Please use this identifier to cite or link to this item: https://scholarbank.nus.edu.sg/handle/10635/135868
Title: TEM TOMOGRAPHY AND HOLOGRAPHY OF LOW DIMENSIONAL OXIDE STRUCTURES
Authors: TAN HUI RU
Keywords: TEM, electron tomography, electron holography, low dimensional, cerium oxide, iron oxide
Issue Date: 30-Dec-2016
Citation: TAN HUI RU (2016-12-30). TEM TOMOGRAPHY AND HOLOGRAPHY OF LOW DIMENSIONAL OXIDE STRUCTURES. ScholarBank@NUS Repository.
Abstract: Through the use of transmission electron microscopy (TEM), electron tomography and holography, cerium oxide (CeO2) and iron oxide (Fe3O4) nanoparticles were studied. Cerium oxide was investigated by electron tomography, revealing details about the structure, growth process, and three-dimensional shape of the as-synthesized CeO2 nanoparticles. The growth of CeO2 nanoparticles in the hydrothermal process was found to follow a two-step mechanism of oriented attachment and Ostwald ripening. The crystallographic orientation of the pores and corresponding aggregation mechanism for the single-crystalline and porous CeO2 can be applied to other porous materials synthesized using self-assembly in solution. The self-assembly of Fe3O4 nanoparticles was examined by electron tomography and holography. Large particles (~100 nm) assembled to chains up to micrometers long, which small particles (~17 nm) formed two-dimensional (2D) arrays. The relationship between axial ratio (width/length of chain/array) and magnetic domain states of chains/arrays was established, and was in good agreement with theoretical predictions. Coercivities of different particle chain lengths could also be determined from in-situ magnetization reversal processes using the technique of electron holography, which could not be obtained from other conventional techniques that give only bulk magnetic information.
URI: http://scholarbank.nus.edu.sg/handle/10635/135868
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