siitonen, E. Fortunato, R. Martins, Solar Cells for
Self-Sustainable intelligent Packaging, J. Materials Chemistry A, 2015, DOI 10.1039/C5TA01752A.
[6] Stora Enso. http://www.storaenso.com. Accessed 15 November 2014.
[7] Martins, R. F. P., Ahnood, A., Correia, N., Pereira, L., Barros, R., Barquinha, P., Costa, R., Ferreira, I. M.M.,
Nathan, A. & Fortunato, E. Recyclable, Flexible, Low-Power Oxide Electronics. Advanced Functional Materials 23,
2153-2161, doi:10.1002/adfm.201202907 (2013).
[8] R. Martins, P. Barquinha, L. Pereira, N. Correia, G. Gonçalves, I. Ferreira, E. Fortunato, “Write-erase and read
paper memory transistor”. Applied Physics Letters, 93 (2008) pp. 203501-203504
[9] E. Fortunato, N. Correia, P. Barquinha, L. Pereira, G. Gonçalves, R. Martins, “High-Performance Flexible
Hybrid Field-Effect Transistors Based on Cellulose Fiber Paper”. IEEE Electron Device Letters, 29, (9) (2008) pp. 988990.
[10] Pedro Barquinha, Rodrigo Martins, Luis Pereira, Elvira Fortunato, Transparent Semiconductors: From
Materials to Devices. West Sussex: Wiley & Sons (March 2012), ISBN 9780470683736
BIOINTERFACES WITH BIO-INSPIRED ORGANIC SEMICONDUCTORS
Eric Daniel Głowacki
Linz Institute for Organic Solar Cells (LIOS), Physical Chemistry, Johannes Kepler University, Linz Austria; email:
[email protected]
We review recent work from our group as well as other researchers demonstrating the efficacy of using naturalorigin materials in semiconductor-based devices for interfacing with biology. Many natural materials offer both
excellent semiconducting properties, and importantly, electronic as well as ionic conductivity. Biochemical systems are
ionic, and not electronic, thus any attempts of active bioelectronics devices must involve ionic/electronic transducing
elements. In particular, progress in the use of nanocrystalline and microcrystalline organic hydrogen-bonded pigments
will be discussed. These materials have been ubiquitous throughout history and are widely produced today industrially
as colorants in everyday products as various as cosmetics and printing inks, and have numerous properties that make
them intrinsically biocompatible. The bioconjugation chemistry of these materials and subsequent deployment in
electronic devices requiring reliable and specific bio-sensing will be covered.
12
VIS-ACTIVE PHOTOCATALYTIC TANDEM SYSTEMS- A FIRST STEP TOWARDS WATER RE-USE
Anca Duta*, Dana Perniu, Crisina Bogatu, Alexandru Enesca
Transilvania University of Brasov, R&D Centre Renewable Energy systems and Recycling, Eroilor 29, 500036 Brasov,
Romania, *Corresponding author: [email protected]
Water is one of the most abundant natural resources; however, water that can be used with convenient costs in
industrial and day-to-day life processes is in much smaller amounts, continuously decreasing as result of the treated
wastewaters discharged in the environment with traces of recalcitrant or toxic pollutants. Cumulative, these pollutants
are slowly degrading the natural water quality, making the treatment processes more expensive. Thus, we are now
facing a water stress. One path to reduce it is to treat wastewater at the quality required for re-use and advanced
oxidation processes, based on heterogeneous photocatalysis are recognized as viable. To reduce the costs in the
photocatalytic processes requires the extended use of Vis- or solar radiation to activate the oxidation mechanism.
Based on a synthetic review of the mostly investigated routs to obtain Vis-active photocatalysts, the paper proposes
a group of tandem composite systems with 3 and 4 components. The activation mechanisms is comparatively discussed
for systems containing SnO2, CuxS and TiO2 or ZnO, deposited as thin films by Spray Pyrolysis.
The photocatalytic efficiency of the thin film tandems was tested on reference systems consisting of a dye
(methylene blue) and a pesticide precursor (phenol) and the factors affecting mineralization are outlined. The stability
of the best performing tandem is discussed based on the photo-corrosion resistance.
The results prove that in optimized photcatalytic systems, under optimized process parameters, the organic
pollutants in water can be mineralized at a level that allow the direct re-use of the treated water.
13
14
Oral Presentations
CORRELATION OF DEFECT STATES WITH P3HT:PCBM SOLAR CELL ELECTRICAL PARAMETERS
Michal Kaiser1,2, Vojtech Nádaždy1
Institute of Physics, Slovak Academy of Sciences; 2Faculty of Electrical Engineering and Information Technology,
Slovak University of Technology in Bratislava; e-mail: [email protected]
1
The understanding of degradation processes and related defect states represents important factor for further
improvement of organic solar cells (OSC). The charge capture and recombination at these states result in carrier
mobility decrease, photocurrent loss, and consequently, in the drop of power conversion efficiency. Most of previous
studies performed with various optical and electrical methods have focused on such a high degree of the organic film
degradation which was far behind OSC functionality and could not be correlated with OSC electrical parameters.
Here we present experiments which correlate defect states in OSC active layer and the degradation of OSC electrical
parameters. We investigated the defect states induced by ambient air, humid air, and UV/Vis irradiation. The purpose is
to identify the impact of these degradation agents on particular photovoltaic process. In order to find this correlation we
used charge deep-level transient spectroscopy (Q-DLTS) which was directly applied to OSC samples. The activation
energy, frequency factor, and the concentration of defect states were investigated with Q-DLTS via temperature and
isothermal scans. The basic electrical parameters of OSC including photocurrent, ideality factor, reverse saturation
current, shunt and series resistances as well as the exciton generation rate and its dissociation probability were
determined from dark and light I-V measurements.
We observed the formation of oxygen-related defect states with energy about 0.1 eV above HOMO of P3HT during
OSC degradation. Our preliminary results suggest that the oxygen-related defect states have a dominant impact on
exciton recombination leading mainly to photocurrent loss. The correlation of these states with OSC electrical
parameters indicates two stages of OSC degradation. The obtained results are discussed and compared with other
relevant published data.
15
BIOLOGIC/POLYMERIC SEMICONDUCTING THIN FILMS BASED PHOTOVOLTAIC CELLS
1
S. Iftimie1, M.E. Barbinta-Patrascu1, A. Radu1, B. Bita1,2, N. Vasile1, N. Korganci1, L. Ion1 and S. Antohe1,3
University of Bucharest, Faculty of Physics, 405 Atomistilor, P.O. Box: MG-11, 077125, Magurele, Ilfov, Romania,
2
National Institute for Research and Development in Microtechnology – IMT Bucharest, P.O. Box:38-160, 023573,
Bucharest, Romania, 3Academy of Romanian Scientists, 54 Splaiul Independentei, 050094, Bucharest, Romania
Photovoltaic cells based on biologic (Chlorophyll-a, Chl-a) and polymeric (poly(3-hexylthiophene-2,5-diyl), P3HT)
and ([6,6]-phenyl-C61 butyric acid methyl ester, PCBM) thin films were fabricated and characterized. Two types of
structures were obtained, either a bi-layer Chl-a/P3HT:PCBM (1:1, wt. %) or a single layer Chl-a:P3HT:PCBM (10:1:1,
wt. %) architecture. The spin-coating technique was used for the deposition of the biologic and polymeric thin films on
the ITO glasses, used as substrate and thermal vacuum evaporation technique was used to prepare the aluminum (Al)
thin film as back contact . The optical and photovoltaic properties of the prepared photovoltaic cells, were analyzed and
compared with those for P3HT:PCBM (1:1, wt. %) structures. Similar values were registered for fill factor and open
circuit voltage, but the spectral response was enlarged for those cells containing Chl-a. For the moment, the short-circuit
current values for the non optimized cells Chl-a/P3HT:PCBM (1:1, wt.%) and Chl-a:P3HT:PCBM (10:1:1, wt.%) were
smaller than for P3HT:PCBM (1:1, wt.%) cells, but the future optimized structures (by a very good control of the film
thickness and design) will have improved performances.
Keywords: polymeric thin films, Chl-a, photovoltaic cells
TOWARDS OFFSETTING UP AN INTERMEDIATE BAND SOLAR CELL BASED ON TITANIUM OXIDES
SOL-GELS
S. Bechu1*, A. Goullet1, L. Cattin-Guenadez1, D. Duche2, J-J. Simon2, M. Girtan3, L. Brohan1, M. Richard-Plouet1
1. IMN-Université de Nantes, Nantes, 2. IM2NP, Marseille, 3. LPHIA, Angers, * corresponding author :
[email protected]
Third generation solar cells aims at increasing efficiency to overtake the 31% theoretical efficiency of simple
junction photovoltaic cells established by Shockley and Queisser [1] in 1961. According to Marti and Luque [2],
intermediate band cell concept could increase the photocurrent via the absorption of sub-bandgap photons without
degrading the voltage.
In this perspective, we developed hybrid photosensitive sols-gels based on titanium clusters with specific optical and
electronic properties [3]. Once illuminated under UV light, an intermediate band appears in the band structure so the
absorption spreads over visible to near infrared due to reduction of Ti(IV) in Ti(III). Thanks to this absorption range
increase, these sols-gels can be used as active layers in solar cell.
In order to optimize light absorption properties of the sol-gel layer, shaping optimisation and optical properties
studies were carried out. Thin films were obtained with an accurate control over thickness in the range from 150 nm to
10 µm. Ellipsometry and XPS studies were respectively undertaken to determine optimal thickness and electronic
structure evolution under UV illumination.
This layer with original properties could be implemented as active layers in new hybrid solar cells.
[1] Shockley, W., Queisser, H.J., Journal of Applied Physics, 32, 510 (1961)
[2] Luque, A., Marti, A., Physical Review Letters, 28, 78, (1997)
[3] Cottineau T., Brohan L., Pregelj M., Cevc P., Richard-Plouet M., Arčon D., Advanced Functional Materials, 18,
2602 (2008)
16
EFFECT OF IONIZING RADIATIONS ON THE CdS/CdTe HETEROJUNCTIONS USED FOR SPACE
APPLICATIONS
A. Radu1, V. Ghenescu2, M.M. Gugiu3, N. Vasile1, N. Korganci1, S. Iftimie1, L. Ion1 and S. Antohe1,4
University of Bucharest, Faculty of Physics, MDEO R&D Center, 077125, Magurele-Ilfov, Romania, 2Institute of
Space Science, 077125, Magurele-Ilfov, Romania, 3Horia Hulubei National Institute for R&D in Physics and Nuclear
Engineering, Magurele-Ilfov, 077125, Romania, 4Academy of Romanian Scientists, 050094, Bucharest, Romania
1
Cadmium sulfide (CdS)/ cadmium telluride (CdTe) heterojunction based photovoltaic cells were fabricated onto
optical glass substrates covered with a thin indium tin oxide (ITO) layer, in superstrate configuration. In order to
minimize the induced deposition defects, the ”window” layer, cadmium sulfide, was deposited by rf-magnetron
sputtering; the substrate was purposely unheated. CdTe layers were deposited on top of cadmium sulfide by thermal
vacuum evaporation (TVE). To complete the photovoltaic structure a copper:gold (Cu:Au) back electrode was
deposited by TVE, too. With high absorption coefficients, suitable band gaps and reduced masses as thin films,
cadmium sulfide and cadmium telluride are candidates for terrestrial and space applications. Our fabricated structures
were irradiated with protons and alpha particles with 500 keV energies and 1011 particles/cm2 fluencies, respectively.
These values are similar with those hitting artificial satellites orbiting the Earth. Electrical and photo-electrical
measurements were performed in dark and AM 1.5, at room temperature. Monte-Carlo numerical simulations showed a
detailed image of interaction between our samples and protons and alpha particles. Determined external quantum
efficiencies values (EQE) decreased after irradiation with protons and alpha particles but the peaks attributed to
fundamental absorption thresholds for CdS and CdTe kept their as grown positions in the case of irradiation with
protons and were slightly shifted in the case of irradiation with alpha particles. Parameters characterizing a photovoltaic
cell, short-circuit current, open circuit voltage and fill factor, were determined and compared for as grown and
irradiated PV cells.
Keywords: cadmium sulfide, cadmium telluride, ionizing radiations, protons, alpha particles
ON THE STRUCTURAL AND OPTICAL PROPERTIES OF HYBRID PEROVSKITE THIN FILMS
Aurelian Catalin Galca, Andrei Gabriel Tomulescu, and Ioana Pintilie
National Institute of Materials Physics, Atomistilor 105 bis, 077125 Magurele, Ilfov, Romania, corresponding author:
[email protected]
Perovskite-based solar cells have been proposed as novel photovoltaic devices with relatively good conversion
efficiency [1-3]. Most of the reported studies are focused only on presenting the solar cells parameters (e.g. quantum
efficiency, spectral response, fill factor), while the pure optical and structural properties of each layer are roughly
presented and discussed.
In this work we report the exhaustive optical and microstructural properties of thin films of the active hybrid
perovskite. The thin films are obtained by using a complex recipe which includes a special cleaning of the amorphous
silicon oxide substrates and a careful mixing and treatment of the precursors, and by using afterwards the spin-coating
technique.
The hybrid perovskite with the chemical formula CH3NH3PbI3-xClx results from the combination of CH3NH3I and
PbI2/PbCl2 solutions. Depending on the preparation conditions the secondary phase of inorganic halide (PbI 2/PbCl2) is
more or less present.
The authors acknowledge funding from EEA Financial Mechanism Office through the project no 8SEE/30.06.2014:
Perovskites for Photovoltaic Efficient Conversion Technology.
References
1. M. M. Lee et al., Science 338 (2012) 643.
2. B. Conings et al. , Adv. Mater. 26 (2014) 2041.
3. H. Zhou et al. , Science 345 (2014) 542.
17
EFFICIENT PEROVSKITE SOLAR CELLS PREPARED BY SOLUTION PROCESSED VIA TWO STEP
DEPOSITION
Viorica Stancu, Marian Sima, Cristina Besleaga, Andrei Tomulescu, Mariana Sima, George Stan, Lucian Pintilie, Ioana
Pintilie
National Institute of Materials Physics,105bis Atomistilor, 077125 Magurele, Ilfov, Romania, [email protected]
Perovskite solar cells are the newest technology of photovoltaic systems. They are attractive due to their properties:
high conversion efficiency, offers significantly higher voltages and their fabrication techniques are simple. The essential
component of these solar cells is a light absorbing semiconductor material with a perovskite polycrystalline structure,
CH3NH3PbX3 (X= Cl, Br, I). In this work, we fabricate perovskite solar cells with high power conversion efficiency
(average value efficience 16.6%) using a two step deposition process of CH 3NH3PbI3-xClx perovskite film. The
preparation process of the perovskite film was completed using a solvent annealing technique, where solvent vapor is
introduced during the crystallization of the perovskite film to increase the crystallinity and grain size. Our perovskite
solar cell structure contains a glass/FTO substrate covered with a compact layer of TiO 2 semiconductor. Over that is
deposit a mesoporous scaffold from the same semiconductor which is in a close contact with a perovskite film.
Perovskite film which can work effectively as both absorber and an electron transporter is covered with a Li doped spiro
OMeTAD film (hole transporter). A metallic contact (Mo and Ag) is deposited on the spiro OMeTAD film.
INVESTIGATION OF NEW ABSORBERS MATERIALS FOR EFFICIENT PHOTOVOLTAIC SOLAR
CELLS
P. Wahnona, P. Palaciosa, E. Menendez-Proupinb, E. Castellanosa, Lucenac, JC Conesac
Instituto de Energía Solar, Universidad Politécnica de Madrid, Ciudad Universitaria, 28040 Madrid, Spain;
b
Departamento de Física, Facultad de Ciencias, Universidad de Chile, Santiago, Chile; cInstituto de Catálisis y
Petroleoquímica, CSIC, 28049 Madrid, Spain; [email protected]
a
One of the challenges of materials science today is to find new technologies that will be able to make the most of
renewable energies. An example of new proposals in this field is the intermediate-band (IB) materials, which promise
higher efficiencies in photovoltaic applications.
We present in this work several materials actively studied as good absorbers for photovoltaic applications. The first
alternative consists in the introduction of a properly chosen transition metal at high concentration in an octahedral
semiconductor which gives in-gap delocalized and partially occupied levels, required by the Intermediate Band concept.
The new intermediate band allows the absorption of low energy photon increasing the photo-current but maintaining the
photo-voltage. We have verified with accurate density functional theory (DFT) calculations and beyond, that
semiconductors as In2S3 and layered SnS2 can provide this situation when an octahedral cation in their structure is
partially substituted by an element such as vanadium. For layered semiconductors, the van der Waals cleavage plane
(0001) is characterized by hexagonal arrays of close packed chalcogenide ions which are covalently bound within X-MX sandwiches. These materials are ideal substrates to study fundamental aspects of the metal/semiconductor interaction.
Experimental work made via wet chemistry methods verifies that new absorption features appear in the optical
absorption spectrum which matches the predicted DFT-based theoretical absorption results. On the other hand, a
photocatalytic process (photooxidation of an organic compound in an aqueous suspension irradiated with wavelengthselected light) is used to experimentally assess, even on polycrystalline powder materials, the ability of subbandgap
photons to produce electron-hole pairs that can be extracted at the materials interface with scarce efficiency degradation
by recombination effects. The spectral responses show that these materials have the appropriate characteristics for
building photovoltaic devices of boosted efficiency using the whole range of the visible light spectrum.
Nowadays other actively studied as novel photovoltaic material is the methyl-ammonium lead iodide perovskite
(CH3NH3PbI3). We have computed its electronic structure and relevant properties of the othorhombic phase with
accurate DFT. The crystal structure, optimized using a van der Waals functional, reproduces closely the unit cell
volume. By combining spin-orbit effects, with hybrid functionals the experimental bandgap is also reproduced. The
computed binding energy of the unrelaxed exciton agrees with recently reported experimental data, and the values
found imply an easy exciton dissociation at room temperature. Fast dynamics and large diffusion lengths of the current
carriers are key for the high photovoltaic efficiencies shown by these materials.
18
STRUCTURAL, MORPHOLOGICAL AND OPTICAL PROPERTIES OF RF-SPUTTERED CdS THIN
FILMS FOR PHOTOVOLTAIC APPLICATIONS
Ovidiu Toma, Sorina Iftimie, Lucian Ion, Stefan Antohe*
University of Bucharest, Faculty of Physics, 405 Atomistilor Street, PO Box MG-11, 077125, Magurele-Ilfov,
Romania, Presenting author: [email protected] , *Corresponding author: [email protected]
Cadmium sulfide (CdS) nanocrystalline semiconductor thin films of different thickness were deposited using the
technique of magnetron sputtering in radio-frequency plasma (RF – MS). As cathodes high purity solid CdS targets
were used while optical glasses were employed as anode-substrates (the substrates were maintained at room
temperatures). Optical, structural and morphological characterizations were carried out for the prepared CdS thin films.
For the characterization of the optical properties of the CdS thin films spectroscopic ellipsometry (SE) was used in the
range of 250 nm to 1700 nm. Optical constants (refractive indices, extinction coefficients, optical band gaps, etc.), as
well as film thicknesses and surface rugosities were measured by spectroscopic ellipsometry. This optical method was
combined with optical spectrophotometry (absorption spectra, transmission spectra, reflection spectra) in UV – VIS –
NIR for a better verification of the results. Structural investigations were carried out by X-Ray diffraction (XRD)
technique, while morphological characterizations were performed using atomic force microscopy (AFM).
19
20
Poster Presentations
OXIDE LAYERS CHARACTERIZATION IN GaSb TECHNOLOGY FOR PHOTOSENSITIVE
STRUCTURES
1
C. Cotirlan-Simioniuc1, C. Logofatu1, R.V. Ghita1, F. Frumosu1, M. Rusu2
National Institute of Materials Physics, P.O.Box MG-7, 077125 Magurele, Ilfov, ROMANIA, E-mail: [email protected]
2
National Institute for Optoelectronics-INOE 2000
GaSb-based semiconductor alloys have potential in cutting-edge applications for mid-infrared optoelectronics (Eg~
0.73 eV at 273 K) and thermophotovoltaics. It is stated [1] that the performance and reliability of GaSb devices largely
depend on surface preparation techniques (e.g. n-GaSb (100)) and requires a significant reduction of high levels of
reverse current and surface instabilities. GaSb surface is much more reactive than that of GaAs or InP and quickly
oxidizes under atmospheric conditions [2]. This work presents an XPS (X-ray Photoelectron Spectroscopy) of the native
oxides on n-GaSb (Te doped ) where the irreversible nature of the reaction is related to the fact that the oxygen atoms
are involved in chemical bonds. The evolution of Ga2O3 and Sb2O3 with temperature is presented in high vacuum
heating. Low temperature action can produce on GaSb a non-equilibrium Ga2O3-Sb2O3 surface oxide layer in wet
thermal oxidation process putted into evidence by XPS analysis. There are discussed the evolution of Sb2O3 and Ga 2O3
in four oxidation processes, namely: dry thermal oxidation in furnace (p=1 atm, T (150-200)0C ); wet thermal oxidation
(water vapors T~(90-100)0C, N2 flux ); dry thermal oxidation at low temperatures (T~550C ) and anodic oxidation. The
quality of surface oxide was also examined by Spectroscopic Ellipsometry technique. Due to the fact that the only stable
phases that can exist in thermodynamic equilibrium with GaSb are Ga2O3 and elementary Sb, the problem of developing
a stable oxide layer on GaSb surface to be used further for device processing is vital in GaSb technology. This work is
devoted to the study of a viable route in the technology of a Schottky photosensitive device on n-GaSb (100).
References
[1] M.Perotin et al, Journal of Electronic Materials, Vol.23, No.1, pp.7-12 (1994).
[2] E Papis-Polakowska , Electron Technology-Internet Journal 37/38, 4, pp.1-34 (2005/2006).
Acknowledgements:
The financial and encouragement support provided by the Ministry of Educations of the Romania-UEFISCDI,
Project No. 68/2014
21
NICKEL OXIDE COMPOSITES AS HOLE TRANSPORT LAYER IN POLYMER PHOTOVOLTAIC CELLS
AND AS ELECTRODE MATERIAL FOR SUPERCAPACITORS
a
Diana M. Brusa, Luis Echegoyenb, Marta E. Plonska-Brzezinska*a
Institute of Chemistry, University of Bialystok, Hurtowa 1, 15-399 Bialystok, Poland. e-mail: [email protected],
b
Department of Chemistry, University of Texas at El Paso, 500 W. University Ave., El Paso, TX 79968, USA.
The main subject of this work was synthesis of Carbon Nano-Onions (CNOs) and NiO composites which were
prepared by loading of Ni(OH)2 in different mass ratio on the carbon structures in the presence of 4-DMAP ((4dimethylamino)pyridine), followed by calcination to obtain CNO/NiO. CNOs consist of 6-8 carbon shells (5-6 nm in
diameter) and they can be also referred as multi-shelled fullerenes. The interest in carbon nano-onions is driven by their
unusual physico-chemical properties as well as by promising applications in electronics, optics, biosensors, and in
energy conversion and storage. CNOs/NiO were characterized by TEM, SEM, XRD, TGA-DTG-DTA, AFM, Raman,
FT-IR spectroscopy, and the cyclic voltammetric and impedimetric measurements.
Carbon-based composites are currently being investigated as supercapacitor electrodes because of the synergistic
properties arising from the carbon materials (high power density) and from the pseudocapacitive nanomaterials (high
energy density). Therefore, NiO/4-DMAP could act as an efficient hole-transport layer (HTL) in polymer solar cells
(PSCs) which are very promising organic-based devices for low-cost solar energy conversion. Nevertheless, one of the
greatest drawback of PSCs is their poor stability in ambient conditions. One of well-known HTL is PEDOT:PSS that is
strongly acidic in nature and lead degradation of the devices and limit their life. Therefore, the alternative is a
substitution of PEDOT:PSS by NiO. The hybrid material characterizes excellent stability, charge transport properties,
charge selectivity and hole collection in PSCs.
We gratefully acknowledge the financial support of the National Science Centre, Poland, grant:
#2012/05/E/ST5/03800 to M.E.P.-B. L.E. thanks the Robert A. Welch Foundation for an endowed chair, grant #AH0033 and the US NSF, grants: CHE-1110967 and CHE-1124075.
HYBRID PEROVSKITE SOLAR CELLS: AGING EFFECTS AND RELIABILITY
C. Besleaga1, V. Stancu1, A.G. Tomulescu1, M. Sima1, L.M. Trinca1, G.E. Stan1, A.C. Galca1, L. Pintilie1, I. Pintilie1,
A. Radu2, S. Iftimie2, L. Ion2, S. Antohe2, A. Nemnes2, C. Goehry3 and A. Manolescu3
1
National Institute of Materials Physics, Atomistilor 105 bis, 077125 Magurele, Ilfov, Romania, 2Faculty of Physics,
University of Bucharest, Atomistilor 405, 077125 Magurele, Ilfov, Romania, 3School of Science and Engineering,
Reykjavik University, Menntavegur 1, IS-101 Reykjavik, Iceland
Perovskite-based solar cells have attracted the interest of the photovoltaics community due to their low fabrication
costs and very good conversion. Up to now, external efficiencies measured on this type of structures surpass 10% [1,2]
with a best of 19% reported by Zhou et al. in 2014 [3]. In this work we report studies on high-performance solar cells
based on CH3NH3PbI3-xClx with PCEs up to 16% on fresh devices. The hybrid perovskite thin film is obtained by spin
coating, as well as the anatase (TiO2) and the spiro-OMeTAD, which play the roles of the blocking layer and the hole
transport material (HTM), respectively. Degradation in time of the prepared devices was observed. The source of this
instability is still under debate, being frequently suggested in literature that the aging of spiro-OMeTAD layer degrades
the cell and its efficiency [4]. The stability in time of the obtained photovoltaic devices, with and without spiroOMeTAD, was assessed and discussed, in the search for performance enhancement paths. The effect of the HTM on the
efficiency was also evaluated with numerical simulations. The research leading to these results has received funding
from EEA Financial Mecanism 2009 - 2014 under the project contract no 8SEE/30.06.2014.
References
1. M. M. Lee et al., Science 338 (2012) 643.
2. B. Conings et al. , Adv. Mater. 26 (2014) 2041.
3. H. Zhou et al. , Science 345 (2014) 542.
4. Anyi Mei et al. , Science 345 (2014) 295-298.
22
ZnO-BASED CONDUCTIVE OXIDE THIN FILMS AS TRANSPARENT CONTACT FOR PHOTOVOLTAIC
CELLS
L.M. Trinca1,2, A.C. Galca1, C. Besleaga1, A.G. Boni1, V. Stancu1, A.G. Tomulescu1, M. Sima1, L. Pintilie1, I. Pintilie1
1
National Institute of Materials Physics, Atomistilor 105 bis, Magurele, Ilfov, Romania,2Faculty of Physics, University
of Bucharest, Atomistilor 405, Magurele, Ilfov, Romania, Contact author: [email protected]
ITO (Sn:In2O3) and FTO (F:SnO2) are the most common conductive oxides (TCOs) used as electrodes for
photovoltaic cells. Due to their high price, researchers are looking forward to replace them with abundant and low
production cost materials that pose both good transparency and conductivity. Al:ZnO (AZO) is given as an alternative,
having resistivities as low as those of ITO (~10-4 cm) and also being highly transparent in visible spectrum.
In this work, AZO thin films were deposited on different substrates (glass, single crystal ZnO, polymer foil, single
crystal SrTiO3). The optical and electrical properties of the films were correlated with the structural properties, with the
nature of the substrate and with the deposition parameters.
The optimized AZO thin film was used as bottom electrode of hybrid perovskite solar cells. The photovoltaic
response (external efficiency) was compared with the one of FTO - solar cell, fabricated in identical conditions.
The research leading to these results has received funding from EEA Financial Mecanism 2009 - 2014 under the
project contract no 8SEE/30.06.2014
Liliana M. Trinca acknowledge to the strategic grant POSDRU/159/1.5/S/137750.
NEW CHALCOGENIDE MATERIAL FOR PHOTOVOLTAIC CELLS
Z.S.ELMandouh and H.A.ELMeleegi
National Research Centre,EL-Tahrir St., Dokki,Cairo, Egypt, Affiliation ID: 60014618
Solar cell has been prepared from PbxIn25-xSe75 thin films by Pulsed Laser Deposition method. Pb0.01In0.24Se75
and Pb0.03In0.22Se75 was confirmed to be p-and n- types respectively using Seebeck experiment as a thermoelectric
effect property proof of the thin film alloys under investigation. The disordered structure of such specimens were
confirmed by diffraction electron microscope mode of JEM-1230 TEM. Current- voltage characteristics where
measured under illumination and in dark using KEITHLEY 6517A and, VIRTINS MULTI-INSTRUMENTS,
oscilloscope and signal generator system. Short circuit current and open-circuit voltage was measured to deduce the
Fill-Factor as a property of such cell. The photoelectric Efficiency assured the participation probability for such
materials as a good candidate for solar cells.
MAPLE OBTAINED METAL PHTHALOCYANINES THIN FILMS ON FLEXIBLE SUBSTRATES
M. Socol1, N. Preda1, O. Rasoga1, C. Breazu1,2, F. Stanculescu2, G. Socol3, F. Gherendi3, M Girtan4
1
2
National Institute of Material Physics,105 bis Atomistilor Street, 077125, Bucharest-Magurele, Romania, University
of Bucharest, Faculty of Physics, 405 Atomistilor Street, 077125, Bucharest-Magurele, Romania, 3National Institute for
Lasers, Plasma and Radiation Physics, 409 Atomistilor Street, 077125, Bucharest-Magurele, Romania, 4Laboratoire de
Photonique d'Angers, Université d’Angers, 2, Bd. Lavoisier, 49045, Angers, France, [email protected]
Organic heterostructures based on metal (Zn and Mg) phthalocyanes (p types semiconductors) and 5,10,15,20tetra(4-pyrydil)21H,23H-porphyne (n type semiconductor) were prepare by Matrix-Assisted Pulsed Laser Evaporation
(MAPLE) tehnique on ITO flexible substrates. Structural, morphological, and optical properties of the bilayer and bulk
heterojunctions were investigated by UV-VIS, Photoluminescence (PL) and FTIR spectroscopy as well as Atomic Force
Microscopy (AFM) and Scanning Electron Microscopy (SEM). The layers preserved the properties of the initial
materials and exhibited a large absorption in the visible range of the solar spectrum. The morphology was characteristic
to the MAPLE organic films with large grains. I-V characteristics of (Al/ZnPc(MgPc)/TPyP/ITO and
Al/ZnPc(MgPc):TPyP/ITO) structures were recorded in dark and under the illumination with an solar simulator
(AM1.5). In the bulk heterojunctions, the current value were found to be improved (at least one order of magnitude)
compared to the value obtained in the bilayer heterojunction in the both case of the structures made with ZnPc or MgPc.
23
EFFICIENCY ENHANCEMENT OF DSSC USING PLASMONIC NANOPARTICLES
a
Mohammed S. Rasheeda, A. K. Alib, Mihaela Girtana , Khaleel I. Hassoonb
POMA Lab., FRE CNRS 2988, Angers University, 2, Bd. Lavoisier, 49045, Angers, France, b Department of Applied
Sciences, University of Technology, Baghdad, Iraq, E-mail address: [email protected]
In this work, Au nanoparticles (NPs) were prepared by pulsed laser ablation in liquid (PLAL) technique using NdYag laser with three different energies per pulse (600, 700, and 800 mJ). The gold NPs have been added to Ru based
dye (N719) in order to form a “plasmonic dye”. After the adding of Au NPs colloidal to N719, the absorbance of the
plasmonic dye has increased significantly compared with the pure dye as revealed by UV-VIS spectroscopic analysis in
the figure below. In order to prepare the photo-electrode of the dye sensitized solar cell (DSSC), titanium dioxide film
of thickness about 10 μm was deposited on a FTO glass and then immersed in the plasmonic dyes for 30 min. The TiO2
coatings were sintered in air at 500 °C for 30 min. The XRD analysis for the sintered TiO 2 pastes showed the usual
peaks observed in TiO2 powders. However, the spectral Responsivity calculations demonstrated enhance photocurrent
in the range from 500-580 nm. IV characteristics of the DSSC under AM1 illumination showed enhanced Isc and Voc
by 19 % and 17% respectively.
References
[1] Guowei Yang, Laser Ablation in Liquids: Principles and Applications in the Preparation of Nanomaterials, 2012
Pan Stanford Publishing Pte. Ltd.
[2] M. D. Brown, T. Suteewong, R. Kumar, V. D’Innocenzo, A. Petrozza, M. M. Lee, U. Wiesner, and H. J.
Snaith, “Plasmonic Dye-Sensitized Solar Cells Using Core-Shell Metal-Insulator Nanoparticles”. Nano Lett. 2011, 11,
438–445.
STRUCTURAL AND OPTICAL PROPERTIES OF RF SPUTTERED ZnO:Ga THIN FILMS
Fawzy. A. Mahmoud1,2*, Mohammed Rasheed3, Ahmed F. Mabied1, M.Girtan3
Solid State Physics Dept., National Research Centre, P.O. 12311, Dokki, Giza, Egypt, 2Renewable Energy Group,
Center of Excellence for Advanced Sciences, National Research Centre, P.O.12311, Dokki, Giza, Egypt, 3Angers
University, Photonics Laboratory, Angers, France
1
ZnO:Ga films were deposited on quartz substrates by RF magnetron sputtering using ZnO:Ga target. Four types of
samples were prepared with various RF magnetron powers of 100, 150, 200 and 300Watt. The properties of these films
were investigated using X-ray diffraction (XRD), optical transmittance and reflectance, FESEM, and spectroscopic
ellipsometry in the spectral region of 200 to 1200 nm. The structural and optical properties of the prepared films were
affected by RF power. Relationships between structure of sputtered ZnO:Ga films and the optical constants were
investigated with varying RF power. The refractive and extinction coefficients were calculated by ellipsometry and the
data were correlated with the spectrophotometry measurements. Also the optical band gap was calculated from both
spectrophotometry and ellipsometry measurements, and very good correlations were founded.
24
NORMAL AND INVERTED ORGANIC SOLAR CELLS BASED ON SMALL MOLECULE COMPOUNDS
M. Socol1, O. Rasoga1, C. Breazu1, 2, N. Preda1, F. Stanculescu2, A. Stanculescu1, G. Socol3, M Girtan4
1
2
National Institute of Material Physics, 105 bis Atomistilor Street, 077125, Bucharest-Magurele, Romania, University
of Bucharest, Faculty of Physics, 405 Atomistilor Street, 077125, Bucharest-Magurele, Romania, 3National Institute for
Lasers, Plasma and Radiation Physics, 409 Atomistilor Street, 077125, Bucharest-Magurele, Romania, 4Laboratoire de
Photonique d'Angers, Université d’Angers, 2, Bd. Lavoisier, 49045, Angers, France, [email protected] and
[email protected]
In order to improve the electrical properties of the normal and inverted solar cell structures based on a zinc
phthalocyanine (ZnPc) and an 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTCDA) donor, respectively acceptor
layer, we study the effect of a fullerene aditional layer inserted between them. Indium tin oxide (ITO) was used as
transparent conductive electrod coated with a poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS)
layer in order to increase the charge conduction. The final structures are: glass/ITO/PEDOT:PSS/ZnPc
/fullerene/NTCDA/Al and: glass/Al/NTCDA/fullerene/ZnPc/PEDOT:PSS/ITO for the inverted one. The metods used
for the realization of the organic thin film structures were thermal vacuum evaporation for the small molecule
compounds and spin-coating for fullerene and PEDOT-PSS layers. Because a determinant role in the electrical
properties is played by the morphology of the layers, atomic force microscopy (AFM) and scanning electron
microscopy (SEM) were used to investigate the surface of the thin films. Optical properties of the coatings have been
investigated by UV-VIS, photoluminescence (PL) and FTIR spectroscopy. I-V characteristics of the realized structures
were recorded in dark and under the illumination with a solar simulator (AM1.5). An improvment in the electrical
properties was observed for the inverted structures.
STRUCTURAL PROPERTIES OF CIGS THIN FILMS DEPOSITED BY MAGNETRON SPUTTERING
TECHNIQUE
a
P. Prepelitaa,1, V. Craciuna, M. Filipescua, I. Stavaracheb, D. Craciuna, F. Garoia, G. Sbarceac, A. Vlada
National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor Street, PO Box MG-36, 077125 Magurele,
Ilfov, Romania (1 Married as Garoi), b National Institute of Materials Physics, Magurele 077125, Romania, c National
Institute for R & D in Electrical Engineering ICPE-CA, Splaiul Unirii Street, Nr. 313, District 3, 030138, Bucharest
Romania
Copper indium gallium selenide (CIGS) thin films with various thicknesses (750 – 1200 nm) were deposited by RF
magnetron sputtering method. To simplify this procedure for deposition of chalcopyrite-type thin films, only a single
CIGS sintered target was used.
Deposition conditions for this study were: Ar pressure p = 4 × 10-4 – 4.3 ×10-4 Torr, deposition rate rd = 1.6 – 1.7
Å/s, 100 mm diameter target (CIGS circular disk of 99.99% purity).
The CIGS layer deposited on Mo coated glass substrate, with a thickness of 500 nm. Next, a CdS layer of 60 nm
was deposited by thermal vacuum evaporation technique. The top transparent contact electrode, ITO, was subsequently
deposited by RF magnetron sputtering method. Atomic force microscopy (AFM) and scanning electron microscopy
(SEM) investigations showed that the surface morphology changes depending on the deposition techniques and it is
influenced by the increase in thicknesses of the layers..
Profilometry measurements showed evidence of changes in the step of the deposited layers, due to the interdiffusion
from the level of each deposited layer or that will be deposited. From X-ray diffraction (XRD) measurements it was
found that all films were polycrystalline. CIGS films have a tetragonal structure with (112) plane parallel with the
surface of the substrate, and the grain size is influenced by thickness. The influence of thickness on the samples
electrical and optical properties was also studied by quantum efficiency measurements.
25
DEGRADATION CHARACTERISTICS OF ZnO:B TREATED H/Ar FOR THIN FILM SOLAR CELL BY
DAMP HEAT
1,3
Jae-Seong Jeong, 2Chang-Keun Park, 2Heon-Do Kim, and 3Joongho Choi
Components and Materials Research Center, Korea Electronics Technology Institute (KETI), 1,3Robust Components and
System Research Center, Korea Electronics Technology Institute (KETI), 2 Advanced process development group,
Jusung Engineering Co. Ltd., 3 Department of Electrical and Computer Engineering, University of Seoul,
The TCO(transparent conducting oxide) thin film is an important layer which influence on Rs (series resistance) of
a-Si:H PV(photovoltaic) modules. ZnO thin film for TCO is known that it is weak to damp heat (85°C, 85%RH) stress.
Therefore robust design of ZnO is need to avoid degradation from moisture. ZnO:B thin film growth by MOCVD was
used for TCO. This study was investigated degradation reaction of ZnO:B thin film treated H/Ar due to the moisture.
Electrical characteristics of ZnO:B thin film treated H/Ar were analyzed. The physical/chemical properties of ZnO:B
thin film treated H/Ar were analyzed by XPS and SIMS.
NEW HYBRID MATERIAL WITH APPLICATIONS IN THE SOLAR ENERGY AREA
Nandina Vlatanescu2, Daniel Berki2, Adina Segneanu1, Daniel Damian1,2 and Ioan Grozescu1,2
National Institute of R&D for Electrochemistry and Condensed Matter INCEMC Timisoara University Politehnica
Timisoara
Current global energy consumption is about 15 TW/year, and over two thirds of it is obtained from fossil fuels. The
energy that arrives on the Earth in an hour from the Sun can provide global annual consumption. It is estimated that
from more than 105 TW of sunlight hitting the earth, up to 600 TW is technically feasible to be used. Solar energy may
be harvested through its conversion to heat (solar- thermal), electrons (photovoltaic), or chemicals (solar-fuels). The
former is perhaps the most straightforward, with installations ranging in scale from 1kW household water heaters to 50
MW power plants located in areas of high solar insolation. Common approaches to solar fuels include the
photoelectrochemical splitting of water to produce H 2 and the reduction of CO2 into liquid fuels such as methanol. Solar
fuels remains the least developed strategy to harness solar energy, and is currently the focus of renewed efforts at the
basic research level.
The paper investigates the synthesis of a new organic-inorganic hybrid material for application in solar energy
area. This new material comprises from an organic phosphorus derivate and Zn, Mg and P oxide type composite.
Complete morpho-structural characterisation of this material was performed using XRD, SEM-EDAX, FT-IR and
UV-Vis spectroscopy.
TIO2 PHOTOCATALYTIC INKS FOR COLD SPRAYING DEPOSITION OF THIN FILMS
Panait Ramona, Nicoara Lavinia, Cristina Bogatu, Dana Perniu, Anca Duta*
Transilvania University of Brasov, The Center Renewable Energy Systems and Recycling, Corresponding author:
[email protected]
Titania nanoparticles are widely investigated considering their applications: from photocatalysis (advanced
wastewaters treatment, air purification), to solar cells, sensors, self-cleaning surfaces, paints, ceramic and coating etc.
Photocatalytic inks represent viable and cost effective solution if special applications like flexible substrates for solar
cells, or self-cleaning fabrics based on photocatalysis are targeted. Due to the nanoparticles spontaneous agglomeration
and sedimentation tendency in the continuous medium, ink stability remains the major problem that can limit the
applications.
In this study, Degussa P25 nanoparticles were dispersed under ultrasonication, in water or water-alcohol media to
obtain stable dispersions. UV-Vis transmittance spectra were used to evaluate the dispersions stability.
To balance the van der Waals attractions and prevent the nanoparticles agglomeration, electrostatic repulsions can
be generated by using different stabilizers: surfactants (cationic-DTAB, HTAB, anionic-SDS, non-ionic-PEG),
polymers (polyvinylpyrrolidone) and capping agents (TODA). The formation and changes in the particles double layer
and the interactions developed at the particles/stabilizers/solvent interface were discussed considering the values of PZC
and dispersion pH, concentration and ionic strength. Based on these, stabilization mechanisms were proposed.
The photocatalytic activity of the stabilized dispersions was tested on thin films obtained by cold spraying
deposition. Methylene blue was used as test solution. Correlations between the film stability- photocatalytic properties
were developed and discussed in direct relation with the dispersion’s composition, but also considering the interactions
between the dispersions components and dispersion – substrate.
26
SYNTHESIS AND CHARACTERISATION OF ANTIMONY SULPHIDE (Sb2S3) THIN FILMS
P.A. Nwofe, and N.E. Idenyi
Division of Materials Science and Renewable Energy, Department of Industrial Physics, Ebonyi State University,
Abakaliki, P.M.B 053, Ebonyi State, Nigeria, E-mail: [email protected] (P.A. Nwofe),
[email protected] (N.E. Idenyi)
Thin films of antimony sulphide were successfully grown using the solution growth technique and the effect of pH
on the properties of the films was investigated. The pH range was varied between 4.2 - 8.5 and other deposition
variables were kept constant. The films were characterised using X-ray diffractometry (XRD) to investigate the
structural properties, Scanning electron microscopy (SEM) to study the morphological properties, Rutherford
Backscattering (RBS) techniques for the compositional analysis, and optical spectroscopy to investigate the
transmittance, absorbance and reflectance versus wavelength measurements. The results show that films with
thicknesses ≤ 500 nm were obtained at pH range of 4.2 - 6.0. Loss of stoichiometry was observed more in the alkaline
range. The results of the optical analysis indicate that the films had direct energy band gap with optical absorption
coefficient (α) > 104 cm-1. The refractive index was typically ≤ 2.5, decreasing with increasing photon energies. The
values of the extinction coefficient and the optical density are typically less than unity. The high optical absorption
coefficient and direct energy bandgap obtained in the study, suggests possible use of the films as absorber layers in thin
film photovoltaic (PV) solar cell devices.
GROWTH AND CHARACTERISATION OF DOPED NANOCRYSTALLINE ANTIMONY SULPHIDE
(Sb2S3) THIN FILMS
P.A. Nwofe
Division of Materials Science and Renewable Energy, Department of Industrial Physics, Ebonyi State University,
Abakaliki, P.M.B 053, Ebonyi State, Nigeria, E-mail: [email protected]
In this study, the influence of zinc (Zn) and copper (Cu) impurities on the properties of antimony sulphide (Sb2S3)
thin films grown using the solution growth technique is reported. The films were deposited at room temperature of
28°C, a deposition time of 4 h, and an initial pH of 4.80. The films were then doped with equal concentrations of the
respective impurities and then annealed at annealing temperature of 300 °C. The films were characterised using X-ray
diffractometry (XRD) to investigate the structural properties, Scanning electron microscopy (SEM) to study the
morphological properties, Rutherford Backscattering (RBS) techniques for the compositional analysis, and optical
spectroscopy to investigate the transmittance, absorbance and reflectance versus wavelength measurements. The results
indicate that the film thickness was typically ≤ 600 nm, with an increase in the film thicknesses of the doped layers
compared to the as-deposited films. Information extracted from the XRD studies were used to deduce the crystallites
size, strain, number of crystallites, and the dislocation density. The transmittances of the doped layers were found to be
reduced compared to the un-doped case. The results of the optical analysis show that the films had direct energy band
gap with optical absorption coefficient (α) > 104 cm-1 in both the doped and un-doped layers. The refractive index was
typically ≤ 3.0, with higher values obtained from the doped layers.
SOLAR-THERMAL COATINGS FOR NOVEL FLAT PLATE SOLAR THERMAL COLLECTORS
Lavinia Nicoara, Anca Duta*, Dana Perniu, Ramona Panait
Transilvania University of Brasov, R&D Centre Renewable Energy systems and Recycling, Eroilor 29, 500036 Brasov,
Romania, *Corresponding author: [email protected]
The extended use of renewable energy systems is one of the main path for implementing sustainable development at
communities’ level. Besides efficiency, the renewables integrated in communities, in/near the buildings have to gain
architectural acceptance. Solar-thermal collectors represent one of the most common solution, already implemented in
the built environment, on rooftops or terraces. However, solar-thermal facades are seldom, especially because of the
common colours of the flat plate solar-thermal collectors (black or dark blue).
The paper discusses the paths to increase the architectural acceptance of the flat plate solar thermal collectors, and
proposes a range of composite nanostructures with various colours (red, green, orange) obtained using alumina matrix
and inorganic oxides (pigments) with controlled morphology. The optical performances are discussed in terms of visabsorptance and thermal emittance and show that spectral selective solar-thermal coatings with spectral selectivity S>9
(market acceptable) can be obtained through wet chemical routes (sol-gel or chemical bath deposition). The addition of
Au-nanoparticles in very low concentrations is also discussed, in terms of material’s control (nucleation) and output
(colour, spectral selectivity). Optimised coatings are presented and the scaled-up flat plate solar-thermal demonstrator is
described.
27
COMPARISON OF THE QUALITY OF PHENYL (3-HEXYTHIOPHENE) (P3HT) BLEND WITH
DIFFERENT ACCEPTOR ORGANIC MOLECULES HETEROJUNCTION ORGANIC SOLAR CELLS
Zainab Alhashim, Iulia Salaoru and Shashi Paul
Emerging Technologies Research Centre, De Montfort University, Hawthorn Building Leicester LE1 9BH, UK
Among the renewable energy technologies, solar cells are one of the fastest growing technologies. Traditional ways
of harvesting this energy from the sun is through the use of inorganic materials such as silicon, CdTe and GaAs in solar
cells. Despite the high conversion efficiency, these traditional inorganic solar cells are very expensive due to their high
costs of production. Because of this, alternative materials for use in solar cells are thus very important. Solar cells from
organic materials offer some important advantages compared such as lightweight, potentially low-cost, environmentally
friendly, no rare metals and minerals, no high temperature required during production and unlimited room for further
material modification and improvement. Nevertheless, two significant problems of organic solar cells still need to be
resolved; these include: a low power conversion efficiency and low stability. Bulk heterojunction organic solar cells are
highly promising and are those that have produced the best power conversion efficiencies.
In this work, bulk heterojunction solar cells made of blend of photoconductive polymer (P3HT) and different small
organic molecules (PCBM, C60, TCNQ) have been fabricated and their quality assessed by their fill factor. The
different heterojunction blends were (P3HT:PCBM, P3HT:C60 and P3HT:TCNQ) investigated.
Ni0.2Ti0.1Y0.16Zr0.54O2-δ AND Cu0.2Ti0.1Y0.16Zr0.54O2-δ AS ANODES FOR IT-SOFCs ANODE
1
Mihaela E. Trandafir1, Simona Șomăcescu2, Jose Calderon-Moreno2, Petre Osiceanu2, Mihaela Florea1
University of Bucharest, Faculty of Chemistry, Bucharest, Romania, 2”Ilie Murgulescu” Institute of Physical
Chemistry, Romanian Academy, Spl. Independentei 202, 060021, Bucharest, Romania
Solid oxide fuel cells (SOFC) offer a promising way of converting chemical energy into electrical energy with great
efficiency. SOFC devices need to possess simultaneously an ionic conductivity induced by the presence of oxygen
vacancies and an electronic conductivity induced by the added metal together with a high porosity allowing the fuel
transport through the anodic layer. Our goal is to develop a synthesis method that favors uniformity of the crystalline
network and an improvement of the ionic and electronic conductivity as well as of the catalytic activity. The selfassembling method using Triton X100 as template was used for synthesis of Ni0.2Ti0.1Y0.16Zr0.54O2-δ (NTYZ) and
Cu0.2Ti0.1Y0.16Zr0.54O2-δ (CTYZ).
The XRD pattern of sample CTYZ corresponds to a fluorite type (Fm3m) cubic stabilized zirconia phase with lattice
parameter c= 5.112 Å. The cubic structure is stable at room temperature due to the incorporation of the yttrium,
titanium and copper cations in the zirconia-based lattice and the formation of quaternary oxide solid solution
nanocrystals, with crystal size around 6 nm. The XRD pattern of sample NTYZ corresponds also to a fluorite type
(Fm3m) cubic stabilized zirconia phase with lattice parameter c= 5.131 Å, with crystal size around 3.4 nm with the
present of bunsenite as minor phase. After calcination at 900 oC, the XRD pattern of sample shows a very significant
growth of the crystallite size of the zirconia phase to about 17 nm, as well as a very small increase in the lattice
parameter, c= 5.134 Å.e structure (less than 5 vol.%), and crystal size of about 28 nm. The new composites show high
methane conversion and CO selectivity in the catalytic partial oxidation of methane. Conductivity results showed a
predominately n-type behaviour, highlighting a promising IT-SOFC anode.
This work was supported by a grant of Partnerships in priority S&T domains Program (PNII), MEN– UEFISCDI,
project number 26/2012.
MODELING THE ELECTRON TRANSFER IN DYE-ELECTROLITE SYSTEMS FOR DYE-SENSITIZED
SOLAR CELLS
Anamaria Trandafir1,2,*, Corneliu I. Oprea1, and Mihai A. Girtu1
„Ovidius” University of Constanţa, Department of Physics, 900527 Constanţa, Romania, 2University of Bucharest,
Faculty of Physics, 077125 Magurele-Ilfov, Romania, *Email: [email protected]
1
Dye-sensitized solar cells have gained widespread attention in the past few years due to low cost fabrication. Since
the conversion efficiency of these photovoltaic systems highly depends on the electron transfer at the dye-electrolyte
interface, we studied the dye regeneration of various dye-electrolyte systems for dye-sensitized solar cells. These
systems are formed of various dyes (L0, D35 and Y123) and Co-based electrolytes. Using density functional theory
(DFT) we determined the potential energy surfaces for the singlet, triplet and quintet states. We applied Marcus theory
to determine the electron transfer rate and reorganization energy for these systems. Optical characterization was
obtained using time dependent DFT for the dyes and electrolytes. Computations were made using the Gaussian03
package.
28
S2
Carbon-based Nanomaterials and Applications
Invited Papers
29
30
WHAT COULD BE BETTER THAN GRAPHENE FOR ENERGY STORAGE AND CONVERSION?
Pedro Gomez-Romero
InstitutCatala de Nanociencia I Nanotecnologia, ICN2 (CSIC-CERCA), [email protected]
Graphene seems to be by all accounts the advanced material of choice for years to come. Its unique combination of
mechanical, electrical, optical and chemical properties add to its chemical simplicity to incite potential applications in a
wide variety of applications from flexible electronics to biomedicine to energy.
In the field of energy conversion and storage graphene is no exception and it has already been claimed as a
champion material for energy storage in supercapacitors providing large active area for capacitive double-layer storage,
or as improved catalyst for the Oxygen Reduction Reaction in Fuel Cells. What then could be better than graphene for
energy storage and conversion?
Hybrid materials offer the opportunity of building synergies thus leading to improved performance over their
individual components. In that way, hybrids based on graphene and a variety of extended phases or molecular species
have been used to design materials with enhanced activity. A wise choice of electroactive species can for instance
improve the energy density of graphene-based supercapacitors through hybridization, and a hybrid with catalytically
active species will benefit from that activity and the conductivity of its graphene support. In this conference this general
hybrid approach will be presented in relation to graphene-based materials for energy storage and conversion and
illustrative examples discussed.
CHARACTERIZATION OF SINGLE NANOPARTICLES BY SUB-WAVELENGTH AFM-RESONANT
RAMAN DEVICE
Angélina D’Orlando, Guy LOUARN, Jean-Yves Mevellec, Bernard Humbert*
Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS, 2 rues de la Houssinière, B.P. 32229, 44322,
Nantes cedex 3, [email protected]
Our group develops a new approach combining an Atomic Force Microscope and a confocal-Raman microscope,
where AFM microscope is used to image and to manipulate nano-particles under the confocal optical microscope
coupled at the Raman spectrometer. Our optical device allows us to scan the resonance effects by tunning the
wavelengths of excitation.
This presentation will show the results obtained with some symmetric structures of assembling of gold nanoparticles (AuNPs), in the vicinity of a single and isolated carbon nanotube (CNT). We will investigate the consequence
on the super-resolved Raman spectra and as a function of the different sub-wavelength-scale geometries of AuNPs
aggregates. We will discuss the different interactions between AuNPs aggregates and the carbon nanotube, including
their impact on resonance effects. In particular, we will focus on the enhancement of the local electrical field by
metallic nano-structures to probe single objects.
These experimental data are interpreted according to finite element models of far and local electromagnetic fields.
Thus, on one hand, we achieve to a better understanding about the tunability of plasmon resonance modes of hometailored nanostructures, including sensitive breaks symmetry modes. On the other hand, the consequences of their
interactions with a substrate or molecule dipole moment, depending on the excitation wavelength (especially in the case
of the inelastic scattering), are studied. All this allows us to understand and predict the experimental observation.
CARBON-BASED NANODEVICES BUMPY ROUTES: INKS, FLAKES, SPAGHETTI, WAFERS
Mircea Dragoman
National Institute for Research and Development in Microtechnology (IMT), Str. Erou Iancu Nicolae 126 A, Bucharest,
Romania, [email protected]
This talk deals with an overview of carbon-based devices starting with a series of devices such as transistors made
on carbon nanotubes with spaghetti-like shapes or using graphene flakes and inks. It was interesting research against the
main stream which reported in the same time billions of transistors integrated in a single chip. Today, the first integrated
circuits based on carbon nanotubes and graphene devices such as radios and computers are reported and will be briefly
reviewed in the talk. Also, the carbon-based devices reaching THz region are appearing with unparallel performances.
In the mean time, other two-dimensional materials such as MoS2 or WS2 have started the bumpy route: inks, flakes,…,
the journey of a thousand miles begins with a single step.
31
32
Oral Presentations
C-C COMPOSITES MWNTS ADDITIVATED MESOPHASE BASE AS ADVANCED MATERIALS FOR
AEROSPACE TECHNOLOGY
Ion Dincă1, 2, George Pelin2, Cristina- Elisabeta Pelin2, Adriana Stefan2 and Adela Bara3
Aerospace Consulting 220 Iuliu Maniu Blvd., 061126, Bucharest, Romania, Corresponding author:
[email protected], 2National Institute for Aerospace Research and Development “Elie Carafoli”, 220 Iuliu Maniu
Blvd., 061126, Bucharest, Romania, 3National Institute for Electrical Engineering Research and Development ICPECA, 313 Splaiul Unirii, 030138, Bucharest Romania
1
C-C (carbon-carbon) composites are new class of engineering materials and were first developed for aerospace
technology (components in missiles, reentry vehicles, in space shuttles and as brake lining and discs material for civil
and military aircraft). Nowadays, different forms of materials are available for numerous industrial applications,
primarily in those areas which require a thermal and corrosion – resistant material which is both lightweight and space
saving. These include for example: vacuum and protective atmosphere furnaces, CVD furnaces, HIP plant, hard metal
industry, sinter pressing technology, semi – conductor technology. CFRC is a singular composite materials consisting of
carbon fiber embedded in a carbonaceous matrix. The main properties of C-C composites are high mechanical
properties at elevated temperatures (1500-2000˚C), very high ablation temperature (20000 kcal/kg), low density (1,6-1,8
g/cm3), high tribological properties. These properties are very dependent of the methods used for production.
The work contain the achievements of INCAS (National Institute for Aerospace Research "Elie Carafoli") in carboncarbon composites, family of materials more and more attractive to high performance applications as well as for
engineering design. There are presented methods to obtain C-C composites phenolic and mesophasic base mechanical
and tribological properties, elemental analyze and structural properties of composites.
The work points out anisotropic character, turbostratic of MWNTs (multi-walled carbon nanotubes) additivated
mesophasic C-C as compared to simple mesophasic or phenolic isotropic composites.
33
AN EXPERIMENTAL STUDY OF CARBON NANOTUBES REINFORCED POLYMER MATRIX
NANOCOMPOSITE LAMINATES BY USING MANY KINDS OF CONVENTIONAL FIBERS
1
Sakineh Khajavi1, Mostafa Samadzadeh2
Department of Mining and Metallurgical Engineering, Amirkabir University of Technology (Tehran Polytechnic),
Tehran, Iran (Corresponding author); 2 Center of Intelligence base experimental mechanics, School of Mechanical
Engineering, University of Tehran, Tehran, Iran; E-mail of corresponding author: [email protected]
This work mainly aims to manufacture kinds of carbon nanotubes incorporated nanocomposite laminates at first. In
the present investigation, a combination of high-intensity ultrasonic liquid processor and high speed sheering were used
to obtain a homogeneous mixture of epoxy resin and carbon nanotubes. The nanocomposite laminates used in this study
were manufactured from prepregs consisting of traditional fibers and epoxy resin filled with carbon nanotubes. Carbon
nanotubes were infused into RenLam CY 219 epoxy resin, using a high-speed mechanical agitator and sonic cavitation.
Tensile tests were performed on unfilled and carbon nanotubes-filled epoxy to evaluate the effectiveness carbon
nanotubes addition on the mechanical properties of many kinds of Conventional Composite Laminates. Based on the
experimental results, highly improvement in Young’s Moduli and Tensile strength for all kinds of composite laminates
were observed and also the effect of fiber type on improving amount of mechanical properties was investigated.
FUNCTIONALIZATION SWCNTs SYNTHESIZED BY KrF EXCIMER LASER ABLATION IN A
NITROGEN ATMOSPHERE.
Jasim Al-zanganawee, Marin Gheorghe, Calin Moise, Adrian Katona, Dionezie Bojin, Marius Enachescu
Center for Surface Science and Nanotechnology, University Politehnica of Bucharest, Splaiul Independentei 313,
Bucharest, Romania. College of Science, University of Diyala,Iraq.
In this work, we report on the synthesis of high quality single wall carbon nanotubes (SWCNTs) at 1100 ˚C using
KrF excimer laser to ablate of mixed 98.8 % graphite, 0.6 at% nickel, and 0.6 at% cobalt target in a Nitrogen
atmosphere. Then we oxidized the product by refluxation in 2.6 M HNO 3. The results from Raman spectroscopy, high
resolution transmission electron microscopy (HRETEM), thermal gravimetric analysis (TGA), and scanning electron
microsopy (SEM) measurements showed that the produced nanotube have short length, narrow dimneter distribution
and the carbon nanotubes product has graphitic, amorphous carbon particles, and metallic catalysts. The results from
Raman spectrum after oxidation of carbon nanotubes products showed that the Radial Breathing Mode (RBM) peaks
intensities upon oxidation of carbon nanotubes changed and reduced after oxidation. The D-band intensity increased
and shifted after oxidation due to functionalization SWCNTs with –OH group. The G-band line shape, position and
intensity changed after chemical treatment. The TEM and TGA showed the quantity of the amorphous carbon and metal
prticles of SWCNTs product became less after oxidation.
CARBON FIBER REINFORCED NANOFILLED POLYAMIDE 6 LAMINATES
Cristina- Elisabeta Pelin1,2, George Pelin1,2, Adriana Stefan1, Ion Dincă3, Ecaterina Andronescu2 and Anton Ficai2
1
National Institute for Aerospace Research and Development “Elie Carafoli”, 220 Iuliu Maniu Blvd., 061126,
Bucharest, Romania, Presenting author: [email protected], *Corresponding author: [email protected],
2
Faculty of Applied Chemistry and Materials Science, Politehnica University of Bucharest, 1-7 Polizu St., 011061,
Bucharest, Romania, 3. Aerospace Consulting 220 Iuliu Maniu Blvd., 061126, Bucharest, Romania
Nowadays there is an increasing interest in using reinforced thermoplastic composites in aerospace applications, due
to their advantages and thanks to the innovative technologies used to obtain them. Montmorillonite filled polyamide 6
hybrid laminates reinforced by carbon fiber fabric were obtained by a simple and cost efficient method that involves
polymer/montmorillonite solvent dissolution, fabric impregnation and high temperature pressing. The new laminated
nanocomposites obtained through this process showed a good bonding between the fibers and matrix and consequently
exhibited high mechanical performance, comparable to the ones presented by extensively used carbon fiber reinforced
epoxy composites.
34
EFFECTS OF GRAPHENE QUANTUM DOTS CO-SENSITIZATION OF NANOPOROUS TIO2
PHOTOELECTRODE
1
I. Mihalache 1*, A.Radoi1, M.Kusko1, C.Kusko1
National Institute for Research and Development in Microtechnologies, IMT-Bucharest, *Physics Department,
University Bucharest, P.O. Box MG-11, 077125 Bucharest, Romania
There has been recent research on Graphene quantum dots (GQDs) properties aiming to emphasize their emerging
potential for future implementation as active layer in optoelectronic device applications. Compared to other
carbonaceous nanomaterials, GQDs have distinctive advantages including charge carriers quantum confinement, the
presence of tunable band gap and strong luminescence. Structural properties together with appropriate surface
functionalities enables the control of optical properties like optical bandgap, static and lifetime features of
photoluminescence and to enhance quantum yield.
Few nanometers size aqueous solution-processable GQDs with different surface functionalities were synthesized
through a bottom-up synthetic root starting from Glucosamine hydrochloride and 2-Amino-2-(hydroxymethyl)-1,3 propanediol as organic precursors.
Further on, the performance of GQDs attached on nanoporous titanium oxide in a typical Gratzel solar cell assembly
was investigated. Electrical measurements demonstrated the potential interplay of GQDs and Ru-dye co-sensitizing a
hybrid TiO2 solar cell. The I-V results showed an improvement of up to 12% in power conversion efficiency after cosensitizing the Ru-dye (~18% of short circuit photocurrent), in conclusion it is reasonable to assume that GQDs are
effective co-sensitizers, mediating light harvesting. We demonstrated that carbonaceous material performs a significant
role in charge separation and collection due to the cascaded alignment of energy level and in reducing electron
recombination due to the redox couple. Energy transfer from GQD to Ru-dye also occurred due to the overlap between
the emission and absorption spectra of dyes.
USING MULTI-WALLED CARBON NANOTUBES IN SPARK PLASMA SINTERED FERROELECTRIC
CERAMICS FOR TAILORING DIELECTRIC AND TUNABILITY PROPERTIES
Cristina E. Ciomaga1,*, Leontin Padurariu1, Lavinia P. Curecheriu1, Isabelle Lisiecki2, Marco Deluca3, Carmen Galassi4
and Liliana Mitoseriu1
1
Dielectrics, Ferroelectrics & Multiferroics Group, Dep. of Physics, Al. I. Cuza Univ. of Iasi, Iasi, Romania; 2CNRS,
Univ Paris 06, UMR 7070, LM2N, bât. F, B.P. 52, 4 place Jussieu, Paris F-75231 Cedex 05, France; 3Inst. für Struktur
& Funktionskeramik, Montanuniversitaet Leoben, P. Tunner Straße 5, 8700 Leoben, Austria; 4ISTEC-CNR, Via
Granarolo no. 64, I-48018 Faenza, Italy; *e-mail: [email protected]
The addition of multi-walled carbon nanotubes (MWCNTs) to Pb(Zr0.47Ti0.53)O3 (PZT) ceramics prepared by spark
plasma sintering is proposed as a method of tailoring electrical properties through the modifications of microstructural
characteristics. The microstructural modifications induce an increase of the inhomogeneity degree of the local electric
fields in material, as described by Finite Element Method (FEM). The addition of even small amounts of carbon
nanotubes strongly reduced the sinterability of PZT ceramics and resulted in the porous and fine-grained
microstructures (relative density of 73% for a MWCNT addition of 0.5%vol. by comparison with 91% in the pure PZT,
produced in the same conditions). A monotonous decrease of permittivity with increasing the MWCNT level from 830
in pure PZT to 627 for x=0.5% vol., at f=1kHz, and low dielectric losses below 2% have been observed. Tunability
increases with respect to the values of dense PZT for small concentration of MWCNT as high as 0.0625% vol. and then
monotonically decreases for higher additions. By FEM it was demonstrated that by addition of 1-D conductive fillers
with compositions below the percolation limits to porous microstructures, the major role in changing the electrical
properties via local field modification is related to the induced porosity rather than to the influence of the small amounts
of MWCNTs survived after sintering and post-annealing treatment. Acknowledgements: This work was financial
supported by CNCS-UEFISCDI project PNII-RU-TE-2012-3-0150.
