Microstructure and Ablation Behavior of C/C-SiC-(ZrHf)C Composites Prepared by Reactive Melt Infiltration Method.

C/C-SiC-(ZrHf)C composites were prepared by the reactive melt infiltration method. The microstructure of the porous C/C skeleton and the C/C-SiC-(ZrHf)C composites, as well as the structural evolution and ablation behavior of the C/C-SiC-(ZrHf)C composites, were systematically investigated. The results show that the C/C-SiC-(ZrHf)C composites were mainly composed of carbon fiber, carbon matrix, SiC ceramic, (ZrHf)C and (ZrHf)Si solid solutions. The refinement of the pore structure is beneficial to promote the formation of (ZrHf)C ceramic. The C/C-SiC-(ZrHf)C composites exhibited outstanding ablation resistance under an air-plasma environment at around 2000 °C. After ablation for 60 s, CMC-1 appeared to possess the minimum mass and linear ablation rates of only 2.696 mg/s and -0.814 µm/s, respectively, which are lower than those of CMC-2 and CMC-3. During the ablation process, a Bi-liquid phase and a liquid-solid two-phase structure were formed on the ablation surface which could act as an oxygen diffusion barrier to retard further ablation, which is responsible for the excellent ablation resistance of the C/C-SiC-(ZrHf)C composites.