Institute of Materials Science - Technische Universität Darmstadt
Transcription
Institute of Materials Science - Technische Universität Darmstadt
Annual Report 2011 Faculty of Materials and Geo Sciences Contents Dean’s Office .................................................................................................................. 4 Institute of Materials Science ......................................................................................... 6 PREFACE ........................................................................................................................ 6 PHYSICAL METALLURGY ....................................................................................................... 10 CERAMICS GROUP .............................................................................................................. 16 ELECTRONIC MATERIALS...................................................................................................... 26 SURFACE SCIENCE .............................................................................................................. 36 ADCANCED THIN FILM TECHNOLOGY ..................................................................................... 48 DISPERSIVE SOLIDS ............................................................................................................. 50 STRUCTURE RESEARCH........................................................................................................ 64 MATERIALS ANALYSIS ......................................................................................................... 69 MATERIALS MODELLING DIVISION ......................................................................................... 76 MATERIALS FOR RENEWABLE ENERGIES ................................................................................. 87 PHYSICS OF SURFACES......................................................................................................... 94 JOINT RESEARCH LABORATORY NANOMATERIALS .................................................................... 99 MECHANICS OF FUNCTIONAL MATERIALS ............................................................................. 106 COLLABORATIVE RESEARCH CENTER (SFB) .......................................................................... 111 DIPLOMA THESES IN MATERIALS SCIENCE ....................................................................... 115 BACHELOR THESES IN MATERIALS SCIENCE ..................................................................... 118 PHD THESES IN MATERIALS SCIENCE ............................................................................. 119 MECHANICAL WORKSHOP ............................................................................................. 121 ELECTRICAL WORKSHOP ............................................................................................... 121 Institute of Applied Geosciences ................................................................................ 122 PREFACE .................................................................................................................... 122 PHYSICAL GEOLOGY AND GLOBAL CYCLES ............................................................................ 124 HYDROGEOLOGY .............................................................................................................. 134 ENGINEERING GEOLOGY .................................................................................................... 139 GEOTHERMAL SCIENCE AND TECHNOLOGY ........................................................................... 140 APPLIED SEDIMENTOLOGY .................................................................................................. 151 GEO-RESOURCES AND GEO-HAZARDS .................................................................................. 158 GEOMATERIAL SCIENCE ..................................................................................................... 167 TECHNICAL PETROLOGY WITH EMPHASIS IN LOW TEMPERATURE PETROLOGY............................. 176 ENVIRONMENTAL MINERALOGY .......................................................................................... 183 DIPLOMA THESES IN APPLIED GEOSCIENCES .................................................................... 189 MASTER THESES TROPHEE IN APPLIED GEOSCIENCES ...................................................... 190 PHD THESES IN APPLIED GEOSCIENCES .......................................................................... 190 Faculty of Materials and Geo Sciences 3 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. Andreas Hoppe (until 31st March 2011) Prof. Dr. Matthias Hinderer (since 1st April 2011) 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 large scale projects: Dr. Sonja Laubach Coordination of the KIVA project: Dr. Silvia Faßbender Public relations: Marion Bracke Media Design: Thomas Keller Publications of Permanent Members of the Dean's Office M.V. Hohmann, P. Ágoston, A. Wachau, T.J.M. Bayer, J. Brötz, K. Albe, A. Klein, Orientation Dependent Ionization Potential of In2O3: A Natural Source for Inhomogeneous Barrier Formation at Electrode Interfaces in Organic Electronics, J. Phys.: Cond. Mat. 23, 334203 (2011); doi: 10.1088/0953-8984/23/33/334203 4 Dean’s Office J. Deuermeier, J. Gassmann, J. Brötz, A. Klein, Reactive magnetron sputtering of Cu2O: Dependence on oxygen pressure and interface formation with ITO, J. Appl. Phys., Vol. 111, 113704 (2011); doi:10.1063/1.3592981 Renard, L.; Elhamzaoui, H.; Jousseaume, B.; Toupance, T.; Laurent, G.; Ribot, F.; Saadaoui, H.; Brötz, J.; Fuess, H.; Riedel, R.; Gurlo, A.; Low-temperature H2 sensing in self-assembled organotin thin films; Chem. Commun., 47(5) (2011) 1464-1466. F. Muench, S. Kaserer, U. Kunz, I. Svoboda, J. Brötz, S. Lauterbach, H.-J. Kleebe, C. Roth, W. Ensinger; Electroless synthesis of platinum and platinum–ruthenium nanotubes and their application in methanol oxidation; JOURNAL OF MATERIALS CHEMISTRY, 21 (2011) 6286-6291. Jacke, S. Song, J. Dimesso, L. Broetz, J. Becker, D. Jaegermann, W., Temperature dependent phosphorous oxynitride growth for all-solid-state batteries JOURNAL OF POWER SOURCES, Vol. 196, 6911-6914, DI 10.1016/j.jpowsour.2010.12.022, AUG 15 2011 Structural characterisation of textured gold nanowires Maurer, F; Brötz, J ; Miehe, G; Karim, S; Fuess, H, INTERNATIONAL JOURNAL OF NANOTECHNOLOGY Volume: 8 Issue: 10-12 Special Issue: SI Pages: 855-867 Published: 2011 Dean’s Office 5 Institute of Materials Science Preface Dear colleagues and friends, The year 2011 was an eventful and successful year for the Department of Materials and Geo Sciences of TU Darmstadt. Details of the activities and achievements related to the Institute of Applied Geosciences are highlighted by the director of the institute, Prof. H.-J. Kleebe, on page 122. 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 increased once again; expenses rose from € 10.2 million in 2010 to € 12.6 million in 2011 and also in terms of teaching a milestone was reached by finishing the elaboration of the Master course, which has already been accredited by ASIIN. The Master course, being an international study course where all courses are held in English, saw its first students in the winter semester 2011/12. 2011 was also the first year having students graduate from the Bachelor course. Most of them want to graduate as a Master of Science in Materials Science and are therefore continuing their studies as students of the consecutive Master course offered by our department. The Bachelor course of our department is still gaining in popularity as is reflected by a new record number of 140 freshmen starting in the winter semester 2011/12, which means a 40% increase as against the previous year, as can be seen in Figure 1. For the first time, a new kind of scholarship, the so-called "Deutschlandstipendium", was awarded to 91 students of TU Darmstadt, 3 of whom being students of the Institute of Materials Science. Regardless of the university in Germany this scholarship always means a donation of € 300 per month, independent of the financial situation of the candidate. One half of the grant is financed by the German Government, the other half is donated by enterprises. The fundraising process and the selection of scholars is organised by the respective university. 6 Preface Coordinated Research Proposals The institute was involved in two large-scale proposals in 2011: SubMateK, applying for a LOEWE Center of Excellence funded by the Hessian State Government, which was coordinated by Prof. Alff together with Prof. Oechsner from the Department of Mechanical Engineering, and TAIFUN, applying for a Center of Excellence funded by the German Federal and State Governments, the coordinators of which are Prof. Riedel and Prof. Rödel. For TAIFUN, the pre-proposal had already been handed in in 2010. For SubMateK, a preproposal was composed due in April 2011. Both pre-proposals received a positive evaluation and therefore successfully reached the next evaluation stepm meaning that both initiatives were invited to elaborate a full proposal. The full proposals were submitted according to schedule in September (TAIFUN) and December (SubMateK), respectively. Another initiative, namely the Graduate School of Energy Sciences and Engineering, in which the Department of Materials and Geosciences is involved together with other Departments of TU Darmstadt, was established within the framework of the Excellence initiative. The decisions on all three proposals, i.e. SubMateK, TAIFUN, and the Graduate School, are not due before June 2012. All three initiatives mark the interdisciplinary approach the university is promoting and for which the Department of Materials and Geoscience 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 Diploma course, thereafter to the Bachelor course. Preface 7 Faculty Members Two new professorships were inaugurated, namely Jun.-Prof. Dr. Bai-Xiang Xu and Prof. Dr. Ralph Krupke, who are heading the groups "Mechanics of Functional Materials" and "Molecular Nanostructures" respectively. We welcome both as new professors to our institute. In 2012, another two new faculty members will be appointed, Prof. Dr. Christina Trautmann (head of the group Ion Beam-Modified Materials) and Prof. Dr. Oliver Gutfleisch (head of the group Functional Materials). 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. In March 2012, Prof. Roth (group of Renewable Energies) will as well leave for the Karlsruhe Institute of Technology (KIT). She will, however, remain with the Department of Materials and Geosciences as an APL-Professor for three more years. We wish both of them all the best for their future careers. Buildings and Lab/Office Space The steadily increasing number of both staff and students (see Fig. 1) at the Institute of Materials Science causes a continuous need for more office and lab space. Therefore, we appreciate that two more stories were added to the CSI-building L1|08, which now comprises four floors. The Dispersive Solids division having moved there in August 2011, the 2nd and 4th floor are now occupied by the groups Dispersive Solids (Prof. Riedel), Joint Research Laboratory Nanomaterials (Prof. Hahn), Molecular Modelling (Prof. Albe), Physics of Surfaces (Prof. Stark), and Surface Science (Prof. Jaegermann). However, to meet the needs of our growing research activities, it is planned to erect a new building with lab and office space in Böllenfalltorweg. The building will be shared with the Chemistry Department and its completion is scheduled for late spring 2013. Mechanical Workshop After the retirement of the head of the mechanical workshop, Jochen Korzer, in 2010, we are glad to have found a new head in Jochen Rank in 2011. Jochen Rank previously gained a lot of experience in the Departments of Chemistry and Mechanical Engineering and now manages the mechanical workshop at our institute with great commitment, enthusiasm, and success. We welcome him to our Department. It is also good news that we will soon purchase a CNC lathe for the mechanical workshop thanks to a grant from the president. Outstanding New Equipment The electron microscopy facility of our department was significantly upgraded by the acquisition of a highly sophisticated new Cs-corrected TEM providing a resolution of 0.8 Å and a focused ion beam (FIB) instrument for nanostructuring of materials and sophisticated lamellae preparation of samples for microscopy. This, together with the recent acquisition of other instruments, means that the Competence Centre Materials Characterisation is now provided with the appropriate equipment to rank among the world's top addresses in materials characterization. Honours, Awards and Special Achievements In 2011, we were proud to celebrate a number of awarded prizes and special achievements: Dr. Olivier Guillon received the Masing Memorial Award. This prize is awarded by the German Society for Materials Science (DGM) for independent research work in the broader 8 Preface field of physical metallurgy achieved by young scientists. Dr. Guillon also received the Materials Science and Technology Prize given to young European materials scientists or engineers in recognition of a significant contribution to a field in Materials Science and Engineering. In addition, Dr. Guillon was awarded with the R. L. Coble Award for Young Scholars, the annual prize of the American Ceramic Society for the world's best young scientist in the field of ceramics. Dr. Guillon is the first young scientist working in Germany to receive this award. In the meantime, he has accepted an offer for a professorship at the Friedrich-Schiller-Universität in Jena. Prof. Hartmut Fuess received the "MaWi-Ehrennadel" for his long-term efforts and commitment for the Institute of Materials Science. Dr. Martin Schidleja was awarded the prize of the "Vereinigung von Freunden der Technischen Universität zu Darmstadt e.V." for his outstanding academic achievements in his doctoral thesis. As usual, the annual awarding of the "MaWi Prize" formed part of the MaWi summer party. The prize winners in 2011 were Ruben Bischler from the division Joint Research Laboratory Nanomaterials for his Diploma thesis on "Tailored Nanostructured Metal Borides," and Ralf Witte, also from the Joint Research Laboratory Nanomaterials, whose Diploma thesis is about "Magnetic Phenomena in Fe-Sc Nanoglasses." The 3rd prize was awarded to Matthias Ehmke for his contribution regarding “Electric fatigue and aging processes in lead-free BNTBT-KN ferroelectrics.” Last but not least, Dr. Yuri Genenko successfully finished his habilitation colloquium. Social Events As every year, our annual summer party was scheduled shortly before the summer break, it being 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. It was for the first time in December 2011 that we celebrated a year-end ceremony for all research groups, staff members and students, something that is formally considered to be the continuation of our traditional MaWi christmas party. Due to the increased number of attendants, this event had to be held in the building of the cafeteria at the Lichtwiese. The celebration including the social programme was organized by PD Dr. Boris Kastening, Heinz Mohren, and students (Fachschaft). During the graduation party the graduates of the year received their certificates (Bachelor, Diploma, and PhD). This being the most important part of the programme, we will now start a new tradition by celebrating Bachelor and Master graduates at the MaWi summer party and PhD graduates at the year-end ceremony. This annual report shall provide you with some information on the most prominent research activities of the individual groups conducted in 2011 which you will find in detail on the following pages. 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 creep, fatigue 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, quantitative image analysis for the characterization of microstructures and high temperature alloys. 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, Canada and USA which also includes exchange of students and scientists. Strong relations with industry (Daimler-Benz, Ecoroll, Heraeus, Opel, PfalzFlugzeugwerke, Plansee, VW) give multiple opportunities for scientific interaction and personal exchange. Department members participate in and organize national and international conferences, seminars and workshops thereby gathering information which supports to keep teaching and research on an actual level. 10 Physical Metallurgy Staff Members Head Prof. Dr. Martin Heilmaier Research Associates Prof. Dr. Clemens Müller Dr.-Ing. Enrico Bruder Dipl.-Ing. Katharina von Klinski-Wetzel Technical Personnel Ulrike Kunz Claudia Wasmund Secretaries Christine Hempel PhD Students Dipl.-Ing. Florian Gang 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 Christoph Baumann Karsten Fischer Michael Bachmann Ioannis Sprenger Rudolf Seiler George Bedenian Ruben Heid Franziska Resch Kathrin Barth Research Fellow Dr. Shanmugasundaram Tharangaju Guest Scientists Dr. Yongzhong Zhan Xiaojiao Yu 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. “Directional Solidification of Multiphase Metallic High Temperature Materials Beyond Nickelbase Superalloys”, DFG, since 08/2010. “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 Physical Metallurgy 11 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 “Integral Sheet Metal Design with Higher Order Bifurcations”, since 2009. Publications J. H. Schneibel, M. Heilmaier, G. Hasemann, T. Shanmugasundaram: Temperature dependence of the strength of fine- and ultrafine-grained materials, Acta Materialia 59 (2011), 1300-1308. O. Hassomeris, G. Schumacher, M. Krüger, M. Heilmaier, J. Banhart: Phase Continuity in High Temperature Mo-Si-B Alloys: A FIB-Tomography Study, Intermetallics 19 (2011), 470475. M. Mousa, N. Wanderka, M. Timpel, S. Singh, M. Krüger, M. Heilmaier, J. Banhart: Modification of Mo-Si alloy microstructure by small additions of Zr, Ultramicroscopy 111 (2011), 706-710. P. Susila, D. Sturm, M. Heilmaier, B.S. Murty, V.S. Sarma: Effect of yttria particle size on the microstructure and compression creep properties of nanostructured oxide dispersion strengthened ferritic (Fe-12Cr-2W-0.5Y2O3) alloy, Mater. Sci. Eng. A528 (2011), 4579-4584. S. Burk, B. Gorr, M. Krüger, M. Heilmaier, H.-J. Christ: Oxidation behaviour of Mo-Si-B-(X) alloys: Macro- and Microalloying (X= Cr, Zr, La2O3), JOM 63, No. 12, (2011), 32-36. E. Bruder, M.O. Görtan, P. Groche, C. Müller: Severe Plastic Deformation by Equal Channel Angular Swaging, Mater. Sci. Forum 667-669 (2011), 103-107. 12 Physical Metallurgy 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 Physical Metallurgy 13 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). 14 Physical Metallurgy 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] 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 15 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 lead-containing high-temperature piezoceramics can be obtained and extensively characterized electrically and mechanically. The scientific effort can be grouped as follows: I. Processing and sintering of oxides Dr. Olivier Guillon - Emmy Noether independent junior research group Following topics are investigated: Continuum mechanical description of sintering in the case of ceramic films and laminates (modelling of shrinkage, stress state, curvature during co-sintering…) Measurement of densification behaviour and viscous parameters by means of sinterforging Macroscopic and microscopic characterization of sintering anisotropy under mechanical loading and geometrical constraint provided by a substrate Drying of thin films from suspensions and conditions for cracking Sintering mechanisms of electrical Field Assisted Sintering Technique and processing of dense nanocrystalline materials Effect of particle size on the phase transformation behaviour of oxides using chip calorimetry and TEM. The considered Materials are mainly Al2O3, ZrO2, ZnO as well as materials for LTCC (Low Tempera-ture Cofired Ceramics) and SOFC (Solid Oxide Fuel Cell) applications. II. Mechanical properties of ceramics and composites Dr. Ludwig Weiler Work on mechanical properties is geared towards an improved understanding of fracture strength, fracture toughness, R-curve behaviour and subcritical crack growth. Together with several European research groups we prepare and characterize metalceramic composites and metal-ceramic functionally graded materials Materials under consideration are Al2O3/Cu and Al2O3/Al. III. Electrical properties of ferroelectrics Dr. Torsten Granzow Materials with a crystalline structure lacking a center of inversion display a multitude of peculiar physical effects, they are therefore prime candidates both for fundamental scientific research as well as practical technical applications. Therefore the focus of the work in this group lies on the reaction of non-centrosymmetric materials to different external stimuli like electric fields, mechanical loads or high temperatures. Ferroelectric behavior and domain switching are of particular interest. Typical objects of the studies are polycrystalline materials based on perovskite structures, which form the most extended and 16 Ceramics Group diverse group of polar materials. These materials are always ferroelastic as well as ferroelectric in the non-cubic phase. The general aim is to develop the understanding of the basic physical principles that allows improvement of the properties of the material or to optimize the use of existing properties in a given application. One topic of investigation is the effect of combined electrical and mechanical loading on domain structures. In this context, the method of stress-supported poling was developed: a high degree of polarization can be reached with comparably small electric fields if a mechanical load is applied perpendicular to the poling direction. The mechanical and electrical behavior of donor- and acceptor-doped materials is investigated. The data will be used to develop a mathematical model that allows a prediction of the development of polarization and strain during an arbitrary electrical, mechanical and thermal procedure from as few parameters as possible. Apart from the research on ferroelectric properties, transitions between different polar phases or polar and non-polar phases are also of interest. One observes a stabilization or destabilization of long-range ferroelectric order by controlled introduction of charged defects, e.g. by a reduction treatment. The work is closely connected to that of the group developing new lead-free piezoelectric materials, as their superior properties are tied to the existence of a high-temperature phase that is probably relaxor-like. The work in this group is embedded in the Collaborative Research Center 595 on electrical fatigue in ferroelectric materials. The aim is to identify the causes for degradation of a material during use of a device and eliminate them as far as possible. Another topic within this project is the connection between domain structure, reversible and irreversible domain wall motion, large-signal parameters such as polarization and strain, and small-signal parameters like the components of the dielectric and piezoelectric tensors. IV. Development of new piezoceramics Dr. Wook Jo In response to the recent demands for environmental friendly piezoelectric 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 leadcontaining 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. Currently, we have extensive and active international collaborations with eminent ferroelectric groups throughout the world. Ceramics Group 17 V. 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. Staff Members Head Prof. Dr. Jürgen Rödel Research Associates Dr. Torsten Granzow Dr. Olivier Guillon Dr. Wook Jo Dipl. Phys. Irene Mieskes Dr. Silke Schaab Dr. Sebastian Schwarz Dr. Kyle Webber Dr. Ludwig Weiler Dr. Jami Winzer Technical Personnel Dipl.-Ing. Emil Aulbach Dipl.-Ing. Gundel Fliß Michael Heyse Secretaries Roswita Geier Gila Völzke PhD Students M. Sc. Matias Acosta Dipl.-Ing. Eva Anton Dipl.-Ing. Raschid Baraki Dipl.-Ing. Robert Dittmer Dipl.-Phys. Daniel Franzbach Dipl.-Ing. Claudia Groh Dipl.-Ing. Gerrit Günther Dipl.-Ing. Christine Jamin Dipl.-Ing. Markus König Dipl.-Ing. Thorsten Leist Dipl.-Phys. Mie Marsilius Dipl.-Ing. Eva Sapper Dipl.-Ing. Silke Schaab Dipl.-Ing. Florian Schader Dipl.-Phys. Deborah Schneider Dipl.-Ing. Yohan Seo Dipl.-Chem. Ina Uhlmann M. Sc. Jami Winzer M. Sc. Jiadong Zang Diploma+Bachelor Students Raschid Baraki Philipp Geiger Lucas Hamm Rebecca Hentschel Timo Prenzer Florian Schader André Schmidt Malte Voegeler 18 Ceramics Group Research Fellow Juri Koruza Tomas Muchenik Cena Michelle Nolan Suyan Tu Guest Scientists Prof. Edwin Garcia (Purdue University) Prof. Mark Hoffman (Univ. of New South Wales, Sydney) Prof. Jacob Jones (University of Florida) Prof. Sergei Kalinin (Oak Ridge Nat. Lab.) Prof. Ho-Yong Lee (Sunmoon University, Korea) Prof. Joe Trodahl (Victoria Univ. Wellington, NZ) Prof. Xiaoli Tan (Iowa State University) Dr. Haibo Zhang (University Beijing) Dr. Ke Wang (AvH) Zilin Yan Dr. Hailong Zhang 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) Melting of ceramic nanoparticles: Application to transient liquid phase sintering (DFG 2006–2011) Synthesis and characterization of nanostructured materials by FAST sintering (DFG 2006-2011) Drying of Thin Films (DFG 2006–2011) Thin film sintering: liquid phase vs. solid state sintering (DFG 2008-2011) Printed Electronics: Thin film ZnO (Merck 2006-2011) Effect of load and temperature on domain switching (DFG 2008-2011) 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” 2009-2012) 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) Ceramics Group 19 Publications Seo, Yo-Han; Benčan, Andreja; Koruza, Jurij; Malič, Barbara; Kosec, Marija; Webber, Kyle G.; Compositional Dependence of R-curve Behavior in Soft Pb(Zr1−xTix)O3 Ceramics, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 94 (12) pp. 4419-4425. ISSN 00027820 Tan, Xiaoli; Ma, Cheng; Frederick, Joshua; Beckman, Sarah; Webber, Kyle G.; The Antiferroelectric ↔ Ferroelectric Phase Transition in Lead-Containing and Lead-Free Perovskite Ceramics, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 94 (12) pp. 40914107. ISSN 00027820 Anton, Eva-Maria; Jo, Wook; Damjanovic, Dragan; Rödel, Jürgen; Determination of depolarization temperature of (Bi1/2Na1/2)TiO3-based lead-free piezoceramics, JOURNAL OF APPLIED PHYSICS, 110 (9) 094108(1-14). ISSN 00218979 Luo, Zhenhua; Granzow, Torsten; Glaum, Julia; Jo, Wook; Rödel, Jürgen; Hoffman, Mark; Effect of Ferroelectric Long-Range Order on the Unipolar and Bipolar Electric Fatigue in Bi1/2Na1/2TiO3-Based Lead-Free Piezoceramics, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 94 (11) pp. 3927-3933. ISSN 00027820 Franzbach, Daniel J.; Xu, Bai-Xiang; Mueller, Ralf; Webber, Kyle G.; The effects of polarization dynamics and domain switching energies on field induced phase transformations of perovskite ferroelectrics, APPLIED PHYSICS LETTERS, 99 (16) 162903-(1-3). ISSN 00036951 Jo, Wook; Schaab, Silke; Sapper, Eva; Schmitt, Ljubomira A.; Kleebe, Hans-Joachim; Bell, Andrew J.; Rödel, Jürgen; On the phase identity and its thermal evolution of lead free (Bi1/2Na1/2)TiO3-6 mol% BaTiO3, JOURNAL OF APPLIED PHYSICS, 110 (7) 074106-1074106-9. ISSN 00218979 Glaum, Julia; Granzow, Torsten; Schmitt, Ljubomira Ana; Kleebe, Hans-Joachim; Rödel, Jürgen, Temperature and driving field dependence of fatigue processes in PZT bulk ceramics, ACTA MATERIALIA, 59 (15) pp. 6083-6092. ISSN 13596454 Bernard, D.; Guillon, Olivier; Combaret, N.; Plougonven, E.; Constrained sintering of glass films: Microstructure evolution assessed through synchrotron computed microtomography, ACTA MATERIALIA, 59 (16) pp. 6228-6238. ISSN 13596454 Tran, Vu Diem Ngoc; Han, Hyoung-Su; Yoon, Chang-Ho; Lee, Jae-Shin; Jo, Wook; Rödel, Jürgen; Lead-free electrostrictive bismuth perovskite ceramics with thermally stable field-induced strains, MATERIALS LETTERS, 65 (17-18) pp. 2607-2609. ISSN 0167577X Webber, Kyle G.; Seo, Yo-Han; Lee, Ho-Yong; Aulbach, Emil; Jo, Wook; Rödel, Jürgen; R-Curve Behavior of Pb(Mg1/3Nb2/3)O3-29 mol% PbTiO3 Single Crystals: The Effect of Crystallographic Orientation and Grain Structure, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 94 (9) pp. 2728-2730. ISSN 00027820 Winzer, Jami; Weiler, Ludwig; Pourquet, Jeanne; Rödel, Jürgen; Wear behaviour of interpenetrating alumina–copper composites, WEAR, 271 (11-12) pp. 2845-2851. ISSN 00431648 Drahus, Michael D.; Jakes, Peter; Erdem, Emre; Schaab, Silke; Chen, Jun; Ozerov, Mykhaylo; Zvyagin, Sergei; Eichel, Rüdiger-A.; Manganese-doped (1−x)BiScO_{3}– xPbTiO_{3} high-temperature ferroelectrics: Defect structure and mechanism of enhanced electric resistivity, PHYSICAL REVIEW B, 84 (6) 064113-1-064113-8. ISSN 1098-0121 20 Ceramics Group Ehmke, Matthias; Glaum, Julia; Jo, Wook; Granzow, Torsten; Rödel, Jürgen; Stabilization of the Fatigue-Resistant Phase by CuO Addition in (Bi1/2Na1/2)TiO3-BaTiO3, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 94 (8) p. 2473. ISSN 00027820 Langer, Jochen; Hoffmann, Michael J.; Guillon, Olivier; Electric Field-Assisted Sintering and Hot Pressing of Semiconductive Zinc Oxide: A Comparative Study, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 94 (8) pp. 2344-2353. ISSN 00027820 Seils, Sascha; Baraki, Raschid; Jamin, Christine; Guillon, Olivier; Free-Standing Patterned Ceramic Structures Obtained by Soft Micromolding, ADVANCED ENGINEERING MATERIALS, 13 (6) pp. 502-508. ISSN 14381656 Chung, Yung-Bin; Park, Hyung-Ki; Lee, Dong-Kwon; Jo, Wook; Song, Jean-Ho; Lee, Sang-Hoon; Hwang, Nong-Moon; Low temperature deposition of crystalline silicon on glass by hot wire chemical vapor deposition, JOURNAL OF CRYSTAL GROWTH, 327 (1) pp. 57-62. ISSN 00220248 Jo, Wook; Rödel, Jürgen; Electric-field-induced volume change and room temperature phase stability of (Bi1/2Na1/2)TiO3-x mol. % BaTiO3 piezoceramics, APPLIED PHYSICS LETTERS, 99 (4) 042901-1-042901-3. ISSN 00036951 Dittmer, Robert; Jo, Wook; Daniels, John; Schaab, Silke; Rödel, Jürgen; Relaxor Characteristics of Morphotropic Phase Boundary (Bi1/2Na1/2)TiO3-(Bi1/2K1/2)TiO3 Modified with Bi(Zn1/2Ti1/2)O3, JOURNAL OF THE AMERICAN CERAMIC SOCIETY n/a. ISSN 00027820 Daniels, John E.; Jo, Wook; Rödel, Jürgen; Rytz, Daniel; Donner, Wolfgang; Structural origins of relaxor behavior in a 0.96(Bi[sub 1/2]Na[sub 1/2])TiO[sub 3]–0.04BaTiO[sub 3] single crystal under electric field, APPLIED PHYSICS LETTERS, 98 (25) 252904-1-252904-3. ISSN 00036951 Guillon, Olivier; Cao, Shaoyong; Chang, Jaemyung; Wondraczek, Lothar; Boccaccini, Aldo R.; Effect of uniaxial load on the sintering behaviour of 45S5 Bioglass® powder compacts, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 31 (6) pp. 999-1007. ISSN 09552219 Anton, Eva-Maria; Jo, Wook; Trodahl, Joe; Damjanovic, Dragan; Rödel, Jürgen; Effect of K0.5Na0.5NbO3on Properties at and off the Morphotropic Phase Boundary in Bi0.5Na0.5TiO3–Bi0.5K0.5TiO3Ceramics, JAPANESE JOURNAL OF APPLIED PHYSICS, 50 (5) 055802.1-055802.7. ISSN 0021-4922 Kwon, O-Jong; Jo, Wook; Ko, Kyeong-Eun; Kim, Jae-Yeol; Bae, Sung-Hwan; Koo, Hyun; Jeong, Seong-Min; Kim, Jin-Sang; Park, Chan; Thermoelectric properties and texture evaluation of Ca3Co4O9 prepared by a cost-effective multisheet cofiring technique, JOURNAL OF MATERIALS SCIENCE, 46 (9) pp. 2887-2894. ISSN 0022-2461 Marsilius, Mie; Granzow, Torsten; Jones, Jacob L.; Quantitative comparison between the degree of domain orientation and nonlinear properties of a PZT ceramic during electrical and mechanical loading, JOURNAL OF MATERIALS RESEARCH, 26 (09) pp. 1126-1132. ISSN 0884-2914 Frederick, Joshua; Tan, Xiaoli; Jo, Wook; Strains and Polarization During Antiferroelectric-Ferroelectric Phase Switching in Pb0.99Nb0.02[(Zr0.57Sn0.43)1−yTiy]0.98O3 Ceramics, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 94 (4) pp. 1149-1155. ISSN 00027820 Guillon, Olivier; Partial Constrained Sintering of Ceramic Layers on Metallic Substrates: A Comparison Between Modeling and Experiments, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 94 (4) pp. 1040-1045. ISSN 00027820 Ceramics Group 21 Leist, Thorsten; Webber, Kyle G.; Jo, Wook; Granzow, Torsten; Aulbach, Emil; Suffner, Jens; Rödel, Jürgen; Domain switching energies: Mechanical versus electrical loading in Ladoped bismuth ferrite–lead titanate, JOURNAL OF APPLIED PHYSICS, 109 (5) 054109-1. ISSN 00218979 Schmitt, Ljubomira A.; Kling, Jens; Hinterstein, Manuel; Hoelzel, Markus; Jo, Wook; Kleebe, Hans-Joachim; Fuess, Hartmut; Structural investigations on lead-free Bi1/2Na1/2TiO3-based piezoceramics, JOURNAL OF MATERIALS SCIENCE, 46 (12) pp. 4368-4376. ISSN 0022-2461 Dittmer, Robert; Jo, Wook; Damjanovic, Dragan; Rödel, Jürgen; Lead-free hightemperature dielectrics with wide operational range, JOURNAL OF APPLIED PHYSICS, 109 (3) 034107-1. ISSN 00218979 Luo, Zhenhua; Glaum, Julia; Granzow, Torsten; Jo, Wook; Dittmer, Robert; Hoffman, Mark; Rödel, Jürgen; Bipolar and Unipolar Fatigue of Ferroelectric BNT-Based Lead-Free Piezoceramics, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 94 (2) pp. 529-535. ISSN 00027820 Marsilius, Mie; Granzow, Torsten; Jones, Jacob L.; Effect of electrical and mechanical poling history on domain orientation and piezoelectric properties of soft and hard PZT ceramics, SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS, 12 (1) 015002. ISSN 1468-6996 Simons, Hugh; Daniels, John; Jo, Wook; Dittmer, Robert; Studer, Andrew; Avdeev, Maxim; Rödel, Jürgen; Hoffman, Mark; Electric-field-induced strain mechanisms in leadfree 94%(Bi[sub 1/2]Na[sub 1/2])TiO[sub 3]–6%BaTiO[sub 3], APPLIED PHYSICS LETTERS, 98 (8) 082901-1. ISSN 00036951 Jo, Wook; Daniels, John E.; Jones, Jacob L.; Tan, Xiaoli; Thomas, Pamela A.; Damjanovic, Dragan; Rödel, Jürgen; Evolving morphotropic phase boundary in lead-free (Bi[sub 1/2]Na[sub 1/2])TiO[sub 3]–BaTiO[sub 3] piezoceramics, JOURNAL OF APPLIED PHYSICS, 109 (1) 014110-1-014110-7. ISSN 00218979 Langer, Jochen; Hoffmann, Michael J. Guillon, Olivier; Electric Field-Assisted Sintering in Comparison with the Hot Pressing of Yttria-Stabilized Zirconia, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 94 (1) pp. 24-31. ISSN 00027820 McKie, Amanda; Winzer, Jami; Sigalas, Iakovos; Herrmann, Mathias; Weiler, Ludwig; Rödel, Jürgen; Can, Nedret; Mechanical properties of cBN–Al composite materials, CERAMICS INTERNATIONAL, 37 (1) pp. 1-8. ISSN 02728842 Jo, Wook; Ollagnier, Jean-Baptiste; Park, Jong-Lo; Anton, Eva-Maria; Kwon, O-Jong; Park, Chan; Seo, Hyun-Ho; Lee, Jong-Sook; Erdem, Emre; Eichel, Rüdiger-A.; Rödel, Jürgen; CuO as a sintering additive for (Bi1/2Na1/2)TiO3–BaTiO3–(K0.5Na0.5)NbO3 leadfree piezoceramics, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 31 (12) pp. 2107217. ISSN 09552219 22 Ceramics Group Stress-Dependent Phase Transitions in Perovskite Ferroelectrics Dr. Kyle Webber Perovskite ferroelectrics are commercially important materials, which are widely used as actuators, sensors, and transducers. Discovered almost 70 years ago, barium titanate (BaTiO3) is an important material for discrete and multilayer capacitors because of its high relative dielectric permittivity. BaTiO3 has received renewed interest as an end member in novel large unipolar strain lead-free ferroelectrics, such as (1-x-y)(Bi1/2Na1/2)TiO3– xBaTiO3–y(K0.5Na0.5)NbO3. Recent governmental regulations in Europe and elsewhere strictly limiting the use of toxic materials have driven the search for environmentally friendly alternatives. BaTiO3 undergoes three well-known first order structural phase transitions. Previous experimental investigations on stress-dependent phase transitions have primarily focused on the effect of hydrostatic and radial pressure on the dielectric properties and the Curie point of single crystal and polycrystalline BaTiO3. An increasing hydrostatic pressure was found to destabilize the lower symmetry phase, leading to a linear decrease in the Curie point. Conversely, radial compression perpendicular to the polarization stabilized the polar order, which was found to result in a nonlinear increase in the Curie point. There have, however, been comparatively few studies on the influence of uniaxial pressure. [1, 2] The present study focused on the effect of uniaxial compressive stress-dependent tetragonal-cubic phase transformation behavior of unpoled, single crystal and polycrystalline BaTiO3. During experimentation the real part of the relative dielectric permittivity was determined as a function of temperature and uniaxial stress. In the unloaded state both single crystal and polycrystalline BaTiO3 displayed permittivitytemperature behavior consistent with previous investigations; an increasing temperature resulted in an initial decrease in permittivity, followed by a subsequent peak in permittivity occurring at the Curie point. The Curie point (TC) of both polycrystalline and single crystal BaTiO3 was observed to rise with increasing mechanical compressive stress with a rate of 0.05 and 0.19 °C/MPa, respectively (Fig 1a). In addition, a comparable shift in the CurieWeiss temperature (was also observed to be -0.1 and -0.19 °C/MPa for polycrystalline and single crystal samples, respectively (Fig 1b)). Previous researchers have assumed that the Curie-Weiss temperature was stress independent, which is typically done to determine the shift of the Curie point with stress. is of the TC for single crystal BaTiO3, strongly indicating that the effect cannot be neglected. This necessitates the rethinking of current theories on the effect of external fields on the phase transformation behavior of perovskite ferroelectrics. Ceramics Group 23 20 Single Crystal Polycrystal 15 0 (a) (b) -5 10 (°C) Tc (°C) -10 5 -15 -20 -25 -30 0 0 50 -35 100 150 200 250 300 0 Compressive Stress (MPa) 50 100 150 200 250 300 Compressive Stress (MPa) Figure 1. Shift of Curie point Tc (a) and Curie-Weiss temperature (b) of single crystal (red squares) and polycrystalline (blue circles) BaTiO3 due to uniaxial mechanical compressive stress. This is particularly significant for ferroelectric thin films, where in-plane strains are large enough to generate new phases [3] and induce ferroelectricity [4], as well as sensors, transducers, and actuators, where mechanical preloads can be significant. From an expansion of the free elastic Gibbs energy density in terms of polarization (LandauGinsburg-Devonshire formalism) an expression for the shift of the Curie point and CurieWeiss temperature for a single tetragonal ferroelectric domain can be found ( ) [ ( ) ] (1) where is the permittivity of free space, C is the Curie constant, Q12 and Q11 are components of the electrostriction tensor, and X is the extensional stress. Interestingly, from Cshear stresses. An additional consequence of the stress-dependent phase transition behavior in ferroelectrics is that the first Landau coefficient in the Gibbs free energy, i.e., the linear dielectric stiffness, becomes stress dependent. Typically, this coefficient is defined as ( )⁄ (2) which assumes that is independent of both electric field and stress. An extension of this classical definition is proposed to account for the effects of stress on the free energy density of a ferroelectric domain, such that (3) 24 Ceramics Group where is the applied stress and stress. is a constant that accounts for the dependence of on Additional experimental and analytical work is required to determine the form and the magnitudes of . A primary experimental difficultly is the measurement of temperature dependent dielectric behavior with a stress applied parallel to the polarization direction. An increasing temperature results in the decrease of the ferroelastic coercive stress, which leads to eventual switching of the polarization perpendicular to the applied stress. Planned future investigations include the inclusion of Equation (3) into a FEM-based phase field model to study the effects on domain wall translation. References: [1] Takagi, Y, E Sawaguchi, and T Akioka, On the Effect of Mechanical Stress upon the Permittivity of Barium Titanate. Journal of the Physical Society of Japan, 3(4): 270-271 (1948) [2] Suchanicz, J, et al., Uniaxial Pressure Effect on the Dielectric Properties of the BaTiO3 Single Crystals. Ferroelectrics, 366(1): 3-10 (2008) [3] Zeches, RJ, et al., A Strain-Driven Morphotropic Phase Boundary in BiFeO3. Science, 326(5955): 977-980 (2009) [4] Haeni, JH, et al., Room-temperature ferroelectricity in strained SrTiO3. Nature, 430(7001): 758761 (2004) Ceramics Group 25 Electronic Materials The department Electronic Materials 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 electronics. Three major research topics are presently addressed: Electronic and optoelectronic properties of organic semiconductors. 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. Beside 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. 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 (phos26 Electronic Material Properties phors) 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:Eu2+ 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. Staff Members Head Prof. Dr.-Ing. Heinz von Seggern Research Associates Dr. Graham Appleby Dr.-Ing. Andrea Gassmann Dr. Joachim Hillenbrand Dr. Christian Melzer Dr. Chandra Suman Dr. Sergey V. Yampolskii Dr. Sergej Zhukov 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. Lorenz Kehrer Dipl.-Phys. Oliver Ottinger M. Sc. Oili Pekkola Dipl.-Phys. Jörg Schütrumpf Dipl.-Ing. Katja Stegmaier Dipl.-Ing. Tobias Könyves-Toth M. Sc. Dan Walker Diploma Students Paul Mundt Elmar Kersting Lars Riekehr Tobias Weiher Stefan Winter Guest Scientists Prof. Ivan H. Bechtold Dr. Gregorio Coutò Faria Prof. Dr. Sergei Fedosov Prof. Dr. Lucas F. Santos Chung-Hwa Wang Electronic Material Properties 27 Research Projects Fatigue of organic semiconductor components (SFB (DFG), 2003-2014) Phenomenological modelling of bipolar carrier transport in organic semiconducting devices under special consideration of injection, transport and recombination phenomena (SFB (DFG), 2003-2014) Polarization and charge in electrically fatigued ferroelectrics (SFB (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) Tetracene based materials for OFET and OLED applications (Förderkennzeichen: Patent Portfolio “Organic semiconductors”, IPB, 2008-2011) Charge carrier injection and transport in doped organic light-emitting diodes (TOPAS, BMBF-OSRAM OS, 2009-2011) Influence of oxygen and water on the optical properties of the x-ray storage phosphor CsBr:Eu2+ (DFG, 2009-2011) Development of fibre-based organic semiconductor devices for textile applications (LUMOLED, BMBF/ VDI/ VDE/ IT, 2010-2012) Publications G. A. Appleby, J. Zimmermann, S. Hesse, and H. von Seggern, Photoluminescence and photostimulated luminescence of oxygen impurities in CsBr, JOURNAL OF APPLIED PHYSICS 109 (2011), 013507. S. Zhukov, S. Fedosov, H. von Seggern, Piezoelectrets from sandwiched porous polytetrafluoroethylene (ePTFE) films: influence of porosity and geometry on charging properties, J. Phys. D: Appl. Phys. 44 (2011), 105501. S. Zhukov, S. Fedosov, H. von Seggern, Importance of geometry and breakdown field on the piezoelectric d33 coefficient of corona charged ferroelectret sandwiches, JOURNAL OF PHYSICS D: APPLIED PHYSICS 44 (2011), 105501. C. Koughia, A. Edgar, C. R. Varoy, G. Okada, H. von Seggern, G. Belev, C. Y. Kim, R. Sammynaiken, S. Kasap, Samarium-doped fluorochlorozirconate glass-ceramics as redemitting x-ray phosphors, JOURNAL OF THE AMERICAN CERAMIC SOCIETY 94 (2011), 543-550. G. A. Appleby, P. Kroeber, J. Zimmermann, and H. von Seggern, Influence of oxygen doping and hydration on photostimulated luminescence of CsBr and CsBr:Eu2+, J. Appl. Phys. 109 (2011), 073510. 