35
EFFECT OF SCAN RATE AND KOH ELECTROLYTE CONCENTRATION IN MESOPOROUS CARBON
ELECTRODE
Farinaa Md Jamila, Mohd Ali Sulaimana, Suhaina Mohd Ibrahima, Abdul Kadir Masromb and Muhd Zu Azhan Yahyac
AMREC, SIRIM Berhad, Lot 34, Jalan Hi-Tech 2/3, Kulim Hi-Tech Park, 09000 Kulim Kedah, Malaysia, bMinistry of
Science, Technology and Innovation, Malaysia, Level 1-7, Block C5, Complex C, Federal Government Administrative
Centre, 62662 Putrajaya, Malaysia, cFaculty of Defence Science and Technology, University Pertahanan Nasional
Malaysia, Kem Sungai Besi, 57000 Kuala Lumpur, Malaysia. Email: [email protected]
a
Effects of scan rate and electrolyte concentration on mesoporous carbon for supercapacitor application have been
studied. A series of mesoporous carbon sample was synthesized using a modification of silica template, SBA-15 and
glucose as carbon precursor. To obtain a large pore of mesoporous carbon sample, an appropriate amount of glucose
was added into a large pore size of SBA-15 using incipient wetness impregnation method. The mesoporous carbon
sample was then carbonized at 875 oC, 2 oC/min for 4 hours under inert condition followed by refluxing process for
silica removal. The effect of different scan rates (10, 20, 30 and 50 mV/s) was investigated using cyclic voltammogram
technique. It reveals that the best scan rate is attributed to 10 mV/s implying that the interaction between the ions and
electrode is greatly increased. While the use of 6M KOH electrolyte concentration was observed to provide the highest
specific capacitance which is due to the sufficient number of ions for double layer building up.
36
URACIL-ASSISTED FORMATION OF A BILAYER GRAPHENE
Mahmoud Mirzaei
Department of Medicinal Chemistry, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical
Sciences, Isfahan, Iran; E-mail: [email protected]
Graphene layers, which are single standing honeycombs sheets of carbon atoms, are important due to their
characteristic surfaces applicable for many applications. As examined earlier, the monolayer graphene show always
metallic properties but their combinations into bilayers could increase the band gaps for yielding semiconducting
properties. However, if the initial metallic properties are still required, it is important to make metallic bilayer
graphenes versus earlier proposed semiconducting bilayers. Indeed, modulating the distance between the highest
occupied and the lowest unoccupied molecular orbitals could make the structures more useful for specific applications,
especially for electronic systems. Within this work, the combinations of two graphene layers through uracil linkages
have been investigated based on density functional theory calculations. First, the individual counterparts of graphene
and uracil have been relaxed to reach minimum energy levels and then the bilayer graphene has been created by new
optimization process. Uracil, the characteristic RNA nucleobase, has two atomic linking sites of N1 and C5 to be used
as linker to combine four corners of two layers. The optimization processes yielded the stable uracil-assisted bilayer
graphene and its properties. The results of binding energies revealed a magnitude of 521.10 eV, which is a good result
of binding strength and stability. Interestingly, the zero magnitude of dipole moment for monolayer graphene has been
increased to 2.01 debye for bilayer graphene. But the magnitude for band gap, defined by energy differences between
HOMO and LUMO levels, has been remained almost unchanged by a magnitude of 0.31 eV in the monolayer to a
magnitude of 0.33 eV in the bilayer graphene. As a conclusion, the stability for a bilayer graphene has been approved
with similar initial metallic property to monolayer but different polarity property as compared by dipole moments. As
well known, the carbon nanostructures are expected to do characteristic electronic roles in biological systems, but the
polarity is an important task for their water solubilities and dispersions.
37
PHOTOLUMINESCENT SILICA MONOLITHS WITH EMBEDDED CARBON DOTS
Cristina Albu, Corneliu S. Stan* and Daniel M. Sutiman
Faculty of Chemical Engineering and Environmental Protection, Gheorghe Asachi Technical University, D. Mangeron
73 Ave., 700050, Iasi, Romania;University "Alexandru Ioan Cuza" Iași, Streed Carol I, Nr. 11, 700506 Iași, România;
[email protected]; * [email protected]
The work reports a new preparation path of photoluminescent Carbon Dots with 35 % PL quantum yield and
shifting blue to green emission according to the excitation wavelength. The preparation path involves the pyrolitic
processing of succinimide (SI) in carefully controlled conditions. The choice for SI is based on our preliminary
experiments which revealed its suitability for producing high quality C-Dots in terms of PL properties, most probable
due to some particular physical-chemical properties such as: low melting point, favorable decomposition scheme and
various functional groups (carbonyl, imide) which seems to have a critical role in achieving the particular PL properties.
The resulted C-Dots are strongly photoluminescent in a wide excitation range (350-450 nm) and easily dispersible in
various solvents including water, ethylic alcohol, acetone, chloroform, DMF and DMSO. Further, the prepared C-Dots
were embedded in silica matrix through a base catalyzed sol-gel process using TMOS as silica precursor and DMF as
drying control additive. The process was carried out in a plastic mould resulting cylindrical shaped monoliths. The
prepared monoliths retained the remarkable photoluminescent properties of the embedded Carbon Dots. Interestingly,
through embedding in the silica matrix, the emission peaks are shifted to lower wavelengths, most probable due to the
interactions of the surface located functional groups of the C-Dots with the silica matrix.
Further, the composition and morphology of the prepared C-Dots were studied using XPS, FT-IR, P-XRD, DLS,
TEM and AFM investigation methods. Steady state fluorescence, absolute PLQY and chromaticity parameters were
investigated in detail for C-Dots samples and for the prepared silica monoliths.
Aknowledgements: This work was supported by the strategic grant POSDRU/159/1.5/S/133652, co-financed by the
European Social Fund within the Sectorial Operational Program Human Resources Development 2007 – 2013.
MODIFIED CARBON NANO-ONIONS FOR SUPERCAPACITOR ELECTRODES
a
Olena Mykhailiv,a Marta E. Plonska-Brzezinska,a* Luis Echegoyenb*
Institute of Chemistry, University of Bialystok, Hurtowa 1, 15-399 Bialystok, Poland, [email protected].,
b
Department of Chemistry, University of Texas at El Paso, 500 W. University Ave., El Paso, TX 79968, USA,
[email protected].
In the recent years, the ability of carbon to exist in different allotropic forms has provided many new varieties of
nanoscale sized shapes with fascinating properties, such as the “higher” fullerenes, graphene, carbon nano-onions
(CNOs), and single and multi-walled carbon nanotube, among many. The onion-like structures show perfectly spherical
multilayered fullerene structures. Because of the high surface area of CNOs, these structures have been frequently used
to prepare Electrical Double Layer Capacitors (EDLCs). Non-modified CNOs have somewhat limited charge
accumulation properties, thus research has focused on their chemical derivatives, which possess different physicochemical characteristics. Due to their advantageous properties, CNO materials are being used in a variety of carbon
electrodes. Wettability is one of these properties, which is mainly determined by the surface functionalities and affect
the capacitance of organic or aqueous supercapacitors. Chemical modification of CNO surfaces has been achieved
through a variety of methods: chemical treatment with nitric and/or sulfuric acids, ozone treatment, and covalent
functionalization with acid derivatives. The electrochemical properties of the CNO films depend on the porous
structures of the carbon surface. In aqueous solutions, all CNO films show the typical behaviour of an ideal double layer
capacitor with promising capacitance values, ranging between 20-40 F/g in acid electrolytic solution (1 M H2SO4).
We gratefully acknowledge the financial support of the National Science Centre, Poland, grant:
#2012/05/E/ST5/03800 to M.E.P.-B. L.E. thanks the Robert A. Welch Foundation for an endowed chair, grant #AH0033 and the US NSF, grants: CHE-1110967 and CHE-1124075.
38
DIELECTRIC PROPERTIES OF POLYACRYLONITRILE - MULTIWALL CARBON NANOTUBE
COMPOSITES
S. Palade1, C. Berbecaru1,5*, A. Pantazi1, S. Vulpe1, L. Ion1, V. Kuncer4, V. Ţucureanu2, O. Oprea3, R.F. Negrea4, D.
Dragoman1,6
1
Faculty of Physics, University of Bucharest, P.O. Box MG-11, 077125 Bucharest, Romania, 2National Research and
Development Institute in Microtechnologies, Str. Erou Iancu Nicolae 126 A, 077190 Bucharest, Romania, 3Faculty of
Applied Chemistry and Materials Science, University Politehnica Bucharest, 1-7 Polizu Str., 011061 Bucharest,
Romania,4National Institute of Materials Physics, Str. Atomistilor 105 bis, P.O. Box MG-7, 077125 Bucharest,
Romania, 5Romanian Materials Science-Crystal Growth Society, 077125 Bucharest, Romania, 6Academy of Romanian
Scientists, Splaiul Independentei 54, 050094 Bucharest, Romania; e-mails: [email protected] ;
*[email protected]
Polyacrylonitrile polymer (PAN)-Multiwall Carbon Nanotube (MWCNT) composites were prepared by mixing
PAN with different MWCNT mass concentrations. Thermal analysis suggests two glass transition temperatures of
unoriented PAN. Good temperature stability, until around 100 oC, was evidenced for both PAN and PAN-MWCNT
composites. Transmission Electron Microscopy shows a good dispersion of nanotubes in the polymer matrix. Infrared
spectrum (FTIR) shows the bonds configuration and reveals strong interactions between PAN and MWCNT. FTIR
spectrum of as prepared PAN suggests that the polymer is not thermally stabilized. XRD shows the existence of
crystalline and amorphous phases, in both PAN and PAN-MWCNT composites. Magnetic activity of the composites
has evidenced the presence of small traces of catalysts in the raw MWCNT. Mossbauer analyses have not shown the
presence of Iron in the raw materials. Dielectric spectroscopy at low frequencies and in a wide temperature range was
also performed. Permittivity showed a strong increase with MWCNT mass content, while dielectric losses are
comparable in all samples. Thermally activated processes, contributions of various polarization mechanisms and
structural changes could cause the changes of permittivity and losses in heating-cooling cycles at different frequencies.
SILICON RUBBER – GOLD DECORATED MULTIWALL CARBON NANOTUBES COMPOSITES –
DIELECTRIC PROPERTIES
A. Pantazi1, S. Palade1, C. Berbecaru1,2*, D. Dragoman1,3
Faculty of Physics, University of Bucharest, P.O. Box MG-11, 077125 Bucharest, Romania, 2Romanian Materials
Science-Crystal Growth Society, 077125 Bucharest, Romania, 3Academy of Romanian Scientists, Splaiul Independentei
54, 050094, Bucharest, Romania; e-mails: [email protected] ; *[email protected]
1
Composites based on silicone rubber (SR) and different (0 ÷ 2.5) wt. % mass content of non-functionalized
multiwall carbon nanotubes (MWCNTs) or MWCNTs functionalized with gold nanoparticles with diameters of 8 ÷ 9
nm were prepared. A good mass stability was evidenced by thermogravimetric investigations of composites. The weak
endothermic effect evidenced by Differential Scanning Calorimetry measurements suggests some structural
rearrangements in the samples. Dielectric investigations of composites were performed on a large frequency (300 Hz ÷
5 MHz) and a wide temperature (-50 ÷ 150) oC ranges in the cooling-heating cycles. The permittivity increases with
increasing nanotube mass concentration, decreases with increasing temperatures and displays weak frequency
dependence. The losses reveal non-uniform dependence on both temperature and frequency. In the cooling-heating
cycles, the permittivities of SR-Au-MWCNT composites are significantly more stable compared to SR- MWCNT
composites. Our results point out the possibility of using these materials as dielectrics for applications in wide
temperature and frequency ranges.
39
MECHANICAL MEASUREMENTS AND MODAL FINITE ELEMENT ANALYSIS APPLIED ON
MULTIWALL CARBON NANOTUBE-EPOXY COMPOSITES
Elena Vajaiac1,2, Adriana Stefan2, Daniela Dragoman1,4, Cristina-Elisabeta Ban2,3, George Pelin2,3
Faculty of Physics, University of Bucharest, P.O. Box MG-11, 077125 Bucharest-Magurele, Romania; 2 National
Institute for Aerospace Research and Development „Elie Carafoli”, INCAS, 061126 Bucharest, Romania; 3 Faculty of
Applied Chemistry and Materials Science, Polytechnic University, 011061 Bucharest, Romania; 4Academy of
Romanian Scientists, Splaiul Independentei 54, 050094 Bucharest, Romania; e-mails: [email protected],
[email protected], [email protected], [email protected], [email protected].
1
We present numerical simulations of the mechanical behaviour of composites containing epoxy resin and different
concentrations (0 wt. %, 0.5 wt. %, 2 wt. % and 4 wt. %) of functionalized multiwall carbon nanotubes (MWCNTs).
Mechanical tests of flexural strength at tensile stress and Young’s modulus for the epoxy-MWCNT composites revealed
an overall improvement of mechanical characteristics for all MWCNT concentrations studied, the improvement being
optimum, however, for low concentrations of nanotubes, as well as a slow decrease of the tensile strength at tensile
stress as the nanotube concentration increases. Introducing the mechanical parameters as input data in simulations
performed using the finite element commercial codes, developed in ANSYS, we were able to replicate the experimental
data of epoxy-MWCNT composites only for polymerization degrees lower than unity. These findings are in agreement
with the preparation method for the epoxy-MWCNT samples, and offer a strong support for future improvements of
mechanical properties modelling using ANSYS. The achievement of more realistic simulations of mechanical
properties of composites is an important step in understanding the behaviour of aeronautical structures.
SERS AND SEIRA STUDIES OF CARBON NANOTUBES ELECTROCHEMICALLY FUNCTIONALIZED
WITH POLY(2,2’- BITHIOPHENE-CO-PYRENE)
1
I. Smaranda1, M. Scocioreanu1, M. Baibarac1*, I. Baltog1, J.Y. Mevellec2, and S. Lefrant2
National Institute of Materials Physics, Bucharest, Romania, 2Institut des Materiaux “Jean Rouxel”, Nantes, France;
Corresponding author : [email protected] and presenting author [email protected]
A new copolymer composite deposited on gold electrode covered with a SWNTs layer was synthesized by
electrochemical oxidation of 2,2’-bithiophene (BTh) and pyrene (Py) dissolved in LiClO 4 and CH3CN . The vibrational
properties of this copolymer (PBTh–Py) were studied by Stokes and anti-Stokes Raman light scattering and FTIR
spectroscopy in grazing angle incidence geometry. The Raman lines at 1464 and 1435 cm-1 assigned to symetric modes
of C=C bound from quinoid and aromatic rings give the characteristic signature of the PBTh-Py copolymer and were
observed when the working electrode is either a blank Au film or a Au support coated with a SWNT film. In the latter
case, the charge transfer that occurs at the interface of the two constituents leads to the functionalization of SWNTs
with the copolymer molecules. The presence of enhanced anti-Stokes Raman lines at -1461, -1435 and -1187 cm−1
indicates an abnormal anti-Stokes Raman effect that occurs under resonant optical excitation of the PBTh–Py/SWNT
composite. FTIR spectroscopy in the grazing-incidence angle reflection geometry, known as Surface Enhanced IR
absorption method (SEIRA), allows to determine the orientation of the copolymer molecules relative to the Au support.
Thus, the measured angles of 850,830,750 and 710 associated to the transition moment for the vibrational FTIR modes of
the bands at 794, 845, 1105 and 1629 cm-1, respectively indicate their orientation relative to the axis of the copolymer
chain.
40
PHOTOLUMINESCENCE PROPERTIES OF COMPOSITES BASED ON POLY(PARAPHENYLENE
VINYLENE) AND REDUCED GRAPHENE OXIDE
M. Ilie, M. Baibarac, I.Baltog
National Institute of Materials Physics, Bucharest, Romania
Corresponding author: [email protected] and presenting author: [email protected]
Functionalization of reduced graphene oxide (RGO) with poly(paraphenylene vinylene) (PPV) was achieved by two
methods, the thermal conversion at the temperature of 300 0C of the PPV precursor solution containg different RGO
weights and by electrochemical polymerization of α, α, α’, α’ – tetrabromo p-xylene in the presence of the solution of
tetrabuthyl ammonium bromide and RGO in dimethylformamide (DMF) using cyclic voltammetry. A
photoluminescence (PL) quencing effect of PPV in the presence of RGO is reported in the case of composites
synthetized by the two methods. Besides, the composites prepared by thermal conversion of the PPV precursor solution
containg different RGO weights show a change in the profile of PL spectra of PPV. This different behavior of PPV in
the presence of RGO originates in the of short and longer repeating units of PPV by thermal conversion and
electrochemical polymerization of α, α, α’, α’ – tetrabromo p-xylene , respectively. Using Surface–Enhanced Raman
Scattering (SERS) in anti-Stokes and Stokes ranges, one observes an increase of the value of the (Iexp/Icalc)anti-Stokes ratio
associated with the Raman line at -1170 cm-1 when the RGO concentration in the composite mass increases as a result
of the non-covalent functionalization process of RGO with PPV, when a π-π* interaction between the basal plane of
RGO with the phenyl rings of the PPV occurs.
CAREFULLY SELECTING THE CARRIER GAS YIELDS TO HIGH QUALITY AND QUANTITY OF
SEMICONDUCTING SWCNTs IN KrF EXCIMER LASER ABLATIONS
Adrian Katona, Calin Moise, Doru Dinescu, Jasim Al-zanganawee, Dionezie Bojin, Marius Enachescu
Center for Surface Science and Nanotechnology-Politehnica University of Bucharest, Romania
The single-wall carbon nanotubes (SWCNTs) were synthesized using KrF 248nm excimer laser and four ablation
gases: argon, nitrogen, neon and helium. We studied the influence of different inert ablation gases on the quality and
conduction character of SWCNTs.
The ablated products were characterized using scanning electron microscopy (SEM), Raman spectroscopy and
thermogravimetric analysis.
We observed linear decrease of ablated mass with the increase of carrier gas molecular mass. Also the collected
mass follows the same trend.
Helium gas proved to be the best ablation gas producing 10 times more SWCNTs than in argon. SEM analysis
revealed micrometers long SWCNTs.
The RBM area and G band Raman analysis have shown no influence of carries gas over the SWCNTs diameters
distribution, respectively conducting character of SWCNTs, in all cases semiconducting SWCNTs being obtained.
Raman analysis showed that in all gases high quality products were obtained.
TGA allowed us to calculate the mass of SWCNTs content in the soot and the highest value was obtained in helium.
After purification Raman analysis showed SWCNTs with single diameter were obtained.
TGA analysis of the raw product obtained in neon and helium showed no fullerene, and in all gases low amorphous
carbon was obtained, results supported by Raman analysis too.
In the present work we showed that the best gas among the other gases used in this study is helium which produced
high quality and the highest quantity of SWCNTs.
41
ZnO NANOWHISKERS TRANSFORMED IN FLOWER-LIKE TYPE IN THE PRESENCE OF C60
FULLERENE
1
A. Matea1, M. Baibarac1, I. Baltog1, S. Lefrant2
National Institute of Materials Physics, Bucharest, Romania, 2Institut des Materiaux “Jean Rouxel”, Nantes, France ;
*
Corresponding author: [email protected] ; Presenting author: [email protected]
Composites based on inorganic nanoparticles (ZnO) and carbon nanoparticles such as carbon nanotubes (singlewalled or multi-walled), graphene and fullerenes have gained a special interest for various applications like gas sensors,
supercapacitors, solar cells, etc. Normally, such composites are prepared by adding the carbon nano-particles in the
synthesis of ZnO. In this way are obtained particles of different composition and architecture. In this context, SEM
investigations reveal that the architecture of ZnO particles changes from nanowhiskers to flowers of 400-500 nm size in
the presence of C60. The photoluminescence (PL) and Raman studies made on such particles indicate a decrease of the
PL intensity and the appearance of a Raman line at 1594 cm-1 as signature of the formation of ZnC60 compound.
Another Raman line situated at 2934 cm-1 indicates an aggregation process of C60 in highly ordered structures which
occurs during flower-like particles growth. Complementary FTIR studies reveal a band situated at 1635 cm-1 assigned to
the bending vibration mode of H2O molecules that appears after an annealing treatment of the reaction mixture that
indicates that during synthesis complexes of the type C60@H2O were formed. If the synthesis is carried out in aqueous
solution at low temperatures that contains Zn(OH) 24 , the transformation of ZnO nanowhiskers into the flower-type
particles is facilitated by the presence of the compounds C120O, C60@H2O and ZnC60 .
42
S3
Thin films and nanostructures of functional
materials
Invited Papers
43
44
CONTROLLED GROWTH OF TRANSITION-METAL NITRIDE ALLOY FILMS VIA HYBRID
HIPIMS/MAGNETRON CO-SPUTTERING USING SYNCHRONIZED METAL-ION IRRADIATION
G. Greczynski,1* J. Lu,1 J. Jensen,1 I. Petrov,1,2 J.E. Greene,1,2 W. Kölker,3 S. Bolz,3 Ch. Schiffers,3 O. Lemmer,3 and L.
Hultman1
1
Thin Film Physics Division, Department of Physics, Linköping University, SE-581 83 Linköping, Sweden, 2Frederick
Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801 and Materials Science Department,
University of Illinois, Urbana, Illinois 61801, 3CemeCon AG, Adenauerstr. 20 A4, D-52146 Wűrselen, Germany
High-power pulsed magnetron sputtering (HIPIMS) is particularly attractive for growth of transition metal (TM)
nitride alloys for two reasons: (i) the ionization degree of sputtered metal flux is higher than during conventional dc
magnetron sputtering (DCMS), and (ii) the metal- and gas-ion fluxes arrive out of phase at the substrate. 1 The former
implies that ion fluxes originating from elemental targets operated in HIPIMS are distinctly different from those that are
obtained during DCMS, which provides the ability to separate the effects of HIPIMS and DCMS metal-ion fluxes on
film properties. The latter feature allows one to minimize compressive stress due to gas-ion irradiation, by
synchronizing the pulsed substrate bias with the metal-rich-plasma portion of the HIPIMS pulse.
For pseudobinary TM nitride systems TiAlN, TiSiN, and TiTaN, we carry out experiments in a hybrid configuration
with one target powered by HIPIMS, the other operated in DCMS mode. 2,3 This allows us to probe the roles of intense
and
metal-ion fluxes (n = 1, 2) from HIPIMS-powered targets on film growth kinetics, microstructure, and
physical properties over a wide range of M1M2N alloy compositions.
TiAlN and TiSiN mechanical properties are shown to be determined by the average metal-ion momentum transfer
per deposited atom
.4 Irradiation with lighter metal-ions (M1 = Al+ or Si+ during M1-HIPIMS/Ti-DCMS) yields
fully-dense single-phase cubic Ti1-x(M1)xN films. In contrast, with higher-mass film constituent ions such as Ti+,
easily exceeds the threshold for precipitation of second phase w-AlN or Si3N4.
Based on the findings described above, a new PVD method is proposed, that relies on the hybrid HIPIMS/DCMS
concept to grow dense, hard, and stress-free thin films at low temperature, with no external heating, where densification
of the magnetron-sputtered material is achieved by pulsed bombardment with heavy-metal ions which are film
constituents, thus avoiding excessive stress. It is demonstrated for the model system TiTaN, with as little as 8 mol% of
TaN, that a fully-dense alloys with high hardness and low residual stress can be obtained with Ts < 130 °C.5
* presenting author
1
G. Greczynski, J. Lu, J. Jensen, I. Petrov, J.E. Greene, S. Bolz, W. Kölker, Ch. Schiffers, O. Lemmer and L.
Hultman, JVSTA 30 (2012) 061504-1
2
G. Greczynski, J. Lu, M. Johansson, J. Jensen, I. Petrov, J.E. Greene, and L. Hultman, Surf. Coat. Technol. 206
(2012) 4202
3
G. Greczynski, J. Lu, M. Johansson, J. Jensen, I. Petrov, J.E. Greene, and L. Hultman, Vacuum 86 (2012) 1036
4
G. Greczynski, J. Lu, J. Jensen, I. Petrov, J.E. Greene, S. Bolz, W. Kölker, Ch. Schiffers, O. Lemmer and L.
Hultman, Thin Solid Films, 556 (2014) 87
5
G. Greczynski, J. Lu, I. Petrov, J.E. Greene, S. Bolz, W. Kölker, Ch. Schiffers, O. Lemmer and L. Hultman, JVSTA
32 (2014) 041515
GIANT BAROCALORIC MATERIALS
Xavier Moya
Ferroelectric materials typically show large changes of polarization and volume near first order phase transitions at
the Curie temperature. These large changes can be exploited by driving the transitions using electric field or hydrostatic
pressure, resulting inlarge electrocaloric or barocaloric effects. I will show that BaTiO3 displays significant
electrocaloric and barocaloric effects at the very sharp first-order ferroelectric phase transition near 400 K. Both caloric
effects may be driven in full by relatively small external fields, thus yielding giant strength electrocaloric and
barocaloric effects.
45
SINGLE-CRYSTALLINE SrRuO3 NANOMEMBRANES – KEY FOR EXPANDING FERROELECTRIC
MATERIALS INTEGRATION
1
Liliana Stan1, Deborah M. Paskiewicz2, Rebecca Sichel-Tissot2, and Dillon D. Fong2
Center for Nanoscale Materials, Argonne National Laboratory, U.S.A., 2Materials Science Division, Argonne National
Laboratory, U.S.A.
Complex oxide heterostructures are attractive for use in multifunctional devices. To realize such devices, materials
with different crystalline structures, lattice constants, and thermal expansion coefficients must be combined to optimize
the overall functionality of each integrated system. The number of epitaxial oxide heterostructures is limited mainly
because the crystal structures and lattice constants of the films and substrates need to be nearly matched. By creating
nanomembranes (NMs) that can be transferred to any new host substrate, considerable advancement in materials
integration, unachievable through conventional epitaxial growth, can be attained. Moreover, transferring the NMs onto
substrates that would allow a portion of the NM to remain freestanding provides a useful way for probing fundamental
materials properties, especially those related to strain engineering.
We produced single-crystalline SrRuO3 (SRO) NMs and used them as growth templates for PbZr1-xTixO3 (PZT)
thin films. Coherent epitaxial SRO films were grown on SrTiO3 (001) (STO) substrates. The SRO NMs were then
released from the STO substrate via selective etching. The epitaxial strain in the SRO film is elastically relaxed upon
release. The SRO NMs were transferred to variety of new substrates and served as epitaxial growth templates for
excellent crystalline quality PZT films. We investigated the effect of temperature and oxygen partial pressure on the
structure of the PZT/SRO heterostructures using in-situ synchrotron x-ray techniques. The polarization direction of the
PZT can be switched by altering the surface of the ferroelectric film in an oxidizing or reducing environment at elevated
temperatures.
Use of the Center for Nanoscale Materials and Advanced Photon Source (sector 33BM-C), Argonne National
Laboratory was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences,
under Contract No. DE-AC02-06CH11357.
FROM PEROVSKITE THIN FILMS TO TETRAGONAL TUNGSTEN BRONZE NANORODS
EPITAXIALLY GROWN BY PLD: A THIN FILM PHASE DIAGRAM INVESTIGATION IN THE
MULTIFUNCTIONAL LEAD-FREE (K,Na) - (Ta,Nb)-O SYSTEM
1
M. Guilloux-Viry1, A. Waroquet1, V. Demange1, B. Gautier2, P. Hamoumou2, V. Bouquet1, S. Députier1
Institut des Sciences Chimiques de Rennes, UMR 6226 CNRS/UR1, Campus de Beaulieu, 35042 Rennes, France,
2
Institut des Nanotechnologies de Lyon, INSA de Lyon, 7, avenue Capelle, Villeurbanne Cédex 69621,France,
[email protected]
Multifunctional materials in the (K,Na) - (Ta,Nb)-O systems have attracted great interest for applications in
microelectronics, electro-optics, and photocatalysis. Nowadays lead free materials are of first importance for
piezoelectric /ferroelectric devices. As an illustration the KTa1-xNbxO3 (KTN) perovskite is well-known to present
large piezoelectric effects and highly tunable properties in microwaves, and some potassium niobates exhibit
photocatalytic activity. Tetragonal tungsten bronze phases (TTB) are also of major interest for new efficient devices on
a reduced scale. After a presentation of the potentialities of these materials, this talk will present how to control the
growth of different phases of interest in the KTN system. Perovskite films were first epitaxially grown on different
substrates by Pulsed Laser Deposition (PLD) which is a suitable method to develop a phase diagram approach. KTN
nanorods were grown by PLD. Precession electron diffraction associated to transmission electron microscopy was used
to solve the crystal structure which appeared to be a TTB type. Various phases in the KTN and KN systems were
synthesized such as KNb3O8 , K4Nb6O17, and the K6Nb10.88O30 TTB phase. Na,K-Nb-O films consisting of
nanorods were also obtained. The film/substrate epitaxial relationships of the different phases which compete were
determined and correlated to the microstructure. Films deposited on Nb:SrTiO3 were characterized by Piezoresponse
Force Microscopy which showed piezoelectric activity for some phases which confirms also the high potentiality of non
perovskite phases in this system.
46
PIEZOELECTRIC MICROSYSTEMS WITH ENHANCED PROPERTIES: A MATERIAL APPROACH
Emmanuel Defay1,2, Veronika Kovacova2, Julie Abergel2, Pierre-Henri Cazorla2, Gwenael Le Rhun2
1
Luxembourg Institute of Science and Technology (Luxembourg), 2CEA LETI (France)
20 years ago, microsystems were based on materials issued from microelectronics, that is to say silicon, silicon
dioxide and aluminium. Nowadays, other materials are integrated into microsystems in order to set new properties as
high-K dielectrics, magnetic layers, metals with improved aging properties or piezoelectric materials. This integration
of new materials has paved the way to plenty of new applications as airbag triggers, RF acoustic filters, integrated
compass, inkjet printing heads, microswitches or all kinds of sensors.
In this talk, we will focus on the material approach that has been pursued for more than ten years in order to improve
at the same time the integration of piezoelectric PZT thin films into microsystems and material properties. Three main
features will be detailed: the crystalline orientation, the optimization of the phase content in morphotropic lead zirconate
titanate (PZT) in order to improve the field-induced phase change and the positive and negative effects of the chemical
built-in gradient in sol gel films.
Two piezoelectric microsystems will be described in order to exemplify this material approach, namely actuated
membranes and a micropump based on PZT thin films.
Ge – BASED NANOSTRUCTURES WITH CHARGE STORAGE PROPERTIES AND HIGH VIS-NIR
PHOTOCONDUCTIVITY
Magdalena Lidia Ciurea
National Institute of Materials Physics, Magurele, Romania, [email protected]
The nanostructures formed of Ge nanoparticles (NPs) and/or nanocrystals (NCs) embedded in oxides are intensively
investigated for applications in non-volatile memories related to their charge storage properties and for optical sensors
and solar cells. In this work we present different nanostructures formed of Ge NPs/ NCs embedded in different oxides
(HfO2, TiO2), some of them having both properties of charge storage and high photoconductivity in VIS-NIR. The
nanostructures were prepared by magnetron sputtering deposition of films (Ge-oxide with different Ge concentrations)
and trilayer structures (HfO2/Ge/HfO2/Si with different thicknesses of Ge middle layer that determine the density of Ge
NPs/ NCs acting as storage nodes) followed by rapid thermal annealing (RTA) under controlled conditions. Firstly,
structure and morphology were investigated by (HR)TEM. For evidencing of charge storage properties, capacitance–
voltage (C–V) characteristics on trilayer structures at different frequencies between 100 kHz and 1 MHz were measured,
and the retention time was determined. For showing the high photoconductivity of films, spectral distributions of
photocurrent (If–λ) and photocurrent–voltage (If–V) characteristics were measured. We obtain memory windows ΔV of
1–3 V (for ±5 V sweeping voltage interval), and after 5000 s the capacitance decreases with about 25% presenting a
plateau trend. We demonstrate that the value of ΔV is correlated with the morphology of trilayer structures.
The films obtained by co-sputtering of Ge and oxide (HfO2, TiO2) followed by RTA nanostructuring are highly
photoconductive, the spectral sensitivity interval varying from VIS to NIR depending mainly on the morphology and
structure, but also on the oxide. The Ge-TiO2 films are more versatile than Ge-HfO2 ones. The spectral If–λ curve
presents a fine structure that can be tuned by controlling the films morphology and structure, which in turn can be tuned
by changing the Ge concentration and RTA conditions. So, the Ge-TiO2 films containing about 30% Ge present a
narrow band of sensitivity centred on 1100 nm if they are annealed at 580–600 oC, while for those annealed at 770–800
o
C, the main photosensitive band is broader and presents two maxima at about 750 and 900 nm. This versatility makes
these films promising for photodetectors discriminating between different slippery road conditions.
47
48
Oral Presentations
ELECTRICAL PROPERTIES OF FIELD EFFECT TRANSISTORS BASED ON SINGLE NANOWIRES
C. Floricaa*, A. Costasa, b, E. Mateia, M.E. Toimil-Moralesc, A.G. Bonia, L. Pintiliea, N. Predaa and I. Enculescua**
National Institute of Materials Physics, Bucharest-Magurele, P.O. Box MG-7, 077125, Romania, bFaculty of Physics,
University of Bucharest, Bucharest-Magurele, P.O. Box MG-11, 077125, Romania, cGSI, Helmholtz Centre, Planckstr.
1, D-64291, Darmstadt, Germany, *[email protected] ; **[email protected]
a
Nanowires are an important class of nanostructures, regarded as highly effective building blocks for electronic
devices. In this work, we report on the preparation, characterization and integration into field effect transistors of
different semiconductor nanowires (n-type and p- type): ZnO, CdTe and CuO. Precise control of the morphology
enables the tailoring of the materials functionality and the ability to design devices.
The electrochemical deposition technique was used to grow ZnO and CdTe nanowires in polycarbonate membranes
as templates. The CuO nanowires were grown using thermal annealing in air of Cu substrates. The structural,
morphological and optical properties of the semiconducting nanowires were investigated for assessing the possibility of
integrating them into field effect transistors. The electrical properties were determined for individual nanowires after
contacting them by e-beam lithography and focused ion beam induced metallization on electrodes prepared by
photolithography. Different metals (Au, Pt, Ti/Au and Ti/Pt/Au) were tested for comparison. Based on the
understanding of the Metal/Semiconductor interface characteristics and on the dominant conduction mechanisms backgated nanowire based transistors were fabricated. The influence of the bottom gate was investigated and it was found
that surface passivation leads to improved transport properties for the ZnO and CdTe nanowires. These devices are
suitable for being used in various electronic circuits where their size related properties can be exploited.
Acknowledgements
The authors acknowledge the financial support of ANCSI, Contract 45 N, Project PN09-450102 and UEFISCDI
IDEI 24/2013. Andreea Costas was supported by the strategic grant POSDRU/159/1.5/S/137750.
49
TRANSPORT PROPERTIES OF TEMPLATELESS ELECTRODEPOSITED ZnO NANOWIRES
Andreea Costasa,b*, Camelia Floricaa, Elena Mateia, Monica Enculescua, Lucian Pintiliea, Ioana Pintiliea, Ionut
Enculescua**
a
National Institute of Materials Physics, PO Box MG-7, 077125, Magurele-Bucharest, Romania, bFaculty of Physics,
University of Bucharest, PO Box MG-11, 077125 Magurele-Bucharest, Romania, *[email protected],
**
[email protected]
ZnO nanowires were electrodeposited onto metallic interdigitated electrodes from a nitrate bath at different
deposition potentials. Photolithography, RF sputtering and vacuum evaporation were used in order to fabricate
interdigitated Ti/Au electrodes on Si/SiO2 substrates. The electrochemical growth led to self-contacting nanowires
allowing the transport characterization without any additional steps of lithography. The structural properties were
evaluated by X - ray diffraction. Scanning electron microscopy was used to analyze the morphology of the nanowires.
Reflection and photoluminescence spectra were measured and the results were correlated to those obtained from the
transport measurements. The electrical investigation, i.e. current-voltage characteristics for various temperatures, was
performed for all samples grown at different electrode potentials. We found that a space charge limited current transport
mechanism can be applied to these self-contacting ZnO nanowires. For samples where high defect related
photoluminescence was observed, we dealt with space charge limited current with uniform trap distribution in an energy
interval. For the case where low defect emission was observed, the shallow level traps became predominant in the space
charge limited current model.
Acknowledgement
The authors acknowledge the financial contribution of UEFISCDI, project PD number 18/2013. Andreea Costas was
supported by the strategic grant POSDRU/159/1.5/S/137750, “Project Doctoral and Postdoctoral programs support for
increased competitiveness in Exact Sciences research”, which is cofinanced by the European Social Foundation within
the Sectorial Operational Program Human Resources Development 2007–2013.
DESIGNING ZnO/POLYMER HYBRID MATERIALS BY ELECTROLESS DEPOSITION AND
ELECTROSPINNING
A. Evanghelidisa,b*, N. Predaa**, C. Floricaa, A. Costasa, b, I. Zguraa, M. Socola, M. Enculescua, and I. Enculescua
National Institute of Materials Physics, Magurele, Bucharest, P.O. Box MG-7, 077125, Romania, bFaculty of Physics,
University of Bucharest, Bucharest-Magurele, P.O. Box MG-11, 077125, Romania, *[email protected];
**
[email protected]
a
In the last years, the preparation of hybrid materials based on inorganic nanostructures and organic polymers has
attracted much interest due to the synergistic effect from the combined desirable properties of the inorganic part
(optical, electrical, mechanical, etc.) with those of the organic part (flexibility, processability, etc.). In this context,
ZnO/polymer hybrid materials were obtained by combining the electroless deposition method with the electrospinning
technique. Both methods are appropriate for industrial production, being simple, cheap, highly efficient and suitable for
covering large areas. A typical three step method, similar to those used for electroless deposition of metals on insulating
substrates, consisting of tin ions pre-activation, palladium activation and ZnO deposition was employed. The deposition
process is based on nitrate ions reduction by dimethylamineborane. The samples were investigated, before and after
ZnO deposition, by scanning electron microscopy, X-ray diffraction, optical spectroscopy and photoluminescence.
Morphological studies revealed that the polymer fibers are homogeneously covered by ZnO hexagonal prisms. The
structural and optical data of the coated polymer fibers show that the ZnO has a hexagonal wurtzite structure and optical
signatures (band-gap value and emission bands) typical for this semiconductor. In this way, using commonly available
raw reagents and without requiring complex installations, both techniques involved in the preparation of these hybrid
materials favour their scaling-up in order to obtain ZnO coated polymer fiber mats with potential applications in
electronic and optoelectronic devices (sensors, photovoltaics, supercapacitors, transparent electrodes etc.).
50
THERMAL TRANSPORT ACROSS FEW-LAYER BORON NITRIDE ENCASED BY SILICA
Yuxiang Ni1, Jiechao Jiang2, Efstathios Meletis2, and Traian Dumitrica1, *
Department of Mechanical Engineering, University of Minnesota, 111 Church Street SE, Minneapolis, MN 55455,
USA, 2Department of Materials Science and Engineering, University of Texas at Arlington, 501 West First St.,
Arlington, TX 76019, USA, *Corresponding author. E-mail: [email protected]
1
Two dimensional hexagonal boron nitride (h-BN) attracted attention for use in applications. Using equilibrium
molecular dynamics, we examine the phonon transport in few-layer h-BN encased by silica (SiO2 ). We report large
interfacial thermal resistances, of about 2.2x10 -8 m2 KW-1, which are not sensitive to the number of h-BN layers or the
substrate crystallinity. The h-BN/SiO2 superlattices exhibit ultra-low thermal conductivities across layers, as low as 0.3
W/mK. They are structurally stable up to 2,000 K while retaining the low-thermal conductivity attributes. Our
simulations indicate that incorporation of h-BN layers and nanoparticles in silica could establish thermal barriers and
heat spreading paths, useful for high performance coatings and electronic device applications.
MAGNETICALLY-DRIVEN ALIGNMENT OF A PHBV ORGANOGEL
Antoine Stopin1, Alexandre Rossignon1, Masoumeh Keshavarz2, Peter C. Christianen2, Davide Bonifazi1
Namur Research College and Department of Chemistry, University of Namur, Rue de Bruxelles 61, 5000 Namur,
Belgium, [email protected] , [email protected] , 2 High Field Magnet Laboratory HFML, Radboud
University Nijmegen, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
1
For the past ten years, the design and synthesis of precisely-ordered functional materials have become the main
target of multiple research groups in the world. Among the different available alignment techniques, the use of an
external magnetic field possesses numerous advantages such as being contact free and homogeneous over the whole
sample.[1] Importantly, the ”freezing” of the magnetically-ordered structure after the removal of the external magnetic
field can be performed via the in-situ formation of a rigid matrix, such as a gel.[2]
In this perspective, we studied the magnetic alignment of an organogel composed by poly(3-hydroxybutyric acid-co3-hydroxyvaleric) acid (PHBV), a bio-sourced polymer. Jellification of PHBV in the presence of a magnetic field (as
low as 2 T) allowed the alignment of the material, as confirmed by birefringence measurements. This alignment is
almost completely retained after turning the magnetic field off, producing an anisotropic organogel.
[1] I. O. Shklyarevskiy, P. Jonkheijm, P. C. M. Christianen, A. P. H. J. Schenning, A. Del Guerzo, J.-P.
Desvergne, E. W. Meijer, J. C. Maan, Langmuir 2005, 21, 2108-2112.
[2] L. Maggini, M. Liu, Y. Ishida, D. Bonifazi, Adv. Mater. 2013, 25, 2462-2467.
CRYSTALLIZATION FEATURES OF THE Ge-HfO2 AMORPHOUS FILMS OBTAINED BY MAGNETRON
SPUTTERING
1
VS Teodorescu1, AV Maraloiu1, R Negrea1,2, A Slav1,2, C Palade1, AM Lepadatu1, ML Ciurea1
National Institute of Materials Physics, Bucharest-Magurele, Romania, 2University of Bucharest, Faculty of Physics,
Bucharest-Magurele, Romania
Thin films of Ge-HfO2 were co-sputtered on oxidized Si[100] substrate, having a Ge/HfO 2 ratio of 25/75 and 50/50.
The Ge-HfO2 film with thickness of 15 nm was covered by a pure HfO 2 film of 20 nm thickness, also deposited by
magnetron sputtering. The whole as-deposited structure is amorphous, and it was crystallized using a rapid thermal
annealing processor at different temperatures between 650 and 850 oC , in argon atmosphere. The film structure was
studied by STEM, EDX and HRTEM, using a cross section (XTEM) specimen preparation, before and after the
annealing. The RTA annealing induces the crystallization of both HfO 2 and Ge-HfO2 films. The sizes of HfO2
crystalline grains are larger than the structure thickness. Generally, any HfO 2 crystalline grains are extended from the
top surface to the interface with the substrate. The bottom part of all HfO 2 crystalline grains has Ge inclusions that are
probably amorphous nanoparticles embedded in the crystallized HfO 2 matrix. These Ge amorphous nanoparticles were
evidenced by STEM observations and have 4 to 5 nm in size. They produce big distortions in the HfO 2 crystalline
lattice, as evidenced by image processing of the HRTEM images. No crystalline Ge nanoparticles were observed and no
traces of any moiré fringes which can results from Ge and HfO2 superposed lattices were evidenced. In our opinion, Ge
nanoparticles remain amorphous due to the high rate of HfO 2 crystal lattice growth.
51
AMORPHOUS Zr-BASED THIN FILMS FABRICATED BY MAGNETRON SPUTTERING FOR
POTENTIAL APPLICATION IN HYDROGEN PURIFICATION
Shahrouz Nayebossadri, John Speight, David Book
School of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham, B15 2TT UK, Email:
[email protected], Tel: (+44) (0) 121 414 5213
Amorphous hydrogen separation membranes are under development because of their resistance to hydrogen
embrittlement, improved mechanical properties, resistance to corrosion and most importantly lower intrinsic cost. The
Closed Field Unbalanced Magnetron Sputter Ion Plating (CFUBMSIP) is a versatile technique for deposition of high
quality thin-films of almost any composition, while enabling the control of film size, thickness and shape. In this work,
it was demonstrated that thin-films (~ 3-6 microns) of amorphous Zr40.5Ni59.5, Zr54Cu46 and Zr30Cu57.5Y12.5 could be
deposited onto glass substrates by the CFUBMSIP technique. XRD measurements only showed one broad peak for each
alloy, with a peak centred between 36 and 42° 2θ, indicating that the films were amorphous. Surface analysis by SEM
and confocal microscopy suggest deposition of continuous films. The thermal stability of the films appears to be mainly
governed by the alloying elements and their compositions. However, the measured activation energies indicated that the
nucleation and growth mechanism in the magnetron sputtered films may be different from that reported for melt-spun
amorphous alloys with similar compositions.
Keywords: Hydrogen Purification, metallic membranes, amorphous alloys, thin films, Zr-based alloys, magnetron
sputtering
CONDUCTION MECHANISMS IN NANOSTRUCTURED Ge-SiO2 AND GeSi FILMS
Ana-Maria Lepadatu, Catalin Palade, Ionel Stavarache, Adrian Valentin Maraloiu, Valentin Serban Teodorescu,
Magdalena Lidia Ciurea
Ge and GeSi based nanostructured films are very interesting as in Ge nanocrystals (NCs) the quantum confinement
is stronger than in Si, so the Bohr exciton radius is much larger. GexSi1-x gives the possibility to tune the forbidden
energy gap by both quantum confinement and composition change. Depending on how the preparation process is
conducted, different morphologies can be obtained in the Ge-SiO2 and GeSi nanostructured films, ranging from (Ge and
GeSi) NCs to (Ge) amorphous nanoparticles (a-NPs) or even both of these types together (with different densities to
each other), all being embedded in amorphous matrix (a-SiO2 or a-GeSi). In these films which essentially represent
percolative systems, hopping and tunneling are basically the governing conduction mechanisms that are correlated with
the film morphology. In this work, we show how the morphology drives the films electrical behavior.
Both Ge-SiO2 films formed of Ge NCs (12 nm size) embedded in a-SiO2 and GeSi films formed of GeSi NCs (7–15
nm) separated by thin a-GeSi regions are deposited by using magnetron sputtering and subsequently annealed under
controlled conditions. In both kind of films, the current–temperature (I–T) dependence presents a mechanism of
thermally activated tunneling of carriers between neighboring NCs (logI~T–1/2). If Ge-SiO2 films are formed of small aGe NPs dispersed in a-SiO2 matrix, meaning that the annealing conditions are not suitable for Ge NCs formation, the I–
T curves are governed by a (Pollak) hopping mechanism (logI~T–1/4) between localized states related to the a-Ge NPs, in
a band around Fermi energy that works up to room temperature.
In the case of GeSi nanostructured films, the current–voltage dependence reveals a high electric field electron
tunneling through the potential barriers given by the a-GeSi regions between the NCs, while the Ge-SiO2 films based on
a-Ge NPs show a conductance that is independent of voltage.
52
SEMICONDUCTING METAL OXIDES FOR GAS SENSING - AN HSAB PERSPECTIVE
B. Serban, M. Brezeanu, O. Buiu, C. Cobianu, A. Stratulat
ACS Wireless and Sensors Laboratories, Sensors and Wireless Laboratory Bucharest, Honeywell Romania
Semiconducting metal oxide (MOX)-based gas sensors became increasingly important due to their significant
merits: detection of large number of gases, low cost, light weight, simplicity in both manufacturing and usage, high
sensitivity. However, although highly important and strongly intercorrelated, neither the cross-sensitivity of these
structures, nor the detection mechanism of desired species is fully understood. No study ever performed did look at the
MOX and the target analyte as a tandem. Moreover, apart from classifying gases as reducing or oxidizing, the nature of
the interaction between the sensed gas molecule and the sensing layer was ignored. It is the purpose of this paper to
introduce the Hard Soft Acid Base (HSAB) concept, as a method to coherently explain this interaction. The HSAB
principle was proven to be useful in selecting and synthesizing gas sensing layers for different types of sensing
structures, based on technologies such as: surface acoustic waves, colorimetric, chemoresistive. The HSAB rule, which
operates with the Lewis acid - Lewis base and with the hard - soft – borderline classifications, states that hard bases
prefer to interact with hard acids, soft bases prefer soft acids, borderline acids prefer borderline bases. As a
consequence, the cations of the metal oxides typically employed as sensing layers and the corresponding gas molecules
can be classified according to the HSAB theory and their matching can be explained. For instance, the HSAB theory
can satisfactorily demonstrate why TiO2 (hard acid) is employed in humidity (hard base) detection, why La2O3 (hard
acid) is used in ethanol (hard base) sensing, and the role played by dopants in increasing the sensitivity of MOX-based
sensor (Cu2O - Cu+ is a soft acid - increases the sensitivity of WO3 towards H2S - a soft base). Along the same lines,
the selection of MOX as fillers for polymers in different types of gas sensors can be analyzed. For example, the HSAB
concept explains the strong interaction between pyrene butyric acid as carboxylate group (hard base), used as fluorofor,
and Al2O3 (hard acid), used as inorganic filler dispersed on a polymer, employed in the design of fluorescence
quenching – based O2 sensors. In conclusion, the HSAB concept proves a valuable tool both for selecting sensing
materials suitable for gas detection and for explaining the phenomena occurring at the interface between the gas and the
sensing layer.
RAPID IN-SITU X-RAY DIFFRACTION DURING THE GROWTH OF FERROELECTRIC
SUPERLATTICES
Benjamin Bein1, Hsiang-Chun Hsing1, Sara J Callori1, a John Sinsheimer1,
Priya V. Chinta2, Randall L. Headrick2, and Matthew Dawber1
1
Dept of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 USA, 2Department of
Physics, Cook Physical Science Building University of Vermont, Burlington, VT 05405 USA
Ferroelectric domains, surface termination, average lattice parameter and bilayer thickness were monitored using insitu synchrotron x-ray diffraction during the growth of BaTiO 3 /SrTiO3 (BTO/STO) superlattices by off-axis RF
magnetron sputtering. A new x-ray diffraction technique was employed which makes effective use of the custom
growth chamber, pilatus detector and synchrotron radiation available at beamline X21, NSLS, BNL. The technique
allows for scan times substantially faster than the growth of a single layer of material, enabling continuous monitoring
of multiple structural parameters as the film grows. Due to the large compressive strain experienced by the BTO layers
in these substrates these superlattices are ferroelectric when grown and display continuous evolution of the polarization
during growth. The effect of electric boundary conditions was investigated by growing the same superlattice
alternatively on STO substrates and 20nm SrRuO 3 (SRO) thin films grown on STO substrates. The experiments provide
insight into the formation and evolution of ferroelectric domains in the situation when the sample is ferroelectric during
the growth process. Besides the fundamental knowledge gained from these studies, being able to monitor the structural
parameters of a growing ferroelectric superlattice at this level of detail provides numerous insights which can guide the
growth of higher quality ferroelectric superlattices in general.
53
THEORETICAL MODELLING OF METAL-FERROELECTRIC-METAL CURRENT-VOLTAGE
CHARACTERISTICS
Lucian D. Filip, Lucian Pintilie
National Institute for Materials Physics, Atomistilor str. 105bis, PO Box MG7, Magurele, Bucharest, Romania, 077125,
[email protected]
Current-voltage (I-V) characteristics measured on metal-ferroelectric-metal (MFM) heterostructures were simulated
by considering a combination of tunnelling and thermal effects. The model assumes that the polarization of the
ferroelectric material is in a saturated state. Its effects are modelled by two sheets of opposite charges that limit the bulk
material. Each sheet has a uniform charge density and opposite signs. The ferroelectric material is considered to be ntype and with a uniform distribution of donor defects, . The regions between each interface and the charged sheets are
assumed to have no polarization and a lower dielectric permittivity ("dead layer" approximation). The whole can be
divided in five regions where the Poisson equation must be solved and the continuity and boundary conditions for the
solutions should be imposed: two "dead layer" regions near each interface, two influence regions in the ferroelectric
bulk representing and a region of the ferroelectric bulk where the electric field is considered to be completely screened.
The two influence regions in the bulk space near the charged sheets represent the extent of the influence of each sheet
on the charge distribution in order to preserve the electrostatic neutrality.
The I-V characteristic was calculated by solving a balance equation for the incoming and outgoing electron currents
through the two interfaces in order to find the existing electron population in the ferroelectric at each voltage step. The
incoming and outgoing currents are a combination of tunnelling and thermionic currents. Good agreement between the
calculated and experimental characteristics was obtained.
ROOM TEMPERATURE GIANT MAGNETORESISTANCE IN LA.67Ba.33Ti.02Mn.98O3 EPILAYERS
A. C. Galca1, Ma. Oumezzine2, Mo. Oumezzine2, I. Pasuk1, C. Chirila1, A. Leca1, A. Kuncser1, C. Ghica1, L. C. Tanase1,
C. M. Teodorescu1, and V. Kuncser1
1
National Institute of Materials Physics, Atomistilor 105 bis, 077125 Magurele, Ilfov, Romania,2Laboratoire de
Physico-chimie des Matériaux, Université de Monastir, 5019 Monastir, Tunisia,corresponding author:
[email protected]
Perovskite manganites, R1-xAx(Mn3+1-xMn4+x)O3 (R – trivalent rare earth, A - divalent alkaline) have attracted
considerable attention due to their magnetocaloric and/or magnetoelectric properties. With this respect, they are
potential candidates to be used in various applications such as: electronics, spintronics, magnetic refrigeration, field
sensors, magnetic information storage or faster reading devices. Downscaling perovskites is prerequisite for integrated
them in nowadays miniaturized devices. Another important aspect regards the best/good functionality at room
temperature.
In this work we present the magnetic and magnetoelectric properties of La .67Ba.33Ti.02Mn.98O3 thin films obtained by
pulsed laser deposition on SrTiO3 substrates. The thin films grew epitaxially as proven by X-ray diffraction and
transmission electron microscopy. The analysis of XPS spectra gives a stoichiometry close to the one of the ceramic
target.
From M(T), a Curie temperature very closed to room temperature was determined. The magnetic entropy change
and relative cooling power will be also presented. A giant magnetoresistance (150% at 300K under 5T) was measured
for the La0.67Ba0.33Ti0.02Mn0.98O3 epilayers.
The authors acknowledge the Romanian Ministry of Education (PN-II-ID-PCCE-2011-2-0006 Project and Core
program PN09-4501) and the Tunisian Ministry of Higher Education and Scientific Research for the financial support.
54
INVESTIGATIONS OF THE RADIATION INDUCED EFFECTS IN PULSED LASER DEPOSITED THIN
FILMS
D. Simeone1, G. Socol2, D. Craciun2, S. Behdad3, B. Boesl3, E. Lambers4, C. Himcinschi5, D. Pantelica6, P. Ionescu6, C.
Martin7, B. Vasile8, H. Makino9, and V. Craciun1
1
DMN/SRMA-LA2M, LRC CARMEN CEA Saclay, France, 2National Institute for Lasers, Plasma and Radiation
Physics, Măgurele, Romania, 3Mechanical and Materials Science Engineering, Florida International University, Miami,
USA, 4MAIC, University of Florida, Gainesville, USA, 5Institute of Theoretical Physics, TU Bergakademie Freiberg,
Freiberg, Germany, 6Horia Hulubei National Institute for Physics and Nuclear Engineering, Măgurele, Romania,
7
Ramapo College of New Jersey, NJ, USA, 8Polytechnic University Bucharest, Romania, 9Research Institute, Kochi
University of Technology, Kochi, Japan
Almost all studies investigating the effects of radiation on the structure and properties of various materials have
been performed on single crystals or sintered pellets having large grain sizes. More recently, there were some specific
applications that required the use of thin films to protect or encapsulate nuclear fuel. Such films are polycrystalline or
even nanocrystalline. The investigations of the effects of radiation on such thin films have shown there are many
differences with respect to the results obtained for single crystal samples. The much smaller grain sizes in such films
allows for short diffusion distances of the defects before encountering grain boundaries that could act as defect sinks.
The role of strain present in films also should be taken into account. The Pulsed Laser Deposition (PLD) technique is
very suitable for these investigations since it can grow some of the highest quality thin films of almost any materials
starting from inexpensive targets. First, it allows the growth of high crystalline quality films at relatively lower substrate
temperatures than other techniques. Secondly, by changing the deposition parameters, films possessing different
chemical compositions and/or structures could be easily obtained. Thirdly, the surface morphology of the deposited
films is very smooth, allowing for the use of characterization techniques such as X-ray reflectivity, grazing incidence Xray diffraction, X-ray photoelectron spectroscopy, or nanoindentation that possess depth resolutions of the order of few
nm. These advantages of PLD grown films are illustrated in this presentation with results obtained on ZrC, ZrN, and
SiC thin films grown on Si substrates that were ion-irradiated at room temperature by 800 keV Ar. The effect of
irradiation on the structure, chemical composition, mechanical, optical and electrical properties of the films were
studied.
MODELING THE SIZE EFFECTS ON THE NONLINEAR DIELECTRIC PROPERTIES IN
NANOSTRUCTURED FERROELECTRIC CERAMICS
Leontin Padurariu1, Lavinia Curecheriu1, Vincenzo Buscaglia2 and Liliana Mitoseriu1,
Dept. of Physics, Al. I. Cuza Univ., 11 Bv. Carol I, 700506 Iasi, Romania; 2 Inst. of Energetics & Interphases CNR, 6
Via De Marini, I-16149 Genoa, Italy;
1
The role of grain size on the tunability (electric field dependence of the dielectric constant) in nanostructured
BaTiO3 ceramics was studied by an experimental-modeling approach. When reducing grain size in ceramics down to
100 nm, the permittivity diminishes below 1000 and a tendency towards linearization of the permittivity vs. field
dependence and lack of saturation is observed. To explain the observed experimental features, the highly
inhomogeneous nature of the nanostructured ceramic was considered. The ceramic was described as a composite
formed by grains with ferroelectric core and low-permittivity linear dielectric grain boundary. The role and contribution
of the grain boundaries increases when reducing grain size at nanoscale. A complex model for describing the grain size
influence on the tunability response in dense nanostructured ceramics was developed on the basis of Landau-GinzburgDevonshire theory and Finite Element Method calculations. Virtual ceramic microstructures with progressive reduction
of grain size were generated and the local electric fields have been computed by finite element approach at various
external voltages. The effective permittivity-field responses eff(E) have been computed by taking into consideration the
specific local field distribution with Finite Element Method (FEM). A remarkable agreement between the experimental
tunability features and model calculations was obtained in describing the reduction of permittivity and tunability and
tendency of linearization of the eff(E) when reducing the ceramic grain size.
Acknowledgements: This work was supported by the CNCS-UEFISCDI Project No. PNII-RU-TE-2012-3-0150.
55
STRUCTURAL AND ELECTRICAL PROPERTIES OF SOME N-DOPED SIC THIN FILMS OBTAINED BY
TVA METHOD
Victor Ciupina, Cristian P. Lungu*, Rodica Vladoiu, Gabriel C. Prodan, Stefan Antohe**, Corneliu Porosnicu*, Iuliana
Stanescu, Ionut Jepu*, Sorina Iftimie**, Marius Belc, Aurelia Mandes, Virginia Dinca,
Eugeniu Vasile***, Valeriu Zarovski*, Virginia Nicolescu****
Ovidius University of Constanta, 124 Mamaia Avenue, Constanta, Constanta, Romania 900527, *National Institute for
Lasers, Plasma and Radiation Physics, P.O. Box MG-36, 077125 Bucharest, Romania, **University of Bucharest,
Faculty of Physics, Atomistilor 405, CP MG - 11, RO – 077125, Romania, ***University Politehnica of Bucharest,
Faculty of Applied Chemistry and Materials Science, No. 1–7 Gh. Polizu Street, Bucharest 011061, Romania,
****CERONAV Constanta, Pescarilor Street no. 69A, 900581 Constanta, Romania
Ionized nitrogen doped Si-C thin films at 200°C substrate temperature were obtained by Thermionic Vacuum Arc
(TVA) method. To increase the energy of N, C and Si ions, -400V, -600V and -1000V negative bias voltages was
applied on the substrate. The 200nm thickness carbon thin films was deposed on Si and glass substrate and then 400nm,
600nm and 1000nm N-SiC coatings on carbon thin films was deposed. To characterize the structure of as-prepared NSiC coatings, TEM, HRTEM and XPS techniques was performed. The crystallinity of N-SiC thin films increase with
increasing of acceleration potential drop, i. e. with energy of N, C and Si ions. It was measured the electrical
conductivity comparing the potential drops on the structure and on a standard resistance, in a constant current mode. To
justify the dependence of measured electrical conductivity by the temperature, we assume a thermally activated
electrical transport mechanism.
56
STRUCTURAL CHARACTERIZATION AND BACTERIAL INHIBITING EFFECT OF ZINC DOPED
HYDROXYAPATITE LAYER
C.L. Popa1,2, C.S. Ciobanu1, M.L. Badea3, P. Chapon4, R.V. Ghita1, S. Antohe2, D. Predoi1*
National Institute for Physics of Materials, P.O. Box MG 07, Magurele, Romania, 2University of Bucharest, Faculty of
Physics, 405 Atomistilor Street, P.O. Box MG1, 077125, Magurele, Romania, 3University of Agronomic Sciences and
Veterinary Medicine, 59 Mărăşti Blvd., 011464, Bucharest, Romania, 4 Horiba Jobin Yvon S.A, 16-18, rue du Canal,
91165 Longjumeau Cedex France; Corresponding author: *[email protected]; Presenting author:
[email protected].
1
The present study is focused on the structural characterization and antimicrobial evaluation of zinc doped
hydroxyapatite (Zn:HAp) thin films. The Zn:HAp thin films were obatined by vacuum deposition technique on a
comercial silicon substrate (111). The crystalline phase of the prepared thin films treated at a temperature of 800oC was
assigned to the hexagonal hydroxyapatite in P63/m space group. The nature of the crystal phase was determined by Xray diffraction (XRD). Scanning Electron Microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy were
also used to investigate the structural and morphological properties of zinc doped hydroxyapatite thin films (Zn:HAp).
The elements Ca, P, O and Zn were found in the Zn:HAp layer. After the heat treatment the Zn:HAp layer presented a
structure resembeling the stoichiometric hydroxyapatite. Moreover, some of the preliminary results on research studies
aimed at combating methicillin-resistant Staphylococcus aureus (MRSA) are presented. The zinc doped hydroxyapatite
coating showed an antimicrobial effect against methicillin-resistant S. aureus within 24 h for all the culture conditions.
Acknowledgements: This work was supported by projects IFA-CEA C4-05/2014. Also this work was supported by
the strategic grant POSDRU/159/1.5/S/137750, ”Project Doctoral and Postdoctoral programs support for increased
competitiveness in Exact Sciences research” cofinanced by the European Social Found within the Sectorial Operational
Program Human Resources Development 2007 – 2013.
57
FREQUENCY RESPONSE OF INTERFACE STATES AND SERIES RESISTANCE IN MOS AND MS
STRUCTURES
N. Doukhane, B. Birouk
Department of electronics, Technology and sciences Faculty, Laboratory of Renewable Energies, University of Jijel,
Algeria; Email: [email protected], [email protected]
The capacitance-voltage (C-V) and conductance-voltage (G/ω-V) characteristics of MOS and MS structures have
been measured in the voltage range from -30 to +30 V and frequency range from 10 KHz to 1MHz. It is found that both
C and G/ω of the MOS and MS capacitors are very sensitive to frequency. The fairly large frequency dispersion C-V
characteristic can be interpreted in terms of particular distribution of interface states at Si/SiO2 interface and the effect
of series resistance. At relatively low frequencies, the interface states can follow an alternating current (AC) signal that
contributes to excess capacitance.
ILLUMINATION EFFECTS ON THE CAPACITANCE-VOLTAGE CHARACTERISTIC OF MOS AND MS
STRUCTURES
N. Doukhane, B. Birouk
Renewable Energies Laboratory, University of Jijel, Department of Electronics, Technology and Sciences Faculty,
Email: [email protected], [email protected]
The objective of this work is the study of MOS and MS capacities carried out starting from thermally oxidized
monosilicon substrates on which was deposited a heavily boron doped polysilicon film, by low pressure chemical
vapour deposition (LPCVD), and serving as grid dielectric, or directly deposited in another case on not oxidized
substrate to obtain PolySi-MonoSi structure. These structures are studied under various illumination conditions, the C-V
characteristic curves of these structures allow us to deduce some practical importance parameters. The results show that
the light influences in the same way that the temperature. It raised from the analysis an improvement in the electric
characteristics capacitance-voltage, of MOS structures with doped polysilicon grid.
EVALUATION OF THE ANTIMICROBIAL ACTIVITY OF DIFFERENT ANTIBIOTICS ENHANCED
WITH SILVER DOPED HYDROXYAPATITE THIN SOLID FILMS
C.L. Popa1,3, C.S. Ciobanu1, P. Chapon2, S. Antohe3, S. L. Iconaru1, D. Predoi1*
National Institute for Physics of Materials, P.O. Box MG 07, Bucharest, Magurele, Romania, 2Horiba Jobin Yvon S.A,
16-18, rue du Canal, 91165 Longjumeau Cedex France, 3 University of Bucharest, Faculty of Physics, 405 Atomistilor
Street, P.O. Box MG1, 077125, Magurele, Romania; Corresponding author: *[email protected]; Presenting author:
[email protected].
1
The inhibitory and antimicrobial effects of silver particles is known from ancient times. In the last years a major
health problem has arisen due to pathogenic bacteria resistance to antimicrobial agents. The effect of the combination of
silver doped hydroxyapatite (Ag:HAp) and the antibacterial activity of antibiotics has not been studied so far. In this
study we reported, for the first time, the preparation and characterization of silver doped hydroxyapatite thin films. The
structural and chemical characterisation of silver doped hydroxyapatite thin films has been evaluated. In order to study
the chemical composition of the coatings, GDOES measurements have been performed, obtaining information on the
distribution of the elements throughout the film. These studies have confirmed the purity of the prepared silver
hydroxyapatite thin films obtained from composite targets containing Ca10-xAgx(PO4)6(OH)2 with xAg=0 and xAg=0.5.
On the other hand, the major aim of this study was the evaluation of the antibacterial activities of ciprofloxacin and
tetracycline in the presence of Ag:HAp thin layer against Staphylococcus aureus and Escherichia coli strains. The
antibacterial activities of ciprofloxacin and tetracycline against Staphylococcus aureus and Escherichia coli test strains
increased in the presence of Ag:HAp thin layer.
Acknowledgements:This work was supported by projects Parteneriate PN-II 259/2014. Also this work was
supported by the strategic grant POSDRU/159/1.5/S/137750, ”Project Doctoral and Postdoctoral programs support for
increased competitiveness in Exact Sciences research” cofinanced by the European Social Found within the Sectorial
Operational Program Human Resources Development 2007 – 2013.
58
THE INFLUENCE OF Ru BUFFER LAYER ON MAGNETORESISTIVE PROPERTIES IN BOTTOM
PINNED SPIN-VALVES
Andrei Jitariu1,2, Hari S. Goripati1, Nicoleta Lupu1 and Horia Chiriac1
National Institute of Research and Development for Technical Physics, Iasi, Romania, 2 Alexandru Ioan Cuza
University, Iasi, Romania; [email protected]
1
Nowadays, spin-valve magnetoresistive sensors are widely used in magnetic field sensing applications due to their
relative small size, low cost and high sensitivity. For low field sensing applications the most important characteristics of
a magnetoresistive sensor are the soft magnetic properties of the free layer and the magnetoresistive ratio (MR). In this
work, the influence of the Ru buffer layer on the MR ratio and the coercive field of the free layer was studied. The spinvalves with the multilayer structure of Ta (5nm)/Ru (x nm)/CoFe (3 nm)/IrMn (20 nm)/CoFe (3 nm)/Cu (3 nm)/CoFe (3
nm)/NiFe (5 nm)/Ta (5 nm) were deposited by magnetron sputtering on glass substrates. The thickness of the Ta buffer
layer was kept constant at 5 nm and the Ru layer thickness was varied as it follows: 0, 5 and 10 nm. It was observed that
the sample without a Ru buffer shows a MR ratio of 3.85% and coercive field of 23 Oe. For the sample with a 5 nm Ru
buffer layer, the MR ratio and the coercive field decrease to 2.74% and 9 Oe respectively. With further increase of Ru
thickness to 10 nm, the MR ratio is decreasing even more, to 2.25% while the coercive field remain constant (9 Oe).
