Microstructure of SiC Fiber Fabricated by Three-stage Chemical Vapor Deposition

Abstract

Continuous silicon carbide(SiC) fiber with carbon coating was fabricated by three-stage chemical vapor deposition(CVD) on tungsten filament heated by direct current(DC),using CH_3SiCl_3 +H_2 as gaseous reactant for SiC sheath and C_2H_2 for the outmost carbon coating,respectively.Microstructure of the SiC fiber was examined by X-ray diffraction(XRD),scanning electron microscope(SEM),Raman spectroscope and transmission electron microscope (TEM).The results show that the SiC fiber consists of tungsten core,a W/SiC interfacial reaction zone, two layers of SiC with total thickness of 41μm and an outermost carbon coating of about 2 urn in thick.The deposited SiC is mainly composed of P-SiC,and exhibits strong〈111〉fiber texture with abundant growth defects,such as co-deposit of free silicon and stacking faults,leading to the lattice imperfection of the SiC sheath.Raman spectrum indicates that the outmost carbon coating decomposed from C_2H_2 involves a mixture of amorphous carbon and graphite crystallite.