Effects of thermal load on mechanical properties and microstructures of 3D SiO2f/Si3N4–BN composites using polyborosilazane

Polyborosilazane was used as a preceramic polymer to fabricate three-dimensional quartz fiber reinforced nitride-based composites (3D SiO2f/Si3N4–BN), and the effects of the ultra-high temperature exposure on the mechanical properties and microstructures were investigated. Ablation test shows that the 3D SiO2f/Si3N4–BN composites have excellent ablation and shock damage resistance with a low surface recession rate of 0.038 mm/s. The flexural strength of the ablated specimen is 96.5 MPa, which is 8.79% lower than that of the as-received specimen. SEM results indicate that there is a reaction at the fiber/matrix interface during ablation testing. Almost no effects of the ultra-high temperature load on the strength. Fiber pull-out and debonding contribute to the high mechanical properties.