Ablation properties and mechanisms of BN-coated C_f-reinforced SiBCNZr ceramic composites under an oxyacetylene combustion torch

The ablation properties and mechanisms of BN-coated C_f-reinforced SiBCNZr composites under an oxyacetylene combustion torch were investigated. The mass and linear ablation rates of the C_f/SiBCNZr ceramic matrix composites were lower than those of C_f/SiBCN and SiC_f/SiBCN composites, reaching 0.0022 mg/s and 0.0136 mm/s, respectively. The ablation resistance of the SiBCN ceramics was enhanced by the addition of Zr, whereas the BN-coated C_f increased the thermal shock resistance of the SiBCNZr ceramics. No macrocracks were found on the ablation surface of the C_f/SiBCNZr specimen. The ablation mechanisms based on different ablation temperatures, phase evolution during ablation, and ablation morphologies in the different ablation regions consisted of oxidation of the carbon fibre and ceramic matrix, emission of various gases, the flow of high-viscosity SiO₂, and denudation of C_f under the erosion of the ablation flame.