28 Electronic Material Properties S. V. Yampolskii, Y. A. Genenko, C. Melzer, H. von Seggern, Self-consistent model of unipolar transport in organic semiconductor diodes: Accounting for a realistic density-of-states distribution, JOURNAL OF APPLIED PHYSICS 109 (2011), 073722. E. J. Feldmeier, C. Melzer, Multiple colour emission from an organic light-emitting transistor, ORGANIC ELECTRONICS 12 (2011) 1166–1169. C. Koughia, G. Okada, D. Tonchev, S. Kasap, A. Edgar, C. R. Varoy, H. von Seggern, Optical and selected thermal properties of samarium-doped fluorochlorozirconate (FCZ) glass-ceramics: Formation and growth of BaCl2 nanocrystals in FCZ glass-ceramics, JOURNAL OF NONCRYSTALLINE SOLIDS 357 (2011), 2272-2277. K. Stegmaier, A. Fleissner, H. Janning, S. Yampolskii, C. Melzer, H. von Seggern, Influence of electrical fatigue on hole transport in poly(p-phenylenevinylene)-based organic lightemitting diodes, JOURNAL OF APPLIED PHYSICS 110 (2011) 034507. G. C. Faria, R. M. Faria, E. R. deAzevedo, H. von Seggern, Temperature dependence of the drift mobility of poly(9,9'-dioctylfluorene-co-benzothiadiazole)-based thin-film devices, JOURNAL OF PHYSICAL CHEMISTRY C 115 (2011), 25479-25483. Electronic Material Properties 29 Oxygen-related threshold voltage shifts in thiophene-based field-effect transistors Lorenz A. Kehrer, Christian Melzer and Heinz von Seggern 10 -4 10 -4 10 -5 10 -5 10 -6 10 -6 10 -7 10 -7 10 -8 10 -9 10 -8 10 -9 10 -10 (1) Dark (2) Illuminated (3) Illuminated (4) Dark (5) Illuminated (6) Dark -40 -30 -20 -10 a) ID (A) ID (A) Printed organic electronic circuits have a great potential as low cost electronics for everyday use, e.g., in radio frequency identification tags. One of the most investigated and promising material for such application is poly(3-hexylthiophene) (P3HT) which exhibits electrical instabilities caused by gases, humidity or light. Such instabilities may be useful for sensing applications, but hamper the reliability of organic devices. E.g. illuminating top-gated P3HT-based p-type organic field-effect transistors (OFETs) in electron accumulation mode in the visible spectral range results in a substantial threshold voltage shift Vth and an increase in the off-current by about three orders of magnitudes. Both phenomena require the presence of oxygen and are persistent for days at room temperature. The origin of this long-lasting instability is attributed to traps which are induced in the semiconductor by oxygen incorporation creating a charge-transfer-complex (CTC) of oxygen and P3HT [1]. The illumination of the devices in electron accumulation with wavelengths in the range of the fundamental absorption of P3HT (< 650 nm) is sufficient for an optical filling of those traps by electrons. This electron trapping shifts the threshold voltage and increases the doping level by accumulation of charge compensating holes. The optically induced instabilities of P3HT-based organic FETs are illustrated in figure 1. 0 VG (V) 10 20 30 10 40 -10 (1) Dark (2) Illuminated (3) Illuminated (4) Dark (5) Illuminated (6) Dark -40 -30 -20 -10 b) 0 10 20 30 40 VG - Vth (V) Figure 1: a) Forward and backward sweeps of transfer curves of the OFETs recorded at VD = -20 V with and without white-light illumination. The OFETs exhibit a W/L ratio of 1000 and were exposed to oxygen by storing them in ambient conditions before measuring the transfer curves in a nitrogen-filled glovebox. Under illumination in electron accumulation an essential shift of the threshold voltage can be observed. b) Forward sweeps of the same transfer curves where the applied gate voltages have been corrected by the respective threshold voltages changes. Figure 1a shows that the P3HT-based thin-film transistors are stable in the dark (curve 1) and under illumination as long as the transistor is operated in hole accumulation, i.e, at negative gate bias (curve 2). By applying positive gate biases (electron accumulation) and by additionally illuminating the devices with visible light, the transfer characteristics start to alter for successive measurement cycles (curve 3). In particular two effects are identified which can be associated to the aforementioned instability mechanism: The off-current increases by about three orders of magnitude and the drain current shifts to positive gate voltages. These effects are stable during the following measurements performed in the dark (curve 4). The slight decrease in the off-current is due to the missing photo current in the 30 Electronic Material Properties dark (curve 4). A second sweep under illumination (curve 5) creates the same changes as the first sweep under illumination, but the impact on the change of the device characteristics is much weaker. While the first sweep under illumination shifted the threshold voltage from -3.8 V to +15.6 V (Vth = 19.4 V), the second illumination step shifts the threshold voltage only from +15.6 V to +17.9 V (Vth = 2.3 V). After four illumination steps the changes are already saturated. In figure 1b the same transfer characteristics are replotted as a function of the effective gate voltage (VG-Vth) where VG has been corrected by the respective threshold voltage Vth obtained for the individual cycles. The result demonstrates that the only effects observed are a light-induced threshold voltage shift and an increase in the off-current while the resulting field-effect mobility remains unchanged. The drain currents are identical in the on-regime (VG-Vth<0), but differ by about three two orders of magnitude in the off-regime (VG-Vth>0). The fact that mainly a positive threshold voltage shift is induced suggests that trapped electrons are introduced by the optical treatment at positive gate biases. Since negative charges in the bulk will be compensated by mobile holes a p-doping of the P3HT results thereby increasing the off-current of the transistor. The long lasting decay of the doping also suggests that a fast recombination of both carrier species does not occur. By storing identical transistors under different environmental conditions, we investigated the origin of the remanent charge carriers. Therefore two sets of transistors were processed with two different 500 nm thick insulators each consisting of Polymethylmethacrylate (PMMA) and PIC01, an insulator provided by PolyIC, respectively. One set was stored under ambient conditions and the second set was stored under oxygen-free conditions inside a nitrogen-filled glovebox. After one week all devices were characterized in the glovebox to avoid any additional oxygen contamination. Figure 2 illustrates the evolution of the threshold voltages on the storage conditions. At first, Vth is determined in the dark for the two storage conditions in order to avoid additional trapping. In this initial state the devices with PMMA show a positive threshold voltage and the devices with PIC01 show a negative one. In both cases the absolute values of |Vth| are smaller than 5 V. Since this behavior was observed for all studied transistors it can be concluded that the utilized insulator is partially responsible for the threshold voltage of the individual P3HT-based devices. After four measuring cycles of the transfer characteristic under illumination a positive threshold voltage shift of more than 10 V has been observed for all transistors stored under ambient conditions and a weaker threshold shift of < 5 V for all transistors stored in the nitrogen atmosphere. From those results it seems reasonable to assign the shift of Vth to the already mentioned oxygen-induced charge-transfer states, whose amount is reduced after long term storage in the glovebox due to diffusion of oxygen out of the device [2]. In field-effect transistors the amount of trapped charges ntr can be estimated from the areal capacitance of the gate dielectric Ĉ and the threshold voltage shift Vth according to the following equations: Cˆ Vth and Cˆ 0 ntr d e where all the used quantities assume there common meaning. With a gate insulator thickness d = 500 nm and a dielectric constant = 3.5 the areal capacitance is calculated to 6.2∙10-9 F/cm². Taking the observed threshold voltage shift of about Vth = 10 V we can determine a trapped or remanent charge density of 4 1011 cm-2 localized at the P3HToxygen charge-transfer complexes at the dielectric/ P3HT interface. Electronic Material Properties 31 Insulator / Storage atmosphere 20 PIC01 / Ambient PIC01 / Nitrogen PMMA / Ambient PMMA / Nitrogen 15 Vth (V) 10 5 0 te d na mi I l lu (3) 60 0s @ mi I l lu (2) (4) na 75 te d e tat ls tia Ini (1 ) °C Treatment steps -5 Figure 2: Vth of the differently stored transistors with PMMA and PIC01 as insulating materials as a function of the following treatments. (1): after exposure to ambient conditions and nitrogen in the nitrogen filled glovebox. (2): after four illumination steps under nitrogen atmosphere directly following (1). (3): after a heating step of 600 s at 75 °C directly following (2). (4): after four additional illumination steps in nitrogen directly following (3). All treatments were performed within one hour in the nitrogen filled glovebox. By increasing the temperature the temporal decay of the optically-induced threshold voltage shift can be accelerated. Keeping the devices with the two different gate insulators for 600 s at 75 °C is sufficient to completely remove the light-induced threshold voltage shifts. As presented in figure 2 a heating step at 75 °C for 600 s in an oxygen-free atmosphere shifts Vth back to its initial value independent on the storage conditions or the gate insulator. After having released the trapped electrons and thereby removing the induced shift of the threshold voltage, it is possible to recharge the devices by an illumination step in the glovebox. This is an indication of the long term stability of the P3HT-oxygen complexes in the system and it demonstrates that these complexes can be charged and discharges reversibly. We want to clearly point out that the relaxation of the optically induced threshold voltage shift itself takes a few days and is much faster than the diffusion of oxygen out of the device, which takes a couple of weeks [2]. At elevated temperatures, e.g. 75 °C, it requires hours to reduce the saturation value of the possible threshold voltage back to its initial value. Therefore the discharging of the relevant traps is significantly shorter than the loss of trap sites by oxygen diffusion out of the active layer. For practical applications, like P3HT-based logic elements it has to be stated that the discussed oxygen-induced instability is relevant cases where the FETs are held in the offstate in ambient conditions and under light exposure. Under these operational conditions a substantial electric field exists inside the P3HT layer and illumination leads to the investigated changes in the FET characteristics affecting the functionality of the employed logic circuits. References: [1] M. S. A. Abdou, F. P. Orfino, Y. Son, and S. Holdcroft, Journal of the American Chemical Society, 1997, 119, 4518-4524. [2] L. A. Kehrer, S. Winter, R. Fischer, C. Melzer, and H. von Seggern, Synthetic Metals, 2012, 161, 2558 – 2561. 32 Electronic Material Properties Influence of oxygen and water on photostimulated luminescence of CsBr and CsBr:Eu2+ J. Zimmermann, G. A. Appleby, P. Kroeber, and H. von Seggern CsBr:Eu2+ storage-phosphor is of interest for radiography applications as it can be grown in the form of needle structured imaging with higher spatial resolution compared to commercial X-ray imaging plates. In a storage phosphor irradiation generates electron-hole pairs, where the electrons are stored as metastable F-centers and the holes are trapped adjacent to the Eu2+-ions. The spatial distribution of the filled traps represents a latent image of the imaging object. The x-ray image is read out by photostimulation with visible light which frees the electrons from the F-centers leading to recombination with the trapped holes. The recombination energy is transferred to Eu2+-ions which emit the so called photostimulated luminescence (PSL) whose intensity as a function of the spatial location of the exciting laser beam forms the radiograph. Oxygen is a natural impurity in CsBr and it contributes to the PSL-process. Water influences the PSL yield drastically if Eu2+ is involved. Enhancement of the PSL yield of CsBr:Eu2+ have been observed following simple hydration of CsBr:Eu2+ at room temperature, which can increase the PSL efficiency of a dry sample by up to a factor of 25 [1]. It is proposed that the Eu2+ ions are not attracting holes without water, which could be explained by a missing compensation for the divalent Europium ion e. g. by O2- or a Cs-vacancy adjacent to Eu2+, and thus the coulombic repulsion of electrons. We investigated the effect of oxygen concentration on the PL and PSL properties of CsBr:O2and CsBr:Eu2+,O2-, as well as the effect of hydration on these materials. CsBr purified from oxygen were doped with CsOH.xH2O and in a second step hydrogen was removed by calcinating the resultant CsBr:OH- together with NH4Br. CsBr:Eu2+,O2- samples were prepared by doping CsBr:O2- with 0.5 mol% EuBr2 or EuBr3.xH2O and dried, sintered and annealed. To study the effects of hydration on CsBr:Eu2+,O2-, samples were exposed to an atmosphere of 99% relative humidity for hydration times of 10 to 60 minutes. To investigate the stability of the PSL enhanced CsBr:Eu2+,O2- (hereafter referred to as CsBr.xH2O:Eu2+,O2-) powdered samples were exposed to different annealing temperatures. Reduced CsBr and CsBr:O2- show a single Gaussian PSL-emission peak at 460 nm (Fig. 1) as reported in [2] for low oxygen concentrations. CsBr:O2- with oxygen concentrations of 0.04 to 0.05 mol% show a second peak at 379 nm which increases in intensity with increasing oxygen concentration. At oxygen concentrations larger than 0.1 mol%, this peak completely dominates the PSL emission. It arises from the CsBr matrix as it is also seen in the PL spectra of reduced CsBr in [2]. With low oxygen concentrations, the PSL process leads to emission from the luminescent oxygen ions. In the case of high oxygen concentrations the formation of oxygen agglomerates are considered to take place which are no longer stimulable by the electron hole decay. Therefore this energy is transferred to the CsBr lattice, stimulating luminescence from the lattice rather than from the oxygen ions themselves. Electronic Material Properties 33 Fig. 1 PSL emission spectra for powdered CsBr:O2- samples following irradiation at 300 K and stimulated at 690 nm. Fig. 2 F-center absorption spectra for powdered CsBr:O2samples following irradiation at 300 K. Inset: FWHM of these absorption spectra. Absorption measurements of x-irradiated CsBr:O2- (Fig. 2) consist of the well-known Fcenter of CsBr at 690 nm. It can be seen that the F-center concentration increases up to a concentration of 1.00 mol% oxygen, and then decreases with higher concentrations. The incorporated divalent oxygen impurities are charge compensated in the monovalent CsBr matrix by bromide-vacancies, which form F-centers during irradiation. The absorption of these oxygen generated F-centers is perturbed by the nearby oxygen ions which leads to the broadening of the spectra indicated by the increasing FWHM of the spectra with increasing oxygen concentration (inset to Fig. 2). With the relatively high oxygen concentration of 5.00 mol%, both the F-center concentration and the FWHM decreases, which we attribute to agglomeration. As prepared dry powdered samples of CsBr:Eu2+,O2- are yellow in color and exhibit only weak PSL. There is no significant influence of oxygen concentration on the PSL emission intensity for dry samples. After exposure to air for 5 min to 60 min, the samples become white while the PSL intensity remains unchanged. Following hydration for 10 min to 60 min the PSL intensity increases by up to a factor of 25 [1]. PSL emission intensity of CsBr:Eu2+ and CsBr:Eu2+,O2- increase strong following hydration for 40 min, while the effect of oxygen concentration on the PSL intensity of CsBr:Eu2+,O2- is that the PSL intensity is slightly higher with concentrations up to 0.05 mol%, and decreases with increasing oxygen concentrations (Fig. 3). Fig. 3 PSL emission intensity of powder and pellet samples of CsBr.H2O:Eu2+,O2- following hydration and then annealing for 30 min at various temperatures. The dashed line indicates the PSL intensity of the samples prior to hydration. All data was recorded at 300 K. 34 Fig. 4 PL emission intensity of Eu2+ excited at 254 nm and the CsBr matrix emission excited at 200 nm for CsBr.H2O:Eu2+,O2- following hydration and then annealing at various temperatures. The dotted line indicates the PL intensity of Eu2+ prior to hydration while the dashed line indicates the PL intensity of the CsBr matrix prior to hydration. All data was recorded at 300 K. Electronic Material Properties The increase in PSL emission intensity in samples with up to 0.05 mol% oxygen doping most likely is due to formation of oxygen correlated anion vacancies which ease the formation of F-centers during x-irradiation. Despite the increase in F-center generation up to 1.00 mol% of oxygen as shown in Fig. 2 the anion vacancies density created by the 0.05 mol% seem to be sufficient for the normally applied x-ray doses. With higher oxygen concentrations the subsequent decrease in PSL emission is probably caused by competition between O2- and Eu2+ luminescence centers following photostimulation. In both cases, oxygen free and oxygen containing CsBr:Eu the water molecules enhance the PSL sensitivity, but they can be removed at higher temperatures. Fig. 4 shows the evolution of the 379 nm intrinsic emission of the CsBr matrix during annealing (stimulated at 200 nm). The loss of PL and PSL emission from Eu2+ following high temperature annealing is considered to be initially due to the driving out of the tightly bound water molecules which form (Eu2+-H2O)-complexes whereat H2O sits in an Cs vacancy adjacent to Eu2+ [3], and finally due to the migration and agglomeration of the now highly mobile Eu2+-ions in which concentration quenching of luminescence occurs. This removal of a homogeneous distribution of Eu2+-ions from the matrix is also likely to be the cause of the reappearance of the luminescence emission from the CsBr matrix. Further hydration of these annealed CsBr.xH2O:Eu2+,O2- samples is unable to restore the PSL activity, indicating that the thermal annealing and associated quenching of PSL emission in CsBr.H2O:Eu2+,O2- is an irreversible process. It can be concluded that strong PSL from CsBr:Eu2+,O2- samples is only observable following exposure to moisture, probably due to the creation of dipoles of Eu2+ and a Cs vacancy with a trapped H2O molecule. It was demonstrated that oxygen doping in CsBr:Eu2+ and subsequent hydration initially improves the PSL efficiency by a small factor due to an increase in F-center concentration, however, oxygen of higher concentratian compete with the Eu2+ and ultimately decrease the PSL considerably. References: [1] G. A. Appleby, J. Zimmermann, S. Hesse, O. Karg, and H. von Seggern, J. Appl. Phys. 105, 2009, 073511. [2] G. A. Appleby, J. Zimmermann, S. Hesse, and H. von Seggern, J. Appl. Phys., 109, 2011, 013507. [3] H. Vrielinck, F. Loncke, J.-P. Tahon, P. Leblans, P. Matthys, F. Callens, Phys. Rev. B 83, 2011, 054102. Electronic Material Properties 35 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, electron diffraction, ion scattering, 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. 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. 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. 36 Surface Science 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. Feng Chen Dr. Gennady Cherkashinin Dr. Lucangelo Dimesso Dr. Xianjin Feng Dr. René Hausbrand Dr. Alexander Issanin Dr. Susanne Jacke PD Dr. Bernhard Kaiser Apl. Prof. Dr. Andreas Klein Dr. Quanbao Ma Dr. Thomas Mayer Dr. Robert Schafranek Dr. Hermann-Josef Schimper Dr. Krishnakumar Velappan Technical Personnel Vitaliy Bezkorovaynyy Dipl. Ing. Erich Golusda Kerstin Lakus-Wollny Dr. Lorenz Nedelmann Andreas Swirschuk Christina Spanheimer Secretaries Marga Lang PhD Students Tobias Adler Alireza Barati Thorsten Bayer Dirk Becker Andreas Decker Murugasen Eswaran Eduard Feldmeier Dominic Fertig Anne Fuchs Jürgen Gassmann Cosmina Ghinea Corinna Hein René Hock Johannes Türck Jürgen Ziegler Mareike Hohmann Shunyi Li Julia Maibach Eric Mankel Andreas Naumann Thi Thanh Dung Nguyen Karsten Rachut Judith Schaffner Stefan Schmid Anja Schneikart Andrè Schwöbel Sebastian Siol André Wachau Karsten Rachut Diploma Students Aiko Bünting Jan Morasch Markus Motzko Silvia Vestweber Mirko Weidner Guests Jenna Curry Jonas Deuermeier Gaku Imamura Dr. Mikhail V. Lebedev Lauren Stützman Surface Science 37 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) Transparent organic phosphorescent devices for application in lighting systems (Osram 2009-2011) Gradients in Cu(In,Ga)Se2 thin film solar cells (BMBF 2009-2012) P-I-N solar cells with alternative highly-absorbing semiconductors (BMBF 2010-2013) LOEWE Schwerpunkt AdRIA (LOEWE-Hessen: 2008-2011) Nanostruktursysteme zur Licht-induzierten Wasserstoffentwicklung („H2-NanoSolar“, BMBF 2009-2012) Synthese, Charakterisierung und Testung von Katalysatoren für die regenerative Erzeugung von Wasserstoff („H2ECO2“, Evonik 2010-2012) Electrochemistry of Surfaces (CSI-DFG, 2008-2012) Inorganic-organic hybride materials for photovoltaic application (BMBF 2008-2011) Organic Photovoltaics for Integrated Energy Supply (BMBF 2008-2011) Morphology and Electronic Structure of Organic/Organic and Organic/Metal-Oxid Hybrid Systems, Innovation Lab GmbH Heidelberg of the BMBF leading edge cluster Forum Organic Electronics (BMBF 2009-2012) n-i-p CdTe Hochleistungs-Dünnschichtsolarzellen: Wissensbasierte Materialien, Bauelemente und Präparation (BMU 2008-2011) Optimierung der Elektrochemie für Elektromobilität – Verbund Süd (BMBF 2009-2011) Funktionsmaterialien und Materialanalytik zu Lithium-Hochleistungsbatterien (2009-2011) Hybridstrukturen aus Phosphoolivinen des Typs LiMPO4 mit C-Nanofilamenten für LiIonen-Batterien, SPP Nanomat (DFG 2008-2012) Insertionsverbindungen und Elektrolyte für Lithium-Ionenbatterien Anwendungen, Verbundvorhaben LISA (BMBF 2008-2011) für solare Grenzflächen und dünne Schichten von Ionenleitern: elektronische Struktur, elektrochemische Potentiale, Defektbildung und Degradationsmechanismen, SFB 595-A3 (DFG 2003-2014) Herstellung und Charakterisierung von Li-Ionen Dünnschichtbatterien SFB-D5 (DFG 20072011) 9D-Sense Autonomous Nine Degrees of Freedom Sensor Module (BMBF/VDI 2011 – 2014) Solid State Lithium Batterien mit organischen Kathoden (Novaled 2011 – 2014) 38 Surface Science Publications Decker, Andreas Suraru, Sabin-Lucian Rubio-Pons, Oscar Mankel, Eric Bockstedte, Michel Thoss, Michael Wuerthner, Frank Mayer, Thomas Jaegermann, Wolfram; Toward Functional Inorganic/Organic Hybrids: Phenoxy-allyl-PTCDI Synthesis, Experimentally and Theoretically Determined Properties of the Isolated Molecule, Layer Characteristics, and the Interface Formation of Phenoxy-allyl-PTCDI on Si(111):H Determined by SXPS and DFT JOURNAL OF PHYSICAL CHEMISTRY C, Vol.115, 21139-21150 DI 10.1021/jp205294h, NOV 3 2011 Schneider, Joerg J. Khanderi, Jayaprakash Popp, Alexander Engstler, Joerg Tempel, Hermann Sarapulova, Angelina Bramnik, Natalia N. Mikhailova, Daria Ehrenberg, Helmut Schmitt, Ljubomira A. Dimesso, Lucangelo Foerster, Christoph Jaegermann, Wolfram; Hybrid Architectures from 3D Aligned Arrays of Multiwall Carbon Nanotubes and Nanoparticulate LiCoPO(4): Synthesis, Properties and Evaluation of Their Electrochemical Performance as Cathode Materials in Lithium Ion Batteries; EUROPEAN JOURNAL OF INORGANIC CHEMISTRY Vol. 28, 4349-4359 DI 10.1002/ejic.201100217, OCT 2011 Schaffner, Judith Motzko, Markus Tueschen, Alexander Swirschuk, Andreas Schimper, Hermann-Josef Klein, Andreas Modes, Thomas Zywitzki, Olaf Jaegermann, Wolfram; 12% efficient CdTe/CdS thin film solar cells deposited by low-temperature close space sublimation JOURNAL OF APPLIED PHYSICS, Vol. 110, 064508, DI 10.1063/1.3639291, SEP 15 2011 Krishnakumar, V. Han, J. Klein, A. Jaegermann, W., CdTe thin film solar cells with reduced CdS film thickness THIN SOLID FILMS, Vol.519, 7138-7141, DI 10.1016/j.tsf. 2010.12.118, AUG 31 2011 Zakutayev, Andriy Tate, Janet Xie, Sujing Gibbons, Brady J. Platt, Heather A. S. Keszler, Douglas A. Barati, Alireza Klein, Andreas Jaegermann, Wolfram, Interdiffusion at the BaCuSeF/ZnTe interface, THIN SOLID FILMS, Vol. 519, 7369-7373, DI 10.1016/j.tsf.2010.12.125, AUG 31 2011 Schaffner, J. Feldmeier, E. Swirschuk, A. Schimper, H. -J. Klein, A. Jaegermann, W., Influence of substrate temperature, growth rate and TCO substrate on the properties of CSS deposited CdS thin films, THIN SOLID FILMS, Vol. 519, 7556-7559, DI 10.1016/j.tsf.2010. 12.181, AUG 31 2011 Feldmeier, E. M. Fuchs, A. Schaffner, J. Schimper, H. -J. Klein, A. Jaegermann, W., Comparison between the structural, morphological and optical properties of CdS layers prepared by Close Space Sublimation and RF magnetron sputtering for CdTe solar cells THIN SOLID FILMS, Vol. 519, 7596-7599, DI 10.1016/j.tsf.2011.01.088, AUG 31 2011 Dimesso, Lucangelo Spanheimer, Christina Jacke, Susanne Jaegermann, Wolfram, Synthesis and characterization of three-dimensional carbon foams-LiFePO(4) composites JOURNAL OF POWER SOURCES, Vol.196, 6729-6734, DI 10.1016/j.jpowsour.2010. 11.015, AUG 15 2011 Jacke, S. Song, J. Dimesso, L. Broetz, J. Becker, D. Jaegermann, W., Temperature dependent phosphorous oxynitride growth for all-solid-state batteries JOURNAL OF POWER SOURCES, Vol. 196, 6911-6914, DI 10.1016/j.jpowsour.2010.12.022, AUG 15 2011 Surface Science 39 Dimesso, Lucangelo Spanheimer, Christina Jacke, Susanne Jaegermann, Wolfram, Synthesis and characterization of LiFePO(4)/3-dimensional carbon nanostructure composites as possible cathode materials for Li-ion batteries IONICS, Vol. 17, 429-435, DI 10.1007/s11581-011-0521-y, JUN 2011 Han, Junfeng Liao, Cheng Jiang, Tao Spanheimer, C. Haindl, G. Fu, Ganhua Krishnakumar, V. Zhao, Kui Klein, A. Jaegermann, W., An optimized multilayer structure of CdS layer for CdTe solar cells application JOURNAL OF ALLOYS AND COMPOUNDS, Vol. 509, 5285-5289, DI 10.1016/j.jallcom.2010.12.085, APR 28 2011 Dimesso, Lucangelo Jacke, Susanne Spanheimer, Christina Jaegermann, Wolfram, Investigation on 3-dimensional carbon foams/LiFePO(4) composites as function of the annealing time under inert atmosphere, JOURNAL OF ALLOYS AND COMPOUNDS Vol. 509, 3777-3782, DI 10.1016/j.jallcom.2010.12.187, MAR 3 2011 Junfeng Han Spanheimer, C. Haindl, G. Ganhua Fu Krishnakumar, V. Schaffner, J. Chunjie Fan Kui Zhao Klein, A. Jaegermann, W., Optimized chemical bath deposited CdS layers for the improvement of CdTe solar cellsSolar Energy Materials and Solar Cells, Vol 95, 816-820, DI 10.1016/j.solmat.2010.10.027, March 2011 Jie Song Jacke, S. Becker, D. Hausbrand, R. Jaegermann, W.; Stabilization of Thin Film LiCoO 2 Electrode by LiPON Coating Electrochemical and Solid-State Letters, Vol. 14, DI 10.1149/1.3511772, Feb. 2011 Klein, Andreas Siepchen, Bastian Spaeth, Bettina Mankel, Eric Mayer, Thomas Jaegermann, Wolfram; Resonant photoemission shake-up satellites from semiconductors with shallow 3d and 4d core levels; PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, Vol. 248, 309-313, DI 10.1002/pssb.201046272, FEB 2011 Han, Junfeng Liao, Cheng Jiang, Tao Fu, Ganhua Krishnakumar, V. Spanheimer, C. Haindl, G. Zhao, Kui Klein, A. Jaegermann, W., Annealing effects on the chemical deposited CdS films and the electrical properties of CdS/CdTe solar cells, MATERIALS RESEARCH BULLETIN, Vol. 46, 194-198, DI 10.1016/j.materresbull.2010.11.014, FEB 2011 Song, Jie Jacke, Susanne Cherkashinin, Gennady Schmid, Stefan Dong, Quanfeng Hausbrand, Rene Jaegermann, Wolfram, Valence Band Offsets of LiPON/LiCoO(2) HeteroInterfaces Determined by X-ray Photoelectron Spectroscopy, ELECTROCHEMICAL AND SOLID STATE LETTERS, Vol. 14, A189-A191, DI 10.1149/2.006112esl Schafranek, Robert Li, Shunyi Chen, Feng Wu, Wenbin Klein, Andreas, PbTiO$_3$/SrTiO$_3$ interface: Energy band alignment and its relation to the limits of Fermi level variation, Phys. Rev. D, Vol. 84, 045317, doi/10.1103/PhysRevB.84.045317 , 2011 Jul Pashchanka, Mikhail; Hoffmann, Rudolf C.; Gurlo, Aleksander; Swarbrick, Janine C.; Khanderi, Jayaprakash; Engstler, Joerg; Issanin, Alexander; Schneider, Joerg J., A molecular approach to Cu doped ZnO nanorods with tunable dopant content DALTON TRANSACTIONS, Vol. 40, 4307-4314, DOI: 10.1039/c0dt01567a, 2011 Schneider, Joerg J.; Hoffmann, Rudolf C.; Issanin, Alexander; Dilfer, Stefan, Zirconia and hafnia films from single source molecular precursor compounds: Synthesis, characterization and insulating properties of potential high k-dielectrics MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS, Vol. 176, 965-971, DOI: 10.1016/j.mseb.2011.05.024, AUG 15 2011 40 Surface Science Hoffmann, Rudolf C.; Differ, Stefan; Issanin, Alexander; Schneider, Joerg J., Field-effect transistor performance of zinc oxide thin films derived from molecular based alkoxyalkyl zinc compounds, PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, Vol. 208, 1708-1713, DOI: 10.1002/pssa.201026694, JUL 2011 C. Pusch, H. Hoche, C. Berger, R. Riedel, E. Ionescu, A. Klein, Influence of the PVD sputtering method on structural characteristics of SiCN-coatings — Comparison of RF, DC and HiPIMS sputtering and target configurations, Surface & Coatings Technology 205, S119 (2011); doi: 10.1016/j.surfcoat.2011.04.095 J Pohl, A Klein, K Albe, Role of copper interstitials in CuInSe2: First-principles calculations Phys. Rev. B 84, 121201(R) (2011); doi: 10.1103/PhysRevB.84.121201 M.V. Hohmann, P. Ágoston, A. Wachau, T.J.M. Bayer, J. Brötz, K. Albe, A. Klein, Orientation Dependent Ionization Potential of In2O3: A Natural Source for Inhomogeneous Barrier Formation at Electrode Interfaces in Organic Electronics, J. Phys.: Cond. Mat. 23, 334203 (2011); doi: 10.1088/0953-8984/23/33/334203 S. Li, C. Ghinea, T. Bayer, M. Motzko, R. Schafranek, A. Klein, Electrical properties of (Ba,Sr)TiO3 thin films with Pt and ITO electrodes: Dielectric and rectifying behaviour J. Phys.: Cond. Mat. 23, 334202 (2011); doi: 10.1088/0953-8984/23/33/334202 F. Chen, R. Schafranek, W. Wu, A. Klein, Reduction induced Fermi level pinning at the interfaces between Pb(Zr,Ti)O3 and Pt, Cu and Ag metal electrodes, J. Phys. D: Appl. Phys. 44, 255301 (2011); doi:10.1088/0022-3727/44/25/255301. J. Deuermeier, J. Gassmann, J. Brötz, A. Klein, Reactive magnetron sputtering of Cu2O: Dependence on oxygen pressure and interface formation with ITO, J. Appl. Phys., Vol. 111, 113704 (2011); doi:10.1063/1.3592981 M.I. Ahmad, C. Fasel, T. Mayer, S.S. Bhattacharya, H. Hahn, High temperature stability of nanocrystalline anatase powders prepared by chemical vapour synthesis under varying process parameters,Applied Surface Science, Vol. 257, 6761-6767, DOI: 10.1016/j.apsusc.2011.02.121, MAY 15 2011 S. Schaefer, A. Petersen, T.A. Wagner, R. Kniprath, D. Lingenfelser, A. Zen, T. Kirchartz, B. Zimmermann, U. Wuerfel, X. Feng, T. Mayer, Influence of the indium tin oxide/organic interface on open-circuit voltage, recombination, and cell degradation in organic small-molecule solar cells,PHYSICAL REVIEW B, Vol.: 83, 165311, DOI: 10.1103/PhysRevB.83.165311, APR 16 2011 A. Fuchs, H.-J. Schimper, A. Klein, W. Jaegermann, Photoemission Studies on Undoped SnO2 Buffer Layers for CdTe Thin Film Solar Cells,Energy Procedia, Vol. 10, 149-155, doi:10.1016/S1876-6102(11)02800-1, 2011 Surface Science 41 Investigations on LiMPO4 (M = Fe, Co, Mn) / carbon foams composites as cathode materials for Li-ions battery L. Dimesso, C. Spanheimer, S. Jacke, T.T.D. Nguyen, W. Jaegermann Since the discovery by Padhi [1], lithium iron phosphate (LiFePO4) is a promising cathode material due to its good thermal stability, the relatively low costs for synthesis and low environmental impact [2]. However one of the main drawbacks of olivine LiFePO4 for the commercial application is its low electronic conductivity and low lithium-ion diffusivity across the LiFePO4/FePO4 interface [3] during the charge/discharge processes. The purpose of the investigation is the preparation, characterization and development of new 3Dcomposites as high power cathode materials for Li-ion batteries. Among the new cathode materials, the transition metals containing phosphates (LiMPO4, with M = Fe, Co, Ni, Mn) have gained considerable interest. Improvements in energy per unit area and high-rate discharge capabilities are two of the benefits that may be realized by using 3-D cells. The use of carbon foams has several advantages: (i) they have low specific resistance (400 – 2500 µΩm); (ii) they allow easier assembly of the positive and negative collectors that operate together in the battery; (iii) the porosity of the carbon foam allows a greater infiltration of the electrolyte into the battery leading to a better electrical contact; (iv) many configurations are possible depending on the particular applications. The composites have been prepared by using a Pechini-assisted sol-gel process. Detailed descriptions of the preparation conditions of the composites can be found in [4, 5]. Aqueous solutions containing lithium, metal transitions ions and phosphates have been prepared, heated up to 80°C and kept at that temperature for 2-4 h. The composites were prepared by soaking the commercial foams in the starting aqueous solution. After soaking, the foams were rinsed slightly with water and dried out by heating at 130°C for 24 h in vacuum. The micrographs in Figure 1a-b show the morphological surface of the used foams. In the untreated foam, the porous architecture of the foams with hierarchical pore size distribution in micro-, meso-, and macropore ranges can be clearly recognized (Figure 1a). In the previous work the authors observed the presence of numerous apertures, suggesting that the interior pore system is interlaced and the nanoporous architecture is uniform. While the carbon serves as an electron conductor, the pores, when filled with liquid electrolyte, serve as a source of Li+ ions. Fig. 1: HREM pictures of a) carbon foam as delivered; b) carbon foam - LiFePO4 composites after annealing at 600°C for 0.4 h prepared by soaking 1A 42 1B Surface Science The micrographs of the LiFePO4 / carbon foams composites prepared by soaking and after annealing at 600°C for 15 minutes under nitrogen are shown in Figure 1b (as example). The micrograph shows a very homogeneous coating of the foam surface and consequently a more homogeneous morphology. By soaking, the foam surface is covered by a continuous layer of liquid in which the Li+, Fe2+ and (PO4)3- ions are uniformly distributed. The slow evaporation of the solvent leads to a “uniform” layer on the foam surface. After annealing under nitrogen for 0.4 h, the formation of a uniform layer of crystalline LiFePO 4 can be observed (Figure 1b). Voltage (V) 0.2 I (mA) Fig. 2: a) CV curve recorded for the composites after annealing at T 600°C for 10 h; b) discharge profile at C/25 discharge rate for composite samples that were annealed at T = 600°C for different times 4.0 0.3 3.6 0.1 0.0 st 1ndCycle 2 Cycle rd 3 Cycle th 4 Cycle th 5 Cycle th 6 Cycle -0.1 -0.2 -0.3 2.4 2.8 3.2 3.6 4.0 t = 0.4 h 3.2 t = 10 h 2.8 20 0 40 60 80 100 -1 Specific capacity (mAhg ) Voltage (V) 2A t=5h 2B The voltammetric curves (CV) for the composites annealed at 600°C for 10 h are shown in Figure 2a. At high annealing times (t ≥ 5 h), a slight higher peak voltage separation was observed (0.13V) during the charging and discharging cycles, whereas the first cycle showed a different shape only. This indicates clearly that the electrochemical kinetics was improved by the annealing. One of the possible explanations is the low polarization overpotential leading to higher Li-diffusion rates. This overpotential usually emerges from a combination of Li-diffusion rates and the intrinsic activation barrier of transferring electrons which could be high due to the small size of the particles that is to say to the high interparticle surface. By increasing the annealing time, the growth of the particles is expected that means a lower interparticle surface, consequently a lower energy barrier for the Li-diffusion in the composite. Moreover, the presence of a carbon layer on the LiFePO4 as detected by the XPS analysis could improve the electronic conduction leading possibly to an improvement of the electrochemical processes. The composites have been prepared into electrodes and cycled at different C-rates ranging from C/25 to C/2.5. The discharge profiles in Figure 2b have noticeably curved profiles even at such a low discharge rate of C/25 for t = 0.4 h and t = 10 h respectively. The 3.4 V voltage drops as the cell discharges due to polarization. On the other site, a less curved profile can be observed in the sample annealed for t = 5 h confirming the good quality of the sample. The experimental data of the LiFePO4 / carbon foams composites (Fe chosen as example) showed an enhancement of the electrochemical performance of the LiMPO4 systems (M = Fe, Co, Mn) used as cathode materials. Surface Science 43 References [1] A.K. Padhi, K.S. Nanjundaswamy, J.B. Goodenough, Phospho-olivines as positive-electrode materials for rechargeable lithium batteries, J. Electrochem. Soc. 144 (1997) 1188 [2] D.H. Kim, J. Kim, Synthesis of LiFePO4 nanoparticles and their electrochemical properties, J. Phys. Chem. Solids 68 (2007) 734 [3] A.S. Andersson, B. Kalska, L. Haggstrom, J.O. Thomas, Lithium extraction/insertion in LiFePO4: an X-ray diffraction and Mössbauer spectroscopy study, Solid State Ionics 130 (2000) 41 [4] L. Dimesso, C. Spanheimer, S. Jacke, W. Jaegermann, Synthesis and characterization of 3dimensional carbon foams - LiFePO4 composites, (15th IMLB Special Issue), J. Power Sources, (2011), 196(16), 6729-6734 (doi: 10.1016/j.jpowsour.2010.11.015) [5] L. Dimesso, S. Jacke, C. Spanheimer, W. Jaegermann, Investigation on 3-dimensional carbon/LiFePO4 composites as function of the annealing time under inert atmosphere, J. Alloys Compd. 509 (2011) 3777 - 3782 44 Surface Science Cathode/electrolyte interfaces in Li-ion batteries: a surface science approach R. Hausbrand, D. Becker, J. Song, S. Jacke, G. Cherkashinin, and W. Jaegermann Li-ion batteries are a hot topic of research due to possible applications in the areas of electromobility and micro-electronics. The advantages of Li-ion batteries over conventional batteries are a comparable high energy density, low self-discharge and long life time. Nevertheless, the envisioned applications demand more stable batteries with even better performance, i.e. higher energy density and longer life-time. Lithium-ion batteries consist of two electrodes (negative and positive, also termed anode and cathode) separated by an electrolyte, a phase which conducts (Li-) ions but no electrons. During operation of a Li-ion battery, Li-ions are shuttled from one electrode to the other, passing the electrode/electrolyte interfaces. In many cases, next to the Li-ion transport, side reactions take place at these interfaces and interlayers form, leading to degradation of the battery performance, i.e. less capacity and power capability. Such a side reaction is the oxidation of the electrolyte at the cathode, contributing to the formation of the solid-electrolyte interface (SEI). Principally, the interface between an electrode material and an electrolyte is an interface between a mixed (electron and ion) conductor (electrode) and a pure ion conductor (electrolyte). Interfaces between two conductors (ionic or electronic) are characterized by the presence of an electric contact potential caused by the equilibration of the electrochemical potential of mobile charge carrier species at the interface (see e.g. [1-3]). The contact potential is distributed between any interfacial dipole layer and a space charge region. The alignment of energy levels (for electrons or ions, respectively) at the interface depends on the original positions of the energy levels within the two solids, the position of the chemical potential of the mobile species as well as on the formation of an interfacial dipole layer. Discontinuities and bending of energy levels at interfaces constitute energy barriers for charge carriers. Therefore the energy level alignment and shape of inner electric potential gradient have significant influence on the rate of charge transfer at the interface. The electronic energy level alignment between electrolyte and cathode material is of interest with respect to electron transfer reactions at the interface. In fact, the electronic alignment determines at which charging level of the cathode a hole transfer to the highest occupied molecular orbital (HOMO) becomes possible (see [4]). Thus the stability of the interface is determined by the relative positions of the electronic energy levels at the interface between cathode material and electrolyte. We believe that the determination of the electronic energy level alignment at the interface may also allow insights into the transfer resistance of ions at the interface, as it reflects the contact potential between the two phases (or inner electric potential gradients, respectively). The contact potential and the electronic energy level alignment, as well as the chemical structure of the interface, is principally accessible by a surface science approach, i.e. surface/interface analysis using photoelectron spectroscopy. In such an experiment, the interface is built-up step by step (e.g. by thin film deposition or low temperature adsorption) and analyzed after each step. While this methodology is quite elaborate, requiring integrated ultra-high vacuum (UHV) systems, it offers a wealth of information. Here we report such type of analysis for the interface of the well-known cathode material LiCoO2, once with an amorphous solid electrolyte (LiPON) [5-6] and once with a common solvent species (diethyl carbonate, DEC) [7]. For the experiments, RF-sputtered thin film LiCoO2 cathodes were used as substrate, onto which either LiPON was deposited by RF-sputter deposition or DEC was adsorbed at very low temperature (nitrogen cooled manipulator). In case of LiPON, the investigation was carried out in an integrated UHV-system belonging to the surface science group (DaiSy-Mat), XPS-spectra were recorded using a PHI 5700 spectrometer and monochromatized Al Kα radiation. In case of DEC, Surface Science 45 the experiment was performed using the SoLiAS station at the BESSY II synchrotron facility. All spectra were recorded with a kinetic energy of around 100 eV. When LiPON is deposited onto LiCoO2, its chemical structure differs significantly from the one in the bulk (fig 1, left), while changes at the surface of LiCoO2 remain minor (not shown). At the interface, the amorphous electrolyte is rich in triply bound nitrogen, which is taken as sign for a comparably high Li-ion conductivity in the interfacial layer. Using the binding energy differences between a core level valence band maxima in the bulk for each material and the binding energy difference of the two core levels at the interface, the valence band offset was determined to be 1.15 eV and 0.65 eV for LiPON deposited at room temperature and at 200°C, respectively (fig. 1, right). The dependence of the valence band offset on the deposition temperature can be related to differing valence band edges of the LiPON, edges in the LiPON, which exhibits a different chemical structure when deposited at higher temperature. The data indicate that the interfacial dipole potential is similar for the two deposition temperatures, which may be used in the future to understand the Li-ion transfer resistance at these interfaces in more detail. LiPON LiCoO2 LiCoO2 Anode 1.15 eV at RT EVB Decreasing conductivity Fig. 1: Composition of LiPON (left) and schematic drawing of energy alignment (right) at the LiCoO 2/LiPON interface. Exposure to DEC-vapor leads physisorbed and chemisorbed/reacted species on the surface of LiCoO2. Figure 2 shows the carbon signal after an exposition of 0.5L (left) and after the experiment and subsequent desorption at room temperature. The latter is viewed as signature of the chemisorbed/reacted species. The data thus clearly indicate chemical interaction between DEC and LiCoO2. 