SYNTHESIS OF C-SIC-TIC COMPOSITE FIBER BY PRECURSOR METHOD

A C-SiC-TiC composite fiber was obtained by heating a C-SiO2-TiO2 precursor, which was prepared from the carbon fiber (Kynol) impregnated with a mixed solution of ethylsilicate and titanium tetraisopropoxide. The reduction mechanism of the precursor has been investigated, The reduction rate was determined by means of a thermobalance in an atmosphere of Ar at temperatures from 1673 to 1973 K, The reaction products were examined by X-ray diffraction, SEM observation and chemical analysis. The precursor hydrolyzed in air was uniform and smooth in appearance, and had a microstructure of intermixed amorphous silica, anatase and carbon, The reduction of TiO2 preceded that of SiO2, Ti3O5 and Ti2O3 were transiently formed until TiO2 was fully reduced to TiC. The atomic ratio of Ti to C in titanium carbide was smaller than unity, The reduction products of SiO2 were SiC and SiO. The carbon core was surrounded by the reduction layer, in which the crystals of Sic and TiC were finely mixed. The reaction mechanism of the precursor changed with reduction time.