Kolan Madhav Reddy
Shanghai Jiao Tong University, China
Title: Nanoscale deformation characterization of light-weight ceramics
Biography
Biography: Kolan Madhav Reddy
Abstract
Lightweight ceramics often composes of oxides, nitrides, carbides and borides have recently gained technological
importance or even still at the development stage with regard to future applications. Therefore experimental
observations of the atomic structure and their deformation mechanisms of lightweight ceramics are of extreme
importance in understanding and tailoring the materials properties. In this presentation, author will demonstrate the
atomic imaging of boron-rich solids (i.e., B4C and B6O) using newly developed annular bright field scanning transmission
electron microscopy (ABF-STEM) technique. The atomistic observations upon deformation provide the direct evidence
for the intragranular amorphous shear bands in both these brittle ceramics. To reduce the brittleness, nano-crystalline
B4C (n-B4C) microstructure with a homogenous distribution of nano-sized pores and amorphous carbon at grain
boundaries (GBs) was synthesized at relatively low temperatures. Transmission electron microscopy (TEM) of n-B4C
reveals that the unusual nanosize effect arises from the deformation reduced elimination of nano-porosity mediated
by grain boundary sliding with the assistance of the soft boundary phases. Finally, our recent observations combined
with computer simulations reveals GB sliding leads to the amorphous band formation at pre-distorted icosahedral GB
regions with initiation of cavitation within the amorphous bands. These theoretical and experimental results provide an
atomistic explanation for the influence of GBs on the deformation behavior of nano-crystalline ceramics.