期刊
ACTA MATERIALIA
卷 56, 期 18, 页码 5276-5284出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2008.07.004
关键词
Nanoparticles; Oxides; Oxidation; Reduction; Transmission electron microscopy (TEM)
资金
- Grant-in-Aid for Scientific Research (Category S)
- Center of Excellence for Advanced Structural and Functional Materials Design
- Ministry of Education, Culture, Sports, Science and Technology, Japan
The structural stability of hollow CuO and NiO nanoparticles associated with reduction and oxidation reactions at high temperatures was studied by transmission electron microscopy (TEM). Hollow Cu2O and NiO in annealing under 5.0 x 10(-5) Pa was observed to have shrunk at 473 and 623 K, respectively, where the reduction reactions from oxides to metals started. As a result of shrinking associated with reduction, hollow oxides turned into solid metal nanoparticles after annealing at higher temperatures for a long time. In addition, hollow oxides shrunk and collapsed through high-temperature oxidation. It was found that shrinking of hollow oxides during oxidation occurs at temperature where the diffusion coefficients of slower diffusing species reach around 10(-22) m(2) s(-1). Annealing at high temperatures both in a vacuum and in air leads to atomic movement that results in the annihilation of nano-holes inside hollow nanoparticles, and a consequent reduction in the extra inner-surface energy. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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