3 0.5 L -CH3 3 DesRT 25x10 Intensity [arb. units] -CH215 O = Intensity [arb. units] 20x10 10 -O-C-O5 20 15 10 5 0 0 280 282 284 286 288 290 binding energy [eV] 292 294 296 280 282 284 286 288 290 binding energy [eV] 292 294 296 Fig. 2: SXPS spectra of carbon signal (C1s) after adsorption of DEC (nominally 0,5L, left) and after adsorption of 8L with subsequent desorption at room temperature (right). The latter can be viewed as the signature of chemisorbed and/or reacted species Subsequent exposure leads to an increase in the amount of adsorbed species and to band bending, illustrated in figure 3 (left) by the decrease of the Co substrate signal and its shift in 46 Surface Science binding energy, respectively. First evaluation of the valence band data (not shown) yields a position of the HOMO of the adsorbed species 4 eV lower than the valence band maximum of LiCoO 2. The situation at the interface is schematically drawn on the right hand side of figure 3. The band bending indicates that charge separation has taken place at the interface, i.e. that a space charge layer has formed in the LiCoO2. In the present case, charge separation can principally be caused by the movement of electrons/holes, ions or both. The position of the HOMO far below the valence band does not favor hole transfer from the LiCoO2 to the adsorbed species, indicating movement of Liions out of the LiCoO2. Li is fully intercalated in the LiCoO2 used in the present investigations and the material is therefore in its discharged state. Charging will lead to more positive potentials and a higher driving force for oxidation of the electrolyte, i.e. a shift of the Fermi level of LiCoO2 and band structure in the volume downwards, but electron transfer may be inhibited by activation energies (band-bending upwards at the interface). Notably, in the case of DEC, the presence of Li-salt is expected to change the band alignment at the interface. Ads.-/ react. layer EVac EC + η + EV + EB Band bending HOMO LiCoO2 Fig. 3: Evolution of intensity and binding energy of cobalt signal (Co3p) with exposition (left) and schematic drawing of electronic energy levels and band bending at the interface (right) In summary, the interface formation between a cathode material (LiCoO2) and a solid electrolyte (LiPON) as well as a liquid electrolyte species (DEC) has been studied by surface analytical methods. In both cases, interlayers are formed. Moreover, the energetic situation does not favor hole transfer from the LiCoO2 to the electrolyte or electrolyte species (i.e. oxidation of the electrolyte). In the case of DEC, we think that Li-ions may be involved in the formation of the contact potential. References 1. 2. 3. 4. 5. 6. 7. Maier, J., Physical Chemistry of Ionic Materials. 2004, Chichester: John Wiley and Sons, Ltd. Sze, S.M., Physics of Semiconductor Devices. 1981, Singapore: John Wiley and Sons, Inc. Weppner, W., Fundamental Aspects of Electrochemical, Chemical and Electrostatic Potentials in Lithium Batteries, in Materials for Lithium-Ion Batteries, C.a.S. Julien, Z., Editor. 1999, Kluwer Academic Publishers: Dordrecht. p. 401-412. Goodenough, J.B. and Y. Kim, Challenges for Rechargeable Li Batteries. Chemistry of Materials, 2010. 22(3): p. 587-603. Jacke, S., et al., Investigation of the solid-state electrolyte/cathode LiPON/LiCoO2 interface by photoelectron spectroscopy. Ionics, 2010. 16(9): p. 769-775. Song, J., et al., Valence Band Offsets of LiPON/LiCoO(2) Hetero-Interfaces Determined by X-ray Photoelectron Spectroscopy. Electrochemical and Solid State Letters, 2011. 14(12): p. A189A191. Becker, D., et al., in preparation Surface Science 47 Adcanced 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 (EIES). The class of oxide ceramics, in particular with perovskite (derived) structures, comprises a stunning variety of new functional materials. 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, Chalmers University of Technology, and Hyderabad University. Throughout 2011 Lambert Alff was working also as a Dean of Studies in the faculty of Materials Science. In this time, the new Master of Science program in Materials Science has started. Lambert Alff has been elected a member of the Senat of TU Darmstadt. Staff Members Head Prof. Dr. Lambert Alff Research Associates Dr. Anastasiya Kolchynska Dr. Jose Kurian Dr. Philipp Komissinskiy Technical Personnel Dipl.-Ing. Gabi Haindl Jürgen Schreeck Secretary Marion Bracke 48 Advanced Thin Film Technology PhD Students Dipl.-Ing. Mehrdad Baghaie Dipl.-Ing. Erwin Hildebrandt Dipl.-Ing. Stefan Hirsch Dipl. Phys. Reiner Retzlaff Dipl. Chem. Mehran Vafaee Dipl.-Ing. Alexander Buckow Dipl.-Ing. Sandra Hildebrandt Dipl.-Ing. Aldin Radetinac BTech. Vikas Shabadi MSc. Diploma Students Maximilian Fries Katharina Kupka Research Projects Superconductivity in water intercalated NaxCoO2 thin films (TU Darmstadt, TU Braunschweig, and Max-Planck-Institute for Solid State Research, Stuttgart) (DFG 2006-2011) 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 2009-2011) 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 2008 - 2010) Oxide-MBE (MPI-FKF/TUD 2007-2012) Publications Lambert Alff, Andreas Klein, Philipp Komissinskiy, and Jose Kurian; Vapor phase deposition of oxides. Ceramics Science and Technology, Volume 3: Synthesis and Processing, I.-W. Chen and R. Riedel eds., pp. 269-290, Wiley-VCH Verlag GmbH, Weinheim, Germany (2011). E. Hildebrandt, J. Kurian, M. M. Müller, T. Schroeder, H.-J. Kleebe, and L. Alff. Controlled oxygen vacancy induced p-type conductivity in HfO2-x thin films. Appl. Phys. Lett. 99, 112902 (2011). A. Radetinac, K. S. Takahashi, L. Alff, M. Kawasaki, and Y. Tokura. Single-crystalline Sr2MoO4 films grown by pulsed laser deposition. J. Cryst. Growth 322, 38-40 (2011). R. Hord, G. Cordier, K. Hofmann, A. Buckow, G. Pascua, H. Luetkens, L. Alff, and B. Albert. Transitions between lanthanum cuprates: crystal structures of T', orthorhombic and K2NiF4type La2CuO4. Z. Anorg. Allg. Chem. 637, 1114 (2011). R. M. Öksüzoglu, M. Yildirim, H. Cinar, E. Hildebrandt, and L. Alff. Effect of Ta buffer and NiFe seed layers on pulsed-DC magnetron sputtered Ir20Mn80Co90Fe10 exchange bias. J. Magn. Magn. Mater. 323, 1827 - 1834 (2011). M. Baghaie Yazdi, M.-L. Goyallon, T. Bitsch, A. Kastner, M. Schlott, and L. Alff. Transparent magnetic oxide thin flms of Fe3O4 on glass. Thin Solid Films 519, 2531 - 2533 (2011). M. Vafaee, M. S. Ghamsari, and S. Radiman. Highly concentrated zinc oxide nanocrystals sol with strong blue emission. Journal of Luminescence 131, 155-158 (2011). Advanced Thin Film Technology 49 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. 50 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 Karen Böhling Nadine Arnold 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. Vassilios Siozios Dipl.-Ing. Alexander Uhl M.Sc. Jia Yuan Dipl.-Ing. Carmen Elena Zvoriste Diploma and Master Students Laurent Couturier Edouard Dassonville Amon Klausmann Michael Krämer Catherine Lottmann Van Lam Nguyen Lukas Mirko Reinhold Alexander Uhl Bachelor Students Daniel Bick Richard Günzler Lukas Riemer Dispersive Solids Dr. Gabriela Mera Prof. Dr. Norbert Nicoloso Dr. Liviu Toma M.Sc. Monika Wilamowska 51 Guest Scientists Dr. Eng. Koji Morita, National Institute for Materials Science, Ibaraki, Japan Dr. Mirabbos Hojamberdiev, Institute of General and Inorganic Chemistry, Uzbekistan Academy of Sciences, Uzbekistan Dr. Ken Niwa, Department of Materials Science and Engineering, University of Nagoya, Japan Prof. Yuichi Ikuhara, Institute of Engineering Innovation, University of Tokyo, Japan Vallachira Pradeep, Universita degli Studi di Trento, Italy Sarabjeet Kaur, Research Institute, C.S.I.R., Bhopal, India Dr. Rahul Harshe, (Engineers), India Research and Development Establishment Stephanie Kaiser, Fraunhofer Insitute of Ceramic Technology and Systems, IKTS, Hermsdorf, Germany Janka Ihring, Fraunhofer Insitute of Ceramic Technology and Systems, IKTS, Hermsdorf, Germany Anne Serin, National Graduate School of Chemistry, Montpellier, France Scarlett J. Widgeon, Department of Chemical Engineering and Materials Science, University of California, Davis, USA Prof. I-Wei Chen, Skirkanich Professor of Materials Innovation, Department of Materials Science and Engineering, Philadelphia, USA Prof. Dr. Corneliu Balan, Politehnica, University of Bucharest, Faculty of Enegetics, Hydraulics Department, Bucharest, Romania Dr. Tomáš Plachký, Institute of Inorganic Chemistry, Slovak Academy of Sciences, Bratislava, Slovakia Guanwei Liu, State Key Lab of New Ceramics and Fine Processing Department of Materials Science and Engineering Tsinghua University, Beijing, China Dr. Olim N. Ruzimuradov, Department of General Chemistry,Faculty of Chemistry, National University of Uzbekistan, Tashkent, Uzbekistan Dr. Ishikawa, Institute of Engineering Innovation, University of Tokyo, Japan 52 Dispersive Solids Research Projects Molecular Routes to SiMBCN Ceramic Nanocomposites (M = Zr, HF) (China Council Scholarship (CSC), Donghua University, Shanghai, China, Sep. 2011 – Aug. 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 Substratwerkstoffe (DFG, June 2011 – June 2014) für thermisch hochbeanspruchte High-Pressure High Temperature Synthesis of Novel Binary and Ternary Superhard Phases in the B-C-N System (DFG, Feb. 2011 – Jan. 2014) 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) 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) FUNEA-Functional Nitrides for Energy Applications (Coordination, EU - Marie Curie Initial Training Network, Feb. 2011 – Jan. 2015) 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) Schwerpunkt Mikrosystemtechnik im Förderprogramm "IKT 2020 - Forschung für Innovationen" (BMBF VDI/VDE/IT, Jan. 2011 – June 2013) Nanostructure and Calorimetry of Amorphous SiCN and SiBCN (DFG, April 2010 – March 2013) Thermoresistant Ceramic Membrane with Integrated Gas Sensor for High Temperature Separation and Detection of Hydrogen and Carbon Monoxide (DFG, Aug. 2010 – July Synthesis, nanostructure and applications of metal carbodiimides (founded by NIMS, Japan, Nov. 2010 – Oct. 2012) Dispersive Solids 53 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- Herstellung und Charakterisierung Sol-Gel-basierter SiOx/GO-Komposite (Bachelor Thesis, Dec. 2011 – March 2012) Herstellung Siliciumoxycarbid-basierter Mikrokomponenten mittels Soft-LithographieVerfahren (Bachelor Thesis, Dec. 2011 – March 2012) Unterstützung Exzellenzprojekte (Dezernat Forschung, Jan 2010 – Jan 2012) SPP 1181: Nanoskalige anorganische Materialien durch molekulares Design: Neue Werkstoffe für zukunftsweisende Technologien (Coordination of DFG SPP 1181 – Nanomat, Nov. 2005 – Dec. 2011) Untersuchung zum Druckkriechverhalten polymerabgeleiteter Siliciumoxycarbid-Keramiken bei hohen Temperaturen (Bachelor Thesis, Aug. 2011 – Nov. 2012) Polymerabgeleitete SiCO/HfO2 und SiCN/HfO2 Keramik-Nanokomposite Höchsttemperaturanwendung (DFG SPP 1181 – Nanomat, Jan. 2007 – Sep. 2011) für Synthesis and High-Temperature Annealing of Novel SiHfBCN Ceramic Composites (Master Thesis, March 2011 – Sep. 2011) Polysilazan-abgeleitete SiCN-Schichten für thermisch hochbeanspruchte Substratwerkstoffe (Diploma Thesis, March 2011 – Aug. 2011) Entwurf und Charakterisierung gedruckter piezoresistiver Dehnungssensoren aus Polysiloxan-CNT-basierten Kompositen (Diploma Thesis in cooperation with FB Elektrotechnik, Dec. 2010 – May 2011) High-Pressure High Temperature Synthesis of Novel Binary and Ternary Superhard Phases in the Si-C-N System (DFG SPP 1236, May 2008 – April 2011) Research Program „Mikrosysteme“ – Integration neuartiger Funktions- und Konstruktionswerkstoffe und deren Anwendung in einem miniaturisierten Ventilsystem – INFUNK (BMBF, Oct. 2008 – April 2011) Development and Structure Formation Mechanism of Self-Supported Ceramic Networks for Multifunctional Applications (Humboldt Fundation, Aug. 2010 – July 2011) 54 Dispersive Solids Modelling of composite pressure cylinder rupture in aerospace application (Diploma Thesis in cooperation with Airbus Operation GmbH, Hamburg und Grenoble INP Phelma, France, Nov. 2010 – April 2011) Detailed characterisation of different grades of cast irons and cast steels – composition of subject cards (Diploma Thesis in cooperation with Ferry Capitain, Joinville, France, Sep. 2010 – March 2011) Neue Anodenmaterialien für Li-Ionen-Batterien (Diploma Thesis, Sep. 2010 – Feb. 2011) Entwicklung neuer Prozesse für die Atmosphärendruckplasmadeposition zur Erzeugung industriell einsetzbarer Oberflächen (Diploma Thesis in cooperation with Siemens AG, Erlangen, Sep. 2010 – Feb. 2011) Improvement of the weld seam corrosion resistance of longitudinally welded condenser tubes through enhancement of the manufacture and heat treatment process (Diploma Thesis in cooperation with Mannheim Power Alstom, TTTMC, Power Plant Chemistry, Sep. 2010 – Feb. 2011) Publications Suffner, J,; Scherer, T.; Wang, D.; Fasel, C.; Jaworska, L.; Hahn, H.; Microstructure and high-temperature deformation behavior of Al2O3-TiO2 obtained from ultra-high-pressure densification of metastable powders; Acta Mater., 59(20) (2011) 7592-7601. Matizamhuka, W.R.; Sigalas, I.; Herrmann, M.; 4 Dubronvinsky, L.; Dubrovinskaia , N.; Miyajima, N.; Mera, G.; Riedel , R.; Characterization of the Materials Synthesized by High Pressure-High Temperature Treatment of a Polymer Derived t-BC2N Ceramic; Materials, 4(12) (2011) 2061-2072. Gurlo, A.; Clarke, D.; High-sensitivity hydrogen detection: hydrogen-Induced swelling of multiple cracked palladium films on compliant substrates; Angew. Chem. Int. Edit., 50(43) (2011) 10130-10132. Seifollahi Bazarjani, M.; Kleebe, H.-J.; Müller, M.M.; Fasel, C.; Baghaie Yazdi, M.; Gurlo, A.; Riedel, R.; Nanoporous Silicon Oxycarbonitride Ceramics Derived from Polysilazanes In situ Modified with Nickel Nanoparticles; Chem. Mater., 23(18) (2011) 41124123. Soehn, M.; Zils, S.; Nicoloso, N.; Roth, C.; Effective debundling of carbon nanotubes and simultaneous synthesis of Pt nanoparticles by Nafion (R) induced emulsions; J. Power Sources, 196(15) (2011) 6079-6084. Boyko, T.D.; Zvoriste, C.E.; Kinski, I.; Riedel, R.; Hering, S.; Huppertz, H.; Moewes, A.; Anion ordering in spinel-type gallium oxonitride; Phys. Rev. B 84(8) (2011) 085203. Dispersive Solids 55 Pashchanka, M.; Hoffmann, R.C.; Gurlo, A.; Swarbrick, J.C.; Khanderi, J.; Engstler, J.; Issanin, A.; Schneider, J.J.; A molecular approach to Cu doped ZnO nanorods with tunable dopant content; Dalton T., 40(16) (2011) 4307-4314. Martínez-Crespiera, S.; Ionescu, E.; Schlosser, M.; Flittner, K.; Mistura, G.; Riedel, R.; Schlaak, H.F.; Fabrication of Silicon Oxycarbide-Based Microcomponents via Photolithographic and Soft Lithography Approaches; Sensor Actuat. A-Phys., 169(1) (2011) 242-249. Sedlacek, J.; Galusek, D.; Riedel, R .; Hoffmann, M.J.; Sinter-HIP of polymer-derived Al2O3-SiC composites with high SiC contents; Mater. Lett., 65(15-16) (2011) 2462-2465. Graczyk-Zajac, M.; Fasel, C.; Riedel, R.; Polymer-derived-SiCN ceramic/graphite composite as anode material with enhanced rate capability for lithium ion batteries; J. Power Sources, 196(15) (2011) 6412-6418. Toma, L.; Fasel, C.; Lauterbach, S.; Kleebe, H.-J.; Riedel, R.; Influence of nano-aluminum filler on the microstructure of SiOC ceramics; J. Eur. Ceram. Soc., 31(9) (2011) 1779-1789. Tamayo, A.; Rubio, J.; Rubio, F.; Oteo, J.L.; Riedel, R.; Texture and micro-nanostructure of porous silicon oxycarbide glasses prepared from hybrid materials aged in different solvents; J. Eur. Ceram. Soc., 31(9) (2011) 1791-1801. Pusch, C.; Hoche, H.; Berger, C.; Riedel, R.; Ionescu, E.; Klein, A.; Influence of the PVD sputtering method on structural characteristics of SiCN-coatings – comparison of RF-, DC- and HiPIMS-sputtering and target configurations; Surf. Coat. Tech., 205(2) (2011) S119-S123. Andrade, M.; Dzivenko, D.; Miehe, G.; Boehler, R.; Hintzen, H. T.; Riedel, R.; Highpressure high-temperature synthesis and structure of beta-MgSiN2; Phys. Status Solidi-R, 5(56) (2011) 196-198. Martinez-Crespiera, S.; Ionescu, E.; Kleebe, H.-J.; Riedel, R.; Pressureless synthesis of fully dense and crack-free SiOC bulk ceramics via photo-crosslinking and pyrolysis of a polysiloxane; J. Eur. Ceram. Soc., 31(5) (2011) 913-919. Ahmad, M.I.; Fasel, C.; Mayer, T.; Bhattacharya, S.S.; Hahn, H.; High temperature stability of nanocrystalline anatase powders prepared by chemical vapour synthesis under varying process parameters; Appl. Surf. Sci., 257(15) (2011) 6761-6767. Papendorf, B.; Nonnenmacher, K.; Ionescu, E.; Kleebe, H.-J.; Riedel, R.; Strong Influence of Polymer Architecture on the Microstructural Evolution of Hafnium-AlkoxideModified Silazanes upon Ceramization; Small, 7(7) (2011) 970–978. Böhme, M.; Ionescu, E.; Fu, G.; Ensinger, W.; Cerium (IV) oxide nanotubes prepared by low temperature deposition at normal pressure; Nanotechnology, 22(6) (2011) 065602. 56 Dispersive Solids Chavez, R.; Ionescu, E.; Balan, C.; Fasel, C.; Riedel, R.; Effect of Ambient Atmosphere on the Cross-Linking Behavior of Polysilazanes; J. Appl. Polym. Sci., 119(2) (2011) 794-802. Galusek, D.; Klement, R.; Sedláček, J.; Balog, M.; Fasel, C.; Zhang, J.; Crimp, M.A.; Riedel, R.; Al2O3–SiC composites prepared by infiltration of pre-sintered alumina with a poly(allyl)carbosilane; J. Eur. Ceram. Soc., 31(1-2) (2011) 111-119. Nuffer, J.; Riedel, R.; Reply to the "Comment on 'Piezoresistive Effect in SiOC Ceramics for Integrated Pressure Sensors"; J. Am. Ceram. Soc., 94(1) (2011) 290. Böhme, M.; Ionescu, E.; Fu, G.; Ensinger, W.; Room temperature synthesis of indium tin oxide nanotubes with high precision wall thickness by electroless deposition; Beilstein J. Nanotechnol., 2 (2011) 119-126. Gurlo, A.; Nanosensors: towards morphological control of gas sensing activity. SnO 2, In2O3, ZnO and WO3 case studies; Nanoscale, 3(1) (2011) 154-165. Renard, L.; Elhamzaoui, H.; Jousseaume, B.; Toupance, T.; Laurent, G.; Ribot, F.; Saadaoui, H.; Brötz, J.; Fuess, H.; Riedel, R.; Gurlo, A.; Low-temperature H2 sensing in self-assembled organotin thin films; Chem. Commun., 47(5) (2011) 1464-1466. Kamrani, S.; Hesabi, Z.R., Riedel, R.; Reihani, S.M.S.; Synthesis and Characterization of Al-SiC Nanocomposites Produced by Mechanical Milling and Sintering; Adv. Comp. Mater., 20(1) (2011) 13-27. Patents Chavez Medellin, R.; Zimmermann, A.; Aichele, W.; Ionescu, E.; Riedel, R.; New tetraamino-disiloxane useful for producing thermoplastic polyimide-based polymers; Patent Number(s): DE102010001071-A1; WO2011089111-A1. Dispersive Solids 57 Nanoporous Silicon Oxycarbonitride Ceramics Derived from Polysilazanes In situ Modified with Nickel Nanoparticles Mahdi Seifollahi Bazarjani,† Hans-Joachim Kleebe,† Mathis M. Müller,† Claudia Fasel,† Mehrdad Baghaie Yazdi,† Aleksander Gurlo,†,‡ and Ralf Riedel† †Technische Universität Darmstadt, Fachbereich Material-und Geowissenschaften, Petersenstrasse 23, D64287 Darmstadt, Germany ‡School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, Massachusetts 02138, United States Chem. Mater. 2011, 23, 4112–4123, DOI: 10.1021/cm200589n Ni-polysilazane precursors were synthesized from polysilazane and trans[bis(2aminoetanol-N,O)diacetato-nickel(II)]. The Ni-polysilazane precursors are superparamagnetic indicating formation of nanosized nickel particles (∼2-3 nm) confirmed by HRTEM as well. The as-obtained Ni-polysilazane precursors were thermolized at 700 °C and transformed to ceramic nanocomposites, manifesting a nanoporous structure, revealing a BET surface area of 215 m²/g, a micropore surface area of 205 m²/g, and a micropore volume of 0.113 cm3/g. Although Si-C-N-(O) ceramics derived from the native polysilazane are nonporous, the pronounced development of porosity in the Ni/Si-C-N-(O) system was attributed to (i) the stabilizing effect of carbosilane bonds, which prohibit the formation of macropores during thermolysis; (ii) the reduced barrier for heterogeneous pore nucleation as a result of in situ created nickel nanoparticles; and (iii) the reduced viscous flow of the pores due to the presence of nickel nanoparticles and turbostratic carbon. The formation of turbostratic carbon is due to the reactions catalyzed by nickel nanoparticles that result in graphene stacking as inferred from the STA-MS studies. As the formation mechanism, structure, composition and the porosity characteristics of the Ni/Si-C-N-(O) nanocomposites differ significantly from those of the Si-C-N-(O) ceramics, this implies a common mechanism involved in the formation of nickel nanoparticles, precipitation of turbostratic carbon and the development of porosity. These common features are as follows: (i) The nickel nanoparticles in the Ni-polysilazane precursors reduce the critical barrier for the formation of gaseous species during the polymer-to-ceramic transformation and facilitate the heterogeneous nucleation of pores due to the release of gasmolecules such as H2 andCH4.72 As the rigid carbosilane bonds formed in the Nipolysilazane precursors are not affected at the temperatures of transamination and exchange reactions (200-500 °C),3,34 the distillation of large polymer fragments does not occur. In this way the formation of macropores and the abnormal pore growth is significantly constrained. Furthermore, higher cross-linking due to the formation of carbosilane units enhances the evolved pore stability during the polymer (Nipolysilazane precursors) to ceramic nanocomposite (Ni/Si-C-N-(O)) transformation.73 (ii) The dehydrogenation-active nickel nanoparticles decrease the starting temperature of the formation of turbostratic carbon by some hundred degrees. The previous studies showed that the turbostratic carbon reinforces the mechanical stability of the surrounding matrices.74 This effect could be easily understood if we consider the structure of turbostratic carbon as being constructed of hexagonal basal planes of perfect graphene sheets which are randomly rotated along the c axis (instead of 58 Dispersive Solids regular ... ABAB... stacking),75 graphene itself possesses the highest intrinsic strength.76 Accordingly, the turbostratic carbon with higher mechanical stability than that of the neighboring nanoporous matrix behaves as in situ formed nanofiller, and subsequently reinforces the nanoporous structure and reduces the nanopores collapse as a result of viscous flow,68,69,71 stabilizing the micro/mesoporosity developed in the entire matrix of the Ni/Si-C-N-(O) nanocomposites. Figure 1. HRTEM images of the thermolysis product of the (a) polysilazane HTT (reference sample) and that of the (b_d) Ni_polysilazane precursor S3 with the Ni(II) complex content of 40 wt % upon thermolysis at 700 °C. The thermolysis product of the polysilazane HTT is fully amorphous, as indicated by the inset (diffraction patterns obtained by Fourier filtered transform (FFT)). In contrast to a, the Ni/Si-C-N-(O) nanocomposite revealed a dark, spherical contrast resulting from the precipitation of crystalline nickel nanoparticles, 2-3 nm in diameter. Note that in the Ni/Si-C-N-(O) nanocomposite the turbostratic carbon was observed throughout the entire sample, suggesting a strong catalytic reaction of the nickel nanoparticles. No lattice fringes or lattice points are seen in the nickel nanoparticles in b and c; however, when using a rather high defocus setting of the objective lens (first pass band), the crystallinity of even very small nanoparticles could be verified in d. Conclusions In summary, a novel strategy to synthesize nanoporous ceramics is proposed. The addition of a Ni(II) complex to a polysilazane effectively turn a nonporous polymer derived ceramic to a nanoporous material. Nickel nanoparticles formed in situ during the synthesis of Nipolysilazane precursors play a major role in modifying the mechanism of polymer-toceramic transformation. They facilitate the precipitation of turbostratic carbon and the heterogeneous nucleation of pores. Furthermore, replacement of unstable silazane linkages Dispersive Solids 59 by stable carbosilane bonds which are not affected by the main polymer chain depolymerization during thermolysis, prohibits the distillation of small polymer fragments limiting pore growth and formation of macrovoids. References (3) (34) (68) (69) (70) (71) (72) (73) (74) (75) (76) 60 Colombo, P.; Riedel, R.; Soraru, G. D.;Kleebe, H. J., Polymer Derived Ceramics: From NanoStructure to Applications; EStech Publications: Lancaster, PA, 2010; p 476. Yive, N. S. C. K.; Corriu, R. J. P.; Leclercq, D.; Mutin, P. H.; Vioux, A. Chem. Mater. 1992, 4, 141. Sanchez-Jimenez, P. E.; Downs, J. A.; Raj, R. J. Am. Ceram. Soc. 2010, 93, 2567. Lipowitz, J.; Rabe, J. A.; Frevel, L. K.; Miller, R. L. J. Mater. Sci. 1990, 25, 2118. Galusek, D.; Reschke, S.; Riedel, R.; Dressler, W.; Sajgalik, P.; Lencees, Z.; Majling, J. J. Eur. Ceram. Soc. 1999, 19, 1911. Borek, T. T.; Ackerman, W.; Hua, D. W.; Paine, R. T.; Smith, D. M. Langmuir 1991, 7, 2844. Izaak, T. I.; Babkina, O. V.; Lyamina, G. V.; Svetlichnyi, V. A. Russian J. Phys. Chem. A 2008, 82, 2111. Williams, H. M.; Dawson, E. A.; Barnes, P. A.; Rand, B.; Brydson, R. M. D.; Brough, A. R. J. Mater. Chem. 2002, 12, 3754. Chasiotis, I.; Ozkan, T.; Naraghi, M. Carbon 2010, 48, 239. Sjostrom, H.; Ivanov, I.; Johansson, M.; Hultman, L.; Sundgren, J. E.; Hainsworth, S. V.; Page, T. F.; Wallenberg, L. R. Thin Solid Films 1994, 246, 103. Hone, J.; Lee, C.; Wei, X. D.; Kysar, J. W. Science 2008, 321, 385. Dispersive Solids Strong Influence of Polymer Architecture on the Microstructural Evolution of Hafnium-Alkoxide-Modified Silazanes upon Ceramization Benjamin Papendorf,* Katharina Nonnenmacher,+ Emanuel Ionescu,* Hans-Joachim Kleebe,+ and Ralf Riedel* * Technische Universität Darmstadt, Institut für Materialwissenschaft, Petersenstrasse 23, D-64287 Darmstadt, Germany + Technische Universität Darmstadt, Institut für Angewandte Geowissenschaften, Schnittspahnstrasse 8, D-64287 Darmstadt, Germany Small, 7(7) (2011) 970–978, DOI: 10.1002/smll.201001938 The present study focuses on the synthesis and ceramization of novel hafniumalkoxidemodified silazanes as well as on their microstructure evolution at high temperatures. The synthesis of hafnia-modified polymer-derived SiCN ceramic nanocomposites is performed via chemical modifi cation of a polysilazane and of a cyclotrisilazane, followed by cross-linking and pyrolysis in argon atmosphere. Spectroscopic investigation (i.e., NMR, FTIR, and Raman) shows that the hafnium alkoxide reacts with the N–H groups of the cyclotrisilazane; in the case of polysilazane, reactions of N–H as well as Si–H groups with the alkoxide are observed. Consequently, scanning and transmission electron microscopy studies reveal that the ceramic nanocomposites obtained from cyclotrisilazane and polysilazane exhibited markedly different microstructures, which is a result of the different reaction pathways of the hafnium alkoxide with cyclotrisilazane and with polysilazane. Furthermore, the two prepared ceramic nanocomposites are unexpectedly found to exhibit extremely different hightemperature behavior with respect to decomposition and crystallization; this essential difference is found to be related to the different distribution of hafnium throughout the ceramic network in the two samples. Thus, the homogeneous distribution of hafnium observed in the polysilazane-derived ceramic leads to an enhanced thermal stability with respect to decomposition, whereas the local enrichment of hafnium within the matrix of the cyclotrisilazane-based sample induces a pronounced decomposition upon annealing at high temperatures. The results indicate that the chemistry and architecture of the precursor has a crucial effect on the microstructure of the resulting ceramic material and consequently on its high-temperature behavior. Polysilazane HTT1800 and cyclotrisilazane (CTS) were reacted with hafnium(IV) nbutoxide at ambient temperature. The reactions were investigated by means of NMR, Fourier-Transform IR (FTIR) and Raman spectroscopy. Whereas CTS can only react at its N–H bonds with hafnium(IV) n-butoxid, HTT1800 additionally has Si–H groups, which might also be involved in the reaction with the hafnium(IV) n-butoxide. Dispersive Solids 61 Figure 1. TEM bright-field images of the samples pyrolyzed at 1100 °C: a,c) the HTT1800-based ceramic and b,d) the CTS-based material. The TEM bright-field images (a,b) are complementary to the SEM images given in Figure 5 since no Hf-segregation is visible in (a) while dark contrast lines are depicted in (b), indicative of a local enrichment of Hf. Insets of (a) and (b) show the corresponding SAED images. Note that the origin of such elongation in Hf-dispersion is still not known. The corresponding HRTEM images given in (c) and (d) clearly show that no local enrichment of Hf is present in (c) while in (d) a dark band (Hf-phase) runs diagonal through the image. Figure 2. XRD patterns of CTS- and HTT1800-based ceramics annealed at 1300 and 1600 °C in argon atmosphere. 62 Dispersive Solids Conclusion The present study clearly emphasizes the influence of the chemistry and molecular architecture of preceramic polymers on the microstructural evolution and high-temperature behavior of the ceramic materials derived from the polymers. Ceramic nanocomposites based on the SiHfCNO-system with extremely different microstructures have been obtained from two different preceramic compounds, namely from a polymeric organosilazane and from an organocyclosilazane monomer. The organosilazanes were modifi ed with hafnium alkoxide and subsequently pyrolyzed in argon atmosphere up to different temperatures above 1000 °C. Electron microscopic investigation (SEM and TEM) of the microstructure of both samples showed a homogeneous dispersion of hafnium in the bulk SiCN matrix on the atomic scale in case of HTT1800 as the precursor. In contrast, the ceramic derived from CST is characterized by a pronounced local enrichment of hafnium, leading to threadlike precipitation of amorphous hafnia. The difference in the microstructural features between both samples is thought to be a consequence of the different reactivity of the preceramic silazanes with respect to hafnium n -butoxide. Thus, the Hf dispersion throughout the SiCN bulk material is mainly determined by the architecture of the preceramic silazane obtained upon chemical modification with hafnium n-butoxide. Subsequent annealing experiments showed that the microstructural features are essentially preserved up to temperatures as high as 1600 °C. In addition to the relationship between the preceramic polymer architecture and the microstructure of the resulting ceramics, a strong effect of the hafnium distribution throughout the ceramic network on the high-temperature stability of the samples was found. Whereas the local enrichment of hafnium within the ceramic SiCN network derived from CST was found to be disadvantageous with respect to the thermal stability at 1600 °C, the HTT1800-sample revealed a homogeneous distribution of hafnium within the ceramic matrix and was found to exhibit a significantly improved stability in terms of decomposition of the SiCN matrix. Dispersive Solids 63 Structure Research In the year 2011, we installed a new six-circle surface diffractometer for heavy sample environments. An UHV-system for the evaporation of metals has been designed and built, together with a transportable baby chamber for Synchrotron campaigns. The Guiniercamera has been tested together with the Tübingen-cryostat (15K-300K), and the CAD4 kappa-diffractometer has been renovated and equipped with a Ag tube for highly absorbing single crystals. Staff Members Head Prof. Dr. rer. nat. Wolfgang Donner Prof. Dr.-Ing. Dr. h.c. Hartmut Fueß Research Associates Dr. Joachim Brötz Dipl. Phys. Martin Mühlbauer Dr. Marton Major Dr. Ljubomira Schmitt Dr. Oleksandr Dolotko Dr. Azza Amin Technical Personnel Dipl. Ing. Heinz Mohren Jean-Christophe Jaud Ingrid Svoboda Sabine Foro Secretary Maria Bense PhD Students Dipl.-Ing. Toni André Groß Dipl.-Ing. Hanna Hahn Dipl.-Ing. Jens Kling Dipl.-Ing. Dominic Stürmer M.Sc. Qiran Li Guest Scientists Dr. Sevi Öz, Ankara University, Turkey Prof. Dr. Ismael Saadoune, Université Cadi Ayyad, Maroc Research Projects DAAD exchange program with Slovakia (2006-2011). Structural investigations into the electric fatigue in piezo-ceramics (DFG-SFB, 2011-2014) Development of electrode materials for high capacitance devices (IDS-FunMat, 2011-2013) The electronic structure of TiO2, VO2 and related transition-metal oxides: A joined electrondensity study of materials in position, momentum and phase space (DFG, 2009-2011) Correlated momentrum, charge and magnetization density in the kagome staircase system Co3V2O8, (DFG, 2009-2011) 64 Structure Research Publications Daniels, J. E.; Jo, W.; Roedel, J.; Rytz, D.; Donner, W., Structural origins of relaxor behavior in a 0.96(Bi1/2Na1/2)TiO3-0.04BaTiO3 single crystal under electric field, Appl. Phys. Lett., 98: 252904 (2011) Deuermeier, J.; Gassmann, Brötz, J.; Klein, A., Reactive magnetron sputtering of Cu2O: Dependence on oxygen pressure and interface formation with indium tin oxide J. Appl. Phys., 109: 113704 (2011) Donner, W.; Chen, C.; Liu, M.; Jacobson, A. J.; Lee, Y.-L.; Gadre, M.; Morgan, D., Epitaxial strain-induced chemical ordering in La0.5Sr0.5CoO3-delta films on SrTiO3 Chem. Mater. 23. 984 (2011) Heiba, Z. K.; Mohamed, M. B.; Abdalslam, M. A.; Fuess, H., Structure, microstructure and magnetic properties of mixed rare earth oxide Dy1-xErxO3, Cryst Res. Techn. (2011) Hinterstein, M.; Rouquette, J.; Haines, H.; Paquet, Ph.; Knapp, M.; Glaum, J.; Fuess, H., Structural description of the macroscopic piezo and -ferroelectric properties of lead zirconatetitanate, Phys. Rev. Lett., 107: 077602 (2011) Hinterstein, M.; Hoelzel, M.; Kungl, H.; Hoffmann, M. J.; Ehrenberg, H.; Fuess, H., In situ neutron diffraction study of electric field induced structural transitions in lanthanum doped lead zirconate titanate, Z. Kristallogr.,226: 155-162 (2011) Hohmann, M. V.; Ágoston, P.; Wachau, A.; Bayer, T.J.M.; Brötz, J.; Albe, K.; Klein, A., Orientation dependent ionization potential of In2O3: A natural source for inhomogeneous barrier formation at electrode interfaces in organic electronics J. Phys. Cond. Mat., 23: 334203 (2011) Ishihara, H.; Natano, N.; Horiuchi, K.;. Terao, H.; Svoboda, I.; Fuess, H., NQR, DSC, and xray structure studies of pyridinium tetrabromozincate and pyridinium tetrabromocadmate (C5H5NH)2MBr4 . nH2O (M = Zn and Cd; n = 0.1: Phase transitions and weak hydrogen bond interactions, Z. Naturf., 66b: 1261-1269 (2011) Jacke, S.; Song, J.; Dimesso, L.; Brötz, J.; Becker, D.; Jaegermann, W.; Temperature dependent phosphorous oxynitride growth for all-solid-state batteries J. Power Sources, 196: 6911-6914 (2011) Jakes, J.; Blickhan, N.; Jekewitz, T.; Drochner, A.; Vogel, H.; Fuess, H.; Eichel, R.A. Interplay between defect structure and catalytic activity in the Mo10-xVx Oy mixed-oxide system: ChemPhysChem, 12: 3578-3583 (2011) Muench, F.; Kaserer, S.; Kunz, U.; Svoboda,I.; Brötz, J.;Lauterbach, S.; Kleebe, H.-J.;Roth, C.; Ensinger; W., Electroless synthesis of platinum and platinum–ruthenium nanotubes and their application in methanol oxidation, J. Mat. Chem., 21: 6286-6291 (2011) Structure Research 65 Nemec, I.; Herchel, R.; Boča, R.; Svoboda, I.; Trávniček, Z.; Dlháň, L.; Matelkovc, K.; Fuess, H. Heterobimetallic assemblies of Ni(II) complexes with a tetradentate amine ligand and diamagnetic cyanidometallates, Inorg. Chem. Act., 366: 366-372 (2011) Renard, L.; Elhamzaoui, H.; Jousseaume, B.; Toupance, Th.; Robot, F.; Saadaoui, H.; Brötz, J.; Fuess, H.; Gurlo, A., Low temperature hydrogen sensing in self-assembled organotin thin film, Chem. Commun., 47(1): 464-1466 (2011) Schierholz, R.; Fuess, H., Symmetry of domains in morphotropic PbZr1-xTixO3 ceramics Phys. Rev.B, 84: 064122 (2011) Schmitt, L. A.; Kling, J.; Hinterstein, M.; Hoelzel, M.; Jo, W.; Klebe, H.J.; Fuess, H. Structural investigations on lead-free Bi1/2Na1/2TiO3 based piezoceramics J. Mater. Sci., 4368-4376 (2011) Singh, A.; Senyshyn, A.; Fuess H.; Pandey, D., Ferroelectric and antiferrodistortive phase transition in the multiferroic (Bi0.8Ba0.2)(Fe0.8Ti0.2)O3: A high temperature neutron powder diffraction study, J. Appl. Phys., 110: 024111 (2011) Singh, A.; Senyshyn, A.; Fuess, H.; Chatterji, T.; Pandey, P., Neutron powder diffraction study of nuclear and magnetic structures of multiferroic (Bi0.8Ba0.2)(Fe0.8Ti0.2)O3: Evidence for isostructural phase transition and magnetoelastic and magnetoelectric couplings Phys. Rev. B, 83(5): 054406 (2011) Takali, F.; Njeh, A.; Fuess, H.; Ben Ghozlen, M. H., X-ray diffraction measurement of residual stress in epitaxial ZnO/α-Al2O3 thin film, Mech. Res. Comm.(2011) Structural characterisation of textured gold nanowires Maurer, F; Brötz, J ; Miehe, G; Karim, S; Fuess, H, INTERNATIONAL JOURNAL OF NANOTECHNOLOGY Volume: 8 Issue: 10-12 Special Issue: SI Pages: 855-867 Published: 2011 92 papers in Acta Cryst. E 66 Structure Research Diffuse Scattering and the Relaxor Behavior of Single Crystal, Lead-Free Piezo-Materials J. Daniels, W. Jo, J. Rödel, D. Rytz, W. Donner Piezoelectric materials find applications as sensors and actuators, e.g. in fuel injectors and inkjet printers. Most industrially used piezo-stacks contain lead, an element that is toxic even in small quantities. It is therefore desirable – and demanded by the EU – to develop lead-free materials with electro-mechanical properties comparable to the existing technology. One of the more promising candidates is bismuth sodium titanate (BNT) and some of its alloys. BNT is a so-called relaxor ferroelectric, i.e. it displays a frequencydependence of the ferrolectric properties that is most likely caused by small structural fluctuations called „polar nano-regions“ (PNR). Fig. 1: (h k 0.5) planes of diffuse scattering for, (a) initial crystal, and (b) an applied electric field of 4.6kV/mm. (c) shows line scans along the (h -1.5 0.5) direction taken from the areas outlined by dashed boxes in (a) and (b). The estimated background intensity level is indicated in (c). Radial intensity artefacts are caused by detector saturation errors during data collection. Structure Research 67 We used Ba-doped BNT (BNT-BT) as a model system to study the nature of the PNR and its relation to the relaxor-behavior. Structural fluctuations show up in diffraction studies as diffuse scattering, and the dependence of the diffuse scattering on an applied electric field should yield information about the atomic structutre of the PNR. The subject of the study was a single crystal of BNT containing 4 at-% BT; the crystal was illuminated by high energy x-rays at the European Synchrotron Radiation Facility in Grenoble (BL ID15B). The resulting intensity distribution in a two-dimensional cut of reciprocal space is shown in Fig.1: sharp half-order reflections that are due to a superstructure of tilted oxygen octahedra are connected by diffuse streaks. The diffuse streaks and the half-order reflections both react upon the application of an electric field: the streak intensity decreases and the reflections become more narrow. Fig. 2: Temperature-dependent permittivity of the unpoled and the poled BNT-4BT single crystal sample. Note the frequency dispersion. The insets are the derivative of the permittivity with respect to temperature, where the difference between the dielectric behaviour of the unpoled and the poled samples is more clearly visible. We designed a structural model for the diffuse scattering in which the streaking of the halforder reflections is caused by stacking faults in the octahedral tilt sequence. The application of an electric field dissolves some of the stacking faults (that serve as PNR’s) and the frequency dependence of the electrical permittivity is changed by this structural modification (see Fig. 2). We are now working on a quantitative description of the stacking fault structure. Reference: J.E. Daniels, W. Jo, J. Rödel, D. Rytz, W. Donner, Appl. Phys. Lett., 98, 252904 (2011). 68 Structure Research 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: Nanochannels, nanowires and nanotubes: Utilizing polymer foils which were irradiated by high energy ions, a set of nanostructures can be produced with a variety of applications. Nanochannels, produced by chemical etching of the irradiated foils, can be transformed into bio-specific sensors or into devices with selective transport properties, depending on the functional groups that are attached to their surfaces. The research is concerned with facile and versatile ways to achieve this attachment as well as with applications, e.g. as sensors for protein analytes or as logic gates. By filling the channels nanowires can be obtained which can be freed from the template by dissolution of the latter. Nanowires can be used for fundamental research, e.g. the investigation of the Kondo effect, but also as nanowire arrays in sensor applications, e.g. as gas sensors. By altering the filling process the resulting structure is not a wire but a tube. The correlation of synthesis conditions, morphological parameters and properties is investigated and optimized towards the utilization in catalysis, particle separation and sensor technology. This work is conducted in collaboration with the GSI Helmholtzzentrum für Schwerionenforschung. Materials in Radiation Fields: The degradation under intense ionizing radiation is investigated for different materials, such as semiconductors, amorphous magnetic alloys, polymers, graphite and scintillators. Many of those materials will be used in components (beam guiding magnets, beam dump, detectors) of the next generation accelerator facility at the GSI Helmholtzzentrum für Schwerionenforschung. In situ characterization is performed at the M-branch of the UNILAC experimental hall in the GSI by various analytical tools, e.g. FT-IR and UV/VIS measurements as well as mass spectrometry. Thin film preparation: Surface coatings and surface modifications are prepared on a scale from single molecular layers to films of about 200 nm thickness. The preparation technique depends on the purpose of the treatment, which can be, to name a few: 1) the synthesis of a functional material, e.g. a gas sensor prepared by electrochemical deposition, or a leadfree piezoelectric thin film prepared by spin- or dip-coating of a sol-gel solution. 2) the synthesis of an additional top-layer to improve certain parameters, e.g. the corrosion protection of light metals and their alloys by atomic layer deposition, or the friction coefficient by addition of a diamond-like carbon layer via plasma based ion deposition. 3) alteration of the surface layer, e.g. increase of hardness or adhesion by implantation of ions. Materials Analysis 69 Thin film analysis: Apart from the analysis of the self-synthesized samples mentioned above a variety of in-house techniques as well as externally available measurement facilities are used for characterization and fault analysis in collaboration with other research groups and institutes. This includes for example oxygen and hydrogen diffusion measurements in bulk samples of ferroelectrics by SIMS or the investigation of the binding states of thin carbonitride films with the substrate by NEXAFS at Bessy II, jointly with the PTB. Other techniques involved are mainly ion beam based – like RBS, NRA and ERDA – but not exclusively so, e.g. positron annihilation spectroscopy is also applied. 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. Christiane Brockmann Dr. Ruriko Hatada Technical Personnel Renate Benz Brunhilde Thybusch Secretaries Antje Pappenhagen PhD Students Anton Belousov Eiko Gütlich Umme Habiba Hossain Stefan Hummelt Markus Krause Vincent Lima Saima Nasir Quoc Hung Nguyen Tim Seidl Sebastian Wiegand Mario Böhme Engy El-Haddad Martin Hottes Sebastian Kamps Renuka Krishnakumar Falk Münch Cornelia Neetzel Markus Rauber Christian Stegmann Diploma Students Marc Adamiak Martin Hottes Jonathan Griebel Anke Schachtsiek Bachelor Students Thomas Paul Kaleja Stefan Vogel Guest Scientists Prof. Nhu-Tarnawska Hoa Kim-Ngan, Pedagogical University of Cracow, Poland Prof. Zbiegnew Tarnawski, AGH University, Krakow, Poland Dr. S. Duvanov, National Academy of Sciences of Ukraine A. Kramchenkov, National Academy of Sciences of Ukraine Barbara Lyson, AGH University, Krakow, Poland Karolina 70 Drogowska, AGH University, Krakow, Poland Materials Analysis Research Projects Preparation of lead free piezo electric thin films (LOEWE Adria, 2008 – 2014) Preparation of thick actuator films on the basis of lead free piezo materials (LOEWE Adria, 2010 – 2011) Investigation of scintillators for high current applications at UNILAC (GSI, 2008 – 2011) 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) Publications Muench, F.; Kunz, U.; Neetzel, C.; Lauterbach, S.; Kleebe, H.