Microstructure and ablation properties of C/C-Zr-Si-O composites prepared by carbothermal reduction of hydrothermal co-deposited oxides

C/C-Zr-Si-O composites were prepared by carbothermal reduction of hydrothermal co-deposited ZrO2, SiO2, and C. The bulk density of composites reached 1.71 g/cm3 with 8 cycles of co-deposition. The matrix of the composites includes ZrC, SiC, ZrO2, and SiO2 with fine grain size (300–500 nm) and homogeneous distribution. The mass and linear ablation rate of C/C-Zr-Si-O composites were 0.112 mg/cm2·s and 0.46 μm/s, respectively, under a plasma flame for 120 s. The attractive ablation resistance of the composites resulted from its unique structure, which tends to form a continuous ZrO2-SiO2 glass layer in the ablation center, a layer of SiO2-ZrO2 bubbles in the transition region, and fluffy SiO2 nanowires layer in the heat-affected region. These ablation layers were barriers to restrain the diffusion of oxidative gas and heat. The C/C-Zr-Si-O composites provide an alternative ceramics system with attractive ablation resistance, while carbothermal reduction of hydrothermal co-deposited oxides is a feasible method for the structural design of carbon fiber reinforced ultra-high temperature ceramic.