Institute of Materials Science - Technische Universität Darmstadt

Transcription

Annual Report
2012
Faculty of
Materials and Geo Sciences
Contents
Dean’s Office .................................................................................................................. 4
Institute of Materials Science ......................................................................................... 6
PREFACE ............................................................................................................................. 6
PHYSICAL METALLURGY ....................................................................................................... 10
CERAMICS GROUP .............................................................................................................. 19
ELECTRONIC MATERIAL PROPERTIES...................................................................................... 29
SURFACE SCIENCE .............................................................................................................. 39
ADVANCED THIN FILM TECHNOLOGY ..................................................................................... 50
DISPERSIVE SOLIDS ............................................................................................................. 52
STRUCTURE RESEARCH........................................................................................................ 67
MATERIALS ANALYSIS ......................................................................................................... 72
MATERIALS MODELLING DIVISION ......................................................................................... 85
MATERIALS FOR RENEWABLE ENERGIES ................................................................................. 97
PHYSICS OF SURFACES....................................................................................................... 110
JOINT RESEARCH LABORATORY NANOMATERIALS .................................................................. 114
MECHANICS OF FUNCTIONAL MATERIALS ............................................................................. 117
FUNCTIONAL MATERIALS ................................................................................................... 124
ION-BEAM MODIFIED MATERIALS........................................................................................ 131
COLLABORATIVE RESEARCH CENTER (SFB) .......................................................................... 137
DIPLOMA THESES IN MATERIALS SCIENCE........................................................................... 140
BACHELOR THESES IN MATERIALS SCIENCE......................................................................... 143
MASTER THESES IN MATERIALS SCIENCE ............................................................................ 145
PHD THESES IN MATERIALS SCIENCE ................................................................................ 145
MECHANICAL WORKSHOP ................................................................................................. 147
ELECTRICAL WORKSHOP ................................................................................................... 147
Institute for Applied Geosciences .............................................................................. 148
PREFACE ......................................................................................................................... 148
PHYSICAL GEOLOGY AND GLOBAL CYCLES ............................................................................ 150
HYDROGEOLOGY .............................................................................................................. 162
ENGINEERING GEOLOGY .................................................................................................... 167
GEOTHERMAL SCIENCE AND TECHNOLOGY ........................................................................... 175
APPLIED SEDIMENTOLOGY .................................................................................................. 184
GEO-RESOURCES AND GEO-HAZARDS .................................................................................. 190
GEOMATERIAL SCIENCE ..................................................................................................... 199
ELECTRON CRYSTALLOGRAPHY ........................................................................................... 208
TECHNICAL PETROLOGY WITH EMPHASIS IN LOW TEMPERATURE PETROLOGY............................. 209
ENVIRONMENTAL MINERALOGY .......................................................................................... 220
DIPLOMA THESES IN APPLIED GEOSCIENCES .................................................................... 228
MASTER THESES TROPHEE IN APPLIED GEOSCIENCES ...................................................... 228
MASTER THESES IN APPLIED GEOSCIENCES...................................................................... 229
BACHELOR THESES IN APPLIED GEOSCIENCES .................................................................. 229
PHD THESES IN APPLIED GEOSCIENCES .......................................................................... 230
HABILITATION IN APPLIED GEOSCIENCES ......................................................................... 230
Faculty of Materials and Geo Sciences
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Dean’s Office
Staff Members
Dean:
Prof. Dr. Ralf Riedel
Vice dean:
Prof. Dr. Christoph Schüth
Dean of studies Materials Science:
Prof. Dr. Lambert Alff
Dean of studies Applied Geosciences:
Prof. Dr. Matthias Hinderer
Scientific coordinator, department
and Materials Science:
PD Dr. Boris Kastening
Scientific coordinator, Applied Geosciences:
Dr. Karl Ernst Roehl
Secretary of department:
Renate Ziegler-Krutz
Secretary of personnel and finances:
Christine Hempel
Competence center for materials characterization:
Dr. Joachim Brötz
IT group:
Dipl. –Ing. (BA) Andreas Hönl
Building services:
Dipl. –Ing. Heinz Mohren
Coordination of the KIVA project:
Dr. Silvia Faßbender
Public relations:
Marion Bracke
Media Design:
Thomas Keller
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Dean’s Office
Publications of Permanent Members of the Dean's Office
B. Kastening, Universal anisotropic finite-size critical behavior of the two-dimensional Ising
model on a strip and of d-dimensional models on films; Phys. Rev. E Volume: 86 Issue: 4
041105 (2012)
Laetitia Renard, Odile Babot, Hassan Saadaoui, Hartmut Fuess, Joachim Brötz, Aleksander
Gurlo,Emmanuel Arveux, Andreas Klein and Thierry Toupance, Nanoscaled tin dioxide films
processed from organotin-based hybrid materials: an organometallic route toward metal oxide
gas sensors, NANOSCALE Volume: 4 Issue: 21 Pages: 6806-6813 (2012)
Abdelfattah Mahmoud, Mayumi Yoshita, Ismael Saadoune, Joachim Broetz, Kenjiro
Fujimoto, Shigeru Ito, LixCo0.4Ni0.3Mn0.3O2 electrode materials: Electrochemical and
structural studies, MATERIALS RESEARCH BULLETIN Volume: 47 Issue: 8 Pages: 19361941 (2012)
Gassmann, Juergen; Broetz, Joachim; Klein, Andreas, Sputter deposition of indium tin oxide
onto zinc pthalocyanine: Chemical and electronic properties of the interface studied by
photoelectron spectroscopy, APPLIED SURFACE SCIENCE Volume: 258 Issue: 8 Pages: 39133919 (2012)
Münch, Falk; Neetzel, Cornelia; Kaserer, Sebastian; Brötz, Joachim; Jaud, Jean-Christophe;
Zhao-Karger, Zhirong; Lauterbach, Stefan; Kleebe, Hans-Joachim; Roth, Christina;
Ensinger, Wolfgang; Fabrication of porous rhodium nanotube catalysts by electroless plating
JOURNAL OF MATERIALS CHEMISTRY Volume: 22 Issue: 25 Pages: 12784-12791 (2012)
Sana Ahmad, Bernard Jousseaume, Thierry Toupance, Odile Babot, Guy Campet, Christine
Labrugère, Joachim Brötz and Ulrike Kunz, A new route towards nanoporous TiO2 as powders
or thin films from the thermal treatment of titanium-based hybrid materials, DALTON
TRANSACTIONS Volume: 41 Issue: 1 Pages: 292-299 (2012)
Thorsten Leist, Joachim Brötz, Yo-Han Seo, Shumeng Cheng, Kyle G. Webber, Crack growth
resistance behavior of lanthanum doped bismuth ferrite–lead titanate: Effect of tetragonality
and mixed phase crystal structures, ENGINEERING FRACTURE MECHANICS 96 267–275
(2012)
Dean’s Office
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Institute of Materials Science
Preface
Dear colleagues and friends,
The year 2012 continued as successful as the previous year for the Department of Materials
and Geo Sciences of TU Darmstadt. Details of the activities and achievements related to the
individual departmental institutes, namely Materials Science and Applied Geosciences, are
highlighted below.
We would like to express our gratitude to all members of the Department – the mechanical
workshop staff, technical and administrative staff, students working on their diploma and
bachelor theses, Ph.D. students, and postdocs – for the outstanding effort and remarkable
enthusiasm they put into their work. The contribution of every single one of them added to
the results presented here. We aim to sustain and promote the motivating and fruitful
atmosphere at our institute in order to continue our commitment and success in the time to
come.
Materials Science
The amount of acquired third party funding has reached a nearly constant value in the
order of 10 million Euro. Presently, the total number of students (bachelor & master) in
materials science amounts round about 500. While the number of freshmen of the bachelor
study course decreased as compared to the year before we expect again a significant
increase up to 150 students starting in the winter semester 2013/14 (see Figure 1). We also
got involved in a new master course Energy Science and Engineering which is an
interdisciplinary course organized by eight individual departments of TU Darmstadt.
Moreover, the Graduate School Materialium has been founded by resolution of the Senate
of TU Darmstadt on May 16, 2012, and is currently being built-up. The Materials Science
and Geo Sciences Department’s Materialium Graduate School offers research-oriented,
doctorate programs culminating in award of the degree of “Dr.-Ing.” or “Dr. rer. nat.” The
programs involved are configured to cover three years. One of the primary goals of
Materialium is to encourage an interdisciplinary integration of the various Ph.D. studies
between research groups inside and outside of the Materials Science Department
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Preface
Coordinated Research Proposals
The institute was actively involved in a variety of coordinated research project applications.
Among them are two new proposals applying for a LOEWE Priority Program funded by the
Hessian State Government. The scientific topics of both proposals are related to i) The
Reduction and Substitution of Rare Earth Elements in High Performance Permanent
Magnets (Response, coordinated by Prof. Gutfleisch) and ii) “Electron Microscopy on
Functional Materials” (TEM-ELF, coordinated by Prof. Kleebe).
In the frame of the federal initiative of excellence, we have been successful in getting
funded an excellence graduate school of energy science and engineering with Prof. Janicka
(Department of Mechanical Engineering) and Prof. Jaegermann from our department as the
spokesmen. All these initiatives mark the interdisciplinary approach the university is
promoting and for which the Department of Materials and Geo Sscience is ideal since its
subjects combine various sciences like chemistry, physics, electrical and mechanical
engineering.
Fig. 1: Number of students (without Ph. D. students) in Materials Science at Technische Universität Darmstadt
over the past 10 years. Until SS08, the freshmen refer to the Diplom course, thereafter to the Bachelor course.
Preface
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Faculty Members
In 2012 two new professorships were inaugurated: Prof. Dr. Christina Trautmann who
heads the group of Ion-Beam-Modified Materials and leads the Materials Research
department at the GSI Helmholtz Centre for Heavy Ion Research. Prof. Dr. Oliver Gutfleisch
is responsible for the group of Functional Materials. Besides that, Prof. Gutfleisch is the
head of the Fraunhofer-Project Group for Materials Recycling & Resource Strategies in
Alzenau close to Hanau which provides us the unique opportunity to closely cooperate with
the Fraunhofer Society in the field of materials science.
After Prof. Heilmaier left the Department of Materials and Geosciences to take up a position
as Director at the Karlsruhe Institute of Technology (KIT) in December 2011 we are looking
forward to replace the position in 2013 by a distinguished colleague. In 2012, our former
Junior-Prof. Christina Roth (group of Renewable Energies) accepted a Professor position at
the Department of Chemistry at FU Berlin.
Buildings and Lab/Office Space
In order to improve and optimize our
lab and office space, we moved the
groups MFM (Prof. XU), PoS (Prof.
Stark) and NM (Prof. Krupke) into the
office building L1|08 located in
Petersenstr. 32. Meanwhile, we could
celebrate the roofing ceremony of our
new lab and office building in the
Böllenfalltorweg where we expect to
move in late September 2013.
Additional lab and office space will be
provided by our University in the
forthcoming years.
Honours, Awards and Special Achievements
In 2012, the following precious awards were granted to faculty members of the materials
science department:
Prof. Fueß received the Max-Perutz-Price of the European Society of Crystallography for his
scientific work and organizational engagement in the field of crystallography. Prof. Hahn was
awarded with the Heyn-Denkmünze and Prof. Riedel with the Tammann-Gedenkmünze. Both latter
awards are delivered by the German Society for Materials Science (Deutsche Gesellschaft für
Materialkunde).
As usual, the annual awarding of the "MaWi Prize" formed part of the MaWi summer party.
The 1st prize was awarded to Ruben Heid from the division PhM for his Diploma thesis on
“Einfluss von gießtechnischen Prozessschwankungen auf das Eigenschaftsspektrum
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Preface
crashrelevanter Aluminium-Druckgusslegierungen”; 2nd prizes were awarded to Tim
Niewelt from the division OF for his Diploma thesis about “Analyse von Defekten in
kristallinem Silizium” and to Joachim Langner from the division EE for his Diploma thesis
about “Ionische Flüssigkeiten als Elektrolyt, Co-Katalysator und Stabilisator in
Brennstoffzellen“. The 3rd prize was awarded to Christian Lohaus for his Bachelor thesis
about “Synthese verschiedener rußgeträgerter Pt-Ru-Au Katalysatoren und Untersuchung
des Degradationsverhaltens”.
Social Events
As every year, our annual summer party was scheduled shortly before the summer break.
This summer party is one of the most important social events of the Materials Science
Institute. It has become a tradition to use this festivity to award the MaWi prize to the three
best students having accomplished their Diploma in the period between the past winter
semester and the present summer semester. The prize winners have already been named
above.
In December 2012 we celebrated the year-end ceremony for all research groups, staff
members and students, including the formal graduate celebration, where Bachelor, Master
and PhD students received their certificates. The celebration including the social
programme was organized by PD Dr. Boris Kastening, Heinz Mohren, and students
(Fachschaft).
Last not least the group Materials Modelling (MM) celebrated its 10th anniversary with a
scientific colloquium at the Lichtenberghaus, where distinguished scientists presented
recent developments and advanced research perspectives in the field of computing in
materials science.
On the following pages, this annual report shall provide you with some information on the
most prominent research activities of the individual groups conducted in 2012.
Prof. Ralf Riedel
Dean of the Department
Preface
9
Physical Metallurgy
Research and teaching of the Physical Metallurgy group in general focus on a deeper
understanding of the relationships between processing, microstructure and properties of
metallic materials. The major goal of this research is on the one hand to quantitatively
describe existing materials with respect to their processing and performance in order to
fully exploit their application potential. On the other hand, we search for and subsequently
develop novel alloy systems with improved properties by utilizing the basic principles of
physical metallurgy. If potential alloy systems may be identified, it is of not only prime
importance to extensively characterize these materials with respect to the foreseen
application but also to give appropriate feedback to the material developers for further
optimization.
Our current research deals with Al, Mg and Ti based light alloys, steels, nickel-base
superalloys and refractory alloys. Mechanical properties such as fatigue, creep and wear are
mainly studied including their interaction with corrosion and oxidation phenomena. Recent
progress includes functionally graded materials as well as improvements in the wear
resistance of metallic alloys by mechanical surface treatments. The major research topics on
which our group presently concentrates are first, ultra-fine grained (UFG) materials which
created special interest in recent years, as they favorably combine very high strength with
good ductility. In several research projects the evolution and the mechanical properties of
these microstructures are investigated and new forming processes for the continuous
production of UFG-bulk materials are developed in collaboration with the department of
mechanical engineering. Second, development of structural metallic materials which could
withstand applications in air at temperatures beyond 1200°C would be attractive not only
from scientific but also industrial standpoints. A successful alloy development would
eventually allow for a substitution of single-crystalline nickel-base superalloys in gas
turbine applications.
Teaching covers basic courses on phase transformation in metals and alloys (including
phase diagrams), mechanical properties of (structural) engineering materials and
fundamentals of deformation and fracture. Special courses are given on solidification and
heat treatment mechanisms and the analysis and characterization of microstructures.
Extensive laboratory exercises on all levels are offered to facilitate and intensify the
technical understanding in these topics and to improve the practical skills for investigating
metallic materials.
The Physical Metallurgy group has numerous collaborations with other groups within the
department and with others of Darmstadt Technical University, in particular with
Mechanical Engineering through the DFG CRC 666. On the national level, cooperation in
academia is characterized by the close relation to the other members of the WAW
(Wissenschaftlicher Arbeitskreis der Universitätsprofessoren der Werkstofftechnik e.V.).
Internationally, we have a continuing cooperation with groups from Australia, Czech
Republic, France, UK, Ukraine, Denmark, Canada and USA which also includes exchange of
students and scientists. Strong relations with industry (Daimler-Benz, Ecoroll, Heraeus,
Opel, Pfalz- Flugzeugwerke, VW) give multiple opportunities for scientific interaction and
personal exchange. Department members participate in national and international
conferences, seminars and workshops thereby gathering information which supports to
keep teaching and research on an actual level.
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Physical Metallurgy
Staff Members
Head
Prof. Dr. Clemens Müller
Research Associate
Dr.-Ing. Enrico Bruder
Technical Personnel
Ulrike Kunz
Claudia Wasmund
Secretaries
Christine Hempel
PhD Students
Dipl.-Ing. Daniel Janda
Dipl.-Ing. Vanessa Kaune
Dipl.-Phys. Peter Pörsch
Dipl.-Ing. Jan Scheil
Dipl.-Ing. Daniel Schliephake
Dipl.-Ing. Lukas Schlicker
Dipl.-Ing. Jennifer Schuster
Dipl.-Ing. Christoph Seemüller
Dipl.-Ing. Jörn Niehuesbernd
Diploma Students
Michael Bachmann
George Bedenian
Thorsten Groeb
Lars Przybilla
Stefan Roth
Bachelor Students
Laura Ahmels
Manuel Kloos
Tobias Opitz
Janik Binzen
Sebastian Bruns
Marcel Jost
Romana Schwing
Theresa Schütz
Research Fellow
Dr. Shanmugasundaram Tharangaju
Petra Neuhäusel
Michael Rohloff
Research Projects
“Beyond Nickelbase Superalloys” (DFG research unit FOR 727, 2007-2013).
“Bulk UFG-Materials Produced by Rotary Swaging”, joint project with PTU-Darmstadt, DFG,
since 10/2008.
“Effect of Load Frequency on the Fatigue Life of Aluminum Wrought Alloys in the VHCFRegime”, joint project with SzM-Darmstadt within the DFG Priority Programm 1466, DFG,
since 04/2010.
“FeAl-based Alloys - Materials, Casting Process and Exhaust Gas Turbocharger”, joint
project with one academic and 4 industrial partners, BMWi, since 08/2010.
“Grain and Phase Boundary Segregation in Multiphase Mo-borosilicides”, SHaRE User
Facility at Oak Ridge National Laboratory, Office of Basic Energy Sciences, U.S. Department
of Energy, 07/2010 - 06/2012.
“Hybrid Silicide-Based Lightweight Components for Turbine and Energy Applications
(HYSOP)”, collaborative project with 7 European partners,EU, since 10/2010.
“Improved Wear Resistance of Forming Tools by Mechanical Surface Treatments” joint
project with PTU-Darmstadt, AIF, since 09/2006.
“Microstructure and Mechanical Properties of Bifurcated Sheet Profiles”, in SFB 666 of the
DFG “Integral Sheet Metal Design with Higher Order Bifurcations”, since 06/2005.
“Technologies of surface modification of bifurcated profiles”, in SFB 666 of the DFG
Physical Metallurgy
11
Publications
J. Schuster, E. Bruder, C. Müller,
Plasmanitriding of steels with severely plastic deformed surfaces, Journal of Materials Science
47 (2012), 7908-7913, DOI: 10.1007/s10853-012-6566-0
E. Bruder,
The effect of deformation texture on the thermal stability of UFG HSLA steel, Journal of
Materials Science 47 (2012), 7751-7758, DOI: 10.1007/s10853-012-6518-8
V. Kaune, C. Müller,
Formation of UFG-surface layers on a HSLA steel by a continuous Surface-SPD-Process,
Materials Science and Engineering A 535 (2012), 1-5, DOI: 10.1016/j.msea.2011.12.012
P. Groche, M. Engels, M. Steitz, C. Müller, J. Scheil, M. Heilmaier,
Potential of mechanical surface treatment for mould and die production, International Journal
of Materials Research 103 (2012), 783-789 DOI: 10.3139/146.110778
P. Groche, M. Steitz, C. Müller, J. Scheil,
Einglättung durch Festwalzen und Festklopfen, wt Werkstattstechnik online 102 (2012), 665671
12
Physical Metallurgy
Local and global elastic anisotropy in ultrafine grained gradient microstructures
Jörn Niehuesbernd1, Clemens Müller1, Wolfgang Pantleon2, Enrico Bruder1
1
Department of Materials Science, TU Darmstadt, D-64287 Darmstadt, Germany
Department of Mechanical Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
2
The steadily increasing expenses for energy and raw material necessitate the development
of components with an increased strength and stiffness, produced with less material usage
and less production costs. An elegant way to increase the stiffness, while reducing the
material usage and thus reducing the weight, is to use bifurcations. Linear flow splitting
(LFS) offers the possibility to produce bifurcated structures integrally with low production
costs, even while using high strength materials. With the aid of obtuse angled splitting rolls,
LFS induces severe plastic deformation at the edge of a sheet [1], thus broadening the
edge. After several splitting steps a bifurcation is being produced (Fig. 1a). Due to the
imposed severe strains an ultrafine grained (UFG) microstructure develops in a surface
layer of the produced flanges [2]. Within the process zone the material flow is
perpendicular to the feed direction (Fig. 1b), thus the direction from the splitting center to
the flange tip can be identified as the rolling direction (RD) (Fig. 1c). Consequently the
feed direction corresponds to the transverse direction (TD) and the direction from the
flange top to the bottom surface is the normal direction (ND).
Previous investigations revealed strong microstructure and yield strength gradients in the
flange thickness direction [3] and also indicated significant variations in the
crystallographic texture along with the other gradients [4]. Thus it is reasonable to assume,
that the Young's modulus exhibits an anisotropic and heterogeneous character as well.
Consequently, elastic material properties obtained by conventional experimental methods
(for example tensile tests) could deviate significantly from the local elastic properties
within the microstructure gradient, since the measured values would only be averages over
the flange thickness. However, in many cases it is important to determine the microscopic
elastic properties more precisely, for example regarding the manufacturing tolerances of
subsequent roll forming.
Since the elastic properties of a material with anisotropic crystallographic properties are
coupled to the crystallographic texture, the local elastic properties can be obtained by
measuring local grain orientations. The calculation of the elastic parameters using
orientation data obtained by electron backscattering diffraction (EBSD) can be carried out
with the well-established methods proposed by Voigt and Reuss [5]. Voigt used the
Fig. 1: (a) function principle of linear flow splitting, (b) material flow in the process zone, (c) chosen
coordinate system
Physical Metallurgy
13
assumption of spatially constant strains within the material, while Reuss proposed constant
stresses. The grain orientations at every discrete measurement point obtained by EBSD can
be used to determine rotation matrices, which rotate the single crystal stiffness and
compliance tensors for all points of the measurement grid. The results of these calculations
are upper and lower bounds, within which the actual values have to lie. A more precise
approximation of the actual elastic properties can be provided by the geometric mean,
which in most cases reveals similarly accurate approximations as self-consistent
approaches, but with substantially less calculation effort [6]. The calculation routines are
analog to Voigt and Reuss, except for the additional calculation of the natural logarithm of
the stiffness and compliance tensors before averaging [7].
The investigations were carried out on linear flow split profiles of a high strength low alloy
steel (H480LA) with a microstructure of the as received material consisting of ferrite grains
and small Fe3C particles (1 vol%) located at the grain boundaries. EBSD measurements
were carried out with an FEI XL30 FEG scanning electron microscope on cross sections of
the profiles at approximately half the distance from the splitting center to the flange tip, at
several positions underneath the split surface (see Fig. 1b). The measured grain
orientations were used to represent the crystallographic textures in terms of orientation
distribution functions (ODF) and for determining the local elastic properties. Ultrasonic
runtime measurements were performed in addition to the EBSD measurements to
determine the macroscopic elastic parameters using Greens formulas [8].
The gradient microstructures obtained by linear flow splitting indicate heterogeneous
forming conditions, which are also reflected by the heterogeneous crystallographic texture
of the flanges (Fig. 3). The severity of the textures, represented by the texture index (TI),
steeply decreases with increasing distance to the split surface. Near the surface a rolling
texture with partial α- and γ-fibers (red/vertical and blue/horizontal lines in figure 3) and
the rotated cube orientation can be found. In a depth between 100 µm and 200 µm the αand γ-fibers start to vanish and are no longer existent at the lower side of the flanges.
Fig. 1: Orientation distribution functions of several measurement positions, shown as sections of the Euler
space with a constant angle ϕ2 = 45°. The 1000 µm measurement corresponds to a position close to the lower
surface.
14
Physical Metallurgy
Simultaneously the Goss orientation ({110} <001>) appears. Its intensity increases along
with the distance to the split surface.
The distribution of the Young's modulus determined from the orientation data reveals
significant differences between the three main sample directions, as can be seen in figure 3
for the 25 µm, 200 µm and 1000 µm measurement positions. Surprisingly the general
distribution does not change significantly with increasing distance to the split surface. Only
the maxima and minima become somewhat less pronounced. Thus, the significant changes
in texture within the flange thickness do not have a substantial effect on the anisotropy of
the Young's modulus of the flanges. The emergence of the Goss orientation nearly
Fig. 3: Direction dependent Young's Modulus at 25
µm, 200 µm and 1000 µm underneath the split
surface, calculated using the geometric mean
Fig. 4: Volume weighted behavior of the anisotropic
Young's modulus of the complete flange in
comparison to the ultrasonic measurements
completely compensates the vanishing of the α- and γ-fibers. Due to these characteristics it
is possible to calculate a macroscopic stiffness tensor, i. e. a geometric mean of the
calculated elastic tensors weighted by the effective volume fraction of the respective layer.
Figure 4 shows the good agreement of this volume weighted geometric mean with the
distribution of the Young's Modulus determined by ultrasonic measurements.
Conclusion
The present investigation demonstrates that it is possible to predict the macroscopic elastic
behavior of severely deformed parts with steep texture and microstructure gradients
sufficiently accurate using orientation data from EBSD measurements. Even while using the
rather simple concept of the geometric mean, the approximations are in good agreement
with ultrasonic measurements, with maximum differences of less than 5%.
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
P.Groche, D.Vucic, M.Jöckel, Journal of Materials Processing Technology 183 (2007), 249–255
T. Bohn, E. Bruder, C. Müller, J Mater Sci 43 (2008), 7307–7312
E. Bruder, T. Bohn, C. Müller, Materials Science Forum 584-586 (2008), 661-666
E. Bruder, J Mater Sci 47 (2012), 7751-7758
P. Spalthoff, W. Wunnike, C. Nauer-Gerhard, H. J. Bunge, E. Schneider, Textures and
Microstructures 21 (1993), 3-16
S. Matthies, M. Humbert, phys. stat. sol. (b) 177, (1993), K47-K50
U. F. Kocks, C. N. Tomé, H.-R. Wenk, Texture and Anisotropy, (1998) Cambridge University Press
R. E. Green, Treatise on Materials Science and Technology Vol. 3: Ultrasonic Investigation of
Mechanical Properties, (1973) Academic Press New York and London
Physical Metallurgy
15
UFG-surface layer on DD11 mild steel profiles produced by Linear Bend Splitting
V. Kaune, C. Müller
Department of Materials Science, TU Darmstadt, D-64287 Darmstadt, Germany
ABSTRACT: An approach to improve global properties of a component is the generation of
an ultrafine-grained (UFG)-surface layer induced by surface severe plastic deformation
(S2PD). Linear Bend Splitting (LBS) is a new continuous process, which generates
bifurcated profiles in integral style from plain metal sheet. Due to the high deformation in
the splitting zone, an UFG-microstructure develops on the surface of the produced flanges
up to a depth of several hundred microns. On the low alloyed mild steel DD11, the
microstructure, the mechanical properties and the deformation behavior of the linear bend
split profiles are investigated.
INTRODUCTION: Severe plastic deformation (SPD)-processes have been established to be
one of the effective methods to generate microstructures in the sub micrometer or even
nanometer regime in various kinds of metals. Typically used SPD-techniques are Equal
Channel Angular Pressing (ECAP), High Pressure Torsion (HPT) or Accumulative RollBonding (ARB), which are based on grain refinement due to the introduction of high strains
into the bulk material [1, 2]. The ultrafine-grained (UFG) microstructures exhibit
outstanding mechanical and physical properties, e.g. high strength [3, 4], enhanced fatigue
strength [5] and high corrosion resistance [6]. The combination of a coarse-grained interior
with an UFG-surface layer is a promising approach to improve the properties of materials or
components, since material failures are mostly initiated from the surface (wear, corrosion,
crack initiation) [7, 8]. To obtain UFG-surface layers, various Surface SPD (S2PD)-processes
have been developed, such as surface mechanical attrition treatment (SMAT) [9], large
strain machining [10] or gradation rolling [11]. However, these processes exhibit high
process duration or a restriction to batch application, which implicates a disadvantage with
regard to a continuous production. One approach which enables the continuous production
of UFG-surface layers is the S2PD-process Linear Bend Splitting (LBS). This massive cold
forming process enables the generation of flanges in integral style out of any position of a
metal sheet. Based on a die bent semi finished product, the LBS process generates a profile
with a newly created flange, a thinned area and two webs with initial thickness (Fig. 1).
Fig. 1: Linear bend split profile (with flange, thinned area and webs), location of tensile specimens and
direction of hardness measurements
16
Physical Metallurgy
EXPERIMENTAL: The material used in this investigation was hot rolled DD11 mild steel
with a ferritic–perlitic microstructure and an average grain size of 16 µm. The linear bend
split profiles were investigated using EBSD (Electron Backscatter Diffraction)
measurements, hardness indentations and tensile tests, notably in the most deformed areas,
i.e. flange, thinned area and the splitting center (see Fig. 1). In addition, the deformation
behavior of the flanges containing an ultrafine-grained microstructure is investigated.
RESULTS AND DISCUSSION: The S2PD-process Linear Bend Splitting (LBS) generates an
ultrafine-grained (UFG) microstructure in the flange, the splitting center and the thinned
area (Fig. 2, left). Perpendicular to the split surface a microstructural gradient exists with a
thickness of the UFG layer of 400 µm-500 µm (Fig. 2, right). Parallel to the surface the
microstructure exhibit in the flange respectively thinned area homogenous grain sizes and
constant mechanical properties. Thereby, the thinned area shows a slightly finer
microstructure and higher hardness/strength compared to the flange.
Fig. 2: EBSD-measurements at the thinned area (left), splitting center (middle) and flange (right) in a depth of
25 µm and 500 µm and Effective grain sizes of the different surface regions within the profile
The local properties depend on the distance to the split surface. On the basis of a developed
correlation between hardness and strength, the local strength at the UFG surface can be
calculated to 1200 MPa [12]. These mechanical properties of the UFG-surface layer
increase the potential for various industrial applications, especially where improved wear
resistance is required or good fatigue properties are desired as long as the maximum stress
arises in the UFG region (e.g. bending load stress).
Physical Metallurgy
17
Fig. 3: Tensile tests of the as received material, the thinned area and the flange of the linear bend split profile
The global properties of the profiles are dominated by the characteristic properties of UFGmicrostructures in terms of high strength, but low uniform elongation and work hardening
(Fig. 3) [13, 14]. The flanges show a ductile deformation and fracture behavior in terms of
necking and dimples, but secondary cracks occur in the UFG part of the fracture surface.
These cracks are orientated parallel to the split surface and indicate weakened grain
boundaries and grain boundary sliding due to the LBS process. Hence, the profiles show a
ductile but low formability under a subsequent tensile load.
References:
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
18
T.G. Langdon, J. Mater. Sci. 42 (2007) 3388-3397.
R.Z. Valiev, Y. Estrin, Z. Horita, T.G. Langdon, M.J. Zehetbauer, Y.T. Zhu, JOM 58 (2006) 33-39.
R.Z. Valiev, I.V. Alexandrov, Y.T. Zhu, T.C. Lowe, JMR 17 (2002) 5-8.
N. Tsuji, J. Phys.: Conf. Ser. 165 (2009).
H. Mughrabi, H.W. Höppel, M. Kautz, Scripta Mater. 51 (2004) 807-812.
P. Frint, M. Hockauf, D. Dietrich, T. Halle, M.F.-X.Wagner, T. Lampke, J. Mater. Sci. 43 (2008) 74097417.
X. Wu, N. Tao, Y. Hong, B. Xu, J. Lu, K. Lu, Acta Mater. 50 (2002) 2075-2084.
K. Lu, J. Lu, Mater. Sci. Eng. A 375-377 (2004) 38-45.
N.R. Tao, J. Lu, K. Lu, Mater. Sci. Forum 579 (2008) 91-108.
M.R. Shankar, S. Chandrasekar, A.H. King, W.D. Compton, Acta Mater. 53 (2005) 4781-4793.
R. Neugebauer, A. Sterzing, M. Bergmann, Mat.-wiss. u. Werkstofftech. 42 (2011) 593-598.
V. Kaune, C. Müller, Mater. Sci. Eng. A 535 (2012) 1-5.
N. Krasilnikov, W. Wojkowski, R. Valiev, Mater. Sci. Eng. A 397 (2005) 330-337.
N. Tsuji, Y. Ito, Y. Saito, Y. Minamino, Scripta Mater. 47 (2002) 893–899.
Physical Metallurgy
Ceramics Group
The emphasis in the ceramics group is on the correlation between microstructure and
mechanical as well as functional properties. A number of processing methods are available
in order to accomplish different microstructure classes, to determine their specific
properties in an experiment and to rationalize these with straightforward modelling efforts.
Thus, a materials optimization is afforded which allows effective interplay between
processing, testing and modelling. In particular, new lead free piezoceramics, lead-free
high-temperature dielectrics and toughened lead-containing piezoceramics can be obtained
and extensively characterized electrically and mechanically.
The scientific effort can be grouped as follows:
I.
Conductivity of oxides and composites
Prof. Jürgen Rödel
In this group, novel ideas on conductivity of oxides are grouped around a theme of
mechanically tuned electrical conductivity. The work includes conductivity in single crystal
oxides modulated by dislocation cores as mediated by plastic deformation as well as
physical phenomena on conductivity across interfaces. Further, varistors are studied, energy
materials and Ag-containing electrical switches.
II.
Development and physics of new piezoceramics
Dr. Wook Jo
In response to the recent demands for environmental friendly piezoelectric and dielectric
materials for electrical and electronic applications, the principal focus of this group is the
development of non-toxic piezoceramics with electromechanical performance comparable
to their lead-containing counterparts. Among all the potentially promising candidates
special attention has been given to bismuth-based materials whose properties can be
effectively tailored using the so-called morphotropic phase boundary (MPB) concept.
Extensive compositional research has been performed on various bismuth-based solid
solution systems that contain a MPB between separating different crystal symmetries of the
members. To better understand the mechanisms governing the enhancement of
electromechanical properties of materials and to make our search for alternative materials
more effective fundamental scientific research on model systems have been performed in
parallel to the compositional investigations. We employ various characterization techniques
such as macroscopic dielectric, ferroelectric and ferroelastic property measurements as well
as crystallographic structural analyses based on synchrotron and neutron diffractions,
Raman, nuclear magnetic resonance, electron paramagnetic resonance spectroscopic
techniques, and transmission electron microscopy. We are also simultaneously establishing
thermodynamic and phenomenological models which are verified by the first principles
calculations. The physical understanding of new lead-free piezoceramics is supported by
work on single crystals and studies on fatigue and aging. A spin-off from the work on leadfree piezoceramics is the work on high-temperature dielectrics, which are demanded for
high-temperature electronics for engines as well as deep-well drilling. Currently, we have
Ceramics Group
19
extensive and active international collaborations with eminent ferroelectric groups
throughout the world.
III.
Mechanical properties of ferroelectrics
Dr. Kyle Webber
The focus of this research group is on the mechanical behavior of ferroelectric materials,
specifically the impact of ferroelasticity on fracture and high temperature constitutive
behavior. To this end, the fracture behavior of novel high toughness piezoceramics is being
investigated as part of an EU Project for the potential inclusion in actuator applications in
extreme environments, such as wind turbines and active damping of motor vibrations.
Work has focused on determining the change in R-curve behavior from an addition of
second phase of tetragonal stabilized zirconia as well as the transition from inter- to
transgranular fracture. Additional investigations on the high temperature constitutive
behavior of ferroelectric materials are also underway. A novel experimental arrangement
has been constructed capable of measuring the strain and polarization of samples in
response to uniaxial compressive stress at temperatures up to approximately 400 °C. This
has been used to investigate hard and soft PZT up to the Curie temperature as well as
current lead-free compositions with more complex phase structures. Phase field modeling is
used to better understand the switching and fatigue behavior of the materials considered.
20
Ceramics Group
Staff Members
Head
Prof. Dr. Jürgen Rödel
Research Associates
Dr. Torsten Granzow
Dr. Wook Jo
Dipl. Phys. Irene Mieskes
Dr. Kyle Webber
Dr. Ludwig Weiler
Dr. Jami Winzer
Technical Personnel
Dipl.-Ing Daniel Isaia
Dipl.-Ing. Gundel Fliß
Michael Heyse
Secretaries
Roswita Geier
Gila Völzke
PhD Students
M. Sc. Matias Acosta
Dipl.-Ing. Raschid Baraki
Dipl.-Ing. Martin Blömker
Dipl.-Ing. Laetitia Carrara
Dipl.-Ing. Robert Dittmer
Dipl.-Phys. Daniel Franzbach
Dipl.-Ing. Claudia Groh
Dipl.-Ing. Gerrit Günther
Dipl.-Ing. Christine Jamin
Dipl.-Ing Markus Jung
Dipl.-Ing. Eva Sapper
Dipl.-Ing. Florian Schader
Dipl.-Phys. Deborah Schneider
Dipl.-Ing. Yohan Seo
M. Sc. Jiadong Zang
Diploma+Bachelor
Students
Aletta Becker
Philipp Geiger
Wolfgang Koch
Research Fellow
Dr. Ke Wang (AvH)
Dr. Haibo Zhang (AvH)
Zilin Yan
Dr. Hailong Zhang
Guest Scientists
Prof. Chae-Ill Cheon (Korea)
Chris Fancher (Purdue University)
Dr. Amreesh Chandrah (IIT Kharagpur)
Eric Patterson (Oregon State University)
Naemul Khansur (UNSW, Australia)
Danka Gobeljic (Universität Duisburg-Essen)
Research Projects
 Processing of textured ceramic actuators with high strain (SFB 595, 2003–2014)
 Mesoscopic and macroscopic fatigue in doped ferroelectric ceramics
(SFB 595, 2003–2014)
 Development of new lead –free piezoceramics (ADRIA, state funding, 2008-2013)
 Development of new high-temperature piezoceramics (ADRIA, state funding, 2008-2013)
 Toughening of ferroelectrics (EU 2009-2012)
 Stress and strain fields in ferroelectrics
(Graduate school “computational engineering” 2009-2017)
Ceramics Group
21

Metal-ceramic composites (EU 2010-2012)

High-temperature dielectrics (DFG 2010-2013)

Mechanical compliance at phase transition points in lead-free ferroelectrics
(DFG 2011-2014)

Lead-free piezoelectric single crystals with high strain: orientation dependence,
polarization rotation and morphotropic phase boundaries (DFG 2011-2014)

Energy absorption of ZnO varistors (DFG 2011-2014)

Ag-based electrical switches (state of Hesse / Umicore)
Publications
Picht, Gunnar ; Webber, Kyle G. ; Zhang, Yining ; Kungl, Hans ; Damjanovic, Dragan ; Hoffmann,
Michael J. : Critical mechanical and electrical transition behavior of BaTiO3: The observation of
mechanical double loop behavior. [Online-Edition: http://dx.doi.org/10.1063/1.4767059] In:
Journal of Applied Physics, 112 (12) 124101(1-9). ISSN 00218979 [Artikel] , (2012)
Franzbach, Daniel J. ; Gu, Y. J. ; Chen, L. Q. ; Webber, Kyle G. : Electric field-induced tetragonal
to orthorhombic phase transitions in [110]c-oriented BaTiO3 single crystals. [Online-Edition:
http://dx.doi.org/10.1063/1.4769368] In: Applied Physics Letters, 101 (23) 232904(1-4). ISSN
00036951 [Artikel] , (2012)
Leist, Thorsten ; Brötz, Joachim ; Seo, Yo-Han ; Cheng, Shumeng ; Webber, Kyle G. : Crack
growth resistance behavior of lanthanum doped bismuth ferrite–lead titanate: Effect of
tetragonality and mixed phase crystal structures. [Online-Edition: http://dx.doi.org/10.1016/
j.engfracmech.2012.08.00...] In: Engineering Fracture Mechanics, 96 pp. 267-275. ISSN 00137944
[Artikel] , (2012)
Acosta, Matias ; Zang, Jiadong ; Jo, Wook ; Rödel, Jürgen : High-temperature dielectrics in
CaZrO3-modified Bi1/2Na1/2TiO3-based lead-free ceramics. [Online-Edition: http://dx.doi.org/
10.1016/j.jeurceramsoc.2012.06.0...] In: Journal of the European Ceramic Society, 32 (16) pp.
4327-4334. ISSN 09552219 [Artikel] , (2012)
Amaral, Luís ; Jamin, Christine ; Senos, Ana M. R. ; Vilarinho, Paula M. ; Guillon, Olivier : Effect
of the Substrate on the Constrained Sintering of BaLa4Ti4O15Thick Films. [Online-Edition:
http://dx.doi.org/10.1111/j.1551-2916.2012.05466.x] In: Journal of the American Ceramic Society,
95 (12) pp. 3781-3787. ISSN 00027820 [Artikel] , (2012)
Seo, Yo-Han ; Webber, Kyle G. ; Benčan, Andreja ; Koruza, Jurij ; Malič, Barbara ; Kosec, Marija;
Rödel, Jürgen : Deconvolving Ferroelastic and Phase Transformation Toughening in
Pb(Zr1−xTix)O3and Pb1−yLay(Zr1−xTix)O3. [Online-Edition: http://dx.doi.org/ 10.1111/
jace.12007] In: Journal of the American Ceramic Society, 95 (12) pp. 3713-3715. ISSN 00027820
[Artikel] , (2012)
22
Ceramics Group
Schaab, S. ; Schulz, M. ; Fritze, H. ; Eichel, R.-A. ; Erdem, E. ; Rüscher, C.H. ; Hummelt, S.;
Granzow, T. : Influence of reducing atmosphere on the defect chemistry of lead lanthanum
zirconate titanate (8/65/35). [Online-Edition: http://dx.doi.org/10.1016/j.ssi.2012.09.003] In: Solid
State Ionics, 228 pp. 56-63. ISSN 01672738 [Artikel] , (2012)
Dittmer, Robert ; Anton, Eva-Maria ; Jo, Wook ; Simons, Hugh ; Daniels, John E. ; Hoffman, Mark
; Pokorny, Jan ; Reaney, Ian M. ; Rödel, Jürgen : A High-Temperature-Capacitor Dielectric Based
on K0.5Na0.5NbO3-Modified Bi1/2Na1/2TiO3-Bi1/2K1/2TiO3. [Online-Edition: http://dx.doi.org/
10.1111/j.1551-2916.2012.05321.x] In: Journal of the American Ceramic Society, 95 (11) pp.
3519-3524. ISSN 00027820 [Artikel] , (2012) Note: SFB 595 A1
Dittmer, Robert ; Jo, Wook ; Rödel, Jürgen ; Kalinin, Sergei ; Balke, Nina : Nanoscale Insight Into
Lead-Free BNT-BT-xKNN. [Online-Edition: http://dx.doi.org/10.1002/ adfm.201200592] In:
Advanced Functional Materials, 22 (20) pp. 4208-4215. ISSN 1616301X [Artikel] , (2012) Note:
SFB 595 A1
Anton, Eva-Maria ; Schmitt, Ljubomira Ana ; Hinterstein, Manuel ; Trodahl, Joe ; Kowalski, Ben ;
Jo, Wook ; Kleebe, Hans-Joachim ; Rödel, Jürgen ; Jones, Jacob L. : Structure and temperaturedependent phase transitions of lead-free Bi1/2Na1/2TiO3–Bi1/2K1/2TiO3–K0.5Na0.5NbO3
piezoceramics. [Online-Edition: http://dx.doi.org/10.1557/ jmr. 2012.195] In: Journal of Materials
Research, 27 (19) pp. 2466-2478. ISSN 0884-2914 [Artikel] , (2012)
Aksel, Elena ; Forrester, Jennifer S. ; Foronda, Humberto M. ; Dittmer, Robert ; Damjanovic,
Dragan ; Jones, Jacob L. : Structure and properties of La-modified Na0.5Bi0.5TiO3 at ambient and
elevated temperatures. [Online-Edition: http://dx.doi.org/10.1063/1.4751357] In: Journal of
Applied Physics, 112 (5) 054111(1-8). ISSN 00218979 [Artikel] , (2012) Note: SFB 595 A1
Han, Hyoung-Su ; Jo, Wook ; Rödel, Jürgen ; Hong, In-Ki ; Tai, Weon-Pil ; Lee, Jae-Shin:
Coexistence of ergodicity and nonergodicity in LaFeO3-modified Bi1/2(Na0.78K0.22)1/ 2TiO3
relaxors. [Online-Edition: http://dx.doi.org/10.1088/0953-8984/24/36/365901] In: Journal of
Physics: Condensed Matter, 24 (36) p. 365901. ISSN 0953-8984 [Artikel] , (2012)
Simons, Hugh ; Glaum, Julia ; Daniels, John E. ; Studer, Andrew J. ; Liess, Andreas ; Rödel,
Jürgen; Hoffman, Mark : Domain fragmentation during cyclic fatigue in 94%(Bi1/2Na1/2)TiO36%BaTiO3. [Online-Edition: http://dx.doi.org/10.1063/1.4745900] In: Journal of Applied Physics,
112 (4) 044101(1-5). ISSN 00218979 [Artikel] , (2012)
Glaum, Julia ; Genenko, Yuri A. ; Kungl, Hans ; Schmitt, Ljubomira A. ; Granzow, Torsten:
De-aging of Fe-doped lead-zirconate-titanate ceramics by electric field cycling: 180°- vs. non-180°
domain wall processes. [Online-Edition: http://dx.doi.org/10.1063/1.4739721] In: Journal of
Applied Physics, 112 (3) 034103(1-9). ISSN 00218979 [Artikel] , (2012) Note: SFB 595
Cooperation B3, C5, D1, T2
Raju, G. B. ; Green, D. J. ; Guillon, Olivier : Evaluation of drying stresses in coatings using an
optical
method.
[Online-Edition:
http://dx.doi.org/10.1088/0957-0233/23/8/085609]
In:
Measurement Science and Technology, 23 (8) 085609(1-7). ISSN 0957-0233 [Artikel] , (2012)
Schwarz, Sebastian ; Thron, Andrew M. ; Rufner, Jorgen ; Benthem, Klaus ; Guillon, Olivier;
Olevsky, E. : Low Temperature Sintering of Nanocrystalline Zinc Oxide: Effect of Heating Rate
Achieved by Field Assisted Sintering/Spark Plasma Sintering. [Online-Edition:
Ceramics Group
23
95 (8) pp. 2451-2457. ISSN 00027820 [Artikel] , (2012)
Sluka, Tomas ; Webber, Kyle G. ; Colla, Enrico ; Damjanovic, Dragan : Phase field simulations of
ferroelastic toughening: The influence of phase boundaries and domain structures. [Online-Edition:
http://dx.doi.org/10.1016/j.actamat.2012.06.023] In: Acta Materialia, 60 (13-14) pp. 5172-5181.
ISSN 13596454 [Artikel] , (2012)
Dittmer, Robert ; Jo, Wook ; Aulbach, Emil ; Granzow, Torsten ; Rödel, Jürgen : Frequencydependence of large-signal properties in lead-free piezoceramics. [Online-Edition: http://dx.doi.
org/10.1063/1.4730600] In: Journal of Applied Physics, 112 (1) 014101 (1-7). ISSN 00218979
[Artikel] , (2012) Note: SFB 595 A1
Dittmer, Robert ; Aulbach, Emil ; Jo, Wook ; Webber, Kyle G. ; Rödel, Jürgen : Large blocking
force
in
Bi1/2Na1/2TiO3-based
lead-free
piezoceramics.
[Online-Edition:
http://dx.doi.org/10.1016/j.scriptamat.2012.03.031] In: Scripta Materialia, 67 (1) pp. 100-103.
ISSN 13596462 [Artikel] , (2012) Note: SFB 595 A1
Guillon, Olivier ; Chang, Jaemyung ; Schaab, Silke ; Kang, Suk-Joong L. ; Randall, C. A.:
Capacitance Enhancement of Doped Barium Titanate Dielectrics and Multilayer Ceramic
Capacitors
by
a
Post-Sintering
Thermo-Mechanical
Treatment.
[Online-Edition:
95 (7) pp. 2277-2281. ISSN 00027820 [Artikel] , (2012)
Wang, Ke ; Hussain, Ali ; Jo, Wook ; Rödel, Jürgen : Temperature-Dependent Properties of
(Bi1/2Na1/2)TiO3-(Bi1/2K1/2)TiO3-SrTiO3
Lead-Free
Piezoceramics.
[Online-Edition:
http://dx.doi.org/ 10.1111/j.1551-2916.2012.05162.x] In: Journal of the American Ceramic
Society, 95 (7) pp. 2241-2247. ISSN 00027820 [Artikel] , (2012)
Yan, Zilin ; Guillon, Olivier ; Wang, Steve ; Martin, Christophe L. ; Lee, Chul-Seung ; Bouvard,
Didier : Synchrotron x-ray nano-tomography characterization of the sintering of multilayered
systems. [Online-Edition: http://dx.doi.org/10.1063/1.4730625] In: Applied Physics Letters, 100
(26) 263107(1-4). ISSN 00036951 [Artikel] , (2012)
Erdem, Emre ; Schaab, Silke ; Jo, Wook ; Ozarowski, Andrew ; Van Tol, Johan ; Eichel, Rüdiger-A.:
High-Frequency EPR Analysis of MnO2-Doped [Bi0.5Na0.5]TiO3-BaTiO3Piezoelectric Ceramics
– Manganese Oxidation States and Materials ‘Hardening’. [Online-Edition: http://dx.doi.org/
10.1080/00150193.2012.675831] In: Ferroelectrics, 428 (1) pp. 116-121. ISSN 0015-0193
[Artikel] , (2012) Note: SFB 595 Cooperation A1, B1
Kwon, O-Jong ; Jo, Wook ; Yoon, Sejin ; Shin, Dongmin ; You, Hyunwoo ; Choi, Kyeongdal; Kim,
Jin-Sang ; Park, Chan : Relation between Seebeck Coefficient and Lattice Parameters of (Ca2−y Sr
y CoO3) x CoO2. [Online-Edition: http://dx.doi.org/10.1007/s11664-012-1983-z] In: Journal of
Electronic Materials, 41 (6) pp. 1513-1518. ISSN 0361-5235 [Artikel] , (2012)
Jo, Wook ; Dittmer, Robert ; Acosta, Matias ; Zang, Jiadong ; Groh, Claudia ; Sapper, Eva ; Wang,
Ke ; Rödel, Jürgen : Giant electric-field-induced strains in lead-free ceramics for actuator
applications – status and perspective. [Online-Edition: http://dx.doi.org/10.1007/s10832-012-97423] In: Journal of Electroceramics ISSN 1385-3449 [Artikel] , (2012) Note: SFB 595 Cooperation A1,
D1
24
Ceramics Group
Genenko, Yuri A. ; Zhukov, Sergey ; Yampolskii, Sergey V. ; Schütrumpf, Jörg ; Dittmer, Robert;
Jo, Wook ; Kungl, Hans ; Hoffmann, Michael J. ; von Seggern, Heinz : Universal Polarization
Switching Behavior of Disordered Ferroelectrics. [Online-Edition: http://dx.doi.org/10.1002/
adfm.201102841] In: Advanced Functional Materials, 22 (11) pp. 2058-2066. ISSN 1616301X
[Artikel] , (2012) Note: SFB 595 Cooperation A1, B7, C5, D1, T2
Sebastian, Tutu ; Sterianou, Iasmi ; Reaney, Ian M. ; Leist, Thorsten ; Jo, Wook ; Rödel, Jürgen:
Piezoelectric activity of (1-x)[0.35Bi(Mg1/2Ti1/2)O3-0.3BiFeO3-0.35BiScO3] - xPbTiO3 ceramics
as a function of temperature. [Online-Edition: http://dx.doi.org/10.1007/s10832-012-9685-8] In:
Journal of Electroceramics, 28 (2-3) pp. 95-100. ISSN 1385-3449 [Artikel] , (2012)
Detsch, Rainer ; Guillon, Olivier ; Wondraczek, Lothar ; Boccaccini, Aldo R. : Initial Attatchment
of rMSC and MG-63 Cells on Patterned Bioglass® Substrates. [Online-Edition: http://dx.doi.org/
10.1002/adem.201180068] In: Advanced Engineering Materials, 14 (3) B38-B44. ISSN 14381656
[Artikel] , (2012)
Marsilius, Mie ; Frederick, Josh ; Hu, Wei ; Tan, Xiaoli ; Granzow, Torsten ; Han, Pengdi:
Mechanical Confinement: An Effective Way of Tuning Properties of Piezoelectric Crystals. [OnlineEdition: http://dx.doi.org/10.1002/adfm.201101301] In: Advanced Functional Materials, 22 (4) pp.
797-802. ISSN 1616301X [Artikel] , (2012)
Daniels, John E. ; Jo, Wook ; Donner, Wolfgang : High-Energy Synchrotron X-Ray Diffraction for
In Situ Diffuse Scattering Studies of Bulk Single Crystals. [Online-Edition: http://dx.doi.org/
10.1007/s11837-011-0230-z] In: JOM, 64 (1) pp. 174-180. ISSN 1047-4838 [Artikel] , (2012)
Benčan, Andreja ; Malič, Barbara ; Drnovšek, Silvo ; Tellier, Jenny ; Rojac, Tadej ; Pavlič, Jernej;
Kosec, Marija ; Webber, Kyle G. ; Rödel, Jürgen ; Damjanovič, Dragan ; Jones, J. L. : Structure
and the Electrical Properties of Pb(Zr,Ti)O3 - Zirconia Composites. [Online-Edition:
95 (2) pp. 651-657. ISSN 00027820 [Artikel] , (2012)
Leist, Thorsten ; Chen, Jun ; Jo, Wook ; Aulbach, Emil ; Suffner, Jens ; Rödel, Jürgen ; Zhang, S.:
Temperature Dependence of the Piezoelectric Coefficient in BiMeO3-PbTiO3 (Me = Fe, Sc,
(Mg1/2Ti1/2)) Ceramics. [Online-Edition: http://dx.doi.org/10.1111/j.1551-2916.2011.04848.x] In:
Journal of the American Ceramic Society, 95 (2) pp. 711-715. ISSN 00027820 [Artikel] , (2012)
Rasp, Tobias ; Jamin, Christine ; Wonisch, Andreas ; Kraft, Torsten ; Guillon, Olivier : Shape
Distortion and Delamination During Constrained Sintering of Ceramic Stripes: Discrete Element
Simulations and Experiments. [Online-Edition: http://dx.doi.org/10.1111/j.1551-2916.2011. 04939.x]
In: Journal of the American Ceramic Society, 95 (2) pp. 586-592. ISSN 00027820 [Artikel] , (2012)
Sapper, Eva ; Schaab, Silke ; Jo, Wook ; Granzow, Torsten ; Rödel, Jürgen : Influence of electric
fields on the depolarization temperature of Mn-doped (1-x)Bi1/2Na1/2TiO3-xBaTiO3. [OnlineEdition: http://dx.doi.org/10.1063/1.3674275] In: Journal of Applied Physics, 111 (1) 014105(1-6).
ISSN 00218979 [Artikel] , (2012) Note: SFB 595 D1
Baraki, Raschid ; Schwarz, Sebastian ; Guillon, Olivier : Effect of Electrical Field/Current on
Sintering of Fully Stabilized Zirconia. [Online-Edition: http://dx.doi.org/10.1111/j.15512916.2011.04980.x] In: Journal of the American Ceramic Society, 95 (1) pp. 75-78. ISSN
00027820 [Artikel] , (2012)
Ceramics Group
25
Stress-Dependent Electromechanical Properties
of Lead-Free Piezoceramics
Robert Dittmer
Piezoelectrics are multifunctional materials that allow a conversion of mechanical into
electrical energy and vice versa. This valuable feature can be used, for example, in the highpressure injection of fuel, ultra-precise positioning, or damping of vibration and noise.
Today’s predominant material is lead zirconate titanate PbZrxTi1-xO3 (PZT). Due to
increasing environmental awareness, the use of the heavy metal lead in consumer products
faces increasing restrictions. This development stipulated extensive research in order to find
lead-free alternatives to PZT.
To date, there are numerous complex material systems based on Bi1/2Na1/2TiO3 (BNT). The
most widely studied system is pseudotbinary B1/2Na1/2TiO3-BaTiO3 (BNT-100xBT). It
displays intriguing field- and temperature-dependent properties, for example, large strains
that may even compete with PZT under certain conditions. One question that has not yet
been answered is whether these strains are attainable also under high mechanical loads. In
practical applications, actuators are usually produced with a compressive pre-stress in order
to minimize detrimental tensile stresses during operation. In addition, actuators naturally
perform work against external loads and at elevated temperatures. Therefore it is of utmost
interest whether lead-free materials are capable of producing high strains also under stress
and across a broad temperature range.
Figure 1: Field-induced strain from 25 °C to 150 °C under compressive stress of 2 MPa, 56 MPa, 112 MPa,
and 224 MPa. The electric field amplitude is varied from 1 kV/mm to 2 kV/mm and 3 kV/mm.
26
Ceramics Group
In order to investigate the stress dependence, a sample of the composition BNT-6BT is
cycled unipolarly in a load frame at 50 mHz. The compressive stress is varied from 2 MPa
to 446 MPa in a temperature range from room temperature up to 150 °C. Figure 1 presents
the thermal evolution of the stress curves at four selected stress states.
Under practically zero-stress (2 MPa) conditions BNT-6BT develops large strains at 125 °C.
The ratio of maximum strain to maximum field Smax/Emax reaches an extraordinarily high
value of almost 900 pm/V. This values declines, however, under the influence of an electric
field. Interestingly, for temperatures below 125 °C the application of moderate stress is
found to enhance the achievable Smax/Emax. The complex stress-dependence is illustrated in
Figure 2.
Figure 2:
a) Maximum strain Smax
b) maximum polarization Pmax as a function of
compressive stress and temperature for 3 kV/mm.
At room temperature BNT-6BT possesses a ferroelectric long-range order, that is, micronsized domains exist. The application of a stress impedes domain switching and,
consequently, Smax and Pmax decrease. The rate of change of Smax() and Pmax() differs,
because the two species of domains, 180° and non-180° domains, display a distinct stressdependence and also contribute in a different manner to polarization and strain.
At temperatures of 50 °C and above the domain mobility is increased. Therefore, the
external stress is capable of inducing a backswitching of domains when the electric field is
removed. For that reason domains can switch back and forth during each cycle,
contributing to the attainable strain and polarization. When the stress becomes too high,
however, the domains are clamped; the electric field is not high enough to switch the
domains anymore and Smax and Pmax decrease. Because of that, a peak exists in Smax() and
Pmax(), delimitating the field- from the stress controlled regime, as illustrated by Figure 3.
For temperatures of 125 °C and beyond, BNT-6BT is an ergodic relaxor, i.e., there are small
polar regions of nanoscopic size instead of large domains. Earlier X-ray diffraction studies
under electric field demonstrated, that these polar nano regions (PNR) may exhibit a
reversible, field-induced coalescence into domains. At some temperature TF-R the
predominant strain mechanism changes from domain switching to phase transition, as
shown in Figure 3. This change in the mechanism is associated with a change in the stress
dependence as every increase in stress yields a decrease in strain and polarization. It is
conjectured that the boarder line between these two mechanisms is stress-dependent.
Ceramics Group
27
Experiments on thin films demonstrated that stress may stabilize the ferroelectric order,
thus, TF-R is suggested to increase with stress.
Figure 3:
Temperature-stress diagram of strain normalized to strain at zero-stress and room temperature
at 3 kV/mm.
In conclusion, both strain and polarization depend on the electric field, temperature, and
stress. The complex interplay between these factors is a result of the balance between
electrical and mechanical driving forces. Further experimental effort is necessary to
elucidate the stress-dependence of TF-R.
28
Ceramics Group
Electronic Material Properties
The Electronic Materials division introduces the aspect of electronic functional materials and
their properties into the Institute of Materials Science. The associated research concentrates
on the characterization of various classes of materials suited for implementation in
information storage and organic and inorganic electronics. Four major research topics are
presently addressed:




Electronic and optoelectronic properties of organic semiconductors.
Charge transport in inorganic semiconductor devices.
Charge transport and polarization in organic and inorganic dielectrics.
Photo- and photostimulated luminescence in inorganic phosphors.
For novel areas of application a worldwide interest exists in the use of organic
semiconductors in electronic and optoelectronic components, such as transistors and lightemitting diodes. So far, multicolour and full colour organic displays have been
implemented in commercially available cameras, car-radios, PDAs, mp3-players and even
television sets. Organic devices reaching further into the future will be simple logic circuits,
constituting the core of communication electronics such as chip cards for radio-frequency
identification (RFID) tags and maybe one day flexible electronic newspapers where the
information is continuously renewed via mobile networks. In view of the inevitable
technological development, the activities of the group are concerned with the
characterization of organic material properties regarding the performance of organic
electronic and optoelectronic devices. The major aspect deals with the charge carrier
injection and transport taking place in organic field-effect transistors (OFETs) and organic
light-emitting diodes (OLEDs). In particular, the performance of unipolar and ambipolar
light-emitting OFETs and the stability of OFETs and OLEDs are subjects of recent
investigations. To conduct these demanding tasks, various experimental techniques for
device fabrication and characterization are installed. Besides basic electric measurement
setups, a laser spectroscopy setup used for time-of-flight as well as for life-time
measurements and a Kelvin-probe atomic force microscope to visualize the potential
distribution of organic devices with nanometer resolution are available.
Even though organic electronics is an emerging field especially for consumer electronics
applications today's electronic devices still mainly rely on conventional silicon technology.
While organic semiconductors have excellent optoelectronic properties they in general
suffer from low charge carrier mobilities limiting the switching rates in organic transistors.
Yet, metal oxides like ZnO, InZnO (IZO) or InGaZnO (IGZO) can bridge the gap between
the high mobility semiconductors like silicon and the low mobility organic semiconductors.
Using metal-organic precursors or nanoparticulate dispersions easy processing procedures
like spin-coating or printing can be applied and yield rather high field-effect mobilities in
the order of 1-10 cm²V-1s-1 for the produced thin film transistors (TFTs). Current research
activities in the group concentrate on the optimization of the processing procedures
especially the decrease of annealing temperatures is desired to make the processes
compatible with organic substrates. Furthermore, the influence of the layer morphology
and the role of the gas atmosphere for the device performance as well as stability issues are
investigated.
29
In the field of polymer electrets current research comprises the characterization of surface
charge distribution, charge stability, and charge transport properties of fluoropolymers, as
well as their applications in acoustical transducers. Present investigations of charge
transport and polarization in organic dielectrics are directed towards the basic
understanding of polarization buildup and stabilization in PVDF and in novel microporous
dielectrics. Latter are scientifically interesting as model ferroelectric polymers. Moreover,
the fatigue behaviour of electrically stressed inorganic PZT ceramics is investigated. The
focus lies on preventing the operational fatigue of ferroelectric devices due to cyclic and
static electrical stress. The available equipment includes poling devices, such as corona and
high voltage setups, and a thermally stimulated current setup to investigate the energetic
trap structure in dielectrics as well as the thermal charging and discharging under high
electric fields. In addition, the laser induced pressure pulse (LIPP) method allows to
investigate the spatial distribution of stored charges in organic as well as in inorganic
ferroelectrics.
The field of photoluminescent and photostimulated luminescent (PSL) materials
(phosphors) is concerned with the synthesis and characterization of suited inorganic
compounds used as wavelength converters in fluorescent lamps and in scintillating and
information storing crystals. Present work is focused on x-ray detection materials, providing
improved resolution and high PSL-efficiency needed in medical imaging. In particular the
storage phosphors CsBr:Eu2+ and BaFBr:Eu2+ are under investigation. Research is
concentrated on the influence of humidity on the sensitivity of CsBr:Eu2+. Before and after
the treatment the materials are studied by means of spectroscopic methods as well as
scanning electron microscopy. The exchange of water during the thermal treatment is
measured in situ by thermal analysis methods. New synthesis methods for BaFBr:Eu 2+ used
in commercial image plates are of interest and new synthesis routes will be tested for other
storage phosphors and scintillators. On the one hand the mechanism of PSL-sensitization,
which is found to be mainly due to the incorporation of oxygen and water, is investigated.
On the other hand the implementation of BaFBr:Eu2+ powders into organic binders in order
to form image plates is in the focus of the work.
In the field of scintillators undoped and doped CsI is investigated concerning the afterglow.
This afterglow is unfavourable in medical applications like CT where a series of images is
made in a very short time. The task is to find the physical reason for this afterglow and a
way to suppress it.
30
Staff Members
Head
Prof. Dr.-Ing. Heinz von Seggern
Research Associates
Dr. Graham Appleby
Dr. Corinna Hein
Dr. Christian Melzer
Dr. Sergej Zhukov
Dr.-Ing. Andrea Gassmann
Dr. Joachim Hillenbrand
Dr. Emanuelle Reis Simas
Dr.-Ing. Jörg Zimmermann
Technical Personnel
Gabriele Andreß
Sabine Hesse
Helga Janning
Bernd Stoll
Secretary
Gabriele Kühnemundt
PhD Students
Dipl.-Ing. Eva Feldmeier
Dipl.-Ing. Tobias Könyves-Toth
Dipl.-Phys. Oliver Ottinger
Marc Rättig
Dipl.-Phys. Jörg Schütrumpf
Dipl.-Ing. Lorenz Kehrer
Dipl.-Ing. Paul Mundt
M. Sc. Oili Pekkola
M. Sc. Riitta Savikoski
M. Sc. Dan Walker
Diploma Students
Lucia Funke
Boris Lehmann
Ralf-Samuel Kühne
Andreas Liess
Bachelor Students
Kristina Braak
Philipp Kröber
Guest Scientists
Prof. Dr. Ivan H. Bechtold
Prof. Dr. Sergei Fedosov
Prof. Dr. Lucas F. Santos
Prof. Dr. Vladislav Cherpak
Dr. Anatoli Popov
Research Projects
Fatigue of organic semiconductor components (SFB 595 (DFG), 2003-2014)
Phenomenological modelling of bipolar carrier transport in organic semiconducting devices
under special consideration of injection, transport and recombination phenomena (SFB 595
(DFG), 2003-2014)
Polarization and charge in electrically fatigued ferroelectrics (SFB 595 (DFG), 2006-2014)
Development and optimization of tuneable optical filters and VCSEL based on piezoelectric
and electret actuators (TICMO Graduiertenkolleg 1037, 2007-2013)
Development of organic piezo sensors (LOEWE AdRIA 26200026, 2008-2014)
Development of fibre-based organic semiconductor devices for textile applications
(LUMOLED, BMBF/ VDI/ VDE/ IT, 2010-2012)
31
Thin film dielectrics for high performance transistors (DFG, 2012-2015)
Development of gate insulators for organic field effect transistors exploiting self-assembly of
block-copolymers (IDS-FunMat (EU), 2012-2015)
Piezoelectric properties of ferroelectrics (DFG, 2012-2015)
Luminescent thin films (Siemens, 2012)
Preparation and characterization of metal-oxide field-effect transistors (MerckLab, 20092015)
Publications
A. Gassmann, C. Melzer, H. von Seggern, The Li3PO4/Al electrode: An alternative, efficient
cathode for organic light-emitting diodes, SYNTHETIC METALS 161 (2012) 2575-2579. DOI:
10.1016/j.synthmet.2011.08.009
L. A. Kehrer, S. Winter, R. Fischer, C. Melzer, H. von Seggern, Temporal and thermal
properties of optically induced instabilities in P3HT field-effect transistors, SYNTHETIC
METALS 161 (2012) 2558-2561. DOI: 10.1016/j.synthmet.2011.08.007
J. Schuetrumpf, S. Zhukov, Y. A. Genenko, H. von Seggern, Polarization switching dynamics
by inhomogeneous field mechanism in ferroelectric polymers, JOURNAL OF PHYSICS D 45
(2012) 165301. DOI: 10.1088/0022-3727/45/16/165301
Y. A. Genenko, S. Zhukov, S. V. Yampolskii, J. Schutrumpf, R. Dittmer, W. Jo, H. Kungl, M.
J. Hoffmann, H. von Seggern, Universal polarization switching behavior of disordered
ferroelectrics, ADVANCED FUNCTIONAL MATERIALS 22 (2012) 2058-2066.
DOI:
10.1002/adfm.201102841
G. C. Faria, H. von Seggern, R. M. Faria, E. R. deAzevedo, Influence of molecular dynamics
on the dielectric properties of poly(9,9-di-n-octylfluorene-alt-benzothiadiazole)-based devices,
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 19 (2012) 11811185. ISSN: 1070-9878
I. H. Bechtold, J. Eccher, G. C. Faria, H. Gallardo, F. Molin, N. R. K. T. de Oliveira, S. Gobo,
H. von Seggern, New columnar Zn-phthalocyanine designed for electronic applications,
JOURNAL OF PHYSICAL CHEMISTRY B 116 (2012) 13554-13560. DOI: 10.1021/
jp307825u
D. E. Walker, M. Major, M. Baghaie Yazdi, A. Klyszcz, M. Haeming, K. Bonrad, C. Melzer,
W. Donner, H. von Seggern, High mobility indium zinc oxide thin film field-effect transistors
by semiconductor layer engineering, ACS APPLIED MATERIALS & INTERFACES 4 (2012)
6835-6841. DOI: 10.1021/am302004j
32
High performance indium zinc oxide thin film field-effect transistors
Daniel Walker, Christian Melzer and Heinz von Seggern
Solution processed inorganic semiconductors such as indium zinc oxide (IZO) offer many
advantages over incumbent technologies. As demand drives display manufactures to
implement new features, such as fast refresh rate, 3d, or OLED displays, the performance of
the back-plane transistors required for the display to function must increase significantly.
Furthermore, as display sizes increase, using masks to pattern material becomes
increasingly challenging and greater efficiency and throughput can be achieved by
depositing the materials directly from solution.
In all experiments described, a highly n++-doped (n~3 x 1017 cm-3) silicon substrate with a
90 nm surface oxide layer and optional 30 nm Au source and drain electrodes deposited on
top of a 10 nm ITO anchor layer, patterned via a lift off technique, have been used. The
schematic device structure is shown in the inset of figure 1a. The substrate was cleaned by
ultra-sonication in acetone to remove a polymer protection layer, and subsequently in
water, acetone and propane-diol for 10 minutes each to obtain a clean and residue free
surface. The substrates were dried in a flow box for at least one hour before being plasma
treated for one minute in an air plasma induced by a PFG300 RF-generator at 70 W which
significantly improves the wetting of the precursor formulation to the substrate.
IZO precursor formulations were prepared from solutions of organo-metallic zinc oximate
precursor or indium oximate precursor complex detailed in references [1] and [2]
respectively, dissolved in 2-methoxyethanol. These were mixed in a 1.66:1 molar ratio of
indium to zinc at an optimum single layer concentration of 30 mg precursor in a total of
1.0 g solvent and precursor mixture (30 mg g-1). This formulation was spin coated onto the
substrate at 2000 rpm for 30 s which was subsequently placed onto a hotplate in air at
450 °C for 10 min in order to decompose the precursor and form the metal-oxide layer. It
was then quench cooled to room temperature on a metal block for 30 s. Subsequent layers
can then be coated by the same method.
Fig. 1: a. Transfer curves of an IZO transistor showing the effect of coating multiple layers. Filled symbols show
the drain current and open symbols the gate current. The calculated mobilities µ are given in cm2V-1s-1. Inset:
The device structure used in these experiments. b. STM line profiles of different IZO films. The multiple layer
films are less rough than the single layer.
33
Transistors with mobilities of around 5 cm2V-1s-1 could be routinely made according to the
method above utilizing single layers of IZO. It was found that when a second layer of IZO
was coated onto the first layer there was a dramatic increase in performance. Coating
further layers had little effect. This result is shown in figure 1a in the form of transfer
curves, which plot the drain current vs. the gate voltage. It is clearly seen that after the
addition of a second layer the current at the drain electrode is higher at any given positive
gate voltage. This translates to an increase in mobility. A similar increase is not observed
when coating the third and fourth layers.
As for single layer IZO formulations the concentration can be optimized for coating
multiple layers. The result was that the optimum formulation concentration for single
layers was different to that when multiple layers were used. In fact it turned out that the
lower the concentration the better the ultimate performance of the device was, although
the low concentrations required many more layers to reach this performance. For example,
the best devices achieved mobilities of around 20 cm2V-1s-1 and required a formulation
concentration of 3-5 mg g-1 coating about 20 layers to do so. Decreasing the concentration
further offered no increase in performance regardless of the number of layers coated.
The reason for this dependence was investigated in some detail and published in reference
[3]. Figure 1b shows STM surface profiles of various different layers offset to the layer
thickness as determined by different techniques, e.g. x-ray diffraction and scanning electron
microscopy. It became evident for the single layer film at optimum concentration of 30 mg
g-1 there are full thickness defects in the material. After coating the second layer these full
thickness variations are absent. Films constructed from low concentration precursor
formulations exhibit a smooth surface absent of such defects. These results were combined
with electron density profiles extracted from x-ray reflectivity data from Strukturforschung
group of Prof. Donner to construct the model of layer formation shown in figure 2.
Fig. 2: Image representing the model proposed describing the layer formation process. The top row of figures
describes single layers and the bottom row multiple layers.
In the case of single layer films made from formulations with a high concentration of
precursor (~100 mg g-1) the electrical performance was poor. This has been attributed to a
low density IZO film (note the density of the IZO material itself is not expected to change,
but the appearance of voids inside the film lowers the film density). As the concentration is
reduced, at some point the internal voids are eliminated, leading to the optimum single
34
layer concentration at around 30 mg g-1. Lowering the concentration further means there is
no longer sufficient material to form a complete layer and the electrical performance suffers
dramatically.
Coating multiple layers from formulations with high concentrations (~100 mg g-1) of
precursor has no effect on the final transistor performance. The initial layer is thick enough
that subsequent layers do not impact the critical channel region. Adding second layers on
optimal single layer devices (30 mg g-1) does have a strong impact on electrical
performance. However, small voids remain at the dielectric interface, limiting the
performance. Coating many thin layers results in a dense, void-free layer offering the best
performance, with mobilities up to 20 cm2V-1s-1.
This work has been completed as part of a collaboration with the Merck-TUD laboratories.
References:
[1] J. J. Schneider, R. C. Hoffmann, J. Engstler, S. Dilfer, A. Klyszcz E. Erdem, P. Jakes, and R. A.
Eichel, Journal Of Materials Chemistry, (2009), 19, 1449-1457.
[2] M. Pashchanka, R. C. Hoffmann, A. Gurlo and J. J. Schneider. Journal of Materials Chemistry,
(2010), 20, 8311-8319.
[3] D. E. Walker, M. Major, M. Baghaie Yazdi, A. Klyszcz, M. Haeming, K. Bonrad, C. Melzer, W.
Donner, H. von Seggern, ACS APPLIED MATERIALS & INTERFACES, 4 (2012) 6835-6841.
35
Inhomogeneous field mechanism model for polarization reversal in virgin and
fatigued ferroelectrics
Sergey Zhukov, Yuri A. Genenko, Jörg Schütrumpf and Heinz von Seggern
The understanding of polarization reversal dynamics of ferroelectrics is of great importance
for practical applications and is being steadily advanced for more than half a century. The
traditional way to describe polarization reversal in ceramics is the Kolmogorov-AvramiIshibashi (KAI) model, which is based on nucleation and domain growth theory [1]. The
KAI model describes the temporal evolution of the switched polarization P(t) as

  t n 


Pt   2 Ps 1  exp     ,

     


(1)
Pt   2 Ps
 1  exp  t /    G log d log ,
P/2Ps
P/2Ps
where Ps is the saturation polarisation,  is the characteristic switching time and n is the
Avrami parameter, which can take the values 1, 2 and 3 reflecting the dimensionality of
nuclei’s growth process. As an example, Fig. 1 relates the KAI model fit to the experimental
results on polarization reversal in La-doped PZT ceramic in virgin and fatigued states. It is
clear seen from Fig. 1b that the classical switching
model is hardly applicable to the fatigued ceramic
1.0
virgin
where the switching transition is very smooth.
KAI Model
Therefore, to describe the global switching
dynamics in fatigued as well as in virgin
0.5
ferroelectrics another model is required.
In 2002 Tagantsev et al [2] introduced an
alternative polarization reversal process known as
a)
0.0
-7
-5
-3
-1
1
3
the nucleation limited switching (NLS model). This
10
10
10
10
10
10
Poling time, s
model treats the material divided into areas of
independent switching dynamics. Therefore, the
6
1.0
4.4*10
KAI Model
system response to the applied electric field may be
represented as:

n
0.5
(2)

0.0
-7
10
b)
-5
-3
-1
1
3
10
10
10
10
10
where G(log ) is the distribution function of the
Poling time, s
nucleation probabilities for log . The used
distribution function is flat in a specific interval Fig. 1: The switching polarization
and decays as 1/x2 outside this region. This measured at applied field of 1.5 kV/mm
approach provides a good description for the for virgin (a) and bipolar fatigued (b) PZT
ceramic. Solid curves are the fitting lines
smooth transitions observed in thin PZT films according to the KAI model with n=1.
although did not clarify the origin of such bell-like
distribution for nucleation probabilities. Later Jo et al [3] have proposed a Lorentzian shape
for the distribution function G(log ) and explained this approach due to dipole-dipole
interactions in the material, which leads to local field variations, and which exhibit also a
36
Lorentzian form. It should be noted that the choice of the distribution function is not
unique. Other types of distribution function are also possible. A Gaussian distribution can
also be well adjusted to the random electric field distribution as has been shown by us in
2010 [4].
Utilizing an idea of a random distribution of the electric field over the switching volume
due to intrinsic inhomogeneities of the material we have developed the Inhomogeneous
Field Mechanism (IFM) model [5,6]. Within this model the resulting temporal evolution of
the switched polarization P after the step application of the electric field Em can be
represented as:

