Microstructure and oxidation behavior of the SiC/PyC multilayer coated carbon fibers

SiC/PyC coated carbon fibers were prepared by two-steps method. The PyC inner layer was prepared by isothermal chemical vapor infiltration and the SiC outer layer was synthesized by the carbothermal-reduction. The microstructures of the as-prepared SiC/PyC coated carbon fibers were characterized by XRD, FESEM and TEM. The oxidation behavior of the uncoated, PyC coated, and SiC/PyC coated carbon fibers were studied by the thermal-gravity analysis. The results show that the SiC and PyC layer deposited on carbon fibers are continuous and uniform. The thickness of PyC inner layer is about 200 nm, and thickness of the SiC outer layer is about 160 nm. High order twin boundaries are observed in the SiC layer. The oxidation resistance of the carbon fiber can be improved by the SiC/PyC multilayer coating. The initial oxidation temperature of the SiC/PyC coated carbon fiber is about 250°C higher than that of uncoated carbon fiber.