The decrease of the MR ratio is most likely due to the current shunting effect in the Ru layer and the decrease of
coercive field can be explained by the change in the crystalline orientation and microstructure of the free layer. It was
shown that by using a Ru buffer the MR ratio decreases, but it lowers the coercive field of the free layer, which is more
advantageous for sensors application. Given that the coercive field of the free layer it is not depending on the thickness
of the Ru layer, its thickness can be lowered even more, to minimize the losses in MR while still maintaining the low
coercive field. The details of the minimum thickness of the Ru layer will be discussed.
ACKNOWLEDGMENT: Financial support by the European Commission (FP7-REGPOT-2012-2013-1, Grant
Agreement no. 316194, NANOSENS) and by the strategic grant POSDRU/159/1.5/S/133652, co-financed by the
European Social Fund within the Sectorial Operational Program Human Resources Development 2007 – 2013 is
gratefully acknowledged.
NEW CATALYSTS FOR CONVERSION OF LIGNIN TO ADD-VALUE PRODUCTS
Cristina M. Opris, Madalina Tudorache, Vasile I. Parvulescu
University of Bucharest, Departament of Organic Chemistry and Catalysis, Bdul Regina Elisabeta 4-12, 030016,
Bucharest, Romania, [email protected]
In the last years, use of renewable class of materials has become a topic of interest in research due to problems
associated with the decrease of minerals reserves [1]. The aim of this study is to synthesize new catalysts based on niobia
and cobalt nanoparticles for the application in lignin depolymerisation.
Bifunctional heterogeneous catalysts were prepared by successive
covery of magnetite by niobia and cobalt-nanoparticles. The synthesis
of these catalysts followed the co-precipitation, microemulsion and
precipitation-deposition methods. Exhaustive characterization of
catalysts was realised by thermal analysis, powder X-ray diffraction,
Fig.1.X-ray
Fig.2.Raman
Raman spectroscopy, XPS, FTIR and DRIFT spectroscopy, BET
diffraction
spectra
analysis before and after catalytic tests (Fig.1 and Fig.2.).
The catalytic results confirmed that each catalyst component play a separate role in this complex reaction. The
acidity is associated to the presence of Bronsted and Lewis acid, which make them suitable for the conversion of lignin
into value-add chemicals.
[1] G. Centi, P. Lanzafame, S. Perathoner, Catalysis Today, 2011, 167, 14-30;
This work was supported by the strategic grant POSDRU/159/1.5/S/137750.
59
PREPARATION OF Fe-Nb-Cr-B GLASSY POWDERS BY HIGH ENERGY PLANETARY BALL MILLING
M. Lostun, H. Chiriac, and N. Lupu
National Institute of Research and Development for Technical Physics, Iasi, Romani a
Amorphous and nanostructured magnetic materials have received enormous attention of researcher in the last years
due to their novel magnetic properties and potential application in high performance electronic devices, health care and
magnetic recording technology [1-3]. In this context, it is extremely important to understand how their reduced
dimensionality is influencing the structural and magnetic behavior in order to make them useful for applications.
In this paper we report our recent results on the Fe79.7-xNb0.3CrxB20 (x = 11.5–13 at. %) submicron powders produced
by high energy planetary ball milling (Retsch PM 200) from glassy melt-spun ribbons precursors. High-energy ball
milling, which for a long time has been used to produce nanocrystalline and amorphous materials, is employed for the
synthesis of submicron particles with high aspect ratios. The synthesis conditions have been investigated for both the
dry and wet milling conditions. The effect of post-milling heat treatment on the magnetic properties of the powders is
also presented. The structural properties have been investigated after each step of the milling process enabling to
determine the effect of different milling conditions on the production of submicron powders. The magnetic properties of
the powders: magnetization, coercive field, Curie temperature, have also been determined. Following the structural and
magnetic characterization we have developed a protocol for wet/dry mechanical milling of Fe79.7-xNb0.3CrxB20 (x=11.5–
13 at. %) glassy melt-spun ribbons which allows us to tailor the magnetic properties of the obtained submicron
magnetic powders up to 400nm, and mainly the Curie temperature around 40-420C.
This work was supported by a CNDI–UEFISCDI grant, Project #148/2012 (HYPERTHERMIA).
[1]. N. Lupu et al., IEEE Trans. Magn. 47, 3791 (2011).
[2]. V. V. Hoang, D. Ganguli, Physics Reports 518, 81 (2012)
[3]. H. S. Huang and J. F. Hainfeld, Int. J. Nanomed. 8, 2521 (2013).
NOVEL HYBRID ZINC OXIDE NANOPARTICLES WITH TUNED OPTICAL PROPERTIES THROUGH
ORGANOSILANE SURFACE MODIFICATION
Aurel Tăbăcaru,1 Viorica Mușat,1 and Nicolae Țigău2
1
Faculty of Engineering, ”Dunărea de Jos” University of Galati, Romania, 2 Faculty of Sciences and Environment,
”Dunărea de Jos” University of Galati, Romania; Email: [email protected]
As part of our previous successful strategy to obtain new photoluminescent hybrid semiconductive nanoparticles
modified with organosilane species, we here report on a novel series of hybrid ZnO NPs grafted with variable amounts
of vinyltrimethoxysilane (VTMS). The choice of this type of organosilane is fundamented by the possibility of tuning
the optical properties of the resulting nanoparticles, taking into account also the nature of the end-group bound to
silicon. When applied as thin films these new nanomaterials, with sizes of 3 to 10 nm, showed excellent optical
transmittance between 85 and 90%, while a significant blue-shift of the photoemission bands was observed on passing
from 578 nm for unmodified ZnO to 546 nm for ZnO modified with the highest organosilane loading. This shift is
associated to the size reduction of ZnO nnaoparticles upon increasing amount of organosilane. An opposite trend of
band gap energies in function of the nanoparticles size, from 3.494 eV for unmodified ZnO to 3.377 eV for ZnO
modified with the highest organosilane concentration, was for the second time detected and discussed. Due to the most
intense emission displayed by the 10% VTMS-modified ZnO NPs, its further implementation as active layer into hybrid
light emitting device (HLED) for optoelectronic applications will be considered.
Acknowledgements. The work of Aurel Tabacaru has been funded by the Sectorial Operational Programme Human
Resources Development 2007-2013 of the Ministry of European Funds through the Financial Agreement
POSDRU/159/1.5/S/132397.
60
SUMMARY OF PHYSICAL PROPERTIES OF A-BiySe1-y THIN FILMS WITH REGARD TO DISORDER
AND QUANTUM SIZE EFFECT
1
1*,2
H.A.ELMeleegi *, and Z.S.ELMandouh2
Electron Microscope Lab., Physics Division, National Research Centre "NRC", ELTahrir St., Dokki, Cairo,Egypt.
P.O.Box: 12622, NRC Affiliation ID: 60014618; 1* email: [email protected]
Quantum size effect of a-BiySe1-y Thin Films was taken into account for the first time upon studying optical,
thermal, and, electrical properties. Also with regard to the role of disorder that characterizing fresh amorphous thin film
samples of a-BiySe1-y Thin Films. EDS,XRD, TEM,SEM, were evidences of the homogeneity and the existence of the
nanostructure among disordered state at the beginning temperature of physical measurements; turning into
polycrystalline at the last range of temperature at which measurements had taken place. Electrical capacitance along
with some other electrical alternative and direct current parameters were investigated. Thermoelectric and photoelectric
energy conversion efficiencies was estimated in order to study the possibility of these thin films for practical
applications. Optoelectronic energy conversion and its' efficiency was calculated. Time of Flight test has been
examined. Carrier-Type Reversal ;the magnificent applicable phenomenon was revealed in this chalcogenide material.
Key Words: Chalcogenides, Review, Quantum size effect, Disorder Role, Thermoelectric, Ferroelectric, and
Photoelectric energy conversion efficiencies, Time Of Flight, Artificial Properties, and Carrier-Type Reversal
Phenomenon.
SYNTHESIS OF ZnO-C NANOPARTICLES BY LASER PYROLYSIS FROM A SOLUTION OF A SOLID
PRECURSOR USING AEROSOL DELIVERY APPARATUS
Alina Ilie1,2 , Lavinia Gavrila1, Claudiu Fleaca1, Ion Morjan1, Anca Badoi1, Catalin Luculescu1, Eugen Vasile3, Ana
Niculescu1
1
National Institute for Lasers, Plasma and Radiation Physics, Magurele, Romania, 2 University of Bucharest, Faculty of
Physics, Bucharest, Romania, 3University Politehnica of Bucharest, Fac Appl Chem & Mat Sci, Dept Sci & Engn Oxid
Mat & Nanomat, Bucharest 011061, Romania ; [email protected]
In this work, we obtained ZnO-C nanoparticles using laser pyrolysis method, starting from ZnSO4 as Zn precursor
which is delivered as an aerosol, from water or isopropyl alcohol, and ethylene or SF6, as a sensitizer. We used N2O or
air ss oxygen source, and Ar for confinement. Our aim is to study the effect of synthesis parameters regarding the
morphology and structure of the ZnO-C nanoparticles, using Raman spectroscopy, X-ray diffraction (XRD),
transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive spectroscopy
(EDS). The results of these studies will be useful in optimizing the synthesis of ZnO-C nanoparticles, in order to obtain
specific characteristics, and also, for choosing the appropriate parameters for the type of the desired outcome.
CHARACTERIZATION OF Mg-Al, Ni-Al AND Ni,Mg-Al LAYERED DOUBLE HYDROXIDES THIN FILMS
DEPOSITED BY PLD
A. Vlad1*, R. Birjega1, A. Matei1, V. Ion1, M. Dumitru1, F. Stokker1, M. Dinescu1, R. Zavoianu2, O.D. Pavel2
National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Str., 77125 Bucharest- Magurele,
Romania; * [email protected] , tel. +4 021 457 44 14, fax +4 021 457 44 14; 2University of Bucharest, Faculty of
Chemistry, Department of Chemical Technology and Catalysis, 4-12 Regina
1
Hydrotalcite like compounds (HTLCs) are layered double hydroxides (LDHs) consisting of positively charged
brucite-like layers and exchangeable interlayer anions, which have received increasing attention in the last years, due to
their versatility and to their prospects in a wide range of technological applications such as catalysis, separation, sensor
and supercapacitors. LDHs containing a transition metal which undergoes a reversible redox reaction in the useful
potential range have been proposed as electrode coating materials due to their properties of charge transport and redox
catalysts in basic solutions.
The properties of Ni-Al, Ni,Mg-Al and, as reference, non-electronically conductive Mg-Al double hydroxides thin
films were investigated by X-Ray Diffraction, Atomic Force Microscopy, Scanning Electron Microscopy, Fourier
Transform Infra-Red Spectroscopy, Secondary Ions Mass Spectrometry, Impedance Analyzer and ellipsometry.The thin
films were deposited on different substrates (Pt/Si, Si, ITO, glass) by using a Nd:YAG laser (1064 nm) working at a
repetition rate of 10 Hz.
All analysis indicated that the effect of the Ni amount on the structural, morphological, optical and electrical
properties of the Ni based LDHs thin films are visible.
61
ATMOSPHERIC PRESSURE PLASMA SYNTHESIS AND CHARACTERIZATION OF ALUMINIUM
PARTICLES
V. Mărăscu1, 2, A. Lazea-Stoyanova1, V. Barna2, I. Chitescu3, G. Dinescu1, 2
National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor Street, Magurele, Romania, 2Faculty of
Physics, University of Bucharest, 405 Atomistilor Street, Magurele, Romania, 3Faculty of Mathematics and Computer
Science, University of Bucharest, 14 Academiei Street, Bucharest, Romania; [email protected],
[email protected]
1
Formation and properties of metallic particles are important topics of study in view of safe operation of International
Thermonuclear Experimental Reactor (ITER). In this line our contribution presents experiments leading to synthesis of
dust particles by means of a plasma method [1]. Having in mind that beryllium has a high environmental and human
toxicity, we have chosen to study aluminium (Al) as its surrogate. Hence, nano and micro Al particles (dust) were
obtained by plasma by setting adequate working parameters so that plasma was seeded with Al atoms, as demonstrated
by Optical Emission Spectroscopy (OES) diagnostic. The experimental setup involves an atmospheric pressure plasma
jet source having an aluminium electrode and working at: 1000 - 2000 sccm argon, 50 - 100 W radiofrequency (RF)
power and 40 - 60 min plasma exposure time. Depending on the plasma power local melting of the aluminium material
is produced by plasma discharge, forming particles (dust) along the gas flow. These particles were collected on Si
substrates and were analysed via Scanning Electron Microscopy (SEM). It was found that the particles properties
depend highly on RF power, exposure time and gas flow. For instance, by varying the working parameters (such gas
flow or RF power) we obtained dust particles having wide size distributions, from 200 nm up to 10 microns, and
various particle density.
References
[1] A. Lazea-Stoyanova, A. Vlad, A. M. Vlaicu, V. S. Teodorescu, G. Dinescu, Synthesis of copper particles by nonthermal atmospheric pressure plasma jet, Plasma Processes and Polymers, DOI: 10.1002/ppap.201 400 197.
ELECTRICAL PROPERTIES OF CHEMICALLY SYNTHESIZED ZnO MICRO/NANOSTRUCTURES
a
C. Floricaa*, N. Predaa**, A. Costasa, b, A. Evanghelidisa, b, I. Zguraa, M. Socola, M. Enculescua, and I. Enculescua
University of Bucharest, Bucharest-Magurele, P.O. Box MG-11, 077125, Romania; *[email protected];
**
[email protected]
Recently, solution-based chemical approaches have attracted researchers’ attention presenting several advantages
such as: easily accessible raw materials, the use of inexpensive equipment, control over morphologies and properties of
the final products by changing the experimental parameters. In this context, the present study is focused on the
deposition of ZnO micro/nanostructures with different morphologies (prisms, rods, flowers and snowflakes) on Aupatterned SiO2/Si substrates obtained by photolithography, a technique yielding large patterned surfaces in a short time.
The ZnO structures were deposited during or after their chemical synthesis. The samples were investigated by scanning
electron microscopy, X-ray diffraction, optical spectroscopy and photoluminescence. Furthermore, the electrical
properties of the deposited ZnO micro/nanostructures were studied, no additional lithographical steps being necessary
for contacting them due to the formation of networks which cross over areas between the interdigitated metallic
electrodes. The structural and optical data of the deposited ZnO show a hexagonal wurtzite structure and optical
signatures (band-gap value and emission bands) typical for this semiconductor. The electrical measurements revealed
that the ZnO samples can present interesting properties useful for chemical sensing. Regardless of their morphology, the
ZnO structures exhibit a similar electrical response in air when they are exposed to ammonia, suggesting potential
sensors applications. In this way, low-cost and easily scalable methods, such as wet chemical synthesis and
photolithography, can be used in order to obtain devices based on such semiconductors nanostructures.
62
A COMPARATIVE STUDY OF CHARGE TRAPPINIG IN HfO2/Al2O3 and ZrO2/Al2O3 BASED
MULTILAYERED MHOS (METAL/HIGH-K/OXIDE/Si) STRUCTURES
D. Spassov1, A. Skeparovski2, A. Paskaleva1 and N. Novkovski2
Institute of Solid State Physics, Bulgarian Academy of Sciences, Tzarigradsko Chaussee 72, Sofia 1784, Bulgaria,
email: [email protected] ,2 Institute of Physics, Faculty of Natural Sciences and Mathematics, University “Ss. Cyril
and Methodius”, Arhimedova 3, 1000 Skopje, Macedonia
1
The electrical properties of multilayered HfO2/Al2O3/HfO2/SiO2 and ZrO2/Al2O3/ZrO2/SiO2 Metal Oxide
Semiconductor (MOS) capacitors were investigated in order to evaluate the possibility of their application in charge
trapping non-volatile memory devices. The HfO2(6 nm)/Al2O3(1 nm)/HfO2 (6 nm) and ZrO2(6
nm)/Al2O3(1nm)/ZrO2(6nm) stacks were deposited by reactive rf magnetron sputtering on Si substrates with thermal
SiO2 with a thickness of 2-5 nm. Al was used as gate and backside electrode. The electrical properties of the capacitors
were evaluated by capacitance-voltage (C-V) and by current-voltage (I-V) measurements. Special attention was paid to
the hysteresis behavior of C-V and I-V curves under various applied voltages, V. Well defined C-V curves with
negligible initial hysteresis were obtained for both types of structures. Both stacks show initial negative oxide charge,
but its density is higher in HfO2-based structures. The increase of the maximum applied voltage over a certain value
during the C-V measurements results in an enlargement of the hysteresis, suggesting injection and capture of charge
carriers into the high-k stacks. The value of the applied voltage needed for appearance of the hysteresis correlates with
the thickness of the thermal SiO2 layer - samples with thicker SiO2 layer exhibit hysteresis at higher V. The analysis of
the C-V shifts reveals that the hysteresis is mainly a result of substrate electron injection through SiO 2 at positive V
while at negative V a detrapping of the captured charge takes place. Larger hysteresis values (wider “memory window”)
is obtained for the HfO2-based stacks. The ZrO2-based samples show higher leakage currents and have lower
breakdown voltage values than HfO2-based ones. The leakier nature of the ZrO2 samples is suggested as the main
reason for their narrower “memory window”.
COMPARATIVE PROPERTIES OF ZNO THIN FILMS DEPOSITED ON MOLYBDENUM AND
PLATINUM ELECTRODES FOR PIEZO-ACOUSTIC DEVICES
O. Mortada1, J-C. Orlianges2, A. Crunteanu1, M. Chatras1, P. Blondy1
XLIM Research Institute UMR7252, CNRS/ University of Limoges, 123 Av. Albert Thomas, 87060 Limoges, France,
2
SPCTS UMR7315 CNRS/ University of Limoges, 12 rue Atlantis, 87068 Limoges, France, [email protected], [email protected]
1
Zinc oxide (ZnO) in the wurzite hexagonal structure exhibits both semiconducting and piezoelectric properties.
Therefore, piezo-acoustic devices, such as surface acoustic wave devices (SAW) [1] or bulk acoustic wave (BAW) [2]
devices have been widely fabricated using this high piezoelectric coupling coefficient oxide.
Here we present a novel piezo-acoustic device, in the form of suspended piezoelectric micro-resonators. The
structure of this type of resonator consists of metal interdigitated electrodes acoustically coupled within a ZnO film
suspended on monocrystalline (100) silicon membranes. The optimisation of such devices allows reaching an
electromechanical coupling coefficient kt2 of 2.2% and a high quality factor Q m of 1460 [3]. In order to better
understand and optimize the behaviour of the fabricated micro-resonators, we investigated two different resonator
configurations: ZnO thin films grown on dissimilar lower electrodes (Mo/SiO2/Si and on Pt/SiO2/Si) by pulsed laser
deposition (PLD) at relatively low temperatures (350°C). The structural properties of the ZnO layers are characterized
using X-ray diffraction (XRD). Out-of-plane Metal-Insulator-Metal (MIM) devices integrating ZnO in two different
designs (Pt/ZnO/(Ti/Au) and Mo/ZnO/(Ti/Au)) were realized and electrically characterized in order to compare the
dielectric properties of ZnO for both configurations.
[1] N. W. Emanetoglu, C. Gorla, Y. Liu, S. Liang and Y. Lu, Mater. Sci. Semicond. Process (1999) 2 p.247
[2] T. Yanagitani, M. Kiuchi, M. Matsukawa, Y. Watanabe IEEE Trans. Ultrason. Ferroelectr. (2007) 54 p.1680
[3] Mortada O., P. Blondy, A. Crunteanu, M. Chatras, J-C Orlianges IEEE International Conference on Electronics,
Circuits and Systems (ICECS) (2014)
63
TRANSPARENT CONDUCTIVE AZO/Ag/AZO THIN FILMS DEPOSITED BY SPUTTERING METHOD
S.H. Mousavi, M.H. Jilavi, P.W. de Oliveira
INM – Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany
Transparent conductive oxides (TCOs) are one of the applicable coatings that can be used in optoelectronic industry
and electronic devices. Recent years, different methods are applied to perform such transparent conductive layers.
Between the different methods, the researchers try to find low-cost and simple processed methods that can be scaled-up
in large amount with high conductivity and transparency properties. Aluminium doped zinc oxide (AZO) is one the
most applicable materials for the transparent conductive layers but approaching to low conductivities with the normal
route is hard. In order to enhance the electrical properties of these thin films, a multilayer thin film of AZO/Ag/AZO
was studied. The effect of silver as intermediate layer was investigated.
The electrical properties of the samples are analysed with 4-point probe where electrical conductivity in the ranges
of 0.5 to 50 kOhm/square for the samples were obtained. Structural and morphological characteristics were also
analysed with X-ray diffraction (XRD) and scanning electron microscopy (SEM). The SEM images show uniform thin
films with the grain sizes less than 50 nm and the XRD patterns confirms the formation of wurzite structure. The optical
properties were also investigated with UV-spectroscopy and ellipsometry to obtain an optimized condition for the
transparency and conductivity due to the thickness of the layers. The samples could be good candidates for application
as TCO material in photovoltaic and optical devices.
SOL–GEL SYNTHESIS, STRUCTURAL AND OPTICAL PROPERTIES OF BORON-DOPED TiO2 THIN
FILMS DEPOSITED ON ITO GLASS SUBSTRATES
a
Saidi Wassilaa, El Maaoui Mohameda, Mohammed S. Rasheedb, Mihaela Girtanb
Research Unit of inorganic chemistry applied, Department of Chemistry, Faculty of Sciences of Tunis, 2092 El Manar,
Tunis, Tunisia; b LPHIA – Photonics Laboratory, LUNAM - Angers University, 2 Bd. Lavoisier, 49045, Angers,
France; [email protected], [email protected], [email protected]
TiO2 exists in three crystalline phases: anatase, rutile and brookite. Of these forms, anatase TiO 2, a wide band-gap
(3.0–3.2 eV) semiconductor, is one of the most prominent oxide materials for performing various kinds of industrial
applications such as photovoltaic [1], photocatalytic [2] and photochromic. Among the applications of TiO 2,
photovoltaic application for dye sensitized solar cell (DSSC) is of great interest these days due to its fine physical,
chemical and optical properties [3]
In this investigation, the boron-doped and undoped high transparent TiO2 films on ITO glass substrates were
prepared by sol–gel spin coating method using titanium (IV) isopropoxide as a Ti source and boric acid (H 3BO3) as B
precursors.
The structural and optical characterizations of boron TiO2 thin films were carried out using X-ray diffraction (XRD)
and UV–vis transmittance spectroscopy.
The results indicated that the films of TiO2, doped with B2O3 in 700°C promote the adhesion layers to the substrate.
In our studies, we observed that the crystallinity of TiO 2 films increases when the molar ratios of TiO2/H3BO3 increases
and the structure changes when this proportion increases.
The transmission of film as an optical parameter was characterized by spectrophotometer. According to
transmission spectrum of film the refractive index and ban gap has been determined. Experimental result has shown that
the prepared film has high transmission and good optical parameters.
References
[1] Noshin Mir, Masoud Salavati-Niasari, Photovoltaic properties of corresponding dye sensitized solar cells: Effect
of active sites of growth controller non TiO2 nanostructures, Solar Energy 86 (2012) 3397–3404
[2] D. Robert, B. Dongui, J.V. Weber, Heterogeneous photocatalytic degradation of 3-nitroacetophenone in TiO2
aqueous suspension, J. Photochem. Photobiol, 156 (2003) 195.
[3] L. Ge, M. Xu, H. Fang, Thin Solid Films 515 (2007) 3414].
64
SILICON SUBSTRAT INFLUENCE ON PYROELECTRIC BEHAVIOR OF Pb(Zr,Ti)O 3 THIN FILMS
1
M. Botea1,2, L.Pintilie1, I.Pintilie1, V. Stancu1
National Institute of Materials Physics, Atomistilor 105bis, Magurele, Ilfov, 77125, Romania, 2 University of
Bucharest, Faculty of Physics, Magurele 077125, Romania ; Contact author: [email protected]
Pyroelectric detectors are still of great interest for applications such as intruder alarms, non-contact temperature
measurements, thermal imaging, IR spectroscopies. In this study is shown the influence of the substrate on the
pyroelectric properties of the Pb(Zr0.2,Ti0.8)O3 (PZT) thin films deposited by sol-gel on platinized silicon (Pt/Si). The
thin films structural properties were investigated by X-ray diffraction (XRD), morphological properties were analised
by SEM and AFM, while the ferroelectric properties were tested by capacitance-voltage (C-V) and hysteresis
measurements at room temperature. The pyroelectric measurements on the PZT thin films were performed with
modulated light from an 800 nm laser diode coupled with a mechanical chopper having variable frequency. The
pyroelectric signal was collected in the voltage mode, with a field effect transistor, and recorded with a lock-in
amplifier. The magnitude of the pyroelectric signal generated by the PZT films depends on the substrate. In this case it
was found that the Si substrate amplifies the pyroelectric signal generated by the PZT layer through photogenerated
carriers. This effect is only present at wavelengths below 1100nm, when the incident light is absorbed in the substrate.
The explanation is that the electric field inside the ferroelectric layer is modulated by the photogenerated carriers. This
finding can be useful for developing new pyroelectric IR detectors with optical amplification.
THERMAL STABILITY OF HIGHLY TEXTURED IRIDIUM THIN FILMS GROWN ON SILICON
SUBSTRATES
L.Trupina1, L. Nedelcu1, M. G. Banciu1, C. C. Negrila1, C. Champeaux2, F. Dumas-Bouchiat2, P. Marchet2, L.
Huitema3, V. Madrangeas3, A. Cruntenau3, D. Passerieux3, D. Cros3, T. Monediere3,
1
National Institute of Materials Physics, Bucharest, Romania, 2SPCTS UMR 7315 CNRS/University of Limoges,
Limoges, France, 3Xlim Laboratory UMR 7252 CNRS/University of Limoges, 87060, Limoges, France
Integration of ferroelectric materials on platinum-coated silicon is problematic due to the difficulty in controlling
phenomena occurring at the interfaces. Therefore, the type of bottom electrode on which the ferroelectric material is
deposited is very important in determining the final properties of the ferroelectric thin film. The growth of iridium thin
films on titanium buffered silicon substrates by DC magnetron sputtering and their stability at high temperature in an
oxidizing environment were investigated. Highly textured (111)Ir thin films of various thicknesses (30 nm∼100 nm)
were grown on titanium buffered Si wafers at 400 oC and 700 oC substrate temperature. These thin films showed a
different behaviour during heat treatment at 700 oC in oxygen atmosphere. The AFM image of the 30nm thick Ir film,
after the thermal treatment, revealed significant changes in the surface morphology. While the initial Ir film surface is
smooth and without surface features having a root-mean-square (rms) roughness of 0.7 nm, after thermal annealing, the
Ir film shows an increased surface roughness by formation of agglomerations up to 30 nm in height. According to the
XPS results, it can be concluded that these changes are due to the diffusion and oxidation of titanium. The 100 nm thick
iridium layer, annealed in the same conditions shows, a good thermal stability with only a slight modification of the
surface morphology. The measured electrical resistivity, before and after thermal annealing, was 11.8 cm and 12.3
cm, respectively. The XPS-survey spectrum showed no sign of titanium on the Ir thin film surface. The obtained
results allowed us to affirm that the Ir(100 nm)/Ti(9 nm)/SiO2/Si structure is electrically and morphologically stable and
can be successfully used as bottom electrode in ferroelectric thin films devices.
EFFECT OF THICKNESS ON THE OPTICAL AND DISPERSION PARAMETERS OF Cd 0.4Se0.6 THIN
FILMS
Sami salman chiad*, Nadir Fadhil Habubi*, Widad Hano Abass** , Muhammad hameed Abdul-Allah***
*Al_Mustansiriyah University, College of Education, Physics Department, Iraq; **AL- Mustansyriah University,
College of Basic Education , Science Department, Iraq; *** University of Diyala, College of Science, Physics
Department, Iraq; Email: [email protected]
Cd0.4Se0.6 thin films have been prepared by chemical bath deposition technique. The optical constants such as
absorbance , reflectance, extinction coefficient ,refractive index , real and imaginary parts of dielectric constant were
studied as a function of thickness variation .It was found that all these constants were affected by thickness by
increasing upon thickness except the refractive index.Dispersion relation was applied in order to show the effect of
thickness on these parameters which were discussed in details through this work.
65
POLYURETHANE MATRIX NANOCOMPOSITES USED TO OBTAIN ANTI-SLIP, ANTI-WEAR AND
FIRE-RESISTANT FLOORS FOR PUBLIC INSTITUTIONS, CIVIL AND INDUSTRIAL BUILDINGS
Marin Laurentiu*1, Pavel Topala1, Marin Catalina Daniela2**, Sandu Teodor2***
Faculty of Real Sciences, Department of Physical and Engineering Sciences, AlecuRussoBalti State University,
Puskin38, Balti, Moldova , 2National Institute for Research and Development in Chemistry and Petrochemistry,
Polymer Department, Spl. Independentei 202, Bucharest,Romania , * [email protected],
**
[email protected], *** [email protected]
1
Research and development activities presented were aimed at obtaining a nanocomposite polyurethane matrix with
special anti-wear, anti-slip and fire-resistant properties. Research and development works were materialized by
obtaining polyurethane nanocomposite matrix, by its physico-chemical modification in order to give the desired
technological properties and by characterization of the obtained material. Polyurethane nanocomposite matrix was
obtained by reacting a PETOL 3 type polyetherpolyol (having a molecular weight of 5000 UAM) with a diisocyanate
under well-established reaction conditions. Target specific technological properties were obtained by physical and
chemical modification of polyurethane nanocomposite matrix. The final result was getting a pellicle material based on
modified nanocomposite polyurethane, with anti-wear, anti-slip and fire-resistant properties, compatible with most
substrates encountered in civil and industrial construction: wood, concrete, metal.
Key words: polyurethane, nano-composite, anti-wear, anti-slip, fire resistant
THE INFLUENCE OF THE THERMAL TREATMENT ON THE PROPERTIES OF SANDWICH-TYPE OF
BISMUTH AND ANTIMONY TRIOXIDES THIN FILMS
Simona Condurache-Botaa,*, Catalin Constantinescub, Raluca Gavrilac, Nicolae Tigaua, ** and Mirela Praislera
Dunarea de Jos University of Galati, 111 Domneasca Street, 800201 Galati, Romania, b National Institute for Laser,
Plasma and Radiation Physics, 409 Atomistilor Blvd., 077125 Magurele, Romania, c National Institute for Research and
Development in Microtechnologies, 126 A Erou Iancu Nicolae Street, 077190 Bucharest, Romania; *corresponding
author: [email protected]; ** presenting author: [email protected]
a
Heterostructures made either by material mixing or by layers overlapping exhibit new and possibly more useful
properties than those of their components. When thermally-treating these hetero-films, in order to stabilize them, one
has to study the changing of their properties, whether this treatment is advisable or not. Such a study has to be
performed especially in the case of overlapping heterostructures, i.e. when preparing sandwich films, since mixing can
occur at the interface and crystalline net mismatch between the neighboring layers may accentuate after annealing. This
article presents the analysis of the annealing-induced changes in the properties of sandwich-type of thin films made of
bismuth trioxide deposited onto antimony trioxide and having glass as bottom layer. The crystallinity of the composing
layers changes rather significantly after the thermal treatment and the roughness expressed as root mean square
decreases. These morpho-structural changes lead to the improvement of the optical transmittance, while the energy
bandgap of the hetero-films either decreases or increases after annealing, depending on the temperature of the glass
substrate during the initial depositions. Such semiconducting heterostructures benefit from the properties of the
composing layers and their thermal treatment smoothens their surfaces and improves their transmittance.
Keywords: thin films,Bi2O3, Sb2O3,heterostructure,thermal treatment.
Acknowledgements: The work of Simona Bota (Condurache-Bota) has been funded by the Sectoral Operational
Programme Human Resources Development 2007-2013 of the Ministry of European Funds through the Financial Agreement
POSDRU/159/1.5/S/132397.
66
INFLUENCE OF DOPING NANOPARTICLES ON THE OPTICAL PROPERTIES OF ELECTROSPUN
POLYMER NANOFIBERS
A. Evanghelidisa,b*, M. Enculescua**, A. Galcaa and I. Enculescua
University of Bucharest, Bucharest-Magurele, P.O. Box MG-11, 077125, Romania, *[email protected];
**
[email protected]
a
Due to the possibility of combining the advantages of using polymers (low cost, flexibility and abundance) with the
phenomena induced by doping materials (magnetic, optic or electric), the fabrication of devices based on polymers that
incorporate various organic or inorganic compounds draws more and more attention. The electrospinning process is a
very efficient method of producing polymer nanofibers with special morphological properties. Our main objective was
to produce dye-doped polymer nanofibers incorporating uniformly dispersed metallic (Ag), semiconductor (TiO2) or
insulating (SiO2) nanoparticles by electrospinning. The features of the electrospinning process allow us to vary the
geometrical parameters of the polymer nanofibers by process parameters such as applied voltage, distance from the
anode to cathode, viscosity of the polymer solution etc. That influences the optical properties of the material. Moreover,
by varying the concentration of the dopants and the size of the doping particles we can achieve a variation of the
refractive index. By controlling the setting of the nanoparticles into the polymer nanofibers we will be able to tune the
optical properties of the doped polymer nanofibers. The morphological properties were evaluated using scanning
electron microscopy and the optical properties were determined by transmission, reflectance and elipsommetry
measurements.
ON THE ELECTRICAL AND OPTICAL PROPERTIES OF AMORPHOUS OXIDE SEMICONDUCTORS
R. Radu1, A. C. Galca1, L. M. Trinca1,2, C. Besleaga1, I. Pintilie1, G Socol3, and V. Craciun3
National Institute of Materials Physics, Atomistilor 105 bis, Magurele, Ilfov, Romania, 2Faculty of Physics, University
of Bucharest, Atomistilor 405, Magurele, Ilfov, Romania, 3National Institute for Lasers, Plasma and Radiation Physics,
Atomistilor 409, Magurele, Ilfov, Romania; corresponding author: [email protected]
1
Currently there is a strong interest in high performance amorphous oxide semiconductors (AOS) in flatpanel,
flexible and touch-screen displays, photovoltaic modules and solid-state lighting. Flexible and transparent electronics
are among the most intriguing applications for AOS. Due to a very good uniformity of the electrical properties and
higher mobility (10~50 cm2/Vs) than amorphous Si thin film transistors (a-Si TFTs) they are used in displays as
switching components in the active-matrix over a large area.
X-ray reflectivity investigations are used to determine the thin films density while X-ray scattering to assess the
structure. High accuracy measurements of the optical constants by spectroscopic ellipsometry are performed to observe
changes of the refractive index and optical band gap values as function of cations stoichiometry.
These AOS thin films are ‘incorporated’ into devices (TFTs, Schottky diodes, MOS capacitors) and their electrical
characteristics are investigated via C-V, I-V experiments performed at different temperatures and frequencies. Specific
microscopic investigations (e.g. Deep-Level Transient Spectroscopy, Thermally Stimulated Current Spectroscopy,
Thermally Dielectric Relaxation Current) are employed to determine the defects type, density and electrical properties
and to identify those having a direct impact on the electrical characteristics of the device.
The authors acknowledge funding from Romanian Space Agency through the STAR project no 65/29.11.2013.
L.M. Trinca acknowledges to the strategic grant POSDRU/159/1.5/S/137750.
67
INFLUENCE OF ANNEALING ON THE STRUCTURAL AND OPTICAL PROPERTIES OF Sb2O3 THIN
FILMS
Nicolae Tigau, Simona Condurache-Bota
Dunarea de Jos University of Galati, 111 Domneasca Street, 800201 Galati, Romania, corresponding author:
[email protected]
Sb2O3 thin films have been deposited onto glass substrates held at 300 K using the thermal evaporation technique
under vacuum. The films were annealed at 523 K in vacuum after evaporation. The structural and morphological
properties of thin films were studied by X-ray diffraction (XDR) and atomic force microscopy (AFM), respectively.
The XRD patterns revealed that the films are polycrystalline have a cubic structure with a strong (222) orientation after
annealing treatment. The structural parameters such as lattice constant, grain size and surface roughness were
calculated. The AFM micrographs showed that the mean surface roughness increase slightly after annealing. Optical
properties were investigated for both the as-deposited and annealed film in the wavelength range of 200-1400 nm. The
optical constant such as refractive index, extinction coefficient, absorption coefficient and band gap energy were
determined from transmission spectra using the Swanepoel’s method.
Keywords: thin films, Sb2O3, annealing effect, structural and optical properties
Acknowledgements: The work of Nicolae Tigau has been funded by the Sectoral Operational Programme Human
Resources Development 2007-2013 of the Ministry of European Funds through the Financial Agreement
POSDRU/159/1.5/S/132397.
EFFECT OF STRUCTURAL PROPERTIES ON SUPERCONDUCTING PROPERTIES OF Nb THIN FILMS
1
Alina Elena Niculescu1, Ciprian Bucur1, Aurelian Catalin Galca2, Cristina Besleaga2, Iuliana Pasuk2
National Institute for Research and Development for Cryogenics and Isotopic Technologies - ICIT Rm. Valcea, Uzinei
Street no. 4, P.O. Box Raureni 7, 240050, Ramnicu Valcea, Romania; 2Laboratory of Multifunctional Materials and
Structures, National Institute of Materials Physics, Magurele, Ilfov, Romania; [email protected]
Niobium thin films with different thickness have been deposited on glass by DC Sputtering at different Ar pressure
(between 6 – 22mBar). The samples were characterized by X-ray diffraction, UV-VIS and electrical resistivity
measurements. From the X-ray diffraction it was observed that between the Bragg-Brentano geometry and Grazing
Incidence measurement there are no differences with respect to the Nb diffraction line intensity, which leads to the
isotropic case (nanocrystallites with all possible orientations concerning with respect to a direction - e.g. normal to the
surface). X-ray reflectivity shows that the full width at half maximum of the [110] lines decreases by increasing the Ar
pressure, which indicates that the mean crystallite size is inversely proportional to the used Ar pressure. From the
electrical resistivity measurement it was observed that the growth process of Nb thin films at different Ar pressure
influences the resistivity and superconducting transition temperature.
POLYMER FIBERS BY SPIN-COATING MACHINE
Iulia Salaoru, Alanod Alshareef and Shashi Paul
Emerging Technologies Research Centre, De Montfort University, The Gateway, Leicester LE1 9BH, United Kingdom.
The attention of making polymer fibers is increasing rapidly, in view of the fact that its usage in a various
applications, for example, polymer fibers in batteries, filtration, sensors and protective clothes. In addition
aforementioned applications, their high surface to volume ratio provide them act as a catalyst supports also in tissue
engineering and drug delivery. There are a number of methods by which one can make polymer fibers but the most
commonly employed methods, to create polymer nano fibers, is electro-spinning.
The aim of this work is making polymer fibers by the using of the spin-coating machine in order to avoid using any
voltage source. Different conditions for spinning process (spin speed, dynamic or static spinning) and different
polymers/concentrations have been used. The polymer fibers with diameter (0.4-2) μm and variable length have been
obtained. The investigation of the uniformity in diameter and the fibres length is investigated by Scanning Electron
Microscopy (SEM).
68
COMPARATIVE STUDY ON THE DEPOSITION OF DEGRADABLE POLYMERIC COATINGS BASED
ON LYSOZYME EMBEDDED INTO PCL/PLGA BLENDS
G. Popescu-Pelin1,2, E. Axente1, F. Sima1, C. Nita1, A. Visan1, I. Zgura3, O.L. Rasoaga3, C.S. Breazu3, A. Stanculescu3,
M. Chiritoiu4, L. Sima4, F. Antohe5, L. Ivan5, G. Socol1, I.N. Mihailescu1
1
National Institute for Lasers, Plasma and Radiation Physics, Magurele, Ilfov, Romania, 2 Faculty of Physics,
University of Bucharest, Magurele, Ilfov, Romania, 3 National Institute of Materials Physics, Magurele, Ilfov, Romania,
4
Institute of Biochemistry, Splaiul Independentei 296, Bucharest, Romania, 5 Institute of Cellular Biology and
Pathology, B.P.Hasdeu 8, Bucharest, Romania
Biodegradable polymers properties are preserved in vivo for a limited period of time and then slowly degrade into
materials that are metabolized and excreted from the body. Lysozyme (Lys) embedded into simple and mixtures of
poly(ε-caprolactone) (PCL) and poly(lactic acid-co-glycolic acid) (PLGA) in different ratios (1:3, 1:1, 3:1) have been
deposited by matrix assisted pulsed laser evaporation (MAPLE) and dip-coating (DC) on Ti, glass and silicon
substrates. We identify the optimum deposition conditions with respect to the structural, morphological, and wettability
properties of films. In the case of MAPLE technique, PCL/PLGA/Lys composite films were deposited at 0.5 J/cm2
laser fluence, while for dip-coating the withdrawal speed was set at 100 mm/min. SEM investigations exhibited a
dependence of surface morphology on the chemical composition, polymeric mixture ratio and deposition method.
Fourier transform infrared (FTIR) spectrometry evidenced that the chemical composition of coatings deposited by both
methods was conserved whereas the X-ray diffraction (XRD) studies revealed the presence of diffraction peaks of PCL
only., Wettability tests performed on the polymeric coatings showed a hydrophilic behavior that depends on the
polymeric mixture ratio and deposition method. In vitro tests performed with respect to osteoblasts and endothelial cells
showed appropriate viability and cell morphologies.
PROTECTIVE AND HARD CARBIDE AND NITRIDE TRANSITIONAL METAL FILMS GROWN BY
PULSED LASER DEPOSITION TECHNIQUE
1
M. Stoicanescu1, D. Cristea1, G. Socol2, D. Craciun2, V. Craciun2 and A. Crisan1
Materials Science Department, Transilvania University; 2National Institute for Lasers, Plasma and Radiation Physics,
Măgurele, Romania
Transitional metal carbides and nitrides have been extensively investigated as hard and protective coatings since
they possess both excellent ceramic properties (high hardness, high melting point, and thermochemical stability) and
metallic properties (good thermal and electrical conductivity, high optical reflectivity in the infrared region). Such
properties are very useful for applications where there is a combination of high temperatures, corrosive gases and high
level of radiation. The Pulsed Laser Deposition (PLD) is the best technique to grow thin carbide and nitride films to
investigate their properties. A simple and easy control of the deposition conditions (substrate temperature, nature and
pressure of the gaseous atmosphere, laser fluence, repetition rate and wavelength) would results in the deposition of
films having various metal to carbon or nitrogen atoms ratios, grain sizes, texture level and stress levels. We deposited
ZrC, ZrN, TiN and TiC thin films using the PLD technique under various conditions on Ti and stainless steel substrates
and investigated their properties. X-ray reflectivity technique was used to measure the films density, while the structure,
texture and microstress levels were obtained from analysis of diffraction patterns obtained in both grazing incidence and
symmetrical X-ray diffraction. Mechanical properties have been assessed by nanoindentation (resulting in hardness and
elastic modulus values) and by scratch testing, in order to obtain the critical loads concerning the adhesion to the
substrate. Hardness values up to 24GPa for ZrC, 29GPa for ZrN, and 32GPa for TiC films have been obtained. These
investigations helped us understanding the interdependence between structure, composition and properties of Zr and Ti
carbide and nitride thin films.
69
MOLECULAR SPINTRONICS AND NANOELECTRONICS USING 1D SPIN CROSSOVER MATERIALS
C. Lefter1,2, S. Tricard2, H. Peng2, L. Salmon2, G. Molnár2, J. Carrey3, P. Demont4, A. Bousseksou2 and A. Rotaru1
Faculty of Electrical Engineering and Computer Science & AMNOL, Stefan cel Mare University, 720229 Suceava,
Romania, 2LCC, CNRS UPR-8241 and UPS, INP, Toulouse, France, LPCNO, 3INSA, CNRS, Université de Toulouse,
Toulouse, France, 4 LPP-CIRIMAT, CNRS & Université de Toulouse (UPS, INP), Toulouse, France
1
In the last years, important achievements have been done in electronics with the contemporary evolution of the
novel disciplines of molecular spintronics and nanoelectronics. A fundamental link between these fields can be
established using spin molecular materials. Spin crossover compounds are molecular materials containing a central 3d 4
– 3d7 transition metal ion in a pseudo-octahedral configuration with organic ligands. These materials present molecular
bistability in their magnetic, optical, electrical and mechanical properties upon application of external stimuli such as
temperature, light, pressure or magnetic field [1]. The spin state dependency of electrical conductivity of molecular
SCO materials has been recently proved [2] and promising results on organizing particles between electrodes arrays or
charge transport investigation on single molecules [3] open new opportunities in the elaboration of SCO based
spintronic and nanoelectronic devices.
In this work we discuss the advantages over more conventional materials, and the potential applications in
information storage and processing of spin crossover materials.
Acknowledgements. This work was supported by the bilateral grant of the Romanian National Authority for
Scientific Research (CNCS–UEFISCDI) and Agence Nationale de la Recherche (ANR), Contract number: 9ROFR/01.02.2013.
References
[1] A. Bousseksou, et al., Chem. Soc. Rev., 40, 3313-3335 (2011).
[2] (a) A. Rotaru et al., Chem. Comm., 48, 4163 (2012); (b) A. Rotaru et al., Adv. Mater., 25, 1745 (2013); (c) C.
Lefter et al., Phys. Status Solidi – R, 8, 191-193 (2014); (d) C. Lefter et al., J. Phys. Chem. C, 119 , 8522 (2015); (e) C.
Lefter et al. Phys. Chem. Chem. Phys., 17, 5151 (2015).
[3] T. Miyamachi et al, Nature Communications, 3, 938 (2012).
STUDY OF THE EFFECT OF ELECTRON RADIATION AND/OR TRIALLYL ISOCYANURATE ON THE
FUNCTIONAL PROPERTIES OF THE THIN FILMS OF POLY(ε-CAPROLACTONE)
1
Rafał Malinowski1, Piotr Rytlewski2, Aneta Raszkowska-Kaczor1, Krzysztof Moraczewski2, Tomasz Żuk1
Institute for Engineering of Polymer Materials and Dyes, 87-100 Toruń, Poland, [email protected];
2
Departament of Materials Engineering, Kazimierz Wielki University, 85-064 Bydgoszcz, Poland
Investigation of the effect of electron radiation and/or triallyl isocyanurate (TAIC) on the functional properties of the
thin films of poly(ε-caprolactone) (PCL) was the aim of the present work. Thin films of primary PCL and PCL
containing 3% TAIC were obtained using a single-screw extruder, type Plasti-Corder Lab Station (Brabender,
Germany). The films irradiation was carried out with the use of a linear accelerator type LAE 13/9, located at the
Institute of Nuclear Chemistry and Technology in Warsaw, Poland. The films were irradiated with the doses of 10, 20,
40, 60 or 90 kGy. The maximum individual dose was 20 kGy. It was limited by an increase in temperature of the
irradiated material, equal to ca. 4-7C for an individual dose of 10 kGy. The mechanical properties during the static
stretching, water permeability, surface free energy, thermal properties by DSC, thermo-mechanical properties by DMA,
structural properties by FTIR, shrinkage and light transmittance were determined. It was found that irradiation PCL and
irradiation PCL containing TAIC causes improved the mechanical properties for some doses. The water permeability of
some irradiated samples decreased. Surface free energy increased, especially for samples containing TAIC. The used
electron radiation and/or TAIC did not affect essentially the light transmittance and thermal and structural properties of
PCL films. Changes occur only in the crystallinity. The degree of crystallinity of irradiated PCL films increases, and
irradiated PCL films containing TAIC decreases.
Acknowledgment: The project has been financed by the National Science Centre (financing granted after DEC2012/07/D/ST8/02773 decision).
70
SYNTHESIS AND CHARACTERISATION OF AN ADVANCED NEW COMPOSITE MATERIAL FOR
ENVIRONMENTAL PROTECTION
1
Daniel Damian1,2, Adina Segneanu1, Nandina Vlatanescu2, Daniel Berki2, Iosif Hulka2, Ioan Grozescu1,2
National Institute of R&D for Electrochemistry and Condensed Matter INCEMC Timisoara, 2University Politehnica
Timisoara
Design of new and efficient materials for nutrients removal from wastewater represents the aim of the area current
research. The purpose of this study was the design and morfo-structural analysis of a composite material based on Al,
clinoptilolite and with Zn, Mg and P oxides with application in wastewater treatment. It was investigated the
preparation of new composite material by mechanical compression of precursors. The morphology and structural
properties of the final product were determinate by scanning electron microscopy SEM) and X-ray diffraction (XRD).
The efficiency of hybrid material to removal nutrients was evaluated on a synthetic wastewater.
71
72
S4
Advanced Biomaterials, Biodevices and
Biotechnology
Invited Papers
73
74
BIOELECTROCHEMICAL CONVERSION OF CO2 TO CHEMICALS: ELECTROSYNTHEIS VIA
BACTERIA AND ENZYMES
Suman Bajracharya(1)(2), Srikanth Sandipam(1), Mohanakrishna Gunda(1), Karolien Vanbroekhoven(1), Deepak Pant(1)*
(1)Separation and Conversion Technology, Flemish Institute for Technological Research (VITO),Boeretang 200, Mol
2400, Belgium, (2)Sub-department of Environmental Technology, Wageningen University, Wageningen, The
Netherlands; *Corresponding author: [email protected]
Background
With the share of renewable electricity increasing in the energy sector, moments of overproduction will occur more
often as well as points in time for which not enough production is available to fulfill the needs. The estimation is that in
a scenario of 100% renewable energy, about 20% of the yearly production will need to be stored in one way or another
to keep the system in balance. Since the Antwerp-Rotterdam-Rhine-Ruhr (ARRR) cluster is the European region where
the highest CO2-emissions are measured (highest production, but also highest population density and energy supply),
this region is well positioned to focus on CO2 and ‘peak shaving’ of renewable energy. Since this region is also one of
the biggest chemical clusters, the conversion of CO2 into new molecules makes sense guaranteeing that the final
balance on energy use and CO2-emissions are lower than in the classical production. Different initiatives are ongoing in
The Netherlands to focus on underground storage (CCS). Nordrhein-Westfalen is putting its money on power to gas.
The harbor of Antwerp, University of Antwerp and VITO have started an initiative to explore technologies for
converting CO2, preferentially coupled to ‘peak shaving’, to building blocks for the chemical sector. Making
technological choices is very difficult, since the selected technology depends on the quality of the CO2 feedstock. Each
of the impurities in the CO2 emission will have its impact on the process. Thus ongoing activities are focusing on listing
the different CO2-emissions and its quality/composition. The different technologies have to be benchmarked for their
robustness and flexibility towards feedstock and energy peaks.
Microbial Electrosynthesis
Research over the years has proven that generation of electric current is possible from the metabolism of organic
substrates in microbial fuel cells (MFCs), with bacteria acting as electrocatalysts. By converting the chemical energy
stored in organic substrates to electricity, MFCs can substantially reduce the operational cost of wastewater treatment
plants, or when fully operational even achieve energy self-sufficiency. On the other hand, microbial electrolysis cells
(MECs) have been used for the production of hydrogen at the cathode by providing a small amount of external electric
energy. However, in recent years, a new concept of microbial electrosynthesis has been applied wherein there are same
kind of setups—generally known as microbial electrochemical systems (MXCs) or bioelectrochemical systems (BES).
These systems are being used for the production of chemicals using bacteria as electrocatalysts [1]. Already the
bioelectrochemical reduction of carbon dioxide to acetate has been achieved [2], as well as the reduction of CO2 to
methane and multi-carbon compounds [3]. Global efforts are underway to utilize several other types of bacteria using a
wide variety of substrates for production of an array of compounds. The key advantage foreseen here is the use of
excess electricity that is often generated renewably such as from solar cells and wind mills, all of which cannot be
utilized immediately. This excess electricity can be fed into a BES system to produce chemical compounds. We will
report our first results with specific bacteria towards bioelectrochemical conversion of CO 2 to organic compounds.
Acetogens like Sporomusa and Clostridium sps. were experimented for their bioelectrochemical CO2 reduction
capacity at -0.6 V vs Ag/AgCl cathode potential. Adjustment of reduction potential and optimization of cell conditions
were carried out in a fed batch reactor with an activated carbon cathode. Production of 67 mg/L ethanol with mixed
culture as biocatalyst was the most remarkable achievement.
Enzymatic Electrosynthesis
Similar to the microbial systems, enzymes can also be used for numerous chemical transformations to be catalyzed
by redox-active enzymes including both the reduction and oxidation of substrates. In one of our projects,
ElectroEnzeQuest, CO2 is used as substrate for the production of methanol which will have a significant positive impact
on environment as well as energy crisis [4]. Electrosynthesis of formic acid was higher at an operational voltage of -1 V
vs. Ag/AgCl (9.37 mg L-1 CO2) compared to operation at -0.8 V (4.73 mg L-1 CO2) which was strongly supported by the
reduction catalytic current. Voltammograms also depicted a reversible redox peak throughout operation at -1 V,
indicating NAD+ recycling for proton transfer from the source to CO 2. Saturation of the product was observed after 45
minutes of enzyme addition and then reversibility commenced, depicting a lower and stable formic acid concentration
throughout the subsequent time of operation. In this presentation, the preliminary step towards methanol synthesis i.e.
formic acid production from CO2, using formate dehydrogenase at cathode will be presented.
[1] Rabaey, K., Rozendal, R. Nature Reviews Microbiology 8, 706-716, 2010.
[2] Nevin, K.P., Woodard, T.L., Franks, A.E., Summers, Z.M., Lovely, D.R. mBio 1 (2), e00103-10, 2010.
[3] Villano, M., Aulenta, F., Ciucci, C., Ferri, T., Giuliano, A., Majone, M. Bioresor Technol 101, 3085-3090, 2010.
[4] Srikanth S., Maesen M., Dominguez-Benetton X., Vanbroekhoven K., Pant D. Bioresource Technology. 165,
350-354, 2014.
Key-words: Electrosynthesis, bioproduction, electro-active bacteria, CO2 reduction, ethanol, formic acid, enzymes.
75
SUSTAINABLE CARBON MATERIALS AND CHEMICALS FROM BIOMASS HYDROTHERMAL
PROCESSES
Magdalena Titirici
Department of Engineering and Materials Science, Queen Mary University of London, Mile End Road, E14NS, London
The creation of new and very importantly greener industries and new sustainable pathways are crucial to create a
world in which energy use needs not be limited and where usable energy can be produced and stored wherever it is
needed.
New materials based on carbon, ideally produced via inexpensive, low energy consumption methods, using
renewable resources as precursors, with flexible morphologies, pore structures and functionalities, are increasingly
viewed as ideal candidates to fulfil these goals. The resulting materials should be a feasible solution for the efficient
storage of energy and gases.
Hydrothermal carbonization [1] is an ideal technology for the production of such low-cost but highly performing
materials out of the most abundant renewable resource on the planet, i.e. lignocellulosic biomass. The practical
approach is very simple and consists in placing a biomass precursor inside an autoclave, in water, followed by
hydrothermal treatment overnight at 160-200°C. Since the production of carbon materials in general implies harsher and
multi-step methodologies along with fossil –based precursors, this process has clear advantages in terms of
sustainability and cost.
Here, I wish to present some of our latest results on the production and characterization of nanostructured
hydrothermal carbons (HTC) and their use in renewable energy related applications, [2], [3].
I will also present some results on the use of HTC as well as heterogenous catalysts to convert levulinic acid
obtained in the liquid phase after biomass hydrothermal treatment into other platform chemicals such as levulinate
esters or gamma-valerolactone [4].
[1] M.-M. Titirici, R. J. White, C. Falco, M. Sevilla, Energy & Environmental Science 2012, 5, 6796-6822.
[2] K. Tang , L. Fu , R J. White , L. Yu , M. Antonietti , J. Maier, M. M. Titirici , Adv. Energy Materials, 2012, 2,
873–877
[3] N. Brun, S. A. Wohlgemuth, P. Osiceanu, M. M. Titirici, Green Chem., 2013, 15, 2514-2524
[4] F. Pileidis, M. Tabassum, S. Coutts, M. M. Ttitirici, Chinese Journal of Catalysis, 2014, 35, 929–936
Keywords: hydrothermal carbonization, porous carbon, energy storage, heterogeneous catalysis
76
Oral Presentations
USING TIME CONTRAST ALGORITM FOR A QUALITATIVE MONITORING OF FE 3O4
NANAOPARTICLE AGGREGATION
Dan Chicea,
Environmental Sciences Department, University Lucian Blaga of Sibiu, Romania, [email protected]
Fe3O4 nanoparticles have been extensively considered for biomedical applications, especially for drug delivery, as
they can be metabolised by living organisms and for tumour treatment by hyperthermia. Fe 3O4 nanoparticles covered by
different surfactants can be produced with a low cost co-precipitation procedure. A batch of Fe3O4 nanoparticles was
produced following a procedure previously described, with known physical and rheological parameters.
Fe3O4 nanoparticles in aqueous suspension remain a nanofluid if different salts with controlled concentration are
added, but aggregate fast when deionised water is the carrier fluid.
Typically the aggregation process dynamics can be monitored using different optical procedures, as Dynamic Light
Scattering (DLS) and Static Light Scattering (SLS). The results presented in the extended paper are a continuation of
the previous work of the author on monitoring Fe 3O4 nanoparticles in aqueous suspension.
The time contrast algorithm uses a time series recorded during a coherent light scattering experiment performed on a
Fe3O4 concentrated nanofluid during it’s rapid aggregation. The time series is analysed both using the teh modified
version of the DLS and the time contrast proposed procedure. The time contrast procedure computes a parameter named
time contrast on equally spaced time slices of the time series. The time contrast parameter variation is compared with
the variation of the average aggregates diameter during nanoparticles aggregation and the results presented and
discussed in the extended paper.
Charsima opal is a dental material currently used as filler in dental restoration. The mechanical properties of the
material strongly depend of the grain structure (size and size distribution). An AFM study of the Charisma opal surface
deposited on a microscope slide was conducted. Tapping mode was used with a medium stiffness cantilever. The
surface topography information was processed using the Gwyddion package and a grain structure and distribution was
derived. Details on data processing and on particular error sources are presented as well.
SEM surface images were acquired and the surface grain structure was analysed using the ImageJ software package.
The two types of results are compared and they reveal that the grain size is in the range of tens of microns to microns.
Details on materials, methods and results are presented in the extended paper, as well.
77
PHYSICOCHEMICAL PROPERTIES AND PROCESSES RELEVANT FOR IN VITRO BIOLOGICAL
STUDIES INVOLVING TIO2 NANOPARTICLES
Traian Popescu1 ([email protected] ), V Raditoiu2, VS Teodorescu1, L Diamandescu1, V Purcar2, AM Vlaicu1, D
Tarabasanu-Mihaila1, AR Lupu3,4* ([email protected] )
1
National Institute of Materials Physics, Romania; 2National Research and Development Institute for Chemistry and
Petrochemistry – ICECHIM, Romania; 3Cantacuzino National Institute for Research and Development in Microbiology
and Immunology, Romania; 4Victor Babes National Institute of Pathology, Romania;
The advancement of nanomedicine requires detailed understanding of the relationship between the structural and
physicochemical properties of nanomaterials and the biochemical processes they induce under in vitro and in vivo
conditions.
In this context, we performed studies aimed to identify and characterize in vitro interactions of TiO2 nanoparticles
(Degussa P25 and two samples, undoped and Fe3+-doped TiO2, synthesized by a hydrothermal procedure in our
laboratory) with respect to properties such as size, shape, crystal structure, specific surface area, semiconductor bandgap
energy, Zeta potentials and photocatalytic capacity.
The results revealed the occurrence of a photocatalytic reaction between TiO 2 and the cell viability indicator MTT
[3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium-bromide], under biologically relevant conditions. The kinetics
and mechanism of the TiO2-MTT reaction were studied in detail.
Regarding their cellular effects, TiO2 nanoparticles with higher surface charge, good colloidal stability and
enhanced photocatalytic properties may preferentially damage cells by induced oxidative stress compared to other TiO 2
nanomaterials.
Acknowledgements: Funding sources SOP HRD/107/1.5/S/82514, PN09-450102/PN09-450103, PN-II-PT-PCCA2013-4-1386, PN-II-PT-PCCA-2013-4-0864 (CLEANPHOTOCOAT) are greatly acknowledged.
VOLTAMMETRIC DETERMINATION OF NEUROTRANSMITTERS AS BIOCHEMICAL MARKERS IN
NEUROLOGICAL DISORDERS
a
Ana Gheorghiu (Ciurea)a, Radu Mutihaca, Constantin Mihailciucb ,Anton Alexandru Ciucub, Jean Ciurea c
University of Bucharest, Faculty of Physics, bUniversity of Bucharest, Faculty of Chemistry, c Neurosurgery
Department, Bagdasar-Arseni Hospital, Bucharest, Romania
In the medical field, the monitoring of the neurotransmitters represents a major demand focusing on the health state
of the patients, with social and economic effects. Levodopa (L-dopa), [(-)-3-(3,4-dihydroxyphenyl)-L-alanine], a
biological precursor of catecholamines, is a naturally occurring amino acid synthesized from L-tyrosine in the human
body. Since the 1960s, it has been used as a drug for the treatment of Parkinson's disease, acting efficiently in the ease
of symptom, and it remains the most effective therapeutic agent in the field of neurology. Parkinson's is a chronic,
progressive neurodegenerative disorder that occurs when the substantia nigra of the mid-brain dies and fails to produce
enough dopamine.
A new, simple and rapid voltammetric method based on a disposable screen-printed carbon electrode (SPCE)
modified with cobalt-phthalocyanine (CoIIPc) is proposed for the determination of L-dopa. The electro-catalytical
mechanism is discussed. Cyclic voltammetric studies showed that modified SPCE improve electrochemical behaviour
of L-dopa, compared to an un-modified SPCE. Estimation of the linear range and limit of detection was performed. The
method could be applied to the determination of L-dopa in biological samples and commercial pharmaceutical
formulation.
Acknowledgement: Ana Ciurea was supported by the strategic grant POSDRU/159/1.5/S/133652 ,"Integrated
system to improve the quality of doctoral and postdoctoral research in Romania and promotion of the role of science in
society " cofinanced by the European Social Found within the Sectorial Operational Program Human Resources
Development 2007-2013.
78
AN AFM AND SEM STUDY OF THE GRAIN STRUCTURE OF A DENTAL RESTORATION MATERIAL
Dan Chicea,
Environmental Sciences Department, University Lucian Blaga of Sibiu, Romania, [email protected]
Charsima opal is a dental material currently used as filler in dental restoration. The mechanical properties of the
material strongly depend of the grain structure (size and size distribution). An AFM study of the Charisma opal surface
deposited on a microscope slide was conducted. Tapping mode was used with a medium stiffness cantilever. The
surface topography information was processed using the Gwyddion package and a grain structure and distribution was
derived. Details on data processing and on particular error sources are presented as well.
SEM surface images were acquired and the surface grain structure was analysed using the ImageJ software package.
The two types of results are compared and they reveal that the grain size is in the range of tens of microns to microns.
Details on materials, methods and results are presented in the extended paper, as well.
BIOLOGICAL ACTIVITY OF SOME NEW METAL CARBOXYLATES WITH AZOLE TYPE LIGANDS
ID Vlaicu1,*, M Badea2, D Marinescu2, Mariana Carmen Chifiriuc3, Coralia Bleotu4
National Institute of Materials Physics, Magurele, Romania, 2 Inorganic Chemistry Department, Faculty of Chemistry,
University of Bucharest, Bucharest, Romania, 3Department of Microbiology, Faculty of Biology, University of
Bucharest, Bucharest, Romania, 4Stefan S Nicolau Institute of Virology, Bucharest, Romania; *Corresponding author email: [email protected]
1
The health problem caused by the bacterial resistance to the usual antimicrobial drugs, there is a continuous need to
develop new antimicrobials. It was demonstrated that the biological activity of the organic compounds is intensified by
coordinating to a metal centre. Azole type compounds (e.g. pyrazoles, imidazoles, benzimidazoles) and their metal
complexes have been proved to possess many pharmacological properties like antimicrobial, anticancer, antiinflammatory, anti-helmintic, etc. In this light, our primary research activities are focused on designing and
characterization of new metal complexes bearing carboxylate and azole type ligands (pyrazoles, imidazoles and
benzimidazoles) which combine the carboxylate group versatility and the azoles pharmacological potential. There have
been synthesized and structurally characterized by several complementary experimental techniques like chemical and
thermal analysis, FTIR and NIR-UV-Vis spectroscopies, and magnetic measurements some new cobalt(II) and
nickel(II) acrylates with imidazoles. The single crystal X-ray analysis of complex [Co(2-MeIm)2(acr)2] (2) shows the
monomeric structure with cobalt ion in a tetrahedral stereochemistry with unidentate fashions adopted by the acrylates
and the imidazoles. Their biological potential was evaluated by biological assays performed against several Gramnegative, Gram-positive and fungal strains by using both reference and clinical multidrug resistant ones. The ability of
complexes to inhibit the microbial colonization on an inert substrate was also determined.
FABRICATION AND CHARACTERIZATION OF POLY(VINYL ALCOHOL)/POLY(ETHYLENE
GLYCOL) THIN FILMS FOR BIOLOGICAL APPLICATIONS
I.Tirca1,2, N. L. Dumitrescu1,2, V.Marascu1,3,A.Bonciu1,3,S.Brajnicov1,M.Dinescu1,V.Dinca1
National Institute for Laser, Plasma and Radiation Physics, RO-077125 Magurele, Bucharest, Romania, 2University of
Craiova, Faculty of Mathematics and Natural Sciences, RO-200585, Craiova, Romania, 3University of Bucharest,
Faculty of Physics, RO-077125, Magurele, Bucharest, Romania; [email protected]
1
In this paper, we report about the deposition of thin films of Poly(vinyl alcohol)(PVA)-Poly(ethylene glycol) (PEG)
copolymers using two different deposition methods: spin coating and MAPLE (Matrix Assisted Pulsed Laser
Evaporation). Poly(vinyl alcohol) (PVA) is a non-toxic, water soluble, biocompatible and biodegradable synthetic
polymer. By its copolymerization with the hydrophilic polymer Poly(ethylene glycol) (PEG), new characteristics such
as tuneable wettability, rate of degradation and coating stability can be obtained . These properties indicate that both
materials are suitable for applications in biological and medical field. Morphological features of thin films were
investigated by AFM (Atomic Force Microscopy) and Scanning Electron Microscopy (SEM) was used to characterise
the microstructure. To study the chemical properties has been used Fourier Transform Infrared Spectroscopy (FTIR).
