ANNUAL REPORT

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DEPARTMENT OF

MATERIALS AND EARTH SCIENCES

Annual Report

2001

Department 11 Materials and Earth Sciences

Materials Science: Petersenstraße 23 • L2 01 • 64287 Darmstadt

Phone 06151/16 53 77 • Fax 06151/16 55 51 http://www.tu-darmstadt.de/fb/ms/

Earth Sciences:

Schnittspahnstraße 9 • B2 01/02 • 64287 Darmstadt Phone 06151/16 25 71 • Fax 06151/16 65 39

http://www.tu-darmstadt.de/fb/geo/

for further information contact: Dr. Joachim Brötz, Phone 06151/16-4392; e-mail: broetz@tu-darmstadt.de

Christine Hempel, Phone 06151/16-66 65; e-mail: hempel@matgeo.tu-darmstadt.de

1. INTRODUCTION 4 2. MATERIALS SCIENCE

Physical Metallurgy 6 Ceramics Group 10

Electronic Material Properties 14 Surface Science 18

Thin Films 21 Dispersive Solids 26 Structure Research 30

Chemical Analytics 38 Theoretical Materials Science 42

Reports of Research Activities 44 Diploma Theses 75 PhD Theses 76 Journal “Thema Forschung” 77

3. APPLIED EARTH SCIENCES

Institute of Geology and Palaeontology

Physical Geology and Global Cycles 79 Hydrogeology 83 Engineering Geology 86 Applied Sedimentology 88

Georesources and geohazards 90

Institute of Mineralogy

Geomaterials Science 92 Petrology and Structural Geology 92 Environmental Geology 92

Reports of Research Activities 96 Diploma Theses 108

Introduction

Hartmut Fuess, Dean In 2001 the department kept on reorganizing successfully. The former Geological-Paleontological Institute and the Institute for Mineralogy merged, founding the new “Institute for Applied Geosciences”. Professor Hoppe was elected as Acting Director of that Institute. The newly created curriculum “Applied Geosciences” has attracted more students in 2001 than the previous, separate curricula of Geology/Paleontology and Mineralogy. Unfortunately Materials Science experienced a slight decrease in the number of new students in spite of continued efforts of the staff members to attract freshmen to our department (Fig. 1).

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Fig. 1. Registered students in Materials Science at the TU Darmstadt During the last year 10 students finished their study with diplomas in Materials Science and 8 in Earth Sciences. Furthermore in Materials Sciences 16 PhD-degrees were attributed. Two scientists, Dr. Markus Rettenmayr (Metallurgy) and Dr. Markus Winterer (Thin Films) obtained the degree of Habilitation.

With the begin of the year, two new colleagues have been appointed as professors: Matthias Hinderer (from Tübingen University) for Applied Sedimentology, and Andreas Hoppe (former Director of Geological Survey of Hessen) for Georesources and Geohazards; Peter Blümel (Professor for Structural Geology and Petrology) retired the same year.

The amount of external funds (Drittmittel) in the Institute of Materials Sciences, still increased last year and has exceeded the limit of 10 Mio. German Marks (5.112.920 Euro). The steady progress in external funding is represented in Fig. 2. Remarkable is the proportion of funds from industry. This money is absolutely necessary in order to run the laboratories and to improve the equipment as direct support by the Land diminished considerably over the years. It has to be noticed, however, that the State of Hessen supplies the basic infrastructure (salaries of staff members, building, power supply). The external funds are essential for running the PhD-programs.

The collaboration with industry in the region Rhein-Main is demonstrated by the MATFORM-organisation which concentrates the materials research activities within the University of Technology.

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The power and potential of MATFORM are exemplified by a special issue of Thema Forschung (see page 77) of the TUD, which has been edited by Professor Jaegermann. This issue clearly documents the variety of research activities in Materials Science in all departments of TUD. The ongoing political discussion about the structure of Universities and the careers they offer has resulted in modifications in the academic hierarchy. As a new element the Juniorprofessorship was introduced, modeled after the American Assistant Professor. It is considered to be a “tenure track position”. In order to implement Juniorprofessorships the Federal Government and the State of Hessen promised to subsidize new positions. Therefore the Materials Science advertised a position for a Juniorprofessor in “Modeling in Materials Science”. It seems, however, doubtful whether an isolated measure may really lead to a “reform” of the existing University structure especially as no consent exists where to go eventually. The Faculty also observed the discussions about introducing Bachelor and Master curricula with interest; eventually these degrees will also be introduced as supplementary curricula offers. Last but not least the award winners of the Faculty have to be mentioned. The prize for the best diploma student (MaWi-Preis) was attributed in 2001 to Christoph Deneke, who performed his diploma thesis in the division Structure Research. Dr. André Zimmermann (now at the Max-Planck-Institute at Stuttgart) who got his PhD in the Ceramics Division was honored by the prize of the “Vereinigung der Freunde der TUD” and Dr. Helmut Ehrenberg (Structure Research) was happy enough to receive two distinctions last year: In March he obtained the Max von Laue-prize of the Deutsche Gesellschaft für Kristallographie (DGK) and in June he was awarded the Adolf Messer-prize (100.000 DM for research) of the Messer foundation, which operated in close cooperation with the TUD.

Institute of Materials Science Physical Metallurgy Research and teaching in the Department of Physical Metallurgy are focused on understanding the relationship between processing, microstructure and properties of metallic materials. The major goal of ongoing research is to describe, in quantitative terms, the basic mechanisms which govern processing and performance in use, and to predict the influence of process variables on materials’ properties during and after solidification, densification, heat treatment, forming, and shaping. Modelling and nu-merical simulation of casting, recrystallization, sintering, forging, sheet drawing, and chip formation are covered. Theoretical results are compared to experimental find-ings obtained by microscopic techniques and all other experimental methods avail-able in the Department. New methods for the quantitative description of microstruc-ture and surface morphology are developed. Current work deals with titanium, alu-minium and magnesium based light alloys, steel, solders, precious and hard metals, superalloys, fibre strengthened aluminium, and other multicomponent alloys. Wear, corrosion and fatigue and their complex interaction are studied. Recent achieve-ments are improved wear of titanium alloys for artificial joints by ion implantation, new alloys for electrical contacts, as well as better understanding of catalytic action of nickel alloys and of the preparation and the properties of functionally graded materials.

Teaching covers lectures on mechanical properties of engineering materials and fundamentals of deformation and fracture, phase diagrams and phase transforma-tions, solidification and heat treatment mechanisms, and image analysis for the characterization of microstructures. Extensive laboratory exercises on all levels are offered to facilitate and intensify the technical understanding in these topics and to improve the practical skills for investigating metallic materials.

Cooperation with other groups in the Institute of Materials Science and of other institutes and departments of Darmstadt Technical University, particularly with those of Mechanical Engineering, Chemistry, Technical Mechanics and Physics, as well as with other universities in Germany (Kaiserslautern, Aachen, Chemnitz, Dortmund) and abroad (Australia, South Africa, India, Switzerland, France, The Netherlands and others) as well as with industry (Acheson, Adam Opel, Daimler-Chrysler, Degussa-Hüls, Heraeus, Hirschvogel, OMG/dmc2, among others) give opportunities for scientific and personal exchange. Participation in conferences, seminars and workshops aid to the actuality of teaching and research.

Staff Members Head

Prof. Dr. Dr. h.c. Hans Eckart Exner

Research Associates Dr.-Ing. Bhaskar Dutta Dr.-Ing. Clemens Müller Dr.rer.nat. Oliver Pompe

PD Dr. rer. nat. Markus Rettenmayr Dr.-Ing. Sheljasko Sheljaskow

Technical Personnel

Ulrike Kunz Heinz Lehmann

Claudia Wasmund

Secretary

Helga Harnack

PhD Students

Dipl.-Ing. Ralf Blümke Dipl.-Ing. Bettina Burghardt Dipl.-Ing. Muriel Graff Dipl.-Ing. Sonja Knies Dipl.-Ing. Ralf Koch Dipl.-Ing. Petra Lambracht

Dipl.-Ing. P. Marx Dipl.-Ing. Michael Nimz Dipl.-Geol. Ute Steinbauer Dipl.-Phys. Sven Thomas Dipl.-Ing. Klaus Wintrich Dipl.-Ing. Guoping Zhao

Guest Scientists

Prof. Dr. Saied El-Ghazaly, Central Metallurgical Research and Development Inst., Helwan, Cairo, Egypt Dr. Xiaoyan Song, Hebei Univ. of Technology, Tianjin, China

Research Projects Crack Growth and Crack Closure in Functionally Graded Materials (DFG, 1998-2002) Influence of Stress State and Friction on Surface Modification and Damage during Sheet Forming (DFG, 1997-2001) Characterization of Chip Formation at Short Time Loading during High Speed Cutting (DFG, 1998-2002) Phase Formation and Surface Properties of Ion Implanted Biocompatible Titanium Alloys with Varying Composition (DFG, 1999-2002) Effective Ecologically Beneficial Process for Surface Coating and Lubrication of Steels in Cold Forging (HEPSCOS) (Bright-Euram-Project of the European Community, 1998-2001) Fatigue Strength of Magnesium Alloys (Adam Opel, Rüsselsheim, 1998-2001) Development of Lead Free Solders (ESEC, Cham, Switzerland and Degussa-Hüls, Hanau, 1999-2002) Investigation of Material Specific Effects on the Switching Behavior of Contact Materials (Degussa-Hüls, Hanau, 1998-2001) Storage and Permeability of Hydrogen in Metals (Daimler-Chrysler, Ulm, 2000-2001) Deformation and Failure of a Single-Crystal Nickel-Base Alloy (DFG, 1997-2002) Recrystallization in Particle Reinforced Materials (AvH-Foundation, 2000-2002) Partition Coefficients in Multicomponent Alloys (DAAD, 2000-2003)

Publications Blümke, R.; Sahm, A.; Müller, C.; Influence of Heat Treatment on Chip Formation in High Speed Milling, in: Schulz, H. (ed.), Scientific Fundamentals of HSC, Hanser Verl., München (2001) 43-52. Dutta, B.; Palmiere E. J.; Influence of Strain and Deformation Temperature on the Static Recrystallization Behaviour of Microalloyed Austenite, in: Gottstein, G.; Molodov, D. A. (eds.), Recrystallization and Grain Growth, Springer Verl., Berlin (2001) 1095-1100. Dutta, B.; Palmiere E. J.; Sellars, C. M.; Modelling the Kinetics of Strain Induced Precipitation in Nb-microalloyed Steels, Acta Mater. 49 (2001) 785-794. Exner, H. E.; Quantitative Metallography in drei Dimensionen/Quantitative Metallography in Three Dimensions, Prakt. Metallogr. 38 (2001) 370-384. Gross, D.; Exner, H. E.; Numerische Simulation materialwissenschaftlicher Phäno-mene, Thema Forschung 2 (2001) 64-70. Exner, H. E.; Sigl, L.; Fripan, M.; Pompe, O.; Fractography of critical and subcritical cracks in hard materials, Int. J. Refract. Met. Hard Mat. 19 (2001) 329-334. Knies, S.; Miehe, G.; Rettenmayr, M.; Ostgard, D. J.; Structure Formation of Activated Nickel Catalysts During Caustic Leaching Nickel-Aluminium Alloys, Z. Metallkd. 92 (2001) 596-599. Liu, G. Q.; Wang, C; Liu, S.; Qin, X. G.; Yu, H. B.; Song, X. Y.; Stereology and 3D Quantitative Characterization of Microstructure for Grain Growth Studies, in: Gottstein, G.; Molodov, D. A. (eds.), Recrystallization and Grain Growth, Springer Verl., Berlin (2001) 595-600. Liu, G. Q.; Yu, H. B.; Song, X. Y.; Qin, X. G.; A New Model of Three-Dimensional Grain Growth: Theory and Computer Simulation of Topology-Dependency of Individual Grain Growth Rate. Mater. Design 22 (2001) 33-38. Liu, G. Q.: Yu, H. B.; Song, X. Y.; Qin, X. G.; Re-examination and Extension of Hillert Theory of Two-dimensional Normal Grain Growth, in: Gottstein, G.; Molodov, D. A. (eds.), Recrystallization and Grain Growth, Springer Verl., Berlin (2001) 263-268. Müller, C.; Blümke, R.; Influence of Heat Treatment and Cutting Speed on Chip Segmentation of Age Hardenable Aluminium Alloys, Mater. Sci. Technol. 17 (2001) 651-654. Müller, C.; Pompe, O.; Neuhäusel, P; Pascuzzi, S.; The Effect of a Deformation Gradient on the Recrystallisation Behaviour of Titanium Grade 2, in: Petzow, G. (ed.), Sonderbände der Praktischen Metallographie, Mücklich, F. (ed.), Vol. 32, Progress in Metallography, MatInfo Werkstoffinformationsgesellschaft, Frankfurt (2001) 117-120. Nimz, M.; Jung, S.; Müller, C.; Pompe, O.; Characterisation of Local Deformations in Deep-Drawing Sheet Steel, in: Petzow, G. (ed.), Sonderbände der Praktischen

Metallographie, Mücklich, F. (ed.), Vol. 32, Progress in Metallography, MatInfo Werkstoffinformationsgesellschaft, Frankfurt (2001) 65-68. Rettenmayr, M.; Exner, H. E.; Directional Solidification, Encyclopedia of Materials: Science and Technology, Elsevier, Oxford (2001). Rettenmayr, M.; Wasmund, C.; Pompe, O.; Formation of Concentration Gradients in Al-Cu Alloys by Means of a Temperature Gradient in the Mushy Zone, in: Petzow, G. (ed.), Sonderbände der Praktischen Metallographie, Mücklich, F. (ed.), Vol. 32, Progress in Metallography, MatInfo Werkstoffinformationsgesellschaft, Frankfurt (2001) 313-316. Rettenmayr, M.; Warkentin, O.; Rappaz, M.; Exner, H. E.; Simulation of Solutal Remelting, Acta Mater. 49 (2001) 2499-2510. Sasikumar, R; Savithri, S.; Rettenmayr, M.; Exner, H. E.; A Model for the Formation of Interdendritic Cavities from Pores Pre-existing in the Melt, Z. Metallkd. 92 (2001) 158-162. Schmidt, H.; Schminke, A.; Schmiedgen, M.; Baretzky, B.; Compound Formation and Abrasion Resistance of Ion-Implanted Ti6Al4V, Acta Mater. 49 (2001) 487-495. Sheljaskow, S.; Tool Lubricating Systems in Warm Forming, J. Mater. Process. Techn. 113 (2001) 16-21. Song, X.; Rettenmayr, M.; Exner, H. E.; Liu, G.; Combined Monte-Carlo/Deterministic Model of Recrystallization and Recovery, in: Gottstein, G.; Molodov, D. A. (eds.), Recrystallization and Grain Growth, Springer Verlag, Berlin (2001) 1013-1020. Song, X.; Rettenmayr, M.; Müller, C.; Exner, H. E.; Modeling of Recrystallization after Inhomogeneous Pre-Deformation, Metall. Mater. Trans. 32A (2001) 2199-2206. Thomas, S.; Müller, C.; Exner, H. E.; Prediction of Local Strain and Hardness in Sheet Forming, Z. Metallkd. 92 (2001) 830-833.

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. Thereby a materials optimization is afforded, which allows effective interplay between processing, testing and modelling. The scientific effort can be grouped as follows: 1. Sintering and mechanical properties of oxides: Investigations on the rheological behaviour of ceramic slips are geared towards an understanding of the processing windows these slips allow as compared to microcrystalline materials. The sintering behaviour is also studied starting from green bodies with different pore size distribution. Sintering of ceramics is also approached using a continuum mechanical description, which affords inclusion of laminate stresses as arise in sintering of thin films and cosintering of several layers. In order to determine the constitutive equations for the sintering bodies, dilatometry and a new hot forging apparatus are used. This equipment together with a substantial modelling effort allows predictions of shrinkage and curvature in multilayer structures. Work on mechanical properties is geared towards an improved understanding of fracture strength, fracture toughness, R-curve behaviour and subcritical crack growth. Recently, an additional focus was placed on microcracking coupled with efforts on finite element modelling and damage evolution on the grain size level. Materials under consideration are ZrO2, Al2O3, Al2TiO5 , CeO2 and Y2O3 . 2. Metal/ceramic composites and gradient materials: Most of our metal/ceramic composites are produced by metal infiltration into a porous preform. The resulting residual stresses, obtainable strength values, reliability, wear and R-curve behaviour are studied. Several methods to prepare graded materials have been developed. A scientific understanding of crack propagation, residual stresses and thermal shock is afforded by altering the respective microstructures by using our processing approach. As metal infiltration is an important part of our strategy, studies were also performed on wetting and have further lead to work on liquid phase joining as well as to work on interface mechanics. Materials combinations are Al2O3/Cu and Al2O3/Al. 3. Piezoelectric materials: Two scientific questions are of interest for this group. Reliability of piezoceramics for applications as actuator materials is under investigation. An increasing number of electrical cycles leads to a progressive loss of obtainable strain and polarisation in these materials. Both microcracking as well as charged vacancies are speculated to contribute to the electrical fatigue effect. In order to investigate the reduced domain - boundary mobility, acoustic emission is used for polycrystalline ceramics. In parallel, Barkhausen pulses and acoustic emission studies are performed on single crystals used as model systems. The second branch is concerned with mechanical properties of ferroelastic materials. Crack propagation depends on crack - and specimen geometry and is experimentally determined and correlated. These investigations consider both a thermodynamic crack equilibrium as well as subcritical crack growth. The process zone in ferroelastic

materials is investigated using a liquid crystal display, an approach which was recently developed in our group. Besides mechanically loaded cracks, electrically driven cracks - as appearing in multilayer actuators - are also investigated. A strain incompatibility between electrically active and inactive material gives rise to the initiation and propagation of cracks at electrode edges. Materials under consideration are lead zirconate titanate as well as barium titanate.

Staff Members: Head

Prof. Dr.-Ing. Jürgen Rödel

Research Associates Dr. Doru Lupascu Dr. Achim Neubrand Dr. Srinivasa Rao

Dr. Ludwig Weiler Dr. Ruzhong Zuo

Technical Personnel

Emil Aulbach Herbert Hebermehl

Secretaries

Roswita Geier Marion Bracke

PhD Students

Dipl.-Phys. Astrid Dietrich Dipl.-Ing. Jens Eichler Dipl.-Phys. Susan Galal Yousef Dipl.-Phys. Brice Kounga

Dipl.-Phys. Patricie Merkert Dipl.-Ing. Sergio dos Santos e Lucato Dipl.-Ing. Ulrich Stiefel Dipl.-Ing. Cyril Verdier

Guest Scientists

Dr. Mark Hoffmann (Univ. of New South Wales, Australien) Tim Chin (Univ. of Washington at Seattle, USA) Arnab Chattophadhyay (Indian Inst. of Technology, Kanpur, Indien) William Blanton (Purdue Univ., Purdue, USA)

Research Projects Coordination of core program "Graded Materials" (DFG, 1995-2001) Colloidal processing of nanocrystalline ceramics (DFG, 1998-2001) Fracture toughness and crack propagation in graded materials (DFG, TU Karlsruhe, Dr. Fett, 1999-2002) Formation and extension of single and multiple cracks in ferroelectrics due to electrical poling: experiment (DFG, TU Dresden, Dr. Bahr, 1999-2002) Damage evolution in ferroelectrics due to interaction between mechanical stresses and electrical fields (DFG, 1996-2001)

Mechanical properties and fracture of metal-ceramic composites (DFG-SFB 298, TUD, Prof. Gross, 2000-2002) Sintering of ceramic films (DFG, 2000-2003) Mechanical properties of materials, processed by pressureless infiltration (VW-Foundation, Prof. Jayaram, Bangalore, India, 1998-2001) Microcracking of oxides: Theory and Experiment (DFG, MPI Stuttgart, 2001-2003) Electrical fatigue in actuators (DFG, 2001) Crack propagation in ferroelectrics: Crack opening displacement and effect of stress state (DFG, 2000-2002) Mechanical properties of nanocrystalline Zirconia (Bosch, 2001-2004) Viscosity of LTCC materials (Philips, 2001)

Publications Kanters, J.; Eisele, U; Böder, H. and Rödel, J.; Continuum Mechanical Description of Sintering Nanocrystalline Zirconia, Adv. Eng. Mat. 3 (2001) 158-162. Chen, W.; Lupascu, D. C.; Rödel, J.; and Lynch, C. S.; A Comparison of the Short Crack in Flexure R-Curve Behavior of Unpoled Ferroelectric 8/65/35 and Quadratic Electrostrictor 9.5/65/35 PLZT, J. Am. Ceram. Soc. 84 (2001) 593-597. Lupascu, D. C.; Kreuzer, M.; Lucato, S. S.; Rödel, J.; Lynch, C. S.; A Liquid Crystal Display of Stress Fields in Ferroelectrics, Appl. Phys. Let. 78 (2001) 2554-2556. Moon, R.; Bowman, K.; Trumble, K.; Rödel, J.; Fracture Resistance Curve Behavior of Multilayered Alumina-Zirconia Composites Produced by Centrifugation, Acta Mater. 49 (2001) 995-1003. Lucato, S. S.; Lupascu, D. C.; Kamlah, M.; Rödel, J.; Lynch, C. S.; Constraint-Induced Crack Initiation at Electrode Edges, Acta Mater. 49 (2001) 2751-2759. Nuffer, J.; Lupascu, D. C.; Rödel, J.; Microcrack Clouds in Fatigued Electrostrictive 9.5/65/35 PLZT, J. Eur. Ceram. Soc. 21 (2001) 1421-1423. Lucato, S. S.; Lupascu, D. C.; Rödel, J.; Crack initiation and crack propagation in partially electroded PZT; J. Eur. Ceram. Soc. 21 (2001) 1425-1428. Skirl, S.; Krause, R.; Wiederhorn, S. M.; Rödel, J.; Processing and Mechanical Properties of Al2O3/Ni3Al Composites with Interpenetrating Network Microstructure; J. Am. Ceram. Soc. 84 (2001) 2034-2040.

Zimmermann, A.; Hoffman, M.; Emmel, T.; Gross, D.; Rödel, J.; Failure of Metal-Ceramic Composites with Sperical Inclusions; Acta Mater. 49 (2001) 3177-3187. Rao, M. P.; Rödel, J.; Lange, F. F.; Residual Stress Induced R-Curves that Exhibit a Threshold Strength; J. Am. Ceram. Soc. 84 (2001) 2722-2724. Nuffer, J.; Lupascu, D. C.; Rödel, J.; Negligible Oxygen Liberation during Bipolar Electric Cycling of Ferroelectric PZT Ceramics; Appl. Phys. Let. 79 (2001) 3675-3677. Kanters, J.; Eisele, U.; Rödel, J.; Simulation and Experiment of Cosintering: Case Study on Nanocrystalline Zirconia, J. Am. Ceram. Soc. 84 (2001) 2757-2763. Moon, R.; Hoffman, M.; Rödel, J.; Hilden, J.; Blanton, W.; Bowman, K.; Trumble, W.; A Weight Function Analysis on Gradient Alumina-Zirconia Composites, in: Functionally Graded Materials 2000, The American Ceramic Society (2001) 781-788. Chung, T.-J.; Neubrand, A.; Rödel, J.; Fett, T.; Fracture Toughness and R-Curve Behavior of Al2O3/Al FGMs, in: Functionally Graded Materials 2000, The American Ceramic Society (2001) 789-796. Hammer, M.; Endriss, A.; Lupascu, D. C.; Hoffmann, M. J.; Correlation between Microstructure, Strain Behavior and Acoustic Emission of Soft PZT Ceramics, Acta Mater. 49 (2001) 1301-1310. Lupascu, D. C.; Microcracking and discontinuous fast switching as acoustic emission sources in 8/65/35 and 9.5/65/35 PLZT relaxor ferroelectrics, J. Europ. Ceram. Soc. 21 (2001) 1429-1432. Karastamatis, T.; Lupascu, D. C.; Lucato, S. S.; Lynch, C. S.; The effect of grain size on the R-curve behavior of Lead-Zirconate Titanate (PZT), SPIE Smart Structures and Materials: Behavior and Mechanics, Proc. 4333, C. S. Lynch Ed. (2001) 38-41. Becker, H.; Tschudi, T.; Neubrand, A.; Spatially Resolved Thermal Diffusivity Measurements for Functionally Graded Materials, Functionally Graded Materials 2000, Ceramic Transactions 114 (2001) 571-578. Neubrand, A.; Kawasaki, A.; Thermal Cycling Behaviour of a Cu/Al2O3 - Functionally Graded Material, Functionally Graded Materials 2000, Ceramic Transactions 114 (2001) 705-712. Schreiber, J.; Neubrand, A.; Wieder, T.; Stalder, M.; Shamsutdinov, N.; Distribution of Macro- and Microstresses in W-Cu-FGM, Functionally Graded Materials 2000, Ceramic Transactions 114 (2001) 603-610. Dietrich, A.; Neubrand, A.; Effect of Particle Size on the Properties of Electrosterically Stabilized Particle Dispersions, J. Amer. Ceram. Soc. 84 (2001) 806-812.

