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

Highlights: • The C/C-Zr-Si-O with a density of 1.71g/cm³ was obtained by 8 cycles of hydrothermal co-deposition/carbothermal reduction. • The mass ablation rate of the composites was as low as 0.112 mg/cm²·s owing to the fine grain and homogeneous Zr and Si. • The formation of ablation bubbles is significant to achieve the attractive ablation resistance of the composites. 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.