E m E max ( t )
0
du
u  ,
u
90
(3)
P , C/cm
2
PEm , t   2 Ps
Em [ kV/mm ]
2.0
1.7
1.5
1.3
1.1
60
where (Em/Emax(t)) is the scaled normalized
derivative P/(ln Em) and Emax(t) is the
30
derivative maximum position calculated for
a)
different durations of poling pulses. IFM model
0
-7
-5
-3
-1
1
3
provides a good description of the experimental
10
10
10
10
10
10
results on polarization switching in virgin and
Poling time t, s
90
fatigued ferroelectrics for a wide field-time
E [ kV/mm ]
2.0
domain as exemplary indicated in Fig. 2. We have
1.7
60
also demonstrated that the model can be
1.5
1.3
successfully applied to the polymer ferroelectrics
1.1
30
as well [7]. Another important feature is that the
all model parameters can be directly determined
b)
from the experiment. Contrary to the Tagantsev’s
0
-7
-5
-3
-1
1
3
10
10
10
10
10
10
NLS and Jo’s switching models discussed above,
Poling time t, s
the IFM approach allows to numerically restore
the local field as well as switching time Fig. 2: Polarization reversal for virgin (a) and
distributions without prior assuming any specific bipolar fatigued to 4.4×106 cycles (b) Laform of them. Systematic studies of polarization doped PZT ceramic measured at different
switching in fatigued PZT [5] and lead-free BNT- applied fields as indicated. Symbols
correspond to the experimental data,
BT ceramics [results not published yet] whereas the solid lines represent the IFM
demonstrate the evolution of statistical field model fits to the data.
distributions with increasing level of fatigue.
Appearance of defects such as micro cracks, domain wall pinning centers or dielectric
surface layers in the course of fatigue are considered as main factors influencing the local
fields and hence the global polarization reversal. All these findings make the advanced IFM
approach an appropriate tool to study the fatigue in ferroelectrics.
P , C/cm
2
m
References:
[1] Y. Ishibashi and H. Orihara. Integrated Ferroelectrics, (1995) 9, 57-61.
37
[2] A.K. Tagantsev, I. Stolichnov, N. Setter, J.S. Cross, and M. Tsukada, Phys. Rev. B, (2002) 66,
214109.
[3] J.Y. Jo, H.S. Han, J.-G. Yoon, T.K. Song, S.-H. Kim, and T.W. Noh, Phys. Rev. Lett., (2007) 99,
267602.
[4] S. Zhukov, Y. A. Genenko, and H. von Seggern. J. Appl. Phys., (2010) 108, 014106.
[5] S. Zhukov, Y. A. Genenko, O. Hirsch, J. Glaum, T. Granzow, H. von Seggern, Phys. Rev. B,
(2010) 82, 014109.
[6] Y.A. Genenko, S. Zhukov, S.V. Yampolskii, J. Schütrumpf, R. Dittmer, W. Jo, H. Kungl, M.J.
Hoffmann, and H. von Seggern, Adv. Funct. Mater., (2012) 22, 2058.
[7] J. Schütrumpf, S. Zhukov, Y. A. Genenko, and H. von Seggern, J. Phys. D: Appl. Phys., (2012),
45, 165301.
38
Surface Science
The surface science division of the institute of materials science uses advanced surface
science techniques to investigate surfaces and interfaces of materials and materials
combinations of technological use. For this purpose integrated UHV-systems have been
built up which combine different surface analytical tools (photoemission, inverse
photoemission, electron diffraction, ion scattering, electron loss spectroscopy, scanning
probe techniques) with the preparation of thin films (thermal evaporation, close-spaced
sublimation, magnetron sputtering, MOCVD) and interfaces. The main research interest is
directed to devices using polycrystalline compound semiconductors and interfaces between
dissimilar materials. The perspectives of energy conversion (e.g. solar cells) or storage
(intercalation batteries) devices are of special interest. In addition, the fundamental
processes involved in chemical and electrochemical device engineering and oxide thin films
for electronic applications are investigated.
The main research areas are:
Electrochemical Interfaces
The aim of this research activity is the better understanding of electrochemical interfaces
and their application for energy conversion. In addition, empirically derived (electro-)
chemical processing steps for the controlled modification and structuring of materials is
investigated and further optimized. In the center of our interest are
semiconductor/electrolyte contacts.
Solar fuels
The direct solar light induced water splitting is investigated using photoelectrochemical
(electrode/electrolyte) or photocatalytic (particle) arrangements. New materials, design
structures, as well as interface engineering approached with advanced catalysts are
investigated. The catalysts are also tested for their application in water electrolysis.
Intercalation Batteries
The aim of this research activity is the better understanding of electronic properties of Liintercalation batteries and of their degradation phenomena. Typically all solid state
batteries are prepared and investigated using sputtering and CVD techniques for cathodes
and solid electrolytes. In addition, the solid-electrolyte interface and synthetic surface
layers are investigated as well as composite systems for increasing the capacity.
Thin film solar cells
The aim of this research activity is the testing and development of novel materials and
materials combinations for photovoltaic applications. In addition, the interfaces in
microcrystalline thin film solar cells are to be characterized on a microscopic level to
understand and to further improve the empirically based optimisation of solar cells.
Surface Science
39
Organic-inorganic interfaces and composites
In this research area we are aiming at the development of composites marterials for (opto-)
electronic applications. The decisive factors, which govern the electronic properties of
interfaces between organic and inorganic materials are studied.
Semiconducting Oxides
The aim of this research area is to understand electronic surface and interfaces properties
of oxides. We are mainly interested in transparent conducting oxide electrodes for solar
cells and organic LEDs but also in dielectric and ferroelectric perovskites.
Surface analysis
The UHV-surface science equipment and techniques using different and versatile integrated
preparation chambers is used for cooperative service investigations.
For the experiments we use integrated UHV-preparation and analysis-systems (UPS,
(M)XPS, LEISS, LEED), spectromicroscopy (PEEM) coupled with UHV-STM/AFM. We
further apply synchrotron radiation (SXPS, spectromicroscopy), scanning probe methods
(STM, AFM), and electrochemical measuring techniques. UHV-preparation chambers
dedicated for MBE, CVD, PVD and (electro)chemical treatment are available.
The members of the group are involved in basic courses of the department’s curriculum and
offer special courses on the physics, chemistry and engineering of semiconductor devices
and solar cells, on surface and interface science, and on thin film and surface technology
and electrochemistry.
Staff Members
Head
Prof. Dr. Wolfram Jaegermann
Research Associates
Dr. Wolfram Calvet
Dr. Gennady Cherkashinin
Dr. Lucangelo Dimesso
Dr. René Hausbrand
Dr. Alexander Issanin
PD Dr. Bernhard Kaiser
Apl. Prof. Dr. Andreas Klein
Dr. Shunyi Li
Dr- Eric Mankel
Dr. Quanbao Ma
Dr. Thomas Mayer
Dr. Hermann Schimper
Technical Personnel
Dipl.-Ing. Erich Golusda
Kerstin Lakus-Wollny
Christina Spanheimer
Secretaries
Marga Lang
Diploma Students
Alexander Benes
Marc Hänsel
Jan Hellmann
Guest Scientists
Colin Schlosser
Andrew Schultz
Ned Tobin
40
Verena Pfeifer
Christian Scichocki
Surface Science
PhD Students
Dipl.-Ing. Tobais Adler
Dipl.-Ing. Thorsten Bayer
Dipl.-Ing. Dirk Becker
M.Sc. Mercedes Carillo Solano
Dipl.-Phys. Andreas Decker
M.Sc. Mariel Grace Dimamay
M.Sc. Murugasen Eswaran
Dipl.-Ing. Edurad Feldmeier
Dipl.-Ing. Dominic Fertig
Dipl.-Ing. Anne Fuchs
Dipl.-Ing. Jürgen Gassmann
Dipl.-Ing. Cosmina Ghinea
Dipl.-Ing. Corinna Hein
Dipl.,-Ing. René Hock
Dipl.-Ing. Johannes Türck
Dipl.-Ing. Mareike Hohmann
Dipl.-Ing. Juliar Maibach
Dipl.-Ing. Jan Morasch
Dipl.-Ing. Markus Motzko
Dipl.-Ing. Andreas Naumann
Dipl.-Ing. ThiThanh Dung
Nguyen
Dipl.-Ing. Ruben Precht
Dipl.-Ing. Karsten Rachut
Dipl.-Ing. Philip Reckers
Dipl.-Ing. Judith Schaffner
Dipl.-Ing. Anja Schneikart
Dipl.-Ing. Andrè Schwöbel
M. Sc. Sebastian Siol
Dipl.-Ing. Jürgen Zigler
Research Projects
Function and fatigue of conducting electrodes in organic LEDs, SFB 595-D3 (DFG 20032014)
Polarization and charge in electrically fatigued ferroelectrics, SFB 595-B7 (DFG 2007-2014)
Integriertes Graduiertenkolleg SFB 595 (DFG 2008-2014)
Tunable Integrated Components for Microwaves and Optics, Graduiertenkolleg 1037 (DFG
2004-2013)
P-I-N solar cells with alternative highly-absorbing semiconductors (BMBF 2010-2013)
LOEWE Schwerpunkt AdRIA (LOEWE-Hessen: 2008-2013)
Kosteneffiziente Produktionsverfahren für CdTe Solarzellen und kupferfreie Rückkontakte
(CTF Solar 2012 – 2013)
Grenzflächen und dünne Schichten von Ionenleitern: elektronische Struktur,
elektrochemische Potentiale, Defektbildung und Degradationsmechanismen, SFB 595-A3
(DFG 2003-2014)
Verbundprojekt: Morphologie und Elektronische Struktur von Organik/Organik- und
Organik/Metalloxid-Hybridsystemen (MESOMERIE) – Teilvorhaben: Photoelektronen- und
Photoemissionsspektroskopie von Organik/Organik- und Organik/Metalloxid-Hybridsystemen (BMBF 2009 – 2014)
9D-Sense Autonomous Nine Degrees of Freedom Sensor Module (BMBF/VDI 2011 – 2014)
Solid State Lithium Batterien mit organischen Kathoden (Novaled 2011 – 2014)
All Oxide PV (EU 2012 – 2014)
Inverted organic solar cells: Charge carrier extraction and interface characterization (DFG
2012- 2014)
Synthese, Charakterisierung, Testung und Optimierung neuer Katalysatoren auf
Trägermaterialien für photokatalytische Zellen (Unterauftrag Evonik Industries AG
„Science-to-Business Eco2 - Ressourceneffizienz durch stoffliche Nutzung von CO2 und
regenerative Erzeugung von Wasserstoff" H2ECO2 FKZ 005-0908-0085, 2009 - 2012)
Surface Science
41
Netzwerkprojekt „Nanostrukturen zur Licht-induzierten Wasserstoffentwicklung: H2NanoSolar“ (BMBF 03SF0353E, 2009 – 2012)
Photoelectrochemical water splitting using adapted silicon based semiconductor tandem
structures (DFG 2012 – 2015)
Coordination SPP1613 Solar H2 (DFG 2012 – 2015)
Publications
T.J.M. Bayer, A. Wachau, A. Fuchs, J. Deuermeier, A. Klein , Atomic layer deposition of
Al2O3 onto Sn-doped In2O3: Absence of self-limited adsorption during initial growth by oxygen
diffusion from the substrate and band offset modification by Fermi level pinning in Al 2O3,
Chem. Mater. 24, 4503-4510 (2012); doi: 10.1021/cm301732t
S. Li, Y. Zheng, R. Jakoby, and A. Klein , Electrically programmable bistable capacitor for
high frequency applications based on charge storage at the (Ba,Sr)TiO3/Al2O3 interface, Adv.
Fun. Mater. 22, 4827-4832 (2012); doi: 10.1002/adfm.201200405
L. Renard, O. Babot, H. Saadaoui, H. Fuess, J. Brötz, A. Gurlo, E. Arveux, A. Klein, T.
Toupance, Nanoscaled Tin Dioxide Films Processed From Organotin-based Hybrid Materials:
An Organometallic Route Toward Metal Oxide Gas Sensors, Nanoscale 4, 6806-6813 (2012);
doi: 10.1039/c2nr31883k
W. Witte, M. Powalla, D. Hariskos, A. Eicke, H.-W. Schock, D. Abou-Ras, R. Mainz, H.
Rodriguez-Alvarez, T. Unold, G.H. Bauer, R. Brüggemann, S.J. Heise, O. Neumann, M.
Meessen, J. Christen, F. Bertram, M. Müller, A. Klein, T. Adler, K. Albe, J. Pohl, M. Martin,
R.A.D. Souza, L. Nagarajan, T. Beckers, C. Boit, J. Dietrich, M. Hetterich, Z. Zhang, R.
Scheer, H. Kempa, and T. Orgis, Chemical gradient in Cu(In,Ga)(S,Se)2 thin-film solar cells:
Results of the GRACIS project, Proc. 27th European Photovoltaic Solar Energy Conference,
Frankfurt, Germany (2012),
F. Chen, A. Klein, Polarization dependence of Schottky barrier heights at interfaces of
ferroelectrics determined by photoelectron spectroscopy, Phys. Rev. B 86, 094105 (2012); doi:
10.1103/PhysRevB.86.094105
D. Dusciac, . Brize, J.-N.l. Chazalviel, Y.-F. Lai, H. Roussel, S. Blonkowski, R. Schafranek,
A. Klein, C.H. de Villeneuve, P. Allongue, F. Ozanam, C. Dubourdieu , Organic Grafting on
Si for Interfacial SiO2 Growth Inhibition During Chemical Vapor Deposition of HfO2, Chem.
Mater. 24, 3135-3142 (2012); doi: 10.1021/cm301247v
P. S. Hoffmann M. I. Kosinova, S. Flege, O. Baake, B. Pollakowski, V. A. Trunova, A. Klein,
B. Beckhoff, F. A. Kuznetsov, W. Ensinger, Chemical Interactions in the Layered System
BCxNy/Ni(Cu)/Si, Produced by CVD at High Temperature, Analytical and Bioanalytical
Chemistry 404, 479-487 (2012); doi: 10.1007/s00216-012-6177-2
P.S. Hoffmann, O. Baake, M.L. Kosinova, B. Beckhoff, A. Klein, B. Pollakowski, V.A.
Trunova, V.S. Sulyaeva, F.A. Kuznetsov, W. Ensinger, Chemical bonds and elemental
compositions of BCxNy layers produced by chemical vapor deposition with trimethylamine
borane, triethylamine borane, or trimethylborazine, X-ray Spectrometry 41, 240-246 (2012);
doi: 10.1002/xrs.2387
P. S. Hoffmann, N. Fainer, O Baake, M. Kosinova, Y. Rumyantsev, V. Trunova, A. Klein, B.
Pollakowski, B. Beckhoff, W. Ensinger, Silicon Carbonitride Nanolayers - Synthesis and
Chemical Characterization, Thin Solid Films 520, 5906-5913 (2012); doi: 10.1016/
j.tsf.2012.04.082
42
Surface Science
D. Proffit, S. P. Harvey , A. Klein , R. Schafranek , J. D. Emery , D. B. Buchholz , R. P. H. Chang,
M. J. Bedzyk, T. O. Mason, Surface Studies of Crystalline and Amorphous Zn-In-Sn-O (ZITO)
Transparent Conducting Oxides, Thin Solid Films 520, 5633-5639 (2012); doi: 10.1016/
j.tsf.2012.04.075
J. Gassmann, J. Brötz, A. Klein, Sputter deposition of indium tin oxide onto zinc
phtalocyanine: Chemical and electronic properties of the interface studied by photoelectron
spectroscopy, Applied Surface Science 258, 3913-3919 (2012); doi: 10.1016/
j.apsusc.2011.12.062
A. Klein Energy band alignment at interfaces of semiconducting oxides: A review of
experimental determination using photoelectron spectroscopy and comparison with theoretical
predictions by the electron affinity rule, charge neutrality levels, and the common anion rule
Thin Solid Films 520, 3721-3728 (2012); doi: 10.1016/j.tsf.2011.10.055
U-C. Chung, D. Michau, C. Elissalde, S. Li, A. Klein, M. Maglione, Evidence of diffusion at
BaTiO3/Silicon interfaces, Thin Solid Films 520, 1997-2000 (2012); doi:
10.1016/j.tsf.2011.09.055
Hock, Rene; Mayer, Thomas; Jaegermann, Wolfram, p-Type Doping of Spiro-MeOTAD with
WO3 and the Spiro-MeOTAD/WO3 Interface Investigated by Synchrotron-Induced
Photoelectron Spectroscopy, JOURNAL OF PHYSICAL CHEMISTRY C 116 18146-18154
DOI: 10.1021/jp301179v ( 2012)
Thomas Mayer, Corinna Hein, Eric Mankel, Wolfram Jaegermann, Mathis M. Müller, HansJoachim Kleebe, Fermi level positioning in organic semiconductor phase mixed composites: The
internal interface charge transfer doping model, ORGANIC ELECTRONICS 13 1356-1364
DOI: 10.1016/j.orgel.2012.03.028 ( 2012)
Lucangelo Dimesso, Dirk Becker, Christina Spanheimer, Wolfram Jaegermann, Investigation
of graphitic carbon foams/LiNiPO4 composites, Journal of Solid State Electrochemistry 16
3791-3798 ( 2012)
Dimesso, L; Jacke,; Spanheimer, C; Jaegermann, W , Investigation on LiCoPO4 powders as
cathode materials annealed under different atmospheres , JOURNAL OF SOLID STATE
ELECTROCHEMISTRY 16 911-919 DOI: 10.1007/s10008-011-1441-5 ( 2012)
Dimesso, L; Cherkashinin, G, Spanheimer, C; Jaegermann, W , Preparation and
characterization of carbon foams-LiCoPO4 composites, JOURNAL OF ALLOYS AND
COMPOUNDS 516 119-125 DOI: 10.1016/j.jallcom.2011.11.147 ( 2012)
Dimesso, L; Spanheimer, C; Jaegermann, W; Zhang, Y ; Yarin, AL , LiFePO4-3D carbon
nanofiber composites as cathode materials for Li-ions batteries, JOURNAL OF APPLIED
PHYSICS 111 064307 DOI: 10.1063/1.3693575 ( 2012)
Pfanzelt, M ; Kubiak, P; Jacke, S; Dimesso, L; Jaegermann, W; Wohlfahrt-Mehrens, M , SEI
Formation on TiO2 Rutile, JOURNAL OF THE ELECTROCHEMICAL SOCIETY 159 A809A814 DOI: 10.1149/2.085206jes ( 2012)
Surface Science
43
Tamez Uddin , Yohann Nicolas , Céline Olivier , Thierry Toupance , Laurent Servant, Mathis
M. Müller , Hans-Joachim Kleebe , Jürgen Ziegler , and Wolfram Jaegermann,
Nanostructured SnO2-ZnO Heterojunction Photocatalysts Showing Enhanced Photocatalytic
Activity for the Degradation of Organic Dyes, INORGANIC CHEMISTRY 51 7764-7773 DOI:
10.1021/ic300794j ( 2012)
L. Dimesso , C. Förster , W. Jaegermann , J. P. Khanderi , H. Tempel , A. Popp , J.
Engstler , J. J. Schneider , A. Sarapulova , D. Mikhailova , L. A. Schmitt , S. Oswald and
H. Ehrenberg, Developments in nanostructured LiMPO4 (M = Fe, Co, Ni, Mn) composites
based on three dimensional carbon architecture, CHEMICAL SOCIETY REVIEWS 41 50685080 DOI: 10.1039/c2cs15320c ( 2012)
Quan-Bao Ma, Bernhard Kaiser, Jürgen Ziegler, Dominic Fertig and Wolfram Jaegermann,
XPS characterization and photoelectrochemical behaviour of p-type 3C-SiC films on p-Si
substrates for solar water splitting, JOURNAL OF PHYSICS D: APPLIED PHYSICS 45, 325101
(2012); doi:10.1088/0022-3727/45/32/325101
J. Ziegler, D. Fertig, B. Kaiser, W. Jaegermann, M. Blug, S. Hoch, and J. Busse, Preparation
and Characterization of GaP Semiconductor Electrodes for Photoelectrochemical Water
Splitting, ENERGY PROCEDIA 22, 108 (2012); doi: 10.1016/j.egypro.2012.05.220
Bernhard Kaiser, Dominic Fertig, Jürgen Ziegler, Joachim Klett, Sascha Hoch, Wolfram
Jaegermann, Solar Hydrogen Generation with Wide-Band-Gap Semiconductors: GaP(100)
Photoelectrodes and Surface Modification, CHEMPHYSCHEM 13, 3053 (2012); doi:
10.1002/cphc. 201200432
Dimesso, L; Spanheimer, C; Jaegermann , Investigation on graphitic carbon foams - LiNiyPO4
(y=0.8-1.0) composites, SOLID STATE SCIENCES 14 1372-1377 DOI: 10.1016/j.
solidstatesciences.2012.07.023 ( 2012)
Cherkashinin, G; Nikolowski, K; Ehrenberg, H; Jacke, S; Dimesso, L; Jaegermann, W, The
stability of the SEI layer, surface composition and the oxidation state of transition metals at
the electrolyte-cathode interface impacted by the electrochemical cycling: X-ray photoelectron
spectroscopy investigation, PHYSICAL CHEMISTRY CHEMICAL PHYSICS 14 12321-12331
DOI: 10.1039/c2cp41134b ( 2012)
JAEGERMANN W; MAYER T, Arrangement for a composite made of inorganic matrix and
embedded organic phase as optoelectronic active medium in light-emitting diode or other e.g.
light emitting transistors, where an organic dye is embedded in an inorganic materia l, Patent
Number: DE102010025991-A1, Patent Assignee: TU DARMSTADT
44
Surface Science
Synchrotron Induced Photoelectron Spectroscopy on Drop Casted Photovoltaic
Donor/Acceptor Bulk Heterojunction : Orbital Energy Line Up in DH6T/PCBM Blends
Julia Maibach a,b, Eric Mankel a,b, Thomas Mayer a,b*, and Wolfram Jaegermann a,b
Institute of Material Science, TU-Darmstadt, b InnovationLab GmbH, Heidelberg
a
High resolution synchrotron-induced photoelectron spectroscopy (SXPS) is most valuable in
determining the electronic properties of semiconductors (SC) and their interfaces. Applying
SXPS to organic SCs prepared from solution is hindered by the pressure gap of preparation
and UHV analysis. With this work we show, that i) thin organic SC films can be prepared
from solution with little enough conta mination to analyze their electronic structure with
highest surface sensitivity, ii) the electronic structure of solution processed organic SC
interfaces can be determined using bulk heterojunction systems (BHJ), and iii) for the
specific donor acceptor system -Dihexylsexithiophene (DH6T) / Phenyl-C61-butyric acid
methyl ester (PCBM) the HOMO line-up changes from 0.94 eV of the pristine materials
comparing their ionization energies to 0.69 eV in the BHJ blend, indicating the formation of
interface dipole potentials. In addition, disproportionate spectral intensities indicate DH6T
surface enrichment in the blend.
Figure 1. Chemical structure of DH6T and PCBM (top). The deposition of these materials from solution was
integrated to the UHV analysis system. Dissolved materials are drop casted at atmospheric pressure under
inert gas. The films are dried in an inert gas jet and directly transferred into the UHV buffer chamber also
vented with inert gas.
Surface Science
45
Results and Discussion
In the O1s spectrum (Figure 2 a) of the pristine PCBM film two oxygen species are clearly
distinguished at 532.4 and 533.8 eV binding energy that are assigned to C=O and C-O-CH3
sites, respectively. In the blend spectrum the PCBM O1s emission is superimposed by O1s
emission from the ITO substrate. This indicates either a reduced film thickness compared to
the pristine material films or a change in film morphology leading to the formation of pin
holes. Due to the low signal to noise ratio and the superimposed ITO emission, O1s binding
energies cannot be unambiguously derived for the blend.
The DH6T S2p emission is clearly resolved as a spin-orbit split doublet (Figure 2 b). The
binding energy of the S2p 3/2 emission is 164.0 eV for pristine DH6T and shifts by 0.1 eV
to lower binding energy in the blend.
Figure 2. a) O1s emission at h = 600 eV excitation energy of the ITO substrate (displayed decreased to 1/5),
PCBM, the PCBM/DH6T blend from 50:50 mixed solution (displayed increased by 5x), and DH6T. In the blend
spectrum emissions of PCBM and ITO substrate are superimposed. b) Corresponding S2p emission at h =
210eV. The S2p doublet is clearly resolved and shifts 0.1 eV to lower binding energy in the blend.
The secondary emission onsets and the valance regions of PCBM, DH6T, and the blend are
shown in Figure 3 a) and b). Due to the high quality of the valence level spectra of the
pristine materials and the blend, difference spectra could be calculated, which are included
in Figure 3 b.
46
Surface Science
Figure 3 a) Secondary electron cutoff and b) valence band spectra of PCBM, the PCBM/DH6T blend, and
DH6T. In b) difference spectra are added that show the emissions of DH6T respective PCBM in the blend.
Work function values and HOMOonset leading edge positions are indicated. Spectra taken are at at hv = 90 eV.
The measured electronic structures are summarized in the energy level line-up diagram Figure 4. Thus the
HOMO energy difference of 0.94 eV in the vacuum level line up reduces to 0.69 eV in the blend, indicating the
formation of a 0.25 eV dipole potential at internal donor/acceptor interfaces.
Figure 4. Electronic structure of pristine DH6T and PCBM films and the energy level line-up in the blend
referenced to common vacuum level. Blend surface and work function are dominated by DH6T. HOMO LUMO
energy gaps are taken from literature.
Surface Science
47
Tandem cells based on silicon for photoelectrochemical water splitting
Bernhard Kaiser, Wolfram Calvet, Eswaran Murugasen and Wolfram Jaegermann
The storage of renewable energies is one of the foremost scientific and engineering
challenges for the coming years, esp. with regard to the planned energy policy in Germany.
To store large amounts of energy chemical compounds, e.g. gasoline and gas, have been
used in the past, because they possess a high energy density and they can easily and
securely be stored and distributed. A similar scheme has to be developed for the storage of
energy from wind and solar radiation. The simplest chemical compound for this task is
hydrogen, which can be easily obtained by the electrolysis of water. To improve the
efficiency of this process, we investigate photovoltaic absorbers, which are used directly to
split water without the need of complicated electronic control units. Since the minimum
energy needed for the generation of hydrogen and oxygen from water is E°= 1.23 eV, a
single absorber material will not be sufficient. Therefore we use a tandem cell design based
on earth abundant silicon, which has been supplied by the FZ Jülich1. The basic setup is
shown in figure 1 (pat. pend.):
UV
-
VIS
-
IR
quantum efficiency
1.0
0.8
0.6
0.4
400
600
800
1000
wavelength (nm)
b)
30x10
bottom
cell
0.2
0
a)
top
cell
-3
illuminated
dark
25
20
OCP = 1.32 V
F.F. = 73.86
 = 9.53 %
ISC= -9.77 mA
Current [A]
15
10
5
0
-5
-10
0.0
c)
0.5
1.0
1.5
Voltage [V]
Fig. 1: a) Schematics of the employed experimental setup. b) Absorption and c) photovoltaic characteristics
(AM 1.5) of the tandem cell.
The tandem cell is used as the cathode in a standard three-electrode electrochemical setup
with a platinum counter and an Ag/AgCl counter electrode. Light rays enter the cell from
the outside, which has the advantage that the light path is unobstructed by bubbles and
light scattering at interfaces and light absorbtion by the electrolyte is avoided. The
electrolyte side of the cell is covered by a thin silver layer, which reflects the incoming light
48
Surface Science
to increase the absorption efficiency and at the same time acts as a buffer layer to shield the
absorber material from the electrolyte and transfers the photoexcited electrons to the redox
couple in solution. The photovoltaic efficieny of the cell is nearly 10% at 1.2 V and 8 mA.
a)
b)
Fig. 2: a) Cyclic voltammogram of the tandem cell under chopped light without modifications. b) SEM picture
showing the topography of the silver layer side of the cell.
From the cyclic voltammogram (figure 2a) an efficiency for photon to current conversion of
about 7% in electrochemical environment is calculated, but also a large loss in photovoltage
due to bad charge transfer characteristics is observed. Therefore, platinum is
electrochemically deposited as catalyst for the hydrogen evolution reaction onto the silver
layer of the tandem cell. The platinum forms nanoparticles with a tube like shape as is
observed from the electron microscope image in figure 3 b). They lead to a much improved
electrochemical behavior as can be seen from figure 3 a).
a)
b)
Fig. 3: a) Cyclic voltammogram of the tandem cell under chopped light with Pt catalyst nanoparticles. b) SEM
picture showing the form of the Pt nanoparticles on the silver layer of the cell.
Further work will investigate on how the efficiency depends on particle form and size and
how to improve the long-term stability of such devices. Additionally cheaper and more
abundant material will be examined to replace the expensive platinum catalyst in the
present device.
References:
[1]
S. Pust, F. Finger, U. Rau; Institut für Energie- und Klimaforschung IEK-5: Photovoltaik,
Forschungszentrum Jülich GmbH.
Surface Science
49
Advanced Thin Film Technology
The Advanced Thin Film Technology (ATFT) group works on advanced thin film deposition
techniques of novel materials. The group is specialized on physical vapor deposition
techniques such as pulsed laser deposition (PLD), advanced oxide molecular beam epitaxy
(ADOMBE) and dc/rf-magnetron sputtering. The ADOMBE system is an in-house
development and has been jointly financed by Max-Planck-Institute for Solid State Research
in Stuttgart and TU Darmstadt. PLD and ADOMBE are part of a cluster system allowing for
in-situ sample exchange between the different deposition methods and characterization
tools. The ADOMBE apparatus is a worldwide unique thin film deposition system which is
dedicated to the growth of complex oxides beyond thermodynamic equilibrium. It allows
for the simultaneous deposition of six elements from electron beam sources and further
elements evaporated from effusion cells. The molecular beams of each element can be
individually controlled by a feed back loop using electron impact emission spectroscopy.
The group is working mainly on oxide ceramics which show a stunning variety of new
functional properties. Examples are high-temperature superconductors, magnetic oxides for
spintronics, high-k dielectrics, ferroelectrics, and novel thermoelectric materials. As a vision
for future, new solid state matter can be created by building hetero- and composite
structures combining different oxide materials. While present day electronic devices heavily
rely on conventional semiconducting materials, a future way to create novel functional
devices could be based (completely) on oxide electronics.
The group uses a Rigaku SmartLab X-ray thin film diffractometer with rotating anode
("synchrotron in house"). Other characterization tools located in the Advanced Thin Film
Technology group include powder X-ray diffraction (XRD), X-ray photoemission
spectroscopy (XPS), high-resolution scanning electron microscopy (HREM) with light
element sensitive EDX, and SQUID magnetometry. A 16 Tesla magnet cryostat allowing
measurements down to liquid helium temperature has been installed. Another magnet
cryostat (10 T) lowers the available temperature range to below 300 mK. This cryostat also
contains high-frequency feed-throughs for electrical characterization (40 GHz). The group
is also using external large scale facilities as synchrotron radiation (ESRF, Grenoble) and
neutron reactors (ILL, Grenoble / HMI and DESY, Berlin) for advanced sample
characterization.
Close cooperation exists in particular with the Max-Planck-Institute for Solid State Research
in Stuttgart, with the Japanese company NTT in Atsugi near Tokio, with the University of
Tokio, and Chalmers University of Technology.
Throughout 2012 Lambert Alff was working also as a Dean of Studies in the faculty of
Materials Science and head of the Graduate School Materialium. Lambert Alff has also
worked as an elected a member of the Senat of TU Darmstadt.
Staff Members
Head
Research Associates
Technical Personnel
Secretary
PhD Students
50
Prof. Dr. Lambert Alff
Dr. Anastasiya Kolchynska
Dr. Jose Kurian
Dipl.-Ing. Gabi Haindl
Marion Bracke
Dipl.-Ing. Mani Arzhang
Dipl.-Ing. Alexander Buckow
Dipl.-Ing. Erwin Hildebrandt
Dipl.-Ing. Aldin Radetinac
BTech. Vikas Shabadi
Dipl. Chem. Mehran Vafaee
Dr. Philipp Komissinskiy
Jürgen Schreeck
Dipl.-Ing. Mehrdad Baghaie
Dipl.-Ing. Stefan Hirsch
Dipl.-Ing. Sandra Hildebrandt
Dipl. Phys. Reiner Retzlaff
MTech. Sharath Ulhas
Research Projects
Superconductivity in water intercalated NaxCoO2 thin films (TU Darmstadt, TU
Braunschweig, and Max-Planck-Institute for Solid State Research, Stuttgart) (DFG 2006-2012)
Superconductivity and magnetism in the phase diagram of bulk La2-xCexCuO4±δ
investigated by muon-spin spectroscopy and neutron scattering (TU Darmstadt, PSI,
Helmholtzzentrum Berlin) (DFG 2009-2012)
Novel arsenic free pnictide superconductors (SPP 1458) (DFG 2010 - 2012)
Doped SrTiO3 for Microwave Applications and Multiferroics as novel materials for tunable
components, within DFG Research Training Group 1037 “Tunable Integrated Components
in Microwave Technology and Optics” (DFG 2008-2012)
LOEWE-Centre AdRIA: Adaptronik – Research, Innovation, Application (HMWK 2011 - 2014)
Oxide-MBE (MPI-FKF/TUD 2007-2012)
Publications
Erwin Hildebrandt, Jose Kurian, and Lambert Alff. Physical properties and band structure of
reactive molecular beam epitaxy grown oxygen engineered HfO2±x., J. Appl. Phys. 112,
114112 (2012).
Daniel Edward Walker , Marton Major , Mehrdad Baghaie Yazdi , Andreas Klyszcs , Marc
Haeming , Klaus Bonrad , Christian Melzer , Wolfgang Donner , and Heinz Von Seggern,
High mobility indium zinc oxide thin film field-effect transistors by semiconductor layer
engineering., ACS Appl. Mater. Interfaces, 2012, 4 (12), pp 6835–6841
Alexander Buckow, Katharina Kupka, Reiner Retzlaff, Jose Kurian, and Lambert Alff,
Superconducting epitaxial thin films of CeNixBi2 with a bismuth square net structure., Appl.
Phys. Lett. 101, 162602 (2012)
S. Hildebrandt, T. Kober, R. Werthschützky, L. Alff., Kristobalitbildung (SiO2) im
Herstellungsprozess überlastfester Differenzdrucksensoren, 16. GMA/ITG-Fachtagung
Sensoren und Messsysteme 2012, Nürnberg, Germany
Sandra Hildebrandt, Andreas Eva, Philipp Komissinskiy, Claudia Fasel, Ingo Fritsch und
Lambert Alff., Sol–gel synthesis of sodium and lithium based materials., J. Sol-Gel Sci Technol
(2012) 63:307-314
A. Kolchinskaya, P. Komissinskiy, M. Baghaie Yazdi, M. Vafaee, D. Mikhailova, N.
Narayanan, H. Ehrenberg, F. Wilhelm, A. Rogalev, and L. Alff., Magnetism and spin-orbit
coupling in Ir-based double perovskites La2−xSrxCoIrO6., Phys. Rev. B 85, 224422 (2012)
M. Kayhan, E. Hildebrandt, M. Frotscher, A. Senyshyn, K. Hofmann, L. Alff, B. Albert.
Neutron diffraction and observation of superconductivity for tungsten borides, WB and W2B4.,
Solid State Sciences 14 (2012) 1656-1659
A. Buckow, R. Retzlaff, J. Kurian, L. Alff. , MBE growth of LaNiBiO1-x thin films., Physics
Procedia 27 ( 2012 ) 300 – 303
H. A. Davani, B. Kögel, P. Debernardi, C. Grasse, C. Gierl, K. Zogal, Å. Haglund, J.
Gustavsson, P. Westbergh, T. Gründl, P. Komissinskiy, T. Bitsch, L. Alff, F. Küppers, A.
Larsson, M.-C. Amann and P. Meissner., Polarization investigation of a tunable high-speed
short-wavelength bulk-micromachined MEMS-VCSEL., Proc. SPIE 8276, 82760T (2012)
Lambert Alff, Andreas Klein, Philipp Komissinskiy, and Jose Kurian., Vapor phase deposition
of oxides., Ceramics Science and Technology, Volume 3: Synthesis and Processing, R. Riedel
and I.-W. Chen eds., 267-289, Published 2012 by Wiley-VCH Verlag GmbH, Weinheim,
Germany
51
Dispersive Solids
The main research interests of the group Dispersive Solids are directed towards the
development of novel strategies suitable for the synthesis of inorganic, oxidic and nonoxidic materials with properties beyond the state of the art. The materials of interest are
advanced oxidic and non-oxidic ceramics with extraordinary properties in terms of thermal
stability, hardness and electronic structure. Therefore, synthesis methods such as polymerpyrolysis, non-oxidic and oxidic sol-gel methods, chemical vapour deposition and novel
high pressure methods have been further developed.
The following topical issues are presently under investigation:
Polymer-Derived Ceramics
The thermolytic decomposition of suitable organosilicon polymers provides materials which
are denoted as polymer-derived ceramics (PDCs). The main emphasis is on the synthesis
and characterization of new ceramic materials in the B-C-N, Si-C-N, Si-O-C, Si-(B,C)-N and
Ti-(B-C)-N systems. The structural peculiarities, thermochemical stability, mechanical and
electrophysical properties of the PDCs have been investigated in a series of PhD theses and
research projects. Due to their outstanding thermochemical stability as well as excellent
oxidation and creep resistance at very high temperatures, the PDCs constitute promising
materials for high temperature applications. Another advantage of the PDC route is that the
materials can be easily shaped in form of fibres, layers or bulk composite materials.
Finally the correlation of the materials properties with the molecular structure of the used
preceramic polymer is elaborated
Molecular Routes to Nanoscaled Materials
The aim is to develop concepts for the production of novel multifunctional inorganic
materials with a tailor-made nanoscaled structure. In accordance with the so-called
“bottom-up” approach, specific inorganic molecules are to be assigned to higher molecular
networks and solid-state structures in the form of molecular nanotools by means of
condensation and polymerisation processes.
High Pressure Chemistry
Ultra-high pressure techniques like laser heated diamond anvil cell (LH-DAC) or multi anvil
devices have been applied to synthesise novel solid state structures which cannot be
produced by other methods, for example, inorganic nitrides. Moreover, the materials
behaviour under pressure such as phase transformations and decomposition can be
analysed.
Functional Materials
Further research topics are related to the development of materials suitable for applications
in the fields of microelectromechanical systems (MEMS), optoelectronics (LEDs), pressure,
temperature and gas sensors as well as thermoresistant ceramic membranes for high
temperature gas separation.
The integration of state-of-the-art in situ and in operando spectroscopic methods is applied
to understand the mechanisms responsible for sensing and catalytic properties.
52
Dispersive Solids
Staff Members
Head
Prof. Dr. rer. nat. habil. Prof. h. c. Dr. h. c. Ralf Riedel
Research Associates
Dr. Dmytro Dzivenko
Dr. Magdalena Graczyk-Zajac
Dr. Aleksander Gurlo
Dr. Emanuel Ionescu
Technical Personnel
Dipl.-Ing. Claudia Fasel
Secretaries
Su-Chen Chang
Natallia Hurlo (substitute)
Tania Fiedler-Valderrama (EU project)
PhD Students
Dipl.-Ing. Miria Andrade
M. Sc. Shrikant Bhat
M. Tech. Maged Bekheet
M. Tech. Yan Gao
M. Sc. Sarabjeet Kaur
Dipl.-Ing. Jan Kaspar
Dipl.-Ing. Amon Klausmann
M. Sc. Wenjie Li
Dipl.-Ing. Christoph Linck
Dipl.-Ing. Benjamin Papendorf
M. Tech. Ravi Mohan Prasad
Dipl.-Ing. Lukas Mirko Reinold
M. Sc. Cristina Schitco
M. Tech. Mahdi Seifollahi
Bazarjani
Dipl.-Ing. Alexander Uhl
M. Sc. Qingbo Wen
M. Sc. Jia Yuan
M. Sc. Cong Zhou
Dr. Gabriela Mera
Prof. Dr. Norbert Nicoloso
Dr. Ravi Mohan Prasad
Dr. Monika Wilamowska
Diploma and Master Sarah Jahn
Students
Michael Krämer
Kerstin Krause
Bernd Mainzer
Ivo Nemetz
Caglar Terzioglu
Bachelor Students
Daniel Bick
Hanna Verena Heyl
Guest Scientists
Dr. Xingang Luan, Associate Professor, Northwestern University
Polytechnical, Schule für Materialien, Xian, Shaanxi, PR China
Prof. Kathy Lu,Virginia Tech, College of Engineering, Department
of Materials Science and Engineering, Blacksburg, USA
Akikazu Fujiwara, Department of Frontier Materials, Graduate
School of Engineering, Nagoya Institute of Technology, Nagoya,
Japan
Pradeep Vallachira, Department of Materials Engineering and
Industrial Technology, University of Trento, Trento, Italy
Dr. Dagmar Galusková, VILA – Joint Glass Centre of the IICh SAS,
TnU AD, FChFT STU, RONA j.s.c., Trencin, Slovakia
Dispersive Solids
53
Michal Vetrecin, Institute of Inorganic Chemistry, Slovak
Academy of Sciences, Bratislava, Slovakia
Ondrej Hanzel, Institute of Inorganic Chemistry, Slovak Academy
of Sciences, Bratislava, Slovakia
Dr. Katja König, Department of Biotechnology, Chemistry and
Environmental Engineering / Section of Chemistry, Aalborg
University, Denmark
Mr. Ali Farsi, Department of Biotechnology, Chemistry and
University, Denmark
Prof. Vittorio Boffa, Department of Biotechnology, Chemistry and
University, Denmark
Duan Li, Department of Materials and Environmental Chemistry,
Arrhenius Laboratory Stockholm University, Stockholm, Sweden
Dr. Kiyoshi Kanamura, Department of Applied Chemistry,
Graduate School of Urban Environmental Sciences, Tokyo
Metropolitan University, Tokyo, Japan
Prof. Dr. Corneliu Balan, Politehnica, University of Bucharest,
Faculty of Enegetics, Hydraulics Departement, Bucharest,
Romania
Jai Seoung Chung, University of Illinois at Urbana-Champaign, IL,
USA
Yohei Shimokawa, Department of Frontier Materials Graduate
School of Engineering, Nagoya Institute of Technology, Nagoya,
Japan
Yuji Masubuchi, Faculty of Engineering, Hokkaido University,
Japan
Dr. Eng. Koji Morita, National Institute for Materials Science,
Ibaraki, Japan
54
Dispersive Solids
Research Projects
SiHfC(N) and SiHfN(C)-based Ultrahigh-Temperature Ceramic Nanocomposites (UHTCNCs) for EBC/TBC Applications (China Council Scholarship (CSC), Oct. 2012 - Oct. 2016)
Ternary M-Si-N Ceramics: Single-Source-Precoursor Synthesis and Microstructure
Characterization (M = transition metal) (China Council Scholarship (CSC), Nov. 2012 Nov. 2015)
Molecular Routes to SiMBCN Ceramic Nanocomposites (M = Zr, HF) (China Council
Scholarship (CSC), Donghua University, Shanghai, China, Sep. 2011 - Aug. 2015)
FUNEA-Functional Nitrides for Energy Applications (Coordination, EU - Marie Curie Initial
Training Network, Feb. 2011 - Jan. 2015)
Novel functional ceramics with substitution of anions in oxidic systems (DFG, SFB 595,
project A4, Jan. 2003 - Dec. 2014)
Adaptronik – Research, Innovation, Anwendung (HMWK-Loewe-AdRIA, Oct. 2008 - Sep.
2014)
Keramische SiCN-basierte Hartstoffschichten für thermisch hochbeanspruchte Substratwerkstoffe (DFG, June 2011 - June 2014)
High-Pressure High Temperature Synthesis of Novel Binary and Ternary Superhard Phases
in the B-C-N System (DFG, Feb. 2011 - Jan. 2014)
Polymer-Processing of Dense and Crack-Free SiC Monoliths (Doctor Thesis, Oct. 2011 - Sep.
2014)
FUNEA - Gas seperation membranes (EU - Marie Curie Initial Training Network, Oct. 2011 Sep. 2014)
FUNEA - Multifunctional perovskite nitrides (EU - Marie Curie Initial Training Network,
Oct. 2011 - Sep. 2014)
Thermoresistant Ceramic Membrane with Integrated Gas Sensor for High Temperature
Separation and Detection of Hydrogen and Carbon Monoxide (DFG, Aug. 2010 - July 2013)
Nanocomposites as anode materials for lithium ion batteries: Synthesis, thermodynamic
characterization and modeling of nanoparticular silicon dispersed in SiCN(O) and SiCObased matrices (DFG, Aug. 2010 - July 2013)
PrintSens: Nanoskalige gedruckte Hybridmaterialien als aktive Funktionselemente in
mikrostrukturierteen Sensorbauteilen (Schwerpunkt Mikrosystemtechnik im Förderprogramm "IKT 2020 - Forschung für Innovationen" (BMBF VDI/VDE/IT, Jan. 2011 - June
2013)
Dispersive Solids
55
Schwerpunkt Mikrosystemtechnik im Förderprogramm "IKT 2020 - Forschung für
Innovationen" (BMBF VDI/VDE/IT, Jan. 2011 - June 2013)
Synthesis and characterization of rare-earth cation-doped silicon carbonitride phosphors
(International Training Program of JSPS, May 2012 – April 2012)
Nanostructure and Calorimetry of Amorphous SiCN and SiBCN (DFG, April 2010 - March
2013)
Photoluminescence of rare-earth cation-doped carbonitrides (International Training
Program of JSPS, Sep. 2012 - Dec. 2012)
Neuartige polymerabgeleitete keramische Nanokomposite als Thermoelektrika (Diploma
Thesis, May 2012 - Nov. 2012)
In situ Raman-spektroskopische Untersuchungen an SiOC-Keramiken unter thermischer
und mechanischer Blastung (Diploma Thesis, May 2012 - Nov. 2012)
Molekulare Synthesemethoden zu Si3N4/MN-basierten Keramik-Nanokompositen (M = Zr,
HF) (Diploma Thesis, May 2012 - Nov. 2012)
Synthesis, nanostructure and applications of metal carbodiimides (founded by NIMS,
Japan, Nov. 2010 - Oct. 2012)
Synthese und Charakterisierung ZnOxNy-basierter Materialien (Bachelor Thesis, May 2012 Sep. 2013)
International Workshop on Spinel-Nitrides and Related Materials, Rüdesheim (DFG, Aug.
2012 - Sep. 2012)
Polymer-Derived SiOC/SiCN – Metal Oxide Ceramic Nanocomposites as Potential Anode
Materials for Li-Ion Batteries (Master Thesis FAME, March 2012 - Aug. 2012)
Feasibility Study PDC SiC (Xycarb Ceramics bv, Jan. 2012 - July 2012)
Non Aqueous Sol-Gel Synthesis of Boron Carbide Based Materials (US Army International
Technolog, Aug. 2009 - June 2012)
Indium oxide (In2O3) under high pressure: rational design of new polymorphs and
characterisation of their physico-chemical properties (DFG, June 2009 - May 2012)
Herstellung
und
Charakterisierung
polymerabgeleiteter
Nanokomposite (Diploma Thesis, Dec. 2011 - June 2012)
Siliciumoxycarbid/CNT-
Adhäsionsverhalten oberflächenfunktionalisierter Partikel durch kovalente Immobilisierung
mit Hilfe von Click-Chemie (Diploma Thesis, Nov. 2011 - May 2012)
56
Dispersive Solids
Herstellung und Charakterisierung Sol-Gel-basierter SiOx/GO-Komposite (Bachelor Thesis,
Dec. 2011 - March 2012)
Unterstützung Exzellenzprojekte (Dezernat Forschung, Jan. 2010 - Jan. 2012)
Publications
L. Renard; O. Babot; H. Saadaoui; H. Fuess; J. Brötz; A. Gurlo; E. Arveux; A. Klein; T.
Toupance; Nanoscaled tin dioxide films processed from organotin-based hybrid materials: an
organometallic route toward metal oxide gas sensors; NANOSCALE, 4(1) (2012) 6806-6813.
E. Kayhan; R.M. Prasad; A. Gurlo; O. Yilmazoglu; J. Engstler; E. Ionescu; S. Yoon; A.
Weidenkaff; J.J. Schneider; Synthesis, Characterization, Electronic and Gas-Sensing
Properties towards H2 and CO of Transparent, Large-Area, Low-Layer Graphene; CHEMISTRY
– A EUROPEAN JOURNAL, 18(47) (2012) 14996–15003.
J. Kaspar; M. Graczyk-Zajac; R. Riedel; Carbon-rich SiOC anodes for lithium-ion batteries:
Part II. Role of thermal cross-linking; SOLID STATE IONICS, 225 (2012) 527–531.
M. Graczyk-Zajac; L. Toma,; C. Fasel; R. Riedel; Carbon-rich SiOC anodes for lithium-ion
batteries: Part I. Influence of material UV-pre-treatment on high power properties; SOLID
STATE IONICS, 225 (2012) 522–526.
S. Hildebrandt; A. Eva; P. Komissinskiy; C. Fasel; I. Fritsch; L. Alff; Sol–gel synthesis of
sodium and lithium based materials; JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY,
63 (2012) 307-314.
W. Li; A. Gurlo; E. Ionescu; R. Riedel; Perovskite Structure Stability in Metal Oxynitrides;
ZEITSCHRIFT FÜR ANORGANISCHE UND ALLGEMEINE CHEMIE, 638(10) (2012) 1631.
E. Ionescu; J. Yuan; B. Mainzer; H.-J. Kleebe; R. Riedel; Synthesis of Ultrahigh-Temperature
Stable Hafnium-Containing Ceramic Nanocomposites; ZEITSCHRIFT FÜR ANORGANISCHE
UND ALLGEMEINE CHEMIE, 638(10) (2012) 1557.
R. Riedel; Nanoscaled inorganic materials by molecular design; CHEMICAL SOCIETY
REVIEWS, 41(15) (2012) 5029-5031.
E. Ionescu; H.-J. Kleebe; R. Riedel; Silicon-containing polymer-derived ceramic
nanocomposites (PDC-NCs): preparative approaches and properties; CHEMICAL SOCIETY
REVIEWS, 41(15) (2012) 5032-5052.
P. Dibandjo; M. Graczyk-Zajac; R. Riedel; V.S. Pradeep; G.D. Soraru; Lithium insertion into
dense and porous carbon-rich polymer-derived SiOC ceramics; JOURNAL OF THE EUROPEAN
CERAMIC SOCIETY, 32(10) (2012) 2495–2503.
Dispersive Solids
57
H.-J. Kleebe; K. Nonnenmacher; E. Ionescu; R. Riedel; Decomposition-Coarsening Model of
SiOC/HfO2 Ceramic Nanocomposites Upon Isothermal Anneal at 1300 °C; JOURNAL OF THE
AMERICAN CERAMIC SOCIETY, 95(7) (2012) 2290-2297.
C. Neetzel; T. Gasi; V. Ksenofontov; C. Felser; E. Ionescu; W. Ensinger; Electroless synthesis
of lepidocrocite (γ-FeOOH) nanotubes in ion track etched polycarbonate templates; NUCLEAR
INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTIONB-BEAM INTERACTIONS
WITH MATERIALS AND ATOMS, 282 (2012) 96–99.
Y. Gao; G. Mera; H. Nguyen; K. Morita; H.-J. Kleebe; R. Riedel; Processing route
dramatically influencing the nanostructure of carbon-rich SiCN and SiBCN polymer-derived
ceramics. Part I: Low temperature thermal transformation; JOURNAL OF THE EUROPEAN
CERAMIC SOCIETY, 32(9) (2012) 1857–1866.
E. Ionescu; B. Papendorf; H.-J. Kleebe; H. Breitzke; K. Nonnenmacher; G. Buntkowsky; R.
Riedel; Phase Separation of a Hafnium Alkoxide-Modified Polysilazane upon Polymer-toCeramic Transformation – A Case Study; JOURNAL OF THE EUROPEAN CERAMIC
SOCIETY, 32(9) (2012) 1873–1881.
M. Seifollahi Bazarjani; S. Foro; W. Donner; A. Gurlo; R. Riedel; trans-Bis(acetato-κO)bis(2aminoethanol-κ2N,O)nickel(II), ACTA CRYSTALLOGRAPHICA SECTION E, E86 (2012)
m567-m568.
M. Hojamberdiev; R.M. Prasad; K. Morita; Y. Zhu; M.A. Schiavon; A. Gurlo; R. Riedel;
Template-free synthesis of polymer-derived mesoporous SiOC/TiO2 and SiOC/N-doped TiO2
ceramic composites for application in the removal of organic dyes from contaminated water;
APPLIED CATALYSIS B-ENVIRONMENTAL, 115-116 (2012) 303-313.
S.J. Widgeon; G. Mera; Y. Gao; E. Stoyanov; S. Sen; A. Navrotsky; R. Riedel; Nanostructure
and Energetics of Carbon-Rich SiCN Ceramics Derived from Polysilylcarbodiimides: Role of the
Nanodomain Interfaces; CHEMISTRY OF MATERIALS, 24 (6) (2012) 1181–1191.
M. Hojamberdiev; R.M. Prasad; K. Morita; M.A. Schiavon; R. Riedel; Polymer-derived
mesoporous SiOC/ZnO nanocomposite for the purification of water contaminated with organic
dyes; MICROPOROUS AND MESOPOROUS MATERIALS, 151 (2012) 330–338.
L. Toma; H.-J. Kleebe; M.M. Müller; E. Janssen; R. Riedel; T. Melz; H. Hanselka;
Correlation Between Intrinsic Microstructure and Piezoresistivity in a SiOC Polymer-Derived
Ceramic; JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 95(3) (2012) 1056-1061.
M. Böhme; E. Ionescu; G. Fu; W. Ensinger; Room temperature synthesis of samarium oxide
nanotubes using cost-effective electroless deposition method; JOURNAL OF EXPERIMENTAL
NANOSCIENCE, 7(3) (2012) 344-353.
P.J. King; T.M. Higgins; S. De; N. Nicoloso; J.N. Coleman; Percolation Effects in
Supercapacitors with Thin, Transparent Carbon Nanotube Electrodes; ACS NANO, 6(2)
(2012) 1732-1741.
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P. Sellappan; L. Toma; G. Miehe; F. Celarie; T. Rouxel; R. Riedel; SiOC Glass-Diamond
Composites; JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 95(2) (2012), 545-552.
R.M. Prasad; G. Mera; K. Morita; M. Müller; H.-J. Kleebe; A. Gurlo; C. Fasel; R. Riedel;
Thermal decomposition of carbon-rich polymer-derived silicon carbonitrides leading to ceramics
with high specific surface area and tunable micro- and mesoporosity; JOURNAL OF THE
EUROPEAN CERAMIC SOCIETY, 32(2) (2012) 477-484.
P. Kroll; M. Andrade; X. Yan; E. Ionescu; G. Miehe; R. Riedel; Isotropic Negative Thermal
Expansion in β-Si(NCN)2 and its Origin; JOURNAL OF PHYSICAL CHEMISTRY C , 116(1)
(2012) 526-531.
M.F. Bekheet; G. Miehe; C. Fasel; A. Gurlo; R. Riedel; Low temperature synthesis of
nanocrystalline MnIn2O4 spinel; DALTON TRANSACTIONS, 41(12) (2012) 3374-3376.
T.D. Sparks; A. Gurlo; D.R. Clarke; Enhanced n-type thermopower in distortion-free LiMn2O4;
JOURNAL OF MATERIALS CHEMISTRY, 22(11) (2012) 4631-4636.
C. Linck; E. Ionescu; B. Papendorf; D. Galuskova; D. Galusek; P. Sajgalik; R. Riedel;
Corrosion behavior of silicon oxycarbide-based ceramic nanocomposites under hydrothermal
conditions; INTERNATIONAL JOURNAL OF MATERIALS RESEARCH, 1 (2012) 31-39.
Patents
I. Fergen; W. Kolbe; M. Kraft; J. Harenburg; M. Zschuppe; R. Riedel; E. Ionescu;
Coating composition for wear resistant and antiadhesive surface coatings; (2012) PATENT
NUMBER: DE102012004278 .
Dispersive Solids
59
Silicon-containing polymer-derived ceramic nanocomposites (PDC-NCs):
preparative approaches and properties
Emanuel Ionescu,a Hans-Joachim Kleebeb and Ralf Riedela
a
Technische Universität Darmstadt, Fachbereich Material-und Geowissenschaften, Fachgebiet Disperse
Feststoffe, Petersenstrasse 32, D-64287 Darmstadt, Germany
b
Technische Universität Darmstadt, Fachbereich Material-und Geowissenschaften, Institut für angewnadte
Geowissenschaften, Schnittspahnstrasse 9, D-64287 Darmstadt, Germany
Chem. Soc. Rev., 41(15) (2012) 5032-5052.
Composites consist by definition of at least two materials (Gibbsian phases) with rather
different properties. They exhibit a heterogeneous microstructure and possess improved
properties with respect to their components. Furthermore, the design of their
microstructure allows for tailoring their overall properties. In the last decades, intense work
was performed on the synthesis of nanocomposites, which have the feature that at least one
of their components is nanoscaled. However, the microstructure–property relationship of
nanocomposite materials is still a challenging topic. This tutorial review paper deals with a
special class of nanocomposites, i.e. polymer-derived ceramic nanocomposites (PDC-NCs),
which have been shown to be promising materials for various structural and functional
applications. Within this context, different preparative approaches for PDC-NCs as well as
some of their properties will be presented and discussed. Furthermore, recent results
concerning the relationship between the nano/microstructure of PDC-NCs and their
properties will be highlighted.
Synthetic approaches for PDC-NCs from preceramic polymers
Common preceramic polymers for the preparation of PDCs are polysilanes,
polycarbosilanes, polysiloxanes, as well as polysilazanes and polysilylcarbodiimides. Since
the Yajima process to synthesize silicon carbide fibers using polycarbosilanes, 1,2 significant
developments in the PDC synthesis and processing have been achieved.3-5 Thus, using
silicon-based polymers, technologically important ceramic components such as complexshaped monoliths, fibers, coatings or infiltrated porous media and powders can be
prepared.
The molecular structure and the type of preceramic polymer influence not only the
composition but also the amount of phases as well as the phase distribution and the
microstructure of the final ceramic. In this way, the chemical and physical properties of
PDCs can be varied and adjusted to a great extent by the design of the molecular precursor.
Therefore, synthesis of preceramic polymers is one of the key issues in the PDC field. There
are several requirements for preceramic polymers in order to be effective for the thermal
decomposition process. The polymers should possess a sufficiently high molecular weight in
order to avoid volatilization of low molecular components, appropriate rheological
properties and solubility for the shaping process, and latent reactivity (i.e. the presence of
functional groups) for subsequent curing and cross-linking steps.3
The synthesis of silicon-based polymers mainly involves reactions of organochlorosilanes
with Li/Na/K to give polysilanes and polycarbosilanes, with water to give polysiloxanes,
with ammonia or amines for the preparation of polysilazanes and with
bis(trimethylsilyl)carbodiimide to synthesize poly(silylcarbodiimides).3
For the synthesis of PDC-NCs, silicon-based preceramic precursors such as polycarbosilanes,
polysiloxanes or polysilazanes have been chemically modified with metallo-organics such as
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Dispersive Solids
metal alkoxides, metal amido complexes, and boroncontaining molecular compounds (i.e.
boranes or borazines), leading to single-source precursors which subsequently are
converted into PDC-NCs upon pyrolysis.
Additionally, the so-called Active Filler Controlled Pyrolysis (AFCOP) process uses blends of
preceramic polymers (such as polysiloxanes or polysilazanes) and active fillers (such as
metallic (B, Ti, Cr, V, Mo) or intermetallic (MoSi2, CrSi2) particles) which lead to SiOC- and
SiCN-based ceramic composites upon polymer-to-ceramic conversion.6 The main effect of
active fillers was acknowledged within the context of reducing the shrinkage and porosity
generation during the pyrolytic conversion of the preceramic polymers. Thus, the AFCOP
technique enables a near-net-shape preparation of polymer-derived ceramic parts with low
porosity.6 Moreover, the ceramic composites obtained by AFCOP may exhibit improved
thermomechanical and functional properties with respect to their analogous filler-free
ternary ceramic systems.
Fig. 1 Preparation of polymer-derived ceramic composites by AFCOP: (a) using intermetallic fillers (as for
SiOC/MoSi2);7 (b) using metallic fillers (as for SiCN/Fe3Si).8
Synthesis of single source preceramic polymers
The focus of the present paper is related to the chemical modification of silicon-containing
polymers with metal alkoxides and their resulting PDC-NCs.
Polycarbosilanes (PCS) are synthesized from polysilanes which rearrange at elevated
temperature to polycarbosilanes via the Kumada mechanism.9 The ceramization of
polycarbosilanes leads to silicon carbide materials (such as SiC fibers). Polycarbosilanes
have been chemically modified with metal alkoxide and acetyl acetonates. Two reaction
pathways of PCS with metal–organic precursors have been reported:
(a) The reaction with metal alkoxides involves the formation of Si–O–M units and evolution
of alkanes (Scheme 1a), as it was observed in the case of chemical modification with
aluminium, titanium and zirconium alkoxide.10-12
(b) If PCS is reacted with metal acetyl acetonates (M=Al, Zr), Si–M bonds are formed and
acetyl acetone is released
(Scheme 1b).13, 14
In a similar way, polysiloxanes having suitable functional groups (such as hydroxyl or
alkoxy) can be chemically modified via sol–gel-like processes by reacting them with
transition metal alkoxides. The modification of a polysilsesquioxane with the metal
alkoxides (i.e. zirconium n-propoxide,15 hafnium n-butoxide16) has been shown to strongly
increase the crosslinking degree of the preceramic precursor (Scheme 2).
Dispersive Solids
61
Scheme 1 Chemical modification of PCS: (a) with
metal alkoxides (as for titanium(IV) n-propoxide, R =
propyl) and (b) with metal acetyl acetonate
complexes (as for aluminium(III) acetyl acetonate).
Scheme 2 Chemical modification of a polysilsesquioxane with zirconium and hafnium
alkoxides.
Polymer-to-ceramic transformation
The polymer-to-ceramic transformation consists of two steps:
(i) Cross-linking of the polymers at low temperatures (100–400 °C) leading to infusible
organic/inorganic networks;
(ii) Ceramization via pyrolysis at temperatures up to 1000–1400 °C. Whereas mainly
amorphous ceramics are obtained upon pyrolysis, subsequent annealing at high
temperatures leads to (poly)crystalline materials.5
The cross-linking process of preceramic polymers is a crucial step in the fabrication of
polymer derived ceramics. During cross-linking the precursors are converted into organic/
inorganic materials. This process prevents the loss of low molecular weight components of
the precursor as well as their fragmentation processes during ceramization, and thus
increases the ceramic yield. Furthermore, the conversion of the polymers into infusible
materials prevents their melting during ceramization while retaining the shape of the
crosslinked polymers upon pyrolysis.
Microstructure of PDC-NCs
Polymer derived ceramics are amorphous materials with nanodomains which persist up to
very high temperatures. PDCs can remain amorphous up to temperatures ranging from
1000 to 1800 °C, depending on the chemical composition and structure. At high
temperatures, devitrification occurs and leads to amorphous multiphase systems and
subsequently to nanocrystal nucleation and growth. Additionally, phase separation may
lead to decomposition which is usually accompanied by the release of gases such as CO, SiO
(from SiOC based systems) or N2 (from SiCN materials).5
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Fig. 2 Proposed microstructural models for SiOC-based materials: (a) silica nanodomains embedded within a
carbon-based network; at the interface mixed SiOxC4_x bonds are present;17 (b) carbon domains (black dots)
embedded within an oxygen-rich SiOC matrix; the interface (light areas) consists of carbon-rich SiOC.18
Conclusions and outlook
Within this review paper, the synthesis of metal-alkoxidemodified silicon-containing
polymers as preceramic precursors for PDC-NCs is presented. Furthermore, their polymerto-ceramic transformation is discussed and compared to that of their non-modified
analogous precursors. The chemical modification of the polymers with metal alkoxides is
shown to strongly affect the cross-linking and ceramization processes upon pyrolysis. This is
related to profound changes of the precursor architecture occurring upon alkoxidemodification. Additionally, the chemical and phase composition as well as the
microstructure of the resulting ceramics is significantly different as compared to the nonmodified PDCs, as discussed in the second part of the paper. In the third part of the present
review selected properties of PDC-NCs are addressed. Within this context, the hightemperature behavior of the PDC-NCs is discussed; thus, their decomposition and
crystallization processes at T >> 1000 °C are presented. Also some details with respect to
the high-temperature oxidation and corrosion behavior of the PDC-NCs are given. In
addition to the high-temperature behavior of PDC-NCs, their electrical and magnetic
properties are briefly highlighted.
Dispersive Solids
63
PDC-NCs present excellent behavior under extreme conditions (e.g. ultrahigh temperatures
as well as oxidative and corrosive environments) and have consequently an enormous
potential as materials for structural applications. They also exhibit interesting functional
properties, e.g. optical, electrical, and magnetic properties which make them excellent
candidate materials for high temperature sensors, micro glow plugs, electrochemical
devices, and MEMS/NEMS operating under harsh conditions.
However, despite numerous case studies related to the effect of the polymer architecture on
the composition and microstructure of the resulting ceramics as well as on their properties,
no systematic/general understanding is yet available concerning these aspects.
Thus, the following requirements should be fulfilled in order to be able to rationally design
PDC-NCs with tailored composition, microstructure and property profile:
(i) Synthesis of preceramic single-source precursors with tailored chemical composition and
architecture should be accessible.
(ii) A fundamental understanding of the relationship between the architecture of the
preceramic precursor and the composition and microstructure of the resulting PDC-NCs is
needed. Here, model systems have to be developed and systematically investigated with
respect to cross-linking and ceramization processes as well as to their microstructure
evolution upon polymer-to-ceramic transformation.
(iii) Extensive experimental and modelling data are necessary in order to assess the
properties of the PDC-NCs (e.g. high-temperature behavior, as well as electrical, magnetic,
or optical properties). This will allow for designing specific ceramic microstructures and
compositions and consequently for preparing ceramic nanocomposites with tailored
properties for applications beyond the present state-of-the-art.
Thus, more intense efforts related to the elucidation of the intimate relationships between
composition, microstructure and properties of PDC-NCs are needed. This will require
extensive synergistic and interdisciplinary approaches to both fundamental research as well
as materials/device engineering and development.
Notes and references
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
64
S. Yajima, Y. Hasegawa, K. Okamura and I. Matsuzawa, Nature, 1978, 273, 525.
S. Yajima, K. Okamura, J. Hayashi and M. Omori, J. Am. Ceram. Soc., 1976, 59, 324.
P. Colombo, G. Mera, R. Riedel and G. D. Soraru, J. Am. Ceram. Soc., 2010, 93, 1805.
E. Ionescu, in Ceramics Science and Technology, ed. R. Riedel and I.-W. Chen, Wiley-VCH, Weinheim,
Germany, 2012, vol. 3, p. 457.
Polymer Derived Ceramics: from Nanostructure to Applications, ed. P. Colombo, R. Riedel, H.-J. Kleebe
and G. D. Soraru, DEStech Publications, Lancaster, PA, 2009.
P. Greil, J. Am. Ceram. Soc., 1995, 78, 835.
J. Cordelair and P. Greil, J. Am. Ceram. Soc., 2001, 84, 2256.
R. Hauser, A. Francis, R. Theismann and R. Riedel, J. Mater. Sci., 2008, 43, 4042.
K. Okamura, Composites, 1987, 18, 107.
F. Babonneau, G. D. Soraru, K. J. Thorne and J. D. Mackenzie, J. Am. Ceram. Soc., 1991, 74, 1725.
T. Ishikawa, T. Yamamura and K. Okamura, J. Mater. Sci., 1992, 27, 6627.
F. Babonneau and G. D. Soraru, J. Eur. Ceram. Soc., 1991, 8, 29.
T. Ishikawa, S. Koji, K. Matsunaga, T. Hogami, Y. Kohtoku and T. Nagasawa, Science, 1998, 282, 1295.
T. Ishikawa, Y. Kohtoku and K. Kumagawa, J. Mater. Sci., 1998, 33, 161.
E. Ionescu, C. Linck, C. Fasel, M. Mu¨ ller, H.-J. Kleebe and R. Riedel, J. Am. Ceram. Soc., 2010, 93, 241.
E. Ionescu, B. Papendorf, H.-J. Kleebe, F. Poli, K. Müller and R. Riedel, J. Am. Ceram. Soc., 2010, 93, 1774.
A. Saha, R. Raj and D. L. Williamson, J. Am. Ceram. Soc., 2006, 89, 2188.
S. J. Widgeon, S. Sen, G. Mera, E. Ionescu, R. Riedel and A. Navrotsky, Chem. Mater., 2010, 22, 6221.
Dispersive Solids
Nanostructure and Energetics of Carbon-Rich SiCN Ceramics Derived
from Polysilylcarbodiimides: Role of the Nanodomain Interfaces
S. Widgeon,† G. Mera,‡ Y. Gao,‡ E. Stoyanov,§ S. Sen,† A. Navrotsky,†,§ and R. Riedel‡
†
Department of Chemical Engineering and Materials Science, University of California at Davis, Davis,
California 95616, United States
‡
Technische Universität Darmstadt, Institut für Materialwissenschaft, Petersenstrasse 23, D-64287
Darmstadt, Germany
§
Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California at Davis, Davis,
California 95616, United States
Chem. Mater., 24(6) (2012) 1181–1191.
SiCN polymer-derived ceramics (PDCs) with different carbon contents have been
synthesized by pyrolysis of poly(phenylvinylsilylcarbodiimide) and of poly(phenylsilsesquicarbodiimide), and their structure and energetics have been studied using
29
Si, 13C, 15N, and 1H solid state nuclear magnetic resonance (NMR) spectroscopy and oxide
melt solution calorimetry. The structure of these PDCs at lower carbon content (35−40
wt%) and pyrolysis temperatures (800 °C) consists primarily of amorphous nanodomains of
sp2 carbon and silicon nitride with an interfacial region characterized by mixed bonding
between N, C, and Si atoms that is likely stabilized by the presence of hydrogen. The
average size of the carbon domains increases with increasing carbon content, and a
continuously connected amorphous carbon matrix is formed in PDCs with 55−60 wt% C.
The interfacial silicon−carbon and nitrogen− carbon bonds are destroyed with concomitant
hydrogen loss upon increasing the pyrolysis temperature to 1100 °C. Calorimetry results
demonstrate that the mixed bonding between C, N, and Si atoms in the interfacial regions
play a key role in the thermodynamic stabilization of these PDC. They become energetically
less stable with increasing annealing temperature and concomitant decrease of mixed
bonds and hydrogen loss.
Summary
The multinuclear NMR spectroscopic results reported here demonstrate that the structure
of carbon-rich SiCN ceramics derived from phenyl-containing polysilylcarbodiimides
consists predominantly of separate amorphous domains of silicon nitride and sp2 carbon.
The results of oxide melt solution calorimetry indicate that after pyrolysis at 800 °C the
HN1 PDC derived from a linear poly(phenylvinylsilylcarbodiimide) is energetically less
stable than the GM35 PDC derived from a branched poly(phenylsilsesquicarbodiimide). The
energetic stabilization of the GM35 ceramic is attributed to the presence of mixed bonding
between N, C, and Si atoms at the interface between the Si3N4 and C nanodomains. This
mixed bonding partly owes its presence to the nature of the polymeric precursor used in the
synthesis of these PDCs.
Dispersive Solids
65
Figure 1. Cartoons of the nanodomain structural models for (a) GM35 and (b) HN1 PDCs. The nanometer-scale
amorphous/ turbostratic carbon and Si 3N4 domains are shown with stripes and dots, respectively, with the
interfacial areas as the white regions. Part (b) shows a continuous matrix of amorphous/turbostratic carbon
with Si3N4 clusters embedded in it. The atomic structures within these domains are shown schematically in the
insets.
The relative concentrations of these mixed bonds decrease upon increase in the pyrolysis
temperature to 1100 °C along with concomitant loss in hydrogen content. It is hypothesized
that the mixed bonding is stabilized via hydrogen bonding at the interfacial regions
between the Si3N4 and C nanodomains and that the loss of this hydrogen at higher
temperature provides the entropic driving force for the destruction of mixed bonding.
66
Dispersive Solids
Structure Research
In the year 2012, we improved the equipment pool of the group by adding a two circle