Contact angle measurements were performed to establish the wettability of the thin films. Above results show that both
methods, spin coating and MAPLE are suitable for depositing the thin polymer films.
Keywords: MAPLE,spin coating, poly(vinyl alcohol)/poly(ethylene glycol)
Acknowledgments: The research leading to these results has received funding from the Romanian Ministry of
National Education, CNCS – UEFISCDI, under the project PN-II-PT-PCCA 239/2014
79
MAGNETITE-BASED NANOSYSTEMS WITH APPLICATIONS IN CANCER THERAPY
R.C. Popescu1,2, D. Savu1, E. Andronescu2, G. Voicu2, L. Mogoanță4, G.D. Mogoșanu5, R. Trușcă2, B.S. Vasile2, M.
Simion3, A.M. Grumezescu2
1
“Horia Hulubei” National Insitute of Physics and Nuclear Engineering, Department of Life and Environmental
Physics; 2 “Politehnica” University of Bucharest, Department of Science and Engineering of Oxide Materials and
Nanomaterials; 3 National Institute for Research and Development in Microtechnologies, Laboratory of
Nanotechnology; 4University of Medicine and Pharmacy of Craiova, Research Center for Microscopic Morphology and
Immunology; 5 University of Medicine and Pharmacy of Craiova, Department of Pharmacognosy & Phytotherapy,
Faculty of Pharmacy;
The potential approach of cancer treatment by using nanotechnology refers to the fabrication of targeted carriers for
anti-tumor substances. Even if there are several Food and Drug Administration- approved nanosystems, there is still a
continuous urge to find more effective treatment options, which are supposed to overcome the short comings of the
existing ones. Tumor resistance to radiotherapy and/or chemotherapy was attempted to be exceeded by using drug
delivery systems, such as our functionalized magnetite nanoparticles, which are transported by active magnetic
targeting at the tumor site. Here, we report the obtaining of Fe 3O4 nanoparticles functionalized with doxorubicin and
gemcitabine, which exhibited in vitro anti-tumor effect against human cancerous cell lines. The nanoparticles were
successfully accomplished through methods such as XRD, SAED, and the samples high level of crystallinity being
proven through the same methods and confirmed through HR-TEM analysis. The functionalization of magnetite with
anti-tumor substances has been highlighted through the thermogravimetric analysis and the hydrodynamic analysis
through DLS. The anti-tumor effect of the obtained systems has been in vitro evaluated using quantitative tests to
estimate the degree of cell proliferation, but also through microscopy qualitative tests, emphasizing the cells
morphology. The in vivo biodistribution test had good results, the vital organ samples proving no nanoparticle
accumulations, with the exception of the spleen, where black-brown deposits have been found.
SYNTHESIS, CHARACTERIZATION AND BIOEVALUATION OF DRUG- COLLAGEN HYBRID
MATERIALS FOR BIOMEDICAL APPLICATIONS
Georgeta Voicu1, Ruxandra- Elena Geanaliu-Nicolae1, Adrian-Alexandru Pîrvan1, Ecaterina Andronescu1, Florin
Iordache2
1
Politehnica University of Bucharest, Faculty of Applied Chemistry and Material Science; 1-7 Gh Polizu Str., 011061
Bucharest, Romania; 2Institute of Cellular Biology and Pathology of Romanian Academy, “Nicolae Simionescu”,
Department of Fetal and Adult Stem Cell Therapy, 8, B.P. Hasdeu, Bucharest 050568, Romania
This work presents a study based on the preparation and characterization of drug-collagen hybrid materials.
Materials used for obtaining drug-collagen hybrids were collagen type I (Coll) as matrix and fludarabine (F) and
epirubicin (E) as hydrophilic active substances. After incorporation of drugs into Coll in different ratios, the obtained
hybrid materials (Coll/F and Coll/E) could be used according to our results as potential drug delivery systems in
medicine for the topical (local) treatment of cancerous tissues (e.g. the treatment of breast, stomach, lung, colorectal or
advanced ovarian cancer).
The materials were characterized considering their composition (by XRD, FT-IR and DTA-TG) and their
morphology (by SEM). The delivery of drug was assessed by UV-Vis.
The in vitro citotoxicity demonstrates an antitumoral activity of the obtained hybrid materials and their potential use
for biomedical applications as drug delivery systems in tumoral treatments.
Acknowledgement:
The work has been funded by the Sectoral Operational Programme Human Resources Development 2007-2013 of
the Ministry of European Funds through the Financial Agreement POSDRU/159/1.5/S/132397.
80
MAPLE FABRICATION OF ANTIMICROBIAL COATINGS FOR MEDICAL APPLICATIONS
A. Visan1, M. Miroiu1, C. Nita1, M. Socol2, I. Zgura2, R. Cristescu1, M.C. Chifiriuc3, L. Sima4, F. Antohe5, I.N.
Mihailescu1, G. Socol1
1
National Institute for Lasers, Plasma and Radiation Physics, Magurele, Ilfov, Romania, 2 National Institute of
Materials Physics, Magurele, Ilfov, Romania, 3 Faculty of Biology, University of Bucharest, Microbiology Immunology
Department, 77206 Bucharest, Romania, 4 Institute of Biochemistry, Splaiul Independentei 296, Bucharest, Romania, 5
Institute of Cellular Biology and Pathology Nicolae Simionescu, Bucharest,Romania, Corresponding author:
[email protected]
In this study, we investigated different synthesis methods for obtaining surfaces able to promote cellular adhesion,
as well as reduce the risk of bacterial contamination, the main challenge being to obtain both effects on the same
metallic implant surface. Lysozyme embedded into blends of polyethylene glycol (PEG) and polycaprolactone (PCL)
were developed via matrix assisted pulsed laser evaporation (MAPLE) technique for long term delivery applications.
Different blend ratios were synthesized and evaluated to optimize protein release profile from fabricated coatings. The
chemical composition (FTIR) and the main surface features which affect and guide cellular and bacterial adhesion like
roughness (AFM), and wettability measurements were investigated. Antimicrobial properties of coatings against
Escherichia Coli, Staphylococcus Aureus, E. Faecalis and B. Subtilis bacteria were also evaluated. In vitro culture tests
on mesenchymal stem and endothelial cells grown on PCL-PEG-Lysozyme coatings showed appropriate viability, good
spreading and normal cell morphology. The release tests of Lysozyme along with biological investigations suggest that
our polymeric composite coatings with adjusted biodegradability may be efficient in preventing implant-related
infections.
Ln(III) DOPED NANOPARTICLES INTERACTION WITH BLOOD PLASMA. DLS AND LUMINESCENCE
SPECTROSCOPY STUDY
Rustem Zairov, Natalya Shamsutdinova, Alsu Mukhametshina,
Svetlana Fedorenko, Alfia Fattakhova, Asiya Mustafina
A.E. Arbuzov IOPC KSC RAS, Kazan (Volga region) Federal University
Nanoparticles are suitable platforms for cancer targeting and diagnostic applications. Typically, less than 10% of all
systemically administered nanoparticles accumulate in the tumour. Here we explore the interactions of blood
components with nanoparticles and describe how these interactions influence solid tumour targeting. In the blood,
serum proteins adsorb onto nanoparticles to form a protein corona in a manner dependent on nanoparticle
physicochemical properties. These serum proteins can block nanoparticle tumour targeting ligands from binding to
tumour cell receptors. Additionally, serum proteins can also encourage nanoparticle uptake by macrophages, which
decreases nanoparticle availability in the blood and limits tumour accumulation. The formation of this protein corona
will also increase the nanoparticle hydrodynamic size or induce aggregation, which makes nanoparticles too large to
enter into the tumour through pores of the leaky vessels, and prevents their deep penetration into tumours for cell
targeting. Recent studies have focused on developing new chemical strategies to reduce or eliminate serum protein
adsorption, and rescue the targeting potential of nanoparticles to tumour cells. An in-depth and complete understanding
of nanoparticle-blood interactions is key to designing nanoparticles with optimal physicochemical properties with high
tumour accumulation (J. Lazarovits et al., 2015).
The silica nanoparticles doped with Tb-thiacalix[4]arene complex synthesised according to Stober and
microemulsion (A.R. Mukhametshina et al., 2014) strategies as well as Tb-betadiketone substituted calix[4]arene (N.A.
Shamsutdinova et al., 2014) and Eu(TTA)3-phosphine oxide polyelectrolyte coated nanoparticles’ (A. Mustafina et al.,
2011) size, zeta potential and photophysical properties were studied in the presence of BSA and blood plasma. The
impact of the nature of polyelectrolyte exterior layer and phospholipid bilayer formation on the nanoparticles surface on
the studied parameters are discussed.
81
IN VITRO OXYTETRACYCLINE CONTROLLED RELEASE FROM MESOSTRUCTURED SILICA AND
ALUMINOSILICATE CARRIERS AND ITS ANTIMICROBIAL ACTIVITY
D. Berger1*, S. Nastase1, R.A. Mitran1, C. Matei1, M. Petrescu1, T. Negreanu-Pirjol2
University “Politehnica” of Bucharest, Department of Inorganic Chemistry, Physical Chemistry and Electrochemistry,
Romania, 2Ovidius University of Constanta, Department of Pharmaceutical Sciences, Romania
1
Mesoporous silica materials have gained more and more interest due to their outstanding properties, such as tunable
pore size, high surface area and pore volume values, biocompatibility, as well as controlled framework composition.
Mesostructured silica and aluminosilicates can be employed as platform for various guest inorganic and organic
compounds, including biologically active molecules due to their excellent adsorption capacity. In general, a support for
drug molecules must be biocompatible and able to load the required amount of pharmaceutical active ingredient
preserving its therapeutic activity and release it gradually over time.
Here we reported studies on obtaining oxytetracycline-based delivery systems containing various mesostructured
silica and aluminosilicate carriers with different antibiotic content in order to establish the influence of structural,
textural and support composition on oxytetracycline release profile. The antibiotic molecules were loaded on support
mesochannels by incipient wetness impregnation method using a concentrated aqueous solution of drug. The hybrid
samples were characterized by small- and wide-angle XRD, FTIR spectroscopy and N2 adsorption-desorption
isotherms. The antibiotic delivery profiles measured by UV-vis spectroscopy in phosphate buffer solution, at 37°C
showed that the presence of aluminium ion in silica framework led to a slower release kinetics. The antimicrobial
activity of oxytetracycline-based hybrids against Staphylococcus aureus was evaluated.
SILICA NANOBIOSTRUCTURES FOR ANTI-STAPHYLOCOCCAL DRUGS DELIVERY
Paul Catalin Balaure1,*, Mihaita Iulian Nita2, Raisa Anamaria Popa1, Alexandru Mihai Grumezescu3, Georgeta Voicu3,
Coralia Bleotu4, Laurentiu Mogoanta5, George Dan Mogosanu6, Alina Maria Holban7,8, Mohamed. D. Hussien7,8,
Mariana Carmen Chifiriuc7,8
1
University Politehnica of Bucharest, Faculty of Applied Chemistry and Materials Science, Organic Chemistry
Department, Polizu Street No. 1-7, 011061 Bucharest, Romania ; 2University Politehnica of Bucharest, Faculty of
Applied Chemistry and Materials Science, Department of Chemical Engineering, Polizu Street No. 1-7, 011061
Bucharest, Romania; 3 University Politehnica of Bucharest, Faculty of Applied Chemistry and Materials Science,
Department of Science and Engineering of Oxide Materials and Nanomaterials, Polizu Street No. 1-7, 011061
Bucharest, Romania; 4 Stefan S. Nicolau Institute of Virology, 285 Mihai Bravu, 030304 Bucharest, Romania;
5
Research Center for Microscopic Morphology and Immunology, University of Medicine and Pharmacy of Craiova, 2
Petru Rareş Street, 200349 Craiova, Romania; 6Department of Pharmacognosy & Phytotherapy, Faculty of Pharmacy,
University of Medicine and Pharmacy of Craiova, 2 Petru Rareş Street, 200349 Craiova, Romania; 7 University of
Bucharest, Faculty of Biology, Microbiology Immunology Department, Aleea Portocalelor no 1-3, 060101 Bucharest,
Romania, 8 Research Institute of the Unversity of Bucharest, Spl. Independentei 91-95, Bucharest, Romania
Staphylococcus aureus is one of the most versatile and resistant Gram positive bacteria, causing severe hospital and
community acquired infections. Recent technological progress suggests that by using engineered nanoshuttles, the
delivery and the efficiency of antibiotics are significantly improved, even for resistant pathogens. The aim of this work
was to obtain silica nanobiostructures and evaluate them for the capacity to improve the delivery of current antibiotics
used for the treatment of S. aureus strains. The prepared nanobiostructures were characterized by FT-IR, XRD, SEM
and TEM. The in vitro microbiological tests proved that the obtained nanobiostructures exhibited a significantly
improved activity against S. aureus, as revealed by the increased diameters of the growth inhibition zones and the
decreased minimal inhibitory concentration values, as well as by the inhibitory effect of sub-lethal antibiotic
concentrations on the ability of the respective pathogenic strains to adhere and colonize different substrata. These
results, correlated with the lack of toxicity against mammalian cells as well as with an appropriate in vivo
biodistribution highlight the promising potential of this carrier for the improvement of the current antimicrobial
therapeutic agents activity. This will decrease the required active doses, reducing the side effects on the host organism.
82
VIABILITY EVALUATION OF HUMAN CANCEROUS CELLS AFTER EXPOSURE TO DIFFERENT
HYPERTHERMIC REGIMES
C. Danceanu1,2, D.D. Herea1, N. Lupu1, H.Chiriac1
National Institute of Research and Development for Technical Physics, Iasi, Romania; 2Faculty of Physics, Alexandru
Ioan Cuza University, Iasi, Romania; [email protected]
1
The aim of this work was to investigate the effect of hyperthermia at different temperatures on the viability of
human osteosarcoma cells (MG-63), using MTT test. Two experiments were performed: the first was carried out by
applying to cancerous cells a self-controlled hyperthermia treatment by using Fe-Cr-Nb-B magnetic nanoparticles in
alternating magnetic fields (AMF), and the second one by heating the cancerous cells in a cell culture incubator. The
results indicated that are differences between the viabilities of the tumor cells obtained in the two hyperthermic regimes.
Namely, at the same temperature, the cells submitted to AMF along with magnetic nanoparticles showed poor cellular
viability. The obtained results could be explained by the fact that in high frequency magnetic fields, the heat generated
by magnetic particles leads to a higher temperature near the particles as compared to the equilibrium temperature of the
entire cell culture medium, affecting at a higher degree the cells in vicinity of the particles. Therefore, close to the
surface of the particles, the temperature could get, for instance, to 50°C, but it decreases for the entire volume of cell
culture medium until an equilibrium temperature is established. The obtained results pointed out the need for a
homogeneous distribution of the magnetic particles in tumor and probably the requirement of a displacement/moving of
the particles between cells during the heating process in order to get in contact with as much as possible surrounding
cells. The results have also showed that tests carried out in cell culture incubator at different temperatures, should be
done in order to establish the optimum temperature to kill the specific cancerous cells.
Acknowledgements
This work was supported by a CNDI–UEFISCDI grant, Project No. 148/2012 (HYPERTHERMIA) and
CNDIUEFISCDI grant, Postdoctoral Project no. 8/2013.
83
THE SYNTHESIS AND BIO FUNCTIONALIZATIONOF IRON BASED NANOPARTICLES BY LASER
PYROLYSIS
Badoi Anca1*, Ilie Alina1, Manda Gina2, Mocanu Mihaela2, Morjan Ion1, Dumitrache Florian1, Fleaca Claudiu1, Gavrila
Lavinia1, Eugeniu Vasile3, Ciuca Ion4
1
National Institute for Lasers, Plasma and Radiation Physics, Bucharest, Romania; 2Victor Babes Natl Inst Pathol,
Bucharest 050096, Romania, 3Univ Politehn Bucuresti, Fac Appl Chem & Mat Sci, Dept Sci & Engn Oxid Mat &
Nanomat, Bucharest 011061, Romania, 4“Politehnica” Univ of Bucharest, Faculty of Materials Science and
Engineering, Splaiul Independentei 313, RO-060042, Bucharest, Romania; *[email protected]
In these latter days the nanoparticles play an important rol in bioresearch because this class of materials have
different applications depending on their functionalization. The main objective of this study is to create a nano
teranostic system for personalized medicine for drug delivery. In this article, we propose an improvement of the surface
of iron oxide based nanoparticles obtained by laser pyrolysis. The method consists in adding another bubbler in that will
put organic substances. These substances will be introduced by ethylene during the synthesis process aimed to creating
functional groups on the surface of magnetic nanoparticles that help to better functionalization and dispersion of
nanoparticles. This nanoparticles were characterized by structural analysis: dynamic light scattering (DLS),
transmission electron microscopy (TEM), scanning electron microscope (SEM), fourier transform infrared spectroscopy
(FTIR), X-ray powder diffraction (XRD) and magnetic analysis. After being analyzed as raw powder nanoparticles
were coated with a bio-polymer, by “layer by layer” method, with chitosan and than the therapeutic agent,
doxorubicine, both of crucial importance, as premises for their biomedical applications. This functionalized
nanoparticles were tested on mice tumor cell type B16F10 to see their biocompatibility and the toxic effect on cancer
cells.
NANO-CHROMATOGRAPHIC MASS SPECTROMETRY COMPARATIVE ANALYSIS OF
HYPERLIPIDEMIA IN TWO ANIMAL MODELS
Viorel-Iulian Suica, Elena Uyy, Raluca Maria Boteanu, Felicia Antohe
Institute of Cellular Biology and Pathology “Nicolae Simionescu”, Bucharest, Romania
Hyperlipidemia is a common risk factor for the initiation and progression of cardiovascular diseases, affecting
complex signaling pathways and often leading to fatal outcome. Membrane microdomains are dynamic nano-assemblies
enriched in signaling proteins, suggesting their active involvement in both physiological and pathological molecular
processes. Two established hyperlipidemic laboratory animal models were used for the current study: the ApoE
deficient mouse and the hyperlipemic Golden Syrian hamster. The mice lot comprised a control Black C57 group (C),
ApoE deficient mice with a hyperlipidemic diet (Am) and ApoE deficient mice with a hyperlipidemic diet followed by
statin treatment (Amt). The hamsters lot included a control group (N), a hyperlipidemic one (A h) fed a high fat diet and
the statin treated hyperlipidemic group (Aht) which received an initial hyperlipidemic diet. Isolation of detergent
resistant membrane (DRM) microdomains was achieved from lung homogenates by sucrose gradient
ultracentrifugation. High performance nano-liquid chromatographic separations coupled to mass spectrometric analysis
followed by bioinformatic study were performed for comparative DRM protein profile. Mounting evidence of the high
degree of protein primary sequence homology between the DRMs extracted from the two organisms was obtained. The
quantitative analysis revealed 830 proteins significantly affected by hyperlipidemia and statin treatment in the two sets
of animals. The projection of the differentially expressed molecules into known signaling pathways allowed us to
pinpoint the over-represented maps altered by the hyperlipidemia condition, either as a consequence of the modified
genetic background, namely antigen processing and presentation, citrate cycle and drug metabolism or by the high fat
diet alone, such as endocytosis and oxidative phosphorylation. Notably, 120 proteins were differentially expressed in
both organisms’ DRMs and were found to be involved in leukocyte trans-endothelial migration, tight junctions and
phagosome signaling.
Acknowledgements The present work was supported by the Romanian Academy and Ministry of Education and
Research grant PN-II-PCCE/CNDI-UEFISCDI no. 153/2012 and POSDRU/159/1.5/S/ 137750.
84
ELECTRICAL ACTIVITY AND ELECTROCHROMIC PROPERTIES OF POLYANILINE-COATED FIBER
NETWORKS FOR TISSUE ENGINEERING APPLICATIONS
Mihaela Beregoi1,2, Cristina Busuioc1,2, Alexandru Evanghelidis1, Elena Matei1, Monica Enculescu1, Ionut Enculescu1
1
National Institute of Materials Physics, 2University Politehnica of Bucharest, [email protected]
Development of new biomaterials with applications in tissue engineering field and in particular as artificial muscles
is a continuous challenge for the researchers who aspire to improve the quality of life. Conducting polymers, like
polyaniline (PANI), polypyrrole, polythyophene and their derivatives are good candidates for such uses due to their
great biomimetic properties owed to unique electronic conduction mechanism, variable monomer oxidation state,
electrical and optical activity, low cost etc. In addition, electrospinning technique is a low cost method, widely used to
synthesis polymeric fiber meshes with potential applications in regenerative medicine and tissue reconstruction.
Thus, combining the electrospinning method advantages, like high surface-to-volume ratio, controlled morphology,
varied composition and flexibility, with the electrical activity of polyaniline, new materials with superior properties than
the materials obtained using only one method can be synthesis.
In this context, a poly(methylmetacrylate) solution was electrospun to obtain randomly oriented polymeric fibers
collected on a cooper frames. Further, a gold layer was sputtered on the resulting webs in order to make them
conductive and improve their mechanical properties. The metalized fibers were then covered with a PANI layer by in
situ electrochemical polymerization starting from aniline and using sulphuric acid as oxidant agent. During the
deposition step, the gold-covered fibers act as working electrode, while platinum plate was used as auxiliary electrode
and saturated calomel as reference. By applying a voltage on the PANI-coated webs in the presence of an electrolyte,
the oxidation state of PANI changes, which is followed by the device colour modification. We also investigated the
morphological and electrical properties of the resulting multilayered samples.
Our preliminary analyses have shown that the proposed method can be successfully used to obtain biomaterials with
reproducible characteristics by using inexpensive starting materials and low power consumption. In future work, some
mechanical tests, in terms of actuation displacement, reaction speed and strain, will be made.
ZrO2/Y2O3 NANOCERAMICS – SYNTHESIS AND CHARACTERIZATION
Alin Gionea, Ecaterina Andronescu, Georgeta Voicu and Adrian Surdu
Politehnica University of Bucharest, Faculty of Applied Chemistry and Material Science, GhPolizu Street 1-7, 011061
Bucharest, Romania, e-mail: [email protected]
The aim of this paper is to obtain zirconia nanoceramics, with possible applications in dental restorations. In the first
step, zirconia nanopowders were obtained through a sol-gel method [1], using different amounts of Y2O3: 2, 2.5 and 3
mol%. After synthesis, the powders were dried at 100 0C and then heat treated to 5000C for 3 hours. The powders were
morphologically and structurally characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and
transmission electron microscopy (TEM). The results showed that the thermal treatment lead to the formation of
tetragonal zirconia.
In the second step, zirconia nanoceramics were obtained. The powders were uniaxial pressed at 100 MPa to obtain
the samples, followed by HIP - hot isostatic pressing for 1h and 2h, at temperatures between 1200 0-13500C under 195
MPa in an argon atmosphere [2]. After HIP, the samples were morphologically and structurally characterized by X-ray
diffraction (XRD) and scanning electron microscopy (SEM). In this step were also studied ceramic properties like
absorption, porosity and relative density. Finally, the samples were tested for biocompatibility, showing good results.
Selective references:
1. B. S. Vasile, C.G., N. Popescu-Pogrion, S. Constantinescu, I. Mercioniu, R. Stan, E. Andronescu, Structural
investigations on yttria - doped zirconia nanopowders obtained by sol-gel method. Journal of optoelectronics and
advanced materials, 2007. 9(12): p. 3774 - 3780.
2. M. Shimazaki, K.H., O. Yamaguchi, S. Inamura, H. Miyamoto, N. Shiokawa, K. Tsuji, Metastable zirconia
phases prepared from zirconium alkoxide and yttrium acetylacetonate. Part 2: Hot isostatic pressing of tetragonal
zirconia solid solution powders. Materials Research Bulletin, 1994. 29(3): p. 277-285.
85
HYDROXYAPATITE PREPARED BY SPARK PLASMA SINTERING
Grigore Florentina, Lungu Magdalena, Talpeanu Dorinel, Velciu Georgeta, Patroi Delia, Sbarcea Beatrice Gabriela,
Marinescu Virgil, Tardei Christu, Dumitru Alina
National Institute for Research and Development in Electrical Engineering, INCDIE ICPE-CA, Splaiul Unirii No.313,
Sector 3, Bucharest – 030138 Bucharest, Romania.
The aim of this study was to obtain dense hydroxyapatite (HA) by a non-conventional innovative sintering technique
Spark Plasma Sintering (SPS) for use as biomaterial. Sintered pieces with diameter of 40 mm and height of 4 ± 0.5 mm
were achieved by SPS process in vacuum with holding pressure of 50 MPa, sintering temperature of 900 oC, 950oC,
1000oC and 1100oC, dwell time of 5 minutes and heating/cooling rate of 100 oC/min. The starting ultrafine HA powders
used in this research work were produced by a precipitation technique from aqueous solutions of calcium nitrate and
diammonium hydrogen phosphate. Besides physical-mechanical testing, the some other techniques like X-ray
Diffraction (XRD), Scanning Electron Microscopy (SEM) were used to characterize the ceramic compact discs. The
average crystallite sizes of the fabricated HA powders were calculated from X-ray scattering and the Scherer formula.
The sintered pieces exhibited a dense structure with low porosity and enhanced mechanical properties due to its
advantages compared with conventional processing techniques. The best properties were obtained for the ceramic
samples sintered at 950oC, which had Vickers microhardness of minimum 5 GPa and Young’s modulus of minimum
120 GPa.
NEW TRENDS IN WASTEWATER TREATMENT-THE USE OF NANOTECHNOLOGIES
1
Ramona Zgavarogea1,2, Violeta Niculescu1*, Corina Ciucure1, Iosif Tempea2
National Institute for Research and Development for Cryogenics and Isotopes Technologies - ICIT Rm.Valcea, E-mail:
[email protected], E-mail (*corresponding author): [email protected]; 2The Faculty of Engineering and
Management of Technological Systems, Politehnica University of Bucharest
Adequate supply of clean and affordable water to meet human regularly supply is one of the main challenges today.
Physical, chemical and biological characteristics of water are modified by the addition of contaminants such as organic /
inorganic material, heavy metals and other toxins, resulting wastewater, and, because of their presence, we struggle to
keep up with the high demand of water supply due to population growth, climate change and environmental protection
insecurity.
In worldwide industries, traditional methods of supply, distribution and purification of water are replaced with new
technologies and designed so that wastewater can be reused and the environment saved from the negative effects of
untreated water. Nanotechnology has great impact in promoting wastewater treatment to improve the treatment. This
paper reports the evolution of different types of nanomaterials used to treat wastewater. Nanotechnologies present a lot
of advantages over conventional methods but still need thorough research to be a success.
SYNTHESIS OF AMPHIPHILIC DRUG CARRIER: OIL-ALGINATE COMPOSITE BEADS
Chih-Hui Yang1, Jei-Fu Shaw1, Alexandru Mihai Grumezescu2, Ming-Han Wen1, Keng-Shiang Huang3*
Department of Biological Science and Technology, I-Shou University, Taiwan; 2Faculty of Applied Chemistry and
Materials Science, Department of Science and Engineering of Oxidic Materials and Nanomaterials, University
Politehnica of Bucharest, Bucharest 011061, Romania; 3The School of Chinese Medicine for Post-Baccalaureate, IShou University, Taiwan
1
Recently, we have described many applications of droplet microfluidic technology in polymer beads generation. In
this study, we employed the microfluidic method for the preparation of oil-alginate composite droplets. Oil-alginate
composite spheres were synthesized by encapsulation of sunflower seed oil in Na-alginate droplets, dropping into Ca2+
solution and in situ solidification. Hydrophilic materials and lipophilic materials could be encapsulated simultaneously
in the same sphere in a one step process. Herein, we have developed a novel approach to an in situ process for
fabricating oil-alginate composite beads with dual encapsulation properties, which are potential multifunctional drug
carriers. We propose a one-step approach for the manufacture of oil-alginate composite spheres that can encapsulate
simultaneously hydrophilic materials and lipophilic materials. The diameters of the fabricated spheres were about 400
μm to 500 μm. The results show that the prepared oil alginate composite ball has potential use as drug carriers in the
future.
86
STUDY OF THE SOLVENTS INFLUENCE ON THE MORPHOLOGICAL AND CHEMICAL
CHARACTERISTICS OF HYDROXYAPATITE THIN FILMS DEPOSITED BY MAPLE
1
N. L. Dumitrescu1,2, I. Tirca1,2, A. Bonciu1,3, V. Marascu1,3,S. Brajnicov1 M. Dinescu1 and V. Dinca1,
National Institute for Laser, Plasma and Radiation Physics, RO-077125 Magurele, Bucharest, Romania, 2 University of
Craiova, Faculty of Mathematics and Natural Sciences, RO-200585, Craiova, Romania, 3University of Bucharest,
Hydroxyapatite ( HA) is a known major inorganic component of bones, being involved in osseointegration process.
Its biological function can be enhanced by modulating morphological characteristics. Within this context, in this paper
we used Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique to obtain HA coatings on various substrates
(e.g Si and Ti based alloys substrates).
The influence on the HA coatings morphology of different solvents or mixtures (e.g. Dimethyl Sulfoxide (DMSO),
chloroform) were studied and correlated to laser deposition parameters.
Morphological investigations were done by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy
(SEM). Contact angle measurements and FTIR measurements were used for determining the wetability and the
chemical integrity of the deposited coatings. Based on the results obtained, the optimal parameters in terms of laser
processing and matrix composition were determined.
Our preliminary results indicate that similar bone microstructure can be obtained by combining matrix
characteristics with laser deposition parameters.
Keywords: MAPLE, Hydroxyapatite (HA)
Acknowledgments: The research leading to these results has received funding from the Romanian Ministry of
National Education, CNCS – UEFISCDI, under the project PN-II-PT-PCCA 239/2014
MAGNETITE NANOPARTICLES USED AS EFFICIENT NANOSHUTTLES FOR POTENTIATING THE
ANTIMICROBIAL ACTIVITY OF NATURAL VOLATILE COMPOUNDS
Alina Maria Holban1,2, Ecaterina Andronescu2, Valentina Grumezescu2, Mariana Carmen Chifiriuc1, Alexandru Mihai
Grumezescu2, Coralia Bleotu3, Bogdan Stefan Vasile2, Lia Mara Ditu1, Carmen Curutiu1, Veronica Lazar1
1
Microbiology and Immunology Department, Faculty of Biology, University of Bucharest, Bucharest, Romania;
2
Department of Science and Engineering of Oxide Materials and Nanomaterials, Faculty of Applied Chemistry and
Materials Science, University Politehnica of Bucharest, Bucharest, Romania; 3St. S. Nicolau Institute of Virology,
Bucharest, Romania
Aim and scope. Functionalized nanopaticles can be utilized for overcoming the inefficiency of current
antimicrobials on resistant pathogens, by stabilizing, potentiating their effect and improving the release kinetics. The
purpose of this study was to develop a biocompatible nanomaterial based on magnetite and different natural, plantderived volatile compounds in order to modulate the in vitro virulence of the opportunistic pathogens Pseudomonas
aeruginosa and Staphylococcus aureus.
Methods. Six clinical and two reference P. aeruginosa and S. aureus strains were used for this study. Magnetite
nanoparticles functionalized with eugenol, eucalyptol and carvone (Fe3O4@) have been synthesized by precipitation
method, characterized by Infrared microscopy, Scanning electron microscopy and High-Resolution Transmision
Electron Microscopy. The minimum inhibitory concentrations (MICs) were established by broth microdilution method.
Adherence ability was assessed by Cravioto modified method and biofilm formation was investigated by a
microdilution assay. The biocompatibility of the nanosystem was assessed in vitro by fluorescence microscopy and
MTT assay, using human cultured endothelial cells.
Results. Our data demonstrate that subinhibitory concentrations of Fe 3O4@Eugenol and Fe3O4@Eucalyptol
exhibited the most significant effects on P. aeruginosa and S. aureus attachment after 24h of treatment. All tested
functionalized magnetite variants proved an inhibitory effect on microbial biofilm formation, in the following
decreasing order: Fe3O4@Eugenol> Fe3O4@Eucalyptol> Fe3O4@Carvone, the most significant inhibitory effect being
observed on P. aeruginosa strains. Microscopy analysis and the MTT assay demonstrated that all used nanosystems
(tested at minimum inhibitory concentration levels) exhibited a low citotoxicity in vitro, allowing the normal growth
and metabolism of cultured endothelial cells.
Conclusions. The obtained functionalized bioactive magnetite nanosystems proved to inhibit attachment and
biofilm formation of some of the most resistant bacteria pathogens, P. aeruginosa and S. aureus in a dose, time and
strain dependent manner. Our study brings new insights in the development of modern therapies based on
nanotechnology aiming to use and potentiate natural compounds to fight resistant infections through modulating
pathogens virulence and biofilm formation.
87
MAPLE GRADIENT DEPOSITION OF HYDROXYAPATITE-BASED BIOCOMPATIBLE FILMS FOR
TISSUE ENGINEERING
1
Anca Florina Bonciu1, Catalin Romeo Luculescu1, Ionut Tirca1
National Institute for Lasers, Plasma and Radiation Physics, Lasers Department, Atomistilor 409, P.O. Box MG-36
Magurele, Ilfov, RO-077125, Romania
In this study we report the preparation of stable hydroxyapatite aqueous dispersions by making use of the
biocompatible polysaccharides for envisioned bone tissue applications. Chitosan and hydroxyapatite were
ultrasonicated under vigorous conditions and then centrifuged. The supernatant was collected and characterized by
electron microscopy and spectroscopic methods (Raman, DLS, EDS). An adherent film of HA-chitosan-collagen was
deposited by MAPLE with a continuous gradient between biocomposites.The films were tested in vitro. The efficiency
of our samples was confirmed by fluorescent staining and viability assays. The proposed approach allowed us to obtain
thin films which showed promising properties as scaffold candidates for bone tissue engineering.
MAGNETITE-BASED DRUG DELIVERY SYSTEMS
R.C. Popescu1,2, V. Grumezescu3, D. Savu1, E. Andronescu2, F. Iordache4, L. Mogoanță5, G.D. Mogoșanu6, R. Trușcă2,
B. Vasile2, M. Simion7, A.M. Grumezescu2
1
“Horia Hulubei” National Insitute of Physics and Nuclear Engineering, Department of Life and Environmental Physics,
Magurele, Romania; 2 “Politehnica” University of Bucharest, Department of Science and Engineering of Oxide Materials and
Nanomaterials, Bucharest, Romania; 3 National Institute for Lasers, Plasma & Radiation Physics, Lasers Department, Magurele,
Romania; 4 “Nicolae Simionescu” Institute of Cellular Biology and Pathology, Flow Cytometry and Cell Therapy Laboratory,
Bucharest, Romania; 5 University of Medicine and Pharmacy of Craiova, Research Center for Microscopic Morphology and
Immunology, Craiova, Romania; 6University of Medicine and Pharmacy of Craiova, Department of Pharmacognosy & Phytotherapy,
Faculty of Pharmacy, Craiova, Romania; 7National Institute for Research and Development in Microtechnologies, Laboratory of
Nanotechnology, Bucharest, Romania;
Nanotechnology has offered a solution to prevent the multitude of side-effects that may appear after chemotherapy by using
magnetic nanoparticles as carriers for active substances.Thus Fe3O4 nanoparticles are suitable for such applications, their
biocompatibility being enriched by the presence of polymers on their surface, resulting proper systems for releasing the anti-tumoral
targeted drugs and reducing the side-effects caused by systemic administration of free form active substances. Functionalized Fe3O4
nanoparticles have been successfully encapsulated in polymeric microshperes, in order to modulate the release of the anti-tumor
substance. The identification of Fe3O4 samples has been successfully accomplished through methods such as XRD, SAED, the
samples high level of cristallinity being proven through the same methods and confirmed through HR-TEM. The functionalization of
magnetite with anti-tumor substances has been emphasized using the TGA. The anti-tumor effect of the obtained systems has been in
vitro provedfor MG-63 osteosarcoma cell line, while the in vivo biodistribution test had good results.
NANOSTRUCTURES BASED ON ZnO AND PHYTOCHEMICAL SUBSTANCES WITH COSMETIC
APPLICATIONS
Vera Alexandra Spirescu1, Ecaterina Andronescu1, Georgeta Voicu1, Laurentiu Mogoanta2, George Dan Mogosanu3,
Alina Maria Holban1,4, Alexandru Mihai Grumezescu1
1
“Politehnica” University of Bucharest, Department of Science and Engineering of Oxide Materials and Nanomaterials;
2
University of Medicine and Pharmacy of Craiova, Research Center for Microscopic Morphology and Immunology;
3
University of Medicine and Pharmacy of Craiova, Department of Pharmacognosy & Phytotherapy, Faculty of
Pharmacy; 4 University of Bucharest, Department of Microbiology, Faculty of Biology;
The aim of this work was to prepare sunscreens based on ZnO, beeswax, shea butter, coconut oil and
phytocomponents, noted Solange (for unfunctionalized ZnO) and Solange L (for functionalized ZnO). The method
used to obtain the UV filter, nanostructurated zinc oxide, was a sol-gel process, which allows obtaining a pure powder,
without the necessity of further calcination, with optimal nanoparticle dimenssions for the selected application. A part
of the obtained nanopowder was functionalized with limonene, a fitochemical substance, for the observance of changes
in smell and UV absorption of the final product (the sun lotion). Regarding the cristalinne structure, the resulted
material showed a hexagonal wurtzite-type structure, typical for zinc oxide, with a preferential orientation (0 0 2) and
free of detectable secondary phases through XRD. The zinc oxide was tested and analyzed by XRD, SEM, TEM,
EDAX, IR, TGA, ZETA potential, the in vivo evaluation of distribution and the antimicrobial profile. It was noticed that
the zinc oxide is optimal for the chosen application in the cosmetic industry. Solange and Solange L were made from
simple ingredients (beeswax, shea butter, coconut oil and simple and (un)functionalized ZnO nanoparticles). After the
execution, the creams were tested for UV absorbance which is the most important characteristic for sunscreen. It was
observed that the creams have a very good UV absorbance, through the entire UV spectrum. The zinc oxide is an
inorganic UV filter that constantly absorbs through the entire UV spectrum, to ~380 nm.
88
SILVER NANOSTRUCTURATED SURFACES PREPARED BY MAPLE FOR BIOFILM PREVENTION
Oana Fufa1,2, Alexandra Elena Oprea1, Ecaterina Andronescu1, Valentina Grumezescu1,3 , Alina Maria Holban1,4,
Laurențiu Mogoantă5, George Dan Mogoșanu6, Gabriel Socol3, Florin Iordache7, Alexandru Mihai Grumezescu1
1
Materials Science, University Politehnica of Bucharest, 1–7 Polizu Street, 011061 Bucharest, Romania; 2Department of
Biomaterials and Medical Devices, Faculty of Medical Engineering, University Politehnica of Bucharest, Polizu Street,
No 1-7, RO-011061m Bucharest, Romania; 3Lasers Department, National Institute for Lasers, Plasma & Radiation
Physics, P.O. Box MG-36, Magurele, Bucharest, Romania; 4Microbiology Immunology Department, Faculty of
Biology, University of Bucharest, 1–3 Portocalilor Lane, Sector 5, 77206 Bucharest, Romania; 4Department of
Biomaterials and Medical Devices, Faculty of Medical Engineering, University Politehnica of Bucharest, Polizu Street,
No 1-7, RO-011061m Bucharest, Romania; 5 Research Center for Microscopic Morphology and Immunology,
University of Medicine and Pharmacy of Craiova, 2 Petru Rareş Street, 200349 Craiova, Romania; 6 Department of
Pharmacognosy & Phytotherapy, Faculty of Pharmacy, University of Medicine and Pharmacy of Craiova, 2 Petru Rareş
Street, 200349 Craiova, Romania; 7Institute of Cellular Biology and Pathology of Romanian Academy, “Nicolae
Simionescu”, Department of Fetal and Adult Stem Cell Therapy, 8, B.P. Hasdeu, Bucharest 050568, Romania
One of the current challenging trends in modern healthcare practice is to diminish the number and significance of
medical complications due to nosocomial infections. Considering therefore the opportunistic activity of some bacterial
pathogens – as a consequence of improper and irrational conventional medication – novel strategies are needed in order
to develop medical devices with surfaces that reduce the risk of infection.
Thus, the aim of this research was to produce improved coatings with higher resistance to pathogenic colonization
and biofilm development for indispensable medical devices – such as different categories of catheters – by the
superficial modification of such devices. The genuine approach proposed in our experimental work consists in using the
novel MAPLE (Matrix Assisted Pulsed Laser Evaporation) technique in order to superficially modify the structure and
the function of the considered medical devices, by manufacturing thin inorganic layers of silver nanoparticles. Silver
nanoparticles were prepared using a facile wet chemical route and their features were further investigated by DTA-TG,
FT-IR, TEM, SAED and EDS. Silver nanopowder was afterwards used via laser processing to produce a thin
homogenous inorganic surface in the considered medical devices, in order to obtain the required improved coatings.
The manufactured surfaces were examined by SEM, TEM, IRM and AFM. By using in vitro (on human cell cultures)
and in vivo (on mice) assays, we were able to investigate the biocompatibility of the silver-based thin films. The
antibiofilm potential of the obtained coatings was investigated both on Gram-positive and Gram-negative in vitro
assays. The promising results regarding higher and longer resistance to bacterial contamination and biocompatibility
distinguish the outstanding potential of the MAPLE method for optimizing day-to-day medical care devices.
BIOCOMPATIBLE CORE/SHELL - CALCIUM CARBONATE/CROSSLINKED ALGINATES FOR
ANTIMICROBIAL THERAPY
Irina Nicoara1, Dana Miu1, Iulian Danciu1, Vlad Blaga1, Alexandra Irimia1, Cerasela Manicioiu1, Georgeta Voicu2,
Alina Maria Holban2,3, Alexandru Mihai Grumezescu2
1
Department of Biomaterials and Medical Devices, Faculty of Medical Engineering, University Politehnica of
Bucharest, Polizu Street, No 1-7, RO-011061m Bucharest, Romania; 2Department of Science and Engineering of Oxide
Materials and Nanomaterials, Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest,
1–7 Polizu Street, 011061 Bucharest, Romania; 3Microbiology Immunology Department, Faculty of Biology,
University of Bucharest, 1–3 Portocalilor Lane, Sector 5, 77206 Bucharest, Romania
Marine species, such as mussel shells, nacre or corals, are intensively studied due to their potential in biomedical
applications as controlled drug delivery systems. The scope of this study is characterizing the obtained calcium
carbonate core-shell coated systems functionalized with sodium alginate and to confirm their applicability in the
medical field. This paper proposes an approach for producing fine powder of calcium carbonate derived from the shells
of mussels that are found on the Black Sea. The powder was obtained by a mechanical processing and then
functionalized with the sodium alginate. The surface of the system thus obtained was cross-linked with Zn2+ and Cu2+
ions. The structural, morphological and also textural aspects of the obtained core/shell systems were examined by XRay Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), infra Red
Microscopy (IRM) and Thermogravimetric Analysis (TGA). The biocompatibility was studied in vitro and in vivo. The
results showed that different concentrations of shell not significantly change the shape and size of CaCO3 rods-like
particles with wides between 537-781 nm. After crosslinked with Cu2+, particles have a tendency to form agglomerates
of thin platelet. The addition of Zn2+ reveals agglomerates in the form of rosettes witch disappear with the increasing
concentration of shell. Due an excellent biocompatibility, a texture suitable for loading bioactive molecules or drugs
and an alternative intake of calcium from natural sources, the core/shell systems demonstrates a great potential for
antimicrobial therapy against Gram-positive and Gram-negative bacterial strains.
89
WOUND DRESSINGS WITH SILVER NANOSTRUCTURES MODIFIED SURFACE TO REDUCE S. aures
AND Ps. aeruginosa COLONIZATION
Daniela Babuș 1 †, Georgiana Dolete 1 †, Cristina Forțu 1 †, Mădălina Ionela Gușă 1 †, Florina Cristina Ilie 1 †, Cosmin
Paștiu 1 †, Mihaela Țone 1 †, Bogdan Stefan Vasile2, Alina Maria Holban2,3, George Dan Mogosanu4, Laurentiu
Mogoanta5, Florin Iordache6, Carmen Mariana Chifiriuc3, Alexandru Mihai Grumezescu2
1
University of Bucharest, 1–3 Portocalilor Lane, Sector 5, 77206 Bucharest, Romania; 4University of Medicine and
Pharmacy of Craiova, Research Center for Microscopic Morphology and Immunology, Craiova, Romania; 5 University
of Medicine and Pharmacy of Craiova, Department of Pharmacognosy & Phytotherapy, Faculty of Pharmacy, Craiova,
Romania; 6Institute of Cellular Biology and Pathology of Romanian Academy, “Nicolae Simionescu”, Department of
Fetal and Adult Stem Cell Therapy, 8, B.P. Hasdeu, Bucharest 050568, Romania; † authors with equal contribution to
this work
The aim of this work was to prepare an antimicrobial wound dressings (WDs) able to modulate microbial biofilms.
The WDs decorated with silver nanoparticles (NanoAg) prepared by chemical reduction method. The NanoAg-WDs
were characterized by XRD, SEM, TEM, SAED and InfraRed Microscopy. Biological characterization consisted in
the in vitro evaluation of the antimicrobial efficiency of NanoAg-WDs against the S. aureus and Ps. aeruginosa, and the
in vivo biodistribution of Ag NP on mice. From the SEM images of NanoAg-WDs it can be observed that the silver
nanoparticles are distributed all over the dressings surface, nanostructures between 25-45 nm with a spherical shape
being seen.These data were confirmed by XRD and TEM analyses that revealed a well crystallized nanoparticles. In
vivo biodistribution show no nanoparticles after 7 days of treatment. Qualitative and quantitative analyses performed on
S. aureus and Ps. aeruginosa clinical strains showed that the NanoAg-WDs have an inhibitory activity against microbial
colonization and biofilm development maintained for up to 3 days. Furthermore, SEM and viable cells count analyses
proved the ability of NanoAg-WDs to interfere with the S. aureus and Ps. aeruginosa biofilm development. All these
data recommend this type of wound dressings for the antibacterial applications and more over, for prevention of
microbial contamination, colonization and biofilm development.
ANTIMICROBIAL ACTIVITY OF MAGNETITE NANOSTRUCTURES COATED WITH Ca+2, Cu+2 and Zn+2
ALGINATES
Daniela Babuș 1 †, Georgiana Dolete 1 †, Cristina Forțu 1 †, Mădălina Ionela Gușă 1 †, Florina Cristina Ilie 1 †, Cosmin
Paștiu 1 †, Mihaela Țone 1 †, Georgeta Voicu2, Alina Maria Holban2,3, Bogdan Stefan Vasile2, Florin Iordache4, Horia
Maniu4, Alexandru Mihai Grumezescu2,*
1
University of Bucharest, 1–3 Portocalilor Lane, Sector 5, 77206 Bucharest, Romania; 4Institute of Cellular Biology and
Pathology of Romanian Academy, “Nicolae Simionescu”, Department of Fetal and Adult Stem Cell Therapy, 8, B.P.
Hasdeu, Bucharest 050568, Romania; † authors with equal contribution to this work
The purpouse of this work was to investigate the potential of magnetite coated with alginates in antimicrobial
applications depending on different types of cross-linking agents (Ca+2, Cu+2 and Zn+2). A magnetite-alginates
nanostructures hve been prepared by co-precipitation method. The prepared magnetite coated with Ca+2, Cu+2 and Zn+2
alginates were characterized by SEM, TEM, IR, DTA-TG and XRD. Also, in vitro and in vivo tests were performed.
Our results are suggesting that the alginates functionalized magnetite nanoparticles possess unique biological
characteristics that make them promising candidates for antimicrobial drug targeting.
90
NANOSTRUCTURATED SURFACE BASED ON MAGNETITE AND PATCHOULI OIL FOR ANTIINFECTIVE WOUND DRESSING
Ioana Raluca Bucur1, Madalina Lemnaru1, Maria Minodora Marin1, Stefania Marin1, Roxana Elena Tiplea1, George
Mihail Vlasceanu1, Georgeta Voicu2, Alexandra Elena Oprea2, Alina Maria Holban2,3, Carmen Mariana Chifiriuc3,
Florin Iordache4, Horia Maniu4, Alexandru Mihai Grumezescu2
1
University of Bucharest, 1–3 Portocalilor Lane, Sector 5, 77206 Bucharest, Romania ; 4Institute of Cellular Biology and
Hasdeu, Bucharest 050568, Romania
The aim of this study was to develop a biocompatible and bioactive wound dressing, containing iron oxide
nanoparticles functionalized with patchouli essential oil in order to obtain improved antimicrobial properties able to
prevent infections and biofilm development. In this work, the wound dressing surface was prepared by co-precipitation
of precursor in an alkaline solution of patchouli oil. The prepared surface was characterized by TEM, SEM, XRD,
DTA-TG and FT-IR. Qualitative and quantitative in vitro cell viability were performed. In vivo tests on mice revealed
a good biodistribution, while antimicrobial tests revealed a strong antibiofilm properties up to 72 hours. Prepared
modified wound dressings can be successfully used in medical applications such as antimicrobial therapy due to their
broad antimicrobial spectrum.
3D SCAFFOLDS BASED ON COLLAGEN, ALBUMIN, PVA AND SILVER NANOSTRUCTURES FOR
TISSUE ENGINEERING APPLICATIONS
Miruna S. Stan1, Ioana Raluca Bucur2, Madalina Lemnaru2, Maria Minodora Marin2, Stefania Marin2, Roxana Elena
Tiplea2, George Mihail Vlasceanu2, Ecaterina Andronescu3, Georgeta Voicu3, Alina Maria Holban3,4, Anca
Dinischiotu1, Alexandru Mihai Grumezescu2
1
Department of Biochemistry and Molecular Biology, Faculty of Biology, University of Bucharest, 91-95 Splaiul
Independentei, 050095 Bucharest, Romania; 2Department of Biomaterials and Medical Devices, Faculty of Medical
Engineering, University Politehnica of Bucharest, Polizu Street, No 1-7, RO-011061m Bucharest, Romania;
3
Materials Science, University Politehnica of Bucharest, 1–7 Polizu Street, 011061 Bucharest, Romania; 4Microbiology
Immunology Department, Faculty of Biology, University of Bucharest, 1–3 Portocalilor Lane, Sector 5, 77206
Bucharest, Romania
The purpose of this study was to obtain a composite based on albumin, a natural protein reported as a possible
source of raw antimicrobial material with features that can be designed for numerous biomedical related purposes, and
silver nanoparticles, utilized to expand the range of applicability of collagen-polyvinyl alcohol scaffolds by enhancing
their activity against antibiotic-resistant pathogens. Homogenous mixtures of various ratios of collagen, albumin and
polyvinyl alcohol solutions were obtained under stirring conditions. The synthesis of AgNPs was accomplished by
reduction of AgNO3. AgNPs were dispersed in the blended mixtures under sonication conditions. The composites were
further cooled and lyophilized. The porous nanostructurated materials were observed at SEM, AFM and subjected to
XRD, IR and DTA-TG. The obtained nanocomposites proved a good antimicrobial activity against both laboratory and
clinically derived, resistant bacterial. In vivo results revealed that silver nanoparticles are rapidly transported and
removed from essential organs, such as brain, spleen, liver and lungs. Furthermore, the utilized wound mouse model
revealed that these composites are significantly stimulating the wound healing. Based on the results suggesting low
cytotoxicity and weak interaction with the living tissues consistent with a promising elimination rate, the proposed 3D
scaffold could prove its efficiency for tissue regeneration purposes. All types of nanocomposites stimulated in vitro cell
proliferation without any cytotoxic effect on cell membrane and actin cytoskeleton of CCD-1070Sk human skin
fibroblasts, the material with an equal ratio of albumin and colagen displaying the best biocompatibility. The excellent
cell adherence and spreading on these Ag-based scaffolds support their usage as substrates in tissue engineering
applications.
91
MODIFICATION OF COVALENT AND IONIC CROSS-LINKED ON CHITOSAN FILM BY GENIPIN AND
TRIPOLYPHOSPHATE AS POTENTIAL MATERIAL IN MEDICAL APPLICATIONS
Siti Farhana Hishama*, Siti Hajar Kasima, Syazana Abu Bakara, Siti Noorzidah Mohd Sabria, Azreena Mastora, Ahmad
Hazri Abdul Rashidb, Kartini Noorsala
a
Advanced Materials Research Centre, Sirim Bhd, Lot 34, Jalan Hi-Tech 2/3, Kulim Hi-Tech Park, 09000 Kulim
Kedah, Malaysia, bIndustrial Biotechnology Research Centre, Sirim Berhad, No. 1, Persiaran Dato’ Menteri, Section 2,
P.O Box 7035, 40911 Shah Alam Selangor, Malaysia. * Corresponding author. Tel.: +604-4017266; fax: +604-4033, Email address: [email protected]
High water affinity and low mechanical properties of film wound dressing based chitosan has limited its usage
period that is required during the application, thus a chemical modification is needed to overcome the problem. The aim
of this study was to investigate the effects of covalent and ionic cross-linked reactions which were respectively done by
using genipin and tripolyphosphate (tpp), on the physical and mechanical properties of chitosan film. Both cross-linked
and uncross-linked films were prepared and characterized. FTIR spectra showed no characteristic of –OCH3 peak from
genipin at 1444 cm-1 which resulted by new covalent bonding in chitosan film that was cross-linked by genipin. An
absorption peak at 896 cm-1 in chitosan cross-linked genipin/tpp film was due to the stretching of P-O. UV-Vis
spectroscopy showed the covalent cross-linked by genipin on the chitosan had reduced the film’s transparency from
77% to 63% while ionic cross-linked by tpp gave slight changes on the properties. As expected, chitosan film with
combination of covalent and ionic cross-linked network showed the higher mechanical strength with average tensile
stress value at 68.07 MPa and produced high water vapour barrier at 69.77 g/m2hr. The water contact angel on the
surface of covalent/ionic cross-linked chitosan film also reached the highest θ at 100.93° indicated more hydrophobic
surface area occurred. All results demonstrated that cross-linked modification on the chitosan film had reduced the
film’s hydrophilicity and increase the mechanical properties of the film.
COMPOSITE NANOSTRUCTURED BIOMATERIALS FOR IMPROVED WOUND HEALING
Miruna S. Stan1, Anca Apostol2, Andreea Carja2, Daniela Cabuzu2, Elena Catrina2, Rebecca Puiu2, Ecaterina
Andronescu3, Alexandra Elena Oprea3, Anca Dinischiotu1, Georgeta Voicu3, Alina Maria Holban3,4, Alexandru Mihai
Grumezescu3
1
Department of Biochemistry and Molecular Biology, Faculty of Biology, University of Bucharest, 91-95 Splaiul
Independentei, 050095 Bucharest, Romania ; 2Department of Biomaterials and Medical Devices, Faculty of Medical
Engineering, University Politehnica of Bucharest, Polizu Street, No 1-7, RO-011061m Bucharest, Romania;
3
Materials Science, University Politehnica of Bucharest, 1–7 Polizu Street, 011061 Bucharest, Romania; 4Microbiology
Immunology Department, Faculty of Biology, University of Bucharest, 1–3 Portocalilor Lane, Sector 5, 77206
Bucharest, Romania
This study aimed to prepare a biocompatible and antimicrobial mixture of albumin-collagen-magnetic nanoparticles
able to improve tissue healing. The collagen gel was mixed with albumin and functionalized magnetite nanoparticles.
The resulting gel was cross-linked with glutaraldehide and further lyophilized. The obtained nanostructured
biomaterials were characterized by SEM, TEM, SAED, IR, AFM, and in vitro and in vivo assays were performed for
proving their biological effects. The results indicated that the obtained nanostructured biomaterials improve the wound
healing and inhibit the microbial colonization of the wound, making them suitable for medical usage. Cell culture
experiments revealed an increased cytocompatibility of these biomaterials compared to control as indicated by human
skin fibroblasts’ adhesion and proliferation, an equal ratio of collagen and albumin being the best choice for cell
growth. Thus, the unique physico-chemical properties of these scaffolds together with the superior cell response
recommend them for skin regenerative medicine applications.
92
MEDICAL SURFACES BASED ON ZnO AND ORANGE OIL FOR ANTI-INFECTIVE THERAPY
Anca Apostol1, Daniela Cabuzu1, Elena Viorica Catrina1, Andreea Carja1, Kanabi Kamaran1, Rebecca Alexandra Puiu1,
Georgeta Voicu2, Alexandra Elena Oprea2, Alina Maria Holban2,3, Carmen Mariana Chifiriuc3, Florin Iordache4,
Alexandru Mihai Grumezescu2
1
University of Bucharest, 1–3 Portocalilor Lane, Sector 5, 77206 Bucharest, Romania; 4Institute of Cellular Biology and
Hasdeu, Bucharest 050568, Romania
This work present a novel nano-modified prosthetic device surface with anti-infective properties, based on
functionalized zinc oxide nanostructures and orange oil. Medical nanosurfaces were characterized by TEM, SEM,
SAED, DTA-TG, XRD, and FT-IR. For the quantitative measurement of biofilm-embedded microbial cells, a culturebased method for viable cell count was used. The optimized medical surfaces proved to be more resistant to microbial
colonization and biofilm formation compared to the uncoated controls. These results corelated with the in vivo
biodistribution open new directions for the design of nanosurfaces for medical purposes.
CHITOSAN-METHYLCELLULOSE HYBRID AS A MOIST SKIN REGENERATION MATRIX
Azreena Mastora , Siti Hajar Kasima, Nurul Awanis Johana, Norhidayah Abua, Abdul Yazid Abdul Manafa, Siti Farhana
Hishama, Kartini Noorsala, Ahmad Hazri Ab Rashidb
a
Biomedical Materials Section, Advanced Materials Research Centre (AMREC), Standards and Industrial Research
Institute Malaysia (SIRIM) Berhad, Lot 34, Jalan Hi-Tech 2/3, Kulim Hi-Tech Park, 09000 Kulim, Kedah, Malaysia;
b
Industrial Biotechnology Research Centre, Standards and Industrial Research Institute Malaysia (SIRIM) Berhad,
No.1, Persiaran Dato’ Menteri, Section 2, P.O. Box 7035, 40700 Shah Alam, Selangor, Malaysia
In this research, methylcellulose which is commonly used in contact lens and artificial tears was mixed with
chitosan. This approach is intended to enhance the ability of porous chitosan scaffold as a skin regeneration matrix in
retaining water to assist new cell regeneration along the wound healing process. Pure chitosan and variants with 10%,
20% and 30% of methylcellulose solutions were fabricated into porous matrix via freeze drying process. Investigation
using Fourier Transformed Infrared Spectroscopy (FT-IR) showed no appearance of new functional group, proving that
only physical mixing interaction occurred between chitosan and methylcellulose. Morphology study via scanning
electron microscope (SEM) depicted interconnecting pores within the matrix, providing spaces for new cell migration.
The dimension of major pores are around 100-200μm, giving enough room space for new cell attachment. Interestingly,
water uptake study showed negligible effect on the addition of methylcellulose towards chitosan. However, dehydration
test proved that methylcellulose has prolonged the water retention time up to 5 days compared to pure chitosan matrix.
In vitro enzymatic biodegradation study results showed the potential of this hybrid porous matrix as a self-degraded
skin regeneration template. This is supported with in vitro cell studies that showed promising cell viability after
treatment with this hybrid matrix.
93
EFFECT OF MAGNETIC NANOPARTICLES DISTRIBUTION IN TUMORAL CELL FOR
HYPERTHERMIA
Samir Taloub1, Farida Hobar1, Iordana Astefanoaei2, Ioan Dumitru2, Ovidiu Florin Caltun2
1Laboratory of Microsystems and Instrumentations (LMI), Electronic Department, Faculty of Science and Technology,
Constantine 1 University, Constantine, 25000, Algeria; 2Laboratory of Magnetic Materials for Technological
Applications (LMAT), Faculty of Physics, Alexandru Ioan Cuza University, Bd. Carol I nr. 11 700506 Iasi Romania;
[email protected] / [email protected] / [email protected] / [email protected] / caltun@ uaic.ro
The knowledge of temperature profiles in space and time throughout tumor tissues is a crucial step in
hyperthermia for cancer treatment. Our study is focused on the spatial-temporal analysis of temperature generated by
magnetic nanoparticles (MNPs) placed in tumoral tissue. In order to predict the temperature distribution during the
treatment, a numerical FEM model of the system consisting of nanoparticles as heating source: i) uniform distributed
nanoparticles (arrays), ii) aggregated clusters, iii) randomly distributed MNPs in tumoral cell, has been simulated
through the Pennes’s model using COMSOL Multiphysics software. Several simulations have been carried out with
function of interparticle distance, particle size distubution, and surface coating effect, a comparison of more realistic
case with clusters and random configuration was accomplished.
Keywords: Magnetic nanoparticles, hyperthermia, arrays, clusters, random, COMSOL Multiphysics.
Figure 1: The 3D spatial temperature distribution for MNPs considered constant rate heating
sources: a) arrays and b) randomly distributed in tumoral cell, after 3μs from the beginning of heating
pro
cess.
SYNTHESIS OF Ni, Co DOPED ZrO2 NANOSTRUCTURES TEMPLATED BY TRITON X 100
Mihaela M. Trandafir1, Simona Șomăcescu2, Jose Calderon-Moreno2, Florentina Neațu1, Ștefan Neațu3, Mihaela Florea1
1
University of Bucharest, Faculty of Chemistry, Bucharest, Romania, 2”Ilie Murgulescu” Institute of Physical
Chemistry, Romanian Academy, Spl. Independentei 202, 060021, Bucharest, Romania, 3National Institute of Materials
Physics, 105bis Atomistilor Street, 077125, Bucharest, Romania
In recent years, due to the rise of the natural gas price and the wish for less dependency on natural gas import, the
production of synthetic natural gas (SNG) has attract considerable attention. SNG is produced via gasification of coal
that generates syngas, followed by subsequent methanation process, in which CO methanation is the key reaction. Ni
based catalysts are the most widely applied and studied methanation materials because of Ni high activity, selectivity,
and relatively low price. The present work focuses on the synthesis of Ni, Co doped ZrO2 nanostructured materials by a
self-assembling method using Triton X100 non-ionic surfactant as template, with low level of environmental pollution.
CO methanation was carried out over Ni, Co doped ZrO2, and the durability of the catalysts was also investigated.
The sample calcined at 600 ºC exhibited the tetragonal phase with very small amount of NiO and CoO secondary
phases. In order to determine the chemical states and to quantify the elements present on the surface and their
quantification the XPS analysis was used. The characteristic binding energies for Zr3d, Ni2p and Co2p are typically
assigned to +4, 3+ and 2+ oxidation states, respectively. The deconvolution of the O1s photoelectron line shows a
surface chemistry with the main lattice bound component (O 2-) as well as the OH groups and water confined on the
outermost surface layer. The preliminary results obtained in CO methanation show that this material represent also a
good candidate for anode in PEMFC applications.
94
This work was supported by a grant of Partnerships in priority S&T domains Program (PNII), MEN– UEFISCDI,
project number 56/2014.
VITROCERAMIC INTERFACE DEPOSITED ON TITANIUM SUBSTRATE BY PULSED LASER
DEPOSITION METHOD (PLD)
Georgeta Voicu1, Dana Miu2, Ionuţ Dogaru1, Sorin Ion Jinga1
1 Politehnica University of Bucharest, Faculty of Applied Chemistry and Material Science; 1-7 Gh Polizu Str., 011061
Bucharest, Romania; 2 National Institute for Laser, Plasma and Radiation Physics-INFLPR, Bucharest-Magurele,
Romania
Pulsed laser deposition (PLD) method was used to obtain biovitoceram thin film coatings on titanium substrates.
The composition of vitroceram targets was from SiO 2 – CaO – P2O5 – (CaF2) systems. The vitroceram masses were
obtained by sol-gel method.
The depositions were performed in oxygen atmosphere (100 mTorr) and substrates were heating at 400°C.
The PLD films deposited were analysed by different experimental techniques: X-ray diffraction, scanning electron
microscopy (SEM, EDX) and the transmission (HRTM, SAED) and infra-red spectroscopy coupled with optical
microscopy. Also, they were tested biologically tested by in-vitro cell culture and determining the contact angle.
The in vitro bioevaluation results are accounting for a high biocompatibilty of the obtained materials demonstrating
their potential use for biomedical applications.
PREPARATION AND CHARACTERIZATION OF UNDOPED AND DOPED ZnO WITH COBALT FOR
ANTIMICROBIAL USE
Georgeta Voicu1, Angelica Oprea (Stoica)1, Ecaterina Andronescu1, Cristina Daniela Ghitulica1, Alexandru Mihai
Grumezescu1, Mariana Carmen Chifiruc2
1
Politehnica University of Bucharest, Faculty of Applied Chemistry and Material Science; 1-7 Gh Polizu Str., 011061
Bucharest, Romania; 2 University of Bucharest, Faculty of Biology, Microbiology Immunology Department, Aleea
Portocalelor no 1-3, 060101 Bucharest, Romania
The objective of the study was to carry out the synthesis by sol-gel method and of undoped and doped ZnO with
cobalt, in different concentrations (0.5-5%), using as stabilizer monoethanol amine (MEA).
The raw materials used were chemically pure. This was used zinc acetate as a precursor of zinc oxide and copper
sulphate as a precursor copper oxide respectively. As a dispersing medium was utilised ethanol and for hydrolysis was
added water. Synthesis was performed with the cobalt-doped ZnO in different proportions: 0%, 0.5%, 1%, 1.5%, 2%
and 5%. Molar ratio ZnO: MEA = 1: 2 was used. The dry gel was thermal treated at 500°C/5h, respectively 1100°C/30
min. The undoped and doped ZnO with Co 2+ thermal treated at 500°C/5h, respectively 1100°C/30 min was wurtzite
type hexagonal structure. It was noted that doping with different concentrations of Co 2+ caused change lattice
parameters and crystallite size, which proves its successful interleaving ZnO lattice.
From the point of view of the microstructure, the thermal treatment 1100°C/30 min led to a higher degree of
compactness of the ZnO granules. At 500°C/5h formed polyhedral particle agglomerations which form of aggregates of
nanometric sizes over 1μm. It was also observed that both samples thermal treated at 500°C/5h and 1100°C/30 min,
doping with Co2+ has increased particle size; the particle size increased with increasing concentration of Co 2+. From the
biological point of view, quantitative analysis of antimicrobial activity have shown that most of the materials tested at
different concentrations inhibited the ability of the strains of B. subtilis, E. coli, S. aureus, Enterococcus faecalis to
colonize the inert substrate and can be used in the design of new strategies antimicrobial.
