Fabrication of low-density carbon-bonded carbon fiber composites with an Hf-based coating for high temperature applications.

A novel Hf-based anti-oxidation coating has been prepared on the surface of low-density carbon-bonded carbon fiber composites (CBCFs). The coating exhibits a gradient transition structure, with mainly HfB, HfSi and SiC ceramics. Oxyacetylene torch testing has been utilized to evaluate the ablation resistance under the condition ranging from 1.6 MW m to 2.2 MW m for 300 s. The experimental results show that the as-prepared Hf-based coating can effectively protect CBCFs under high-temperature oxidation conditions. The surface maximum temperature can reach 1616-2037 °C, and the mass ablation rates vary from -3.5 × 10 g s cm to 1.5 × 10 g s cm. The formation of a dense SiO glass layer embedded with HfO grains or particle accumulation in the HfO layer is responsible for the good ablation resistance.