3D SiC_f/BN–SiC/SiBCN composites were fabricated via precursor impregnation and polymer infiltration pyrolysis (PIP). Oxidation behavior of the composites heated in air at 800 °C, 1000 °C and 1200 °C for 50 h was investigated. Following the oxidation treatment, it was found that the bending strength of the composites at different oxidation temperatures was degraded. The weight loss of the composites decreased gradually over the range of oxidation times of 1–50 h. In order to clarify the oxidation mechanism of the composites, reconstructed images, microstructures, phase compositions, the oxide layer formed on the composites and main chemical reactions were all analyzed. It was revealed that the degradation in the fracture strength of the composites was closely related to the oxidation of SiBCN matrix and BN-SiC interphase, whereas there was no signs of oxidation products about SiC fiber, which indicated that SiC fiber could be protected from oxygen by SiBCN matrix at 800−1200 °C in air.

3D碳化硅_˚F/ BN–SiC / SiBCN复合材料是通过前体浸渍和聚合物渗透热解（PIP）制成的。研究了在空气中分别于800°C，1000°C和1200°C加热50 h后复合材料的氧化行为。在氧化处理之后，发现复合材料在不同氧化温度下的弯曲强度降低。复合材料的失重在1–50 h的氧化时间范围内逐渐降低。为了阐明复合材料的氧化机理，分析了重建图像，微观结构，相组成，复合材料上形成的氧化层以及主要化学反应。结果表明，复合材料断裂强度的下降与SiBCN基体和BN-SiC界面的氧化密切相关，