diffractometer with Göbel mirror and various analyzer stages (HOPG, LiF, Si). The
diffractometer is able to either use a wafer chuck as a sample holder or to carry a 2000K
Bühler furnace. The source/mirror unit is mounted with a 5 degree angle with respect to
the horizontal in order to facilitate grazing indidence and reflectometry studies. Now a total
of nine diffractometers and three cameras can be used for structure research.
Staff Members
Head
Prof. Dr. Wolfgang Donner
Prof. Dr. Dr. h.c. Hartmut Fueß
Research Associates
Dr. Joachim Brötz
Dr. Marton Major
Dr. Ljubomira Schmitt
Dr. Azza Amin
Technical Personnel
Dipl. Ing. Heinz Mohren
Jean-Christophe Jaud
Maria Bense
Ingrid Svoboda
Sabine Foro
PhD Students
M. Sc. Qiran Li
M. Sc. Marco Léal
Dipl.-Ing. Florian Pforr
Dipl.-Ing. Dominik Stürmer
Master/Diploma
Students
Ali Soleimani Dorceh
Ludmilla Konrad
Guest Scientists
Prof. Dr. Ismael Saadoune,
Université Cadi Ayyad, Maroc
Prof. Dr. Mustafa Tombul,
Univerity of Kirikkale, Turkey
Assoc. Prof. Dr. Sevi Öz,
University of Ankara, Turkey
Secretary
Research Projects
Structural investigations into the electric fatigue in piezo-ceramics (DFG-SFB, 2011-2014)
Development of electrode materials for high capacitance devices (IDS-FunMat, 2010-2013)
Phase transitions in thin potassium sodium niobate films (IDS-FunMat, 2012-2015)
Publications
Heiba ZK; Mohamed MB; Fuess H; Effect of Mn doping on structural and magnetic
susceptibility of C-type rare earth nano oxides Er2-xMnxO3, MATERIALS RESEARCH
BULLETIN Volume: 47 Issue: 12 Pages: 4278-4282 DOI: 10.1016/j. materresbull.
2012.09.018 Published: DEC 2012
Structure Research
67
Renard L; Babot O; Saadaoui H; Fuess H; Brötz J; Gurlo A; Arveux E; Klein A; Toupance T;
Nanoscaled tin dioxide films processed from organotin-based hybrid materials: an
organometallic route toward metal oxide gas sensors, NANOSCALE Volume: 4 Issue: 21
Pages: 6806-6813 DOI: 10.1039/c2nr31883k, Published: NOV 7 2012
Bhaskar A; Bramnik NN; Trots DM; Fuess H; Ehrenberg H; In situ synchrotron diffraction
study of charge-discharge mechanism of sol gel synthesized LiM0.5Mn1.5O4 (M = Fe, Co),
JOURNAL OF POWER SOURCES Volume: 217 Pages: 464-469 DOI: 10.1016/j.jpowsour.
2012.06.032 Published: NOV 1 2012
Mohamed MB; Hinterstein M; Fuess H; Dielectric anomaly and magnetic properties of
multiferroic GaFe0.75Mn0.25O3, MATERIALS LETTERS Volume: 85 Pages: 102-105 DOI:
10.1016/j.matlet.2012.07.007 Published: OCT 15 2012
Theissmann R; Fuess H; Tsuda K; Experimental charge density of hematite in its magnetic low
temperature and high temperature phases, ULTRAMICROSCOPY Volume: 120 Pages: 1-9
DOI: 10.1016/j.ultramic.2012.04.006 Published: SEP 2012
Balevicius V; Aidas K; Svoboda I; Fuess H; Hydrogen Bonding in Pyridine N-Oxide/Acid
Systems: Proton Transfer and Fine Details Revealed by FTIR, NMR, and X-ray Diffraction,
JOURNAL OF PHYSICAL CHEMISTRY A Volume: 116 Issue: 34 Pages: 8753-8761 DOI:
10.1021/jp305446n Published: AUG 2012
Brucher O; Bergstrasser U; Kelm H; Hartung J; Greb M; Svoboda I; Fuess H; Controlling 6endo-selectivity in oxidation/bromocyclization cascades for synthesis of aplysiapyranoids and
other 2,2,6,6-substituted tetrahydropyrans, TETRAHEDRON Volume: 68 Issue: 34 Pages:
6968-6980 DOI: 10.1016/j.tet.2012.05.013 Published: AUG 26 2012
Schierholz R; Fuess H; Ferroelectric domains in PZT ceramics at the morphotropic phase
boundary. Can the splitting of reflections in SAED patterns be used for the distinction of
different pseudo-cubic phases?, JOURNAL OF APPLIED CRYSTALLOGRAPHY Volume: 45
Pages: 766-777 DOI: 10.1107/S0021889812022583 Part: Part 4 Published: AUG 2012
Essehli R; El Bali B; Faik A; Benmokhtar S; Manoun B; Zhang Y; Zhang XJ; Zhou Z; Fuess
H; Structural changes upon lithium insertion in Ni0.5TiOPO4, JOURNAL OF ALLOYS AND
COMPOUNDS Volume: 530 Pages: 178-185 DOI: 10.1016/j.jallcom.2012.03.103
Published: JUL 2012, Senyshyn A; Boysen H; Niewa R; Banys J; Kinka M; Burak Y; Adamiv
V; Izumi F; Chumak I; Fuess H
High-temperature properties of lithium tetraborate Li2B4O7, JOURNAL OF PHYSICS DAPPLIED PHYSICS Volume: 45 Issue: 17 Article Number: 175305 DOI: 10.1088/00223727/45/17/175305 Published: MAY 2 2012
Heiba ZK; Mohamed MB; Fuess H; XRD, IR, and Raman investigations of structural properties
of Dy2-xHox O3 prepared by sol gel procedure, CRYSTAL RESEARCH AND TECHNOLOGY
Volume: 47 Issue: 5 Pages: 535-540, DOI: 10.1002/crat.201200032 Published: MAY 2012
68
Structure Research
Sebova M; Boca R; Dlhan L; Nemec I; Papankova B; Pavlik J; Fuess H; Direct determination
of zero-field splitting in Co(II) complexes by FAR infrared spectroscopy, INORGANICA
CHIMICA ACTA Volume: 383 Pages: 143-151 DOI: 10.1016/ j.ica. 2011.10.073 Published:
MAR 30 2012
Hoelzel M; Senyshyn A; Juenke N; Boysen H; Schmahl W; Fuess H; High-resolution neutron
powder diffractometer SPODI at research reactor FRM II, NUCLEAR INSTRUMENTS &
METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS
DETECTORS AND ASSOCIATED EQUIPMENT Volume: 667 Pages: 32-37 DOI:
10.1016/j.nima.2011.11.070 Published: MAR 1 20121
Nemec I; Herchel R; Salitros I; Travnicek Z; Moncol J; Fuess H; Ruben M; Linert W; Anion
driven modulation of magnetic intermolecular interactions and spin crossover properties in an
isomorphous series of mononuclear iron(III) complexes with a hexadentate Schiff base ligand,
CRYSTENGCOMM Volume: 14 Issue: 20 Pages: 7015-7024 DOI: 10.1039/c2ce25862e
Published: 2012
Abdelfattah Mahmoud, Mayumi Yoshita, Ismael Saadoune, Joachim Broetz, Kenjiro
Fujimoto, Shigeru Ito, LixCo0.4Ni0.3Mn0.3O2 electrode materials: Electrochemical and
structural studies, MATERIALS RESEARCH BULLETIN Volume: 47 Issue: 8 Pages: 19361941 (2012)
Gassmann, Juergen; Broetz, Joachim; Klein, Andreas, Sputter deposition of indium tin oxide
onto zinc pthalocyanine: Chemical and electronic properties of the interface studied by
photoelectron spectroscopy, APPLIED SURFACE SCIENCE Volume: 258 Issue: 8 Pages: 39133919 (2012)
Münch, Falk; Neetzel, Cornelia; Kaserer, Sebastian; Brötz, Joachim; Jaud, Jean-Christophe;
Zhao-Karger, Zhirong; Lauterbach, Stefan; Kleebe, Hans-Joachim; Roth, Christina;
Ensinger, Wolfgang; Fabrication of porous rhodium nanotube catalysts by electroless plating
JOURNAL OF MATERIALS CHEMISTRY Volume: 22 Issue: 25 Pages: 12784-12791 (2012)
Sana Ahmad, Bernard Jousseaume, Thierry Toupance, Odile Babot, Guy Campet, Christine
Labrugère, Joachim Brötz and Ulrike Kunz, A new route towards nanoporous TiO2 as powders
or thin films from the thermal treatment of titanium-based hybrid materials, DALTON
TRANSACTIONS Volume: 41 Issue: 1 Pages: 292-299 (2012)
Thorsten Leist, Joachim Brötz, Yo-Han Seo, Shumeng Cheng, Kyle G. Webber, Crack growth
resistance behavior of lanthanum doped bismuth ferrite–lead titanate: Effect of tetragonality
and mixed phase crystal structures, ENGINEERING FRACTURE MECHANICS 96 267–275
(2012)
Structure Research
69
X-ray Reflectivity from Spin-Coated Electronic Materials
Marton Major, Daniel E. Walker, Heinz von Seggern, and Wolfgang Donner
Next generation field effect transistors are made of Indium Zinc Oxide (IZO) and are
usually being deposited onto the substrate by spin coating with subsequent annealing. It
turned out that the quality (conductivity) of the films very much depends both on the
concentration of the IZO solution and the number of cycles in which they are deposited.
We used x-ray reflectomotry in order to elucidate the density profile in such films and
thereby clarify the processes responsible for the above mentioned behavior.
Fig. 1: Reflectivities from IZO films
made from different solution
concentrations and with various
numbers of cycles (1, 2 and 5). The
x-ray wavelength used is 0.154 nm.
Figure 1 shows reflectivty
curves for IGZO films made
from different concentrations.
The black dotes are the
measured data, the red lines
are fits according to the Parrat
formalism. It can be seen from
the data that the smoothest
film (i.e. slowest decay of
reflected intensity) is the one
that was obtained by five
subsequent deposition cycles.
Furthermore, the reflectivity
curves from the 100 mg/g
solution shows a beating from
two different frequencies,
corresponding to two maxima
in the lectron density. A
careful fitting results in the
electron desnity profiles in
figure 2, corrsponding to the
straight lines in figure 1.
70
Structure Research
Fig. 2: Electron densities (normalized to the bulk densities) as a function of depth as obtained from fits to the
data in Fig.1.
It becomes clear from the obtained electron density profiles what happens in the films: the
most dense films, and therefore the ones with the smallest number of voids and the best
electrical performance, can be made using several deposition cycles with a low solution
density, e.g. five depositions with 5 mg/g. Higher solution densities or fewer cycles lead to
low-density films with a large number of voids and poor performance.
References:
D. E. Walker, M. Major, M. B. Yazdi, A. Klyszcz, M. Haeming, K. Bonrad, C. Melzer, W. Donner, H.
v. Seggern, ACS Applied Materials and Interfaces Vol.4, p. 6835 (2012)
Structure Research
71
Materials Analysis
The Materials Analysis group participates in two of the five Research Clusters of the
Technische Universität Darmstadt: New Materials and Nuclear and Radiation Science. On the
one hand the group is concerned with the characterization of self-synthesized modern
materials, on the other hand with effects on materials caused by exposition to detrimental
influences like ion irradiation. The research aims for clarification of the correlation of
materials properties and synthesis or exposition parameters, respectively, by investigation
of the elemental composition and the chemical binding.
Current research topics are:
Advanced 3-D Nanoobjects: Nanochannels, -wires, -tubes, and –networks: In
collaboration with the GSI Helmholtz Centre for Heavy Ion Research, nanoporous
membranes are formed by ion irradiation of polymer foils producing latent ion damage
tracks which are chemically etched to nanochannels. These ion track (nano) filters can be
used for filtering particles from liquids, collecting aerosols, for gas separation, and for
analyzing small (bio)molecules. In the latter case, the nanochannel walls are chemically
modified so that the nanochannel sensor becomes sensitive and selective to certain
molecular species. Apart from polymer-based nanochannels, anodically oxidized aluminium
(AAO) is used. Filling the polymer or AAO nanochannels galvanically with metals, such as
copper, gold or platinum, and dissolving the templates, nanowires are formed. Here,
different metal deposition conditions are used in order to obtain monometal but also
multimetal (e.g. CuCo- and CuFe) nanowires.
By redox-chemical reactions, the nanochannel walls can be coated with metal or metal
oxide films, such as Ni, Cu, Ag, Au, Pt, Pd, and ZnO, SnO2, TiO2, In2O3, FexOy. Thus,
nanotubes can be formed. Here, different morphologies are available, ranging from smooth
compact nanotube walls to nanoporous walls to rough or peaked structures.
When the nanochannels are crossed, the resulting nanowires are interconnected, forming
nanowire networks. Dimensions, surface topography, microstructure, and crystallinity of
these nanostructures are investigated. Macroscopic properties such as thermal stability,
electrical conductivity and catalytic activity are analysed.
Additionally, the obtained properties are evaluated with respect to applications as sensors,
for gas flow or acceleration measurements, catalysts, for chemical reactions in
microreactors, or electrodes in fuel cells.
Thin film and coating deposition and analysis: In thin film and coating technology, the
identification of chemical compounds, phases and binding conditions is of basic
importance. Different methods are used for the formation of thin films (nanofilms), thick
films and coatings.
Surface modifications are achieved by ion implantation via plasma immersion ion
implantation (PIII). Different gaseous species are used such as oxygen, nitrogen and
hydrocarbons, depending on the property to be modified, e.g. hardness, wear resistance,
lifetime and biocompatibility. Films of diamond-like carbon (DLC) are deposited by plasma
immersion ion implantation and deposition (PIII&D). The influence of the addition of
different elements, especially metals, to the DLC films is investigated for their chemical and
phase composition, microstructure, adhesion, and in relation to biological applications,
tribological properties, corrosion and wear protection of metal substrates, wettability, and
72
Materials Analysis
temperature stability. This technique is also suitable for the coating of complex shaped
substrates, e.g. the inner surfaces of tubes.
Oxide films, such as lead-free piezoelectrics like sodium potassium niobate (NKN) which
can be used as sensors or actuators, depending on the film thickness, are prepared by solgel technique combined with spin coating or dip coating. In collaboration with different
institutions, thin films of boron carbonitride and silicon carbonitride are prepared by
plasma enhanced chemical vapour deposition (PECVD). The atomic binding states are
investigated by Near Edge X-ray Absorption Fine Structure (NEXAFS at PTB/BESSY II)
measurements, partially in Total reflection and Glancing Incidence X-ray Fluorescence
(TXRF, GIXRF) geometry, and by X-ray Photoelectron Spectrometry (XPS). The chemical
film composition is analyzed by Secondary Ion Mass Spectrometry (SIMS), the phase
composition by X-ray diffraction.
Materials in radiation fields: Irradiation of materials with energetic particles (protons,
heavy ions) and electromagnetic radiation (X-rays, gamma-rays) may lead to degradation
of the materials’ properties. This happens to components in space vehicles, in nuclear
facilities and in particle accelerators. Polymers with their covalent bonds are particularly
sensitive towards ionizing radiation. Polyimide, vinyl polymers and fiber-reinforced
polyepoxides, which are components of superconducting beam guiding magnets at the
future FAIR synchrotron and storage rings, oxides such as alumina which are used as beamdiagnostic scintillator screens, and semiconductor components such as CCDs are irradiated
and characterized for their properties, such as polymeric network degradation, mechanical
strength, electrical resistance, dielectric strength, and optical properties. Apart from basic
questions on material’s degradation mechanisms by energetic radiation, the investigations
are used to estimate service life-times of the materials/components.
Staff Members
Head
Prof. Dr. Wolfgang Ensinger
Research Associates
Dr. Mubarak Ali
Dr. Adam G. Balogh
Dr. Stefan Flege
Dr. Peter Hoffmann
Dr. Olaf Baake
Dr. Mario Böhme
Dr. Ruriko Hatada
Dr. Markus Rauber
Technical Personnel
Renate Benz
Brunhilde Thybusch
Secretaries
Antje Pappenhagen
PhD Students
Anton Belousov
Engy El-Haddad
Martin Hottes
Sebastian Kamps
Stephan Lederer
Vincent Lima
Falk Münch
Cornelia Neetzel
Tim Seidl
Sebastian Wiegand
Materials Analysis
Eva-Maria Felix
Umme Habiba Hossain
Stefan Hummelt
Markus Krause
Alice Lieberwirth
Renuka Krishnakumar
Saima Nasir
Quoc Hung Nguyen
Christian Stegmann
73
Diploma Students
Jonathan Griebel
Anke Schachtsiek
Sebastian Bohn
Anja Habereder
Rene Fischer
Guest Scientists
Karolina Drogowska, AGH University, Krakow, Poland
Prof. Dr. Takaomi Matsutani, Kinki University, Higashiosaka,
Japan
Dr. S. Duvanov, National Academy of Sciences, Sumy, Ukraine
Dr. V. Voznyi, National Academy of Sciences, Sumy, Ukraine
Stephan Lederer
Raphael Simon
Ulla Hauf
Alexandra Bobrich
Research Projects
Preparation of lead free piezo electric thin films (LOEWE Adria, 2008 – 2014)
FAIR accelerator: Investigations of alterations of material properties by beam losses
(BMBF/GSI, 2009 – 2012)
FAIR accelerator: Scintillator materials for diagnostics of high currents (BMBF/GSI, 2009 –
2012)
Simulations on the influence of swift ion irradiation on materials of FAIR-components (GSI,
2010 – 2013)
Investigation of the influence of swift ion irradiation on polymers and composite materials
of FAIR-components (GSI, 2010 – 2013)
Investigation of the chemical bindings in interfaces of boron- and siliconcarbonitrides with
the substrate (DFG, 2010 – 2012, jointly with PTB Berlin)
NanoC – Preparation, modification and characterization of nanochannels in polymer
membranes (Beilstein-Institut, 2009 – 2013)
NanoMag – Spin-dependent scattering in magnetic and Kondo nanowires (Beilstein-Institut,
jointly with Goethe Universität Frankfurt am Main, 2009 – 2013)
3-Dimensional micro-nano-integration for gas flow sensor technology (BMBF, 2011-2013,
jointly with Institut für Elektromechanische Konstruktionen, TU Darmstadt)
Electromechanical sensors with one-dimensional nano objects (BMBF, 2011-2013, jointly
with Institut für Elektromechanische Konstruktionen, TU Darmstadt)
Investigation of technologically important nanostructured materials via high resolution ion
beam analysis (DLR, 2011 – 2013)
Beam diagnosis and radiation damage diagnosis – Scintillator materials for high current
diagnosis (BMBF/GSI 2012 – 2015)
Beam diagnosis and radiation damage diagnosis – radiation damage of accelerator
components made out of plastics and countermeasures (BMBF/GSI 2012 – 2015)
New technologies for efficient solar energy systems (DFG, 2012 - 2013)
74
Materials Analysis
Publications
K. Baba, R. Hatada, S. Flege, W. Ensinger; Preparation and properties of Ag containing
diamond-like carbon films by magnetron plasma source ion implantation; ADVANCES IN
MATERIALS SCIENCE AND ENGINEERING, 2012 (2012) 536853.
K. Drogowska, S. Flege, C. Schmitt, D. Rogalla, H.-W. Becker, H. K. N. Nhu-Tarnawska, A.
Brudnik, Z. Tarnawski, K. Zakrzewska, M. Marszalek, A. G. Balogh; Hydrogen charging
effects in Pd/Ti/TiO2/Ti thin films deposited on Si(111) studied by ion beam analysis methods;
ADVANCES IN MATERIALS SCIENCE AND ENGINEERING, 2012 (2012) 269603.
T. Seidl, O. Baake, U.H. Hossain, M. Bender, D. Severin, C. Trautmann, W. Ensinger; Insitu investigation of polyvinyl formal irradiated with GeV Au ions; NUCLEAR INSTRUMENTS
AND METHODS IN PHYSICS RESEARCH SECTION B: BEAM INTERACTIONS WITH
MATERIALS AND ATOMS 272 (2012) 400-404.
W. Ensinger, S. Flege, M. Kiuchi, K. Honjo; Chromium Nitride Films Formed by Ion Beam
Assisted Deposition at Low Nitrogen Ion Energies in Comparison to High Energies;
NUCLEAR INSTRUMENTS AND METHODS IN PHYSICS RESEARCH SECTION B: BEAM
INTERACTIONS WITH MATERIALS AND ATOMS 272 (2012) 437-440.
W. Ensinger, S. Flege, K. Baba; Platinum implantation into tantalum for protection against
hydrogen embrittlement during corrosion; NUCLEAR INSTRUMENTS AND METHODS IN
PHYSICS RESEARCH SECTION B: BEAM INTERACTIONS WITH MATERIALS AND ATOMS
272 (2012) 441-445.
K. Drogowska, Z. Tarnawski.A. Brudnik, E. Kusior, M. Sokołowski, K. Zakrzewska, A.
Reszka, Nhu-T.H. Kim-Ngan, A.G. Balogh; RBS, XRR and optical reflectivity measurements of
Ti-TiO2 thin films deposited by magnetron sputtering; MATERIALS RESEARCH BULLETIN 47
(2012) 296–301.
M. Ali, S. Nasir, P. Ramirez, I. Ahmed, Q.H. Nguyen, L. Fruk, S. Mafe, W. Ensinger; Optical
Gating of Photosensitive Synthetic Ion Channels; ADVANCED FUNCTIONAL MATERIALS 22
(2012) 390-396.
Q.H. Nguyen, M. Ali, R. Neumann, W. Ensinger; Saccharide/glycoprotein recognition inside
synthetic ion channels modified with boronic acid; SENSORS AND ACTUATORS B:
CHEMICAL 162 (2012) 216-222.
F. Muench, C. Neetzel, S. Lauterbach, H.-J. Kleebe, W. Ensinger; Impact of specifically
adsorbing anions on the electroless growth of gold nanotubes; JOURNAL OF
NANOMATERIALS 2012 (2012), 104748.
S. Flege, R. Hatada, W. Ensinger, K. Baba; Properties of Hydrogenated DLC Films as Prepared
by a Combined Method of Plasma Source Ion Implantation and Unbalanced Magnetron
Sputtering; JOURNAL OF MATERIALS RESEARCH 27 (2012) 845-849.
S. Flege; Comment on “Corrosion behavior of low energy, high temperature nitrogen ionimplanted AISI 304 stainless steel”; PRAMANA – JOURNAL OF PHYSICS 78 (2012) C333.
S. Müller, C. Schötz, O. Picht, W. Sigle, P. Kopold, M. Rauber, I. Alber, R. Neumann, M.E.
Toimil-Molares; Electrochemical Synthesis of Bi1–xSbx Nanowires with Simultaneous Control
on Size, Composition, and Surface Roughness; CRYSTAL GROWTH AND DESIGN 12 (2012)
615–621.
Materials Analysis
75
O. Picht, S. Müller, I. Alber, M. Rauber, J. Lensch-Falk, D.L. Medlin, R. Neumann, M.E.
Toimil-Molares; Tuning the Geometrical and Crystallographic Characteristics of Bi 2Te3
Nanowires by Electrodeposition in Ion-Track Membranes; JOURNAL OF PHYSICAL
CHEMISTRY C 116 (2012) 5367–5375.
A.G. Balogh, K. Baba, D.D. Cohen, R.G. Elliman, W. Ensinger, J. Gyulai; Modification,
Synthesis, and Analysis of Advanced Materials Using Ion Beam Techniques; ADVANCES IN
MATERIALS SCIENCE AND ENGINEERING 2012 (2012) 431297.
B. Schuster, F. Fujara, B. Merk, R. Neumann, T. Seidl, C. Trautmann; Response behavior of
ZrO2 under swift heavy ion irradiation with and without external pressure; NUCLEAR
INSTRUMENTS AND METHODS IN PHYSICS RESEARCH SECTION B: BEAM
M. Ali, P. Ramirez, H.Q. Nguyen, S. Nasir, J. Cervera, S. Mafe, W. Ensinger; Single CigarShaped Nanopores Functionalized with Amphoteric Amino Acid Chains: Experimental and
Theoretical Characterization; ACS NANO 6 (2012) 3631-3640.
S. Flege, W. Ensinger; Mass Spectrometry in Semiconductor Research; Chapter 40 in: M.S.
Lee (Ed.) Handbook of Mass Spectrometry, Wiley Series on Pharmaceutical Science and
Biotechnology: Practices, Applications and Methods, John Wiley and Sons, ISBN 978-0-47053673-5, 2012.
M. Boehme, E. Ionescu, G. Fu, W. Ensinger; Room temperature synthesis of samarium oxide
nanotubes using cost-effective electroless deposition method; JOURNAL OF EXPERIMENTAL
NANOSCIENCE 7(2012) 344-353.
S. Nasir, M. Ali, W. Ensinger; Thermally controlled permeation of ionic molecules through
synthetic
nanopores
functionalized
with
amine-terminated
polymer
brushes;
NANOTECHNOLOGY 23 (2012) 225502.
C. Neetzel, T. Gasi, V. Ksenofontov, C. Felser, E. Ionescu, W. Ensinger; Electroless Synthesis
of Lepidocrocite (γ-FeOOH) Nanotubes in Ion Track Etched Polycarbonate Templates;
NUCLEAR INSTRUMENTS AND METHODS IN PHYSICS RESEARCH SECTION B: BEAM
A.G. Balogh; Irradiation induced defect formation and phase transition in nanostructured
ZrO2; NUCLEAR INSTRUMENTS AND METHODS IN PHYSICS RESEARCH SECTION B:
BEAM INTERACTIONS WITH MATERIALS AND ATOMS 282 (2012) 48-58.
F. Muench, C. Neetzel, S. Kaserer, J. Brötz, J.-C. Jaud, Z. Zhao-Karger, S. Lauterbach, H.-J.
Kleebe, C. Roth, W. Ensinger; Fabrication of porous rhodium nanotube catalysts by electroless
plating; JOURNAL OF MATERIALS CHEMISTRY 22 (2012) 12784-12791.
P.S. Hoffmann, N.I. Fainer, O. Baake, M.L. Kosinova, Y.M. Rumyantsev, V.A. Trunova, A.
Klein, B. Pollakowski, B. Beckhoff, W. Ensinger; Silicon Carbonitride Nanolayers – Synthesis
and Chemical Characterization; THIN SOLID FILMS 520 (2012) 5906-5913.
M. Rauber, W. Ensinger; Organization of Nanowires into Complex 3D Assemblies by Template
Electrodeposition; MRS ONLINE PROCEEDINGS LIBRARY 1439 (2012) mrss12-1439-aa03-09.
P.S. Hoffmann, O. Baake, M. L. Kosinova, B. Beckhoff, A. Klein, B. Pollakowski, V.A.
Trunova, V.S. Sulyaeva, F.A. Kuznetsov, W. Ensinger; Chemical bonds and elemental
compositions of BCxNy layers produced by chemical vapor deposition with trimethylamine
borane, triethylamine borane, or trimethylborazine; X-RAY SPECTROMETRY 41 (2012) 240246.
76
Materials Analysis
S. Wiegand, S. Flege, O. Baake, W. Ensinger; Synthesis and characterization of
(Na0.5K0.5)NbO3 (NKN) thin films formed by a diol-based sol-gel process; JOURNAL OF
MATERIALS SCIENCE&TECHNOLOGY 28 (2012) 500-505.
P.S. Hoffmann, M.I. Kosinova, S. Flege, O. Baake, B. Pollakowski, V.A. Trunova, A. Klein, B.
Beckhoff, F.A. Kuznetsov, W. Ensinger; Chemical Interactions in the Layered System
BCxNy/Ni(Cu)/Si, Produced by CVD at High Temperature; ANALYTICAL AND
BIOANALYTICAL CHEMISTRY 404 (2012) 479-487.
I. Strašík, . Chetvertkova, E. Mustafin, M. Pavlovič, A. Belousov; Depth profiling of residual
activity of 237U fragments as a range verification technique for 238U primary ion beam;
PHYSICAL REVIEW SPECIAL TOPICS – ACCELERATORS AND BEAMS 15 (2012) 071001.
T. Seidl, A. Plotnikov, E. Mustafin, R. Lopez, D. Severin, E. Floch, C. Trautmann, A.
Golubev, A. Smolyakov, D. Tommasini, W. Ensinger; Influence of swift heavy ion beams and
protons on the dielectric strength of polyimide; POLYMER DEGRADATION AND STABILITY
97 (2012) 2396-2402.
P. Ramirez, M. Ali, W. Ensinger, S. Mafe; Information processing with a single
multifunctional nanofluidic diode; APPLIED PHYSICS LETTERS 101 (2012) 13310.
M. Ali, S. Nasir, Q.H. Nguyen, R. Neumann, W. Ensinger; Biochemical Sensing with
Chemically Modified Synthetic Ion Channels; in: J. Edel, T. Albrecht (Eds.) Nanopores for
Bioanalytical Applications, RSC Publishing, 2012, ISBN: 978-1-84973-527-8, pp. 32-37.
A. Alcaraz, M. Ali, W. Ensinger, S. Mafe, F. Münch, S. Nasir, P. Ramirez; Biomimetic
Nanopores with Amphoteric Amino Acid Groups. Effects of a pH Gradient on the Ionic
Conductance and Selectivity; in: J. Edel, T. Albrecht (Eds.) Nanopores for Bioanalytical
Applications, RSC Publishing, 2012, ISBN: 978-1-84973-527-8, pp. 57-61.
S. Nasir, M. Ali, Q. H. Nguyen, W. Ensinger; Stimuli-triggered Permeation of Ionic Analytes
Through Nanopores Functionalised with Responsive Molecules; in: J. Edel, T. Albrecht (Eds.)
Nanopores for Bioanalytical Applications, RSC Publishing, 2012, ISBN: 978-1-84973-527-8,
pp. 76-82.
Q. H. Nguyen, M. Ali, S. Nasir, W. Ensinger; Fabrication of Nanochannel Arrays for the
Selective Transport of Ionic Species; in: J. Edel, T. Albrecht (Eds.) Nanopores for
Bioanalytical Applications, RSC Publishing, 2012, ISBN: 978-1-84973-527-8, pp. 83-88.
E. Gütlich, P. Forck, W. Ensinger, B. Walasek-Höhne; Scintillation Screen Studies for HighDose Ion Beam Applications; IEEE TRANSACTIONS ON NUCLEAR SCIENCE 59 (2012)
2354-2359.
R. Krishnakumar, F. Becker, W. Ensinger, P. Forck, R. Haseitl, B. Walasek-Höhne; Imaging
Properties of Scintillation Screens for High Energetic Ion Beams; IEEE TRANSACTIONS ON
NUCLEAR SCIENCE 59 (2012) 2301-2306.
B. Lyson-Sypien, A. Czapla, M. Lubecka, K. Zakrzewska, M. Radecka, A. Kusior, A. Balogh,
S. Lauterbach, H. Kleebe; Gas sensing properties of TiO2 – SnO2 nanomaterials; in: The 14th
International Meeting on Chemical Sensors 2012, AMA Association for Sensor Technology,
2012, ISBN: 978-3-9813484-2-2, pp. 1611-1614.
M. Ali, S. Nasir, P. Ramirez, J. Cervera, S. Mafe, W. Ensinger; Calcium Binding and Ionic
Conduction in Single Conical Nanopores with Polyacid Chains: Model and Experiments; ACS
NANO 6 (2012) 9247–9257.
Materials Analysis
77
S. Wiegand, S. Flege, O. Baake, W. Ensinger; Influence of different heat treatment programs
on the properties of sol-gel synthesized (Na0.5K0.5)NbO3 (KNN) thin films; BULLETIN OF
MATERIALS SCIENCE 35 (2012) 745-750.
W. Westmeier, R. Brandt, R. Hashemi-Nezhad, R. Odoj, W. Ensinger, M. ZamaniValasiadou, A Sosnin; Correlations in Nuclear Interactions between E CM/u and Unexplained
Experimental Observables; WORLD JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY 2
(2012) 125-132.
A. Belousov, E. Mustafin, W. Ensinger; Short and long term ionizing radiation effects on
charge-coupled devices in radiation environment of high-intensity heavy ion accelerators;
JOURNAL OF INSTRUMENTATION 7 (2012) C11002.
E. Marin, A. Lanzutti, M. Lekka, L. Guzman, W. Ensinger, L. Fedrizzi; Chemical and
mechanical characterization of TiO2/Al2O3 atomic layer depositions on AISI 316 L stainless
steel; SURFACE COATINGS AND TECHNOLOGY 211 (2012) 84-88.
M. Rauber, F. Muench, M. E. Toimil-Molares, W. Ensinger; Thermal stability of electrodeposited platinum nanowires and morphological transformations at elevated temperatures;
NANOTECHNOLOGY 23 (2012) 475710.
E. Marin, L. Guzman, A. Lanzutti, W. Ensinger, L. Fedrizzi; Multilayer Al2O3/TiO2 Atomic
Layer Deposition coatings for the corrosion protection of stainless steel; THIN SOLID FILMS
522 (2012) 283–288.
F. Muench, S. Lauterbach, H.-J. Kleebe, W. Ensinger; Deposition of Nanofilms inside a
Polymer Template:Formation of Metal Nanotubes; E-JOURNAL OF SURFACE SCIENCE AND
NANOTECHNOLOGY 10 (2012) 578-584.
R. Hatada, K. Baba, S. Flege, S. Nakao, W. Ensinger; Preparation of Diamond-like Carbon
Films by Plasma Source Ion Implantation with External Glow Discharge; TRANSACTIONS OF
THE MATERIALS RESEARCH SOCIETY OF JAPAN 37 (2012) 227-232.
C. Neetzel, F. Münch, A. Schachtsiek, W. Ensinger; Copper Nanowires, Nanotubes, and
Hierarchical Nanopatterns: One-Dimensional Architectures using Ion Track Etched Templates;
TRANSACTIONS OF THE MATERIALS RESEARCH SOCIETY OF JAPAN 37 (2012) 213-216.
78
Materials Analysis
Photo-Induced pH–Tunable Ionic Transport in Nanopores Modified with
“Caged” Lysine
Saima Nasir, Mubarak Ali, Quoc Hung Nguyen and Wolfgang Ensinger
During the recent years nanoscale pores have been studied extensively due to the new basic
phenomena involved and their potential applications in nano/biotechnology [1]. Tracketched polymer membranes containing single conical nanopores and multipore arrays are
of particular interest because they mimic some of the transport properties of biological ion
channels [2]. Recent advances concerning the fabrication processes and the tailoring of the
surface properties have permitted to control the pore geometry and the response to external
stimuli [2-5]. Recently, we have reported synthetic nanopores sensitive to ultraviolet (UV)
light [4]. The pores are chemically modified with photo-labile hydrophobic protecting
groups that are covnverted into hydrophilic groups upon UV light irradiation. The UV light
constitutes a facile way to change the pore surface functionalities externally, without
causing further damage to the active groups that are covalently attached to the pore wall.
In this report we describe a method to obtain photo-sensitive nanopores in which
amphoteric groups are generated after UV treatment [5].
Single asymmetric nanopores (Fig. 1a) as well as multipore membranes containing arrays
of pores (5×107 pores cm-2) were fabricated in heavy ion tracked polyethylene
terephthalate (PET) membranes of thickness 12 µm by well-established track-etching
techniques [3-5]. The pore surface and inner pore walls were chemically modified with the
monolayers of amino acid “caged” lysine chains through carbodiimide coupling chemistry
[5]. The immobilized lysine chains contain photolysable 4,5-dimethoxy-2-nitrobenzyl
(NVOC) moieties that are attached to the –NH2 and –COOH groups at the α–carbon atom in
lysine molecule. Upon UV treatment, the uncharged aromatic chromophore NVOC moieties
are cleaved, leading to the generations of hydrophilic “uncaged” amphoteric groups
sensitive to environmental pH on the pore surface (Fig. 1a).
(b)
1.5
Before UV irradiation1.5
1.0
pH 5.0
Current (nA)
UV irradiation
0.5
After UV irradiation
1.0
pH 9.5
pH 5.0
pH 3.0
pH 3.0
Current (nA)
(a)
0.0
-0.5
pH 9.5
pH 5.0
pH 3.0
0.5
0.0
-0.5
-1.0
-1.0
-1.5
-1.5
[Ge
-1
0
1
2
benVolatge (V)
Voltage (V)
Sie
Fig. 1: (a) Schematic presentation of a conical nanopore surface decorated with “caged”ein
lysine chains having
photo-labile NVOC moieties which are removed by UV light leading to exposure of pH-sensitive
amphoteric
Zita
groups. (b) pH-dependent I–V curves of a single conical nanopore before and after UV irradiation.
t
aus
de
m
Dok
Materials Analysis
79
um
ent
pH 9.5
-2
-1
0
1
2
-2
Due to the presence of uncharged photolabile N OC groups in the immobilzed “caged”
lysine chains on the pore surface, before UV irradiation the ionic current rectification
characteristic of the conical nanopore is lost as shown in the I–V curve (Fig. 1b left). After
exposing the modified pore to UV light irradiation, the NVOC groups are detached from the
immobilized lysine chains and the amphoteric groups are exposed on the pore surface.
Because of amphoteric nature of the resulting end groups, the pH of the surrounding
solutions dictates the pore net charge and permselectivity. I–V curves presented in Fig. 1b
confirm the successful uncaging of –NH2 and –COOH groups of immobilized lysine chains
after UV irradiation. Under basic conditions (pH = 9.5), both groups are deprotonated and
the nanopore (cation-selective) rectifies the ionic current flowing across the membrane due
to the presence of ionized –COO‾ groups. In acidic solution (pH = 3.0) the I–V curve is
flipped (inversion of rectification), indicating the change of surface charge from negative to
positive because of protonated amine (–NH3+) groups, and the pore is now anion-selective.
Finally, at the intermediate pH = 5.0, the pore behaves like an ohmic resistor because the
net pore charge is zero due to the ionization of both (–COO‾ and –NH3+) groups (Fig. 1b
right).
Fig. 2: pH-dependent flux of (a) MV2+ and (b) NDS2- analyte through modified membrane having arrays of
conical nanopores before and after UV irradiation.
Moreover, we have also investigated the UV-light-induced permeation of divalent analytes
across the nanoporous membrane functionalized with “caged” lysine chains prior to and
after UV treatment [5]. The membrane sample separated the feed compartment filled with
an aqueous solution containing either cationic (methylviologen ion, MV2+) or anionic (1,5naphthalene disulfonate ion, NDS2-) analyte and the permeate compartment contains a
buffer solution only. The flux of analyte molecules was obtained by monitoring the
concentration of MV2+ (Fig. 2a) and NDS2- (Fig. 2b) in the permeate chamber from UV
absorbance.
Before U irradiation, the pore is in hydrophobic (“OFF”) state and the divalent ions in the
external solutions can hardly enter and pass through the nanopores. The resulting analyte
fluxes are therefore relatively small at all pH values. After UV irradiation the pore switches
80
Materials Analysis
to hydrophilic (“ON”) state and the analyte fluxes depend markedly on environmental pH
(Fig. 2).
In conclusion we have described the transport properties of conical nanopores
functionalized with photosensitive lysine chains. The experiment concerns with the I–V
curves of the single nanopore functionalized with “caged” and “uncaged” lysine before and
after UV irradiation, respectively, and the fluxes of divalent positive and negative analytes
through the multipore membranes. The photochemical gating of nanoscale pores will
constitute a subject of current interest because of the potential applications in separation
and targeted drug delivery processes.
References:
[1]
[2]
[3]
[4]
[5]
(a) K. Healy, Nanomedicine 2, 459 (2007); (b) J. Griffiths, Anal. Chem. 80, 23(2008)
M. Ali, P. Ramirez, S. Mafe, R. Neumann, and W. Ensinger, ACS Nano 3, 603-608 (2009).
S. Nasir, M. Ali, and W. Ensinger, Nanotechnology 23, 225502 (2012).
M. Ali, S. Nasir, P. Ramirez, I. Ahmed, Q. H. Nguyen, L. Fruk, S. Mafe, and W. Ensinger, Adv.
Funct. Mater. 22, 390-396 (2012)
S. Nasir, P. Ramirez, M. Ali, I. Ahmed, L. Fruk, S. Mafe, and W. Ensinger, J. Chem. Phys. 138,
034709 (2013)
This work has financially been supported by Beilstein-Institut in Frankfurt/Main in the frame of the
project NanoBiC.
Materials Analysis
81
Synthesis of oxidic copper and cobalt nanostructures of different morphologies
T. Matsutani, C. Neetzel, F. Muench, W. Ensinger
The investigation of bundled one-dimensional nanostructures by self-assembly methods can
be easily carried out by anisotropic crystal growth which is directly related to the crystal
structure. However, this process is limited to a few materials. In order to break the
symmetry of the crystal growth, nanowire synthesis can be driven by screw dislocation
where low precursor supersaturation and the presence of appropriate dislocation sources is
essential. [1]
In order to prepare morphology-controlled copper oxide/cobalt oxide heterostructures in
micro- and nanometer scale, we investigated two different synthesis routes that are related
to each other according to their mechanism but can be distinguished by their chemical
reaction route. However, in both cases a ligand is required to build strong complexes
resulting in low concentrations of free metal ions in the precursor solution. In the case of
copper and cobalt ions, we compared ammonia as well as tartrate.
The synthesis process via the ammonia route is accomplished with a three step route where
firstly a copper ammonia complex is generated, followed by a ligand exchange process
leading to the precipitation of copper hydroxide. By annealing, CuO is produced via
dehydratation.
Concentration ratios of the precursor solution as well as the resulting yields measured by
EDX are listed in Table 1. According to the yield composition, the turnover for copper oxide
is higher which can be explained by stronger copper ammonia complexes according to the
related complex stability constants.
Table 1: Composition and yield of CuO/Co3O4 heterostructures
Sample #
precursor
composition
Cu2+z1Co2+z2
yield
composition
CuO(x)Co3O4(y)
(1)
(2)
(3)
(4)
(5)
z1:z2 = 1:0
z1:z2 = 7:1
z1:z2 = 5:1
z1:z2 = 3:1
z1:z2 = 1:10
x:y = 1:0
x:y = 8.6:1
x:y = 6.9:1
x:y = 4.1:1
x:y = 1.2:10
Figure 1 depicts the resulting morphologies of samples (1) to (5). Pure copper oxide
deposition results in a network composed of needle-like structures with diameters of about
10 nm and lengths of 2 µm. With increasing Co3O4 and decreasing CuO content the
structure morphology changes from needle-like architectures to plate-formed shapes.
Obviously, the bundled network-like formation degenerates with decreasing copper content
in the precursor-solution which indicates that its concentration is crucial for the onedimensional growth process in aqueous solution under these conditions. Sample (5) shows
clearly identifiable thin plate structures of round shapes with diameters of approximately 5
µm. The reason for this observation can be explained by the crystal growth of the
intermediate cobalt hydroxide complex. Co(OH)2 consists of a layered structure where
neighboring layers are bound to each other by weak van der Waals forces. Thus, the (100)
plane is stable. [1]
82
Materials Analysis
For the fabrication of Cu2O nanostructures with low CoO contents in aqueous solution, we
applied the well-known Fehling’s reagent with -D-glucose as reducing and tartrate as
complexing agent. Tartrate generates a coordination complex with copper and cobalt metal
ions which on one hand decreases the concentration of the related free metal ions in the
solution and on the other hand prevents the undesirable precipitation of Co(OH) 2 and
Cu(OH)2. Additionally to the earlier procedure, the concentration of the reducing agent as
well as the concentration of copper and cobalt salts in the precursor solution is
indispensable. As listed in Table 2, the specific concentration of the Fehling and reducing
solution were varied in our experiments.
First, we synthesized pure Cu2O structures and varied the concentration of copper metal
ions in the precursor solution (samples (6) and (7)). As it is clearly recognizable (see
Figure 3(a) and 3(b)) needle-like structures can be obtained by adding a low concentration
(Table 2) of metal ions. An increasing amount of copper(II)ions already causes the
formation of particles with diameters of about 250 nm. Therefore, we kept the
concentration of the Cu2+ precursor constant and varied the concentration of cobalt ions in
order test the morphology influence of this species in a heterostructural precipitation. By
adding 1:1 = Cu2+:Co2+ (sample (8)) we observed cubic like structures with uniform
lateral edges of 100 nm as shown in Fig. 3. EDX as well as XRD measurements (not shown
here) confirm the precipitation of both cobalt and copper oxidic structures.
Table 2: Composition of initial Cu
Sample #
CuSO4.5H2O
[mol/L]
CoSO4.7H2O
[mol/L]
Na2C4H4O6
[mol/L]
2+
and Co
2+
for Fehling's reaction
(6)
(7)
(8)
(9)
0.004
0.006
0.004
0.004
-
-
0.004
0.0004
0.005
0.007
0.009
0.005
We expected to obtain structural analogies to sample (7) by keeping the concentration of
copper precursor ions constant and adding a 1:0.1 quantity of cobalt ions (sample (9)).
However, SEM investigations show that the morphology seems to be different (Fig. 3(d)).
Particles with diameters of approximately 50 nm agglomerate together at certain positions
resulting in a crossed one-dimensional growth in each direction. Thus, branched networks
could be obtained. The reason for these occurrences could be that -D-glucose acts as
surfactant and promotes the growth in a certain direction as it also described in the
literature. [2] On the other hand, such morphologies were not obtained for sample (7);
therefore, the addition of cobalt ions leads to a drastic change of the structural material
architecture. However, this synthesis route seems to be more sensitive towards small
changes of concentration in the precursor solution. Moreover, the influence of the reducing
material should be considered accurately for further investigations.
The results indicate that, dependent on the precursor concentration of copper and cobalt
ions, it is possible to prepare morphology controlled heterostructures in a reproducible way.
Further investigations will be carried out for the fabrication of needle-like structures with
high Co3O4 contents.
Materials Analysis
83
Fig. 1: CuO/Co3O4 heterostructures
of different ratios: (a) sample (1),
(b) sample (2), (c) sample (3), (d)
sample (4)
Fig. 2: CuO/Co3O4
sample (5)
nanoplates:
Fig. 3: CuO nanoneedles obtained
by precipitation of Cu(OH)2 and
annealing
References:
[1]
[2]
84
Y. Li, Y. Wu, Chem. Mater. 2010, 22, 5537-5542.
G. Filipic, U Cvelbar, Nanotechnol., 2012, 23, 1-16
Materials Analysis
Materials Modelling Division
The research of the Materials Modelling Division is focused on multi-physics modelling of
defect structures in functional oxids, nanoalloys and energy materials. We are combining
electronic structure calculations with atomistic modelling methods and continuum
descriptions depending on time and length scales involved.
Quantum mechanical calculations based on density functional theory are used for electronic
structure calculations. Large-scale molecular dynamics with analytical interatomic
potentials are the method of choice for studying kinetic processes and plastic deformation.
Kinetic lattice Monte-Carlo simulations are extensively used for simulations of diffusional
and transport processes on extended time scales. The group is operating several HPCcomputers and has access to the Hessian High Performance Computers in Frankfurt and
Darmstadt.
The current research topics are:
 Functional oxides
o Defects and diffusion in TCOs
o New lead-free ferroelectrics: Ordering effects and defects
o Finite-size effects in oxide nanoparticles
 Nanoalloys
o
o
o
o
Plasticity of nanocrystalline metals and alloys
Metallic nanoglasses
Nanophase diagrams
Metallic nanoparticles under nanoextrusion
 Energy materials
o
o
o
o
Interfaces in Li-intercalation batteries
CIS/CIGS absorber materials
High-pressure phases of nitrogen
Superalloys (Mo-Si-B)
Within the bachelor program the Materials Modelling Division is offering classes on
thermodynamics and kinetics as well as defects in materials. Lectures and lab classes on
simulation methods and programming techniques are offered as elective courses in both,
the bachelor and master program.
85
Staff Members
Head
Prof. Dr. Karsten Albe
Emeritus Professor
Prof. Dr. Hermann Rauh, M.A., C.Phys., F.Inst.P., F.I.M.
Research Associates
Dr. Antti Tolvanen
Dr. Jochen Rohrer
PD Dr. Yuri Genenko
Dr. Galina Yampolskaya
Dr. Sergey Yampolskii
Dr. Omar Adjaoud
Dr. Alexander Stukowski
Dr. Peter Agoston
Dr. Yvonne Ritter
Dr. Daniel Sopu
Secretary
Renate Hernichel
PhD Students
Dipl.-Phys. Johann Pohl
Dipl.-Ing. Manuel Diehm
Dipl.-Ing Melanie Gröting
Dipl.-Ing. Silke Hayn
Dipl.-Ing. Jonathan Schäfer
Dipl.-Ing. Arno Fey
M.SC. Olena Lenchuk
M.SC. Dinh Bao Nam Ngo
Dipl.-Phys. Rainer Schulz
Diploma Students
Ofer Hirsch
Tobias Brink
Jens Wehner
Bachelor Students
Stephen Weitzner
Daniel Simon
Leonie Koch
Research Fellow
Dr. Guang-Tong Ma (AvH)
Guest Scientists
Dr. Yuri Nikolaenko, Donetsk Institute of Physics and Technology,
Academy of Sciences of Ukraine (from 01/03 to 15/04/2012).
Research Projects
Forschergruppe 714, Plasticity of nanocrystalline metals and alloys, (DFG AL 578/7-2,
2006-2012)
86
Quantenmechanische Computersimulationen zur Elektronen- und Defektstruktur oxidischer
Materialien (SFB 595, Teilprojekt C1, 2007-2014)
Atomistische Computersimulationen von Defekten und deren Bewegung in Metalloxiden
(SFB 585, Teilprojekt C2, 2003-2014)
Phänomenologische Modellierung von Injektion, Transport und Rekombination in
Bauelementen aus organischen Halbleitern sowie aus nichtorganischen Ferroelektrika (SFB
C5, 2003-2014)
Erforschung der Phasenstabilität und Niederdrucksynthese von festem Stickstoff mittels
atomistischer Computersimulationen und Experimenten (DFG AL 578/3-2, 2010–2012))
Beyond Ni-Base Superalloys: Atomistische Modellierung des Einflusses von
Legierungszusätzen auf die Korngrenzeigenschaften in Mo-Si-B und Co-Re Superlegierungen (DFG Forschergruppe 727, AL 578/9-1, 2010–2013)
Nanosilicon dispersed in SiCN(O) and SiCO-based ceramic matrices derived from
preceramic polymers: new composite anode materials for lithium ion batteries.
(DFG SPP 1473 „Wendelib“, DFG AL 578/10-1, 2011–2013)
Mechanische und kinetische Eigenschaften metallischer
Sekundärphasen (DFG AL578/13-1, 2011–2013)
Gläser
mit
nanoskaligen
Atomic scale modeling of metallic nanoparticles embedded in nanoscale carbon structures
(DFG KO 3861/2-1, 2010–2012)
Bleifreie Piezokeramiken, LOEWE-Schwerpunkt ADRIA (HMWK, 2011-2013)
BMBF-GRACIS, Chemische Gradienten in CU(In,Ga) Se2 Solarzellen: Grenzflächenuntersuchungen und theoretische Modellierung (03SF0359E, 2009-2012)
PPP Finnland, Atomic level simulations of structure and growth of nanoalloys (DAAD 2011–2013)
Topological Engineering of Ultra-Strong Glasses (DFG AL 578/15-1, 2012-2014)
Modeling the electrocaloric effect in lead-free relaxor ferroelectrics: A combined atomisticcontinuum approach (DFG AL 578/16-1, 2012-2014)
HZB-Helmholtz Zentrum Berlin, Virtuelles Institut (HZB VH-VI-520 2012-2017)
Publications
C. Melzer, Y.A. Genenko, S.V. Yampolskii, K. Stegmaier, O. Ottinger, H. von Seggern,
Charge carrier injection and transport in OLEDs: single-particle versus mean-field approach, J.
Photon. Energy, 1, 011014 (2011).
87
H.S. Ruiz, A. Badía-Majós, Y.A. Genenko, H. Rauh, S.V. Yampolskii, Superconducting wire
subject to synchronous oscillating excitations: Power dissipation, magnetic response, and lowpass filtering, Appl. Phys. Lett., 100, 112602 (2012).
J. Schütrumpf, S. Zhukov, Y.A. Genenko, H. von Seggern, Polarization switching dynamics
by inhomogeneous field mechanism in ferroelectric polymers, J. Phys. D: Appl. Phys. 45,
165301 (2012).
Y.A. Genenko, S. Zhukov, S.V. Yampolskii, J. Schütrumpf, R. Dittmer, W. Jo, H. Kungl, M.J.
Hoffmann, H. von Seggern, Universal polarization switching behavior of disordered
ferroelectrics, Adv. Funct. Mater. 22, 2058-2066 (2012).
J. Glaum, Y.A. Genenko, H. Kungl, L.A. Schmitt, T. Granzow, De-aging of Fe-doped leadzirconate-titanate ceramics by electric field cycling: 180°- vs. non-180° domain wall processes,
J. Appl. Phys. 112, 034103 (2012).
H. Rauh, G.I. Yampolskaya, S.V. Yampolskii, Optical transmittance of photonic structures
with logarithmically similar dielectric constituents, J. Opt. 14, 015101 (2012).
P. Manuel Diehm, Peter Agoston, and Karsten Albe, Size-Dependent Lattice Expansion in
Nanoparticles: Reality or Anomaly?, ChemPhysChem 13, 2443 – 2454 (2012).
M. Gröting, I. Kornev, B. Dkhil, K. Albe, Pressure-induced phase transitions and structure of
chemically ordered nanoregions in the lead-free relaxor ferroelectric Na½Bi½TiO3, Phys. Rev. B
86, 134118 (2012).
J. Schäfer and K. Albe, Competing deformation mechanisms in nanocrystalline metals and
alloys: Coupled motion versus grain boundary sliding, Acta Materialia, 60 (17) pp. 60766085 (2012).
J. Schäfer, Y. Ashkenazy, K. Albe, R. S. Averback, Effect of solute segregation on thermal
creep in dilute nanocyrstalline Cu alloys, Materials Science and Engineering A, 546 (307) pp.
307-313 (2012).
Y. Rittera and K. Albe, Chemical and topological order in shear bands of Cu64Zr36 and
Cu36Zr64 glasses, J. Appl. Phys., 111 (10) p. 103527 (2012).
J. Schäfer and K. Albe, Influence of solutes on the competition between mesoscopic grain
boundary sliding and coupled grain boundary motion, Scripta Materialia, 66 (5) pp. 315-317,
(2012).
S. Fähler, U. K. Rößler, O. Kastner, J. Eckert, G. Eggeler, H. Emmerich, P. Entel, S. Müller,
E. Quandt, K. Albe, Caloric Effects in Ferroic Materials: New Concepts for Cooling, Advanced
Engineering Materials, 14 (1-2) pp. 10-19 (2012).
J. Pohl, C. Stahl, K. Albe, Size-dependent phase diagrams of metallic alloys: A Monte Carlo
simulation study on order-disorder transitions in Pt-Rh nanoparticles, Beilstein Journal of
Nanotechnology, 3 pp. 1-11 (2012).
88
Size-Dependent Lattice Expansion in Nanoparticles: Reality or Anomaly?
P. Manuel Diehm, Peter Agoston, Karsten Albe
For nanoparticles it is well established that their properties change with particle size.[1,2]
This size dependence can be used to great advantage, because it offers an independent way
for adjusting important material properties, including catalytic activity, magnetic and
electronic properties, or intercalation ability. This has prompted the use of nanoparticles in
technological applications, such as sensors, fuel cells and batteries. Lattice parameters are a
basic quantity that characterize any crystalline material and thus their variation directly
affects the properties mentioned above. Therefore, the understanding of the size
dependence of the lattice parameters is necessary to gain insight into the size dependence
of many technologically important properties of nanoparticles.
For nanoparticles of many noble metals it is known that the lattice parameters get smaller
with decreasing particle size.[3] Extensive investigations of the past decade have shown that
this effect is reversed in many oxide nanoparticles, for which an increase of lattice
parameters with decreasing particle size is observed. This lattice expansion is widely
perceived as unusual or even anomalous behavior,[4] whereas the contraction observed in
metal particles is considered the standard case. To investigate this seemingly anomalous
effect, we conducted a review of relevant experimental and theoretical literature and used
molecular statics and density functional theory calculations to determine the origin of the
effect.
The survey of experimental results leads to three general observations. First, it is obvious
that lattice expansion occurs in a wide range of different oxide materials and therefore the
effect is not a rare occurrence. In fact, lattice expansion seems to be the standard case for
oxide materials, while lattice contraction is the exception. Second, the lattice expansion
seems to be generally anisotropic, as is evidenced by the results on hexagonal and
tetragonal materials, where the changes of the non-equivalent lattice parameters show clear
differences. In the cases of TiO2 and tetragonal perovskites, the lattice expands in the
crystallographic a direction, while it contracts in c direction. Third, the magnitude of lattice
expansion varies even within the same material. This is most obvious for CeO2, for which
most data is available and where the reported changes for particles of comparable size
range from a contraction of 0.32% up to an expansion of 6.8%. Any explanation of the
effect should be able to explain these three points.
Two major theories have been suggested in literature. One model attributes lattice
expansion to a finite size effect on the lattice sums of the electrostatic interaction. The other
model ascribes the cause to a lattice dilation through vacancies. However, a closer
inspection of both models reveals that they are insufficient to explain even the basic
phenomenon. Molecular statics calculations reveal that the finite size effect on lattice sums
is restricted to the region close to the surface and does not reach into the particle.
Therefore, it is unable to cause directly a dilation of the particle. The vacancy model fails,
because it would require a size dependent increase of the concentration of bulk vacancies,
which is thermodynamically infeasible.[5] In light of the failure of these theories we
investigated a third model, in which lattice expansion is caused by negative surface stresses.
This model is based on the theoretical observation, that surface stresses (
of solid
89
surfaces can also be negative. This can be seen from the Shuttleworth equation, [6]
, where the strain derivative of the surface energy
can be
negative, causing the overall surface stress to become negative. According to the
generalized capillary equation,[7]
, the negative surface stress leads to a
negative capillary pressure ( ), which causes the particle to dilate. In principle, this model
can describe the experimentally observed lattice expansion. The observed anisotropy comes
naturally from the anisotropy of the surface stress and its varying magnitude for different
surface orientations. The variation in the magnitude of the overall lattice expansion in the
same material can be explained by the sensitivity of surface stresses to atmospheric
conditions, because surface modifications through adsorption or reconstruction will also
modify the surface stress.
To confirm our theoretical considerations, we conducted molecular statics relaxations on
nanoparticles of two prototype materials which have a positive (MgO) and a negative
surface stress (GaN), respectively. The results are shown in Fig. 1 and confirm the
thermodynamic predictions. The positive surface stress in MgO leads to an overall
contraction of the particle, while the negative surface stress in GaN causes a dilation in the
particle bulk.
Fig. 2: The shape of the particles used in the relaxation calculations. a) A cubical MgO particle exhibiting {100}
surfaces and b) a hexagonal prismatic GaN particle with {1100}, (0001) and (0001) surfaces. Panels (c) and (d)
show the local atomic strain in a cut across the particles. Green color corresponds to zero strain, blue shades
signify negative strains (i.e. contraction), and yellow–red shades denote positive strains (i.e. expansion).
Finally, we use density functional theory (DFT) calculations to demonstrate the occurrence
of negative surface stresses in oxide materials. The results confirm, that negative surface
stresses can occur in relevant materials. There are many possible mechanisms to explain
90
why surface stresses become negative. Examples are the
to
rehybridization of lowly
coordinated atoms at the surface of partly covalent materials, which leads to larger in-plane
bond-lengths or the creation of surface vacancies and the corresponding surface
relaxations.
References:
[1]
[2]
[3]
[4]
[5]
[6]
[7]
R.S. Berry, Nature 1998, 393, 212.
H. Gleiter, Acta Mater. 2000, 48, 1-29.
C. W. Mays, J. S. Vermaak, D. Kuhlmann-Wilsdorf, Surf. Sci. 1968, 12, 134-140.
S. Tsunekawa, K. Ishikawa, Z.-Q. Li, Y. Kawazoe, A. Kasuya, Phys. Rev. Lett.
2000, 85, 3440.
M. Müller, K. Albe, Acta Mater. 2007, 55, 3237– 3244.
R. Shuttleworth, Proc. Phys. Soc. London Sect. A 1950, 63, 444.
J. Weissmüller, J. W. Cahn, Acta Mater. 1997, 45, 1899 –1906.
91
The role of copper interstitials for diffusion in CuInSe2: First-principles calculations
Johan Pohl, Karsten Albe
Researchers from the Materials Modelling Group at TU Darmstadt have recently elucidated
the role of copper interstial defects for diffusion using first-principles hybrid functional
calculations. Understanding and controlling copper diffusion in CuInSe2-based solar cells is
essential for optimizing photovoltaic devices based on this absorber material. Copper
redistribution at the CuInSe2/CdS interface has been proposed to be responsible for
voltage-bias induced metastable behaviour of CuInSe2 solar cells. Copper migration from
the interface into the bulk has also been observed during the deposition of the CdS buffer
layer on CuInSe2 at a certain Fermi pinning level by researchers of the Thin Films group.
The fact that the copper vacancy diffusion mechanism cannot account for fast ion
conductivity and is insensitive to drift from electric fields due to its rather high migration
barrier of 1.26 eV suggests that alternative copper diffusion mechanisms, such as copper
interstitial diffusion, are operational. However, local DFT calculations with static band-gap
corrections report formation energies larger than 2 eV for the copper interstitial, which
makes a significant contribution of interstitials to the copper diffusion unlikely.
The calculations have shown that the copper interstitial in CuInSe2 can occur in distinct
stable configurations on four different crystallographic sites. These positions are the
octahedral (with respect to the cations) site A, the tetrahedral site B, and the two trigonal
planar sites C and D.
Using the generalized-gradient approximation (GGA) the trigonal planar site C is the
ground state of the single positively charged copper interstitial. Its formation energy,
however, is only 0.03 eV lower compared to the octahedral site A (quoted for a Fermi
energy at the valence band maximum and copper-rich conditions). The GGA values without
band gap correction for sites A through D are all very similar and close to 1 eV. Using the
hybrid functional HSE06 with adapted screening parameter, however, we find significantly
lower formation energies from 0.17 to 0.38 eV. The hybrid functional values reverse the
energetic order between site A and C, i.e. the octahedral site A is the ground state for
HSE06, while the trigonal planar sites C and D are 0.04 eV higher in energy. Although
these energy differences are small, an accurate treatment of the exchange-corrleation
energy therefore is important for obtaining the correct ground state in the case of the
copper interstitial.
92
The very similar formation energies of sites A,
C and D show that the octahedral copper
interstitial has significant freedom to move
within the selenium tetrahedron (see figure).
Following the analysis of the stable sites, two
possible migration mechanims of the copper
interstitial
were
identified.
A
direct
mechanism, where the octahedral copper
interstitial (site A) migrates via the tetrahedral
saddle point site (site B), and an indirect
interstitialcy mechanism, where the octahedral
interstitial knocks out a copper atom from a
lattice site to the next octahedral site. The
hybrid functional gives a migration barrier of
0.22 eV for the direct mechanism and a barrier
of 0.34 eV for the indirect mechanism. Similar
to the copper vacancy migration, the GGA
functional gives slightly lower migration
barriers.
As photo-enhanced copper diffusion may occur, it is also interesting to compare the
migration barriers for different charge states. We find that the migration barriers of the
neutral charge state are only reduced by at most 0.04 eV in comparison to the positive
charge state, which is unlikely to account for a significant enhancement of copper diffusion.
The occurence of direct and indirect diffusion paths is in line with the finding of Cahen et
al., who stated that the better than expected stability of p-n junctions in CuInSe2 may be
explained by more than one active diffusion mechanism. For typical copper-poor p-type
high-grade photovoltaic material, the typical Fermi level lies 0.25 eV above the VBM and
the chemical potential is -0.5 eV, which gives an approximate activation energy of 1.14 eV
for the direct and 1.26 eV for the indirect diffusion mechanism, both being close to the
activation energy of 1.26 eV for the vacancy mechanism. This shows that all three
mechanisms similarly contribute to the copper self-diffusion in high-grade photovoltaic
CuInSe2, which poses a challenge to the experimental detection of these mechanisms.
In conclusion, the rather low formation enthalpies and the low migration barriers clearly
show that not only the copper vacancy but also the interstitial is an important defect
driving copper diffusion phenomena in CuInSe2. A direct and an indirect migration
mechanism with migration barriers as low as 0.22 and 0.34 eV make the copper interstitial
susceptible to space-charge induced drift. These barriers are consistent with a number of
physical models that have been invoked for different phenomena related to copper
diffusion in the literature.
References:
J. Pohl, K. Albe, Phys. Rev. B 84, 121201 (2012).
93
Thermo-electromagnetic properties of
a magnetically shielded superconductor strip
G.T. Ma1,2 and H. Rauh1
1
2
Institute of Materials Science, Darmstadt University of Technology, 64287 Darmstadt
Applied Superconductivity Laboratory, Southwest Jiaotong University, 610031 Chengdu
Type-II superconductors are widely used for their exceptional properties which set them off
against conductors in the normal state, e.g. the ability to carry large electrical currents with
only minimum hysteretic ac loss and the capacity to withstand high magnetic fields.
Although these properties do not go unlimited, they can be improved by taking advantage
of the shielding effect of magnetically susceptible environments. Thus, magnetically
sheathed single or composite superconductor cables stand out for weakening the (applied
and self-induced) magnetic fields experienced by their superconducting constituents.
Heterostructures made up of thin superconductor strips and para- or soft-magnetic shields
of specially tailored shapes – elements of both large-scale power and microelectronic device
applications deemed particularly promising – admit intricate control of the supercurrent
density and the magnetic flux. Lowering the flux density near the edges of such strips
entails a distinct mitigation of the influence of the self-induced magnetic field exerted upon
the strips.
Motivated by these opportunities for guiding the magnetic flux and by the necessity to
include the action of the cryogenic part, developing further previous investigations on
purely electromagnetic grounds, we here study numerically thermo-electromagnetic
properties of a thin type-II superconductor strip surrounded by open cavity soft-magnetic
shields and subject to an oscillating transverse magnetic field, as depicted in Fig. 1.
Fig. 1: Cross-sectional view of a superconductor strip of width 2 w (dark shading; thickness not to scale!)
located between the two bulk soft magnets (light shading) of a wedge-shaped magnet configuration
extending infinitely in the z-direction of a Cartesian coordinate system x, y, z adapted to the strip. The
definition of the distance between the edges of the strip and the magnets a is indicated.
Our numerical simulations resort to the quasistatic approximation of a vector potential
approach in conjunction with the classical description of conduction of heat. The
underlying definition of the superconducting constituent makes use of an extended
‘smoothed’ Bean model of the critical state, which includes the field- and temperature
dependence of the induced supercurrent as well. The delineation of the magnetic shields
exploits the reversible-paramagnet approximation in the Langevin form, as appropriate for
magnetizations with narrow Z-type loops, and considers induced eddy currents too. The
94
coolant is envisaged as acting like a bath that instantly takes away surplus heat. Based on
the Jacobian-free Newton-Krylov approach and the backward Euler scheme, the numerical
analysis at hand is tailored to the problem of a high width/thickness aspect ratio of the
superconductor strip.
Assigning representative materials characteristics and conditions of the applied magnetic
field, our findings for the thermal transient state include an overall rise of the maximum
temperature Tmax recorded on the magnetically shielded superconductor strip which tends
to saturation in a superconducting thermo-electromagnetic steady state above the operating
temperature, modulated by oscillations of twice the frequency of the applied magnetic field
(Fig. 2). The effect of magnetic shielding here is twofold at least: to mitigate the rise of the
Fig. 2: Maximum temperature Tmax of the magnetically shielded superconductor strip as a function of time t
during the thermal transient state for an applied transverse magnetic field with amplitude Ha = 50 A/mm and
frequency f = 50 Hz, referring to the normalized distance between the edges of the strip and the magnets
a w = 0.2. Numerical results corresponding to the limit a w  ∞ of an electromagnetically isolated strip
(thin line) are shown for comparison.
Fig. 3: Distribution of temperature T as a function of the normalized coordinate x/w over the width of the
magnetically shielded superconductor strip at different instants of time t during the thermal transient state for
an applied transverse magnetic field with amplitude Ha = 50 A/mm and frequency f = 50 Hz, referring to the
normalized distance between the edges of the strip and the magnets a w = 0.2 (left) and a w  ∞, as for an
electromagnetically isolated strip (right).
maximum temperature Tmax, and hence to lend increased thermal stability to the
superconductor strip, but also to curtail the gradients of temperature T itself, and therefore
95
to smooth the temperature profile along the width of the strip (Fig. 3). Results obtained for
the thermo-electromagnetic steady state show that magnetic shielding can have a profound
influence on electromagnetic observables of the superconductor strip too: to wash out the
profile of the magnetic induction and lower its strength, to relax the profile of the
supercurrent density and increase its strength, to tighten the profile of the power loss
density and reduce its strength, all inside the superconductor strip. The hysteretic ac loss
suffered by the superconductor strip is seen to be cut back or, at most, converge on that of
an unshielded strip, thermo-electromagnetic coupling merely playing an insignificant part
thereby (Fig. 4).
Fig. 4: Normalized hysteretic ac loss Uac H a2 suffered by the magnetically shielded superconductor strip as a
function of the normalized amplitude H a H c of the applied transverse magnetic field in the thermoelectromagnetic steady state, referring to the normalized distance between the edges of the strip and the
magnets a w = 0.2. Numerical results corresponding to the limit a w  ∞ of an electromagnetically isolated
strip (thin line) are shown forcomparison.

