High-temperature oxidation behavior of SiBN fibers in air

SiBN fibers are one of the most admirable microwave-transparent reinforced materials for high Mach number aircrafts.Currently,the detailed high-temperature oxidation behavior of SiBN fibers has not been studied yet.In this work,we studied the high-temperature oxidation behavior of SiBN fibers with different boron contents at the temperature range of 1000–1400℃in air.Si BN fibers started to be oxidized at 1100℃,with SiNand BN phase oxidized to SiOand BO,respectively.Due to the gasification and the escape of molten BOat high temperatures,amorphous SiOcould be remained at the fiber surface.As the fiber further oxidized,the molten BOat the inside may infiltrate into the fiber interior to react with SiN,causing the precipitation of hexagonal boron nitride (h-BN) nanoparticles and the formation of SiO/BN layer.Finally,complex oxidation layers with two distinct concentric sublayers accompanied with two transition sublayers could be formed after the oxidizing treatment.