科研之友
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摘要
Single crystalline, arc-melted and SPS poly-crystalline NbSi2 samples were prepared for oxidation experiment at 1023 K, and the effects of cracks, pores and grain boundary on the oxidation behavior of NbSi2 were investigated. For arc-melted poly-crystalline samples, NbSi2 fully turned into powders after 3 h exposure at 1023 K, which is known as the "pesting" phenomenon. As a comparison, no pesting was found in the dense SPS poly-crystalline samples and single crystals after 89 h. The oxide formed on NbSi2 at 1023 K consists of Nb2O5 and minor SiO2. The Nb2O5 is lose and nonprotective, which spalls from the sample during oxidation. The oxidation kinetics of all the NbSi2 samples at 1023 K follows a linear law. The oxidation rate is intrinsically determined by the reaction rate between the matrix and the oxygen in air, which in turn is determined by the exposure area of the sample. The NbSi2 poly-crystalline sample shows a much larger weight change than that of the single crystalline sample, indicating grain boundaries and pores increase the effective area of oxidation reaction. A relevant model was proposed.
- 出版日期2005-6
- 单位上海交通大学
