Ablation behavior of Csf/SiC‐BN composites with polyborosilazane as sintering aids: High‐temperature damage mechanism

Abstract Microstructural evolution and high‐temperature ablative damage mechanism of C sf /SiC‐BN composites with and without polyborosilazane (PBSZ) as sintering aids that can convert to polymer‐derived SiBCN ceramics (PDCs‐SiBCN) by cross‐linking and pyrolysis during sintering were studied. The density of C sf /SiC‐BN composites increases from 2.17 to 2.25 g/cm 3 with 10 wt.% sintering aids because PBSZ promotes rearrangement and redistribution of raw materials by pyrolysis during the sintering process. With the increase of carbon fiber content, ablation performance (mass ablation rate: 15.25 mg/s; linear ablation rate: 0.100 mm/s) negligibly decreases, compared to counterparts with lower fiber content (mass ablation rate: 16.53 mg/s; linear ablation rate: 0.072 mm/s) because the presence of PDCs‐SiBCN partially compensates for the detrimental effect of carbon fibers on ablation performance. C sf /SiC‐BN composites with and without PBSZ show similar phase composition mainly containing quartz, amorphous SiO 2 , and matrix crystallization products and morphology after ablation because of similar phase composition before ablation. The ablation mechanism is oxidative corrosion and mechanical scouring and stripping.