-J.; Ensinger, W., 4(Dimethylamino)pyridine as a powerful auxiliary reagent in the electroless synthesis of gold nanotubes, LANGMUIR, 27: 430–435 (2011) Boehme, M.; Fu, G.; Ionescu, E.; Ensinger, W., Cerium (IV) oxide nanotubes prepared by low temperature deposition at normal pressure, Nanotechnology, 22: 065602 (2011) Boehme, M.; Ensinger, W., Fabrication of zinc oxide nanotubes by chemical bath deposition using ion track-etched templates, IEEE Trans. Nanotech., 10: 63-69 (2011) Boehme, M.; Ionescu, E.; Fu, G.; Ensinger, W., Room temperature synthesis of indium tin oxide nanotubes with high precision wall thickness by electroless deposition Beilstein Journal of Nanotechnology, 2: 119-126 (2011) Materials Analysis 71 Ali, M.; Tahir, M. N.; Siwy, Z.; Neumann, R.; Tremel, W.; Ensinger, W., Hydrogen peroxide sensing with horseradish peroxidase-modified polymer single conical nanochannels, Anal. Chem, 83: 1673–1680 (2011) Ali, M.; Ramirez, P.; Nawaz Tahir, M.; Mafe, S.; Siwy, Z.; Neumann, R.; Tremel, W.; Ensinger, W. Biomolecular conjugation inside synthetic polymer nanopores via glycoprotein– lectin interaction, Nanoscale, 3: 1894-1903 (2011) Baake, O.; Seidl, T.; Hossain, U. H.; Delgado, A. O.; Bender, M.; Severin, D.; Ensinger, W. An apparatus for in situ spectroscopy of radiation damage of polymers by bombardment with high-energy heavy ions, Rev. Sci. Instrum., 82: 045103 (2011) Muench, F.; Kaserer, S.; Kunz, U.; Svoboda, I.; Brötz, J.; Lauterbach, S.; Kleebe, H.-J., Roth, C.; Ensinger, W., Electroless synthesis of platinum and platinum–ruthenium nanotubes and their application in methanol oxidation, J. Mater. Chem., 21: 6286-6291 (2011) Boehme, M., Ensinger, W., From nanowheat to nanograss: A preparation method to achieve free standing nanostructures having a high length/diameter aspect ratio Adv. Eng. Mater., 13: 373-375 (2011) Suchanicz, J.; Kim-Ngan, N.-T.; Konieczny, K.; Jankowska-Sumara, I.; Balogh, A. G., Soft and hybrid-doped Pb(Zr,Ti)O3 ceramics under stress, electric field, and temperature loading, J. Appl. Phys., 109: 104105 (2011) Radecka, M.; Pamula, E.; Trenczek-Zajac, A.; Zakrzewska, K.; Brudnik, A.; Kusior, E.; KimNgan, N.-T.; Balogh, A. G., Chemical composition, crystallographic structure and impedance spectroscopy of titanium oxynitride TiNxOy thin films, Solid State Ionics, 192: 693-698 (2011) Kurbatov, D.; Opanasyuk, A.; Duvanov, S. M.; Balogh, A. G.; Khlyap, H., Growth kinetics and stoichiometry of ZnS films obtained by close-spaced vacuum sublimation technique, Solid State Sci., 13: 1068-1071 (2011) Rauber, M.; Alber, I.; Müller, S.; Neumann, R.; Picht, O.; Roth, D., Schökel, A.; ToimilMolares, M. E.; Ensinger, W., Highly-ordered supportless three-dimensional nanowire networks with tunable complexity and interwire connectivity for device integration, Nanolett., 11 2304–2310 (2011) Boehme, M.; Voelklein, F.; Ensinger, W., Low cost chemical sensor device for supersensitive pentaerythritol tetranitrate (PETN) explosive detection based on titanium dioxide nanotubes Sensors Actuat B-Chemical, 158: 286-291 (2011) Muench, F.; Rauber, M.; Stegmann, C.; Lauterbach, S.; Kunz, U.; Kleebe, H.-J.; Ensinger, W., Ligand-optimized electroless synthesis of silver nanotubes and their activity in the reduction of 4-nitrophenol, Nanotechnology, 22: 415602 (2011) 72 Materials Analysis Hoffmann, P.; Fainer, N.; Kosinova, M.; Baake, O.; Ensinger, W., Compilation on synthesis, characterization, and properties of carbonitrides of silicon and boron in: Silicon CarbideMaterials, Processing and Applications in Electronic Devices, Ed. Mukherjee, M.; InTech (2011), ISBN 978-953-307-968-4. Flege, S.; Hatada, R.; Baba, K.; Ensinger, W., Fluorine and carbon ion implantation and deposition on metals by plasma source ion implantation Surf. Coat. Tech., 206: 963-966 (2011) Flege, S.; Hatada, R.; Baba, K.; Ensinger, W., Methane plasma-based ion implantation of metallic and galvanically oxidized tantalum, Surf. Coat. Tech., 206: 951-954 (2011) Ali, M.; Nasir, S., Nguyen, H. Q.; Sahoo, J. K.; Tahir, M. N.; Tremel, W.; Ensinger, W. Metal ion affinity-based biomolecular recognition and conjugation inside synthetic polymer nanopores modified with iron–terpyridine complexes J. Am. Ceram. Soc., 133: 17307-17314 (2011) Hatada, R.; Flege, S.; Ensinger, W.; Baba, K., Comparison of the surface modification of tungsten and gold by methane plasma source ion implantation, IEEE T. Plasma Sci., 39: 30803084 (2011) Baba, K.; Hatada, R.; Ensinger, W.; Flege, S, Deposition of diamond-like carbon films on inner wall surfaces of millimeter size diameter steel tubes by plasma source ion implantation IEEE T. Plasma Sci, 39: 3140-3143 (2011) Muench, F.; Oezaslan, M.; Seidl, T.; Lauterbach, S.; Strasser, P.; Kleebe, H.-J.; Ensinger, W. Multiple activation of ion track etched polycarbonate for the electroless synthesis of metal nanotubes Appl. Phys. A-Mater., 105: 847-854 (2011) Kim-Ngan, N.-T. H.; Havela, L.; Adamska, A. M.; Daniš, S.; Pešička, J.; Macl, J.; Eloirdi, R.; Huber, F.; Gouder, T.; Balogh, A. G., Characterization of U-based thin films: the UFe2+x case J. Phys.: Conference Series, 303: 012012 (2011) Westmeier, W.; Odoj, R.; Tyutyunnikov, S. I.; Hashemi-Nezhad, S. R.; Ensinger, W.; Zamani-Valasiadou, M.; Brandt, R.; Thomauske, B. ,Experiments on transmutation of longlived radioactive wast, ATW – Int. J. Nuclear Power, 56: 620-628 (2011) Alber, I.; Sigle, W.; Müller, S.; Neumann, R.; Picht, O.; Rauber, M.; van Aken, P. A., ToimilMolares, M. E., Visualization of multipolar longitudinal and transversal surface plasmon modes in nanowire dimers ACS Nano, 5; 9845–9853, (2011) DOI: 10.1021/nn2035044 Materials Analysis 73 Light-triggered Ionic Transport Through Photosensitive Synthetic Nanopores S. Nasir, Q.H. Nguyen, M. Ali, and W. Ensinger The generation of nanofluidic systems that respond to external stimuli are crucial to mimic and exploit the functionality of ion channels in living organisms. To achieve active control over ionic transport, the pore surface is decorated with a variety of functionalities that respond to external stimuli such as solution pH-value, temperature, light and biomolecules. The design of nanopores sensitive to ultraviolet (UV) light still constitutes a challenge for current technologies. Unlike a chemical stimulus, UV light is noninvasive and the whole process can be tuned by manipulating the light wavelength. Here, we describe a novel technique in which photolabile protecting groups (PPGs) were immobilised onto the pore surface to miniaturise photosensitive nanofluidic devices. For this purpose, polyethylene terephthalate (PET) foils of 12µm thickness were irradiated with swift heavy ions (Au at 11.4 MeV/u) with either a single ion or 5×108 ions cm-2 at the UNILAC linear accelerator (GSI, Darmstadt). The fabrication of a single conical nanopore and an array of cylindrical nanopores is achieved through well known asymmetric and symmetric track-etching techniques [1], respectively. Track-etched nanopores contain carboxylic acid (-COOH) groups on the surface and pore walls. The -COOH groups were exploited for the immobilisation of 4-oxo-4-(pyren-4-ylmethoxy) butanoic acid (PYBA) as a photolabile molecule in a two-step reaction process. Firstly, -COOH groups were converted into amine groups by reacting with ethylenediamine via carbodiimide coupling chemistry. Secondly, surface amine groups were allowed to react with PYBA molecules in the presence of N-(3dimethylaminopropyl)-N′-ethylcarbodiimide. Fig. 1: Schematic presentation of wettability changes occuring in PYBAmodified nanopores after UV-light irradiation-induced photodegradation of PYBA and subsequent creation of a charged surface state [2]. For the case of a single conical nanopore, the success of chemical modification reactions was corroborated by measuring the current–voltage (I–V) characteristics, which are dictated by the electrostatic interaction of the charged pore surface with the mobile ions in an electrolyte solution. Figure 2a shows that after amination the permselectivity of the nanopore is switched from cation- to anion-selective, leading to the inversion of current rectification due to the change of pore surface charge from negative (COO-) to positive (NH3+). As expected, the immobilisation of PYBA molecules resulted in the loss of surface charge due to the presence of uncharged terminal pyrene moieties (Fig.1). Eventually, the PYBA-modified pore behaved like an ohmic resistor (Fig. 2a). Upon UV365nm light 74 Materials Analysis irradiation, the ester bonds adjoining the pyrene chromophore were cleaved, resulting in the generation of -COOH functionalities on the surface and inner pore walls (Fig.1), which restores the cation-selective behaviour of the pore. Figure 2b shows permeation data of methylviologen (MV2+) and naphthalene disulfonate (NDS2-) transported per cm2 of the PYBA-modified membrane containing an array of cylindrical nanopore (~ 20 ± 3nm) before and after UV treatment [2]. (a) 1.0 - Current (nA) –COO Light off + –NH3 0.5 Light on 0.0 -0.5 -1.0 -2 (b) -1 0 1 2 -2 -1 0 1 2 Voltage (V) Voltage (V) Before UV irradiation After UV irradiation Nanomoles per cm 2 12 2+ 2+ MV 2NDS MV 2NDS 9 Fig. 2: a)I/V-characteristics of the single conical nanopore with carboxyle and amine groups (left), and PYBA-modified pore before and after UVirradiation (right) b)Permeation data (nanomoles transported as a function of time) of charged analytes (methylviologen cation, naphthalene disulfonate anion) through a PYBA-modified multipore membrane, before and after UV-induced PYBA bond cleavage 6 3 0 40 80 120 Time (min) 160 40 80 120 160 Time (min) In conclusion, we demonstrated the design of a light-gated nanofluidic device based on synthetic nanopores modified with photolabile PYBA molecules. UV light treatment leads to the generation of hydrophilic groups and concomitant permselective transport of ionic species through the nanopores. It is anticipated that such nanofluidic devices will readily find applications in light-induced sensing and controlled drug release processes. References: [1] M. Ali, S. Nasir, H.Q. Nguyen, J.K. Sahoo, M.N. Tahir, W. Tremel, W. Ensinger, J. Am. Chem. Soc. 133 (2011) 17307. [2] M. Ali, S. Nasir, P. Ramirez, I. Ahmed, H.Q. Nguyen, L. Fruk, S. Mafe, W. Ensinger, Adv. Funct. Mater. 22 (2012) 390. This work has financially been supported by Beilstein-Institut in Frankfurt/Main in the frame of the project NanoBiC. Materials Analysis 75 Materials Modelling Division The research of the Materials Modelling Division is focused on multi-physics modelling of defect structures in functional oxides, 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. In 2011 a new high-performance CPU-GPU hybrid machine with 840 processor cores, which was funded by a BMBF-grant, became operational. 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 Plasticity of nanocrystalline metals and alloys o Metallic nanoglasses o Nanophase diagrams o Metallic nanoparticles under nanoextrusion Energy materials o Interfaces in Li-intercalation batteries o CIS/CIGS absorber materials o High-pressure phases of nitrogen o 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. A new master course on “Theoretical materials science” is currently under preparation. 76 Materials Modeling Division Staff Members Head Prof. Dr. Karsten Albe Emeritus Professor Prof. Dr. Hermann Rauh, M.A., C.Phys., F.Inst.P., F.I.M. (since April 2011) Research Associates Dr. Antti Tolvanen Dr. Jochen Rohrer PD Dr. Yuri Genenko (since April 2011) Dr. Galina Yampolskaya (since April 2011) Dr. Sergey Yampolskii (since April 2011) Secretary Renate Hernichel PhD Students Dipl.-Ing. Peter Agoston M.Sc. Daniel Sopu Dipl.-Phys. Johann Pohl Dipl.-Ing. Manuel Diehm Dipl.-Ing. Yvonne Ritter Dipl.-Ing. Melanie Gröting Dipl.-Ing. Silke Hayn Dipl.-Ing. Jonathan Schäfer Dipl.-Ing. Arno Fey M.Sc. Olena Lenchuk Diploma Students Arno Fey Ofer Hirsch Bachelor Students Konstanze Kalcher Stephen Weitzner Research Fellow Dr. Guang-Tong Ma (AvH) Guest Scientist Konstantin Avchachov Research Projects Forschergruppe 714, Plasticity of nanocrystalline metals and alloys, (DFG AL 578/7-2, 2006-2012) Quantenmechanische Computersimulationen zur Elektronen- und Defektstruktur oxidischer Materialien (SFB 595, Teilprojekt C1, 2007-2014) Materials Modeling Division 77 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 Gläser mit nanoskaligen Sekundärphasen (DFG AL578/13-1, 2011–2013) 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) PhD-Theses Agoston, Peter, Point defect and surface properties of In2O3 and SnO2: A comparative study by first-principles methods , [Online-Edition: urn:nbn:de:tuda-tuprints-27811] , TU Darmstadt (2011). D. Sopu, Molecular Dynamics Simulations of Metallic Nanoglasses. [Online-Edition: urn:nbn:de:tuda-tuprints-28453] TU Darmstadt (2011). Y. Ritter, Molecular Dynamics Simulations of Structure-Property Relationships in Cu-Zr Metallic Glasses. [Online-Edition: urn:nbn:de:tuda-tuprints-28685] TU Darmstadt (2012). 78 Materials Modeling Division Publications J. Pohl, K. Albe, Thermodynamics and kinetics of the copper vacancy in CuInSe2, CuGaS2 , CuInSe2, and CuGaS2 from screened-exchange hybrid density functional theory, J. Appl. Phys., 110 (2011) 109905. J. Pohl, K. Albe, Void formation in melt-grown silicon studied by molecular dynamics simulations: From grown-in faulted dislocation loops to vacancy clusters , App. Phys. Lett., 99 (2011) 081910. J. Pohl, A. Klein, K. Albe, Role of copper interstitials in CuInSe2: First-principles calculations. Phys. Rev. B (Rapid Comm.), 84 (2011) 121201. Y. Ritter, K. Albe, Thermal annealing of shear bands in deformed metallic glasses: Recovery mechanisms in Cu64Zr36 studied by molecular dynamics simulations , Acta Mat. (2011), 59, 7082-7094. Y. Ritter, D. Sopu, H. Gleiter, K. Albe, Structure, stability and mechanical properties of internal interfaces in Cu64Zr36 nanoglasses studied by MD simulations , Acta Mat., 59 (2011) 6588-6593. N. Q. Vo, J. Schäfer, R. S. Averback, K. Albe, Y. Askenazy, P. Bellon, Reaching theoretical strengths in nanocrystalline Cu by grain boundary doping , Scripta Mat., 65 (2011) 660-663. M. V. Hohmann, P. Agoston, A. Wachau, T. J. M. Bayer, J. Brötz, K. Albe, A. Klein, Orientation dependent ionization potential of In2O3: A natural source for inhomogeneous barrier formation at electrode interfaces in organic electronics, J. Phys. Cond. Mater. , 23 (2011) 334203. P. Agoston, K. Albe, Thermodynamic stability, stoichiometry, and electronic structure of bccIn2O3 surfaces. Phys. Rev. B, 84 (2011) 045311. D. Sopu, J. Kotakoski, K. Albe, Finite-size effects in the phonon density of states of nanostructured germanium: A comparative study of nanoparticles, nanocrystals, nanoglasses, and bulk phases. Phys. Rev. B, 83 (2011) 245416. M. Gröting, S. Hayn, K. Albe, Chemical order and local structure of the lead-free relaxor ferroelectric Na1/2Bi1/2TiO3, J. Solid State Chem., 184 (2011) 2041. W. N. Li, H. L. Duan, K. Albe, J. Weissmüller, Line stress of step edges at crystal surfaces. Surf. Sci., 605 (2011) 947. J. Schäfer, A. Stukowski, K. Albe, Plastic deformation of nanocrystalline Pd-Au alloys: On the interplay of grain boundary solute segregation, fault energies and grain size , Acta Mater., 59 (2011) 2957. Materials Modeling Division 79 P. Agoston, K. Albe, Disordered reconstructions of the reduced SnO2-(110) surface, Surf. Sci., 605 (2011) 714. D. Sopu, Y. Ritter, H. Gleiter, K. Albe, Deformation behavior of bulk and nanostructured metallic glasses studied via molecular dynamics simulations , Phys. Rev. B, 83 (2011) 100202 P. Agoston, K. Albe, R. M. Nieminen, M. J. Puska, Reply: “Comment on Intrinsic n-type Behavior in Transparent Conducting Oxides: A Comparative Hybrid-Functional Study of In2O3, SnO2, and ZnO”, Phys. Rev. Lett., 106 (2011) 069602 D. Gross, R. Müller, M. Müller, B. Xu, K. Albe, On the origin of inhomogenous stress and strain distributions in single-crystalline metallic nanoparticles, Int. J. Mat. Res. 102 (2011) 743 C. Koerber, A. Wachau, P. Agoston, K. Albe, A. Klein, Self-limited oxygen exchange kinetics at SnO2 surfaces, Phys. Chem. Chem. Phys., 13 (2011) 3223-3226. S.V. Yampolskii, Y.A. Genenko, C. Melzer, and H. von Seggern, Self-consistent model of unipolar transport in organic semiconductor diodes: accounting for a realistic density-ofstates distribution, J. Appl. Phys., 109 (2011) 073722 . K. Stegmaier, A. Fleissner, H. Janning, S.V. Yampolskii, C. Melzer, and H. von Seggern, Influence of electrical fatigue on hole transport in poly(p-phenylenevinylene)-based organic light-emitting diodes J. Appl. Phys., 110 (2011) 034507 . Y. A. Genenko, H. Rauh, and P. Krüger, Finite-element simulations of hysteretic ac losses in a bilayer superconductor/ferromagnet heterostructure subject to an oscillating transverse magnetic field, Appl. Phys. Lett., 98 (2011) 152508. K. Albe, P. Agoston, J. Pohl, Ab-initio modeling of defects in semiconductors, in, Advanced Characterization Techniques for Thin Film Solar Cells“ edited by Daniel Abou-Ras, Thomas Kirchartz and Uwe Rau, Wiley-VCH (2011), p. 479-497 80 Materials Modeling Division Chemical order and local structure of the lead-free relaxor ferroelectric Na1/2Bi1/2TiO3 Melanie Gröting, Silke Hayn, Karsten Albe Na1/2Bi1/2TiO3 (NBT) is a model relaxor ferroelectric with two different cations (Na+ and Bi3+) on the A-site of the perovskite structure. NBT-based materials show extraordinarily high strains and are amongst the most promising candidates to substitute the toxic PbZr1/2Ti1/2O3 (PZT) in piezeoelectric applications. Especially, recent results on N Na1/2Bi1/2TiO3-BaTiO3-K1/2Na1/2NbO3 (NBT-BT-KNN) solid solutions revealed promising piezoelectric properties.[1,2] The origin of this material’s relaxor behavior is still controversial, but in B-site mixed perovskites it is generally associated with heterovalent disorder.[3] NBT has aliovalent cations on the A-site (Na+ and Bi3+) in the exact ratio 1:1. For B-site mixed perovskites chemical ordering is generally understood.[4] Order, commonly rock-salt (111)-order, occurs when the charge difference between the cation species occupying the same crystallographic site is q≥2. In contrast, A-site ordering is much less common. There exist only a few examples where Asite order is experimentally found. Examples can be found in a review recently published by King and Woodward.[5] They show that A-site order commonly occurs in {001}-layers, but that charge differences between the cations of q≥2 are not sufficient to cause ordering. Systematic oxygen vacancies, vacancies in the A-sublattice or B-site ordering are necessary to stabilize chemical A-site order in mixed perovskites. In order to gain insights into the chemical ordering tendency, its driving force and the consequences for the local structure we investigated six different cation configurations in 2x2x2 (pseudo)cubic perovskite supercells using total energy calculations based on electronic density functional theory. We calculated total energies of the different Bi/Naorders in ideal cubic perovskite structures and in relaxed structures, the results are shown in Fig. 1 (contributions from ionic and cell shape relaxation are given separately). In the ideal perovskites the different configurations reveal only small variations in total energy of less than 120 meV, with 110-order being the most favored and 001-order being the most unfavored order type. Taking structural relaxations into account the maximal difference is almost doubled (220 meV). The most Fig. 1: Total energies from DFT calculations in ideal perovskite stable structure now is the layered (green) and relaxed structures (blue and red). The total energy 001-configuration, while the rockof the ideal perovskite 001 is set to zero. Energy changes from salt ordered system 111 becomes cell shape relaxation (red) are very small. the most unfavored one. Materials Modeling Division 81 In the perovskite structure oxygen is quasioctahedrally coordinated by Bi/Na- and Ti-atoms, with two Ti-atoms in the apical positions of the octahedron at a distance of a/2 and four Bi/Naatoms in the equatorial positions at a distance of a 2 , resulting in six possible oxygen environments characterized by the Bi/Na4xNa, 4xBi, 1xBi/3xNa, Fig. 2: Oxygen environments in the 2xBi/2xNa coordination: (cis)- and 2xBi/2xNa (trans)-coordination. The 3xBi/1xNa, and 2xBi/2xNa in cis- or transcis-coordination allows relaxation of the oxygen coordination, the latter two are shown in Fig. 2. anion while the trans-coordination does not. Oxygen ions are expected to displace, if there are significant differences in size, charge or bond strength of the coordinating cations and if the oxygen ion is not an inversion center. Hence, among the six possible coordinations, there are three where no displacement of the oxygen ion is possible (inversion symmetry), namely 4xNa, 4xBi and 2xBi/2xNa (trans), one coordination where displacing is severely facilitated 2xBi/2xNa (cis), while in 3xBi/1xNa and 1xBi/3xNa smaller displacements towards the Bi ions can occur. These displacements can help to release local stresses and to compensate local charge imbalances, thus stabilizing certain configurations. Local ionic displacements are observed mainly on the oxygen sublattice in the exact way postulated by Knapp,[6] while almost no displacements on the two cation sublattices are observed. Moreover structural relaxation can reverse the stability of the considered configurations with respect to the ideal perovskite structure. In the rock-salt ordered structure all oxygen anions are in the 2xBi/2xNa (trans) coordination, which explains why this configuration does not relax at all. We report for the first time on displacive disorder on the oxygen sublattice, which up to now has been neglected in experimental studies and should be investigated in more detail in future research. In order to identify the driving force for these oxygen displacements we present partial densities of state in Fig. 3, before and after relaxation of the chemical configuration 001 in comparison with 111. It can be seen that upon relaxation additional Bi 6s-states arise at the top of the valence band. Although the maximum of 6s-states stays below the valence band around -10.0 eV, there is a significant increase of the state density in the anti-bonding region above -2 eV, these states mix with both the Bi 6p-states and the O 2p-states, which is characteristic for the formation of a stereochemically active Bi3+ lone pair.[7] This hybridization of Bi 6sp─O 2p states leads to a considerable energy gain, which increases the stability especially of structures with layers of high Bi-concentrations in {001}-planes. This kind of planes was considered by Kreisel et al. to explain the diffuse scattering patterns indicative for Guinier-Preston-Zones.[8] Generally, chemical ordering will occur if there is a decisive energy difference between a most favored ordered configuration and other structures and if this energy difference is higher than the entropy contribution of mixing. We find an energy difference of 34 meV between the two most stable structures with 001- and 10-01-order. The entropy contribution of mixing to the free energy in the disordered state can be approximated by the configurational entropy of an ideal solution with xBi=xNa=0.5 by -TS=-kBT [- xBiln xBi - xNaln xNa] 82 Materials Modeling Division Fig. 3: Densities of states of chemical configurations 111 (left) and 001 (right) before (black dotted line) and after relaxation (filled). Energies are given relative to the valence band maximum. On structural relaxation possible in all structures except the 111 configuration - band gaps are enlarged and changes especially of the Bi 6s- and O 2p-state densities occur. This approximation gives a lower limit for the ordering temperature, since the ideal solution model is overestimating the mixing entropy. At sintering conditions the energy equivalent TS is more than twice the obtained energy difference between the most stable ordered states, thus the disordered state is favored over all ordered states. The critical temperature is about 570 K. Chemical long-range ordering can therefore be ruled out, but short-range ordering with alternating layers of Bi and Na along 001 -directions is still possible to occur. Thus, depending on synthesis conditions, different degrees of short-range order can be expected. References: [1] [2] [3] [4] [5] [6] [7] [8] W. Jo, T. Granzow, E. Aulbach, J. Rödel, D. Damjanovic, J. Appl. Phys., 105 (2009) 094102. J. Rödel, W. Jo, K. T. P. Seifert, E. M. Anton, T. Granzow, D. Damjanovic, J. Amer. Cer. Soc. 92 (2009) 1153-1177. A. A. Bokov, Z. G. Ye, J. Mat. Sci. 41 (2006) 31-52. P. K. Davies, H. Wu, A. Y. Borisevich, I. E. Molodetsky, L. Farber, Ann. Rev. Mat. Res. 38 (2008) 369-401. G. King, P. M. Woodward, J. Mat. Chem. 20 (2010) 5785-5796. M. C. Knapp, P. M. Woodward, J. of Sol. State Chem. 179 (2006) 1076- 1085. L. A. Olsen, J. Lopez-Solano, A. Garcia, T.Balic-Zunic, E. Makovicky, J. Sol. Stat. Chem. 183 (2010) 2133-2143. J. Kreisel, P. Bouvier, B. Dkhil, P. A. Thomas, A. M. Glazer, T. R. Welberry, B. Chaabane, M. Mezouar, Phys. Rev. B 68 (2003) 014113. Materials Modeling Division 83 Optical transmittance of photonic structures with logarithmically similar dielectric constituents H. Rauh, G.I. Yampolskaya, S.V. Yampolskii Photonic crystals in the traditional sense are regularly structured, synthetic composites made up of materials with different refractive indices. The spatial variation of the refractive index significantly modifies the spectral characteristics of electromagnetic waves, bringing about features such as transparency bands and stop bands or bandgaps. It would be extremely desirable to find optical-mirror and filter properties—high reflectance over some range of frequency and high transmittance, or selectivity, otherwise—united in one single photonic device. Exploring photonic structures which reveal transparency at low frequencies, but opacity, or possibly selectivity, at higher frequencies, thus suggests itself. By means of a vector potential approach, we have explored, both analytically and numerically, the optical transmittance of one-dimensional photonic structures in the form of logarithmically similar, layered stacks made up of pairs of lossless dielectric plates, assuming linearly polarized electromagnetic radiation at normal incidence. Resorting to an analysis of the respective photonic modes, the dependence on frequency (or, equivalently, the variation with the characteristic structural length) of the optical property addressed has been established for a singly logarithmic stack (Fig. 1) as well as for two of its symmetric derivatives, an outbound doubly logarithmic stack (Fig. 2 (left)) and an inbound doubly logarithmic stack (Fig. 2 (right)). Fig. 1: Schematic view of a singly logarithmic stack with dielectric constituents a (red) and b (yellow) embracing four unit cells, characterized by a layering of the type abab... (left) or baba... (right) and excited by normally incident electromagnetic radiation with the electric (magnetic) field oriented parallel to the x-axis and the magnetic (electric) field oriented parallel to the y-axis of a Cartesian coordinate system x, y, z. Fig. 2: Schematic view of an outbound doubly logarithmic stack (left) and of an inbound doubly logarithmic stack (right) with dielectric constituents a (red) and b (yellow) embracing eight unit cells, characterized by a layering of the type abab...abba...baba and excited by normally incident electromagnetic radiation with the electric (magnetic) field oriented parallel to the x-axis and the magnetic (electric) field oriented parallel to the y-axis of a Cartesian coordinate system x, y, z. 84 Materials Modeling Division Let us consider a series of one-dimensional, layered stacks of pairs of dielectric plates based on one or two sets of m 2 unit cells numbered by the index μ, spreading infinitely along the x- and y-directions, with respective extent dμ in the z-direction of a Cartesian coordinate system x, y, z. Each unit cell includes alternating constituents a and b characterized by respective thicknesses da,μ=αdμ and db,μ=βdμ with definite structural parameters 0<α,β<1, where α+β =1, so that dμ=da,μ+db,μ, for μ=1, 2, ... , m. The stacks themselves reveal logarithmic similarity by dint of reduced thicknesses da,μ and db,μ, and therefore reduced lateral extent dμ, when following the sequence μ =1, 2, ... , m, such that the ratio of the thicknesses of any corresponding successive plates, and hence the ratio of the widths of any two adjacent unit cells, is the same constant, da,μ+1/da,μ=db,μ+1/db,μ=dμ+1/dμ≡ introducing the fixed structural parameter 0<τ<1, which admits the representations da,μ=ατμ−1d1 and db,μ=βτμ−1d1, and consequently dμ= τμ−1d1. The total lateral extent of the first μ unit cells thus is lμ = d ≡ 1 1 1 d1 and the respective distances at which the constituents a and b accommodated in the next unit cell terminate are la,μ+1=lμ+da,μ+1 and lb,μ+1=lμ+db,μ+1 for μ=1, 2, ... , m−1. The optical properties of the constituents a and b are supposed to be entirely determined by fixed values of the principal components of their respective tensors of electric permittivity εν=εa>1 and εν=εb>1 for ν = x, y, neglecting electromagnetic dispersion as well as dissipation and assuming in-plane crystalline isotropy. Our investigations yielded the following key results: (i) the transmittance of the singly logarithmic stack shows single oscillatory maxima of almost full height at low frequencies and total quench, i.e. full reflectance, at larger frequencies, combining properties of a practically ideal transmission filter and of a perfect mirror alike (Fig. 3); (ii) the transmittance of the outbound doubly logarithmic stack shows twinned oscillatory maxima of full height at low frequencies, supplemented with a sharp, full resonance at a higher frequency against a background of suppressed transparency, revealing traits of a practically Fig. 3: Transmittance Tsl of the singly logarithmic stack of total lateral extent lm as a function of the normalized frequency ωd1/2πc in the case of linearly polarized electromagnetic radiation due to on-axis propagation, for the structural parameters m = 25, α = 0.1, β = 0.9, τ = 0.95 and the dielectric parameters εa = 20, εb = 1.5, referring to a layering of the type abab... (left) and, respectively, baba… (right). ideal transmission filter and of a perfect band-pass filter at the same time (Fig. 4 (left)); (iii) the transmittance of the inbound doubly logarithmic stack shows twinned oscillatory maxima of full height at low frequencies, supplemented with a series of pairs of sharp Materials Modeling Division 85 spikes of full transparency for higher frequencies against a background of suppressed transparency, equally revealing traits of an ideal transmission filter and of a perfect bandpass filter at the same time (Fig. 4 (right)). Fig. 4: Transmittance Tdl(o) of the outbound doubly logarithmic stack (left) and Tdl(i) of the inbound doubly logarithmic stack (right) of total lateral extent 2lm as a function of the normalized frequency ωd1/2πc in the case of linearly polarized electromagnetic radiation due to on-axis propagation, for the structural parameters m = 25, α = 0.1, β = 0.9, τ = 0.95 and the dielectric parameters εa = 20, εb = 1.5, referring to a layering of the type abab...abba...baba. The sharp, full resonance of the transmittance found in the case of the outbound stack and the pairs of sharp spikes of full transparency found in the case of the inbound stack derive from different origins: the former is due to a localized photonic mode associated with the internal defect of the outbound stack; the latter, in contrast, arise from extended photonic modes that spread across the entire domain of the inbound stack. Our study proves that one-dimensional photonic structures generated by logarithmically similar dielectric constituents are indeed capable of unfolding desirable and useful optical properties in one single photonic device: transparency at low frequencies, but opacity, or selectivity, at higher frequencies. 86 Materials Modeling Division Materials for Renewable Energies Research in the Renewable Energies group focuses on nanoscaled catalysts applied predominantly in low and intermediate temperature fuel cells, but also in heterogeneous catalysis applications, using advanced ex situ, in situ, and, in particular, operando techniques. The systematic structural and electrochemical characterization 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 cyclic voltammetry (CV) and single cell fuel cell experiments. 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, e.g. electron conducting oxides and polymers, which do not suffer from corrosion in the severe conditions of the cathode side 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. Furthermore, shape-selected nanoparticles are 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 membrane-electrode assemblies (MEA) allowing for a welldefined 3D architecture. Electron microscopy is applied for the electrodes’ detailed characterization. For this specific purpose, new techniques have been developed and established in the group starting from sample preparation by ultramicrotomy and Wood’s alloy infiltration to very sophisticated mapping methods. For the first time, the focused ion beam (FIB) technique was applied to obtain 3D reconstructions of the porous electrodes. • In situ studies In situ and operando X-ray absorption studies play an important role in our recent activities with respect to the systematic investigation of reaction and degradation mechanisms. A special 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 membrane-electrode assembly (MEA). By this approach, electrode areas with more severe degradation can be identified. In addition to the 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 with further catalyst optimization. In 2011, the novel technique has been applied to direct methanol fuel cells and HT-PEM fuel cells, and a “cross-talk” between both electrodes via protons was unravelled. Since March 2011, Prof. Roth holds a group leader position at the Institute for Applied Materials (IAM) – Energy Storage Systems (ESS) (Head: Prof. Helmut Ehrenberg) at Karlsruher Institute of Technology (KIT) in Karlsruhe. Research at IAM-ESS focuses on electrochemical storage technology in general, while the Roth group is in particular interested in redox-flow batteries. Financial support is provided by DFG, BMWi, BMBF, and EU as well as by the respective synchrotron facilities and industrial partners. The group`s research interests are covered by a lecture on “Applied electrochemistry: fuel cells and batteries” and a practical course “Xray absorption spectroscopy – fundamentals and data analysis”. Furthermore, a workshop on “Scientific work and presentation skills” is mandatory for the bachelor students. Materials for Renewable Energies 87 Staff Members Head Prof. Dr.-Ing. Christina Roth Secretaries Maria Bense (joint with Profs. Donner and Xu) PhD Students Dipl.-Ing. Susanne Zils MSc. Ditty Dixon Dipl.-Ing. Sebastian Kaserer Dipl.-Ing. (FH) Hanno Butsch (extern) Dipl.-Ing. Alexander Schökel Dipl.-Ing. Benedikt Peter Dipl.-Ing. André Wolz Diploma Students Manfred Kerner Christoph Rakousky (extern) Joachim Langner Christoph Schwöbel Guest Scientists Manoj Krishnan (DAAD) Research Projects German-Canadian fuel cell cooperation (BMWi project 2010-2012) 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 F. Ettingshausen, J. Suffner, S. Kaserer, H. Hahn, C. Roth, ’Sb-doped SnO2 hollow spheres offering micro and nano porosity for the fuel cell electrode structure’, Advanced Energy Materials 1 (4) (2011) 648-654, DOI: 10.1002/aenm.201100077. M. Soehn, S. Zils, N. Nicoloso, C. Roth, ’Effective debundling of CNTs and simultaneous synthesis of Pt nanoparticles by Nafion® induced emulsions’, J. Power Sources 196 (2011), 6079-6084. D. Dixon, K. Wippermann, J. Mergel, A. Schoekel, S. Zils, C. Roth, ’Degradation effects at the methanol inlet, outlet and center region of a stack MEA operated in DMFC’, J. Power Sources 196 (2011) 5538-5545. F. Muench, S. Kaserer, U. Kunz, I. Svoboda, S. Lauterbach, H.-J. Kleebe, C. Roth, W. Ensinger, ’Electroless synthesis of platinum and platinum-ruthenium nanotubes and their application in methanol oxidation’, J. Mater. Chem. 21 (2011) 6286-6291. M. Rauber, I. Alber, S. Müller, R. Neumann, O. Picht, C. Roth, A. Schoekel, M. E. Toimil-Molares, W. Ensinger, “Highly-ordered supportless 3-D nanowire networks with tuneable complexity and interwire connectivity for device integration”, Nano Letters 11 (6) (2011) 2304-2310. C. Roth, D. E. Ramaker, 'EXAFS investigations of PEM fuel cells'. Modern Aspects of Electrochemistry, ed. C. Vayenas, 51, chapter 3 (2011) 159-201. 88 Materials for Renewable Energies Effective debundling of CNTs and simultaneous synthesis of Pt nanoparticles by Nafion® induced emulsions Matthias Soehn, Susanne Zils, Norbert Nicoloso, Christina Roth Carbon nanotubes, discovered by Iijima in 1991 [1], show unique properties regarding chemical stability, electronic conductivity and tensile strength. They also provide a high surface area of up to 2200 m2g-1, which is essential for good catalytic activity. Without oxidative treatment hydrophobic surface properties can be observed. Depending on their morphology, carbon nanotubes (CNT) are separated into single wall (SWNT) and multi wall nanotubes (MWNT). Both types have a high aspect ratio with diameters of 1-20 nm and lengths of a few micrometers. Many groups focus on carbon nanotubes as a replacement for the commercial carbon black as catalyst support. Carbon nanotubes have the disadvantage that they apparently offer less anchor sites for the deposition of metallic nanoparticles. Therefore, they require specific pre-treatments, as for example the addition of hydrophilic groups by acid treatment or organic groups like diazonium salts. However, probably due to their higher crystallinity they undergo less support corrosion in the extreme environment of PEM fuel cells. A common way to deposit nanometer-sized catalyst particles with a narrow size distribution homogeneously on a high-surface area carbon support, for instance Vulcan XC-72 or Ketjen black, is reduction via ethylene glycol as described by Bock et al. [2]. This method is rather facile, reproducible and also cheap, as compared to chemical vapour deposition and the like. It is also suitable to deposit Pt on CNTs, but unfortunately the 1-dimensional nature of the CNTs is prone to form aggregates and “nests” in ethylene glycol or other polar liquids. These cannot easily be penetrated by the reactants. And thus, it proves difficult to obtain homogeneous nanoparticle dispersions on CNTs, especially at the high metal loadings required for direct methanol fuel cells (DMFC). Usually, surfactants like sodium dodecyl sulfate or block copolymers are used to mediate between polar liquids and CNTs. For fuel cell operation and also other catalytic reactions, these have to be removed prior to their application, as they might affect further reactions negatively. Moreover, surfactants seem to increase the contact resistances within a CNT buckypaper. This paper presents a method to debundle and finely disperse CNTs in aqueous solution by using Nafion® ionomer and butyl acetate to form a stable emulsion [3]. This helps to make a larger fraction of the CNTs accessible to the reducing agent, so that 3 nm Pt particles with a very narrow size distribution are homogeneously deposited on the support. In the same step, the CNTs are coated with Nafion® to improve their ionic conductivity. This appears to be also advantageous for the final electrode manufacturing step, since it allows applying the conventional airbrush technique also in those cases, in which CNTs are used as support material. Catalyst synthesis 60 mg multi wall carbon nanotubes (Elicarb© from Thomas Swan, U.K.) are mixed and stirred with 60 ml nitric acid (68%) and treated with ultrasound (Hielscher UPV 100) for 10 min to remove metallic impurities. After diluting with water, the suspension is vacuumMaterials for Renewable Energies 89 filtrated over a 47 mm polycarbonate membrane with 0.4 µm pore size. Remaining acid is removed by rinsing with water several times. The wet CNT residue is removed from the polycarbonate membrane and mixed with 60 ml butyl acetate while stirring and ultrasonic treatment for 10 min, leading to a homogeneous dispersion. For the platinum precursor solution, 145 mg potassium hexachloroplatinate (Sigma-Aldrich) is dissolved in 10 ml ultrapure water at 50°C. 60 ml ethylene glycol and the platinum precursor solution are mixed with the MWNT-butylacetate dispersion in a 250 ml round bottom flask. After adding 0.5 ml of 5% Nafion® solution (Dupont D521) and another 15 min of ultrasonic treatment and stirring, the two phase boundary between the liquids disappears and a homogeneous milky-grey emulsion is created. The emulsion is heated in an oil bath from room temperature to 170°C and the mixture is held for 120 min under reflux conditions while stirring. Samples are taken during the synthesis for a detailed investigation by XRD. After cooling down, the catalyst-solvent mixture is filtered over a polycarbonate filter. Rinsing with 1:1 isopropanol-water removes the remaining ethylene glycol and butyl acetate. After removal of the filter, the wet residue is mixed with 30 ml isopropanol and 30 ml water by ultrasonic treatment to create a sprayable ink. Nafion® and/or PTFE solution can be added here. MEA preparation and electrochemical investigation by IV curves For membrane preconditioning, pieces of Nafion® 117 are heated up to 80°C in 500 ml of 1 M sulphuric acid with 20 ml of 30% hydrogen peroxide solution for 2 h. After rinsing with DE-water, the membrane is fixed to a heated table (110°C) by means of a mild vacuum. Airbrush is used to apply the aqueous catalyst ink onto the membrane. 2 ml ink is sprayed on each side, which corresponds to a maximum Pt loading of 0.2 mg cm-2. Each layer is allowed to dry before it is covered by the next one. The MEA is covered with two pieces of carbon cloth and fixed between gold-plated stainless steel plates with a meander flow field. The cell is fed with pure H2 and O2 at atmospheric pressure. Both gases are humidified by bubblers at 90°C. The cell temperature is set to 75 °C. After a couple of hours in cell conditioning, IV curves are recorded in potentiostatic mode with an electronic load, compensating contact resistances. Results and discussion Nafion® induced emulsions A mixture of CNTs and butyl acetate leads to a homogeneous black dispersion after ultrasonic treatment. Adding ethylene glycol and yellow-coloured aqueous K2PtCl6 solution, a sharp phase boundary is observed (Fig. 1, left). Even with strong ultrasonic treatment it is not possible to mix the phases. If some Nafion® solution is added, a stable grey emulsion is created, however. Obviously, Nafion® acts like a surfactant. Microscopic analysis shows spheres (diameter of ~50 µm) with a black shell in clear liquid (Fig. 1, middle). To distinguish ethylene glycol and butyl acetate, fluorescin (CAS: 2321-07-5) is used as colouring agent. Without the black MWNTs, it can be clearly seen in Figure 1 right that the colourless butyl acetate is located inside the spheres, whereas the ethylene glycol phase remains outside. This effect can be explained by the amphiphilic nature of Nafion ® with its hydrophobic tetrafluoroethylene chains and hydrophilic SO3- groups. A Critical Micelle Concentration (CMC) could not be detected by diluting experiments with the Nafion ® solution. Therefore, the influence of other surfactants could be excluded. 90 Materials for Renewable Energies Figure 1: left: CNT-butylacetate phase (black) and ethylene glycol with platinum precursor (yellow) before ultrasonic treatment; middle: micro spheres of butyl acetate with walls of CNT- Nafion® composite in ethylene glycol; right: ethylene glycol (coloured yellow with fluorescin) and butyl acetate (inside the spheres) without CNTs. For the observed effects we assume a model as depicted in Figure 2: Nafion ® acts as an emulsifying agent and forms the boundary between ethylene glycol and butyl acetate. The carbon nanotubes tend to move towards the hydrophobic side chains of the Nafion ® molecules. This leads to a high interface area of approx. 