Electronic Material Properties The division Electronic Materials (ELMA) has been founded to introduce the aspect of functional materials and their properties into the Institute of Materials Science. 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 properties of organic semiconductors, Charge transport and polarization in organic dielectrics, and Photo- and photostimulated luminescence in inorganic phosphors. In the field of organic semiconductors a worldwide interest exists in the use of organic semiconductors in novel electronic devices, such as displays and organic electrical circuits. An already commercialized application is a multicolor car radio display supplied by Pioneer Corporation consisting of vacuum-deposited layers of functional small organic molecules. Applications reaching further into the future will be simple organic circuits based on semiconducting polymers. Which will be found in communication electronics such as circuits on chip cards, barcodes and maybe one day in an electronic newspaper where the information is continuously renewed via local area networks (LAN). The activities of ELMA are concerned with the characterization of organic materials properties. In this respect a set of experimental techniques for the evaluation of functional electronic properties are installed and will be refined in the future. Two major aspects are addressed: the first one is the detection and characterization of electronic traps in organic semiconductors and their correlation to charge transport properties, such as carrier mobility number of trapped charges, etc. The second one is to understand the limits of electronic conduction in highly ordered and intentionally disordered organic semiconductors. In the field of charge transport and polarization in organic dielectrics the necessary measuring equipment is presently installed. This includes poling equipment such as corona charging, and thermal charging under high electric fields as well as techniques to study the charge transport in dielectric films such as the pressure-pulse-step method to determine the spatial distribution. A thermally stimulated current setup to investigate the energetic trap structure in dielectrics is already functioning. Also a high voltage switching equipment for ferroelectric polymers has been introduced which may be applied up to 4000V in 150ns with poling currents as high as 60A. Presently investigations are directed towards the basic understanding of polarization buildup and stabilization in PVDF which is scientifically still under debate. Further a project on piezoelectric foams as a novel class of piezoelectric materials has been started. The field of photo- and photostimulated luminescent materials (phosphors) is concerned with the synthesis and characterization of suited inorganic compounds. Such materials are utilized as wavelength converters in fluorescent lamps and in scintillating and information storing crystals. Challenges are the sensibilization of such phosphors in respect to the radiation energy under investigation which can range from ultraviolet to hard γ-rays or thermal neutrons. Present work is focussed on materials suitable for the detection of thermal neutron images as needed in radioactive waste monitoring, medical treatments and neutron diffraction in materials

science. Scientifically the energy transfer process from the absorption of thermal neutrons to the generation of photostimulable centers has to be understood and optimized. This does not only imply the optimization of the phosphors but also the optimization of the detecting layers in respect to spatial resolution and detection efficiency. Started is a new research topic in this field of quantum cutters. These are materials that emit two light-particles (photons) upon the absorption of one high energy photon. Such materials are foreseen to be essential components in future high efficiency energy saving lamps which will function without mercury and so have a low environmental impact. In respect to teaching ELMA contributes to the topics of electronic properties of organic and inorganic materials. The understanding of electrical, optical, dielectric and magnetic properties of matter and their relation to structural properties such as crystalline and amorphous phases are the dominant tasks. The basic understanding is to give students the intellectual tools at hand to utilize the relation between function and structure to design special materials for special properties and applications.

Staff Members Head

Prof. Dr. Heinz von Seggern

Research Associate Dr. Enver Bulur Prof. Dr. Sergei Fedosov

Dr. Anthony O'Mullane Dr. Roland Schmechel

Technical Personnel

Gabriele Andreß Sabine Hesse

Bernd Stoll

Secretary

Gerlinde Dietrich

PhD Students

Dipl.-Phys. Torsten Finnberg Dipl.-Ing. Holger Heil Dipl.-Ing. Robert Kolb

Dipl.-Ing. Michael Schlapp Dipl.-Chem. Norwin von Malm Dipl.-Ing. Jörg Zimmermann

Diploma Students

Aline Hepp Jörg Lindner

Jens Niemax

Research Projects Development of Novel Photostimulable Storage Phosphors for the Detection of Thermal Neutrons (HMI, 1999-2002) Development of Field Effect Transistors from Organic Thin Films (DFG, 2001-2002) Chemically Fixed pn-Junction in Polymeric Double Layers suited for Application in Organic Electronics (DFG, 2000-2001, Fraunhofer-Inst. Teltow IAP)

Impurities in Organic Semiconductors I (DFG, 2000-2003, Chemical Analytics) Impurities in Organic Semiconductors II (DFG, 2000-2003, Chemical Analytics) Improvement of Detective Quantum Efficiency of Neutron Image Plates (DFG, 2000-2003) Piezoelectric sensor materials from porous polymers (AiF, 2000-2003, DKI) Development of Neutron Image Plates (Forschungszentrum Jülich, 2000-2003) Charge Storage and Piezoelectricity of Porous and Cellular Electret Films (VW-Stiftung, 2001-2004) Development of Functional Polymers for Integrated Organic Circuits (PODOS), (BMBF Project with Siemens, 2001-2004) Characterization of traps in organic semiconductors by Thermally Stimulated (TSC) (BMBF Project with Covion, 2001-2003) Photo-induced charge transfer in the novel low bandgap polymer semiconductors and their use in photovoltaic devices (EU Project, 2001-2003)

Publications Heil, H.; Steiger, J.; Karg, S.; Gastel, M.; Stößel, M.; Ortner, H.; Seggern, H. von; Mechanism of Injection Enhancement in Organic Light-Emitting Diodes through an Al/LiF Electrode, J. Appl. Phys. 89 (2001) 420-424. Malm, N. von; Steiger, J.; Schmechel, R.; Seggern, H. von; Trap engineering in organic hole transport materials, J. Appl. Phys. 89 (2001) 5559-5563. Schmechel, R.; Winkler, H.; Xaomao, L.; Kennedy, M.; Kolbe, M.; Benker, A.; Winterer, M.; Fischer, R. A.; Hahn, H.; Seggern, H. von; Luminescence properties of nanocrystalline Y2O3:Eu3+ in different host materials, J. Appl. Phys. 89 (2001) 1679-1686. Schmechel, R.; Winkler, H.; Xaomao, L.; Kennedy, M.; Kolbe, M.; Benker, A.; Winterer, M.; Fischer, R. A.; Hahn, H.; Seggern, H. von; Photoluminescence Properties of nonocrystalline Y2O3:Eu3+ in different environments, Scripta Mat. 44 (2001) 1213-1217. Heil, H.; Steiger, J.; Schmechel, R.; Seggern, H. von; New Device architecture for red emitting OLEDs with Eu(dbm)3phen emission layer, J. Appl. Phys. 90 (2001) 5357-5362. Steiger, J.; Karg, S.; Schmechel, R.; Seggern, H. von; Aging Induced Traps in Organic Semiconductors; Synth. Metals 122 (2001) 49-52.

Seggern, H. von; Fedosov, S.; Switching in Ferroelectric Polymer Materials: Role of a Novel Displacement Component, Mater. Sci. (Russ) 6 (2001) 9-17. Seggern, H. von; Rehahn, M.; Mehr Information durch mehr Licht: Organische Leuchtdioden fürs tägliche Leben, Thema Forschung (TU Darmstadt) 2 (2001) 22. Seggern, H. von; Schmechel, R.; Elektronische Fallen in organischen Halbleitern, GIT Polymer Forschung in Darmstadt (2001) 50-51. Karg, S; Steiger, J., Seggern, H. von; Determination of Trap Energies in Alq3 and TPD, Synth. Metals 111-112 (2000) 277-280. Steiger, J.; Karg, S.; Seggern, H. von; Electronic traps in OLED Transport Layers: Influence of Doping and Accelerated Aging, Proc. SPIE 4105 (2001) 256-264.

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 (photo-emission, electron diffraction, ion scattering, scanning probe techniques) with the preparation of thin films and interfaces in cluster tools. The main research interest is directed to devices using novel polycristalline compound semiconductors and inter-faces between dissimilar materials. The perspectives of energy converting devices as e. g. solar cells are of special interest. In addition, the fundamental processes in-volved in chemical and electrochemical device engineering are investigated. The main research areas are: • Electrochemical Interfaces

The aim of this research activity is the better understanding of electrochemical interfaces and contact formation. In addition, empirically derived (electro)chemical processing steps as the controlled modification and structuring of materials is investigated and further optimized. In the center of our interest are semiconductors and ion conductors.

• Van der Waals semiconductor heterojunctions and multilayers

The aim of this research acitivity is the testing and development of 2D-semi-conductors (layered chalcogenides) for optoelectronic devices. In addition, van der Waals layers are investigated as passivating layers for 3D semiconductors and as buffer layers of lattice mismatched materials combinations. Furthermore the decisive factors, which govern the electronic properties of heterojunctions, are studied.

• 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 microcristalline thin solar cells are to be characterized on a microscopic level to understand and to further improve the empirically based optimisation of solar cells.

• Surface analysis

The UHV-surface science equipment and techniques using different and versatile integrated preparation chambers is used for cooperative service investigations.

For the experiments we use integrated UHV-preparation and analysis-systems (UPS, (M)XPS, LEISS, LEED), spectromicroscopy (PEEM) coupled with UHV-STM/AFM. We further apply synchrotron radiation (SXPS, spectromicroscopy), scanning probe methods (STM, AFM), and electrochemical measuring techniques. UHV-preparation chambers dedicated for MBE, CVD, PVD and (electro)chemical treatment are available. The members of the group are involved in basic courses of the department’s curriculum and offer special courses on the physics, chemistry and engineering of semiconductor devices and solar cells, on surface and interface science, and on thin film and surface technology.

Staff Members Head

Prof. Dr. Wolfram Jaegermann

Research Associates Dr. Ralf Hunger Dr. Andreas Klein

Dr. Thomas Mayer Dr. Andreas Thißen

Technical Personnel

Martin Bepler Dipl.-Ing. Erich Golusda

Secretary

Marga Lang

PhD Students

Dipl.-Phys. Martin Beerbom Dipl.-Ing. Jochen Fritsche Dipl.-Ing. Rainer Fritsche Dipl.-Ing. Stefan Gunst Dipl.-Ing. Daniel Kraft

Dipl.-Ing. Marco Lammer Dipl.-Ing. Frank Säuberlich Dipl.-Ing. Elmar Wisotzki Qihui Wu

Diploma Student Jürgen Ell David Ensling Bengt Jäckel Wolfram Kolbe

Frauke Rüggeberg Thomas Schulmeyer Sebastian Weber Ulrich Weiler

Humboldt-scholarship holder

Dr. Obaidul Islam Dr. Guangming Liu

Research Projects Nanostructuring of surfaces of intercalation phases (ion conductors) with scanning probe techniques (DFG core program “Grundlagen der elektrochemischen Nanotechnologie”, 1999-2001)

Elementary processes at semiconductor/electrolyte interfaces: Systematic compari-son of UHV-methods after emersion and in model experiments (DFG, 1999-2001) Quasi van der Waals buffer layers for the deposition of lattice mismatched compound semiconductors on silicon (DFG, 1999-2001) Interfaces and inhomogeneities of polycristalline CdTe thin film solar cells (BMBF, 1999-2001) Interfaces of two-dimensional semiconducting layered chalcogenides morphology and electronic properties (BMBF, Erforschung kondensierter Materie, Verbundpro-jekt, Halbleitergrenzflächen, 1998-2001, HMI, Berlin) Dedicated preparation-, transfer and spectrometersystem for the analysis of materials modifications and -synthesis at solid-liquid-interfaces with synchrotron radiation (BMBF, 2001-2004) ZnO for Thin Film Solar cells; Materials and Interface Research (BMBF, 2001-2003)

Photovoltage optimization of II-VI compound thin film solar cells (BMBF, 2001-2004) Silicon-organic pigment material hybrids for photovoltaic application (VW-Stiftung, 06-10/01)

Publications Fritsche, J.; Thißen, A.; Klein, A.; Jaegermann, W.; Oriented growth and band lineup at the CdS/CdTe interface, Thin Solid Films 387 (2001) 158-160. Fritsche, J.; Gunst, S.; Golusda, E.; Lejard, M. C.; Thißen, A.; Mayer, T.; Wendt, R.; Gegenwart, R.; Bonnet, D.; Klein, A.; Jaegermann, W.; Surface Analysis of CdTe thin film solar cells, Thin Solid Films 387 (2001) 161-164. Klein, A.; Tiefenbacher, S.; Eyert, V.; Pettenkofer, C.; Jaegermann, W.; Electronic band structure of single crystal and single layer WS2: Influence of interlayer van der Waals interactions, Phys. Rev. B 64 (2001) 1-14. Mayer, T.; Black Spots on Carbon Steel after Contact to Lubricating Oil with Extreme Pressure Additives: An ESCA Study, Appl. Surf. Sci 179 (2001) 257-262. Saltas, V.; Papageorgopoulos, C. A.; Papageorgopoulos, D. C.; Tonti, D.; Petten-kofer, C.; Jaegermann, W.; Synchrotron radiation studies of transition metal selenide thin-films formation on Ti, Mo and Cu substrates: in and out diffusion of Li, Thin Solid Films 389 (2001) 307-314. Sánchez-Royo, J. F.; Segura, A.; Lang, O.; Schaar, E.; Pettenkofer, C.; Jaegermann, W.; Roa, L.; Chevy, A.; Optical and photovoltaic properties of indium selenide thin films prepared vy van der Waals epitaxy, J. Appl. Phys. 90 (2001) 2818-2823.

Thin Films

The scientific program of the Thin Films Division combines the synthesis, the characterization with the determination of the properties and the theoretical modeling/simulation of nanostructured materials. Nanostructured materials with structural features in the nanometer range can be found in the form of clusters, thin films, multilayers and nanocrystalline materials often expressed by their dimensional-ity of 0, 1, 2 and 3. The ultimate goal of the research program is to achieve a better understanding of the fundamental atomistic processes and properties of materials which are dominated by grain boundaries and interfaces. In selecting the materials and the properties, the potential for technological applications is considered. The materials investigated include metals, amorphous and crystalline alloys, semi-conductors, oxide, nitride and carbide ceramics in the form of clusters, thin films, multilayers and bulk nanocrystalline materials. Most synthesis techniques are based on vapor phase processes such as Molecular Beam Epitaxy (MBE), Chemical Vapor Deposition (CVD) and DC- and RF- Magnetron Sputtering for thin films and multilayers and Chemical Vapor Synthesis (CVS) and Inert Gas Condensation (IGC) for clusters and nanocrystalline materials. The high quality and reproducibility of the materials are achieved by establishing clean conditions such as ultra-high vacuum environments, computer control of the synthesis parameter and in-situ analysis techniques such as Reflection High Energy Electron Diffraction (RHEED) or Aerosol Mass Spectrometry. The characterization of the materials is performed in part in collaboration with research groups in the Materials Science Department and other institutions using modern analytical methods. These include X-Ray Diffraction (XRD), High Resolution Scanning Electron Microscopy (HRSEM) and Transmission Electron Microscopy (HRTEM), Electron MicroProbe Analysis (EMPA), Secondary Ion Mass Spectroscopy (SIMS), Atomic Force and Scanning Tunneling Microscopy (AFM/STM), Mössbauer Spectroscopy (MS) and Depth-sensitive Conversion Electron Mössbauer Spectroscopy (DCEMS), Auger Electron Spectroscopy (AES), X-ray Photoelectron Spectroscopy (XPS), Ion Scattering Spectroscopy (ISS), nitrogen adsorption and in cooperation with several national and international research facilities, e.g. Small Angle Neutron Scattering (SANS) and Extended X-ray Adsorption Fine Structure (EXAFS). In addition, several accelerator facilities are used for ion beam analysis, such as Rutherford Backscattering Spectroscopy (RBS) or Nuclear Reaction Analysis (NRA), of thin film structures and nanocrystalline materials after ion implantation and ion beam modification. Atomic scale computer simulations are in the focus of the materials modeling activities. The main tool is the molecular dynamics method. Large scale computer simulations of several million of atoms can be performed on our recently installed 18-processor parallel cluster computer (DAMASCOS). The development of reactive analytical potentials allows us to simulate a variety of elemental and compound systems. Total energy calculations within the density functional theory are used for materials characterization, kinetic Monte-Carlo methods for studying materials processes on time scales, that are not accessible by the MD-method. A wide range of optical, electronic, magnetic, mechanical and catalytic properties of these materials are investigated. For example, the giant or tunneling magneto-resistance effect (GMR, TMR) and the atomic transport in multilayers and in nano-crystalline materials, have been studied intensively. An understanding of the atomistic processes can be deduced from the knowledge of the detailed

microstructure and of the structure/property relationships leading to optimized engineering properties for applications. These include materials for resistive gas sensors based on semiconducting oxides, catalysts and calorimetric gas sensors based on noble metals on nanocrystalline oxides and motion sensors for automotive applications based on the GMR-effect in multilayers and granular thin films. Besides the teaching of mandatory undergraduate and graduate courses, the Thin Films Division offers several elective courses for students: • Synthesis of novel high-technology materials; • Modification and analysis of materials using ion beam techniques; • Phase transformation in solids; • Introduction to high resolution scanning electron microscopy.

Staff Members: Head: Prof. Dr.-Ing. Horst Hahn Research Associates: Dr. Karsten Albe Dr. Adam G. Balogh Dr. Mohammad Ghafari Dr. Uwe Keiderling

Dr. Branko Stahl Dr. Markus Winterer

Secretaries: Renate Hernichel Marion Bracke Technician: Jürgen Schreeck PhD Students : Dipl.-Ing. Mete Berber Dipl.-Ing. Wolfram Berky

Dipl.-Ing. Joachim Brehm Dipl.-Ing. Yong-San Cho Dipl.-Ing. Jörg Ebert Dipl.-Ing. Andrew Johnson Dipl.-Ing. In-Kyum Lee Dipl.-Phys. Marcel Müller Dipl.-Phys. Ralf Nagel Dipl.-Ing. Michael Schallehn

Dipl.-Ing. Stefan Seifried Dipl.-Ing. Johannes Seydel Dipl.-Ing. Hermann Sieger

Diploma Students : Jens Ellrich Sebastian Gottschalk Irina Mazilu Holger Schmitt

Andreas Volland Victor Bulto Guest Scientists: Dr. Sabari Bhattacharya, Indian Inst. of Technology,

Kanpur, India Dr. Gilberto Bejarano, CCA Asistencia Técnica a la

Industria, Cali, Columbia Dr. Darko Hanzel, Inst. J. Stefan, Ljubljana, Slovenia Dr. Raghurama Raju, Jawaharlal Nehru Centre,

Bangalore, India Prof. Dr. Vladimir Srdic

Research Projects Chemical Vapor Synthesis of Transparent Conducting Oxides (bmb+f, Degussa, Frankfurt, 2000-2003) Degradation mechanisms of multilayered Giant Magneto Resistance thin films (bmb+f, Bosch, Stuttgart, 1997-2002) Aerosol Mass Spectroscopy of nanopowders prepared by Chemical Vapor Synthesis (DFG, 1997-2001) Ion beam mixing and radiation enhanced diffusion in metal-ceramic interfaces (GSI, Darmstadt, 1999-2001) Ion beam mixing of nanocrystalline oxides (GSI, Darmstadt, 2000-2003) Synthesis of nanocrystalline functional gradient materials by chemical vapor processes (DFG core program „Functional Gradient Materials“, 1996-2001) Chemical Vapor Synthesis of binary oxide nanopowders and scale-up of the CVS process (DFG core program „Processing of Powders“, Degussa, Frankfurt, 2000-2003) Synthesis and characterization of nanocrystalline oxides for gas sensors (DAAD program, 1999-2002) Spin valves for angular sensors in automobiles (Bosch, Stuttgart, 1999-2002) Mössbauer studies and magnetization of amorphous FeSc-alloys (DFG, 1998-2001) Synthesis of ultrathin zirconia electrolyte layers for SOFC by gas phase processes (DFG core program „Novel Structures for Fuel Cells“, 2000-2002) Molecular Dynamics simulations of atomistic processes during interface gliding (DFG, 2001-2003) Local structure of nanocrystalline perowskites (DFG, 1999-2002) Surface magnetism in nanocrystalline powders, thin films and single crystals (DFG, 2000-2003) Functionalization of nanopowders by gas phase processing (SusTech GmbH&Ko., KG, 1999-2004) Synthesis of nanocrystalline non-agglomerated oxide powders using wet chemical processes. Preparation of nano-dispersions in liquids. Characterization and optimiza-tion of the functional properties (otpical, electrical, magnetic) of powders, coatings and bulk materials (SusTech GmbH&Ko., KG, 2000-2004)

Publications Betz, U.; Padmanabhan, K. A.; Hahn, H.; Superplastic Flow in Nanocrystalline and Sub-Microcrystalline Yttria-Stabilized Tetragonal Zirconia, J. Mat. Sci. 36 (2001) 5811-5821. Betz, U.; Bhattacharya, S. S.; Hahn, H.; Some Studies on the Superplastic Deforma-tion Behavior of Nanocrystalline Yttria Stabilized Zirconia Based Ceramics, Scripta Mat. 44 (2001) 1553-1556. Ghafari, M.; Stahl, B.; Banihashemi, S. H.; Müller, M.; Hahn, H.; Magnetic interactions in amorphous Fe-Sc alloy, J. of Magn. and Magn. Mat. 226-230 (2001) 1555-1557. Schmechel, R.; Winkler, H.; Xaomao, L.; Kennedy, M.; Kolbe, M.; Benker, A.; Winterer, M.; Fischer, R. A.; Hahn; H.; Seggern, H. von; Photoluminescence Properties of Nanocrystalline Y2O3:Eu3+ in Different Environments, Scripta Mat. 44 (2001) 1213-1217. Seifried, S.; Winterer, M.; Hahn, H.; Nanocrystalline Gradient Films Through Chemical Vapor Synthesis, Scripta Mat. 44 (2001) 2165-2168. Schmechel, R.; Winkler, H.; Xiamao, L.; Kennedy, M.; Kolbe, M.; Benker, A.; Winterer, M.; Fischer, R. A.; Hahn, H.; Seggern, H. von; Luminescence properties of nanocrystalline Y2O3:Eu3+ in different host materials, J. Appl. Phys. 89 (2001) 1678-1686. Srdic, V.; Winterer, M.; Möller, A.; Miehe, G.; Hahn. H.; Nanocrystalline Zirconia Surface Doped with Alumina: Chemical Vapor Synthesis, Characterization and Properties; J. Am. Ceram. Soc. (2001) 2771-2776. Ashkenazy, Y.; Averback, R. S.; Albe, K.; Nanocluster rotation on Pt surfaces: Twist boundaries; Phys. Rev. B 64, 205409 (2001) 1-9. Nagel, R.; Weyrich, K.; Hofmann, D. H. H.; Balogh, A. G.; Heavy ion induced intermixing of metal/SiC interfaces, NIMB 178/1-4, (2001) 315 ff. Nagel, R.; Balogh, A. G.; On the behaviour of enhanced mixing in metal/ceramic interfaces, NIMB 175-177 (2001) 398 ff. Nagel, R.; Alof, C.; Balogh, A. G.; Boerma. A. G.; Arnoldbik, W.; Study of magnetic multilayers by RBS with nanometer resolution; NIMB 183/1-2 (2001) 140 ff. Puff, W.; Balogh, A. G.; Vacancy-type defects in proton-irradiated InAs; Mat. Sci. For. 73 (2001) 363 ff. Brunner, S.; Puff, W.; Balogh. A. G.; Mascher, P.; Characterization of radiation induced defects in ZnO probed by positron annihilation spectroscopy; Mat. Sci. For. 141 (2001) 363 ff.

Keiderling, U.; Seydel, J.; Winterer, M.; Wiedenmann, A.; Hahn, H.; Time-resolved In-Situ SANS Investigation of the Sintering Behavior of Nanocrystalline Y2O3-Doped ZrO2 Ceramics; Proc. 7th European Conference On Advanced Materials Euromat 2001, Rimini, Italy, June 10-14 2001, CD-ROM (2001). Keiderling, U.; Winterer, M.; Benker, A.; Seydel, J.; Wiedenmann, A.; Hahn, H.; Sintering Behavior of Nanocrystalline ZrO2/Y2O3 Mixed Ceramics Analyzed with SANS; Scripta Mat. 44 (2001) 2087-2091. Ghafari, M.; Stahl, B.; Banihashemi, S. H.; Müller, M.; Hahn, H.; Magnetic Interactions in Amorphous Fe-Sc Alloys; J. Magn. Magn. Mat. 226 (2001) 1555-1557.

Dispersive Solids Our research is based on the development of strategies for producing novel inorganic, oxidic, and non-oxidic materials. The main focus is the synthesis of ceramics with properties which exceed the present state of the art. Synthesis methods like the sol-gel-technology, polymer pyrolysis and chemical vapour deposition (CVD) are used and continuously further developed. Moreover molecular, oligomeric, and polymeric ceramic precursors as well as inorganic materials derived therefrom are synthesized and characterized. Further emphasis is put on the transformation of the precursors into ceramic components (for example layers, fibers, bulk materials, composites, membranes) and the characterization of their chemical and physical materials properties. The aim of our research activities is to correlate those properties with the composition and structure of the molecular precursors. The present projects include the following four main topics: material synthesis, properties, modelling, as well as processing and applications.

