1992 Volume 100 Issue 1165 Pages 1103-1108
The effect of SiC coating on the pyrolysis of SiC fiber (Nicalon) has been investigated. SiC coating was carried out by chemical vapor deposition at 1473K using a mixture of CH3SiCl3 and H2 as source gases. The composition and crystallinity of the coating changed with the flow rates of CH3SiCl3 and H2. The composition of the coating with an increase in H2 gas flow rate was close to that of stoichiometric SiC as determined by the scanning Auger electron spectroscopy. X-ray diffraction patterns showed that the coating was β-SiC crystallites. The rate of pyrolysis of Nicalon with and without SiC coating was measured with a thermobalance in an argon atmosphere at temperatures from 1673 to 1973K. The rate of pyrolysis of SiC coated Nicalon was mixed-controlled by both diffusion of SiO and CO gases through the coating and crystal growth of SiC in the fiber. These results showed that high-temperature pyrolytic reaction of Nicalon was suppressed by coating SiC on the fiber.