12 m² for this 120 ml batch, providing an excellent debundling of the CNTs, which increases the homogeneity of the following deposition of nanoscaled platinum particles. Concurrently, Nafion® and CNTs are perfectly mixed, which is essential for a good three-phase contact of the catalyst particles. Butyl acetate has been chosen because it was reported by Uchida [4] that a Nafion® solution tends to form colloids with solvents having a dielectric constant between 3 and 10. Figure 2: Modell of CNT – Nafion® emulsion and formation of the micro spheres. Materials for Renewable Energies 91 Structural and electrochemical characterization Figure 3 proves the uniform distribution of platinum on the multi walled carbon nanotubes. The derived particle statistics show a narrow size distribution of 3 nm ± 0.5 nm, providing a high active area for catalytic reactions. This has been verified by XRD measurements during the catalyst synthesis. The yield of the platinum deposition is nearly 100 %, as no traces of Pt could be found in the filtrate using XRF analysis (not shown here). Pt particle size distribution 40 rel. Frequency 35 rel. Frequency (%) 30 25 20 15 10 5 0 1 2 3 4 5 6 7 Particle size (nm) Figure 3: TEM image of Pt/MWNTs after synthesis and corresponding particle size distribution. Dispersions of carbon nanotubes and water form paper-like structures while drying. If this dispersion is dried directly on a sheet of Nafion® 117, the residue is very inhomogeneous because the resulting CNT paper tends to shrink during drying, while the highly hygroscopic Nafion® substrate swells. Both effects can be prevented using a heated vacuum table for the substrate and a conventionally-applied airbrush technique [5] for applying the aqueous Pt/MWNT/Nafion® dispersion. Here, the good blending between Nafion® and MWNTs leads to a good dispersion of solid matter in water/isopropanol. Consequently, agglomerations are prevented, which could otherwise block the nozzle of the airbrush device. The liquid is separated into small droplets during spraying, which dry immediately on the heated Nafion® surface. Thus, shrinking is limited to a very small region and a homogeneous dull black surface can be obtained. Each layer is allowed to dry by moving the airbrush pistol in serpentine movements. The mechanical stability of the electrode was suitable for different layer thicknesses. The electrode material sticks tightly to the membrane even without any additional temperature or pressure treatment. A porous feltlike nanotubes-structure can be observed, which provides a good electrical contact to the GDL as well as an excellent permeability for gases. The suitability of such a membrane-electrode assembly (MEA) for fuel cell applications was demonstrated in single cell fuel cell tests. The MEA with a platinum loading of 0.2 mg cm-2 on each side was equipped with a conventional carbon gas diffusion layer and tested in a fuel cell test bench with pure H2 and O2. After a few hours of operation, an IV curve was recorded. Power densities up to 450 mW cm-2 were observed and the suitability of the novel synthesis technique thus demonstrated. 92 Materials for Renewable Energies Conclusion The presented work describes a new emulsion-based method to finely disperse CNTs in a polar liquid. It significantly reduces aggregation of the support material by providing an excellent debundling of the CNTs during synthesis. Consequently, the support is easily accessible to the hydrophilic Pt precursors so that even at high metal loadings necessary for DMFC operation a high dispersion of the catalytically active nanoparticles was obtained. By using Nafion® as a surfactant, a homogeneous distribution of the proton conductive ionomer in the electrode was achieved. The resulting Pt/MWNT/Nafion® composite material is more hydrophilic than the untreated MWNTs, which is needed to create a homogeneous ink suitable for airbrush spraying onto a hot substrate. Nafion® contents were optimized for both synthesis and fuel cell operation. Consequently, highly efficient CNT electrodes could be manufactured as proven by characteristic IV curves with peak power densities of 770 mW cm-2. Acknowledgments Financial support by the EC integrated project CANAPE (Contract No. 500096) is gratefully acknowledged. We also want to thank C. Fasel, J.C. Jaud and D. Stuermer for TGA and XRD measurements. References S. IIJIMA, HELICAL MICROTUBULES OF GRAPHITIC CARBON , NATURE. 354 (1991) 56-58. C. BOCK, C. PAQUET, M. COUILLARD , G.A. BOTTON, B.R. MACDOUGALL , SIZE-SELECTED SYNTHESIS OF PTRU NANO -CATALYSTS: REACTION AND SIZE CONTROL MECHANISM , JOURNAL OF THE AMERICAN CHEMICAL SOCIETY. 126 (2004) 8028-8037. M. SOEHN, S. ZILS, N. NICOLOSO , C. ROTH, EFFECTIVE DEBUNDLING OF CNTS AND SIMULTANEOUS SYNTHESIS OF P T NANOPARTICLES BY N AFION® INDUCED EMULSIONS, JOURNAL OF POWER SOURCES. 196 (2011) 6079-6084. M. UCHIDA, Y. AOYAMA, N. EDA, A. OHTA, INVESTIGATION OF THE MICROSTRUCTURE IN THE CATALYST LAYER AND EFFECTS OF BOTH PERFLUOROSULFONATE IONOMER AND PTFE-LOADED CARBON ON THE CATALYST L AYER OF POLYMER ELECTROLYTE FUEL C ELLS, JOURNAL OF THE ELECTROCHEMICAL SOCIETY. 142 (1995) 4143-4149. M.S. WILSON, S. GOTTESFELD , HIGH PERFORMANCE CATALYZED MEMBRANES OF ULTRA -LOW PT LOADINGS FOR POLYMER E LECTROLYTE FUEL CELLS, JOURNAL OF THE ELECTROCHEMICAL SOCIETY. 139 (1992) L28-L30. Materials for Renewable Energies 93 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 Agarwal Dr. Marek Janko Technical Personnel N.N Secretary Imke Murschel PhD Students Dipl.-Biol. Elke Kämmerer Dipl.-Min. Maximilian Köhn Dipl.-Phys. Agnieska Voß Bachelor, Master, and Silke Pufahl Diploma Students Sandra Schäfer Sandro Setzer Dr. Christian Dietz M. Sc. Kim Lieu Phuong (LMU) M.Sc. Assma Siddique M.Sc. Limor Zemel Lukas Romanowski Marcus Schulze Research Projects Titanomagnetite STA 1026/2-1 (LMU, DFG 2007 – 2011) Nanostruktur und Benetzungseigenschaften von Porenraumoberflachen (LMU, BMBF 2008 – 2011) 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) 94 Physics of Surfaces Publications Bauer M., Davydovskaya P., Janko M., Kaliwoda M., Petersen N., Gilder S. and Stark R. W. Raman spectroscopy of laser-induced oxidation of titanomagnetites; J. RAMAN SPECTROSC. 2011; 42:1413 – 1418 Wei T., Gong J., Rössle S. C., Jamitzky F., Heckl W. M., Stark R. W. A leucine-rich repeat assembly approach for homology modeling of the human TLR5-10 and mouse TLR11-13 ectodomains; J. MOL. MODEL. 17 (2011) 27-36. Peter D., Dalmer M., Lechner A., Gigler A. M., Stark R. W., Bensch W. Measurement of the mechanical stability of semiconductor line structures in drying liquids with application to pattern collapse. J. MICROMECH. MICROENG; 21 (2011) 025001. Gorbushina A. A., Kempe A., Rodenacker K., Jütting U., Altermann W., Stark, R. W., Heckl, W. M., Krumbein, W. E.; Quantitative 3-dimensional Image Analysis of Mineral Surface Modifications – Chemical, Mechanical and Biological; GEOMICROBIOLOGY J. 28 (2011) 172 – 184 Physics of Surfaces 95 Mechanical stability of semiconductor line structures in drying liquids D. Peter1, M. Dalmer1, A. Lechner2, A. M Gigler3, R. W Stark4 and W. Bensch5 1 Lam Research AG, SEZ Str. 1, 9500 Villach, Austria 2 Department of Microsystems Engineering, FH Regensburg, 93049 Regensburg 3 Department of Earth and Environmental Sci., LMU München, 80333 München 4 Center of Smart Interfaces & Institute of Materials Science, TU Darmstadt, 64287 Darmstadt 5 Department of Inorganic Chemistry, Christian-Albrechts-Universität zu Kiel, 24098 Kiel Each wafer of a state-of-the-art dynamic random access memory (DRAM) product is subject to more than 100 cleaning steps during the manufacturing process. Current cleaning techniques can be categorized into two technologies: ‘dry’ cleaning based on plasmas or vapors or ‚wet’ cleaning based on liquids, such as the RCA (‘Radio Corporation of America’) cleaning sequence [1]. A typical wet cleaning technique includes etching of the surface layer and rinsing the contamination, such as, polymers, particles, or metal ions, from the surface. As the requirements for material loss are becoming increasingly strict, this limits the etching of the surface layer and therefore the choice of possible cleaning approaches [2]. High aspect ratio structures such as stacked capacitors, shallow trench insulators, and gate structures are very sensitive to lateral forces. These not only occur in advanced cleaning processes, but also during basic wet processing due to drag forces in the fluid, centrifugal forces during spin cleaning, or capillary forces [3]. Forces need to be controlled for a non-damaging wet cleaning process. To ensure optimum process performance with future and therefore smaller technology generations, a better understanding of the stability of high aspect ratio structures is required. To this end, the stability of nanostructures with respect to lateral forces has been characterized mostly in air [4–8]. However, the liquid media used in wet processing may also affect the stability of the nanostructures, for example by stress corrosion processes or viscous effects. We thus investigate the lateral stability of polysilicon line structures against an AFM tip in various solvents. The damage size was influenced by the physical properties of the liquid. AFM-induced collapse To induce collapse of the line structures, low feedback parameters were used such that the AFM tip did not follow the local topography. Thus, the tip exerted lateral forces on the test structure (Figure 1). Typically, the following events occurred: (i) The AFM tip touched the wall-like structure only on the top because of the high aspect ratio of the structure compared to the geometry of the AFM tip. (ii) Without the topographic feedback, the tip exerted lateral forces on the structure. The force increased proportionally with the torsional stiffness of the cantilever, up to the point where the stress induced by the AFM tip exceeded the fracture limit of the line structure (figure 2). (a) (b) Figure 1. Principle of lateral force microscopy (a) and tip induced collapse (b). 96 Physics of Surfaces Test structures and media The structures for fracture testing were purchased from IMEC (Leuven, Belgium). The patterns consisted of lines with a length of a few millimeters. Each line consisted of a stack of 100 nm polysilicon on top of a thin silicon oxy-nitride (2.4 nm) layer, with a SiO2 cap of 50 nm as shown in figures 2(a) and (b). The nominal line width was 40 nm with a spacing of 1 μm and for the visualization of the damage also 50 nm structures with a spacing of approximately 200 nm were used. The liquids used for the experiments included isopropanol (IPA, VLSI grade), propylene carbonate (PC, IUPAC: 4- methyl-1,3-dioxolan-2-one (Selectipur)), and de-ionized water (DI water, 18.2 M� (Milli-Q)). DI water mixtures with sucrose were used to obtain higher viscosities. Two solutions of 30 wt% and 40 wt% sucrose were prepared and are referred to as S30 and S40. The samples and the AFM tip were completely immersed in the liquid. The amount of liquid was sufficiently large such that the thickness of the liquid (several millimeters) did not influence the AFM measurements. Figure 2. The design of the patterns (a) and two SEM micrographs showing a set of line structures (b). The shape of the damage generated with the AFM tip was similar for all tested media. The yield line of the structure was always symmetrically curved which indicates a conchoidal fracture. Differences were observed in the lengths of the broken parts of the line. The corresponding debris usually consisted of only a single piece (figure 3). Fracture mechanism A stress corrosion crack (SCC) process is a possible candidate to explain the fracture. SCC lowers the absolute fracture strength of the Si−O−Si bonds. Such a process has been observed for polysilicon [9] and single-crystal silicon [10] in DI water. However, the opposite was also reported for the latter [11]. Michalske et al [12] suggested a model for a SCC process for silicon oxide. It explains the reduced stability of the Si−O−Si bond due to the bond angle variation which increases its chemical reactivity. Thus, no influence of the surface tension, density, or viscosity would be expected on the fracture force. Figure 3. SEM micrograph of characteristic round damage as observed for tests in air. Sample covered in Pt for better contrast. Physics of Surfaces 97 Figure 4. Experimental collapse forces in various media. The box encloses 50%. The asterisks denote the extreme values measured. For every medium there are data points from at least 20 different measurements except for S30 and PC+IPA . The SCC process is a very slow process, and crack tip velocities between 10 −6 and 10−7 m s−1 are expected [11], much smaller than the Rayleigh wave speed in silicon (2–3 km s−1) at which cracks usually propagate. Taking into account that the fracture process occurs within less than 2 ms would allow SCC-assisted rupture lengths of only a few nanometers. Thus, SCC can only be responsible for a small part of the rupture line, which is 40 nm perpendicular to the line and larger than 300 nm along with the line. Characteristic differences occurred in the lengths of the generated damage mainly depending on the bulk properties of the liquid media. The fracture force (Fig. 4) and the damage size (not sgown) did not correlate with each other. A two-step breaking model seems favorable where the fracture force is determined by the crack initiation and the damage size determined in a second step by the bulk of the surrounding liquid. A stress corrosion crack process has to be excluded due to the time scale of the rupture. For the crack initiation, a stress corrosion crack process on the surface can explain the influence of the surrounding media. With further reduction of the line width in future structures, a higher influence of the media on the mechanical stability is expected. References: [1] Kern W and Puotinen D A 1970 RCA Rev. 31 187 [2] International Technology Roadmap for Semiconductors, Front End Processes 2007 www.itrs.net [3] TanakaT,MorigamiMandAtodaN1993Japan.J.Appl. Phys. 32 6059 [4] Kim T G, Wostyn K, Mertens P W, Busnainan A A and Park J G 2010 Nanotechnology 21 015708 [5] Peter D, Dalmer M, Kruwinus H, Lechner A, Gaulhofer E and Bensch W 2008 ECS Trans. 13 323 [6] Kim T G, Wostyn K, Mertens P W, Busnainan A A and Park J G 2007 ECS Trans. 11 123 [7] Kawai A and Kaneko Y 2000 Japan. J. Appl. Phys. 39 1426 [8] KimS-K,JungM-H,KimH-W,WooS-GandLeeH2005 Nanotechnology 16 2227 [9] Kahn H, Ballarini R, Bellante J J and Heuer A H 2002 Science 298 1215 [10] KomaiK,MinoshimaKandInoueS1998Microsyst.Technol. 5 30 [11] WongBandHolbrookRJ1987J.Electrochem.Soc.1342254 [12] Michalske T A and Freiman S W 1983 J. Am. Ceram. Soc. 66 284 98 Physics of Surfaces 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. Peter Marek 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. Azad Jaberi Darbandi 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 Diploma Students Ruben Bischler Ralf Witte Joint Research Laboratory Nanomaterials Dr. Martin Hollertz Dr. Mohammad Ghafari 99 Research Projects EU-Projekt, 7th Framework, MAHEATT FP7-ENERGY-NMP-2008-2011 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 262/1-1, 2009 – 2011) Investigation of non-equilibrium phonon populations in biased metallic single-walled carbon nanotubes (DFG OR 262/1-2, 2011-2013) MIME – Molecule Interferometry and Metrology (DFG HH 1344/24-1, 2008 – 2011) Reversibles Durchstimmen der elektronischen Transporteigenschaften in oxidischen leitfähigen Nanostrukturen zur Anwendung im Bereich der druckbaren Elektronik (DFG HA 1344/25-1, 2010 – 2013) HMWK III.3.2 – 408/07.001, Investitionsfonds und Forschungsförderung (2009 – 2011) Förderung durch Mittel des Helmholtz Institut Ulm (2010-2014) Publications J. Suffner, D. Wang, C. Kübel, H. Hahn; Metastable phase formation during flame spray pyrolysis of ZrO2(Y2O3)-Al2O3 nanoparticles. Scripta Materialia, 2011. 64 781-784 A. Castrup, C. Kübel, T. Scherer, H. Hahn; Microstructure and residual stress of magnetron sputtered nanocrystalline palladium and palladium gold films on polymer substrates. J. Vac. Sci. Technol. A 29 (2), 021013-1 – 021013-6 G. Günther, E. Aulbach, H. Hahn, O. Guillon; High-temperature chip calorimeter with atmosphere control. Thermochimica Acta 522,1-2 (2011), 77-85 J. Suffner, T. Scherer, D. Wang, C. Fasel, L. Jaworska, H. Hahn; Microstructure and High Temperature Deformation Behavior of Al2O3 –TiO2 Obtained from Ultra High Pressure Densification of Metastable Powders. Acta Materialia 59 (2011), 7592-7601 S. Dasgupta, R. Kruk, N. Mechau, H. Hahn; Inkjet printed, high mobility inorganic-oxide field effect transistors processed at room temperature. ACS Nano 5 (12),(2011) 9628-9638 J. Suffner, S. Kaserer, H. Hahn, C. Roth, F. Ettingshausen; Sb-doped SnO2 hollow spheres offering micro and nano porosity for the fuel cell electrode structure. Advanced Energy Materials 1, 4 (2011), 648-654 100 Joint Research Laboratory Nanomaterials P.L. Marek, H. Hahn, T.S. Balaban; On the way to biomimetic dye aggregate solar cells. Energy & Environmental Science 4, 7 (2011), 2366-2378 Imteyaz Ahmad, C. Fasel, Th. Mayer; et al., High temperature stability of nanocrystalline anatase powders prepared by chemical vapour synthesis under varying process parameter Applied Surface Science 257, 15 (2011) 6761-6767 S. Indris, M. Scheuermann, S. Becker, V. Sepelak, R. Kruk, J. Suffner, F. Gyger, C. Feldmann, A. Ulrich, H. Hahn; Local structural disorder and relaxation of Sn02 Nanostructures studies by 119Sn MAS NMR and 119Sn Mössbauer Spectroscopy. Journal of Physical Chemistry 115, 14 (2011), 6433-6437 Y. Zhang, H. Hahn; Characterization of the free volume in a Zr(45.0)Cu(39.3)Al(7.0)Ag(8.7) bulk metallic glass by reverse Monte Carlo simulation and density measurements. Journal of Non-crystalline Solids 357, 5 (2011), 1420-1425 D.J. Babu, A.J. Darbandi, J. Suffner, SS Bhattacharya, H. Hahn; Flame spray synthesis of nano lanthanum strontium manganite for solid fuel cell applications. Transactions of the Indian Institute of Metals 64, 1-2 (2011), 181-184 Joint Research Laboratory Nanomaterials 101 Nanoglasses - a way to new amorphous structures R. Witte, T. Feng, J. Fang, R. Kruk, M. Ghafari, R. A. Brand, H. Gleiter, H. Hahn The relation of structure and properties has been ever since of fundamental importance in materials science and, consequently, tailoring material properties is a major interest in materials research. Two developments had a major impact on materials science and opened new research fields: (1) the discovery of amorphous metals by the Duwez Group in the 1960s [1], which meanwhile led to bulk metallic glasses with many technological applications and (2) the introduction of nanocrystalline materials by H. Gleiter in the 1980s with research activities worldwide and many industrial applications [2]. The combination of the structural features of these two materials classes, i.e. an amorphous, disordered structure and a high density of internal interfaces, will give rise to a new class of nanostructured, amorphous materials, denoted nanoglasses [3]. Nanoglasses are produced from glassy nanoparticles (NPs) which are synthesized in an inert-gas condensation process (IGC) in a controlled environment (either He-gas or UHV). In a subsequent in-situ compaction step, the NPs form the solid nanoglass. Microstructurally, nanoglasses may be described by amorphous regions connected by interfaces [3]. The atomic density in the interfaces is reduced compared to the core of the particles. This is shown schematically in Fig. 1. Indeed, it was found by small-angle X-ray scattering and positron annihilation lifetime spectroscopy, that the interfacial regions in a Fe25Sc75 nanoglass exhibit a reduced atomic density or an enhanced free volume of up to 6% per atom [4]. Furthermore, it can be anticipated that the interfacial regions have a different electronic structure due to large changes of the number of nearest neighbors and changed interatomic distances. As a consequence, the properties of amorphous material can be tailored by varying the concentration of interfaces, i.e. by a variation of the initial particle size. Fig. 1. Schematics of the atomic density distribution in a nanoglass (Figure taken from [4]). A first example of a material property which is drastically modified by the introduction of interfaces in a metallic glass have been found for a Fe90Sc10 nanoglass prepared by the IGC process and consolidation [5]. Characterization has been performed by XRD, scanning tunnelling microscopy (STM), Mössbauer spectroscopy and SQUID magnetometry. The amorphous Fe90Sc10 is a perfect model system for the investigation, as the magnetic properties are known to depend strongly on atomic density and local atomic arrangements. The results obtained from the Fe90Sc10 nanoglass (NG) have been compared with the 102 Joint Research Laboratory Nanomaterials corresponding conventional metallic glass (MG) with identical composition as a reference, prepared by melt spinning. Fig. 2 displays STM images of a Fe90Sc10 nanoglass sample after mechanical polishing. The granular nanostructure can be clearly seen. From the line scan a particle size of about 10 nm (in agreement with TEM investigations on the loose nanopowder, not shown here) with grooves of about 1 nm depth indicating the interfacial regions. It should be noticed that the STM image contains information on the topography of the sample surface as well as on the electronic structure. Further investigations are carried out in order to distinguish between these two contributions. Fig. 2. STM images of polished surfaces of a Fe90Sc10 nanoglass. The granular nanostructure is clearly pronounced. The inset shows a linescan on the indicated positions. Fig. 3 a) and b) show room temperature Mössbauer spectra of reference metallic glass and nanoglass. The spectrum of the reference sample exhibits a broad distribution of (nonmagnetic) quadrupole splitting (QS), typical of paramagnetic amorphous alloys in agreement with an earlier investigation [6]. Surprisingly, the Mössbauer spectrum of the nanoglass of the identical composition is completely different. It exhibits a broad magnetic sextet resulting from magnetic order in the material. As ferromagnetism has not been observed at room temperature for any of the compositions studied in amorphous FexSc100-x [7], chemical inhomogeneities, e.g. Sc segregation to the surface of the NPs, cannot account for the observed ferromagnetism in the nanoglass at ambient temperature. Joint Research Laboratory Nanomaterials 103 Fig. 3. a) and b) Mössbauer spectra measured at RT of the reference metallic glass and the nanoglass. Based on the structural model of amorphous regions connected by interfaces, the Mössbauer spectrum of the nanoglass is fitted using two components. The first represents a paramagnetic component fitted with a QS distribution, and the second component is a distribution of magnetic hyperfine fields. The magnetic component is associated with the interfacial regions and the paramagnetic areas with the cores of the primary nanoparticles. These observations may be understood in the context of the Bethe-Slater formalism which describes the sign and magnitude of the magnetic exchange interaction in Fe and Fe-based alloys depending strongly on the interatomic spacing. An increase of the average volume per atom, as in the case of the interfacial regions in the nanoglasses, will result in a larger ground state magnetic moment and, thus, an increase of TC. The average magnetic moment per Fe atom <MFe> was determined by magnetometry. Fig. 4 shows hysteresis measurements at 300 K and at 10 K. As expected from the Mössbauer experiments the nanoglass is ferromagnetic at 300 K and the sample saturates in an external field of 4.5 T. At 10 K <MFe> reaches a value of about 1.74 µB in an applied field of 4.5 T. 104 Joint Research Laboratory Nanomaterials Fig. 4. Magnetization measurements of a Fe90Sc10 nanoglass at 10 K and 300 K. From the combination of the average magnetization and the local spectroscopic information obtained from Mössbauer spectroscopy at 10 K (not shown, fraction of the the interfacial component: 35%), the magnetic moment of the Fe atoms located in the interfaces MFeIF is determined, yielding an average magnetic moment per Fe atom in the interfacial regions of 2.4 to 2.6 µB. This compares to a saturation magnetization of about 1.5 µB in the metallic reference glass. In conclusion, the introduction of interfaces in a metallic Fe90Sc10 glass, results in drastic changes of the magnetic properties, namely an increase of the transition temperature and enhanced local magnetic moments in the interfaces. References [1] Klement, W., Willens, R., and Duwez, P., Nature 187, 869-870 (1960). [2] Gleiter, H. Proceedings of the Second Risø International Symposium on Metallurgy and Materials Science, 15-22 (1981). [3] Gleiter, H. Acta Mater. 56, 5875-5893 (2008). [4] Fang, J. X., Vainio, U., Würschum, R., Wang, X.L., Wang, D., Ghafari, M., Jiang, F., Sun, J., Hahn, H., Gleiter, H., NanoLetters, 12, 458-463 (2012). [5] Witte, R., Fang, J.X., Feng, T., Ghafari, M., Kruk, R., Brand, R.A., Wang, D., Hahn, H., Gleiter, H., submitted to NanoLetters (2012). [6] Day, R., Dunlop, J., Foley, C., Ghafari, M., and Pask, H., Solid State Com. 56, 843-845 (1985) [7] Müller, M., Ghafari, M., Banihashemi, S., Stahl, B., and Hahn, H., Phys. Stat. Sol. A 189, 10431049 (2002) Joint Research Laboratory Nanomaterials 105 Mechanics of Functional Materials The research group was established in August 2011. We are interested in continuum modeling and numerical simulation of functional materials and systems. Functional materials and systems usually involve different phenomena at a variety of length scales, and 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. The current research topics include: Phase field simulation of ferroelectric domain structures. As one of the typical functional materials, ferroelectric ceramics have the electromechanical coupling effect, which is intrinstically based on the micro-domain structures in the material. We are engaged in continuum modeling of the ferroelectric domain structures via the phase field theory. The developed model characterizes itself by a clear cut physical definition of the material parameters and was verified with experimental results as for several typical micromechanical and homogenized mesoscopic material responses. The model was also used to study the nonlinear fracture properties in ferroelectric single crystals. Nonlinear electromechanical modeling and simulation of dielectric elastomer. Unlike the piezoelectric ceramics, the deformable dielectric elastomer provides large actuation displacement (up to 200%) but small actuation forces. Instead of the perovskite lattice structure in piezoelectric, the coupling effects of dielectric elastomer rely on the electrostatic force on the material polarization, which can be represented as eigenstress, i.e. the Maxwell stress. Nonlinear analytical and numerical models have been developed to investigate the deformation and the electromechanical stability issue of dielectric elastomer actuators. Analytical solutions on micromechanics and elasticity theory: Micromechanics are of great importance to study the effective properties of heterogeneous materials such as composites and polycrystalline materials. The foundation of micromechanics and the analytical homogenization approaches is the Eshelby inclusion problem. Studies have been conduncted regarding the inclusion geometry, interface properties, and the average values of the non-uniform stress and strain fields inside an inclusion. 106 Mechanics of Functional Materials Staff Members Head J. Prof. Ph.D Baixiang Xu Research Associates Dipl. -Ing. Peter Stein Secretaries Frau Maria Bense PhD Students M. Sc. Shabeer Khan Publications B.-X. Xu, R. Mueller, M.-Z. Wang; The Eshelby property of sliding inclusions, Ach. Appl. Mech., 81 (2011) 19-35. D. J. Franzbach, B.-X. Xu, R. Mueller, K.G. Webber; The effects of polarization dynamics and domain switching energies on field induced phase transformations of perovskite ferroelectrics; Appl. Phys. Letter, 99 (2011), 162903. D. Gross, R. Mueller, M. Mueller, B.-X. Xu, K. Albe; On the origin of inhomogeneous stress and strain distributions in single-crystalline metallic nanoparticles; Int. J. Mat. Res. (formerly Z. Metallkd.) 102 (2011), 743-747. Mechanics of Functional Materials 107 Continuum mechanical modelling and simulation of functional materials Bai-Xiang Xu, Ralf Müller, Dietmar Gross, Markus Klassen Phase field simulation of ferroelectric domain structures What makes the ferroelectrics favorable in application is primarily their large electromechanical coupling effect. This coupling is intrinsically based on its microstructure. In particular, perovskite ferroelectrics, one of the most important families in ferroelectrics, undergoes a cubic-to-tetragonal phase transformation when the material is cooled down below its Curie temperature. This phase transformation introduces spontaneous polarization and strain, with six variants determined by the crystallographic orientation of the polarization. Groups of unit cells with polarization of the same direction are called domains, which are separated by domain walls. The interaction of this micro domain structure with external electrical and/or mechanical loadings enables eventually the electro-mechanical coupling effect. Due to the heterogeneity and the micro scale, the switchable domain structure is not directly accessible to mesoscopic experimental measurements. Limited by the computation cost, atomistic simulation may also be insufficient for a fully understanding of the microstructure and its influences. The phase field theory has become an increasingly important simulation approach in the study of morphological evolution of heterogeneous materials and has lately been introduced to simulate the polarization and domain structure evolution of ferroelectrics. The method replaces the usual interface conditions by a partial differential equation for the evolution of the order parameter, i.e. the spontaneous polarization. The domain wall is therefore smoothed out with a finite thickness. The formulation is based on a free energy functional which includes the electrical enthalpy, the domain separation energy (polynomial of the order parameter) and the interfacial energy (the gradient term of the order parameter). The domain structure evolution is then treated as the consequence of the minimization process of the total free energy of the system, requiring no switching criteria and no prior assumption on domain geometries. A 3D implementation of the model was completed using the finite element method with the program FEAP. An implicit time integration is used for the evolution, and the Newton iteration is adopted for the nonlinear system of equations. As an example, the domain structure evolution of a BaTiO3 single crystal has been simulated, in which the volume force and charge are neglected. The material is under traction free and charge free boundary conditions, and for the polarization the zero flux condition is adopted. Starting from an initial random distribution, the domain structure evolves eventually to a vortex structure, with all the polarizations parallel to the surface, see Fig. 1. 108 Mechanics of Functional Materials Fig. 1: Domain structure evolution (from left to right) of a free standing ferroelectric single crystal under charge free boundary condition. Dynamic analysis of dielectric elastomer actuators (DEA) Dielectric elastomers are widely used for artificial muscles and haptic displays, thanks to its practical features e.g. large deformation, low cost and high fracture toughness. Due to the electromechanical coupling effect, dielectric elastomers can be actuated under an electric loading. To achieve various applications, the material works usually under dynamic electric loadings, and hence the dynamic response of the material should be taken into account. The material behaviour of dielectric elastomers is strongly nonlinear in both geometry and constitutive relations. In this work the dynamic response of dielectric elastomers with stretching deformation under merely electric loading is studied. An electrode-elastomerelectrode sandwich structure shown in Fig. 2, which is the prototype of a dielectric elastomer actuator (DEA), is considered in the modelling. Due to the incompressibility of the material and the homogeneity of the actuator, the equation of motion can be given as an ordinary differential equation of the stretch of the actuactor in the thickness direction. By using the Euler-Lagrange equation, the equation of motion for the DEA has been derived. The nonlinear equation was solved numerically with software Matlab. For a DEA of 5mm x 5mm x 1mm under constant electric field and starting from a rest undeformed configuration, the vibration diagram is presented in Fig. 3(a). It can be seen that the frequency of the vibration varies with the applied electric potential: the higher the potential is, the smaller the vibration frequency becomes. Nonlinear dependence of the vibration amplitude on the applied electric potential is also shown in Fig. 3(b), in comparison with the compression of the DEA for the quasi-static case. Results show that at the critical state before instability, the DEA with dynamic effects can reach the maximal deformation of around 51% under the nominal electric field of 21.28 kV/mm. Fig. 2: DEA. Mechanics of Functional Materials Fig. 3: Vibration under constant electric field. 109 Dependence of the DEA performance on the frequency of the applied electric loading is studied, while the amplitude of the nominal electric field remains constant. Results show that the DEA experiences oscillations with varying amplitudes under the harmonic electric loading. Dynamic blow-up is detected at frequencies between 340 Hz and 405 Hz. It implies that the applied frequency coincides with one of the natural frequencies, and thus resonance effects occur. For the frequency slightly below or above the resonance frequency range, the vibration remains stable. In Fig. 4 are the motions and the phase diagrams of the DEA under the harmonic excitation with the frequencies 335 Hz and 410 Hz, respectively. The system experiences strong oscillations under these two frequencies. After introducing a damping effect, the oscillation is damped out to be constant vibration, as shown in Fig. 5(a). The amplitude of the constant vibration after damping is documented. It is shown that a large peak appears around 346 Hz. Fig. 4. Phase diagram. Fig. 5: The resonance effect. 110 Mechanics of Functional Materials 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 17 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. Jürgen Rödel. Contact: SFB 595 Electrical Fatigue in Functional Materials Institute of Materials Science Petersenstr. 23 64287 Darmstadt Tel.: +49 6151 16 - 6362, 6315 Fax: +49 6151 16 - 6363, 6314 Building/Room: L201 / 55 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. Collaborative Research Center (SFB) 111 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 112 Collaborative Research Center (SFB) 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 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 Collaborative Research Center (SFB) 113 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 114 Collaborative Research Center (SFB) Diploma Theses in Materials Science Lukas Schlicker, Wärmebehandlung von Aluminium AA6060 und Entwicklung eines Polierverfahrens zur Probenpräparation für VHCF- Ermüdungsexperimente, 30.03.2011 Christoph Baumann, Creep and Fatigue Behaviour of a Hafnium-free Version of Alloy RR1000, 08.03.2011 Martin Hottes, Untersuchung der Mikrostruktur, Zusammensetzung und Oberfläche von galvanisch hergestellten Nickelfolien in Bezug auf ihre korrosiven Eigenschaften, 30.03.2011 Katrin Barth, Mikrostruktur, Oxidation und mechanische Eigenschaften von EisenAluminiden, 28.03.2011 Jürgen Ziegler, Präparation und Charakterisierung von GaP-Halbleiterelektroden für die photoelektrochemische Wasserspaltung, 28.02.2011 Laurent Couturier, Detailed characterization of different grades of spheroidal cast ironsComposition of subject cards , 15.03.2011 Caterine Lottmann, Influence of the weld seam corrosion resistance of longitudinally welded condenser tubes through enhancement of the manufacture and heast treatment process, 28.02.2011 Lukas Mirko Reinold, Neue Anodenmaterialien für Lithiumionenbatterien, 25.02.2011 Rudolf Seiler, Entwicklung einer Kurzzeit-Prüfmethode für Beschichtungen auf Metallen, 26.04.2011 Ruben Heid, Einfluss von gießtechnischen Prozessschwankungen auf das Eigenschaftsspektrum crashrelevanter Aluminium-Druckgusslegierungen, 31.04.2011 Silvia Vestweber, Optische Charakterisierung von Bariumstrontiumtitanat, 31.05.2011 Adnan Adilovic, Einfluss des Herstellungsverfahrens auf die mechanischen Eigenschaften von Stahlfeinblechen, 04.05.2011 Ahmed Kariouh, Organische Solarzellen auf Basis von Merocyaninfarbstoffen- Herstellung unter verschiedenen Atmosphären, 28.02.2011 Florian Schader, Die Temperaturabhängigkeit der dielektrischen Eigenschaften bleifreier Ferroelektrika unter mechanischer Belastung, 28.02.2011 Lars Riekehr, Funktionalisierung polymerer Dielektrika für organische Feldeffekttransistoren, 31.05.2011 Paul Mundt, Organische Leuchtdioden auf zylindrischen Substraten, 31.05.2011 Diploma Theses in Materials Science 115 Aiko Bünting, Ladungsträgerinjektion in Bariumstrontiumtitanat mit Hilfe dünner Zinnoxid, 14.07.2011 Edouard Dassonville, Modelling of composite pressure cylinder rupture in aerospace application, 02.05.2011 Sylvain Moissonnier, Comparison of different concepts of TRIP, DP and FB steels, 26.04.2011 Tobias Weiher, Ladungsstabilität in Polyvinylidendifluorid, 07.07.2011 Jörn Niehuesbernd, Mechanisches Legieren von Kupfer-Chrom, 20.07.2011 Mirko Weidner, Elektrische, optische und strukturelle Charakterisierung gesputterter Zinnoxid-Schichten, 31.05.2011 Manfred Kerner, Mikrowellenunterstütze Polyolsynthese von Platinnanopartikeln auf verschiedenen Kohlenstoffträgern, 27.05.2011 Aldin Radetinac, Dünnschichtwachstum von SrMoO3 mittels gespulster Laserablation (PLD) zur Anwendung als Elektrodenmaterial für Ba0,6Sr0,4TiO3 Varaktoren, 11.07.2011 Marc Henryk Adamiak, Tests an Schwefelsensoren für das Floatbad Floatkammeratmosphäre im Labor und unter Indistriebedingungen, 29.07.2011 und die Raschid Baraki, Einfluss eines E-Feldes auf das Sinterverhalten, 06.05.2011 Amon Elias Klausmann, Entwicklung neuer Prozesse für die Atmosphärendruckplasmadeposition zur Erzeugung industriell einsetzbarer Oberflächen, 30.05.2011 Franziska Resch, Elektrische Leitfähigkeit und Wärmekapazität von CuCr-Kontaktwerkstoffen verschiedener Zusammensetzungen, 29.07.2011 Philip Jan Reckers, Photoelektronenspektroskopie an einer Merocyanin/C60 Grenzflächen, 30.06.2011 Klaus Wedlich, Bewertung eines leitfähigen, stromtragfähigen und co-sinterfähigen Materialsystems für Interkonnektoren, 04.10.2011 Markus Motzko, Aluminiumdotiertes Zinkoxid Cadmiumtellurid-Dünnschichtsolarzellen, 11.08.2011 als Frontkontaktmaterial für Arno Fey, Thermodynamic stability of Cadmium and Zinc Stannate and their point defects: A comparative study using first-principles methods, 01.07.2011 André Schwöbel, Dünnschichttransistoren auf Basis von (Ba, Sr)TiO3, 29.09.2011 116 Diploma Theses in Materials Science Ioannis Sprenger, Bestimmung der Austrittsarbeit von Kupfer und Chrom und des Legierungssystems Cu-Cr, 10.10.2011 Krystyna Bachtin, Untersuchung der Alterungsstabilität stabilisierter Katalysatoren für die PEM-Brennstoffzellen, 19.09.2011 Ruben Precht, Herstellung und Charakterisierung von anorganisch-organischen Schichten zur Anwendung in LEDs, 06.10.2011 Alexander Uhl, Herstellung und Charakterisierung Polymer-abgeleiteter SiCN-Schichten auf MoSiB-Substraten, 29.09.2011 Joachim Klett, Optimierung von GaP-Rückkontakten zur photochemischen Wasserspaltung, 07.10.2011 Charlotte Cochard, Modelisation of photovoltaic process for artificial synthesis applications, 12.09.2011 Lydia Colom, Pickling inhibitor behaviour on steel surfaces in different acidic media, 07.09.2011 Boris Gusarov, Solution processed amorphous GalnZn oxide Thin-film transistors, 02.09.2011 Valliere Lande De, Tailored platinum zircomia interface for improved exhaust gas sensors, 15.09.2011 Nguyen Van Lam, Molecular Approaches to Novel SiHfBCN Ceramic Nanocomposites: Synthesis and High Temperature Behavior, 13.09.2011 Soleimani Doecheh, Study of Krypton/Xenon Storage and Separation in Micropous Frameworks, 02.09.2011 Omar Pecho, Thin Ni-CGO Films for micro-Solid Oxide Fuel Cell Anode Application, 15.09.2011 Diploma Theses in Materials Science 117 Bachelor Theses in Materials Science Michael Brilz, 30.09.2011 Statische Debye-Waller-Faktoren von (1-x)Bi0.5Na0.5TiO3-BaTiO3, Marcus Schulze, Mikrostrukturierte Polyelektrolyt-Filme, 08.08.2011 Hans Florian Wardenga, Deintercalation of sodium and intercalation of water in NaxCoO2 thin films made by pulsed laser deposition technique, 16.09.2011 Sandra Schäfer, Strukturierung biofunktionaler Beschichtungen, 30.09.2011 Constanze Kalcher, Molekulardynamische Simulation mechanischer Eigenschaften von metallischen Gläsern , 28.09.2011 Silke Christina Pufahl, Veränderung der Steifigkeit und der Elastizität von Kollagen unter UV-A Bestrahlung, 04.10.2011 Ralph Dachauer, Oxidationseigenschaften von mechanisch legierten Eisenaluminiden mit bis zu 5 at% Titan, 09.11.2011 Jari Uhde, Oxidationsverhalten von mechanisch legiertem Fe3Al mit Mikrolegierungszusätzen von Nb und Zr, 21.10.2011 Tanju Sirman, Mechanisches Legieren von Wolfram und Kupfer, 10.10.2011 Malte Vögler, Einfluss der Temperatur und korngröße auf die Bruchzähigkeit von Bleizirkonat-Titanat Keramik, 01.09.2011 Christian Lohaus, Synthese verschiedener rußgeträgerter Pt-Ru-Au Katalysatoren und Untersuchung des Degradationsverhaltens, 14.10.2011 Lukas Hamm, Systematische Untersuchung der gezielten Beeinflussbarkeit Kristallstrukturen und Morphologie von Aluminiumphosphaten, 13.10.2011 von Andreas Eva, Synthese von Li(Ni1/3Mn1/3Co1/3)O2 und Li(Ni1/2Co1/2)O2 mittels Sol-Gel Technik als Targetmaterial für die gepulste Leserdeposition (PLD), 31.10.2011 Thomas Paul Kaleja, Templatgestützte Synthese asymmetrischer Cu-Mikrodrähte sowie die Untersuchung der Auswirkun organischer Additive auf den elektrochemischen Herstellungsprozess, 15.12.2011 Anke Silvia Ulrich, Organische Heterogrenzflächen für die solare Energiewandlung: synchrotroninduzierte Photoelektronenspektroskopie am Modellsystem DH6T/C60, 18.11.2011 Richard Günzler, Untersuchung zum Druckkriechverhalten Siliciumoxcarbid-Keramiken bei hohen Temperaturen, 24.11.2011 118 polymerabgeleiteter Bachelor Theses in Materials Science PHD Theses in Materials Science Enrico Bruder; Thermische Stabilität von Stählen mit ultrafeinkörnigen Gradientengefügen und deren mechanische Eigenschaften, 18.1.2011 Jens Suffner; Synthese und mechanische Eigenschaften ultrafeinkörniger ZrO2(Y2O3) - Al2O3 Komposite aus metastabilen Pulvern, 21.1.2011 Frank Ettingshausen; Elektrodendegradation in Polymerelektrolyt-Membran Brennstoffzellen, 7.3.2011 Markus König; Herstellung und Charakterisierung des Sinterverhaltens von dünnen Schichten und Massivkörpern aus nanoskaligem Zinkoxid, 31.3.2011 Thorsten Leist; Herstellung und Schaltverhalten neuer bismuthaltiger Hochtemperaturpiezokeramiken, 8.3.2011 Carmen Elena Zvoriste; High-Pressure Synthesis, Crystal Structure and Physical Properties of Gallium Oxonitride, 9.3.2011 Peter Agoston; Point Defect and Surface Properties of In2O3 and SnO2: A Comparative Study by First-Principles Methods, 6.7.2011 Eva-Maria Anton; Elektrische Eigenschaften, Struktur und Depolarisationsverhalten von Bi1/2Na1/2TiO3-Bi1/2K1/2TiO3-basierten bleifreien Piezokeramiken, 26.8.2011 Aiswarya Bhaskar; Investigations on LiM0.5Mn1.5O4 (M = Fe, Co, Ni) Spinels as High-Volt Cathode Materials for Rechargeable Lithium-Ion Batteries, 6.4.201 Ricardo Chavez; Synthese thermoplastischer Si-basierter Polymere mit hoher thermischer Beständigkeit für die Herstellung von Bauteilen, 23.08.2011 Gregorio Couto Faria; Structure and dynamics of poly(9,9-dioctylfluoren-2,7-diyl-cobenzothiadiazole) (F8BT) and correlations with its electrical properties, 16.9.2011 Eiko Gütlich; Abbildungseigenschaften von Szintillatoren für Schwerionenstrahlen und diesbezügliche Modellrechnungen, 19.7.2011 Shunyi Li; Grenzflächenmodifizierung kathodenzerstäubter (Ba, Sr)TiO3-Dünnschichten, 22.6.2011 Margarete Mie Marsilius; Schaltverhalten ferroelektrisch-ferroelastischer Materialien, 01.06.2011, Mohamed Bakr Mohmoud Mohamed; Physical properties of doped multiferroic GaFeO3, 5.4.2011 PHD Theses in Materials Science 119 Silke Schaab; Influence of charged defects on the polarization dynamics and phase transitions in the relaxor ferroelectric PLZT, 25.05.2011 Bastian Siepchen, Modelluntersuchungen an Heterogrenzflächen von II-Vi-Halbleitern, 1.4.2011 Daniel Sopu; Molecular Dynamics Simulations of Metallic Nanoglasses, 1.9.2011 Jami Susan Winzer; Production and Characterisation of Alumina-Copper Interpenetrating Composites, 29.09.2011, Toni André Groß; Synthese und Charakterisierung von Spinell-Sialon, 18.10.2011, Jens Kling, Strukturuntersuchungen an bleifreien Ferroelektrika mittels TEM, 5.12.2011 Yvonne Ritter; Molecular Dynamics Simulations of Structure-Property Relationships in Cu-Zr Metallic Glasses, 16.12.2011 Katja Stegmaier; Elektrische Ermüdung polymerbasierter organischer Leuchtdioden, 4.11.201 Alan Logéat; Experimental Study on Lithium-conducting Garnet Ceramics as Solid Electrolyte, 9.12.2011 120 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 2011 the workshop was involved in the following major projects: Components for Evaporation System for Rotated Fibre Substrates UHV-preparation chambers (electro)chemical treatment Components for six-circle diffractometer Design and manufacturing of a protection chamber for x-rays with up to 150keV photons UHV baby chamber for x-ray diffraction experiments dedicated for MBE, CVD, PVD, PLD and 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 121 Institute of 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 its research activities as well as the study programs on our key topics in Water – Energy – 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. However, 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. Our consecutive Bachelor and Masters program Angewandte Geowissenschaften is fully implemented now and proves to be very attractive for prospective students. In October 2011, about 160 freshmen enrolled in our Bachelor program, which is an about 4-fold increase compared to the number of freshmen we had last year. We are very pleased by this upgrowth and attribute it, next to some demographic reasons, to our focused and now visible research profile. However, this development comes to a time where our 50 year old building in the Schnittspahnstraße undergoes major stepwise refurbishment. This was absolutely necessary due to the outdated and frequently failing infrastructure. Five groups of the institute are therefore now located in the Mornewegstraße close to the main train station, while three groups, some laboratories, the lecture hall and seminar rooms remained in the Schnittsphanstraße. The hydrochemistry labs have been moved to a facility in Biebesheim. This situation requires increased efforts from everybody to keep the institute ‘alive’ and to handle the sheer number of students. However, we are very excited about the prospects of a modern and inspiring working environment that already takes shape. 