In conclusion, a self-consistent approach such as the one described above, with its
simultaneous regard of electromagnetic and thermal traits, is called for if the time to reach
the thermo-electromagnetic steady state as well as the stability of this state, apart from the
temperature profile along the width of the magnetically shielded superconductor strip,
were to be addressed. On the other hand, a limitation to a purely electromagnetic
approach, neglecting the production of heat, seems sufficient for estimating the hysteretic
ac loss suffered by the strip in the thermo-electromagnetic steady state. The computational
method developed as it stands is easy to handle and ready to use, without the need for
adaptations of existing codes in multi-physics software packages.
96
Materials for Renewable Energies
Research in the Renewable Energies group focuses on electrochemical energy technologies,
such as fuel cells and batteries. Novel catalysts, electrodes and electrode processing
techniques are being developed, but also sophisticated methods for their in-situ
characterization. Systematic structural and electrochemical characterization of the new
materials is carried out in order to unravel the structure-properties correlation. Techniques
used for structure analysis include X-ray absorption spectroscopy (XAS), transmission
electron microscopy (TEM), and X-ray diffraction (XRD), whereas the electrocatalytic
performance is tested in both model experiments and under realistic operation conditions.
The group’s recent scientific activities can be divided into the following three areas:

New catalyst concepts
Our main focus is on the design of alternative support materials for fuel cells, which do not
suffer from corrosion in the severe operation conditions and may be promising candidates
to replace the standard carbon support. Different morphologies, e.g. fibres or hollow
spheres, contribute to an improved control in 3D electrode design and thus allow for an
efficient mass transport. Furthermore, shape-selected nanoparticles exposing highly active
crystal facets are being investigated and indicate improved electrocatalytic activities.

Functional electrode design
Beyond the conventional preparation techniques, advanced layer-by-layer (LbL) techniques
are used in the fabrication of fuel cell electrodes allowing for a well-defined 3D
architecture. A likewise promising approach, which also offers high flexibility and a facile
up-scaling, is the electrospinning technique. Thin fibres with solid, porous, but also coreshell structure can be spun and deposited as an arbitrary mesh or in an aligned fashion.
These structures have been used as electrodes in both fuel cells and batteries. Electron
microscopy is applied for the electrodes’ detailed characterization. For this specific purpose,
new techniques have been developed and established in the group, as for instance the
focused ion beam (FIB) technique in cooperation with the HZB, Berlin. FIB/SEM was
applied to obtain 3D reconstructions of the porous fuel cell electrodes before and after
operation as well as for comparison of the different electrode processing techniques.

In situ studies
In situ and operando X-ray absorption studies play an important role in our activities with
respect to the systematic investigation of reaction and degradation mechanisms. A versatile
in situ sample environment has been designed and successfully implemented at various
synchrotron facilities. It enables the spatial and time resolved study of different areas of the
fuel cell electrodes in various operation conditions (direct methanol, direct ethanol
operation, but also for intermediate temperature PBI fuel cell studies). In addition to the
97
conventional EXAFS analysis the novel delta µ XANES technique is applied in cooperation
with Prof. David Ramaker, George Washington University. This technique enables us to
study adsorbates attached to the active catalyst surface, so that reaction mechanisms can be
followed directly during operation. The results provide important insights, which will help
to further catalyst optimization. In 2012, the delta µ XANES technique has been applied to
intermediate temperature PBI fuel cells. At the cathode side, the adsorption of phosphoric
acid species could be followed temperature and potential dependent. The effect of anode
humidification on CO poisoning at different temperatures was also studied, and the
importance of water being present at the anode side underlined.
In July 2012, Prof. Christina Roth was appointed full professor at the FU Berlin and now
heads the group Applied Physical Chemistry.
Financial support is provided by DFG, BMWi, BMBF, and EU as well as by the respective
synchrotron facilities and industrial partners.
Staff Members
Head
Prof. Christina Roth
Secretary
Maria Bense (joint with Prof. Donner and Prof. Xu)
PHD students
Dipl.-Ing. (FH) Hanno Butsch Dipl.-Ing. Sebastian Kaserer
Dipl.-Ing. Benedikt Peter
Dipl.-Ing. Alexander Schökel
Dipl.-Ing. André Wolz
Diploma students
Anja Habereder
Research Projects
German-Canadian fuel cell cooperation (BMWi project 2010-2013)
New developments in intermediate temperature fuel cells (EU project 2010-2012)
New concepts for a controlled 3D design of porous electrodes (DFG project 2010-2013)
Publications
J. Melke, A. Schoekel, D. Gerteisen, D. Dixon, F. Ettingshausen, C. Cremers, C. Roth, and D.
E. Ramaker, “Electrooxidation of Ethanol on Pt. An in situ and time-resolved XANES study”, J.
Phys. Chem. C 116 (4) (2012) 2838–2849.
98
A. Habereder, D. Dixon, M. Farmand, S. Kaserer, C. Roth, D. E. Ramaker, „Space resolved, in
operando X-ray absorption spectroscopy: Investigations on both the anode and cathode in a
direct methanol fuel cell“, J. Phys. Chem. C 116 (13) (2012) 7587-7595.
A. Wolz, S. Zils, D. Ruch, N. Kotov, C. Roth, M. Michel, “Incorporation of Indium Tin Oxide
Nanoparticles in PEMFC Electrodes”, Adv. Energy Mater. 2 (2012) 569-574, doi:
10.1002/aenm.201100711.
H. Butsch, C. Roth, D. Ritzinger, A. Helmboldt, G. Hoogers, A. Bock, "Spatially resolved
contact pressure and contact resistance measurements at the gas diffusion layer - a novel tool
for PEM fuel cell development", J. Electrochem. Soc. 159 (6) (2012) B709-B713.
H. Nuss, C. Roth, Solid State Chemistry 2011, Nachrichten aus der Chemie 60 (3) (2012)
251-264.
C. Roth, „Nicht nur als Diamant wertvoll: Kohlenstoffmaterialien im neuen Licht zukünftiger
Anwendungen“, Labor&more Journal 04.12 (2012) 26-29.
Published books
Polymer electrolyte membrane and direct methanol fuel cell technology (PEMFCs and DMFCs),
Vol. 1 and 2, ed. C. Hartnig, C. Roth, Woodhead Publishing 2012.
99
Incorporation of Indium Tin Oxide Nanoparticles
in PEMFC Electrodes
André Wolz, Susanne Zils, David Ruch, Nicholas Kotov, Marc Michel, Christina Roth
Introduction
Carbon materials suffer from corrosion at the cathode of polymer electrolyte membrane
fuel cells (PEMFCs). In the presence of water, carbon support materials are oxidized to
carbon dioxide even at low potentials. Hence, nowadays it is very fashionable to look for
alternative support materials, like oxides or conductive polymers. The choice of a support
material other than carbon black makes it mandatory to think about the preparation
method of the electrode layer and its resulting electrode structure. The nano-sized oxide
particles have to be assembled differently from the sub-micrometer sized carbon black
particles to yield an equally promising structure. A schematic of such an electrode design is
depicted in Fig. 1.
Fig. 1. Schematic of a 3D electrode design incorporating nano-sized oxide support particles (Pt/ITO) and
Nafion-coated multi-walled carbon nanotubes (MWCNT/Nafion) into a fast sprayed multi-layer electrode.
The electrode structure is known to have a significant impact on the cell performance [1]. A
homogeneous and porous structure favors mass transport of the reactants, and a good
accessibility of the Pt nanoparticles results in a high Pt utilization. Recently, a novel
electrode preparation technique has been introduced by which it was possible to assemble
1D support materials into 3D networks [2, 3]. The networks had a multilayered
architecture of polyaniline and carbon nanotubes, both decorated with Pt, and the
electrodes reached 3 times higher Pt utilizations at the cathode side than conventional
electrodes. This technique is referred to as the ‘fast multilayer’ technique.
100
The same technique was used by Zils et al. [4] to manufacture electrodes with carbon black
material and Nafion layers, which were then compared to an airbrushed MEA with the
same catalyst composition. Focused ion beam tomography (FIB) measurements revealed a
much more homogenous structure with a small average pore size for the multilayer
electrode than for the airbrushed one. Single-cell tests furthermore demonstrated a two
times higher Pt utilization showing the suitability of this technique as a fast and easy
method for fuel cell electrode preparation.
This study shows the results for the incorporation of nano-sized alternative support
materials into advanced electrode architectures. It will give a first impression of how oxide
nanoparticles can be assembled in a fuel cell electrode. The obtained results will bridge the
gap between the previous results of electrochemical studies and the performance as catalyst
material in a real fuel cell environment.
Experimental
Pt decoration of ITO nanoparticles
ITO nanoparticles (NP) were decorated with Pt NP after a reduction of PtCl4 precursor by
sodium borohydride (NaBH4). 120 mg ITO NP and 51.8 mg PtCl4 (99.99+%) were
dispersed in 20 ml ultrapure water (MilliQ - MQ), the amount of PtCl4 corresponding to a
Pt loading of 20 wt%. After a homogenous dispersion was obtained, a solution of 51.8 mg
NaBH4 in 10 ml MQ was added. The dispersion turned black immediately. Afterwards, the
solution was diluted with deionized water, filtered through a 0.02 µm Anopore™ Inorganic
Membrane (Whatman®) and dried at 30°C under vacuum.
Functionalization of the multiwall carbon nanotubes (MWCNT)
The MWCNT were treated in concentrated acids in order to functionalize their surface and
to remove remaining amorphous carbon species. 20 mg MWCNT were dispersed in 6 ml
HNO3 (p.a., 65%) and 6 ml H2SO4 (ACS reagent, 95-98%) and sonicated for 30 min.
Afterwards, the nanotubes were diluted with copious amounts of MQ, filtered with a
0.45 µm polycarbonate track-etch membrane, rinsed with MQ water and dispersed in a
solution of 5 ml ethanol and MQ (80:20 by volume). A mixture of 0.34 ml Nafion ® solution
in 5 ml ethanol/MQ (80:20) solution was prepared and the MWCNT dispersion added
dropwise to the ionomer dispersion. As the second ink, 40 mg of Pt/ITO (20 wt% Pt
loading) was dispersed in 10 ml ethanol/MQ solution (80:20).
Electrode preparation
Polymer electrolyte membranes of Nafion® 117 were purchased from Ion Power Inc., USA.
The membrane was mounted in a home built spraying plate with vacuum feature. The plate
was heated up to 80°C and a solution of 80 mg Pt on Vulcan-XC72 (HiSPEC™ 3000,
Johnson Matthey), 0.4 ml Nafion® 117 solution (5%), 3.6 ml MQ, and 12 ml ethanol was
coated onto the membrane by EcoSpray containers (Labo Chimie France). The cathode was
assembled by alternating layers of Pt/ITO and MWCNT/Nafion® (referred to as multilayer
electrode: ML-MEA). For comparison, a second electrode was sprayed, consisting of a
standard Pt/CB anode with the same loading used before and a Pt/CB cathode, with a Pt
loading and Nafion® content equal to the Pt/ITO cathode.
101
Structural characterization
The ITO supported Pt NP were characterized by X-ray diffraction (XRD). The XRD was
carried out with a X’Pert-Pro diffractometer in reflection geometry operating with Cu Kα1
and Kα2 radiation (λ=1.54060 Å). Rietveld refinement was used to estimate the particle
sizes of ITO and Pt. Scanning electron microscopy (SEM) was applied for the
characterization of the Pt/ITO electrode using a FEI Quanta 200 FEG, equipped with a field
emission gun operating at 15 kV.
Electrochemical characterization
Cyclic voltammograms (CVs) were measured with a Gamry Reference 600 potentiostat
(USA) in a standard glass three-compartment electrochemical cell (Bio-Logic SAS), with a
glassy carbon working electrode (Ø 3 mm, BASi Instruments, USA), a Pt wire serving as
counter electrode, and an Ag/AgCl reference electrode (ASL, Japan). The potential between
the working electrode (WE) and reference electrode was cycled 10 times between -0.21.2 V with a sweep rate of 50 mV s-1. The electrolyte was prepared with MQ water and
HClO4 (Sigma-Aldrich, 70%) at a concentration of 0.1 (M). The electrolyte was purged for
5 min with Ar.
Polarization curves of the electrodes were collected with a FuelCon Evaluator C50 test
bench (FuelCon AG, Germany), in which the Pt/ITO-MWCNT/Nafion® electrode was used
as cathode and the standard Pt/CB electrode as anode. Humidified hydrogen was fed to the
anode with a flow rate of 200 ml min-1 and high-purity oxygen was provided to the cathode
at a flow rate of 100 ml min-1. The anode/cathode gas humidifiers were set to 80°C and the
cell temperature to 75°C. The polarization curves were recorded automatically with the
software package FuelWork by increasing the current in 0.1 A steps after a steady state
potential has been reached.
Results and discussion
Pt nanoparticles on indium tin oxide nanoparticles have been considered as possible fuel
cell catalyst materials. However, tests in a real fuel cell environment are still lacking. After
the successful deposition of Pt on ITO the effect of electrode structure on the fuel cell
performance is studied. The assembly of Pt/ITO with 20 wt% Nafion® ionomer in the
electrode did not show any performance at all. This could be attributed to the very dense
electrode structure formed by the nano-sized support and the ionomer preventing the
desired gas transport. To enhance the porosity of the electrode network, the incorporation
of Pt/ITO catalyst into a multi-walled carbon nanotubes (MWCNTs) network (coated with
Nafion®) is proposed. The nanotube network has the advantage to be highly electron
conductive and the ionomer coating ensures the proton conductive character of the
electrode. The catalytic active species Pt on ITO is embedded into the structure during the
preparation process.
Single cell tests of the proposed electrode design have been performed, and the polarization
and power density curves can be found in Fig. 2. The novel electrode design reached a
maximum power density of 73 mW cm-2 at a current density of 0.12 A cm-2. The power
density is comparable to the conventionally prepared Pt/CB electrode. The Pt utilization for
the multilayer electrode is 1468 W g(Pt)-1 compared to 1723 W g(Pt)-1 for the standard
cathode.
102
Fig. 2. Comparison of the polarization and power density curves of the multilayer electrode design (Pt/ITOMWCNT/Nafion) and a conventionally prepared electrode (Pt/CB-Nafion).
It is remarkable that both MEAs show almost the same performance while possessing two
completely different morphologies. The spherical carbon black particles are in the
micrometer range with micro- and macropores, whereas the ITO particles are in the
nanometer range. The surface area of carbon black peaked at around 200 m2 g-1 and is
therefore much higher compared to ITO (27 m2 g-1 according to the supplier).
SEM micrographs have been recorded after the single cell measurements (Fig. 3). In the
crosssectional view, the electrode thickness was measured to be 5.4 µm. The low and high
magnification micrographs of the electrode surface indicate the mentioned network
structure provided by the multi-walled carbon nanotubes, in which the Pt/ITO component
is embedded. In Fig. 3, right single nanotube fibers are visible, and the structure seems to
be highly porous as intended.
Fig. 3. SEM micrographs of the advanced multi-layered electrode structure incorporating oxide-supported Pt
nanoparticles; in high magnification the carbon nanotubes can be seen.
103
Conclusion
This study showed a simple preparation technique for advanced electrode structures, which
succeeded in incorporating a nano-sized oxide supported Pt component (Pt/ITO) into a 3D
porous electrode network. Commercially available indium tin oxide (ITO) nanoparticles
(<50 nm) were used as support for Pt nanoparticles in combination with Nafion® coated
multi-walled carbon nanotubes (MWCNT) on the cathode side of a PEMFC. The MWCNT
promote a high electronic conductivity and help to form a porous network structure, which
was used to accomodate the Pt/ITO nanoparticles. The architecture favored the reactant
permeability, and a better accessibility of the active Pt sites was obtained. The conductivity
within the electrode was provided by only a negligible amount of highly conductive
MWCNTs. Single cell measurements show a maximum power density of 73 mW cm-2 and a
Pt utilization of 1468 mW mgPt-1 for the cathode. The performance data and the Pt
utilization are comparable to a standard Pt/carbon black electrode (Pt/CB) indicating that
it actually may be possible to replace carbon black by more stable oxides without a loss in
performance. Besides this, it is shown for the first time that ITO can serve as support
material under real fuel cell conditions. This might open the way to the manufacturing of
cost-efficient and easily prepared fuel cell electrodes with an enhanced long-term stability.
Acknowledgments
Financial support by the National Research Fund, Luxembourg is gratefully acknowledged.
We also want to thank C. Fasel, U. Kunz and J.-C. Jaud for their help with sample
preparation, TGA and XRD measurements.
References
[1]
[2]
[3]
[4]
104
R. O'Hayre, D. M. Barnett, F. B. Prinz, J. Electrochem. Soc. 2005, 152, A439.
A. Wolz, S. Zils, M. Michel, C. Roth, J. Power Sources 2010, 195, 8162.
S. Zils, A. Wolz, M. Michel, C. Roth, ECS Trans. 2010, 28, 33.
S. Zils, M. Timpel, T. Arlt, A. Wolz, I. Manke, C. Roth, Fuel Cells 2010, 10, 966.
In Situ and Time-Resolved XANES Study of the Electrooxidation of
Ethanol on Pt
Julia Melke, Sebastian Kaserer, Alexander Schoekel, Dietmar Gerteisen, Ditty Dixon, Carsten
Cremers, David E. Ramaker, Christina Roth
Introduction
Ethanol is an attractive alternative fuel in polymer electrolyte fuel cells - thus its
electrochemical oxidation on Pt has been studied for several years [1-3]. The ethanol
oxidation reaction (EOR) is a complex multistep reaction that involves several adsorbed
species like acetyl, adsorbed acetate, carbon monoxide (CO) and CHx-species, and generally
yields some acetic acid, but mainly acetaldehyde along with the desired carbon dioxide as
final product. Except for the formation of acetaldehyde, oxidation to other products such as
acetic acid and carbon monoxide requires an oxygen atom source normally provided by the
activation or dissociation of water. The activation of water on Pt generally occurs around
0.55 V (RHE), and below this potential the Pt surface is covered mainly by CO(ads) and
CHx, as shown by various studies in the literature. Adsorbed acetate was observed to be
reversible and seems to reduce the number of available sites for the EOR. The EOR also
depends on anion adsorption from the electrolyte and the crystal structure of the catalysts.
X-ray absorption spectroscopy is especially suited to study reaction and degradation
mechanisms, such as the EOR, in-situ and under realistic operation conditions, since both
changes in the catalyst structure (EXAFS) and the kind and amount of adsorbates on the Pt
surface (delta µ XANES) can be followed at once. In our previous X-ray absorption
spectroscopy study, potential-dependent changes in the delta  XANES were observed
during the EOR at steady state conditions [4]. In contrast, for the first time in this work, we
report, time-resolved adsorbate coverages on a real working fuel cell anode during ethanol
oxidation. The ethanol oxidation reaction is studied using X-ray absorption spectroscopy
during chronoamperometric cell operation. The analysis of the XANES region of the Pt L3
edge by the delta μ XANES technique allows the coverage of the Pt surface with OH, n-fold
O and C-species to be followed in-situ. The current-voltage characteristics and the coverage
are modelled by means of a multi-step reaction mechanism based on a modified ButlerVolmer approach that additionally includes adsorbate-adsorbate lateral interactions. The
model is validated against experimental current and surface coverage data over time. With
the model, the importance of acetaldehyde formation via initial C-H vs O-H bond cleavage
is examined, the latter dominating at higher potentials on vacant sites remaining in the
oxygen coverage coming from water activation.
105
Experimental
Commercially-available carbon-supported Pt (40 wt% Pt on Vulcan XC-72) purchased from
Johnson Matthey was used as catalyst. The catalysts coated membranes (CCMs) were
prepared by spraying an ink on the polymer electrolyte Nafion®115. The ink was fabricated
by dispersion of the catalyst powder in high purity water and 5% Nafion® solution. The ink
was sprayed in several layers on the membrane, which was then dried for 1h at 130°C in a
drying chamber and pressed at 130°C with 1 KN cm-2.
X-ray absorption spectroscopy measurements were carried out at beamline X1 at Hasylab,
Hamburg in transmission mode for the Pt L3-edge at 11564 eV during electrochemical
operation. Therefore the CCM was sandwiched between Au-coated stainless steel endplates
with integrated, interdigitated flow fields and X-ray transparent Kapton foil windows.
Below the X-ray transparent window, a part of the cathode catalyst layer was removed.
Between flow field and electrode a Toray TGP H 90 gas diffusion layer was placed.
Hydrogen (N 5.0) was supplied at 50 ml min-1 by a flow controller (Bronkhorst,
Netherlands). The liquids were supplied at 1.2 ml min-1. Potentiostatic U/i curves were
recorded using a commercial potentiometer.
The electrochemical characterization was carried out in a fuel cell during half cell tests,
which means that the cathode side was fed with hydrogen instead of oxygen, serving as a
dynamic hydrogen electrode (DHE). First, the anode was measured in its dry state,
subsequently reduced with hydrogen at 50°C and then cooled down to ambient
temperature and flooded with high purity water. Potentials of 0.45 V and 0.75 V vs. DHE
were applied in order to use these measurements as reference data. This procedure was
followed by replacing the water with 1 M aqueous methanol solution and a potential of
0.45 V vs. DHE applied. Then again water was fed to the anode side and a potential of
0.75 V vs. DHE was held for at least 1.5 h to oxidize all carbon containing adsorbates
remaining on the surface. Finally, the water was replaced by 1 M aqueous ethanol solution
and several potentials were applied. At each potential step, several quick-EXAFS spectra
were recorded from E = 11300 eV to 12800 eV using a Si(111) double-crystal
monochromator. A thin Pt metal foil was used as reference for energy calibration. The
intensities of the focused beam and the transmitted beam were detected by three gas-filled
ion chambers in series.
EXAFS The EXAFS analysis was done for the water measurement at 0.45 V, only, to
estimate the particle size and the dispersion. Extraction of the EXAFS data from the
measured absorption spectra was performed with the programs Athena and Artemis. For
comparison, the catalyst particle size was also determined by XRD measurements of the
pristine catalyst powder. The particle size obtained was 2.7 nm by Rietveld refinement
using the Software FullProf.
XANES The XANES region was analyzed by the Δμ-technique. The absorption coefficient
was obtained equivalent to the EXAFS region, with the exception that the normalization
was carried out between 20 eV and 150 eV relative to the Pt L3 edge. The normalized data
were further aligned using the reference foil data. The ∆µ was obtained by subtracting the
measurement for water at 0.45 V vs. DHE from the appropriate spectra (Fig. 1).
106
Figure 1. Δμ-results during ethanol oxidation at several potentials measured vs. DHE. For comparison
calculated Δμ by the FEFF8, labeled OH, O, and COatop, are shown. The simulations are reported previously.
MODELING The kinetics of the EOR was modeled by assuming that the dominant
contributions to the current originate from acetaldehyde and CO2 formation. Further, the
ethanol reaction rates are considered to be uniform and the same regardless of whether the
Pt site is located at a corner, edge, or terrace of the Pt cluster. The estimated Pt particles
size is around 1.6 nm, so that the fraction of face and edge-corners sites is about 0.8 and
0.2, respectively. The intrinsic rate of each reaction is given by a rate constant kf and kb
determined by the forward and backward activation energy ( kf/b = exp(-ΔGf/b/RT) ). The
potential dependence of the rate of each considered reaction step is described by a Butler
Volmer expression. In addition, a Frumkin isotherm is introduced in order to account for
adsorbate-adsorbate interactions on the surface. Each reaction is modeled as source or
drain term for the involved chemical species or charge carriers. These source and drain
terms are coupled by continuity equations, which are solved numerically using the Software
Mathematica® 7.
Chemical reactions
The EOR is modeled via the reaction pathways summarized in Fig. 2: the formation of
acetaldehyde and CO2 is considered as products, with the former as the main reaction
product and the intermediate CO adsorbate enroute to the latter the main poison on this
catalyst blocking the EOR at lower potentials. The formation of adsorbed CHx and CO from
acetaldehyde is neglected in our kinetics model here. As summarized in Fig. 2, the model
includes parameters for 7 forward rates and 3 reverse rates (assuming 4 rates are
irreversible), with 6 symmetry coefficients (the two acetaldehyde rates are assumed to be
equal), and 6 Frumkin interaction coefficients (C1-C1,C1-C2,C1-O, C2-O, O-OH and O-O).
Reactants
Figure 2. Schematic of 7 reactions (3 assumed to be in
equilibrium) as indicated by heavy arrows, 4 adsorbates
(ethoxy* adsorbate assumed to be a short-lived
intermediate and therefore not accumulating on
surface), and 6 Frumkin interaction parameters indicated
by 4 light dotted arrows and 2 squares.
107
θ(ML/MASA)
Fig. 3 shows the time evolution of the measured (points) and simulated (lines) surface coverages
for different potential steps.
U = 0.55 V
θ(ML/MASA)
U = 0.85 V
U = 0.65 V
U = 0.9 V
U = 0.7 V
U = 0.92 V
θ(ML/MASA)
U = 0.6 V
θ(ML/MASA)
U = 0.80 V
θ(ML/MASA)
time /s
U = 0.75 V
time /s
 C-species
 O (n-fold)
 OH (atop)
measured
C-species
O (n-fold)
OH (atop)
simulated
Figure 3. Time-resolved OH(atop), O(n-fold) and C-species coverage for ethanol oxidation at several potentials
measured vs. DHE. Points refer to experimental data, solid lines show simulation results.
The starting potential of all steps was 0.45 V and hence at time t = 0 the surface is covered
mainly with C1-species as previously discussed. For all potential steps, except 0.55 V, a
decrease in C-species compared to the starting potential can be observed. In the potential
range between 0.6 V and 0.65 V the absolute decrease is small, but for long times the trend
becomes visible. At potentials U ≥ 0.7 V the decrease in C-species coverage is very obvious.
Furthermore, for potentials U < 0.75 V, only OH is observed apart from C-species. At
potentials U ≥ 0.75 V, coverage with OH(ads) decreases over time and in parallel O(ads)
formation is observed.
108
The comparison of the experimental and simulated coverages (Fig. 3) and the experimental
and simulated currents (not shown here) shows reasonable agreement. The behaviour of
the coverage, especially at potentials U ≥ 0.75 V is reproduced. For potentials U < 0.75 V
the very strong dynamic behavior seen in the simulated coverages at very short time scales
(10 s) was so far not measurable, since the time resolution in the XANES measurements is
too low and the signal-to-noise ratio too high. The current simulation reproduces the large
experimentally observed overshoot at the higher potentials U ≥ 0.75 V, but the small
experimentally observed overshoot in the current at lower potentials U < 0.75 V is not
reproduced.
Conclusion
This study shows for the first time, time-dependent adsorbate coverages of C-, OH- and Ospecies on carbon-supported Pt catalysts of a real CCM operated with ethanol as fuel. These
results were used to validate a detailed time-dependent kinetic model describing the
ethanol oxidation by a dual path mechanism, similar to what is found for methanol
oxidation. The two paths involve either acetaldehyde or CO2 formation by initial C-H bond
scission or acetaldehyde by initial O-H bond scission. It is remarkable that with this
relatively simple model involving C1 (CO and CHx), CH3CHOH, OH, and O adsorbates, all
measured quantities such as the time-dependent coverages and currents, can be reproduced
with a reasonable number of free parameters and in excellent agreement with the
experimental data.
Certainly other reactions may also play a role in the ethanol oxidation reaction, altering the
overall rate and distribution of products. We have emphasized in this work the reduction of
the number of parameters in the model (and hence the number of reactions), and therefore
the simplification of the kinetic model to the essential dominant reactions. Despite this
simplification, the kinetic model is able to simulate both the time dependent adsorbate
coverages and current; the adsorbate coverages available for the first time in this work. It is
hoped that knowledge of the adsorbate coverages on real catalysts under operating
conditions sufficiently validates this kinetic model, so that it can be used in a predictive
fashion to learn how to design new and better catalysts.
Acknowledgments
The kind support by S. Mangold and D. Batchelor from the ANKA synchrotron facility and A.
Webb and M. Hermann from the HASYLAB synchrotron facility is gratefully acknowledged.
References
[1]
[2]
[3]
[4]
Lamy, C.; Lima, A.; LeRhun, V.; Delime, F.; Coutanceau, C.; Léger, J.-M. J. Power Sources, 2002,
105, 283-296.
Parsons, R.; Vandernoot, T. J. Electroanal. Chem., 1988, 257, 9.
Wang, J.; Wasmus, S.; Savinell, R.F. J. Electrochem. Soc., 1995, 142, 4218-4224.
Melke, J; Schoekel, A.; Dixon, D.; Cremers, C.; Ramaker, D. E.; Roth, C. J. Phys. Chem. C, 2010,
114, 5914 –2925.
109
Physics of Surfaces
Physical properties of surfaces and interfaces are relevant in nearly all areas of science and
engineering. The fundamental interactions between surfaces, the surrounding fluid and
small objects in the fluid play an important role, for example in biology, biotechnology,
mechanical engineering, or petroleum geology. The common research question can be
expressed as “How does the interplay between physical surface properties, surface and
interface chemistry, and fluid flow affect the entire system?”
We follow an interdisciplinary approach focusing on physical, chemical and biological
properties of surfaces. The connection between surfaces and fluids is of particular interest
because it is essential in various technological systems. Our research targets at a better
understanding of the interplay between surface pattering (morphological and chemical)
and modification with the fluid flow. Experimental methods such as microscopy,
microfluidics, or spectroscopy are important tools.
Staff Members
Head
Prof. Dr. Robert Stark
Research Associates
Dr. Suman Narayan
Dr. Marek Janko
Technical Personnel
Marie-Christine Apfel
Secretary
Imke Murschel
PhD Students
Dipl.-Biol. Elke Kämmerer
Dipl.-Min. Maximilian Köhn
M.Sc. Na Liu
Dipl.-Phys. Agnieska Voß
Bachelor, Master, and Anne Kirsten
Diploma Students
Aurelie Degroote
Dr. Christian Dietz
M. Sc. Kim Lieu Phuong (LMU)
M.Sc. Andreas Plog
Dipl.-Phys. Simon Schiwek
M.Sc. Assma Siddique
M.Sc. Limor Zemel
Julian Mars
Research Projects
Funktionale Polymer-Peptidoberflächen (CSI, 2010 – 2012)
Influence of elasticity, density and chemical composition of extracellular matrices on the
spatiotemporal dynamics of plasma membranes (CSI, 2010 – 2012)
Wafer cleaning (Industrie 2011 - 2012)
Low friction coatings (Industrie 2011 – 2012)
Generation of composites from borides with tuneable electrical conductivities using
peptides optimized by genetic engineering; characterization of the bio-solid interactions by
modelling and AFM STA 1206/5-1 (DFG SPP 1569 2012 – 2013)
110
Physics of Surfaces
Publications
D. Peter, Dalmer M., Lechner A., Gigler A. M., Stark R. W., Bensch W. The influence of
liquid media on the fracture strength of polysilicon nanostructures. ULTRA CLEAN
PROCESSING OF SEMICONDUCTOR SURFACES X. Mertens P., Meuris M., Heyns M. (Eds).
(2012); 187:127-130.
B. Kremer, Bauer M., Stark R. W., Gast N., Altermann W., Gursky H. J., Heckl W. M.,
Kazmierczak J. Laser-Raman and atomic force microscopy assessment of the
chlorococcalean affinity of problematic microfossils. J. RAMAN SPECTROSC., 43 (2012)
32-39.
M. Janko, Stark R. W., Zink A. Preservation of 5300 year old red blood cells in the Iceman.
JOURNAL OF THE ROYAL SOCIETY INTERFACE. 9 (2012) 2581-2590.
Gigler A. M., Dietz C., Baumann M., Martinez N. F., Garcia R., Stark R. W. Repulsive
bimodal atomic force microscopy on polymers. BEILSTEIN JOURNAL OF
NANOTECHNOLOGY 3 (2012) 456-463.
Shimizu S., Shimizu T., Thomas H. M., Matern G., Stark R. W., Balden M., Lindig S.,
Watanabe Y., Jacob W., Sato N., Morfill G. E. Synthesis of diamond fine particles on
levitated seed particles in a rf CH4/H-2 plasma chamber equipped with a hot filament. J.
APPL. PHYS. 112 (2012) 073303.
Davydovskaya P., Janko M., Gaertner F., Ahmad Z., Simsek O., Massberg S., Stark R. W.
Blood platelet adhesion to printed von Willebrand factor. J. BIOMED. MATER. RES. A. 110
A (2012) 335-341.
Klein K., Gigler A. M., Aschenbrenner T., Monetti R., Bunk W., Jamitzky F., Morfill G., Stark
R. W., Schlegel J. Label-Free Live-Cell Imaging with Confocal Raman Microscopy.
BIOPHYS. J. 102 (2012) 360-368.
Bauer M., Davydovskaya P., Janko M., Kaliwoda M., Petersen N., Gilder S., Stark R. W.
Raman spectroscopy of laser-induced oxidation of titanomagnetites. J. RAMAN
SPECTROSC. 42 (2012) 1413-1418.
Shalev T., Gopin A., Bauer M., Stark R. W., Rahimipour S. Non-leaching antimicrobial
surfaces through polydopamine bio-inspired coating of quaternary ammonium salts or an
ultrashort antimicrobial lipopeptide. JOURNAL OF MATERIALS CHEMISTRY 22 (2012)
2026-2032.
Fabritz S., Hörner S., Könning D., Empting M., Reinwarth M., Dietz C., Glotzbach B.,
Frauendorf H., Kolmar H. and Avrutina O. From Pico to Nano: Biofunctionalization of
Cube-octameric Silsesquioxanes by Peptides and Miniproteins. ORGANIC &
BIOMOLECULAR CHEMISTRY 10 (2012) 6287-6293.
Physics of Surfaces
111
Repulsive Bimodal Atomic Force Microscopy on Polymers
Alexander M. Gigler1, Christian Dietz2, Maximilian Baumann1,
Nicolás F. Martinez3, Ricardo García3 and Robert W. Stark2
1
Center for NanoScience (CeNS) and Dept. of Earth and Environmental Sciences, Ludwig-MaximiliansUniversität München, Theresienstraße 41, 80333 Munich, Germany
2
Center of Smart Interfaces and Department of Materials Sciences, Technische Universität Darmstadt,
Petersenstr 32, 64287 Darmstadt, Germany
3
Instituto de Microelectrónica de Madrid, c/ Isaac Newton 8, Tres Cantos, 28760 Madrid, Spain
Bimodal atomic force microscopy [1-4] can provide high-resolution images of polymers. In
the bimodal operation mode, two eigenmodes of the cantilever are driven simultaneously.
When examining polymers, an effective mechanical contact is often required between the
tip and the sample to obtain a compositional contrast, so particular emphasis was placed on
the repulsive regime of dynamic force microscopy. We thus investigated bimodal imaging
on a polystyrene-block-polybutadiene diblock copolymer surface and on polystyrene. The
attractive operation regime was only stable if the amplitude of the second eigenmode was
kept small compared to the amplitude of the fundamental mode. To clarify the influence of
the higher eigenmode oscillation on image quality, the amplitude ratio of both modes was
systematically varied. Fourier analysis of the time series recorded during imaging showed
frequency mixing. However, these spurious signals were at least two orders of magnitude
smaller than the first two fundamental eigenmodes. Thus, repulsive bimodal imaging of
polymer surfaces yields a good signal quality for amplitude ratios smaller than
A01/A02=10:1 without affecting the topography feedback.
Imaging of a Polystyrene-block-polybutadiene diblock copolymer
We explored the imaging capabilities of repulsive bimodal AFM with a 60-nm-thick film of
polystyrene-block-polybutadiene (SB) diblock copolymer. To this end, we systematically
varied the amplitude ratios A01:A02 between the first and second eigenmodes for bimodal
imaging while keeping A01 = 27 nm constant. Figure 1 shows the recorded amplitude (a)
and phase images (b) of the first eigenmode as well as the amplitude (c) and phase images
(d) of the second eigenmode while varying the amplitude ratio A01:A02 between the two
eigenmodes stepwise from 1:1 (top) to 50:1 (bottom). The amplitude of the first
eigenmode did not change considerably because the feedback of the instrument kept this
parameter constant. The two polymer blocks of the cylindrical structure of the block
copolymer are increasingly indistinguishable in the phase image of the first eigenmode (Fig.
1(b)) when increasing the amplitude ratio. By contrast, there is an optimum amplitude
ratio with respect to the contrast in the second eigenmode images. We find that the best
contrast is obtained for amplitude ratios smaller than 10:1, which is different from the
results obtained in the attractive regime, where the optimum contrast implies freeamplitude ratios larger than 10:1 [5]. Note that the image contrast is related to the signalto-noise ratio and thus difficult to quantify for heterogeneous samples. The conclusions
drawn here are on the basis of the optical impression of the authors.
Comparing these observations with bimodal-spectroscopy measurements on polystyrene
leads to the same conclusions. The maximum phase shift ΔΦ1 between the oscillator at
resonance (far away from the sample surface) and at the closest tip-sample distance (lowest
112
Physics of Surfaces
amplitude) gives the highest value for an amplitude ratio of 1:1 and decreases with
increasing ratio. This agrees with Fig. 1(b). The total free amplitude A01+A02 is highest for
an amplitude ratio of 1:1 and leads to the highest impact of the tip on the sample and
hence to the maximum phase response. In case of the second eigenmode and considering
only the repulsive regime, the maximum phase response ratio A01:A02 is between 10:1 and
4:1 at a given amplitude (setpoint), which is in good agreement with the contrast found in
Fig. 1(d). When operating the AFM in the repulsive regime, we assume that there is a
minimum amplitude of the second eigenmode necessary to sense the mechanical
differences between both types of polymers, which differ considerably in stiffness.
However, if the amplitude of the additional oscillation becomes too large, the bimodal
technique might become destructive to the surface structure, counteracting a good phase
contrast.
Figure 1. First (a, b) and second eigenmode (c, d) amplitude (a, c) and phase images (b, d) measured on the
surface of a thin film of a cylinder forming SB diblock copolymer. The amplitude ratio A1/A2 was varied from
50:1 to 1:1 while keeping A01 = 27 nm constant. The best contrast was observed for ratios between 10:1 and
2:1.
Summary
Bimodal AFM imaging is fully compatible with repulsive operation. We found that the firsteigenmode image quality in the repulsive regime is not affected by the second-eigenmode
excitation for large amplitude ratios, A01/A02. For small ratios, a crosstalk between the two
eigenmodes occurred for stiff samples (e.g., silicon), rendering a stable operation of the
AFM impossible. On softer samples (e.g., polystyrene), operation parameters corresponding
to different operation regimes for both modes were found. To optimize the imaging of
heterogeneous polymers, the amplitude ratio is a key parameter. On the SB sample, the
optimum amplitude ratio for imaging polymer samples in the repulsive regime was less
than 10:1. Our data imply that the small oscillation of the second eigenmode does not
affect the amplitude behavior of the first eigenmode at setpoint ratios that are typically
used for imaging. Under such conditions, the imaging process seems to be largely
independent from the additional modulation. A stable repulsive regime is also indicated by
the time-trace analysis, which shows regular oscillations in both eigenmodes with only
minimal nonlinear effects.
References
[1]
[2]
[3]
[4]
[5]
Rodriguez, T.R.; Garcia, R. Appl. Phys. Lett. 2004, 84, 449-451.
Proksch, R. Appl. Phys. Lett. 2006, 89, 113121.
Martinez, N.F.; Patil, S.; Lozano J.R.; Garcia, R. Appl. Phys. Lett. 2006, 89, 153115.
Kawai, S.; Glatzel, T.; Koch, S.; Such, B.; Baratoff, A.; Meyer E. Phys. Rev. Lett. 2009, 103, 220801.
Patil, S.; Martinez, N. F.; Lozano J. R.; Garcia, R. J. Mol. Recognit. 2007, 20, 516–523.
Physics of Surfaces
113
Joint Research Laboratory Nanomaterials
The Joint Research Laboratory Nanomaterials was established in 2004 to enhance the
cooperation between the Institute for Nanotechnology at the Karlsruhe Institute of
Technology and the Institute of Materials Science at the Technische Universität Darmstadt.
Start-up funds to establish the laboratory were provided by both institutions and the State
of Hessen. Scientific personnel is financed by the Institute for Nanotechnology at Karlsruhe
Institute of Technology and by external grants of funding agencies in Germany and of the
EU as well as by industrial cooperations. The laboratory interacts in several areas with
research groups in Materials Science and Chemistry. The research activities are
concentrated in the area of nanoparticulate systems, their synthesis and processing,
microstructural characterization and their properties. The focus is currently on developing
nonporous structures as bulk materials and as thin films for the development of tailored
and tuneable nanomaterials with applications ranging from printable electronics to energy
materials. An additional engineering focus of the research is on the stability of
nanostructured materials under operation conditions, such as high temperatures and gas
environments, as well as the study of mechanical performance of nonporous structures. The
nanomaterials are prepared using Chemical Vapor Synthesis and Nebulized Spray Pyrolysis
starting from metal-organic precursors and metal salts. Using these methods a wide range
of nanostructures can be synthesized. In addition to several synthesis systems,
characterization equipment is available including X-ray diffraction, nitrogen adsorption,
light scattering and Zeta potential, gas chromatography and, in cooperation with the
Surface Science Group, special equipment for in-situ characterization of battery materials
using surface analytical techniques.
Staff Members
Head
Prof. Dr.-Ing. Horst Hahn (Director Institute for Nanotechnology)
Research
Associates
Dr. Matti Oron-Carl
Dr. Ruzica Djenadic
Secretary
Renate Hernichel
PhD Students
Dipl.-Ing. Azad Jaberi Darbandi
Dipl.-Ing. Mohsen Pouryazdan
Dipl.-Ing. Philipp Leufke
Dipl.-Ing. Babak Nasr
Dipl.-Ing. Nina Schweikert
M.Sc. Dechao Wang
Dipl.-Ing. Clemens Wall
Dipl.-Phys. Sebastian Becker
Dipl.-Ing. Christopher Loho
Dipl.-Ing. Ira Balaj
114
Dr. Mohammad Ghafari
Dipl.-Ing. Ralf Witte
Dipl. Phys. Arne Fischer
Dipl. Ing. Holger Hain
Dipl. Ing. Klaus Maximilian
Dipl. Ing. Aaron Weis
Dipl. Ing. Ralf Witte
M.Sc. Cahit Benel
M.Sc. Cheng Huang
M.SC. Aeenehvand, Fatemeeh
M.Sc. Garlapati Suresh Kumar
M.Sc. Massoud Nazarian-Samani
M.Sc. Mohammad Fawey
Guest Scientists
Bojana Mojic, University of Novi Sad
Mariam Mohri, University of Teheran
Research Projects
EU-Projekt, 7th Framework, MAHEATT FP7-ENERGY-NMP-2008-2012
Plastizität in Nanokristallinen Metallen und Legierungen (DFG HA 1344/22-2,2009 -2012)
Tuneable Magnetic Nanostructures. Property Characterization and Modeling (DFG HA
1344/28-1, 2010 – 2013)
Investigation of non-equilibrium phonon populations in biased metallic single-walled
carbon nanotubes (DFG OR 262/1-2, 2011-2013)
Reversibles Durchstimmen der elektronischen Transporteigenschaften in oxidischen
leitfähigen Nanostrukturen zur Anwendung im Bereich der druckbaren Elektronik (DFG HA
1344/25-1, 2010 – 2013)
BMBF, Elektrospeicher im System – Zuverlässigkeit und Integration (325/20514659/
NANOMIKRO, 2012-2014)
Förderung durch Mittel des Helmholtz Institut Ulm (2010-2014)
Publications
N. Schweikert, R. Heinzmann, A. Eichhoefer; et al.; Electrochemical impedance spectroscopy
of Li4Ti5O12 and LiCoO2 based half-cells and Li4Ti5O12/LiCoO2 cells: Internal interfaces and
influence of state-of-charge and cycle number, SOLID STATE IONICS Volume: 226 Pages:
15-23 DOI: 10.1016/j.ssi.012.08.002 Published: OCT 15 2012
M. Pouryazdan, D. Schwen, D. Wang, et al; Forced chemical mixing of immiscible Ag-Cu
heterointerfaces using high-pressure torsion, PHYSICAL REVIEW B Volume: 86 Issue: 14
Article Number: 144302 DOI: 10.1103/PhysRevB.86.144302 Published: OCT 1 2012
J. Biener, S. Dasgupta, L. Shao, et al.; Macroscopic 3D Nanographene with Dynamically
Tunable Bulk Properties, ADVANCED MATERIALS Volume: 24 Issue: 37 Pages: 50835087 DOI: 10.1002/adma. 201202289 Published: SEP 25 2012
P. Nisha, S. Pillai, Savitha, A. Darbandi, et al; Critical behaviour and magnetocaloric effect
of nano crystalline La0.67Ca0.33Mn1-xFexO3 (x=0.05, 0.2) synthesized by nebulized
spray pyrolysis, MATERIALS CHEMISTRY AND PHYSICS Volume: 136 Issue: 1 Pages:
66-74 DOI: 10.1016/j.matchemphys.2012.06.029 Published: SEP 14 2012
115
P. Leufke, R. Kruk, D. Wang, et al; Ferroelectric vs. structural properties of large-distance
sputtered epitaxial LSMO/PZT heterostructures , AIP ADVANCES Volume: 2 Issue: 3 Article
Number: 032184 DOI: 10.1063/1.4756997 Published: SEP 2012
K. Okamura, H. Hahn; Potential distribution in channel of thin-film transistors , APPLIED
PHYSICS LETTERS Volume: 101
Issue: 1
Article Number: 013504 DOI:
10.1063/1.4733290 Published: JUL 2 2012
T. Enz, R. Theissmann, H. Hahn; Thermal degradation of microporous Sm2O3-MgO
nanocomposites at isothermal conditions and surface chemical properties , JOURNAL OF THE
EUROPEAN CERAMIC SOCIETY Volume: 32 Issue: 8 Pages: 1613-1624 DOI: 10.1016/
j.jeurceramsoc. 2012.01.004 Published: JUL 2012
P. Leufke, A. Mishra, A. Beck, et al.; Large-distance rf- and dc-sputtering of epitaxial La1xSrxMnO3 thin films , THIN SOLID FILMS Volume: 520 Issue: 17 Pages: 55215527 DOI: 10.1016/j.tsf.2012.04.064 Published: JUN 30 2012
M. Ghafari, H. Hahn, R. Brand, et al.; Structure of iron nanolayers embedded in amorphous
alloys , APPLIED PHYSICS LETTERS Volume: 100 Issue: 20 Article Number: 203108
DOI: 10.1063/ 1.4717711 Published: MAY 14 2012
M. Ghafari, S. Kohara, H. Hahn, et al; Structural investigations of interfaces in Fe90Sc10
nanoglasses using high-energy x-ray diffraction , APPLIED PHYSICS LETTERS Volume: 100
Issue: 13 Article Number: 133111 DOI: 10.1063/1.3699228 Published: MAR 26 2012
C. Chappaz-Gillot, P. Marek, B. Blaive, et al.; Anisotropic Organization and Microscopic
Manipulation of Self-Assembling Synthetic Porphyrin Microrods That Mimic Chlorosomes:
Bacterial Light-Harvesting Systems, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
Volume: 134 Issue: 2 Pages: 944-954 DOI: 10.1021/ja203838p Published: JAN 18 2012
A. Kilmametov, A. Balogh, M. Ghafari, et al; Radiation effects in bulk nanocrystalline FeAl
alloy , Source: RADIATION EFFECTS AND DEFECTS IN SOLIDS-INCORPORATING PLASMA
SCIENCE AND PLASMA TECHNOLOGY Volume: 167 Issue: 8 Special Issue: SI Pages:
631-639 DOI: 10.1080/10420150.2012.666241 Published: 2012
K. Okamura, B. Nasr, R. Brand, et al; Solution-processed oxide semiconductor SnO in pchannel thin-film transistors , Source: JOURNAL OF MATERIALS CHEMISTRY Volume:
22 Issue: 11 Pages: 4607-4610 DOI: 10.1039/c2jm16426d Published: 2012
J.X. Fang, U. Vainio, W. Puff, et al.; Atomic Structure and Structural Stability of Sc75Fe25
Nanoglasses , Source: NANO LETTERS Volume: 12 Issue: 1 Pages: 458-463 DOI: 10.1021/
nl2038216 Published: JAN 2012
C. Huang, M. Moosmann, J. Jin, et al.; Polymer blend lithography: A versatile method to
fabricate nanopatterned self-assembled monolayers , BEILSTEIN JOURNAL OF
NANOTECHNOLOGY Volume: 3 Pages: 620-628 DOI: 10.3762/bjnano.3.71 Published:
SEP 4 2012
116
Mechanics of Functional Materials
The research at the Division of Mechanics of Functional Materials is focused on the
constitutive modeling and the simulation of functional materials and systems such as
 piezoelectric ceramics,
 deformable dielectrics, and
 lithium-ion battery electrodes.
These materials are characterized by a coupling of multiple physical fields at a variety of
length-scales. Their macroscopic responses depend on the microstructure and its
thermodynamic kinetics. The main features of our research therefore include coupled fields
(e.g. mechanical, electrical, chemical), microstructure evolution, mesoscopic material
properties, and homogenization. Primary tools of our research are continuum models and
Finite Element numerical simulations. New concepts such as phase-field models or
Isogeometric Analysis are regarded to an increasing extent in our work.
Phase field simulation of domain structure of ferroelectric ceramics
Ferroelectrics are widely used as actuators, sensors, and memory devices. A distinguishing
feature of ferroelectrics is that they possess different spontaneous polarization states.
Application of an electric field allows switching between these states and the cycling
loading of a specimen by the latter gives rise to nonlinear hysteretic behavior.
Two kinds of degradation phenomena take place in ferroelectrics: aging and fatigue. Aging
in ferroelectrics is defined as the gradual change of ferroelectric properties with time under
constant boundary conditions, e.g., the decrease of switchable spontaneous polarization.
Fatigue in ferroelectrics, on the other hand, is defined as the change of ferroelectric
properties with increasing number of load cycles. These degradation effects can originate
from several mechanisms such as internal bias field, domain wall pinning, dead layers near
the electrodes, or mechanical degradation. Common point defects in ferroelectrics are
oxygen vacancies which can result, for instance, from extrinsic doping and
nonstoichiometry. Consequently, these vacancies are an important factor in the
aforementioned degradation mechanisms.
These influences are studied by means of phase field models in which the spontaneous
polarization is introduced as an order parameter. Its evolution is subject to the LandauGinzburg equation that is minimizing the total Helmholtz enthalpy. This allows, e.g., to
model the effect of internal bias fields induced by the defect dipoles. Furthermore, one can
consider the space charge introduced by the oxygen vacancies due to semiconduction
features. These charges can accumulate at certain locations, resulting in otherwise instable
domain structures.
Nonlinear electromechanical modeling of deformable dielectrics
Dielectric elastomer actuators (DEA) outperform most large displacement actuators in
terms of weight, cost, and efﬁciency. A typical DEA exhibits an electrode-elastomerelectrode sandwich structure. The electromechanical coupling effects of dielectric
elastomers rely on the electrostatic force on the material polarization, which can be
represented as eigenstress, i.e. the Maxwell stress. These stresses are considered in
nonlinear Finite Element formulations. Despite promising performance under laboratory
conditions, DEAs have complex failure mechanisms, which were studied intensively. As the
applied voltage increases, the elastomer reduces its thickness and in return the voltage
117
induces an even higher electric field. This positive response may lead to the collapse of the
devices, namely the so-called electromechanical instability. Analytical results can be
obtained for the electromechanical instability problem due to the Maxwell stress.
On the other hand, ferroelectrets, known as electrically charged micro-porous foam, have a
very large longitudinal piezoelectric eﬀect and have received wide applications as sensors
particularly in acoustical devices. During a charging process electric breakdown (Paschen
breakdown) may take place in the air pores of the foam, thus introducing free charge pairs.
Those charges can be separated by electrostatic forces and relocated at the interfaces
between the polymer and the electrically broke-down medium. The development of this
free charge density along the interfaces is the key for the piezoelectricity of ferroelectrets.
In order to simulate the hysteresis curve of the charge density development at the
interfaces, nonlinear Finite Element simulations based on internal variables are employed,
allowing a faithful reproduction of experimental results.
Simulation of diffusion introduced stresses in the Lithium-ion batteries via
Isogeometric Analysis
Lithium-ion batteries are an important energy storage system. They are the predominant
power source for portable electronic devices such as cellphones and tablet PCs and
potentially for Plug-in hybrid electric vehicles (PHEV). Current efforts in the scientifc
community aim at increasing both the capacity of the batteries and attainable charge rates.
Another major research direction is concerned with prolongation of the batteries’ lifetime.
Lithium-ion battery cells comprise three main components: a cathode, which commonly
consists of a lithium compound such as LiCoO or LiFePO4 , an anode, which is often made
of Si or C, and an electrolyte. The electrodes exist in various designs, for instance as thin
film substrates, porous electrodes, or as nanowire assemblies. During charge processes, Li
ions migrate from the cathode through the electrolyte to the anode where they are
intercalated into the active anode material. This process is reversed during discharge. The
diffusion of the Li ions within both electrodes and throughout the electrolyte as well as the
chemical reactions at the electrodes’ surfaces impose limits on the achievable charge rates.
The batteries’ capacity, on the other hand, is mainly determined by the anode material. Key
factors directly related to these limits are the large mechanical stresses and the induced
fracture in the active materials. The (de)intercalation processes lead to large volumetric
strains (expansions up to 400% have been observed with Si anodes) and result in high
stress levels. Over several hundred charge-discharge cycles this causes material fatigue of
the electrodes, cracking and a literal pulverization of the active material, accompanied by
capacity loss of the battery cell. The understanding of the damage processes in the
electrodes’ particles and their influence on the mechanical-electrochemical properties is
hence of utmost importance.
Higher-order Finite Element procedures based on the concept of Isogeometric Analysis are
applied for the treatment of the coupled nonlinear constitutive equations, allowing for a
unified treatment of diverse particle shapes and electrode geometries.
118
Staff Members
Head
Jun. Prof. Boshi (Dr.) Baixiang Xu
Research Associates
Dr. -Ing. Peter Stein
Secretaries
Frau Maria Bense
PhD Students
Dipl.-Ing. Yinan Zuo, M.Sc.
Ying Zhao, M.Sc.
Yangbin Ma, M.Sc.
Research Projects
Phase-field simulation of ferroelectrics with defects (Project in SFB 595, 2012-2014)
Simulation of the electrocaloric effect of relaxor ferroelectrics (Project in SFB 1599, 2013-2015)
Isogeometric simulation of diffusion-induced stress in Lithium-ion battery electrodes
(Project in GSC CE, 2013-2015)
Publications
Stein, P., Hsu, M.-C., Bazilevs, Y., Beucke, K.: Operator- and Template-Based Modeling of
Solid Geometry for Isogeometric Analysis with Application to Vertical Axis Wind Turbine
Simulation, Comput. Methods Appl. Mech. Engrg., 213 (2012), 71-83
B.-X. Xu, R. Mueller, A. Theis, M. Klassen, D. Gross: Dynamic analysis of dielectric elastomer
actuators, Appl. Phys. Letter, 100, 112903, 2012
M. Klassen, B.-X. Xu, S. Klinkel and R. Mueller: Material modeling and microstructural
optimization of dielectric elastomer actuators, Technische Mechanik, 32, 1, 38–52, 2012
M. Khalaquzzaman, B.-X. Xu, S. Ricker, R. Müller: Computational homogenization of
piezoelectric Materials using FE^2 to determine configuratonal forces, Technische Mechanik,
Technische Mechanik, 32, 1, 21-37, 2012
M.Z. Wang, B.-X. Xu, B.S. Zhao: On the generalized plane stress problem, the Gregory
decomposition and the Filon mean method, Int. J. Elast. 1, 1-28, 2012
M.Z. Wang, B.-X.Xu, Y.T. Zhao: General representations of polynomial elastic fields, J. Appl.
Mech. ASME, 79, 021017, 2012
F. Yang, G. Hu, B. Xu, W. Wu, C. Yang, H. Wu: Statistical mechanical origin of hysteresis in
ferroelectrics, J. Appl. Phys. 112, 034113, 2012
B.-X. Xu, A. Theis, R. Mueller, M. Klassen, D. Gross: Dynamic modeling of dielectric elastomer
actuators with sandwich structure, Proc. SPIE, 8409, Third International Conference on
Smart Materials and Nanotechnology in Engineering, 840924, 2012,
B.-X. Xu, R. Müller, M. Klassen, D. Gross: Nonlinear dynamics of the dielectric elastomer
actuator, Proc. Appl. Math. Mech. 12, 335-356, 2012
R. Mueller, M. Klassen, B. Xu: Numerical Modeling Aspects of Dielectric Elastomer Actuators,
Proc. Appl. Math. Mech. 12, 409-410, 2012
Md. Khalaquzzaman, B.-X. Xu, R. Mueller: Computational homogenization of materials with
small deformation to determine configurational forces, Proc. Appl. Math. Mech. 12, 423-424, 2012
119
Phase field simulation of polarization switching of aged ferroelectric single crystals
Y. N. Zuo, P. Stein, B. X. Xu
Ferroelectric materials exhibit a large electromechanical coupling effect. Consequently, they
have garnered much interest in the recent years for actuator and sensor applications. In
order to enhance their properties, the materials are doped with foreign atoms, causing
defects in their crystal lattice. A common kind of point defect are oxygen vacancies that
greatly affect the electromechanical properties of ferroelectrics [1]. The understanding of
such effects is important in explaining the mechanism of aging and fatigue of ferroelectrics.
Experiments demonstrated, for instance, that the gradual degradation is caused by the
dipoles induced by the oxygen vacancies [2]. Furthermore, aged ferroelectrics crystals
exhibit large recoverable strain and double hysteresis loops [3-5].
In order to describe the motion and distribution of oxygen vacancies, various analytical and
numerical methods have been developed, for example the analytical phenomenological
model described by Dawber and Scott [6]. Lo et al. [7] proposed a 2D four state Potts
model, disregarding, however, the effects of the domain wall and the electrostatic field.
Xiao [8] and Hong et al. [9] employed phase-field models for studying the interaction of
oxygen vacancies with domain structures in ferroelectric single crystals. They treated
oxygen vacancies as point defects. Unfortunately, they were are not able to capture the
character of the bias field caused by the vacancies and, as a result, they predict a memory
effect in the ferroelectrics. In a recent approach, Zhang et al. [10] developed a phase-field
model that treats oxygen vacancies as defect dipoles.
In the present work, a phase field model is employed to investigate the domain structure,
its switching property, and the influence of the oxygen vacancies. In addition to the exterior
electric field, the interior field induced by the dipoles also plays a role. The evolution of the
domain structure is hence a compromise between the two fields, minimizing the total free
energy. The model is built within the framework of the Landau-Ginzburg theory, using the
polarization as an order parameter. The model has been implemented using the Finite
Element Method. Due to the computational cost, numerical simulations are conducted for a
single crystal in 2D. This can result in discrepancies between model and physical reality.
Nonetheless, the model used here sheds light onto some aspects of oxygen vacancies and it
captures the mechanism of pinning effect of them, as shown later.
Simulations have been conducted for BaTiO3 with different initial domain structures under
a cycling electric field. The applied material parameters are listed in the reference. The
discretization employs bilinear 4-node elements with five degrees of freedom per node,
namely the components of the spontaneous polarization, the electric potential, and two
nodal displacements. The model equations are integrated using a backward Euler scheme
and within each time step the nonlinear systems of equations of the nodal unknowns are
solved by a Newton-Raphson iteration.
120
Fig. 1: A schematic sketch of the polarization distribution for a 90° domain structure. The red arrows and
white arrows denote defect dipoles and spontaneous polarization, respectively.
In the BaTiO3 studied here, the material is supposed to have been aged for sufficient long
time. The motion of the oxygen vacancies is slow compared to the domain evolution
processes. Accordingly, the amount of vacancies is considered to be fixed as the
polarization domains evolve. Furthermore, the oxygen vacancy density is assumed to be
uniform within the body studied. We study a rectangular disc made of BaTiO3 with a size of
1.6*10-6 x 8*10-7 m, where (001) is aligned with the y-axis. The electric potential on the
lower boundary is fixed to zero and the electric potential on the upper edge is described as
a triangle function with the maximum value 4*106 V. The disc is sufficiently restrained
against rigid-body movements and is subject to stress-free boundary conditions. Flux-free
boundary conditions are applied for the polarization field.
Fig. 2: The polarization hysteresis loop for a rank-2 domain structure with different magnitudes of the
defectpolarization.
121
Both rank-2 domain structure with 90° and 180° domains and rank-1 domain structure with
180° domains can be observed in ferroelectric crystals. As the ferroelectric ceramics ages,
the spontaneous polarization configuration arrives at a rank-1 or rank-2 domain structure,
and the defect polarization tends to be aligned with the spontaneous polarization, resulting
in a minimization of electrostatic energy. On that grounds, the directions of the
spontaneous and the defect polarizations are initialized to be aligned in our simulations.
We have studied a rank-2 domain structure with a vortex domain configuration as shown in
Fig. 1. Three simulations have been performed with a uniform distribution of magnitudes
0.5*10-5 C/m², and 1.1*10-4 C/m², respectively. Each simulation has run over two load
cycles.
The increasing exterior electric field leads to a growth of the domains favored by the
electric field. After reaching a certain threshold, the electric field leads to switching of the
domains against the field, and a single domain arises. With further loading the polarization
increases only linearly, corresponding to the saturation point on the hysteresis curve plotted
in Fig. 2. Upon removal of the electric field, and given defect dipoles of sufficient
magnitude (about 4.5*10-5 C/m²), the spontaneous polarization tends to revert to the
defect polarization as it minimizes the total energy of the depolarization and the inner
defect field. As a result, the overall polarization again becomes nearly zero which is
commonly called the “memory effect”.
Fig. 3: The strain butterfly loop for a rank-2 domain structure for different magnitudes of the defect
polarization
122
The electric required field for saturation of polarization increases with the magnitude of the
defect dipoles, resulting in a shift of the saturation point. Meanwhile, the double loop
becomes more pronounced, and the accessible recoverable strain is larger than the defect
free case, demonstrated in Fig. 5. As seen from Fig. 3, the overall behavior of the
ferroelectrics is almost becoming linear for large defect dipoles. This corresponds to the
experimental observations made on ferroelectric single crystals [3-5].
References:
[1]
De Araujo, C.A.P., Cuchiaro, J.D., McMilan, L.D., Scott, M.C., and Scott, J.F. (1995), Fatiguefree ferroelectric capacitors with platinum electrodes. Nature, 374, 627-629
[2] Arlt, G., and Neumann, H. (1998), Internal bias in ferroelectric ceramics: Origin and time
dependence. Ferroelectrics, 87, 109-120
[3] Ren, X. (2004), Large electric-field-induced strain in ferroelectric crystals by point-defect
mediated reversible domain swithching. Nature Materials, 3, 91-94
[4] Zhang, L.X., and Ren, X. (2005), In-situ observation of reversible domain switching in aged
Mn-doped BaTiO3 single crystals, Phys. Rev. B, 71, 174108
[5] Ren, X., and Zhang, L.X. (2006), Electro-shape-memory effect in ferroelectric martensite.
Mater. Sci. Eng. A, 438-440, 1071-1076
[6] Dawber, M., and Scott, J.F. (2000), A model for fatigue in ferroelectric perovskite thin films.
Appl. Phys. Lett., 76, 1060-1062
[7] Lo, V.C., Chung, W.W., Cao, H.X., and Dai, X. (2008), Investigating the effect of oxygen
vacancy on the dielectric and electromechanical properties in ferroelectric ceramics. J. Appl.
Phys., 104, 064105
[8] Xiao, Y. (2004),The influence of oxygen vacancies on domain patterns in ferroelectric
perovskites, PhD thesis, California Institute of Technology, Pasadena
[9] Hong, L., Soh, A.K., Du, D.G., and Li, J.Y. (2008) Interaction of O vacancies and domain
structures in single crystal BaTiO3: Two-dimensional ferroelectric model. Phys. Rev. B, 77,
094104
[10] Zhang, Y.H., Li, J.Y., and Fang, D.N. (2010), Oxygen-vacancy-induced memory effect and
large recoverable strain in a barium titanate single crystal. Phys. Rev. B, 82. 064103
123
The Functional Materials Research Group joined the Institute of Material Science in 2012.
Formerly at IWF Dresden, Prof. Oliver Gutfleisch and 5 members moved to Darmstadt in
the summer and the group has grown to more than 15 researchers and students since. Our
research interests are directed towards permanent magnets, magneto caloric materials for
magnetic refrigeration and magnetic shape memory. The group works in close collaboration
with the IWKS Fraunhofer in Hanau (Project group for materials recycling and resource
strategies) of which Oliver Gutfleisch is one of the directors.
Research Interests:
Permanent magnets:
Permanent magnets are used in a wide variety of industrial and household appliances, but
most importantly are crucial for clean technologies such as wind turbines and electro mobility. In order to achieve energy efficient power generation for future generations novel
permanent magnet materials need to be investigated. The supply of rare earths needed for
the magnets is threatened due to economic circumstances. Our Research focuses on both
Rare-earth reduced as well as novel rare earth free materials. In 2012 the group’s efforts
included:
124