Acknowledgement:
The work has been funded by the Sectoral Operational Programme Human Resources Development 2007-2013 of
the Ministry of European Funds through the Financial Agreement POSDRU/159/1.5/S/134398.
95
MICROFLUIDIC SYNTHESIS OF CHLOROPHYLL EXTRACTION –LOADED PCL COMPOSITE
MICROPARTICLES
Ching-Ju Hsiao1, Mao-Chen Huang1, Pei-Fan Chen1, Ruo-Yun Chung1, Jiun-Hua Chou1, Chih-Hui Yang1*, KengShiang Huang2*, Jei-Fu Shaw1*
1
Dept. of Biological Science & Technology, I-Shou University, Taiwan; 2Dept. of School of Chinese Medicine for Post
Baccalaureate, I-Shou University, Taiwan; Email: [email protected] ; [email protected]
Chlorophyll has many benefits for human body. It is known to improve the health of the circulatory, digestive,
immune and detoxification systems of the body. However, Chl can’t be preserved at the environment of high
temperature and light exposure for a long time due to it is chemical structure is easily degradable. This characteristic
causes that human body is difficult to absorb Chl effective components. In order to solve this problem, we utilize
polycaprolactone (PCL) polymer encapsulation technology to increase the stability of Chl . In particular, we also
established a microfluidic platform provide the control of composite beads diameter. The new composite beads is
potential to be a health food. Result show that Chl effective components via the microfludic platform can be
encapsulated effectively and still preserve its effective components.
Keywords: Chlorophyll , PCL, PVA, microfluidic
References
[1] Mario, G.F; Joshua, B. Digestion, absorption, and cancer preventative activity of dietary chlorophyll derivatives.
Nutrition Research, 2007, 27, 1-12 1.
[2] Ching, Y.H.; Yue, H.C.; Pi, Y.C.; Chiao, M.C.; Ling, L.H.; Shene, P.H. Naturally occurring chlorophyll
derivatives inhibit aflatoxin B1-DNA adduct formation in hepatoma cells. Mutation Research. 2008, 657, 98-104.
[3] Rabie, K.; Erin, G.; Lin, L.; Usha, T. Quantitative analysis and free-radical-scavenging activity of
chlorophyll,phytic acid, and condensed tannins in canola. Food Chemistry. 2010, 122, 1266-1272.
[4] Toru, O.; Yubi, T.; Misaki, I.; Takanori, F.; Natsuki, T.; Satoshi, I. Radical reaction of chlorophyll derivatives
triggered by AIBN. Tetrahedron Letters. 2014, 55, 725-727.
[5] Tammie, J.M.; Michael, T.S.; Margaret, P.M.; Cliff, B.P.; Jerry, D.H.; Roderick, H.D.; David, E.W.; George,
S.B. Cancer chemoprevention by dietary chlorophylls: A 12,000-animal dose–dose matrix biomarker and tumor study.
Food and Chemical Toxicology. 2012, 50, 341-352.
[6] Tirthartha, C.; Sudipta, B.; Amit, K.D.; Mrinal, K.M. A structurally novel hemopexin fold protein of rice plays
role in chlorophyll degradation. Biochemical and Biophysical Research Communications. 2012, 420, 862-868.
[7] Chih, H.Y.; Keng, S.H.; Alexandru, M.G.; Chih, Y.W.; Shian, C.T.; Szu, Y.C.; Yu, H.L.; Yung, S.L.Synthesis of
uniform poly(d,l-lactide) and poly(d,l-lactide-co-glycolide) microspheres using a microfluidic chip for comparison.
Electrophoresis. 2013, 35, 2-3.
[8] Keng, S.H.; Chih, H.Y.; Chao, P.K.; Ming, D.K.; Alexandru, M.G.; Yung, S.L.; Chih, Y.W. Synthesis of
uniform core-shell gelatin-alginate microparticles as intestine-released oral delivery drug carrier. Electrophoresis. 2013,
35, 330-336.
[9] Yung, S.L.; Chih, H.Y.; Chin, Y.W.; Alexandru, M.G.; Chih, Y.W.; Wan, C.H.; Szu, Y.C.; Keng, S.H. A
microfluidic chip using phenol formaldehyde resin for uniform-sized polycaprolactone and chitosan microparticles
generation. Molecules. 2013, 18, 6521-6531
DRUG RELEASE KINETICS FROM CARBOXYMETHYLCELLULOSE-BACTERIAL CELLULOSE
COMPOSITE FILMS
Juncu Gheorghe, Anicuta Stoica-Guzun*, Marta Stroescu, Gabriela Isopencu, Sorin Ion Jinga
Faculty of Applied Chemistry, University Politehnica of Bucharest, Romania; [email protected]
(corresponding author); [email protected] (presenting author)
Bacterial cellulose is already known as a versatile biopolymer used as reinforced material in many composites which
have applications in pharamaceutical and biomedical field. The aim of this study is to investigate the ibuprofen sodium
salt release from carboxymethylcellulose-bacterial cellulose (CMC-BC) composite films and to develop a model to
predict the release drug kinetics. Different ratios of CMC-BC were used for composite films obtaining. Fourier
transformed infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were applied to characterize these films. Taking
into account the hydrophilic character of both biopolymers used, swelling equilibrium in different pH-media (simulate
different physiological condition) was also studied. A mathematical model considering the swelling of composite films
was proposed. The numerical results of the model confirm the observed experimental behaviour. The composite films
CMC-BC could be used for drug delivery systems.
96
MECHANICAL AND ELECTROCHEMICAL PROPERTIES OF TITANIUM IMPLANTS COATED WITH
HARD COATINGS BY PLD
G. Socol1, D. Craciun1, V. Craciun1, G. Dorcioman1, D. Cristea2, M. Stoicanescu2, L. Floroioan3, M. Badea3, D.
Pantelica4, P. Ionescu4
1
National Institute for Lasers, Plasma and Radiation Physics, Măgurele, Romania; 2Materials Science Department,
Transilvania University, Brasov, Romania; 3 Fac Elect Engn & Comp Sci,Transilvania Univ Brasov, Brasov, Romania;
4
Horia Hulubei National Institute for Physics and Nuclear Engineering, Măgurele, Romania
In order to improve the mechanical and chemical stability of the titanium implants in the biological environment we
coated their surface with different hard (ZrN, ZrC, TiN and SiC) coatings by pulsed laser deposition (PLD) technique.
The thin films were deposited at room temperature using a KrF laser under CH 4 or N2 atmosphere. After deposition, the
mechanical properties of the films were characterized by nanoindentation and scratch tests. The structural properties
and mass density were obtained from grazing incidence X-ray diffraction and X-ray reflectivity investigations. The
chemical composition was measured by Rutherford backscattering spectrometry (RBS). Electrochemical measurements
involving corrosion and electrochemical impedance spectroscopy studies were carried out in physiological solutions in
order to investigate the corrosion behavior of the medical titanium, bare or covered with TiN, ZrN and ZrC thin films
and to compare their performance. The dependence of their corrosion resistance parameters on time was inferred and
the involved electrochemical parameters were also estimated by fitting the experimental data via equivalent electric
circuits. The obtained results support the application of TiN, ZrN and ZrC coatings for the development of advanced
highly stable implants and prostheses that cannot be affected by corrosion.
THE EFFECT OF VISIBLE LIGHT ON GOLD NANOPARTICLES AND SOME BIOEFFECTS ON
ENVIRONMENTAL FUNGI
Maria Andries1, Daniela A. Pricop1, Lacramioara Oprica2 and Felicia Iacomi1
2
Faculty of Physics, University “Alexandru Ioan Cuza”, Carol I Bd., No. 11, 700506, Iasi, Romania; Faculty of
Biology, University “Alexandru Ioan Cuza”, Carol I Bd., No. 11, 700506, Iasi, Romania
1
For this study were synthesized gold nanoparticles (AuNPs) in sodium citrate, in alkaline conditions at a
temperature of 85 °C and under magnetic stirring. Equal volumes of such prepared colloidal suspension were exposed in
visible light at different wavelengths for 90min at constant room temperature. The UV-Vis spectra have revealed an
increase in the intensity of the absorption band characteristic to AuNPs following light exposure due to the effect of
surface plasmon resonance (SPR). This effect is explained by interband transition of the electrons in surface layer of
metallic gold. The AuNPs ability of photocatalytic reduction monitored by manipulating wavelengths of incident light
was tested on environmental fungi cellulolytic fungi, with a role in the degradation of cellulosic waste. The study
analyzes the comparative fungal response to AuNP supply in their culture medium, with focus on protein synthesis and
peroxidase type enzymes activity aiming to design possible biotechnological tool for controlled degrading of wood
waste.
GLIAL CELLS GROWTH ON NANOFIBROUS POLYMER SCAFFOLD WITH MAGNETIC PARTICLES
INSERTION FOR NEURITE SUPORT AND PREFERENTIAL GROWTH DIRECTION
a
S. Vulpea, Anca Dumitrua, A. Radua, Adela Banciub, D. D. Banciub, Beatrice Mihaela Radub,c
Faculty of Physics, University of Bucharest, Romania; bFaculty of Biology, University of Bucharest, Romania;
c
Department of Neurology and Movement Sciences, University of Verona, Italy
Glial cells growth on specific support is an important factor that affects nutrition and neuronal cell signal.
Continuous efforts are made to exploit the specific ability of glial cells in different therapy. Therefore, glial cells are
used as a therapeutic agent for the spinal cord trauma.
The use of nanofibrous polymer scaffold with magnetic particles insertion may achieve a scaffold with the ability to
be remotely controlled and modulated in terms of 3D architecture. This is a useful approach in the treatment of central
nervous system because the therapeutic agent can be introduced through very small holes in the polymer without
mechanical stress. In the absence of such approach, scaffold medical devices would do more harm by affecting the
surrounding of sensitive neural tissue.
The paper aims to investigate the glial cells growth on nanofibrous polymer scaffold with magnetic particles
insertion. The ability of nanofibrous polymer scaffold with magnetic particles insertion to provide a modular support
for glial cells growth which can be magnetic modulated can be exploited for neuronal growth in preferential direction.
The nanofibrous polymer scaffold has been characterized using X-ray diffraction, scanning electron microscopy (SEM)
and vibration sample magnetometery. The glial cells growth was monitored using SEM and optical fluorescence
microscopy.
97
STUDY OF GLIAL CELLS ADHESIONS ON BIOPOLYMER FIBRES
a
Adela Banciub, S. Vulpea, Anca Dumitrua, A. Radua, C. Berbecarua, D. D. Banciub, Beatrice Mihaela Radub,c
Faculty of Physics, University of Bucharest, Romania; bFaculty of Biology, University of Bucharest, Romania;
c
Department of Neurology and Movement Sciences, University of Verona, Italy
Glial cells, the most abundant cell types in the central nervous system, are important to neuronal metabolism.
The development of biopolymers fibres by the electrospinning technique has gained considerable interest for neural
tissue engineering applications. Three dimensional (3D) fibrous scaffolds which can provide guidance for cell migration
and directional axonal regeneration across the glial scar and lesion site in nervous system is a promising strategy in
tissue engineering. Increased biocompatibility is required for the glial cell growth on 3D biopolymer scaffold.
This research aims to investigate the growth of glial cells on both hydrophobic and hydrophilic 3D biopolymer
scaffold. The growth of glial cell on different biopolymer scaffold was investigated in vitro and monitored by scanning
electron microscopy and fluorescence microscopy.
The results showed a good adhesion of glial cell on both hydrophobic and hydrophilic 3D biopolymer scaffold.
However, the hydrophilic 3D biopolymer scaffold favours a better growth of glial cell.
NANOCARRIER DELIVERY SYSTEMS BASED ON CHITOSAN AND ANTIOXIDANTS
Cornelia Nichita1,2, Radu Tamaian2,3 Georgeta Neagu1, Ioan-Daniel Stamatin4
National Institute for Chemical-Pharmaceutical Research and Development, 112 Vitan Street, 031299, Bucharest,
Romania, Phone: +4021.321.62.60, Fax: + 4021.322.29.17, e-mail: [email protected]; 2 University of
Bucharest, Faculty of Physics, 3Nano-SAE Research Centre PO Box MG-38, Bucharest-Magurele, Romania; 3 National
Institute for Research and Development for Cryogenic and Isotopic Technologies – ICSI Rm. Vâlcea, 4th Uzinei Street,
Râmnicu Vâlcea, VL, Romania; 4 SC BioLumiMedica SRL, 232-234th Șerban Vodă Street, Bucharest, Romania
1
In pharamaceutical design one of the most important challenge is design of nanocarriers for drug delivery with high
potential for molecular recognition to a target or/and to preserve structural integrity of the active principles such as
antioxidants. The aim is to improve therapeutical performances. In this respect, the study reports a nanocarrier between
chitosan and antioxidants, with controlled delivery and release mechanism. The encapsulation of antioxidants in the
nanocarrier system based chitosan raise to an increased solubility at gastrointestinal tract level, enhanced stability,
sustained delivery and protection from physical and chemical degradation. The experiments were performed a) in vitro:
the cytotoxicity at cellular level was detected by MTS 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide
assay, the antioxidant properties were studied using the chemiluminescence technique, DPPH(2,2-diphenyl-1picrylhydrazyl) free radical scavenging assay; b) and in silico: molecular docking. In addition DLS was used to measure
the hydrodynamic size and polydispersity index and UV-Vis reveal a series of properties such as spectral characteristcs
and encapsulation efficiency of nano-delivery systems.
STUDY OF THE STABILITY OF BSA/PEDOT:PSS MIXTURE SOLUTION AS PART OF BIOSENSING
DEVICES PLATFORM
1
O. Brîncoveanu1,2, A. Ioanid1, S. Iftimie1, M. Enachescu2, S.Antohe1
Faculty of Physics, University of Bucharest, 077125, Romania, 2 Center for Surface Science and Nanotechnology,
University Politehnica of Bucharest, 060042 Romania; Contact e-mail: [email protected]
Bovine serum albumin (BSA):poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) solutions
with the molar ratio 10:1 were prepared and deposited as thin film by spin-coating. Optical glasses covered with a thin
gold layer deposited by thermal vacuum evaporation were used as substrates. Optical investigations of
BSA:PEDOT:PSS solutions were performed for various concentration ratios, at room temperature. A slightly
dependence of optical absorption peaks intensity on concentration was observed. Moreover, thermogravimetric
characterization showed good stability in air and nitrogen atmosphere of BSA:PEDOT:PSS solution. Morphological
features of our Au/BSA:PEDOT:PSS fabricated samples were analyzed by atomic force microscopy (AFM) and
compared with individual Au layer and bi-layer Au/PEDOT:PSS structure.
Keywords: biosensors, BSA, PEDOT:PSS
Acknowledgement. The work has been funded by the Sectoral Operational Programme Human Resources
Development 2007-2013 of the Ministry of European Funds through the Financial Agreement
POSDRU/159/1.5/S/137750.
98
S5
Advances in surface science and engineering
Invited Papers
99
100
DEVELOPMENT OF PIEZOELECTRIC BASED SENSORS BY LASER ASSISTED DEPOSITION
TECHNIQUES
Fabio Di Pietrantonio
Inst. of Acoustics and Sensors, National Research Council, Rome, Italy
The increasing demand of sensors for food safety, security, biodefense and process industry gave rise to the
development of new approaches and technologies for the fabrication of piezoelectric based bio and chemical sensors
showing high performances, such as Surface Acoustic Waves (SAW) and Film Bulk Acoustic Resonators (FBARs)
sensors. These sensors show great potential to discriminate low concentrations of different volatile species providing
important advantages, like low cost, miniaturization, portability and high sensitivity. For the implementation of sensors,
piezoelectric devices need to be covered with interactive materials, such as polymers or biomolecules. However,
conventional deposition procedures present some issues concerning, in particular, the repeatability and the uniformity of
the coating layer. In order to overcome these problems, laser assisted deposition techniques, such as Laser Induced
Forward Transfer (LIFT) and Matrix Assisted Pulsed Laser Deposition (MAPLE) can be conveniently used. In this
context, the implementation of different types of bio and chemical sensors and the study of their performances in terms
of sensitivity, resolution and selectivity are presented and the capabilities and the advantages of these deposition
techniques are demonstrated.
DIELECTRIC SPECTROSCOPY OF POLAR NANOSTRUCTURED MATERIALS
1
F. Craciun1, N. D. Scarisoreanu2, R. Birjega2 and M. Dinescu2
CNR-ISC, Istituto dei Sistemi Complessi, Area della Ricerca di Roma-Tor Vergata, Via del Fosso del Cavaliere 100,
Roma, Italy, 2National Institute for Laser, Plasma and Radiation Physics, 077125, Magurele, Romania
Nanoscale inhomogeneities in polar materials have been intensively studied, since they can give rise to a wide range
of interesting phenomena like glassy behavior, huge dielectric susceptibility, non-ergodic behavior, memory effects [1]
etc.
Polar nanostructures with a certain degree of cooperativeness will be considered here. Random bonds, random fields
and quenched impurities are, in this case, the causes of “confinement”, instead of restricted geometry, as in the case of
isolated nanostructures.
Cooperative polar nanostructures can sometimes organize themselves in hierarchical structures, under the effects of
competition and randomness. A particularly interesting case is that of ferroelectric relaxors [1,2], which can be
described as ensembles of polar nanoregions in a cubic matrix. These nanostructures are not confined within the same
region or with the same strength at all temperatures, but they evolve. A slight size increase with temperature decreasing
has a dramatic impact on relaxation time distribution, which shifts towards smaller times and drags the material into a
zone of frozen degrees of freedom.
Every investigation technique can give a different picture of relaxors. Specifically, on the time scale of e.g. neutron
scattering (~10-12 s) the polar nanoregions appear static, but they behave as dynamic entities on smaller time scales. In
this case one can have a dynamic distribution of polar nanoregions and what is measured over the specific time scale is
an average spectrum. The cooperativeness bewteen the polar nanoregions is reflected into the non-exponential dynamic
of the relaxation.
Complex dielectric spectroscopy is a powerful technique used to reveal the dynamics of polar nanoregions and to
track their temperature evolution. It can cover a large dynamical range and provides information on the polar entities
reorientation, interactions, activation energies and relaxation frequencies.
Here we present results of low-signal measurements of the real and immaginary parts of the dielectric susceptibility,
in a frequency range 102 Hz < f< 106 Hz and for temperatures 100 K < T< 600 K, on materials with different types and
degrees of polar inhomogeneities. Dielectric resonance spectroscopy [3] has been also employed. Specifically, Ladoped Pb(Zr,Ti)O3 (PLZT) and Ba-doped (Na,Bi)TiO3 (BNBT) materials are considered. The effect of polar
nanoregions, including their coalescence and percolation in case of low doping [4] , on the dielectric response, has been
pursued. Effects of spatial confinement within 2D geometries and strain fields [5] on polar materials with different
degrees of inhomogeneities have been also considered.
1. F. Cordero, F. Craciun, A. Franco, D. Piazza, Galassi, Phys. Rev. Lett. 93, 097601 (2004).
2. F. Cordero, M. Corti, F. Craciun, C. Galassi, D. Piazza and F. Tabak, Phys. Rev. B 71, 094112 (2005).
3. F. Craciun, Phys. Rev. B 81, 184111 (2010).
4. F. Craciun, C. Galassi and R. Birjega, J. Appl. Phys. 112, 124106 (2012).
5. N. D. Scarisoreanu, F. Craciun, R. Birjega, A. Andrei, V. Ion, R. F. Negrea, C. Ghica, M. Dinescu, J. Appl. Phys.
116, 074106 (2014).
101
102
Oral Presentations
SURFACE MODIFICATION OF PMMA FOILS USING AN ATMOSPHERIC PRESSURE PLASMA JET IN
PRESENCE OF WATER VAPORS
T. Acsente, M.D. Ionita, M. Teodorescu, V. Marascu, G. Dinescu
National Institute for Laser, Plasma and Radiation Physics, Atomistilor 409. str., Bucharest-Magurele, Romania;
[email protected]
We report on modification of polymethyl methacrylate (PMMA) foil surfaces using a non-thermal atmospheric
pressure plasma jet generated by a discharge with bare electrode (DBE). The main goal of this work is to increase the
wettability of the PMMA foils. The discharge is maintained by a 13.56 MHz power supply operated at a constant
applied power (15W), the working gas being either dry or water humidified Ar. The treatments of the polymeric
samples are performed by scanning their surface with the plasma jet using an X-Y translation table. Dry Ar plasma
treatments are performed with different exposure durations (increasing the number of scans). Humid Ar plasma
treatments are performed at different contents of water vapors in the discharge, the duration of the treatment being fixed
(one scan). The effects of plasma treatments are evaluated using water contact angle (WCA) measurements, atomic
force microscopy (AFM), and Fourier transform infrared (FTIR) spectroscopy. The untreated PMMA surfaces present a
specific WCA of 80O and a roughness (RMS) of 25nm. The lowest value of WCA (35O) is obtained using humid Ar
plasma, the RMS value remaining practically unchanged (27nm). A similar increase of the PMMA foils wettability is
obtained and after five scans with dry Ar plasma jet, the RMS increasing up to 32 nm. FTIR investigations prove that
both types of treatments produce similar chemical changes on the PMMA samples surfaces. The time preservation of
the hydrophilic behavior is identical for both types of treatments, the WCA value recovering to that of the untreated
PMMA sample after 20 days.
In conclusion, proper adjustment of the water quantity in the atmospheric pressure plasma jet leads to optimisation
of PMMA foils treatment: a minimum value of WCA is obtained while the sample surface is only slightly roughened.
Still, the treatments must be performed immediately before utilization of the PMMA components.
103
COMMON-PATH SPECTRAL INTERFEROMETER FOR REAL-TIME OBSERVATION OF
ULTRASHORT LASER INDUCED OPTICAL BREAKDOWN IN TRANSPARENT DIELECTRICS
Cristian Sarpe1*, Thomas Winkler1, Lasse Haahr-Lillevang2, Nikolai Jelzow1, Nadine Götte1, Bastian Zielinski1, Arne
Senftleben1, Peter Balling2 and Thomas Baumert1
1
University of Kassel, Institute of Physics, Kassel, Germany, *corresponding author: [email protected]; 2Aarhus
University, Department of Physics and Astronomy, Aarhus, Denmark,
Laser processing of transparent dielectric materials by using ultrashort laser pulses is widely used in scientific
laboratories and for industrial mass production. Structures with a resolution below micrometer can be now produced in
almost any transparent medium. In previous studies we have shown that temporally tailored ultrashort laser pulses are
suitable for robust manipulation of optical breakdown. The first step in laser ablation of high bandgap materials is the
generation of a high density free electron plasma. By using trains of pulses generated using a liquid crystal modulator
pulse shaper the precision of femtosecond-laser machining results in microstructures one order of magnitude below the
optical diffraction limit [1-3]. The explanation for this consists in the way in which the temporally asymetric pulses
address the two ionization mechanisms (multiphoton ionization and electron-electron impact ionization) through which
the free electrons are generated. Here we present our studies to investigate the early-time dynamics of the optical
breakdown by using a robust spectral interference technique with an enlarged temporal measurement window [4]. The
phase shift between a reference and a probe pulse produced in a common-path interferometer gives accurate
information about the density of the free electrons and its dependence on different parameters of the shaped pulses.
Recently we improved our experimental setup in order to record the spectral interference on a one-dimensional slice
through the interection area to also reveal the spatial distribution of the free electron plasma.
[1] L. Englert et al., Opt. Expr. 15, 17855 (2007), [2] L. Englert et al. JLA 24, 042002 (2012), [3] M. Wollenhaupt et
al., JLMN (2009) 4 (3) 144-151, [4] C. Sarpe et al., NJP 14, 075021 (2012)
MOLECULAR POLARIZABILITY NEAR METAL SURFACES
Cristian M. Teodorescu
National Institute of Materials Physics, Atomiştilor 105b, 077125 Măgurele-Ilfov, Romania
A basic electrostatic mechanism (the formation of image dipoles in a metal surface) will be proposed, yielding a
consistent increase (by several orders of magnitude) of the molecular polarizability near metal surfaces. This
mechanism is proposed as an alternative to assess the Surface Enhanced Raman Scattering (SERS) effect. I will discuss,
in the framework of this model, some peculiarities of SERS: (i) the occurence of this effect especially when one uses
noble metal surfaces (Au, Ag); (ii) the consistent increase of SERS when the metal surface is nanostructured; (iii) the
observed strong dependencies of the SERS amplification factors on the distances between molecules and metal
surfaces; (iv) the observed E4 dependence (E = electric field of the incoming electromagnetic radiation); (v) the
observed shift between the energy of the maximal SERS effect and the energy of the surface plasmons. The treatment of
the SERS effect by this model will result in a consistent formula of the SERS amplification factor as function on the
distance between the molecule and the metal substrate, the polarizability of the free molecule, the frequency of the
exciting radiation, the plasma frequency of the metal, and the temperature [1]. In a second part of the talk, I will analyze
within the same framework the case of electrically polarizable media, with evidence of spontaneous polarization for
some molecules, and for hysteretic polarization behaviour of single molecules. I will also discuss some puzzling
ferroelectric hysteresis curves observed experimentally and propose a way to synthesize ‘artificial’ ferroelectrics.
[1] C.M. Teodorescu, Image molecular dipoles in Surface Enhanced Raman Scattering, Phys. Chem. Chem. Phys.,
accepted (2015). DOI: 10.1039/C4CP05082G.
104
EFFECTS OF Sr ENRICHEMENT AND OXYGEN VACANCIES ON THE ELECTRONIC STRUCTURE OF
La1-xSrxMnO3 (001) SURFACE
D.G. Popescu1, M. Husanu1*
1National Institute of Materials Physics, Atomistilor 105b, 077125 Magurele-Ilfov, Romania.
Half metal, La1-xSrxMnO3 (LSMO), x=0.3 perovskite oxide has been grown on a SrTiO3 buffer by pulsed laser
deposition. Using a combination of photoelectron spectroscopy and ab-initio calculations, we show that the surface
layer results in Sr-enrichement to x=0.4 during the growth procedure. The implications of the increased hole doping on
the magnetic properties of the surface are examined in connection with the spin-dependent transport applications. We
obtain that oxygen vacancies are more likely to appear in the MnO 2 layers than in the (La,Sr)O ones leading to a shift of
the valence band and core levels towards higher binding energies and destroy its half metallic character.
Angle-resolved photoemission in conjuntion with theoretical band structure calculations allows us to clearly
identify the surface states associated to the eg electrons near the Fermi level, having in-plane symmetry.
FIRST PRINCIPLES CALCULATIONS OF PHENOL ADSORPTION ON PRISTINE AND
HYDROGENATED Al-DOPED BORON NITRIDE SHEET.
Yuliana Elizabeth Avila Alvarado1, Gregorio Hernández Cocoletzi2, María Teresa Romero de la Cruz1
1
Universidad Autónoma de Coahuila, 2Benemérita Universidad Autónoma de Puebla
First principles total energy calculations have been performed to study the structural and electronic properties of
phenol adsorption on pristine (BN) and hydrogenated Al-doped (Al-BN) boron nitride sheet. Calculations have been
made within the periodic density functional theory as implemented in the PWscf code of the QUANTUM ESPRESSO
package. The exchange-correlation energies were treated with the generalized gradient approximation (GGA). Electronion interactions were modeled with pseudopotentials. The electron states were expanded in plane waves with an energy
cutoff of 30 Ry. A supercell with 4x4 periodicity was used. In addition, the non-local correlation energies were
accounted using the van der Waals density functional (vdW-DF) method. The most stable configuration for BN-phenol
systems was the parallel orientation onto stacked site, in this case the molecule was placed upon N atom. For
hydrogenated Al-BN phenol system, Al doping induces a strong interaction between the phenol molecule and doped
layer yielding chemical adsorption. Also the electronic band structure was calculated for the most stable configurations.
The BN-phenol system keeps the insulating property with an indirect band gap approximately 4.6 eV. These results are
in good agreement with previous reported results. Hydrogenated Al-BN system shows a metallic behavior.
EVIDENCE OF STRUCTURAL HETEROGENEITIES IN ZINC OXIDE THIN FILMS GROWN BY PULSED
LASER DEPOSITION
M. Nistor1, J. Perrière2,3, C. Hebert2,3, N. Jedrecy2,3, W. Seiler4, O. Zanellato4, X. Portier5, R. Perez-Casero6, E. Millon7
1
National Institute for Lasers, Plasma and Radiation Physics, L22, P.O.Box MG-36, 77125 Bucharest, Romania;
2
Sorbonne Universités, UPMC Univ Paris 06, UMR 7588, INSP, 4 Place Jussieu, F-75005 Paris, France ; 3CNRS, UMR
7588, INSP, 4 Place Jussieu, F-75005 Paris, France ; 4PIMM, UMR CNRS 8006 Arts et Métiers ParisTech, 151
Boulevard de l’Hopital, 75013 Paris, France ; 5CIMAP, CEA/CNRS UMR 6252/ENSICAEN/UCBN, 6 Boulevard du
Maréchal Juin, 14050 Caen Cedex, France ; 6Departamento de Fisica Aplicada, Facultad de Ciencas, Universidad
Autonoma de Madrid, C/Francisco Tomas y Valiente 7, 28049 Madrid, Spain ; 7Univ. Orleans, UMR CNRS 7344,
GREMI, 14 Rue Issoudun, F-45067 Orleans 2, France
Pulsed laser deposition is a well known method for growing complex oxide thin films presenting a wide range of
functional properties. A limitation of this method for industrial applications is the very anisotropic expansion dynamics
of the plasma plume which induces difficulties to grow films with homogeneous thickness and composition on a large
scale. The specific aspect of the crystalline uniformity has not been investigated in detail, despite its important role on
oxide films properties. In this work, the crystalline parameters and the texture of ZnO films are studied as a function of
position with respect to the central axis of the plasma plume [1]. We demonstrate the existence of large structural nonuniformities in the films. Indeed, the distribution of crystallite orientations drastically depends on the position with
respect to the plume axis, i.e. on the oblique incidence of the ablated species. The origin of these non-uniformities, in
particular the unexpected tilted orientation of the ZnO c-axis may be attributed to the combined effects of the oblique
incidence and of the ratio between oxygen and zinc fluxes reaching the surface of the growing film. [1] J. Perrière, C.
Hebert, N. Jedrecy, W. Seiler, O. Zanellato, X. Portier, R. Perez-Casero, E. Millon, and M. Nistor, J. Appl. Phys. 116,
123502 (2014)
105
ATOMIC FORCE MICROSCOPY STUDY OF POLYETHYENE GLYCOL POLYCAPROLACTONE
METHYL ETHER COPOLYMER COATINGS OBTAINED BY MATRIX ASSISTED PULSED LASER
EVAPORATION
S. Brajnicov1, L. Rusen1, M. Filipescu1, N. L. Dumitrescu1,2, I. Tirca1,2, M. Dinescu1 and V. Dinca1
National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Street, PO Box MG-16, Zip RO-077125,
Magurele, Bucharest, Romania; 2University of Craiova, Faculty of Mathematics and Natural Sciences, RO-200585,
Craiova, Romania
1
Copolymers are widely used for creating bio-interfaces used for in vitro studies. Controlling the bio-interface
physical and chemical characteristics is an important factor within bio-applications field. In the last years, lasers based
methods are known as suitable tools for creating surfaces for biological studies. In this work, we study the influence of
various parameters in obtaining functional coatings of PEG-PCL Me coatings by matrix-assisted pulsed laser
evaporation (MAPLE). Different parameters, such as laser fluence (0.2 - 0.9 J/cm2), number of pulses target
composition (0.5-1.5wt.%) and solvent type were used for obtaining polymeric coatings. Their morphological
characteristics were analyzed by Atomic force microscopy (AFM) technique and correlated with the deposition
parameters used. It is shown that the homogeneity, density and the roughness of the coatings are related both to laser
deposition parameters but also to target composition and matrix type. By increasing laser fluence roughness of the
samples increased and various morphological features such as droplets appears on the surface of the coatings. Changing
the matrix implies variation in surface features from smooth to high roughness or even the cracks or irregular island
structures. By the MAPLE ability to change surface coating morphology, an important step in creating functional and
tunable bio-interfaces can be envisaged.
Acknowledgments
The research leading to these results has received funding from the Romanian Ministry of National Education,
CNCS – UEFISCDI, under the project PN-II-PT-PCCA 239/2014
106
EFFECT OF LOW TEMPERATURE OXYGEN PLASMA TREATMENT ON THE WETTING PROPERTY
OF SELF-ASSEMBLED POLYMER SPHERES
N. Predaa*, I. Zguraa**, M. Socola, A. Evanghelidisa,b, C. Floricaa, A. Costasa,b, M. Enculescua, and I. Enculescua
a
National Institute of Materials Physics, Magurele, Bucharest, P.O. Box MG-7, 077125, Romania
b
Faculty of Physics, University of Bucharest, Bucharest-Magurele, P.O. Box MG-11, 077125, Romania
*
[email protected]; **[email protected]
One of the key factors in applications which deal with nanostructured materials is the control of their surface wetting
properties. Due to the fact that polymeric self-assembled sphere arrays can be used as substrates for the deposition of
semiconductor or metallic materials, they are particularly interesting for manipulating surface wettability. A powerful
tool for modifying the wettability of polymer surfaces is plasma treatment. In this context, the present study is focused
on the influence of a low temperature oxygen plasma treatment on the wettability of polymeric nanostructures surfaces.
The polymer spheres were prepared by the surfactant-free emulsion polymerization method, being further assembled by
dip-coating and electrospraying. The samples were investigated, before and after oxygen plasma treatment, by scanning
electron microscopy, atomic force microscopy and contact angle measurements. A strong dependence between the
polymer nanostructures surface wetting properties and their morphologies was put in evidence. Thus, using water or
ethanol as dispersion medium, the polymer spheres were assembled into hydrophilic colloidal crystals and hydrophobic
(or even superhydrophobic) complex spherical cage-like structures. By applying an oxygen plasma treatment, the
superhydrophobic polymer surface became hydrophilic. Such polymer spheres arrays with tuneable surface wettability
can have potential applications in different areas. Thus, by increasing the polymer surface free energy, an improvement
of the adhesion between the polymer substrate and a potential deposited material can be achieved. Furthermore, the
oxygen plasma treatment is responsible for the formation of the reactive sites on polymer surfaces, which can be used
for their functionalization with various chemical compounds.
COMPLEX TREATMENT TO MAKE NEW SURFACE FUNCTIONALIZATION OF SOME WOOL
TEXTILES
Maria Birzu1,2, Ligia Frunza2, Irina Zgura2, S. Frunza2, C.P. Ganea2, L. Diamandescu2, V.F. Cotorobai2
National Institute of Statistics, Bucharest, Romania; 2National Institute of Materials Physics, 077125 Magurele,
Romania
1
Wool is a natural fiber which is much used in industry for clothing and home. Functionalization of wool textiles is
necessary in order to improve the wettability and wicking properties.
In the present work, functionalization was performed by covering the chosen wool textiles with nanoparticles of
titanium dioxid. Two methods were applied: sol-gel (starting from titanium isopropoxide) and sputtering (with TiO 2 as
target). We have used our recent experience concerning TiO 2 deposition upon polyester textile materials [i, ii].
Before deposition the samples were cleaned in isopropilic alcohol and then shortly pretreated in oxygen plasma.
The complex characterization was performed either for the original samples and for the treated ones by several
investigations methods such as: optical microscopy visualization, FTIR, UV-vis spectroscopy, XPS, thermogravimetry,
XRD. Wetting properties were tested by sessile drop method under static conditions. Catalytic activity of TiO2
deposited samples was checked in the decomposition of methylene blue with a PCC2 (Ulvac Riko) apparatus.
We found that oxide particles are amorphous, the deposition represents ca. 8 wt%, the deposited layer cover rather
uniformly the whole fiber surface.
The oxide particles reacted mostly with the OH groups on the wool surface.
After deposition, the fabric samples change the wettability properties, one of the reasons being the additional
roughness introduced by the oxide nanoparticles.
Functionalization of the wool surface was in addition proven by alternating illumination/darkness experiments.
References
I. Zgura, S. Frunza, M. Enculescu, et al., Rom. J. Phys., in press 2015.
ii
I. Zgura, S. Frunza, L. Frunza, et al., Rom. Rep. Phys., accepted 2015.
i
107
SURFACE MORPHOLOGY AND WETTING PROPERTIES OF THIN LAYERED DOUBLE HYDROXIDES
FILMS PRODUCED BY LASER TECHNIQUES
A.Matei1, R. Birjega1, A.Vlad1, R.Zavoianu2. O.D.Pavel2, M.C. Corobea3, M. Dinescu1
1. National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Str., 077125 Bucharest, Magurele,
Romania; 2. University of Bucharest, Faculty of Chemistry, Department of Chemical Technology and Catalysis, 4-12
Regina Elisabeta Bd., Bucharest, Romania; 3. National R.&S. Institute for Chemistry and Petrochemistry, ICECHIM,
202 Splaiul Independentei Str., CP-35-274, 060021, Bucharest, Romania
Thin films of layered double hydroxides have been deposited by PLD (pulsed laser deposition). Pressed pellets of
Mg-Al or Zn-Al LDH (layered double hydroxides) were irradiated by laser light at 1064, 532 and 266 nm, with
fluencies in the range 1.5-3 J/cm2. Oriented thin films with good adherence, preserving the target stoichiometry were
obtained by laser deposition. The surface quality of the thin LDH films of different thickness deposited on silicon
substrates was investigated with scanning electron microscopy and atomic force microscopy. The surface wettability
was evidenced by contact angle and sliding angle measurements. The influence of the films surface morphology, on
their wetting capabilities, is presented and discussed. The ability to produce hydrophobic surface from unmodified MgAl or Zn-Al LDH targets by tailoring the surface morphology via deposition conditions was analyze in comparison with
thin films obtained from organo-LDH modified targets.
STUDY OF THE SOLVENTS INFLUENCE ON THE MORPHOLOGICAL AND CHEMICAL
CHARACTERISTICS OF HYDROXYAPATITE THIN FILMS DEPOSITED BY MAPLE
1
N. L. Dumitrescu1,2, I. Tirca1,2, A. Bonciu1,3, V. Marascu1,3,S. Brajnicov1 M. Dinescu1 and V. Dinca1,
National Institute for Laser, Plasma and Radiation Physics, RO-077125 Magurele, Bucharest, Romania, 2 University of
Craiova, Faculty of Mathematics and Natural Sciences, RO-200585, Craiova, Romania; 3University of Bucharest,
Hydroxyapatite ( HA) is a known major inorganic component of bones, being involved in osseointegration process.
Its biological function can be enhanced by modulating morphological characteristics. Within this context, in this paper
we used Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique to obtain HA coatings on various substrates
(e.g Si and Ti based alloys substrates).
The influence on the HA coatings morphology of different solvents or mixtures (e.g. Dimethyl Sulfoxide (DMSO),
chloroform) were studied and correlated to laser deposition parameters.
Morphological investigations were done by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy
(SEM). Contact angle measurements and FTIR measurements were used for determining the wetability and the
chemical integrity of the deposited coatings. Based on the results obtained, the optimal parameters in terms of laser
processing and matrix composition were determined.
Our preliminary results indicate that similar bone microstructure can be obtained by combining matrix characteristics
with laser deposition parameters.
Keywords: MAPLE, Hydroxyapatite (HA)
Acknowledgments: The research leading to these results has received funding from the Romanian Ministry of National
Education, CNCS – UEFISCDI, under the project PN-II-PT-PCCA 239/2014
THIN FILMS OF FERROCENE-BASED COMPOUNDS FOR NON-LINEAR OPTICAL APPLICATIONS
A.Matei1, C. Constantinescu1, A. Vlad1, I. Ionita1,2, M. Dinescu1, A. Emandi1,3
INFLPR - National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor Str., Magurele RO-077125,
Bucharest, Romania; 2UB - University of Bucharest, Faculty of Physiscs, 405 Atomistilor Str., Magurele RO-077125,
Bucharest, Romania; 3INOE 2000 - National Institute for Optoelectronics, 1 Atomistilor Str., Magurele RO-077125,
Bucharest, Romania
1
Thin films of ferrocene and ferrocene-based derivatives have been demonstrated to exhibit nonlinear optical
behaviour when irradiated with a femtosecond Ti:sapphire laser. Such thin films have been grown on Si substrates, at
room temperature, by matrix-assisted pulsed laser evaporation (MAPLE). Frozen targets have been made using
ferrocenes dissolved in choice solvents (benzene or dimethyl sulfoxide, 0.8-1%), and subsequently irradiated with a
Nd:YAG laser (4ω / 266 nm, 7 ns, 10 Hz) with fluences in the range of 0.1 – 0.4 J/cm2. The surface morphology,
chemical structure and optical properties of the films have been investigated by Fourier transform infrared
spectroscopy, atomic force microscopy, scanning electron microscopy, and spectroscopic-ellipsometry. Finally, we
discuss on their nonlinear optical properties with respect to literature data.
108
OPTICAL AND ELECTRICAL PROPERTIES OF (Ba1−xCax)(ZryTi1−y)O3 EPITAXIAL THIN FILMS
GROWTH BY PULSED LASER DEPOSITION
A.I. Bercea (1,2); N.D. Scarisoneanu (1), V. Ion (1), A. Andrei (1), F. Craciun (3), R. Birjega (1) and M. Dinescu (1)
National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor St, RO-077125, Magurele, Romania;
2)
University of Bucharest, Faculty of Physics, 405 Atomistilor St, RO-077125, Magurele, Romania; 3) CNR-ISC, Istituto
Dei Sistemi Complessi, Via del Fosso del Cavaliere 100, I-00133 Rome, Italy
1)
Piezoelectric and ferroelectric materials are keys to modern technologies due to his high dielectric constant and
strong piezoelectric response and in last period new materials with excellent properties were developed. Lead free
(Ba1−xCax)(ZryTi1−y)O3 (BCZT) with high value of dielectric constant and longitudinal piezoelectric coefficient d33
around 650 pC/N.
In this work, epitaxial thin films of BCTZ were deposited, from ceramic targets, using pulsed laser deposition
method (PLD) with a ArF excimer laser, on Pt/Si, SrTiO3 substrates and Nb doped SrTiO3.
The properties of the BCTZ thin films such as optical and electrical properties were investigated by Spectroscopic
Ellipsometry (SE) and dielectric spectroscopy. Surface topography and crystalinity were investigated by AFM and XRD
tehniques.
Pure perovskite structures have been obtained. The films deposited on Pt/Si substrates are policrystalline and show
(110) and (111) orientation, while films deposited on SrTiO3 and Nb:SrTiO 3 substrates are epitaxialy growth.
For all samples a high refractive index and low extinction coefficient were obtained in UV-VIS range of wavelength
(n>2 and k<10-4). Excellent dielectric properties have been obtained in low frequency regime (relative permittivity of
about 2000 and tangent loss ~ 3% at frequency of 10 KHz).
PROPERTIES OF THIN FILM OF DOPED AND UN-DOPED BiFeO3 OBTAINED BY PULSED LASER
DEPOSITION
V. Ion (1,2), N.D. Scarisoneanu (1), A. Andrei (1), S. Antohe (2), R. Birjega (1), A.I. Bercea (1,2) and M. Dinescu (1)
1) National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor St, RO-077125, Magurele, Romania;
2)University of Bucharest, Faculty of Physics, 405 Atomistilor St, RO-077125, Magurele, Romania
The perovskitic materials with a small band gap value such as multiferoic bismut ferrite (BiFeO3) become in last
period very attractive for photovoltaic applications. The band gap value of BiFeO3 (Eg~2.8 eV) corresponding to
maximum absorptivity at visible wavelengths and if is doped with different elements such as Yttrium or Lanthanum an
additional sub-band will be created within the change gap of the material.
In this work, we report the properties of thin films of BFO and doped BFO deposited by pulsed laser deposition
method (PLD) on various substrates. The purpose of this study was to obtain thin films of doped and un-doped BFO
with different values of band gap which make this material a candidate for photovoltaic applications.
A parametric study on the influence of nature of substrate, temperature during deposition and gas pressure, on the
properties of the BFO thin layer was carried out.
Crystallinity properties and topography of surface of thin films were studied using X-ray diffraction, atomic force
microscopy (AFM).
The optical properties were determined by spectroscopic ellipsometry (SE) and the values of band gap (Eg) where
determined from Tauc plot.
109
BIOCOMPATIBILITY STUDIES ON (Ba1−xCax)(ZryTi1−y)O3 THIN FILMS GROWTH BY MATRIX
ASSISTED PULSED EVAPORATION
V. Ion (1), N.D. Scarisoreanu (1), M. Icrivezi(2), A. Andrei (1), A.I. Bercea (1), R. Birjega (1), J. Banita(2), A. Bonciu(1), V.
Dinca(1), A. Roseanu(2), M. Dinescu (1)
1)
National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor St, RO-077125, Magurele, Romania;
2)
Institute of Biochemistry of the Romanian Academy, 296 Splaiul Independentei, RO-060031 Bucharest, Romania
Bulk lead-free (Ba1−xCax)(ZryTi1−y)O3 (BCZT) materials have attracted a lot of attention in the last period from
the scientific community for replacing piezoelectric and ferroelectric materials containing toxic elements in different
applications. Our approach is to explore the biocompatibility properties of BCTZ materials taking into account their
superior piezoelectric properties for electrically stimulated implant designs.
The BCTZ thin films have been obtained using Matrix Assisted Pulsed Laser Evaporation method. This method
allows the use of different types of substrates from flexible kapton to biocompatible metallic alloys due to low
deposition temperature.
Starting from a frozen target of nanopowders of BCTZ 45 composition and methanol, thin films of BCTZ 45 have
been obtained on Pt-coated kapton substrates. The cell proliferation studies have been made using epithelial embryonic
kidney HEK 293 cells and malignant melanoma A 375 cells which were seeded onto BCTZ 45 biomaterial. The results
suggest that BCTZ 45 material led to an increase proliferation level compared to borosilicate glass coverslip
irrespective of the cell line tested. The immunofluorescence study shows that the two cell lines used in our experiment
adhere on BCTZ45 material and display normal morphology on both glass coverslip and BCTZ45 material.
HYBRID PECVD/PVD SYNTHESIS OF Cu-POLYSILOXANE NANOCOMPOSITES
1
B. Mitu1, S. Somacescu2, L. C. Nistor3, V. Ion1, V. Satulu1, G. Dinescu1
National Institute for Lasers, Plasma and Radiation Physics, PO Box MG-36, 077125 Magurele Bucharest, Romania;
2
“Ilie Murgulescu” Institute of Physical Chemistry, 202 Spl. Independentei, 060021, Bucharest, Romania; 3 National
Institute of Materials Physics, PO Box MG-7, 077125, Magurele Bucharest, Romania; e-mail: [email protected]
Functional nanocomposites consisting of metal nanoparticles incorporated in organic matrices are of interest for a
growing field of applications, due to their special optical, electronic, magnetic and biomedical properties. Widely used
methods for the synthesis of nanocomposite materials are those based on combined techniques, for example hybrid
Plasma Enhanced Chemical Vapor Deposition and Physical Vapor Deposition (PECVD/PVD) processes. In such
approaches, PECVD is used for the organic matrix grow whereas the nanoparticles are produced either sequential or at
the same time by PVD. The metal filling factor and nanoparticles size distribution in the metal-polymer composite can
be tuned by the deposition conditions, such as the power injected in plasma, gas flow rate, working pressure, or
deposition time in the case of sequential approach.
In the present contribution we report on the synthesis of Cu-polysiloxane composites in a hybrid PVD/PECVD
system. The matrix is obtained by a radiofrequency (RF) discharge using hexamethyldisiloxane as precursor and the
metal particles are obtained by RF magnetron sputtering of a copper target. The deposition process was monitored by
Optical Emission Spectroscopy (OES) and Mass Spectrometry (MS). The composition of the material was revealed
through Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) investigations.
The structural properties of Cu-polysiloxane-like composites were evidenced by Transmission Electron Microscopy
(TEM) technique, while the optical properties were analysed by Spectroscopic Ellipsometry (SE). The topographical
aspects of resulted materials surface were studied by Atomic Force Microscopy (AFM) technique. The effect of
substrate positioning with respect to the two plasma sources was studied, and it is shown that a large variety of filling
factors can be obtained in different positions on a silicon wafer in only one step.
110
OPTICAL AND STRUCTURAL CHARACTERIZATION OF In2O3 THIN FILMS GROWN BY
RADIOFREQUENCY DISCHARGE ASSISTED PULSED LASER DEPOSITION
A. Nedelcea(1), M. Dumitru(1), M. Filipescu(1), V. Ion(1), N.L. Dumitrescu (1), M. Dinescu(1)
1) National Institute for Lasers, Plasma and Radiation Physics, Bucharest Magurele, PO BOX MG36 Romania
Indium oxide is a n-type semiconductor and due the excellent properties is used in many application, such as:
resistive element in integrated circuits; in alkaline batteries to suppress gassing and as an anti-arcing additive in high
current electrical switches and contactors; glass coloring; thin film infrared reflectors transparent for visible
light, optical coatings, etc. Due the low reflectivity of In2O3 thin films also is used as antireflection coating for solar
cells.
In this work, In2O3 thin films are grown on silicon and glass substrates by pulsed laser deposition (PLD) and radio
frequency discharge assisted pulsed laser deposition (RF-PLD). The different laser wavelengths and radiofrequency
plasma discharge power where used. The deposition parameters (substrate temperature, gas pressure, etc) are controlled
to obtain crystalline and amorphous films and to eliminate the metallic Indium droplets build-up.
Properties of indium oxide thin films were determined with Atomic Force Microscopy (AFM), Scanning Electron
Microscopy (SEM), Secondary Ion Mass Spectrometry (SIMS) and X-Ray Diffraction (XRD).
Reflection and transmission of In2O3 thin films where determined by spectro-elipsometry (SE) technique.
MULTI-LAYER AND SELF-ASSEMBLED In2O3 THIN FILM TRANSISTORS PRODUCED BY PULSED
ELECTRON BEAM DEPOSITION
F.Gherendi, M.Nistor and N.B.Mandache
National Institute for Lasers, Plasma and Radiation Physics (NILPRP), Plasma Physics and Nuclear Fusion Laboratory
(L 22), Str. Atomistilor 409, P.O. Box MG-36, Magurele-Bucharest, Romania
In this work we report on the fabrication of In2O3 transparent thin film transistors (TTFT) by pulsed electron beam
deposition (PED), in successive deposition processes in a multi-layer channel and source-drain structure, and also in a
self-assembled source-channel-drain structure in a single deposition process with a special shadow mask technique.
Y2O3 thin films grown by RF magnetron deposition were used as gate insulator.
A comparative electrical characterization of multilayer and self-assembled In2O3 TTFTs was made. The
measurements were performed in the dark, in air and at room temperature.
The multilayer TTFTs are fabricated in the top gate – bottom contacts geometry, with the source and drain contacts
grown at 1.3x10-2 mbar oxygen pressure, and the channel layer grown at a higher oxygen pressure of 2x10 -2 mbar. They
have the following electrical characteristics: a subthreshold swing of ~0.6 V/decade, I on/Ioff of 4x104, threshold voltage
of +0.93 V and saturation channel mobility of 19 cm2/Vs.
The self-assembled TTFTs were fabricated by a simultaneous growth of the source, channel and drain in a single
indium oxide film at an oxygen pressure of 1.3x10 -2 mbar, the channel being grown in the shadow of a 100μm diameter
wire placed at 50μm distance from the substrate. The resistivity in the channel region of such a self-assembled structure
was calculated from the measured source-drain resistance and the channel thickness measured by profilometry. This
resistivity is four orders of magnitude greater than in the source and drain regions of the same film, similar to the
resistivity of the films grown at 2x10-2 mbar oxygen pressure without mask.
These self-assembled TTFTs are better performing, with a subthreshold swing of ~0.26 V/decade, I on/Ioff of 106-107,
a slightly larger threshold voltage of +1.06 V and a saturation channel mobility of ~40 cm 2/Vs.
111
112
S6
Advanced ceramics: synthesis, properties, and
applications
Invited Papers
113
114
INFLUENCE OF GRAIN SIZE AND SOLUTE CONTENT ON THE DIELECTRIC AND FERROELECTRIC
BEHAVIOUR OF Ba(Ti,Zr)O3 CERAMICS
A. C. Ianculescu1, C. A. Vasilescu1, D. Berger1, I. Pintilie2, L. Trupină2, L. P. Curecheriu3, and L. Mitoşeriu3
„Politehnica” University of Bucharest, 1-7 Gh. Polizu, 011061 Bucharest, Romania, 2National Institute of Materials
Physics, Bucharest-Magurele, 077125, Romania, 3Al. I. Cuza University, Bv. Carol 11, Iasi, 700506, Romania
1
BaTi1-xZrxO3 (BTZ with x = 0.10, 0.15 and 0.20) nanopowders were synthesized by the modified Pechini method.
By modifying the sintering strategy and conditions, samples with different average grain sizes ranged between 40 nm 70 m, were obtained. Thus, highly-densified BTZ ceramics were prepared by conventional sintering at 1300 oC/8 hours
and 1400oC/4 hours, as well as by spark plasma sintering (SPS) at a temperature of 1050 oC/2 min and a pressure of 76
MPa. The impedance spectroscopy analysis performed in the range of temperature (20 – 140)oC indicates specific
features related to grain size effects. Unlike the traditional processing by the solid state reaction method, whereby very
sharp ferroelectric – paraelectric phase transitions, specific to a typical ferroelectric behaviour were generally reported
for BTZ compositions with lower Zr concentrations (x  0.13), in the case of the preparation starting from powders
synthesized by the modified Pechini method, more diffuse ferroelectric – paraelectric phase transitions, characteristic to
a ferroelectric - relaxor crossover, were observed, even for the composition with x = 0.10, irrespective of the sintering
procedure. For all the BTZ ceramics under investigation the increase of Zr addition induces an obvious decrease of the
Curie temperature. The diffuseness of the mentioned phase transition increases not only with Zr content, but also with
grain size. For the coarse-grained BTZ ceramics prepared by conventional sintering at 1400 oC/4h permittivity
maximum values ranged between 8000 - 17000 were recorded at a fixed frequency of 20 kHz. Unlike this case, a strong
depression of the permittivity maximum from ~ 1200, for x = 0.10, towards values below 500 for x = 0.15 and 0.20 and
a relative thermal stability of the dielectric properties was obtained in the nano-scaled spark plasma sintered ceramics.
TUNABLE FERROELECTRIC MATERIALS FOR RF- MICROWAVE APPLICATIONS: HIGHFREQUENCY PROPERTIES AND INTEGRATION IN FREQUENCY-AGILE DEVICES
L. Huitema1, V. Madrangeas1, A. Cruntenau1, D. Passerieux1, D. Cros1, T. Monediere1, C. Champeaux2, F. DumasBouchiat2, P. Marchet2, L. Nedelcu3, L.Trupina3, G. Banciu3, M. Cernea3
1
Xlim Laboratory UMR 7252 CNRS/University of Limoges, 87060, Limoges, France, 2SPCTS UMR 7315
CNRS/University of Limoges, Limoges, France, 3NIMP Laboratory, Bucharest, Romania
Ferroelectric (FE) thin film capacitors can be a convenient technology for tuning microwave devices. The high
agility of ferroelectric materials with an applied DC bias is presented to be employed for tunable systems. Existing
reconfiguration solutions are based on varactor diodes, Micro-Electro-Mechanical systems (MEMS), PIN diodes, field
effect transistors (FET) or on the introduction of tunable ferroelectric materials. Among these, PIN diodes present only
two possible states (On/Off) and, like the FETs devices, have high power consumption. Varactor diodes present high
capacitance tunability but have a very low power handling capability (although they are widely referenced for
frequency tunable antennas). In this framework, two solutions with low power consumption are emerging for the
conception of reconfigurable circuits: MEMS and ferroelectric materials. The potential of ferroelectric materials is
evaluated within practical devices to meet the current requirements for highly reconfigurable, integrated, efficient and
low power-consuming systems.
In this context, the integration of agile capacitors based on ferroelectric materials within compact devices to be
reconfigurable will be presented. Indeed, the high agility these materials with an applied DC bias voltage and their
reasonable loss tangent values can be employed to develop tunable systems. Particularly, reconfigurable filters, phase
shifters and frequency agile antennas based on different ferroelectric materials will be discussed. The characterization
of their dielectric properties at RF frequencies will be presented followed by their integration inside the devices.
Reconfigurable components could present either a 2D-shape, i.e. interdigital capacitors or a 3D-shape as the MetalFerroelectric-Metal tunable components. Designs and performances of the devices incorporating these two kinds of
ferroelctric-based components will be presented and detailed.
115
DECIPHERING THE FERROELECTRIC ORDER IN FINITE-DIMENSIONAL PEROVSKITES
Gabriel Caruntu
Department of Chemistry and Biochemistry, Science of Materials (SAM) Program Central Michigan University Mount
Pleasant, MI, 48859, USA; E-mail: [email protected], Web site: http://people.cst.cmich.edu/carun1g/index.htm
Ferroelectricity in finite-dimensional systems continues to arouse interest, motivated by predictions of vortex
polarization states and the utility of ferroelectric nanomaterials in memory devices, actuators and other applications.
Critical to these areas of research are the nanoscale polarization structure and scaling limit of ferroelectric order, which
have been studied in the work presented here using monodisperse, aggregate-free BaTiO3 individual nanocrystals
comprising a single ferroelectric domain. A quantitative insight into phase transitions and finite-sized effects was
obtained by Raman spectroscopy, which indicated the presence of a tetragonal distortion in the BaTiO 3 nanocrystals.
These results were further confirmed by fitting different structural models (pseudo-cubic and tetragonal) to synchrotron
X-Ray diffraction data using pair distribution function (PDF) analysis. Moreover, maps of ferroelectric structural
distortions obtained from aberration-corrected transmission electron microscopy revealed the existence of a coherent,
nearly linear, monodomain polarization state at nanometer dimensions. The persistence of ferroelectric coherence in
BaTiO3 is further supported by single-particle studies with off-axis electron holography and piezoresponse force
microscopy (PFM) measurements of individual nanocubes demonstrating ferroelectric switching behavior at room
temperature. A reversible room-temperature polarization switching was found to persist to a size down to 5 nm
dimensions. This is the smallest size in which a switchable intrinsic lattice polarization was demonstrated to date in
free-standing ferroelectric nanocrystals. Interestingly, the ferroelectric coherence is facilitated in part by control of
particle morphology, which along with electrostatic boundary conditions was found to determine the spatial extent of
cooperative ferroelectric distortions. This work provides atomic-scale insight into the fundamental nature of
ferroelectric order down to its ultimate size limit and demonstrate the utility of colloidal morphology control as a means
of stabilizing the polar state at nanoscale dimensions. The experimental results presented here reveal the ultimate limit
of the ferroelectric state and provide a pathway to unravelling the fundamental physics of nanoscale ferroelectricity at
the smallest possible size scales. This work points the way to multi-Tbit/in2 memories and provides a glimpse of the
structural and electrical manifestations of ferroelectricity down to its ultimate limits.
SUPERCONDUCTIVITY IN FeSe-BASED INTERCALATION COMPOUNDS
Y. Koike, T. Hatakeda, S. Hosono, T. Noji, T. Kawamata, M. Kato
Department of Applied Physics, Tohoku University, Sendai 980-8579, Japan
Recently, we have succeeded in the synthesis of several FeSe-based intercalation superconductors where both alkali
metal (Li, Na) and linear organic-molecule (ethylenediamine (C2H8N2), hexamethylenediamine (C6H16N2)) are cointercalated between FeSe layers. The superconducting transition temperature, T c, is 45 K in Ax(C2H8N2)yFe2-zSe2 (A =
Li, Na) with the interlayer spacing, namely, the distance between neighboring Fe layers, d, of 10.4 Å and 11.0 Å,
respectively [1,2], and 38 K in Lix(C6H16N2)yFe2-zSe2 with d = 16.2 Å [3]. Accordingly, it has been concluded in the
FeSe-based intercalation superconductors that Tc increases with increasing d, is saturated at about 45 K and then
decreases. In Ax(C2H8N2)yFe2-zSe2 (A = Li, Na), we have succeeded in observing zero-resistivity, using the sintered
pellet samples [4]. It has been found that the electrical resistivity in the normal state is metallic and that the
superconducting onset-temperature is as high as 57 K, which may be due to the large superconducting-fluctuation. To
the surprise, moreover, it has been found that both the crystal structure and superconductivity of the sintered pellet
sample of Lix(C2H8N2)yFe2-zSe2 are resistant to the atmospheric exposure at least up to several days, which is suitable
for applications [4].
[1] T. Hatakeda, T. Noji, T. Kawamata, M. Kato, Y. Koike, J. Phys. Soc. Jpn. 82, 123705 (2013).
[2] T. Noji, T. Hatakeda, S. Hosono, T. Kawamata, M. Kato, Y. Koike, Physica C 504, 8 (2014).
[3] S. Hosono, T. Noji, T. Hatakeda, T. Kawamata, M. Kato, Y. Koike, J. Phys. Soc. Jpn. 83, 113704 (2014).
[4] T. Hatakeda, T. Noji, S. Hosono, T. Kawamata, M. Kato, Y. Koike, J. Phys.: Conf. Ser. 568, 022032 (2014).
116
SYNTHESIS AND COLLOIDAL PROCESSING OF ADVANCED LEAD-FREE DIELECTRIC AND
FERROELECTRIC CERAMICS
José M.F. Ferreira* Ajay Kaushal, and Susana M. Olhero
Department of Materials and Ceramic Engineering (DEMaC), Centre for Research in Ceramics and Composites,
CICECO, University of Aveiro, 3810-193 Aveiro, Portugal. *E-mail: [email protected]
The properties of advanced functional ceramics and their performance in industrial applications are strongly
influenced by the selected composition, the synthesis procedures of the powders and processing treatments. PZT-based
ceramics have been widely used for piezoelectric actuators, sensors and transducers for decades due to their excellent
piezoelectric properties. However, lead-containing compounds pose serious environmental concerns. Also, the
composition of lead-based piezoelectric materials is unstable and hard to control in production because of the high
volatilization of lead oxide during the sintering process. These concerns have fostered the search for lead-free materials
with excellent piezoelectric properties to replace the PZT-based ceramics. The fabrication of the functional ceramics is
another challenge, especially for micro scale components, and when the process involves a dispersion of the powders in
water. Alkaline earth-containing compounds are prone to undergo hydrolysis and non-stoichiometric dissolution
reactions in aqueous media. Preventing such reactions while effectively dispersing the powders to form stable and high
concentrated suspensions and is of paramount importance to enhance the performance of advanced functional ceramics.
Recently we demonstrated how ferroelectric and lead-free piezoelectric ceramics with superior properties could be
successfully synthesized and processed in aqueous environments. The key issues related to the synthesis, aqueous
processing and properties of BaTiO3 (BT), (Ba,Sr)TiO3 (BST), and lead-free piezoelectric ceramics,
0.5Ba(Zr0.2Ti0.8)O30.5(Ba0.7Ca0.3)TiO3 (BZTBCT) will be reviewed in this presentation.
TAILORING MICROSTRUCTURE AND PROPERTIES OF FERROELECTRIC CERAMICS USING
SPARK PLASMA SINTERING
C. Elissalde1, J.Lesseur1, R. Ephere2, M. Legallais1, G. Philippot1, U-C. Chung1, M. Albino1, G. Chevallier2,
A. Weibel2, P. Veber1, M. Deluca3, C. Aymonier1, D.Bernard1, F.Mauvy1, M. Maglione1 and C. Estournès2
1
CNRS, ICMCB, Univ. Bordeaux, UPR 9048, F-33600 PESSAC, France, 2CNRS; Institut Carnot Cirimat; F-31062
Toulouse, France, Université de Toulouse; UPS, INP; 3Materials Center Leoben Forschung GmbH, Institut für Strukturund Funktionskeramik, 8700 Leoben, Austria; [email protected]
The quest for improved functionalities in ferroelectric ceramics requires the control of their composition,
microstructure and defect chemistry (free charges, oxygen vacancies, hydroxyl group) allowing to tune the dielectric
characteristics (permittivity, transition temperatures, dielectric losses). This is a major issue to face the drastic
expectations in terms of integration and multifunctionality in many fields of applications. Spark Plasma Sintering (SPS)
is nowadays well recognized as an efficient tool to yield ceramics with controlled micro-nanostructures in particular in
the field of ferroelectric materials. The simultaneous action of uniaxial pressure and pulsed electrical current ensures
efficient heat transfer leading to fast sintering kinetics. As a result, grain size, strain and interfaces driven properties can
be expected. However minimizing extrinsic contributions to the dielectric properties remains a difficult task. Both the
quality of the initial powders (crystallinity, stoichiometry, hydroxyl groups content) and the control of charged defects
in the final ceramics are mandatory to improve dielectric performances. First, we will show the influence of the SPS
processing conditions on the electrical behavior and microstructural features of barium titanate based ceramics.
Complex impedance spectroscopy was combined with dielectric measurements to discriminate the grain and grain
boundary contributions. In a second part, we will describe an original approach to produce composites
(BaSrTiO3/MgO) with tunable properties through the control of the MgO inclusions morphology. Spark Plasma
Sintering not only ensures a high quality of ceramics in terms of density and interfaces but also enables to adjust the
deformation of the inclusions according to their initial mechanical strength.
117
SPARK PLASMA SINTERING OF CERAMIC POWDERS: FROM EVIDENCE OF SPECIFIC EFFECTS
TO THE ELABORATION OF COMPLEX ARCHITECTURES AND SHAPES
C. Estournès1, R. Marder2, R. Chaim2, R. Epherre1, C. Elissalde3, M. Maglione3, G. Chevallier1, C. Manière1, L.
Durand4
1
CNRS, Univ. Toulouse, Institut Carnot CIRIMAT 118 route de Narbonne, 31 062 TOULOUSE Cedex 9, France,
2
Technion Israel Institute of Technology, HAIFA 32000, Israel, 3CNRS, Univ. Bordeaux, ICMCB, UPR 9048, F-33600
PESSAC, France, 4CNRS, Univ. Toulouse, CEMES, 29 Rue Jeanne Marvig - BP 4347 31055 TOULOUSE CEDEX 4 France
Pulsed Electric Current Sintering (PECS) techniques have known a huge development over the last two decades. In
particular, SPS is an extremely powerful technique to sinter all classes of materials (metals, ceramics and polymers) as
well as their composites. Thanks to the increase in sintering kinetics it allows, its field of activity also extends to the
synthesis, the assembly, and the preparation of new materials (nanocomposites, multimaterials, nanoceramics) or graded
materials (in composition, microstructure, porosity).
