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(2), Hf(2)Si and SiC ceramics. Oxyacetylene torch testing has been utilized to evaluate the ablation resistance under the condition ranging from 1.6 MW m(−2) to 2.2 MW m(−2) 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(−5) g s(−1) cm(−2) to 1.5 × 10(−5) g s(−1) cm(−2). The formation of a dense SiO(2) glass layer embedded with HfO(2) grains or particle accumulation in the HfO(2) layer is responsible for the good ablation resistance.