Staff Members Head

Prof. Dr. Ralf Riedel

Research Associates Dr. Uwe Beyer Dipl.-Ing. Claudia Fasel Dr. Ralf Hauser Dr. Christoph Konetschny Dr. Isabel Kinski Dr. Edwin Kroke

Dr. Saifun Nahar-Borchert Dr. Hyung Suh Park Dr. Sylvia Rastätter Dr. Andreas Zerr Dr. Yanping Zhou

Technical Personnel

Ildiko Balog Nelli Groß

Secretary

Su-Chen Chang

PhD Students

Dipl.-Min. Michael Eberhardt M. Tech. Rahul Harshe Dipl.-Ing. Frank Hönack Dipl.-Ing. Elisabeta Horvath-Bordon

Dipl.-Ing. Alexander Klonzcynski Dipl.-Ing. Marcus Schwarz Dipl.-Ing. Wolfgang Völger

Diploma Student Thomas Utschig

Rama Subrahmanyam Komaragiri

Guest Scientists

Prof. Dr. Corneliu Balan, Politehnica, Univ. of Bucharest, Romania Dr. Navin Chandra, Regional Research Laboratory CSIR, Bhopal, Indien Dr. Liudmila Chybusava, Univ. Informatik u. Elektronik, Minsk, Weißrußland Dr. Jinwang Li, Inst. of Chemical Metallurgy Chinese Academy of Sciences, Beijing, China Prof. Zhi-Chang Wang, Northeastern Univ., Shenyang, China Gleb Yurkov, Inst. of General and Inorganic Chemistry, Russia Academy of Science, Moscow, Rußland Rama Subrahmanyam Komaragiri, Dept. of Physics, Indian Inst. of Technology, Madras, India

Research Projects Synthesis of ceramic Ti-(C,N)-materials from high cross-linked inorganic-organic tita-nium polymers (DeBeers, Johannesburg, South Africa, since 1996) High pressure synthesis of SiCN-materials (DeBeers, Johannesburg, South Africa, 2000-2001) Electrical properties of precursor-derived ceramics in the system Si-O-C (Bosch, Stuttgart, since 1996) Precursorkeramik (DFG core program “Synthesis and high-temperature stability of amorphous ceramics in the system Si-B-C-N from polymeric preliminary stages and their application for carbon-fibres coatings about the fluid-coating-method”, with Prof. Dr. U. Klingebiel, Inorganic Chemistry, Univ. Göttingen; Prof. Dr. R. Gadow, Ferti-gungstechnologie keramischer Bauteile, Univ. Stuttgart; Dr. H.-J. Kleebe, Material-forschung, Univ. Bayreuth, since 1997) Precursorkeramik (DFG core program “Molecular design of preceramic polymers using quantum mechanical method: synthesis of novel metallocarbodiimide-polymers and –gels”, Priv.-Doz. Dr. J. Woltersdorf, MPI, Halle, since 1997) Precursorkeramik (DFG core program “Novel nitrogen rich ceramic materials in the binary system C/N” since 1997) Determination of phase relations in the system Si-B-C-N in laser-heated diamond high-pressure anvil cell (DFG, 1997-2001) Precursorkeramik (DFG core program “Oxidation und corrosion of Si-(B)-C-N materials from polymeric precursors”, Prof. Dr. K. G. Nickel, Mineralogy, Petrology & Geochemistry, Univ. Tübingen, since 1998) Neue Precursorkeramik aus kondensierten molekularen Vorstufen (DFG core program “Polysilazane, Polyborosilazane and further Si/(B)/C/N-polymers as laminate

device for the manufacture of Si3N4-multi-layer prefabricated parts in foil construction”, Prof. J. Heinrich, TU Clausthal, since 1998) Nanostrukturierte Gradientenwerkstoffe auf Precursorenbasis für komplexe Zerspa-nungswerkzeuge: Synthesis of filled Ti/C/N-precursor polymers for the coating of po-rous ceramic substrates with nanostructured wear resistant hard material layers (BMBF, CeramTec, 1999-2001) Mikrostrukturierte Komponenten für die Informationstechnik und mehrfunktionelle, hochtemperaturstabile Sensoren auf der Basis präkeramischer Polymere: Develop-ment of filled functionalized polysiloxane systems for the manufactur of microstruc-tured ceramic prefabricated parts (BMBF, Bosch, 1999-2001) Novel cutting-tool materials for the machining of compacted graphite iron (Produk-tionstechnik und spanende Werkzeugmaschinen, TU Darmstadt; Sintercast, Fried-richsdorf; Ford; Eisenwerke Brühl, Brühl, since 1999) SiC-Faserverbundwerkstoffe für Technologieinnovationen in der Energie-, Umwelt- und Verkehrstechnik: Manufacturing of SiC-fibres from Silylcarbodiimides (BFS, Fraunhofer Inst. of Silicate Research, since 1999) Structural investigations of the pyrolytic polymer-transformation of non-oxide first-class performed ceramics (DAAD-PROCOPE, Prof. Dr. F. Babonneau, Chimie de la Matière Condensée, Univ. Paris, 1998-2001) Material modification of bushing post insulators (Siemens Energieübertragung und -verteilung, since 2000) Synthesis of novel materials and improvement of the properties for the application as nitrogen-oxid storing catalytic converters of modern fuel-injection engines (dmc2, Degussa Metals Catalysts Cerdec, Hanau, since 2000) Inorganic Membranes (JFCC, Nagoya, Japan, 2000-2001) Anorganic/organic hybrid materials and ceramics of non-oxide carbodiimid-gels (DFG, since 2000) Superhard materials (scientific technologic cooperation with South Africa, since 2000) III-V-Group semiconductor materials (Merck, Darmstadt, since 2001) PACVD-synthesis and charakterisation of Si(B)CN hard material films for tribological applications (DFG, since 2001)

Publications Nicolich, J. P.; Hofer, F.; Brey, G.; Riedel, R.; Synthesis and Structure of Three-Dimensionally Ordered Graphite-Like BC2N Ternary Crystals, J. Am. Ceram. Soc. 84 (2001) 279-82.

Gastel, M.; Konetschny, C.; Reuter U.; Fasel, C.; Schulz, H.; Riedel, R.; Investigation of the Wear Mechanism of Cubic Boron Nitride Tools Used for the Machining of Compacted Graphite Iron and Grey Cast Iron, Int. J. Refract. Met. Hard Mat. 18 (2001) 287-296. Kroke, E.; Völger, K.-W.; Klonczynski, A.; Riedel, R.; A Sol-Gel Route to B4C, Angew. Chem. Int. Edit. 40 (2001) 1698-1700 und Eine Sol-Gel-Route zur Synthese von B4C, Angewandte Chemie 113 (2001) 1751-1753. Wang, Z.-C.; Gerstel, P.; Kaiser, G.; Kummer, H.; Bill, J.; Aldinger, F.; Riedel, R.; B[C2H4Si(CH3)NH]2[C2H4Si(CH3)N(SiH2Ph)]n: The First Polyborosilazane Precursor for Silicoboron Carbonitride Stable to 2200 °C, Chem. Lett. (2001) 296-297. Ramakrishnan, P. A.; Wang, Y. T.; Balzar, D.; An, L.; Haluschka, C.; Riedel, R.; Hermann, A. M.; Siliconboron Carbonitride Ceramics: A New Class of High-Temperature, Dopable Electronic Materials, Appl. Phys. Lett. 78 (2001) 3076-3078. Iwamoto, Y.; Völger, W.; Kroke, E.; Riedel, R.; Crystallization Behavior of Amorphous Si-C-N Ceramics Derived from Organometallic Precursors, J. Am. Ceram. Soc. 84 (2001) 2170-2178. Wang, Z.-C.; Aldinger, F.; Riedel, R.; Novel Si-B-C-N Materials Thermally Stable up to 2200°C, J. Am. Ceram. Soc. 84 (2001) 2179-2183. Galusek, D.; Riley, F. L.; Riedel, R.; Nanoindentation of a Polymer-Derived Amorphous Silicon Carbonitride Ceramic, J. Am. Ceram. Soc. 84 (2001) 1164-1166. Li, Y.-L.; Kroke, E.; Riedel, R.; Fasel, C.; Gervais, C.; Babonneau, F.; Thermal Cross-Linking and Pyrolytic Conversion of Poly(ureamethylvinyl)silazanes to Silicon-Based Ceramics, Appl. Organomet. Chem. 15 (2001) 820-832. Hering, N.; Schreiber, K.; Riedel, R.; Lichtenberger, O.; Woltersdorf, J.; Synthesis of Polymeric Precursors for the Formation of Nanocrystalline Ti-C-N/Amorphous Si-C-N Composites, Appl. Organomet. Chem. 15 (2001) 879-886. Raj, R.; An, L.; Shah, S.; Riedel, R.; Fasel, C.; Kleebe, H.-J.; Oxidation Kinetics of an Amorphous Silicon Carbonitride Ceramic, J. Am. Ceram. Soc. 84 (2001) 1803-1810. Herrmann, A. M.; Wang, Y.-T.; Ramakrishnan, P. A.; Balzar, D. An, L.; Haluschka, C.; Riedel, R.; Structure and Electronic Transport Properties of Si-(B)-C-N Ceramics, J. Am. Ceram. Soc. 84 (2001) 2260-2264. Raj, R.; Riedel, R.; Soraru, G. D.; Introduction to the Special Topical Issue on Ultrahigh-Temperature Polymer-Derived Ceramics, J. Am. Ceram. Soc. 84 (2001) 2158-2159. Zerr, A.; A New High-Pressure δ-Phase of Si3N4, Phys. Status Solidi (b) 227, No. 2 (2001) R4-R6.

Structure Research The investigation of the correlation between materials properties and the corresponding crystal structure is the central activity of the Structure Research group. The characterization of structure and nanomorphology at an interatomic length scale requires different types of radiation. Therefore a variety of diffraction and microscopic techniques have been established in the structure research group. Thus almost any structural defect or any type of material has successfully been studied, ranging from crystalline materials, amorphous solids to surfaces and interfaces. In addition, we operate two powder diffractometers at large scale facilities; one dedicated for experiments with synchrotron radiation at the HASYLAB synchrotron in Hamburg, the other for neutron diffraction at the neutron research reactor FRM II in Munich. One of the main objectives in structure research is the selective improvement of materials. For example materials for applications in heterogeneous catalysis are investigated and optimised by systematic analysis of the respective structure-property relationship. Simultaneously, magnetic materials and ionic conductors play an important part in current research activities. Materials under present investigation are anode catalysts in DMFC fuel cells, magnetic alloys, as well as polymers modified by heavy-ion bombardment at GSI, Darmstadt. Research on complex oxides and pigments are carried out in collaboration with Merck and together with OMG, projects on three-way- and diesel catalyst are in progress. The funding of the research activities is based on the infrastructure provided by the university. The actual projects are mainly supported by public science organisations (BMBF, DFG) and to a large extend by co-operations with industry. These joint ventures proved to be beneficial to both partners. The scientific staff is involved in basic teaching of the department’s curriculum and offers special courses in crystallography and x-ray diffraction. Additionally, more application-oriented topics, e.g. battery materials as well as spectroscopy and diffraction in applied catalysis, were presented in lectures.

Staff Members Head

Prof. Dr. Hartmut Fueß

Research Associates

Dr. Carsten Bähtz Dr. Kirill Bramnik Dr. Joachim Brötz Dr. Thorsten Buhrmester Dr. Helmut Ehrenberg

Dr. Ralph Gilles Dr. Natalia Leyzerovich Dr. Gerhard Miehe Dr. Hermann Pauly Dr. Hans Weitzel

Technical Personnel

Dipl.-Ing. Heinz Mohren Jean Christophe Jaud

Dipl.-Ing. Bernhard Krimmer Ingrid Svoboda

Secretaries

Marianne Binder Maria Holzmann

PhD Students

Dipl.-Ing. Andreas Adams Dipl.-Ing. Adnan Adla Dipl.-Phys. Ilker Dinçer Dipl.-Chem. Tatiana Dunaeva Dipl.-Chem. Matthias Feger Dipl.-Ing. Frank Haaß Dipl.-Ing. Markus Hölzel Dipl.-Phys. Achim Hohl Dipl.-Phys. Victor Joco Dipl.-Phys. Michael Knapp Dipl.-Phys. Aris Kounis

Dipl.-Ing. Ingo Lappas Dipl.-Ing. Nathalie Martz Dipl.-Phys. Martin Moneke Dipl.-Ing. Alexander Morlang Dipl.-Phys. Vedran Rajevac Dipl.-Phys.Nizar Rammeh Dipl.-Ing. Christina Roth Dipl.-Ing. Ralf Theissmann Dipl.-Min. Claudia Wahl Dipl.-Chem. André Yonkeu

Diploma Student

David Hayem

Guest Scientists

Dipl.-Phys. Igor Djerdj, Univ of Zagreb, Croatia ! Dr. Mohamed Ellouze, Univ. of Sfax, Tunisia Prof. Dr. Filiz Ercan, Hacettepe Univ. of Ankara, Turkey Dipl.-Ing. Milan Gembický, Univ. of Bratislava, Slovakian Republic Dr. Egbert Gomez, Univ. of Sao Paulo, Brasil "#$% Dipl.-Phys. Anouar Njeh, Univ. of Sfax, Tunisia $!!, Univ. of Bratislava, Slovakian Republic Prof. Dr. David Rafaja, Charles Univ. Prag, Czech Republic Prof. Dr. K. V. S. Rama Rao, India Inst. of Tech., Madras, India Dr. Koh Saitoh, Tohoku Univ. Sendai, Japan Prof. Dr. Delegiin Sangaa, National Univ. Ulaan Baator, Mongolia Dr. Andrei Skomorokhov, Institute for Physics and Pow. Eng., Russia Prof. Dr. Michiyoshi Tanaka, Tohoku Univ. Sendai, Japan

Research Projects Resonant and high-resolution powder diffraction on polycrystalline materials at HASYLAB in Hamburg (BMBF, 2001-2004) Ternary rare-earth rhenium oxides (DFG, 1998-2002) Ternary rhenium oxides with alkaline-earth metals (BMBF, 1998-2002) Interfaces in micro-crystalline quartz (DFG, 1998-2001) Chemical composition, nanomorphology and electrolytic activity of catalytic materials for direct methanol fuel cells (DFG, 1998-2002) Correlation between properties and structure in niobates (DFG, 1999-2002) Investigation of the Pd/Rh-interaction with substrate oxides in respect of sintering behaviour and catalytic activity (DMC2, 1999-2001)

Design and realisation of a neutron powder diffractometer at the FRM-II at TUM in Garching (BMBF, 1998-2003) Inelastic neutron scattering investigation of lattice dynamics in nitrided metals (BMBF, 2000-2002) Research and development of catalysts for engines operated with diesel fuels (DMC2, 2000-2003) Ion traces in polymers (GSI, 1998-2002) Ion traces in insulators (GSI, 2001-2004) Development of novel interference pigment materials (Merck, 1999-2002) Application of the generalized Debye scattering formula in powder diffraction (DFG, 1998-2001) Function and dynamics of oxygen in Mo / V mixed oxides catalytic materials for partial oxidation of aldehydes (DFG in collaboration with Prof. Dr. H. Vogel, TUD and Prof. Dr. M. Martin, RWTH-Aachen, 2000-2002) Design and investigation of new oxygen storage systems to be used in three-way-catalysts (OMG, 2001-2004) Structural characterization of silicon monoxide SiO (DFG, 2000-2002) Lattice dynamics of superionic copper selenide (DFG, 2001-2003) In-situ studies of intercalation batteries (DAAD, 2002-2003, with the Universidad San Pablo, Spain) Oxygen conductivity in rare earth / lanthanum - gallium oxides (DAAD, 2001/2002 with the Univ. of Lviv, Ukraine) Microstructure of WS2 layers (DAAD, 1999-2001, with the Univ. of Bordeaux, France) Properties of compound materials (DLR, 1999-2001, with the Univ. of Ankara, Turkey) Coordination Compounds as Materials (BMBF, 1998-2001) Superionic compounds (Monbushu, 1999-2001, with the Univ. of Hiroshima, Japan) GMR materials (1999-2001, with the Univ. of Sfax, Tunisia)

Publications Abakumov, A. M.; Rozova, M. G.; Shpanchenko, R. V.; Mironov, A. V.; Antipov, E. V.; Bramnik, K. G.; Synthesis and crystal structure of the lithium perrhenate mono-hydrate LiReO4⋅H2O, Solid State Sciences 3 (2001) 581-586. Adla, A.; Buschmann, V.; Fuess, H.; Trautmann, C.; Investigation of heavy ion tracks in polymers by transmission electron microscopy, Nucl. Instr. and Meth. B 185 (2001) 210-215. Arici, C.; Svoboda, I.; Sari, M.; Atakol, O.; Fuess, H.; Bis(N,N-dimethylformamide) [µ-N,N‘-bis(salicylidene)1,3-propane-diaminato]nickel(II)dibromozink(II), Acta Cryst. C 57 (2001) 31-32. Atakol, O.; Nazir, H.; Arici, C.; Svoboda, I.; Fuess, H.; Crystal structure of bis (N,N‘-dimethylformamide) (µ-acetato) [µ-N,N‘-bis(salicilidene)-2-hydroxy-1,3-propanedia-mine] nickel(II), Main Group Met. Chem. 24 (2001) 125-126. Balevicius, V.; Fuess H.; Hydrogen bonding, molecular-ionic interactions, and evolu-tion of phase diagrams of aqueous solutions, Envir. Chem. Phys. 223 (2001) 71-76. & & ! & ' #& Fuess, H.& ( ) "% &Papánková, B.; Renz, F.; Vrbová, M.; Werner, R.; Strong cooperativeness in the mononuclear iron(II) derivative exhibiting an abrupt spin transition above 400 K, Inorg. Chem. 40 (2001) 3025-3033. Bramnik, K. G.; Ehrenberg, H.; Fuess, H.; Preparation, crystal structure, and magnetic studies of a new Sr7Re4O19 double oxide and its relation to the structure of Ba7Ir6O19, J. Solid State Chem. 160 (2001) 45-49. Brötz, J.; Fuess, H.; Anisotropic strain in YBa2Cu3O7-δ films analysed by deconvolu-tion of two-dimensional intensity data, J. Appl. Cryst. 34 (2001) 13-15. Danilkin, S. A.; Hoser, A.; Wieder, T.; Fuess, H.; Phonon dispersion and elastic constants in Fe-Cr-Mn-Ni austenitic steel, J. Mater. Sci. 36 (2001) 811-814. Elmali, A.; Elerman, Y.; Svoboda, I.; Bis[2-(2-oxido-1-naphtylmethylidene-amino)-phenyl]disulfidechloroiron(III), Acta Cryst. C 57 (2001) 375-376. Elmali, A.;. Elerman, Y.; Svoboda, I.; 5-Chloro-N-(2-hydroxy-5-methyl-phenyl)-salicylaldimine, Acta Cryst. C 57 (2001) 485-486. Fuess, H.; Röntgenbeugung in: Amthauer, G.; **#+, - -chemische Untersuchungsmethoden in den Geowissenschaften, E. Schweitzer-bart’sche Verlagsbuchhandlung, Stuttgart 2 (2001) 1-18. Fuess, H.; Synchrotronstrahlung . /& ** # +,Physikalisch-chemische Untersuchungsmethoden in den Geowissenschaften, E. Schweitzerbart’sche Verlagsbuchhandlung, Stuttgart 2 (2001) 19-32.

Fuess, H.; Neutronenstreuung . /& ** # +,Physikalisch-chemische Untersuchungsmethoden in den Geowissenschaften, E. Schweitzerbart’sche Verlagsbuchhandlung, Stuttgart 2 (2001) 43-59. Gilles, R.; Krimmer, B.; Saroun, J.; Boysen, H.; Fuess, H.; The concept of the new structure powder diffractometer (SPODI) at the FRM-II in Garching, Mat. Sci. For. 378-381 (2001) 282-287. Goossens, A. M.; Wouters, B. G.; Grobet, P. J.; Buschmann, V.; Fiermans, L.; Martens, J. A.; Synthesis and characterization of epitaxial FAU-on-EMT zeolite overgrowth materials, Eur. J. Inorg. Chem. (2001) 1167-1181. Gowda, B. T.; Paulus, H.; Fuess, H.; Structural studies on substituted N-(phenyl)-2,2-dichloroacetamides, 2,4-XC6H⋅NCO⋅CHCl2 (X=H, Cl or CH3), Z. Naturforsch. 56 a (2001) 386-394. Gräf, I.; The Use of Ion Beam Etching in Composite Layered Materials Part I: Thermally Sprayed Layers of Steel or Mixed Metal on Steel, Prakt. Metallogr. 38 (2001) 287-300. Gräf, I.; The Use of Ion Beam Etching in Composite Layered Materials Part II: Thermally Sprayed Layers of Electrolytic Copper on Various Substrate Materials, Prakt. Metallogr. 38 (2001) 617-626. Gräf, I.; The Use of Ion Beam Etching in Composite Layered Materials Part III: Thermally Sprayed Layers of Special Metals on Steel, Prakt. Metallogr. 38 (2001) 699-714. Grohe, B.; Miehe, G.; Wegner, G.; Additive controlled crystallization of barium titanate powders and their application for thin-film ceramic production: Part I. Powder Synthesis, J. Mater. Res. 16 (2001) 1901-1910. Grohe, B.; Miehe, G.; Wegner, G.; Additive controlled crystallization of barium titanate powders and their application for thin-film ceramic production: Part II. From nano-sized powders to ceramic thin films, J. Mat. Res. 16 (2001) 1911-1915. Haaß, F.; Buhrmester, T.; Martin, M.; High temperature in situ x-ray absorption studies on the iron valence in iron-doped nickel oxide (Ni1-x Fex)1-δO, Solid State Ionics 141-142 (2001) 289-293. Haaß, F.;. Buhrmester, T.; Martin, M.; Quantitative elaboration of the defect structure of iron doped nickel oxide (Ni1-xFex)1-δO by in situ x-ray absorption spectroscopy, Phys. Chem. Chem. Phys. 3 (2001) 4806-4810. Hartmann, T.; Ehrenberg, H.; Miehe, G.; Buhrmester, T.; Wltschek, G.; Galy, J.; Fuess, H.; Preparation and crystal structure of Re3O10, J. Sol. State Chem. 160 (2001) 317-321. Herzberg, O.; Ehrenberg, H.; Kitchin, S. J.; Harris, K. D. M.; Epple, M.; Structural aspects of the solid-state polycondensation reaction in alkali 4-halogenomethyl-benzoates, J. Sol. State Chem. 156 (2001) 61-67.

Ishihara, H.; Okajima, T.; Horiuchi, K.; Svoboda, I.; Fuess, H.; Isolated versus condensed anion structure VII: X-ray structure analysis of 1,3-Propanediammonium dibromodichlorocadmate(II), [H3N(CH2)3NH]CdBr2Cl2, and estimation of stability of five-coordinated halide anions, MX5

3-(M=Cd,Zn:X=Cl,Br) by means of ab-initio MO calculations, Z. Naturforsch. 56 a (2001) 641-646. Kavlakoglu, E.; Elmali, A.; Elerman, Y.; Werner, R.; Svoboda, I.; Fuess, H.; Crystal Structure and Magnetic Properties of a Linear Trinuclear Ni(II) Complex, Z. Natur-forsch. 56 b (2001) 43-48. Kervan, S.; Elerman, Y.; Elmali, A.; Theissmann, R.; Magnetic properties of PrMn2-

xFexGe2 compounds, J. Alloys Comp. 327 (2001) 27-30. Knapp, M.; Ehrenberg, H.; Fuess, H.; Hahn, U.; Hesse, M.; Schulte-Schrepping, H.; Wroblewski, T.; Pneumatically bent mirrors: an additional degree of freedom for beam conditioning in high-resolution powder diffraction, Nucl. Instr. Meth. A 467-468 (2001) 291-293. Knapp, M.; Ruschewitz, U.; Structural phase transitions in CaC2, Chem. Eur. J. 7 (2001) 874-880. Kounis, A.; Miehe, G.; Saitoh, K; Fuess, H.; Sterzel, R.; Assmus, W.; Structure analysis of a Zn-Mg-Er cubic phase (R-phase) and relation to icosahedral phases, Phil. Mag. Lett. 81 (2001) 395-403. Knies, S., Miehe, G.; Rettenmayr, M., Ostgard, D. J.; Structure formation of activated nickel catalyst during caustic leaching of a nickel-aluminium alloy, Z. Metallkd. 92 (2001) 596-599. %0& & !&!!&Svoboda, I.; Fuess, H.; Structure and zero-field splitting in bis(1,2-dimethylimidazole)bis(acetato)nickel(II) molecular complex, Chem. Phys. Lett. 347 (2001) 397-402. Mattern, N.; Zinkevich, M.; Ehrenberg, H.; Knapp, M.; Handstein, A.; Crystal structure and magnetic properties of Gd1+nFe12x-yMox+y, Mat. Sci. For. 378-381 (2001) 402-407. Nazir, H.; Arici, C.; Svoboda, I.; Düzgün, E.; Atakol, O.; Fuess, H.; Crystal structure of bis (N,N‘-dimethylformamide)(µ-acetato)[µ-(N,N‘-bis(salicydene)-2-hydroxy-1,3-pro-panediamine]-nickel(II)cadmium(II), Main Group Met. Chem. 24 (2001) 313-314. Paszkowicz, W.; Knapp, M.; Domagala, J. Z., Kamler, G., Podsiadlo, S., Low-temperature thermal expansion of Mg3N2, J. Alloys Comp. 328 (2001) 272-275. Pelka, J. B.; Paszkowicz, W.; Dluzewski, P.; Brust, M.; Kiely, C. J.; Knapp, M.; Czerwosz, E.; Characterisation of thin films containing Au and Pd nanoparticles by grazing incidence X-Ray diffraction and related methods, J. Alloys Comp. 328 (2001) 248-252. Poth, T.; Paulus, H.; Elias, H.; Dücker-Benfer, C.; van Eldik, R; Kinetics and mechanism of water substitution at half-sandwich iridium(III) aqua cations Cp*Ir(A-

B)(H2O)2+/+ in aqueous solution (Cp*=η5-pentamethylcyclopentadienyl anion; A-B = Bidentate N,N or N,O ligand), Eur. J. Inorg. Chem. (2001) 1361-1369. Roth, C.; Martz, N.; Fuess, H.; Characterization of different PtRu catalysts by X-ray diffraction and transmission electron microscopy, Phys. Chem. Chem. Phys. 3 (2001) 315-319. Roth, C.; Götz, M.; Fuess, H.; Synthesis and characterisation of carbon-supported Pt-Ru-WOx catalysts by spectroscopic and diffraction methods, J. Appl. Electrochem. 31 (2001) 793-798. Saitoh, K.; Tsuda, K.; Terauchi, M.; Tanaka, M.; Distinction between space groups having principal rotation and screw axes, which are combined with twofold rotation axes, using the coherent convergent-beam electron diffraction method, Acta Cryst. A 57 (2001) 219-230. Sari, M.; Dormus, S.; Atakol, O.; Svoboda, I.; Fuess, H.; Bis[µ-N,N‘-bis (salicilidene)-1,3-propandiamine-cooper(II)diiodolead(II), Acta Cryst. E 57, (2001) m201-m203. Sigmund, J.; Saglam, M.; Vogt, A.;. Hartnagel, H.L.; Buschmann, V.; Wieder, T.; Fuess, H.; Microstructure analysis of ohmic contacts on MBE grown n-GaSb and investigation of submicron contacts, J. Cryst Growth 227-228 (2001) 625-629. Sondergeld, P.; Fuess, H.; Ishihara, H.; Schmahl, W. W.; Multiple twinning of (Et4N)2ZnCl4, Z. Kristallogr. 216 (2001) 462-469. Spange, S.; Gräser, A.; Müller, H.; Zimmermann, Y.; Rehak, P.; Jäger, C.; Fuess, H.; Baehtz, C.; Synthesis of inorganic/organic host-guest hybrid materials by cationic vinyl polymerization within Y zeolites and MCM-41, Chem. Mater. 13 (2001) 3698-3708. Staub, U., Shi, M.;. O’Connor, A.G.; Kramer, M.J.; Knapp, M.; Site-specific electronic structure of Pr in Pr1+xBa2-xCu3O7-δ, Phys. Rev. B 63 (2001) 134522-134527. Strunz, P.; Mukherij, D.; Gilles, R.; Wiedenmann, A.; Fuess, H.; Determination of γ‘ solution temperature in Re-rich Ni-base superalloy by small-angle neutron scattering, J. Appl. Cryst. 34 (2001) 541-548. Svoboda, I.; Arici, C.; Nazir, H.; Dormus, Z.; Atakol, O.; Fuess, H.; -N-N‘-Bis(salicylidene)-2,2‘-dimethyl-1,3-propanediamine](piperidine) copper(II) dibromo-zinc(II), Acta Cryst. E 57 (2001) m584-m586. Toimil Molares, M. E.; Brötz, J.; Buschmann, V.; Dobev, D.; Neumann, R.; Scholz, R.; Schuchert, I. U.; Trautmann, C.; Vetter, J.; Etched heavy ion tracks in polycarbonate as templates for copper nanowires, Nucl. Instr. Meth. B 185 (2001)192-197. Vasylechko, L.; Savytskii, D.; Matkovski, A.; Berkowski, M.; Knapp, M.; Bismayer, U.; Room and high temperature structures of the La1-xNdxGaO3 (x=0.27 and 0.37) perovskites determined by synchrotron X-ray diffraction, J. Alloys Comp. 328 (2001) 264-271.