122 Institute for Applied Geosciences - Preface End of 2011, Prof. Andreas Henk from Freiburg accepted the call from the TU Darmstadt to join the faculty at the Institute of Applied Geosciences and, in March 2012, he will be chair of the Fachgebiet Engineering Geology. We all are very excited about this positive development and look forward to welcome Prof. Henk early next year. As it is the 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 croweded but, finally, everyone was ‘baptised’ and officially a new member of the geology students. Institute of Applied Geosciences - Preface 123 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. 124 Physical Geology and Global Cycles Staff Members Head Prof. Dr. Stephan Kempe Research Associates Dr. Günter Landmann Technical Personnel Ingrid Hirsmüller Secretaries Kirsten Herrmann PhD Students Shahrazad Abu-Ghazleh Hans-Peter Hubrich Diploma Students Ingo Bauer Jürgen Krumm Research Projects Geomorphology and Paleoclimatology of Lake Lisan Terraces, Dead Sea, Jordan (DFG, DAAD). Global quantification of the CO2-sink chemical weathering and the resulting riverine transports of dissolved solids into coastal waters (DFG). Tectonic structure of the southern boundary of the Harz Mountain and its development since the Permian. Within the frame of a PhD-Study Hans-Peter Hubrich will carry out a new geological mapping of the southern Harz mountain range. Objective is a regional map in the scale 1:10 000 that will cover an area of 5 x 100 km. The approach includes: Compilation of about 40 unpublished maps carried out as diploma thesis. Compilation of results obtained during students mapping courses. Assimilation of existing geological maps (small sub-areas and ‘GK 25’) after careful consideration of own mapping results. First results are already available covering the area Badenhausen (near Osterode) to Bad Sachsa. These include the petrographic characterisation of the carbonates, maps of Karst features and Quaternary deposits as well as a fault map. It turns out that about 50 % of the faults are striking around 120°. The project is expected to be completed in 2012. Publications Abu Ghazleh, S., Abed, A.-A., Kempe, S., 2011: The dramatic drop of the Dead Sea: background, rates, impacts and solutions. – In: Badescu, V. & Cathcart, R.B. (eds.), Macroengineering Seawater in/and Unique Environments. Arid Lowlands and Water Bodies Rehabilitation, Springer, Heidelberg: 77-105. Hartmann, J., Levy, J., Kempe, S., 2011: Increasing dissolved silica trends in the Rhine River: an effect of recovery from high P loads? – Limnology, 12: 63-73. DOI 10.1007/s10201-010-0322-4. Physical Geology and Global Cycles 125 Landmann, G., Steinhauser, G., Sterba, J.H., Kempe, S., Bichler, M., 2011: Geochemical fingerprints by activation analysis of tephra layers in Lake Van sediments, Turkey. - Applied Radiation and Isotopes 69: 929-935. Kazmierczak, J., Kempe, S., Kremer, B., López-Garcia, P., Moreira, D., & Tavera, R., 2011: Hydrochemistry and microbialites of the alkaline caldera Lake Alchichica, Mexico. – Facies: 57: 543-570. DOI 10.1007/s10347-010-0255-8. Kempe, S., Hubrich, H.P., 2011: Inscriptions of historically known persons in Postojnska jama. –Acta Carsologica 40(2): 397-415. Kempe, S., Kazmierczak, J., 2011: Soda lakes. – In: Reitner, J., and Thiel, V. (eds.) Encyclopedia of Geobiology, Springer, 824-829. Kempe, S., Kazmierczak, J., 2011: Soda ocean hypothesis. – In: Reitner, J., and Thiel, V. (eds.) Encyclopedia of Geobiology, Springer, 829-833. 126 Physical Geology and Global Cycles Lake Van, Turkey: Evidence for a lake level drop of 500 m in the period 20-15 ka BP Günter Landmann and Stephan Kempe Lake Van, the largest soda lake on Earth and the 3rd largest closed lake by volume, is located on the Eastern Anatolian High Plateau, Turkey (Fig. 1). As a terminal lake, its level reacts very sensitively to climate changes and its great depth of 451 m allows it to survive even pronounced dry periods. It is thus the major climate recorder in the Near East. Results of 19 sediment cores taken from different water depths were used to reconstruct the lake level history (Fig. 2; Tab. 1; Landmann, 1996; Landmann et al., 1996). All cores taken from the main basin and most of the cores from shallower depth can be correlated by means of twelve tephra layers deposited by volcanic eruptions but also by other conspicuous marker layers and lamination patterns. Because slumping and turbidites occur frequently in this tectonically active region, careful correlation between cores is important to assure the completeness of the sediment column of each core. Fig. 1: Map of Lake Van with the location of cores taken in 1974 (triangles), in 1990 (circles) and of core VAN 04-2 (Litt et al., 2009; grey circle). A high stand up to 70-80 m above the present lake level is documented by terrace sediments (Schweizer, 1975; Valeton 1978), yielding a floating varve chronology of 606 years fixed by 14C-dating to the period 20.1-20.7 cal. ka BP (Kempe et al., 2002). This varved section is underlain by sandy gravel marking the transgression of the glacial lake and overlain by a slumped, 6 m thick section representing the start of a pronounced regression of the lake. Physical Geology and Global Cycles 127 Fig. 2: Lake level fluctuations of Lake Van in the past 21 ka (redrawn after Landmann et al., 1996). Shaded areas mark major periods with a negative water balance. Maximum depth of Lake Van today is 451 m; the dotted line gives the present lake level at about 1650 m a.s.l. The white arrow marks the time period when Lake Van level was below 1222 m a.s.l. discussed in the present paper. Tab. 1 Features used for lake level reconstruction (Landmann et al., 1996; Reimer et al., 2009). Feature Interpretation Remarks several dated levels from cores of different depth dated ca. level on/offset of varves water depth at core locality >/< 40 m Artemesia pellets salinity 80-100 per mill archaeological sites Urartu high stand terraces above present level level still stands sublacustrine terraces level still stands ca. dated level 14 highest terrace is dated by C (Kempe et al., 2002) not dated pollen data e.g., Van Zeist & Woldering (1978) climate proxy increasing Mg-carbonates increasing terrigenous material 18 increasing δ O of carbonate Regression Regression increasing salinity shorten of distance from river mouth data from Lemcke (1996) increasing porosity Transgression decreasing salinity Regression In the paper we present new evidence that the lake fell dry at around 15 ka BP, i.e. within 5 ka after the lake reached its glacial high stand 70-80 m above its present level. This evidence is derived from sediment cores covering the last 15 ka. Sediment of the deep main basin is continuously varved back to 14.7 ka BP. Two cores (K10 and K6; Fig. 1), penetrate the laminated layers and reach hard, not laminated sediment that contains: Clasts of 1-3 cm large pumice lapilli and up to 5 mm large pyroxene phenocrysts. Concentration of particles >1 mm increase significantly within the not laminated layers demonstrating the increase of transport energy. 128 Physical Geology and Global Cycles Ooids with a nucleus consisting of clay minerals and an aragonitic cortex. The micritic aragonite of some ooids reveals concentric structures showing enhanced Si, Mg and Fe concentrations. Aragonitic ooids were also described from the Great Salt Lake, Utah, where the Mg/Ca ratio of the water is > 20 (e.g., Fabricius and Klingele, 1970). For comparison the Mg/Ca ratio of Lake Van is > 40 today (Reimer, 1995). According to Füchtbauer (1988) recent ooid formation takes place almost exclusively in warm, very shallow (1-2 m) water. Coated grains with a nucleus formed mainly from clay minerals and a zonal cortex consisting mainly of Fe and S. The diameter of the nucleus is about 100 µm, the thickness of the cortex ranges from 38 to 70 µm. Shrinkage cracks appear between nucleus and cortex. The multi-phase structure of the grain allowed only semiquantitative analysis. Microprobe mapping revealed a zonal structure of the cortex with maximum concentration of Fe and S inwards, decreasing and replaced by Si, Al, Mg and traces of P towards the outer rim. Smaller grains (< 10 µm) showing high concentration of Ti and Ca are distributed on the surface, whereby the first are especially found on the nucleus and the latter especially on the cortex. Due to its spherical shape and the element composition we assume that the cortex has been primarily build as pyrite which is now weathered. Pyrite is known to form by early diagenesis under reduced conditions and weathers fast in contact with oxygen. Formation of secondary minerals. Semi quantitative EDX analysis of a fragmented grain, 1.2 mm long and about 0.8 mm wide, detected mainly the element Fe (56-59 weight percent) and traces of S, Si, Na, F and Mg. The main element composition resembles those of goethite, a weathering mineral common in tropical soil. Iron oxide schlieren indicating that the sediment was oxygenated. Today, the zone of sulphate reduction starts immediately below the water-sediment interface (Reimer et al., 2009). Such situation may have prevailed for the last 13.4 ka as revealed by an abrupt increase of the organic sediment fraction at that time. Only sediments older than this were oxygenated. Ostracode shells from four different unknown species of the family Limnocytheridae. Adult (size 0.3-0.6 mm) and juvenile shells of ostracodes are well preserved, suggesting that these sediments were not transported. Recent ostracodes of the family Limnocytheridae are found in habitats having a salinity of 0 to 10 ppt. Since the species have not yet been determined, the salinity of their habitats can only be estimated but may be 18 ppt at most (Ian Boomer, University Birmingham, personal communication). These textures are interpreted as being the result of a lake level regression to below 428 m and a consecutive transgression. This interpretation is supported by the pollen record showing a very low total concentration of pollen and spores within the unvarved sediment section but high concentration of Artemesia and Chenopodiaceae (Van Zeist and Woldering, 1978; Wick et al., 2003; Litt et al., 2009). Pollen grains from steppe plants such as Artemisia and chenopods are common during cooler and/or drier phases (Litt, personal communication). A low lake level during the Late Glacial period is also deduced from high concentration of terrigenous material within the sediment of the unvarved section. Sedimentation velocity of clastics depends mainly on grain size and density. Coarse and dense particles are deposited close to the river mouths while fine particles are distributed lake-wide. At Lake Van, this scheme leads to an increase of terrigenous material (and annual sediment deposition) with Physical Geology and Global Cycles 129 decreasing distance from shore. High concentration of terrigenous material therefore indicates a low lake level, equivalent to a short distance between river mouth and core locality. Core K6 (Fig. 1; total core length 992 cm) can be correlated with core K10 down to the core depth of 920 cm, corresponding to an age of about 13 650 a BP (Landmann, 1996). Below, it contains a slumped section (920-935 cm) followed by regularly laminated sediment supposed to represent the shallow lake phase. Accumulation rate within this section is 10.8 mm a-1, that is more than 20-fold higher than the average accumulation rate for the past 14.7 ka. Evidence for this regression in the period 20-15 ka BP is also derived from pore water chemistry. Salinity in all cores reveals a linear increase downcore reflecting upward diffusion of salt (Reimer et al, 2009). During the regression increasingly concentrated brines formed that penetrated into the pore space of the sediment by replacing older pore water of lower salinity. Water balance calculation suggest that a lake level drop of 500 m within less than 5000 years can not be explained by a low precipitation alone but must also have been caused by a higher evaporation than today. A simultaneous lake level drop is also reported for Lake Lisan, the precursor of the Dead Sea (e.g., Landmann et al., 2002). References: [1] Fabricius, F.H., Klingele, H., 1970. Ultrastrukturen von Ooiden und Oolithen: Zur Genese und Diagenese quartärer Flachwasserkarbonate des Mittelmeeres. Verh. Geol. Bundesanst., 594-617. [2] Füchtbauer, H., Richter, D.K., 1988. Karbonatgesteine. In: Füchtbauer, H. (Ed.) Sedimente und Sedimentgesteine. E. Schweizerbart’sche Verlagsbuchhandl., Stuttgart, 233-434. [3] Kempe, S., Landmann, G., Müller, G., 2002. A floating varve chronology from the Last Glacial Maximum terrace of Lake Van/Turkey. Zeitschr. f. Geomorph. 126, 97-114. [4] Landmann, G., 1996. Van See/Türkei: Sedimentologie, Warvenchronologie und Paläoklima der letzten 15 000 Jahre. Ph.D. Thesis, Facult. Geosci. Univ. Hamburg. [5] 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. Quatern. Int. 89/1, 45-57. [6] Landmann, G., Reimer, A., Kempe, S., 1996. Climatic induced lake level changes of Lake Van/Turkey during the transition Pleistocene/ Holocene. Global Biogeochem. Cy. 10(4), 797-808. [7] Lemcke, G., 1996. Paläoklimarekonstruktion am Van See (Ostanatolien, Türkei). Ph.D. Thesis 11786, Eid. Techn. Hochsch. [8] Litt, T., Krastel, S., Sturm, M., Kipfer, R., Örcen, S., Heumann, G., Franz, S.O., Ülgen, U.B., Niessen, F., 2009. ’PALEOVAN’ International Scientific Drilling Programm (ICDP): site survey results and perspectives. Quat. Sci. Rev. 28, 1555-1567. [9] Reimer, A., 1995. Hydrochemie und Geochemie der Sedimente und Porenwässer des hochalkalinen Van Sees in der Osttürkei. Ph.D. Thesis, Facult. Geosci. Univ. Hamburg. Reimer, A., Landmann, G., Kempe, S., 2009. Lake Van, Eastern Anatolia, hydrochemistry and history. Aquat. Geochem. 15, 195-222. [10] [11] Schweizer, G., 1975. Untersuchungen zur Physiogeography von Ostanatolien und Nordwestiran. Tübinger Geogr. Studien 60, 139. [12] Valeton, I., 1978. A morphological and petrological study of the terraces around Lake Van. In: Degens, E.T., Kurtman, F. (Eds.) The Geology of Lake Van. Miner. Res. Explor. Inst. Turkey 169, Ankara, 64-80 [13] Van Zeist, W., Woldering, H., 1978. A postglacial pollen diagram from Lake Van in eastern Anatolia. Rev. Paleobot. Palynol. 26, 249-276. [14] Wick, L., Lemcke, G., Sturm, M., 2003. Evidence of Late-Glacial and Holocene climatic change and human impact in eastern Anatolia: high resolution pollen, charcoal, isotopic and geochemical records from the laminated sediments of Lake Van, Turkey. The Holocene 13, 665-675. 130 Physical Geology and Global Cycles Atmospheric CO2 consumption by chemical weathering in North America Nils Moosdorf, Jens Hartmann, Ronny Lauerwald, Benjamin Hagedorn and Stephan Kempe CO2 consumption by chemical weathering is an integral part of the boundless carbon cycle, whose spatial patterns and controlling factors on continental scale are still not fully understood. A dataset of 338 river catchments throughout North America was used to empirically identify predictors of bicarbonate fluxes by chemical weathering and interpret the underlying controlling factors. Detailed analysis of major ion ratios enables distinction of the contributions of silicate and carbonate weathering and thus quantifying CO2 consumption. Extrapolation of the identified empirical model equations to North America allows the analysis of the spatial patterns of the CO2 consumption by chemical weathering. Runoff, lithology and land cover were identified as the major predictors of the riverine bicarbonate fluxes and the associated CO2 consumption. Other influence factors, e.g. temperature, could not be established in the models. Of the distinguished land cover classes, artificial surfaces, dominated by urban areas, increase bicarbonate fluxes most, followed by shrubs, grasslands, managed lands, and forests. The extrapolation results in an average specific bicarbonate flux of 0.3 Mmol km-2 a-1 by chemical weathering in North America, of which 64% originates from atmospheric CO2, and 36% from carbonate mineral dissolution. Chemical weathering in North America thus consumes 50 Mt atmospheric CO2C per year. About half of that originates from 10% of the area of North America. Fig. 1: Observed specific bicarbonate fluxes of the considered monitorring stations (from Mossdorfer et al., 2011, Geochim. Cosmochim. Acta 75, 7829–7854). The estimated strength of individual predictors differs from previous studies. This highlights the need for a globally representative set of regionally calibrated models of CO2 consumption by chemical weathering, which applies very detailed spatial data to resolve the heterogeneity of earth surface processes. Physical Geology and Global Cycles 131 Distribution, sizes, function and heritage importance of the Harrat Al Shaam desert kites: the largest prehistoric stoneworks of mankind? Stephan Kempe and Ahmad Al-Malabeh The Harrat Al Shaam, the lava deserts of Jordan, features the largest concentration of desert kites so far analyzed (e.g., Kempe & Al-Malabeh, 2010a). Our GoogleEarth count runs to at least 530 such kites, while aerial photography counts yielded 1155 kites (see Kennedy, 2011, Table 1). In Saudi Arabia we have counted 254 more and Kennedy (2011) counted 407 kites in Syria. Few kites occur also in Turkey, on the Sinai and in Usbekistan. This shows that the largest numbers of kites is concentrated in Jordan, forming a significant part of its prehistoric heritage. Desert kites are km-long stone wall constructions, consisting of two or more widely gaping guiding walls that converge to an opening (gate) behind a small sill. Behind is a walled enclosure. In the early stages, these enclosures were bag-like, later clover-like and in the latest development they attain a ha-sized, star-shaped shape. At the apexes of the inward curved enclosure walls, so called “blinds” were erected, 3 to 5 m wide stone circles. Some kites have well over a dozen of such circles (Fig. 1). These circles were interpreted as “hides” for hunters to shoot gazelle. However, we argue that these were the actual traps. Once the gazelle had jumped into them, they could not jump out again lacking forward speed. More than 95% of the Jordanian kites open SE ward, arranged in eight chains extending N-S throughout the Harrat, thus effectively intercepting animal migration towards Syria and the Mediterranean Coast. In all probability they were built in early Neolithic times to intercept gazelle (G. subgutturosa). We present statistical evaluation of two such chains: The Eastern Border Chain and the Usaykim-Safawi Chain. Both chains follow sections of the eastern Harrat border and are thus comparable in situation. Analysis shows that the kites of the Eastern Border Chain are significantly larger than those of the Usaykim-Safawi Chain, both concerning their guiding wall length as well as the sizes of their enclosures. However, the Usaykim-Safawi Chain has more of the older kite types (bagand clover-shaped) and may therefore have been occupied first. The overall length of walls existing in this chain (including guiding walls, enclosure perimeters and the additional meander walls and meander section walls) amount to 264 km. This allows estimating that the entire wall length exiting in the Harrat may be as much as 3780 km representing a stone volume half of that of the Cheops pyramid. Thus the Harrat Al-Sham desert kites are a most valuable and yet not well-known part of the heritage of Jordan. Many kites, however, have already been destroyed due to field clearing and bulldozing. 132 Physical Geology and Global Cycles Fig. 1: Kite No 18 (32° 5.719'N - 37° 6.525'E) of the Usaykhim Castle - Safawi Chain. The kite has clearly elongated ventral wings with elongated blinds along their apexes. It is well preserved and was built according to a clear design. Later alterations include a wall cutting off the northern wing to create an animal pen. The kite is the second structure at this place, to the north the walls of an earlier, unfinished kite is visible. Building started with the curved enclosure walls and some guiding wall sections. This kite had a straight ventral wall, perpendicular to the gate way. This apparently represents an earlier design that was abandoned and replaced by the design with ventral wings. In the older kite there is also a “circular path” of unknown purpose. Note that NE is up. References: [1] [2] Kempe, S., Al-Malabeh, A., 2010: Hunting kites (‘desert kites’) and associated structures along the eastern rim of the Jordanian Harrat: A geo-archaeological Google Earth Images Survey. – Zeitschrift für Orient-Archäologie 10(3): 46-86. Kennedy, D., 2011: The “works of the old men” in Arabia: remote sensing in interior Arabia. – J. Archaeol. Sci. in press. Physical Geology and Global Cycles 133 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. We are especially excited about the funding for a second phase of our water resources management project in Saudi Arabia, which is a part of the BMBF funded joined project IWAS. 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. Two field sites in Saudi Arabia are in operation now and data on climatic parameters are collected and also automatically on unsaturated zone moisture contents in high spatial and temporal resolution. The field activities are complemented by two PhD students focusing on process oriented studies in the laboratory and one PhD student focusing on the hydrogeochmical evolution of the large aquifers on the Arabian Peninsula. A strategic collaboration was established with the IWW Water Center in Mülheim. IWW is a private non-profit research institute with a focus on drinking water. Six departments carry out basic and applied research covering the entire drinking water supply chain: Water resources management, Water technology, Water networks, Water quality, Applied Microbiology, and Management consulting. Projects are directed to the impact of climate change and risk management, to environmental behavior of pollutants, to economic evaluation of technologies, to integrated water resources management, to the development of sustainability indicators and to financing needs of adaptation processes. Prof. Dr. Christoph Schüth was elected as one of five Scientific Director at IWW for the department of water resources management. First joined projects were initiated, e.g. on the fate of nitrate in the Hessian Ried, funded by the Hessian Agency for the Environment and Geology (HLUG). As the building of the Institute of Applied Geosciences in the Schnittspahnstraße is currently undergoing major refurbishment, part of the laboratories of the hydrogeology group moved to the Biebesheim office of IWW. We are hosted there at the facility of the Wasserverband Hessisches Ried (WHR) in a modern laboratory building, which is gratefully acknowledged. Dr. Andreas Kallioras left the group as he was offered a tenure track position at the Technical University of Athens in the School of Mining and Metallurgical Engineering. However, he will continue to cooperate with us on the project in Saudi Arabia. Three new PhD students joined the group, Abidur Khan, working on a project concerning heavy metal contamination of surface water and groundwater in Dhaka city Bangladesh, Anja Wolf, working on water quality issues at the Three Gorges Dam in China (together with IWW), and Laith Latai, working on the detection of oil spills and water contamination in the Kirkuk area in Irak using remote sensing techniques. We are very excited to expand our international focus into other regions of the world with severe environmental problems. 134 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 Ahmed Abdulhamza MSc Michaela Laxander Dipl. Ing. Anja Wolf MSc Mustafa Yasin MSc Laith Latai Diploma Students Christoph Kludt Manuel Lindstedt Isimemem Osemwegi Berhane Asfaw Research Fellow Dr. Andreas Kallioras Guest Scientists Prof. Dr. Adnan Afaj Research Projects Management of regional groundwater resources – Saudi Arabia (BMBF: 2011-2013). SAFIRA 2: The treatment train approach (BMBF: 2009-2011) 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: 2008-2011) 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 Ravbar, N., Engelhardt, I., Goldscheider, N. (2011); Anomalous behaviour of specific electrical conductivity at a karst spring induced by variable catchment boundaries: the case of the Podstenjsek spring, Slovenia .- Hydrological Processes, 25: 2130-2140. Engelhardt, I., Piepenbrink, M., Trauth, N., Stadler, S., Kludt, C., Schulz, M. Schüth, C. & Ternes, T.A. (2011): Comparison of tracer methods to quantify hydrodynamic exchange within the hyporheic zone. - Journal of Hydrology, 400: 255-266. Hydrogeology 135 Soil column experiments to quantify groundwater recharge in arid areas Heike Pfletschinger, Irina Engelhardt, Christoph Schüth The quantification of vadose zone water fluxes in arid regions poses many difficulties due to low water input, coupled thermal and isothermal processes, spatial and temporal highly variable meteorological conditions as well as measurement errors. Nevertheless, water flux processes in the vadose zone have to be understood and quantified as they govern rates of direct groundwater recharge. To quantify vadose zone water fluxes under controlled conditions, laboratory soil column experiments were developed that mimic atmospheric and soil water conditions as they can be expected in arid regions (Fig. 1). The experimental setup allowed to measure water content and temperature distribution within a 90 cm deep soil profile in high temporal and spatial resolution using a TDR Taupe cable [1] and TDR rod sensors. At the top of the column, a head space with con-trollable air stream, water input and applied temperature accounted for the simulation of changing atmospheric conditions. At the column bottom, temperature and outflow pressure were applied to obtain a tempera-ture gradient within the column and water discharge under controlled pressure conditions. Fig. 1: Experimental setup The setup with the two TDR sensor systems was tested in a two-stage experiment. The column was filled with the silica sand having a volumetric water content of 0.07 cm3/cm3. The temperature was fixed at 50°C at the top and at 15°C atthe bottom. The inflowing air stream was applied with a constant flow of 5 l/min and a relative humidity between 5 and 10%. The suction at the bottom was held constant at 60 mbar. First, a uniform overhead irrigation of 0.55 mm/min was applied until steady-state conditions were reached for column water content, temperature distribution, water outflow and evaporation. After stopping overhead irrigation, measurements continued until again steady state was reached for the aforementioned parameters. Figure 2 (left) shows the results of the overhead irrigation phase. Initially, the volumetric water content in the upper part of the column increased to a maximum of 0.13 cm3/cm3, indicating unsaturated downward flow of water. Discharge at the bottom of the column started about 5 h after irrigation started. After overhead irrigation stopped, the sand drained within about 10 h to a homogenous water content of 0.09 cm3/cm3 (Fig. 2 right). Within the first hour of drainage, water content in the upper profile part rapidly decreased inducing a significant lowering of the unsaturated hydraulic conductivity. Due to higher water contents at the bottom of the 136 Hydrogeology column, water moved faster to the lower end until equilibrium was reached throughout the whole column. Thus, drainage appeared to be almost homogeneous in the entire column. Fig. 2: left: Infiltration front and discharge during wetting with continuous irrigation of 0.55 mm/min measured with the TDR cable (continuous line) and TDR point measurements (circles). Right: Water content and evaporation during drainage and drying measured with the TDR cable (continuous line) and TDR point measurements (circles). The experimental setup in general proved to be applicable to study water fluxes in the vadose zone in high resolution. In the controlled column experiments, textbooklike infiltration curves could be obtained using the TDR ‘Taupe’ cable. The TDR cable sensor is therefore an ideal tool to obtain continuous soil saturation profiles and thus to trace wetting and evaporation fronts. However, its installation, as well as the interpretation of data, needs some care and is limited at the sensor transition and thus, in the experimental setup, at the column top. According to the experiments, a numerical model was set up in Hydrus-1D, simulating coupled water, vapor and temperature fluxes in variably-saturated media (Šimunek et al., 2009). Hydraulic and thermal soil parameters, which are implemented into the model, were calibrated with experimental data of water content and temperature profiles at different times as well as transient water discharge and evaporation. Amongst the calibrated parameters, those controlling high saturated flow were less sensitive than those controlling evaporation and drainage, whereas highest sensitivities were obtained for the air entry pressure of the retention function of Brooks and Corey [3]. With the calibrated model, predictive scenario modeling was performed representing annual changing soil Hydrogeology 137 moisture conditions to identify parameters of primary importance for possible groundwater recharge in arid regions. The predictive modeling emphasized the high importance of single precipitation amounts on deep infiltration and percolation which can induce groundwater recharge. For annually low precipitation amounts, the residual water content of the ambient soil mainly determines percolation processes. Vapor fluxes, induced by temperature gradients, plays a major role in total water fluxes under low saturated conditions. In conclusion, the laboratory experiments were a good tool for first estimates of vadose zone water fluxes under arid conditions and were essential for the model setup and calibration. Based on the calibrated model further predictions upon vertical water fluxes and deep percolation for critical meteorological conditions could be made. By this, the model offers a valuable tool for groundwater management issues, especially regarding smart field observation and measurement schemes and initial predictions on soil water states for expected future hydrological and microclimatological changes. References: [1] [2] [3] 138 Brandelik A, Huebner C, Schuhmann R (1998) Moisture sensor for large area layers. German patent no. 4432687, European patent no. 0804724, US patent no. 5942904, 16 June 1998. Šimonek J., Šejna M., Saito H., Sakai M., van Genuchten M.T. (2009) The Hydrus-1D software package for simulating the movement of water, heat, and multiple solutes in variably saturated media. Version 4.08. HYDRUS Software Series 3. Department of Environmental Sciences. University of California. Riverside. USA. pp. 330. Brooks RH, Corey AT (1964) Hydraulic properties of porous media. Hydrology Papers No. 3. Colorado State Univ, Fort Collins. Hydrogeology Engineering Geology Engineering Geology is an applied earth science and a branch of the applied geology which requires multidisciplinary knowledge within both, natural sciences (geology, chemistry, physics, mathematics) and engineering sciences. The common aims of all special subjects contributing to engineering geology are the investigation, the use, the protection and the remediation of the upper parts of the earth's crust. Engineering Geology seizes the behaviour of rocks and rock masses according to the genetic material properties and their development in earth’s history. It quantifies the mechanical, physical and hydromechanical characteristics and the behaviour of soils and rocks in detail and in the assembly. Important corresponding special subjects are soil and rock mechanics, civil services, foundation engineering, tunnel and cavity construction, drilling technology, measurement engineering and applied subjects of hydrology and hydrogeology, petrology and geochemistry. Engineering geology has thus strong relations with geotechnical engineering. It translates the results and knowledge of the geosciences into the engineering requirements. Engineering Geology contributes to the fact that buildings of all kinds can be built and heated surely and economically. For this purpose the building ground and other underground conditions for engineering structures, such as geothermal power plants, traffic routes (e.g. roads, bridges, tunnels) as well as other infrastructure such as caverns, dams, pipelines as well as buildings such as high rise buildings, halls, wind power stations as well as water-structural plants such as water gates, dams, and dykes, are investigated. At present, the Chair of Engineering Geology is represented by the Chair of Geothermal Science and Technology. However, in March 2012, Prof. Andreas Henk from Freiburg will join our faculty and continue to represent this important topic in applied geosciences. We all wish Prof. Henk a successful start in 2012 and look forward to welcome him at the TU Darmstadt. Institute of Applied Geosciences – Engineering Geology 139 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. Since September 2009 Prof. Sass holds this chair and in October 2009 the position of associate professor was filled. This position is hold by PD Dr. Götz, focussing on the facies-related characterization of geothermal reservoirs. 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 2011. Field courses and excursions in 2011 focused on geothermal energy in China, New Zealand, Jordan, Germany and the Netherlands. Staff Members Head Prof. Dr. Ingo Sass Associate Professor PD Dr. Annette E. Götz (in June 2011 call to the Rhodes University, Südafrika) Research Associates M.Sc. Achim Aretz M.Sc. Selcuk Erol Dipl.-Geol. Philipp Mikisek Dipl.-Ing. Robert Priebs Dr. Wolfram Rühaak 140 Dipl.-Ing. Kristian Bär Dipl.-Ing. M.Sc. Sebastian Homuth Dipl.-Ing. M.Sc. Johanna Rüther Dipl.-Ing. Johannes Stegner Geothermal Science and Technology Technical Personnel Gabriela Schubert Rainer Seehaus Secretaries Simone Roß-Krichbaum Dunja Sehn PhD Students Dipl.-Ing. Hauke Anbergen M.Sc. Yixi Gu Dipl.-Ing. Heiko Huber M.Sc. Liang Pei M.Sc. Sana’a Al-Zyoud Dipl.-Geol. Ulf Gwildis Dipl.-Geol. Clemens Lehr Diploma Students Barbara Breuer (Diplom) Jan Hesse (Diplom) Matthias Nehler (Diplom) Johanna Rüther (Diplom) Andreas Schumann (Diplom) Bastian Welsch (Diplom) Oliver Geist (Diplom) Ulrike Klaeske (Diplom) Robert Priebs (Diplom) Raffael Schäffer (Diplom) Michael Thomson (M.Sc., RES) Marcin Wronowski (M.Sc., RES) Guest Scientists ERASMUS Viktor Hlavička, BSc, TU Budapest, Ungarn Máté Tóth, BSc, TU Budapest, Ungarn DAAD Prof. Dr. B.N. Upreti, Tribhuvan University Kathmandu, Nepal EU-Programm Pioneer into Practice (PiP) Dr inż. Łukasz Szałata, Universität Breslau, Polen Guest Lecturers Dr.-Ing. Ulrich Burbaum (CDM Consult Alsbach) Prof. Dr. Rolf Bracke (Geothermiezentrum Bochum) Dr. Thomas Nix (LBEG Hannover) Prof. Dr. Martin Sauter (Universität Göttingen) Dr. Tomas Fernandez-Steeger (RWTH Aachen) Prof. Dr. Ákos Török (TU Budapest) Research Projects started in 2011 Mitteltiefer Hochtemperatur-Erdsonden-Wärmespeicher (MHEW) zum Betrieb konventioneller Wärmeversorgungsnetze ohne Wärmepumpen Research proposal, Bundesministerium für Wirtschaft und Technologie, Experimentelle Untersuchungen zur Verifizierung eines Mehrphasenmodells Wärmetransportverhalten im Untergrund Funding: 3 Years, Bundesministerium für Wirtschaft und Technologie für das Machbarkeitsstudie „Machbarkeit und Nutzung von tiefer geothermischer Energie am Flughafen Frankfurt Funding: 2010-2012, FRAPORT AG Charakterisierung des Geothermischen Reservoirpotenzials des Permokarbons in Hessen und Rheinland-Pfalz Funding: 2 Years, Bundesministeriums für Umwelt, Naturschutz und Reaktorsicherheit Geothermal Science and Technology 141 Entwicklung von wartungsarmen PEHD-Filterelementen für oberflächennahe geothermische Brunnenanlagen Funding: 3 Jahre, Deutsche Bundesstiftung Umwelt Quantitativer Einfluss des Wasserhaushalts, der Umwelttemperatur und der geothermischen Kennwerte auf die Wärmeableitung erdverlegter Starkstromkabel Research proposal, NATURpur Institut für Klima- und Umweltschutz Rock and Hydrothermal Fluid Interactions and Their Impacts on Permeability, Reservoir Enhancement and Rock Stability Research proposal, DAAD Research Projects continued and finalized in 2011 Rock mechanical and geothermal evaluation of basaltic rocks in Harrat Al-Shaam, Jordan – DAAD-funded project in collaboration with Hashemite University of Jordan, Zarqa. 3D-Model of the deep geothermal potential of the Federal State of Hesse/Germany – Funding: HMUELV (Hessian Ministry for Environment, Energy, Agriculture and Consumer Protection); in collaboration with HLUG (Hessian Agency for the Environment and Geology). 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. Long-term effect of a seasonal thermal storage on the subsurface: a case study from the Upper Muschelkalk, SW Germany – Industry-funded project (CDM Consult GmbH, Crailsheim) in collaboration with ITW, University of Stuttgart. 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. Cooperation with the School of Renewable Energy Science (RES), Akureyri, Iceland The cooperation between the Chair of Geothermal Science and Technology and RES was established in 2008. In 2009, the TU Darmstadt Energy Center signed to collaborate with RES in energy research and education. Prof. Sass continued his lectures as part of the RES Master Programme in Geothermal Energy. Two students from RES joined the group of Prof. Sass at TUD in 2011 to prepare and finish their Master theses. 142 Geothermal Science and Technology Publications Arndt, D., Bär, K., Fritsche, J.-G., Kracht, M., Sass, I. & Hoppe, A. (2011): 3D structural model of the Federal State of Hesse (Germany) for geo-potential evaluation. ZDGG, 162 (4): 353-369. Bär, K., Arndt, D., Fritsche, J.-G., Götz, A.E., Kracht, M., Hoppe, A. & Sass, I. (2011): 3DModellierung der tiefengeothermischen Potenziale von Hessen: Eingangsdaten und Potenzialausweisung. ZDGG, 162 (4): 371-388. Bär, K., Felder, M., Götz, A.E., Molenaar, N. & Sass, I. (2011): The Rotliegend Reservoir System of the nor-thern Upper Rhine Graben (Germany): From Pores to Production. Geophysical Research Abstracts, Vol. 13: EGU2011-A-1190, Abstracts of the Contributions of the EGU General Assembly; Wien. Bär, K., Felder, M., Götz, A.E., Molenaar, N. & Sass, I. (2011): The Rotliegend Reservoir System of the northern Upper Rhine Graben (Germany): From Outcrop Analogue Studies to Geothermal Reservoir Assessment. - International Conference and Exhibition (ICE) 2011, American Association of Petroleum Geologists (AAPG), Mailand. Burbaum, U., Böhme, T. & Sass, I. (2011): Hydroschildvortrieb im Lauenburger Ton: Untersuchungen zur Adhäsivität des Baugrunds. Geotechnik, 34(2): 108-114. Diersch, H.-J.G., Bauer, D., Heidemann, W., Rühaak, W. & Schätzl, P. (2011): Finite element modeling of borehole heat exchanger systems - Part 1. Fundamentals. Computers & Geosciences. [in press] Diersch, H.-J.G., Bauer, D., Heidemann, W., Rühaak, W. & Schätzl, P. (2011): Finite element modeling of borehole heat exchanger systems - Part 2. Numerical simulation. Computers & Geosciences. [in press] Götz, A.E. (2011): The Anisian Carbonates of the Peri-Tethys Basin: from Reservoir Characterization to Subsurface Utilization. - International Conference and Exhibition (ICE) 2011, American Association of Petroleum Geologists (AAPG), Mailand. (Poster) Götz, A.E. & Lenhardt, N. (2011): The Anisian carbonate ramp system of Central Europe (Peri-Tethys Basin): sequences and reservoir characteristics. Acta Geologica Polonica, 61(1): 59-70. Homuth, S., Götz, A.E., Sass, I. (2011): Outcrop analogue studies for reservoir characterization of deep geothermal systems in Upper Jurassic limestone formations (South Germany). - International Conference and Exhibition (ICE) 2011, American Association of Petroleum Geologists (AAPG), Mailand. Homuth, S., Götz, A.E. & Sass, I. (2011): Outcrop analogue studies for reservoir characterization and prediction of deep geothermal systems in the Molasse Basin, Germany. Geophysical Research Abstracts, Vol. 13, EGU 2011-999, Wien. ( Homuth, S., Hamm, K. & Sass, I. (2011): Borehole Heat Exchanger Logging and Cement Hydration Heat Analyses for the Determination of Thermo-Physical Parameters. Bulletin of Engineering Geology and the Environment. [in review] Huber, H., Arslan, U., Stegner, J. & Sass, I. (2011): Experimental and numerical modelling of geothermal energy transport, Proceedings 13th International Conference of the International Association for Computer Methods and Advances in Geomechanics (IACMAG 2011), Melbourne, Australia, 09.