HIGH-TEMPERATURE CRYSTALLIZATION BEHAVIOR OF SI-TI-C-O FIBER CURED BY ELECTRON-BEAM IRRADIATION

The crystallization at high temperatures based on the pyrolysis of commercial Si-Ti-C-0 fibers with 18%O and 13%O is considered to be related to the oxygen content introduced by the thermal oxidation curing process. In order to improve heat-resistance of Si-Ti-C-0 fiber, the fiber with lower oxygen content than that of commercial kinds has been developed using the electron irradiation curing process. The Si-Ti-C-O fiber with 6%O has been synthesized, and the crystal structure was amorphous containing microcrystallines. The pyrolysis rate of the fiber was measured with a thermobalance at temperatures from 1573 to 1973 K in an argon stream. The pyrolysis products were investigated by X-ray diffraction, SEM and TEM observation. Results are compared with that of commercial Si-Ti-C-0 fibers with 18%O and 13%O. The amorphous Si-Ti-C-0 fiber crystallized to beta-SiC and TiC, with evolution of SiO and CO. The activation energy was 357 kJ/mol for fiber with 6%O, and the crystallization was determined by the crystal growth of SiC controlled by the diffusion of carbon in the fiber. Lowering of oxygen content in Si-Ti-C-0 fiber by the electron irradiation curing process was found to effective for the suppression of pyrolysis.