Tuning the BN/SiC dual-layer interphase for superior high-temperature mechanical properties in SiC_f/SiC composites

By optimizing the BN/SiC dual-layer interphase in SiC_f/SiC composites, this work significantly enhances high-temperature mechanical properties. The thickness of the SiC layer was designed to be 0 nm (000T), 500 nm (500T) and 900 nm (900T). Introducing a SiC interphase improved crack deflection, with thickness having little effect on this function. The 900T specimen exhibited excellent ultimate tensile strength (267 ± 7 MPa) and failure strain (0.89 ± 0.03 %) at 1350 °C in air. Its lower density and Young’s modulus increased the proportional limit stress and reduced the crack opening displacement (COD), minimizing the oxidation-induced fiber damage. In-situ tensile tests confirmed smaller COD in 900T than in 500T. Acoustic emission data indicated that an appropriate SiC layer thickness delays fiber fracture, maintaining mechanical properties in oxidative environments. This work provides new and deep insights for the low-cost and efficient preparation of high-performance SiC_f/SiC composites.