Abstract
Silicon oxycarbide (SiOC) ceramics are expected as one of the oxidation resistant matrices for ceramic matrix composites. In the present study, silicon oxycarbide ceramics were synthesized through the Sol-Gel route with low environmental impact. The gels were synthesized from ethylalcohol, methyltriethoxysilane (MTES), hydrochloric acid (HCl) and purified water (H2O), and they were pyrolyzed at 1000, 1500 and 1700oC. The structures of gels after heat treatment were analyzed by X-ray diffraction (XRD). XRD results indicated that 硫-SiC was obtained in the present method and crystallization was increased with increasing heat treatment temperature, whereas the number of cracks also increased with increasing heat treatment temperature. For this reason, heat treatment temperature for fabricating composites was decided as 1000oC. Oxidation tests at 1150oC resulted in no weight change in fabricated composites. In order to weaken the fiber/ matrix interfacial shear strength, carbon was coated on the fiber surfaces with epoxy resin acetone solutions. Tensile strength of unidirectional bundle composites with 20% epoxy content solutions became four times as large as that of the specimen without solution. Tensile strength of textile composites also became three times. However tensile strength after oxidation was very low. The silica formation strengthened the fiber/ matrix interfacial shear strength, which result in the reduction of tensile strength.