In recent investigations on different ceramic powders (LiF, NiO, and YAG) local melting of the particle and nanoparticle surfaces have been clearly shown, confirming the formation of spark and plasma during the SPS [i,ii]. The
different behavior of various oxide systems depend on the material properties, and the pressure and its application
regime. These features also determine the nano-micro-structure evolution during the sintering.
Due to the lower temperature and the shorter durations achieved during SPS, interdiffusion or reaction between two
adjacent materials can be limited, favoured or controlled. The potentialities of this technique to design new materials or
architectures will be illustrated through few examples. 2D, 3D and core/shell architectures have been prepared by SPS
to obtain ferroelectric ceramics with modulated properties [iii,iv]. In particular emphasis will be placed on the large
flexibility of experimental SPS parameters which allow to control the morphology and the anisotropy of dielectric
inclusions (spheres, ellipsoids) into a ferroelectric matrix which significantly impacts the dielectric and ferroelectric
properties of these multimaterials [v,vi].
Recently, the modeling of Spark Plasma Sintering by finite element method has known drastic development.
Coupling three main physics, Electric Thermal and Mechanic (ETM), it allows now to predict the temperature, grain
size and porosity during the process up to the densification of more or less complex shape materials. The electrical and
thermal parts of the ETM model are used to calculate the temperature at any point of the SPS tool and column. These
simulations have pointed out the great effect of the electrical and thermal contact resistances between the different parts
of the tool to explain the thermal gradient measured experimentally at this place. Then, the calculated temperature is
used to activate the sintering phenomena governed by the mechanical part of the ETM model. Both sintering models of
Olevsky [vii] and Abouaf [viii] used to predict the densification of an alumina nano-powder are in agreement and give
good results compared to the experimental sintering curve. Last, a grain growth law was coupled with Olevsky's
densification model which has shown the great effect of the grain growth at the end of the sintering stage. Finally this
type of modeling allowed us to define the optimized SPS parameters and tool geometry in order to minimize the
porosity gradient in a complex shape part.
Reference
[i] R. Marder, C. Estournès, G. Chevallier, S. Kalabukhov, R. Chaim, J Mater Sci 49 (2014) 5237–5245.
[ii] R. Marder, C. Estournès, G. Chevallier, R. Chaim, J. Eur. Ceram. Soc., 35(1), (2015), 211-218.
[iii] C. Elissalde, C. Estournès, M. Maglione, J. Amer. Ceram. Soc., 90 (3), 2007, 973.
[iv] U.-C. Chung, C. Estournès, C. Elissalde, M. Paste, J.P. Ganne, M. Maglione, Applied Physics Letters, 92 (4), 2008, 042902/1.
[v] R. Berthelot, B. Basly, S. Buffiere, J. Majimel, G. Chevallier, A. Weibel, A. Veillere, L. Etienne, U-C. Chung, G. Goglio, M. Maglione, C.
Estournes, S. Mornet and C. Elissalde, J. Mater. Chem. C, 2014, 2, 683–690.
[vi] J. Lesseur, U.C.Chung, D. Bernard, C. Estournès, M. Maglione and C. Elissalde, J. Eur. Ceram. Soc. 35 (2015) 337–345.
[vii] E.A. Olevsky, C. Garcia-Cardona, W.L. Bradbury, C.D. Haines, D.G. Martin, D. Kapoor, J. Amer. Ceram. Soc., 95 (2012) 2414-2422.
[viii] M. Abouaf, J.L. Chenot, J. of theorical and applied mechanics. Vol 5, No 1 (1986) 121-140.
118
Oral Presentations
THE INFLUENCE OF HEATING RATE ON SUPERCONDUCTING CHARACTERISTICS OF MgB2
PROCESSED BY EX-SITU SPARK PLASMA SINTERING
P. Badica, M. Burdusel, S. Popa, G. Aldica
National Institute of Materials Physics, Atomistilor 105 bis, 077125 Magurele, Romania
The MgB2 superconductor is a reliable choice for practical applications. It shows several advantages over
commercial classic superconductors or over high temperature superconductors. Among them we shall note that MgB 2 is
a light-weight material, non-toxic, available, and relatively cheap. It has the highest critical temperature Tc of 39 K
among binary simple compounds, it shows unconventional physics which has positive implications for the use of
doping elements for the control of the superconducting properties, and the coherence length is relatively large so that
grain boundaries are transparent to the super current flow and, in fact, they are effective pinning centres enhancing
critical current density Jc and the irreversibility magnetic field Hirr. Considering presented aspect as well that Mg is
volatile and is easily oxidized, in this work it is proposed a study of the heating rate influence on the functional
superconducting characteristics of MgB2 bulk samples with high density (> 93% of the theoretical density) obtained by
spark plasma sintering. Raw material was a commercial MgB 2 powder. A heating rate of 20, 110, 235, 355, and 475
K/min was applied for a SPS heating in vacuum.
A high heating rate is leading to a sharp superconducting transition in the M-T measurements and x-ray diffraction
analysis indicates a low amount of MgO and MgB 4 impurity phases. On the other hand, many flux jumps occurred at 5
K in the M-H loops. The sample processed with the lowest heating rate of 20 K/min, has the lowest critical current
density Jc(H) in the 5-20 K range. A microstructure with wavy and not well defined grain boundaries was revealed by
electron microscopy in the sample obtained for a high heating rate, while the sample processed with a low heating rate
is composed of grains and blocks with well defined straight edges.
An optimum sample showing the highest value of the product Jc(0) x 0Hirr is determined for a heating rate of 110
K/min.
119
GAS-SENSING PROPERTIES OF Cr DOPED BaSrTiO 3 MATERIALS
C.E. Simion1a), C.F. Ruşti3, O.G. Florea1, A. Sackmann2, R.M. Piticescu3, P. Osinceanu 4 and A. Stănoiu1
National Institute of Materials Physics, Atomistilor 105bis, P.O. Box MG-7, 077125, Bucharest-Magurele, Romania
a)
Presenting and corresponding author: [email protected]; 2AG Weimar, Institute of Physical and Theoretical Chemistry,
University of Tübingen, Auf der Morgenstelle 15, D-72076 Tübingen, Germany; 3National R&D Institute for Nonferrous and Rare Metals, 102 Biruintei Blvd, Ilfov, Romania; 4 “Ilie Murgulescu” Institute of Physical Chemistry of the
Romanian Academy;
1
The traffic pollution monitoring sites are using expensive spectroscopic devices, therefore is a continuous demand
for developing low cost and low power consumption gas sensors based on ceramic type materials.
Ba1-xSrxTiO3 (x=0.3) BST doped with 0.1, 1 and 5%mol Cr was selected as sensitive layer, due to its unique
ferroelectric properties suitable for different applications in particular gas sensor. Doped BST was obtained in one step
by hydrothermal synthesis at high pressure (>100 atm) and low temperature (200°C). The as obtained powder was
characterized in terms of chemical composition by ICP-OES technique, structure and morphology by XRD and SEM,
respectively chemical bonding energies of constituting elements by XPS analysis. The XRD analysis have indicate the
existence of the tetragonal phase.
Cr doped BST powders were deposited by screen printing onto Al2O3 commercial substrates and subsequently tested
towards: carbon monoxide (CO), methane (CH4), nitrogen dioxide (NO2), hydrogen sulphide (H2S), ammonia (NH3)
and sulphur dioxide (SO2). The experimental evaluation have been done under real operating conditions id est. relative
humidity: 0-70%, normal atmospheric pressure and dynamic gas flow. Specific range of concentrations were spanning,
according with detection limit for each test gas.
Gas-sensing properties: sensitivity, selectivity, stability, response and recovery times were analysed from both
fundamental and applicative interest.
A COMBINED ANALYSIS OF FUNCTIONAL PROPERTIES OF PEROVSKITE OXIDE CERAMICS
N. Horchidan1*, A. Ianculescu2, and L. Mitoseriu1
Dielectrics, Ferroelectrics & Multiferroics Group, Department of Physics, Alexandru Ioan Cuza University of Iasi, Blv.
Carol I 11, 700506, Iasi, Romania; 2Dept. of Oxide Materials Science & Eng., Polytechnics Univ. Bucharest, Romania;
*e-mail: [email protected]
1
The high permittivity combined with low losses makes Ba(SnxTi1-x)O3 (BSnT) system as a valuable candidate for
high permittivity applications, with similar performance with other known solid solutions of barium titanate. The room
temperature (RT) permittivity of BSnT can be driven to very high values by using specific Sn substitutions, due to the
shift of the ferroelectric-paraelectric phase transition towards smaller temperature when increasing the Sn addition. In
addition, a transformation from normal ferroelectric to a relaxor state with diffuse phase transition is promoted by Sn
addition, and the critical concentration corresponding to the ferroelectric-relaxor crossover is strongly dependent on the
sintering parameters. In the present work, the role of microstructure on the dielectric and ferroelectric properties of
BSnT ceramics was analysed. The ceramic compositions (x=00.20) were prepared using classical preparation method
and different sintering treatments in order to generate different microstructures (grain size, porosity) in the final
ceramics. The study presents a field-induced dielectric and ferroelectric analysis combined with Raman investigations
in order to obtain new insights concerning the superposition of phases, evolution of ferroelectric domains with Sn
addition and for the identification of composition-induced modifications of the structural phase transitions. The
sintering at higher temperature favours the stability of the ferroelectric state even for higher Sn addition x, fact
confirmed by Raman results and empirical parameters calculated using fits of a modified Curie-Weiss law. A lower
sintering temperature favours the existence of phase coexistence, the increase of RT permittivity and the predominance
of relaxor character. Acknowledgements: The financial support of the CNCS-UEFISCDI Project No. PN-II-ID-PCE2011-3-0745 is highly acknowledged.
120
MODELLING CAPACITANCE-VOLTAGE CHARACTERISTIC OF EPITAXIAL BaTiO3 THIN FILMS
Dorin Rusu, Lucian Pintilie *, Lucian Filip*, Ciceron Berbecaru**
Faculty of Physics, University of Bucharest, Fizicienilor Nr.5, Magurele 077125, Romania; *INCDFM, Atomistilor,
105 bis, Magurele 077125, Romania; **Romanian Materials Science-Crystal Growth Society, 077125 Bucharest,
Romania
Electric capacity of BaTiO3 thin films and its dependence on the applied voltage is simulated employing a simple
model. Ferroelectric polarization is considered to be uniform in the ferroelectric bulk and it has been approximated as
two charged sheets located in the vicinity of each interface. A passive non-switchable layer and detrimental to
ferroelectricity called “dead layer” is considered at both interfaces. A uniform spatial charge distribution is considered
in the vicinity of the charged sheets in the bulk region and Poisson equation is solved. Specific boundary conditions are
used, i.e. zero electric field and potential energy in the bulk region. At the opposite electrode, due to the fact that the
film has its own free charge located near the interface if voltage is applied, the contact is presumed to be purely
resistive. To derive the capacitance, an equivalent circuit is considered that replaces one of the interfaces with a
capacitance, an R-C parallel group related to the ferroelectric bulk and a resistance given by the resistive contact.
Values of the components in the equivalent circuit were obtained by fitting experimental data with the simulated curves.
Good qualitative agreement was obtained with experimental data obtained in the literature [1].
[1] Pintilie, L. Hrib, I. Pasuk, C. Ghica, A. Iuga, and I. Pintilie, J. Appl. Phys. 116, 044108 (2014)
THE STRUCTURAL AND DIELECTRIC PROPERTIES OF ZINC SUBSTITUTED NICKEL-COBALT
FERRITE NANOPARTICLES SYNTHESIZED BY CITRATE-GEL COMBUSTION
A. C. Galca1, B. Arayedh2, Ma. Oumezzine2, Mo. Oumezzine2, M. Enculescu1, and A. Iuga1
National Institute of Materials Physics, Atomistilor 105 bis, 077125 Magurele, Ilfov, Romania; 2Laboratoire de
Physico-chimie des Matériaux, Université de Monastir, 5019 Monastir, Tunisia; corresponding author:
[email protected]
1
Ni0.8-xZnxCo0.2Fe2O4 nanoparticles (x = 0, 0.05, 0.1 and 0.2) were prepared by citrate-gel auto-combustion method.
The structural investigation using powder X-ray diffraction (XRD) showed the formation of single-phase cubic spinel
structures with Fd-3m space group for all prepared samples. As the Zn2+ concentration is increased, the values of the
lattice constant and mean crystallite size structural parameters undergo significant change. In this work we present a
simple way to determine the absolute lattice parameter and values of the inevitable z-displacement.
The absolute experimental lattice parameters obeys closely the Vegard’s law derived ones, suggesting that the
cations concentration is the same as the one calculated prior chemical synthesis.
Dielectric parameters were measured in the frequency range (102 - 106 Hz) at different temperatures. The results will
be discussed with respect to the structural properties and chemical composition.
The authors acknowledge the Romanian Ministry of Education (PN-II-ID-PCCE-2011-2-0006 project and core
program PN09-4501) and the Tunisian Ministry of Higher Education and Scientific Research for the financial support.
LOCAL MICROSTRUCTURE OF LEAD TITANATE PIEZOCERMICS WITH DILUTE CONTENT OF
MAGNETIC IONS
Elena Dimitriu1, Marin Cernea2, Roxana Trusca3, Rodica Ramer4
REGO COM Srl, Calea 13 Septembrie 115, 050716 Bucharest-5, Romania. E-mail: [email protected];
2
National Institute of Materials Physics, P.O. Box MG7, Str. Atomistilor 105 bis, Magurele-Bucharest RO-77125,
Romania. 3METAV-R&D S.A., P.O.22, Bucharest, Romania. 4 School of Electrical Engineering and
Telecommunication, University of South Wales, Sydney 2052, Australia
1
In this work the microstructure of piezoelectric ceramics with the compositions (Pb, Fe, Sm) (Ti, Mn)O 3 and (Pb,
Nd) (Ti, Mn)O3, characterized by weak ferromagnetic properties, has been investigated. The materials were prepared by
oxide method. The phase formation and the morphology of the poled sintered specimens were examined by X-ray
diffraction technique and scanning electron microscopy. A very compact structure consisting of unusual step-andterrace zones, with various orientations, and an average steps height of few nanometres, are observed in the (Pb, Fe,
Sm) (Ti, Mn)O3 sample. A different nanostructure is developed in the (Pb, Nd) (Ti, Mn)O 3 material; grains of variable
sizes together with huge prismatic habitus and platelets are present. The inhomogeneity of the chemical composition at
the nanoscale level, evidenced in the energy dispersive X-ray analysis with the microprobe technique, was theoretically
discussed by using the supercell geometry method. The (Pb, Fe, Sm) (Ti, Mn)O3 ceramic with both dielectric,
piezoelectric and magnetic properties is a promising multiferroic material.
121
INVESTIGATION OF MULTIFUNCTIONAL COMPOSITES PREPARED BY USING SrTiO 3@BaTiO3
CORE-SHELL PARTICLES AS REACTIVE PRECURSORS
1
M. Airimioaei1, M. T. Buscaglia2, V. Buscaglia2, L. Mitoseriu1, C. E. Ciomaga1 and L. P. Curecheriu1
Dept. of Physics, Alexandru Ioan Cuza University, Blv. Carol I, nr.11, 700506, Iasi, Romania; 2 Institute for Energetics
& Interphases IENI-CNR Genoa, Via de Marini 6, I16149, Genoa, Italy
Starting from the results of Finite Element (FEM) calculations which indicated that permittivity can be lowered to
hundreds and tunability preserved or even increased in composites with dielectric inclusions embedded into a
ferroelectric matrix, we have prepared a composite ceramic with the paraelectric phase (SrTiO3) fully isolated by the
ferroelectric phase (BaTiO3). Because the synthesis of these kinds of materials needs a good microstructure control, our
idea was to use the core shell approach. We chose as paraelectric phase SrTiO3 and as ferroelectric phase BaTiO3
starting from the following considerations: SrTiO3 has a moderate dielectric constant around 300, high dependence of
the dielectric constant on the applied field at low temperature and low losses, while BaTiO3 has high dielectric constant,
high dependence of the dielectric constant on the applied field at room temperature, low losses and piezoelectric
properties.
The multifunctional ceramic composites with the 0-3 connectivity were obtained by spark plasma sintering of
composite powders formed by SrTiO3@BaTiO3 core-shell particles. In order to prepare SrTiO3@BaTiO3 core-shell
particles we have used a multistep process: (i) synthesis of the SrTiO 3 cores; (ii) coating the SrTiO3 cores with a shell of
amorphous TiO2; (iii) transformation of SrTiO3@TiO2 core-shell particles into SrTiO3@BaTiO3 core-shell particles.
After each step of synthesis, the phase formation and morphologies have been investigated by using X-ray
diffraction (XRD) and scanning electron microscopy (SEM). The low-field dielectric properties have been investigated
and discussed as a function of microstructural and compositional details.
Acknowledgements: The financial support of PNII-PT-PCCA-2013-4-1119 MECOMAP grant is highly
acknowledged.
METHOD TO IMPROVE THE CHARACTERISTICS OF DIELECTRIC RESONATOR ANTENNAS
M. G. Banciu, L. Nedelcu, D. C. Geambasu
National Institute of Materials Physics, Magurele, Jud. Ilfov, Romania, [email protected]
Microwave antennas with axially symmetric dielectric resonator are investigated in this work. In a previous work we
showed that the antennas with very high (about 90) dielectric constant exhibit narrow antenna bandwidth [1]. For
antennas with cylindrical homogeneous resonators in a single-mode excitation case, the fractional bandwidth (FBW)
dramatically increases when the ratio diameter over height d/h ratio approaches zero. However, very thin and long
resonators are difficult to be manufactured and the mode excitation is also difficult. Among the low-frequency
resonance modes, it is shown that mode HE111 offers higher FBW than the modes TM011 and TE011, and the FBW
increases with the d/h ratio increase. However, such low profile antennas loose the attractiveness for applications due to
the increased diameter of the resonator. In order to overcome this difficulty we propose antennas with nonhomogeneous resonators. The resonators will consist of such different dielectric low-loss high dielectric constant
materials as barium neodymium titanate, zirconium tin titanate or calcium silicate. For larger bandwidth, we investigate
the mode coupling not only in cylindrical resonators but also in resonators of a truncated–cone shape.
Acknowledgement – This work was supported by a grant of the Romanian National Authority for Scientific
Research, Programe for research- Space Technology and Avanced Research - STAR, project ADANSPACE no.
240/2013.
Keywords: microwave antennas, dielectric bandwidth, antenna characteristics.
References
[1] O. G. Avadanei, M. G. Banciu, L. Nedelcu, “Higher-order modes in high-permittivity cylindrical dielectric
resonator antenna excited by an off-centered rectangular slot”, IEEE Ant. Wireless Propag. Lett, vol. 13, pp. 1595-1588
(2014).
122
PROPERTIES OF BISMUTH FERRITE POWDERS SYNTHESIZED BY SOFT CHEMISTRY ROUTES
D. Berger1*, A.I. Iorgu1,2, Z. Jaglicic3, F. Maxim2, M. Dragomir, C. Matei1
University “Politehnica” of Bucharest, Department of Inorganic Chemistry, Physical Chemistry and Electrochemistry,
Romania, 2Romanian Academy, “Ilie Murgulescu” Institute of Physical-Chemistry, Bucharest, Romania, 3Institute of
Mathematics, Physics and Mechanics, University of Ljubljana, Slovenia
1
One of the most studied compounds is bismuth ferrite, a well known multiferroic material, which exhibits
simultaneous ferroelectric and antiferromagnetic properties at room temperature. BiFeO 3 is relatively difficult to be
obtained as pure crystalline compound, impurities like Bi25FeO39 and Bi2Fe4O9 phases can appear [1,2].
Our work was focused on the study of the influence of hydrothermal reaction conditions (the mineraliser nature with
various concentrations, temperature, reaction time, surfactant etc.) on the formation of single phase bismuth ferrite and
its morphology. The powders were investigated by XRD, Raman spectroscopy, SEM and TEM. Magnetic properties
were evaluated on selected samples using a SQUID magnetometer. The (T) curves were collected at 1000 Oe in the
temperature range of 2 - 300 K. The isothermal magnetization hysteresis loops were measured at 2 and 50 K for
magnetic fields in the range -60  60kOe. The properties of hydrothermally obtained powders were compared with
bismuth ferrite synthesized by solution combustion method.
References
1. G. Catalan, J.F. Scott, Adv. Mater. 21 (2009) 2463-2485.
2. A.I. Iorgu, F. Maxim, C. Matei, L.P. Ferreira, L. Ferreira, M.M. Cruz, D. Berger, J. Alloy. Comp. 629 (2015) 62-68
123
124
ADDITION OF SiC AS NANO POWDERS OR WHISKERS INTO MgB2 PROCESSED BY EX-SITU SPARK
PLASMA SINTERING
G. Aldica, M. Burdusel, S. Popa, P. Badica
National Institute of Materials Physics, Atomistilor 105 bis, 077125 Magurele, Romania
MgB2 superconductor is considered a candidate for large scale applications competing with practical Nb-based
classic superconductors and with high temperature superconductors in the temperature range of 10-30 K. For its
successful application, enhancement and control of the critical current density Jc especially at high magnetic fields is
required, while a conveniently high critical temperature Tc is preserved.
Nano powders of SiC or whiskers were mixed with a commercial MgB2 powder. Mixtures were processed by spark
plasma sintering at 1150C for 3 min. Bulk samples with densities above 95% of theoretical value were obtained.
Carbon substitution for boron in the crystal lattice of MgB 2 is recognized in literature to produce disorder acting as
effective vortex pinning centers at medium and high magnetic fields promoting enhancement of the critical current
density. A higher carbon level introduced in the crystal lattice of MgB 2 decreases the critical temperature. Our results
are consistent with reported observations. However, there are few interesting details. Depending on the morphology of
SiC the magnetically measured superconducting transition curves show differences in their shapes. This suggests that
apart from a different average amount of carbon substitution level, the uniformity of the substitution is very different.
This is reflected in the shape of the Jc-H curves. A sample added with a powder containing both nano particles and
whiskers of SiC shows intermediate properties and demonstrates the possibility of refined tuning of the superconducting
properties.
125
STUDIES ON PREPARATION, CHARACTERIZATION AND HUMIDITY SENSING OF MgSUBSTITUTED YPO4
A.A.Hanna1, M.Sh.Khalil1, S.M.A.Mousa2, M.A.Sherief1*, G.M.Elkomy3
Inorganic Chemistry Department National Research Centre, Dokki, P.O.Box: 12622, Postal code: 11787, Cairo,
Egypt; 2 Chemistry Department and 3 physics Department; Corresponding author: *Inorganic Chemistry Department,
National Research Centre, Dokki, Cairo, Egypt. Tel: +20.10.5249230; fax: +20.2.33335968. E-mail:; [email protected] , [email protected]
1
YPO4 and Mg2P2O7 mixed ceramic semiconductor samples were prepared and investigated to be used as humidity
sensors. The samples were characterized using XRD, Surface area, SEM, and electrical conductivity under the effect of
humidity at room temperature was measured and discussed. The adding of Mg 2P2O7 improves the surface area of YPO4
which affected on the electric conductivity. The humidity sensing of the pure and mixture samples was studied by
dependences of the electrical conductivity on the mixture content and the sensitivity was also calculated. The results
indicated that the electrical conductivity increased as relative humidity increased up to 76% due to the protonic
conductivity which specified the action of water content on the phosphate molecules.
SYNTHESIS OF CUBIC AND HEXAGONAL NANO CRYSTALLINE AlN BY LIQUID PHASE
ELECTRICAL DISCHARGE
Reza Ebrahimi-Kahrizsangi, Ali Tavakoli
Advanced Materials Research Center, Materials Engineering Department, Najafabad Branch, Islamic Azad University,
Najafabad, Isfahan, Iran; [email protected]
In this study, Nanocrystalline h-AlN and c-AlN were synthesized in liquid ammonia and liquid nitrogen by the
electrical discharge method. The influence of effective process parameters on the particle size and Al conversion rate
was investigated. The structure, particle size, and morphology were evaluated using X-ray diffraction and scanning
electron microscopy. According to the results, reducing the spark energy leads to a decrease in the particle size and an
increase in purity. 98.4% and 12.1% purities were achieved for h-AlN and c-AlN powders, respectively.
Keywords: D. AlN; B. Nanocrystalline; A. Electrical Discharge; A. Spark Erosion
EXPERIMENTAL STUDY ON EFFICIENCY OF DIFFERENT SYNTHETIC HYDROXYAPATITE
POWDERS FOR LEAD REMOVAL FROM AQUEOUS SOLUTIONS
C. Tardei1, C. M. Simonescu2*, F. Grigore1, D. Talpeanu1, M. Dragne3
National Institute for R&D in Electrical Engineering ICPE-CA, 313 Splaiul Unirii, 031066, Bucharest, Romania;
[email protected]; 2 University Politehnica of Bucharest, Faculty of Applied Chemistry and Materials Science,
Department of Analytical Chemistry and Environmental Engineering, 1 – 7 Polizu Str., 011061, Bucharest, Romania;
[email protected]; 3 SC KEMCRISTAL SRL, 51 Muncii Str., 915200, Fundulea, Călăraşi,
Romania
1
This study evaluated crystalline and poorly-crystalline hydroxyapatite sorbents, after synthesis and aqueous lead
uptake process, in response to reaction time, solution pH, and Pb(II) concentration by batch experiments. We have
prepared hydroxyapatite (HAP) synthetic powders with different particle size and morphology, and investigated their
removal efficiency of Pb(II) ions from aqueous solutions with various initial Pb(II) ion concentrations. Equilibrium
soprtion isoterms of Pb(II) are analyzed by the Langmuir and Freundlich isotherm models. The kinetic processes of
Pb(II) adsorption on this adsorbent were described by applying pseudo-first-order, pseudo-second-oder and intraparticle
difussion models. The mechanism of lead uptake was examined by XRD analysis. By analysing of XRD patterns it can
be concluded that lead removal by HAP involves both surface complexation and calcium hydroyapatite dissolution
followed by less soluble Pb10(PO4)6(OH)2 precipitation. The results indicated that HAP can be used as an effective
adsorbent for removal of Pb(II) from aqueous solutions.
126
PREPARED AND ELECTRICAL CHARACTERIZATION OF FLEXIBLE PIEZOELECTRIC BT/SILICONE
RUBBER NANOCOMPOSITE
1
T. Malaeru1, J. Pintea1, G. Georgescu and D. Patroi1
National Institute for Electrical Engineering, INCDIE ICPE-CA Bucharest, Romania, Splaiul Unirii,No. 313, Sector 3,
e-mail: [email protected]
The flexible piezoelectric nanocomposites were synthesized by dispersing BaTiO3 (BT) nanoparticles in a polymer
matrix of silicon rubber type GLAOBASIL AL/20S and doped with a small amount of carbon nanotubes (MW-CNTs).
The BT nanoparticles were obtained by co-precipitation method, oxalate route modified by controlling the pH
parameter. The sample precursor was sintered in air, at temperatures between 1000 and 1200 0C, for 4h. X-ray
diffraction and scanning electron microscopy were used for compositional, structural and morphological
characterization of BT nanoparticles. XRD patterns showed that BT nanoparticles obtained at 1200 0C/4h have the
tetragonal perovskite structure as pure phase, the unit cell parameters values a = 3,9940Å, c = 4,038Å, and an average
size of 38,05 nm.
The dielectric and piezoelectric properties of flexible nanocomposites were determined on samples having the
geometry of 11,25x12x0.4 mm, in the range of frequencies at 40 Hz – 500 KHz using impedance analyzer. The
piezoelectric constant kp was calculated using the resonance and antiresonance values. The sample containing 50% BT
nanoparticles showed the highest value of piezoelectric constant (kp = 0.4).
Keywords: Nanocomposite, Piezoelectric, BaTiO3, Nanoparticles
Acnowledgements: The research was supported by NUCLEU Program PN 50301/2014.
SYNTHESIS AND CHARACTERIZATION OF HYDROPHOBIC SUPERPARAMAGNETIC Fe 3O4
NANOPARTICLRS
1
T. Malaeru1, W. Kappel1, E.A. Patroi1 and G. Georgescu
National Institute for Electrical Engineering, INCDIE ICPE-CA Bucharest, Romania, Splaiul Unirii,No. 313, Sector 3,
This paper reports the synthesis and characterization of hydrophobic superparamagnetic Fe 3O4 nanoparticles through
a simple and efficient in air atmosphere co-precipitation route. The hydrophobic surfactants agents (oleic acid,
oleylamine) were added in the magnetite crystal growth stage.
The resulting hydrophobic Fe3O4 nanoparticles have been characterized by X-ray diffraction (XRD), Fourier
transform spectroscopy (FT-IR), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM)
and vibrating sample magnetometer (VSM) at room temperature.
XRD patterns showed that the prepared Fe3O4 nanoparticles have face-centred cubic structure as pure phase, other
phases of iron oxides such as maghemite or hematite being absent in samples. The results revealed the formation of
Fe3O4 nanoparticles with average size of 9,32nm. FT-IR spectra of the prepared nanoparticles confirm the formation of
Fe-O bonds in the crystalline lattice of Fe3O4, as well as covalent bonds between the carboxyl and amino groups of the
surfactants agents and hydroxyl groups on the surface of Fe 3O4 nanoparticles.
Room temperature magnetization measurements showed that all sample of the hydrophobic Fe3O4 nanoparticles
exhibited superparamagnetic behaviour at 300 K.
Keywords: Superparamagnetic, Fe3O4, Co-precipitation, Hydrofobic
Acnowledgements: The research was supported by NUCLEU Program PN 50303/2014.
127
SYNTHESIS AND CHARACTERIZATION OF COBALT OXIDE Ca3Co4O9 USED AS THERMOELECTRIC
MATERIAL
Gabriela Telipan, Teodora Malaeru, Virgil Marinescu
Research and Development National Institute for Electrical Engineering ICPE-CA, Bucharest, ROMANIA;
[email protected]
Recently, p-type layered cobalt oxides, including Ca3Co4O9 have attracted much attention toward the realization of
oxide thermoelectric (TE) devices because of their good TE performance and advantages over conventional
intermetallic alloys of Bi2Te3/Sb2Te3 in terms of thermal stability at high temperature and low toxicity. Ca3Co4O9 is a
semiconductor type p with band gap 0.018 eV, which has a misfit structure consisting of single [CoO2] layer of CdI2
type stacked with [CoCa2O3] rocksalt type layers, with different in-plane lattice parameter[1,2}
Ca3Co4O9 was synthesized by sol gel method using the acid citric as complexing agent. The molar ratio acid
citric/Ca+Co=1:3, starting with Ca(NO3)2x4H2O and Co(NO3)2x6H2O as precursors salts. The obtained powder was
grounded, pressed into disc form with dimensions 4 mm x 2.25 mm under a pressure of 150 MPa, at a hydraulic press
type MAYER and sintered at 920oC for 4h in vacuum hot pressing in the hot isostatic pressing technique in Ar
atmosphere at a pressure 70 MPa. X-ray diffraction was evidentiated a monoclinic crystalline phase with 38 nm
crystallite sizes. SEM images shows a platelet shapes of particles with dimensions between 642 nm and 1.44 μm. The
elemental analysis realized by EDAX method was determined a composition in concordance with stoechiometric
composition as: Ca 24.32%, Co 46.23%, O 29.44%. The electrical resistivity, carrier density, Hall mobility were
measured with Van der Pauw method The electrical resistivity is 1.26x10-4 Ωm, carrier density is 1.56x1020 cm-3 and
Hall mobility is 1.078x102 cm2/Vs. The thermal conductivity determined with flash diffusivity method is 0.2 W/mK.
References
[1]. Athorn Vora-ud, Tosawat Seetawan, Ackadech Ratchasin, Journal of Material Science and Applied Energy 1(1) (2012) 19-21
[2]. Tsunehiro Takeuchi, PHYSICAL REVIEW B 69,2004, 125410.
STRUCTURAL, MAGNETIC and MAGNETOCALORIC PROPERTIES IN MANGANITE of Pr2/3A1/3MnO3
type, A=(Sr,Ba)
1
A. Bezergheanu1, C.B.Cizmas1
Transilvania University of Brasov, Dep. Electrical Engineering & Applied Physics, 29 Eroilor Blvd., 500036, Brasov,
Romania, e-mail: [email protected]
Magnetic materials showing a large magnetocaloric effect (MCE) have attracted considerable attention for their
potential application in magnetic refrigeration technology. Structural, magnetic and magnetocaloric effect of
Pr2/3A1/3MnO3 were A=Ba, Sr manganites with perovskite type structure
5.0
5T
were studied. The samples were prepared by the conventional ceramic
Pr Ba MnO
4.5
4T
3T
method. X-ray analysis showed the presence of only one single phase.
4.0
2T
The magnetic measurements were performed in the temperature range
1T
3.5
4.2 - 700K and external magnetic fields up to 7T. The adiabatic magnetic
3.0
entropy changes, |ΔS|, were determined from magnetization data.
2.5
Transition temperature for A=Ba is 195K and respectively 280K for
2.0
A=Sr. A large magnetocaloric effect (MCE) has been obtained in studied
1.5
samples with adiabatic magnetic entropie change.
1.0
Acknowledgements: This paper is supported by the Sectoral
0.5
Operational
Programme Human Resources Development (SOP HRD),
0.0
150 160 170 180 190 200 210 220 230 240 250 260
financed from the European Social Fund and by the Romanian
Temperature (K)
Government under the project number POSDRU/159/1.5/S/134378 and
Fig. 1 – Temperature dependences of the
by the structural founds project PRO-DD (POS-CCE, O.2.2.1., ID 123,
magnetic entropy change of Pr2/3Ba1/3MnO3 SMIS 2637, ctr. No 11/2009) for providing the infrastructure used in this
work.
1/3
3
-S m (J/kg*K)
2/3
128
DECOUPLING OF ENERGY TRANSFER WITH EXTRA DC CURRENT IN THE CASE OF A SELFLIMITING TRANSFORMER USING FLUX TRANSFER
Janos Kosa, Sahure Gecer, Ekrem Yanmaz, Ercan Ertekin, Ali Gencer
Ankara University, Center of Excellence for Superconductivity Research, Turkey ; (presenting and corresponding
author: Janos Kosa visiting scientist, [email protected] )
In previous work a single-phase and a three-phase self-limiting transformers was developed using magnetic flux
transfer between the independent primary and secondary iron cores.
The paper shows a type in which we can switch off, more precisely, limit energy transfer between primary and
secondary sides. An extra DC current breaks energy transfer in case of need. In our experiments, the coupling
superconducting wire had DC and AC current simultaneously, in fault and no-fault conditions. The designed individual
model is able to limit the fault current using the transfer of magnetic flux between independent iron cores. Presumably
we can and will apply this idea as it will give further possibilities for us in the field of science and industry.
THE INFLUENCE OF MICROSTRUCTURAL CHARACTERISTICS ON CORROSION BEHAVIOUR OF
STEAM OXIDIZED POWDER METALLURGY ALLOYS
Florentina Potecasu, Mihaela Marin, Octavian Potecasu
“Dunarea de Jos” University of Galati, Faculty of Engineering, Departament of Material Science and Engineering;
[email protected]
The purpose of this paper is to analyse the effect of microstructural characteristics on sintering time on the pore
morphology, microstructural changes and corrosion resistance. The iron based powders were compressed in a mold
using uniaxial pressing and the applied pressure was 600 MPa at room temperature. The specimens dimensions are  8
 6 mm. The green compacts were sintered at 1.150 °C and the sintering time was 60 minutes. Afetr sintering, steam
oxidized was applied at temperature of 550 °C and time was 60 minutes. The microstructures of the specimens were
investigated to correlate with the mechanical properties and corrosion resistance also. The corrosion behavior of
samples was evaluated using potentiodinamic polarization technique in 3.5% NaCl solution. Parameters like icorr,
cathodic (  c) and anodic (  a) were obtained after the extrapolation of the Tafel plots. A correlation between
microstructures of the alloys, mechanical properties and corrosion resistance was established.
ENHANCING THE WEAR PORPERTIES AND CORROSION BEHAVIOUR OF IRON BASED POWDER
METALLURGY ALLOYS BY CARBURIZING IN FLUIDIZED BED
Mihaela Marin, Octavian Potecasu, Florentina Potecasu
“Dunarea de Jos” University of Galati, Faculty of Engineering, Departament of Material Science and Engineering,
Galati, Romania; [email protected]
This research aims to investigate the influence of termochemical treatment (carburizing in fluidized bed) on the
microstructure, and consequently, the wear resistance and corrosion behaviour of iron based powder metallurgy alloys.
The three powders used in this study are unalloyed and alloyed with Cu, Ni and Mo. The powders were uniaxial pressed
at 600 MPa at room temperature with the specimens dimensions of  8  6 mm. After compaction, the green
compacts were subjected to sintering. The sintering temperature was 1150 °C ad the sintering time was 60 minutes.
After sintering, the carburizing in fluidized bed was applied at tempearture 900°C for 40 minutes. Wear resistance of
surface samples subject to carburizing in fluidized bed shows a significant improvement as compared to that in the
sintered condition. Due to an increased hardness, surface shows superior resistance to wear conditions. Corrosion
behaviour of heat treated sintered speciments was investigated by using electrochemical techniques in 3.5% NaCl
solution. The electrochemical results indicate that a more porous sample is more predictible to corrosion attack than a
less porous sample.
129
POSITRONIUM TRAPPING IN ADVANCED HUMIDITY-SENSITIVE NANOSTRUCTURED MgO-Al2O3
CERAMICS
1
Halyna Klym1, Adam Ingram2, Oleh Shpotyuk3,4 and Ivan Hadzaman5
Lviv Polytechnic National University, 12 Bandera str., 79013 Lviv, Ukraine, [email protected]; 2Physics Faculty of
Opole University of Technology, 75 Ozimska str., 45370, Opole, Poland; 3Vlokh Institute of Physical Optics, 23,
Dragomanov str., 79005, Lviv, Ukraine; 4Institute of Physics of Jan Dlugosz University, 13/15 al. Armii Krajowej,
42201 Czestochowa, Poland; 5Drohobych Ivan Franko State Pedagogical University, 24 I. Franko str., 82100,
Drohobych, Ukraine
Nanostructured MgO-Al2O3 ceramics are perspective materials for humidity sensors due to formation of uniform
porous structure, which promotes effective cooperative adsorption of water molecular from the surface towards
ceramics bulk. The positron annihilation PA method based on the fact that the unstable positron-electron system
(positronium Ps) is repelled from ionic cores of atoms and tends to location in open pores. In the ground state, the Ps
exists as singlet para-positronium p-Ps and triplet ortho-positronium o-Ps. Since the positron wave function overlaps
with electrons outside o-Ps, the positron-electron pair annihilates, this process being called “pick-off” annihilation. . To
clarify this feature, we shall study the PA characteristics of spinel MgO-Al2O3 ceramics affected to water sorption
treatment enhancing o-Ps decaying over positron trapping modes.
It is shown that the radius of free volumes where o-Ps are trapped in ceramics was calculated using the Tao-Eldrup
model with character lifetimes 3 and 4. With increasing of ceramics sintering temperature, the free volume radius R3
increases from 3.09 to 3.31 Ǻ and R4 left nearly at the same level (~18 Ǻ) in the samples taken after initial drying. In
water-immersed samples, both nanopore radii R3 and R4 decrease with amount of adsorbed water, these changed being
harmonized with nanopore content. In final, after ceramics drying, the initial state of these nanopores is partially
restored. Thus, both types of inner nanopores in ceramics are practically identical in respect to efficiency of water
sorption, but primary functionality of these ceramics is defined by smaller nanopores (defined by third component) due
to their prevailing content.
A COMPLEMENTARY ANALYSIS BASED BY FORC METHOD USED FOR HIGH FIELD
CHARACTERIZATION OF DIFFERENT FERROELECTRIC SYSTEMS
N. Horchidan*, L. Padurariu, and L. Mitoseriu
Dielectrics, Ferroelectrics & Multiferroics Group, Department of Physics, Alexandru Ioan Cuza University of Iasi, Blv.
Carol I 11, 700506, Iasi, Romania; *e-mail: [email protected]
Besides to classical high field characterization, P(E) hysteresis loops and ɛ(E) tunability, the experimental-modeling
approach of the FORC diagrams is a useful tool in ferroelectric materials characterization. The FORC diagrams give
additional information on the reversible/irreversible (i.e., non-switching/switching) contributions to the polarization and
on the field dependence of the differential susceptibilities. Furthermore, FORC diagrams are sensitive to parameters
such as the crystalline orientation, defects and fatigue phenomena and to the frequency of the applied field.
Ferroelectrics materials with homogeneous composition and well-defined rectangular hysteresis loops are characterized
by FORC distributions with a sharp maximum located at well-defined fields (Ec,M, Ebias,M) and with almost zero
reversible (non-switching) component, while broader distributions with an important reversible component are
characteristic of materials that are non-oriented, non-homogeneous, porous, with structural or charge defects. Therefore,
the FORC distributions can give fingerprints of the ferroelectric systems from the point of view of their local switching
properties. In present work, the FORC analysis is used in order to describe the switching evolution with increasing Sn
content in BaSnxTi1-xO3 (BTS) solid solutions and the influence of length scale mixing degree of soft and hard materials
in PZT-based ceramic composites. For BTS ceramics a clear trend of reducing switchable (irreversible, non-zero
coercivity) contribution with respect to the non-switchable (reversible) contribution to the ferroelectric polarization for
increasing Sn content (Fig.1) was observed. In case of PZT-based composite ceramics, the FORC diagrams provide
additional information about the influence of powders mixing (micro/macro mixing) on the reversible/irreversible
contributions to the polarization. Acknowledgements: This work was supported by the Romanian UEFISCDI grant PNII-PT-PCCA-2013-4-111.
130
HYDROXYAPATITE NANOPOWDERS OBTAINED BY SOL-GEL METHOD. SYNTHESIS AND
PROPERTIES
B. A. Sava1, C. Tardei2*, C.A. Simonescu3, A. Cucos2 and L. Boroica1
National Institute of Laser, Plasma and Radiation Physics, 409th Atomistilor str., 077125, Magurele, Romania,
[email protected] , 2 National Institute for R&D in Electrical Engineering ICPE-CA, 313 Splaiul
Unirii, 031066, Bucharest, Romania, [email protected], 3 University Politehnica of Bucharest, Faculty of
Applied Chemistry and Materials Science, Department of Analytical Chemistry and Environmental Engineering, 1 – 7
Polizu Str., 011061, Bucharest, Romania
1
Hydroxyapatite – HAP - nanopowders were obtained by sol-gel method, using as raw materials phosphorus oxide,
calcium nitrate and ethanol, at pH 0.5-1. The gels were obtained at room temperature or at 60oC, dried at 80oC and
thermal treated at 600, 700, 800 or 900 oC.
XRD pattern revealed only the HAP presence, in the case of the samples treated at for the 600oC and one maximum
specific for β tricalcium phosphate - βTCP – in the case of sample treated at 700oC which indicates the beginning of
HAP decomposing. The diffraction spectra for samples treated at 800 and 900 oC indicate the presence of HAP and
βTCP, meaning that a more important part of HAP is decomposed. The IR absorption band at 3572-3573 cm-1,
attributed to O-H bond stretching vibration together with symmetrical stretching bands of phosphate ion, from 10371049 and 1088-1129 cm-1 confirm the HAP presence in the samples thermal treated at 600 and 900 oC. The TG, DTG,
DTA shows two endotherm effects at low temperatures and one at high temperatures, between whom two exothermic
effects appears.
DIELECTRIC PROPERTIES OF PROTON-IRRADIATED Mg4Nb2O9 CERAMICS
L. Nedelcu 1, C. D. Geambasu 1, M. G. Banciu 1, M. M. Gugiu 2, V. Ghenescu 3, T. Preda 3
National Institute of Materials Physics, Bucharest-Magurele, Romania, [email protected]; 2 Horia Hulubei National
Institute of Physics and Nuclear Engineering, Bucharest-Magurele, Romania; 3 Institute of Space Science, BucharestMagurele, Romania
1
Low-loss dielectric materials continue to improve both terrestrial and space telecommunications. Of these, ceramics
represent cost-effective solutions for manufacturing of substrates, filters, antennas, waveguides, photonic crystals,
metamaterials etc. In this work, we report the effect of proton irradiation on the microwave dielectric properties of
Mg4Nb2O9 (MNO) materials. The MNO samples prepared by solid-state reaction method from high purity MgO and
Nb2O5 oxides have been structurally and morphologically characterized by X-ray diffraction and scanning electron
microscopy. Microwave properties were measured on Mg4Nb2O9 dielectric resonators with a Network Analyzer. In
order to simulate the exposure to cosmic radiation for a long time, accelerate ageing of Mg4Nb2O9 materials by proton
irradiation was performed. The MNO samples have been exposed to protons with 500 keV energy at a fluency of 10 12
particles/cm2. Particles’ flows were perpendicular to the samples’ surface and covered them entirely. The irradiation
procedure was made using a Cockcroft-Walton Tandetron accelerator. As-sintered ceramics exhibit a dielectric constant
around 13.5 and losses lower than 3x10-4 at 10 GHz. No significant variation of the dielectric constant was noticed for
irradiated samples. On the other hand, increases of the microwave dielectric loss with about 20 % have been evidenced
after proton exposure. The radiation-induced dielectric loss will be discussed with respect to the protons penetration
depth and their deposited energy.
Acknowledgements: This work was supported by a grant of the Romanian National Authority for Scientific
Research, Programme for Research - Space Technology and Advanced Research - STAR, project number 85.
131
TUNABLE MICROWAVE FILTER BASED ON MAGNETOELECTRIC COMPOSITES
Cristina E. Ciomaga1*, Ovidiu G. Avadanei1, Ioan Dumitru1, Florin Tufescu1,2 and Liliana Mitoseriu1
1
Department of Physics, Al. I. Cuza Univ. of Iasi, 11 Carol I Bv., 700506, Iasi, Romania
2
GRADIENT SRL, str. Codrescu no. 17, Iasi 700495, Romania
*e-mail: [email protected]
Tunable microwave devices are widely used in radar, telecommunication, and rf measurement systems. In the last
years, a promising technology for tunable microwave devices, which combines the advantages of using the ferrite and
ferroelectric devices, has been developed. Thus, magnetoelectric tunable microwave filter have been proposed and
prepared by using MnFe2O4–Pb0.988(Zr0.52Ti0.48)0.976Nb0.024O3 ferrite-ferroelectric composite material. The complex
permittivity and permeability of MF-PZT ceramics, measured in the range of frequency (1MHz ÷ 1 GHz), are derived
from the properties of PZTN ferroelectric phases (εPZT and μPZT=1), with a strong dilution effect due to the nonmagnetic
MnFe2O4 phase (small magnetic proprieties μMnFe2O4 and a dielectric constant εMnFe2O4 smaller than εPZT in
radiofrequency and microwave range). The microwave properties of the filter has been investigated by experiment and
simulations. We have found that the electromechanical resonance frequency of MF-PZTN composite can be tuned by an
applied magnetic field. With increasing magnetic field from 0 to 2kOe, the resonance frequency can be shifted.
Acknowledgements: This work was supported by CNCSIS-UEFISCSU project PN-II-PT-PCCA-2013-4-1119
THE EFFECT OF THERMAL TREATMENT ON STRUCTURAL AND OPTICAL PROPERTIES OF ZnO
NANOPARTICLES
C. Irina-Moisescu1, P. Vlazan2, P. Sfirloaga2, I. Miron2, I. Grozescu1,2
Politehnica University of Timisoara, P. Victoriei, No.2, 300006, Timisoara, Romania; 2National Institute for Research
and Development in Electrochemistry and Condensed Matter, P. Andronescu St., No. 1, 300224, Timisoara, Romania
[email protected]
1
Zinc oxide (ZnO) nanoparticles are used in different industrial applications due to their optical properties (band gap
value around 3.3 eV) [1].
In this paper, zinc oxide nanoparticles were synthesized by sol-gel method using zinc nitrate, isopropyl alcohol and
citric acid. The sol-gel route was achieved at 80°C.The obtained gel was thermally treated at different temperatures
(300, 400, 500 and 600°C) to observe the effect of temperature on the structural and optical properties of the materials.
Thus, the nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UVVis spectroscopy. Also, the luminescence properties (PL) were determined.
Refrences
[1] T.K. Gupta, Application of Zinc Oxide Varistors, J. Am. Ceram. Soc. 73 (1990) 1817-1840.
Acknowledgement
This paper is supported by the Sectoral Operational Programme Human Resources Development (SOP HRD),
ID134378 financed from the European Social Fund and by the Romanian Government.
132
S7
Ferroelectrics, Nonlinear Optical and
Luminescent Materials, Properties and
Applications
Invited Papers
133
134
ELECTRO-OPTIC SAMPLING OF TERAHERTZ PULSES USING FERROELECTRIC CRYSTAL AND
NON-COLLINEAR CHERENKOV PHASE-MATCHING
Masahiko Tani1, Gabriel Banciu2, Liviu Nedelcu2, Shinpei Ozawa1, Shogo Azuma1, Satoshi Tsuzuki1, Takashi Furuya1,
Stefan Funkner1, Gudrun G. Niehues1, Elmer S. Estacio3, Kazuyoshi Kurihara4, Kohji Yamamoto1, Michael Bakunov5
1
Research Center for Development of Far-Infrared Region, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan;
2
National Institute of Materials Physics; Atomistilor 105bis, 077125, Magurele, Ilfov, Romania; 3 University of
Philippines Diliman, 1101 Philippines; 4 Faculty of Education and Regional Stduies, Uiversity of Fukui, 3-9-1 Bunkyo,
Fukui 910-8507, Japan; 5 University of Nizhny Novgorod, 603950, Russia; E-mail: [email protected]
I/I
×10-5
8
6
4
2
0
-2
-4
10
BaTiO3
LiNbO3
15
Time(ps)
20
Normalized FFT amplitude spectra(a.u.)
In this paper we report the electro-optic (EO) sampling of terahertz pulses using ferroelectric crystal and noncollinear Cherenkov phase-matching. The Cherenkov phase-matching makes it possible to achieve an effective velocity
matching in ferroelectric crystal, which has a large refractive index and strong absorption in the THz frequency region.
In this paper we demonstrate efficient EO sampling using LiNbO3 and BaTiO3 crystals in the Cherenkov- phasematching scheme. It is shown that the efficiency of EO sampling with BaTiO3 is much reduced compared to that with
LiNbO3 due to the strong THz absorption even though the EO coefficient of BaTiO3 is three times higher than that of
LiNbO3. We discuss the possibility to realize an efficient THz EO sampling by using Sr(x)Ba(1-x)NbO3 crystal,
whose THz absorption could be reduced compared to that of BaTiO3 without reducing the EO coefficient from that of
BaTiO3 by controlling the Sr ratio "x" to Ba.
Full Abstract:
In this paper we report a non-collinear electro-optic (EO) sampling of THz pulsed radiation using ferroelectric
crystals. Some ferroelectric crystals exhibit large electro-optic coefficients. For example, r33 = 31 [pm/V] for LiNbO3,
and r33 =97 and r42 =1640 [pm/V] for BaTiO3, while r41 =4.3 [pm/V] for ZnTe, which is the most popularly used nonferroelectric crystal for THz EO sampling. However, such large EO coefficients have not been exploited for EO
sampling of THz radiation so far because of the large velocity mismatch between the optical probe pulse and THz
radiation, which seriously degrades the EO sampling efficiency for THz radiation. Recently, we succeeded efficient
detections of THz radiation by using non-collinear Cherenkov phase-matching technique [1] and Si-prism-coupled
LiNbO3 crystal. The non-collinear Cherenkov phase-matching makes it possible to use nonlinear optical media with a
large velocity mismatch, such as LiNbO3 in THz EO sampling. In addition, we were also successful for detection of
THz radiation using BaTiO3 crystal in a similar experimental configuration. Figure 1(a) shows the THz waveforms
detected with LiNbO3 and BaTiO3 in the Cherenkov phase-matching scheme for the same THz radiation source (a
photoconductive antenna), and Fig. 1 (b) shows corresponding amplitude spectra. We can see that the efficiency of EO
sampling with BaTiO3 is much reduced compared to that with LiNbO3 even though the EO coefficient of BaTiO3 is
three times higher than that of LiNbO3. The spectral bandwidth for BaTiO3 is also much reduced compared with that of
LiNbO3. The poor performance of BaTiO3 as the THz EO sampling detector is explained by its strong absorption in
THz frequency region compared to LiNbO3. There are two possibilities for improving the efficiency of THz EO
sampling with BaTiO3 crystal.
1) To replace Ba with Sr (or other atoms) making Sr(x)Ba(1-x)TiO3 (BST) crystal with an appropriate molar ratio "x".
2) To introduce an optical waveguide structure, which confines the probe laser beam very close to the interface of
Si prism and BaTiO3 crystal.
We discuss the optical property of BST, which we fabricated, and the possibility to realize an efficient THz EO
sampling by using BST crystal, whose THz absorption could be reduced compared to that of BaTiO 3 without reducing
the EO coefficient from that of BaTiO3 by controlling the Sr ratio "x" to Ba.
(a)
(b)
1
BaTiO3
LiNbO3
0.1
0.01
1E-3
0
1
2
3
Frequency(THz)
4
Fig. 1 (a) THz waveforms detected with Cherenkov-phase-matched EO sampling using LiNbO3 and BaTiO3. (b)
Corresponding FFT amplitude spectra of the waveforms shown in (a).
[1] M. Tani, et al, Opt. Express 19, 19901 (2011).
135
USES OF PHOSPHOR MATERIALS FOR PRACTICAL APPLICATIONS
HC Swart, JJ Terblans, RE Kroon, OM Ntwaeaborwa, MYA Yagoub, E. Coetsee, Vinod Kumar.
Department of Physics, University of the Free State, Bloemfontein, ZA9300, South Africa.
Phosphor materials are an integral part of our daily life. Luminescent compounds and materials have numerous uses,
most notably in detectors of various sorts, but also in consumer products such as displays, light emitting diode (LED)
lighting and watches. The emission properties, whether of a fast decay rate fluorescent material or a slow decay rate
phosphorescent material, are defined by the chemical composition and the physical structure of the luminescent
material. Phosphor hosts, defects, dopant concentration and valence state are some of the important parameters to be
considered when designing new phosphor materials. The crystal field that is determined by the environment in the host
material in combination with the dopant ion with the correct valence state can be used to obtain emissions from the
Ultra violet (UV) to the infra-red (IR) wavelength ranges. Phosphor materials have been successfully used to improve
the efficiency of various applications. ZnO nanoparticles both undoped and doped with different rare earth elements
were synthesized by several synthesized techniques. The strong deep level emission (DLE) and near band edge
emission could be tuned to cover a wide spectral range. The DLE emission was shown to be due to oxygen vacancies.
The strong DLE, covering a wide spectral range of ~375-650 nm, signifies the potential optoelectronics application in
the near white LED applications. The major problem that limits solar cells’ efficiency is their insensitivity to the whole
solar spectrum which is the so-called spectral mismatch. Therefore, several mechanisms have been explored based on
photoluminescence to convert the solar cell spectrum where the spectral response of the solar cell is low to regions
where the spectral response of the solar cell is high. The energy transfer from Eu2+ to Pr3+ and Yb3+ ions in a SrF2 host is
one example. The Eu2+ (4f65d→4f7) emission band lead to efficient energy transfer from Eu2+ to the Pr3+ ions in the
SrF2 samples and it showed the quantum cutting process with Yb 3+. It was also shown that Pr3+ emits strongly in the
NIR region where it overlaps with the Yb3+ emission.
CHEMISTRY OF CARBON MONOXIDE ON LEAD ZIRCO-TITANATE (001) SURFACES
Liviu C. Tănase1, Laura E. Ştoflea1, Silvano Lizzit2, Paolo Lacovig2, Cristian A. Tache1,2, Luminiţa Hrib1, Lucian
Trupină1, Lucian Pintilie1, Nicoleta G. Apostol1, and Cristian M. Teodorescu1
1
National Institute of Materials Physics, Atomiştilor 105b, 077125 Măgurele-Ilfov, Romania; 2Elettra Sincrotrone
Trieste, S.S. 14 - km 163,5, Area Science Park, 34169 Basovizza-Trieste, Italy
Atomically clean lead zirco-titanate PbZr0.2Ti0.8O3 PZT(001) single crystal layers are synthesized by pulsed laser
deposition followed by in situ annealing in oxygen atmosphere. Depending on the preparation conditions, the out-ofplane polarization of the layers could be varied and analyzed by X-ray photoelectron spectroscopy via the surface band
bending of the core levels [1,2], together with low energy electron diffraction (LEED) and piezoresponsive force
microscopy (PFM). It was found that only for layers featuring a polarization oriented inwards, P(-), carbon monoxide
(CO) is adsorbed at room temperature, with a saturation coverage lower than one CO molecule per surface unit cell of
PZT. CO adsorbs in both molecular (oxidized) and dissociated (reduced) states, with a large majority of the reduced
state. CO desorbs with increasing temperature (above 700 K) or when the surface is irradiated with soft X-rays. Other
phenomena, such as sticking of CO-terminated contaminants on areas exhibiting outwards polarization P (+) [3] or lightinduced surface reductive properties [4] will also be discussed. Hence, ferroelectric polarization combined with optical
irradiation may be used to control molecular processes involving CO adsorption, desorption, oxidation and reduction.
Ferroelectric surfaces will be discussed in the framework of their applications as tunable catalysts.
[1] N.G. Apostol, L.E. Stoflea, G.A. Lungu, C. Chirila, L. Trupina, R.F. Negrea, C. Ghica, L. Pintilie, and C.M.
Teodorescu, Appl. Surf. Sci. 273, 415-425 (2013).
[2] L.E. Stoflea, N.G. Apostol, C. Chirila, L. Trupina, R. Negrea, L. Pintilie, and C.M. Teodorescu, J. Mater. Sci.
49, 3337-3351 (2014).
[3] L.E. Ştoflea, N.G. Apostol, L. Trupină, and C.M. Teodorescu, J. Mater. Chem. A 2, 14386-14392 (2014).
[4] D.G. Popescu, M.A. Huşanu, L. Trupină, L. Hrib, L. Pintilie, A. Barinov, S. Lizzit, P. Lacovig, and C.M.
Teodorescu, Phys. Chem. Chem. Phys. 17, 509 - 520 (2015).
136
APPLICATION OF CRYSTAL GROWTH PROCESSES TO THE PRODUCTION OF EUTECTIC OXIDES
T. Duffara, M. Cherifb ,a, L. Carrozb ,c, O. Benamarad, M. Parliere
a- SIMaP-EPM, Grenoble-INP-CNRS-UJF, BP 75, 38402 Saint Martin d’Hères cedex, France; b- SNECMA
Villaroche, Rond-point René Ravaud, 77550 Réau, France; c- RSA, 380 Rue Rn 85 BP 16, 38560 Jarrie, France; dILM; e- ONERA
Ceramics are materials with a refractory behavior but generally poor mechanical properties, due partly to intrinsic
bonding and partly to the forming process (mainly sintering). However, eutectic oxides grown from the melt show a
microstructure, at the micrometer scale, leading to very good mechanical properties at high temperatures. Thus,
directional solidification processes have been extensively investigated to control the microstructure of these eutectic
materials. This microstructure is related to the liquid-solid phase transition which depends on process design, cooling
rate, temperature gradient at the solidification interface, convective level in the melt and chemical composition. Our
study focuses on the directional solidification of Al2O3-YAG-ZrO2 ternary eutectic system. This material exhibits a
complex, fully embedded microstructure resulting in a high strength at high temperature (close to its melting point
1715°C) and a good resistance to oxidation. Due to these properties, it is an ideal candidate for high temperature
structural applications.
In order to understand the relationship between the microstructure and the process parameters, it is necessary to
investigate a wide range of growth rates, temperature gradients and convective levels in the melt. In this purpose several
crystal growth processes (Bridgman, Micro-pulling down and EFG) have been applied to the growth of these eutectics,
because they offer the possibility to control precisely the growth conditions. Numerical simulation of these three
processes allowed to know precisely the growth conditions. The eutectic spacing and the microstructure shape are
studied for all grown samples and it will be shown that, thanks to the use of this various, complementary techniques,
several growth regimes have been identified, leading to different types of microstructures.
FERROELECTRIC BaTiO3/SrTiO3 SUPERLATTICES: INTERFACES AND LATTICE STRAIN EFFECTS
E. Khestanova1, N. Dix1, I. Fina1, J.M Rebled1,2, C. Magen3, S. Estrade2, F. Peiro2, J. Fontcuberta1 and F. Sanchez1
1
Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC), Spain. E-mail: [email protected] ; 2LENS MIND/IN2UB, Universitat de Barcelona, Spain; 3Instituto de Nanociencia de Aragón (INA), Zaragoza, Spain
Superlattices (SPLs) consisting of ferroelectric/paraelectric oxide layers present a large interest due to their
flexibility for tuning of ferroelectric properties. In such SPLs a large number of interfaces between ferroelectric and
paraelectric materials are present, and additionally the lattice strain in the SPLs can differ notably with respect to single
phase films. Discerning between strain and interface effects on the ferroelectric properties of superlattices constitutes a
bottleneck.
We have fabricated BaTiO3/SrTiO3 (BTO/STO) SPLs by pulsed laser deposition (PLD) assisted by high pressure
reflection high energy electron diffraction (RHEED) for real time control of the number of monolayers. A series of
SPLs were grown on TiO2-terminated SrTiO3(001) substrates, with La0.7Sr0.3MnO3 as bottom electrode. RHEED and
atomic force microscopy confirm persistent layer-by-layer and atomically flat surfaces in complex M x (n-BTO / nSTO) SPLs, with period n from 1 to 10 and M adjusted to have total of 120 monolayers. X-ray reflectivity and X-ray
diffractometry (XRD) patterns show Kiessig and Laue fringes signaling the high quality of the samples. XRD reciprocal
space maps and high resolution transmission electron microscopy confirmed coherent growth. Ferroelectric
measurements show that SPLs have polarization along the out-of-plane direction. The remnant polarization (Pr) ranges
from a few μC/cm2 to more than 20 μC/cm2, increasing (decreasing) with the number of interfaces (STO thickness in
each period). We present a thin film growth strategy that permits changing lattice strain for a fixed M x (n-BTO / nSTO) SPL architecture, and we show that Pr is much less sensitive to lattice strain than to the number of interfaces.
137
BRIGHT TERAHERTZ-WAVE GENERATION USING NONLINEAR OPTICAL CONVERSION: TOWARD
MEGA-WATT PEAK INTENSITY
Hiroaki Minamide
RIKEN center for Advanced Photonics (RAP), RIKEN
The terahertz (THz) wave range, with only poor sources available, has long been an unexplored electromagnetic
wave range, but recent remarkable enhancement of the source power has paved the way to further development of THz
wave technology. The field strength of the THz wave has lately reached the MV/cm level, which can implement a
nonlinear response of various materials by such intense peak-power, and might facilitate control by a THz wave such as
coherent control or structural phase transition in applications.
Recently in our group, a remarkable breakthrough related to radiation peak-power over ten kilowatt or broad-band
frequency-tunability covering tens of THz frequency were achieved using nonlinear optical wavelength-conversion in a
MgO doped LiNbO3 or organic nonlinear crystals of DAST and BNA. In addition, highly sensitive detection of
terahertz-waves with wide dynamic range using frequency up-conversion at room temperature was obtained.
This talk describes advanced studies of intense Terahertz-wave generation and the sensitive detection.
ACKNOWLEDGEMENTS
This work was partially supported by Collaborative Research Based on Industrial Demand of the Japan Science and
Technology Agency (JST), and JSPS KAKENHI Grant Numbers 26246046, 26620162, 15K18080, 25220606,
26287067, 26390106, 15K18079.
_____________________________________________________________________________________________
REFERENCES
[1] H. Minamide, S. Hayashi, K. Nawata, T. Taira, J. Shikata, and K. Kawase, Journal of Infrared, Millimeter, and
Terahertz Waves 35, 25 (2014).
[2] S. Hayashi, K. Nawata, T. Taira, J. Shikata, K. Kawase, and H. Minamide, Scientific Reports 4, 05045 (2014).
[3] H. Minamide and H. Ito, Comptes Rendus Physique 11, 457 (2010).
[4] H. Minamide, T. Ikari, and H. Ito, REVIEW OF SCIENTIFIC INSTRUMENTS 80, 123104 (2009).
[5] H. Minamide, J. Zhang, R. X. Guo, K. Miyamoto, S. Ohno, and H. Ito, Appl. Phys. Lett. 97, 121106 (2010).
[6] S. Fan, F. Qi, T. Notake, K. Nawata, Y. Takida, T. Matsukawa, and H. Minamide, Opt Express 23, 7611
(2015).
[7] S. Fan, F. Qi, T. Notake, K. Nawata, T. Matsukawa, Y. Takida, and H. Minamide, Appl. Phys. Lett. 104,
101106 (2014).
[8] F. Qi, S. Fan, T. Notake, K. Nawata, T. Matsukawa, Y. Takida, and H. Minamide, Opt. Lett. 39, 1294 (2014).
[9] F. Qi, S. Z. Fan, T. Notake, K. Nawata, T. Matsukawa, Y. Takida, and H. Minamide, Laser Phys Lett 11,
085403 (2014).
[10] F. Qi, K. Nawata, S. Hayashi, T. Notake, T. Matsukawa, and H. Minamide, Appl. Phys. Lett. 104, 031110
(2014).
[11] K. Nawata, T. Notake, H. Ishizuki, F. Qi, Y. Takida, S. Fan, S. Hayashi, T. Taira, and H. Minamide, Appl.
Phys. Lett. 104, 091125 (2014).
It is well know that MgO-doped lithium niobate (MgO:LiNbO3) crystal has excellent characteristics for efficient
tunable/broadband terahertz (THz)-wave generation. Over the past few decades, high-output-power, compact, stable,
and room-temperature THz-wave sources via optical frequency down-conversion in MgO:LiNbO3 crystals have
been studied intensively. In particular, THz-wave parametric generations/oscillations (TPGs/TPOs) based on
stimulated phonon-polariton scattering in MgO:LiNbO3 crystal can produce widely-tunable monochromatic
THzwave
pulses in the frequency range between 1 to 3 THz [1]. More recently, not only intense generation but also
sensitive detection of THz waves in TPG has been achieved by applying injection-seeding to one of the
downconverted
waves [2]. These attractive features of injection-seeded TPGs (is-TPGs) are quite suitable for some of
practical applications.
However, efficient THz-wave generation/detection in MgO:LiNbO3 crystal is limited due to the strong
absorption of THz wave by crystal itself. Therefore, to overcome this problem, we demonstrate high-peak-power
THz-wave generation and highly-sensitive detection by using efficient surface-coupling configuration based on
trapezoidal MgO:LiNbO3 crystals. The peak power of more than 1 kW and dynamic range up to 70 dB are
successfully obtained.