-11.05.2011, Vol. 1, 455-459. Geothermal Science and Technology 143 Huber, H., Arslan, U., Stegner, J. & Sass, I. (2011): Inaccuracies in geothermal field tests. International Conference on Advances in Geotechnical Engineering (ICAGE 2011), 07.09.11.2011, Perth, Australia. Mikisek, P., Bauer, D., Homuth, S., Götz, A.E., Heidemann, W., Sass, I. & MüllerSteinhagen, H. (2011): Thermal Effect of a Borehole Thermal Energy Store on the Subsurface. Geothermics. [in review] Philipp, S., Parchwitz, S. & Götz, A.E. (2011): Geothermal Potential of the Upper Muschelkalk in Northeastern Germany. - Geophysical Research Abstracts, Vol. 13: EGU2011A-2487, Abstracts of the Contributions of the EGU General Assembly; Wien. Rüther, J., Björnsson, A., Hamm, K., Homuth; S. & Sass, I. (2011): Validation of a newlydeveloped thermal conductivity sensing system using Icelandic basalts. Geothermics. [in review] Sass, I. (2011): Empfehlungen des Arbeitskreises Geothermie. Oberflächennahe Geothermie „Planung, Bau, Betrieb und Qualitätssicherung“. FH-DGG und FI-DGGT/DGG. [accepted] Sass, I. & Bär, K. (2011): Identification of a hydrothermal reservoir system in the northern Upper Rhine Graben (Germany). HADES Workshop, GNS Science, Taupo, Neuseeland (25. Mai 2011) Sass, I. & Burbaum, U. (2011): Geotechnische Analyse zum Schadensfall Staufen. Geotechnik. [in review] Sass, I. & Götz, A.E. (2011): The Thermofacies Concept. - Proceedings of the 36th Stanford Geothermal Workshop; Stanford. Sass, I. & Lehr, C. (2011): Improvements on the thermal response test evaluation applying the cylinder source theory. - Proceedings of the 36th Stanford Geothermal Workshop; Stanford. Sass, I. & Götz, A.E. (2011): Geothermal Reservoir Characterization: A Thermofacies Concept. Terra Nova. [accepted] Siratovich, P., Homuth, S., Björnsson, A. & Sass, I. (2011): Thermal Stimulation of Geothermal Reservoirs and Laboratory Investigation of Thermally Induced Fractures. - 2011 GRC Annual Meeting, San Diego, California. 144 Geothermal Science and Technology Outcrop analogue studies for reservoir characterization of deep geothermal systems in Upper Jurassic limestone formations (South Germany) Sebastian Homuth The utilization of deep geothermal systems is based on a detailed knowledge of their distinct reservoir characteristics. In the early stages of hydrothermal reservoir exploration, the thermo-physical characterization of the reservoir is mainly accomplished by evaluation of already existing drilling data in the vicinity of the target area and in some cases seismic surveys. For reservoir predictions, the main geothermal parameters such as permeability, porosity, thermal conductivity, thermal diffusivity, specific heat capacity and reservoir heat flow have to be quantified. In addition to these thermo-physical parameters in-situ stress field analysis and structural tectonic data is important to assess. Outcrop analogue studies enable the determination and correlation of thermo-physical parameters and structural geology data with regional facies patterns. An outcrop analogue investigation examines the same rock formations (stratigraphy, lithology, facies) as the potential reservoir formations from which fluids at according depth are discharged. An outcrop analogue study of the target formation Malm of the Upper Jurassic, which is the most promising formation for deep geothermal projects in the German Molasse Basin, has to include facies studies following a thermofacies concept [1]. For the economic utilization of deep geothermal reservoirs, a sufficient high flow rate of thermal waters throughout the reservoir to the production well is necessary. This flow rate is mainly controlled by the reservoir permeability. In the Molasse Basin in southeast Germany the limestone formations of the Upper Jurassic contain the main flow paths through tectonic elements such as faults, joints and fractures, and to some extend also, typically for limestone formations, through karst phenomena. To characterize those fracture controlled reservoirs the orientation of fractures, fracture width, surface roughness of fractures as well as the connectivity of fractures and possible secondary mineralization in the fracture system is important. These analyses enable to assess the natural or due to stimulation measures artificially generated possible reservoir permeability in advance of drilling operations. To forecast geometries and further properties of existing fracture systems in three dimensions for geothermal appropriate depth, the definition of seismic analyses is not sensitive enough [2]. Also drill cores from exploration drillings are often not available or giving only a limited set of information. Therefore, it is necessary to obtain thermo-physical and structural geological data from outcrops, like it is done in the petroleum exploration [3]. Finally, the correlation of distinct sedimentary facies and their thermo-physical parameters may contribute to establish integrated structural 3D reservoir models. The inferred predictions from the laboratory testing can be validated with actual drilling data and pump test data from recent drill sites. Due to the fact that a precise classification of facies zones in the target depth of the geothermal reservoir is not possible, the outcrop analogue study is focusing on the two different facies areas exposed in the Southern German Swabian and Franconian Alb. According to the Dunham classification of carbonate rocks the following facies types are detected in the study area: mudstones, wackestones, grain-/packstones and rud/floatstones. The investigations are carried out on three different scales: (1) The macro scale including an outcrop mapping to detect the litho types, structural elements and facies patterns in the Geothermal Science and Technology 145 outcrop; (2) the meso scale, to determine thermo-physical properties of different litho types in the laboratory; and (3) the micro scale, to analyze microstructures, cements, porosities, etc. in thin sections. To determine the thermo-physical properties of the sampled formations a thermal conductivity scanner (optical scanning method after [4] and an air driven permeameter [5] and porosimeter are used. The matrix permeability of all measured carbonates is quite low except for some grainstones with higher permeabilities and porosities. Thick-bedded and platy limestones show thermal conductivities around 2 Wm-1K-1, characteristic for limestones. Permeabilities range from 0.05 mD to 100 mD. Mudstones (marly limestones) have lower thermal conductivities than thick bedded and platy limestones, by having the same range of permeabilities as the thick-bedded limestones. The thermal conductivities of different reefal limestones show values of 1.8 to 2.5 Wm-1K-1. Due to the higher content of secondary mineralized silicates in the reefal structures, these carbonates show the highest values of thermal conductivity of all studied carbonates. The comparatively high thermal conductivity corresponds to low permeability. In general it can be inferred that the Swabian mud-dominated facies have lower permeabilities than the Franconian reef-dominated facies. The only exception is for the grainstones of the Swabian facies which have 1-2 magnitude higher permeabilities as the mud-dominated Swabian carbonates. The data shows in general very low permeability for all types of investigated carbonates, so no hydraulically effective support from the matrix of the Malm aquifer can be inferred. However, in places the Malm aquifer is very productive, being able to produce discharge rates of over 100 l/s. So the main hydraulic flow must be related to fracture systems and karst phenomena. By looking at karst structures two general facies related karstification structures can be observed: (1) In terms of thick-bedded or platy limestone facies karstification occurs only along major fractures and faults; (2) in case of reefal limestones and bioclastic limestones the karstification occurs on a larger scale due to the primary and secondary porosity of these facies. The thermo-physical parameters are determined on oven dried samples. To obtain realistic parameters under reservoir conditions, it is possible to calculate these values for water saturated rocks under reservoir pressure and temperature conditions for relevant depths [6,7,8]. These parameters can be validated in a Thermo-Triax-Cell simulating the existing temperature and pressure conditions in the target horizon of a geothermal reservoir and furthermore induces a pore pressure on the rock sample. This device offers the opportunity to determine permeabilities from outrop samples under realistic reservoir conditions. First results show that 3D prognosis of reservoir properties by applying facies models to the deeper subsurface can be implemented as an additional exploration tool. The determination of geothermal reservoir properties serves to distinguish between petrothermal and hydrothermal systems and can also be used for optimized drilling design purposes. Outcrop analogue studies offer effective opportunities to gain data to be transferred to greater depths and higher temperatures which lead to a better understanding of production capacities of geothermal reservoirs. Furthermore, these studies provide a sufficient data base to determine thermo-physical reservoir characteristics of the rock matrix of geothermal reservoir formations. Facies concepts are applied as an exploration tool producing conservative results. Adding information of secondary porosities, karstification and stress field into a reservoir model will lead to higher reservoir capacities. Based on the investigation of the matrix parameters the sustainable heat transport into the utilized 146 Geothermal Science and Technology geothermal reservoir can be assessed. Thus, the long term capacities for different utilization scenarios can be calculated more precisely. Investigations on the lateral extension and facies heterogenity will give insight on the transmissibility of different target horizons. The thermofacies related characterization and prediction of geothermal reservoir parameters is therefore a powerful tool for the design, extension, operation and quality management of planned and existing geothermal reservoir, respectively. The key to reliable reservoir prognosis, reservoir stimulation, and sustainable reservoir utilization is to integrate thermofacies and structural geology data into 3D reservoir models. References: [1] [2] [3] [4] [5] [6] [7] [8] Sass, I. & Götz, A.E. (2011): The Thermofacies Concept. - Proceedings of the 36th Workshop on Geothermal Reservoir Engineering Stanford University, SGP-TR-191; Stanford, California. Philipp, S., Hoffmann, S., Müller, C., Gudmundsson, A. 2005. Verringerung des Fündigkeitsrisikos für tiefengeothermische Projekte durch strukturgeologische Geländestudien und Numerische Modell. Geothermische Jahrestagung 2005, Unterschleißheim, 113–124. Jahn, F., Graham, M., Cook, M. 2008. Hydrocarbon Exploration & Production, Volume 55, Second Edition (Developments in Petroleum Science), Elsevier Science, 470. Popov, Y.A., Berezin, V.V., Semionov, V.G. & Korosteliov, V.M. (1985): Complex detailed Investigations of the thermal properties of Rocks on the basis of a moving point Source. Earth Physics Vol. 21, No. 1, Izvestiya. Jaritz, R. (1999): Quantifizierung der Heterogenität einer Sandsteinmatrix am Beispiel des Stubensandsteins (Mittlerer Keuper, Württemberg). – Tübinger Geol. Arbeiten, C 48: 104 S., Tübingen. Pape, H.G., Clauser, C. & Iffland, J. (2000): Variation of Permeability with Porosity in Sandstone Diagenesis Interpreted with a Fractal Pore space Model. Pure appl. geophys., 157: 603-619. Basel. Vosteen, H.D. & Schellschmidt, R. (2003): Influence of temperature on thermal conductivity, thermal capacity and thermal diffusivity for different types of rock. Physics and Chemistry of the Earth, 28: 499 509. Popov, Y., Tertychnyi, V., Romushkevich, R., Korobkov, D. & Pohl, J. (2003): Interrelations Between Thermal Conductivity and Other Physical Properties of Rocks: Experimental Data. Pure Appl. Geophys., 160: 1137 1161. Basel. Geothermal Science and Technology 147 3D-Model of the deep geothermal potential of the federal state of Hesse/Germany Kristian Bär, Dirk Arndt, Johann-Gerhard Fritsche, Matthias Kracht, Ingo Sass & Andreas Hoppe Within the scope of the research project “3D-Model of the deep geothermal potentials of Hesse” the deep geothermal potential of the Federal State of Hesse was quantified and assessed in a qualitative analysis. The quantification of the heat stored under ground and the qualitative analysis was done for different geothermal systems. These are hydrothermal and petrothermal systems, as well as fault zones and deep borehole heat exchangers. Fig. 1: View onto the southern part of the northern Upper Rhine Graben, the Odenwald and the HorloffGraben region northeast of Frankfurt. The model is five times vertically exaggerated. [1] Fig. 2: View of the hydrothermal potential of the Rotliegend in die northern Upper Rhine Graben (five times vertically exaggerated) For the assessment of the deep geothermal potential, knowledge of the geological structure and the geothermal properties of the potential reservoir rocks are indispensable. Therefore, a 3D model of the deep geothermal potential of the Federal State of Hesse (Germany) has been developed [1]. The modelling was conducted using the software GOCAD. More than 4150 well data from the Hessian well database, hosted by the Geological Survey of Hesse (HLUG), as well as from the Hydrocarbon Well Database of the German Geological Surveys, hosted by the Geological Survey of Lower Saxony (LBEG), were used. Furthermore, all geological crosssections from geological maps and from other literature were taken into account. Additional data such as contour maps, palaeogeographic maps and existing structural models were used. In order to provide uncertainty information to third party users, it was 148 Geothermal Science and Technology integrated into the model itself. Stratigraphic Grids were created from the structural model, attributed with rock physical data [2]. Systematic measurements of thermophysical and hydraulic rock properties such as thermal conductivity, heat capacity and permeability of relevant geologic formations have been combined with in-situ temperature measurements, hydrothermal upwelling zones, characteristics of geological faults and were added to the 3D geological structural model. Using a multiple criteria approach, the various rock and reservoir properties were assessed incorporating their relevance for the different geothermal systems to allow the qualitative analysis. Therefore, threshold values for each parameter were defined specifying whether the potential is very high, high, medium, low or very low. This method was tested for the onedimensional case (virtual drilling) and the two-dimensional case (geological- geothermical cross-sections) before being applied to the 3D model. Depending on these parameters, the model is highly capable to evaluate geopotentials. The presented method for geopotential evaluation is based on the Analytic Hierarchy Process (AHP), which is a very common Multiple Criteria Decision Support System. The method can be used to identify and visualise different geopotentials cell based using many different parameters determining each potential. In addition to the evaluation of the deep geothermal potential the model and the presented method can be used to evaluate further geopotentials. The intersection of different potentials may then help to identify and visualise their conflicts of use and their synergetic use, respectively. The resulting geothermal model, which incorporates the quantification and the qualitative analysis, is an important tool, which can be used at an early stage of the planning phase for the design of geothermal power plants. Furthermore, it allows quantification of the deep geothermal potential and is intended to be an instrument for public information. References: [1] [2] Arndt, D., Bär, K., Fritsche, J.-G., Kracht, M., Sass, I. & Hoppe, A. (2011): 3D structural model of the Federal State of Hesse (Germany) for geo-potential evaluation. – Z. dt. Ges. Geowiss. 162 (4): 353–370, Stuttgart (Schweizerbart). Bär, K., Arndt, D., Fritsche, J.-G., Götz, A.E., Kracht, M., Hoppe, A. & Sass, I. (2011): 3DModellierung der tiefengeothermischen Potenziale von Hessen – Eingangsdaten und Potenzialausweisung. – Z. dt. Ges. Geowiss., 162 (4): 371–377, Stuttgart (Schweizerbart). Geothermal Science and Technology 149 Effect of hydrothermal alteration on rock properties in active geothermal setting Philipp Mikisek, Greg Bignall, Sepulveda, Ingo Sass Hydrothermal alteration records the physical-chemical changes of rock and mineral phases caused by the interaction of hot fluids and wall rock, which can impact effective permeability, porosity, thermal parameters, rock strength and other rock properties. In this project, an experimental approach has been used to investigate the effects of hydrothermal alteration on rock properties. A rock property database of contrastingly altered rock types and intensities has been established. The database details horizontal and vertical permeability, porosity, density, thermal conductivity and thermal heat capacity for ~300 drill core samples from wells THM12, THM13, THM14, THM17, THM18, THM22 and TH18 in the Wairakei-Tauhara geothermal system (New Zealand), which has been compared with observed hydrothermal alteration type, rank and intensity obtained from XRD analysis and optical microscopy. Samples were selected from clay-altered tuff and intercalated siltstones of the Huka Falls Formation, which acts as a cap rock at Wairakei-Tauhara, and tuffaceous sandstones of the Waiora Formation, which is a primary reservoir-hosting unit for lateral and vertical fluid flows in the geothermal system. The Huka Falls Formation exhibits argillic-type alteration of varying intensity, while underlying Waiora Formations exhibits argillic- and propylithic-type alteration. Fig. 1: Measurement equipment to analyse thermal and hydraulic rock properties and selected core samples of the Wairakei-Tauhere geothermal system. We plan to use a tempered triaxial test cell at hydrothermal temperatures (up to 200°C) and pressures typical of geothermal conditions, to simulate hot (thermal) fluid percolation through the rock matrix of an inferred “reservoir”. Compressibility data will be obtained under a range of operating (simulation reservoir) conditions, in a series of multiple week or month-long experiments that will monitor change in permeability and rock strength accompanying advancing hydrothermal alteration intensity caused by the hot brine interacting with the rock matrix. We suggest, our work will provide new baseline information concerning fluid-rock interaction processes in geothermal reservoirs, and their effects on rock properties, that will aid future decision-making, resource management and sustainable use of geothermal resources. 150 Geothermal Science and Technology 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 2011, 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, and Saudi Arabia. The project in Saud Arabia runs in the context of exploring deep water resources together with Applied Sedimentology 151 Prof. Schüth (Hydrogeology) and in cooperation with the GIZ (Gesellschaft für I(nternational Zusammenarbeit; früher GTZ), the UFZ (Umweltforschungszentrum HalleLeipzig), 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. 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). In September, Jianguang Zhang commenced with his PhD work in the sedimentology group supported by a Chinese grant. A new PhD was started to investigate the cuases of natural radioactivity in deep groundwaters of Saudi Arabia. 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 für Geowissenschaftliche Gemeinschaftsaufgaben). He is also the representative of the German-speaking sedimentologists (Section of Sedimentology in Geologische Vereinigung and SEPM-CES) and he is coorganizer of the SEDIMENT conference in Hamburg 2012. Staff Members Head Prof. Dr. Matthias Hinderer Research Associates Dr. Jens Hornung Postdoctoral Students Martin Kastowski PhD Students Hussain Al-Ajmi Alexander Bassis Weihua Bian Dennis Brüsch Daniel Franke Technical Personnel Erich Wettengl (until 30.5.2011) Secretary Kirsten Herrmann 152 Dr. Olaf Lenz Inge Neeb Frank Owenier Sandra Schneider Jianguang Zhang Applied Sedimentology 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 Research Group RIFT-LINK “Rift Dynamics, Uplift and Climate Change: Interdisciplinary Research Linking Asthenosphere, Lithosphere, Biosphere and Atmosphere” (DFG HI 643/71). 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 the Wajid group (Southwestern Saudi Arabia). (PhD thesis financed by Umweltforschungszentrum LeipzigHalle, GIZ Eschborn, and the Ministry of Water and Energy in Riyadh, Saudi Arabia), Analysis of radioactive anomalies in Paleozoic.mesozoic aquifers of the Arabian Platform (PhD thesis). Publications Frechen, M., Ellwanger, D., Hinderer, M., Lämmermann-Barthel, J., Neeb, I. & Techmer, A.,(2010): Reply to Preusser et al. On Frechen et al..”Late Pleistocene fluvial dynamics in the Hochrhein Valley and the Upper Rhine Graben: chronological frame. Int. Journal of Earth Sciences, Springer-Verlag. DOI 10.1007/s00531-011-0638-2 Hornung, J. & Hinderer, M. (2011): 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. 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. Kastowksi, M., Hinderer, M. & Vecsei, A. (2011): Long term carbon burial in European lakes: analysis and estimate. Global Biogeochemical Cycles, 25. Lenz, O.K., Wilde, V., Riegel, W. (2011): Short-term fluctuations in vegetation and phytoplankton during the Middle Eocene greenhouse climate: a 640-kyr record from the Messel oil shale (Germany). International Journal of Earth Sciences 100 (8): 1851-1874; DOI 10.1007/s00531-010-0609-z Applied Sedimentology 153 Lenz, O.K., Wilde, V., Riegel, W. (2011): Lake Messel, an extraordinary archive for the middle Eocene greenhouse climate. In: Lehmann, T., Schaal, S.F.K. (eds.): The World at the Time of Messel: Puzzles in Palaeobiology, Palaeoenvironment, and the History of Early Primates. Frankfurt am Main, 102 -103. Riegel, W., Wilde, V., Lenz, O.K. (2011): The edge of the sea at the time of Messel: Mangroves and related coastal wetlands in the Eocene of the Helmstedt mining district. In: Lehmann, T., Schaal, S.F.K. (eds.): The World at the Time of Messel: Puzzles in Palaeobiology, Palaeoenvironment, and the History of Early Primates. Frankfurt am Main, 141-142. 154 Applied Sedimentology Towards better accuracy of the TDR-method: Substrate sensitive moisture detection based on dielectric permittivity variations Frank Owenier, Jens Hornung und Matthias Hinderer Dielectric permittivity is an important parameter for all investigations based on electromagnetic waves (e.g. GPR = Ground Penetration Radar and TDR = Time-domain Reflectance measurements). In combination with the electric conductivity, it is crucial for the determination of the propagation velocity, the reflection coefficient and the decay of the electromagnetic wave. GPR and TDR measurements became widely used techniques to investigate the structure of the shallow subsurface and their change in humidity in the field. This includes monitoring of water infiltration, soil water content, shallow groundwater, as well as structural and geotechnical properties of soils and shallow rock formations. Frequency-dependent measurements of permittivity were carried-out with an impedance analyzer, which works in a frequency range from 10MHz up to 1GHz [1, 2]. This is inside the range of TDR applications (20KHz up to 20GHz) and ground penetrating radar (40MHz up to 900MHz). Fig. 1: Comparison of the pure reference materials (“endmembers”) with the Topp equation; measurements at 200MHz. The relationship between dielectric permittivity and volumetric moisture content of the sample material is described in polynomial equations of third degree in the form y=ax3+bx2+cx+d. The much-used Topp equation can be applied only in exceptional cases, or determined in the cases for which the curve was originally designed [3]. As part of this work, for the most important sediments (sand, clay, and carbonate) a relation between the volumetric moisture content and dielectric permittivity was established (Fig.1). The results show that there are clear correlations between the composition of the sediment on the one side and the permittivity associated with the water content on the other side. As part of the work, different bulk densities were considered. It was worked out that the influence of water on the permittivity is larger than that of the porosity. Consequently, the method is applicable both to undisturbed, as to disordered samples and designed to be Applied Sedimentology 155 applied directly in the field for these different substrate compositions in mobile devices or for permanent installations after compositional laboratory analyses. Hence, four factoral diagrams were established to individually calibrate each of the four factors of the polynom of third degree to moisture contents in relationship of a three principal component substrate (Fig. 2a-d). Fig. 2: Figure 20c-d: Ternary diagrams sand-carbonate-illite of the polynominal equation between permittivity (Real part) and volumetric moisture of the type y = ax3+bx2+cx+d. To use these diagrams the sedimentological composition of soil or other materials has to be derived from standard laboratory or simple field tests and its composition plotted into the triangular diagrams. Then at the point of composition the value for the four factors a, b, c, and d can be read off the corresponding diagram. The provided diagrams are valid for a frequency range of 50MHz to 1GHz. The clay mineral in these ternary diagrams is illite, as it was used for mixed substrates. Because of the large differences in the electrical behavior of various clay minerals the model is valid for illitebearing soils (or on soils with clay minerals that have a similar cation exchange capacity as illite). In any case, investigations of the clay mineralogy (XRD investigations) should be 156 Applied Sedimentology obtained. In these ternary diagrams, the results for the real part of permittivity habe been registered. The imaginary parts of permittivity of the measured samples (apart from very clay-rich substrates) are by a factor of 4 to 16 lower than the real parts, so that electrical loss for most substrates has only a minor influence. In two case studies natural materials were measured and compared to the predicted results. Deviations were less than 10% whearas traditional calibration shows deviations up to 160250%. For natural minerals it has been shown that different clay mineral compositions lead to differences in the imaginary part of permittivity. The precise knowledge of the composition of the substrate of vital importance for TDR measurements. References: [1] Owenier, F., Hornung, J. & Hinderer, M. (2011): Dielectric permittivity of geologi materials at different water contents – measurements with an impedance analyzer. 2011 6th International Workshop on Advanced Ground Penetrating Radar, Aaachen, 22-24 June 2011. [2] Salat, C. & Junge, A. (2010): Dielectric fractions of soil samples from eastern Spain (1), 1-9. [3] Topp, G.C., Davis, J.L., Annan, A.P. (1980): Electromagnetic determination of soil water content: measurements in coaxial transmission lines. Water Resources Research, H. 16 (3), 574-582. Formation of maar-diatreme-volcanoes. International Maar Conference. Terra Nostra 2000/6:284-291. Applied Sedimentology permittivity at 200MHz. of fine-grained Geophysics. 75 157 Geo-Resources and Geo-Hazards In times of rapid population growth and the resulting extension 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 as well as the prevention of the consequences of big natural phenomena turning into catastrophes more and more often is often not understood by decision makers who were not able to spend long years of studies on understanding the four-dimensional space-time-development of our earth. On the other hand, the metabolism of cities with its growing needs for clean water and raw material for constructions simultaneously egesting waste into its neighbourhood require a thorough understanding of its undergrounds and peripheries as well as safe construction sites. Geo Information Systems (GIS) and 3D-techniques like gOcad are powerful tools to qualify and to quantify resources and hazards in the peripheries of urban areas as they enable the aggregation of complex geological and spatial data to thematic maps for a better understanding and interpretation. Staff Members Head Prof. Dr Andreas Hoppe Research Associates Dipl.-Geoökol. Monika Hofmann Dipl.-Geol. Ina Lewin Dr. Rouwen Lehné PhD students Dipl.-Ing. Dirk Arndt Dipl.-Geogr. Constanze Bückner Dipl.-Geogr. Sigrid Hade Dipl.-Geol. Marie Luise Mayer Students Anna Ender Hanna Reinheimer Marie Mohr Nicole Mertz Kristel Franklin Kevin England 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) Research Projects The interdisciplinary project about the “Intrinsic Logic of Cities” funded by a Hessian initiative for excellence (LOEWE program) where Andreas Hoppe served as speaker of an interdisciplinary group concentrating an “Urban Development and Sustainability” resulted in a book on “Space and Time of Cities” and the concept for a “A Comparison of Cities in Maps illuminating the Interdependencies between Natural Framework Conditions and Socialisation” elaborated by Andreas Hoppe and Constanze Bückner. 158 Geo-Resources and Geo-Hazards Prem Thapa from Tribhuvan University of Nepal is performing a research on modelling of landslide hazard and 3D geology in the Lesser Himalaya, central Nepal. Modelling processes have revealed that critical factors effect for spatial localisation of landslides in diverse geo-environmental conditions are due to slope gradient and orientation of rock discontinuities with respect to hill-slopes. The validation of model is manifested by success and prediction rates which ranged from 90% to 94%. Integration of computed landslide hazard in 3D geological perspective has demonstrated that optimised approach of implicit structural modelling from sparse data is quite useful to interpret geologic-boundary surfaces for evaluating the geo-hazard and risk. Rouwen Lehne with Marie-Luise Mayer continued with a 4D reconstruction of the uppermost layers (Quaternary) in the northern Upper Rhine Graben in a project supported by the Hessian Geological Survey (HLUG) in order to evaluate the geopotentials of nearsurface resources and hazards. A geodetic measurement program to detect recent movements in the Northern Upper Rhine Valley in cooperation with the Czech Academy of Sciences (Prague) and supported by DFG was continued. Ina Lewin elaborates a 3D model for a small area in the Neogene Hanau-Seligenstadt Basin between the Odenwald and Spessart Mts based on drillings and radar mapping. Those investigations serve for a groundwater model combining local sedimentological architecture with hydraulic data as well as high-resolution temperature data gained from several multiparameter stations in monitoring wells. The project is supported by the local water distributor (Zweckverband Gruppenwasserwerk Dieburg) in order to find fast flow paths between their pumping wells and nearby sand and gravel pit. Dirk Arndt completed a goCad based 3D model of the Federal State of Hesse showing the top of Quarternary and Tertiary, Muschelkalk, Buntsandstein, Zechstein, Rotliegend and Pre-Permian. A new AHP (Analytic Hierarchy Process) based method was developed and implemented allowing to evaluate geo-potentials from the gridded and attributed volumes in 3D. The work is part of an R&D project evaluating the deep seated geothermal potential for Hesse (financed by the Hessian Ministry of Economy). Monika Hofmann evaluates geo-resources and geo-hazards for a sustainable growth of the fast growing megacity of Belo Horizonte (Minas Gerais, Brazil) with a spatial decision support system after having compiled, interpreted, and stored all relevant geoscientific information in an electronic data base. The investigation in Olympia (Greece) to decipher the Holocene evolution of landscape (in cooperation with the German Archeological Institute, DAI) continued. Recent efforts resulted in a high precision Digital Elevation Model (1:5.000). Additionally, a drilling campaign and radon measurements on prominent faults have been carried out. Andreas Hoppe serves as chief-editor of the “Zeitschrift der Deutschen Gesellschaft für Geowissenschaften” (ZDGG; listed in ISI) and has been appointed as consulting editor of Geological Quaterly. As speaker of the Evenarí Forum for German-Jewish Studies at Technische Universität Darmstadt he organized for the winter term 2011/2012 a series of lectures on “Jewish Life in Germany after Auschwitz”. Geo-Resources and Geo-Hazards 159 Publications Arndt, D., Bär, K., Fritsche, J.-G., Kracht, M., Sass, I. & Hoppe, A. (2011): 3D structural model of the Federal State of Hesse (Germany) for geo-potential evaluation. – Z. dt. Ges. Geowiss., 162 (4): 353-369, Stuttgart. Bär, K., Arndt, D., Fritsche, J.G., Götz, A.E., Hoppe, A., Kracht, M. & Sass, I. (2011): 3DModellierung der tiefengeothermischen Potenziale von Hessen – Eingangsdaten und Potenzialausweisung. – Z. dt. Ges. Geowiss., 162 (4): 371-388, Stuttgart. Bückner, C. (2011): Der Eigenlogik mit dem Netzwerk auf der Spur - GIS als Werkzeug in der interdisziplinären Stadtforschung. – ArcAktuell 2/2011: 17. Hoppe, A., ed. (2011): Raum und Zeit der Städte – Städtische Eigenlogik und Jüdische Kultur seit der Antike. – 229 p., Frankfurt am Main (Campus Verlag) [ISBN 978-3-59339536-4]. Hoppe, A. (2011): Vorwort. – In A. Hoppe, ed.: Raum und Zeit der Städte, 7-9, Frankfurt am Main (Campus Verlag). Hoppe, A. (2011): Geowissenschaften und die Eigenlogik der Städte. – In A. Hoppe, ed.: Raum und Zeit der Städte, 25-46, Frankfurt am Main (Campus Verlag). Hoppe, A., Hofmann, M., Lehné, R. & Simons, U. (2011): Spatial decision support systems for geopotentials in the periphery of urban areas. - Freiberger Forschungshefte C 358 (C. Breitkreuz & H.-J. Gursky, eds.: Geo-risk management – a German Latin American approach): 131-134, Freiberg. Hoppe, A. & Schüth, C. (2011): Waterworks Biebesheim and groundwater enrichment in the northern Upper Rhine Graben. - Freiberger Forschungshefte C 358 (C. Breitkreuz & H.J. Gursky, eds.: Geo-risk management – a German Latin American approach): 173-175, Freiberg. Lang, S., Hornung, J., Krbetschek, M., Ruckwied, K. & Hoppe, A. (2011): Tektonik und Sedimentation am Rand des Oberrheingrabens in Darmstadt im Mittel- und Oberpleistozän. – Geol. Jb. Hessen 137: 19-53, Wiesbaden. Lehné, R.J., ed. (2011): GIS and 3D-modelling in geosciences.- Z. dt. Ges. Geowiss. 162 (4): 351-451, Stuttgart . Schumann, A, Arndt D., Wiatr, T, Götz, A.E. & Hoppe, A. (2011): High-Resolution 3D Terrestrial LaserScanning of a Mineral Deposit for Extraction Management Optimization. – Z. dt. Ges. Geowiss. 162 (4): 435-442, Stuttgart. Thapa, P. B. (2011): Landslide susceptibility modelling in the central Nepal Lesser Himalaya. – Z. dt. Ges. Geowiss., 162 (4): 405-420, Stuttgart. 160 Geo-Resources and Geo-Hazards 3D geological modelling of the Lesser Himalaya, central Nepal P. B. Thapa1,2, D. Arndt2, A. Hoppe2, R. Lehné2 1 Department of Geology, Tri-Chandra Campus, Tribhuvan University, Kathmandu, Nepal Institut für Angewandte Geowissenschaften, Technische Universität Darmstadt, Germany 2 Background An enhanced technique of three dimensional (3D) geological modelling is carried out in the Lesser Himalaya, central Nepal using geological object computer aided design (GOCAD). The modelling site is bounded by the latitudes 2737’38” and 2745’37” N, and the longitudes 8457’38” and 8508’2” E. It covers an area of 254.7 km2 and is characterized by complex mountainous terrain with elevation ranging from 540 m to 2503 m. Litho-stratigraphy comprises six different units consisting of sedimentary, metamorphic and igneous rocks, Precambrian to Palaeozoic in age (Stöcklin & Bhattarai 1977). Low- to mediumgrade metamorphic rocks such as meta-sandstones, slates, phyllites, marbles, quartzites and schists are the main lithology. Limestone crops out in the eastern region whereas granite intrusion occurs in the western and southern parts. The area is geo-dynamically represented by the closure of the Mahabharat Synclinorium. The attitude of strata is variable; in general, strata in the southern belt are dipping 32–85 northeast to north and 45–81 to southwest in the northern belt. 3D Geological Modelling 3D geological modelling is often performed to represent, and eventually better understand the geometric, topological and physical properties of geological objects. A 3D geomodel provides new information either visually or by performing quantitative analyses in the modelled geological objects (Lee 2004, Zlatanova et al. 2004). In recent years, geomodelling has upgraded classical maps by providing a definite 3D description. Structural information and an appropriate Fig. 1: Projected lithological boundaries (outcrop curves), extension of the major geological units representative cross section and orientation vectors. of the area can be extracted from the models. Mathematically and geometrically derived 3D geological models are important for volume and shape of the geological features. Even for non-specialists, a model is self-explanatory. Skilled geologist may know how to translate 3D into 2D but no matter how experienced one can be, this mental translation is bound to be qualitative, hence inaccurate and sometimes incorrect. Therefore, interactive and quantitative aspects of 3D geomodelling open up entirely new perspectives. Tools for 3D modelling are mainly designed for data-rich environment. However many geological investigations are limited to sparse or poorly distributed data. This research has applied the innovative way to compute model using optimum available data which include Geo-Resources and Geo-Hazards 161 lithological boundaries, representative cross section and orientation vectors (Fig. 1). Considering nature of data, the model setup is made by means of implicit approach (Caumon et al. 2007) to interpolate the data; a GOCAD workflow integrates model properties for determining the spatial locations/geometry. ArcGIS functions were used to create a spatial database. GIS Shapefiles were imported in GOCAD as point or curve objects and converted into analytical format. The topographic surface was created from point set data of digital elevation model (DEM). Other imported geoobjects (outcrop boundary curves, orientation vector points) were projected vertically on it. Geological cross section was imported as 2D voxet and digitised in curves. The coordinates of an orientation vector (v) were implemented from the dip direction θ (azimuth) and dip angles through the following trigonometric formula (Eq. 1): sin( ) cos( ) v cos( ) cos( ) cos( ) (1) To support interpolation, the 3D vector has to be oriented normal (perpendicular) to the stratigraphic layers. By controlling the representation in space of the orientation vector, it takes advantage of a variety of interpolation scheme. The model configuration was performed by setting appropriate constraints by means of various GOCAD plugins and then discrete smooth interpolation (DSI) algorithm was run to compute rock strata geometry. The DSI optimizes all three spatial coordinates of mesh vertices. It allows to interpolate the functions of the discrete model, like geometry or properties, while honouring a set of constraints Ci. The algorithm converges towards a solution (Eq. 2); R* R c c (2) cC where, R(|) is the local roughness at node , (|c) is a constraint defined for node , is a stiffness coefficient, and c, . are weight coefficients (Mallet 2002). This generic method permits the usage of heterogeneous data as constraints for the interpolation. It is always reproducible, on what primary data an interpolated object is based on. Iteration of DSI interpolation generates a smooth surface, the boundary of which coincides with lines representing the original boundary surface and four stratigraphic bottom surfaces were obtained. In some cases, surface adjustment was also made locally by region interpolation. After building all the surfaces of geological units, surfaces have to be selected to delimit top and base while outer borders of both surfaces are given by the area of interest (AOI). In order to model the main stratigraphic units, the DEM is used as top surface while the base is a surface with a constant depth about 2500 m below mean sea level. A systematic sequence of steps has built the rock strata units from base to top. The operations are automatic or interactive and allow options to improve the modelling. Finally, a 3D volume model was constructed as Model3D (Fig. 2) that revealing a syncline structure and intrusive bodies. Dynamic visualisation is possible from slicing tool by moving in all directions. 162 Geo-Resources and Geo-Hazards Fig. 2: 3D geological model of the Lesser Himalaya, central Nepal. It can be concluded that optimised approach of implicit structural modelling from sparse data is quite illustrative and can interpret geologic-boundary surfaces where boreholes data are not available. Moreover, the modelling of subsurface geometry and properties is a key element to understand geo-hazard and risk which will be incorporated in the further development of this research. In geo-hazard (e.g. mass movement) workflow, natural property of surfaces will become more critical rather than volume. Acknowledgment: The first author is grateful to the Alexander von Humboldt Foundation for a research fellowship. References: [1] [2] [3] [4] [5] Caumon, G., Antoine, C. & Tertois, A.-L. (2007): Building 3D geological surfaces from field data using implicit surfaces. - in 27th GOCAD meeting. Nancy (France), pp. 6. Lee, J. (2004): A Spatial Access-Oriented Implementation of a 3-D GIS Topological Data Model for Urban Entities, GeoInformatica, 8(3): 237–264. Mallet, J.-L. (2002): Geomodeling. - Applied geostatistics series, Oxford University Press, New York, 599 p. Stöcklin, J. & Bhattarai, K. D. (1977): Geology of Kathmandu Area and Central Mahabharat Range, Nepal Himalaya, Kathamdnu: HMG/UNDP Mineral Exploration Project. Technical Report, New York (Unpublished). Zlatanova, S., Rahman, A. A. & Shi, W. (2004): Topological models and frameworks for 3D spatial objects, Computers & Geosciences, 30(4): 419–428. Geo-Resources and Geo-Hazards 163 Improvement of groundwater models by additionally use of detailed sedimentological and hydraulical data – Example: Babenhausen (Hesse, Germany) I. Lewin, A. Hoppe, C. Schüth Institut für Angewandte Geowissenschaften, Technische Universität Darmstadt, Germany Babenhausen is located south of Frankfurt am Main in the Hanau-Seligenstadt Basin. Lang (2007) proved there a shifting of the river Main from a western position in the Pliocene to an eastern position in the Upper Pleistocene which caused in the vicinity of Babenhausen an interfingering of fluvial sediments of the river Main with fluvial sediments of the local high areas. For that reason there is a heterogeneous series of clay, silt, as well as sand and gravel which is actually mined in dredging lakes. As the fluvial sediments also bear a productive aquifer which is intensely used, a possible contamination of the groundwater by sand and gravel mining has to be excluded. The objective of this study is to identify preferential flowpaths in this system by developing a transient groundwater model between a dredging lake and a pumping well. The collection of detailed sedimentological and hydraulical data is of particular importance. They will be integrated in a geological 3D object model including its specific values of hydraulical conductivity. Test site The least distance between dredging lake east of Babenhausen and a pumping well is 430 m. A test site with a size of 50 m to 40 m has been installed in between. It is located in the riparian zone of the dredging lake and has seven multi-level monitoring wells in two transects parallel to the lakefront. Most of the monitoring wells were built by direct-push methods. Especially, a dual tube method has been used in order to extract undisturbed sediment samples. There are two monitoring wells with a diameter of two inch and a depth of about 15 m, four monitoring wells with a diameter Fig. 1:Ground penetrating radar and monitoring wells with logs of of one inch and a depth of about hydraulical conductivities and grain sizes (z-scaling: 5) 15 to 25 m and one with a diameter of two inch inside the lake. All monitoring wells consist of HDPE filter-screens with filter slots of 0.3 mm along its whole lengths. 