Vasylechko, L.; Niewa, R.; Borrmann, H.; Knapp, M.; Savytskii, D.; Matkovski, A.; Bismayer, U.; Berkowski, M.; R-3c-Pbnm phase transition of La1-xSmxGaO3 (0<x<0.3) perovskites and crystal structures of the orthorhombic and trigonal phases, Solid State Ionics 143 (2001) 219-227. Yamada, L.; Tsuda, T.; Holst, C.; Okuda, T.; Ehrenberg, H.; Svoboda, I.; Fuess, H.; Characteristic Phase Transition of [C5H5NH]SbBr4 Having a Hypervalent Bond Studied by Single Crystal X-Ray Diffraction and 2H NMR, Bull. Chem. Soc. Jpn. 74 (2001) 77-83. Yonkeu A. L.; Buschmann, V.; Miehe G.; Fuess, H.; Goossens, A. M.; Martens, J. A.; Structural characterisation of a new “core-shell” zeolite overgrowth system: faujasite on micro sized EMT-crystals, Crystal Engineering 4 (2001) 254-267.

Chemical Analytics We are active in the following fields: Corrosion phenomena

High temperature corrosion of iron- and nickel-based PM-ODS superalloys Corrosion of graphite tube assemblies in atomic absorption spectrometry Corrosion of metals in polymer technology Corrosion of vessel materials for ultratrace analysis Corrosion of medieval glasses

PM-technology Investigations of the reduction process of MoO3 by hydrogen Surface chemistry of water atomized aluminium alloy powders Effect of trace impurities in hard metals

Particle characterization Single particle characterization mainly by electron probe methods of – environmental particles – industrial aerosols for occupational health evaluation – wear particles in polymer technology (in co-operation with the DKI) – Diesel soot from Otto- and Diesel-engines (Prof. Hohenberg, Department of

Mechanical Engineering)

Process analytics Development of a fast and simple method for the determination of toxic metal traces in industrial waste waters Fast materials identification by X-ray fluorescence analysis including the Compton scattering and statistical principal component analysis (Merck, Darmstadt)

Analytical methods development Development of a portable µ-XRS with polycapillary optics and drift chamber detector for cultural and forensic applications

Wear studies Study of the wear process of cutting of compacted graphite iron used for high compression Diesel motors (Production Engineering and Machine Tools, Department of Mechanical Engineering)

Activation analytical techniques Particle induced gamma-ray emission, charged particle activation analysis and neutron activation analysis techniques for the determination of fluorine, boron, and of other elements in human bone samples (IAEA Vienna)

Staff Members Head

Prof. Dipl.-Ing. Dr. techn. Hugo M. Ortner

Research Associates Dr. Christiane Brockmann Dr. Stefan Flege Dr. Martin Heck

Dr. Peter Hoffmann Dr. Thorsten Kessler Dr. Chaturvedula Sastri

Technical Personnel

Dorothea Berres

Brunhilde Thybusch

Secretary

Antje Pappenhagen

PhD Students

Dipl.-Ing. Roy T. Fox Dipl.-Ing. Burkhard Höflich

Dipl.-Ing Jamila Saroukh

Guest Scientists

Prof. Dr. E. Bulska, Dept. of Chemistry, Univ. of Warsaw, Poland Dr. Anatol Dedik, Inst. of Technical Physics of the Ukrainian Academy of Sciences, Charkow, Ukraine Dipl.-Ing. Canan Ekinci Dogan,. Technical Univ. of Istanbul, Turkey Prof. Dr. P. Munkhbaatar, Mongolian Univ. of Science and Technology, Ulaan Baatar, Mongolia Dr. K. S. Patel, Univ. of Raipur, India

Research Projects Quantification of wear in extruders for polymer production by continuous and time resolved X-ray fluorescence analysis (AiF, German Plastics Inst., Darmstadt, 2000-2002) Analytical investigations on graphite corrosion in electrothermal atomic absorption spectrometry ( in co-operation with the Inst. for Analytical Chemistry, Univ. of Warsaw and the Dept. of Chemistry, Federal Univ. of Santa Catarina, Florianopolis, Brazil, since 1996) Single particle characterization of industrial aerosols for occupational health evaluation (National Inst. of Occupational Health, Oslo, Norway, since 1998) Investigations on the wear of cutting tools on the basis of cubic boron nitride during machining of cast iron with vermicular graphite (co-operation with the Inst. of Production engineering and Machine Tools, Faculty of Mechanical Engineering of the Darmstadt Univ. of Technology and SinterCast Inc., Clarkston, USA, 1998-2001) Bulk- and topochemical investigations of trace contaminations in organic semicon-ductor materials (co-operation with the group for electronic properties of materials in our department, DFG, 1999-2003)

Determination of the morphology, size distribution, elemental and phase composition of particles from various sources (BMBF, 1998-2002) Particle induced gamma-ray emission, charged particle activation analysis and neutron activation analysis techniques for the determination of F, Cu, Zn, B, and of other elements in human bone samples (IAEA Vienna; 2001-2002) Solid sampling analytics with atomic absorption spectrometry and laser ablation ICP-OES (E. Merck KGaA, Analytical Research, 2001-2002)

Publications Bichlmeier, S.; Janssens, K.; Heckel, J.; Gibson, D.; Hoffmann, P; Ortner, H. M.; Component Selection for a Compact Micro--XRF Spectrometer, X-Ray Spectr. 30 (2001) 8-14. Hoffmann, P.; Dedik, A. N.; Deutsch, F.; Ebert, M.; Hein, H.; Hoffmann, H.; Lieser, K. H.; Ortner, H. M.; Schwarz, M.; Sinner, T.; Weber, S.; Weidenauer, M.; Weinbruch, S.; Iron in the Atmosphere, in: Jaenicke, R. (ed.), Dynamics and Chemistry of Hydrometeors. Final Report of the Collaborative Research Centre 233 "Dynamik und Chemie der Hydrometeore", Wiley VCH, DFG, Weinheim, Bonn (2001) 440-467. Wohlgemuth, J.; Pfäfflin, D.; Jaeschke, W.; Deutsch, F.; Hoffmann, P.; Ortner, H. M.; Photochemical Formation of Hydrogen Peroxide in Atmospheric Droplets: The Role of Iron, Oxalate and Trace Metals on The H2O2-Production, in: Jaenicke, R. (ed.), Dynamics and Chemistry of Hydrometeors, Final Report of the Collaborative Research Centre 233, "Dynamik und Chemie der Hydrometeore", Wiley VCH, DFG, Weinheim, Bonn (2001) 346-362. Heil, H.; Steiger, J.; Karg, S.; Gastel, M.; Ortner, H. M.; Seggern, H. von; Stössel, M.; Mechanisms of Injection Enhancement in Organic Light-Emitting Diodes Through an Al/LiF-Electrode, J. Appl. Phys. 89 (2001) 420-424. Hoche, H.; Scheerer, H.; Flege, S.; Broszeit, E.; Berger, C.; Ortner, H. M.; PVD-CrN coated Magnesium Alloy AZ91hp and Steel 100Cr6- Investigations on the Influence of the Substrate Materials on Coating Properties, Mat.-Wiss. u. Werkstofftech. 32 (2001) 1-7. Wagner, B.; Bulska, E.; Hulanicki, A.; Heck, M.; Ortner, H. M.; Topochemical Investigation of Ancient Manuscripts, Fresen. J. Anal. Chem. 369 (2001) 674-679. Deutsch, F.; Hoffmann, P.; Ortner, H. M.; Field Experimental Investigations on the Fe(II)- and Fe(III)-Content in Cloudwater Samples, J. Atmosph. Chem. 40 (2001) 87-105. Bulska, E.; Thybusch, B.; Ortner, H. M.; Surface and Subsurface Examination of Graphite Tubes After Electrodeposition of Noble Metals for Electrothermal Atomic Absorption Spectrometry, Spectrochim. Acta Part B 56 (2001) 363-373.

Deutsch, F.; Hoffmann, P.; Ortner, H. M., Comparison of the Concentrations of Chemical Components in Cloudwater Samples Collected During Four Different Field Campaigns, J. Atmosph. Chem. 40 (2001) 295-304. Reiff, F.; Bartels, M.; Gastel, M.; Ortner, H. M., Investigation of Contemporary Gilded Forgeries of Ancient Coins, Fresen. J. Anal. Chem. 371 (2001) 1146-1153. Kemmler, B.; Hoffmann, P; Cremer, M.; Ortner, H. M.; Mennig, G., Quantification of corrosion phenomena in plastic processing machines, Fresen. J. Anal. Chem. 371 (2001) 874-881. Patel, K. S.; Shukla, A.; Goswami, A.; Chandavanshi, S. K.; Hoffmann, P.; A new spectrophotometric method for the determination of total and ferric iron in rain water at the ppb level, Fresen. J. Anal. Chem. 369 (2001) 530-534. Ebert, M.; Weinbruch, S.; Rausch, A.; Gorzawski, G.; Wex, H.; Hoffmann, P.; Helas, G., The complex refractive index of aerosols during LACE 98 as derived from the analysis of individual particles, J. Aerosol Sci. 32 (2001) 683-684. Patel, K. S.; Shukla, A.; Agarwal, N.; Hoffmann, P.; Visible Spectrophotometric Deter-mination of Tantalum in Soil, Sediment, Minerals and Alloys. J. AOAC Int. 84 (2001) 399-405. Sastri, C. S.; Iyengar, V.; Blondiaux, G.; Tessier, Y.; Petri, H.; Hoffmann, P.; Aras, N. K.; Zaichick, V.; Ortner, H. M.; Fluorine determination in human and animal bones by particle-induced gamma-ray emission, Fresen. J. Anal. Chem. 370 (2001) 924-929. Hoffmann, P.; Kessler, T.; Ortner, H. M.; Identifikation von Substanzen durch chemo-metrische Auswertung von EDRFA-Spektren, 8. Anwendertreffen Röntgenfluores-zenz- und Funkenemissionsspektrometrie, Steinfurt, 2001 (2001) 80-92. Ortner, H. M.; Sterkel, S.; Knapp, G.; Maichin, B.; Kettisch, P.; Kocsis, L.; Mihaly, J.; Mink, J.; High-Purity Quartz Vessels for Digestive Sample Preparation, Mikrochim. Acta 137 (2001) 229-241. Ortner, H. M.; Die Bedeutung der Analytik für die Materialwissenschaft und die materialerzeugende Industrie, Thema Forschung 2 (2001) 142-155.

Theoretical Materials Science Teaching by this Division addresses the atomistic foundations of materials science, including the concepts underlying their representation, from the theoretical physics point of view. Research focuses on materials modelling, being a powerful tool for materials development. Experimental results will be understood - and predictions of further observations given - in the light of theoretical evidence, both to aid the optimization of the properties or the performance of materials which already exist and to guide the design of new materials with properties, or behaviour, required in future engineering applications. Modelling transition metals and related alloys, high-temperature superconductors and organic dielectrics lies at the heart of current activities. For the first class of materials, represented by tantalum and ferritic/martensitic steels, the goal is examining their suitability for structural components of high-power spallation neutron sources that are exposed to the intense proton beam. Irradiation-induced hydrogen production under the operating conditions of the envisaged European spallation source is predicted to generate high internal concentrations of atomic hydrogen which, further enhanced by stress-driven hydrogen accumulation near microstructural cracks, may lead to a severe degradation of the mechanical properties of steel, whereas no noticeable deterioration is to be expected in the case of tantalum. For the second class of materials, typified by YBa2Cu3O7 and Bi2Sr2Ca2Cu3O10 in thin film or bulk form, great interest is directed towards investigating extended defects, e.g. low-angle grain and twin boundaries which are considered as weak-links between superconducting grains. There are two principal aims: (i) exploring the connection between the electromagnetic response (e.g. the current-voltage relation) and the characteristic defect morphology so as to obtain insight into constitutive parameters of superconducting films; (ii) searching for possibilities to improve the current-carrying capability of superconducting bulk materials, which is limited by the above-mentioned types of defect. Preliminary studies of novel heterostructures involving superconductor strips with a single grain boundary defect, placed in open magnetic cavities, show that magnetic shielding here is a promising way forward. Finally, for the third class of materials, represented by Alq3, emphasis is on real-time modelling of charge transport by injected carriers and thermally stimulated luminescence phenomena with the aim of extracting, in conjunction with experiments, information about the electronic structure of inherent traps, thereby assisting technological exploitation and further materials development. The theories underlying these investigations range from microscopic to macroscopic; their realization employs analytical as well as computational techniques.

Staff Members Head Prof. Dr. Hermann Rauh, M.A., C.Phys., F.Inst.P., F.I.M., O.I.A. Research Associate Dr. Yuri A. Genenko Secretary N.N.

Visiting Scientists Dr. Carsten Rieck, Theoretical Physics, Univ. of Hamburg Prof. Dr. Hans Ullmaier, Solid State Research, Research Centre Jülich

Publications Rauh, H.; Ullmaier, H.; Hydrogen Concentrations near Cracks in Target Materials for High-Power Spallation Neutron Sources, J. Nucl. Mater. 295 (2001) 109-120. Genenko, Y. A.; Rauh, H.; Snezhko, A., A Novel Magnet/Superconductor Hetero-structure for High-Field Applications, Supercond. Sci. Technol. 14 (2001) 699-703.

Reports of Research Activities

Fatigue crack growth in titanium with functionally graded microstructure

C. Müller, B. Burghardt

A quantitative model is presented for describing fatigue crack growth in materials with a microstructural gradient in the presence of roughness induced crack closure. Size gradients of microstructural features (lamellae packages) were obtained by recrystallization in a temperature gradient after introducing a deformation gradient into TIMETAL1100 with lamellar microstructure. The local package width, B, increases over a length of 20 mm from 50 µm at high deformation and a recrystallization temperature of 1012 °C to 150 µm at the lowest deformation and 1025 °C, and can be described by

B = B0 + c1 l (1)

where l is the distance from beginning of the graded microstructure (0 < l < 20 mm), B0 is the package width at l = 0 mm and c1 = 4,3 · 10-3.

Fracture surfaces in the lamellar microstructures show fracture along crystallographic facets (Fig. 1) resulting from crystallographic crack growth induced by planar slip. The surface roughness is described by the standard deviation of height distribution, SH. As shown in Fig. 2, SH increases with increasing lamellae package width but is independent of the applied load as well as of the crack growth direction. Thus, surface roughness is constant for homogeneous microstructures over the entire fracture surface. In the graded material SH increases from 10 µm at l = 0 mm (package width B0 = 50 µm) to 44 µm at l = 20 mm (B = 150 µm) and can be described in the range 50 < B < 150 µm as

SH = SH0+c2 (B - B0) (2)

where SH0 = 10 µm and c2 = 0,34.

In graded microstructures, the well established Paris law relating crack velocity to stress intensity ((da/dN - ∆K) curves) is not the appropriate way to describe the crack propagation behaviour, owing to the fact that the curve becomes dependent on crack length.

Fig. 1. Fracture surfaces of TIMETALL 1100. The average width of lamellae packages are 50 µm (a) and 150 µm (b).

40 60 80 100 120 140 160

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Fig. 2. Standard deviation of the height distribution, SH, as a function of lamellae pack-age width, B, for homogeneous and graded microstructures.

Fig. 3. Crack length versus number of cycles (a – N) curve of the graded microstructure: Compari-son of experimental data and calculated function.

In contrast to homogeneous microstructures, many curves exist for one graded microstructure, depending on the testing conditions such as the applied load interval ∆F, the initial crack length ai, or the specimen size. The crack growth behaviour of graded microstructures can be calculated from (da/dN - ∆K) curves of only two homogeneous microstructures, provided that it behaves locally identically to the corresponding homogeneous microstructure. This assumption is a reasonable one for microstructures exhibiting roughness induced crack closure. Crack growth curves were determined for the two homogeneous materials with ∆F held constant whereby ∆K increases due to the increasing crack length. Crack propagation rates in the coarse microstructure are lower than in the fine microstructure. The parameters of the Paris law were obtained by numerical integration in an iterative process according to ASM standard procedure. The crack propagation rate in graded microstructures can now be described as a function of the applied stress intensity range, ∆K, by da/dN = c(B) ∆K m(B) (3) where, for the material studied here, c(B) = 1,8 · 10-13 exp (-1,06 · 104 B) and m(B) = 4.7 (as m is independent of the lamellae package width). In order to determine the (a - N) curve for graded materials, the lamellae package width is described as a function of the crack length. We obtain B = B0 + c1 (a - a0) (4) and

da/dN = 1,8 · 10-13 exp [-1,06 · 104 (B0 + c1 (a-a0))] ∆K 4,7 (5) By numerical integration of equation (5) the (a – N) curve was calculated for crack growth in the graded microstructure for an initial crack length ai = 9,58 mm and a constant load interval ∆F = 1,13 kN. As shown in figure 3, the calculated curve is in excellent agreement with the experimentally obtained data.

Al/SiC composites for electronic packaging applications by pressureless infiltration

B. Srinivasa Rao, J. Rödel

Packaging of high density integrated circuits is currently driven by miniaturisation and portability. Traditional packaging materials such as Kovar (Ni-Fe based alloy) no longer meet the heat dissipation requirements although it has a low coefficient of thermal expansion (5.9 ppm/ºC). In addition to a low coefficient of thermal expansion (CTE) and high thermal conductivity, weight of the package has become a major factor in designing electronic packages for airborn applications such as aircraft, spacecraft and satellites. These factors made packaging designers to look for alternate materials such as Al/SiC which not only possess the requisite properties such as low CTE matching with that of a semiconductor, and dielectric materials, used as substrates, and high thermal conductivity (160-180 W/m K) but also has low density (3 g/cm3 which is only 35% of the density of Kovar, 8.4 g/cm3). The CTE of Al/SiC can be tailored anywhere between 5-18 ppm/ºC by changing the Al:SiC ratio in the composite while maintaining a thermal conductivity of 160-180 W/m K which makes it very attractive for the package designer as greater flexibility is available in terms of choosing components with different CTE for different parts of the package. Currently, Al/SiC electronic packages are being used in a variety of applications such as cellular phone base stations, laptop computers and in communication and power systems in satellites, aircraft and spacecraft.

Fig. 1. CTE of Al/SiC as a function of vol% SiC (0-100ºC).

Al/SiC composites, with a SiC volume fraction in the range of 50-70%, for electronic packaging applications are mainly produced by infiltration, pressure assisted (squeeze casting) or pressureless, of molten Al or Al-alloys into porous SiC preforms. The ability of pressureless infiltration in producing near net or net shaped components cost effectively gives it a distinct advantage over pressure infiltration which requires expensive tooling and equipment. Pressureless infiltration of Al-alloys into ceramic preforms was first reported to be possible only in the presence of pre-

5.6 5.6

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55 65 67

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alloyed Mg and a nitrogen atmosphere. However, Srinivasa Rao and Jayaram at the Department of Metallurgy, Indian Institute of Science, Bangalore, India, devised a new technique of pressureless infiltration which overcomes the above mentioned two restrictions, pre-alloying Al with Mg and maintaining a N2 atmosphere, thereby making it possible to infiltrate Al-alloys into porous SiC preforms in air. In principle, Al-alloys without any pre-alloyed Mg can be infiltrated into ceramic preforms, presence of Mg in the alloy increases the rate of infiltration. Prototype Al-alloy/SiC electronic packages have been produced by infiltrating Al-5 wt% Mg-15 wt% Si alloy into 55, 65 and 67 vol% SiC preforms by this new technique. Such a high percentage of Si is required in the alloy to prevent the formation of deleterious Al4C3 at the SiC/Al interface. It also reduces the CTE and increases the thermal conductivity although it makes the composite more brittle. The thermal expansion coefficient of these composites is 8.5 ppm/ºC and 5.6 ppm/ºC, respectively, as shown in Fig. 1.

Fig. 2. Microstructure of Al / 67% SiC composite.

The microstructure of Al / 67 vol% SiC composite is shown in Fig. 2. SiC particles of 76-12345-6789 :6.1-achieve such a high volume fraction by cold pressing which was not possible when a single particle size (25-67 , ; < ; =7> ? being tested by the Indian Space Research Organisation for replacing the Kovar Carrier plates currently being used for supporting the microwave integrated circuit substrates in its communication satellites. Thermal expansion and thermal diffusivity behaviour of these composites over a temperature range of 20-300ºC are currently being studied.

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Fig. 1. Comparison of PSL after neutron and γ-irradiation, for samples displaying only PSL(n) the PSL(γ) was not determined; PSL(γ) superimposed on the PSL(n) intensity.

Materials for neutron image plates with low γ-sensitivity

M. Schlapp, H. von Seggern

Neutron image plates provide a mean for the two-dimensional, position-sensitive detection of neutrons. They consist of a neutron converter and a storage phosphor dispersed in an organic binder supported on a polymer sheet. After absorbing a neutron, the converter emits ionising radiation which can create electron/hole pairs in the storage phosphor. These pairs either recombine giving rise to spontaneous luminescence or generate defects acting as storage centres for both electrons and holes. Holes are stabilised in the vicinity of divalent activator Eu2+-ions and electrons are trapped in anion vacancies forming colour centres. The spatial distribution of these PSL centres represents a latent image of the lateral neutron exposure. Upon photostimulation, electrons are liberated from the traps and subsequently recombine with holes resulting in a characteristic activator emission which can be detected. Several ways have been proposed to make x-ray image plates sensitive to neutrons. Today a mixture of BaFBr:Eu2+ as storage phosphor and Gd2O3 as converter is most widely used and commercially available. The disadvantage of BaFBr:Eu2+ as x-ray storage phosphor is its high γ-sensitivity in neutron experiments with a significant γ-background. One way, besides shielding the image plate with lead, is the use of storage phosphors with a smaller effective atomic number which results in a lower γ-sensitivity due to smaller absorption. Two promising candidates are presently known: KCl:Eu2+ and KBr:Eu2+ which have already be demonstrated to be applicable as x-ray, electron beam and UV storage phosphors.

In order to compare the neutron and γ-ray sensitivity of the samples, the intensity at the photostimulation peak maximum was taken as a measure. Furthermore, the PSL intensity was normalised to the fraction of neutrons absorbed by the sample to obtain the PSL signal per ab-sorbed neutron. While the PSL(n) was measured for all samples, the determination of γ-sensitivity was done only on selected samples (see dark-grey bars in Fig. 1). Three different storage phosphors (BaFBr:Eu2+, KCl:Eu2+ and KBr:Eu2+) with two different con-verters namely GdF3 and LiF were investigated. From Fig. 1 it can be seen that BaFBr:Eu2+ samples show the highest PSL(n) when a fraction of 35 mol% GdF3 was added, while for LiF a maximum is reached at 70 mol%. These results are in good agreement with those published by Thoms et al. but differ slightly from those published by

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Takahashi et al. The same dependence can also be observed for potassium halide samples. In case of neutron capture occurring at the 6Li-ions an amount of 4.79 MeV usable energy is set free by 3H and 4He particle emission while for Gd with an total energy yield of up to 8.54 MeV only one conversion electron with an average energy of 70 keV can be used to create defects in the phosphor. The PSL output per absorbed neutron could ideally be 68 times higher for Li than for Gd converters. However, the samples measured show only a factor of 10. This can be attributed most probably to two reasons: firstly, not all absorbed neutrons can be detected due to the limited range of the read-out beam, which in our case was less than the thickness of the powder (1 mm). This can be improved when 6LiF is utilised instead of natLiF resulting in a higher absorption close to the surface. Secondly, a strong self-absorption of secondary particles has to be expected. This can be understood by a comparison of the voids generated by the packing of the phosphor grains filled with converter material and the range of the 3H and 4He particles being only 5–35 µm in the materials investigated. From these arguments the use of smaller storage phosphor particles would be favourable. This, however, counteracts the optical penetration depth of the read-out beam. In addition, the PSL sensitivity is diminished with decreasing grain size. In order to determine the n/ γ-ratio, the γ-sensitivity of various samples was measured. The PSL(γ) of selected specimens is indicated in Fig. 1. The n/ γ-ratio displayed in Fig. 2 is derived from the PSL of neutrons divided by the PSL arising from γ-rays only. The here determined n/ γ-ratio only allows a relative comparison of different detector materials.

The different n/ γ-ratios can be interpreted as follows: From Fig. 1 it is evident that the PSL(γ) is mainly dependent on the fraction of storage phosphors in the mixture and less from the type of the neutron converter. This is basically valid for all three phosphors utilised. The maximum difference is in all cases less than a factor of two. The large difference in the n/ γ-ratio can therefore only result from a large difference in neutron-sensitivity. This difference results from a higher PSL output for 6Li converters compared to Gd converters due to the higher usable energy output of the respective conversion process. The actual difference in the n/ γ-ratio amounts to a factor of 2-8 in favour of the 6Li converters which is in agreement with calculations by Masalovitch et al. Summarising it can be stated that in KCl-LiF a high neutron sensitivity as well as a low γ-sensitivity are combined establishing the base for a very attractive detector material for neutron image plates, especially to be used in experiments in surroundings with a high γ-background.

