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铁道科学与工程学报

JOURNAL OF RAILWAY SCIENCE AND ENGINEERING

Vol. 17    Special 1    November 2007

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Oxidation mechanisms of C-SiC-TaC-C composites prepared by
chemical vapor infiltration
State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China

Abstract:To improve the oxidation-resistance properties, SiC and TaC species were introduced in C/C composites by chemical vapor infiltration (CVI) methods. The oxidation-resistance properties of C-SiC-TaC-C composites were studied by X-Ray diffractometry (XRD), JEOL−6360LV scanning electronic microscopy (SEM) and AdventurerTM electronic balance with precision of 0.1 mg. The results show that, 1) the oxidation rate of the composites increases continuously with time at all experimental temperatures; 2) The oxidation rate increases with temperature within 700−1 100 ℃, slowly in 700−800 ℃, acutely in 800−1 100 ℃; it reaches a maximum value at 1 100 ℃, then decreases within 1 100−1 400 ℃; 3) The relationship curve of oxidation rate with temperature can be divided into three regions. The oxidation rate is controlled by reactivity in region Ⅰ, the mixed effects of reactivity and gas diffusion in region Ⅱ, gas phase diffusion in region Ⅲ; 4) The composites exhibit a higher oxidation onset temperature in low temperature region and a lower oxidation rate at high temperature due to the oxidation of TaC to (Ta, O) and the formation of the dense SiO2-Ta2O5 oxide layer respectively. With the addition of SiC/TaC species, the oxidation-resistant properties of C/C composites can be improved effectively.

 

Key words: C/C composites; TaC; chemical vapor infiltration; oxidation-resistance

ISSN 1672-7029
CN 43-1423/U

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