164 Geo-Resources and Geo-Hazards Sedimentological data In order to visualise the heterogeneities of fluvial sediments and to analyse the size of sediment-structures at the test site, ground penetrating radar was used (Fig.1).In the upper part we detected lateral accretion elements (9.5 m wide and 0.6 m high) which are typical for meandering river systems. The lower part shows channel structures with cross-bedding (10.0 m wide and 0.8 m high) which are typical for braided river systems. Furthermore, we analysed the undisturbed sediment samples layer-oriented by sieve and sedimentation analysis (Fig. 2). We calculated hydraulic conductivities between 1,02•10-3 and 7,46•10-9 m/s. Multi-layer pumping tests in the monitoring wells showed hydraulic conductivities between 2,43•10-4 and 3,34•10-6 m/s (Drefke 2010), about one order of magnitude lower compared to the sieve and sedimentation analysis. This difference might be a result of the multi-layer pumping test itself: pumping tests were done every meter and cover 80 cm. So the multi-layer pumping tests do not fit with the depth and thickness of sediment layers. The calculated hydraulic conductivities for multilayer pumping test are cumulative values of several sediment layers. Hydraulical data In order to monitor the groundwater table digital data loggers were installed in the monitoring wells. Additionally, five monitoring wells were equipped with automatic data loggers for monitoring water temperatures in high resolution continuously in depths between 2.1 and 8.7 m. These depths are configured by the results of layer-oriented sieve analysis in order to observe layers with high hydraulic conductivities, separated through layers with low hydraulic conductivities. In three monitoring wells 8 temperature probes were installed and two monitoring wells got 4 temperature probes. During a pumping test in a drinking water well 430 m away from the test site we detected variable groundwater temperatures, for example in well GWM_K1 in a depth of 4,7 m at the beginning of the pumping test temperature in- Geo-Resources and Geo-Hazards Fig. 2: Hydraulic conductivities of sieve and sedimentation analysis compared with hydraulic conductivities of multi-layer pumping tests for GWM_T1A / GWM_T1B 165 creased and with the end of the pumping test temperature decreased (Fig. 3). In the depth of 7,6 and 8,7 m daily variations of temperature have been measured. Minimum temperature is in each case at about noon, likely due to daily variations of temperature in the dredging lake, time-delayed by silting layer. Fig. 3: Groundwater temperature in well GWM_K1 during pumping test in drinking water well Outlook Further investigations will extrapolate and integrate the data from the test site as well in the depth as in the vicinity of test site and drinking water well. A geological 3D object model, including those characteristic values of hydraulic conductivity will be the basis of a transient groundwater model. It will be calibrated with the help of a tracer test between the test site and the drinking water well which is actually running. Acknowledgement The financial support of this study by the local drinking water supply “Zweckverband Gruppenwasserwerk Dieburg” is gratefully acknowledged. References: [1] Drefke, C. (2010): Identifikation von differentieller Advektion in einem porösen Lockergesteinsaquifer zwischen Baggersee & Rohwassergewinnungsbrunnen mittels tiefenorientierter Korngrößenanalyse, Multilevel-Pumpversuchen & Multilevel-Temperaturmessungen. Studienarbeit, TU Darmstadt, unveröffentlicht. [2] Lang, S. (2007): Die geologische Entwicklung der Hanau-Seligenstädter Senke (Hessen, Bayern). Dissertation, TU Darmstadt, http://elib.tu-darmstadt.de/diss/000782/. 166 Geo-Resources and Geo-Hazards 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. In 2011, four new electron microscopes were installed at the Fachbereich 11, Material- and Geosciences, which allow for state-of-the-art material characterization on the atomic scale. Staff Members Head Prof. Dr. Hans-Joachim Kleebe Research Associates Dr. Stefan Lauterbach Dr. Ingo Sethmann Postdoctoral Students Dr. Ana Ljubomira Schmitt Dr. Andrew Stewart Geomaterial Science 167 PhD Students Jens Kling Horst Purwin Margarete Schloßer Mathis M. Müller Stefania Hapis Stefanie Schultheiß 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 Katharina Nonnenmacher Xiaoke Mu Eric Detemple Dmitry Tyutyunnikov Cigdem Özsoy Miriam Höner David Wiesemann Research Projects TEM Investigations on Cubic Crystal Shapes of Corundum-Type Indium Oxide; Novel HighPressure Phases Mechanisms of Electrochemical Corrosion of Polycrystalline SiC Ceramics (DFG 20072011). Polymer-derived SiCO/HfO2 and SiCN/HfO2 Ceramic Nanocomposites for Ultrahightemperature Applications, SPP-1181 (DFG 2007-2012) Investigation of Strengthened Hydroxyapatit/ß-Tricalcium Phosphate Composites with Tailored Porosity (DFG 2008-2011) 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 2007-2011) 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) 168 Geomaterial Science 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) Publications Müller, M.M., Kleebe, H.-J., Lauterbach, S., Zito, G. (2011): Crystallographic orientation relationship between bastnaesite, fluocerite and cerianite observed in a crystal from the pikes peak pegmatites, Zeitschrift für Kristallographie, 226, 467-475. Muench, F., Kaserer, S., Kunz, U., Svoboda, I., Brötz, J., Lauterbach, S., Kleebe, H.-J. Roth, C., Ensinger, W. (2011): Electroless synthesis of platinum and platinum-ruthenium nanotubes and their application in methanol oxidation, Journal of Materials Chemistry 21, 6286-6291. Muench, F., Kunz, U., Neetzel, C., Lauterbach, S., Kleebe, H.-J., Ensinger, W. (2011): 4(Dimethylamino)pyridine as a Powerful Auxiliary Reagent in the Electroless Synthesis of Gold Nanotubes, Langmuir, 27, 430-435. Papendorf, B., Nonnenmacher, K., Ionescu, E., Kleebe, H.-J., Riedel, R. (2011): Strong Influence of Polymer Architecture on the Microstructural Evolution of Hafnium-AlkoxideModified Silazanes upon Ceramization, Small, 7, 970-978. Glaum, J., Granzow, T., Schmitt, L.A., Kleebe, H.-J., Rödel, J., (2011): Temperature and driving field dependence of fatigue processes in PZT bulk ceramics, ACTA Materialia, 59, 6083-6092. Martinez-Crespiera, S., Ionescu, E., Kleebe, H.-J., Riedel, R. (2011): Pressureless synthesis of fully dense and crack-free SiOC bulk ceramics via photo-crosslinking and pyrolysis of a polysiloxane, Journal or the European ceramic society, 31, 913-919. Schmitt, L.A., Kling, J., Hinterstein, M., Hoelzel, M., Jo, W., Kleebe, H.-J., Fuess, H. (2011): Structural investigations on lead-free Bi(1/2)Na(1/2)TiO(3)-based piezoceramics, Journal of Materials Science, 46, 4368-4376. Toma, L., Fasel, C., Lauterbach, S., Kleebe, H.-J., Riedel, R. (2011): Influence of nanoaluminum filler on the microstructure of SiOC ceramics, Journal of the European Ceramic Society, 31, 1779-1789. Hildebrandt, E., Kurian, J., Müller, M.M., Schroeder, T., Kleebe, H.-J., Alff, L. (2011): Controlled oxygen vacancy induced p-type conductivity in HfO(2-x) thin films, Applied Physics Letters, 99, Article number 112902. Bazarjani, M.S., Kleebe, H.-J., Müller, M.M., Fasel, C., Yazdi, M.B., Gurlo, A., Riedel, R. (2011): Nanoporous Silicon Oxycarbonitride Ceramics Derived from Polysilazanes In situ Modified with Nickel Nanoparticles, Chemistry of Materials, 23, 4112-4123. Geomaterial Science 169 Jo, W., Schaab, S., Sapper, E., Schmitt, L.A., Kleebe, H.-J., Bell, A.J., Rödel, J. (2011): On the phase identity and its thermal evolution of lead free (Bi(1/2)Na(1/2))TiO(3)-6 mol% BaTiO(3), Journal of Applied Physics, 110, Article Number 074106. Muench, F., Rauber, M., Stegmann, C., Lauterbach, S., Kunz, U., Kleebe, H.-J., Ensinger, W. (2011): Ligand-optimized electroless synthesis of silver nanotubes and their activity in the reduction of 4-nitrophenol, Nanotechnology, 22, Article Number: 415602. Muench, F., Oezaslan, M., Seidl, T., Lauterbach, S., Strasser, P., Kleebe, H.-J., Ensinger, W. (2011): Multiple activation of ion track etched polycarbonate for the electroless synthesis of metal nanotubes, Applied Physics A-Materials Science & Processing, 105, 847-854. 170 Geomaterial Science Fe3+/ΣFe ratios in clinopyroxene and garnet as a function of temperature Horst Purwin, Stefan Lauterbach, Hans-Joachim Kleebe Institute for Applied Geosciences, Geomaterial Science, Technische Universität Darmstadt, Germany The garnet-clinopyroxene geothermometer is one of the most widely applied methods for obtaining equilibrium temperatures of eclogites and other (ultra)basic metamorphic rocks containing garnet and clinopyroxene (e.g., garnet-peridotites). It is based on a Fe2+-Mg exchange reaction between these two minerals. However, in former studies, only the total iron content of the samples, determined by electron probe micro-analysis (EPMA), was considered for the calibration of this geothermometer (e.g.,[1], [2], [3], [4]), since it was assumed that the ferric iron content in the experiments was negligible. Due to previous studies, the calibration experiments must have produced garnets and clinopyroxenes with substantial Fe3+ contents, and the reason for the unreliability of Fe-Mg exchange geothermometry is deduced to uncertainties of the Fe3+ content in natural phases and phases generated in the experiments from which the thermometer formulations were calibrated [5]. As a step forward to improve the garnet-clinopyroxene geothermometer we investigate the Fe3+ content in synthetic clinopyroxene and garnet as a function of temperature in order to explore the effect of considering or neglecting Fe3+ on geothermometry. Synthetic eclogite of the system CaO-FeO-Fe2O3-MgO-Al2O3-SiO2 was produced in graphite/Pt capsules at a pressure of 30 kbar and temperatures ranging from 1000°C1300°C using a Belt apparatus. One long-term experiment with a run period of two months was performed at 800°C and 25 kbar in a piston-cylinder apparatus The oxidation state (expressed as Fe3+/ΣFe ratio) of clinopyroxene and garnet was investigated by electron energy-loss spectroscopy (EELS). This method is performed on a transmission electron microscope (TEM) providing a high spatial resolution which is required for measuring the phases near grain boundaries. The combination of EELS and energy-dispersive X-ray spectroscopy (EDS) allow a quantification of Fe2+ and Fe3+. In addition to EDS, main element composition was also determined by EPMA in samples produced at 1000°C1300°C. At 800°C the small grain sizes of < 2 μm prohibit “clean” microprobe analyses of one phase. Run products consist of clinopyroxene, garnet and quartz assemblages (Figure 1). A typical EEL spectrum of synthetic clinopyroxene is shown in Figure 2. Based on a modified L3/L2 intensity ratio the Fe3+/ΣFe ratio of the sample can be calculated [6]. The results show significant amounts of ferric iron in both, clinopyroxene and garnet. Temperature calculations using phase compositions obtained by EDS were found to yield a rough estimate of the equilibrium temperature but not a precise one which is required to assess the influence of Fe3+ on geothermometric calculations. For the latter purpose, EPMA data is needed, also from the samples produced at 800°C. Since in these fine-grained samples, the low spatial resolution of EPMA (approximately 3 µm) only allows mixed analyses of two or three phases (garnet-clinopyroxene, garnet/clinopyroxene-quartz and garnet-clinopyroxene-quartz), it is planned to obtain the compositional data of garnet and clinopyroxene indirectly by constructing a triangle of the “hypothetical mixtures”, in which the end-points correspond to the “clean” compositions of the three phases. Geomaterial Science 171 Fig. 1: Back-scattered electron image of synthetic eclogite, produced at 1100°C and 30 kbar, consisting of garnet (Gt), clinopyroxene (Cpx) and quartz (Qz). Fig. 2: Typical EEL spectrum of synthetic clinopyroxene (synthesis conditions: 1100°C, 30 kbar) showing the iron L2,3-edge. The spectrum was treated as described by [6] in order to determine the Fe3+/ΣFe ratio from a modified integral L2,3 white-line intensity ratio. The quantification according to [6] includes an absolute error of 5% Fe3+/ΣFe. References: [1] [2] [3] [4] [5] [6] 172 Ellis, D.J. & Green, D.H. (1979), An experimental study of the effect of Ca upon garnet-clinopyroxene Fe-Mg exchange equilibria, Contrib. Mineral. Petrol., 71, 13-22 Krogh, E.J. (1988), The garnet-clinopyroxene Fe-Mg geothermometer – a reinterpretation of existing experimental data, Contrib. Mineral. Petrol., 99, 44-48 2+ Ai, Y. (1994), A revision of the garnet-clinopyroxene Fe -Mg exchange geothermometer, Contrib. Mineral. Petrol., 115, 467-473 Nakamura, D. (2009), A new formulation of the garnet-clinopyroxene geothermometer based on accumulation and statistical analysis of a large experimental data set, J metamorph. Geol., 27, 495-508 Canil, D. & O’Neill, H.St.C. (1996), Distribution of ferric iron in some upper-mantle assemblages, J. Petrology, 37, 609-635 van Aken, P.A., Liebscher, B., Styrsa, V.J.(1998), Quantitative determination of iron oxidation states in minerals using Fe L2,3-edge electron energy-loss near-edge structure spectroscopy. Phys. Chem. Minerals, 25, 323-327. Geomaterial Science Electrochemical corrosion of silicon carbide ceramics U. Sydow1, M. Herrmann2, M.M. Müller3, H.-J. Kleebe3, A. Michaelis1,2 1 Technical University Dresden, Institute of Materials Science, Dresden, Germany 2 Fraunhofer Institute for Ceramic Technologies and Systems, Winterbergstraße 28, Dresden, Germany 3 Technische Universität Darmstadt, Institute of Applied Geosciences, Darmstadt, Germany Silicon carbide materials are nowadays widely used in wear applications, i.e., as sealings for pumps which convey a wide range of media in industrial applications. The corrosion resistance of SiC ceramics strongly depends on the preparation technology and the composition. The solid phase sintered SiC materials (SSiC), which normally contain only some B4C and a small volume fraction of carbon secondary phase, exhibit in a wide range of media and conditions an excellent corrosion resistance. Even in HF solutions SSiC shows a high stability in contrast to other Si based ceramics [1-2]. The high corrosion resistance of the SSiC materials is – besides the good tribological properties – the reason for the use of these materials in sealings and in other chemical equipments [3]. SiC itself is an intrinsic semiconductor and has specific electrical resistivities as low as some m [3]. Commonly used sintering additives such as boron or aluminium enhance the conductivity of the material, especially if the materials are tempered at elevated temperatures. Therefore, electrochemical corrosion can be a cause of severe material degradation. Damage patterns for SiC sealings have been reported which strongely suggest electrochemical corrosion as the primary cause for material degradation [4]. The corrosion rates of ceramics are generally very small as compared to metal corrosion. Though some features of the electrochemical corrosion of SiC like SiO2 passive layer formation in acids are established, no detailed information about the mechanisms and the correlation between microstructure and corrosion resistivity are available as yet [5-7]. The standard reduction potentials are given relative to the normal hydrogen electrode (NHE): In acidic environments: SiO2 + 4H+ + 4e- ⇄ Si + 2H2O E° = -0.857 V (1) SiO2 + C + 4H+ + 4e- ⇄ SiC + 2H2O E° = -0.673 V (2) SiO2 + 6H + CO + 6e ⇄ SiC + 3H2O E° = -0.276 V (3) E° = -0.222 V (4) E° = -1.698 V (6) E° = -1.515 V (7) E° = - 1.113 V (8) E° = - 0.149 V (9) + - + - SiO2 + 8H + CO2 + 8e ⇄ SiC + 4H2O In alkaline environments: SiO32- + 3H2O + 4e- ⇄ Si + 6OHSiO32SiO32SiO32- + C + 3H2O + 4e ⇄ SiC + 6OH - - + 4H2O + CO + 6e- ⇄ SiC + 8OH+ 5H2O + CO32- Geomaterial Science + 8e ⇄ SiC + 12OH - - 173 TEM studies were performed on a SSiC material upon electrochemical attack in acidic medium. A CM20STEM microscope (FEI, Eindhoven, The Netherlands), equipped with an energy-dispersive X-ray spectrometer (EDS) was employed, operating at 200 keV. TEM foil preparation was performed using standard ceramographic techniques of grinding, polishing and Ar-ion thinning. However, in order to preserve the thin surface layer formed upon electrocorrosion, the sample was ground from the backside down to 80 mm and subsequently ion thinned also from the backside (using only one Ar-gun). Finally, the sample was lightly carbon coated in order to minimize charging under the incident electron beam. Fig. 1: TEM micrograph of the sample SSiC-D after electrochemical corrosion in 0.5 M H2SO4 at 2V. The central grain shown in (a) reveals a nearly unaffected SiC grain; while the neighbouring particles are transformed to amorphous SiO2 (compare EDS spectra to the right). Note the electrochemical attack is strongly pronounced at grain boundaries (see inset (b)), reflecting the initial microstructure. A detailed analysis of the corroded surface in H2SO4 by transmission electron microscopy (TEM) revealed a strong attack at the grain boundaries and the formation of an oxide layer. This SiO2 layer represents the initial microstructure, i.e., the individual SiC grains are transformed into amorphous SiO2, as can be seen in Figure 1. Here, the central grain is still crystalline SiC, while the surrounding particles are predominantly composed of silica (see EDS spectra to the right). It is not clear yet, why the corrosive attack at grain boundaries is more pronounced, but it is assumed that those interfaces are less ordered (different orientation of the neighbouring grains) and, therefore, promote the electrochemical attack along SiC grain boundaries. 174 Geomaterial Science In alkaline media, an anisotropic electrochemically etched pattern with deep pits is formed. Above pH values of 12, silicon dioxide is unstable and no amorphous silicon dioxide layer can be found after anodic oxidation in NaOH. This explains the differences of damage patterns in acidic and alkaline media: predominant formation of SiO2 in acidic media (Equations (2-4)) and by the preferential formation of soluble silicate species in alkaline media (Eqs. (7-9)). Also in alkaline solutions the electrochemical attack depends on the crystallographic orientation. The results reveal that the corrosion rate of the SiC is strongly correlated with the local conductivity. This is also in agreement with the fact that for the SiC materials with low conductivity a much lower corrosion rate was typically observed. References: [1] [2] [3] [4] [5] [6] [7] K.A. Schwetz, J. Hassler, cfi/Ber. DKG, 2002, 79(11), D14-D19. M. Herrmann, J. Schilm, G. Michael, cfi/Ber. DKG, 2003, 80(4), E27. K.A. Schwetz, in: R. Riedel, (Ed.), Handbook of Ceramic Hard Materials, Wiley-VCH, Weinheim, 2000, 683-748. F. Meschke, A. Kailer, cfi/Ber. DKG, 2003, 81(8), E19. R. Divakar, S.G. Seshadri, M. Srinivasan, J. Am. Ceram. Soc., 1989, 72(5), 780. G.S. Cook, J.A. Little, J.E. King, Br. Corros. J., 1994, 29(3), 183. Andrews, M. Herrmann, M. Sephton, C. Machio, A. Michaelis, J. Eur. Ceram. Soc., 2007, 27, 2127. Geomaterial Science 175 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 176 Technical Petrology with Emphasis in Low Temperature basin analyses, hydrocarbon exploration, geothermic prospections and energy researches. 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 palaeogeothermics, and in the external orogens investigation. research, 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 (Silesia, SW Poland and southern Norway). Determination of water-rock interaction and water chemistry in the basement crystalline ground waters and their usage as potable water (Odenwald, Bergstraße, Hesse, Germany). 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 NW Turkey A broad analytical spectrum must be applied in low-temperature petrology due to very small grain-size. In the Technical Petrology group, general microscopy (MPV coal reflection microscopy, fluorescence microscopy, transmitted light microscopy) and basically XRD Technical Petrology with Emphasis in Low Temperature 177 powder and texture studies (Clay and XRD Laboratory and a research XRD Laboratory recently installed with thankful help by Merck KGaA) can be combined with ICP-AES, TOC, AOX and gas chromatography (GC-ECD, GC-MS) in the Organic Geochemical Laboratory (installed with thankful help by the Hessische Industriemüll GmbH). 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. 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 Alexander Müller Christian Adam Erika Dörner Rebecca Kämmerling Robert Priebs Technical Personnel Dr. Norbert Laskowski Secretary Natali Vakalopoulou Buffet Guest Scientist Prof. Dr. Ömer Bozkaya (ERASMUS) 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). Structural, stratigraphic and diagenetic analysis of the Jurassic-Early Cretaceous foreland Trojan-basin in central North Bulgaria – (DAAD, ERASMUS. Cooperation with St. Kl. Ohridski University of Sofia, BG). Origin of the ophiolite-related Al-(Mg) metamorphites – case study of sapphirine and corundum amphibolites from the Central Dinaridic Ophiolite Zone (CDOB, NE Bosnia and Herzegovina). – (DFG and DAAD. Cooperation with University of Heidelberg). 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. 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 University of Zadar and University of Zagreb, HR). 178 Technical Petrology with Emphasis in Low Temperature Very low to low-temperature coal and clay-mineral indicators, comparative application from diagenesis to green- and blueschist facies. – (No founding. Cooperation with University of Basel, CH). 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 DAAD. 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. 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 and DAAD, 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 and 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 abandoned pyrite mine in Wieściszowice, Lower Silesia, SW Poland (Cooperation with the Warsaw University of Technology, PL and Jagiellonian University of Krakow, PL) Publications Le Bayon, R., Brey, G.P.; Ernst, W.G. and Ferreiro Mählmann, R. (2011): Experimental kinetic study of organic matter maturation: Time and pressure effects on vitrinite reflectance at 400 °C, Organic Geochemistry, v. 42, p. 340-355. Uzarowicz, Ł., Skiba, S., Skiba, M. and Šegvić, B. (2011) Clay-mineral formation in soils developed in the weathering zone of pyrite-bearing schists: A case study from the abandoned pyrite mine in Wieściszowice, Lower Silesia, Sw Poland, Clays and Clay Minerals, v. 59, p. 581-594. doi: 10.1346/CCMN.2011.0590604. Kandler, K., Schütz, L., Jäckel, J., Lieke, K., Emmel, C., Müller-Ebert, D., Ebert, M., Scheuvens, D., Schladitz, A., Šegvić, B., Wiedensohler, A. and Weinbruch, S. (2011) Ground-based off-line aerosol measurements at Praia, Cape Verde, during the Saharan Mineral Dust Experiment: microphysical properties and mineralogy, Tellus B, doi: 10.1111/j.1600-0889.2011.00546.x. Technical Petrology with Emphasis in Low Temperature 179 Experimental investigations on vitrinite reflectance: toward a tool to model maturation and metamorphic conditions in low temperature metasedimentary terranes Le Bayon Ronan, Ferreiro Mählmann Rafael There are many reasons to study the metamorphism in low to very low temperature metamorphic terranes, but all are ultimately related to a fuller understanding of the Earth’s geodynamic evolution. It is very difficult to carry out metamorphic studies in terranes consisting mostly of low temperature metamorphic rocks because such conditions lead to sluggish reactions. Furthermore, the methods (e.g., b0 value) constraining the metamorphic conditions are often/only qualitative and have limitations. An alternative method is to use organic matter to estimate the metamorphic conditions in the very low to low temperature metasedimentary terranes. The presence of vitrinite phytoclasts provide an opportunity to understand metamorphic and geodynamic evolution by determining rock pressure– temperature conditions and the degree of maturity with respect to hydrocarbon generation. Nevertheless, clarification of the physical parameters that control vitrinite reflectance is necessary. We carried out laboratory rate studies to elucidate and quantify the effects of time (t), temperature (T) and pressure (P) on vitrinite reflectance (VR). A series of confined system maturation experiments was conducted at various pressures (from 2 to 25 kbar) and temperatures (from 200 to 450 °C). Experiments were performed on xylite of swamp cypress and involved run lengths from 0 s to dozens of days. Our experimental results demonstrate temperature and heating time to be important variables that promote VR increase and therefore the maturation of Type III organic material. VR increases with time at each investigated pressure. Despite rapid initial kinetics, the increase in VR decelerates with time at each pressure. When VR < ~1.3-1.5%, increasing pressure reduces the rate of VR increase and hence retards the initial VR enhancement with time. The retarding effect of pressure on VR increase diminishes with enhancing VR. The retardation of VR increase is insignificant for geological maturation at T ≥ 300 °C because a VR of ~1.3-1.5% is attained in only a few hours or days. When VR > ~1.3-1.5%, increasing pressure counteracts the deceleration of VR increase with time and thus greatly enhances the increase in VR with time. The strong effect of the experimental heat-up on VR is obvious even for very short experiments and must be corrected in kinetic analysis. The evolution of VR with heating time, temperature and pressure from an initial VR of 0% is well described at the investigated experimental P–T conditions by our new power law rate equation VR(P, T, t) = (k(P, T) t)^n(P, T) where the exponent n(P, T) and the rate constant k(P, T) depend on P and T. We regard this preliminary kinetic formulation as a step toward a general equation describing VR evolution as a function of time, pressure and temperature for Type III organic matter. This VR rate equation will be a useful tool to model VR in sedimentary basins and to estimate the P–T–t conditions in metamorphic terranes occurring in various tectonic settings (e.g., exhumed subducted terranes, collided terranes in orogenic wedges). This will aid to gain insight into geodynamic evolution of sedimentary and metamorphic terranes and to improve hydrocarbon generation modeling in sedimentary basins. 180 Technical Petrology with Emphasis in Low Temperature Composition and manufacture technology of hellenistic fineware recovered from dalmatian coast (croatia) Branimir Šegvić1, Lucijana Šešelj 2, Rafael Ferreiro Mählmann1 1 Technische Universität Darmstadt, Institute of Applied Geosciences, Technical Petrology, Darmstadt, Germany 2 University of Zadar, Department of History, HR-23000 Zadar, Croatia Commencing with the 4th century BC, Greek colonisation became widely present along the Croatian Adriatic coast. Simultaneously, a number of native settlements have been established. For our study on the Hellenistic ceramic manufacture technology, we have chosen pottery from three archaeological sites: (i) the Hellenistic sanctuary at Cape Ploca, (ii) the native settlement Resnik, and (iii) the Greek colony Issa (Vis) (Fig. 1a). The analysed pottery were locally produced and therefore the comparison of the pottery manufacture-levels of Greek communities (Vis) with the native ones (Resnik and Cape Ploca) is of interest [1]. Fig. 1: Geographic map of middle Dalmatia, showing archaeological sites of analysed potsherd recovery (a) and XRD patterns showing different compositions of analysed ceramics (b). Our analysis included artefacts spanning from the 3rd to the late 1st century BC. All analysed shards depict similar petrographical features, like low porosity and partly vitrified dark (Vis) or reddish matrix (Cape Ploca and Resnik). Temper material consists mainly of Qtz, Cal and few grog fragments. Generally, fine silt-sized and amount of temper Qtz, Fsp and Ms, signify that they were natural ingredients of raw material. Hence, the pottery-paste preparation was primarily simple and seldom involved artificially added materials or granulometric separation. XRD analysis revealed that in part of samples from Caple Ploca and Resnik, traces of 10 Å phyllosilicates were preserved (Fig. 1b), which limits the firing to 450-600 °C. Presence of Cal corroborates that finding, along with observed effect of clay mineral rehidroxylation, posterior to firing. The EMPA analyses revealed presence of “metamorphosed vermiculite”, known to emerge in schistoic metapelites at around 550 °C and low pressures. Furthermore, presence of Alm is also reported, setting the upper limit of firing to ~900 °C. On the other hand, samples from Vis, apart from having the highest content of amorphous Technical Petrology with Emphasis in Low Temperature 181 matter (Fig. 1b), are featured by the presence of newly formed phases like Mel, And, Pig and An. Structurally, these phases are reported to appear as fibro-nematoblastic laths of clear habitus, merged within the glass pockets of andesitic composition. Moreover, the strong vitrification of these potsherds is witnessed by SEM analysis through the creation of uniformly distributed, partly coalesced, spherical voids. Such a microstructure is taken as an indicator for elevated sintering temperatures, ranging between 850 and 1050 °C, which is in line with the formation of clusters of Ca-silicates and silica rich glasses. Prior to contacts with Greeks all native pottery in Croatia was hand-made and open-fired, implying the coarse fabric of clay vessels. For the first time in Hellenistic period the new technology of pottery making (e.g. wheel, kiln-firing) was introduced in the region. Greek pottery is fired at higher temperatures for a longer period, under controlled conditions, thus depicting better quality. The indigenous pottery is fired at lower temperatures and its quality oscillates. This was probably due to the demanding market and massive production and not the lack of technological knowledge. References: [1] Šegvić, B., Šešelj, L., Slovenec, Da., Lugović, B., Ferreiro Mählmann R. On the provenance, manufacture technology and circulation of Hellenistic pottery from Eastern Adriatic: a case study of three archaeological sites in Dalmatia (Croatia). Submitted to Geoarchaeology 2010. 182 Technical Petrology with Emphasis in Low Temperature 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 PD Dr. Martin Ebert Dr. Nathalie Benker Postdocs Dr. Dirk Scheuvens Dr. Annette Worringen Dr. Konrad Kandler Technical Personnel Thomas Dirsch Secretaries Astrid Zilz PhD Students Dipl.-Met. Dörthe Müller-Ebert Dipl.-Ing. Kirsten Lieke Dipl.-Ing. Thomas Herrmann Diploma Students Simon Jäckel Miriam Küpper Franziska Fischer Katharina Schütze Bachelor Students Markus Hartmann Carolin Tissen Research Fellow Dipl.-Ing. Hauke Gorzawski Environmental Mineralogy 183 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 Gjønnes K., Skogstad A., Hetland S., Ellingsen D.G., Thomassen Y., and Weinbruch S. (2011): Characterization of workplace aerosols in the manganese alloy production industry by electron microscopy, Anal. Bioanal. Chem., 399, 1011-1020. Berlinger B., Benker N., Weinbruch S., L’Vov B., Ebert M., Koch W., Ellingsen D.G., and Thomassen Y. (2011): Physicochemical characterization of different welding aerosols., Anal. Bioanal. Chem., 399, 1773-1780. Schumann U., Weinzierl B., Reitebuch O., Schlager H., Minikin A., Forster C., Baumann R., Sailer T., Graf K., Mannstein H., Voigt C., Rahm S., Simmet R., Scheibe M., Lichtenstern M., Stock P., Rüba H., Schäuble D., Tafferner A., Rautenhaus M., Gerz T., Ziereis H., Krautstrunk M., Mallaun C., Gayet J.-F., Lieke K., Kandler K., Ebert M., Weinbruch S., Stohl A., Gasteiger J., Groß S., Freudenthaler V., Wiegner M., Ansmann A., Tesche M., Olafsson H., and Sturm K. (2011): Airborne observations of the Eyjafjalla volcano ash cloud over Europe during air space closure in April and May 2010., Atmospheric Chemistry and Physics, 11, 2245-2279. Ebert M., Worringen A., Benker N., Mertes S., Weingartner E., and Weinbruch S. (2011): Chemical composition and mixing-state of ice residuals sampled within mixed phase clouds., Atmospheric Chemistry and Physics, 11, 2805-2816. Formenti P., Schütz L., Balkanski Y., Desboeufs K., Ebert M., Kandler K., Petzold ., Scheuvens D., Weinbruch S., and Zhang D. (2011): Recent progress in understanding physical and chemical properties of African and Asian mineral dust., Atmospheric Chemistry and Physics, 11, 8231-8256. Kandler K., Schütz L., Jäckel S., Lieke K., Emmel C., Müller-Ebert D., Ebert M., Scheuvens D., Schladitz A., Segvic B., Wiedensohler A., and Weinbruch S. (2011a): Ground-based off- 184 Environmental Mineralogy line aerosol measurements at Praia, Cape Verde, during the Saharan Mineral Dust Experiment: microphysical properties and mineralogy., Tellus B, 63, 459-474. Kandler K., Lieke K., Benker N., Emmel C., Küpper M., Müller-Ebert D., Ebert M., Scheuvens D., Schladitz A., Schütz L., and Weinbruch S. (2011b): 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 B, 63, 475-496. Lieke K., Kandler K., Scheuvens D., Emmel C., von Glahn C., Petzold A., Weinzierl B., Veira A., Ebert M., Weinbruch S., and Schütz L. (2011): Particle chemical properties in the vertical column based on aircraft observations in the vicinity of Cape Verde Islands., Tellus B, 63, 497-511. Scheuvens D., Kandler K., Küpper M., Lieke K., Zorn S.R., Ebert M., Schütz L., and Weinbruch S. (2011): Individual-particle analysis of airborne dust samples collected over Morocco in 2006 during SAMUM 1., Tellus B, 63, 512-530. Ansmann A, Petzold A, Kandler K, Tegen I, Wendisch M, Müller D, Weinzierl B, Müller T, Heintzenberg J (2011): Saharan Mineral Dust Experiments SAMUM-1 and SAMUM-2: What have we learned? Tellus 63B, 403 – 429. doi: 10.1111/j.1600-0889.2011.00555.x. Knippertz P, Tesche M, Heinold B, Kandler K, Toledano C, Esselborn M (2011): Dust Mobilization and Aerosol Transport from West Africa to Cape Verde—a Meteorological Overview of SAMUM-2. Tellus 63B, 430 – 447. doi: 10.1111/j.1600-0889.2011.00544.x. Schladitz A, Müller T, Nowak A, Kandler K, Lieke K, Massling A, Wiedensohler A (2011): In-situ aerosol characterization at Cape Verde. Part 1: Particle number size distributions, hygroscopic growth, and state of mixing of the marine and Saharan dust aerosol. Tellus 63B, 531 – 548. doi: 10.1111/j.1600-0889.2011.00569.x. Müller T, Schladitz A, Kandler K, Wiedensohler A (2011): Spectral particle absorption coefficients, single scattering albedos, and imaginary parts of refractive indices from ground based in-situ measurements at Cape Verde Island during SAMUM-2. Tellus 63B, 573 – 588. doi: 10.1111/j.1600-0889.2011.00572.x. Petzold A, Veira A, Mund S, Esselborn M, Kiemle C, Weinzierl B, Hamburger T, Ehret G, Lieke K, Kandler K (2011): Mixing of mineral dust with urban pollution aerosol over Dakar (Senegal): Impact on dust physico-chemical and radiative properties. Tellus 63B, 619 – 634. doi: 10.1111/j.1600-0889.2011.00547.x. Groß S, Gasteiger J, Freudenthaler V, Wiegner M, Geiß A, Schladitz A, Toledano C, Kandler K, Tesche M, Ansmann A, Wiedensohler A (2011): Characterization of the planetary boundary layer during SAMUM-2 by means of lidar measurements. Tellus 63B, 695 – 705. doi: 10.1111/j.1600-0889.2011.00557.x. Gasteiger J, Wiegner M, Groß S, Freudenthaler V, Toledano C, Tesche M, Kandler K (2011): Modeling lidar-relevant optical properties of complex mineral dust aerosols. Tellus 63B, 725 – 741. doi: 10.1111/j.1600-0889.2011.00559.x. Environmental Mineralogy 185 Köhler C H, Trautmann T, Lindermeir E, Vreeling W, Lieke K, Kandler K, Weinzierl B, Groß S, Tesche M, Wendisch M (2011): Thermal IR Radiative Properties of Mixed Mineral Dust and Biomass Aerosol during SAMUM-2. Tellus 63B, 751 – 769. doi: 10.1111/j.16000889.2011.00563.x. Heinold B, Tegen I, Schepanski K, Tesche M, Esselborn M, Freudenthaler V, Groß S, Kandler K, Knippertz P, Müller D, Schladitz A, Toledano C, Weinzierl B, Ansmann A, Althausen D, Müller T, Petzold A, Wiedensohler A (2011): Regional modelling of Saharan dust and biomass burning smoke – Part 1: Model description and evaluation. Tellus 63B, 781 – 800. doi: 10.1111/j.1600-0889.2011.00570.x. Wagner, R., Ajtai, T., Kandler, K., Lieke, K., Linke, C., Müller, T., Schnaiter, M. and Vragel, M. (2011): Complex refractive indices of Saharan dust samples at visible and near UV wavelengths: a laboratory study, Atmospheric Chemistry and Physics Discussions 11, 21363–21427. Engelmann, R., Ansmann, A., Horn, S., Seifert, P., Althausen, D., Tesche, M., Esselborn, M., Fruntke, J., Lieke, K., Freudenthaler, V. and Groß, S. (2011): Doppler lidar studies of heat island effects on vertical mixing of aerosols during SAMUM-2, Tellus B 63, 448–458. 2. Tagungsbeiträge (Proceedings) Scheuvens D., Dirsch T., Küpper M., Ebert M., and Weinbruch S. (2011): Schadstoffe an der Christuskirche in Mainz und am Bayerischen Nationalmuseum in München: Einzelpartikelanalyse, PM-Messungen und Auswertungen von ZIMEN-Daten., In: Wirkung verkehrsbedingter Immissionen auf Baudenkmäler, IFS Bericht 37/2011, 55-77. 186 Environmental Mineralogy Aerosol deposition in the main African dust transport region: establishing a long-term time series at Sao Vicente, Cape Verde K. Kandler1, L. Mendes Neves2, N. Niedermeier3, and T. Müller3 1 Institute of Applied Geosciences, Technische Universität Darmstadt, Germany 2 Instituto de Nacional de Meteorologie e Geofisica, Mindelo, Cape Verde 3 Institut für Troposphärenforschung, Leipzig, Germany 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). While the shortcomings in the past can’t be changed, a quasi-continuous measurement of aerosol deposition was installed in the middle of December 2012 at the Cape Verde Atmospheric Observatory (http://ncasweb.leeds.ac.uk/capeverde/), at the Island of Sao Vicente Island, Cape Verde. Aerosol deposition is measured by a passive aerosol sampler, modified from Ott and Peters (2008) “type A – flat plates” by introduction of a liquid trap and lowering the recipient position slightly below the level of the lower plate. 25 mm diameter aluminum stubs coated with standard electron microscopy carbon adhesives were used as sampling surface. The analysis was made with an acceleration voltage of 20 kV and a beam diameter of 2.6 nm. The particles were classified according to their chemical composition into eight classes (Fig. 1). For details on the materials and methods as well as the data processing refer to Kandler et al (2011). Three samples in December 2011 could be analyzed as a start of the time series (total of 1841) particles. Trajectory calculations (HYSPLIT/GDAS) showed that during all period dust was transported straight from Mauritania and South Morocco to Cape Verde (about 24 to 30 h transport time from the coast), so the differences in dust abundance – also seen in the aerosol volume concentrations measured by Scanning Mobility Particle Sizer and Aerodynamic Particle Sizer (74, 33 and 48 cm3/m3 for SVS_101/2/3) – are most probably linked to dust emission variation. The relative abundance of dust increases with the particle size between 1.5 and 10 µm (Fig. 1). The ratio of quartz to the silicate dust varies between 0.1 and 0.3. Sulfate plays a minor role during the more maritime periods and is absent during the dustier phase. Interestingly, the amount of mixed particles (internal mixtures of dust and sea-salt) is largely higher for particles of 5 – 10 µm diameter than for those with 2.5 – 5 µm. This points to an increased deposition flux of dust particles internally mixed with sea-salt, as proposed by Zhang Environmental Mineralogy 187 (2008). It indicates that during the observed dust intrusions, larger pure particles have already been removed by sedimentation. Oxides Quartz Silicates Mixtures Chlorides Sulfates Carbonates Other SVS_101 2011-12-13 16:30 to 2011-12-14 17:30 SVS_102 2011-12-14 17:30 to 2011-12-16 12:30 SVS_103 2011-12-16 12:30 to 2011-12-19 14:30 0.0 0.2 0.4 0.6 0.8 relative abundance 1.0 0.0 0.2 0.4 0.6 0.8 relative abundance 1.0 0.0 0.2 0.4 0.6 0.8 1.0 relative abundance Fig. 1: Relative abundance of different particle species in the aerosol sediment at Sao Vicente, Cape Verde. Left: 1.5 - 2.5 µm; center: 2.5 - 5 µm; right: 5 µm References: [1] [4] Kandler, K., Lieke, K., Benker, N. 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. Ott, D.K., Peters, T. (2008) A Shelter to Protect a Passive Sampler for Coarse Particulate Matter, PM10-2.5. Aerosol Sci. Technol. 42, 299-309. Trapp, J.M., Millero, F.J., Prospero, J.M. (2010) Temporal variability of the elemental composition of African dust measured in trade wind aerosols at Barbados and Miami. Mar. Chem. 120, 71-82. Zhang, D. (2008) Effect of sea salt on dust settling to the ocean. Tellus 60B, 641-646. 188 Environmental Mineralogy [2] [3] Diploma Theses in Applied Geosciences Bauer, Ingo; Geologie, Petrographie und Pyroductgenese des Kahuku-Ranch-Gebietes, Big Island, Hawaii, 04.11.2011 Breuer, Barbara; Ingenieur- und hydrogeologische Untersuchungen zum Schadensfall Staufen im Breisgau, 11.04.2011 Ceglarek, Jan; Detailuntersuchung sedimentologischer Prozesse an einem quartären alpinen Schwemmfächer, mittels eines mit Georadar aufgenommenen dreidimensionalen Untergrundmodels (Illgrabenfächer, Schweiz), 31.03.2011 Fiedler, Holger; Untersuchung der Vergleichbarkeit von Adhäsionsversuchen mit flachen und kegelförmigen Teststempeln an bindigen Böden, 12.07.2011 Fischer, Franziska; Chemische Charakterisierung der Aerosolpartikel des Hinter- und Vordertaunus, 23.08.2011 Hoppe, Nadja; Die Chemie einer Hochwasserwelle des Rheins, 06.01.2011 Jäckel, Simon; Charakterisierung und Optimierung eines Staubdosiersystems für PM10Äquivalenzuntersuchungen, 27.10.2011 Kludt, Christoph; Arzneimittelabbau in Abhängigkeit von der Redoxzonierung im Interaktionsbereich zwischen Oberflächen- und Grundwasser - am Beispiel des Schwarzbachs, 06.07.2011 Müller, M. Mathis; Sintermechanismen im LiF dotierten Mg-Al-Spinell, 05.05.2011 Priebs, Robert; Properties of Geothermal Reservoir Rocks: Comparison between Ohaaki Field (NZ) and Saar-Nahe-Basin (GER), 12.09.2011 Rohm, Melanie; Golddekoration von CdSe/CdS Hetero-Nanostrukturen - Synthese und elektronenmikroskopische Untersuchungen, 06.01.2011 Rüther, Johanna; Thermofazielle Interpretation des Permokarbons im Sprendlinger Horst, 21.09.2011 Schumann, Andreas; Die Kalklagerstätte Großenlüder-Müs - Fazies, Tektonik und 3DModellierung, 15.02.2011 Diploma Theses in Applie Geosciences 189 Master Theses TropHEE in Applied Geosciences Asfaw, Berhane; Chlorine and carbon isotope effects during reductive dechlorination of TCE and cis-DCE using ZVI in bench scale column experiments, 07.03.2011 Khan, Abidur; Analysis and determination of soil moisture content profile by the application of pilot Time Domain Reflectometry (TDR) prototype sensors, 14.02.2011 Osemwegie, Isimemen; Geochemical and isotopic composition of groundwater from hand dug wells within the precarious settlements of Southern Abidjan, Cote d'Ivoire, 02.05.2011 Xiao, Lu; Water Quality in Western Uganda - Evaluation of human impact, 10.11.2011 PhD Theses in Applied Geosciences Shahrazad Abu Ghazleh; Lake Lisan and the Dead Sea: Their Level Changes and the Geomorphology of their Terraces, 9.2.2011 Martin Kastowski; Abschätzung der Kohlenstoffspeicherung und freisetzung in Seen Europas - Ein Beitrag zur Eingrenzung der fehlenden Senke im globalen Kohlenstoffkreislauf, 7.7.2011 Kirsten Inga Lieke; Distribution and Mixing State of Saharan Dust in the Vertical Column Airborne Observations over the Atlantic Ocean in the Cape Verde region, 8.4.2011 190 Master- and PhD Theses in Applie 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] 191 Master- and PhD Theses in Applie Geosciences
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