Understanding the interplay between structural, morphological and magnetic
properties for Nd-Fe-B, Sm-Zr-Co-Cu-Fe, Fe-Pt, Mn-Bi, MnAl, Mn2Ga -type alloys.
Control of hysteresis, texture sqareness and thermal stability by microstrucutre and
chemistry.

Researching and developing several novel microstructural-engineering strategies that
will dramatically improve the properties of Nd-Fe-B-type magnets based purely on
light rare earths elements. The main focus of our research has been on increasing the
coercivity enabeling these magnets to be used for applications above 100°C.

A specific emphasis is placed on the hydrogenation-disproportionation-desorptionrecombination process (HDDR). This technique offers the possibility of making submicron grain sizes with pronounced texture in Nd-Fe-B type alloys.

A development of the net-shape processing technologies for resonance efficiency and
hot deformation.

Research into a new generation of novel rare-earth-free materials for high
performance permanent magnets.
Magnetocaloric Materials:
Magnetocaloric materials change their thermodynamic state when placed in a magnetic
field and may potentially be useful for a new energy efficient technology for refrigeration.
Magnetic refrigeration is based on the reversible magnetisation and demagnetisation of
such a magnetocaloric material by external magnetic fields, resulting in a change in
temperature. The changes in temperature are transferred to the refrigerator volume by
means of heat exchangers. This technology simultaneously eliminates the need for harmful
refrigerant gases and reduces the energy requirements and hence carbon dioxide emissions.
The group concentrates on both fundamental and practical aspects of room temperature
magnetic cooling. This involves the study of fundamental magnetocaloric material
properties and the performance of the materials under test, as well as potential impact on
product design. This includes work on resource efficient fabrication and the design of
demonstators.
The group’s recent activities include:

Synthesis, structural and chemical characterization of new materials. These include
prospective magnetic refrigerants, such as La(FeSiCo)13, (MnFe)2(P,Si), Gd5(SiGe)4
etc. and investigations of quasi-static and dynamic MCE in prospective magnetic
refrigerants.

Research into the first-order transition in Heusler alloys with magnitudes of
adiabatic temperature change higher than 6 K in a 1.9 T field. For example Ni-MnIn-based Heusler alloys cool when magnetized and heat when demagnetized. This
so-called inverse MCE originates from a structural transition from the
paramagnetic/antiferromagnetic martensite phase to the ferromagnetic austenite
phase on the application of a magnetic field.

Development of new morphologies aimed at maximizing the surface area to volume
ratio of magnetocaloric regenerator structures.

Development of a new experimental set-up for precise magnetocaloric effect (MCE)
measurements over the temperature range 70 - 600 K and in magnetic-fields with
strengths up to 9 T. The device provides a unique opportunity to perform direct
Tad(H) measurements.
125
Staff Members
Head
Prof. Dr. Oliver Gutfleisch
Research Associates
Dr. Bianca Frincu
Dr. Barbara Kaeswurm
PD Dr. Michael Kuzmin
Dr. Iliya Radulov
Dr. Konstantin Skokov
Administration
Ms Brigitte Azzara
PhD Students
Imants Dirba, M.Sci.
Dipl.-Ing. Maximilian Fries
Dipl.-Phys. Tino Gottschall
Dipl.-Ing. Konrad Löwe
Dipl.-Wi.-Ing. Simon Sawatzki
Dipl.-Ing. Christoph Schwöbel
Diploma Students
Ms Almut Dirks
Visiting Scientists
Hong Jian, B. Eng.
Prof. Dr. Toshiyuki Shima
Publications
Understanding the microstructure and coercivity of high performance NdFeB-based
magnets; Scripta Materialia 67 (2012) 536–541; T.G. Woodcock, Y. Zhang, G. Hrkac, G.
Ciuta, N.M. Dempsey, T. Schrefl, O. Gutfleisch, and D. Givord
Reversible solid-state hydrogen-pump driven by magnetostructural transformation in the
prototype system La(Fe,Si)13Hy; J. Appl. Phys. 112, 083918 (2012); M. Krautz, J. D.
Moore, K.P. Skokov, J. Liu, C. S. Teixeira, R. Schaefer, L.Schultz, and O. Gutfleisch
Magnetocaloric effect of an Fe-based metallic glass compared to benchmark gadolinium; J.
Appl. Phys. 112, 123918 (2012); A. Waske, H. Hermann, N. Mattern, K. Skokov, O.
Gutfleisch, and J. Eckert
Procedure for numerical integration of the magnetocaloric effect; J. Appl. Phys. 112,
063920 (2012); J. D. Moore, K. P. Skokov, J. Liu, and O. Gutfleisch
Evaluation of the reliability of the measurement of key magnetocaloric properties: A round
robin study of La(Fe,Si,Mn)H-delta conducted by the SSEEC consortium of European
laboratories; International Journal of refridgeration 35 (2012) 1528; K. Morrison, K.G.
Sandeman, L.F. Cohen, C.P. Sasso, V. Basso, A. Barcza, M. Katter, J.D. Moore, K.P.
Skokov, O. Gutfleisch
126
Exploring La(Fe,Si)13-based magnetic refrigerants towards application; Scripta Materialia,
Volume 67, Issue 6, September 2012, Pages 584–589; J. Liu, J.D. Moore, K.P. Skokov, M.
Krautz, K. Löwe, A. Barcza, M. Katter, O. Gutfleisch
Ultra-fine grained Nd–Fe–B by high pressure reactive milling and desorption; J. Magn.
Magn. Mater. 324 (2012) 2731–2735; K. Gueth, J. Lyubina, B.Gebel, L. Schultz,
O.Gutfleisch
Giant magnetocaloric effect driven by structural transitions; Nature Materials; 11,620–
626(2012); J. Liu, T. Gottschall, K. P. Skokov, J. D. Moore& O. Gutfleisch
Hysteresis and magnetocaloric effect at the magnetostructural phase transition of Ni-Mn-Ga
and Ni-Mn-Co-Sn Heusler alloys; Physical Review B 85, 014430 (2012); V. Basso, C. P.
Sasso, K. P. Skokov, O. Gutfleisch and V.V. Khovaylo
Magnetocaloric materials with first-order phase transition: thermal and magnetic hysteresis
in LaFe11.8Si1.2 and Ni2.21Mn0.77Ga1.02 (invited); J. Appl. Phys. 111, 07A910 (2012); K. P.
Skokov, V. V. Khovaylo, K.-H. Müller, J. D. Moore, J. Liu, and O. Gutfleisch
Magnetostructural transition and adiabatic temperature change in Mn–Co–Ge magnetic
refrigerants; Scripta Materialia 66 642–645 (2012); J. Liu, K. Skokov and O. Gutfleisch
Effect of carbon on magnetocaloric effect of LaFe11.6Si1.4 compounds and on the thermal
stability of its hydrides; J. Appl. Phys. 111, 07A927 (2012); C.S. Teixeira, M. Krautz, J. D.
Moore, K. Skokov, J. Liu, P. A. P. Wendhausen, and O. Gutfleisch
The effect of the thermal decomposition reaction on the mechanical and magnetocaloric
properties of La(Fe,Si,Co)13; Acta Materialia 60 4268–4276 (2012); K. Löwe, J. Liu, K.
Skokov, J. D. Moore, H.Sepehri-Amin, Ka.Hono, M. Katter, O. Gutfleisch
127
Giant magnetocaloric effect driven by structural transitions
J. Liu, T. Gottschall, K.P. Skokov, J.D. Moore and O. Gutfleisch
Magnetic cooling could be a radically different energy solution substituting conventional
vapour compression refrigeration in the future. For the largest cooling effects of most
potential refrigerants we need to fully exploit the different degrees of freedom such as
magnetism and crystal structure. We report now for Heusler-type Ni–Mn–In–(Co) magnetic
shape-memory alloys, the adiabatic temperature change ΔTad = -3.6 to -6.2 K under a
moderate field of 2 T. Here it is the structural transition that plays the dominant role
towards the net cooling effect. A phenomenological model is established that reveals the
parameters essential for such a large ΔTad. We also demonstrate that obstacles to the
application of Heusler alloys, namely the usually large hysteresis and limited operating
temperature window, can be overcome by using the multi-response to different external
stimuli and/or fine-tuning the lattice parameters, and by stacking a series of alloys with
tailored magnetostructural transitions.
Fig. 1: Contributions from the magnetic and structural part for a first-order magnetic transition to the MCE.
Giant MCE materials have a strong coupling between crystallographic structure and
magnetism whereby a magnetic field can induce a simultaneous change of magnetic and
lattice entropies. For example, in Gd5Si2Ge2, a magnetic-field-induced transformation from
the paramagnetic, monoclinic phase to the ferromagnetic, orthorhombic phase brings about
128
a giant MCE where lattice entropy change due to structural transition contributes to more
than half of the total entropy change ΔS. Another example can be found in some recently
reported Ni-Mn-based Heusler alloys. These materials cool when magnetized and heat
when demagnetized [1]. This so-called inverse MCE originates from a structural transition
from the paramagnetic/ antiferromagnetic martensite phase to the ferromagnetic austenite
phase on the application of a magnetic field. One way forward in the development of more
efficient magnetic refrigerants is to focus on maximizing the structural (lattice) contribution
to the total entropy change in moderate magnetic Fields [2]. This has proved to be a
difficult challenge to solve without introducing unwanted side effects. A schematic
illustrating the different contributions to the total MCE in the case of the inverse MCE is
given in Fig. 1.
The temperature dependence of magnetization at several magnetic fields for
Ni45.2Mn36.7In13Co5.1 (denoted as In13Co5) is shown in Fig. 2a. For In13Co5, at a low field
of 10 mT and on heating, the non-magnetic martensite transforms to ferromagnetic
austenite in a temperature range between As = 317 K and Af = 327 K. On cooling, the
martensite starts to form at Ms = 319 K and finishes at Mf = 311 K. The equilibrium
martensitic transformation temperature Tm decreases rapidly on increasing the magnetic
field at a rate of dTm/dH of -5.5 Kelvin per Tesla (K T-1). From the direct ΔTad measurement,
the cooling behaviour of the composition is shown in Fig. 2b.
Fig. 2: Sensitivity of structural transition temperatures to the strength of magnetic field and associated giant
cooling effect for Ni–Mn–In–(Co)
The In13Co5 sample exhibiting very large ΔTad cools by 6.2 K at 317 K in ΔH = 1.9 T,
indicating an inverse MCE at the martensitic transition. In contrast, at the Curie
temperature of the austenite phase (404 K), a positive peak in ΔTad of +2.0 K was observed,
corresponding to a conventional MCE.
129
When compared with other near-room-temperature magnetic refrigerants, Ni-Mn-In-(Co)
alloys combine quite a number of advantages, such as a high adiabatic temperature change
in low field, a large cooling span resulting from stacking materials, a rare-earth-free and
non-toxic element constitution, easy fabrication, single-phase nature, high strength and
superelastic strain, and good oxidation resistance. In addition to the MCE, several other
interesting physical phenomena have been observed in Ni-Mn-based alloys such as
metamagnetic shape-memory effects [3], giant barocaloric effects [4] and large
magnetoresistivity [5]. From the present findings, we demonstrate that a sharp structural
transition width and an optimized sensitivity of the transition to the field change, together
with a dominant structural contribution, are vital to accomplish a full phase conversion and
to bring about interesting physical properties. More broadly speaking, this criterion goes
beyond Heusler-type alloys, and is applicable for other first-order transition materials
where the dominant effect originates from completed structural transitions. Concerning the
detrimental hysteresis, we predict a reduction by fine-tuning lattice parameters or applying
external bias stimuli such as pressure.
References:
[1]
[2]
[3]
[4]
[5]
130
Krenke, T. et al. Inverse magnetocaloric effect in ferromagnetic Ni-Mn-Sn alloys. Nature
Mater. 4, 450-454 (2005).
Pecharsky, V. K., Gschneidner, K. A. Jr, Mudryk, Y. & Paudyal, D. Making the most of the
magnetic and lattice entropy changes. J. Magn. Magn. Mater. 321, 3541-3547 (2009).
Kainuma, R. et al. Magnetic-field-induced shape recovery by reverse phase transformation.
Nature 439, 957-960 (2006).
Manosa, L. et al. Giant solid-state barocaloric effect in the Ni-Mn-In magnetic shape memory
alloy. Nature Mater. 9, 478-481 (2010).
Yu, S. Y. et al. Magnetic field-induced martensitic transformation and large magnetoresistance
in NiCoMnSb. Appl. Phys. Lett. 90, 242501 (2007).
Ion-Beam Modified Materials
The research activities of this group focus on interaction processes of energetic (MeV to
GeV) heavy ions with matter. The specific properties of ion beam induced modifications are
investigated with respect to track formation and damage efficiency in different material
classes. Of particular interest are performance limits of materials under extreme conditions.
This includes the high-dose environments and prolonged radiation exposure as well as the
question how solids respond to the simultaneous exposure to pressure and ion beams.
Furthermore, the knowledge on ion tracks in solids is applied for promoting heavy ion
beams as tool for producing micro- and nanostructures of high aspect ratio such as
nanochannels and nanowires and characterizing their specific properties. The irradiation
experiments are in general performed at the GSI facilities using the linear accelerator
UNILAC and the heavy ion synchrotron SIS.
The following topical issues are presently under investigation:
Fabrication of nanowires:
Nanowires fabricated by the template method are excellent objects to investigate size and
geometry effects on technologically relevant optical, electrical, and thermal properties. In a
first step, thin polymer foils are irradiated with a defined number of energetic heavy ions
(penetration range up to 100 µm). Subsequent chemical etching in a suitable solution
dissolves the damage trails produced by the ion projectiles. The etching process converts
the track of each individual ion into an open channel. The size and the shape of the channel
can be adjusted by controlling the etching conditions (e.g., temperature, time,
concentration, admixtures to etchant, etc.). To grow nanowires, the material of interest is
electrodeposited into the channels of the track-etched template. Recent research activities
specifically focus on the growth and characterization of antimony, bismuth, and bismuthcompound nanowires and the investigation of quantum- and finite-size effects, which are
expected to improve their thermoelectric performance. We also investigate localized surface
plasmon resonances of gold-silver nanowires and nanowire dimers. Nanowire dimers
separated by a gap of few nm are attracting strong interest because at the position of the
gap, the electric field is highly enhanced. This effect is of interest for application e.g. in
surface enhanced Raman spectroscopy.
Materials performance under extreme conditions:
The development of high-power heavy-ion accelerators poses new challenges to materials
that have traditionally served in the nuclear field. At the planned Facility for Antiproton
and Ion Research (FAIR), key accelerators components like targets, beam absorbers,
collimators, and stripper foils have to perform in severe high-dose radiation conditions,
experiencing dimensional and structural changes, stresses and severe degradation of
properties that control thermal-shock and fatigue resistance. Current activities concentrate
in particular on radiation effects of carbon and carbon-based compound materials,
presently the best choice for high temperature and high dose applications. The campaign
includes the characterization of beam-induced effects by different methods including
microscopic and spectroscopic techniques as well as functional tests (nanoindentation,
bending test, infrared radiometry, thermo-mechanical and electrical performance, etc.).
Ion Beam Modified Materials
131
Staff Members
Head
Prof. Dr. Christina Trautmann
PhD Students
Dipl. Ing. Loic Burr
Dipl. Phys. Marco Cassinelli
Dipl. Ing. Christian Hubert
Dipl. Ing. Katharina Kupka
Dipl. Phys. Liana Movsesyan
Diploma Students
Michael Wagner
Sonja Madloch
Research Projects
Fabrication of Bi-based nanowires and their characterisation with respect to thermoelectric
properties (FIAS 2011-2014)
Fabrication of semiconducting nanowires using the ion track technology (Beilstein Institute,
2012 – 2015)
Fabrication and controlled surface functionalisation of mesoporous SiO2 materials and iontrack nanochannels (DFG, Forschergruppe (FOR 1583), 2011-2014)
Radiation hardness of carbon stripper foils under high current UNILAC operation (BMBF,
Verbundforschung, 2012 – 2015)
Radiation hardness of carbon-based components for the future FAIR facility (GSI, 2012-2015)
Investigation of response of graphite and new composite materials for Super-FRS target and
beam catchers to intense ion beam-induced thermal stress waves (BMBF,
Verbundforschung, 2012 – 2015)
Publications
I. Alber, W. Sigle, F. Demming-Janssen, R. Neumann, C. Trautmann, P. A. Van Aken and M.
E. Toimil-Molares; Multipole surface plasmon resonances in conductively coupled metal
nanowire dimers, ACS NANO, 6 (2012) 9711-9717.
I. Alencar, S. Guedes, R. Jonckheere, C. Trautmann, C. J. Soares, P. Moreira, E. a. C. Curvo, C. A.
Tello, W. M. Nakasuga, A. N. C. Dias and J. C. Hadler; Projected length annealing of etched Sm152 ion tracks in apatite, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH
SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 288 (2012) 48-52.
A. O. Delgado, M. A. Rizzutto, D. Severin, T. Seidl, R. Neumann and C. Trautmann; Latent
track radius of PTFE irradiated with high energy ion beam, NUCLEAR INSTRUMENTS AND
METHODS IN PHYSICS RESEARCH SECTION B: BEAM INTERACTIONS WITH MATERIALS
AND ATOMS, 273 (2012) 55-57.
N. Khalfaoui, J. P. Stoquert, F. Haas, C. Trautmann, A. Meftah and M. Toulemonde;
Damage creation threshold of al2o3 under swift heavy ion irradiation, NUCLEAR
INTERACTIONS WITH MATERIALS AND ATOMS, 286 (2012) 247-253.
J. Krauser, A. K. Nix, H. G. Gehrke, H. Hofsaess, C. Trautmann and A. Weidinger;
Conductivity enhancement of ion tracks in tetrahedral amorphous carbon by doping with N,
132
Bb, Cu and Fe, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION
B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 272 (2012) 280-283.
M. Lang, F. Zhang, W. Li, D. Severin, M. Bender, S. Klaumünzer, C. Trautmann and R. C.
Ewing; Swift heavy ion-induced amorphization of CaZrO3 perovskite, NUCLEAR
F. Lu, M. Lang, M. Huang, F. Namavar, C. Trautmann, R. C. Ewing and J. Lian; ZrSi
formation at Zr/Si interface induced by ballistic and ionizing radiations, NUCLEAR
M. D. Rodriguez, B. Afra, C. Trautmann, M. Toulemonde, T. Bierschenk, J. Leslie, R.
Giulian, N. Kirby and P. Kluth; Morphology of swift heavy ion tracks in metallic glasses,
JOURNAL OF NON-CRYSTALLINE SOLIDS, 358 (2012) 571-576.
B. Schuster, F. Fujara, B. Merk, R. Neumann, T. Seidl and C. Trautmann; Response behavior
of zro2 under swift heavy ion irradiation with and without external pressure, NUCLEAR
T. Seidl, O. Baake, U. H. Hossain, M. Bender, D. Severin, C. Trautmann and W. Ensinger;
In-situ investigation of polyvinyl formal irradiated with GeV Au ions, NUCLEAR
INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS
WITH MATERIALS AND ATOMS, 272 (2012) 400-404.
T. Seidl, A. Plotnikov, E. Mustafin, R. Lopez, D. Severin, E. Floch, C. Trautmann, A.
Golubev, A. Smolyakov, D. Tommasini and W. Ensinger; Influence of swift heavy ion beams
and protons on the dielectric strength of polyimide, POLYMER DEGRADATION AND
STABILITY, 97 (2012) 2396-2402.
P. Serbun, F. Jordan, A. Navitski, G. Mueller, I. Alber, M. E. Toimil-Molares and C.
Trautmann; Copper nanocones grown in polymer ion-track membranes as field emitters, THE
EUROPEAN PHYSICAL JOURNAL APPLIED PHYSICS, 58 (2012) 10402.
S. Sorieul, X. Kerbiriou, J. M. Costantini, L. Gosmain, G. Calas and C. Trautmann; Optical
spectroscopy study of damage induced in 4H-SiC by swift heavy ion irradiation, JOURNAL OF
PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL, 24 (2012) 125801.
M. E. Toimil-Molares, L. Rontzsch, W. Sigle, K. H. Heinig, C. Trautmann and R. Neumann;
Pipetting nanowires: In situ visualization of solid-state nanowire-to-nanoparticle
transformation driven by surface diffusion-mediated capillarity, ADVANCED FUNCTIONAL
MATERIALS, 22 (2012) 695-701.
M. Toulemonde, W. Assmann, C. Dufour, A. Meftah and C. Trautmann; Nanometric
transformation of the matter by short and intense electronic excitation: Experimental data
versus inelastic thermal spike model, NUCLEAR INSTRUMENTS AND METHODS IN PHYSICS
RESEARCH SECTION B: BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 277
(2012) 28-39.
M. Toulemonde, A. Benyagoub, C. Trautmann, N. Khalfaoui, M. Boccanfuso, C. Dufour, F.
Gourbilleau, J. Grob, J. Stoquert, J. Costantini, F. Haas, E. Jacquet, K. O. Voss and A.
Meftah; Dense and nanometric electronic excitations induced by swift heavy ions in an ionic
CaF2 crystal: Evidence for two thresholds of damage creation, PHYSICAL REVIEW B, 85
(2012) 054112-1-16.
H. Q. Zhang, N. Akram, P. Skog, I. L. Soroka, C. Trautmann and R. Schuch; Tailoring of
KeV-ion beams by image charge when transmitting through rhombic and rectangular shaped
nanocapillaries, PHYSICAL REVIEW LETTERS, 108 (2012) 193202-1-5.
133
Structural changes induced by intense swift heavy-ion beams
in carbon-based materials
K. Kupka1,2, C. Hubert1,2, D. Nguyen1,4, M. Tomut1,3 and C. Trautmann1,2
1
GSI, Darmstadt, Germany; 2TU Darmstadt, Germany; 3NIMP Bucharest, Romania;
4
Hochschule RheinMain, Germany
For the planned Facility for Antiproton and Ion Research (FAIR) at GSI, new high
performance materials, able to withstand high beam intensities, are required for targets and
stripper foils. Carbon-based materials such as amorphous carbon, graphite, or carbon-fiber
carbon composites (CFCs) are used due to low energy deposition in the material and good
thermo mechanical properties. To predict component lifetimes, micro-structural changes in
these materials under heavy ion exposure and the subsequent changes in thermomechanical properties are investigated.
Beam-induced modifications in graphitic and carbon-based materials were studied using Xray diffraction (XRD) and Raman spectroscopy. In addition, swelling-induced stresses were
estimated based on profilometry measurements of irradiation-induced sample curvature.
Graphite targets
High-density isotropic graphite samples were irradiated at the UNILAC linear accelerator
facility of GSI with 3.6 MeV/u 197Au ions, accumulating fluences of up to 1014 ions/cm2.
XRD measurements were performed at the P02 beam line of PETRA III (DESY, Hamburg)
revealing significant intensity changes and broadening of the 002 and 004 reflections. The
evolution of the x-ray diffractograms with increasing ion fluence is shown in Fig. 1 (left).
Peak broadening is attributed to a larger variation of distances between graphitic layers in
the lattice. With increasing fluence, interstitial clusters merge generating new graphitic
planes. This process, together with the induced plane bending, leads to the formation of a
turbostratic graphitic structure.
Fig. 1: Left: X-ray diffractograms of high-density isotropic graphite irradiated with 3.6 MeV/u Au ions, showing
intensity decrease and broadening of the 002 and 004 reflections with increasing fluence; Right: Bending
radius (blue) and calculated stress (red) of irradiated high-density isotropic graphite measured using a DEKTAK
profilometer.
134
Structural changes within the irradiated layer induce swelling resulting in stress at the
interface between the irradiated layer (~45µm) and the non-irradiated substrate. Analysing
the curvature of irradiated isotropic graphite cantilevers by profilometry allowed us to
calculate the stress using the Stoney formula [1]. Above a critical fluence corresponding to
overlapping of ion tracks, the swelling induced stress increases significantly as seen in
Figure 1 (Right).
Carbon stripper-foils
Solid stripper foils have been used for many years in ion accelerator technology to produce
projectiles of high charge states. Due to large beam intensities and pulsed beam structure at
FAIR, new challenges are faced to ensure reliable working solid stripper foils. Many factors
have an impact on the lifetime of carbon-based foils: beam-induced temperature rise, stress
waves induced by the pulsed beam structure, phase transformations, fatigue, sublimation,
as well as expansion or compaction of the irradiated material [2]. A systematic
investigation of processes leading to failure is needed in order to predict and increase the
lifetime of the stripper foils. In this context, our investigations focus on understanding the
contribution of radiation damage and stress waves induced by the pulsed beam to final
failure.
Irradiation experiments varying fluence, ion species, and pulse length were carried out at
the M-Branch of the UNILAC. Figure 2 (left) shows radiation–induced material
transformations in the beam spot that depends on the time structure of the beam, including
compaction and phase transformations. Raman spectroscopy reveals that these changes are
related to graphitization, as indicated by the formation of the graphitic peak (G) (Fig. 2,
right).
Fig. 2: Left: Amorphous carbon stripper foils exposed to different fluences up to 51014 ions/cm² of (a) 3.6
MeV/u 197Au and (b) 4.8 MeV/u 238U beam. Right: Raman spectra of amorphous carbon stripper foils, pristine
and irradiated with 4.8 MeV/u 238U ions (5.71014 ions/cm²) and 3.6 MeV/u 197Au ions (51014 ions/cm²) [2].
Our studies give evidence that with increasing ion fluence, the carbon material evolves
towards a structure with highly defective bent graphitic layers, independent of the starting
pristine phase. Further irradiation experiments are targeting the influence of energy
deposition in the transformation process. Given the large amount of carbon allotropes and
multiple possibilities of transformation routes, generation of other carbon phases at
extreme irradiation conditions will be investigated.
135
Acknowledgment
We thank the GSI target lab for stripper-foil fabrication and foil handling support. We also
thank D. Severin, M. Bender, and the UNILAC machine group for help during the
irradiation experiments. K. K. and C. H acknowledge financial support by the graduate
school HGS-HIRe, the BMBF (project 05P12RDRBL) (K. K.) as well as by the F&E GSI
cooperation contract (C.H.).
References:
[1]
[2]
136
N. Schwarzer, F. Richter – On the determination of film stress from substrate bending:
Stoney´s formula and its limits
M. Tomut et al., GSI Scientific Report 2011, 412
Collaborative Research Center (SFB)
“Electrical Fatigue in Functional Materials”
2003 – 2014
www.sfb595.tu-darmstadt.de
The center for collaborative studies (Sonderforschungsbereich) has been awarded by the
Deutsche Forschungsgemeinschaft in 2002 to TU Darmstadt and is centered in the
Department of Materials and Earth Sciences with important contributions from the
Department of Chemistry as well as the Mechanical Engineering Department of the
University of Karlsruhe. The center was renewed in 2006 and again in 2010 and is now in
the third and final four-year funding period.
It is comprised of a total of 19 projects and financial resources for the current four yearperiod of about 8 Mio. €. The center has an active guest program with guests visiting from
2 days to 3 months. In 2008, an integrated graduate school was also implemented with
graduate students visiting from other Universities for time frames between 1 to 12 months.
For specific information, please contact either the secretary of the center, Mrs. Gila Völzke,
or the director of the center, Prof. Karsten Albe.
Contact:
SFB 595 Electrical Fatigue in Functional Materials
Institute of Materials Science
Petersenstr. 23
64287 Darmstadt
Tel.: +49 6151 16 - 6362
Fax: +49 6151 16 - 6363
Building/Room: L201 / 121
E-mail: [email protected]
[email protected]
Electrical fatigue in functional materials encompasses a set of phenomena, which lead to
the degradation of materials with an increasing number of electrical cycles. Electrical
cycling leads to both reversible and irreversible currents and polarisations. Ionic and
electronic charge carriers interact with each other and with microstructural elements in the
bulk as well as at interfaces (grain boundaries and domain walls) and interphases
(electrode/electrolyte). This in turn causes local changes in the distribution of electric
currents and electric potentials. As a consequence local overloads and material degradation
ensues and leads to irreversible loss of material properties. This material degradation can
lead finally to mechanical damage as well as to dissociation reactions. The basic
phenomena of electrical fatigue are not yet understood on a microscopic level.
A key feature of the center is therefore the steady comparison between theory and
experiment. This is utilized to find the physico-chemical origins of electrical fatigue as well
as to develop strategies for new materials and improved material combinations. The
materials of interest are ferroelectrics, electrical conductors (cathode materials for lithium
batteries and transparent conducting oxides) and semiconducting polymers.
The goal of this center of excellence is the understanding of the mechanisms leading to
electrical fatigue. An understanding of the experimental results is supported by concurrent
materials modelling which is geared to encompass different time and length scales from the
material to the component. In the third phase next to a quantitative modelling the
development of fatigue-resistant materials and in the case of ferroelectrics, lead-free
piezoceramics, is of particular focus.
137
Projects:
Division A: Synthesis
A1 - P.I.: Prof. J. Rödel
Topic: Manufacturing of textured ceramics actuators with high strain
A2 [ended 2010], P.I.: Prof. M. J. Hoffmann
Topic: Manufacturing and characterization of PZT-ceramics under dc loading
A3 - P.I.: Prof. W. Jaegermann
Topic: Boundary layers and thin films of ionic conductors: Electronic structure,
electrochemical potentials, defect formation and degradation mechanisms
A4 - P.I.: Prof. R. Riedel
Topic: Novel functional ceramics using anionic substitution in oxidic systems
A5 - P.I.: Prof. M. Rehahn
Topic: Synthesis of semiconducting model polymers and their characterization before and
after cyclic electric fatigue
Division B: Characterization
B1 [ended 2010], P.I.: Dr. R.-A. Eichel
Topic: EPR-Investigations of defects in ferroelectric ceramic material
B2 [ended 2010], P.I.: Dr. A. G. Balogh
Topic: Investigations of the defect structure and diffusion in ferroelectric materials
B3 - P.I.: Prof. H.-J. Kleebe / Prof. W. Donner
Topic: Structural investigations into the electrical fatigue in PZT
B4 - P.I.: Prof. H. Ehrenberg
Topic: In-situ investigations of the degradation of intercalation batteries und their
modelling
B7 - P.I.: Prof. H. v. Seggern / Prof. A. Klein
Topic: Dynamics of electrical properties in fatigued PZT
B8 - P.I.: Prof. Christian Hess
Topic: In situ characterization of intercalation batteries using Raman spectroscopy
B9 - P.I.: Prof. Gerd Buntkowsky / Dr. Hergen Breitzke
Topic: Characterization of structure-property relationships of functional materials using
solid state NMR
138
Division C: Modelling
C1 - P.I.: Prof. K. Albe
Topic: Quantum mechanical computer simulations for electron and defect structure of
oxides
C2 - P.I.: Prof. K. Albe
Topic: Atomistic computer simulations of defects and their mobility in metal oxides
C3 [ended 2010], P.I.: Prof. R. Müller / Prof. W. Becker
Topic: Microscopic investigations into defect agglomeration and its effect on the mobility of
domain walls
C5 - P.I.: Dr. Y. Genenko / Prof. H. v. Seggern
Topic: Phenomenological modelling of bipolar carrier transport in organic semiconducting
devices under special consideration of injection, transport and recombination phenomena
Division D: Component properties
D1 - P.I.: Prof. J. Rödel
Topic: Mesoscopic and macroscopic fatigue in doped ferroelectric ceramics
D3 - P.I.: Prof. A. Klein
Topic: Function and fatigue of conducting electrodes in organic LEDs and piezoceramic
actuators
D4 - P.I.: Dr. A. Gassmann / Prof. H. v. Seggern
Topic: Fatigue of organic semiconductor components
D5 [ended 2011] - P.I.: Prof. W. Jaegermann
Topic: Processing and characterization of Li-ion thin film batteries
Division T: Industry transfer
T1 - P.I.: Prof. H. Ehrenberg
Topic: In operando investigations of fatigue of commercial battery types using neutron
tomography and diffraction
T2 - P.I.: Prof. M. Hoffmann
Topic: Influence of PbO stoichiometry on microstructure and properties of PZT ceramics
and multilayer actuators
Integrated Graduate school
MGK
P.I.: Prof. A. Klein
139
Diploma Theses in Materials Science
Philip Wagner; Prozessoptimierung für Platin-Iridium-Medizindrat; 27.02.2012
Joachim Langner; Ionische Flüssigkeiten als Elektrolyt, Co-Katalysator und Stabilisator in
Brennstoffzellen, 16.03.2012
Karsten Fischer; Charakterisierung kugelgestrahlter Spaltbiegeprofile, 19.03.2012
George Bedenian; Untersuchung der mechanischen Eigenschaften von Warmumgeformtem
Karosseriestahl, 28.03.2012
Tim Niewelt; Analyse von Defekten in kristalline, Silizium, 30.03.2012
Michael Bachmann; Herstellung und Oxidation von Niobsilizid-Legierungen, 10.04.2012
Timo Alexander Prenzer; Verformung von Gläsern beim chemischen Vorspannen,
30.04.2012
Sarah Jahn; Adhässionsverhalten oberflächenfunktionalisierter Partikel durch kovalente
Immobilisierung mittels Klick-Chemie, 14.05.2012
Maximilian Fries; Sputtered MoSi2, Thin Films, 15.05.2012
Ofer Hirsch; Screening of local depolarization fields in ferroelectric perovskites due to natural
non-stoichiometry and (intentional or unintentional) acceptor doping, 15.05.2012
Miriam Höner; Stabilitätsmodell für neuartigen Knochenzement, 15.05.2012
Lars Przybilla; Thermomechanische Analyse eines Metallmatrix-Komposites mit interpenetrierender Struktur, 15.05.2012
Christoph Georg Rakousky; Neue Kohlenstoffkomponenten für Gasdiffusionsschichten,
15.05.2012
Holger Wüst; Kristallisationsverhalten von ALD-Oxidschichten, 15.05.2012
Katharina Kupka; Superconducting Pnictide Thin Films of CeNiBi2 Grown by Reactive
Molecular Beam Epitaxy, 16.05.2012
Rebecca Hentschel; The Stability of Praseodymium-Based Zinc Oxide Ceramic Varistors,
21.05.2012
Sören Trollst; Herstellung und Charakterisierung von kathodenzerstäubten Bismutnatriumtitanat-Dünnschichten, 21.05.2012
140
Christoph Andreas Schwöbel; Titanoxid - Komposite für den Einsatz in Brennstoffzellen,
23.05.2012
Stefan Winter; Einflüsse verschiedener Schichtdicken auf Poly(3-hexylthiophen)-basierte
organische Feldeffekttrasistoren, 24.05.2012
Jan Morasch; Diskontinuierliche Änderung des Titangehaltes in STO- und BST-Dünnschichten
in Abhängigkeit des Target-Substrat-Abstandes, 28.05.2012
Florian Pforr; Einkristall-Röntgenbeugung an 0,96(Bi1/2Na1/2TiO3)-0,04(BaTiO3) in der
Diamantstempelzelle, 28.05.2012
Jonathan Griebel; Aufbau und Anwendungen einer Anlage zur PlasmaimmersionsIonenimplantation (PIII), 29.05.2012
Stephan Lederer; Herstellung und Charakterisierung von AL-Si-N-Nanokompositschichten
über Gasphasenprozesse, 01.06.2012
Natascha von Morze; Entwicklung und Charakterisierung von intrinsischen amorphen
Silizium Passivierschichten für Heterojunction Solarzellen, 01.06.2012
Elmar Kersting; 2D-Simulation von organischen Feldeffekt Transistoren, 04.06.2012
Miriam Botros; Herstellung und Charakterisierung von gesputterten Zn(O,S)-Pufferschichten
für Cu(In,Ga)Se2-Solarzellen, 06.06.2012
Boris Alexander Lehmann; Einfluss natürlicher Verunreinigungen und Gitterdefekte auf die
Eigenschaften von Csl, 09.07.2012
Stefan Roth; Einfluss extremer Kaltverfestifgung auf die Ausscheidungshärtung von
Aluminiumlegierungen der 6xxx-er Serie, 15.07.2012
Anke Schachtsiek; Synthese und Charakterisierung von kupferbasierten Mikro- und
Nanodrähten verschiedener Geometrien, 21.05.2012
Karl Krämer; SiOC/CNT- und SiCN/CNT-basierte polymerabgeleitete
Nanokomposite: Herstellung und elektrische Eigenschaften, 22.08.2012
Keramik-
Sebastian Bohn; Stromfreie Synthese metallischer und bimetallischer Nanostrukturen für
katalytische Anwendungen, 11.09.2012
Raphael Simon; Materialanalytische Benchmarkuntersuchung
konzepten an Nutzfahrzeugen, 12.09.2012
von
Korrosionsschutz-
Ailine Jennifer Trometer; Photostrommessungen an Kohlenstoffnanoröhren, 29.10.2012
Tobias Brink; Atomistic Computer Simulations of Amorphous Silicon Oxycarbide, 02.11.2012
141
Bernd Mainzer; Molekulare Synthesemethoden und Hochtemperaturverhalten
Si3N4/Hf(C)N-basierten Keramik-Nanokompositen, 02.11.2012
von
Sascha Seils; Krichverformungs- und Oxidationsverhalten von Ti-44,5Al-6Nb-0,2B-0,2C,
02.11.2012
Kerstin Krause; Raman-spektroskopische und Widerstandsmessungen an piezoresistiven
kohlenstoffreichen SiOC-Keramiken, 14.11.2012
Maybritt Kühn; Korrelation morphologischer und elektronischer Eigenschaften von dotierten
organischen Halbleitersystemen, 14.11.2012
Andreas Liess; Einflüsse auf die Lumineszenzeigenschaften von Thallium-dotiertem
Cäsiumiodid, 14.11.2012
Martin Müggenburg; Wälzbeanspruchung ultrafeinkörniger Gefüge, 14.11.2012
Ivo Nemetz; Synthese und thermoelektrische Eigenschaften polymerabgeleiteter SiOC/MoSi2Komposite: Eine Machbarkeitsstudie, 14.11.2012
Moritz Warmbier; Kritische Parameter eines neuartigen Knochenzementes, 14.11.2012
Daniel Bayat; Temperaturabhängige Veränderung der offenen Klemmspannung unter
Lichtbestrahlung in Cu(In,Ga)Se2-Dünnschichtsolarzellen, 15.11.2012
Michael Wagner; Fabrication of Antimony 3D Nanowire Networks for Thermoelectric
Applications, 07.12.2012
Lucia Funke; Neue Leuchtstoffe auf der Basis von Cal2, 15.11.2012
Mario Klaric; Alterung kommerzieller Lithium-Ionen Sekundärzellen: Untersuchung der
Degradation von Elektrodenmaterialien und Korrelation zur Impedanzspektroskopie,
12.12.2012
Rene Laquai; Resistivity and Epitaxy of Hafnium Oxide Thin Films grown by Reactive
Molecular Beam Epitaxy, 13.12.2012
Aurelie Degroode; Maßnahmen zur Reibungsreduzierung, 14.12.2012
Ralf-Samuel Kühne; Alterungsmechanismen von High-Power-LEDs in der Langzeitlagerung,
20.12.2012
142
Bachelor Theses in Materials Science
Stefan Vogel, Stromfreie Synthese von Silber-Nanostrukturen als Opfertemplate für
katalytische Anwendungen, 16.01.2012 MA
Sandro Setzer, Nanostructured polymer fibers with enhanced adhesion to polymer matrices,
20.02.2012 PoS
Noll, Timo, Elektrische und optische Charakterisierung von Zinn-dotiertem Indiumoxid,
29.02.2012 OF
Daniel Sebastian Bick, Sol-Gel-Herstellung und Charakterisierung neuartiger SiliciumoxidGraphen-Nanokomposite, 16.03.2012 DF
Wolf, Johanna,
27.03.2012 MA
Charakterisierung
der
Beschichtungsqualität
eines
Sputter-Coaters,
Kühne, Kai, Charakterisierung von gesputterten ITO-Schichten, 02.04.2012 OF
Simon, Judith, Optoelektronische Messungen an organisch-anorganischen Kompositen,
02.04.2012 OF
Stühn, Lukas, Synthese und Charakterisierung eines arsenfreien, Sb-basierten PniktidSupraleiters, 03.04.2012 DS
Romanowski, Lukas David, Scanning probe microscopy of antiphase boundaries in iron
oxide thin films, 04.04.2012 PoS
Siebers, Marius, Synthese und elektrische Charakterisierung eines Bi basierten PniktidSupraleiters, 04.04.2012 DS
Xifan Wang, Radio Frequency Sputtering of Cu2O Films for Photovoltaic Application,
08.04.2012 OF
Christopher Wolf, Elektrochemische Abscheidung eindimensionaler Nanostrukturen mit
verschiedenen Geometrien aus Kupfer und Kupfer-Kobalt, 09.05.2012 MA
Sabrina Heidt, Efect of A-site Lanthanum Doping of Bi0,5Na0,5TiO3-Bi0,5K0,5TiO3 on ist
Electrical and Electromechanical Properties, 01.07.2012 NAW
Andreas Hubmann, Untersuchung der Schottky-Bariere an den BaTiO3/RuO2-Grenzflächen
in Abhängigkeit der dieelektrischen Polarisation und kristallographischen Orientierung,
13.07.2012 OF
Laura Ahmels, Erzeugung von Verformungsmartensit in austenitisch-ferritischem Gusseisen
durch Festklopfen, 31.07.2012 PHM
143
Daniel Simon, Deformation mechanisms in nanocrystalline copper: Molecular dynamics
simulations on the influence of strain rate and temperature, 15.08.2012 MM
Svenja Heise, Materialanalytische Untersuchungen von Gläsern aus Gräbern des 6./7. Jhr n.
Ch., 18.08.2012 MA
Philipp Kröber, Verkapselung und Analyse von Cäsiumfluorid-Pellets, 31.08.2012 EM
Kristina Braak, Untersuchung von Parylen C für Transistorenanwendungen, 31.08.2012 EM
Mansfeld, Marc, Simulation von CdTe-Dünnschichtsolarzellen mithilfe der Software Scaps,
12.09.2012 OF
Konrad Eiler, Untersuchung der Auswirkung einer Plasmavorbehandlung im Hinblick auf die
Haftung von DLC-Schichten, 28.09.2012 MA
Hanna Verena Heyl, Synthese und Charakterisierung ZnOxNy-basierter Materialien,
30.09.2012 DF
Markus Antoni, Synthese und Charakterisierung dünner KNN-Schichten, 01.10.2012 MA
Johannes Kroder, Untersuchung der Halbleiter-Dieelektrikum-Grenzfläche in IndiumZinkoxid-Transistoren, 02.10.2012 EM
Johannes Dingeldein, Herstellung von DLC-Schichten, 15.10.2012 MA
Tobias Opitz, Einfluss von Kurzzeitwärmebehandlung auf das Gefüge und die mechanischen
Eigenschaften von Spaltprofilen, 15.10.2012 PHM
Janek Binzen, Ermüdungsverhalten plasmanitrierten IFG-Gradientengefüge, 19.10.2012
PHM
Sebastian Bruns, Untersuchung der Scherbandbildung in Spalt-Profilen mit UFG-Gefüge,
19.10.2012 PHM
Manuel Kloose, Einfluss von Eisen auf die Oxidationseigenschaften von Niob-Siliziden,
22.10.2012 PHM
Anne Kirsten, Glass Surface Functionalization for Establishment of a Collagen Based Micro
Cell Culture System for Biological Applications, 20.11.2012 PoS
144
Master Theses in Materials Science
Tesfaye Belete, Preparation of Lithium Ion Phospate Films by Spin Coating
Meihdi Oussalah, Ion implantation in Gallium Nitride for High Electron Mobility Transistors
(HEMT) Normally of structureres
Ahmad Choudhary, Synthesis and Characterization of Garnet-Based Solid Elextrolyte for
Lithium Ion Batteries
Caglar Terzioglu, Synthesis and Electrochemical Behaviour of Metal Substituted SiOC-Based
Polymer-Derived Ceramic Nanocomposites
Alexandre Ouzia, Feasability study of a slit for the LBS line of the Linac 4
PHD Theses in Materials Science
Dipl.-Ing. Mario Böhme: Prozessentwicklung zur templatgestützten Synthese metalloxidischer
Nanoröhren sowie Exploration zu deren Anwendungspotenzial, 24.1.2012
Dipl.-Ing. Eva Feldmeier: Ambipolare Feldeffekttranistoren mit spannungsabhängiger
Emissionsfarbe, 27.1.2012
Dipl.-Ing. Christopher Siol: Quasistatische und transiente Oberflächenpotentialverteilungen
organischer Feldeffekttransistoren, 7.2.2012
Dipl.-Chem. Benjamin Papendorf: Keramische Nanokomposite auf Basis von SiOC / HfO2
und SiCN / HfO2: Herstellung und Untersuchungen zum Hochtemperaturverhalten, 15.2.2012
Dipl.-Ing. Susanne Zils: Elektronenmikroskopische Untersuchungen zum Wasserhaushalt in
Polymerelektrolytmembran-Brennstoffzellen, 2.3.2012
Dipl.-Chem. Sebastian Kamps: Untersuchungen und Herstellung von hydrophoben und
superhydrophoben Beschichtungen zur Verbesserung des Wärmeübergangs durch dauerhafte
Tropfenkondensation, 22.3.2012
Dipl.-Ing. Laura Bohne: Integrierte 3D-Lithium-Ionen-Dünnschichtbatterien: Dünnschichtkathoden auf strukturierten Substraten und elektrochemische Eigenschaften, 19.4.2012
Dipl.-Ing. Peter Marek: Biomimetic Dye Aggregate Solar Cells, 20.4.2012
Ditty Dixon M. Sc.: Spatially resolved studies in direct methanol fuel cells, 9.5.2012
Azad Jaberi Darbandi M.Sc.: Nanoparticulate Cathode Films for Low Temperature Solid
Oxide Fuel Cells, 29.5.2012
Master Theses in Materials Science
145
Ravi Mohan Prasad M.Tech.: Polymer-Derived Microporous Ceramics for Membranes and
Sensors for High Temperature Hydrogen Purification and Sensing, 11.6.2012
Dipl.-Ing. Corinna Hein: Anpassung der
Heterokontakten, 29.6.2012
elektronischen
Struktur
an
organischen
Dipl.-Ing. Judith Schaffner: Herstellung von CdTe-Dünnschichtsolarzellen bei reduzierten
Abscheidetemperaturen, 17.9.2012
Engy El' Haddad M. Sc.: Sorption and Desorption Processes of Organic Contaminants on
Carbonaceous Materials, 21.9.2012
Dipl.-Phys. Oliver Michael Ottinger: Modellierung der Ladungsträgerinjektion und des
Raumladungsaufbaus in organischen Dioden, 30.12.2012
Dipl.-Ing. (FH) Gerrit Günther: Size-dependent High-Temperature Behavior of Bismuth
Oxide Nanoparticles, 14.12.2012
Dipl.-Phys. Andreas Decker: Farbstoffsensibilisierung
photovoltaische Anwendungen, 14.12.2012
von
Dünnschichtsilizium
für
Dipl.-Wirtsch.-Ing. (FH) Hanno Butsch: Entwicklung neuartiger Gasdiffussionslagen (GDL)
und von Methoden zu deren Charakterisierung, 19.12.2012
146
PhD Theses in Materials Science
Mechanical Workshop
The mechanical workshop of the Institute of Materials Science is designing, manufacturing
and modifying academic equipment for a broad range of projects. In the year 2012 the
workshop was involved in the following major projects:

Components for Evaporation System for Rotated Fibre Substrates

UHV-preparation chambers dedicated for MBE, CVD, PVD, PLD and (electro)
chemical treatment

Components for six-circle diffractometer

Design and manufacturing of a protection chamber for x-rays with up to 150 keV photons

UHV baby chamber for x-ray diffraction experiments
Staff Members
Head
Jochen Rank
Technical Personnel
Frank Bockhard
Volker Klügl
Ulrich Füllhardt
Herry Wedel
Electrical Workshop
The electrical workshop of the Institute of Materials Science was involved in the following
projects:

Maintenance and repair of various academic equipment like the Electron Probe
Micro-Analyzer (EPMA), Secondary Ion Mass Spectrometry (SIMS), sintering
furnace, Transmission Electron Microscopy (TEM), X-Ray powder Diffractometer
(XRD) and Molecular Beam Epitaxy (MBE)

Design and development of electronic components for specific research projects like
temperature control unit, data logging, power controller, high voltage amplifier,
high voltage power supply, measuring amplifier, high temperature furnace for
impedance measurements

Development of testing software (V-Basic / LabView / i-Tools)
Staff Members
Electronic Personnel
Michael Weber
Mechanical and Electrical Workshop
147
Institute for Applied Geosciences
Preface
Many of todays major societal challenges are to a large extent geoscientific challenges. The
efficient management of water- and other geo-resources, the securing of our future energy
demands, or the understanding of the effects of the anthropogenic alteration of global
cycles are vital for the future development of our society.
The Institute of Applied Geosciences has continued its efforts to focus research as well as
the study programs on our key activities in Water – Energy – Environment.
Our consecutive Bachelor and Masters program ‘Angewandte Geowissenschaften’ is fully
implemented and proves to be very attractive for prospective students. In October 2012,
106 freshmen enrolled in our Bachelor program, which is an approximately 4-fold increase
compared to the number of freshmen of previous years. We are very pleased by this
upgrowth and attribute it, in addition to demographic reasons, to our focused and visible
research profile.
The first renovation phase of our
50
year
old
building
is
continuously progressing and we
all
look
forward
to
the
inauguration of the new building
some time next year. In the
meantime, all groups of the
Institute, after having been
separated for nealy one year,
moved back and are now located
in their familiar environment. We
are very excited about the
prospects of a modern and
inspiring working environment.
Our international master’s program TropHEE (Tropical Hydrogeology, Engineering Geology
and Environmental Management) started the reaccreditation process with a reshaped
curriculum that focuses now even more on water and water/environmental management.
14 students from around the world, mostly supported by grants from DAAD and BMBF,
enrolled this year. We are very pleased to see that TropHEE attracts an increasingly number
of students from Germany and Europe, indicating the ample importance of the covered
topics.
End of 2012, due to the effort of Prof. Hans-Joachim Kleebe, the Institute was able to
welcome PD Dr. Ute Kolb from Mainz as a newly installed KIVA Professor. Her main
research focus is on Electron Crystallography and, therefore, Prof. Kolb will greatly
contribute to the continuous extension of the activities in the area of Electron Microscopy.
148
Institute of Applied Geosciences – Preface
We all are very excited about this positive development and look forward to strongly
interact with Prof. Ute Kolb.
On the same token it is worth noting that Prof. Kleebe applied for research funding in the
6th framework of LOEWE (State of Hesse) to expand the running activities in Electron
Microscopy. We hope, that his proposal will be successful and that it will be possible to
further strengthen the area of Transmission Electron Microscopy, one very important
characterization tool for the entire Department Material- and Geosciences.
As it is a long tradition in Geosciences to conclude the year with the ‘Barbara Fest’, all
faculty, staff and students got together to discuss the events of the year as well as the future
in a very friendly and positive atmosphere. Due to the high number of freshmen, the
welcome ceremony of the new students was rather crowded but, finally, everyone was
‘baptised’ and officially accepted as a new member of the geology students.
Institute of Applied Geosciences – Preface
149
Physical Geology and Global Cycles
In the solar system, Earth is a unique rocky planet with an ocean and an atmosphere. It is
inhabited by bacteria since about 4 billion years and by higher life – plants and animals –
since ca. 600 million years. Organisms, air, water, and rocks are interconnected in a never
ending cycle of matter and energy: The Earth System.
The crustal plates of Earth are driven by radioactive heat. This causes creation of new crust
at mid-oceanic ridges at rates of several centimeters per year. On the other side, plate
margins become subducted into the mantle again or fold up vast mountain ranges, like the
Alps and the Himalayas, combining rocks of very different origin. During subduction the
basaltic crust is partially melted, generating more felsic magmas which rise to form plutons
and to cause lines of andesitic volcanoes such as occurring around the entire Pacific Rim.
This is called the endogenic cycle of rocks.
At the same time Earth receives solar radiation which moves air and water in gigantic
cycles around the planet. Specifically the water cycle causes the denudation of mountains
by mechanical erosion and the leveling of plains by chemical weathering, the latter aided
tremendously by vegetation and its CO2-input to soils. This is called the exogenic cycle of
rocks.
This exogenic cycle is increasingly impacted by mankind. The radiation balance of the
atmosphere has been upset by the emission of carbon dioxide, methane, and other trace
gases. Earth is warming. Industrially produced chlorinated hydrocarbons have risen to the
stratosphere, weakening the protective ozone layer. Dust from traffic, industry and
agriculture produces reagents which alter air chemistry, causing unprecedented interactions
with the marine realm, vegetation and even rocks through acidification, excessive
deposition of nutrients and salts. Dry and wet deposition of anthropogenic (i.e. produced
by humans) particles can be measured world-wide. The population explosion caused the
intensification of agriculture and an alarming loss of topsoil while reducing the extent of
natural ecosystems at the same time. Artificial fertilization of soils causes wide-spread
nitrate pollution of shallow ground waters. Urbanization alters the water cycle above and
below ground. Local leakage of chemicals impacts soil, rivers and ground water. Civil
engineering causes alterations in almost all rivers world-wide, and even coastal oceans
show increasing eutrophication, siltation and ecosystem changes in the water column and
in their shallow sediments. Scars left by mining of minerals and fossil energy are visible
everywhere and cause increasing problems. Throughout the globe man has changed the
rate of natural processes. He spreads ever further into the landscape, utilizing regions and
building in areas which are not suitable for construction, considering their natural risks.
Thus, damage of natural catastrophes rise each year, endangering the world insurance
system. These processes and their consequences are topics in Environmental Geology.
Understanding Global Change and accepting the responsibility of mankind to conserve the
planet and its resources for future generations are prerequisites for ensuring a sustainable
development. The division of Physical Geology and Geological Cycles at the Institute for
Applied Geosciences addresses questions important to environmental geology both in the
present and in the geological past.
150
Institute of Applied Geosciences – Physical Geology and Global Cycles
Staff Members
Head
Prof. Dr. Stephan Kempe
Research Associates
Dr. Günter Landmann
Technical Personnel
Ingrid Hirsmüller
Jürgen Krumm
Secretaries
Kirsten Herrmann
Pia Cazzonelli
PhD Students
Ingo Bauer, Christina Bonanati
Hans-Peter Hubrich
Student research
projects
Sven Philipp
Research Projects
3D Scanning of caves and speleogenetic process studies
Pyroducts (Lava Tunnels) in the Kahuku Ranch area, Hawaii Volcanoes National Park
Desert Kites in the Harrat of Jordan
Dekapolis Tunnel, a presumably >100 km long Roman aqueduct system in Northern
Jordan
Tectonic structure of the southern boundary of the Harz Mountain and its development
since the Permian
Paleoclimate of the Lake Van region (Eastern Anatolia) in the period 20-15 ka BP
Past climate reconstruction on sediment of the Layla Lake, Saudi Arabia
Water level changes of Lake Lisan: Implications for paleoclimatic changes of the Jordan
Valley.
Publications
Book
Hanselmeier, A., Kempe, S., & Seckbach, J., (eds.) (2012): Life on Earth and Other
Planetary Bodies. – Cellular Origin, Life in Extreme Habitats and Astrobiology, Volume 24,
533pp, Springer: Dortrecht, Heidelberg, New York London.
Articles and book chapters
Moosdorf, N., Hartmann, J., Lauerwald, Hagedorn, B.K. & Kempe, S., 2011: Atmospheric
CO2 consumption by chemical weathering in North America. - Geochimica et Cosmochimica
Acta, 75 (24): 7829-7854. (not listed in 2011!)
Kempe, S., 2012: Volcanic rock caves. – In: White, W. & Culver, D.C., (eds.), Encyclopedia
of Caves, 2nd ed. Academic Press /Elsevier, Amsterdam, 865-873.
151
Al-Malabeh, A., & Kempe, S., 2012: Hypogene point karstification along Wadi Sirhan
Graben (Jordan): A sign of oilfield degassing?- Acta Carsologica 41: 35-45.
Kempe, S., & Kazmierczak, J., 2012: Caldera lakes of Niuafo‘ou Island, Tonga:
Hydrochemistry and carbonate deposits. – In: “Life on Earth and Other Planetary Bodies”,
in: Hanselmeier, A., Kempe, S., Seckbach, J. (eds.), Springer, Dortrecht, Heidelberg, New
York, London, 197-234.
Lauerwald, R., Hartmann, J., Moosdorf, N., Kempe, S., & Raymond, P.A. 2012: What
controls the spatial patterns of the riverine carbonate system? A case study for North
America. - Chemical Geology, 337-338: 114–127.
Kremer, B., Kazmierczak, J., Łukomska-Kowalczyk, M., & Kempe, S., 2012: Calcification
versus silicification: assessment of the fossilization potential of cyanobacteria from
stromatolites of Niuafo‘ou caldera lakes (Tonga) and implications for the Archean fossil
record. – Astrobiology 12(6): 535-548. DOI: 10.1089/ast.2011.0742
152
Exploration of the more than 100 km long Roman Dekapolis aqueduct tunnels
in northern Jordan
Stephan Kempe, Ahmad Al-Malabeh and Ingo Bauer
The Dekapolis was a loose confederation of cities east of the Jordan valley during the
Roman Empire. Gadara (Umm Qais, northern Jordan) was located on a ridge above Lake
Tiberias and provided with water through a ca. 20 km long tunnel. Prof. Mathias Döring
(Hochschule Darmstadt, now retired) advanced the hypothesis, that water was collected in
channels as far away as southern Syria and connected to Gadara by a tunnels >100 km
long, supplying Abila (Quwailiba) as well. This would be the longest aqueduct tunnel of
classical antiquity. The tunnel goes underground near Al-Turra (Jordan) at 434.3 m
altitude, Gadara is at 352.5 m, the difference in altitude is 81.8 m; the linear distance is 29
km, resulting in a slope of 2.8 permil. However, the tunnel takes detours around side
valleys of the Yarmouk River and Döring suggested a tunnel length of 106 km, yielding a
slope of 0.77 permil. The tunnel needs to cross an aqueduct-bridge at Wadi Shelalal with its
entrance at 425.1 m altitude. The remaining 94 km have again a slope of 0.77 permil.
These slopes are at the lowest limits of antique water systems (aqueducts providing
Jerusalem had slopes of 0.9 to 2.8 permil) and the antique author Vitruvius suggested 5
permil for aqueducts.
We surveyed several tunnel sections and these have (i) a higher overall slope, (ii) a
significant sinuosity factor, making the tunnels even longer, and (iii) most importantly are
sloping in the wrong direction (i.e. not towards Gadara). (e.g. Hobras I has a length 995 m
and a slope of 8.4 permil; Hobras II has a length of 282 m and a slope of 4 permil). Thus
the hypothesis to be tested is if the tunnels we can access today do really belong to one
super-tunnel or if they are separate tunnels for local use. The tunnels have been built in
"qanat" technique, i.e. there were building
entrances ca. every 40 m. Almost all of these
entrances were however blocked after completion
to prevent dirt and animals to pollute the aqueduct
water. Some blockages have since collapsed and
give access to tunnel sections. In the suggested
project we would gather a team of cavers and
survey as many sections as possible. Together with
precise altitude measurements of the entrances we
hope to piece together the overall course, length
and slope of the tunnel. It will not be possible to
access the entire tunnel since sections of it are
buried and do not have modern access.
Nevertheless we hope to prove or disprove the
hypothesis. Entrances and tunnels are of prime
pictorial value including water stretches,
inscriptions, mud-paintings and spectacular
entrances in a grandiose landscape of northern
Jordan.
Fig. 1 View into one of of the aqueduct tunnels of the Dekapolis tunnel system dug into upper Cretaceous
marls interrupted by flint benches. After the winter the tunnel holds local seepage water. Photo: S. Kempe;
scale: A. Al-Malabeh.
153
Kahuenaha Nui (Hawaii): A cave developed in four different lava flows
Ingo Bauer1, Stephan Kempe1, and Peter Bosted2
(Hawai‘i Speleological Survey)
1
Institute of Applied Geosciences, University of Technology Darmstadt, Schnittspahnstr. 9,
D-64287 Darmstadt, Germany,
2
Cave Conservancy of Hawaii: P.O. Box 7032 Ocean View, Hawaii 96737-7032
Exploration and survey of the Kahuenaha Nui Cave in March 2011 yielded astonishing
insights into the processes that act to enlarge the tunnels of underground lava conduits
(pyroducts). The cave is situated in lavas of the SW Rift of the Mauna Loa, Hawaii, within
the area of the former Kahuku Ranch, south of the Belt Road at an altitude of 564 m a.s.l.
On the geological map of Hawaii, these lavas belong to the stratigraphic group Qk2, dated
to between 1500 and 3000 a BP. These flows are bordered by the 1868 pahoehoe (phh)
flow in the E and the 1887 a‘a flow in the W and occupy ca. 70 km2. The cave survey
yielded a total length of 1,850 m, a total vertical extent of 55 m, and an average slope of
5.7° (Bauer 2011; Table 1). The cave features a main trunk that is up to 18 m wide and 11
m high. Its floor is in parts formed by terminal a‘a. Above this trunk passage, we explored
numerous small to very small interconnected phh ducts. At the entrance puka (breakdown
hole) and at a large open puka we were able to study the cave stratigraphy (Fig. 1) and
thus its formation process. The trunk passage formed by eroding an underlying a‘a rubble
layer (Fig. 2). In places even the underlying a‘a core layer has been cut into. Above, a stack
of seven superimposed pahoehoe flows with small ducts occurs (Fig. 3), forming the
primary roof of the cave. The lava flowing in this stack of sheets managed to combine into
one flow, eroding the main trunk underneath. Sometimes after the cave formed first an a‘a
flow and then a thin pahoehoe flow transgressed the area covering the primary roof of the
cave. Under the additional load it partly collapsed, not only exposing the transgressed a‘a
but also forming the two entrances. This cave-forming mechanism is fundamentally
different from the “inflation” and the “crusting-over of channels” mechanisms identified as
pyroduct formation modes so far.
Fig. 1. Stratigraphic column of Kahuenaha Nui at Puka 2.
154
Fig. 2. Outcrop of the a’a-core with
overlying a’a-rubble at Station 12.
The phh-flow cut through both
layers. View southwest. Photo by
Stephan Kempe.
Fig. 3. Uphill view from
Confluence Hall. Arrow points
to one of the initial conduist in
the phh stack that drained into
the main passage. Photo by
Peter and Ann Bosted.
Total length
Total depth
Horizontal length
Horizontal extension
Highest survey point
Lowest survey point
Longest way to origin
Area coverage
Average slope
Average surface slope
Sinousity
Maximum width
Maximum height
Striking direction
Main trunk length
1,846 m
-55 m
1,812 m
560 m
564 m a.s.l.
509 m a.s.l.
660 m
1.54 km2
5.7°
4.0°
1.18 m
18.9 m
11 m
224° (NE–SW)
458 m
Table 1. Kahuenaha Nui survey data.
155
Erosion of underlying rock beds plays an important role during the formation of pyroducts
(Greeley et al., 1998; Kempe, 1997, 2002, 2009, 2012). Two a‘a flows are of significance
for the genesis of Kahuenaha Nui. The first one (layers 1 ac and 2 ar, Fig. 1) forms the base
of the pyroduct, the second transgressed during a later eruption (layers 10ar, 11ac, 12ar).
Initially a network of numerous small pyroducts was established, basically following the
surface morphology. These pyroducts interacted while the phh flow branches at preexisting tumuli. The parallel flows erode the underlying lava. Due to variations in flow
velocity and resistance of the base layer one branch degrades the lower bed faster, draining
other small pyroducts. These initial pyroducts can be seen at several places in Kahuenaha
Nui. Figure 3 illustrates the dense network of contemporaneously active pyroducts. The
erosion rate increases as the main flow hits the underlying a‘a-rubble, resulting in fast
lateral and downward extension. The small number of lavafalls gives evidence for fast
downward erosion. Rather than local erosion by lavafalls the base layer denudates. Fast
lateral erosion produces quite a number of lavaballs, causing temporary blockage of cave
passages. The created jam boosts the establishment of parallel, simultaneously active
pyroducts. If there is enough time for the cave roof to consolidate, the newly generated
flow can superimpose the older flow, while both trunks are still active, termed a
“superimposed trunk system”. Fast downward erosion of basal a‘a-layers facilitates this
process.
Up to now three modes of lava tunnel formation have been described (Kempe, 2010).
Figure 4 shows the already known inflation mode (1a) and two modes of crusting-over of
channels (1c and 1d). Our investigation led to the conclusion that Kahuenaha Nui (Fig. 5)
represents a fourth type of genesis: Confluence of lavas from smaller conduits of
superimposed sheets of pahoehoe (Fig. 4, 1d). While a first sheet of phh establishes a
pyroduct it is overridden and buried by a second sheet, likewise establishing a pyroduct.
This process happened several times. At the same time the lowest phh-flow erodes down.
The tubes merge and drain into the main passage until the lowest tube contains all the
flow. Lateral and downward erosion creates a large tunnel. In addition, breakdown and
removal of its blocks by the flowing lava enlarges the passage upward.
Fig. 4. Three modes of lava tunnel formation are already known (1a, 1c, 1d). 1a shows the inflationary
type. 1c and 1d represent two modes of crusting over of channels, Kahuenaha Nui seems to represent a
fourth type of genesis (1b).
156
Fig. 5 a, b, c. Survey of Kahuenaha Nui
cave representing 1.85 km passages of
interconnected phh pyroducts and the
underlying erosive trunk passage (Bauer,
2011).
157
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
158
Bauer, I., 2011. Geologie, Petrographie und Pyroductgenese des Kahuku-Ranch-Gebiets, Big
Island, Hawaii. Dipl. Thesis, Institute of Applied Geosciences, Technical University
Darmstadt, Germany. (unpubl.)
Greeley, R., Fagents, S.A., Harris, R.S., Kadel, S.D., & Williams, D.A., 1998. Erosion by
flowing lava, field evidence. J. Geophys. Res., 103 (B11), 27, 325-327, 345.
Kempe, S., 1997. Lavafalls: a major factor for the enlargement of lava tubes of the Ai-la‘au
Shield phase, Kilauea, Hawaii. Proc. 12th Int. Congr. of Speleology, La Chaux-de-Fonds,
Switzerland, 1, 445-448.
Kempe, S., 2002. Lavaröhren (Pyroducts) auf Hawaii und ihre Genese. In: Angewandte
Geowissenschaften in Darmstadt, Rosendahl W, Hoppe A (Eds.), Schriftenreihe der
Deutschen Geologischen Gesellschaft, 15, pp. 109-127.
Kempe, S., 2009. Principles of pyroduct (lava tunnel) formation. Proc. 15th Int. Congr. of
Speleology, Kerrville, Texas, July 19-26, 2009, 669-674.
Kempe, S., 2012. Volcanic rock caves. In: White WB, Culver DC (Eds.), Enzyclopedia of
Caves, 2nd ed., Academic Press/ Elsevier, Amsterdam, pp. 865-873.
Kempe, S., Bauer, I., Bosted, P., Coons, D., & Elhardt, R., 2010. Inflationary versus crustedover roofs of pyroducts (lava tunnels). Proc. 14th. Int. Symp. Volcanospeleol., Undara,
Australia, 2010, 93-101.
Oberwinder, M., 1996. Genese und interne Struktur des oberen Teils des Lavastroms von
1801 (Huehue Flow, Hualalai, Hawaii). Dipl.-Thesis Institute of Applied Geosciences,
Technical University Darmstadt, Germany. (unpubl.).
Paleoclimate of the Lake Van region (Eastern Anatolia) in the period 20-15 ka BP
G. Landmann, S. Kempe
Lake Van is a closed lake and therefore its lake level is highly sensitive to climatic changes.
In our previous studies of Lake Van sediments we reconstructed lake level changes of the
past 21 ka (Landmann et al. 1996; Kempe et al., 2002). Sediments of the lowest section of
the two longest cores are not varved, contain a high content of dolomite and
protodolomite, ooids, rounded pumice pieces and ostracods of the genus Limnocythere, all
interpreted to reflect a lake level regression by at least of 428 m. This interpretation is
supported by the salinity of pore water which increases with sediment depth, reflecting
upward diffusion of salts (Fig. 1; Reimer et al., 2009). The concentration gradients of pore
water differ between cores and depend on the water depth of the core recovery. Cores from
the deep basin show higher gradients because the salinity of lake water intruding into the
sediment increase in the course of the regression.
Fig. 1. Chloride concentration of
pore water of cores from
different water depths. The
dotted lines give the linear
regressions. The shaded area
marks a section of core K6 that
was replaced by older slump
sediments. Inset: the solid line
shows the Cl-gradient (lower Xaxis) versus basin depth. The
dotted line provides the salinity
increase (upper X-axis) during a
lake level decrease by keeping
the total salt amount constant.
Similarity in shape of the curves
suggested that the salt was
deposited during a strong lake
level regression.
At around 15 ka the lake
level had dropped to at
least 428 m (Landmann et
al., 1996). This conclusion
was questioned by other
investigators (Litt et al.,
2009; Cukur et al., 2013).
To estimate the salinity
reached during this minimum lake stage, the upward transport of salt from the sediment
pore space was calculated. The model considers two processes of salt transport: diffusion
and compaction caused by the ongoing sedimentation. Input parameters are an initial
chloride concentration, a diffusion coefficient of 5.9 10-10 m2s-1 (Li & Gregory, 1974), a
porosity profile (Φ=0.5+0.48e-0.08depth) and an average sedimentation rate of 0.64 mm a-1
(average of core K10, 420 m water depth, for the time period 0-8.8 ka including tephra
layers, turbidites and slumps). A good fit between the measured Cl-concentration of the
159
deep basin cores and the model data is obtained by running the time loop for 15 ka
(corresponding to 9.6 m of sedimentation), starting with an initial Cl-concentration of 3000
mmol L-1 in the pore water equivalent to a NaCl-salinity of 175 g L-1 (Fig. 2).
Fig. 2.
Chloride
concentration
measured in pore water of cores from
different water depths (black, see Fig.
1) and calculated for several time
periods
by
considering
upward
transport of chloride caused by
diffusion and compaction (red). The
calculations start with an initial chloride
concentration of 3000 mmol L-1 at the
sediment-water interface with a
deposit of 12 m pore water with this
concentration. Because the model
simulates the ongoing sedimentation
process, curves reach higher depth with
increasing time loops.
The model results reveal that
most of the recent chloride mass
in the water of Lake Van is
brought from below by upward diffusion from the sediments. When the lake started
refilling, it was therefore low in Cl-contration explaining the occurence of well-preserved
ostracodes shells of four unknown species of the family Limnocytheridae within the
lowermost sediment of core K10. Recent ostracodes of the family Limnocytheridae are
found in habitats having a salinity of 0-10 ppt (Ian Boomer, University Birmingham,
personal communication). The model explains also the long-lasting stratification of Lake
Van in the period 10.7-3.7 ka BP because loss of salt from the lower water body at the
pycnocline was replenished at the sediment water interface by upwards diffusion (Reimer
et al., 2009).
Sedimentary features like the lack of lamination, large clasts, the presence of ooids, the
formation of secondary minerals and the presence of iron oxide schlieren, can all be
explained by assuming a playa stage prevailing during the deposition of the lowest
sediment section of core K10. Occasionally appearing floods (caused by rare torrential rains
or rapid snowmelt events) could be strong enough to transport the observed clasts into the
main basin. During dry stages, capillary ground water can transport ions into the
oxygenated horizon. This may explain the formation of dolomite, iron oxide and secondary
minerals. At around 14.7 ka BP, marked by the sand layer, a more permanent water body
provided suitable conditions for ooide formation. Soon after the lake became deep enough
to allow the formation and preservation of varves (Landmann et al., 1996). During that
stage accumulation rates of 10.8 mm a-1, that is about 20 times higher than for the recent
deep lake, were reached.
This scenario of a shallow lake before 15 ka is supported by geochemical and mineralogical
evidence and by pollen data (Reimer et al., 2009; Litt et al., 2009). Parameters indicating
terrigenous contribution (like Fe, Ti, quartz) show maxima in the lowermost core section
while those representing riverine input (aragonite, Ca and Sr) have minima. A drop of Lake
Van level of about 500 m within a period less than 5 ka is a pronounced climate event that
may have teleconnections because it is also recorded in the central Sahara (e.g., Maley,
160
2000) and in the Dead Sea record (e.g., Landmann et al., 2002). However, sharp lake level
regressions allow not directly to differentiate between a reduced precipitation or an
enhanced evaporation. More detailed quantification of those parameters can be obtained by
water (or energy) balance modelling. We therefore suggest to study the pore water
chemistry and the mineralogy of sediment deposited in the period 20-15 ka BP which will
allow to improve the quality of our models.
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
Cukur, D., Krastel, S., Demirel-Schlüter, F., Demirbag, E., Imren, C., Niessen, F., Toker, M., &
PaleoVan-Working Group, 2013: Sedimentary evolution of Lake Van (Eastern Turkey)
reconstructed from high-resolution seismic investigations. Int. J. Earth Sci. 102, 571-585.
Kempe, S., Landmann, G. & Müller, G., 2002: A floating varve chronology from the Last
Glacial Maximum terrace of Lake Van/Turkey. – Zeitschr. Geomorphol., Supplem. 126
Research in Mountains and Deserts of Africa and Central Asia, 97-114.
Landmann, G., Reimer, A. & Kempe, S., 1996: Climatic induced lake level changes of Lake
Van/Turkey during the transition Pleistocene/ Holocene. - Global Biogeochemical Cycles
10(4), 797-808.
Landmann, G., Abu Qudaira, G. M., Shawabkeh, K., Wrede, V. & Kempe, S., 2002:
Geochemistry of Lisan and Damya Formation in Jordan and implications on palaeoclimate. –
Quaternary Intern. 89/1, 45-57.
Li, Y.-H. & Gregory, S., 1974: Diffusion of ions in seawater and in deep-sea sediments.
Geochim. Cosmochim. Acta 38, 703-714.
Litt, T., Krastel, S., Sturm, M., Kipfer, R., Örcen, S., Heumann, G., Franz, S.O., Ülgen, U.B. &
Niessen, F., 2009: 'PALEOVAN' International continental scientific drilling program (ICDP):
site survey results and perspectives. - Quaternary Science Reviews 28, 1555-1567.
Maley, J., 2000: Last Glacial Maximum lacustrine and fluviatil formations in the Tibesti and
other Saharan mountains, and large-scale climatic teleconections linked to the activity of the
Subtropical Jet Stream. - Global and Planetary Change 26, 121-136.
Reimer, A., Landmann, G. & Kempe, S., 2009: Lake Van, Eastern Anatolia, hydrochemistry
and history. - Aquatic Geochem. 15, 195-222
161
Hydrogeology
The Hydrogeology Group focuses on three main research areas, (I) the fate of organic
contaminants in the environment, (II) the development of novel methods to remediate soil
and groundwater contaminations, and (III), on water resources management from a local
to a regional scale. In all three research areas externally funded projects are currently
running, some as part of larger joint projects with national and international pertners.
Our water resources management project in Saudi Arabia, which is a part of the BMBF
funded joined project IWAS, is continuing and the cooperation with our partners from the
Helmholtz Center for Environmental Research (UFZ) in Leipzig, GIZ/Dornier consult in
Riyadh, and with the Ministry of Water and Electricity in Saudi Arabia (MOWE) proved to
be very successful. From March 14-17 2012, the Conference "Hydrogeology of Arid
Environments" was held at BGR in Hannover as part of the project activities. The
conference was organized by the hydrogeology group, GIZ and BGR, in cooperation with
FH-DGG. The conference had been launched to better understand the dynamics of
groundwater resources under changing climate and hydrological conditions as well as to
address the challenges in groundwater use. The conference served as a platform for the
exchange of experiences, ideas and concepts on the hydrogeology of arid environments. It
focused on the assessment of the water cycle and its interactions, the assessment of
groundwater resources, economic processes, and aspects of water resources engineering
and management. The large number of about 200 participants demonstrates the interest in
the conference.
We are very excited about our refurbished building of the Institute of Applied Geosciences
in the Schnittspahnstraße. Our hydrochemisty lab moved back from Biebesheim into the
laboratories that now offer an excellent working environment. We also expanded our
analytical capabilities by adding an isotopic analyzer for oxygen 18 and deuterium that will
play n important role in education as well as in research.
162
Institute of Applied Geosciences – Hydrogeology
Staff Members
Head
Prof. Dr. Christoph Schüth
Research Associates
Dr. Irina Engelhardt
Dr. Thomas Schiedek
Technical Personnel CTA Rainer Brannolte
Chem. Ing. Claudia Cosma
Chem. Ing. Zara Neumann
PhD Students
Dipl. Geol. Sybille Ambs
MSc Abidur Khan
MSc Heike Pfletschinger
Dipl.I ng. Nils Michelsen
MSc Engy El Hadad
MSc Michaela Laxander
Dipl. Ing. Anja Wolf
MSc Mustafa Yasin
MSc Laith Latai
Dipl. Ing. Christoph Kludt
Diploma Students
Suraya Fatema
Manuel Lindstedt
Jannes Winicker
Elena Knipp
Terence Ngole
Tanya Bammidi
Indriani Preiß
Steven Okoth
Research Projects
Management of regional groundwater resources – Saudi Arabia (BMBF: 2011-2013).
Improved management of contaminated aquifers by Integration of source tracking,
monitoring tools and decision strategies – INCOME (EU-Life program: 2008-2012)
Ermittlung der Relevanz von ‘Cold Condensation’ Prozessen in Mittel- und Hochgebirgen
(DFG: 2008-2012)
Prozessorientierte Untersuchung zum Nitratabbauvermögen der Grundwasserkörper im
Hessischen Ried (HLUG: 2011-2013)
Heavy metal contamination of surface water and groundwater resources in the industrial
area of Dhaka City, Bangladesh (BMBF-IPSWAT, 2011-2014)
Detection of oil spills and water contamination in the Kirkuk area, Irak, using remote
sensing data (DAAD 2011-2014)
Publications
Dávila Pórcel, R.-A.; De León Gómez, H.; Schüth, C. (2012): Urban impacts analysis on
hydrochemical and hydrogeological evolution of groundwater in shallow aquifer Linares,
Mexico. Environmental Earth Sciences, 66, 1871-1880.
Chaplin, B.P.; Reinhard, M.; Schneider, W.F.; Schüth, C.; Shapley, J.R.; Strathmann, T.J.;
Werth, C.J. (2012): A Critical Review of Pd-Based Catalytic Treatment of Priority
Contaminants in Water. Environmental Science and Technology, 46, 3655-3670.
Pfletschinger, H.; Engelhardt, I.; Piepenbrink, M.; Königer, F.; Schuhmann, R.; Kallioras, A.;
Schüth C. (2012): Soil column experiments to quantify vadose zone water fluxes in arid
settings. Environmental Earth Sciences, 65, 1523-1533.
163
Surface-water groundwater interaction monitored at the Schwarzbach site
Irina Engelhardt, Christoph Kludt, Christoph Schüth
Water exchange between surface-water and the adjacent groundwater body plays an
important role for groundwater quantity and quality and thus influences its usability for
public water supply. Especially, within the hyporheic zone a large number of processes
occur that alter the groundwater chemistry (e.g. Bencala, 2000). Hyporheic exchange is
primarily responsible for transporting oxygen, organic matter and anthropogenic
contaminants into the hyporheic zone. Additionally biogeochemical formations that occur
at the streambed/aquifer interface have a major impact on water quality (Massmann et al.,
2009). The transport rate and fate of anthropogenic contaminants into this exchange zone
mainly depends on the volume and composition of the surface-water entering the hyporheic
zone and its residence time within this exchange zone. In the last years, pharmaceutical
pollutants have been recognized as a threat to water quality (e.g. Ternes, 1998).
Frequently, when river bank filtration or artificial groundwater recharge are applied for
drinking water production polar organic pollutants, such as pharmaceuticals and pesticides,
were detected in elevated concentrations in wells of waterworks nearby (Heberer, 2002).
At the first glance, it can be presumed that concentrations of pharmaceuticals or pesticides
might be negligible in groundwater bodies where exfiltration prevails. However, even
under effluent hydraulic conditions transport of contaminants from surface-water into
groundwater may occur by down-welling resulting from turbulences generated by bottom
irregularities (Bencala, 1984). It is a function of downwelling by turbulences can evoke
macro-pores that may allow preferential flow and also the co-existence of spatially irregular
oriented redox-zones (Fischer et al., 2005). This co-existence of redox-zones is detected in
contrast to traditionally assumed redox fronts. However, a key in understanding all bioand geochemical processes within the hyporheic zone is the quantification of exchange
rates and flow patterns between surfacewater and groundwater.
To study hyporheic zone processs in
detail, a test site at the Schwarzbach was
constructed. The Schwarzbach is located
in the agriculturally used flat plain of the
Rhine valley southwest of Frankfurt
Airport and is part of a complex connected
river system (Fig. 1) with a catchment
area of 478 km2. The longtime mean
discharge of the Schwarzbach is about 0.6
m3 s-1. However, discharge directly
responses to precipitation events and after
intense rainfalls the total discharge can
rise to 3.0–3.8 m3 s-1.
Fig. 1: Location of the Schwarzbach test site.
About 50% of the Schwarzbach discharge
consists of waste water originating from municipal wastewater treatment plants (WWTP)
and the WWTP connected to Frankfurt Airport. Groundwater flow in the area is directed in
general from the east to the river Rhine in the west with a mean hydraulic gradient of
0.5‰. The upper porous aquifer in contact with the Schwarzbach consists of Pleistocene
164
unconsolidated glacial sediments with highly permeable sand and gravels and interbedded
lenses of clay and silt. This results in local groundwater storeys with hydraulic windows
that allow vertical exchange. The aquifer is covered with low permeable Holocene mud
sediments. About 5 km up-gradient from the river Rhine the test site was established. It
was equipped with 17 multi-level monitoring wells along three transects with a lengths of
up to 220 m that were oriented perpendicular to the streambed and in parallel to the
regional groundwater flow field. One monitoring well was placed directly beneath the river
bed (Fig. 2). All monitoring wells were installed by direct-push methods and were
constructed by either 32 mm or 50
mm diameter PE (polyethylene)
filter-screens with 0.3 mm filter
slots along the whole length of the
well, and were thus appropriate
for multi-level sampling when
using bafflepacker devices. The
depth to the groundwater table at
the test site ranges between 0.9
and 1.4 m.
Due to the impact of regional flow
on the surface-water groundwater
exchange, a three-dimensional
Fig. 2: Multilevel monitoring network along a potential flow
flow pattern may develop. Thus,
line. The investigated transect covers 227 m downgradient
the observation wells are build
and 26 m upgradient of the river bank. U, silt ; T, clay; fS, fine
sand; mS, middle sand; gS, coarse sand; fG, fine gravel.
along three potential path lines
over a length of 220 m and a
width of 25 m. The extension of
each transect equals a potential flow line and is derived from measured hydraulic pressure
heads: The differences of the measured hydraulic gradients between the three investigated
path lines show negligible three-dimensional effects. Hence, a two-dimensional monitoring
concept was considered as sufficient.
Piezometric pressure heads and environmental tracers such as temperature, stable isotopes,
chloride, X-ray contrast media, and artificial sweetener were investigated within the
hyporheic zone and river water plume. Vertical profiles of environmental tracers were
collected using multilevel wells within the neutral up-gradient zone, beneath the river bed,
and within the horizontal proximal and distal down-gradient zone. As an example, Figure 3
shows the seasonal variations of temperature in the Schwarzbach and the river bed.
Infiltration velocities were calculated from pressure heads, temperature fluctuations and
gradients. The amount of river water within groundwater was estimated from vertical
profiles of chloride, stable isotopes, and persistent pharmaceuticals. Profiles of stable
isotopes and chloride reveal the existence of down-welling within the shallow hyporheic
zone that is generated by river bed irregularities. Due to down-welling an above-average
migration of river water into the hyporheic zone establishes even under upward hydraulic
pressure gradients. The investigated environmental tracers could not distinctively display
short-time-infiltration velocities representative for flood waves, while average infiltration
velocities calculated over several months are uniform displayed. Based on vertical
temperature profiles the down-gradient migration of the river water plume could be
observed even after long periods of effluent conditions and over a distance of 200 m from
165
the river bank. X-ray contrast
media and artificial sweeteners
were
observed
in
high
concentrations
within
the
proximal zone, but were not
detected at a distance of 200 m
from the river bank. Using
temperature as environmental
tracer within the hyporheic
zone
may
result
in
overestimating the migration
Fig. 3: Seasonal temperature oscillations and lag time between
of pollutants within the river
the Schwarzbach and the groundwater vertical beneath the river
water plume as the process of
bed and perpendicular to the river bank.
natural attenuation will be
neglected. Furthermore, temperature was not able to display the effect of down-welling.
Stable isotopes and chloride were found to be suitable environmental tracers to forecast the
release and fate of organic contaminants within the hyporheic zone.
The Schwarzbach site that is now in operation for three years represents an excellent
reference case to study surface-water groundwater interaction. It serves as a long term
observatory for related research not only for the hydrogeology group, but also for partners
that are interested in the approach.
Literature
Bencala, K.E., 1984. Interactions of solute and streambed sediment. 2. A dynamic analysis of
coupled hydrologic and chemical processes that determine solute transport. Water Resour. Res. 20
(12), 1804–1814.
Bencala, K.E., 2000. Hyporheic zone hydrological processes. Hydrol. Process. 14, 2797–2798.
Fischer, H., Kloep, F., Wilzcek, S., Pusch, M.T., 2005. A river’s liver – microbial processes within the
hyporheic zone of a large lowland river. Biogeochemistry 76, 349–371.
Heberer, T., 1995. Identification and quantification of pesticide residues and environmental
contaminants in ground and surface water applying capillary gas chromatography–mass
spectrometry. Wissenschaft & Technik, Berlin.
Massmann, G., Dünnbier, U., Heberer, T., Pekdeger, A., Richter, D., Sültenfuß, J., Tosaki, Y., 2009.
Hydrodynamische und hydrochemische Aspekte der anthropogen und natürlich induzierten
Uferfiltration am Beispiel von Berlin/Brandenburg. Grundwasser 14, 163–177.
Ternes, T.A., 1998. Occurrence of drugs in German sewage treatment plants and rivers. Water Res.
32, 3245–3260.
166
Engineering Geology
Since March 2012 the Engineering Geology section is headed by Prof. Dr. Andreas Henk
who formerly was a Professor of Applied Geology at Albert-Ludwigs-Universität Freiburg.
Engineering Geology is a branch of geology that deals with the characterization of soil, rock
and rock masses for the location, design construction and operation of engineering works.
In particular, it addresses the interaction between earth and earth processes on one side
and human made structures and human activities on the other. Typical fields of activity for
the engineering geologist are site investigations for construction work, landslide and slope
stability and underground excavations like tunnels and caverns. In the past years rock
mechanical techniques and concepts have be increasingly applied to depth of up to 5 km to
characterize the geomechanical behavior of rock masses used as hydrocarbon or geothermal
reservoirs. Reservoir geomechanics is also the main research focus of the new Engineering
Geology group at TU Darmstadt. Work concentrates, among others, on reservoir-scale
numerical simulations which on the basis of finite element techniques provide a tool for a
prediction of tectonic stresses and fractures networks. Such information is relevant not only
for optimal exploration and efficient use of hydrocarbon and geothermal reservoirs, but
also for CO2 sequestration as well as radioactive waste repositories. Besides various general
methodological aspects numerical modeling techniques are applied to data from a gas field
in northern Germany and a CO2-injection site in Australia to assess the model’s value in the
real world. These modeling studies are supplemented by outcrop studies. Large surface
exposures serve as reservoir analogs and provide detailed fracture information which can
also be used for upscaling of borehole data and discrete fracture network (DFN) models.
Besides the ongoing research activities the time since March 2012 was filled with much
work ranging from hiring scientific, administrative and technical staff to furnishing offices
and labs. After the interim phase at Mornewegstrasse, the Engineering Geology section now
resides in the second floor of the renovated geology building which also provides excellent
new lab facilities.
Staff Members
Head
Prof. Dr. Andreas Henk (since March 2012)
Research Associates
M.Sc. Karsten Fischer
Dipl. Geol. Christian Heinz
M.Sc. Dennis Laux
Dipl. Geol. Christoph Wagner
Technical Personnel Reimund Rosmann
(since April 2013)
PhD Students
M.Sc. Chiara Aruffo
Secretary
Dipl. Kffr. Stefanie Kollmann
Institute of Applied Geosciences – Engineering Geology
M.Sc. Bastian Weber
(since February 2013)
167
Research Projects
Prediction of tectonic stresses and fracture networks with geomechanical reservoir models
(DGMK Projekt 721, ExxonMobil, GDF SUEZ, RWE Dea)
PROTECT - PRediction Of deformation To Ensure Carbon Traps (BMBF)
Buidling and populating geomechanical reservoir models – a case study from the Upper
Rhine Graben (GDF SUEZ)
LIDAR-based analysis of fracture networks (PhD thesis)
Publications
Fischer, K. & Henk, A. (2012): Geomechanical Reservoir Modeling – a geological
application of high-performance computing. Conference Proceedings, 8th Joint
BFG/bwGRiD Conference & Workshop on High-Performance Grids, 23.-25. Mai 2012,
Freiburg.
Fischer, K. & Henk, A., (2012): Building 3D Geomechanical Models – Some Practical
Aspects of Mesh Generation and Boundary Conditions. Conference Proceedings, 74th EAGE
Conference & Exhibition, 04.-07. Juni 2012, Kopenhagen.
Nemcok, M., Henk, A., Allen, R., Sikora, P. J. & Stuart, C. (2012): Continental break-up
along strike-slip fault zones; observations from the Equatorial Atlantic. – In: Mohriak, W.
U., Danforth, A., Post, P. J., Brown, D. E., Tari, G. C., Nemcok, M. & Sinha, S. T. (eds.):
Conjugate Divergent Margins. Geological Society, London, Special Publications, 369. doi:
10.1144/SP369.8..
Ziesch, J., Aruffo, C. M., Tanner, D. C., Beilecke, T., Krawczyk, C. M. and Henk, A. (2012):
Sub-seismic deformation prediction of potential pathways and seismic validation— joint
project PROTECT. EGU General Assembly 2013, Vienna/Austria; Geophysical Research
Abstracts 15.
168
Field-scale geomechanical modeling of an intensely faulted gas reservoir
Fischer, K. & Henk, A.
The tectonic stress field strongly affects the optimal exploitation of conventional and
unconventional hydrocarbon reservoirs. Among others, wellbore stability, orientation of
hydraulically induced fractures and - particularly in fractured reservoirs - permeability
anisotropies depend on the recent in situ stresses. However, stress magnitudes and
orientations are frequently not homogeneous but substantially modified by the presence of
faults as well as lithological changes and contrasts in rock mechanical properties (Fjaer et
al. 2008, Zoback 2007). In some fault-controlled reservoirs, local stress reorientations of up
to 90° relative to the regional trend have been reported (Yale 2003). 3D geomechanical
reservoir models can be used as tools to predict such stress field perturbations and related
changes in fracture characteristics. In order to provide robust predictions, the numerical
models have to account for the complexities of real reservoir structures with respect to
subsurface geometry, inhomogeneous material distribution and nonlinear rock mechanical
behavior. A workflow for geomechanical reservoir modeling utilizing the Finite Element
Method (FEM) is presented and applied to an intensely faulted gas reservoir in Northern
Germany.
For this case study, lithostratigraphic horizons and faults were interpreted from 3D seismic
data and their geometry was transferred to the FEM software. More than 80 faults are
incorporated and modeled by contact elements. These elements consider shear and normal
stresses (depending on the frictional properties assigned) and allow for differential
displacement between the independently meshed fault blocks. Reservoir-specific material
properties for all relevant lithologies were adopted from rock mechanical tests on drill cores
as well as geomechanical log data. Vertical boundary conditions include a lithostatic
pressure load derived from the integrated density of the overburden. Magnitudes and
orientations of the regional maximum and minimum horizontal stresses were taken from
publications (e.g., Roeckel & Lempp 2003) and applied to the model by calibrated
displacements yielding the respective stress magnitudes. Due to the field-scale size of the
model covering more than 400 km², a highly effective way of element sizing and
distribution had to be developed. The final model comprises about 4 million elements with
a resolution inside the reservoir region of 100m x 100m x 25m (length x width x depth).
The total amount of elements and the complexity of the geomechanical model required the
use of massive parallel computing techniques on HPC (high-performance computing)
devices to achieve calculation times of less than one day. The final modeling outcome
includes, among others, the 3D stress tensor throughout the model from which various
other stress quantities including the slip and dilation tendencies of the faults could be
derived (Fig. 1). Modeled stresses were compared to observational data like stress
orientations from borehole breakouts as well as stress magnitudes from extended leak-off
tests. After iterative optimization, the validated geomechanical reservoir model can now be
used for stress prediction between existing wells or in undrilled parts of the reservoir.
References
[1]
Fjaer, E., Holt, R.M. & Horsrud, P. (2008): Petroleum-related rock mechanics. - Elsevier Science and
Technology, 514 p.
[2]
Roeckel, T. and Lempp, C., 2003. The State of Stress in the North German Basin, Erdöl Erdgas Kohle,
119(2), 73-80.
169
[3]
Yale, D.P., 2003. Fault and stress magnitude controls on variations in the orientation of in situ stress.
In: M. Ameen (Ed.) Fracture and In-Situ Stress Characterization of Hydrocarbon Reservoirs.
Geological Society, London, 55-64.
[4]
Zoback, M.D. (2007): Reservoir Geomechanics. - Cambridge University Press, 449 p.
Fig.1: Top: Oblique view showing top reservoir (color-coded for depth) and faults (grey) of the modeled gas
field in Northern Germany. An area of more than 400 km² is covered. Bottom: Oblique view on the reservoir
showing some of the geomechanical modeling results. The reservoir layer is contoured with the magnitude of
the minimum horizontal stress (Shmin), while the faults show the shear stress acting on them.
Acknowledgements
This work has been funded by ExxonMobil Production Deutschland GmbH, Gaz de France Suez E&P
Deutschland GmbH and RWE Dea AG within the frame of the DGMK (Deutsche Wissenschaftliche Gesellschaft
für Erdöl, Erdgas und Kohle e.V.) project 721.
170
Seismo-mechanic workflow to ensure CO2 storage in the Otway Basin, Australia
Aruffo, C.M., Henk, A. & PROTECT Research Group
Introduction
In recent years reducing greenhouse gas emissions has become a topic of main interest and
with this purpose in mind the CO2CRC (Cooperative Research Centre for Greenhouse Gas
Technologies) was established in Australia in 2003. The pilot project for carbon dioxide
storage is the CO2CRC Otway Project, which started in 2005 in Nirranda South, Victoria,
Australia. At this site CO2 which is produced from the Buttress Field is injected into the
adjacent depleted natural gas field, the Naylor Structure. The main objective of the
CO2CRC Otway Project is to demonstrate that carbon capture and storage (CCS) is
technically and environmentally safe. With this aim, it has to be taken into account that
subsurface injection of CO2 might potentially find pathways to return to the surface,
especially along faults. Therefore an accurate analysis of stresses and fractures within the
injection area is necessary in order to avoid this occurrence. Furthermore it is of primary
importance to identify the probable CO2 distribution in the deeper subsurface and the
petrophysical boundary conditions that determine CO2 propagation.
The PROTECT Research Group (PRediction Of deformation To Ensure Carbon Traps) uses
data from the CO2CRC Otway Project to study the structural framework and recent tectonic
stresses to verify potential pathways between reservoir and surface as well as their
structural, physical and temporal features. Within this project, universities, research
institutes and a private company work together with the objective to develop, benchmark
and verify a seismo-mechanic workflow across different scales for a safe monitoring prior,
during and after CO2 injection (Krawczyk et al. 2011). This new workflow encompasses
different approaches of geophysical, geological and numerical deformation model building,
together with the application of structural and petrophysical boundary conditions, to
predict and verify the leakage potential between depth and surface.
Workflow
Fig 1 Workflow of the PROTECT project (Krawczyk et al., 2011).
171
The PROTECT Research Group collaborates to create a dynamic risk profile which is
generally applicable to CO2 reservoirs. Using a combination of methods, the leakage
potential of reservoir and overburden will be assessed, thus, providing sensitive monitoring
strategies and assuring long-term storage integrity. The multi-phase workflow (Fig.1) starts
from 3D seismic data and well data, which allow working in parallel at large, medium and
small scale thus providing an interactive validation between work packages.
Results from the different studies will lead to the prediction of sub-seismic faults and
fractures, which will be further completed by 2D seismic validation and thermo-hydromechanical/chemical modeling.
The entire project is divided into four different work packages with the following aims: subseismic deformation prediction by retro-deformation, spatial mapping of fractures and
faults by coherency analysis of seismic data, stress and deformation prediction with
geomechanical forward modeling and thermo-hydro-mechanical/chemical benchmarking of
geological CO2 storage processes.
The joint starting point for each group participating in the PROTECT project is a structural
model derived from an interpretation of 3D seismic data from the Otway Basin area. Based
on this structural model the subsurface structure will be kinematically restored. This
provides the strain distribution from which the possible fracture orientations caused by the
faulting processes is extrapolated. In contrast, geomechanical modeling based on Finite
Element (FE) techniques uses a forward modeling approach and reservoir-specific
mechanical properties derived from well data to infer the present-day stress field as well as
various paleo-stress fields. Strain predictions from both retro-deformed and forward
geomechanical model will be compared with a coherency analysis of the initial seismic data
set. This combination of methods will provide a powerful tool to categorize, validate and
demonstrate the leakage potential of the overburden above the reservoir. In areas where we
have preliminary predicted deformation, we will acquire new S-wave 2D seismic lines to
produce higher resolution images, which allows for a much higher resolution in the upper
hundreds of meters than the present 3D seismic survey.
Seismic interpretation, retro-deformation and set-up for geomechanical modeling
CO2CRC chose the onshore Otway Basin, Victoria, Australia as location for a pilot project to
assess the viability of CO2 injection. The site was selected due to good porosity and
permeability of its reservoir rock (van Ruth et al. 2007), in addition to the presence of a
production field of gas and a depleted reservoir nearby. We carried out a seismic
interpretation of the 3D seismic data set (Urosevic et al. 2011) of the Otway Basin area
using the Petrel® platform, which allowed us to build a 3D structural model (Ziesch et al.
2012). The study area is approximately 5 km x 8 km encompassing the wells for CO2
injection and monitoring. The seismic data was interpreted down to 2.2s TWT. We
identified 10 stratigraphic horizons and 59 faults, 25 of which can be considered as major
faults. This structural model allowed us to identify a complex of conjugate normal faults,
three of which reach the uppermost seismically-visible horizon at about 500 m depth.
The structural model is the joint starting point for all the scientific partners who collaborate
in the PROTECT project. It will be used to perform a retro-deformation of the stratigraphic
volumes along the seismically-visible faults, in order to determine the accumulated
deformation and thus the sub-seismic strain variation around the faults. The calculated
strain tensors can be used to determine which areas are fractured as well as the orientation
172
of fractures and their density, taking into account changes in lithology. Simultaneously we
have done the preparatory work for transfer the geometry of the area of study into the
finite-element-based simulator Ansys® (Henk and Fischer 2011). This has been necessary
as the finite difference grid which typically is generated in Petrel® for flow simulation
purposes, is not suitable for geomechanical modeling because of specific requirements of
the finite element (FE) technique and FE fault modeling respectively. For this reasons
horizon lines, the intersection lines between the horizons and the faults surfaces, are
converted to polygons and further to points to obtain xyz-coordinates in ASCII format
which can be exported from Petrel® and imported into Ansys®. In Ansys® points are
reconnected by splines that follow exactly the fault traces and in combination with the fault
surfaces, fault block volumes are generated, that can be meshed in 3D elements. In some
cases it has been necessary to introduce auxiliary surfaces (‘pseudo-faults’) in order to
provide a more accurate topology inside these blocks. They will be merged after geometry
transfer so that a coherent fault block is achieved again. Subsequently we will incorporate
in our work data from well log and reports. Lithostratigraphic layers will be populated with
material parameters like Young’s Modulus, Poisson’s Ratio, density, cohesion, angle of
internal friction and pore pressure. Similarly, values for cohesion and angle of internal
friction will be assigned to each fault. Thus we will obtain a subsurface model with a
detailed mechanical stratigraphy that comprises not only the reservoir horizon but also the
entire overburden up to the Earth’s surface. A second stage of modeling will include also
lateral variations of the material parameters to further improve the accuracy of the study.
The geomechanical model will provide a detailed description of the local stress field so that
any stress perturbation resulting from faults and lithological changes can be addressed. The
regional stress field i.e., the orientation and magnitude of σHmax and σhmin, is
incorporated as boundary conditions applied to the sidewalls of the model.
Conclusions
Geomechanical aspects of CO2 storage in the Otway area have already been investigated by
van Ruth et al. (2006 and 2007) and Vidal-Gilbert (2010) during the assessment of the
area undertaken by CO2CRC. They focused mainly on the immediate injection area,
analyzing a small portion of reservoir around the wells for injection and monitoring. The
PROTECT Research Group aims to contribute to the work of CO2CRC, and in this view it
has expanded the area of research to an area of ca. 40 km2, so that the impact of CO2
storage onto the major faults surrounding the injection facilities can be studied.
Furthermore the expansion of the model up to the surface, allows us to investigate also the
stresses acting on the entire overburden, not only on the reservoir. This will help to identify
and monitor potential leakage pathways: risk assessment in this direction indicates a
maximum leakage rate of less than 0,1% y-1 to the atmosphere to ensure effective climate
abatement (Jenkins et al. 2011).
3D interpretation of seismic data around the CO2 production and injection wells in the
Otway area has shown a complex structure which deserves further investigation. The retrodeformation approach has a primary importance to better understand the distribution of
strain and the possible fracture orientation which could be caused by the faulting process.
On the other hand the geomechanical model will be able to describe accurately the in-situ
stresses including the tendency of the faults to slip or dilate in the present tectonic regime.
This information will help to assess the reactivation potential of the faults during and after
CO2 injection. Furthermore the comparison of both retro-deformation and geomechanical
173
methods with coherency analysis will lead to a better calibration of our fracture prediction.
The validation of this new workflow will help to predict and verify the potential leakage
and possible reactivation of faults in order to ensure safety of CO2 storage, additionally
with respect to public acceptance of CCS.
Acknowledgments
This work was sponsored in part by the Australian Commonwealth Government through the
Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC). PROTECT (PRediction
Of deformation To Ensure Carbon Traps) is funded through the Geotechnologien Programme (grant
03G0797) of the German Ministry for Education and Research (BMBF). The PROTECT research
group consists of Leibniz Institute for Applied Geophysics in Hannover, Technical University
Darmstadt, Helmholtz-Zentrum für Umweltforschung in Leipzig, Trappe Erdöl Erdgas Consultant in
Isernhagen (all Germany) and Curtin University in Perth, Australia.
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
174
Henk, A. and Fischer, K. [2011] Building and calibrating 3D geomechanical reservir models a worked example. 73rd EAGE Conference & Exhibition.
Jenkins, C. R., Cook, P. J., Ennis-King, J., Undershultz, J., Boreham, C., Dance, T., de Caritat,
P., Etheridge, D. M., Freifeld, B. M., Hortle, A., Kirste, D., Paterson, L., Pevzner, R., Schacht,
U., Sharma, S., Stalker, L. and Urosevic, M. [2011] Safe storage and effective monitoring of
CO2 in depleted gas fields. Proceedings of the National Academy of Sciences 109(2), E35E41.
Krawczyk, C. M., Tanner, D. C., Henk, A., Trappe, H. and Urosevic, M. [2011] Sub-/seismic
deformation prediction - Development of a new seismo-mechancal workflow in the Otway
Basin for verification of communication between reservoir and surface. 1st Sustainable Earth
Science conference, http://www.earthdoc.org.
Urosevic, M., Pevzner, R., Shulakova, V., Kepic, A., Caspari, E. and Sharma, S. [2011]
Seismic monitoring of CO2 injection into a depleted gas reservoir–Otway Basin Pilot Project,
Australia. Energy Procedia 4, 3550-3557.
van Ruth, P. and Rogers, C. [2006] Geomechanical analysis of the Naylor structure, Otway
Basin Australia. CO2CRC (RPT06-0039), 26.
van Ruth, P., Tenthorey, E. and Vidal-Gilbert, S. [2007] Geomechanical Analysis of the
Naylor structure, Otway Basin, Australia - Pre-injection. CO2CRC (RPT07-0966), 27.
Vidal-Gilbert, S., Tenthorey, E., Dewhurst, D., Ennis-King, J., Van Ruth, P. and Hillis, R.
[2010] Geomechanical analysis of the Naylor Field, Otway Basin, Australia: Implications for
CO2 injection and storage. International Journal of Greenhouse Gas Control 4(5), 827-839.
Ziesch, J., Aruffo, C. M., Tanner, D. C., Beilecke, T., Krawczyk, C. M. and Henk, A. [2012]
Sub-seismic deformation prediction of potential pathways and seismic validation— joint
project PROTECT. EGU General Assembly 2013, Vienna/Austria; Geophysical Research
Abstracts 15, 1 p..
Geothermal Science and Technology
Geothermal Energy is defined as the heat of the accessible part of the earth crust. It
contains the stored energy of the earth which can be extracted and used and is one part of
the renewable energy sources. Geothermal Energy can be utilized for heating and cooling
by applying heat pumps as well as it can be used to generate electricity or heat and
electricity in a combined heat and power system.
The field of Geothermal Science has natural scientific and engineering roots. Geothermal
Science connects the basic knowledge with the requirements of practical industry
applications. Geothermal Science is in interdisciplinary exchange with other applied
geological subjects such as hydrogeology and engineering geology and therefore is a logic
and proper addition to the research profile of the Technische Universität Darmstadt.
The broad implementation of geothermal energy applications and the utilization of the
underground as a thermal storage will help to reduce CO2 emissions and meet the
according national and international climate protection objectives. Furthermore, the
utilization of geothermal energy will strengthen the independency on global markets and
the utilization of domestic resources. Geothermal Energy will be an essential part of the
decentralized domestic energy supply and will contribute an important share of the desired
future renewable energy mix.
Regarding the worldwide rising importance of renewable energy resources, Geothermal
Science is one of the future's most important field in Applied Geosciences. In 2009, the
industry-funded Chair for Geothermal Science and Technology was established at the TU
Darmstadt – the first foundation professorship in energy science of the university.
The Chair of Geothermal Science and Technology deals with the characterization of
geothermal reservoirs, starting from basic analyses of thermo-physical rock properties,
which lead to sophisticated calculation of the reservoir potential of distinct rock units.
Reliable reservoir prognosis and future efficient reservoir utilisation is addressed in outcrop
analogue studies world-wide. Organisation of a highly qualified geothermal lab and
experimental hall (TUD HydroThermikum) started already in 2007 and was continued in
2012. Field courses and excursions in 2012 focused on geothermal energy in New Zealand,
Jordan, Germany and Austria.
Staff Members
Head
Prof. Dr. Ingo Sass
Research Associates
M.Sc. Achim Aretz
M.Sc. Swaroop Chauhan
Dipl.-Ing. M.Sc. Sebastian
Homuth
Dipl.-Ing. Robert Priebs
Dr. Wolfram Rühaak
Dipl.-Ing. Johannes Stegner
Dr. Kristian Bär
Dipl.-Ing. Christoph Drefke
Dipl.-Geol. Philipp Mikisek
Dipl.-Ing. Mathias Nehler
Dipl.-Ing. M.Sc. Johanna Rüther
Dipl.-Ing. Rafael Schäffer
Dipl.-Ing. Bastian Welsch
Technical Personnel Gabriela Schubert
Rainer Seehaus
Secretaries
Dunja Sehn
Simone Roß-Krichbaum
Institute of Applied Geosciences – Geothermal Science and Technology
175
PhD Students
Dipl.-Ing. Hauke Anbergen
M.Sc. Yixi Gu
Dipl.-Ing. Heiko Huber
M.Sc. Liang Pei
Dr.-Ing. Sana’a Al-Zyoud
Dipl.-Geol. Ulf Gwildis
Dipl.-Geol. Clemens Lehr
Students
M.Sc. Kirsten Bauer
Dipl.-Ing. Christoph Drefke
Jan Hesse (Dipl.-Ing.)
Michael Hubert (B.Sc.)
Dipl.-Ing. Ulrike Klaeske
Dipl.-Ing. Wladimir Kowalew
M.Sc. Larissa Langer
Dipl.-Ing. Mathias Nehler
B.Sc. Thomas Rybak
B.Sc. Björn Schwalb
M.Sc. Aga Zeleke
Florian Dönges (M.Sc.)
Claus Heldmann (M.Sc.)
Dipl.-Geogr. Susan Holz
B.Sc. Stefanie Kellmann
Bishnu Koju (M.Sc. TropHEE)
B.Sc. Sebastian Kurka (M.Sc.)
M.Sc. Ufondu Lotanna
Susan Reker (Dipl.-Geol.)
Dipl.-Ing. Rafael Schäffer
Dipl.-Ing. Bastian Welsch
Guest Scientists
EU-Programm Pioneer into
B.Sc. Manuel Quilis, Energía
Practice (PiP)
Geotérmica S.L.U., Valencia,
M.A. Desislava Stoycheva,
Spanien
Johannes Gutenberg University,
Mainz
Guest Lecturers
Dr.-Ing. Ulrich Burbaum (CDM Consult Alsbach)
Prof. Dr. Rolf Bracke (Geothermiezentrum Bochum)
Dr. Thomas Nix (LBEG Hannover)
Dr. Thomas Kölbel (EnBW Karlsruhe)
Dr. Frieder Enzmann (Johannes Gutenberg Universität Mainz)
Research Projects started in 2012
Quantitativer Einfluss des Wasserhaushalts, der Umwelttemperatur und
geothermischen Kennwerte auf die Wärmeableitung erdverlegter Starkstromkabel
Funding: 2 years, E.ON Bayern AG
der
Entwicklung von thermophysikalisch optimierten Bettungsmaterialen für Mittel- und
Niederspannungskabeltrassen
Funding: 2 years, HeidelbergCement, Baustoffe für Geotechnik GmbH & Co. KG
Untersuchung
und
Bewertung
gekoppelter
Konzepte
zur
CO2-neutralen
Heizwärmeversorgung des Campus Botanischer Garten der Technischen Universität
Darmstadt (Kopplung von Solarthermie, Geothermie und einem Blockheizkraftwerk)
Research proposal, Energietechnologieoffensive Hessen, HA Hessen Agentur GmbH
Mitteltiefer
Hochtemperatur-Erdsonden-Wärmespeicher
(MHEW)
konventioneller Wärmeversorgungsnetze ohne Wärmepumpen
Research proposal, Bundesministerium für Wirtschaft und Technologie,
zum
Betrieb
Vorschlag für eine Forschungsbohrung: 1.000 m Kristallin - geothermisches Potenzial des
Grundgebirges im Bereich des nördlichen Oberrheingrabens
176
Research proposal, Leibniz-Institut für Angewandte Geophysik, Hannover
Entwicklung von numerischen Simulations- und Parameterschätzerverfahren zur ThermoHydro-Mechanisch gekoppelten Simulation des Untergrunds - Kurztitel: THM-Modul
BMU/PTH; Research proposal, Bundesministerium für Umwelt, Naturschutz und
Reaktorsicherheit
Geothermal investigations and scientific consulting for the deep geothermal drilling project
in Geretsried, Bavaria in collaboration with ENEX Power Germany GmbH
Research Projects continued and finalized in 2012
Rock and Hydrothermal Fluid Interactions and Their Impacts on Permeability, Reservoir
Enhancement and Rock Stability, Funding: 3 Years, DAAD
Experimentelle Untersuchungen zur Verifizierung eines Mehrphasenmodells für das
Wärmetransportverhalten im Untergrund, Funding: 3 Years, Bundesministerium für
Wirtschaft und Technologie
Machbarkeitsstudie „Machbarkeit und Nutzung von tiefer geothermischer Energie am
Flughafen Frankfurt, Funding: 2010-2013, FRAPORT AG
Charakterisierung des Geothermischen Reservoirpotenzials des Permokarbons in Hessen
und Rheinland-Pfalz
Funding: 2 Years, Bundesministeriums für Umwelt, Naturschutz und Reaktorsicherheit
Entwicklung
von
wartungsarmen
PEHD-Filterelementen
für
oberflächennahe
geothermische Brunnenanlagen, Funding: 3 Years, Deutsche Bundesstiftung Umwelt
Rock mechanical and geothermal evaluation of basaltic rocks in Harrat Al-Shaam, Jordan –
DAAD-funded project in collaboration with Hashemite University of Jordan, Zarqa.
Scientific consulting and supervision of an enhanced hydrothermal power plant system,
Upper Rhine Valley – private client, confidential.
Soil abrasion effects on tunnel boring machines – Industry-funded project (CDM Inc.
Seattle) in collaboration with Pennstate University, Institute of Soil and Rockmechanics.
Evaluation of thermal response tests using a cylinder source approach (Type Curve Fitting
Method) – Industry-funded project (Geotechnisches Umweltbüro Lehr).
Development of a thermal conductivity measuring device for soil or cuttings
In collaboration with DIN-Innovation of normalisation and standardization.
Umweltauswirkungen von Fracking bei der Aufsuchung und Gewinnung von Erdgas aus
unkonventionellen Lagerstätten – Risikobewertung, Handlungsempfehlungen und
Evaluierung bestehender rechtlicher Regelungen und Verwaltungsstrukturen
Funding: 1 Year, BMU-UBA; in collaboration with ahu AG, IWW, Rheinisch-Westfälisches
Institut für Wasser, Beratungs- und Entwicklungsgesellschaft mbH, Mühlheim a.d.R.
Ein neues FEM Programmmodul zur Thermo-Hydro-Mechanischen Kopplung; Aufbau einer
internationalen Kooperation, Funding: 3 Months, DFG
Hydrogeologische und geothermische Untersuchungen der Heilquellen und Heilbrunnen
Bad Soden-Salmünsters, Funding: 6 months, Spessart-Therme Kur- und Freizeit GmbH
177
Messstellenkonzept Sprudelhof Bad Nauheim, Funding: 6 months, Stiftung Sprudelhof Bad
Nauheim.
Publications
Al-Zyoud, S.; Rühaak, W.; Sass, I. (2012): The Potential of Shallow Groundwater Resources
for Cooling Purposes - a Geothermal Case Study in North East Jordan. In: Stanford
University (Hg.): Proceedings Stanford Geothermal Workshop. 37th Workshop on Reservoir
Engineering. Stanford, U.S.A.
Aretz, A.; Bär, K.; Sass, I. (2012): Geothermal reservoir properties of the Rotliegend
(Permocarboniferous) sediments in the Saar Nahe Basin (South-West Germany). In:
European Geosciences Union (Hg.): European Geosciences Union Geophysical Research
Abstracts. European Geosciences Union General Assembly 2012. Wien, Austria.
Homuth, S.; Götz, A. E.; Sass, I. (2012): Facies related thermo-physical characterization of
the Upper Jurassic geothermal carbonate reservoirs of the Molasse Basin, Germany. In:
European Geosciences Union (Hg.): European Geosciences Union Geophysical Research
Abstracts. European Geosciences Union General Assembly 2012. Wien, Austria.
Mikisek, P.; Bignall, G.; Sass, I.; Sepulveda, F. (2012): Effect of hydrothermal alteration on
rock properties in an active geothermal setting. In: European Geosciences Union (Hg.):
European Geosciences Union Geophysical Research Abstracts. European Geosciences Union
General Assembly 2012. Wien, Austria.
Rühaak, W.; Bär, K.; Sass, I. (2012): Estimating the subsurface temperature of
Hessen/Germany based on a GOCAD 3D structural model - a comparison of numerical and
geostatistical approaches. In: European Geosciences Union (Hg.): European Geosciences
Union Geophysical Research Abstracts. European Geosciences Union General Assembly
2012. Wien, Austria.
Sass, I.; Burbaum, U. (2012): Geothermische Bohrungen in Staufen im Breisgau:
Schadensursachen und Perspektiven. In: Geotechnik.
Sass, I.; Götz, A. E. (2012): Geothermal reservoir characterization: a thermofacies concept.
In: Terra Nova 24 (2), S. 142–147.
Sass, I.; Homuth, S.; Heidenreich, S.; Rüther, J.; Walch, A. (2012): Entwicklung und
Untersuchung poröser, hochdichter Polyethylen -Filterelemente für Brunnenanlagen. In: R.
Liedl (Hg.): Grundwasserschutz und Grundwassernutzung. Modelle, Analysen und
Anwendungen; Kurzfassungen der Vorträge und Poster. Tagung der Fachsektion
Hydrogeologie in der DGG (FH-DGG). Dresden, Germany.
Sass, I.; Schäffer, R. (2012): The Thermal Waters of Jordan. In: European Geosciences
Union (Hg.): European Geosciences Union Geophysical Research Abstracts. European
Geosciences Union General Assembly 2012. Wien, Austria.
Sass, I.; Stegner, J. (2012): Coupled Measurements of Thermophysical and Hydraulical
Properties of Unsaturated and Unconsolidated Rocks. In: Stanford University (Hg.):
Proceedings Stanford Geothermal Workshop. 37th Workshop on Reservoir Engineering.
Stanford, U.S.A.
178
Effect of thermophysical and hydraulic properties of trench fill materials on warmingup of buried cables
Johannes Stegner, Christoph Drefke, Mathias Nehler
In the coming years, the use of renewable energy sources will increase. Small power plants
using geothermal and other forms of renewable energy will cause a decentralization of
electric power production and this requires extensive changes to the electric supply
network. Power lines previously serving electricity consumers may in future reverse the
direction of the current flow incorporating decentralized electricity producers.
Considerable amounts of heat are emitted by underground power cables under electrical
current flow. The maximum current rating of the cables is limited by the maximum
conductor temperature. This is set for medium and low voltage cables to a maximum of
90 °C.
The dimensioning of the distances between cables to avoid mutual heating, as well as the
maximum current load relies on standardized values. These values are considered as
conservative limits, because any thermal overload can significantly reduce the lifespan of
the cables. For the use of cable routes next to other utility lines that are already in place,
partially still no binding standards exist. Optimization of the supply grid can be achieved by
reducing the distances between underground cables and by increasing the electric current
load limits for these routes. All measurements for a grid optimization are of considerable
economic interest.
Medium and low voltage cables are usually laid at a depth of 80 cm. In order to optimize
the distances between cables, precise knowledge of the thermophysical and hydraulic
properties and their interrelation in the partially saturated surrounding unconsolidated
rocks is required.
Within the research project several parts can be distinguished. Laboratory tests (figure 1)
after [1] are conducted on unconsolidated rocks from the project area in Bavaria
(Germany), determining the relevant geomechanical and thermophysical properties and
compiling the data in a geographic information system (GIS).
Fig. 1: A.1: Columnar test. A.2: Typical arrangement of probes at one level within the column. Line source
device after [2] for measuring the thermal conductivity, tensiometer for measuring capillary tension and FDRsensor for the measurement of water saturation. The corresponding measuring area is colored yellow. B.1:
Evaporation test of type HYPROP® after [3] with integrated full-space line source for thermal conductivity
measurement. B.2: Sketch of the experimental setup.
179
In addition, field investigations on an underground cable test field (figure 2) in which the
cables are embedded in representative (well-defined) soils and thermally enhanced bedding
materials are conducted, as well as monitoring of real cable projects.
Fig. 2: Test field for buried cables with the locations of the installed instrumentation. The cables are buried in
accordance with the german standards DIN.
180
The results of all tests are used for the calculation of heat flow using FEM modelling and
analytical methods. The results can be used to optimize the design of electrical cable routes
as well as the design of shallow geothermal installations, or to calculate the freezing
behaviour of paved surfaces.
References:
[1]
[2]
[3]
Sass, I. & Stegner, J. (2012): Coupled Measurements of Thermophysical and Hydraulical
Properties of Unsaturated and Unconsolidated Rocks. Proceedings, 37th Workshop on
Geothermal Reservoir Engineering Stanford University, 30 January – 1 February 2012, SGPTR-194, Stanford, California.
Blackwell, J.H. (1954): A transient flow method for determination of thermal constants of
insulating materials in bulk, J. Appl. Phys., 25, 137–144.
Schindler, U. (1980): A rapid method for measuring the hydraulic conductivity of partially
saturated soils from cores samples, Arch. Acker- u. Pflanzenbau u. Bodenkunde, 24, 1–7.
181
A linear elasticity module for extending classical heat and
groundwater flow transport codes
Wolfram Rühaak
A numerical code for solving linear elasticity, based on the Finite Element Method (FEM) in
3D has been developed. At its current state it is intended to be coupled into existing 3D
flow- and heat-transport codes to enable this way a hydro-mechanical and thermo-hydromechanical coupled modelling. A standalone version may be developed in future.
The general concept of THM coupled modelling is shown in Fig. 1.
Fig. 1: Thermo-hydro-mechanical coupling approach and the respective constitutive laws.
Besides of commercial all-in-one solutions (e.g. COMSOL Multiphysics, ABAQUS, ANSYS), a
coupling of TOUGH2 with additional mechanical codes is often used (e.g. TOUGH-BIOT,
TOUGH-FLAC), besides numerous other codes OpenGeoSys should be named for a research
code with THMC capabilities. The code presented here is LGPL licensed open source and
coupled to the commercial software FEFLOW. FEFLOW is one of the most used programs
for groundwater, mass- and heat-transport modelling, worldwide. It is endowed with a very
user friendly and powerful user interface and besides of the parallelised (OpenMP)
computational core it has also powerful pre- and post-processing capabilities, including 2D
and 3D GIS data, to name some. FEFLOW is by default able to compute thermo-hydrochemical (THC) coupled processes. By adding the newly developed mechanical plug-in it
becomes a THMC simulator.
182
Research and Development of porous, high-density polyethylene screens for shallow
geothermal well systems
Johanna Rüther, Steffen Heidenreich, Astrid Walch, Ingo Sass
Screens of geothermal wells are used in sand control applications to support the gravel
pack installed in the annulus space. Further requirements of screens are, for the most part,
insufficiently satisfied with current technology. Therefore a new screen system is being
researched and developed in a DBU promoted project in cooperation with Co. Pall
Filtersystems GmbH and the Chair of Geothermal Science and Technology at Technische
Universität Darmstadt. In this study, not only are the hydraulic and geotechnical problems
questioned, but are the processes causing deteriorating well performance investigated.
Plugging varities such as aggradation and colmation in the screen and near-wellbore area
generate problems within well operation and maintenance. Failure of wells is a mandatory
research field for geothermal well systems. In the geothermal case the clogging of the
screens is not only affected by physical, but also chemical and microbiological processes.
The production of high-density polyethylene (PE-HD) screens is a newly developed and
researched sintering process [1]. These screens are made of a hydrophobic, nonpolar
thermoplast. Small-sized pores, with a diameter from 20 to 1000 µm, inhibit the initial
growth of microorganisms and the deposition of particles in the screen [2]. The applied
pore size for geothermal well systems are 500 and 1000 µm.
The groundwork for this study is the improvement of the screen manufacturing. The
challenge is to ensure a screen system with homogenous pores that will enhance the
hydraulic characteristics. In addition to enhancing hydraulic properties, the strength of the
screens must be optimized to adequately resist the strains commonly found within
geotechnical environments. These parameters are supplementary analyzed in focus of
geothermal application with a thermotriaxial device.
First hydraulic experiments in the laboratory have been done to estimate the screen
transmitting capacity [3]. On the basis of these tests colmation processes for different
suspension scenarios were analyzed and the particle size of retaining fines were quantified.
Laboratory experiments have been transferred to test field scenarios in order to investigate
the long term performance of the screen. Conventional screens have been installed in these
test field sites next to the porous PE-HD screens to compare their characteristics
directionally.
Further application-oriented research is planned by simulating chemical and
microbiological failure scenarios and investigating different maintenance methods.
References:
[1]
[2]
[3]
HEIDENREICH, S. & WALCH, A. (2012): Brunnenfilterrohre aus gesintertem porösen HDPE.bbr 09/2012: 34-37.
OKUBO, T. & MATSUMOTO, J. (1982): Biological Clogging of Sand and Changes of Organic
Constituents During Artificial Recharge – Water Res. 17/7: 813-821.
SASS, I., RÜTHER, J., HOMUTH, S., HEIDENREICH, S. & WALCH, A. (2012): Entwicklung
und Untersuchung poröser, hochdichter Polyethylen -Filterelemente für Brunnenanlagen.- FHDGG Jahrestagung. Deutsche Gesellschaft für Geowissenschaften/Fachsektion Hydrogeologie,
Dresden.
183
Applied Sedimentology
Sedimentary rocks cover about 75% of the earth’s surface and host the most important oil
and water resources in the world. Sedimentological research and teaching at the Darmstadt
University of Technology focus on applied aspects with specific emphasis on
hydrogeological, engineering and environmental issues. One key issue in this context is the
quantitative prediction of subsurface reservoir properties which is essential in modelling of
regional groundwater hydrology, oil and gas exploration, and geothermal exploitation.
However, also basic sedimentological research is carried out, e.g. the use of sediments as
archives in earth history to reconstruct geodynamic, climatic and environmental processes
and conditions in the past. To predict groundwater movement, pollutant transport or
foundations of buildings in sedimentary rocks a detailed knowledge about the hydraulic,
geochemical or geotechnical properties is needed which often vary about several
magnitudes. This kind of subsurface heterogeneity can be related to distinct
sedimentological patterns of various depositional systems. In addition, changes of
depositional systems with time can be explained by specific controlling parameters e.g.
changes in sea level, climate, sediment supply and are nowadays described by the concept
of sequence stratigraphy. The research in applied sedimentology also includes modelling of
erosion and sediment transport and its implication for the management of rivers and
reservoirs with the help of GIS.
For any subsurface management a quantitative 3D model is a prerequisite, either related to
water and geothermal energy or to gas, oil, and CO2 storage. Together with the group of
Prof. Schüth (Hydrogeology) and Prof. Sass (Geothermics) the sedimentology group
focusses on detecting the large to meso-scale sedimentary architecture and permeabilities
of sedimentary reservoir rocks in order to achieve an optimized subsurface management of
water and renewable energy resources.
To detect subsurface heterogeneities at a high resolution, the sedimentology group hosts a
georadar equipment for field measurements. This geophysical device is composed of
various antennas and a receiver unit. Sophisticated computer facilities are provided to
process the data and construct real 3D subsurface models. The group shares their
equipment and facilities with the Universities of Frankfurt (Applied geophysics), Tübingen
(Applied sedimentology), Gießen (soil sciences), the RWTH Aachen and industrial partners.
These institutions founded the Georadar-Forum which runs under the leadership of Dr.
Jens Hornung (http://www.georadarforum.de/). Thanks to funding via a DFG research
grant we could invest into a shear wave measuring unit in 2011, which will extent our
abilities for subsurface surveys down to several hundred meters and through materials,
weakly penetrable by electromagnetic waves. For quantification of reservoir properties a
self-constructed facility for permeability measurements of soil and rock materials exists
which is further developed. This lab is also fundamental to geothermal research.
In 2012, the group participated in the DFG Research Unit RiftLink
(http://www.riftlink.de/) and two European Research Groups within the EUCORES
Programme (TOPOEurope, SedyMONT). The topic of these research projects are in the
context of earth surface processes, palaeoenvironmental reconstructions and georisk
assessments. Field work was undertaken in East Africa, the Alps, Saudi Arabia, and
southern Peru. The project in Saud Arabia runs in the context of exploring deep water
184
Institute of Applied Geosciences – Applied Sedimentology
resources together with Prof. Schüth (Hydrogeology) and in cooperation with the GIZ
(Gesellschaft für I(nternational Zusammenarbeit), the UFZ (Umweltforschungszentrum
Halle-Leipzig), and the Ministry of Water and Energy of Saudi Arabia (MOEWE). The aim is
to investiate the storage properties of large sedimentary aquifers and their relation to the
amount and quality of substracted groundwater in a hyperarid area suffering from water
scarcity. A PhD of a Saudi Arabian PhD student from the MOEWE could be completed in
2012.
Based on previous work of the group several research initiatives are running at the
moment, e.g. past environmental pollution in Central Europe as reconstructed from lake
sediments, Mesozoic palaeoenvironmental evolution in NW China (initiative together with
University of Bonn and Jilin University, China), and high-resolution palaeoclimatic studies
in Messel and similar maar lakes (DFG). Jianguang Zhang continued his PhD with a
Chinese grant. A new PhD was started to investigate the sedimentological causes of natural
radioactivity in deep groundwaters of Saudi Arabia. Here, we applied for a new DFG grant.
Prof. Hinderer has been elected as member and speaker of the "Wissenschaftlicher Beirat
Beschleunigungsmassenspektrometer, DFG University of Cologne” by the DFG senat
commission of common geoscientific research (DFG-Senatkommission Zukunftsaufgaben
der Geowissenschaften). He is also the representative of the German-speaking
sedimentologists (Section of Sedimentology in Geologische Vereinigung and SEPM-CES)
and co-organized the SEDIMENT conference in Hamburg 2012. He was nominated as new
member of the editorial board of the International Journal of Earth Sciences.
Staff Members
Head
Prof. Dr. Matthias Hinderer
Research Associates
Dr. Jens Hornung
Postdoctoral Students
Dorthe Pflanz
PhD Students
Hussain Al-Ajmi
Alexander Bassis
Weihua Bian
Dennis Brüsch
Daniel Franke
Technical Personnel
vacant in 2012
Secretary
Kirsten Herrmann
Dr. Olaf Lenz
Inge Neeb
Frank Owenier
Sandra Schneider
Jianguang Zhang
Research Projects
Linking source and sink in the Ruwenzori Mountains and adjacent rift basins, Uganda:
landscape evolution and the sedimentary record of extreme uplift: Subproject B3 of DFG
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Research Group RIFT-LINK “Rift Dynamics, Uplift and Climate Change: Interdisciplinary
Research Linking Asthenosphere, Lithosphere, Biosphere and Atmosphere” (DFG HI 643/72).
Spatial distribution of modern rates of denudation from cosmogenic Nuclides and Sediment
Yields throughout the Alps (EUCORES programme TOPOEurope, Research Unit TOPO Alps,
IP 3, DFG HI 643/9-1).
High resolution 3D architectural analysis and chronology of alluvial fan deposits in
mountain landscapes: A case study of the Illgraben fan, Switzerland (EUCORES programme
TOPOEurope, Research Unit SedyMONT, IP 6, DFG HI 643/10-1).
Monitoring of soil water content with ground penetrating radar (PhD thesis).
Climatic and tectonic interplay in central Asian basins and its impact on paleoenvironment
and sedimentary systems during the Mesozoic (2 PhD theses).
Sedimentology, dynamic stratigraphy and hydrofacies model of Paleozoic and Mesozoic
aquifers in Saudi Arabia. (PhD thesis financed by Umweltforschungszentrum Leipzig-Halle,
GIZ Eschborn, and the Ministry of Water and Energy in Riyadh, Saudi Arabia).
Provenance of Paleozoic clastic sediments and reasons for radioactive anomalies in
groundwaters on the Arabian Platform (PhD thesis)
Aggradation of alluvial fans in the Eastern Cordillera in response to humidity changes and a
climate gradient from the Altiplano to theAmazon Basin (two Master theses and
preparation of a DFG project)
Periglacial eolian sediments in southern Hessia and their genesis (Diploma und BSc theses
and preparation of a DFG project)
Publications
Hornung, J. & Hinderer, M. (2012): Depositional dynamics and preservation potential in a
progradational lacustrine to fluvial setting: Implications for high resolution sequence
stratigraphy (Upper Triassic, NW-China). SEPM Spec. Publ. 97: 281-310.
Hinderer, M. (2012): From gullies to mountain belts: a review of sediment budgets at
various scales. Sedimentary Geology 280: 21-59.
Pflanz, D., Gaedicke, C., Freitag, R., Krbetschek, M., Tsukanov, N. and Baranov, B. (2012):
Neotectonics and recent uplift on Kamchatka Cape Peninsula (Russia)
Int J Earth Sci (Geol Rundsch) DOI 10.1007/s00531-012-0830-z
Riegel, W., Wilde, V., Lenz, O.K. (2012): The Early Eocene of Schöningen (N-Germany) –
an interim report. Austrian Journal of Earth Sciences, 105 (1): 88 – 109.
Roller, S., Wittmann, H., Kastowski, M., Hinderer, M. (2012): Erosion of the Rwenzori
Mountains, East African Rift, from insitu produed cosmogenic 10Be. Journal of Geophysical
Research, AGU.
186
Paleozoic source to sink relationship along the Trans-Gondwana Mountain Belt (East
Africa, Arabia)
Alexander Bassis, Matthias Hinderer, Guido Meinhold, Cornelia Spiegel
Sandstone aquifers in northern Africa and on the Arabian Platform bear important fossil
groundwater resources which are presently heavily mined. Besides quantitative restrictions
of groundwater mining in these regions, these groundwaters often show increased natural
radioactivity, mostly from 228 Ra. The source of this radioactivity is assumed to be heavy
minerals which are enriched in specific horizons or lithofacies types depending on former
source areas of the sands and their enrichment under specific depositional processes. An
ongoing PhD project tries to better understand these processes in order to better predict
natural groundwater radioactivity in deep aquifers of arid regions. The project has been
also submitted as a DFG project.
After the formation of the Gondwana supercontinent and throughout the Paleozoic, a thick
pile of mostly clastic sediments has been deposited on the northern Gondwana margin.
Deposition took place in a supposed “Super Fan” which was supplied by erosion of the
Transgondwana super mountains, also known as the East African Orogen (EAO, Fig. 2).
Fig. 2: Map of Gondwana showing
position of the cratonic nuclei
(modified after Gray et al. 2008).
The collision zone marks the East
African–Antarctic
orogen,
also
known as the Transgondwanan
supermountain. The dashed line
marks the outline of the Arabian–
Nubian Shield.
Abbreviations: ANS – Arabian–
Nubian Shield, CAFB – Central
African fold belt, DB – Damara belt,
IB – Irumide belt, KB – Kibaran belt,
M
–
Madagascar,
MB
–
Mozambique belt, NA – North
Australia, RP – Río de la Plata
Craton, SA – South Australia, SF –
São Francisco Craton, TC – Tanzania
craton, TSB – Trans-Saharan fold
belt, WA – West Australia.
The Arabian-Nubian Shield was formed as part of this super orogeny. Although the super
fan model has been used to explain the thick Paleozoic clastic sequences in North Africa, its
eastern extend has yet to be determined (Fig. 2).
187
Fig. 2: Plate-tectonic reconstruction
of northern Gondwana (460 Ma)
adapted from von Raumer and
Stampfli (2008) showing the
Transgondwanan supermountain
and the Gondwana super-fan
system (modified after Meinhold et
al. 2013). The two different cross
patterns for the Transgondwanan
supermountain represent major
and old (eroded) mountains
respectively. Blue arrows show
main sediment transport directions.
Red circles represent localities
discussed by Meinhold et al. (2013).
In this project we aim to use sediment provenance in order to test this model with data
from the Arabian Shield and Platform, using U/Pb dating on detrital zircons, whole rock
geochemistry, single grain geochemistry and low temperature thermochronology (zircon
fission track dating/ZFT). Samples from the sediment sink were taken from two main areas
and cover most of the Paleozoic succession: the Wajid area on the southeastern edge of the
Arabian Shield (“Wajid area”, Fig 3) and from central to north-central Saudi Arabia (“Saq
area”, Fig. 3).
Fig. 3: Generalized geologic map of
the Arabian Peninsula, showing the
study areas. Modified after Powers et
al. (1966).
So far there is only scarce data on sediment provenance of Paleozoic clastics from the
Arabian Peninsula and no zircon U/Pb or ZFT ages. Until now, authors have suggested a
very proximal sediment source. With our study we aim to improve the understanding of
sediment provenance on the eastern Gondwana margin using state of the art techniques not
only in the sediment sink, but also in probable source areas. These possible source areas
encompass not only the proximal Arabian Shield, but also other, more distal parts of the
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EAO, like the Neoproterozoic diamictites of the Bunyoro-series near Hoima in Uganda,
where another project of our working group is running.
In the course of a recently conducted field campaign to Saudi Arabia, over 170 samples
were taken from the two sampling areas on the Arabian Platform as well as several areas on
the Precambrian Shield. Laboratory work will be conducted at the TU Darmstadt as well as
at the universities of Göttingen and Bremen together with cooperating working groups.
The outcome of this study will improve not only the general understanding of sediment
provenance in the region but also the impact of the two large Paleozoic glaciations on
sediment provenance and it will further refine the Gondwana super fan model (Keller et al.,
2011). In addition, we will provide basic data for better prediction of natural groundwater
activity on the Arabian Platform.
References
[1]
[2]
[3]
[4]
Gray, D.R., Foster, D.A., Meert, J.G., Goscombe, B.D., Armstrong, R., Trouw, R.A.J.,
Passchier, C.W., 2008. A Damaran orogen perspective on the assembly of southwestern
Gondwana. In: Pankhurst, R.J., Trouw, R.A.J., Brito Neves, B.B., De Wit, M.J. (Eds.), West
Gondwana: Pre-Cenozoic correlations across the South Atlantic region. Geological Society of
London, Special Publication, 294, 257-278.
Keller, M, Hinderer, M., Al Ajmi, H. & Rausch, R., 2011. Paleozoic glacial depositional
environments of SW Saudi Arabia: Process and Product. Spec. Publication Geological Society
of London, 354: 129-152.
Meinhold, G., Morton, A.C., Avigad, D., 2013. New insights into peri-Gondwana
paleogeography and the Gondwana super-fan system from detrital zircon U-Pb ages.
Gondwana Research, 23, 661-665.
Powers, R.W., Ramirez, L.F., Redmond, C.D., Elberg, E.L., 1966. Geology of the Arabian
Peninsula: sedimentary geology of Saudi Arabia. U.S. Geological Survey Professional Paper
560-D, 147 pp.
189
Geo-Resources and Geo-Hazards
In times of rapid population growth and the resulting strain of the resilience of natural
systems, geosciences in particular have become an increasingly important research area.
However, geoscientific knowledge about material flows from and back into the
environment and about the prevention of catastrophic consequences of big natural
phenomena is often not understood by decision makers, who were not able to spend long
years on understanding the four-dimensional space-time-development of our earth. On the
other hand, the metabolism of cities, its growing needs for clean water and raw material for
constructions while simultaneously egesting waste into its neighbourhood, require a
thorough understanding of its undergrounds and peripheries as well as safe construction
sites.
Computer based Geo Information Systems and 3 to 4D-techniques are powerful tools to
qualify and to quantify resources and hazards in the peripheries of urban areas. They
enable the aggregation of complex geological and spatial data to thematic maps for a better
understanding and interpretation by local decision makers.
Staff Members
Head
Prof. Dr Andreas Hoppe
Research Associates
Dipl.-Geoökol. Monika
Dipl.-Geol. Ina Lewin
PhD students
Dipl.-Ing. Dirk Arndt
Dipl.-Geogr. Constanze Bückner
Students
Filipe Lopes Chaves
(BSc Belo Horizonte)
Marie Mohr (BSc)
Nicole Schmuck
(BSc Frankfurt a.M.)
Student apprentices
Alexandra Knicker
(Iowa State Univ., 8 weeks)
John Wall (North Carolina
State Univ., 4 weeks)
Technical Personnel
Dipl.-Kartogr. (FH) Ulrike Simons
Holger Scheibner
Secretary
Pia Cazzonelli
Guest Scientist
Prof. Dr. Prem B. Thapa (Georg Forster Research Fellow, Alexander
von Humboldt Foundation)
190
Hofmann Dr. Rouwen Lehné
Hannah Budde (MSc
Geowiss.)
Dipl.-Geol. Marie Luise Mayer
Bastian Neef (BSc), Obinna
Nzekwe (MSc)
Steven Owuor (MSc)
Narmada Rathnayake (MSc)
Institute of Applied Geosciences – Geo-Resources and Geo-Hazards
Research Projects
Constanze Bückner and Andreas Hoppe reported their first results within an
interdisciplinary project about the “Intrinsic Logic of Cities” (funded by a Hessian initiative
for excellence, LOEWE program) in a book comparing the cities of Mainz and Wiesbaden.
Constanze Bückner won with an essay about „City and Countryside – Two Environments“
2nd price in a competition „The Future World“ offered by the German Ministry of Science
(BMBF) together with the newspaper “Die Welt”.
Prem Thapa from Tribhuvan University of Nepal continued with modelling of mass
movements, wrote books about “Geo-informatics/-modelling” and “Landslide and Debris
Flow Hazard” and supervised two MSc theses dealing with landslide hazards in Nepal.
Rouwen Lehné developed in cooperation with the Hessian Geological Survey (HLUG) a GIS
and gOcad based 3D model of the Quaternary in the northern Upper Rhine Graben.
Outcomes of the ongoing project have been presented at several national and international
conferences. He served as speaker of the Section Geoinformatics within the German
Geological Society (DGG), has been re-elected for another 2 years and chaired a scientific
session during the annual meeting of the DGG in Hannover. Furthermore he settled a cooperation with the Estonian Land Board in order to realize the first gOcad based geological
3D model for the northeastern part of the country by the use of well information, especially
to deepen understanding of distribution and quality of resources (i.e. oil shale and black
shale) as well as the shape of the pre Quaternary surface.
Hannah Budde joined the group in autumn. In the frame of a cooperation with the HLUG
she will elaborate a computer based 3D-visualisation especially of the Tertiary and
Quaternary units of the “Lower Main Plain”, the area south of the Rhenish Massif which
covers huge parts of the metropolitan region Rhein-Main. Hannah Budde has been elected
to the board of the section Geoinformatics of the DGG.
Ina Lewin analysed the specific sedimentary conditions for a small area in the Neogene
Hanau-Seligenstadt Basin between the Odenwald and Spessart Mts three-dimensionally
(gOcad) and estimated the groundwater flow with the help of a tracer test in cooperation
with the “Zweckverband Gruppenwasserwerk Dieburg”.
Dirk Arndt finished a goCad based geological 3D model of the Federal State of Hesse in an
approx. 1:300.000 scale and successfully defended it as a doctoral-thesis (http://
tuprints.ulb.tu-darmstadt.de/3082/).
The evaluation of geopotentials in the surroundings of the fast growing capital of Minas
Gerais (Brazil) by Monika Hofmann led to a first draft of her doctoral thesis.
Andreas Hoppe, Rouwen Lehné and Ulrike Simons continued in cooperation with the
German Archeological Institute (DAI) the investigations about Olympia (Greece) to
decipher the Holocene evolution of landscape and presented the first results in a
multimedia presentation within an exhibition of the DAI “Mythos Olympia” in MartinGropius-Bau in Berlin (which will move to Athens and Doha in 2013).
191
Andreas Hoppe served as chief-editor of the “Zeitschrift der Deutschen Gesellschaft für
Geowissenschaften” (German Journal of Geosciences). As speaker of the Evenarí Forum for
German-Jewish Studies at Technische Universität Darmstadt he guided an interdisciplinary
group of students to an excursion to Israel and the Occupied Territories under the topic of
“water within natural and cultural development and politics”, and he organized for the
winter term 2012/2013 a series of interdisciplinary lectures on “Catastrophes”. In Bologna,
he was chairman of a “Urban Geology” session during an international meeting about Geo
Information Systems.
Publications
Bückner, C. & Hoppe, A. (2012): Kartierte Städte – Mainz und Wiesbaden im
Spannungsfeld von Naturraum und Vergesellschaftung. - 226 S., Frankfurt/M. (Campus)
[ISBN 978-3-593-39573-9].
Hoppe, A., Lehné, R., Hecht, S. & Vött, A. (2012): Olympia im Kontext der jüngsten Erdund Landschaftsgeschichte. – In Heilmeyer, W.-D., Klatsas, N., Gehrke, H.-J., Hatzi, G.E. &
Bocher, S., Mythos Olympia – Kult und Spiele, 232-235, München (Prestel) [ISBN 978-37913-5212-1].
Lamelas, M.T., Marinoni, O., de la Riva, J. & Hoppe, A. (2012): Comparison of multicriteria
analysis techniques for environmental decision making on industrial location. – In Chiang
Jao (ed.), Decision Support Systems, 15 pp., Rijeka-Shanghai-New York (Intech) [ISBN
978-953-51-0799-6] doi 10.5772/51222.
Lang, S. & Seidenschwann, G. (2012): Die pliozäne Entwicklung der Hanau-Seligenstädter
Senke, des Kinziggebietes und des Vorspessarts. – Jber. Wett. Ges. ges. Naturkunde 165:
79-132, Hanau.
Schumann, A., Arndt, D., Wiatr, T., Götz, A.E. & Hoppe, A. (2012): Extraction management
optimisation with TLS and 3D modelling / Optimierung des Abraummanagements mit TLS
und 3D-Modellierung. – ZKG International (Zement Kalk Gips) 7: 47-53, Gütersloh.
Thapa, P.B. (2012): Geo-informatics/-modelling - “Landslide Hazard and Risk”. Mahesh
Printing Publisher, First Edition, Kathmandu, Nepal, 147 p [ISBN 978-9937-2-5348-2].
Thapa, P.B. (2012): Landslide and Debris Flow Hazard - “Modelling/simulation &
mitigation”. ST Publisher, First Edition, Kathmandu, Nepal, 163 p [ISBN 978-9937-2-5544-8].
Thapa, P.B. & Hoppe, A. (2012): 3D modeling of geological features. – Bulletin of Nepal
Geological Society 29: 67-72, Kathmandu, Nepal.
192
Sonnenenergie aus Baggerseen im Ballungsraum Rhein-Main-Neckar?
Andreas Hoppe1, Alexandra Knicker2, Rouwen Lehné1, Christian Lerch3 & Marie Mohr1
1
Inst. Angew. Geowiss. TU Darmstadt, 2Iowa State University, 3Viernheim
Mit der „Energiewende“ in der Bundesrepublik Deutschland, ausgelöst durch ein Erdbeben
in Japan am 11.3.2011 und dadurch ausgelösten Folgekatastrophen (Tsunami,
Kernschmelzen im Atomkraftwerk Fukushima) stieg und steigt immer noch die Nachfrage
nach „alternativer Energie“. Dazu gibt es bereits Ideen und auch schon Umsetzungen von
Großprojekten wie „Desertec“ (zur Gewinnung von Solarstrom in sonnenreichen Wüsten)
und Windanlagen in der Nordsee. Diese Ansätze erfordern jedoch lange Transportstrecken
für den produzierten Strom bis zum Kunden und „verbrauchen“ dabei neben
Investitionsmitteln auch große Flächen für die notwendigen Infrastrukturen. Dezentrale
Stromgewinnung nahe am Verbraucher wäre die ökonomisch und ökologisch günstigere
Lösung, zumal wenn sie aus regenerativen Energiequellen käme und zudem zu
„intelligenten Netzen“ der Stromgewinnung und Speicherung verknüpft würde und
außerdem eine „Wertschöpfung vor Ort“ ermöglichen könnte.
Abb. 1 Die nördliche Oberrheinebene (rechts mit Blick auf den Melibokus) ist bereits zu fast einem Viertel mit
Siedlungen und Gewerbeflächen (rot) sowie Verkehrswegen überbaut. Die restliche Fläche wird intensiv für
landwirtschaftliche Sonderkulturen, den Abbau von Sand und Kies, die Gewinnung von Grundwasser und
geothermischer Energie sowie den Naturschutz und Freizeitaktivitäten genutzt.
Für den Ballungsraum Rhein-Main-Neckar, einem der finanzstärksten Räume Europas,
bietet das geologische Senkungsgebiet des Oberrheingrabens sehr günstige naturräumliche
Voraussetzungen: Es befriedigt u.a. den Bedarf an Grundwasser und Massenrohstoffen und
erlaubt hohe landwirtschaftliche Erträge. Allerdings ist das Gebiet inzwischen zu einem
großen Teil mit Siedlungen und Verkehrsinfrastruktur versiegelt (Abb. 1) und
Flächennutzungskonflikte nehmen zu. Fläche ist also knapp. Wir haben daher einen
Gedanken bayerischer Kollegen (Gillhuber & Poschlod, 7th Euregeo 2012: 566-7, Bologna)
193
aufgenommen, die in aufgelassenen Kiesgruben und Steinbrüchen nutzbare Flächen für die
Energiegewinnung sehen.
Flächen für die Gewinnung oberflächennaher Rohstoffe werden von Vielen vor einer
Abbaubewilligung heftig verteidigt und als „Flächenverbrauch“ gewertet, während nach
einem erfolgten Abbau von Sand und Kies der dann offen liegende Grundwasserspiegel
oder Baggersee von wiederum ielen als „Flächengewinn“ für die Freizeitgestaltung oder
den Naturschutz betrachtet wird. Angesichts des Rohstoffhungers unserer Gesellschaft sind
es im nördlichen Oberrheingraben inzwischen große Flächen, deren potenzielle Nutzung
für Solaranlagen also untersucht werden sollte. Dazu haben wir die Möglichkeiten
Geographischer Informationssysteme (GIS) genutzt und die potenziellen Wasserflächen
betrachtet:
Dabei zeigt sich, dass theoretisch eine Wasserfläche von etwa 45.000.000 Quadratmetern
bzw. gut 4.500 Hektar zu Verfügung stünde. Geht man davon aus, dass eine Solarzelle pro
Quadratmeter derzeit maximal 108 Watt pro Stunde erzeugen kann und dass die mittlere
Sonnenscheindauer zwischen Karlsruhe und Frankfurt bei etwa 1.840 Stunden pro Jahr
liegt, so ließe sich eine theoretische Ausbeute von mehr als 10 Millionen Kilowattstunden
pro Jahr abschätzen (108 W/h x 45.000.000 m2 / 1 m2 x 1840 h/a = 8.942.400.000
kWh/a). Setzt man dies ins Verhältnis zu dem von der Weltbank 2009 für Deutschland
angegebenen durchschnittlichen Jahresverbrauch von 6.779 Kilowattstunden pro Person, so
ließe sich damit theoretisch der Energiebedarf von mehr als 1,3 Millionen Menschen oder
der doppelten Einwohnerzahl von Frankfurt a.M. befriedigen.
Selbstverständlich sind dies rein theoretische Überschlagsrechnungen: Die Wasserfläche
ließe sich nicht zu 100% nutzen, da andere Nutzungsansprüche dem entgegenstehen, und
sicher käme die Energieausbeute in dem geschätzten Umfang nicht ohne Verluste beim
Verbraucher an. Andererseits scheinen selbst bei einer Nutzung von nur einem Drittel der
Wasserfläche in der Oberrheinebene erhebliche Energieausbeuten möglich.
Schwimmende Solaranlagen auf Baggerseen ließen sich in ihrer Ausrichtung einfach dem
täglichen Sonnengang anpassen. Die durch die Abdunkelung der Wasserfläche
entstehenden unterschiedlichen Temperaturen an der Wasseroberfläche würden vermutlich
außerdem eine Zirkulation im Wasserkörper in Gang setzen, die zur Sauerstoffanreicherung
führen könnte.
Ein Problem von Solaranlagen ist der nicht immer kongruente Zeitraum von
Stromgewinnung und -verbrauch. Neben den hier nicht diskutierten technischen
Möglichkeiten zur Speicherung von Solarenergie sei auf die Vorteile des Naturraumes für
den nördlichen Oberrheingraben zumindest hingewiesen: die mögliche Nutzung von
Wasserspeichern. Dazu bietet sich das Rheinische Schiefergebirge am Nordrand des
Ballungsraumes an. Die geologischen Voraussetzungen sind hier günstig, und
ausgearbeitete Pläne für eine Talsperre liegen vor – etwa seit den 1980er Jahren für das
nur wenige Kilometer westlich von Mainz und Wiesbaden gelegene Ernstbachtal.
194
What buried Olympia?
Andreas Hoppe, Rouwen Lehné, Marie Mohr & Ulrike Simons
Institute of Applied Geosciences, Technische Universität Darmstadt
In ancient Greece, in the Holy District of Altis (see the descriptions of the Greek historian
Pausanias, written in 2nd century BC; cf. Sinn 2004, Heilmeyer et al. 2012), men met every
four years at Olympia for the ancient Olympic tournaments. It is a place at the confluence
of two rivers: the turbulent Alpheios and the Kladeos (a tributary of the Alpheios).
Receiving its waters from a large catchment area, the Alpheios is 110 km long and the main
river of the northern Peloponnese.
Fig. 1: The north-western part of the Peloponnese, with the Alpheios as the main river, is an active
neotectonic-seismic area due to (see inset) eastward subduction along the Hellenian Arc against a movement
of the Anatolian Plate to the west which results in a north-south dilatation of the Gulf of Corinth.
But why was it necessary to excavate this area, done systematically since the 19th century,
after it was rediscovered a century earlier? It was previously hidden under a conical alluvial
fan of the Kladeos, the so called Olympia Terrace (Fig. 2), comprising mainly of silty
sediments up to 6 m thick. Now, the top of the flat lying terrace, in the bed of the Alpheios
south of Olympia, is approx. 33 m above sea-level with sharp ridges up to 7 m high in some
places. A narrow valley, between 8 and 10 m deep, was incised through the Olympia
Terrace by the Kladeos.
195
Hypotheses to explain the burial of Olympia are manifold (cf. Hoppe et al. 2012): (i)
flooding by episodic outburst of karst lakes in the higher hinterland of the Alpheios, (ii)
settlement of the area and the resulting changes in land use (e.g. deforestation) that caused
higher rates of soil erosion, (iii) climatic fluctuation with phases of higher precipitation and
soil erosion and (iv) earthquakes in 521 and 551 BC that destroyed Olympia and resulted
in flooding and sedimentation of the Altis. However, as of yet, there is no evidence to
support the theories of higher erosion induced by land use changes or climatic change. Nor
may episodic flooding alone explain a thick alluvial cone of the Kladeos.
Fig. 2: Recent extent of the Olympia Terrace (yellow) around Olympia (left). Catchment area of the Kladeos
(right) composed of marine Pliocene (dark yellow), younger Pliocene continental sediments (green),
Pleistocene conglomerates (light brown) and the Holocene Olympia Terrace (yellow) which was later incised
and filled by alluvial deposits of the Kladeos (dark brown).
Recent investigations by a joint group from Darmstadt and Mainz Universities (Vött et al.
2010) generated a fifth hypothesis: a tsunamigenic origin of the burial of Olympia, which is
supported by the presence of marine gastropods found in drill cores from the Olympia
Terrace. Thus, Vött el al. (2012) postulate that a tsunami wave, which followed the wide
valley of the lower Alpheios, passed through a morphologic saddle north of Olympia
(labelled “Pass” in Fig. 2a) at an altitude of more than 60 m and then ran down the Kladeos
bed, bringing with it the observed marine fauna as well as the sediments hiding the Altis.
However, a Kladeos cone generated by a tsunami seems unlikely because it would have
required a runup of almost 20 km inland with a height of 60 m above sea level as well as
large amounts of sediment to cover the ancient Olympia. As is known from recent
observations, the top of a tsunami consists in the majority of water (cf. Bahlburg & Spiske
2012). So, even if autochthonous marine sediments were mobilized by a tsunami running
down the valley of the Kladeos, the thick sedimentary pile hiding the Altis cannot be
explained by the small catchment area that lies between the “pass” and Olympia (Fig. 2b).
196
A more likely interpretation, which combines existing information on the regional geology
(Streif & IGME 1982) and geomorphology, new field investigations (drilling, dating,
component and grain size analysis) and geomorphological analysis using IKONOS-data
(1x1 m resolution) as well as a digital elevation model (based on topographic maps 1:5,000
and 1:50,000) is:
The surroundings of Olympia are composed mainly of fine grained marine sediments of the
Pliocene age which are overlain by younger continental sediments including Pleistocene
conglomerates which form, on the east and west of Olympia, a hard ridge or a barrier for
the Alpheios 6 km west of Olympia. This can be seen by a sudden northward bend of the
river (Fig. 2). The estimated volume of the Holocene Olympia Terrace, calculated using a
GIS-based analysis, is approx. 15,000,000 m3. The catchment area of the Kladeos is almost
33 km2.
The accumulation of the Kladeos cone and the Olympia Terrace respectively is assumed to
have begun in ancient Greece due to the presence of a man-made wall west of the Altis.
This wall was very likely built to avoid flooding of the Holy District by the Kladeos (cf.
Heilmeyer et al. 2012). The rising levels of the Kladeos, accompanied by sedimentation,
continued for several centuries. This is indicated by remnants of organic material found
2.35 m below the today´s surface which, when dated, revealed a 14C age of 1875±30
years.
The blocking of the Alpheios west of Olympia with sediments was likely due to an episodic
flood or mass movement (whether triggered by earthquake and/or heavy precipitation is
not known). This in turn lowered the transport energy of the Alpheios east of the
bottleneck, as water levels rose, which then affected the Kladeos, so that the Kladeos
suddenly lost gradient leading to deposition of eroded sediment from its upper catchment
area. It is known from the classical diagram of Hjulstrom (1935) that flow speed and grain
size determine whether a particle is eroded, transported or deposited.
Evidence indicates that during the Plio-/Pleistocene times fine grained marine sediments
were washed through the Kladeos and Alpheios valleys into the Mediterranean. The
blocking of the Alpheios bottleneck, west of Olympia in historical times, reduced the flow
speed of the Kladeos which then led to the deposition of eroded sediments from upstream
thus burying the Altis. Some marine fauna from Pliocene sediments was obviously included.
Opening of the bottleneck, post-Roman times, allowed a “normal” discharge of the rivers,
and the now more rapidly moving waters of the Kladeos incised into its own alluvial fan.
Similarly, the rapidly moving waters of the Alpheios eroded the Olympia Terrace leaving
steep and high cliffs south of the Altis.
Very likely (and unfortunately) this recent erosion has taken away remnants of the
Hippodrome as well – the antique place for horse races which has been described in detail
by Pausanias. It is believed that it was situated east of the Altis which is now the bed of the
young, eroding and anastomosing Alpheios.
197
Acknowledgements
We cordially thank the Deutsches Archäologisches Institut with Hans-Joachim Gehrke and Reinhard
Senff as well as Andreas Vött from Universität Mainz for manifold support in Olympia.
References
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Heilmeyer, W.-D., Klatsas, N., Gehrke, H.-J., Hatzi, G.E. & Bocher, S., Hg. (2012): Mythos
Olympia – Kult und Spiele. – 594 pp., München (Prestel).
Hoppe, A., Lehné, R., Hecht, S. & Vött, A. (2012): Olympia im Kontext der jüngsten Erd- und
Landschaftsgeschichte. – In Heilmeyer, W.-D., Klatsas, N., Gehrke, H.-J., Hatzi, G.E. &
Bocher, S., Mythos Olympia – Kult und Spiele, 232-235, München (Prestel).
Hjulstrom, F. (1935): The morphological activity of rivers as illustrated by River Fyris. – Bull.
Geol. Inst. Uppsala 25: 221-527.
Sinn, U. (2012): Das antike Olympia – Götter, Spiel und Kunst. – 276 pp., München (Beck).
Streif, H. & Institute of Geology & Mineral Exploration (1982): Geological Map of Olympia
1:50.000, Athens.
Vött, A., Bareth, G., Brückner, H., Fountoulis, I., Gehrke, H.-J., Hoppe, A., Lang, F., Lehné,
R., Sakellariou. D. (2010): Beachrock-type deposits document tsunamigenic destruction of
Olympia's ancient harbour (Greece). – Schriftenr. Dt. Ges. Geowiss. 68 (GeoDarmstadt2010):
574-575, Stuttgart.
Vött, A., Fischer, P., Hadler, H., Handl, M., Henning, P., Lang, F., Ntageretzis, K., Röbke, B. &
Willershäuser, T. (2012): Testing the Olympia Tsunami Hypothesis (OTH) – new results
from tsunami modeling and palaeotsunami studies in the lower Alpheios River valley
(Peloponnese, Greece). – Program Deuqua 2012, 2 pp., Bayreuth.
Geomaterial Science
Geomaterial Science (formerly Applied Mineralogy) explores the formation/processing
conditions, composition, microstructure and properties of minerals, rocks in addition to
material science related compounds. The study of the latter material group focuses on both
basic science and potential industrial applications. Research activities include a
comprehensive characterization of relevant natural and synthetic phases, their performance
under pressure, temperature, deformation and local chemical environment as well as
tailored synthesis experiments for high-tech materials.
The experimental studies comprise the crystal chemistry of minerals and synthetic
materials, in particular, their crystal structure, phase assemblage, deformation behaviour
and microstructure evolution. The microstructure variation (e.g., during exposure to high
temperature) has an essential effect on the resulting material properties, which is true for
synthetic materials as well as for natural minerals. Therefore, the main focus of most
research projects is to understand the correlation between microstructure evolution and
material properties.
An important aspect of the Fachgebiet Geomaterial Science is the application of
transmission electron microscopy (TEM) techniques for the detailed micro/nano-structural
characterization of solids. TEM in conjunction with spectroscopic analytical tools such as
energy-dispersive X-ray spectroscopy (EDS), electron energy-loss spectroscopy (EELS) and
energy filtered imaging (GIF) are employed for detailed microstructure and defect
characterization on the atomic scale. High-resolution imaging of local defects in addition to
chemical analysis with high lateral resolution (down to a few nanometers) is similarly
applied to high-performance materials as well as natural minerals.
Recent research projects involve topics such as fatigue of ferroelectrics, re-calibration of the
clinopyroxene-garnet geothermometer with respect to small variations in the Fe2+/Fe3+ratio, defect structure in Bixbyite single crystals (and their corresponding exaggerated grain
growth), morphology of In2O3 nanocrystals, transparent ceramics (spinel), interface
structures in polycrystals, high-temperature microstructures, and the study of
biomineralisation and biomaterials.
Institute of Applied Geosciences – Geomaterial Science
199
Staff Members
Head
Prof. Dr. Hans-Joachim Kleebe
Research Associates
Dr. Stefan Lauterbach
Dr. Leopold Molina-Luna
Dr. Ingo Sethmann
Postdoctoral Students
Dr. Ana Ljubomira Schmitt
Dr. Andrew Stewart
PhD Students
Jens Kling
Horst Purwin
Margarete Schloßer
Mathis M. Müller
Stefania Hapis
Stefanie Schultheiß
Katharina Nonnenmacher
Xiaoke Mu
Eric Detemple
Dmitry Tyutyunnikov
Cigdem Özsoy Keskinbora
Michael Scherrer
Marc Rubat du Merac
Ekin Simsek
Marina Zakhozheva
Scientific Assistant
Dr. Gerhard Miehe
Senior Scientist
Prof. Dr. Wolfgang F. Müller
Diploma Students
Anja Christmann
Holger Wüst
Technical Personnel
Bernd Dreieicher
Secretary
Angelika Willführ
David Wiesemann
Moritz Warmbier
Research Projects
TEM Investigations on Cubic Crystal Shapes of Corundum-Type Indium Oxide; Novel HighPressure Phases
Polymer-derived SiCO/HfO2 and SiCN/HfO2 Ceramic Nanocomposites for Ultrahightemperature Applications, SPP-1181 (DFG 2007-2012)
Investigation of Strengthened Hydroxylapatit/ß-Tricalcium Phosphate Composites with
Tailored Porosity (DFG 2008-2012)
Nanostructure and Calorimetry of Amorphous SiCN and SiBCN Ceramics (DFG 2009-2012)
Indium oxide (In203) under high pressure: rational design of new polymorphs and
characterisation of their physico-chemical properties (DFG 2009-2012)
Structural Investigations of Fatigue in Ferroelectrics, SFB-595,
Characterization of Lead-Free Ferroelectrics (DFG 2007-2014).
detailed
TEM
Temperature and Pressure Dependence of the Fe2+/Fe3+-Ratio in Omphacite for ReCalibration of the Fe-Mg Geothermometer (DFG 2007-2012)
200
Institute of Applied Geosciences – Electron Crystallography
TEM Characterization of Various Materials/Composites in the LOEWE Excellence Initiative
AdRIA (Adaptronik – Research, Innovation, Application)
Investigation of the Atomic and Electronic Structure of Perovskite-MultilayerHeterojunctions (in collaboration with the MPI Stuttgart, Prof. P. van Aken)
Phase Developments and Phase Transformations of Crystaline Non-Equilibrium Phases (in
collaboration with the MPI Stuttgart, Prof. P. van Aken).
Precipitation mechanisms of Ca-oxalate in the presence of Ca-phosphates and osteopontin
molecules related to kidney stone formation (DFG 2011-2013)
Microstructure Formation of Superhard Boron Suboxide Materials (DFG 2012-2014)
Publications
F. Muench, C. Neetzel, S. Lauterbach, H.-J. Kleebe, W. Ensinger, „Impact of Specifically
Adsorbing Anions on the Electroless Growth of Gold Nanotubes,“ Journal of Nanomaterials,
Article Number: 104748 (2012).
F. Muench, C. Neetzel, S. Kaserer, J. Brötz, J.-C. Jaud, Z. Zhao-Karger, S. Lauterbach, H.-J.
Kleebe, C. Roth, W. Ensinger, “Fabrication of porous rhodium nanotube catalysts by
electroless plating”, Journal of materials chemistry, 22 [25] (2012) 12784-12791.
E. Ionescu, H.-J. Kleebe, R. Riedel, „Silicon-containing polymer-derived ceramic
nanocomposites (PDC-NCs): preparative approaches and properties,” Chemical Society
Reviews, 41 [15] (2012) 5032-5052.
R.M. Prasad, G. Mera, K. Morita, M.M. Müller, H.-J. Kleebe, A. Gurlo, C. Fasel, R. Riedel,
“Thermal decomposition of carbon-rich polymer-derived silicon carbonitrides leading to
ceramics with high specific surface area and tunable micro- and mesoporosity”, Journal of
the European Ceramic Society, 32 [2] (2012) 477-484.
L. Toma, H.-J. Kleebe, M.M. Müller, E. Janssen, R. Riedel, T. Melz, H. Hanselka,
“Correlation between intrinsic microstructure and piezoresistivity in a SiOC polymerderived ceramic,” Journal of the American Ceramic Society, 95 [3] (2012)1056-1061.
M. Schlosser, H.-J. Kleebe, “Vapor Transport Sintering of Porous Calcium Phosphate
Ceramics”, Journal of the American Ceramic Society, 95 [5] (2012)1581–1587.
M. Thiele, M. Herrmann, J. Rathel, H.-J. Kleebe, M.M. Müller, T. Gestrich, A. Michaelis,
“Preparation and properties of B6O/TiB2-composites”, Journal of the European Ceramic
Society, 32 [8] (2012) pp. 1821-1835.
201
G.D. Soraru, R. Pena-Alonso, H.-J. Kleebe, “The effect of annealing at 1400 degrees C on
the structural evolution of porous C-rich silicon (boron) oxycarbide glass,” Journal of the
European Ceramic Society, 32 [8] (2012) pp. 1751-1757.
E. Ionescu, B. Papendorf, H.-J. Kleebe, H. Breitzke, K. Nonnenmacher, G. Buntkowsky, R.
Riedel, “Phase separation of a hafnium alkoxide-modified polysilazane upon polymer-toceramic transformation – A case study”, Journal of the European Ceramic Society, 32 [9]
(2012) Special Issue: SI, pp. 1873-1881.
Y. Gao, G. Mera, H. Nguyen, K. Morita, H.-J. Kleebe, R. Riedel, “Processing route
dramatically influencing the nanostructure of carbon-rich SiCN and SiBCN polymer-derived
ceramics. Part I: Low temperature thermal transformation”, Journal of the European
Ceramic Society, 32 [9] (2012) Special Issue: SI, pp. 1857-1866.
H.-J. Kleebe, K. Nonnenmacher, E. Ionescu, R. Riedel, „Decomposition-Coarsening Model of
SiOC/HfO2 Ceramic Nanocomposites Upon Isothermal Anneal at 1300 degrees C,” Journal
of the American Ceramic Society, 95 [7] (2012) 2290-2297.
M.T. Uddin, Y. Nicolas, C. Olivier, T. Toupance, L. Servant, M.M. Müller, H.-J. Kleebe, J.
Ziegler, W. Jaegermann, “Nanostructured SnO2-ZnO Heterojunction Photocatalysts
Showing Enhanced Photocatalytic Activity for the Degradation of Organic Dyes,” Inorganic
Chemistry, 51 [14] (2012) 7764-7773.
O.T. Johnson, I. Sigalas, M. Herrmann, H.-J. Kleebe, “Densification and properties of
superhard B6O materials with cobalt additions,” Journal of the European Ceramic Society,
32 [10] (2012) 2573-2579.
T. Mayer, C. Hein, E. Mankel, W. Jaegermann, M.M. Müller, H.-J. Kleebe, „Fermi level
positioning in organic semiconductor phase mixed composites: The internal interface
charge transfer doping model,” Organic Electronics, 13 [8] (2012) 1356-1364.
E.-M. Anton, L.A. Schmitt, M. Hinterstein, J. Trodahl, B. Kowalski, W. Jo, H.-J. Kleebe, J.
Roedel, J.L. Jacob, „Structure and temperature-dependent phase transitions of lead-free
Bi1/2Na1/2TiO3-Bi1/2K1/2TiO3-K0.5Na0.5NbO3 piezoceramics”, Journal of Materials Research,
27 [19] (2012) 2466-2478.
M.M. Müller, H.-J. Kleebe, “Sintering Mechanisms of LiF-Doped Mg-Al-Spinel”, Journal of
the American Ceramic Society, 95 [10] (2012) 3022-3024.
P. Schloth, M.A. Weisser, H. Van Swygenhoven, S. Van Petegem, P. Susila, V. Subramanya
Sarma, B.S. Murty, S. Lauterbach, M. Heilmaier, “Two strain-hardening mechanisms in
nanocrystalline austenitic steel: An in situ synchrotron X-ray diffraction study”. Scripta
Materialia, 66 [9] (2012) 690-693.
202
Fe3+/ΣFe ratios in clinopyroxene and garnet
as a function of temperature
Horst Purwin, Stefan Lauterbach, Hans-Joachim Kleebe
Purpose of the examination was the ongoing dispute about the validity of the temperatures
calculated from the Fe-Mg exchange geothermometer. This geothermometer is based on
the exchange of iron and magnesium between pyroxenes and garnet in eglogites, rocks
which experienced high pressure and high temperature during subduction. For the
calculation of the so called equilibrium temperature, the distribution coefficient KD is
needed. The formula is given by: KD=(Fe2+/Mg)Gt/(Fe2+/Mg)Cpx. The formula also shows
that all iron is expected to be in the 2+ oxidation state. One of the most used calibration
for the geothermometer was reported by Krogh (1988), using all iron from the analysis as
Fe2+. Since most of the eglogites under investigation exhibit a more or less pronounced
Fe3+ content, it is commonly assumed that the temperatures calculated based on this
calibration deviate up to several hundred °C from the real temperatures.
For this investigation, samples with eglogitic composition in the system CaO-FeO-Fe2O3MgO-Al2O3-SiO2 (CFFMAS) with main phase composition clinopyroxene, garnet and quartz
were synthesized in a piston cylinder apparatus (in cooperation with Prof. Brey; GoetheUniversität Frankfurt) at 2,5 GPa and temperatures between 800°C (2 month runtime) and
1300°C (runtime 3 days). Different capsule materials – graphite and rhenium – were used
to obtain different oxygen fugacities respectively oxidation conditions. The synthesized
samples were analyzed by means of electron probe microanalysis (EPMA) to reveal the
chemical composition. The samples were furthermore prepared for TEM investigations.
Fig. 1. a) Bright field TEM image of a garnet / clinopyroxene assemblage. The white circles in the image
indicate the area used for EELS and EDS analysis. b) EELS spectra (processed) of garnet and clinopyroxene
from areas indicated in a).
Here, the oxidation state (Fe3+/Fe) was determined with electron energy loss
spectroscopy (EELS) and the overall chemical composition was analyzed locally with EDS,
as indicated in Figures 1 and 2. The obtained Fe3+/Fe ratio was combined with the
chemical composition from EPMA results to calculate the distribution coefficient based on
solely Fe2+ and on the total Fe content.
203
The clinopyroxenes from the samples synthesized under reducing conditions (graphite
capsules) showed a Fe3+/Fe content ranging from 22.2±3.4% at 800°C and 13.3±5.4% at
1300°C. The according garnets were within 10.8±1.5% Fe3+/Fe at 800°C and 15.4±4.7
Fe3+/Fe at 1300°C. Calculated temperature based on the total iron content and using the
calibration from Krogh (1988) resulted in values similar to those from Krogh.
Fig. 2. Typical ED-spectra for
clinopyroxene (Cpx) and
garnet (Gt) from the
indicated areas in Fig. 1. a)
The carbon signal are from
slight contamination out of
the pumping system and do
not stem from the sample.
The experiments are therefore consistent with those performed by Krogh. Repeating the
calculations with respect to the measured Fe3+/Fe ratio in the clinopyroxene and garnet
phases revealed an average deviation of the computed temperature from the real
temperature by 33°C in the range of 800°C<Texp<1200°C and 77°C at 1300°C (Fig. 3).
Fig. 3. Difference between the calculated equilibrium (Tcalc) and experimental temperature (Texp) plotted
versus experimental temperature. a) Calculation based on total iron (SFe); b) calculation based on Fe2+
content. All calculations were done using the calibration by Krogh (1988). Symbols representing different
starting compositions for the HP/HT synthesis runs.
204
Samples produced under oxidizing conditions (Re-capsule) showed similar Fe3+/Fe ratios
as the corresponding runs in graphite capsules. Therefore, the calculated temperatures have
comparable differences to the experimental temperatures as for the graphite experiments.
Why the clearly higher oxygen fugacity does not result in a higher Fe3+/Fe ratio is yet
unknown. One possible explanation is that the maximum amount of Fe3+ in clinopyroxenes
is limited due to their crystal chemistry.
The main result from this PhD work can be summarized as follows: For the CFFMAS system
under investigation, a new calibration with respect to the Fe3+/Fe ratio is not necessary!
The temperatures calculated assuming that all Fe is in the Fe2+ oxidation, neglecting the
Fe3+ component, state provide reliable rock formation temperatures.
References:
E.J. Krogh, “The garnet-clinopyroxene Fe-Mg geothermometer – a reinterpretation of existing
experimental data”, Contributions to Mineralogy and Petrology, 99 (1988) 44-48.
205
Combined Hydrothermal Conversion and Vapor Transport Sintering for AgCl-modified
Calcium Phosphate Scaffolds
Margarete Schlosser, Stefanie Schultheiss, Ulla Hauf, Ingo Sethmann, Hans-Joachim Kleebe
Two processing methods were successfully combined to obtain AgCl-modified calcium
phosphate scaffolds with prospective antibacterial properties: (i) hydrothermal conversion
of macroporous biogenic carbonates and (ii) vapor transport sintering. Hydrothermal
conversion of two precursor materials, i.e., coral skeletons and sea urchin spines, resulted
in the pseudomorphic replacement of highly porous calcium carbonates by calcium
phosphate scaffolds. Vapor transport sintering of these scaffolds within a reactive AgCl
atmosphere facilitated near net-shape processing accompanied by the condensation of
finely dispersed AgCl particles over the scaffold’s surface. The phase chemistry was
analyzed with WDXRF, XRD and EDS, and the microstructure development was
characterized by SEM and TEM imaging. Thermodynamic calculations were carried out to
gain a theoretical understanding of the vapor transport process.
Fig. 1 (left): SEM images of a coral-derived ceramic after VT-sintering at 1100°C for 6 h. AgCl particles (white;
Z-contrast) are finely dispersed throughout the scaffold’s interior.
Fig. 2 (right): SEM images of a sea urchin-derived ceramic after VT-sintering at 1100°C for 6 h. AgCl particles
(white; Z-contrast) are finely dispersed throughout the scaffold’s interior.
Two biogenic carbonate minerals were selected as precursor materials for this study: coral
skeletons (Porites sp.; aragonite) and sea urchin spines (Heterocentrus mammilatus; Mgbearing calcite). Aliquots of the sample material were cleaned in H2O2 for 6 h to remove
206
organic residue. Hydrothermal conversion into calcium phosphate was accomplished by
immersion in one-molar solution of (NH4)2HPO4 within Teflon™-lined autoclaves that
were held in a box furnace at 180°C for two weeks. Before and after thermal treatment, the
autoclaves were weighed. Evaporation losses were found to be consistently below 0.5 wt%.
Afterwards, the samples were rinsed thoroughly with deionized water and dried at 110°C
for 6 h. To obtain enough sample material for characterization, 15 g of each precursor
mineral were converted in five autoclave runs. After conversion, samples were sealed off in
evacuated silica ampoules together with an AgCl powder additive (0.3 g per 1 g sample
material) which creates a reactive chloride atmosphere at elevated temperatures. VTsintering was carried out at 1100°C for 6 h.
Microstructure Development
During VT-sintering, sample shrinkage is dramatically reduced, as compared to free
sintering in air. Moreover, particles of the volatile AgCl sintering agent condense
throughout the ceramic scaffold, as determined with EDS. The condensate size is restricted
by the containing pores (Figs. 1 and 2). Statistical analysis of SEM images confirmed that
the average macropore size of hydrothermally converted coral- and sea urchin scaffolds was
not affected by the sintering process and remained constant at ca. 200 µm and 30 µm
(Feret’s diameter), respectively. In contrast, microporosity contained in the trabecula, i.e.,
the scaffold’s struts, was subject to slight coarsening. After sintering for 6 h, the average
pore diameters increased from the nm-scale in the hydrothermally converted samples to ca.
4 µm for coral- and 2 µm for sea urchin-derived ceramics. It follows from these observations
that the microporosity can be controlled by adjusting the holding time.
Conclusions
The combination of two processing methods, namely (i) hydrothermal conversion of
biogenic carbonate scaffolds and (ii) vapor transport sintering, produces the interconnected
pore geometry and phase composition as required for bone graft ceramics.
The Mg-content of the carbonate precursor materials used, i.e., coral skeletons and sea
urchin spines, determines the phase composition of the conversion product by stabilizing
Mg-bearing β-TCP at the expense of HA. Sintering in AgCl atmosphere facilitates both,
microstructural coarsening without macropore shrinkage, as well as the condensation of
finely dispersed AgCl particles throughout the scaffold. Representing a novel class of
ceramic composites, these materials are promising with regard to the well-known
antibacterial properties of Ag+ ions. Moreover, the major phases present in the converted
scaffolds remain stable during VT-sintering, allowing the fabrication of both HA and MgTCP ceramics.
The thermodynamic calculations performed provide a theoretical understanding of the
vapor transport process in the system β-TCP – AgCl. Because of the high availability of
reactive chloride in the sintering atmosphere, the volatilization of rate-determining Ca is
strongly enhanced due to CaCl2 formation, thus promoting material transport via
evaporation and condensation.
References:
M. Schlosser, H.-J. Kleebe, “ apor Transport Sintering of Porous Calcium Phosphate Ceramics”,
Journal of the American Ceramic Society, 95 [5] (2012)1581–1587.
207
Electron Crystallography
Electron crystallography uses electron radiation to characterize the structure of matter by
imaging, diffraction and spectroscopy from fully crystalline, highly disordered to
amorphous materials. The majority of investigations are performed using transmission
electron microscopes (TEM) which comprise the optimal tool for structural investigation in
the nano regime. Apart from imaging techniques in parallel illumination, scanning
methods, allowing for a variety of sequential data collection methods, are becoming more
and more popular.
The scientific approach of this group lies mainly on the development of electron diffraction
techniques.
The Automated electron Diffraction Tomography (ADT) method, invented by this group,
consists of a new data collection concept and is applicable to nano particles down to a size
of some tens of nanometer. Using ADT nearly kinematical 3D electron diffraction data can
be collected from a selected nano crystal being suitable for a full “ab-initio” structure
solution, i.e. based only on electron diffraction data. In contrast to high resolution imaging
this approach is applicable to material even highly sensitive to the electron beam (e.g.
drugs, MOFs, zeolites, hybrid material).
Apart from the structure determination of highly crystalline nano particles with even
complicated structural features, a quantitative approach to describe disordered structures is
under development. It is planned to use approaches (e.g. pair distribution function) already
successfully are becoming applied to X-ray data.
Application as well as development of the above described ADT method has a high demand
for cooperation. First contacts have been established directly in the Department 11
“Material- and Geosciences”, while new cooperations with the departments of Chemistry,
Mathematics, Informatics and Engeneering are planned.
Prof. Kolb started to build up the group in the Institute of Applied Geosciences in November
2012. In addition she has been assigned as Equal Opportunities Officer.
Staff Members
Head
208
Prof. Dr. Ute Kolb
Technical Petrology with Emphasis in Low Temperature Petrology
Petrology is devoted to study the genesis and the mineralogical evolution of a rock with a
specific bulk composition at various physical and chemical conditions. The scientific and
educational fields of this branch within the applied geosciences are based on crucial
knowledge in magmatic-, metamorphic-, hydrothermal petrology, mineralogy, structural
geology, tectonophysics, geothermal geology, sediment petrography, thermodynamics/
kinetics and geochemistry.
Technical Petrology aims to assess the physical and chemical properties of natural or
synthetic rocks for applied purposes at various physical and chemical conditions (e.g.
pressure, temperature, chemical composition). The Technical Petrology group is in
particular devoted to study the low temperature domain. These low temperature studies
serve as an aid to qualify and quantify processes occurring in hydrocarbon prospecting,
geothermal system, and geodynamic study.
The principal motivation of our Low-Temperature Petrology research group is to
understand and to quantify low temperature petrologic processes. For this purpose, an
effort is addressed to innovate new tools to calibrate and to model the metamorphic P-T-Xd-t conditions in low-grade rocks. A multidisciplinary approach is necessary because
crystallization and recrystallisation are not obvious at low temperature. Hence, our work
links field and experimental petrology, analytical methods, thermodynamic and kinetic
modelling. Similar approaches are easily applied in archaeometry in order to characterise a
range of firing temperatures and to describe recrystallisation processes of starting clay
material. Opposite to prograde diagenetic to metamorphic processes, presented working
philosophy is employed to describe the reverse cycles of destruction and weathering of
rocks and the formation of clays and techno soils.
The main research interests of the Technical Petrology Group are focussed on the following
topics:
Experimental Petrology

