CVD法によりコーティングを行ったSiC系繊維の熱分解挙動  [in Japanese] Pyrolytic Behavior of CVD Coated SiC Fibers  [in Japanese]

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 1473 K using a mixture of CH_3SiCl_3 and H_2 as source gases. The composition and crystallinity of the coating changed with the flow rates of CH_3SiCl_3 and H_2. The composition of the coating with an increase in H_2 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 1973 K. 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.