Device architecture for Eu(dbm)3phen based red emitting OLEDs

H. Heil, J. Steiger, R. Schmechel, H. von Seggern

A great challenge in field of organic light emitting diodes (OLEDs) is the realization of an efficient pure red light emitting diode with a narrow emission line. Such an emitter is very useful for completing a full color display based on the principle of additive color mixing. One way to tackle the problem is to use an metal-organic Eu-complex in which the Eu3+ ion acts as the emission center. The spectral properties of Eu3+ are ideal for the use in full color displays as known from inorganic luminescent materials in cathode-ray and projection television tubes. This work concentrates on the efficient integration of a given Eu-complex into an OLED structure. In order for such a molecule to be excited three principle mechanisms are considered: (a) The dye is excited by an energy transfer from the host to the dye molecule. In this case an exciton has to be formed within the emitting layer whose energy is transferred resonantly to the dye molecule. A spectral overlap between the emission band of the host and the absorption band of the dye is necessary. However, this precondition is not realized by the here given compounds. (b) The dye becomes excited by charge transfer from the host, meaning an electron and a hole are transported separately to combine on the dye molecule which then acts as a recombination center. This requires an attractive force to either electrons or holes to be captured by the dye molecule. Thermodynamically such an attractive force is given, if the HOMO of the dye lies above and the LUMO below the HOMO and LUMO of the host transport material, respectively. If one of the charge carriers is trapped in the energetically favored HOMO or LUMO (trap), the other if present in the layer has a higher probability to recombine on the dye. Exact this excitation mechanism was realized by the structure a) of Fig. 1. The hole blocking layer was chosen to shift the recombination zone into the hole transport layer (HTL), were the doped dye molecules forms an electron trap state.

Fig. 1. Realized device structures

HTLα-NPD+ -

Emission layer(host+3% dye)

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(c) The emission layer is composed of the pure dye. The dye becomes excited by first injection of electrons and holes into the emission layer and second reunion of the charge on the dye molecule. This was realized by device structure b) in Fig. 1. The excitation of the dye is most efficient if the carrier injection into the layer is balanced. Since there is no barrier for holes to travel from the dye layer into the electron transport layer (ETL) in the device b), an additional charge blocking layer can be incorporated to fix the injected charge carriers in the emission layer and to control the charge carrier balance, as it was realized in device structure c) of Fig. 1. In principle device a) in Fig.1 is working quite well, however, there is a basic problem with Eu3+ based emitters: Due to a long life time of about 0.3ms the excited state 5D0 can quickly be filled and the emission accordingly saturated. The electrons and holes tend to recombine in the normal matrix, which causes a blue emission from the HTL α-NPD (see Fig.2). The following short quantitative calculation shows clearly that the saturation in device a) of Fig.1 is possible: The total number of Eu3+ ions in the HTL per cm2 is of the order of n = 1014cm-2. The lifetime of the excited state was determined to be τ = 0.3ms. Therefore the maximum current density I which can be caused by recombination on the Eu ions is:

20 53 cmmA

neI ==

τ (1)

This maximum current density is exceeded under normal driving conditions. To overcome this problem only the density of Eu3+ can be increased. This leads to the device structure b) in Fig.1 with a pure emitting layer. However, the emission spectra of this OLED (Fig.2) shows beside the desired red emission of Eu3+ additionally a green Alq3 emission around 550nm. This indicates that some holes can travel through the whole emission layer and recombine with the electrons in the electron transport layer (ETL).

To prevent the through put of holes through the emission layer a hole blocking layer was inserted in device c) of Fig. 1. Under this condition finally a pure red Eu3+ emitting OLED was achieved as can be seen in Fig. 2. The resulting light output could be further increased by four times by doping the emission layer with hole transport materials (device d) in Fig.1). This makes the injections of holes into the dye layer easier. The devices are not tuned with respect to layer thickness.

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In situ CdCl2-Activation of the CdS/CdTe-Heterojunction

T. Schulmeyer, J. Fritsche, A. Thißen, A. Klein, W. Jaegermann, M. Campo* and J. Beier*

ANTEC Technology GmbH, Arnstadt, Germany Polycrystalline thin film solar cells like CdTe/CdS-cells have the advantage of reasonable conversion efficiencies (CdTe: @ 10 %) combined with a low-cost production process. For this reason, these cells have been intensively investigated during recent years and have reached the edge to production. CdTe thin film solar cells as prepared by ANTEC are composed of the layers glass/ITO(indium tin oxide)/CdS/CdTe/metallic back contact (Fig. 1). CdS and CdTe are deposited onto glass/ITO substrates by close-space sublimation. After the deposition of the CdTe an empirical ‘magic’ production step, a thermal activation of the CdTe film with CdCl2, follows. Without activation, no conversion efficiency can be achieved. The reason for the increase in efficiency is still not understood. In this work, the activation-process has been simulated in ultrahigh vacuum (UHV) for the first time. Thus a systematic investigation of the influence of the activation-step by X-ray induced photoelectron spectroscopy (PES) (XPS, hν = 1486.6 eV) was possible. For a simulation of the activation-step inside UHV, the crucible of the CdCl2-source and the surface of the CdTe-sample should provide a closed system. The experimental setup during the activation-step is shown in Fig. 2.

From these self activated samples complete solar cells have been prepared by ANTEC. So it has been possible to record current/voltages characteristics of the cells and to determine the efficiencies. In Fig.3 a I/V-characteristic of a non- and an UHV-activated sample is shown. After activation a maximum efficiency of 9.1 % has been reached. It is thus demonstrated that the UHV activation leads to the results similar to the activation in the production-line showing the technological relevance of the model experiment.

sample heating

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Fig. 2. CdCl2-source and CdTe-sample during the UHV activation process.

Fig. 1. Schematic diagram of the layer-sequence of a typical ANTEC solar-cell.

CdS - 150 nm

metallic back contact 250nm

glass substrate

Te - 20 nm

CdTe - 8 µm

ITO - 240 nm

SnO2 - 30 nm

For the investigation of the CdS/CdTe-Heterojunction thin CdTe-films with a thickness of about 50 nm have been used. The CdS- and CdTe-layer has been deposited by physical vapour deposition onto SnO2/ITO/glass substrates as used by ANTEC. The activation-process has been carried out in a temperature range from 420 to 450 °C. Activated and non-activated CdTe/CdS/SnO2/ITO-layers have been investigated by X-ray photoelectron spectroscopy (XPS) including depth profiling using Ar+-ion sputtering. The integral intensities of the element-resolved emission lines represent the elemental concentration of the sample surface. A depth profile of Tellurium and Sulphur of an activated and a non-activated sample is shown in Fig. 4. It is clearly seen that the activation process leads to an intermixing zone between the CdTe- and the CdS-layer.

The energy differences between the S 2p or the Te 4d and the valence band maxima of CdS and CdTe are known from reference experiments. Thus the relative position of the Fermi-level with respect to the VBM is accessible from the spectra. A valence

Fig. 4. Sputter depth profile of Tellurium and Sulphur intensities of activated and non activated CdS/CdTe heterointerfaces. The activation leads to an interdiffusion at the interface.

Fig.3. IV-Characteristics of a non-activated and an UHV-activated sample. The UHV-activated sample reached an efficiency of 9,1 %.

band offset of 0,94 eV ± 0,12 eV is found for both non activated and activated samples. Therefore no influence of the activation is visible. The evolution of the valence band maxima, as calculated from the spectra, is shown in the left part of Fig.5. In the right part the derived band alignment of the CdS/CdTe-heterojunction is shown. Fig. 5. Evolution of the Fermi level position in the band gap (left) and band alignment of the CdS/CdTe-heterojunction (right).

Chemical Analysis of Electrochemically Modified Semiconductor Surfaces by Synchrotron Induced Photoelectron Spectroscopy

T. Mayer, M. Beerbom, J. Ell, W. Jaegermann

Wet chemical processes are widely applied in semiconductor device production because unique properties of surfaces and interfaces may be reached and costs are low as compared to vacuum processing. A detailed characterization of the chemical composition of surfaces after electrochemical treatment with modern UHV surface science techniques is hindered by the pressure gap and contamination when electrodes are emersed from the electrolyte and transferred into the UHV analysis chamber. Therefore, we have directly attached an electrochemical cell to a UHV system, allowing for wet chemical processing under clean inert gas atmosphere and transfer into UHV without exposure to ambient air. This preparation cell is used either in our laboratory with an X-ray excitation source or it is transferred to the synchrotron facility BESSY. A drop of the solution is deposited on top of the sample surface and, in the case of electrochemical preparation, the counter and reference electrodes are immersed into the drop. After preparation the liquid is blown off by a jet of N2 gas and the sample is transferred to a buffer chamber which is rapidly pumped down.

Fig. 1. GaAs (110) cleaved, emersed from water after 2s and after additional 3min compared to H2O adsorption at 100K. As 3d and Ga 3d core level lines are displayed.

Fig. 2. Etching of an oxidized GaAs (110) surface with aqueous HCl (3%). After rinsing with water an elementary As layer with a thickness of about 2 atomic layers is left on the surface.

Synchrotron spectra obtained with this system on wet processed samples are of comparable quality as spectra taken after all vacuum processing as demonstrated for GaAs/H2O interaction displayed in Fig. 1. Here As and Ga core emissions of the UHV cleaved GaAs (110) surface, this surface emersed from deionized H2O after 2s and after additional 3min are compared to spectra taken on a different sample after adsorption of 0.5L H2O at 100K. The surface sensitivity reached is indicated by the intensity ratio of approx. 2/3 of the single layer surface emission (SCLS) to the bulk emission of the freshly cleaved sample. Despite the great discrepancy in preparation conditions, both processes give similar results namely dissociative adsorption of H2O creating a layer of As-H and Ga-OH surface molecules.

Fig. 3. GaAs / ZnSe band alignment for cleaved GaAs (110) and the HCl-etched substrate. The valence band offset is decreases by 300 meV after the electrochemical processing step.

Wet chemical surface modifications may find applications e.g. in engineering band alignments of heterojunctions. Interfaces of II-VI and III-V materials have to be optimized for optoelectronic integration. As an example we compare the band alignment of lattice matched ZnSe on GaAs (110) as obtained by XPS for CVD layers of ZnSe on cleaved and on etched GaAs samples. From the spectra displayed in Fig. 2 the chemical composition of a HCl etched sample is determined to be elementary As and some leftover Ga-oxide, which is rinsed of by deionized water. After the electrochemical processing the sample is covered with about 2 atomic layers of elementary As. As compared to the cleaved sample the valence band offset is reduced by 300 meV due to the As interlayer. The course of the bands for a cleaved n-doped and an etched p doped sample is depicted in Fig.3. Examples of technically relevant processes analyzed with this system so far are: Te back contact formation of CdTe solar cells by preferential etching of Cd, Schottky contact formation by pulse plating of Pt on GaAs wavers and electrochemical oxidation and reduction of different GaAs surfaces. The work on interface modification of III-V/II-VI heterostructures will be continued in the near future.

First Seeheim Conference On Magnetism

M. Ghafari September 9, 2001 - September 13, 200, Seeheim, Germany

The First Seeheim Conference on Magnetism (SCM 2001) was held from September 9 to 13, 2001, at the Lufthansa Training Center in Seeheim, located conveniently in Central Germany and easily accessible by air, train and car. We selected Seeheim as the location in the hope that it would help to create an informal, friendly and productive atmosphere among the researchers from throughout the world. SCM 2001 was focused on the latest developments in specific fields of magnetism (nanostructured materials, surfaces, interfaces and nanoparticles) and covered fundamental aspects of magnetism as well as applications. The most recent results were presented in the form of invited and contributed talks and posters. There were 196 registered participants from 36 countries, representing academic institutions and industries. A total number of 200 papers, correlating nanostructured and magnetic properties, were selected for presentation. Throughout the whole meeting a total of 71 talks were given and the remaining 129 papers were scheduled for poster presentations. In the session on magnetism of nanomaterials, a large number of papers were received- a satisfactory result that fulfilled the purpose of the meeting. In order to have more discussion among the researchers from different fields, the topics were not strictly divided according to subjects. The Topics areas were : - HARD AND SOFT MAGNETIC MATERIALS - MAGNETIC INTERACTIONS - MAGNETIZATION PROCESSES - SPIN-DEPENDENT TRANSPORT PROPERTIES - NANOSTRUCTURED MATERIALS - APPLICATIONS The proceedings of the conference will be published in the journal "Physica Status Solidi" as a regular issue in January, 2002. We are looking forward to welcoming again all the participants of SCM 2004 at the second Seeheim conference on magnetism, planned for 2004 at Seeheim.

Modeling Metal-Semiconductor Interaction: Analytical Bond-Order Potential for Platinum-Carbon

K. Albe, K. Nordlund*, R. S. Averback**

*Accelerator Lab, Univ. of Helsinki, Finland; **MRL, Univ. of Illinois at Urbana-Champaign, USA Realistic analytical potentials are the key ingredient of molecular-dynamics (MD) and Monte-Carlo (MC) simulations which are nowadays standard methods in the arena of computational materials science. For covalent materials as well as many metals a number of realistic potential models were developed during the past decade and successfully used in various applications. There are only a few studies, however, that deal with systems where both covalent and metallic bonds are present because of the lack of appropriate analytical potentials. On the other hand there is much interest, of course, in materials properties and processes that involve chemical interactions between metals and covalent materials, like i.e. carbon. Typical examples include the fabrication of nano-electronic sensors by growing nano-structured metallic films on semi-metallic inert substrates via cluster beam or vapor deposition techniques. By metal cluster deposition an agglomeration of confined quantum systems can be obtained, new diffusion mechanisms of huge clusters on graphite have been identified and "soft landing" as well as penetration of metal clusters has been observed. Finally, metals play a dominant role for the synthesis of carbon nanostructures where they act both as condensation seeds or as catalysts. A computationally efficient interatomic potential that realistically describes the structure and chemistry of both covalently bonded materials and metals is therefore very useful for atomistic simulations of materials processes. In this study we have devised such a potential and derived a parameter set for Pt/C. Platinum is of obvious importance for catalytic devices, but there are also several bulk and interface problems related to Pt/C. One example is the optimization of

multilayers that are used as reflector and dispersive element in the optical system of synchrotron beamlines. From a theoretical point of view, carbon and platinum are immiscible systems that do not form a carbide structure. Since the electronegativity difference of Pt and C is small, charge transfer is negligible. Therefore this system is an ideal choice for an analytical description using a short-ranged potential. Our basic formalism relies on the bond-order approach as devised by Tersoff-Abell where the total potential energy of a system is written as a sum over individual bonds:

[ ])()()(2

1ijRijijAij

jicut rVbrVrfE −= ∑

≠

Fig. 1. Fit of the Pauling energy-bond relation for Pt-C interaction (♦ ) to results from DFT-calculations and experiment (open symbols).

The bond strength is calculated from Morse-like pair-functions that describe the interatomic repulsion VR and attraction VA. The attractive term is moderated by the bond-order parameter bij that depends on the local coordina-tion, bond angles and dis-tances as well as atom types, while the range of interaction is determined by the cutoff function fcut. At this point the important insight is that covalent materials and d-transition metals both can be described within the second moment tight-binding approxi-mation. Therefore one com-prehensive analytical form is sufficient to model the Pt/C system. The decisive step in adjusting the potential para-meters is the fit of the Pauling criterion that relates equilib-rium distances and energies. In light of the sparse experi-mental information available, several quantum-mechanical calculations based on density-functional theory (DFT) were carried out to guide the fitting

of the potential. For the zinc blende (B3), CsCl (B2) and NaCl (B1) structure with a stoichiometric basis of Pt and C atoms, bond distances as well as total energies were calculated. The energetically most favored configuration is the NaCl-lattice. Additional calculations showed that the B1 and B2-phases of PtC are stable with respect to shear deformation while the zinc blende is not. The latter was therefore not considered for the potential fitting. Fig. 1 shows an example for the Pt-C interaction. Compared are DFT-results with the prediction of the analytical potential for the dimer, B1 and B2 structures. In case of Pt a wide range of experimental data can be used for adjusting the potential parameters. Table 1 gives a comparison with the data derived from the analytical bond-order potential (ABOP). Note, that only the cohesive energy, lattice constant and elastic properties were part of the fitting procedure, while defect properties, melting point and surface energies were calculated from the final parameterization. Obviously, the overall agreement is very good. An important result gleaned from this study is that short-ranged bond-order potentials offer a realistic description of thermomechanical properties for Pt and potentially of other d-transition metals. The quality of the potential is at least comparable to the modified embedded-atom method (MEAM) and gives in general better agreement with reference data, both fitted and non-fitted, than the other potential models without angularity.

Exp. ABO Ecoh (eV) 5.77 5.77 a (Å) 3.92 3.92 c11 (GPa) 358 351.5 c12 (GPa) 253 248.1 c44 (GPa) 77.4 89.5 B (GPa) 288.4 282.6 B' (5.4-5.9) 5.52 C' (GPa) 52.2 51.6 c44 /C' 1.48 1.73 Tmelt (K) 2045 2100(20) Evac (eV) 1.35 1.21 ∆Vvac /Ω -0.2 -0.33 Eint (eV) 3.5(6) 5.34 ∆Vint /Ω 1.8 1.86 Es(eV/Å2) (100) 0.11 0.123 (111) 0.09 0.091 (110) 0.24 0.119 (110)(2x1) 0.112

Table 1. Materials properties of platinum as derived using the Pt-potential of this work in comparison to experimental data. ABO is the analytical bond-order potential derived in this work. Given are cohesive energy per atom, lattice constant, elastic moduli, bulk modulus B, pressure derivative of the bulk modulus B', Young's modulus C', anisotropy ratio, melting point, vacancy formation energy and relaxation volume, interstitial formation energy and relaxation volume and surface energies for different orientations. Ω is the ideal atomic volume.

Using Brenner’s carbon potential for modeling the pure C-C inter-action several MD-simulations were carried out on basis of the new potential model. Fig. 2 shows an example of two Pt nanoclusters sintering on a (111) diamond surface at room tem-perature. The simulations reveal extremely fast thermal diffusion of the nanoclusters on this surface, while the sintering process is significantly slowed down due to the cluster-surface interaction despite of the only weak adhesion between cluster and surface.

Fig. 1. Simulation: Sintering of two Pt nanoclusters on (111) diamond at room temperature.

Introduction to the Special Topical Issue on Ultrahigh-Temperature Polymer-Derived Ceramics

Rishi Raj*, Ralf Riedel, Gian Domenico Soraru**

*Univ. of Colorado at Boulder, Colorado, USA; **Univ. of Trento, Trento, Italy

Polymer-derived ceramics (PDCs) have a polymer-like nanostructure and ceramic-like properties, e.g., creep and oxidation resistance. These unusual properties are exhibited by the ceramic in the “amorphous” state, which can persist at temperatures as high as 1800°C. This special issue contains a collection of papers on the synthesis, structure, and properties of these new and interesting materials. The systems (those recognized so far) that exhibit the nanostructure and properties of PDCs belong to two families: the silicon oxycarbides and the silicon carbonitrides. In both cases, the amorphous phases are formed in carbon-rich regimes, relative to the stoichiometric mixtures of the crystalline forms. Taken at face value, this observation implies that if all bonds were to be randomly distributed, then, in the case of the Si-O-C system, for example, all the Si atoms would be bonded to either C or O atoms, and all O atoms would be bonded to Si atoms but some C atoms would be bonded to each other. The role of this excess carbon - or “free carbon” - in the nanostructure evolution, the stability of the nanostructure, and its properties is a key question in understanding the nanostructural evolution of PDCs from the polymeric state. The organics from which the ceramics are derived often form plastics that are highly cross-linked and most likely contain ring structures. The glass-transition temperature of these plastics usually is greater than their pyrolysis temperature; therefore, shapes cut or formed in the plastic state are retained in the ceramic state. Complex forms can be made in the organic form, just prior to pyrolysis, which yield self-similar ceramic devices and components. Recently, the construction of micro-electronic mechanical system (MEMS) devices by microcasting, photopoly-merization, and printing methods has been demonstrated. The low-cost nature of this process, the wide range of structures that can be produced by it, and the multi-functionality of the materials themselves suggest vast potential for their applications in extreme environments. The transition from the plastic to the ceramic is accompanied by the release of hydrocarbons and shrinkage. Although the shrinkages are comparable to the sintering process, the gas evolution can produce cracking if the “diffusion distance” for the escaping molecules in the solid state is too great. This factor limits the processing to a length scale of <1 mm in the shortest dimension. Therefore, fibers (see Fig. 1), coatings, MEMS, and porous compacts are entirely feasible, whereas large, fully dense components are not, at least currently. Adding new properties to PDCs while retaining their high-temperature mechanical and oxidation resistance is a new edge in the rainbow of the science and technology of PDCs. An example is given in Fig. 2, which shows the semiconducting nature of silicon carbonitride (SiCN) materials. The direct organic-to-ceramic route offers possibilities for manipulating the polymeric structure and retaining its functional features in the ceramic state. The possibilities are endless; however, achieving them would require rational, scientifically based approaches that combine chemistry,

physics, and materials science. The barriers to these developments are scientific. The interdisciplinary nature of the critical issues requires new and deliberate collaborations in the field of nanoscience. Chemical designs of precursor molecules, molecular simulations, characterization of the nanostructure by spatially resolved spectroscopic methods (ranging from nuclear magnetic resonance (NMR) to electron energy-loss spectroscopy (EELS)), and the physics of materials that contain a three-dimensional dispersion of nanophases with quantum properties are examples of the crossdisciplinary issues that will chart the future science and technology of PDCs.

Fig. 1. Mechanical strength of ceramic fibers made from polymer-derived SiCN.

Fig. 2. High-temperature semi-conduction in SiCN, showing an example.

Novel Silicon-Boron-Carbon-Nitrogen Materials Thermally Stable up to 2200°C

Zhi-Chang Wang*, Fritz Aldinger**, Ralf Riedel

*Dept. of Chemistry, Northeastern Univ., Shenyang, China; ** Pulvermetallurg. Laboratorium, Max-Planck-Inst. für Metallforschung and Inst. für Nichtmet. Anorg.

Materialien, Univ. Stuttgart, Germany Three novel Si-C-B-N ceramic compositions, namely Si2.9B1.0C14N2.9, Si3.9B1.0C11N3.2 and Si5.3B1.0C19N3.4, were synthesized using the polymer-to-ceramic transformation of the polyorganoborosilazanes [B(C2H4Si(Ph)NH)3]n, [B(C2H4Si(CH3)NH)2–C2H4Si-(CH3)N(SiH2Ph))]n, and [B-(C2H4Si(CH3)–N(SiH2Ph))3]n, where Ph is phenyl (C6H5), at 1050°C in argon. The Si-B-C-N ceramics exhibited significant stability with respect to composition and mass change in the temperature range between 1000°and 2200°C, including isothermal annealing of the samples at the final temperature for 30 min in argon. The mass loss rate at 2200°C was as low as 1.4 wt%· h-1 for Si5.3B1.0C19N3.4, 1.7 wt%· h-1 for Si2.9B1.0C14N2.9, and 2.4 wt%· h-1 for Si3.9B1.0C11N3.2. The measured amount of mass loss rate was comparable to that of pure SiC materials. As crystalline phases, β-Si3N4 and β-SiC were found exclusively in the samples annealed at 2200°C at 0.1 MPa in argon. For thermodynamic reasons, β-Si3N4 should have decomposed into the elements silicon and nitrogen at that particular temperature and gas pressure. However, the presence of β-Si3N4 in our materials indicated that carbon and boron kinetically stabilized the Si3N4-based composition. Fig. 1. TGA measurements in 0.1 MPa argon for the amorphous Si-B-C-N ma-terials obtained at 1050°C. Mass loss as a function of temperature at 1000°C < T ≤ 2200°C:

(a) Si2.9B1.0C14N2.9, (b) Si3.9B1.0C11N3.2, and (c) Si5.3B1.0C19N3.4.

Mass loss as a function of time at 2200°C for 30 min:

(d) Si2.9B1.0C14N2.9, (e) Si3.9B1.0C11N3.2, and (f) Si5.3B1.0C19N3.4.

Structural and electrochemical characterization of Pt-Ru catalysts for fuel cell applications

C. Roth, N. Martz and H. Fuess

Due to growing environmental problems, the demand for highly-efficient, low to zero emission processes, turning fossile and renewable combustibles into fast-available energy, constantly increased. In this respect, fuel cells seem to be one of the key technologies for the next generation, as they present an attractive alternative for both stationary as well as mobile applications in industry and for transportation purposes. Low-temperature polymer electrolyte fuel cells (PEMFC), using either methanol or reformate gas as anode feed, are considered to be the most promising candidates to compete with the conventional Otto motor. However, even low CO concentrations in the feedstock lead to severe deactivation of the carbon-supported platinum catalyst, standardly used to accelerate the hydrogen oxidation reaction. Hence, current research concentrates on the development of new systems as well as the improvement of already existing catalyst systems by doping the platinum catalyst with other (transition) metals to yield less CO-sensitive catalyst formulations. Recent investigations mainly dealt with the measurement of the catalysts electrocatalytic activity, whereas systematic studies of the catalyst structure by spectroscopic, microscopic and diffraction techniques were comparatively scarce. Thus, in our work, the emphasis is put on gaining a more detailed insight into the apparent correlation between the microstructure and the electrocatalytic activity of the respective catalyst systems by combined structural and electrochemical characterization. Binary Pt-Ru systems were prepared by different synthesis pathways and their specific structural features were investigated by x-ray diffraction (XRD), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS) and x-ray absorption spectroscopy (XAS). Fig. 1. Cyclic voltammograms (left) and fuel cell test curves (right) of differently synthesized carbon-supported Pt-Ru catalysts. The corresponding electrocatalytic activity was evaluated by both real fuel cell tests and cyclic voltammetry (CV) and compared to a commercial catalyst purchased from E-TEK Inc. (Fig. 1).

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As clearly demonstrated by these electrochemical results, the electrocatalytic performance of a catalyst system is not only determined by its composition, but also by its structural features, like the average particle size and the degree of alloy formation. In the work presented, these parameters were varied and their impact on the electrocatalytic performance was tested (Fig. 2).