138
CREATING ELECTRIC DIPOLE IN NANO-COMPOSITE – APPLICATIONS IN INFORMATION
STORAGE AND ENERGY GENERATION
Zahra Al Halafi, Iulia Salaoru and S Paul
Emerging Technologies Research Centre, De Montfort University, Hawthorn Building, The Gateway Leicester LE1
9BH, United Kingdom; [Email: [email protected] ]
Intensive research is currently underway to exploit the highly interesting properties of nano-bits (“nano-sized
particles and organic molecules”) for optical, electronic and other applications. The basis of these unique properties is
the small-size of these structures which results in quantum mechanical phenomena, such as Coulomb Blockade, etc. A
nano-composite (in context of this work) is a blend (or an admixture) of organic polymer, small molecules and /or
nanoparticles. The small molecules and/or nano-particles are selected in such a way so that it can create an internal
electric in the nano-composite or nano-composite should display ferroelectric behaviour. We have demonstrated the
effect of internal electric field both in emerging two terminal memory and organic photovoltaic solar devices. Memory
devices play an important role in the electronics arena and inspire advances in various technologies. This work
describes the use of nano-bits in flash and organic memory devices. Also, we have demonstrated that incorporation
ferroelectric nano-particles (such as BaTiO3 and SrTiO3) has resulted in higher efficiency organic photovoltaic solar
cell. In this presentation, the progress in the use of “nano-bits” in memory devices and photovoltaic solar cells over the
last ten years will be presented.
Key References
S. Paul, IEEE Transaction on Nanotechnology, (2007), 6, 191-195.
S. Paul, A. Kanwal, and M. Chhowalla, Nanotechnology (2006), 17, 145-151.
D Black, I Salaoru and S Paul (2014) , EPJ Photovoltaics, 5, art no. 50403
D Prime, D. and S. Paul . (2010) Applied Physics Letters, 96 (4) 043120
D Black, S Paul and I Salaoru (2010), Nanoscience and Nanotechnology Letters, 2 (1), pp. 41-45
TUNABLE FERROELECTRIC POLARIZATION AND ITS INTERPLAY WITH SPIN-ORBIT COUPLING
IN PEROVSKITE HALIDE SOLAR CELLS
Alessandro Stroppa1
1
Domenico Di Sante1, Paolo Barone , Menno Bokdam2, Georg Kresse2, Cesare Franchini2,M.-H. Whangbo3, Ionel
Humelnicu4,Silvia Picozzi1
1CNR-SPIN, L'Aquila, Italy; 2Faculty of Physics, Center for Computational Materials Science, University of Vienna,
A-1090 Wien, Austria; 3Department of Chemistry, North Carolina State University, Raleigh, North Carolina 276958204, USA; 4"A.I. Cuza" University of Iasi, Iasi, Romania
Ferroelectricity is a potentially crucial issue in halide perovskites, breakthrough materials in photovoltaic research.
Using density functional theory simulations and symmetry analysis, we show that the lead-free perovskite iodide
(FA)SnI3, containing the planar formamidinium cation FA, (NH 2CHNH2)+ ,is ferroelectric. In fact, the perpendicular
arrangment of FA planes, leading to a 'weak' polarization, is energetically more stable than parallel arrangements of FA
planes, being either antiferroelectric or 'strong' ferroelectric. Moreover, we show that the 'weak' and 'strong' ferroelectric
states with the polar axis along different crystallographic directions are energetically competing. Therefore, at least at
low temperature, an electric field could stabilize different states with the polarization rotated by π/4, resulting in a
highly tunable ferroelectricity appealing for multistate logic. Intriguingly, the relatively strong spin-orbit couling in
noncentrosymmetric (FA)SnI 3 gives rise to a co-existence of Rashba and Dresselhaus effects and to a spin texture that
can be induced, tuned and switched by an electric field controlling the ferroelectric state.
139
140
Oral Presentations
PHOTOELECTRON SPECTROMICROSCOPY OF LEAD ZIRCO-TITANATE (001) SURFACES
1
Laura E. Ştoflea1, Liviu C. Tănase1, Nicoleta G. Apostol1, Alexei Barinov2, and Cristian M. Teodorescu1
National Institute of Materials Physics, Atomiştilor 105b, 077125 Măgurele-Ilfov, Romania; 2Elettra Sincrotrone
Trieste, S.S. 14 - km 163,5, Area Science Park, 34169 Basovizza-Trieste, Italy
This contribution demonstrates the ability to image ferroelectric
domains with binding energy contrast for the photoelectron
spectroscopy with sub-m spatial resolution. Domains with
different out-of-plane polarization manifest by core level shifts due
to surface band bendings [1,2]. Such shifts are evident also in
spectromicroscopic images obtained for core levels of
PbZr0.2Ti0.8O3(001) (see Figure 1). As compared with
piezoresponse force microscopy (PFM), the photoemission
spectromicroscopy has the advantage to assess directly the areas
with different polarization, without any previous poling [3]. Surface
reduction, clustering and cluster migration will also be discussed.
[1] N.G. Apostol, L.E. Stoflea, G.A. Lungu, C. Chirila, L.
Trupina, R.F. Negrea, C. Ghica, L. Pintilie, and C.M. Teodorescu,
Appl. Surf. Sci. 273, 415-425 (2013).
[2] L.E. Stoflea, N.G. Apostol, C. Chirila, L. Trupina, R.
Negrea, L. Pintilie, and C.M. Teodorescu, J. Mater. Sci. 49, 33373351 (2014).
[3] D.G. Popescu, M.A. Huşanu, L. Trupină, L. Hrib, L. Pintilie,
A. Barinov, S. Lizzit, P. Lacovig, and C.M. Teodorescu, Phys.
Chem. Chem. Phys. 17, 509 - 520 (2015).
141
Figure 1
OPTICAL PROPERTIES OF DYE-DOPED NANOSTRUCTURES
Monica Enculescu
National Institute of Materials Physics, PO Box MG-7, 77125, Magurele-Bucharest
[email protected]
Produced either as free-standing objects, as hierarchical structures or as complex assemblies, embedded in a
template or templateless, nanostructures were proved to possess fascinating properties and are extremely useful, taking
into account the increasingly technological necessities. Dye doping of nanostructures is extremely efficient for
obtaining special optical properties. We produced two types of low dimensional structures with tailored optical
properties, dye-doped nanorods grown in polymer template membranes and dye-doped nanofibers produced by
electrospinning. Firstly, we present our studies regarding the optical properties of dye-doped nanorods grown in etched
ion track polymer templates. This type of membranes present parallel nanopores with diameters down to 10 nanometers
and are suitable for the growth of semiconductor or metallic wires as well as insulating rods. We obtained potential
tunable emitting nanostructures that can overcome the present limitations of solid state dye doped materials. Secondly,
by a simple technique such as electrospinning we synthesized dye-doped polymer nanofibers. The variations of process
parameters allow us to change the morphology of the dye-doped fibers and by that we can tune their emissive
properties. Although different in many aspects, both types of nanostructures present remarkable emitting properties with
high intensities and up-converting luminescence.
UPCONVERSION LUMINESCENCE IN CaSc2O4 CODOPED WITH Er3+ AND Yb3+
1
A. Stefan1,2, S. Georgescu1, O. Toma1, C. Matei1,2
National Institute for Laser, Plasma and Radiation Physics, Magurele, Jud. Ilfov, 077125, Romania, 2 University of
Bucharest, Faculty of Physics, Magurele, Jud. Ilfov, 077125, Romania; [email protected]
The calcium scandate (CaSc2O4) is a new and promising host for efficient upconversion [1] due to low energy
phonons (540 cm-1), short distances between positions that can be occupied by the dopants (assuring an efficient energytransfer) and high solubility of ytterbium ions. Concentration-optimized CaSc2O4: Er3+/ Yb3+ phosphor presents efficient
Yb3+  Er3+ energy transfer and strong green ((2H11/2, 4S3/2)(Er3+)  4I15/2(Er3+)) and red ((4F9/2)(Er3+)  4I15/2(Er3+))
luminescence.
The calcium scandate ceramic samples doped with Er3+ and Yb3+ were synthesized by the solid state reaction method
(at 1500ᵒC for 4 h) from stoichiometric quantities of high purity oxides (Sc2O3, Er2O3, Yb2O3) and CaCO3.
The upconversion luminescence is analyzed through spectral distributions, power dependences, and lifetime
measurements. The room-temperature luminescence spectra were excited at 488nm and 980 nm and recorded in the
wavelength domain 500–1700 nm. Yb3+ → Er3+ energy transfer processes of the emitting levels of Er 3+ are discussed
and the back-transfer Er3+ → Yb3+ was evidenced. The decay curves of metastable levels ( 2H11/2, 4S3/2), 4F9/2, 4I13/2 of
Er3+ and 2F5/2 of Yb3+ were analysed and the lifetimes of the metastable levels were measured.
Acknowledgment: This work was supported by (UEFISCDI), in the frame of the Project IDEI 82/06.10.2011
References
[1] J. Li, J. Zhang, Z. Hao, X. Zhang, J. Zhao, Y. Luo, J. Appl. Phys. 113, p. 223507, (2013).
142
THERMALLY STABLE ENCAPSULATION MATERIAL BASED ON GREEN AND RED LANTHANIDE
PHOSPHOR FOR WHITE LIGHT EMITTING DIODES
Wedianti Shualdi*, Nik Mohd Azmi Nik Abd Aziz, Nurul Huda Yusoff, Nor Adhila Muhammad,
Khairuldin Mohd Isha
Energy Materials Section, Advanced Materials Research Centre (AMREC), Standards and Industrial Research Institute
Malaysia (SIRIM) Berhad, Lot 34, Jalan Hi-tech 2/3, Kulim Hi-tech Park, 09000 Kulim, Kedah. *Corresponding
author. Tel: +6044017267; Fax: +044033225; Email: [email protected]
This study reported thermal stability of hybrid sol-gel encapsulation materials doped with lanthanides complexes for
generating white light. Red and green lanthanide phosphor, Eu(tta)3phen and Tb(4DBBA)3TPPO were incorporated
into VTES:TEOS hybrid sol-gel and dispensed into 360 nm to 390 nm ultraviolet light emitting diode (UV LED)
packages. Thermal properties of developed encapsulation material were analysed by TGA. A thermal aging test up to 96
hours was done to check the stability of developed encapsulation material towards UV LED junction temperature of
120oC and the luminescence properties changes was observed using photoluminescence measurement. To check the
encapsulation material stability on forward voltage, the operation voltage has been increased from 3.0V to 4.0V. The
photometric measurement were recorded using integrating sphere for the properties of Colour Rendering Index (CRI),
colour temperature and Commission Internationale de L’Eclairge (CIE) colour coordinates. Based on the results,
developed encapsulation material produced white colour with CIE colour coordinate of (0.32, 0.35), CRI up to 75 and
colour temperature around 6000K.
DEVELOPMENT OF NEW NONLINEAR OPTICAL CRYSTALS FOR EFFICIENT BLUE LASER
SOURCES
Alexandru Achim1, Lucian Gheorghe1, Voicu Flavius1
National Institute for Laser, Plasma and Radiation Physics, Bucharest R-077125, Romania
1
The availability of laser frequencies in the visible range is limited by laser materials and pump sources.
LaCa4O(BO3)3 (LaCOB) crystal is a member of the ReCa4O(BO3)3 family (where Re = Y, La, Gd) and crystallizes in
the monoclinic biaxial system belonging to the Cm space group [1,2]. Previous researches on NLO properties of
LaCOB crystal [3] has predicted that non-critical phase matching (NCPM) wavelength along Z axis is in the range of ~
998 nm, which is close to the emission wavelength of highly efficient fiber-coupled laser diodes in the 900-980 nm
wavelength range. NCPM is advantageous because of its large angular acceptance and because it eliminates the walkoff between fundamental and harmonic radiations which lead to the highest efficiency. Thus, by a partial cationic
substitution of Ca2+ ions with Sr2+ ions in LaCOB crystal its NLO properties can be modified in a controlled way in
order to achieve new NCPM conditions for second harmonic generation (SHG) of specific fundamental wavelengths in
the 900-980 nm range, preserving in the same time the congruent melting character which offers the possibility to
obtain large crystals from melt. In this way it will be possible to obtain high-power blue laser emission (450 - 490 nm)
by SHG of powerful fiber-coupled laser diodes in NCPM conditions that ensure maximum conversion efficiency.
Single crystals of La(Ca1-xSrx)4O(BO3)3 with large size and good quality have been grown by Czochralski method.
According to our assumptions, the obtained results demonstrate that the grown crystals can convert the infrared
radiation (989 - 946 nm) into blue laser radiation (495 - 473 nm) by type-I NCPM SHG processes along Z axis.
[1] T. Sasaki, Y. Mori, M. Yoshimura, Y.K. Yap, T. Kamimura, Mater. Sci. Eng., vol. 30, pp. 1 (2000).
[2] A. B. Ilyukhin, B. F. Dzhurinskii, Russ. J. Inorg. Chem., vol. 38, pp. 847 (1993).
[3] Z.P.Wang et all, Laser Phys Lett , vol. 11, pp.5 (2014)
This work was supported by the Romanian MEN-UEFISCDI, Partnerships program, Grant agreement No.10/2014.
143
GROWTH AND CHARACTERIZATION OF Sm:ASL CRYSTALS FOR VISIBLE LASERS
L. Gheorghe, A. Achim, G. Stanciu, F. Voicu, C. Gheorghe
National Institute for Laser, Plasma and Radiation Physics, Solid-State Quantum Electronics Laboratory, 077125
Magurele, Bucharest, Romania
In the last few years, yellow-orange lasers in the range of 570 - 620 nm have attracted a lot of attentions for
important applications in the fields of medicine, astronomy, remote sensing and visual displays. Laser emission in this
wavelength range can be obtained either by direct emission from materials activated with suitable laser ions or by
nonlinear optical methods such as sum-frequency mixing and stimulated Raman scattering (SRS); this wavelength
range cannot be generated by the frequency-doubling technique because there are no solid-state lasers emitting in the
corresponding range of fundamental frequencies. The visible emission properties of some trivalent rare earths (RE 3+)
can avoid the difficulties of nonlinear processes, but the pumping problems with classical lamps or luminescence
quenching processes, have determined a reduced number of studies for many years. Presently, this can be surmounted
by the recent development of InGaN laser diodes in the 405 nm range.
Sr1-xSmyLax-yMgxAl12-xO19 (Sm:ASL) crystals are of interest as solid-state laser materials emitting in the visible
range, especially for diode pumping due to their partially disordered nature. This work reports on the synthesis and
growth conditions of Sm:ASL single crystals of good optical quality by the Czochralski method. Structural properties
were investigated by X-ray diffraction measurements. The polarized absorption and emission spectra of Sm 3+ ions in the
grown crystals were measured and analyzed. It was concluded that Sm:ASL single crystals are promising candidates to
obtain efficient yellow-orange laser emission.
This work was supported by the Romanian MEN-UEFISCDI, Partnerships program, Grant agreement No.10/2014.
144
FERROELECTRIC MATERIALS INVESTIGATED BY TERAHERTZ TIME-DOMAIN SPECTROSCOPY
M. G. Banciu1, L. Nedelcu1, H. V. Alexandru2, L. Gheorghe3, C. D. Geambasu1, and M. Tani4
National Institute of Materials Physics, Magurele, Romania, 2Faculty of Physics, University of Bucharest, Romania;
3
National Institute for Laser, Plasma and Radiation Physics, Magurele, Romania; 4Research Center for Development of
Far-Infrared Region, University of Fukui, Fukui, Japan
1
The advanced materials play a special role in the rapid evolution of Terahertz technologies enhancing the possibility
of developing new applications [1]. Electro-optic crystals are frequently required for electro-optic rectification used by
Terahertz wave generation, as well as for Terahertz wave detection via electro-optic sampling. In this work, we
investigate the possibility of employing some non-conventional ferroelectric materials in THz applications. The
preparation and morpho-structural analysis of barium strontium titanate (Ba1-xSrxTiO3) and potassium dihydrogen
phosphate (KH2PO4) are presented [2]. The THz properties of prepared ferroelectric samples are investigated by THz
time-domain spectroscopy up to 1 THz for bulk samples and up to 3 THz for the BST films grown by Pulsed Laser
Deposition on MgO (100) substrates.
Keywords: ferroelectrics, THz time domain spectroscopy, birefringence
References
M. G. Banciu, L. Nedelcu, K. Yamamoto, S. Tsuzuki, and M. Tani, “THz-TDS investigations on dielectrics for
microwave applications”, Invited Paper, Proceedings of the 5 th International Workshop on Far-Infrared Technologies
2014 (IW-FIRT 2014), University of Fukui, Japan, 5-7 March (2014).
H. V. Alexandru, S. Antohe, “Prismatic faces of KDP crystal, kinetic and mechanism of growth from solution”, J.
Cryst. Growth, pp. 149-157, vol. 258 (2003).
Acknowledgement - This work was supported by a grant of the Ministry of National, Education, CNCS – UEFISCDI,
project number PN-II-ID-PCE-2012-4-0654.
145
VARIATION OF THE MAGNETIC AND ELECTRICAL PROPERTIES IN (1-x)BiFeO3-xBaTiO3 SOLID
SOLUTIONS
Jana Pintea, Alina Dumitru, Delia Patroi, Ionut Balan, Virgil Marinescu
National Institute for Research and Development in Electrical Engineering ICPE-CA; [email protected]
Multiferroic materials have been received much attention because of their potential applications for new types of
electronic devices (e.g., multiple-state memories and new date storage media).
BiFeO3 is a representative multiferroic material which has ferroelectric (Tc = 1103K) and antiferromagnetic (T N=
643K) properties.
In this work, the effect of BaTiO3 content in BiFeO3-BaTiO3 system on the crystal structure, the magnetic properties
and the electrical properties were investigated. The (1-x)BiFeO3-xBaTiO3 (x=0.3, 0.4, 0.5) ceramics were prepared by
the solid-state reaction method.
EXCITON-PHONON COUPLING IN PbI2 LAYERED STRUCTURE THAT MANIFESTS AS STIMULATED
RAMAN PROCESS
A. A. Nila1, M.Baibarac1, I.Baltog1
National Institute of Material Physics, Laboratory of Optical Processes in Nanostructured Materials, PO Box MG-7,
RO-77125, Bucharest, Romania; Corresponding author: [email protected] and presenting author:
[email protected]
1
Enhancement of the Raman intensity under excitation laser light situated near the edge of the fundamental
absorption band is a subject still incompletely elucidated. Theory devoted to this phenomenon has established that it
originates in an exciton-phonon interaction process, known as the Frohlich interaction. The coupling strength of exciton
with phonon can be estimated by Fermi's golden rule, which is dependent especially by the spatially restricted of
exciton's wave-function. Such a phenomenon is observed for the first time in PbI 2 layered structure. The main features
of the exciton-phonon interaction process are: i) it is conditioned of an optical excitation inside the fundamental
absorption band; ii) it is conditioned by the existence of excitonic emission what means that it increases with the
excitonic light intensity; iii) its occurrence is different over Stokes and anti-Stokes Raman branches as result of the
different overlapping of the Stokes and anti-Stokes Raman spectral ranges and the excitonic photoluminescence band
profile and iv) it is conditioned by the strong diffusive power of the material that explains why this phenomenon was
generally observed in powders or nanoscaled materials. As novelty in this work we demonstrate that the interaction
exciton-phonon manifests as a stimulated Raman effect that results from the mixing of two optical fields, the pump laser
light and the excitonic photoluminescence light.
STUDY OF ALUMINUM OXIDE DOPED WITH TERBIUM AT DIFFERENT CONCENTRATIONS.
Luis Mariscal Becerra, Carlos Miguel García Rosas, Sergio Humberto Ramírez Ramírez.
Physics Institute – UNAM, Faculty of Science – UNAM, Faculty of Science – UNAM. [email protected] ,
[email protected] , [email protected]
Different emission intensities that occur in aluminum oxide powders correspond to different doping terbium
concentrations, such sample powders were synthesized via evaporation technique by evaporation technique. This were
characterized using luminescence techniques, x-ray diffraction and Energy Dispersive Spectroscopy (EDS). The
emission spectra for each of the distinct terbium doping percentages show terbium's typical transitions in 494, 543, 587
and 622nm, these correspond to 5D4→7F6, 5D4→7F5, 5D4→7F4 and 5D4→7F3, respectively. When excited at room
temperature at λ = 380nm . X-ray difraction results show the presence of both γ-400 phase and γ-440 phase at 45.90
degrees and 67.38 degrees for the two hour thermally treated compounds. EDS analyses indicate 60% of oxygen and
40% of aluminum with presence of terbium doping in the compound.
146
THE STUDY OF STRUCTURAL, MAGNETIC AND ELECTRIC/FERROELECTRIC PROPERTIES IN
EPITAXIAL MULTIFERROIC HETEROSTRUCTURS BASED ON PZT/CFO GROWN BY PLD
A.G. Boni1,2, C. Chirila2, L.Hrib2,S.Greculeasa2, V. Kuncser, I. Pasuk2, L. Trupina2, R. Negrea2, I. Pintilie2, L. Pintilie2
1
University of Bucharest, Faculty of Physics, Magurele 077125, Romania ; 2 National Institute of Materials Physics,
Atomistilor 105bis, Magurele, Ilfov, 77125, Romania ; [email protected]
Symmetric Pb(Zr0.2Ti0.8)O3-CoFe2O4(PZT-CFO) structures with two different bottom electrode SrRuO 3 and
(La,Sr)MnO3 are grown on SrTiO3 (001) substrates using PLD. Structural characterization by X-ray diffraction and
transmission electron microscopy show the epitaxial relationship between the layers. The magnetic properties as
remnant magnetisation, coercive field and anisotropy are determined by the choice of the bottom electrode. The
association between the hard magnetic spinel CFO and the ferromagnetic half-metallic oxide LSMO enhance the
ferromagnetic properties. Both structures present very good ferroelectric properties, with rectangular hysteresis loops
and butterfly-shape of current-voltage characteristics. In the case of the structure with LSMO bottom electrode this
properties are affected by a higher leakage current. The impedance as a function of frequency measurements for
different temperatures reveals a Maxwell-Wagner relaxation process due to an accumulation of charges at the interfaces
between PZT and CFO. The dependence of current on voltage and temperature, reveals that in both cases there
are a competition between bulk limited and electrode limited conduction mechanisms. The bulk limited
regime is most likely space charge limited currents, the electrode limited is a Schottky emission with the
potential barriers around 0.72eV for SRO electrode and 0.25-0.3eV for LSMO bottom electrode.
ONE DIMENSIONAL NANOSTRUCTURES SYNTHESISED BY HORIZONTAL TUBE FURNACE
S.H. Mousavi1, S.A. Jafari Mohammadi2, P.W. de Oliveira1
1) INM – Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany; 2) Department of
Chemistry, College of Science, Islamshahr Branch, Islamic Azad University, Tehran, Iran
III-nitride and II-VI oxides are wide band gap semiconductors which have unique applications in both optoelectronic and optical devices. They exhibits interesting optical properties that could be applied in quantum confined
structures and light emitting devices [1,2].
In this work, we report a chemical technique for synthesis of one dimensional nanostructures in a horizontal three
zone furnace with alumina tube. AlN and ZnO with different morphologies and sizes are grown on different substrates
by thermal evaporation of source materials and gas transport in cold zone of furnace using a carrier gas.
The effect of substrate, additional metal sputtering, gas flow flux and vacuum conditions are investigated on the
structural and morphological studies by means of the field emission SEM, EDX and XRD. Photoluminescence spectra
of the nanostructures show high intensity optical emission at room temperature around UV and blue wavelength which
is very interested for LED applications.
[1] X.W. Sun, J.Z. Huang, J.X. Wang and Z. Xu, Nano Lett. 8 (2008) 1219.
[2] A. Khan and M.E. Kordesch, Mater. Res. Soc. Symp. Proc. 872 (2005) 1.
147
148
S8
Advanced Materials Characterization and
Modeling
Invited Papers
149
150
MOLECULAR ENGINEERING THROUGH SERENDIPITY
Davide Bonifazi
Namur Research College (NARC) and Department of Chemistry, University of Namur, Rue de Bruxelles 61 , 5000,
Namur, Belgium, email: [email protected]
Organic architectures are considered amongst the most promising candidates for engineering molecular-based
devices. It is however necessary to develop systems that can form at interfaces organized molecular assemblies
featuring addressable and controllable arrangements. In this respect, the hierarchical self-assembly of organic molecules
featuring complementary non-covalent recognition sites
allowing the simultaneous assembly of several units and longrange order is one of the most promising approaches.
In this talk, I will describe our approaches to engineer
multidimensional structures through the exploitation of weak
interactions established by programmed organic-based
molecules. Quoting a letter (dated 28 January 1754) from
Horace Walpole to Horace Mann, he said he formed it from
the Persian fairy tale “The Three Princes of Serendip”, whose
heroes "were always making discoveries, by accidents and
sagacity, of things they were not in quest of". Therefore,
specific serendipitous examples will be discussed with the
attempt to answer to the question of whether and how the
supramolecular approach can bridge organic chemistry with
molecular organization and to which extend we can achieve
macroscopic functions solely through molecular engineering.
DISCOVERY OF NEW Mg-RICH PHASES IN RE-TM-Mg (RE = Rare-Earth, T = TRANSITION METAL)
SYSTEMS. ABOUT SOME APPLICATIONS SUCH AS HYDROGEN STORAGE,…
E. Gaudin and J-L Bobet
CNRS, Univ. Bordeaux, ICMCB, UPR 9048, F-33600 Pessac, France; [email protected]
The discovery of new ternary alloy is a great challenge for the solid state chemists. The Mg-rich part of the RE-TMMg diagram (RE = Rare-Earth, TM = Transition metal) is reinvestigated and a lot of new compounds are highlighted.
According to the low weight and cost of magnesium and also of the possible improvement of the corrosion resistance
due the RE, such compounds could be of great interest in term of applications such as : hydrogen storage, structural
material,…
The focus will be done on 3 new compounds: LaCuMg8[1], Gd13Ni9Mg78[2] and NdNiMg5 [3]. LaCuMg8 [1]
crystallizes in the La2Mg17 structure type (S.G. P63/mmc) with the lattice parameters a = 10.1254(2) and c = 10.0751(2)
Å. The Mg atoms form hexagonal tubes along the c-axis filled by La and Mg. The Cu atoms are located in these tubes
on or around the La and Mg positions, inducing disorder.
For Gd13Ni9Mg78[2] the determination of the structural parameters is more complex because of the difficulty to
obtain a well-crystallized sample. A mixing of amorphous and crystallized part is usually observed. From initial XRD
analysis, an average cubic structure with lattice parameter a = 4.55 Å could be assumed. The subsequent TEM analysis
shows a possible modulation along both a* and b* axis.
NdNiMg5 [3] crystallizes with an unusual structural type (SG : Cmcm, a = 4.4799(2), b = 9.9827(3), c = 13.7854(10)
Å). Its structure is made of infinite layers of Mg atoms which form blocks stacked along the c axis. These blocks, with a
close-packed array of Mg atoms, are separated by infinite NiNd layers and connected through short Mg-Mg bonds. In
the NiNd layer the Ni and Nd atoms form an ordered graphite-type network.
Hydrogen sorption properties will be presented and also the first mechanical and corrosion resistance tests will be
presented. Finally, some other properties like magnetic and electrical ones will be discussed briefly to open new
applications areas.
[1] Couillaud, S; Gaudin, E; Bobet, J.L. Intermetallics (2011) 19, 336.
[2] Couillaud, S.; Gaudin, E.; Weill, F.; Gomez, S.; Stan, C.; Planté, D.; Miraglia, S.; Bobet, J.L.;
Acta Mater. (2012) 60, 4144
[3] Ourane, B.; Gaudin, E.; Zouari, R.; Couillaud, S; Bobet J.L., Inorg. Chem. (2013) 52, 13289
151
NEW DIMENSIONS IN ENERGY MATERIALS
Duncan H. Gregory
School of Chemistry, University of Glasgow, Glasgow G12 8QQ, UK.
With the steady depletion of fossil fuels, concerns over climate change and other environmental issues and the need
for secure sources of fuel supply, the need to explore alternative sources of energy is becoming more urgent. This
situation presents a fundamental challenge for chemistry and for materials chemistry especially, since not only are
means to produce hydrogen sustainably required, but also we will require new materials to convert and store this energy
effectively. One can thus consider storing electrical energy directly (for example in batteries) or indirectly using an
energy vector – such as hydrogen – which can be used in a conversion device such as a fuel cell.
Our research at Glasgow is concerned with many of these aspects at the interface of materials chemistry and energy.
This talk will consider how, for example, one might design and produce new materials that can store hydrogen
(Figs.1,2) for use with fuel cells (for energy conversion) and have high ionic conductivity and high lithium storage
capacity for use as electrodes in secondary batteries (for energy storage; Fig. 3). In fact, some materials with the same
origin can serve both these purposes. Additionally, this talk will consider other types of energy conversion and storage
materials and how one might employ nano-design strategies in developing new sustainable energy materials.
Figure 1 Hydrogen uptake in
the Li-N-H system
Figure
2
Lithium
nitride nanowires
Figure 3 Structure of lithium
nitridometallate anode materials
CONTROLLING MAGNETIC FUNCTIONALITY BY LIGHT: FROM FUNDAMENTALS TO
NANOSCALE ENGINEERING
Theo Rasing
Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525AJ Nijmegen, the Netherlands;
[email protected]
From the discovery of sub-picosecond demagnetization over a decade ago to the recent demonstration of
magnetization reversal by a single 40 femtosecond laser pulse, the manipulation of spins by ultra short laser pulses has
become a fundamentally challenging topic with a potentially high impact for future spintronics, data storage and
manipulation and quantum computation. The realization that femtosecond laser induced all-optical switching (AOS) as
observed in ferrimagnets exploits the exchange interaction between their sublattices, opens the way to engineer new
magnetic materials for AOS. Another challenge is how to bring the optical manipulation of magnetic media to the
required nanoscale, which may be possible using plasmonic or wave-shaping techniques. Recent results with engineered
hybrid magnetic materials and nanofocusing will be discussed, showing the practical potential of AOS.
Recent references:
A.Kirilyuk, et al, Rev. Mod.Phys. 82, 2731-2784 (2010)
I.Radu et al, Nature 472, 205 (2011)
J. Mentink et al, Phys.Rev.Lett.108,057202(2012)
T. Ostler et al, Nature Comm. 3, 666 (2012)
C. Graves et al, Nature Materials 12, 293 (2013)
R. Evans et al, Appl.Phys.Lett., 2014
S. Mangin et al, Nature Materials 2014
L. LeGuyader et al, Nature Comm. 2015
152
LOCAL FIELD ENGINEERING FOR TAYLORING ELECTRICAL PROPERTIES
IN FERROELECTRIC-BASED COMPOSITES
Leontin Padurariu1, Lavinia Curecheriu1, Vincenzo Buscaglia2, Carmen Galassi3 and Liliana Mitoseriu1,
Dept. of Physics, Al. I. Cuza Univ., 11 Bv. Carol I, 700506 Iasi, Romania; 2 Inst. of Energetics & Interphases CNR, 6
Via De Marini, I-16149 Genoa, Italy; 3ISTEC-CNR, Via Granarolo no. 64, I-48018 Faenza, Italy
1
The interfaces between regions with contrasting permittivities in composites modify the local field distribution. The
effective macroscopic properties of composites are a result of this local field inhomogeneity and therefore, the
properties of ferroelectric-based composites can be tailored by controlling the microstructure characteristics (local field
engineering) or by adequate choice of the phase constituents and phase interconnectivity. This approach can be applied
to design ferroelectric-magnetic composites with specific dielectric/ferromagnetic properties. Since the local field
inhomogeneity increases when the difference in permittivities of the constituent phases is higher, porous ferroelectric
structures ensuring a maximum permittivity contrast have a great potential in order to reach desired ferro/dielectric
properties, although porosity is usually considered detrimental in electroceramics.
Based on this idea, 3D FEM models have been developed to compute local field distributions in realistic
microstructures in order to explore the possibility to maximize their ferroelectric (switching) or non-linear dielectric
responses (tunability). The role of nanostructuring and of porosity on the macroscopic properties (effective permittivity,
tunability, P(E) hysteresis loops) were studied theoretically and validated for BaTiO3 nanostructured ceramics, for a
few types of PZT ceramics with various porosities, including anisotropic, and for PbTiO3 films with vertical
nanoporosity. As a first step, different realistic 3D microstructures were generated. Local field distributions were
computed by 3D FEM calculation and used as inputs in switching (Preisach) or tunability (Johnson) models, in order to
derive the ferro/dielectric and tunability responses. If properly engineered in well-controlled microstructures, porosity
may be used as an elegant factor to enhance functionalities as result of the field concentration in specific regions.
Acknowledgements: This work was supported by the Romanian CNCS PN II-PCE-2011-3-0745 project.
GROWTH OF InSb AND InI CRYSTALS ON EARTH AND IN MICROGRAVITY
A. G. Ostrogorsky1, A. Churilov2, M. Volz3, V. Riabov1, L. van den Berg4
Illinois Institute of Technology, Chicago, IL 60616; 2Radiation Monitoring Devices, Inc., Watertown, MA 024724699; 3MSFC, Huntsville, AL; 4Constellation Technology Corporation, Largo, FL 33777
1
During the past 40 years, the semiconductor crystal growth experiments conducted in space demonstrated
(i) that weak convection existed in virtually all melt-growth experiments. (ii) de-wetting significantly
reduced the level of stress-induced defects, (iii) particularly encouraging results were obtained in vaporgrowth experiments.
In 2002, seven crystal growth experiments was preformed at the International Space Station (ISS), within the
SUBSA (Solidification Using a Baffle in Sealed Ampoules) investigation. Four Te- and and three Zn-doped InSb
crystals were directionally solidified at 0.5 cm/hr. The specially designed transparent furnace provided a sideview to the melt. This enabled particularly precise seeding, and observation of the translation of the solidliquid interface.
At present, under sponsorship of CASIS ( Center for the Advancement of Science in Space, www.iss-casis.org)
we are conducting ground-based experiments with indium mono-iodide (InI) in preparation for the “SUBSA
II” flight investigation, planned for 2017. The experiments include: i) Horizontal Bridgman (HB) growth and ii)
Vapor Transport (VT) growth. Finite element modeling is conducted, to optimize the design of the flight ampoules, for
vapor and melt growth.
153
TITANATE PEROVSITE DEFECT CHEMISTRY
John Irvine, Dragos Neagu
University of St Andrews – [email protected]
Metal particles supported on oxide surfaces promote many of the reactions and processes that underpin the global
chemical industry and are key to many emergent clean energy technologies. At present, particles are generally prepared
by deposition or assembly methods which, although versatile, usually offer limited control over several key particle
characteristics, including size, coverage, and especially metal-surface linkage. Here metal particles are grown directly
from the oxide support though in situ redox exsolution. We demonstrate that by understanding and manipulating the
surface chemistry of an oxide support with adequately designed bulk (non)stoichiometry, one can control the size,
distribution and surface coverage of produced particles. We also reveal that exsolved particles are generally epitaxially
socketed in the parent perovskite which appears to be the underlying origin of their remarkable stability, including
unique resistance of Ni particles to hydrocarbon coking, whilst retaining catalytic activity.
154
Oral Presentations
TUNABLE TERAHERTZ METAMATERIALS BASED ON HYBRID INTEGRATION OF THE VO2 METALINSULATOR TRANSITION MATERIAL
J. Leroy1, G. Humbert 1, J-C. Orlianges2, C. Champeaux2, P. Blondy1, A. Crunteanu1
XLIM Research Institute UMR 7252, CNRS/University of Limoges, 123 avenue Albert Thomas, 87060 Limoges,
France , 2SPCTS UMR 7513, CNRS/University of Limoges, 12 rue Atlantis, 87068 Limoges, France ;
[email protected]
1
Despite a high application potential, the use of terahertz (THz) frequencies for communication technologies is
currently limited by the small number of existing terahertz components and, in particularly, of tunable THz devices. Our
approach for obtaining tunable functions in the THz frequency region is to combine a THz “passive” metamaterial (twodimensional array of periodical sub-wavelength metallic structures fabricated on a sapphire substrate) and a vanadium
dioxide (VO2) thin film (or structured VO2 patterns) deposited on the same substrate. The interest in using VO2 in the
design of metamaterials comes from its ability to perform a reversible phase transition (or metal-insulator transition MIT) from a semiconductor state (at room temperature) to a metal state (at temperatures higher than 68°C). The MIT is
accompanied by large, abrupt changes in the material’s electrical and optical properties (resistivity, refractive index, and
permittivity) for frequencies from RF-microwave up to the THz and optical regions. In VO2 thin films the MIT can be
triggered using different external stimuli: temperature, electronically or optically and even under external stress or
pressure. The transition time can occur on timescales as low as hundreds of femtoseconds for the optically-activated
transition, while for the electrically-triggered MIT, activation times down to few nanoseconds have been reported.
We will present the design, simulation, fabrication and practical demonstration of tunable VO 2-based THz
metamaterials devices. We show that the broadband metal-insulator transition (MIT) of VO2 leads to significant
variations in the THz transmission of the realized structures (as recorded by terahertz time-domain spectroscopy (THzTDS) in the frequency range 0.1-1 THz) under the effect of thermal stimuli but also by applying an electric voltage
across the metametarial device.
155
SILICON NANOCARBIDE EFFECT ON LAMINATED COMPOSITES
George Pelin1,2, Cristina- Elisabeta Pelin1,2 Adriana Stefan1,*, Ion Dincă3, Ecaterina Andronescu2 and Anton Ficai2
1. National Institute for Aerospace Research and Development “Elie Carafoli”, 220 Iuliu Maniu Blvd., 061126,
Bucharest, Romania, Presenting author: [email protected], *Corresponding author: [email protected], 2.
Faculty of Applied Chemistry and Materials Science, Politehnica University of Bucharest, 1-7 Polizu St., 011061,
Bucharest, Romania, 3. Aerospace Consulting 220 Iuliu Maniu Blvd., 061126, Bucharest, Romania
Phenolic resin composites have attractive proprieties for applications in a wide range of fields from wood and
adhesive industry to automotive, aeronautics and aerospace industries. The paper presents the obtaining of nanofilled
phenolic resin based composites reinforced with bidimensional fabric. Different contents of silicon nanocarbide were
dispersed into the phenolic resin matrix using ultrasonication method, to ensure an optimum dispersion of the nanofiller.
Several layers of bidimensional fabric were impregnated with the simple and nanofilled resin and the final laminated
composites were obtained using high temperature pressing method following a multistage temperature program.
The obtained materials properties were evaluated in terms of mechanical, tribological and thermal stability under
load, and the fracture cross section after mechanical testing was characterised by SEM microscopy analysis.
LIGHT CONFINEMENT IN A TWO DIMENSIONAL Ge PHOTONIC CRYSTAL
D.G. Popescu1, C.P. Ganea1, C. Florica1, I. Anghel2, M. Husanu1*
National Institute of Materials Physics, Atomistilor 105b, 077125 Magurele-Ilfov, Romania. 2National Institute for
Laser, Plasma & Radiation Physics, Atomistilor 409, 077125, Magurele, Romania
1
Light confinement in a two dimensional photonic crystal (2DPhC) with hexagonal symmetry is studied using infrared reflectance spectromicroscopy and numerical calculations. The structure has been realized by laser ablation, in a Indoped Ge wafer, using a pulsed laser (λ=775 nm) for creating a lattice of holes with precise symmetry, which perforate
the Ge slab.
Correlating the spectral signature of the photonic gaps recorded experimentally with the results obtained in the finite
difference time domain and finite difference frequency domain calcuations, we established the relationship between the
geometric parameters of the structure (lattice constants, shape of the hole) and its efficiency in trapping and guiding the
radiation in a well-defined frequency range. Besides the TE gap in the low energy range, a second one is identified in
the telecommunication range, originating in the localization of the leaky modes within the radiation continuum. The
emerging picture is of a device with promising characteristics as an alternative to Si-based technology in photonic
device fabrication with special emphasize in energy storage and conversion.
ATOMIC SCALE ELEMENTAL MAPPING OF LIGHT ELEMENTS IN MULTILAYERED PEROVSKITE
COATINGS
R.F. Negrea1, 2, C.Ghica1, V.S. Teodorescu1
National Institute of Material Physics, Atomistilor Str. 105bis, Magurele, Bucharest, Romania; 2 University of
Bucharest, Faculty of Physics, Atomistilor Str. 405, Magurele, Bucharest, Romania
1
Over time, a great challenge in transmission electron microscopy (TEM) was to obtain images at atomic resolution.
Nowadays spherical aberration corrected transmission electron microscopes offer unprecedented capabilities in
materials structural characterization down to atomic resolution. Electron Energy Loss Spectroscopy (EELS) – Spectrum
Imaging (SI) and Annular Bright Field (ABF) imaging allow to simultaneously identify both the position and nature of
the atomic species in a crystalline material. These techniques, along with conventional high-resolution transmission
electron microscopy are particularly useful in heterostructures characterization, like interfaces in epitaxial multilayers,
for identifying possible atomic interdiffusion at sub-nanometric scale. This work presents the structural and
compositional microanalysis down to atomic resolution of an epitaxial BaTiO 3/SrRuO3/SrTiO3 (BTO/SRO/STO)
ferroelectric heterostructure using complex complementary analytical electron microscopy techniques. The atomic
arrangement of both heavy and light atomic species across the interfaces in the BTO/SRO/STO heterostructures is
revealed. The SRO and BTO layers have been deposited by pulsed laser deposition (PLD) from stoichiometric targets
using a KrF* excimer laser (Lambda Physik COMPex 205) with a 248 nm wavelength. Transmission electron
microscopy observations have been performed using a probe-corrected analytical high-resolution JEM ARM 200F
electron microscope operated at 200 kV.
156
EPITAXIAL GROWTH OF SINGLE-DOMAIN HEXAGONAL BORON NITRIDE
Nicoleta G. Apostol1,3, Fabrizio Orlando2, Luca Omiciuolo2, Paolo Lacovig1, Rosanna Larciprete4, Alessandro
Baraldi2,5, and Silvano Lizzit1
1
Elettra-Sincrotrone Trieste S.C.p.A., AREA Science Park, S.S. 14 km 163.5, 34149 Trieste, Italy; 2 Physics
Department and CENMAT, University of Trieste, Via Valerio 2, 34127 Trieste, Italy; 3 National Institute of Materials
Physics, Atomistilor 105b, 077125 Magurele-Ilfov, Romania; 4 CNR-Institute for Complex Systems, Via Fosso del
Cavaliere 100, 00133 Roma, Italy, 5 IOM-CNR, Laboratorio TASC, AREA Science Park, S.S. 14 km 163.5, 34149
Trieste, Italy
Starting from the intensively studied and fascinating properties, together with the wide range of potential
applications of graphene (GR), there is also significant interest in other two-dimensional (2D) atomic crystals and, in
particular, in hexagonal boron nitride (h-BN) [1], which provides a superior insulating platform for high-performance
GR devices [2]. However, for the full potential of 2D atomic crystals to be exploited, there are multiple challenges that
the scientific community must address, such as the development of reliable methods for the growth of high-quality GR
and h-BN single layers. In order to find the optimum approach for growing high-quality films, a better understanding of
the h-BN growth mechanism is highly needed. In this contribution, we present structural investigations of h-BN grown
on Ir(111) by chemical vapor deposition (CVD) of borazine [3]. Using synchrotron radiation photoelectron
spectroscopy, photoelectron diffraction and low energy electron diffraction (LEED), we show that high-temperature
borazine deposition gives rise to a h-BN monolayer formed by domains with opposite orientations with respect to the
Ir(111) crystal, while a h-BN monolayer with single orientation (fcc) can be synthesized by dosing borazine at room
temperature and subsequently annealing the sample [4]. Our results can be interpreted as an advance into producing hBN monolayers with single orientation with respect to the surface (fcc).
[1] M. Corso, W. Auwarter, M. Muntwiler, A. Tamai, T. Greber, J. Osterwalder, Science 303 (2004) 217; [2] C.R.
Dean, A.F. Young, I. Meric, C. Lee, L. Wang, S. Sorgenfrei, K. Watanabe, T. Taniguchi, P. Kim, J. Hone, Nature
Nanotechnology, 5 (2010) 722; [3] F. Orlando, R. Larciprete, P. Lacovig, I. Boscarato, A. Baraldi, S. Lizzit, Journal of
Physical Chemistry C, 115 (2012) 157; [4] F. Orlando, P. Lacovig, L. Omiciuolo, N.G. Apostol, R. Larciprete, A.
Baraldi, S. Lizzit, ACS Nano, 8 (2014) 12063.
CHARGE STORAGE PROPERTIES OF MOS-LIKE CAPACITORS WITH Ge NANOCRYSTALS
EMBEDDED IN HfO2
Catalin Palade, Adrian Slav, Ana-Maria Lepadatu, Adrian Valentin Maraloiu, Sorina Lazanu, Valentin Serban
Teodorescu, Magdalena Lidia Ciurea
The non-volatile memories based on Ge nanocrystals (NCs) embedded in high-k oxide matrices as HfO2 represent a
promising alternative to “classical” non-volatile memories as HfO2 allows using a thinner gate oxide in C-MOS devices,
as the equivalent oxide thickness is smaller than for SiO2. This makes possible to reduce the size of the memory devices
without affecting their performance (by the leakage current increase). The Ge NCs embedded in HfO2 act as charge
storage nodes which increase the memory window and charge retention time of the device.
In this paper we investigate HfO2/Ge/HfO2/p-Si trilayer nanostructures by using magnetron sputtering as a
deposition method and subsequent annealing in a rapid thermal annealing processor. The rapid thermal annealing at
different temperatures in the range of 600–1000 oC was performed for Ge nanostructuring. The MOS capacitors were
obtained by thermal evaporation of Al bottom and top contacts on the structures. The C–V characteristics were
measured at different sweeping voltages and frequencies between 100 kHz and 1 MHz. The morphology of capacitors
was investigated by transmission electron microscopy (TEM). The nanostructures annealed at low temperature (600 oC)
keep the trilayer morphology of the as-deposited structures as high resolution TEM reveals. The high angle annular dark
field-scanning TEM images evidence the presence of Ge nanoparticles (NPs) embedded in crystallized HfO2 matrix (if
Ge forms amorphous NPs or NCs it cannot be observed in high resolution TEM because of the very close values of
lattice constants corresponding to Ge and HfO2). With the annealing temperature increase, the trilayer morphology is
lost. Also, the Ge NPs concentration decreases as the formation of Ge NPs is hindered by the Ge fast diffusion. The C–
V characteristics show that the charge storage properties are better for capacitors annealed at low temperatures, so that
the memory window decreases from about 1.2 to 0.2 V when the annealing temperature increases from 600 to 1000 oC.
The memory window is independent of the frequency, meaning that it is produced by the Ge NCs, only. Consequently,
the Ge NPs evidenced by the morphology investigations are crystallized.
157
Ge-TiO2 NANOSTRUCTURED FILMS FOR VIS-NIR PHOTODETECTORS
Adrian Slav, Catalin Palade, Ana-Maria Lepadatu, Adrian Valentin Maraloiu, Valentin Serban Teodorescu, Magdalena
Lidia Ciurea
TiO2 is one of the most investigated metal oxides due to its multifunctional properties determined by its wide
forbidden band gap. The germanium-titania (Ge-TiO2) nanostructured systems, defined as a TiO2 matrix with embedded
Ge nanocystals (NCs), represent a new promising class of optoelectronic materials.
In this work we report our results on the photoconductive properties of the Ge-TiO2 nanostructures deposited by
magnetron sputtering and nanostructured by rapid thermal annealing (RTA) at 580 oC and 700 oC. The electrical and
photoconductive properties have been studied in relation with the films structure and morphology. For this, two kinds of
Ge-TiO2 structures with relatively low (25%) and high (50%) content of Ge were prepared. The films with 50–100 nm
thickness were deposited on oxidized p-type Si substrate. For this, previously to Ge-TiO2 deposition, Si wafers were
oxidized by RTA, the obtained SiO2 film having 20–30 nm thickness. The electrical and photoconductive measurements
were performed in planar geometry using the Al electrodes thermally evaporated.
The structure and morphology of the films were investigated by X-ray diffraction and cross-section transmission
electron microscopy (XTEM). The XTEM images taken on the annealed films reveal the presence of Ge NCs with 10–
15 nm sizes and cubic structure, that are surrounded by rutile (GeTi)O2 matrix together with TiO2 NCs with anatase
structure.
The spectral dependence of the photocurrent measured on the films shows that they are photosensitive in different
wavelength intervals from VIS to NIR. Also, the shape of the spectral curves is controlled by the RTA conditions, but it
is influenced by the Ge-TiO2 composition, too. The photoconductive properties of Ge-TiO2 nanostructured films can be
easily tuned by customizing the density and size of Ge NCs dispersed in the TiO2 matrix. Therefore, the Ge-TiO2
nanostructured films can be successfully used for photoconductors applications in selective wavelength ranges.
BONDING MECHANISMS AND CAUSAL RELATIONSHIPS WITH MAGNETIC PROPERTIES IN
EXTENDED COORDINATION SYSTEMS. CASE STUDIES IN THE CHALLENGE OF PROPERTY
DESIGN AT NANOSCALE.
Marilena Ferbinteanu, Fanica Cimpoesu
University of Bucharest, Institute of Physical Chemistry
In the quest for nano-sized materials with potential applications in new technologies and devices, the molecular
magnetism based on coordination systems shows a valuable path, including the idea of structure-property rationales.
Polynuclear coordination compounds are already in the range of nanometers and many consecrated magnetic materials
that can be prepared at nano-scale granulation, such as oxides, have as bonding and exchange coupling mechanisms the
same causal engines identified in coordination systems. Based on this paradigm, several case studies are taken, relating
the magnetic properties with methods of electron structure calculations and phenomenological models. Placing on equal
footing the experimental and theoretical chemistry, we draw a red line in the concern of understanding and predicting
magnetic properties. To build a system behaving as magnet at molecular or nano-scale, some prerequisites must be
fulfilled, a key role belonging to the magnetic anisotropy, which is related in complex manner with certain asymmetry
features of the environment around the metal ions. A very subtle balance of the factors belonging to the chemical
environment and electron configuration of the metal ions occurs in the case of lanthanide-based systems. In this domain
we hold pioneering advents in approaching the electron structure of lanthanide complexes and lattices, establishing
rational structure –property relationships useful as leverages in the newly contoured domain of spintronics. Aside the
magnetic anisotropy, a local feature, the final shape of magnetic behavior is modulated by exchange effects that are
deciding the final properties at extended scale. The molecular magnetism was born several decades ago translating at
molecular scale problems basically known at the level of solid state physics. Nowadays is the time to remake the
reverse route, reinvesting the insight gained at molecular level back into the extended systems of the nowadays
expanding nano-sciences realm. Using examples from our own chemical synthetic outcome, or relevant prototypic cases
from literature, we propose a walk on the borderline of chemistry and physics of extended coordination systems.
158
PREDICTION OF HALF-METALLIC FERROMAGNETISM IN ZIRCONIUM BASED FULL-HEUSLER
COMPOUNDS
Anca Birsan1,2 ([email protected] ),Petru Palade1,Victor Kuncser1
National Institute of Materials Physics, 105 bis Atomistilor Street, PO Box MG-7, 077125, Magurele-Ilfov, Romania,
2
University of Bucharest, Faculty of Physics, 105 Atomistilor Street, PO Box MG-11, 077125 Magurele-Ilfov, Romania
1
The novel approaches based on the synergistic use of charge and spin dependent electron transport in
multifunctional materials such as Heusler compounds, may lead to their interesting practical applications in
magnetoelectronics or spintronics (e.g. spin valves or nonvolatile memory components). While high spin polarization is
highly desirable for efficient spintronic devices, half metallic materials are promising candidates for use as spin
injectors. Although many Heusler compounds were reported in the literature as half-metallic ferro/ferrimagnets, only a
few contain elements exhibiting low toxicity and therefore being susceptible of convenient preparation and processing.
In this respect, a theoretical description of electronic structure and ground-state magnetism of zirconium based fullHeusler compounds is provided via the Density Functional Theory and the possibility to obtain a high spin-polarized
current through such systems is analyzed.
Acknowledgments: The financial support provided through the CORE-PN45N projects and the PN-II-PT-PCCA2013-4-0971 Partnerships project is acknowledged. A. B. was supported by the strategic grant
POSDRU/159/1.5/S/137750.
MAPPING THE PARAMAGNETIC IMPURITIES DISTRIBUTION IN NANOSTRUCTURED FILMS BY
EPR
D. Ghica, M. Stefan, C. Ghica, and G. E. Stan
National Institute of Materials Physics, P.O. Box MG-7, Magurele, Ilfov, Romania; [email protected]
Magnetic and electrical properties of the nanostructured ZnO films are affected by the non-random impurities
distribution in the film due to segregation at grain boundaries (GBs) or extended defects. Currently used methods for
mapping the nature and distribution of low concentration (< 1%) of impurities are very complex and laborious. Electron
paramagnetic resonance (EPR) spectroscopy provides a simple, statistically relevant and non-destructive method for the
identification, quantitative evaluation and determination of the localization of the paramagnetic impurities present in
nanostructured films.
The method was demonstrated by correlated EPR and transmission electron microscopy investigations on a ZnO
film deposited onto r-cut sapphire by RF magnetron sputtering at RT, containing trace amounts of Mn 2+ ions as native
impurities. In the as-deposited ZnO film the Mn2+ ions were all localized at GBs, in nano-pockets of highly disordered
ZnO dispersed between nanocrystalline columns. After annealing the film at 600 oC, where the intercrystalline region
was considerably reduced, about 37% of the Mn2+ ions migrated into the peripheral atomic layers of the ZnO columns
neighboring the GBs.
In the case of a ZnO film doped with 1% Mn deposited in the same conditions, besides the isolated Mn 2+ ions
localized at the GBs, the formation of a separate manganese-rich phase in the intercrystalline region was observed.
M. Stefan, S.V. Nistor, D. Ghica, Cryst. Growth Des. 13, 350 (2013).
D. Ghica, M. Stefan, C. Ghica, G.E. Stan, ACS Appl. Mater. Interfaces 6, 14231 (2014).
159
MULTIFERROIC AND MAGNETOELECTRIC METAL-ORGANIC FRAMEWORKS
Alessandro Stroppa1
Paolo Barone1, Domenico Di Sante1, Prashant Jain2,Manuel Perez-Mato3, Anthony K. Cheetham4, Harold W. Kroto5,
7
Martijn Marsman6, Ionel Humelnicu ,Silvia Picozzi1
1CNR-SPIN, L'Aquila, Italy; 2Los Alamos National Lab,30 Bikini Atoll Rd Los Alamos NM 87545-0001 (505) 6645265; 3Departamento de Fisica de la Materia Condensada, Facultad de Cienca y Tecnologia UPV/EHU, Bilbao, Spain;
4Department of Materials Science and Metallurgy, University of Cambridge (UK); 5Department of Chemistry and
Biochemistry, Florida State University, Tallahassee, FL 32306 (USA); 6Faculty of Physics, Center for Computational
7
Materials Science, University of Vienna, A-1090 Wien, Austria; "A.I. Cuza" University of Iasi, Iasi, Romania
Ferroelectric materials, whose spontaneous polarization can be switched by an external electric field, have a wide
range of applications in device electronics. Recent discoveries of ferroelectricity in organic solids have been limited to
some well-known polymer ferroelectrics or a few low molecular mass compounds. Computational approaches based on
density functional theory represent a valuable tool in order to predict or suggest new organic ferroelectrics with large
values of ferroelectric polarization. In particular, the modern theory of polarization is used and symmetry analysis gives
an important help for gaining insights into the mechanisms responsible for the ferroelectric polarization.
Here we will focus on the description of the ferroelectric and magnetic properties of complex organic-inorganic
systems, such as metal-organic frameworks (MOFs). In particular, MOFs with a perovskite topology show promising
new routes for the cohexistence of ferroelectricity and magnetism, i.e. multiferroicity, as well as, their couping, i.e.
magnetoelectricity.
MICROMAGNETIC VS. MULTI-COMPONENT STONER-WOHLAFRTH INTERPRETATION OF
MAGNETIZATION REVERSAL IN MAGNETIC NANOSIZED SYSTEMS
Andrei Kuncser1,2, Corneliu Ghica1, Stefan Antohe2 and Victor Kuncser1
National Institute of Materials Physics, 77125, Bucharest-Magurele, Romania; 2Faculty of Physics, University of
Bucharest, 77125, Bucharest-Magurele, Romania
1
The magnetization reversal in magnetic nanosized systems of reduced dimensionality depends strongly on the
morphology, structure and composition of the constituents as well as on the interfacial couplings, also dependent on the
specific interface morphology. The deep understanding on how each of these aspects may influence the shape of a
hysteresis loop opens the path for complex simulations, if these are grounded on realistic input parameters obtained
experimentally by various investigation techniques. Two different approaches for the numerical simulation of magnetic
hysteresis loops are discussed: a home made Stoner-Wohlfarth based numerical software for magnetic multicomponents and a micromagnetic modeling software (OOMMF) developed by Applied and Computational
Mathematics Division of ITL/NIST. Micromangetic modeling is among the most powerful and versatile modeling
techniques, but it has the drawback concerning the huge computational power and time required in order to obtain
reliable results. On the other hand, the numerical implementation of the Stoner-Wohlfarth model for magnetic multicomponent systems is very time-efficient and requires very little resources but can be applied only for a magnetic
monodomain systems. Given a powerful enough computational environment, micromagnetic simulations have been
performed and the results have been compared with the simulations obtained by the home made multi-component
Stoner-Wohlfarth based program in order to find the optimal approach for various low dimensional magnetic
nanosystems of technological interest as well as the realistic limits of the Stoner-Wohlfarth approximation. Simulations
performed on simple ferromagnetic layers of different thicknesses, both homogeneous as well as with compositional
gradient, on interfacial exchange coupled and independent magnetic bilayers (e.g. as in a spin valve structure) and on
bidimensional magnetic nanoentities with easy axis distribution are presented and compared with experimental results.
160
PROBING THE ANNEALING INDUCED TRANSFORMATIONS IN SEMICONDUCTOR
NANOSTRUCTURES BY EPR
M. Stefan, D. Ghica, and S. V. Nistor
National Institute of Materials Physics, P.O. Box MG-7, Magurele, Ilfov, Romania; [email protected]
Probing the structural and chemical changes undergone by doped nanostructured semiconductors under thermochemical treatments allows the fine tuning of the synthesis parameters in order to obtain nanostructures with controlled
doping levels, nanocrystals size and structure.
Electron paramagnetic resonance (EPR) spectroscopy can detect with high sensitivity the presence and amount of
paramagnetic impurities in the II-VI semiconductor nanostructures, determine the configuration of their neighboring
ligands and the local structural/bonding modifications induced by external excitations (temperature, radiation). With
proper adjustments of the EPR experiments and accurate numerical analysis of the resulting spectra a wealth of
information can be obtained about the local structure, particle size and phases present in the nanostructures.
As an example we present the results of our EPR investigations on ZnO and ZnS nanostructures (nanostructured
films, simple and core-shell nanoparticles), using low concentrations of Mn2+ ions as atomic probes with low perturbing
effects. The annealing induced changes in the structure and composition of the investigated materials could be detected
and monitored with an accuracy level that is not always available with other regularly employed structural methods,
such as XRD or TEM.
M. Stefan, S. V. Nistor, D. Ghica, Cryst. Growth Des. 13, 350 (2013).
S. V. Nistor, D. Ghica, M. Stefan, L. C. Nistor, J. Phys. Chem. C 117, 2201 (2013).
D. Ghica, M. Stefan, C. Ghica, G. E. Stan, ACS Appl. Mater. Interfaces 6, 14231 (2014).
UP-SCALING OF AN ELECTROMAGNETIC STIRRING CONFIGURATION FOR SILICON
DIRECTIONAL SOLIDIFICATION
Radu Andrei Negrila, Alexandra Popescu and Daniel Vizman
Physics Faculty, West University of Timisoara, Bd. V. Parvan 4, 300223 Timisoara, Romania
One of the key issues in the directional solidification (DS) process of crystalline Silicon is to control of the melt
flow structure in order to achieve the best possible quality of the crystallized material, by avoiding turbulent flows, the
precipitation of impurities in poorly mixed melt areas and achieving a total mixing regime for optimal axial impurity
segregation. Based on the idea of melt stirring from Electromagnetic Czochralski method, a configuration with two
electrodes in contact with the melt surface was proposed for the electromagnetic stirring of a melt in a vertical magnetic
field. In order to understand the basic features of the melt flow in a DS-like configuration under electromagnetic
stirring, an isothermal model experiment in a rectangular crucible filled with a room temperature GaInSn melt very
similar with liquid silicon and a corresponding STHAMAS3D time-dependent numerical model were developed. The
model experiment configuration gives rise to an electromagnetic Lorentz force distribution which has a significant melt
stirring effect. Parametrical studies were performed for a range of I and B values and have lead to the identification of
different flow structures, which were correlated to the ratios of the forcing parameters and inertial forces. Here, this
electromagnetic stirring was studied for different crucible sizes. The results have revealed that by increasing the
crucible size, the transition between flow structure installs at higher current intensities I for the same applied magnetic
field B than in the case of a smaller melt size. The results offer an understanding of the impact of the increase in melt
volume on the flow structures which is important for the control of melt convection in a beneficial way when up-scaling
the melt geometry to sizes relevant for industrial application in DS of Silicon.
161
COMPARATIVE STUDY OF OXIDATION PROCESSES OF NiCoCrAlY BOND LAYERS FOR THERMAL
BARRIER COATINGS
(1)
Mercioniu I.(1), Vlaicu A.-M. (1), Ghica C.(1), Manoliu V.(2), Mihailescu A.(2), Ionescu Gh. (2)
I.N.C.D. Fizica Materialelor, str. Atomistilor 105 bis, Magurele, 077125, Romania; (2) INCAS – National Institute of
Aerospace Research “Elie Carafoli”, B-dul Iuliu Maniu no. 220, sector 6, 061226, Bucuresti, Romania;
[email protected]
NiCoCrAlY bond layers deposited on NiCoCr alloys from Amdry 997 powders by APS and HVAF have been
subjected to thermal treatments for five hours at temperatures between 700 – 1200 °C. The resulting oxide phase
composition at the surface of the bond layers determined by XRD structural analysis shows that the oxidation processes
are greatly diminished for the HVAF samples compared to the APS deposited samples. Activation energy plots in terms
of total oxidation percentage vs (1/T) show further details of the oxidation dynamics for the two sets of samples. These
results are further correlated with SEM and EDS mappings of the layers cross-sections, showing the formation of Alrich TGO layers on the surface of HVAF deposited bond layers.
OUT OF PLANE COHERENCE LENGTH AND MICROSTRAIN OF RF SPUTTERED ZnO THIN FILMS
A.C. Galca, C. Besleaga, G.E. Stan, C. Ghica, and I. Pasuk
National Institute of Materials Physics, Atomistilor 105 bis, 077125 Magurele, Ilfov, Romania; corresponding author:
[email protected]
X-ray diffraction (XRD) and transmission electron microscopy (TEM) are employed to characterize series of
textured zinc oxide thin films synthesized by radio-frequency magnetron sputtering at room temperature under different
argon/oxygen working atmospheres by keeping the total pressure at a low value of 0.3 Pa, and using mild-pressed ZnO
target. The asymmetry of the 00l diffraction peaks recorded on as deposited samples is a finger-print of a double layer
structure.
Each peak has a pseudo-Voigt profile. The classical Williamson-Hall plot reveals unphysical negative slope. By
using a modified Williamson-Hall analysis, the crystalline coherence length and microstrain of the distinct layers were
assessed.
The validity of our algorithm and the resulted values of the two quantities, are discussed considering the growth
mechanism under different working atmosphere and thin film homogenization after thermal treatment at 450◦C for one
hour.
The authors are grateful to the financial support from the Romanian Ministry of National Education through the
Core program PN09-4501.
ELECTRONIC STRUCTURE AND MAGNETIC PROPERTIES OF THE Fe16N2 DOPED WITH Ti
1
Diana Benea1, Olivier Isnard2 and Viorel Pop3
Babes Bolyai University Faculty of Physics, 400084 Cluj-Napoca, Romania; 2Univ. Grenoble Alpes, Inst. Neel, F38042 Grenoble, France; 3CNRS, Inst. NEEL, F-38042 Grenoble, France; Email: [email protected]
Detailed theoretical investigations on the electronic and magnetic properties of ′′-Fe16N2 doped with Ti have been
performed. The investigations of the electronic and magnetic properties have been done using the Korringa-KohnRostocker (KKR) band structure, whilst the disorder in the systems has been accounted for by means of the Coherent
Potential Approximation (CPA). The electronic correlations have been included using the LSDA+U method. In the spin
resolved density of states (DOS) the covalent nature of the interatomic bands and the N-2p and Fe/Ti-3d hybridization
can be observed. The change in the local environment by Ti substitution is evidenced in the distribution of local
magnetic moments and hyperfine magnetic fields calculated for (Fe,Ti)16N2. We found that Fe sites with N nearest
neighbours (4e and 8h) in both Fe16N2 and (Fe,Ti)16N2 compounds exhibit a relatively small hyperfine field (about -23
and -21 T), while Bhf is much higher on 4d sites (about -30 T). As the Ti substitution is used in practice to increase the
thermal stability of the ′′-Fe16N2, our calculations may offer insights into the change of the magnetic properties by
doping, which are very important for practical applications.
162
EFFECT OF MALEIC ANHYDRIDE-ANILINE DERIVATIVES MONOMERS BUFFER LAYER ON THE
PROPERTIES OF PENTACENE (RUBRENE)/ PBD (TPyP) BI-LAYER ORGANIC STRUCTURES
Carmen Breazu1,4, Marcela Socol1, Ana-Maria Albu 2, Mihaela Girtan3, Anca Stanculescu 1, Florin Stanculescu4
National Institute of Materials Physics, 105 bis Atomistilor Street, P.O. Box MG-7, 077125, Bucharest-Magurele,
Romania, e-mail: [email protected], 2Department of Polymer Science, University “Politehnica” of Bucharest, Bucharest,
Romania, 3Laboratoire LPHIA, Université d'Angers, LUNAM, 2 Bd. Lavoisier, 49045, Angers, 4University of
Bucharest, Faculty of Physics, Bucharest-Magurele, Romania
1
The electrical conduction in organic heterostructures is limited by the difficulty to obtain a good charge carrier
injection from electrodes because of high value of the ionisation energy (IE) determining high energetic barrier. A
solution to surpass this problem is offered by an adequate device structure including a buffer organic layer with IE level
situated between the WF of the transparent conductor and IE of the organic layer.
