cfaed Seminar Series

cfaed Seminar Series

Prof. David Rafaja , Institute of Materials Science, TU Bergakademie Freiberg

Interface phenomena in nanostructured materials

12.01.2017 (Thursday) , 13:00 - 14:00
Seminar Room 115 (HAL) , Hallwachsstr. 3 , 01187 Dresden

Internal interfaces like crystallite, grain or phase boundaries are very important
microstructure features, as they influences significantly the physical properties of solids. In
nanostructured materials, the density of internal interfaces is extremely high, thus the
interfaces and interface phenomena become a dominant factor that affects the properties
of nanocrystalline materials and nanocomposites. This generally well-known and
frequently utilized relationship between the microstructure and properties is also the basic
idea behind the “defect engineering”, which employs the internal interfaces as a kind of
microstructure defects to tailor the materials properties.
In this talk, local heteroepitaxy and specific orientation relationships between neighbouring
nanocrystallites in compact nanocomposites will be discussed as examples of the
interface phenomena, which facilitate the formation of lattice strains at internal interfaces,
and are therefore often used to increase the materials hardness and/or to stabilize
metastable phases at high temperatures. The increase of the hardness will be illustrated
on the transition metal nitrides containing aluminium and on the boron nitride
nanocomposites. The prospects of the stabilization of metastable phases will be illustrated
on the ternary systems (TM,Al)N and (Cr,Zr)2O3-x. The effect of further microstructure
defects, e.g., stacking faults, on the phase transformations and decomposition of
metastable phases will be discussed. Additionally, this talk will show the complementarity
of the diffraction, microscopic and spectroscopic methods when they are applied to study
nanostructured materials.

David Rafaja studied the Solid State Physics at the Faculty of Mathematics and Physics,
Charles University in Prague. He specialized in the structure and microstructure analysis of
solids using diffraction and spectroscopic methods and electron microscopy. Until now, he
is using these methods to describe the relationships between the crystal structure and/or
microstructure of solids and the materials properties.
Already in his diploma and PhD theses, he modified the conventional X-ray diffraction
methods to be applicable for the study of thin films and multilayers, and investigated the
relationship between the microstructure of hard coatings and their properties. In his
habilitation thesis, he further developed experimental methods for microstructure analysis.
From 1993 to 2002, David Rafaja served as a head of the X-ray diffraction laboratory at
the Department of Semiconductor Physics, Charles University Prague and as associated
professor in the Department of Condensed Matter Physics (Charles University Prague). At
the beginning of 2003, he was appointed to the university professor at the TU
Bergakademie Freiberg.
From 1993 to 2002, David Rafaja spent almost two years in the Institute for Chemical
Technology of Inorganic Materials at TU Vienna, where he investigated mainly diffusion
processes in binary systems with finite geometry, one year in the Department of Materials
and Earth Sciences at TU Darmstadt working on magnetic multilayers, and several months
in the Institute of Crystallography at the Amsterdam University.
Currently, David Rafaja is director of the Institute of Materials Science and dean of the
Faculty of Materials Science and Materials Technology at the TU Bergakademie in
Freiberg, member of the Board of Directors at the International Centre for Diffraction Data
(ICDD, Pennsylvania) and head of the section Crystallography at the Deutsche
Physikalische Gesellschaft.

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