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Fig. 2. Comparison of XRD patterns and HRTEM images of sample I (right picture) and the commercial catalyst (left picture). In addition to the structural characterization before and after fuel cell testing by several bulk and surface methods, changes in the catalyst structure during operation in a real fuel cell can be monitored by in-situ EXAFS measurements. For this purpose, a special apparatus has been designed and was already successfully operated at beamline X1 at the synchrotron laboratory in Hamburg (Germany). With respect to the obtained results, combined structural and electrochemical charac-terization of the catalyst systems has proved to be an important tool in fuel cell research. Hence, future work will continue focussing on the influence of different structural features on the specific properties of the fuel cell catalysts. Support by the Deutsche Forschungsgemeinschaft is acknowledged with thanks.

Position-Sensitive Detector System for High Resolution X-Ray Powder Diffraction using Imaging Plates

M. Knapp, V. Joco, C. Bähtz, H. H. Brecht*, A. Berghäuser*, H. Mohren,

H. Ehrenberg, H. von Seggern, H. Fuess *Mineralog.-Petrograph. Inst., Univ. Hamburg

At the high-resolution powder diffractometer B2 at HASYLAB / DESY in Hamburg a new one-dimensional curved detector was developed for Debye-Scherrer geometry using imaging plate (IP) technology. An angular range up to 110° is accessible with a resolution down to 0.040° FWHM, which is limited by the capillary thickness of the sample. It suits to existing sample environments like capillary furnace and He-closed-cycle cryostat. In a further step, the adaptation of a vacuum chamber is planned to enable experiments at very long wavelengths up to 2.4 Å and to provide a very low background signal. Complementar-ily, a high resolution scintillation counter with analyzer crystal and FWHM below 0.010° can be used. Imaging plates are capable to store x-ray radiation over a wide dynamic range of at least five orders of magnitude in x-ray dose. Radiation thereby generates a latent image in form of locally trapped electron hole pairs. The so stored information can be recovered by optical stimulation of electrons at a wavelength of 635 nm to escape from their traps and subsequently recombine with holes under the emission of blue light at 390 nm.

The detector is constructed as a section of a circle and the investigated sample is at its centre. The detector includes a linear motor, which is mounted on a 20 mm thick aluminium base plate (Fig. 1). The scanner-head itself (see below) is fixed on a wagon guided by a curved rail with low mechanical tolerance. In a distance of 350 mm from the centre of the detector (sample) the IP is glued onto a cylindrical back plate. The overall deviation of the curvature from an ideal circle is below 0.1 mm. All the used detector components are shielded from radiation by an aluminium-lead housing except for a 15 mm

wide entrance slit for the scattered x-ray radiation. This slit covers the full angular range of the detector and allows for the expose of the IP. For protection against light the slit is covered by a black plastic foil. The position information of the scanner-head is provided by an optical measuring system with a grid resolution acquisition is triggered by an optical switch. The scanner-head is fabricated out of aluminium (Fig. 2). It consists of an integrating optical sphere with a polished surface in combination with a laser diode and a photomultiplier tube (PMT). The luminescence is stimulated by the laser diode with adjustable line focus. The width of the line is

Fig. 1. Mechanical setup of the detector with linear motor, curved rail and IP holder.

Fig. 3: Rietveld refinement of LaB6/Si in 0.2 mm capillary at 0.70956 Å. Exposure time: 30 seconds

determined via the “knife-edge-method“ to 25 principle of the scanner head is such that the laser beam passes through the integrating sphere and stimulates the IP. Thereby emitted light is collected by the integrating sphere and measured by a PMT through a blue filter. A microcontroller handles data acquisition and transfer, motor control and additional functions like switching of the erasing lamp. The output voltage from the PMT is converted by a 16 Bit AD converter and stored temporarily in the microcontroller. After readout, the data set is transferred via a web-server chip (TCP/IP) to the main computer. The remaining intensity on the IP can finally be erased by a halogen lamp, which is placed next to the scanner-head. The controller and the readout electronics are placed outside the detector. The typical time for exposure of the IP is several minutes depending on the sample. Readout and erasure takes about 10 seconds each and data transfer

and conversion about 40 seconds, which definitely can be reduced further.

Fig. 3 shows a Rietveld refinement performed with the GSAS program package. All reflection profiles show regular shapes and can be fitted with pseudo-Voigt functions. The data were taken from a 0.2 mm LaB6/Si capillary at 0.70956 Å exposed for 30 seconds. Particular care has been taken on aligning the capillary.

The new detector system is capable of high-resolution measurements in a wide angular range. The spatial resolution is placed between that of an analyser crystal (0.01° FWHM) and of parallel foils (0.1° FWHM), and, better than what can typically be reached with

standard laboratory instruments (0.06° FWHM). Depending on the measured samples and the specific tasks a decrease in measuring time of several decades can be achieved with respect to already available detectors. There-fore, measurements of kinetics and solid state reactions can be performed by allowing Rietveld refinement of crystal structures.

Financial support by the Bundes-ministerium für Bildung und Forschung is gratefully acknowledged under grant no.: 05KS1RDA9

Fig. 2. Scanner head (closed) with PMT and laser diode.

Fig. 1. Picture of the VMP-40 multi channellpotentiostat.

Insertion electrodes used in Li-Ion battery systems.

T. Buhrmester, N. Leyzerovich, H. Fuess

In modern life, long stand-by and working periods in electronic devices, e.g. mobile telephones and mobile computers, challenge the development of new energy storage equipment. Secondary high capacity battery systems with high specific energy densities are among fuel-cell systems like DMFC’s (direct methanol fuel cells) currently most promising. Due to the easy handling and the acceptable prices, especially Li-ion battery systems are intensively investigated in industry and in academic research institutions. For an effective development of such high-energy-density cells, high-capacity electrode materials are essential. The most promising systems to replace nickel-cadmium, or nickel-metal-hydride electrodes are lithium rocking chair systems. In these systems the cell stack is composed of either a lithium-, or a carbon black anode connected to a lithium-ion-accepting cathode via a lithium-ion-conducting, non-aqueous electrolyte. Lithium is preferred to other alkali metals because of its small radius and low density, as well as for being the most electropositive of the alkali earth family. The choice of the cathode is more flexible as various materials are capable of intercalating lithium ions and therefore work as cathodes. The so called lithium insertion/extraction reaction imposes a major task to the cathode material, the incorporation of lithium ions while compensating the electronic balance by passing an electron per ion into the current collector. These reactions are mostly topotactical or topochemical reactions in the structure of the host system, which in many cases is an oxide. Associated with this behaviour as a reservoir is the reversible change of the structural and electronic properties of the system. In many cases the reaction induces the reversible formation of metastable phases accompanied by minor reversible and irreversible modifications of the structure. The latter case predetermines the stability and therefore the life time of the electrode and also for the complete cell. The insertion electrodes can be classified as mixed-valence compounds having a mixed ionic-electronic conductivity. Typical systems are TiS2, LiWO3, LiMO2 (M = 9 Co, Ni) and

LiMn2O4. In this context it is necessary to point out that nearly all available materials show deviations from ideality, the most common is additional irreversible uptake of guest ions which reduces the specific energy density from theoretical values. As an example, the theoretical operating voltage of a Li/Li1-xCoO2 system is 3.9 V and the energy density is of the order of 1070 Wh kg-

1 at room temperature. Taking the masses of the electrolyte, separators and excess electrode materials supplementary hardware into account, the practical energy density is about 200 Wh kg-1, which is still a remarkable value.

Nevertheless the systems mentioned above have at least two of the so called plateaus of nearly constant voltage over an infinite change of the molar fraction of the guest ion

Fig. 2. Galvanostatic cycling of α-CuMoO4 (cut-off voltages 1.5 V and 3.2 V, current densitiy 0.47 mA cm-2).

lithium. For Li1-xCoO2, three lattice distortions have been found by x-ray diffraction techniques. For Li1-xNiO2, which exhibits a layered structure consisting of cubic close-packed O2- ions with Ni3+ oxide layers, analogous to the former cobalt system, the equivalent structural observation is true at slightly different molar values of the guest ions. The solid solution of nickel cobalt oxide inhibits Li to penetrate the intersheet gap by stabilizing the structure in two dimensions at a dopand level of approx. 30 % Co (Li[Ni0.7Co0.3]O2), which increases the life time of cells drastically and therefore this system is the most favoured cathode material in rocking chair battery applications at present.

In-situ x-ray diffraction measurements are currently planned to investigate the interfacial layers between electrolyte and cathode as well as the consistency of the cathode itself. A new parallel multi-potentiostat device (VMP-40, see Fig. 1) is in operation to cycle the cells ex-situ as well as during the x-ray investigation. In combination with x-ray absorption studies and possibly grazing incident experiments, the interface can be characterised more precisely and tailored to a higher performance of these cells. Another challenging task is the development of new cathode materials. With our new set-up, different 3d and 4d element oxides with interesting structural features e.g. molybdenum zinc/copper oxides are currently under investigation (see Fig. 2). Preliminary results have shown, that in case of copper doped molybdenum oxide a precipitation of copper takes place at the surface of the specimen.

Analytical Investigations Concerning the Varying Wear Behaviour of Cutting Tools Used for the Machining of

Compacted Graphite Iron and Grey Cast Iron

M. Heck; H. M. Ortner; S. Flege; U. Reuter*; H. Schulz* * Inst. of Production Engineering and Machine Tools, Faculty of Mechanical Engineering

Compacted graphite iron (CGI) is the material for the upcoming new generation of high-power diesel engines. Due to its increased strength compared to grey cast iron (CI) it allows an increase in the cylinder-pressures and therefore a better fuel economy and a higher power output are possible. First examples of such engines are the 3.3 l Audi V8 TDI and the 4.0 l BMW V8. The reason why CGI is not used to a larger extent in large scale production up to now is its much more difficult machinability as compared to conventional CI, especially at high cutting speeds. In modern transfer lines high cutting speeds are used in the cylinder-boring operation. And especially in these continuous cutting operations the tool life decreased due to the change from CI to CGI by about a factor of 20. As was found out previously by us, the difference in tool lifetime can be explained by the formation of a MnS-layer on the tool surface in the case of CI. This layer cannot form when machining CGI because the formation of MnS-inclusions is not possible in this material due to the higher magnesium content which in turn is responsible for the formation of the graphite vermicles. The MnS-layer acts as a lubricant and prevents the adhesion of workpiece particles. This is the reason for the greatly reduced wear of CI in high speed machining operations. This MnS-layer is inspected closer by X-ray diffraction, X-ray induced photoelectron spectrometry, atomic force microscopy and secondary ion mass spectrometry in this work. Furthermore, available information on the performance of MnS as lubricant in PM-steels is comparatively discussed. This knowledge led to an economic solution of high productivity machining of CGI. The key was to reduce the cutting speed, replacing single insert tools with multiple insert tools. This allowed to increase the feed rate. By increasing the feed rate in the same amount than decreasing the cutting speed, the same productivity can be realized. This concept is leading to a number of multiple insert tools thus realizing a high productivity machining of CGI cylinder-bores with multi-layer-coated carbide tools. The significance of chemical analytics for the successful solution of ardent technological problems has thus been demonstrated. Only by a broad overview on the wide range of methods today available for bulk and topochemical materials characterization it is possible to select the best combination of methods and to perform the necessary analytical investigations in an optimal way. This is a decisive help to solve problems in materials technology and to assist new materials developments in permanent close contact to the responsible material scientists.

Fig. 1. Formation of a MnS-protective layer when cutting grey iron (top) at high cutting speeds (800 m/min) in comparison with massive deterioration of the cBN-cutting tip when cutting compacted graphite iron with no detectable MnS-traces on the surface (bottom).

Fig. 2. Determination of the composition and thickness of the MnS-layer on a DBC 50 cutting tip (from De Beers, material cBN) after cutting CI-25 at 800 m/min and for a cutting length of 352 m. Deter-mination by secondary ion mass spectrometry (SIMS) with a SIMS-instrument ims 5f of Cameca (Paris) using O- primary ions with an energy of 17.0 keV. A crater of 100 x 100 µm2 was sputtered through the layer and the crater depth was subsequently measured by atomic force mi-croscopy with a CP5 Research AFM of Thermomicroscope (Sunnyvale, USA).

Fig. 3. Element mappings of the rake face of a DBC50 cutting tip by electron probe microanalysis with a CAMECA Camebax instrument (Paris). Mappings were performed in the wave-length dispersive mode. Depicted area is approximately 1 x 1 mm2. The formation of the MnS-layer on CI-25 is clearly visible contrary to CGI-HP where only a Mn-deposition is seen due to the Mn-content of CGI of 0.40% (w/w). Iron, too, is deposited on the rake face in all cases. CI-25 was cut with the cBN-cutting tip at 800 m/min and for a cutting length of 352 m.

CI 25 CGI HP Cutting speed

[m/min Mn S Fe Mn S Fe

100

200

400

800

Novel design of a smart magnet/superconductor heterostructure

Y. A. Genenko, H. Rauh, A. Snezhko*

*Faculty of Physics and Mathematics, Charles Univ., Prague We investigate current distributions in a thin, flat superconductor ring located between two coaxial cylindrical soft magnets of high permeability. Such a heterostructure protects the Meissner state of the ring even in the presence of strong total supercurrents, preventing entry of magnetic flux from the edges of the ring. A Fredholm integral equation governing the current distribution in the Meissner state of the ring is derived and solved numerically for different relative permeabilities of the magnets and various distances between the magnets and the ring. This reveals that the current distribution tends to become homogeneous when the relative permea-bilities are increased, the effect already saturating at values of these quantites of a few hundred. When the distances between the magnets and the ring are reduced, the current peaks near the circumferences of the ring decrease, thereby contributing to the large total supercurrent as well as to the strong longitudinal component of the magnetic field. The magnet/superconductor heterostructure considered here may therefore serve as a precursor of an electromagnet with flat superconducting coils. Entry of magnetic flux into a flat superconductor, and the consequential destruction of the Meissner state, is prevented by edge barriers of various kinds. The reduction of the edge current peaks below the values controlled by these barriers and the transition towards homogeneous sheet current distributions exhibited in Fig. 1 leads to an increase of the total current, whose magnitude in the flux-free state may be comparable with that in the critical state, providing the barriers are high enough. However, even when distinct edge barriers are absent, almost the entire superconductor ring may remain flux free if the total current is slightly less than the critical current. Such a situation may favour ac applications of the suggested heterostructure, anticipating electromagnetic losses will be reduced.

0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.50

5

10

15

20

25

30

µ2 = 20, 200, 1000

µ2 = 1

Sh

ee

t c

urr

en

t d

en

sity

(a

.u.)

Radial coordinate (a.u.)

Fig. 1. Distribution of the sheet current as a function of the radial coordinate of the magnet/ superconductor heterostructure, for the inner ring radius R1=0.87 and the outer ring radius R2=1.45, the radius of the inner magnet r1=0.80, and the radius of the outer magnet r2=1.50, when the relative permeability of the inner magnet µ1=1, whereas the relative permeability of the outer magnet µ2=1, 20, 200, 1000.

Superconductor strip near a planar magnetic shield

Y. A. Genenko, H. Rauh, A. Snezhko* *Faculty of Physics and Mathematics, Charles Univ., Prague

Magnetic materials were recently used to improve the performance of multifilament superconductor tapes by shielding self-induced as well as external magnetic fields, resulting in critical current enhancements and ac loss reductions. This could be explained by substantial current redistributions in superconductor strips placed near bulk shields of highly permeable soft magnets. Since in unrestricted two-dimensional geometries the magnetic field decreases asymptotically with inverse distance only, the shielding effect may be much weaker in real magnetic environments of finite extent, using relatively thin magnetic cover layers. To characterize qualitatively the role of dimensional restriction in the magnetic shielding problem at hand, we study the current-carrying Meissner state of a superconductor strip located near a finite, planar magnetic wall.

Using the method of magnetic surface charge, we investigate transport current distributions for different values of the parameters involved, viz. the relative permeability of the magnet, µ, the thickness of the magnet, D, and the distance of the magnet to the superconductor strip, a. All current patterns obtained exhibit sharp peaks at the edges of the strip, but the peak at the side adjacent to the magnet falls, allowing for the total current to be enhanced (Fig. 1).

We establish that the current peak reduction caused by magnetic shielding saturates fast when the thickness of the magnet is increased. For small values of a and D, the current peaks exhibit a pronounced dependence on these parameters and on the image current strength, q=(µ-1)/(µ+1) if q → 1, the latter fact representing a novel feature compared with the case of unrestricted shields. We observe that a substantial peak reduction occurs when µD ≈1 with µ>>1. This means that a thin magnetic environment may be used as well to control current distributions in superconductor strips, provided that the small thickness of the shield is compensated by a high magnetic permeability.

-1.0 -0.5 0.0 0.5 1.00

1

2

3

4

5

Sh

ee

t cu

rre

nt

de

nsi

ty (

a.u

.)

Transverse coordinate

Fig. 1. Distribution of the sheet current as a function of the transverse coordinate across the strip, with D and a normalized with respect to half-width of the strip.

Diploma Theses Ellrich, Jens; Herstellung und Charakterisierung von FePt Nanoteilchen, Thin Films, November 2001. Gottschalk, Sebastian; Wachstum und Charakterisierung von Hoch-ε Oxiden: Epitaktische Pr2O3 Schichten auf Si (111) als alternative Gate Dielektrika; Thin Films, November 2001. Hepp, Aline; Comparison of two Evaporation Techniques with respect to Properties of Organic Devices, Electronic Materials, October 2001 Lindner, Jörn; Characterization of Storage Phosphors with Cathodoluminescence, Electronic Materials, November 2001 Mazilu, Irina; Molekulardynamische Simulationen der Selbstdiffusion auf einer fcc (100) Oberfläche, Thin Films, November 2001. Metzger, Eva; Crack Propagation and Crack Closure in a Directionally Solidified Aluminium Alloy, Physical Metallurgy, November 2001 Niemax, Jens; Charge Transport in Organic Transistors, Electronic Materials, November 2001 Schmitt, Holger; Grenzflächeneigenschaften in TMR-Strukturen, Thin Films, November 2001. Utschig, Thomas; Herstellung und Untersuchung von Kontaktwerkstoffen aus alkalisch gefällten Verbundpulvern auf Silber-Zinnoxid-Basis mit co-gefällten Additiven, Dispersive Solids, OMG dmc²-division, November 2001 Volland, Andreas; Einfluß der Teilchengröße auf elektrische und magnetische Eigenschaften granularer FeCoCu-Schichten, Thin Films, July 2001.

PhD Theses Blümke, R.; Gefügeeinfluß auf die Spanbildung beim Hochgeschwindigkeitsfräsen, Influence of Microstructure on Chip Formation in High Speed Milling, Physical Metallurgy, January 2001 Bramnik, K. G.; Ternary and Quaternary Phases in the Alkali-Earth-Rhenium-Oxygen System, Structure Research, June 2001 Buhrmester, C.; Orientierungsunordnung in den chlorsubstituierten Pivalinsäure-(CH3)3-

x(CH2Cl)xCCOOH und Neopentanderivaten (CH3)4-yC(CH2Cl)y,, Structure Research, received at the Dept. of Chemistry, February 2001 Graff, M.; Einfluß oxidischer Zusätze auf die Phasenbildung und die Schalteigenschaften von Kontaktwerkstoffen auf Silber/Zinnoxid-Basis, Influence of Oxide Additives on the Phase Formation and the Switching Properties of Contact Materials on the Basis of Silver/Tin Oxide, Physical Metallurgy. January 2001 Gunst, S.; Nanostrukturierung von Übergangsmetalldichalkogeniden durch Interkalation und Deinterkalation, Oberflächenforschung, Juli 2001 Kessler, T.; Multivariat-statistische Auswertung von energiedispersiven Röntgenfluores-zenzspektren zur Identifizierung von Substanzen, Chemical Analytics, July 2001 Knies, S.; Herstellungsprozeß und Mikrostruktur von aktivierten Nickelkatalysatoren, Production Process and Microstructure of Activated Nickel Catalysts, Physical Metallurgy, February 2001 Kounis, A.; Strukturuntersuchung von ikosaedrischen Quasikristallen und deren Approxi-manten aus dem ternären System Zn-Mg-(Y, Er), Structure Research, April 2001 Lappas, I.; Heterogene Katalyse in überkritischen Medien Charakterisierung von Metall- und Legierungskatalysatoren, Structure Research, February 2001 Leinert, B.; Entwicklung eines Anreicherungsverfahrens von Metallen aus Abwasser-proben mit isotachophoretischer Endbestimmung, Chemical Analytics, received at the Dept. of Structural Engineering and Geodesy, July 2001 Merkert, P.; Mechanische Eigenschaften von nanokristallinem Ytriumoxid, Ceramics Division, May 2001 Moneke, M.; Die Kristallisation von verstärkten Thermoplasten während der schnellen Abkühlung und unter Druck, Structure Research, July 2001 Nagel, R.; Ionenstrahlmischen an Metall/Keramik Schichten, Thin Films, November 2001. Pflamm-Jonas, T.; Auslegung und Dimensionierung von kurzfaserverstärkten Spritzgussbauteilen, Design and Dimensioning injection molded parts reinforced by short-fiber, Physical Metallurgy, February 2001 Steiger, J.; Ladungstransport in organischen Halbleitern, Charge Transport in Organic Semiconductors, Electronic Materials, December 2001

Thomas, S.; Constitutive Equations and Numerical Methods for Describing Deformation and Damage, Physical Metallurgy, August 2001 Yonkeu, A. L.; Phasenanalyse und strukturelle Untersuchungen neuer “Core-Shell”-Aufwachsungssysteme von Zeolithen mittels Röntgendiffraktometrie und Elektronen-mikroskopie, Structure Research, July 2001

Journal “Thema Forschung“ Issue 2/2001 - ISSN 1434-7768 MATFORM: Vom Material zum Bauteil - Materialforschung an der TUD A. Articles from the Institute of Materials Science Seggern, H. von; Rehahn, M.; Mehr Information durch mehr Licht: Organische Leucht-dioden fürs tägliche Leben, Thema Forschung 2 (2001) 22-27. Jaegermann, W., Klein, A.; Mayer, T.; Thißen, A.; Dünnschichtsolarzellen – Material-forschung in Grenzbereichen, Thema Forschung 2 (2001) 40-49. Riedel, R.; Rastätter, S.; Kinski, I.; Neue Synthesestrategien zur Herstellung keramischer Materialien, Thema Forschung 2 (2001) 50-54. Nuffer, J.; dos Santos e Lucato, S.; Lupascu, D.; Rödel, J.; Eigenschaften und Anwendun-gen keramischer Aktuatorwerkstoffe, Thema Forschung 2 (2001) 56-62. Gross, D.; Exner, H. E.; Numerische Simulation materialwissenschaftlicher Phänomene, Thema Forschung 2 (2001) 64-70. Lemeš, Z.; Harkopf, T.; Roth, C.; Fuess, H.; Seydel, J.; Hahn, H.; Die Brennstoffzelle – eine Option für die Zukunft? Thema Forschung 2 (2001) 80-87. Ortner, H. M.; Die Bedeutung der Analytik für die Materialwissenschaft und die material-erzeugende Industrie, Thema Forschung 2 (2001) 142-155. B. Articles from other institutes Haase, W.; Tschudi, T.; Multifunktionale Polymere, eine Herausforderung für die Elektronik und Optik, Thema Forschung 2 (2001) 28-33. Scheerer, H.; Hoche, H.; Broszeit, E.; Berger, D.; Tribologische Eigenschaften von PVD CRN Beschichtungen im Trockenlauf bei Erhöhter Temperatur, Thema Forschung 2 (2001) 34-39. Granacher, J.; Scholz, Al.; Schwienheer, M.; Berger, C.; Modellierung des Kriechverhaltens warmfester Stähle und Nickelbasis-Legierungen, Thema Forschung 2 (2001) 72-79.

Gleiter, U.; Wörner, J.-D.; Bastian, M.; Rehan, M.; Kunststoffe – als Konstruktionswerkstoffe im Bauwesen im Aufwind, Thema Forschung 2 (2001) 88-95. Seeger, T.; Greuling, S.; Vom Bauteil zum Werkstoff und zurück – Lösungsstrategie zur Lebensdauerberechnung von Schweißverbindungen, Thema Forschung 2 (2001) 96-105. Ruland, T.; Kerber, A.; Schwalke, U.; Weil, C.; Jakoby, R.; Neue Materialien in der Mikroelektronik und Mirkowellentechnik: Anforderungen und innovative Anwendungen, Thema Forschung 2 (2001) 106-115. Rupp, A.; Wallmichrath, M.; Hanselka, H.; Werkzeuge und Methoden zur Auslegung moderner Stahlleichtbau Karosserien, Thema Forschung 2 (2001) 116-125. Kaiser, B.; Teller, C.; Berger, C.; Technische Federn – „einfache“ Bauteile mit extremen Anforderungen, Thema Forschung 2 (2001) 126-131. Claus, P.; Luft, G.; Vogel, H.; Entwicklung neuer Materialien für die Katalyse, Thema Forschung 2 (2001) 132-141.

Applied Earth Sciences Physical Geology and Global Cycles In the solar system, Earth is an 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 an unending 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-ocean ridges at rates of several centimetres per year. On the other side, plate margins collide, 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 subduc-tion the basaltic crust is partially melted generating more felsic magmas which rise to form continental-type 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 their 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 tracegases, Earth is warming. Industrially produced chlorinated hydrocarbons have risen to the stratosphere, threatening the protective ozone layer. Dust from traffic, industry and agriculture produce reagents which alter the air chemistry, causing unprecedented interac-tions with the marine realm, with vegetation and even with 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 the alarming loss of topsoil and cuts down on the extent of natural ecosystems at the same time. The artificial fertilization of soils causes wide-spread nitrate pollution of shallow ground waters and urbanization alters the water cycle above and below ground. Local leakage and accidents with chemicals impact soil, rivers and ground water. Civil engineering, discharges and denudation cause alterations in almost all rivers world-wide and even coastal seas show increasing eutrophication, silta-tion and ecosystem changes in the water column and in the shallow sediments. The scars left by the mining of minerals and fossil energy are visible everywhere and cause increas-ingly problems. Everywhere man has changed the rate of natural processes. He spreads ever further into the landscape, utilizing regions and building in areas which should not be used considering their natural risks. Therefore damages through natural catastrophes rise traumatically endangering the world insurance system. All these processes and changes and their consequences are topics of Environmental Geology. Understanding global change and accepting the responsibility of mankind for this planet and its resources for future generations are prerequisites for the planning of a sustainable development.

