| CZECH NANO TEAM | Physics of Nanostructures and Nanotechnologies

• Mechanical properties of materials, dislocation processes.
• Atomic structure of extended defects, grain boundaries, migration and segregation effects.

• Nano-scale phenomena such as misfit dislocations at interfaces between thin films and substrates.

• Structure and properties of intermetallics, computer modelling of crystal defects and interfaces.

The supervisor of 3 successful diploma theses, 2 PhD and CSc theses.

Publications:

Author or co-author of more than 160 scientific publications, editor of 2 books, joint papers with the University of Pennsylvania, University of Tokyo, Université Paris Sud, Kyoto University etc. The obtained results were cited in more than 1000 papers.

Selected stays abroad:

• In 1980-81 visiting scientist at University of Pennsylvania in Philadelphia (Prof. D.P.Pope) for 12 months

• In 1988 Matsumae fellowship at University of Tokyo (Prof. S.Takeuchi) for 6 months

• In 1991-95 professeur invité and visiting scientist at CEMES CNRS Toulouse for 5 months in total

• In 1994-00 invited by Prof. V.Vitek from University of Pennsylvania in Philadelphia for 6 months in total

• In 1995-01 professeur invite and visiting scientist at Université Paris XI Orsay for 4 month in total

• In 1996-02 invited by Prof. M.Yamaguchi from Kyoto University for 6 months in total

Selected solved international projects:

• USA-NSF INT-93-07418 (1993-95) "Atomic structure of asymmetrical grain boundaries and nucleation of phase transformations at grain boundaries"

• EC-CIPA CT 93 0112 (1994-97)"Grain boundaries and material properties"

Selected related publications from last 5 years:

• V. Paidar, L. Wang, M. Šob, V. Vitek: A study of the applicability of many-body central force potentials in NiAl and TiAl, Modelling Simul. Mater. Sci. Eng. 7, 369-381(1999)

• V. Paidar: Non-radial interaction forces between superpartials in B2 and L12 ordered alloys, Phil. Mag. A 80, 2957-2970 (2000)

• V. Paidar, V. Vitek: Stacking fault-type interfaces and their role in deformation. In, Intermetalic Compounds, Progress (Eds. J.H. Westbrook, R.L. Fleischer). Vol. 3, John Wiley, Chichester, 437-467 (2002)

• V. Paidar, K. Kishida, M. Yamaguchi: Polarization of plastic deformation modes in PST TiAl crystals, J. Mater. Res. 18, 702-708 (2003)

• P. Lejček, S. Hofmann, V. Paidar: Solute segregation and classification of [100] tilt grain boundaries in a-iron: consequences for grain boundary engineering. Acta Mater. 51, 3951-3963 (2003)

Group members:

Václav Paidar, Pavel Lejček, Juliana Gemperlová, Jaromír Kopeček, Barbora Bártová

Main Research Subjects:

Preparation of two-dimensional objects (grain boundaries), study of their equilibrium properties (corrosion, chemical composition) as well as dynamic behavior (migration). The purpose is to obtain a database of anisotropic properties of these objects with a prospective use in technology of production of advanced materials with optimum properties via Grain Boundary Engineering (controlled character and distribution of interfaces in a poly- and micro-crystalline materials). The studies are performed in cooperation with numerous foreign laboratories in Max–Planck–Institute for Metals Research, Stuttgart, Germany, Ecole Nationale Superieure des Mines, St. Etienne, France, or Tohoku University, Sendai, Japan.

The members of the team have a large experience in TEM studies including contrast simulations of interfaces especially grain boundaries. Developed one-grain dark field technique could be applied to studies of various internal interfaces.

Modelling of interface structures on atomic level, evaluation of interface effects on the physical and chemical properties of materials with interfaces.

Selected Specific Equipment:

For preparation of poly- and microcrystalline alloys, a vacuum furnace Balzers VSG-02 will be employed. Model materials for the study of the properties of interfaces – bicrystals – will be prepared using the new optical furnace for floating–zone–melting technique FZ–T–12000–X–VI–VP (Japan). For characterization of these interfaces, methods of X–ray diffraction topography will be used. Chemical composition of the interfaces is studied by AES and HREM at well-equipped foreign laboratories. The laboratory is equipped for precise metallographic preparation of the samples.

The transmission electron microscope Jeol JEM 1200EX is available for conventional TEM study of structure analysis. The equipment for preparation of quality samples is indispensable for successful studies of interface defects. At present, Twin Jet Electropolisher (Fischione) is used, and in 2004, we will buy Ion Miller for TEM thin foil preparation and surface processing of materials that cannot be electrolytically polished as semiconductors, ceramics, heterogeneous metallic materials, multilayers, plasma sprayed or thermally sprayed layers, metallic glasses or composites.

Additional recent selected publications by group members:

• J. Kopeček, P. Kratochvíl, D. Rafaja, D. Plischke: Ordering in the sublattices of Fe3Al during the phase transformation B2↔D03, Intermetallics 7, 1367-1372 (1999)

• J. Adámek, P. Lejček: Melt growth of non-isoaxial bicrystals of an Fe–3%Si alloy, J. Crystal Growth 211, 461–465 (2000)

• T. Vystavel, J. M. Pénisson, A. Gemperle: High resolution and conventional Electron Microscopy study of a =3 [101]{121} twin grain boundary in molybdenum, Phil. Mag. A 81, 417-429 (2000)

• P. Lejček, O. Schneeweiss: Solute segregation at ordered grain boundaries, Surface Sci. 487, 210–222 (2001)

• P. Lejček, S. Hofmann: Grain boundary segregation, anisotropy and prediction, in: Encyclopedia of Materials: Science and Technology – Updates, K.H.J. Bunshaw, R.W. Cahn, M.C. Flemings, E.J. Kramer and S. Mahajan, Eds., Pergamon, Amsterdam, #200115, pp. 1–7 (2002)

• A. Gemperle, J. Gemperlová, N. Zárubová: Refined prediction and observation of dislocation structures in a low  symmetric grain boundaries, Interface Sci. 10, 59-65 (2002)

• J. Gemperlová, A. Jacques, A. Gemperle, N. Zárubová: Transformation of slip dislocations in 3 grain boundary, Interface Sci. 10, 51-57 (2002)

• M. Polcarová, J. Brádler, A. Jacques, P. Lejček, A. George, O. Ferry: Grain boundary migration observed by in-situ synchrotron radiation topography, J. Phys. D: Appl. Phys. 36, A98–A101 (2003)

• P. Lejček, A. Fraczkiewicz: Boron segregation in intermetallics: on the possible origin of a low-level intergranular segregation, Intermetallics 11, 1053–1063 (2003)