Preparation and oxidation behavior of Cf/C–TaC composites

Abstract

Cf/C–TaC composites, which possesses excellent anti-ablation properties, are potential candidate materials for applications in the extreme environments associated with hypersonic flight and rocket propulsion. In this paper, Cf/C–TaC0.89 composites were prepared by chemical vapor infiltration to achieve a TaC matrix with a C/Ta atomic ratio of 0.89. The isothermal oxidation behavior of the composites at 1200–1600 °C was investigated, and the minimum time for the self-healing of microcracks on the composite surface was calculated based on the oxidation process obeying either a parabolic or a linear law. The results indicate that the oxidation process is controlled by surface kinetics in the initial 0–10 min at 1200–1400 °C and 0~5 min at 1500–1600 °C even if a dense oxide layer is formed. After that, the controlling mechanism becomes the diffusion of oxidative gases in a TaCxOy layer, a diffusion barrier layer existed in the oxidation of refractory carbides. The formation of the TaCxOy layer is attributed to the low C/TaC ratio of the TaC0.89 phase and the diffusion behavior of O atoms in Ta octahedral interstitial sites.