Abstract
The pyrolysis of a low-oxygen SiC fiber, prepared by the electron-irradiation curing method, has been investigated in N2 atmosphere at temperatures from 1673 to 1973K. Then, the pyrolytic behavior in N2 was compared with that in Ar. The fiber absorbed a considerable amount of nitrogen, and consequently, the mass loss caused by the pyrolysis was compensated. While the nitrided layer retarded the crystallization into β-SiC below 1773K, this effect disappeared above 1873K. As a result of the reaction of SiO with carbon, coarse SiC particles grew on the surface of the fiber heat-treated at 1973K. The tensile strength of the fiber was inversely proportional to the square root of the SiC crystal size. For SiC crystals with the same size, the strength was much higher in N2 than in Ar, because of smoothness of the surface.
