Oxidation behaviors of SiC_f/BN/SiC mini-composites at 1300–1500^oC and tensile strength distribution

This work investigates the oxidation behaviors and tensile strength distribution of a continuous silicon carbide fiber-reinforced silicon carbide mini-composites with the BN interface (SiC_f/BN/SiC). The specimens were subjected to a 100-h oxidation from 1300 °C to 1500 °C in air. Microstructural characterization was performed using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. Tensile strength was statistically evaluated via Weibull distribution. Micro/nano-mechanical tests were used to quantify the modulus and hardness of fibers and matrix, as well as the interfacial shear strength. The results indicate that the SiC_f/BN/SiC mini-composites exhibit higher weight gain rate, lower tensile strength retention with greater scatter at higher oxidation temperature. The weight gain is attributed to the oxidation of the SiC matrix at the surface and within internal open pores, leading to the formation of SiO₂. The degradation of tensile strength is primarily attributed to the reduction in interfacial load-transfer capacity and the weakened cooperative load-bearing ability between fibers and matrix. Annular cracks between the interface and fibers lead to a notable reduction in interfacial shear strength at 1300 °C. The borosilicate glass phase fills the annular cracks and the BN interface presents fragments at 1400 °C and 1500 °C.