Fabrication, mechanical properties and ablation performance of SiCnw/PyC-C/C-HfC-SiC composites with a Si-rich coating via film boiling chemical vapor infiltration and gaseous silicon infiltration

SiC nanowire/pyrocarbon (SiCnw/PyC) strengthened C/C-HfC-SiC composites with a Si-rich coating were prepared efficiently by film boiling chemical vapor infiltration (FBCVI) in conjunction with gaseous silicon infiltration (GSI). The core-shell structure built by FBCVI could reinforce the matrix, improve thermal conductivity, and facilitate the preparation of the Si-rich coating. After ablation at a heat flux of 2.38 MW/m², the composites demonstrated excellent ablation resistance, whose linear and mass ablation rates were 1.02 μm/s and 0.25 mg/s. The core-shell structure and the Si-rich coating were desirable for a low ablation temperature (1885 °C), promoting the formation of a dense Hf–Si–O layer with repairing properties toughened by small grains. This study offered a novel combined process to prepare thermally protective composites strengthened by the core-shell structure.