General Program IM2018

ABSTRACT
GRAIN BOUNDARY AND SURFACE DYNAMICS IN
CERAMICS
Many experimental investigations have been tried for understanding the
dislocation-grain boundary interaction in materials, but these experiments were
mostly carried out statically, and the dynamic behavior is still not well understood
yet. It has been known that several oxide crystals can be plastically deformed
even at R.T. by dislocation slip like metals. In this study, the in-situ nanoindentation
experiments were conducted for SrTiO3 single crystal and its bicrystals inside
TEM. For bicrystal experiments, various types of GBs including CSL (Coincidence
Site Lattice) GBs and low angle tilt and twist GBs were prepared. Various interface
phenomena such as dislocation pile-up at GBs, jog formation, jog-drag motion
were dynamically observed. The dislocation-GB interaction and its dependence
on the GB characters will be discussed in detail.
The properties of lithium ion battery (LIB) cathodes strongly depend on the
diffusion of lithium ions during charge/discharge process. Then, direct visualization
of lithium site is required to understand the mechanism of the diffusion of lithium
ions. In this study, aberration corrected STEM were applied to directly observe the
{010} surface, which coresponded to perpendular to the 1-D diffusion orientation,
of the olivine LixFePO4. It was found that orientation of boundary layers at the
FePO4/Li2/3FePO4 interface gradually changed from lower index planes to
higher index planes. The mechanism of the lithiation/delithiation from and to the
surface will be discussed based on the observation results.
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