Microstructure and Properties of Continuous Fiber Reinforced SiBCN Matrix Composites

By virtue of its unique molecular network structure, precursor-derived SiBCN ceramics (PDCs-SiBCN) show excellent high-temperature stability and oxidation resistance. By introducing continuous fibers into SiBCN ceramics to construct a multi-scale reinforcement system, the toughness of brittle ceramics can be enhanced, the bearing capacity can be improved, the service life can be prolonged, and the damage tolerance can be optimized, which is expected to provide a candidate material for the thermal protection system of a new generation of spacecraft with integrated thermal protection/bearing. In this chapter, the microstructure and properties of carbon(C) fiber, silicon carbide (SiC) fiber, and SiBCN fiber reinforced SiBCN matrix composites were systematically studied. Based on different fiber characteristics, continuous fiber reinforced SiBCN-based composites have different performances in thermal stability and oxidation resistance: Carbon fiber offers excellent high-temperature stability in inert environments, withstanding temperatures up to 1500 °C. However, its long-term oxidation resistance is insufficient. Consequently, C/SiBCN composites demonstrate strong high-temperature thermal stability but slightly weaker oxidation resistance; SiC fiber can form a dense SiO2 protective layer in an oxidizing atmosphere, so the SiC/SiBCN composites show excellent oxidation resistance. SiBCN fiber possesses similar components to the matrix, resulting in excellent physicochemical compatibility in SiBCN/SiBCN composites. In the future, the research of continuous fiber reinforced SiBCN matrix composites should focus on the gradient design of fiber/matrix interface, the optimization of infiltration process of three-dimensional braided preform, and the construction of service performance database in extreme environment, so as to promote the engineering application of this material in aerospace fields.