Application of Electron Crystallography Methods in Metallurgy

Date:
13
Wednesday
November
2019
Lecture / Seminar
Time: 11:00-12:00
Location: Perlman Chemical Sciences Building
Lecturer: Prof. Louisa Meshi
Organizer: Department of Molecular Chemistry and Materials Science
Details: Department of Materials Engineering, Ben-Gurion University of the Negev
Abstract: Due to the direct correlation among the physical properties and crystal structur ... Read more Due to the direct correlation among the physical properties and crystal structure of materials, study of the latter is crucial for fundamental understanding of the properties. In the era of nano-science, objects of interest are getting smaller and traditional single-crystal and powder X-ray diffraction methods cannot be applied for characterization of their atomic structures due to the unavailability of single crystals and/or small quantity and size of these crystals in the multiphase specimens. Thus, electron crystallography (EC) (which is defined as a combination of electron diffraction and imaging methods) is sometimes the only viable tool for the analysis of their structure. In the previous century, electron diffraction (ED) was considered to be unsuitable for structure determination due to the problems of data quality arising from dynamical effects. At the last decades, researchers have shown that influence of dynamical effects can be substantially reduced if beam precession (PED) is used and/or data collection is performed in the off-axis conditions - enabling solution of atomic structures with various complexity (from inorganics to proteins). Our group focuses on development and application of EC methods for structure solution of nano-sized precipitates and characterization of structural defects in steels and light alloys. This study is technologically essential since precipitates and defects dictate physical properties of these structural materials. It must be noted that, atomic structures of intermetallics were not solved previously using solely ED methods. Reason for that is in the nature of intermetallic compound's structures. Contrarily to other complex materials, the atomic distances and angles of intermetallics are not fixed and coordination polyhedra are usually unknown. Thus, structure solution of these compounds is harder to validate. In the present seminar, contribution of our group in the development of routine structure solution path for aluminides (as an example of intermetallics) will be presented. In addition, characterization of structural defects, influencing the performance of the studied materials, will be shown.
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