In this study, novel polyborosilazane-derived SiBCN(O) ceramic was used as self-healing component in self-healing C f /SiBCN(O) composite, which was prepared by polymer infiltration and pyrolysis (PIP) process. Molecular-level structure design of boron-containing ceramic precursors was utilized to achieve uniform dispersion of boron-containing self-healing components in prepared composites. No elemental diffusion was observed at the interface of ceramic matrix and carbon fibers, which resulted in stable SiBCN(O) structure. In addition, boron was uniformly distributed in C f /SiBCN(O) composite ceramic matrix , which was beneficial for self-healing of cracks. Cracks and indentations were able to heal at high temperatures in air. The best crack-healing behavior occurred in air atmosphere at 1000 °C, with nearly complete crack healing. This excellent self-healing behavior was achieved because silicon and boron atoms in SiBCN(O) ceramic reacted with available oxygen at high temperatures to form SiO 2 (l), B 2 O 3 (l), and B 2 O 3 ·xSiO 2 liquid phases, which effectively filled cracks. In general, as-prepared C f /SiBCN(O) composite exhibited excellent self-healing properties and shows great application potential in high-temperature environment applications such as aviation, aerospace, and nuclear power.
To enhance the ablation resistance of porous C sf /MA–SiBCN composites, the polymer infiltration and pyrolysis (PIP) process is adopted to obtain layered C sf /SiBCN composites containing MA–SiBCN and PDCs–SiBCN. After ablation for 10 s, the ablative layer fails to remain on the C sf /MA–SiBCN surface with mass ablation rate of 0.062 g/s and linear ablation rate of 0.208 mm/s, while the dense C sf /SiBCN surface is covered by a dense and stable ablative layer mainly consisting of amorphous SiO 2 glassy phase due to the synergistic ablation effect of MA–SiBCN and PDCs–SiBCN, which could resist the intense scour by ablation flame and prevent internal corrosion, and thus the ablation resistance improves with a 37% decrease in mass ablation rate (0.039 g/s) and an 18% decrease in linear ablation rate (0.171 mm/s), respectively.
To achieve low-temperature densification of short carbon fiber reinforced mechanical alloyed SiBCN composites (C sf /MA-SiBCN) and fill the research gap of high-temperature mechanical properties of C sf /MA-SiBCN composites, C sf /SiBCN composites containing both polymer derived SiBCN (PDCs-SiBCN) and MA-SiBCN were prepared by the densification of C sf /MA-SiBCN composites at 1100 °C via the repeated polymer infiltration and pyrolysis (PIP) process. Unlike traditional hot-pressed C sf /MA-SiBCN composites, the as-prepared C sf /SiBCN composites exhibit 2D layered structure and short carbon fibers are evenly distributed in the matrix. On this basis, mechanical properties and microstructural evolution were fully studied from room temperature (RT) to 1600 °C. The strength of 7 th PIP-ed composites at RT increases by 55.9% compared with that of C sf /MA-SiBCN composites because of higher density (2.00±0.01 g/cm 3 ) and lower porosity (4.14%±0.28%). At 1400 °C, the strength of C sf /SiBCN composites shows slightly higher value compared with the strength at RT. At 1600 °C, some SiC crystals and pores are observed in the interfacial region, and thus C sf /SiBCN composites show nonbrittle fracture behavior at 1600 °C with a strength retention ratio of 41.8%.
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