The division of Physical Geology and Geological Cycles at the Institute for Applied Geo-sciences addresses several questions important to environmental geology both in the pre-sent and in the geological past. These can be summarized as follows: • Paleoclimatology (through the study of varved sediments in the Dead Sea Basin/

Jordan and in Lake Van/Turkey and through the study of speleothems) • Carbonate geochemistry through time (through the study of alkaline crater lakes,

stromatolites and through modeling of early ocean conditions also for other planets and moons of the solar system)

• Karst and cave development (through the studies of cave development in limestone, gypsum and lava and through the study of cave deposits and their paleontological content and geochemical composition)

• Biogeochemistry of rivers (through the study of the biogeochemistry of rivers such as the Ebro and Rhine or in Patagonia).

Currently two German research funded projects are pursued, the reports of which follow below.

Staff Members Head

Prof. Dr. Stephan Kempe

Research Associates Dr. Günter Landmann Dr. Wilfried Rosendahl

Dr. Petra Rottenbacher

Technical Personnel

Ingrid Hirsmüller

Jürgen Krumm

Secretaries

Kirsten Herrmann Edith Paulitz

Monika Schweikhard

Diploma Students

Sigrid Belzer Robert Bienkowsky Michael Kauer

Vera Mügge Stefanie Müller

Research Projects Kempe & Rosendahl: Speleothemes and Pleistocene climate in Central Europe (DFG, 1999-2001) Rosendahl: Interdisciplinary project HIMAP in the Alpine Martell Valley, Italy The project HIMAP (Hinteres Martelltal Projekt) involves different disciplines (geology, hydrogeology, hydrochemistry, hydrology, glaciology, climatology, engineering geology, sedimentology and socio-economic sciences) of the University of Technology Darmstadt (National Park Stilfser Joch / Italie, 2001-2005)

Rosendahl: Chronological position of quaternary Hominid remains from open air sites in Hessia (Dept. of Antiquities Hessia 2001-2003) Rosendahl: Interdisciplinary geological and palaeontological research of the "Neue Laubenstein-Bärenhöhle", the first alpine cave bear cave in Gemany (Naturkunde- & Mammutmuseum Siegsdorf, 2001-2005) Rosendahl: Absolute chronology of tufa dams in the Swabian Alb and the Eifel area (City of Bad Urach and Maarmuseum Manderscheid, 2001-2003)

Publications Darag, R.; Rosendahl, W;: Die Neue-Laubenstein-Bärenhöhle (1341/33)/Chiemgau - Ent-deckung und erste Forschungsergebnisse. Mitt. Verb. dt. Höhlen- und Karstforsch. 47 (2001) 60-66. Ernst, A. M.; Mauser, W.; Kempe, S.; Interdisciplinary perspectives on freshwater: avail-ability, quality, and allocation, in: Ehlers, E.; Krafft, T. (eds.), Understanding the Earth System (2001) 265-274. Kempe, S.; Bauer, I.; Henschel, H. V.; Expedition Report, Hawaii, March 2001, Newsletter Hawaii Speleol. Survey of the Nat. Speleol. Soc. 10 (2001) 3-10. Kempe, S.; Liebezeit, G.; Duman, M.; Asper, V.; Extrusion: the formation mechanism for the presumed "turbidites" of the deep Black Sea? Senckenbergiana maritima 31 (2001) 11-16. Kempe, S.; Reinboth, F.; Die beiden Merian-Texte von 1650 und 1654 zur Baumanns-höhle und die dazugehorigen Abbildungen, Die Höhle 52 (2001) 33-45. Kempe, S.; Rosendahl, W.; Höhlensinter als Klimaarchive, in: Negendank, J. F. W.; Berger, A. (red.), Klimaweißbuch. Klimainformation aus geowissenschaftlicher Forschung (Fallstudien), Stand und notwendige Erfordernisse der Paläoklimaforschung, Terra Nostra, Schriften der Alfred-Wegener-Stiftung 7 (2001) 128-135. Kempe, S.; Straßenburg, J.; Belzer, S.; Henschel, H. V.; Fahlbusch, K.; Der Darmstädter Granodiorit im Stollen unter der Dieburger Straße, Mathildenhöhe, Darmstadt, Jber. Mitt. Oberrhein. Geol. Ver., N.F. 83 (2001) 51-63. Rosendahl, W.; Zum Oberpleistozän in der hessischen Oberrheinebene. Geologie und Paläontologie. (Exkursion A am 17. April 2001), Jber. Mitt. Oberrhein. Geol. Ver., N.F. 83 (2001) 37-50. Rosendahl, W.; Geologisch-Paläontologischer Vergleich der cromerzeitlichen Neckar-ablagerungen von Frankenbach und Mauer (Frankenbacher Sande / Mauerer Sande) und ihrer Deckschichten, Jber. Mitt. Oberrhein. Geol. Ver., N.F. 83 (2001) 293-316. Rosendahl, W.; Die Zoolithenhöhle bei Burggaillenreuth/Fränkische Schweiz, in: Weidert, W. K. (ed.), Klass. Fundstellen der Paläontologie 4 (2001) 235-244.

Rosendahl, W.; Neandertal und Neandertaler, in: Weidert, W. K. (ed.), Klass. Fundstellen der Paläontologie 4 (2001) 255-264. Rosendahl, W.; Die cromerzeitliche Neckarablagerung von Heilbronn. Frankenbach (Frankenbacher Sande). Eine wichtige Bezugslokalität für die Mauerer Sande, in: Wagner, G. A.; Mania, D. (eds.) Frühe Menschen in Mitteleuropa. Chronologie, Kultur und Umwelt (2001) 155-163. Rosendahl, W.; Mittelpleistozäne Insektenreste aus einem Stalagmiten der Zoolithen-höhle/Fränkische Alb (Süd-Deutschland). Natur und Mensch. Jahresmitteilung der Naturhistor. Gesellschaft Nürnberg 2000 (2001)159-168. Rosendahl, W.; Grupe, G.; Mittelwürmzeitliche Höhlenbären und ihre Nahrungspräferenz. Forschungen aus der Neuen Laubenstein-Bärenhöhle / Chiemgau. Mitt. Bayer. Staatsslg. Paläont. hist. Geol. 41 (2001) 85-98. Rosendahl, W.; Wrede, V.; Karsterscheinungen und Geotopschutz im nördlichen Sauer-land, scriptum 8 (2001) 85-98.

Hydrogeology Hydrogeology is dealing with groundwater under natural conditions as well as under the influence of man, e.g. sealing of terrains, contaminated sites or agriculture. Equally important parts are the hydraulics, balance and quality and protection of groundwater. Hydrogeologists are working in the field, in the laboratory and with EDV. With this the hydrogeology delivers essential contributions to evaluation and management of water resources. There are important connections to the fields of engineering geology, sedimentology, environmental science and construction engineering, as well as to the conservation of nature.

Staff Members Head

Prof. Dr. Götz Ebhardt

Research Associates

Dr. Bernd Eccarius PD Dr. Peter Harres

Dr. Thomas Schiedek

Technical Personnel

Rainer Brannolte

Secretaries

Kirsten Herrmann Edith Paulitz

Monika Schweikhard

PhD Student

M.Sc. Segun M.A. Adelana Dipl.-Geol. Meike Beier

Dipl.-Geol. Uwe Werner

Diploma Students

Christian Lerch Kai Marquardt

Svenja Schüffler Mike Walker

Research Projects Balance of water and substances in urban areas - example of the city of Darmstadt - (Hess. Landesamt für Umwelt u. Geologie 2000-2003) Stable isotopes of nitrate and ammonium as a tracer for groundwater changes in urban agglomerates (Centre of Environmental Research Leipzig-Halle 2000-2003) Interdisciplinary project HIMAP in the Alpine Martell Valley, Italy (Nationalparkverwaltung Stilfser Joch/Glurns, Hydrographisches Amt, Bozen, Amt für Wildbach- und Lawinen-verbau, Bozen, Amt für überörtliche Raumordnung, Bozen, Amt für Geologie und Baustoff-prüfung, Kardaun, 2001-2004)

Publications Ebhardt, G.; Eccarius, B.; Lessmann, B.; The volcanic Vogelsberg, Germany. A complex hydrogeologic system, in: Seiler, K.-P.; Wohnlich, S. (eds.): Proc. XXXI. IAH Congress: New Approaches To Characterising Groundwater Flow, Vol. 2, Munich, Balkema (2001) 1175-1178. Ebhardt, G.; Ehrenberg, K.-H.; Hottenrott, M.; Kött, M.; Leßmann, B.; Nesbor, H.-D.; Geologie und Hydrogeologie des südwestlichen Vogelsberges und seiner Umrahmung (Exkursion C am 19. April 2001), Jber. Mitt. Oberrhein. Geol. Ver., N.F. 83 (2001) 65-87. Ebhardt, G.; Greifenhagen, G.; Lessmann, B.; Analysis of groundwater-level records and aquifer water balances, in: Seiler, K.-P.; Wohnlich, S. (eds.): Proc. XXXI. IAH Congress: New Approaches To Characterising Groundwater Flow, Suppl. Vol., Munich, Balkema (2001) 12-15. Ebhardt, G.; Harres, H. P.; Iven, H.; Pöschl, W.; Toussaint, B.; Vogel, H.; Hydrogeologie, Wasserwirtschaft und Ökologie im Hessischern Ried (Exkursion H am 20. April 2001), Jber. Mitt. Oberrhein. Geol. Ver., N.F. 83 (2001) 185-210. Eccarius, B.; Ebhardt, G.; Isotope studies of phenol lake/groundwater interaction at Deuben, Germany, in: Seiler, K.-P.; Wohnlich, S. (eds.), Proc. XXXI. IAH Congress: New Approaches To Characterising Groundwater Flow, Vol. 1, Munich, Balkema (2001) 487-491. Eccarius, B.; Christoph, G.; Ebhardt, G.; Gläßer, W.; Grundwassermodellierung zur Ge-fährdungsabschätzung eines phenolverseuchten Tagebaurestsees, Grundwasser, 6 (2001) 61-70. Harres, H. P.; Landschaftsdegradation durch Erzbergbau im Mittelmeergebiet. Das Bei-spiel Südsardinien, Petermanns Geogr. Mitt. 4 (2001) 84-93. Harres, H. P.; Harres, L. E.; Entwicklung und Anbaumethoden der Landwirtschaft, Schrif-tenreihe WAR Darmstadt 133 (2001) 3-13. Harres, L. E.; Harres, H. P.; Ergebnisse bisheriger Vergleichsuntersuchungen zwischen konventionellen und alternativen Anbaumethoden, Schriftenreihe WAR Darmstadt 133 (2001) 14-23. Harres, H. P.; Harres, L. E.; Zur geographischen Struktur des Untersuchungsgebietes im Griesheimer Raum, Schriftenreihe WAR Darmstadt 133 (2001) 26-40. Harres, H. P.; Kunze, D.; Schröder, W.; Untersuchungsstandorte und Instrumentierung, Schriftenreihe WAR Darmstadt 133 (2001) 41-47. Harres, H. P.; Die Bodenverhältnisse im Griesheimer Untersuchungsgebiet, Schriftenreihe WAR Darmstadt 133 (2001) 48-53. Harres, H. P.; Harres, L. E.; Niederschläge und Niederschlagsstrukturen, Schriftenreihe WAR Darmstadt 133 (2001) 54-64.

Hock, H.; Harres, H. P.; Harres, L. E.; Hoffmann, P.; Die chemische Analytik des Nieder-schlagswassers, Schriftenreihe WAR Darmstadt 133 (2001) 65-77. Hock, H.; Brockmann, C.; Harres, H. P.; Hoffmann, P.; Kessler, T.; Ortner, H.; Chemisch-analytische Untersuchungen von Böden, Bodenwasser, Dünger und Pflanzenproben auf den Versuchsparzellen, Schriftenreihe WAR Darmstadt 133 (2001) 97-140. Harres, H. P.; Harres, L. E.; Interpretation der chemisch-analytischen Untersuchungs-ergebnisse im Hinblick auf den Einfluss unterschiedlicher Landbewirtschaftung auf Boden und Sickerwasser, Schriftenreihe WAR Darmstadt 133 (2001) 141-164.

Engineering Geology Engineering Geology uses geoscientific methods for the solution of tasks in planning and execution of building measures. This contains investigations for the attitude of sediments and rocks as building ground or building material and for geological processes influencing these characteristics. Engineering geology is consequently a link between geosciences and engineering sciences. For the engineering geology, problems in technical environ-mental conservation are of increasing importance. The division of engineering geology is equipped with modern, computer controlled test appliances and carries out investigations of soils and rocks, corresponding to valid standards. The equipment contains triaxial- and box shear-testing machines, permeame-ter, swell- and shrink-testing machines, compression-permeability-machines and a strength test apparatus of the company CONTROLLS. For the determination of strength- and deformation-characteristics of rocks, a modern, computerbased testing system of the company FORM+TEST Riedlingen was installed. Researchfields are the determination of soil physical characteristics of loose soils, stress-strain-behaviour of soils and rocks, swelling analysis of the „Messel oil shale“ and the spe-cial geotechnical characteristics of rubble-recycling-materials and slags from waste incin-eration facilities. These works are often carried out in partnership with the industry.

Staff Members Head

Prof. Dr. Herward Molek

Research Associates

Dipl.-Geol. Nicole Dumet Dipl.-Geol. Thomas Nix

Dr. Harald Vogel

Technical Personnel

Horst Gareis Gabriela Schubert

Secretaries

Kirsten Herrmann Edith Paulitz

Monika Schweikhard Maria Specchiarello

PhD Student

Dipl.-Geol. Gabriele Aderhold

Diploma Students

Faiza Aissaoui Marcus Glab Stephan Hillmanns

Jochen Hofmann Markus de Jesus Oliveira

Special courses En-gineering Geology for Departement of Civil Engineering and Sur-veying

Barbara Schneider-Muntau

Research Projects Evaluation of the geotechnical safety of river-dikes in Hessen (Reg.-Präs. Darmstadt, 2001-2002) Interdisciplinary project HIMAP in the Alpine Martell Valley, Italy (Nationalparkverwaltung Stilfser Joch/Glurns, Hydrographisches Amt, Bozen, Amt für Wildbach- und Lawinen-verbau, Bozen, Amt für überörtliche Raumordnung, Bozen, Amt für Geologie und Baustoff-prüfung, Kardaun, since 2001)

Publications Ebhardt, G.; Harres, H.-P.; Iven, H.; Pöschl, W.; Toussaint, B.; Vogel, H.; Hydrogeologie, Wasserwirtschaft und Ökologie im Hessischen Ried, Jber. Mitt. Oberrhein. Geol. Ver., N.F. 83 (2001) 185-210. Harms, F.-J.; Aderhold, G.; Hoffmann, I.; Molek, H.; Nix, T.; Rosenberg, F.; Grube Messel bei Darmstadt (Südhessen), Jber. Mitt. Oberrhein. Geol. Ver., N.F. 83 (2001) 145-183. Molek, H.; Harms, F.-J.; Nix, T.; Aderhold, G.; Neues zur Geologie und Ingenieurgeologie des Unesco-Welterbes Grube Messel bei Darmstadt (Südhessen), Jber. Mitt. Oberrhein. Geol. Ver., N.F. 83 (2001) 285-292.

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 Darm-stadt University of Technology focus on applied aspects with specific emphasis on hydro-geological, engineering and environmental issues. However, also research related to oil exploration is carried out with a speciality in palynology. To predict groundwater move-ment, 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 con-cept 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. Currently, a georadar equipment is going to be established as specific method of the near-surface exploration of soils and rocks.

Staff Members Head

Prof. Dr. Matthias Hinderer

Research Associates

Dr. Annette Götz Dr. Jens Hornung

Technical Personnel

Erich Wettengl

Secretaries

Kirsten Herrmann Edith Paulitz

Monika Schweikhard

PhD Student

Dipl.-Geogr. Holger Schäuble

Diploma Students

Katrin Ruckwied

Research Projects Computer-aided global analysis of modern denudation rates in small to medium-sized drainage basins (river loads, reservoir siltation, lake sedimentation) (DFG, 2001-2003) Sedimentology and palynofacies of the Upper Cretaceous (Vocontian Basin, SE France) (DFG, 2000-2002) Sediment budget of the upper Middle Keuper (DFG-Stipendium 2001-2003)

Publications Einsele, G.; Yan, J. P.; Hinderer, M.; Atmospheric carbon burial in modern lake basins and its significance for the global carbon budget, Global and Planetary Change 30 (2001) 167-195. Götz, A. E.; Feist-Burkhardt, S.; Dittrich, D.; Lithostratigraphie und Palynofazies des Unteren Muschelkalk (Mitteltrias, Anis) der Forschungsbohrung Onsdorf (Saargau), Mainzer geowiss. Mitt. 30 (2001) 43-66. Hinderer, M.; Late Quaternary denudation of the Alps, valley and lake fillings and modern river loads, Geodinamica Acta 14 (2001) 231-263. Hinderer, M.; Einsele, G.; The world's large lake basin's as denudation-accumulation sys-tems and implications for their lifetimes, J. Paleolimnology 26 (2001) 355-372. Schiedek, T.; Hinderer, M.; Atmosphärischer Eintrag und Verbleib von Schadstoffen in Boden und Grundwasser. Erfahrungen aus SW Deutschland, Jber. Mitt. Oberrhein. geol. Ver., NF 83 (2001) 365-377.

Georesources and geohazards This specialty has been newly established at Darmstadt University of Technology in 2001. It teaches phenomena and risk management of geohazards like earthquakes and volcanic eruptions. It will concentrate on georesources like soils, ground water and mineral re-sources and its evaluation and regionalization respectively in order to enable the use of complex geoscientific data for ecologic, economic, and regional planning purposes. A newly installed geographic information system will support the investigations.

Staff Members Head Prof. Dr. Andreas Hoppe Research Associates Dipl.-Geol. Stefan Lang Dr. Oswald Marinoni Dipl.-Ing. Christian Lerch Technical Personnel NN

Research Projects Investigation of the architecture of a terrestrial subsidence basin of Plio-/Pleistocene age (Hanau-Seligenstädt Basin) and regionalization and evaluation of its georesources sup-ported by a geographical information system (2001-2004) Use of statistical methods for optimized risk/geohazard-management decisions. Methods of risk management strategies. Use of environmental valuation methods for environmental and economic regional planning purposes and their implementation in a GIS-based expert-system (2001-2006)

Publications Hoppe, A.; Schulz, R.; Die Forschungsbohrung Vogelsberg 1996. Einführung und Ergeb-nisse, Geol. Abh. Hessen 107 (2001) 5-14.

Hoppe, A.; Schulz, R. (ed.); Die Forschungsbohrung Vogelsberg 1996. Einblicke in einen miozänen Vulkankomplex. Mit Beiträgen von P. J. F. Bogaard, H. Buness, C. Bücker, K.-H. Ehrenberg, K. Grimm, A. Hoppe, M. Hottenrott, L. Jabri, A. Kött, B. Leßmann, E. Martini, D. Nesbor, J. Pross, R. Pucher, G. Radtke, C. Rolf, K.-J. Sabel, H.-J. Scharpff, E. Schnepp, R. Schulz, J. Struck, K. Wiegand, G. Wörner, T. Wonik, Geol. Abh. Hessen 107 (2001) 215 S.

Hug, N.; Gaupp, R.; Hoppe, A.; Sedimentologische Untersuchungen an Rotsedimenten der Perm-Trias-Grenze in Hessen, Schriftenreihe dt. geol. Ges. 13 (2001) 54.

Lang, S.; Gaupp, R.; Voigt, T.; Sedimentologische Aspekte des Thüringer Chirotherien-sandsteins (Buntsandstein, Trias), Schriftenr. dt. geol. Ges. 13 (2001) 63. Marinoni, O.; Alber, M.; Rockmass. Interactive determination of Bieniawski's Rock Mass Rating (RMR), Educational Software distributed by the International Society for Rock Me-chanics (ISRM) (2001).

Institute of Mineralogy The Institute of Mineralogy includes three professorships with the following research and teaching areas: Geomaterials Science (W. F. Müller), Structural Geology/Petrology (P. Blümel), and Applied Mineralogy/Environmental Mineralogy (S. Weinbruch). In 2001, after the retirement of P. Blümel, a chair for Technical Petrology will be established in order to support the new curriculum Applied Geosciences.

Geomaterials Science Geomaterials Science investigates composition, microstructure, properties, behavior and formation conditions of minerals, rocks, melts and fluids. Fields of research of the group in Darmstadt are crystal chemistry of rocks and ceramics. Specifically, we are studying the real structure, phase transformations and deformational behavior of crystals, pre-dominantly by transmission electron microscopy. Areas of interest are: microstructure, mineral reactions and pressure-temperature history of metamorphic rocks (together with the former co-worker Priv.-Doz. Dr. Esther Schmädicke, now Professor at the University Erlangen-Nürnberg); formation conditions and thermic and deformational history of mete-orites; electronic structures and coordination of elements in oxides and silicates; micro-structure and properties of ceramics.

Petrology and Structural Geology The mineralogical and structural transformations of the earth´s crust and mantle are ana-lyzed by field mapping and rock microscopy, and by microchemical, stereological, X-ray and thermobarometric methods. Research objects are: (1) the Austroalpine nappes, (2) the mid-European Variscides and (3) the southern Uralides.

Environmental Mineralogy Environmental mineralogy focuses its research on the characterization of individual aero-sol 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) 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 at working places and in urban environments. 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 health effects. Our research is carried out in cooperation with the following national and international partners: Max Planck Institute for Chemistry (Department of Biogeochemistry) in Mainz, Institute for Atmospheric Physics (University of Mainz), Forschungszentrum Karlsruhe (In-

stitut für Meteorologie und Klimaforschung), Institute for Tropospheric Research in Leipzig, Paul Scherrer Institut (Laboratory of Atmospheric Chemistry) in Villigen (Switzerland) and National Institute of Occupational Health in Oslo (Norway). Other fields of research include high temperature oxidation of metals and alloys, exsolution and coarsening in pyroxenes, and cosmochemistry.

Staff Members Head

Prof. Dr. Peter Blümel Prof. Dr. Wolfgang F. Müller

Prof. Dr. Stephan Weinbruch

Research Associates Dipl.-Min. Reinhold Apfelbach P.-D. Dr. Peter van Aken Dr. Martin Ebert

Dr. Stefan Lauterbach Dr. Dirk Scheuvens P.-D. Dr. Eckardt Stein

Technical Personnel

Thomas Dirsch Josef Kolb

Saskia Leißler Gerlinde Seifert

Secretaries

Petra Gebert

Christa M. Reinhard

PhD Students

Dipl.-Geol. Eric Barnert Dipl.-Ing. Hauke Gorzawski

Dipl.-Ing. Annette Rausch Dipl.-Ing. Volker Styrsa

Research Projects Quantitative determination of the Fe2+/Fe3+ ratio in oxides and silicates by electron energy loss spectroscopy (DFG 2001) Cooling rates of chondrules from meteorites as determined by the kinetics of coarsening of pigeonite/diopside exsolution lamellae (DFG 2001) Transmission electron microscopy of a talc-chlorite-amphibole fels from the pilot conti-nental deep drilling project, Bavaria (DFG 2001) TEM study on eclogites from the Tauern window, Eastern Alps: the microstructure as re-sult and indicator of metamorphic processes (DFG 2000-2002) Crystal chemistry and microstructures of Fe2SiO4 – Fe3O4 spinelloids (DFG 2000-2002) Optical properties of atmospheric aerosols during the Lindenberg Aerosol Characterization Experiment (LACE 98) derived from the analysis of individual particles (BMBF, 1998-2001, Max Planck Inst. of Chemistry, Dept. of Biogeochemistry, Mainz, and division Chemical Analytics)

Transmission electron microscopy of soot during the AIDA campaign (Forschungszentrum Karlsruhe, Inst. für Meteorologie und Klimaforschung, 1999-2003) Characterization of individual aerosol particles during the Cloud and Aerosol Charac-terization experiment (CLACE) at the Jungfraujoch (2000-2001, Paul Scherrer Inst., Labo-ratory of Atmospheric Chemistry, Villigen, Switzerland) Characterization of diesel soot (Inst. für Verbrennungskraftmaschinen, Dept. of Mechanical Engineering, and Chemical Analytics Division, TU Darmstadt) Characterization of working place aerosols (National Inst. of Occupational Health, Oslo, Norway, and Chemical Analytics Division) Cooling rates of chondrules derived from the wavelength of exsolution lamellae in iron-bearing clinopyroxene (1997-2001, Dept. of Geological Sciences, Rutgers Univ., Piscataway, USA) Hygroscopic behavior of individual aerosol particles Petrostructural and P-T-t-d evolution of the austroalpine Campo crystalline complex (Northern Italy) (DFG 2001)

Publications Ebert, M.; Weinbruch, S.; Quellenidentifizierung auf Basis der elektronenmikroskopischen Einzelpartikelanalyse., in: Workshop PMx-Quellenidentifizierung: Methoden und Ergebnisse (eds. U. Quass and T. Kuhlbusch), Ministerium für Umwelt, Naturschutz, Landwirtschaft und Verbraucherschutz Nordrhein-Westfalen (2001) 62-65. Ebert, M.; Weinbruch, S.; Rausch, A.; Gorzawski, G.; Wex, H.; Hoffmann, P.; Helas, G.; The complex refractive index of aerosols during LACE 98 as derived from the analysis of individual particles, J. Aerosol Sci. 32 (2001) 683-684.

