Effect of Zirconia Content on the Oxidation Behavior of Silicon Carbide/Zirconia/Mullite Composites |
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| Authors: | Cheng-Yuan Tsai Chien-Cheng Lin Avigdor Zangvil Ai-Kang Li |
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| Affiliation: | Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 300, Taiwan;Materials Research Laboratory and Department of Materials Science and Engineering, University of Illinois, Urbana, Illinois 61801;Materials Research Laboratory, ITRI, Chutung 310, Taiwan |
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| Abstract: | The oxidation of hot-pressed SiC-particle (SiCp)/zirconia (ZrO2)/mullite composites with various ZrO2 contents, exposed in air isothermally at 1000° and 1200°C for up to 500 h, was investigated; an emphasis was placed on the effects of the ZrO2 content on the oxidation behavior. A clear critical volume fraction of ZrO2 existed for exposures at either 1000° or 1200°C: the oxidation rate increased dramatically at ZrO2 contents of >20 vol%. The sharp transition in the oxidation rate due to the variation of ZrO2 content could be explained by the percolation theory, when applied to the oxygen diffusivity in a randomly distributed two-phase medium. Morphologically, the composites with ZrO2 contents greater than the critical value showed a large oxidation zone, whereas the composites with ZrO2 contents less than the critical value revealed a much-thinner oxidation zone. The results also indicated that the formation of zircon (ZrSiO4) at 1200°C, through the reaction between ZrO2 and the oxide product, could reduce the oxidation rate of the composite. |
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