Synthesis and characterisation of the coalification processes by means of optical
parameters that are used to determine kinetics of maturation.

Synthesis and characterisation of mineral reactions as well as firing structures and
textures in ceramic materials. This aims to enhance knowledge on the ancient
pottery production technology and to assess its socially embedded impacts.
Coal Petrology:

The application of vitrinite reflectance and other coal petrological parameters to
determine a grade of diagenesis and incipient metamorphism.

Development of geothermobarometers based on the maturation kinetics of vitrinite.
For the first time it will be possible to use barometric as well as thermometric models
to establish geothermal gradients. These can be used in orogenic researches,
sediment basin analyses, hydrocarbon exploration, geothermic prospections and
energy researches.
Institute of Applied Geosciences – Technical Petrology
209
o
Improvement of methods related to hydrocarbon exploration.
o
Improvement of methods related to the low-grade metamorphism
characterisation.
o
Application of the bituminate reflectance in the kerogene research,
palaeogeothermics, and in the external orogens investigation.
Clay Mineralogy

The application of Kübler Index and other clay mineral parameters to determine a
grade of diagenesis and incipient metamorphism.

Development of Geothermobarometers based on the reaction kinetics in the reaction
progress and aggradation of clay minerals to micas. These can be used in orogenic
researches, sediment basin analyses, hydrocarbon exploration, and geothermic
prospections.
o
Improvement of methods related to hydrocarbon exploration.
o
Improvement of methods related to the low-grade metamorphism
characterisation.
Archaeometry and Clay Mineralogy:

Determination and investigation on the production technology of the Iron Age,
Hellenistic and Roman pottery fineware.
o
Determination of firing conditions and duration of peak ceramic firing.
o
Characterisation of applied raw material.
o
Provenance of exploited raw material.
o
Reconstruction of ancient trade routes by characterisation of nonlocal clayey
raw and temper material.
Environmental Geology:

Reaction processes reconstruction that take place in the mining damps, recognition
of soil alteration via acid rock drainage, quantification of clay mineral degradation
and clay-rock-water interactions.

Determination of water-rock interaction and water chemistry in the basement
crystalline ground waters and their usage as potable water.
Low-Temperature Petrology s.l.:

Orogen and palaeogeothermal researches in foreland basins of the Alps, Vosges,
Dinarides, Carpathians, Stara Planina (Bulgaria), Balkanides, Variscides of the
Bosporus and Turkey.
A broad analytical spectrum must be applied in low-temperature petrology due to very
small grain-size. Technical Petrology group maintains a Microscopy Laboratory (MPV coalreflection microscopy, fluorescence microscopy, transmitted light microscopy). The former
210
Institute of Applied Geosciences – TechnicalPetrology
XRD laboratories (Clay and XRD Laboratory and a research XRD Laboratory) had to be
moved and merged with the awkward geochemical laboratory. The ICP-AES, TOC, AOX and
gas chromatography together with the Organic Geochemical Laboratory was closed in
2012. A non-completed refurbishment of the Geoscience Institute and missing financial
support forced us to accept an adverse decision. We did not change the photographs of the
laboratories on the wep page to testify the need to get back ideal working conditions. A
XRF laboratory (Wave-dispersive BRUKER S8-Tiger) was installed in 2008 and is
maintained together with the research groups of Chemical Analytics and Environmental
Mineralogy. A CCA coal-reflection camera (A.S. & Co. GmbH) and Zeiss 6000 reflection
microscope was installed in 2012 with „TUD 2020 Pakt“ co-founding.
Staff Members
Head
Prof. Dr. Rafael Ferreiro Mählmann
Research Associates
Dr. Ronan Le Bayon
PD Dr. Eckardt Stein
Dr. Branimir Šegvić
Diploma- and
BSc-MSc Students
Alexej Philipp
Tobias Hill
Erika Dörner
Technical Personnel
Dr. Norbert Laskowski
Secretary
Natali Vakalopoulou Buffet
Research Projects
Petrology of the Phyllite-Diabas-zone at the Kaschana pass in the Stara Planina of central
Bulgaria – (DAAD, ERASMUS. Cooperation with St. Kl. Ohridski University of Sofia, BG;
University of Freiburg im Braisgau, D).
Structural, stratigraphic and diagenetic analysis of the Jurassic-Early Cretaceous foreland
Trojan-basin in central North Bulgaria – (ERASMUS. Cooperation with St. Kl. Ohridski
University of Sofia, BG).
Geochronology and tectono-thermal history of the Penninic-Austroalpine boundary (Arosa
Zone) in Eastern Switzerland; a multi-methodical comparison of methods. - (SNF and
Willkomm Fond, actual without founding. Cooperation with University of Bern, CH and
Department für Zivilschutz, Bern, CH).
Composition, manufacture technology, and circulation of Hellenistic pottery from Eastern
Adriatic: a case study of three archaeological sites in Dalmatia (Croatia). – (MZOS.
Cooperation with Croatian Geological Survey Zagreb, Institute of Archaeology - Museum
Zagreb, University of Zadar and University of Zagreb, HR).
Very low to low-temperature coal and clay-mineral indicators, comparative application
from diagenesis to green- and blueschist facies. – (No founding, project concluded in 2012.
211
Cooperation with University of Basel, CH; University of Sivas, TR; Institut Polytechnique
LaSalle Beauvais, F; University of Granada, E). See review paper in the references, project
rejected by DFG founding.
Organic matter studies on graptolite-schist, their hydrocarbon potential and maturation
level to determine the palaeo-geothermal history and to elucidate geodynamic processes
(Bulgaria and Turkey). – (Different national science founds and ERASMUS. Cooperation
with St. Kl. Ohridski University of Sofia, BG and University of Sivas, TR).
Experimental kinetic study of organic matter maturation: an appraisal of pressure,
temperature and time effects on reflectance properties of vitrinite. - (DFG, project
concluded in 2012. Cooperation with University of Frankfurt a. M.; University of Mainz;
University of Göttingen and Stanford University, USA).
Bituminite parameters to determine thermal metamorphism - field data and experimental
studies. - (Different science founds, DAAD and ERASMUS. Cooperation with University of
Chile, Santiago de Chile, CL; Institutul Geologic al Romaniei, Bucharest, RO; University
Complutense, Madrid, E; Stanford University, USA; Peking University, China; ETH Zürich,
CH; St. Kl. Ohridski University of Sofia, BG and University of Sivas, TR).
Clay-mineral formation in soils developed in the weathering zones of pyrite-bearing schists:
A case-study from the abundant pyrite mine in Wieściszowice, Lower Silesia, SW Poland
(No founding. Cooperation with the Warsaw University of Technology, PL and Jagiellonian
University of Krakow, PL)
Weathering mechanisms in an acid drainage environment – example from the clayey
alteration products of sulphide-bearing metamorphic rocks at Kristiansand in Southern
Norway (No founding)
Publications
Šegvić, B., Śeśelj, L., Slovenec, D., Lugović, B., Ferreiro Mählmann, R. (2012): Composition,
Technology of Manufacture, and Circulation of Hellenistic Pottery from the Eastern
Adriatic: A Case Study of Three Archaeological Sites along the Dalmatian Coast, Croatia.
Geoarchaeology, 27, 63 – 87.
Le Bayon, R., Buhre, S., Burkhard, C., Schmidt, C., Ferreiro Mählmann, R. (2012):
Experimental organic matter maturation at 2 kbar: Heat-up effect to low temperatures on
vitrinite reflectance. International Journal of Coal Geology. DOI:10.1016/j.coal.2011.12.
002, 92, 45–53.
Le Bayon, R., Adam, A., Ferreiro Mählmann, R. (2012): Experimentally determined
pressure effect on vitrinite reflectance at 450 °C. International Journal of Coal Geology.
DOI:10.1016/j.coal.2011.12. 007, 92, 69-81.
212
Šegvić, B., Ugarković, M., Laskowski, N., Ferreiro Mählmann, R. (2012): Material
characteristics and production technology of Greek pottery manufacturing in the Adriatic –
case study of hellenisticIissa. In: Frank Schlütter, Susanne Greiff and Michael Prange
(Hrsg.), Archäometrie und Denkmalpflege 2012, Metalla Sonderheft 5, 163-166.
Ferreiro Mählmann, R., Nieto, F., Bozkaya, Ö., Potel, S., Günal Türkmenog˘lu, A.(2012):
Preface: clay mineral diagenesis and very low-grade metamorphic processes. Proceedings of
the 2011 Frey–Kübler symposium. Swiss Journal of Geosciences, DOI: 10.1007/s00015012-0114-4, 105 (2012), 117-120.
Ferreiro Mählmann, R., Bozkaya, Ö., Potel, S., Le Bayon, R., Śegvić, B., Nieto, F. (2012):
The pioneer work of Bernard Kübler and Martin Frey in very low-grade metamorphic
terranes: paleo-geothermal potential of variation in Kübler-Index/organic matter
reflectance correlations. A review. Swiss Journal of Geosciences, DOI: 10.1007/s00015012-0115-3, 105 (2012), 121-152.
Ferreiro Mählmann, R., Frey, M. (2012): Standardisation, calibration and correlation of the
Kübler-index and the vitrinite/bituminite reflectance: an inter-laboratory and field related
study. Swiss Journal of Geosciences, DOI: 10.1007/s00015-012-0110-8, 105 (2012), 153170.
Le Bayon R. (2012): Laboratory organic matter maturation at high pressures: heat-up effect
on vitrinite reflectance. Swiss Journal of Geosciences, DOI: 10.1007/s00015-012-0109-1,
105 (2012), 171–181.
Ferreiro Mählmann, R., Giger M. (2012): The Arosa zone in Eastern Switzerland: oceanic,
sedimentary burial, accretional and orogenic very low- to low grade patterns in a tectonometamorphic mélange. Swiss Journal of Geosciences, DOI: 10.1007/s00015-012-0103-7,
105 (2012), 203–233.
Uzarowic Z., Šegvić, B., Michalik, M., Bylina. P. (2012): The effect of hydrological
conditions and the pH of environment on phyllosilicate transformations in the weathering
zone of pyrite-bearing schists in Wiesciszowice (SW Poland). Clay Minerals, 47, 401-417.
Ferreiro Mählmann, R., Bozkaya, Ö., Potel S., Nieto, F. (2012): Clay mineral diagenesis and
low-grade metamophism. Guest Editors of the Special Issue in the Swiss Journal of
Geosciences. 207p. Proceedings of the Euroclay 2011 Frey–Kübler symposium held in
Antalya, Turkey.
Kasbohm, J., Pusch, R., Nguyen-Thanh, L., Hoang-Minh, T. (2012). Lab-scale performance
of selected expandable clays under HLW repository conditions. Environmental Earth
Sciences, DOI 10.1007/s12665-012-2085-1.
213
Material Characteristics and production technology of Greek pottery manufacturing in
the Adriatic – Case study of Hellenistic Issa
Branimir Šegvić1, Marina Ugarković2, Norbert Laskowski1, Rafael Ferreiro Mählmann1
1
Technische Universität Darmstadt, Institute of Applied Geosciences, Germany
2
Institute of Archaeology, Zagreb, Croatia
Introduction
In heyday of ancient Greek expansion throughout the Mediterranean (8th- 6th c. B.C.)
several colonies were founded in the Adriatic; however on the Eastern side of Middle
Adriatic such activity is evidenced only from the Late Classical times. In the early 4th c.
B.C., two Greek colonies were founded in this region: Issa and Pharos (nowadays cities of
Vis and Stari Grad on the islands of Vis and Hvar, respectively; Fig. 1). Issa flourished from
4th-1st c. B.C., presenting the only Greek colony in the middle Adriatic with an
unearthened Late Classical/Early Hellenistic- Late Hellenistic necropolis.
Fig. 1. Geographic map showing the location of the Greek colony of Issa at the island of Vis (circled in).
Regional location of the research is shown in the inset.
The pottery samples used for this study are taken from the vases found as grave offerings in
this necropolis. 43 representative samples, dating from Early to Late Hellenistic, were
chosen from 16 graves, with an assumption of their provenance according to stylistic
analysis. The varieties of presented shapes comprise of bowl, kantharos, kylix, lekanis,
oinochoe, olpe, pelike, pyxida, skyphos, small stamnos and unguentarium.
Using an archaeometric approach, it is our aim to define the pottery’s composition,
manufacture technology and provenance. By comparison with available archaeometric data
on Hellenistic pottery from Vis (Čargo and Miše; 2010 Šegvić et al., 2012), we strive to
complete the picture on the nature of socially embedded ceramic manufacture in the Greek
colony of Issa. Further on, we aim to report on the firing induced reaction and
transformation processes in the ceramic material, having taken place on the microscopic
scale between the clayey matrix and different kind of silicate inclusions, or within the
inclusions themselves. At present, we can report on the results of XRD mineralogy of
selected potsherds, as well as on their textural and microtextural characteristics revealed by
optical microscopy and SEM/EDX investigations, respectively. The XRF and EMPA
measurements are still in progress.
214
A great majority of samples is consisted of quartz, Al-rich diopside, plagioclase, K-feldspar,
10Å mica-like phyllosilicate and hematite, as evidenced by their XRD mineralogy (Fig. 2,
Vis 35). A smaller portion of analysed pottery additionally contains sub-calcic pyroxene
(pigeonite) and a phase from melilite group (gehlenite). High amount of amorphous matter
is present in those artefacts (background bulging in Vis 13, Fig. 2). Rarely, ceramic mineral
paragenesis is dominated by quartz and calcite, having in addition 14Å- and 15Åphyllosilicates and a low amount of amorphous matter (Fig. 2, Vis 36).
Fig. 2. Selected XRD diffraction spectra of analysed pottery. Mineral abbreviations: phy. - phyllosilicates,
Qtzquartz, Cal-calcite, Kfs-K-feldspar, Pl-plagioclase, Didiopside, Pgt-pigeonite, Hem-hematite.
Optical microscopy and SEM/EDX analyses revealed that all samples are featured by
optically inactive groundmass, mostly yellow to dark red in colour, having different
proportions of inclusions and temper material. In samples containing the 14Å- and 15Åphyllosilicates, we report a large amount of non-plastic inclusions coarser than 20 µm.
These comprise of grog, textural clay features (TCF), quartz and K-feldspar, along with a
smaller amount of mica, amphibole, and clinopyroxene. Sporadically, huge quantities of
fossil fragments are present, containing those made of micritic to palisade calcite (bivals,
bryozoas and different foraminiferas, Fig. 3b) and silica (radiolarians and sponge spicules).
Sintered and partly melted clayey matrix, which gave rise to the formation of ubiquitous
irregularly-shaped pores (Fig. 3a), is characteristic for the rest of the analysed samples.
Here, the non-plastic inclusions are less frequent and, by rule, show obvious signs of firing,
such as exfoliation, melting bubbles, or chemical depletion. For instance, quartz is
frequently featured by the decrease of Si toward its rims and the incorporation of elements,
like Al, K, Ca, and Fe, whereas calcite underwent a complete thermal obliteration. Kfeldspar tends to be occasionally zoned, having unusually Ca-rich margins. Such Ca
enrichment in quartz and feldspar we explain by enhanced grain boundary diffusion
triggered by surplus of Ca after calcite (and lime) dissolution. Most striking thermal
alterations are shown by mica (Fig. 3a). Following exfoliation and enlargement of its 001
planes, the Fe-rich phase starts to emerge after the rapid removal of Fe from the mica
215
octahedral sheet and its concentration along the exfoliation margins (white areas in mica,
Fig. 3a). As temperature increases, mica melting takes place due to OH release from its
octahedral hydroxyl sites, having led to local enhancement of aH2O and melting point
decrease (black bubbles in mica, Fig. 3a). Eventually melt pocket domains are formed
(black square, Fig. 3). High Ca mobility in ceramic systems enabled formation of gehlenite
along extended exfoliation planes (gray matter in mica, Fig. 3a).
Fig. 3. SEM imagery of samples Vis 35 (a) and Vis 36 (b). Mica showing a different stage of thermal alteration,
from exfoliation cracking along its 001 planes to the crystallization of the Fe-rich phase and gehlenite, and
finally emergence of melting bubbles. Corresponding EDX spectras shown above. Note reticulated clayey
matrix, having lots of rounded porous space (a). Pottery sample containing a large quantity of fossil material
and coarse quartz inclusions (b). For details see text.
Conclusions
Firing temperatures are inferred to be moderate, reaching 650°C for specimens containing
calcite, whereas for those having reaction clinpyroxene, gehlenite, and metastable mica,
temperatures might have exceeded 900°C. At this point, the hypothesis of local origin of
analysed material remains open, except in the rare cases when typical fossil community
that corresponds to the Cretaceous bedrocks of Vis is indicated (Borović et al., 1977).
References
[1]
[2]
[3]
216
Borović I, Marinčić S, Majcen Ž (1977) Basic geological map of SFR Yugoslavia. Sheet Vis,
scale 1:100000. Belgrade, Serbia: Geological Survey, Zagreb-Federal Geological Survey.
Čargo B, Miše M (2010). Pottery production in Issa. Vijesnik za arheologiju i povijest
dalmatinsku, 103, 7-40.
Šegvić B, Šešelj L, Slovenec D, Lugović B, Ferreiro Mählmann R (2012) Composition,
Technology of Manufacture, and Circulation of Hellenistic Pottery from the Eastern Adriatic:
A Case Study of Three Archaeological Sites along the Dalmatian Coast, Croatia.
Geoarchaeology, 27, 63-87.
The pioneer work of Bernard Kübler and Martin Frey in very low-grade metamorphic
terranes: paleo-geothermal potential of variation in Kübler-Index/organic
matter reflectance correlations. A review
Rafael Ferreiro Mählmann1, Ömer Bozkaya2, Sébastien Potel3, Ronan Le Bayon1, Branimir
Šegvić1 and Fernando Nieto4
1
Technical and Low Temperature Petrology, Institut für Angewandte Geowissenschaften,
Technische Universität Darmstadt, Germany
2
Department of Geological Engineering, Cumhuriyet University, Sivas, Turkey
3
Institut Polytechnique LaSalle Beauvais, Equipe B2R, Beauvais Cedex, France
4
Departamento de Mineralogía y Petrología y IACT, Universidad de Granada, CSIC, Granada, Spain
Low-temperature metamorphic petrology occupies the P–T field between sedimentary and
metamorphic petrology. Two important pillars of low-temperature metamorphism are coal
petrology and claymineralogy. When low temperature petrology was established bridging a
hiatus between the two classical geological disciplines of sedimentary geology and
metamorphic petrology, geologists faced a need for the usage of different terminology
tenets.Martin Frey and Bernard Kübler were two pioneers in low-grade metamorphic
petrology. They focused their research on clarifying the relationships of clay mineralogy
and organic petrology to metamorphic pressure (P) and temperature (T) conditions. The
ultimate aim of M. Frey and B. Kübler was to establish a correlation between clay indices
and organic parameters for different geodynamic setting and therefore for various
pressure– temperature (P–T) conditions occurring in low grade metamorphic terranes. For
this purpose, a special attention was addressed to the correlation between the Kübler-Index
(KI) and vitrinite reflectance (VR). All these efforts are dedicated to estimate the P–T
conditions and thus to gain insight into the geodynamic evolution of low-grade
metamorphic terranes. B. Kübler and M. Frey honored here concentrated their studies to
the Helvetic Central Alps area. The very lowgrade Helvetic domain is therefore of basic
interest of this study. Ensuing the extensive compilation of data from the Helvetic domain,
a reinterpretation of Kübler and Frey’s research is presented in the light of last decade’s
scientific progress (Ferreiro Mählmann et. al. 2012).
An importat advance in the knowlede about the physical meening of KI was possible
through high resolution transmission electron microscopy (HRTEM) images. It was not
until the 1990s that the physical meaning of the KI was confirmed and qualified by direct
observations of illite crystals in HRTEM images (Fig. 1). The pioneering paper by Merriman
et al. (1990) established the first empirical correlation of the anchizone limits with
crystallite size. During this decade, various studies used more samples to complete the
knowledge (Fig. 1) of the relation between KI and crystallite domain size, including the
determination of crystallite domain size and the defect free area size (Warr and Nieto
1998). Although definition of an illite crystallite domain is difficult, a general agreement
about the relation was found and summarized by Merriman and Peacor (1999), who
presented various curves, compiled from different authors (see Fig. 1), which define a
relation well-adjusted to values theoretically predicted by the Scherrer equation. Measured
sizes are far from homogeneous at the level of sample, with the variance clearly increasing
toward higher grades if referring to neo-formed illite crystallites. At lower grades the
variance may be also very high due to common coarser clastic mica (Frey 1987; Ferreiro
Mählmann and Giger 2012).
217
Fig. 1 Plot from Merriman and Peacor (1999) showing the relationship between Kübler index and HRTEM
measured illite-muscovite crystallite thickness along c*, with representative lattice-fringe images from epizone
(sample 16 of Abad et al. 2003b, KI 0.23), anchizone (sample Pw-81 of Abad 2002, KI 0.32) and diagenetic
zone (sample ES-77 of Abad et al. 2003c, KI 0.77; note white fringes, which represent the smectite layers); KI
∆° 2.
The scattering of the sizes determined by HRTEM is greater for the epizone in relation to
the anchizone (Fig. 1), with the most homogeneous values of sizes at the level of sample
found in the diagenetic zone. The average or modal sizes only represent a general tendency
of variation. If we take into account the internal differences of sizes at the level of sample,
the minor differences between authors represented in Fig. 1 are not significant. During the
last decade, HRTEM and AEM analysis have documented the textural evolution of the rocks
at diagenetic and very low-grade metamorphic grades (Fig. 1), separating the contribution
of the detrital phases and described the chemical compositional evolution of the various
minerals. The evolution from high-grade diagenesis to low epizone, is characterized by a
lack of significant qualitative changes in the texture and mineral composition of
phyllosilicates. This leads to an increase in domain size and diminution in crystalline
defects as the only clear changes in the illite-chlorite system, which justifies the extended
use of the KI (Abad et al. 2006) and a temperature and pressure dependent correlation
with VR to determine geothermal conditions.
218
A comprehensive dataset available enables to discriminate many factors influencing the
Kübler-Index and organic-matter reflectance alongside to time, temperature and pressure
(Ferreiro Mählmann et. al. 2012). The correlation is restricted to the KI and organic matter
reflectance (mostly VR) because most of the studies used both methods. Organic matter
reflectance (OMR) includes data from vitrinite reflectance and bituminite reflectance
measurements. Geodynamics has important control on the KI/VR (OMR) correlation.
Tectonic units having a similar geodynamic evolution are featured by the comparable
KI/OMR trends, related to the particular paleo-geothermal conditions. Obviously the
KI/OMR correlations provide a mean to characterise geothermal gradients and
metamorphic very-low-grade pressure–temperature conditions. In terranes where high
deformations rates are reported, exceeding the high anchizone conditions, strain promotes
the kinetic effects of temperature and pressure on the VR (Fig. 2).
Fig. 2 Conclusive Kübler-Index/vitrinite reflectance plot showing strong geothermal (heat flow) dependent
trend evolutions regarding the geodynamic setting. A highgrade contact-metamorphic overprint can blur
trend evolutions caused by increased burial or tectonic overburden. If a regular increase with depth is
recognised, flattening of the gradient is observed due to higher vitrinite reflectance with temperature rise.
Another factor is an increase in strain. Strain and hyperthermal flow enhances the vitrinite reactivity in respect
to Kübler-Index values. The latter is probably much more pressure dependent than expected until now.
References:
[1]
[2]
R. Ferreiro Mählmann, Ö. Bozkaya, S. Potel, R. Le Bayon, B. Śegvić, F, Nieto. The pioneer
work of Bernard Kübler and Martin Frey in very low-grade metamorphic terranes: paleogeothermal potential of variation in Kübler-Index/organic matter reflectance correlations. A
review. Swiss Journal of Geosciences, DOI 10.1007/s00015-012-0115-3, 105 (2012), 121-152.
Clay mineral diagenesis and low-grade metamophism. Rafael Ferreiro Mählmann, Ömer
Bozkaya, Sébastien Potel and Fernando Nieto (2012). Guest Editors of the Special Issue in
the Swiss Journal of Geosciences. 207p. Proceedings of the EUROCLAY 2011 Frey–Kübler
symposium held in Antalya, Turkey.
219
Environmental Mineralogy
Environmental mineralogy focuses its research on the characterization of individual aerosol
particles by electron beam techniques (high-resolution scanning electron microscopy,
transmission electron microscopy, environmental scanning electron microscopy).
We study individual aerosol particles in order to derive the physical and chemical
properties (e.g., complex refractive index, deliquescence behavior, ice nucleation) of the
atmospheric aerosol. These data are of great importance for modeling the global radiation
balance and its change due to human activities.
We are also interested in studying the particulate matter exposure in urban environments
and at working places. As aerosol particles may have adverse effects on human health, the
knowledge of the particle size distribution and the chemical and mineralogical composition
of the particles is of prime importance in order to derive the exact mechanisms of the
adverse health effects.
Our research is carried out in cooperation with the following national and international
partners: Max Planck Institute for Chemistry in Mainz, Institute for Atmosphere and
Environmental Sciences (University of Frankfurt) Institute for Atmospheric Physics
(University of Mainz), Institut für Steinkonservierung (IFS) in Mainz, Institute for
Meteorology and Climate Research (Karlsruhe Institute of Technology), Institute for
Tropospheric Research in Leipzig, Institute of Atmospheric Physics (German Aerospace
Center DLR) in Oberpfaffenhofen, Paul Scherrer Institute (Laboratory of Atmospheric
Chemistry) in Villigen (Switzerland), National Institute of Occupational Health (STAMI) in
Oslo (Norway), and the Norwegian University of Life Science (UMB) in Ås (Norway).
Staff Members
Head
Prof. Dr. Stephan Weinbruch
Research Associates
APL Prof. Dr. Martin Ebert
Dr. Nathalie Benker
Postdocs
Dr. Dirk Scheuvens
Dr. Annette Worringen
PD Dr. Konrad Kandler
Technical Personnel Thomas Dirsch
Secretaries
Astrid Zilz
PhD Students
Dipl.-Met. Dörthe Müller-Ebert
Dipl.-Ing. Thomas Herrmann
Diploma Students
Simon Jäckel
Miriam Küpper
Katharina Schütze
Bachelor Students
Markus Hartmann
Carolin Tissen
Research Fellow
Dipl.-Ing. Hauke Gorzawski
220
Institute of Applied Geosciences – Environmental Mineralogy
Research Projects
Environmental scanning electron microscopical studies of ice-forming nuclei (DFG
Forschergruppe INUIT).
Electron microscopy of Saharan mineral dust (DFG Forschergruppe SAMUM).
Source apportionment of rural and urban aerosols.
Characterization of volcanic aerosols from the Eyjafjallajökull eruption.
Characterization of working place aerosols (National Institute of Occupational Health, Oslo,
Norway).
Environmental scanning electron microscopical studies of the hygroscopic behaviour of
individual aerosol particles.
Influence of traffic on the surface of monuments.
Influence of traffic control on PM and NOX imissions.
Publications
Kohoutek S., Weinbruch S., Boltze, M. Reduction Potential of Environment-Responsive
Traffic Control on Roadside Particulate Matter and Nitrogen Oxide Concentrations,
TRANSPORTATION RESEARCH RECORD Issue: 2270 Pages: 162-170 DOI: 10.3141/227019 Published: 2012
Bingemer H., Klein H. Ebert M., Haunold W. Bundke U., Herrmann T., Kandler K.,. MüllerEbert D, Weinbruch S., Judt A., Wéber A., Nillius B., Ardon-Dryer K., Levin Z., Curtius J.
(2012): Atmospheric ice nuclei in the Eyjafjallajökull volcanic ash plume. Atmos. Chem.
Phys. 12, 857 – 867. doi: 10.5194/acp-12-857-2012
Wagner R., Ajtai T., Kandler K., Lieke K., Linke C., Müller T., Schnaiter M., Vragel M.
(2012): Complex refractive indices of Saharan dust samples at visible and near UV
wavelengths: a laboratory study. Atmos. Chem. Phys. 12, 2491 – 2512. doi: 10.5194/acp12-2491-2012
Müller D., Lee K.-H, Gasteiger J., Tesche M., Weinzierl B., Kandler K., Müller T., Toledano
C., Otto S., Althausen D., Ansmann A. (2012): Comparison of Optical and Microphysical
Properties of Pure Saharan Mineral Dust Observed With AERONET Sun Photometer, Raman
Lidar, and In-Situ Instruments During SAMUM 2006. J. Geophys. Res. 117, D07211. doi:
10.1029/2011JD016825
Niedermeier N., Held A., Müller T., Heinold B., Schepanski K., Tegen I., Kandler K., Ebert
M., Weinbruch S., Read K., Lee J., Fomba K. W., Müller K., Herrmann H., Wiedensohler A.
(2012): Mass deposition fluxes of Saharan mineral dust to the tropical northeast Atlantic
Ocean: an intercomparison of methods. Atmos. Chem. Phys. Discuss. 12(12), 33025-33081.
doi: 10.5194/acpd-12-33025-2012
221
Weinbruch S., Wiesemann D., Ebert M., Schütze K., Kallenborn R., Ström J. (2012)
Chemical composition and sources of aerosol particles at Zeppelin Mountain (Ny Ålesund,
Svalbard): An electron microscopy study, Atmospheric Environment, 49, 142 – 150, 2012.
Kahnert M., Nousiainen T., Lindqvist H., Ebert M. (2012) Optical properties of light
absorbing carbon aggregates mixed with sulfate: assessment of different model geometries
for climate forcing calculations, OPTICS EXPRESS, 20, 10042 - 10058, 2012.
Weinbruch S., Dirsch T., Kandler K., Ebert M., Heimburger G., Hohenwarter F. (2012)
Reducing dust exposure in indoor climbing gyms, J. Environ. Monit., 14, 2114 – 2120,
2012.
Scheuvens D., Schütz L., Kandler K., Ebert M., Weinbruch S. (2012) Bulk composition of
northern African dust and its source sediments – a compilation, Earth-Science Reviews,
2012.
Ebert M., Müller-Ebert D., Benker N., Weinbruch S. (2012) Source apportionment of
aerosol particles near a steel plant by electron microscopy, J. Environ. Monit., 14, 32573266, 2012.
222
Size distribution and chemical composition of ice nuclei at a rural site in Germany
M. Ebert1, T. Hermann1, H. Bingemer2, H. Klein2, J. Curtius2, and S. Weinbruch1
1
Environmental Mineralogy, Institute of Applied Geosciences,
Technical University Darmstadt, 64287 Darmstadt, Germany
2
Institute for Atmospheric and Environmental Sciences, Goethe - University,
Altenhöferallee 1, D-60438 Frankfurt/M., Germany
By the static vacuum diffusion chamber FRIDGE. atmospheric ice nuclei (IN) concentrations
are determined at Mount Kleiner Feldberg (Rhein-Main Area, Germany) on a daily basis for
more than 3 years now (Bingemer et al., 2012).
The determined differences in the monthly mean concentrations of IN of about one order of
magnitude with high values in early summer and low values in winter could have a
significant effect on primary ice formation in mixed phased clouds and the development of
precipitation over large areas of Central Europe.
Based on these measurements the aerosol optical thickness of mineral dust (AODDust)
turned out to be an especially important proxy for the IN-concentrations.
In order to proof the origin of the IN at Kleiner Feldberg the chemical composition and
morphology and size of particles that had been identified as ice nuclei by FRIDGE were
determined by environmental scanning electron microscopy (ESEM) combined with energydispersive X-ray microanalysis (EDX). In total more than 1000 individual IN were analyzed
in 23 selected FRIDGE samples. The unambiguous identification of the analyzed particles as
IN was enabled by a high precision laser engraved coordinate system on the substrates.
Eight groups of IN were distinguished: alumosilicates, quartz, Ca- and Mg-carbonates, Casulfates, metal/metal oxides, biological particles, soot, other C-rich particles, and
sulfates/nitrates/ chlorides.
Fig 1. Particle group number abundance of IN at Kleiner Feldberg for six size classes .
223
All other particles were summarized in a ninth “mixtures/other” group. This classification
reflects the major composition of a particle. Minor compounds, which are present as
coating, agglomerate or heterogeneous inclusion within individual particles were not
considered for classification.
In total 30% of all identified IN belongs to the sulfates/nitrates/chlorides group. Because of
methodical considerations this group was removed from the graphs in Figure 1 and 2
The size resolved particle group number abundance of the IN is shown in Figure 1, the total
size distribution in Figure 2. Most abundant particle groups acting as IN are the soil groups
alumosilicates, quartz and carbonates (orange bars) with in total 53%, followed by
biological particles (plant fibers, pollen) with 27%, soot (8%) and metal/metal oxides
(4%). While higher amounts of soot (average geometric diameter (d)= 0.7 µm) were only
found in the smallest size bin (<2 µm) soot, biological particle dominates within the largest
size bins (> 16 µm). Because of the large particle diameters of the biological IN (d= 15.3
µm), these particles are very likely originating from local sources, while a major part of the
alumosilicates (d= 3,3 µm) will also originate from long range transport (desert dust).
N = 712
dØ: 4,4 µm
Fig. 2 Size distribution of IN at Kleiner Feldberg (N=number of analyzed IN; d= average geometric diameter).
224
Aerosol deposition in the main African dust transport region:
establishing a long-term time series at São Vicente, Cape Verde
K. Kandler, S. Weinbruch
Introduction
Mineral dust is one of the dominating aerosol species in the atmosphere. Particularly, the
tropical North Atlantic Ocean is heavily affected by dust, changing cloudiness, precipitation,
nutrient fluxes into the ocean, radiation balance etc. A number of field experiments with
different foci recently investigated dust properties (e. g., SAMUM, AMMA, SHADE, PRIDE,
GERBILS). However, these experiments usually lasted a short time, usually a few weeks,
some a season. As a result, they captured a low number of dust episodes only. Given the
highly episodic nature of dust outbreaks and a potential inter-annual variation, the question
arises, how these experiments should be rated with respect to an annual average, or how
they can be compared to each other. This actual problem arises from the nonexistence of
longer time series in the tropical North Atlantic Ocean (except at Barbados; Trapp et al,
2010). To overcome these shortcomings, a quasi-continuous measurement of aerosol
deposition was installed in the middle of December 2011 at the Cape Verde Atmospheric
Observatory (http://ncasweb.leeds.ac.uk/capeverde/), at São Vicente Island, Cape Verde.
Sampling and Analysis
Particle collection





sedimentation trap with rain shelter
dry deposition, mainly by sedimentation
dominated by particles larger than approximately 1 µm
carbon adhesive substrate
collection time between few hours (during dust events) and ten days, data shown
here between Jan 24 and Feb 19, 2012
Analysis






automated scanning electron microscopy with energy-dispersive X-ray detection
particle size (projected area diameter) and shape measurements by image analysis
scanning of 80% of the particle cross section with electron beam to get chemical
information representative for the total particle
quantification of single particle chemical composition with particle size correction
statistical significant numbers of particles are analyzed (for this work, 22,000)
classification according to chemical composition
Sampling on Cape Verde
 unique situation due to extremely uniform wind direction distribution (trade winds –
NNE)
 as result, the sedimentation trap acts as horizontal elutriator
 gradients in particle concentration (Fig. 1a)
 gradients in particle size distribution (Fig. 1b)
 to achieve comparability between samples, analysis of the very center only
(approximately 1 mm²)
225
Particle mixing state and deposition coincidence
A particular detection problem exists for internal mixtures of different aerosol species (e. g.,
dust/sea-salt, dust/sulfate): the coincidence of one particle depositing on (or close) to
another, so a false internal mixture is measured. For an infinitesimal small particle – which
is, in our case, a particle smaller than the lateral resolution of a single pixel – the mixing
coincidence probability (MCP) equals to the area fraction covered by the already deposited
particles. For larger particles, the MCP depends on the size distribution. Assuming a
monodisperse distribution of spherical particles and widely spaced deposition (i. e. low area
coverage), the MCP of an incoming particle of the same size is four times the covered area
fraction, and the MCP of a double sized particle is nine times the covered fraction – and so
on.
As a result, we observe that the number of detected strongly internally mixed particles
(SIMP; at least 20 atom% contribution of different aerosol species) is dependent on the
substrate loading (Fig. 2). For dust/sulfate mixtures, the abundance of SIMP follows MCP
for small particles, for the dust/sea-salt mixing it follows a MCP for equal-sized particles (at
5 µm). This leads to the conclusion that the occurrence of SIMP on substrate is no direct
proof for their atmospheric existence. To address this problem, an extrapolation to zero
coverage (regression) is made. It shows that in average there is a (size-dependent) fraction
of SIMP (e. g. 0.15 for particles between 5 µm and 10 µm) not influenced by deposition
coincidence.
We can observe further that the ratio of abundance of different species influences the MCP
(inter-species MCP is highest for similar abundance). However, to assess this mixing
probability, further model experiments have to be carried out. Apart from SIMP, weak
internal mixtures, i. e. small amounts of sulfate attached to silicate particles, are always
very abundant (> 95 % of the particles), maybe in part owing to the comparatively long
atmospheric exposition time.
General composition and iron contribution
In general, the relative composition varies heavily between dust and marine phases,
showing that the dust, if present, dominates over all other aerosol types. During these dust
phases, a Ca-rich mode is present, similarly as reported before for other regions (Kandler et
al., 2009). Despite the long exposition times, pure sulfate particles are a minor component,
indicating that sea-salt processing to sodium sulfate does not occur frequently on the
substrate. Fig 3 shows the size distribution of the iron contribution to the aerosol. It
exhibits a similar behavior as reported before for Cape Verde (Kandler et al., 2011) for
particles smaller than 10 µm, but higher iron contents for larger particles. During the
observed dust intrusion, only a low variation in iron distribution was observed.
226
10
5
5
Y, mm
Y, mm
10
0
0
-5
-5
-10
-10
-10
0
-5
25
0
X, mm
5
50
75
100
particles per unit area
1 µm - 2.5 µm
-10
10
-5
0
X, mm
5
10
0.00
0.25
0.50
0.75
1.00
1.25
area concentration ratio ([4 µm; 8 µm] vs. [2 µm; 4 µm])
125
2.5 µm - 5 µm
0.8
relative abundance of mixed particles
Fig. 1a (left): Map of particle number
concentration per area on the sampling
substrate for particles with diameters
between 2 and 4 µm (marine phase, Jan.
30, 2012 to Feb. 2); main wind direction is
shown by the white arrow. 1b (right):
Same as Fig. 1a, but instead the ratio of
the concentration of larger particles (4
µm < d < 8 µm) to smaller ones (2 µm < d <
4 µm) is shown
5 µm - 10 µm
10 µm - 25 µm
0.16
0.7
0.14
dust/sulfate
dust/sea-salt
0.6
0.12
0.5
0.10
0.4
0.08
0.3
0.06
0.2
0.04
0.1
0.02
0.0
0.00
0.02
0.04
0.06
0.08
covered area fraction
n=533
1.0
0.10
0.00
0.00
Fig. 2 Relative abundance of strongly
internally mixed particles (SIMP) as
function of the area fraction covered by
particles; the lines give the linear
regressions
0.02
0.04
0.06
0.08
covered area fraction
n=656 n=907n=1391n=1265n=693 n=209
0.10
n=28
0.9
other
relative abundance
0.8
Fe-0
0.7
Fe-100
0.6
Fe-50
0.5
Fe-20
0.4
Fe-10
Fig. 3 Size-resolved iron distribution
among the particles during the dust
phase Feb 6 to 10, 2012
Fe-5
0.3
Fe-3
0.2
Fe-2
0.1
0.0
1
10
particle diameter, µm
References
[1]
[2]
[3]
Kandler, K., et al. (2009): Size distribution, mass concentration, chemical and mineralogical
composition, and derived optical parameters of the boundary layer aerosol at Tinfou,
Morocco, during SAMUM 2006. Tellus 61B, 32-50. doi: 10.1111/j.1600-0889.2008.00385.x
Kandler, K., et al. (2011): Electron microscopy of particles collected at Praia, Cape Verde,
during the Saharan Mineral dust experiment: particle chemistry, shape, mixing state and
complex refractive index. Tellus 63B, 475-496. doi: 10.1111/j.1600-0889.2011.00550.x
Trapp, J. M., et al. (2010): Temporal variability of the elemental composition of African dust
measured in trade wind aerosols at Barbados and Miami. Mar. Chem. 120, 71-82. doi:
10.1016/j.marchem.2008.10.004
227
Diploma Theses in Applied Geosciences
Bonanati, Christina; GIS-Based feasibility study on detecting hidden recent active tectonic
structures by means of soil air radon measurements in the Canterbury Plains, New Zealand,
23.07.2012
Christmann, Anja; Synthese und Charakterisierung von strukturierbaren Sol-Gel-Systemen
über die UV-Nanoimprint-Lithographie, 04.04.2012
Drefke; Christoph; Untersuchung der thermischen Eigenschaften von Lockergesteinen,
20.09.2012
Heberer, Susanne; Petrografische und geochemische Untersuchungen an den WajidSandsteinen, Saudi-Arabien, 18.06.2012
Klaeske, Ulrike; Untersuchung der hydraulischen Kennwerte des Permokarbons in Hessen
und Rheinland-Pfalz, 12.11.2012
Kowalew, Wladimir; Errichtung einer Versuchsanlage für einen Feldtest verschiedener
Erdwärmesondentypen, 14.08.2012
Küpper, Miriam; Electron microscopy of inorganic particles deposited in the lungs of nickel
refinery workers, 13.12.2012
Lindstädt, Manuel; Hydrochemical Investigations of the Groundwater in the Pine Ridge
Reservation/South Dakota with Special Focus on Groundwater Radioactivity, 08.08.2012
Nehler, Mathias; Influence of Hydrothermal Alteration on Permeability and Thermal
Conductivity of the Huka Fall and Waiora Formation in the Tauhara Geothermal Field
(Taupo Volcanic Zone, New Zealand), 20.09.2012
Schäffer, Rafael; Hydrogeologische und geothermische Untersuchungen der Heilquellen
und Heilbrunnen Bad-Soden-Salmünsters, 21.06.2012
Welsch, Bastian; Forschungsbohrungen Heubach: Untersuchungen zu den geothermischen
Reservoireigenschaften des Odenwald Kristallins, 26.10.2012
Wiesemann; David; Methodologische Unterscheidung der beiden Pyroxenoide Rhodonit
und Pyroxmangit, 17.08.2012
Master Theses TropHEE in Applied Geosciences
Derbe, Destaye; GIS Based Water Budget Model and Stable Isotope Variation in Surface
Waters of the Western East African Rift, 27.01.2012
Lobo Coutinho, Luiz; The use of Multipurpose Artificial Reefs for Coastal Protection,
22.08.2012
228
Diploma- and Master Theses in Applied Geosciences
Nzekwe, Obinna; Spatial Analysis and Environmental Impact Assessment of Ordovician Oil
Shale using ARCGIS: a case study of Northern Estonia, 10.12.2012
Owuor, Steven Okoth; Hydraulic Characteristics and Hydrochemistry of Nairobi area,
Kenya, 26.09.2012
Ribero do Vale Pedreira, Raissa; Application of DRASTIC & GALDIT indexes for the
vulnerability assessment of coastal aquifers in the Mediterranean Basin, 02.04.2012
Ufondu, Lotanna; The Geothermal Potentials of the Middle and Lower Benue Trough
Nigeria, 24.01.2012
Master Theses in Applied Geosciences
Bauer, Kirsten; Hydrogeologische und geothermische Untersuchungen
Neufassungen der Kursaalquellen in Stuttgart - Bad Cannstatt, 02.10.2012
an
den
Knipp, Elena, Charakterisierung des Nitratabbaupotenzials an Bohrkernproben aus dem
Hessischen Ried - Methodenvalidierung zur Lokalisierung regionaler Abbauhorizonte,
29.11.2012
Langer, Larissa; Planung und Erkundung für den Bau des oberflächennahen geothermalen
Brunnentestfeldes Crailsheim, 18.10.2012
Bachelor Theses in Applied Geosciences
Hartmann, Markus; Abschätzung von Quantifizierungsfehlern
mikroskopischen Einzelpartikelanalyse, 29.05.2012
der
elektronen-
Hill, Tobias; Water mechanisms in an acid drainage environment – example from the clayey
alteration products of sulphide-bearing metamorphic rocks (Kristiansand, Southern
Norway), 15.10.2012
Kellmann, Stefanie; Entwicklung einer Bewertungsmatrix für Entsorgungsvarianten bei
Gewässersedimenten; 30.10.2012
Mohr, Marie; 3-D-Rekonstruktion der Olympia-Terrasse (Griechenland) zur Bilanzierung
von Massenverlagerungsprozessen, 22.5.2012
Neef, Bastian; GIS-Basierte Kompilierung von vulkanischen Ausbruchsereignissen und
deren Begleiterscheinungen in Südisland zur Visualisierung und Animation von
Zeichenreihen, 22.10.2012
Philipp, Sven; Geologische Kartierung des Zechsteins am südöstlichen Harzrand bei
Breitungen, 31.05.2012
Institute of Applied Geosciences – Master- and Bachelor Theses in Applied Geosciences
229
Schwalb, Björn; Thermofazielle und petrophysikalische Untersuchung der Bohrung
Solnhofen-Maxberg und weiterer Aufschlussproben der Fränkischen und Schwäbischen Alb,
22.05.2012
Tissen, Carolin; Chemische und morphologische Charakterisierung von Eiskeimen,
09.07.2012
Wiesner, Peter; Sedimentgeologische Strukturanalyse eines distalen Fächerteils des
alluvialen Illgrabenfächers mittels Georadar, 30.10.2012
PhD Theses in Applied Geosciences
Heike Pfletschinger: Development of Laboratory Experiments and Numerical Modeling
Techniques to Quantify Vadose Zone Water Fluxes in Arid Regions, 17.4.2012 - Supervisor:
Prof. Schüth
Dipl.-Ing. Geowiss. Dirk Arndt: Geologische Strukturmodellierung von Hessen zur
Bestimmung von Geopotenzialen, 9.7.2012 - Supervisor: Prof. Hoppe
Dipl.-Ing. Geowiss. Kristian Manuel Bär: Untersuchung der tiefengeothermischen Potenziale
von Hessen, 9.7.2012 - Supervisor: Prof. Sass
Sana'a Al-Zyoud, M. Sc.: Geothermal Cooling in Arid Regions: An Investigation of the
Jordanian Harrat Aquifer System, 16.8.2012 – Supervisor: Prof. Sass
Margarete Schloßer M.A.: Vapor Transport Sintering of Calcium Phosphate Ceramics,
14.12.2012 - Supervisor: Prof. Kleebe
Dipl.-Ing. Eric Detemple: Charakterisierung von LaNiO3-basierten Übergittern mittels
transmissionselektronenmikroskopischer Methoden, 17.12.2012 - Supervisor: Prof. Kleebe
Dipl.-Geow. Horst Purwin: Eine experimentelle Studie des Oxidationszustandes von Eisen
in Granat und Klinopyroxen als Funktion der Temperatur im System CaO-FeO-Fe2O3-MgOAl2O3-SiO2: Implikationen für die Granat-Klinopyroxen-Geothermometrie, 17.12.2012 Supervisor: Prof. Kleebe
Habilitation in Applied Geosciences
Dr. Konrad Kandler: Physikalische und chemische Eigenschaften von Wüstenäerosol im
Hinblick auf seine Klimawirksamkeit, 12.12.2012 – Supervisor: Prof. Weinbruch
230
Institute of Applied Geosciences – PhD Theses in Applied Geosciences
Materials Science:
Petersenstraße 23 L2/01
64287 Darmstadt
Applied Geosciences:
Schnittspahnstraße 9 B2 01/02
64287 Darmstadt
Phone: +49(0)6151/16-5377
Fax: +49(0)6151/16-5551
www.mawi.tu-darmstadt.de
Phone: +49(0)6151/16-2171
Fax: +49(0)6151/16-6539
www.iag.tu-darmstadt.de
For further information contact:
Dr. Joachim Brötz, Phone: +49(0)6151 / 16-4392; eMail: [email protected]
Dipl.-Ing.(BA) Andreas Chr. Hönl, Phone: +49(0)6151 / 16-6325, eMail: [email protected]
Institute of Applied Geosciences – Master- and Bachelor Theses in Applied Geosciences
231

Institute of Materials Science - Technische Universität Darmstadt

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