Frost, D. J.; Langenhorst, F.; Aken, P. A. van; Fe-Mg partitioning between Ringwoodite and Magnesiowüstite and the effect of pressure temperature and oxygen fugacity, Physics and Chemistry of Minerals 28 (2001) 455-470. Hoffmann, P.; Dedik, A. N.; Deutsch, F.; Ebert, M.; Hein, M.; Hofmann, H.; Lieser, K. H.; Ortner, H. M.; Schwanz, M.; Sinner ,T.; Weber, S.; Weidenauer, M.; Weinbruch, S.; Iron in the atmosphere, in: Dynamics and chemistry of hydrometeors (ed. R. Jaenicke), WILEY-VCH (2001) 440-467. Rausch, A.; Trautmann, T.; Weinbruch, S.; Helas, G.; Calculation of scattering and absorption of light by irregular shaped and mixed particles, J. Aerosol Sci. 32 (2001) 419-420.

Schmädicke, E.; Okrusch, M.; Schubert, W.; Elwart, B.; Gorke, U.; Phase relations of calc-silicate assemblages, in: The Auerbach marble Odenwald Crystalline Complex, Germany., Miner Petrol 72 (2001) 77-111. Aken, P. A. van; Langenhorst, F.; Nanocrystalline, porous periclase aggregates as product of brucite dehydration, European Journal of Mineralogy 13 (2001) 329-341. Weinbruch, S.; Müller, W. F.; Hewins, R. H.; A transmission electron microscope study of exsolution and coarsening in iron-bearing clinopyroxene from synthetic analogues of chondrules, Meteoritics & Planetary Science 36 (2001) 1237-1248. Weinbruch, S.; Müller, W. F.; Hewins, R. H.; A transmission electron microscope study of exsolution and coarsening in iron-bearing clinopyroxene from synthetic analogues of chondrules, Meteoritics & Planetary Science (2001) 1237-1248. Will, T. M.; Schmädicke, E.; A first find of retrogressed eclogues in the Odenwald Crystalline Complex, Mid-German Crystalline Rise, Germany: evidence for a so far unrecognised high-pressure metamorphism in the Central Variscides, LITHOS 59 (2001) 109-125.

Reports of Research Activities

Speleothems and Pleistocene climate in Central Europe

W. Rosendahl, S. Kempe The Pleistocene climate history of Central Europe is characterized by a high variability, higher than in most other regions of Earth. This is due to the influence of the North Atlantic and its leading role in amplifying Glacial/Interglacial cycles and its interaction with the ma-jor transient continental ice masses. Some authors suggest that the glacially important Dansgaard/Oeschger Cycles are induced by internal periodic instabilities of the North Atlantic. Layers of coarse lithoclastics, which occur in North Atlantic sediments (so-called Heinrich layers) are witnesses of periodic wide-spread collapses of the Laurentian ice shield with severe climatic consequences for the climate in Europe. Also, the sudden ter-minations of the glacial periods can only be caused by short-term changes in the Earth System, such as the onset of the deep ocean circulation in the North Atlantic. The climatic record of the past several hundred thousand years has been recovered in a high resolution from ice cores both from Greenland and Antarctica, showing that the Northern Hemisphere is imposing its climate variability unto that of the southern hemisphere, albeit with attenu-ated amplitudes. Historically, geological records from continental Europe were therefore leading in identify-ing past climate changes, such as is documented in the names of the Interglacial and post-Glacial climate periods of the last glaciation cycle. Further back, however, this record is largely blank (perhaps with the exception of glacial loess covers and isolated paleolimnic records) and the paleoclimatologist needs to recur to the isotopic chronology established from continuous marine sediment and ice cores. Caves, however, provide a protected environment, where continental high resolution records can be found. Specifically the growth of speleothems provides a record which has largely been unread in Europe. This has many reasons. Some of them are methodologi-cally and others are inherent to the cave environment and the speleothems themselves. Also, not many geologist are familiar with the potential of cave speleothems and only few have first hand access to these resources. Methodologically is was first necessary to develop a dating technique, which could look beyond the time range of the 14C determination. After initially using U/Th α spectrometry, the development of U/Th TIMS dating now allows to use smaller samples and to obtain more precise dates, even for those time ranges, which so far were the realm of the 14C technique. The environmental reasons for being so slow in uncovering the cave-based climate record are several. The first is accessibility of the record. Many caves are protected under natural preservation regulations. Others lack sinter, or are only accessible to divers and even if they occur in quarries, where sampling could be conducted, this is often forbidden by the quarry owners or news of the resource reach the university teams too late. But the most discouraging fact is: the sinter in Central European caves appears to be a large jumble of broken masses, all encased in an impenetrable layer of Postglacial and Holocene sinter. This situation is unlike the situation in caves form more southern latitudes, where the stalagmites have apparently grown throughout much longer time periods and appear to be larger and less damaged. We are convinced that this broken nature of the sinter record is itself a climate record and that it is related to the large and frequent climatic changes in Europe itself, i.e. it has been

caused by the wide-spread occurrence of ice in caves under glacial and permafrost condi-tions. We therefore have essentially a punctuated record, consisting of continuous inter-glacial and interstadial sections separated by glacial hiatuses. The climate record in Central European caves will therefore need to be pieced together from many individual observations. This is a task which will take many years. The project ”Sinter and Paleoclimate in Central Europe during the Pleistocene” was started in 1999 and continued in 2001. One group (Prof. Dr. B. Hansen & Dr. B. Wiegand, Univ. of Göttingen) conducted the U/Th dating and measure isotopic composition of the sinter, while the second group (Kempe & Rosendahl) conducted the field research and collected the accompanying evidence such as sedimentological, mineralogical, paleontological and ecological data.

Fig. 1. TIMS-U/Th dated Speleothem samples from several german caves and their correlation with the SPECMAP chronostratigraphie of the last 350 000 years (SPECMAP after Martinson et al. 1987).

A Floating Varve Chronology from the Last Glacial Maximum Terrace of Lake Van/Turkey

S. Kempe, G. Landmann, G. Müller

Lake Van, Eastern Anatolia, Turkey, is - with a volume of 576 km3 - the 4th largest closed lake on Earth and one of the deepest (450 m). The lake is situated in a mountainous region (lake level at 1,648 m above sea level, m a.s.l.) were the Atlantic, Mediterranean, monsoonal and continental climate systems interfere with each other. Because of its alkaline chemistry (pH 9.78) aragonite and calcite are precipitated at river mouths (whitings) and in the water column. This produces a pronounced seasonal sedimentary signal, i.e. the formation of varves.

Because of these facts, Lake Van offers a high potential for paleoclimatic studies. Terraces at elevations of 12, 30, 55 and 80 m above the present lake level were noticed by travelers early on and studied in detail by Schweizer (1975). During three expeditions (1974, 1989 and 1990) we recovered sediment cores from the lake and studied their varve record (Kempe, 1977; Landmann 1996; Lemcke, 1996; Landmann et al., 1996 a,b). This record covers the last 15,000 years.

Here we present a floating varve chronology of 606 varves from the lake terrace at Güselsu in the SE corner of the lake (Fig. 1; Müller, 1994, unpublished). It documents the glacial highstand of Lake Van. Its age is fixed by three 14C determinations of organic remains which yield a calibrated (Bard et al., 1998) age of 20.3 cal. ka BP in the middle of the varved sequence. The profile documents that the glacial transgression (marked by the deposition of gravel and sand) reached 1,666 m a.s.l. at 21 cal. ka BP. At 20.7 cal. ka BP tripartite varves of a calcareous, clayey silt became discernable, indicating that the lake level had reached ca. 1,700 m a.s.l., i.e. water depth at this site reached about 30 m, deep enough to prevent the varves from being disturbed by wave action. Annual varve thickness was 0.9 cm/a in the following 400 years. Upward the varve thickness increased and slumps occurred, indicating a slow recession of the lake level. The carbonate phase in the varves is calcite, but SEM investigation reveals that part of the calcite is pseudomorphic after aragonite, indicating that glacial Lake Van was also highly alkaline and had a high Mg/Ca ratio, just as the lake today. By ca. 16 cal. ka BP the lake - in spite of its enormous depth - must have dried up completely: In the central basin the postglacial varve sequence is underlain by hard, dolomitic layers which we interpret as having formed during subaerial exposure. At 15 cal. ka BP the lake started to fill up again and soon was deep enough to preserve an unbroken Late Glacial and Holocene varve record.

This lake level history is similar to that of other deep lakes in the region, for example of the Lake Lisan/Dead Sea.

Fig. 1. Glacial terrace of Lake Van: The 606 years floating chronology from the outcrop Güselsu.

age [cal. ka BP]

20.1 20.3 20.5 20.7

pro

file

hei

gh

t [m

]

0

2

4

6

8

10

12

slumped sections14C-dates from plant remains

coarse laminated

3-phase varve cycle:- micritic calcite (summer)- silty-sandy detritus (spring)- clayish detritus (winter)

17.480 ± 220

17.550 ± 220 17.250 ± 115 = 20.3 cal. ka BP

average accumulation rate 0.9 cm

a -1

~1670[m a.s.l.]

Interdisciplinary project HIMAP in the Alpine Martell Valley, Italy

B. Eccarius, W. Rosendahl, P. Rottenbacher, T. Schiedek, H. Vogel

The project HIMAP (Hinteres Martelltal Projekt) is dealing with different disciplines of the Technical University of Darmstadt. The area is a test site for an international cooperation (Germany/Italy) with emphasis on future climate change. The investigation area is located in the National Park Stilfser Joch in the Alps of South Tyrol, Northern Italy. The valley extends about 25 km in NE-SW direction from an altitude of 700 m to 3.769 m (Cevedale Peak). The river Plima is mainly fed by melt water from several glaciers covering about 5 % of the area. In the central part the river is dammed by the Zufritt reservoir used for hydroelectric power plant. The geology consists mainly of metamorphic and magmatic rocks. The dominant lithology is composed of mica schist, phyllite, amphibolite, pegmatite and marble. In the Martell Valley ore exploitation on copper, iron, alunite, silver and gold were carried out in the last centuries. The youngest deposits are glacial tills and reservoir lake sediments. The morphology is strongly formed by glacial erosion. The steep slopes are furrowed by fluviatil erosion, rock and snow avalanches. The subprograms of the project are: 1) Geology. The region is geologically poorly mapped. Therefore a detailed mapping campaign has already started. 2) Hydrogeology. In the main valley the increasing farming and the tourism results in decreasing groundwater levels and water shortage. How does climate affect this in future? 3) Hydrochemistry: Due to the former ore exploitation several little rivers are contaminated with heavy metals. The intensive agriculture (apples, strawberries and wine) leads to rising levels in pesticides. Several spatial and temporal measurements are necessary to suggest precaution or remediation techniques. 4) Hydrology: It is planned to calculate the actual water balance from the glaciers to the reservoir, validated with the data from the lake level, the flow through of the Plima river and the pressure tunnel for hydroelectric power. Then a model is built up to simulate and optimize the reservoir running. With data from the other subprograms the future climate change is going to be tested within the model. Important processes like water shortage, flooding, extreme events should be evaluated in risk assessment scenarios. 5) Quaternary geology: Different works started to re-map glacial maximum, advance and retreat, debris, tills and soils in comparison to former investigations. On the glacier ice cores for analysis of hydrochemistry (inorganic, organic, isotopes) are planned. 6) Climatology: The actual climatic data (decades) of the surrounding stations should be analyzed and interpolated for the Martell valley. Future climate predictions of global and regional models should be critically evaluated for the use in the project. 7) Engineering geology: Due to the glacier retreat and the rising precipitation a detailed mapping of risk areas for intensified avalanches has started. Especially the processes affecting the mass movements should be cleared in detail with lab and field experiments. 8) Sedimentology: The reasons above (more rain, floods and avalanches) automatically enlarges the sediment load of the Plima river and fills the reservoir. This endangers the profitability. Sedimentation rates are going to be determined and interpolated in the future. 9) Socio-economic sciences: All the mentioned aspects are affecting life in the region in terms of economy (water and energy prices, resources management, life in risk areas), health (water and food quality) and future standard of living.

Urban inputs and fluxes in the groundwater under the area of Darmstadt

M. Beier, G. Ebhardt

Growing and condensing urban areas represent a danger to groundwater quantity and quality. The sealing of the surface reduces the natural recharge from precipitation whereas additional, artificial recharge comes from water exfiltrating from sewers and mains. While this has a positive effect on the groundwater balance, the groundwater quality is deteriorated by input of sewage. Other impacts on the groundwater quality can come from the use of road salt in the winter and the high density of active or abandoned industrial plants or traffic installations, e.g. gas stations, where for example spillage or leakage of various substances can take place. The study in the urban area of Darmstadt deals with the impact of these specifically urban factors on the groundwater. Final aim is to estimate the anthropogenic and natural fluxes. To determine the characteristics of urban inputs, samples of dissolved road salt, sewage and precipitation water were analysed. The groundwater was sampled in 50 observations wells or springs in March 2001 and in 56 points in September 2001. The sampling points were arranged in three measuring profiles perpendicular to the groundwater flow, recording the groundwater characteristics upstream, in the centre and downstream of the city. The change of groundwater quality under the city was determined by comparing these profiles. The groundwater flow in the study area is directed westwards crossing two basically different kinds of aquifers. In the east, there are hard rock aquifers (crystalline rocks of the Odenwald and sediments and volcanic rocks of Lower Permian age). The more important aquifers are the quaternary sediments in the west, composed of gravel and sand interbedded with clay and silt which cause a multiaquifer formation. From the hard rock to the quaternary aquifer, the groundwater quality changes naturally, verified by increasing calcium and bicarbonate contents, pH values and the electrical conductivity. Yet many properties of the groundwater quality can be attributed to urban input. Phosphate, potassium, boron, COD, ammonia respectively nitrate, temperature and electrical conductivity are increased in the centre and downstream of the city. These parameters typically show high values in sewage and thus are attributed to the impact of sewage leakage. Approximately 14% of the sewers in Darmstadt are estimated as being leaky, but the spatial distribution of the leakages is not known. High values of sodium, chloride and conductivity are referred to the influence of road salt. Samples from industrial areas show high values for several parameters, including conductivity, sulphate, sodium, chloride and boron. Additional to the urban and geogenic influences, agricultural input is decisive for the groundwater quality in parts of the Darmstadt area. Increased concentrations of nitrate are often related to agricultural land use, though they can also be connected to fertilisation of parks and gardens inside the city. The quality properties are not distributed homogeneously, but show a high variation. Neighbouring sampling points with the same screen depth may show significant differences in the groundwater quality. In many samples, some of the parameters typical for a certain influence are considerably increased, while others remain close to of the natural background. To regionalize the data, chosen parameters will be analysed with geostatistical methods, applied separately for the three measuring profiles. With the help of a newly built groundwater model, fluxes between the three profiles upstream, in the centre and downstream of the city will be determined.

Guideline for evaluation of geotechnical safety of river dikes

H. Vogel, H. Molek

River dikes are one of the most important instruments of technical flood control. They protect housing areas and industrial plants, nowadays situated in the formerly natural flood areas of the rivers. Especially in the state of Hessen, great efforts are undertaken continuously to adapt the river dams and dikes to the new, increasing safety requirements. The authorities have to use their short financial resources for reconstruction or sanitation of the weakest dikes first. For a comparative evaluation of the geotechnical safety of all dikes, a guideline was developed. This guideline puts together all relevant parameters and offers a procedure that allows evaluation of geotechnical safety of river dikes. In the first step all parameters are collected, which are somehow important for stability- and risk assessment of river dikes. Altogether 24 parameters were identified. For example the parameter enclose the dikes • geometry (crest height, crest level, slope inclination, …) • internal structure (bedding, homogeneity, subdivision into zones, sealings, drainage

system, …) • building material (mechanical properties, …) • geological and hydraulic underground situation (stratification, thickness, …) • stability analysis (stability of slopes, base failure stability, …) • actual situation (damages, flood behaviour, installations, …). These parameters are weighted, because they are not all of the same importance for safety evaluation. On the basis of empirical criterions, the quality of each parameter is scored with points in the range of the weighting. Adding all points and multiplicate the sum with two factors leads to a score for each dike. One factor stands for the relation of the number of available parameters to the total number of possible parameters. The other one stands for the quality of the given parameters. The resulting score corresponds to the geotechnical condition of the evaluated dike. The higher the score, the better the dike. Normally, only a part of the relevant parameters is available. Therefore the guideline gives the possibility to assess, if the given informations (parameters) are enough to carry out reliable geotechnical risk assessment. In the case, that enough parameters are available, the dike section is sorted into the priority-list, with the weakest dikes at the top. If not enough parameters are available, first more investigations - especially to get the higher weightened parameters - have to be carried out to give additional informations. These sections are sorted in a second list. After additional investigations and new evaluation adding to priority list will be possible. Used by an expert, the new guideline is a helpful tool for a comparative evaluation of geotechnical safety of river dikes and enables the authorities to organize the dikes in a list of priorities.

Swelling and shrinking of clay as trigger factors for mass movements

T. Nix, H. Molek

The investigations on mass movements of the Messel sediments presumed swell- and shrink-deformations of the bituminous clay as one of the trigger factors for initial displacements in molecular scale. A causal relation to the development of sections of weakness was supposed. Swell-tests verified the high potential swelling capacity of the Messel sediments. The swelling process of the clay minerals (smectite and mixed-layer minerals) is not blocked by the rather immobile organic matter. In contrast the actual swelling capacity of the undisturbed Messel sediments is low (Fig. 1). The actual swelling is, among other things, limited by the high natural initial saturation of the sediments. That means, swell processes are of minor importance as trigger factors for mass movements in Messel. Nevertheless structural changes and the development of local concentrations of stress have to take in account even for the low actual swelling properties (osmotic swelling).

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Fig. 1. Results of the swell tests (actual swelling capacity, undisturbed samples). Modest changes in water content initiate shrink-processes of the laminated sediments. Due to the different physical and mechanical properties of the single layers, fissures are produced parallel to lamination. Owing to these fissures, the shear strength of the sediment is reduced to residual shear strength. The shrinkage process of the fine laminated organic rich clay is of major importance as a trigger factor for mass movements. Especially shallow slides within the weathered zone use the shrinkage cracks by preference as sliding surfaces.

A new GIS-based global denudation model

M. Hinderer, H. Schäuble, P. Suess* *Inst. für Geologie und Paläontologie, Univ. Tübingen, Tübingen

Quantification of sediment fluxes is an important task to understand and model the evolution of sedimentary basins and the interplay of uplift and erosion in the hinterland. However, a review of sediment fluxes and denudation rates in the literature shows that extensive data sources from disciplines such as isotope geochemistry, physical geography, agricultural sciences, and water engineering have been largely ignored by sedimentologists and modellers so far. In particular, a large gap exists between micro-scale and global-scale studies although these offer important insight in the control of denudation on medium-sized systems and are necessary for regional and global up- and downscaling. We try to close this gap by (i) a new data base with emphasis on modern medium-size systems, (ii) by using global digital data bases for basin characterisation, and (iii) by development of a new GIS-based denudation model that combine existing micro-scale and large-scale approaches. This approach of understanding processes of modern sedimentary systems will be used to gain new insights into fossil denudation- accumulation systems.

Sedimentology and Palynofacies of the Upper Cretaceous (Vocontian Basin, SE France)

A. Götz, M. Hinderer, S. Feist-Burkhardt*

*The Natural History Museum, Dept. of Palaeontology, London Sedimentology and palynofacies of Upper Cretaceous platform carbonates are studied in outcrops from SE France representing a palaeogeographic cross-section from the proxi-mal part of the platform to the distal basin. Based on the well established lithostratigraphic and biostratigraphic framework, the stratigraphic and spatial distribution patterns of sedi-mentary organic matter are analysed with respect to relative sea level changes. The main factors influencing the stratigraphic and spatial variations of land-derived, relatively allochthonous and marine, relatively autochthonous organic particles are the proximity of land, the organic productivity, the level of biodegradation and the hydrodynamic conditions of the depositional system. Palynofacies parameters used for palaeoenvironmental and sequence stratigraphic interpretations are (1) the ratio of continental to marine constituents (CONT/MAR ratio), (2) the ratio of opaque to translucent phytoclasts (OP/TR ratio), and (3) the relative proportion and species diversity of marine plankton. Ternary diagrams are used to decipher transgressive-regressive trends within the succession by significant proximality changes. The integrated study of sedimentary and organic facies enables a detailed reconstruction of the sedimentary system and contributes to establish a high-resolution cyclo- and sequence stratigraphic framework for the Upper Cretaceous of the Vocontian Basin.

Fig. 1. Idealized palaeogeographic and stratigraphic trends of the palynofacies parameters used for basin analysis in the Upper Cretaceous of SE France.

In-situ Observation of the Hygroscopic Behavior of Individual Aerosol Particles

by Environmental Scanning Electron Microscopy

M. Ebert, M. Hof, S. Weinbruch The hygroscopic behavior of aerosol particles is of great importance for many fields of environmental science. For example, increasing relative humidities in the atmosphere leads to a hygroscopic growth of aerosol particles caused by the uptake of water. This process severely influences light scattering, cloud formation and precipitation. In addition, the atmospheric lifetime and the chemical reactivity of the particles are also changed [e.g., 1]. The hygroscopic properties of aerosol particles are also important in environmental and occupational health studies, as the deposition of the particles in the respiratory system is effected by the hygroscopic growth [e.g., 2]. In conventional electron microscopes, samples can be studied only at high vacuum condi-tions. Therefore, all volatile components (e.g., nitrates, organics) and adsorbed water are lost during analysis. This major drawback of electron microscopy is now overcome by the new technique of environmental scanning electron microscopy (ESEM). In this instrument, samples can be studied in-situ at different gas compositions and pressures up 2000 Pa. If water is used, the known partial pressure can be directly translated into the relative humid-ity (RH) in the sample chamber. The high pressure in the sample chamber enables the electron microscopical study of water in the liquid state. Furthermore, the gaseous atmos-phere in the sample chamber leads to charge equilibrium on the sample surface. There-fore, insulating samples need no conductive coating. The hygroscopic behavior of the atmospheric aerosol has been studied for a long time [e.g., 3]. At very low relative humidities, the soluble components (inorganic salts) are solid. As the relative humidity is increased, the particles remain solid up to a characteristic threshold value (well below 100% RH), where the particles adsorb water, leading to a satu-rated aqueous solution [e.g., 4]. This process is called deliquescence and the corre-sponding relative humidity the deliquescence relative humidity (DRH). Further increase of the relative humidity leads to additional water condensation and, thus, to droplet growth. If the relative humidity over the droplets is decreased again, water evaporation is observed. However, crystallization does only occur at relative humidities well below the DRH due to the slow nucleation kinetics. Environmental scanning electron microscopy enables the investigation of the deliques-cence behavior of submicrometer particles by imaging (secondary and backscattered electrons) and by energy-dispersive X-ray spectroscopy. In our first experiments, we have studied the deliquescence behavior of NaCl, (NH4)2SO4, Na2SO4 and NH4NO3 particles (common salts in the atmospheric aerosol) in the size range of 0.1 to 20 µm. All experi-ments were carried out at a temperature of 5°C. One example (Na2SO4) is given in Figure 1. At a relative humidity of 80% (Fig. 1a) the particle is still solid, at 85% RH a liquid is observed (Fig. 1b). At a temperature of 5°C, the DRH of Na2SO4 is about 82.5% (Fig. 2). Decreasing the RH leads to crystallization again (Fig. 1c).

In Fig. 2, the deliquescence relative humidities obtained by environmental scanning elec-tron microscopy are compared with the data of Tang and Munkelwitz [5] and a good agreement is observed. Fig. 1. Secondary electron images of a Na2SO4 particle at various relative humidities: a) solid particle at 80% RH, b) saturated liquid at 85% RH, c) crystallized particle at 60% RH.

Fig. 2. Deliquescence relative humidities (T = 5°C) of different salts observed in the ESEM and calculated from the data of Tang and Munkelwitz [5]. As we have demonstrated for a variety of pure inorganic salts that the deliquescence rela-tive humidity can be determined accurately by environmental scanning electron micros-copy, we now want to study ambient aerosol particles which often consist of complex mix-tures of various phases. References [1] Charlson, R. J.; Schwartz, S. E.; Hales, J. M.; Cess, R. D.; Coakley, J. A.; Hansen, J. E.; Hämeri, K.; Laaksonen, A.; Väkevä, M.; Suni, T.; J. Geophys. Res. 106 (2001) 20749– 20757. [2] Foster, W. M., in: Holgate, S. T.; Samet, J. M.; Koren, H. S.; Maynard, R. L.; Academic Press (1999) 295-324. [3] Junge, C.; 1952, Beiheft, 1-55. [4] Seinfeld, J. H.; Pandis, S. N.; Wiley (1998) [5] Tang, I. N.; Munkelwitz, H. R.; Atmos. Environ. 27A (1993) 467-473.

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Diploma Theses Bienkowski, R.; Stratigraphie der Mauna Loa Lavaflüsse des Kanohina Gebietes (Nord), Ocean View/Big Island, Hawaii-USA, Geologische Kartierung, Physical Geology, July 2001. Glab, M.; Localisation of sensitive reservoir settings for induced seismicity using Finite Element Analysis - A geomechanical investigation on fault reactivation due to gas produc-tion from Dutch subsurface (in engl.), Engineering Geology, February 2001. Kauer, M.; Stratigraphie der Mauna Loa Lavaflüsse des Kanohina Gebietes (Süd), Ocean View/Big Island, Hawaii-USA, Geologische Kartierung, Physical Geology, July 2001. Lerch, C.; Hydrogeologische Modellierung im Stadtgebiet Darmstadts, Hydrogeology, No-vember 2001. Marquardt, K.; Entwicklung einer Methode zur Berücksichtigung des Flächenverbrauchs als Umweltwirkungskategorie, Hydrogeology, February 2001. Mügge, V.; Geologische Kartierung des Marteller Höhenweges (Martelltal/Südtirol) als Grundlage für ein Geopfadkonzept, Physical Geology, December 2001 Schüffler, S.; Analyse des Einflusses des kontaminierten Flusses San Antonio de los Banos auf die Entnahmezone der Brunnengalerie Acueducto Cuenca Sur, Provinz Havana, Cuba, Hydrogeology, November 2001. Walker, M.; Kleingartenanlagen als Stoffquelle für das Grundwasser urbaner Gebiete – Dargestellt am Beispiel der Stadt Halle an der Saale, Hydrogeology, May 2001.