Please use this identifier to cite or link to this item: http://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
Source: 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 (CeO<sub>2</sub>) and iron oxide (Fe<sub>3</sub>O<sub>4</sub>) 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 CeO<sub>2</sub> nanoparticles. The growth of CeO<sub>2</sub> 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 CeO<sub>2</sub> can be applied to other porous materials synthesized using self-assembly in solution. The self-assembly of Fe<sub>3</sub>O<sub>4</sub> 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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