標題: Oxygen Diffusivities and Surface Exchange Coefficients in Porous Mullite/Zirconia Composites Measured by the Conductivity Relaxation Method
作者: Ko, Hong-Da
Lin, Chien-Cheng
材料科學與工程學系
Department of Materials Science and Engineering
公開日期: 1-一月-2010
摘要: Oxygen diffusivities and surface exchange coefficients in various porous mullite/zirconia composites were measured at oxygen partial pressures ranging from 20.2 to 2.02 kPa using the conductivity relaxation method. However, the oxygen diffusivities in porous high-zirconia composites could not be determined because of the predominant surface exchange reaction. Oxygen diffusivities and surface exchange coefficients in low-zirconia composites increased with the zirconia content, while the surface exchange coefficients in high-zirconia composites were approximately constant. A percolation threshold of the surface exchange coefficients occured at similar to 40 vol% zirconia for porous zirconia/mullite composites. The oxygen diffusivities in porous low-zirconia composites were independent of the oxygen partial pressure, implying that oxygen diffusion in these composites was related to the migration of oxygen vacancies, whose concentration was independent of the oxygen partial pressure. The surface exchange coefficients of high-zirconia composites decreased with increasing oxygen partial pressure. Finally, it was inferred that the rate-limiting step for oxygen surface exchange could be the charge-transfer process.
URI: http://dx.doi.org/10.1111/j.1551-2916.2009.03382.x
http://hdl.handle.net/11536/6261
ISSN: 0002-7820
DOI: 10.1111/j.1551-2916.2009.03382.x
期刊: JOURNAL OF THE AMERICAN CERAMIC SOCIETY
Volume: 93
Issue: 1
起始頁: 176
結束頁: 183
顯示於類別:期刊論文


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