This paper presents some investigations on the optical and electrical properties of the structures containing a
monomer synthesised from maleic anhydride and aniline derivatives layer deposited by vacuum evaporation between
the glass/ITO and Si electrodes. The effect of a buffer layer on the electrical properties of the heterostructures based on
single/multiple active organic layers [p type: pentacene; rubrene; n type: 2-(4-biphenyl)-5-(4-tert-buthylphenyl)1,3,4oxadiazole (PBD); 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine, synthetic (TPyP)] sandwiched between
glass/ITO and Si electrodes was also studied.
We have evidenced injection contact behaviour for most of the heterostructures, with the exception of glass/ITO/
monomer/PBD/Si[n] showing very good rectifier diode behaviour, emphasising the influence of the morphological and
structural particularities of the organic films and of dipolar layer developed at the contact with electrodes. The effect of
the space charge accumulation and charge carrier trapping on the electrical conduction has also been discussed.
EMPIRICAL CORRELATIONS FOR EFFECTIVE SEGREGATION COEFFICIENT
A.G. Ostrogorsky
MMAE, Illinois Institute of Technology, Chicago, IL 60616
Mass transfer Nusselt number (Nu), often called Sherwood number is a dimensionless coefficient used to quantify
the complex boundary condition of convection, involving
advection and diffusion. In Bridgman growth and zone
refining melt, solute transport at the solid-liquid interface
is controlled by natural convection. Thus, Nu for mass
transfer is a function of the Grashof number (Gr) and
Schmidt (Sc) numbers.
Because of the complexity of the natural convection in
liquid metals, all Nu correlations, are empirical, based on
laboratory experiments. Here we derive a correlation for
the effective segregation coefficient, keff, as a function of
the equilibrium segregation coefficient k0, dimensionless
growth rate, or Peclet number, Pe and Nu
keff =f(k0, Pe, Nu)
or
keff =f(k0, Pe, Gr, Pr, Sc).
The correlations are applied to the experimental and
numerical data for Bridgman growth,
earth and in
microgravity and zone refining.
Solid agreement is
demonstrated.
163
164
MAGNETIC PROPERTIES AND GIANT MAGNETOIMPEDANCE IN FINEMET MICROWIRES
A. Donac1, 2, S. Corodeanu1, N. Lupu1, H. Chiriac1
1National Institute of Research and Development for Technical Physics, Iasi, Romania, 2Faculty of Physics, Alexandru
Ioan Cuza University, Iasi, Romania; [email protected]
Amorphous and nanocystalline microwires have attracted considerable attention during last years due to their
outstanding magnetic properties that make them excellent candidates, as sensitive elements, for sensor devices [1, 2].
The aim of this work is to investigate the influence of the diameter reduction on their magnetic characteristics and
giant magneto-impedance (GMI) response in FINEMET (Fe73.5Si13.5B9Cu1Nb3) microwires by taking into account their
potential use in low field and acoustic magnetic sensors. The FINEMET microwires with diameters between 50 μm and
10 μm were prepared by successive cold drawing of an amorphous wire with initial diameter of 105 μm which was
obtained by in rotating water melt spinning. All samples were annealed in vacuum for 1 hour at temperatures between
300C and 600C, to decrease the internal stresses induced during preparation and subsequent cold drawing and to
achieve the optimum nanocrystalline structure.
The magnetic properties were measured in longitudinal direction using an a.c. fluxmetric method at 50 Hz. The
results show that the maximum magnetic permeability 5,3105 was obtained for the wire with a diameter of 35 μm
annealed at 500 ˚C. The coercivity decrease when the annealing temperature is increasing up to 550 ˚C and increase for
higher temperatures for all sample. The GMI response was measured using an impedance-meter, in the frequency range
10-250 MHz. The maximum values of the GMI response 248% was obtained at a frequency of 100 MHz for the wire
with the diameter of 10 μm annealed at 550 ˚C.
Work supported by the Romanian Ministry of Education and Scientific Research under the Nucleu Programme (Project PN 09-43 01 01) and
POSDRU project (Contract nr. 159/1.5/S/133652)
[1] A. Zhukov, M. Ipatov, M. Churyukanova, S. Kaloshkin, V. Zhukova, J. Alloys Compd. Vol.586, pp.279–286 (2014).
[2] N. Yudanov, L. Panina, A. Morchenko1, V. Kostishyn1, P. Ryapolov, J. Nano- Electron. Phys., Vol. 5, No 4, pp.04004 (1-4) (2013).
165
EFFECT OF ELECTROLYTE – ELECTRODE INTERACTION ON THE DISTRIBUTION OF PLATINUM
NANOPARTICLE DEPOSITS OBTAINED VIA A LIPOSOMAL TEMPLATE
A.I. Căciuleanu, T. Spătaru, and N. Spătaru
”Ilie Murgulescu” Institute of Physical Chemistry of the Romanian Academy; [email protected]
Liposomes are sperical vesicular colloidal systems with applications spanning multiple fields, from cellular
membrane modeling and drug delivery to self-assembly of various structures with electrocatalytic properties.
The scope of this work was to assess the electrochemical properties of platinum nanoparticle deposits obtained via
liposomal templates and determine if the type of electolyte – electrode interaction prior to or during the
electrodeposition step influences nanoparticle distribution.
The platinum source was chloroplatinic acid, in the form of the aqueous phase entrapped in liposomes prepared
through the lipid film hydration method. After electrodeposition through controlled potential methods and a thermal
treatment step in order to remove organic residue from around the platinum aggregates, the electrode morphology was
evaluated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X–ray photoelectron
spectroscopy (XPS), while the electrocatalytic response was assessed via cyclic voltammetry.
STUDY OF Ni-O SYSTEM WITH A CHARGE TRANSFER POTENTIAL IMPLEMENTED IN THE
LAMMPS CODE
a
Kahina Lounisa*, El Hocine Megchichea, Hand Zeniab
Laboratoire de Physique et Chimie Quantique , Université Mouloud Mammeri, BP 17, 15000 Tizi-Ouzou, Algérie; b
Laboratoire de Physique Théorique, Université Abderrahmane Mira, Dz-06000, Béjaia, Algérie; * Email:
[email protected]
Nickel-based alloys are known for their good resistance to oxidation and corrosion phenomena, to which they owe
their widespread use in many technological fields such as aeronautics and energy production. Several experimental and
theoretical studies have been conducted on this type of alloy with the aim to optimize their performance. A fairly recent
experimental study performed on a series of oxidized nickel samples showed an accelerated oxidation process, and this
speedup has been associated with presence of defects: native and/or generated during the oxidation process. In order to
check the hypothesis, one of us has conducted first-principles calculations on the Ni-O system containing small point
defects such as monovacancies and divacancies. These calculations pointed to a strong interaction of oxygen dissolved
in the matrix with the vacancy. A further hypothesis put forth, as a result, that this type of interaction could explain the
experimental findings, and this through a novel diffusion mechanism of oxygen by pairs (oxygen-vacancy).
Nevertheless, a first-principles quantum approach to calculations requires significant resources and is unable to permit
exploration of the scales of space and time to observe and study the phenomena at play in the system. To remedy this
“shortcoming”, the method of molecular dynamics is the preferred one. Compared with quantum approaches, the
accuracy of the results of this method is closely related to the quality of the interaction potential used for the description
of the system. To this end, we propose to present our results of calculations on the system Ni-O and NiO with a new
potential (EAM-CTIP) developed by Zhou and Wadley that we have implemented in the computer code LAMMPS
and optimized for a satisfactory reproduction of the behavior of oxygen in solution in the nickel in the presence of
vacancies. The results we have obtained concerning the stability of Ni, NiO and oxygen-vacancy complexes, are in
good agreement with other experimental and theoretical studies found in the literature.
CHARACTERIZATION OF TINI SHAPE MEMORY ALLOYS OBTAINED BY SPARK PLASMA
SINTERING PROCESS
a
Cristiana Diana Cirsteaa, Magdalena Lungua, Violeta Tsakirisa, Andrei Cucosa, Felicia Toleab, Vasile Cirsteac,
INCDIE ICPE-CA, Bucharest, Romania, [email protected]; bNational Institute for Materials Physics, cMilitary
Equipments and Technology Research Agency, Clinceni, Romania
The special properties of TiNi shape memory alloys depend on their microstructure and their thermo-mechanical
state. This paper presents thermal and mechanical tests used to characterize the TiNi alloys obtained by spark plasma
sintering.
166
THE PIC METHOD FOR LASER-PLASMA ACCELERATION NUMERICAL MODELING WITH
POSSIBLE APPLICATIONS IN MATERIALS EVALUATION
Dragos Tatomirescu1, Alexandra Popescu1, Gabriel Pascu1, and Daniel Vizman1
Faculty of Physics, West University of Timisoara, Bd. V. Parvan 4, 300223 Timisoara, Romania
1
With the latest advances in laser technology, increasingly high beam energies and intensities can be achieved, thus
making possible the study of the interaction between high intensity lasers and cold plasmas. The evaluation of cosmic
radiation (CR) effects on condensed matter can be done either by directly studying the effects in space, which is
restricted by cost and limited to just a few procedures available on-site [1-3], or by simulation in laboratories on Earth.
A good opportunity to boost research in this field comes from the construction of laser-plasma accelerators with their
ability to produce a wide range of particle species (gamma, electrons, protons, medium weigh nuclei) of high energies.
Such laser-plasma interactions are currently modeled using the Particle-In-Cell (PIC) method [4]. In this paper we
are going to present the evolution of maximum proton energy with target thickness using the PICLS numerical tool [5].
The goal is to determine the optimal target thickness required for studying the effects of CR on the various materials
used for space applications. For this purpose we used a 2D simulation box containing an overdense sandwich target
composed of two layers of protons and electrons surrounding a layer of deuterons and electrons.
References:
1. V. Benghin et al., Adv. Space Res. 36, 1749–1752, (2005).
2. Z. Koliskova et al., Adv. Space Res. 49, 230–236, (2012).
3. P. Brekke, N.A.T.O. Science Series 176, (2003).
4. J. M. Dawson, Rev. Mod. Phys. 55, 403–447 (1983).
5. Y. Sentoku et al., J. Comput. Phys. 227, 6846–6861 (2008).
INKJET PRINTING OF POLYVINYL ALCOHOL MULTILAYERS FOR ADDITIVE MANUFACTURING
APPLICATIONS
Iulia Salaoru, Zuoxin Zhou and Gregory J.Gibbons
WMG, University of Warwick, Coventry, CV4 7AL, UK
3D Ink jet printing technology is based on the Additive Manufacturing concept [1] and has gained a large interest in
the recent years. The factors driving this continuous interest are mainly attributed to its efficiency in material use,
digital and additive patterning, large area capability, compatibility with rigid/flexible substrates, and low-cost. Inkjet
printing is with no doubt one of the most promising technologies for applications in microelectronic [2] and
optoelectronic devices [3].
Inkjet printing is a non-contact method, and works by ejecting ink through very fine nozzles. The physical properties
(surface tension and viscosity) of the ink play a crucial role on the quality/morphology of the printed film. Here we
demonstrate that Inkjet printing technology is capable of produce polymer-based multi-layer structures. In this work, a
number of polyvinyl alcohol water based inks were formulated. A range of humectants were investigated to improve the
viscosity and surface tension, and to prevent blocking of the printer nozzles.
The surface tension of the formulated inks was tested at room temperature using the pendent drop method via a
Drop Shape Analyser. The ink’s surface tension was in the range from 30 to 40 mN/m. The viscosity of a liquid was
measured by employing cylindrical rotational viscometry with the values in (3-10) cP range. A proprietary 3D Inkjet
printing machine was utilized to print polymer multilayer structures. The surface profile and the thickness uniformity of
Inkjet printed multi-layers were evaluated by optical contour and FT-IR microscopy. The measured thicknesses were in
the range from 35µm, in the case of 25 printed layers, to 600 µm for 1500 layers.
[1] N.Hopkinson, R.Hague, P.Dickens, Rapid manufacturing: an industrial revolution for the digital age. West
Sussex, UK, John Wiley and Sons; 2006
[2] M.Toda, Y.Chen, S.K.Nett, A.N.Itakura, J.Gutmann, R.Berger, , J. of Phys. Chem. C, 2014, 118, 8071-8078
[3] V.Fauzia, A.Umar, M.M.Salleh, M.Yahya,ICSE2010 Proc.Melaka, Malaysia, 60, 2010
167
SYNTHESIS AND CHARACTERIZATION OF SnS NANOWIRES
Mahesh D. Chaudhary, Sunil H. Chaki
P.G. Department of Physics, Sardar Patel University, Vallabh Vidyanagar-388120, Gujarat, India; Corresponding
author Email: [email protected]
SnS nanowires were synthesized by chemical route at ambient temperature. Stannous chloride and sodium sulphide
was used as a source of Sn+2 and S-2 ions respectively. The elemental stoichiometric analysis of SnS nanowires was
done by employing energy dispersive analysis of X-rays (EDAX) technique. The structural study of the as-synthesized
nanowires was studied by X-ray diffraction (XRD). The grain size was determined using X-ray diffraction (XRD) data
employing Scherrer’s formula and Hall-Williamson plot. The residual strain produced in the synthesized nanowires
during the synthesis was obtained from Hall-Williamson plot. The transmission electron microscopy (TEM) image
showed that the synthesized nanowires have average crystallite size of 11 nm. The synthesized SnS nanowires were
shows the optical direct bandgap 1.49 eV and 0.84 eV indirect bandgap. The thermal decomposition of SnS nanowires
was studied employing thermogravimetric (TG), differential thermogravimetric (DTG) and differential thermal analysis
(DTA). Thermal activation energy values of SnS nanowires were determined using Coats-Redfern (CR) relations. The
thermodynamic parameters such as the enthalpy change (ΔH*), entropy change (ΔS*) and free energy change (ΔG*)
related to the thermal decomposition process were calculated. The electrical transport properties study on the pellet
prepared from the nanowires of SnS showed them to be semiconducting and p-type in nature. The current-voltage (I-V)
plot of the silver (Ag)/ SnS nanowires pellet for dark and incandescent illumination showed ohmic and diode like
behaviour respectively. The obtained results are discussed in details.
COMPUTER MODELLING OF THE THERMAL DISTRIBUTION IN A PARABOLOIDAL OPTICAL
CONCENTRATOR OF SOLAR ENERGY FOR WATER HEATING
Beatrice Arvinti, Marius Costache and Floricica Barvinschi
Fundamental of Physics for Engineers, “Politehnica” University Timişoara, Bv. V.Pârvan, no.2
300323 Timişoara, România
Concentrators with different shapes are widely used in order to focus the solar light and to increase the efficiency of
solar energy for heating. In this paper we present a numerical simulation of the temperature distribution in a small static
paraboloidal concentrator used for heating two pipes with water, under different direct solar radiation intensities: from
400 W/m2 to 900 W/m2. Our simulations are done with the software COMSOL Multiphysics 3.5 and we compare the
results obtained when the inner surface of the paraboloidal concentrator is covered by nanometric vacuum deposited
film of Aluminium or Silver. Even during winter, when the intensity of direct solar radiation is between 400 W/m 2 and
540 W/m2, the results of our calculations show an increased temperature of water.
In a future work we intend to add a small photovoltaic cell in our model, and we should thus obtain a hybrid
concentrator which produces both heated water and electricity.
EFFECT OF TEMPERATURE ON THE CUT OFF FREQUENCY OF AlGaN/GaN High ELECTRON
MOBILITY TRANSISTORS
R. Yahyazadeh, Z. Hashempour
Department of Physics, Khoy branch, Islamic Azad University, , Khoy-IRAN
An analytical- numerical model for the cut off frequency of AlGaN/GaN based high electron mobility transistors
has been developed that is capable to predict accurately the effects of temperature on the electronic current of two
dimensional quantum well , transconductance[1], depletion layer capacitances[2] and cut off frequency in different
temperature. In addition taking into account the combined contributions from each of the individual electron scattering
mechanisms. Salient futures of the model are incorporated of fully and partially occupied sub-bunds in the interface
quantum well[3]. In addition current in the barrier of AlGaN, traps density field in AlGaN[4], gate leakage, interface
trap in the device are also taken into account. Close agreement with the experimental data confirms the validity of the
present model.
[1].Z.Hashempour, A.Asgari, S.Nikipar, M.R.Abolhasani, M.Kalafi, Phisica E 41 (2009) .
[2]. R.Yahyazadeh, A.Asgari, and M.Kalafi, Physica E, 33 (2006) .
[3].S.Rajan, S.P.Denbaars, And U.K.Mishra, Appl.Phys.Lett.88 (2006).
[4]. P. Gangwani, S.Pandey, S Halder, M Gupta, R.S.Gupta Microelectronic Journal 38 (2007) 848
168
INTERACTION OF SOME BIMETALIC CATALIST NANOPARTICLES DEPOSITED ON SUPPORT: XPS
STUDIES
L. Frunza1*, C. C. Negrila1, I. Zgura1**, C. Căpăţ2, I. Udrea2, E. A. Olaru2, C. Bradu2, I. Balint3, R. State3, F. Papa3
1
National Institute of Materials Physics, Magurele, 2University of Bucharest, Research Center for Environmental
Protection and Waste Management, Bucharest, 3Institute of Physical Chemistry of the Romanian Academy, Bucharest
* [email protected]; ** [email protected]
The metal catalysts have been prepared for the reduction of nitrates in the aqueous phase. Deposition of Pd and Cu
(nano)particles occurred either on anionic resin support or powder of alumina or titanium oxide, by different methods
(alkaline polyol method or by classical impregnation). The samples were characterized structurally and
morphologically. It was found that, in general, nanoparticles have a Pd crystalline core and a coating of amorphous Cu.
This work presents photoelectrons spectroscopy study of interaction of these bimetallic nanoparticles with the
support. For recording spectra was used a spectrometer SPECS with PHOIBOS 150 analyzer; X-ray source was
monochromatic type XR-50M, operating on the Al anode. The charge compensation was made with a flood gun type
Specs FG15/40. It was determined the surface composition, which highlighted the preferential deposition of Cu on Pd
crystallites, which modified the desired ratio of the two metals. The state of Pd was characterized by the maximum of
binding energy (BE) due to the level of Pd3d5 / 2: the interaction with the support led to the displacement of this
maximum. The deposition of the nanoparticles on TiO2 and Al2O3 leads to lower values of BE than for the
impregnation on the same supports. Pd is in metallic state, but on used catalysts, his state is closer oxidized form, PdO,
or to a form with a fence oxide. Furthermore, some of the maximum may be associated with the Pd binding to oxygen
atoms of polyvinyl pyrrolidone, the polymer with which it had deposited of the nanoparticles.
The BE values for Cu2p3/2 are similar for all catalysts and shows a state close to Cu0, but also sometimes caused
Cu (I) in Cu2O and Cu (II) peaks, although the distinction between Cu0 CuO and Cu (I) is difficult to make. However,
no shake-up satellites show no species Cu (II). In contrast, used catalysts containing oxides of Cu.
NANOSTRUCTURED MATERIALS AS EFFICIENT CATALYSTS: CHARACTERIZATION OF A
HYDROTALCITE DOCKED RH COMPLEX
Florentina Neatu1,2, Madalina Ciobanua1, Laura Stoflea1, Ligia Frunza2, Vasile I.Pârvulescu1 and Véronique Michelet3
1
University of Bucharest, Dept. Organic Chem. Biochem. & Catal., 030016 Bucharest, 2National Institute of Materials
Physics, 077125 Magurele. 3PSL Research University, CNRS Institut de Recherche de Chimie Paris,75005 Paris
Rh complex (with 3,3,3-phosphane-triylbenzene carboxylic acid) was successfully immobilized onto a layered
double hydroxide Zn-Al (LDH) to convert selectively in aqueous media both the symmetric and nonsymmetric alkynes
into functionalized alkenes, with boronic acids [i]. The use of water requires the presence of cooperative catalysts that
should be able to combine the high catalytic efficiency with the metal recycling and the easy product/catalyst
separation.
Here we focus on the catalysts characterization. This was done using several techniques: N2 adsorption–desorption
isotherms of the LDH support and the Rh-catalysts were measured with a Micromeritics ASAP2020. DRIFT
spectroscopy, powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) in an analysis chamber
(Specs) on powders pressed on carbon tapes. Chemical composition of the catalysts was determined by Atomic
Emission Spectroscopy (ICP-AES) etc.
XRD shows patterns indicating the partial insertion of the ligand between the layers of the LDH.
DRIFT analyses were recorded for both LDH and Rh-complex/LDH materials. No significant difference could be
observed between the two spectra, except an increase in the range assignable to the phenyl group of the ligand.
ICP-AES analysis indicated a similar Rh content.
No change of the binding energies of Al2p and Zn2p after the ionic exchange with complexes was observed,
meaning that the oxidation state of the constitutive elements was not altered by ionic exchange.
Reference
F. Neatu, M. Ciobanu, L. Stoflea, L. Frunza, V.I. Pârvulescu, V. Michelet, Catal. Today 247 (2015) 155–162
169
DISLOCATION DENSITY AND ETCH PITS MORPHOLOGY ON CLEAVAGE PLAN OF YbF 3 DOPED
BaF2 CRYSTALS
Marius Stef and Irina Nicoara
West University of Timisoara, Dept. of Physics, Blvd. V. Parvan 4, Timisoara, Romania, e-mail: [email protected]
Growth and characterization of new laser materials is an important field of the materials science. Recently [1-4] it
has been shown that MF2 (M=Ca, Ba, Sr) crystals are efficient laser host for trivalent RE (rare earth) ions. The
crystalline imperfections of the crystals influence the laser performance, thus the study of the dislocations is important
because the dislocation density is a measure of the crystal quality. By doping MF2 crystalline host with YbF3, both Yb2+
and Yb3+ ions will coexists in the crystal; Yb3+ ions are responsible for emission in near IR [3,4] spectral domain and
Yb2+ ions are responsible for the emission in UV and VIS domain [5,6]. The properties of the YbF3 doped MF2 crystals
are strongly dependent on the quality of the crystals and on the YbF 3 concentration. The aim of this paper is the study of
crystal quality of the various transparent YbF 3 doped BaF2 crystals obtained by Bridgman method in graphite crucible
in vacuum (~10-3 torr). The rate of the crucible lowering was 4 mm/h. In this paper we have studied the influence of
dopant concentration on the etch pits morphology and dislocation density. For this purpose the chemical etching
method has been used [7]. This method consists in immersing the freshly cleaved sample, the (111) plane, in 2N HCl at
600C for 2 minutes. The dislocation density depends on the YbF 3 concentration added to the melt.
References
[1] C. Labbe, J.L. Doualan, P. Camy, R. Moncorgé, and M. Thuau, Opt. Commun. 209 (2002) 193-196.
[2] P. Camy, J.L. Doualan, S. Renard, A. Braud, V. Ménard, and R. Moncorgé, Opt. Commun. 236 (2004) 395-398.
[3] V. Petit, P. Camy, J.L. Doualan, and R. Moncorgé, Appl. Phys. Lett. 88 (2006) 051111.
[4] J. L. Doualan et al. Laser Physics 20 (2010) 533-536.
[5] J. Rubio, J. Phys. Chem. Solids 52 (1991)101.
[6] I. Nicoara, L. Lighezan, M. Enculescu, I. Enculescu, J. Cryst. Growth 310 (2007) 2026-2029.
[7] S. Amelinckx, The direct observation of dislocations, Academic Press, N.Y., 1964,
COMMON AND DIFFERENT DOPING PATTERNS WITHIN COMPLEXES OF Co 2+ IN Bi12SiO20 AND Co3+
IN Bi12TiO20
Petya Petkovaa, Karem Boubakerb, Petko Vasileva, Mustafa Mustafaa, Darina Bachvarovaa and Ayşe Yumakc
a
Shumen University “Konstantin Preslavsky”, 115 Universitetska street, 9712 Shumen, Bulgaria, ae-mail:
[email protected]; bUnité de physique des dispositifs à semi-conducteurs, Faculté des sciences de Tunis, Université de
Tunis El Manar, 2092 Tunis, TUNISIA; cPhysics Department, Faculty of Arts and Sciences, Marmara University,
34722 Göztepe, Istanbul, TURKEY
We have investigated the absorption of the Co doped Bi 12MO20 (M = Si, Ti) in the spectral region 12 092–18 149
cm-1. The observed absorption band is due to the Co-impurity in the visible spectral region. This absorption band does
not contain information about the exact energy position of the Co levels. Therefore, we have calculated the second
derivative of absorption. It is established that Co2+ ions are surrounded by distorted tetrahedral coordination in Bi 12SiO20
(BSO) and polyhedral ones in Bi12TiO20 (BTO). We have calculated the crystal field parameter Dq and the Racah
parameters B and C for these ions. The energy level structure of the Co2+ ion in BSO and this of Co3+ ion in Bi12TiO20
along with elements from the Lattice Compatibility Theory are also presented.
QUANTUM MECHANICAL TRANSMISSION WITH ABSORPTION OF Co(NO 3)2(H2O)6 AND
Ni(NO3)2(H2O)6
a
Petya Petkovaa, Petko Vasileva, Mustafa Mustafaa and Darina Bachvarovaa
Shumen University “Konstantin Preslavsky”, 115 Universitetska street, 9712 Shumen, Bulgaria, ae-mail:
[email protected]
In this work, we studied the aqueous solutions of cobalt and nitrate as absorptive medium. We first observed the
variation with energy the transmission and the reflection from a rectangular barrier and the corresponding well without
the presence of absorption. Then, we described the variation of transmission, reflection and absorption generated by a
purely absorptive domain of width a and strength W0. The one dimensional time independent Schrödinger equation is
solved in the case of ZnO thin films. In this connection, we determined the values of: real part of optical potential V0,
wave function Φ, absorption potential strength W0 and incident energy E.
170
BALLISTIC ELECTRON TRANSPORT IN WRINKLED METAMATERIALS
T.L. Mitran, G.A. Nemnes., L. Ion and Daniela Dragoman
Faculty of Physics, MDEO Research Center, University of Bucharst P.O. Box
MG-11, 077125 Magurele-Ilfov, Romania
The precise control of transport properties in semiconductor materials has been one of the main goals of solid state
physics. One of the research directions that aims to accomplish this is the study of nanostructured and meta-materials.
The engineering of artificial materials has appeared mainly through the need to control the refraction index of
electromagnetic metamaterials used for radio, microwave and optical frequencies. With the help of modern technical
production methods, it is now possible to apply these concepts to the nanoscale, not for electromagnetic waves but for
electron transport. One recent method that has been proposed for the control of wave propagation is the use of layered
media with interfacial wrinkling. We have used a similar concept in order to control the transport properties of twodimensional semiconductors by including wrinkled scattering potentials with tunable properties (number of scattering
potentials, potential energy, width and spatial density of wrinkles). The studied systems are made up of a rectangular
scattering region with two ideal leads and contain multiple one dimensional scattering potential that span parallel to the
direction of the leads. The scattering potentials are present in the leads in order to preserve the continuity of the system,
but are kept straight and are only wrinkled in the scattering region. The transmission function is studied for different
values of scattering potentials parameters using the scattering formalism of the R-matrix method.
CONSOLIDATION OF VERY DEGRADED WOOD ARTEFACTS BY RESIN IMPREGNATION AND
GAMMA IRRADIATION
Silvana Vasilca1,2, Ioana Rodica Stanculescu1,2, Cosmin Pintilie1, Marian Virgolici1, Bogdan Lungu1, Valentin Moise1,
Catalina Ghinea3, Laurent Cortella4, Quoc-Khoi Tran4
1. Horia Hulubei National Institute of Physics and Nuclear Engineering, Centre of Technological Irradiations IRASM,
007125, Magurele, Romania, [email protected]; 2. University of Bucharest, Faculty of Chemistry, Department of
Physical Chemistry, 030018, Bucharest, Romania; 3. University of Bucharest, Faculty of Physics, Atomistilor street
405, Magurele, Ilfov; 4. Atelier Régional de Conservation-Nucléart, CEA-Grenoble, France
Cultural heritage artifacts infested with microorganisms or other pests can be saved from further destruction, using
the treatment with ionizing radiation before restoration. After the radiation treatment, both effects, the biocide one
regarding the microbial load of the objects and the secondary effects of the radiation on the materials (chain scission,
cross-linking etc.), depend on the adsorbed dose. High doses of radiation will exponentially decrease the biological load
and low doses will lead to slight effects on the irradiated materials. A special application of gamma irradiation is the
consolidation of highly degraded wood by impregnation with standard unsaturated polyester resin. Usually, free radical
polymerization is initiated by peroxides, but in the case of radiopolymerization, the initiator is the radiation and
chemical activation is no longer needed. The in situ radiation cross-linked resin improves the properties of the material.
The correlation between the thermogravimetric and infrared spectroscopy results was done in order to indentify the
changes in the wood structure after the radiation-curing of the resin. Bruker Vertex FTIR/FT-Raman spectrometer and
TG/DSC - Netzsch STA 409 PC Luxx Simultaneous Thermal Analyzer equipped with a TGA-IR unit were used.
Vibrational spectra ensured information, on one hand about the changes in the molecular structure of different wood
components due to photophysical or biological decay and, on the other hand about the radiation-polymerized resin.
Thermal analysis showed changes of the chemical composition and the thermal stability of the wooden objects, due to
gamma irradiation consolidation and, of course, because of the artifacts’ degradation history.
Acknowledgement: This work was supported by an IFA-CEA grant, contr. no. C3-05/2013.
171
OPTICAL CHARACTERIZATION OF SOME TRANSPARENT OXIDES THIN FILMS
P. Prepelitaa,1, V. Craciuna, M. Filipescua, D. Craciuna, F. Garoia, G. Sbarceab, I. Stavarachec, A. Vlada, C. Viespea
National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor Street, PO Box MG-36, 077125 Magurele,
Ilfov, Romania; b National Institute for R & D in Electrical Engineering ICPE-CA, Splaiul Unirii Street, Nr. 313,
District 3, 030138, Bucharest Romania; c National Institute of Materials Physics, Magurele 077125, Romania; (1Married
as Garoi)
a
Transparent and conductive oxides thin films (ITO, SnO2), with thickness values in the range 230 – 370 nm, were
grown onto glass substrates using the RF magnetron sputtering technique. After deposition, the samples were annealed
in air at temperatures up to 650 K. In this study, a stylus profilometer (Ambios, XP–2) was used to measure the
thickness of the oxide thin films. Structural and optical properties of both as-deposited and annealed samples were
investigated by XRD and GIXRD. The surface morphology of the obtained films was investigated by AFM and SEM
techniques. Influences of post deposition thermal treatment on morphological properties of these oxides were discussed
based on XRD measurements. Transmittance spectra, in double-beam configuration, were recorded in the 190 – 3000
nm wavelength range and, from these, optical constants (i.e. Drude damping coefficient, Drude frequency, complex
permittivity, refractive indices, extinction coefficients) were obtained for these oxides of various thicknesses. High
absorption coefficients and suitable optical bandgap values of 3.5 – 3.7 eV were obtained. The electrical conductivity
was measured using the four points method. Current – voltage characteristics of the oxide thin films were recorded at
temperatures ranging from 300 K to 480 K. An electrical analysis of the conduction mechanisms specific for different
voltage ranges was also performed.
THE ROLE OF PROCESS CONTROL AGENT ON MICROSTRUCTURE AND MAGNETIC PROPERTIES
OF BALL MILLED FINEMET POWDERS
1
Luiza Budeanu1,2 , Horia Chiriac1, George Stoian1, Nicoleta Lupu1
National Institute of Research & Development for Technical Physics, 47 Mangeron Blvd., Iasi, Romania; 2Faculty of
Physics, Alexandru Ioan Cuza University, 11 Carol I Blvd., Iasi, Romania
In this paper we present the results about the influence of oleic acid (OA) and stearic acid (SA) as a process control
agent on the microstructure and magnetic properties of Fe73.5Cu1Nb3Si13.5B9 (FINEMET) powders obtained by ball
milling process using FINEMET ribbons as precursor material. The ribbons prepared by rapid quenching from the melt
were vacuum annealed for 1 hour at temperatures of 420°C and 450°C for embrittlement temperature which is below
the nanocrystallization temperature (520°C - 550°C), in order to prevent crystallization.
SEM images show a decrease of the average particle size around 8 µm with the increase of the ball milling time to
72 hours for both process control agents. The thermomagnetic curves indicate an increase of the amount of
nanocrystalline phase with the increasing of the milling time for powders ball milled in SA while the powders ball
milled in OA present a smaller rate of nanocrystallization. The crystallization state during ball milling process indicated
by the thermomagnetic curves was confirmed by existence of specific diffraction peak at around 2θ=45° corresponding
to the (110) reflection of α-Fe(Si) phase from XRD analysis of powders. The crystalinity ratio (X c) relative to the
amorphous residual matrix remains almost constant (around 50%) for the powders ball milled in OA, independent of
milling time and annealing temperature of as-cast ribbons, whilst Xc increases to around 60% for powders ball milled
for 72 hours in SA. Comparing both types of process control agents we can observe that the soft magnetic properties of
the powders ball milled in OA remain almost unchanged compared with the precursor material, independent of the
annealing treatment of ribbons and time of ball milling.
ACKNOWLEDGMENTS
Financial support by the Romanian NUCLEU Program (Project No. PN 09-43 01 02), is gratefully acknowledged.
L. Budeanu thanks for the financial support provided by the strategic grant POSDRU/159/1.5/S/137750.
172
ESR OF IRRADIATION POINT DEFECTS IN 17O AND 13C DOPED Si-FZ SINGLE CRYSTALS AT HIGH
DOSES OF 27MeV ELECTRONS
A. C. Joita1,2, S. V. Nistor1, D. Ghica1, R. Radu1 and I. Pintilie1
National Institute of Materials Physics, Magurele, Ilfov, Romania; 2University of Bucharest, Faculty of Physics,
Magurele, Ilfov, Romania
1
Improving the radiation tolerance of silicon tracking detectors of the LHC (Large Hadron Collider) to very high
fluencies of charged and neutral particles requires to understand the radiation damage mechanisms responsible for the
observed silicon-sensor performance degradation during operation [1]. We studied the role of oxygen and carbon
impurity atoms in the formation and structure of the irradiation paramagnetic point defects (IPPDs) in crystalline silicon
employed in producing the tracking detectors for LHC. The investigations were performed by Q-band (34 GHz)
electron spin resonance (ESR) spectroscopy from 296K down to 20K, on high resistivity (3-4 kOhm cm) n-type silicon
(FZ-Wacker), doped with either 17O or 13C enriched isotopes and irradiated with 27MeV (2 x 1016 cm-2) electrons.
Besides the isotropic ESR spectra reported in the as-irradiated samples [2], new anisotropic ESR spectra were observed
during 1060 nm in-situ optical excitation at different temperatures. Further changes in the EPR spectra took place in the
samples subjected to isochronal annealing from 150 0C up to 300 0C in steps of 50 degrees. The quantitative analysis of
the EPR spectra recorded with the magnetic field in a (110) plane, at different temperatures, at low and high microwave
power levels resulted in the identification of several IPPDs, characterized by different spin Hamiltonian parameters and
local symmetry. Structural models of the resulting IPPDs are proposed and used to explain the observed changes in the
EPR spectra of annealed samples. A tentative comparison with thermally stimulated currents (TSC) data on such
samples subjected to similar irradiation and thermal treatments is also presented. [1] R. Radu, E. Fretwurst, R. Klanner,
G. Lindstroem, I. Pintilie, Nucl. Instrum. & Meth. Phys. Res. A730 , 84 (2013); [2] S. V. Nistor, D. Ghica, I. Pintilie,
E. Manaila, Rom. Repts. Phys. 65, 812 (2013). Presenting author e-mail: [email protected]
ELECTRICAL AND MECHANICAL PROPERTIES OF PP/PANI COMPOSITES
M. Kılıç1, Ü. Alkan2, Y. Karabul1, H. B. Yamak3, M. Okutan1 and O. İçelli1
Department of Physics, Faculty of Science and Letters, Yıldız Technical University, Istanbul, Turkey; 2 Department of
Computer Engineering, Gelişim University, İstanbul, Turkey ; 3Department of Metallurgical and Materials Engineering,
Faculty of Chemistry-Metallurgical, Yıldız Technical University, Istanbul, Turkey; E-mail: [email protected]
1
Studies of Polypropylene (PP) materials and their composites with the organic or inorganic additives are motivated,
in part, by their technological applications owing to its good electrical properties, environmental stability, low
production cost, and ease of synthesis. In addition this, special interest was focused on polyaniline (PANI) because of
low production cost, relatively high level of electrical conductivity, as well as fine environmental stability. PP/PANI
blends and composites have already been obtained using different methods. However, few studies have focused on
PP/PANI composites obtained by the hot pressing method.
In this study, PANI doped PP in different concentrations composite films were obtained by the hot pressing method
(15 MPa, 438 K, 10 min).These composites were characterized by FTIR spectroscopy, differential scanning calorimetry
(DSC), stress-strain measurements, and electrical measurements.
THE EFFECT OF THE MAIN GROUP ELEMETS ON THE HALF METALLIC PROPERTIES IN
SCANDIUM BASED HEUSLER COMPOUNDS
Anca Birsan1,2 ([email protected])
National Institute of Materials Physics, 105 bis Atomistilor Street, PO Box MG-7, 077125, Magurele-Ilfov, Romania,
2
University of Bucharest, Faculty of Physics, 105 Atomistilor Street, PO Box MG-11, 077125 Magurele-Ilfov, Romania
1
The interest in Heusler compounds grew in the recent years due to the discovery of their half-metallic properties,
suitable for spintronic applications The new half-metallic ferromagnetic scandium-based Heusler materials were
identified by applying ab initio electronic-structure calculations within the Density Functional Theory framework,
compatible with semiconductors, due to large enough spin-flip gaps. The effect of the main group elements on the half
metallic properties was analysed. The results demonstrate that even though the main group elements carry a low
magnetic moment, they alter the spin polarization, resulting in a change of half metallic properties in the studied
compounds. In addition, the size of the band gap, from minority spin channel decreases while the atomic radius of the
main element becomes larger.
Acknowledgments: The author acknowledges the financial support provided through the CORE-PN45N projects
and the strategic grant POSDRU/159/1.5/S/137750.
173
A COMPREHENSIVE STUDY ON EFFECT OF GAMMA RADIATION FOR BASALT REINFORCED LOW
DENSITY POLYETHYLENE
1
Y. Karabul1, M. Kılıç1, Ü. Alkan2, M. Okutan3, M. Okutan1 and O. İçelli1
Department of Physics, Faculty of Science and Letters, Yıldız Technical University, Istanbul, Turkey; 2 Department of
Computer Engineering, Gelişim University, Istanbul, Turkey ; 3 Department of Radiotherapy, Oncology Institute,
Istanbul University, Istanbul, Turkey ; E-mail: [email protected]
Low density polyethylene (LDPE) has been utilized widely in many areas since the middle of twentieth century. The
opportunity of crosslinking LDPE and numerous other polymers with high energy radiation has led to a lot of useful
applications. Also, basalt is a very common volcanic rock that is dark colored and relatively rich in iron and magnesium
almost located each country in the world. It is used for a comprehensive variety of purposes. These rocks have been
used in the refused rock industry, to produce building tiles, construction industrial, highway engineering. Powders and
fibers of basalt rocks are commonly used of radiation shielding, thermal stability, heat and sound insulation. Moreover,
it has fine variety of thermal efficiency, large tensile strength and resistance to acids, corrosion, ultraviolet light,
radiation, and vibration. The basalt reinforced polyethylene products are obtainable in a number of types such as, loops,
2‐dimensional mesh, spirals as well as straight rods. In this work, LDPE-Basalt composite films were irradiated by Co60 gamma-rays in the dose range varied from 5 to 50 gray. The caused modifications in the chemical construction and
dielectric attributes for the irradiated films were researched. The construction changes: crystallinity and feasible
molecular modifications of the polymer were identified by using Fourier Transform Infrared Spectroscopy (FTIR). The
final investigation of this work was to examine the electrical characteristic of LDPE-Basalt composites in addition to
the dielectric strength ∆ϵ.
DISPLACIVE TRANSFORMATION AND TWINNED NATURE OF PRODUCT STRUCTURES IN SHAPE
MEMORY ALLOYS
Osman Adiguzel
Firat University, Department of Physics, 23169 Elazig, Turkey
Shape memory alloys have a peculiar property to return to a previously defined shape or dimension when they are
subjected to variation of temperature. These alloys recover original shape on heating after deformation in low
temperature product phase condition. Shape memory effect is facilitated by martensitic transformation governed by
changes in the crystalline structure of the material, and shape memory properties are intimately related to the
microstructures of the alloy. Thermal induced martensite occurs as multivariant martensite in self-accommodating
manner on cooling from high temperature parent phase region, and this martensite is called self-accommodated
martensite or multivariant martensite. Deformation of shape memory alloys in martensitic state proceeds through a
martensite variant reorientation.
Martensitic transformations occur with cooperative movement of atoms by means of lattice invariant shears on a
{110} - type plane of austenite matrix which is basal plane of martensite. The lattice invariant shears occurs, in two
opposite directions, <110 > -type directions on the {110}-type basal plane. This kind of shear can be called as
{110}<110> - type mode, and possible 24 martensite variants occur.
Martensitic transformation is a shear-dominant solid-state phase transformation, by which the ordered parent phase
structures turn into complex layered structures. Martensitic structures occur as martensite variants in a selfaccommodating manner through twinning Shape memory properties are intimately related to the microstructures of the
material, especially orientation relationship between the various martensite variants. Twinning and detwinning
processes can be considered as elementary processes activated during the transformation. In particular, the detwinning
is essential as well as martensitic transformation in reversible shape memory effect. By applying external stress, the
martensitic variants are forced to reorient into a single variant leading inelastic strains. Deformation of shape memory
alloys in martensitic state proceeds through a martensite variant reorientation of twins.
Copper based alloys exhibit this property in metastable phase region, which has bcc-based structures at high
temperature parent phase field, and these structures martensitically turn into layered complex structures with lattice
twinning following two ordered reactions on cooling.
In the present contribution, x-ray diffraction and transmission electron microscopy (TEM) studies were carried out
on two copper based alloys which have the chemical compositions in weight; Cu-26.1%Zn 4%Al and Cu-11%Al6%Mn. X-ray diffraction profiles and electron diffraction patterns reveal that both alloys exhibit super lattice reflections
inherited from parent phase due to the displacive character of martensitic transformation.
Keywords: Shape memory effect, martensitic transformation, self-accommodation, twinning and detwinning,
layered structures.
174
ELECTRONIC TRANSPORT PROPERTIES OF NBTI IN COPPER MATRIX SUPERCONDUCTING
WIRES
Alina Elena Niculescu, Iuliana Piciorea, Alexandru Rizoiu, Stanica Enache
National Institute for Research and Development for Cryogenics and Isotopic Technologies - ICIT Rm. Valcea, Uzinei
Street no. 4, 240050, Ramnicu Valcea, Romania; [email protected]
This work is presenting the study of signal-to-noise assessment, the electronic transport properties of NbTi wires
extruded in a Cu matrix with 0.4mm in diameter and volume ratios of NbTi:Cu = 1.35:1. Normal-state
magnetoresistance, I-V characteristics and superconducting state critical currents are thoroughly investigated.
Additionally, we investigated the critical current density as a function of temperature and field using the expressions
for the critical temperature, critical magnetic field and Pinning force in NbTi. The measurements undertaken in this
research cover a range of the magnetic field between 0T to 7T at temperatures ranging from 1.9K to 10K.
In order to measure the electrical resistance down to cryogenic temperature (2K) it has been used the Physical Property
Measurement System (PPMS). The measurements have been done in various magnetic fields, up to 7T. The values of
the measured resistance were the bases of the calculation and obtaining data for electrical resistivity, critical current
density (Jc) and pinning force (Fp).
CHARACTERIZATION OF ZINC FERRITE NANOPOWDERS IRRADIATED BY SLOW HIGHLY
CHARGED IONS
Ioan Dumitru1, Elena Vasilica Gafton1, Radu Ciocarlan2, Martino Trassinelli3, Ovidiu Florin Caltun1, Aurel Pui2, Rolf
Hempelmann4, Dominique Vernhet3
1
Alexandru Ioan Cuza University, Faculty of Physics, 11 Carol I Blv, Iasi 700506, Romania; 2Alexandru Ioan Cuza
University, Faculty of Chemistry, 11 Carol I Blv, Iasi 700506, Romania; 3CNRS and Université Pierre et Marie Curie,
INSP, UMR7588, 4 Place Jussieu, F-75005 Paris, France ; 4Physikalische Chemie, Universitaet des Saarlandes,
Saarbruecken, Germany ; [email protected]
Nanaoparticles and thin films of spinel zinc ferrite (ZnFe2O4) has attracted more attentions due to their particular
magnetic properties and extraordinary gas sensing properties, mainly determined by their microstructure which can be
affected by the synthesis conditions and methods. Tailoring of magnetic and structural properties of magnetic
nanopowders by ion irradiation [1, 2] is a work of interest for technological application. To study the influence of lower
energy irradiation process on physical properties of zinc ferrite nanoparticles a series of samples were obtained by
coprecipitation route [3]. The influence of concentration of NaOH coprecipitation agent on synthesis process and on
final properties of zinc ferrite nanoparticles was investigated by X-ray powder diffraction (XRD), transmission electron
microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR). It was observed that all samples are obtained
in pure phases and the nanoparticles’ surface is activated with groups belonging to the surfactant. From TEM analysis
the size distribution of the particles in between 7-10 nm was determined.
Structural and magnetic properties of these zinc ferrites nanoparticles were under investigation before and after
being irradiated by a 90 keV neon beam. The XRD patterns and hysteresis loop at room temperatures were recorded for
the pristine and irradiated specimens in order to observe the structural change and magnetic properties variation. It was
observed that ion bombardment at such low energy does not affect the chemical composition but changed significantly
their magnetic properties.
[1] Rao, B.P., Rao, K.H., Subba Rao, P.S.V., Mahesh Kumar, A., Murthy, Y.L.N., Asokan, K., Siva Kumar, V.V.,
Kumar, R., Gajbhiye, N.S., Caltun, O.F, Nuclear Instruments and Methods in Physics Research, Section B: Beam
Interactions with Materials and Atoms, Volume 244, Issue 1, February 2006, Pages 27-30
[2] Singh, J.P., Srivastava, R.C., Agrawal, H.M., Kumar, R., Radiation Effects and Defects in Solids, Volume 166,
Issue 8-9, August 2011, Pages 564-570
[3] Gherca, D., Pui, A., Nica, V., Caltun, O., Cornei, N., Ceramics International, Volume 40, Issue 7 Part A, 2014,
Pages 9599-9607
175
MAGNETORESISTANCE IN SPIN-VALVE DEVICES WITH ORGANIC SEMICONDUCTOR SPACER
A. Carlescu1,2, C. Bernhard1, I. Deac3, A. Popa4, D. Lazar4, P. Traian Jr. 5, F. Iacomi2
University of Fribourg, Departament of Physics, Chemin du Musée 3,CH-1700 Fribourg, Switzerland; Author e-mail:
[email protected]; 2”Alexandru Ioan Cuza” University of Iasi, Faculty of Physics, B-dul Carol I,Nr. 11,
700506 Iasi, Romania; 3“Babes-Bolyai” University, Faculty of Physics, Mihail Kogalniceanu No. 1, RO-400084,
Cluj-Napoca, Romania; 4INCDTIM Cluj-Napoca, 67-103 Donat, PO 5 Box 700, 400293 Cluj-Napoca, Romania;
5
Technical University of Cluj-Napoca, Material Science and Engineering Departament, Memorandumului Street, No.
28, Cluj-Napoca 400114, Romania
1
Recent observations of magnetoresistance (MR) effects in OSCs organic semiconductors has opened up the potential
of these materials for spin-conserved transport. We have embarked on studying magneto-transport response of organic
spin-valves made of evaporated Alq3 (tris(8-hydroxyquinolinato)aluminium) spacer sandwiched between two
ferromagnetic (FM) electrodes with spin-injecting capability. Epitaxial La0.67Sr0.33MnO3 (LSMO) thin films were grown
by pulsed laser deposition; the organic spacer Alq3 and the top ferromagnetic electrode Co were deposited using
thermal evaporation method in vacuum. The films thickness was determined with X-ray reflectrometry (XRR) and the
simulations of the XRR data have been performed using the software package GenX. The layers structural
characterization was done using X-ray refflectormetry (XRD) using in-plane configuration with parallel beam. From the
electron spin resonance (ESR) curves the linewidth and the g factor were calculated. Magnetoresistance measurements
were performed -as a function of temperature using the four point probe option of a physical properties measurement
system (PPMS) from Quantum Design (Model QD6000) and Cryogenic 7T
The spin valves exhibited a negative magnetoresistence and the temperature dependence of the electrical resistance
R(T) showed a metallic behavior in the temperature range 10 – 300 K. This behavior indicates a decrease of the electric
charge carriers scattering due to the enhancement of magnetism in the LSMO and Co electrodes. This effect seems to be
more important than the increase of the Alq3 barrier resistance at low temperatures.
Keywords:spin valve; spintronics; magnetoresistance; X-ray reflectivity; organic semiconductor;
176
LATE NEWS 177
178
Invited Papers
OXIDE THIN FILMS AND NANOSRUCTURES
FOR TRANSPARENT ELECTRONICS, SPINTRONICS AND SENSORS
Felicia Iacomi
Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Romania, [email protected]
The present contribution reports recent results obtained on n and p type metal oxides (In2-(x+y)SnxZnyO, In2Zn1-xCoxO, Zn1-xNixO, Ti1-xMnxO2, Ni1-xCoxFe2O4, Zn1-xCoxFe2O4, LaPbMnO3, LaSrMnO3) thin films
deposited on different substrates (glass, quartz, alumina, silicon, etc) by using different deposition methods (spin
coating, vacuum thermal evaporation, rf magnetron sputtering) and on some magnetic nanostructures (with ferrite or
perovskite structures) obtained by co-precipitattion, auto-combustion, or by isolation in mesoporous matrices. Thin
films and nanostructures structural and functional investigations (XRD, SEM, XPS, EPR, optical, electrical, magnetic,
gas sensing techniques) proved that by controlling the doping, post deposition annealing and UV irradiation procedures
one can finely tune the structural, optical, electronic, magnetic and gas sensing properties providing the proper
functionality for the targeted application.
(x+y)SnxMnyO,
Dielectric spectroscopy in ferroelectric relaxation of TGS crystal.
Horia V. Alexandru*, Carmen Mindru, Constantin Paul Ganea1) and Nicoleta Vineticu
University of Bucharest, Faculty of Physics
1
) National Institute of Material Physics Bucharest-Magurele
* Academy of Romanian Scientists, 54 Splaiul Independentei, Bucharest, Romania.
Triglycine sulphate (TGS) is a ferroelectric crystal with a typical second order transition of order–disorder type. It
has a monoclinic structure and a complicated ferroelectric domains evolution, in the ferro phase, crossing down the
Curie point (49oC). About 80% of the measured dielectric constant value is related with the ferroelectric domain walls
oscillation. There is a continuous decreasing variation of the dielectric constant due to the topographic changes of the
ferroelectric domain evolution. However, repeating the same trace from 65oC and than down through the Curie point at
a pace of 0.6oC/min, data are quite reproducible for the same sample. Pure TGS crystal was grown in the paraelectric
phase (54oC) and sample of 1 mm x 0.5 cm2 were cleaved from the grown crystals and silver electrodes were painted.
Both components of permittivity were measured on the frequency range 1-107 Hz and on a large temperature range in
ferro phase. Two fundamental relaxations which have a real physical support and an intermediate one, we have found in
Cole-Cole representations. The higher frequency relaxation having H = (3-4)10-7 sec, almost constant on the
temperature range over zero Celsius up to 45oC is related to a long distance order in the lattice. It has non-Arrhenius
temperature dependence. In the lower frequency region the relaxation time L ~10-3 sec is related with ferroelectric
domain relaxation, with the activation energy of ~0.70 eV. An unusual mid frequency relaxation time of M ~10-5 sec,
we have detected for the first time in the literature, (JOAM 14 (1912) 157-162 and thesis Carmen MÎNDRU). This type
of relaxation does not seem to have a real physical support being rather an interaction of the previously two related
mechanisms. Some other peculiar aspects evidenced by the dielectric spectroscopy on the mentioned frequency range
shall be presented.
179
DOWN THE FERROELECTRIC TRANSITION
Carmen Mîndru ¹, Nicoleta Vineticu¹, Constantin Paul Ganea² and Horia V. Alexandru¹,*)
¹ Faculty of Physics, University of Bucharest, Romania
² National Institute of Materials Physics, Bucharest-Magurele, Romania
*) Academy of Romanian Scientists
Triglycine sulphate (TGS) – a ferroelectric crystal, having para- ferro transition point around TC = 49.2°C, was
studied for its properties and its behavior in the vicinity of the ferroelectric transition.
The sample used derives from a single crystal grown from an aqueous solution by slow evaporation of the solvent at
52°C (in paraelectric phase). Measurements were performed on a wide temperature range (-120° C/ +65° C), after a
scheduled program and a frequency range between 1Hz and 10MHz.
Permittivity components and the arcs Cole- Cole were traced.
The study of the three identified relaxation mechanisms allowed the characterization of these by estimating their
relaxation time and the activation energy.
The HFR (high frequency relaxation) has a non-Arrhenius-temperature dependence and the
relaxation time τH is almost constant on a large temperature range, down the Curie point
For the LFR (low frequency relaxation) the time τL=(10-3 – 4⋅10-2) s was estimated on the 5-50oC temperature range
and supports an Arrhenius temperature dependence with the activation energy of EA=0.69eV.
The MFR (middle frequency relaxation) has a strange temperature dependence. Besides, on the temperature range
(20-45) oC, a sort of instability appears. Far from transition (5-20) oC it has activation energy of 0.44 eV.
The author Nicoleta VINETICU acknowledge the financial support of the structural founds project POSDRU ID
137750.
INFLUENCE OF ANNEALING CONDITIONS ON FUNCTIONAL PROPERTIES OF Ni, Co DOPED ZnO
THIN FILMS GROWN BY SPIN COATING
M. Toma1, L.M. Cosovanu1, O. Vasilovici1, F. Enescu1, V. Tiron1, G.G.Rusu1, M. Dobromir1, D. Timpu2, F. Iacomi1
Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Romania, [email protected]; [email protected]
Nanocrystalline thin films of low Ni, Co doped ZnO were deposited onto glass and quartz substrates by using a spin
coating method. Post-annealings were performed at 450C and 650 C. Structural, optical and magnetic properties were
investigated by using, X-ray diffraction, X-ray photoelectron spectroscopy, UV-VIS and electron paramagnetic
spectroscopies. The surface morphology, roughness and piezoelectric properties were investigated by atomic force
microscopy and showed the influence of dopant nature and annealing temperature. At low doping level, local structure
remains identical to ZnO with subtle increase in the bond length. XPS and the optical absorption measurements indicate
valence +2 both for Ni and Co. Undoped as well as doped ZnO thin films are weakly ferromagnetic proving that
ferromagnetic ordering in thin films is primarily a manifestation of point defects and incorporation of transition metal
impurities plays a secondary role.
180
THE OPTICAL AND ELECTRICAL PROPERTIES OF Al AND Si CO-DOPED ZnO THIN FILMS
PREPARED BY A SPIN COATING TECHNIQUE
A. Abbassi1, Mihaela Toma2, G. G. Rusu2, V. Nica2, H. Ez-Zahraouy1, F. Iacomi2
Faculty of Sciences, Mohammed V University, Rabat, Morocco, 2Faculty of Physics, Alexandru Ioan Cuza University
of Iasi, Romania, [email protected], [email protected]
1
Zinc oxide co-doped with different amounts of aluminum and silicon were deposited by spin coating on quartz
substrates from solutions containing zinc acetate, aluminum acetate and tetraethyl ortosililate and dimethylphormamide
as a solvent. The used solutions had certain compositions in order to obtain thin films with Zn+Al contents in the range
2at% - 6at%. After deposition thin films were submitted to different annealings, at 450°C, 650 °C and 800 °C and
structural and functional investigated. XRD patterns evidenced the ZnO wurtzit structure. XPS analysis sustain the
entrance of Al3+ and Si3+in Zn lattice sites. Optical investigations evidenced that the optical band gap varies between
3.23eV to 3.33eV, showing an increase with increasing the silicon amount. All the studied thin films have a
transmittance over 80% being suited for active transparent layers. Electrical properties showed a higher electrical
conductivity for the thin films having 3at%Si and 1%Al. The electronic and optical properties were probed with
different approximations; the generalized gradient approximation (GGA) and mBJ using the FP-LAPW method.
Contributions in the Optimization of the Electron Diffraction Precession System for the Examination of Thin
Films by Electron Diffraction
Radu MANU2, Victor CIUPINĂ1,2, Gabriel PRODAN1, Ştefan Gabriel TUTUN2,
Lucian PETRĂŞESCU2, Nicoleta VINETICU2, Oana BRÎNCOVEANU2, Iulian PRIOTEASA2
1
Ovidius University, of Constanta, Mamaia 124, Constanţa, 900527, Romania
2
Faculty of Physics, University of Bucharest, Atomiştilor 405, Măgurele, Ilfov, Romania
[email protected]
Nanostructured materials are accurately investigated using transmission electron microscopy (TEM), but
compromise must be taken when information are acquired using electron diffraction technique, the errors data being
larger compared with X-Ray diffraction. To improve the quality of electron diffraction pattern and the data extracted
from this, we use a simple precession device applied to the electron beam before the interaction with the sample, the
final image being refocused by microscope lens. In this way we eliminate the dynamic effects that appear during the
rotating crystal method. Crystalline structure analysis can be done in two-step: first, crystallographic information and
cell parameters determination and second, refinement of the unit cell, including atom position. The crystalline structure
data extracted from electron diffraction pattern is improved by means of statistical method. In this respect we apply is
Cohen method with a model implemented by Nielson-Riley adapted for electron diffraction by simple trigonometric
approximation valid in electron diffraction case (sinƟ = 0, cosƟ = 1).
Keywords:Nanostructurated materials, TEM, Precession System, Cohen method
181
APPLICATION OF POROUS COPPER PLATES IN PEM FUEL CELLS
Cristina Mihaela Sima, Victor Ciupina
Department of Solid-State Physics, University of Bucharest, Bucharest-Magurele 077125, Romania, Department of
Physics, Ovidius University of Constanta, Constanta 900527, Romania
The performance of a Proton Exchange Membrane Fuel Cell (PEMFC) is strongly influenced by the gas diffusion
layer’s (GDL`s) interdependent properties such as gas and water transport including, as well, the micro and macro
substrates. To avoid electrode flooding the GDL must be design with adequate combination of hydrophilic and
hydrophobic characteristics. A copper based GDL, which represents the aim of this paper, can be a good alternative to
achieve this characteristics, instead of using the usual Toray based GDL. The GDL copper plate was obtained as result
of a thermal treatment in Ar-H2 gas mixture. For the porous structure achievement we used a combination based on
copper filings with different amounts of naphthalene. By using this type of porous GDL we manage to solve two issues:
gas transport from the flow-field channels to the catalyst layer and the water removal, fact confirmed by the running
tests.
Keywords: PEM fuel cell, GDL, carbon black, catalyst layer, water management, gas channels
SYNTHESIS BY CHEMICAL METHOD OF Zn-Ni-Fe MIXED SPINEL NANOFERRITES
1
Elena Chitanu1, Mirela Maria Codescu1, Delia Patroi1, Eugen Manta1, Wilhelm Kappel1, Virgil Marinescu1
R&D National Institute for Electrical Engineering ICPE-CA Bucharest, 313 Splaiul Unirii, Bucharest – 3, Phone / fax:
+40 21 3467231 e-mail: [email protected]
Zn-Ni-Fe mixed spinel ferrites nanoparticles were prepared by chemical method using salts of Zn, Ni and Fe. The
crystalline structures of the synthesized nanoferrites were investigated by X-ray diffraction and the morphology of the
nanoparticles was studied by scanning electron microscopy. The mixed spinel nanostructures were magnetic
characterized by magnetometry. The performed study highlights the influence of chemical composition and temperature
of further annealing on crystalline structure and magnetic properties of the investigated nanoferrites. Finally, the
possibility to choose the adequate composition and the suitable processing in order to obtain desired magnetic
nanomaterials were presented.
182
Bdul. Pipera nr. 1H, Complex Vile Class, Vila P03 Voluntari, Ilfov
Tel:021-269.12.77 Fax:021-269.12.99
E-mail:
[email protected]
Web:
www.agirom.ro
Agilrom Scientific SRL is the representative in Romania for companies Agilent
Technologies and Keysight Technologies, leaders in the production of equipment and
consumables for laboratories.
Established in 1992, Agilrom SCIENITIFIC managed to reach one of the most important
companies in the field of laboratory equipment, with a portfolio over 100 instruments:
Molecular absorption spectroscopy in the UV, Vis and IR
Absorption and emission atomic spectrometry AAS, ICPOES, MPAES
Inductively coupled plasma mass spectrometry with simple and triple quadrupole
Molecular biology, genetics and genomics
Gas chromatography and mass spectrometry SQ, QQQ, the Q-TOF
Liquid chromatography and mass spectrometry SQ, QQQ, TOF, Q-TOF
Atomic force microscopy, Nanoindenter and FE-SEM
W h o W e A re
N ite c h is o n e o f th e to p R o m a n ia n s u p p lie rs o f h ig h -te ch n o lo gy in stru m en ts fo r g e n e ra l
laboratory, d ia gn o s tic a n d re s e a rc h p u rp o se s .
D a te o f fou n dation :
M a in O ffice :
A d d re ss :
Phone:
Fa x :
e-m ail / w e b site :
S u b sid ia rie s :
2001
B u ch a re s t
B d . B u cu re s tii N o i nr. 2 1 2 A se c to r 1 B u c h a re s t
+40 21 6 6 8 6 8 19, 6 6 8 6 8 76
+40 21 6 6 8 6 9 3 0
o ffic e @ n ite c h .ro
w w w .n itech .ro
T im is o a ra , C Iu j-N apo ca, lasi, N a n o Te a m D ivisio n , N ite c h M e dic a l, N ite ch M o ld o v a
O u r c o m p a n y h a s im ple m en te d a n d m ain tain s a qu ality m a n a g e m e n t s y ste m w h ic h fu lfills
th e re qu ire m e n ts o f the s ta n da rd S R E N IS O 9001:2008.
W hat We D o
N ite c h s u p p lie s a n d s e rv ic e s labo rato ry e q u ip m e n t fo r th e fo llo w in g in du stries:
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N ite c h ’s Te a m
G e n e ra l M a n a g e r: M r. N ic o la e S ta n c u (20 y e a rs e x p e rie n c e in m a n a g in g )
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O u r P ro d u c t M a n a g e rs a n d S e rv ic e E n g in e e rs h a v e b e e n tra in e d in R o m a n ia a n d a b ro a d (E u ro pe, U S A )
in o rde r to prov ide s p e c ia lize d te c h n ic a l su p po rt to a ll o u r c u s to m e rs.
M a rke tin g a c tiv itie s
In fo N ite c h - o u r o w n pu blicatio n w ith n e w s , interview s, a rtic le s in labo rato ry fie ld
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O n lin e in fo r m a tio n - y o u c a n fin d th e latest n e w s a b o u t o u r pro du ct ra n g e a n d N ite c h ’s activity o n
IS O 9001
High-technology SysTems and Equipment
for RESearch, Industry and Science
HISTERESIS S.R.L. is specialized in distribution of high-technology equipment for research and
industry on the Romanian market, covering various fields, from lasers, optics and spectroscopy, to
vacuum technologies, material characterization and thin films measurement.
HISTERESIS is exclusive representative of QUANTEL (France /USA),
world leader in pulsed solid state lasers (Nd: YAG, nanosecond);
HISTERESIS is official representative of Agilent Technologies (Italy/USA) Vacuum Products Division, world leader in vacuum technologies (dry pumps,
turbomolecular pumps, ionic pumps, leak detection, vacuum measurement etc.)
HISTERESIS is exclusive representative of ALTECHNA – Lithuanian laser
technology company group working in photonics and lasers research since 1996
HISTERESIS is official distributor of AVANTES (Netherlands) – one of the
world main manufacturers of compact spectrometers, light sources and fiber
optics.
HISTERESIS is official distributor of ALLECTRA - manufactures and
supplies a full range of HV (high vacuum) and UHV (ultra high vacuum)
components including custom products
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Laser Deposition and PED - Pulsed Electron Deposition systems for thin film
deposition, and Magma magnetic field imaging systems for failure analysis
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isotropic graphite, specialized carbon products and carbon products for general
industries; composite materials made from carbon and ceramic, metal or
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HISTERESIS S.R.L. offers expertise in spotting the best solutions for the research
projects in large areas such as physics, chemistry, analytical and environmental sciences,
but also for university and high-school didactic purposes.
PREZENTARE
Today, when there is a rapid expansion of telecommunications and information processing market, COMTEST
Company offers high quality measurement equipments
COMTEST act as an unique distributor in Romania of Keysight Technologies, Division of measuring
equipments for electronics and communication technologies
Our company offers a wide range of instruments and electronic systems with standard or custom monitoring
tools, management and optimization of communication networks and services , software design tools and
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equipment , mobile communications networks and services .
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leader in first class and electronic and communication technologies used in:
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COMTEST represent Amplifier Research Company in Romania, which is the worldwide leader in EMC and
power amplifiers. Complete solutions: amplifiers, antennas, directional couplers, signal generators, system
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COMTEST represent Comtest Engineering Holland Company in Romania, the leading manufacturer of
anechoic rooms and integration of EMC laboratories. The best EMC laboratory in Romania, accredited
standards CISPR 16 was implemented by Comtest Engineering Holland in collaboration with our team.
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You can find more information about advertised products from:
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tel.: +40 75 3089091;
fax: +40 21 2110884
web: www.comtest.ro
adresa: Foisorului nr. 107, etaj 2, Sector 3, Bucureşti
The underlying company’s motto is: “Quality is the difference”.
Analytik Jena is a leading provider of high-end analytical instruments and bio-analytical systems for
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The products of Analytik Jena have an intelligent design and enhanced quality because:
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- Elemental Analysis: Carbon, Sulfur, Nitrogen and Chlorine (multi EA® series)
The PlasmaQuant® MS series offers two high-performance models with lowest operating cost. At the
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Analytik Jena brings an innovation on the market – the contrAA® series – which exceeds the
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AMS 2000 Trading Impex SRL – Analytic laboratory Division is the exclusive distributor
in Romania of Rigaku Corporation – Japan. We provide installation, training and service
for all equipments.
Rigaku business lines:
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o
single crystal X-ray diffraction (protein and small molecule)
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o
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 Rigaku Raman technologies
o Innovative new Raman hand held spectrometers - World’s highest performance hand held
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(2000 TRADING IMPEX)
Str. Ion Tuculescu Nr. 37A, Bucuresti, Sector 3, Romania
E-mail: [email protected] Phone: +40 1 3247050 / +40722687855; Fax: +40 1 3247679

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