Preparation and oxidation behavior of Cf/C-TaC composites

C-f/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, C-f/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 degrees 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 degrees C and 0 similar to 5 min at 1500-1600 degrees 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.