Preparation and Tensile Test of SiC Fiber Fabricated by Three-stage Chemical Vapor Deposition

Continuous silicon carbide(SiC) fiber with carbon coating was fabricated by three-stage chemical vapor deposition(CVD) on W filament heated by direct current(DC),using CH_3SiCl_3 as gaseous reactant for SiC as well as C_2H_2 for the outmost carbon coating.Young's modulus and tensile strength of the fiber were tested at room temperature, while Weibull distribution was conducted for evaluation of the tensile properties of the fiber.Fracture morphology,phase structure and microstructure of the fiber were investigated by scanning electron microscope (SEM),X-ray diffraction(XRD) and transmission electron microscope(TEM).Results show that the SiC fiber, from W core to outside,exhibits a W/SiC interfacial reaction layer with a thickness of about 0.35μm,two layers of SiC and an even carbon coating.XRD pattern indicates that the SiC layers are all composed of P-SiC,which corresponds to diffraction angle of 35.6°,60.1°,72.1°and 75.7°.The mean tensile strength and Weibull modulus of the fiber reach 3266 MPa and 16.3,respectively.Furthermore,fracture mechanism of the fiber is discussed.