Sol-gel processing of silicon based matrixes for carbon fiber reinforced ceramic composites

Sol-Gel processing of ceramics as matrixes for fiber reinforced composites offers flexibility of using polymer composites processing techniques and avoids fiber damage due to conventional high temperature melt processing infiltration techniques used for glass and ceramic matrix composites. Studies have been performed to develop Si,C,O based matrixes through copolymerization of furfuryl alcohol and hydrolyzed TEOS as well as through organic-inorganic hybrid gels from TEOS and 1,4 Butanediol. In FFA - TEOS system, copolymerization with optimized mol ratio of the two results in resinous mass. This precursor on pyrolysis to 1000 degrees C results in Si-O-C type amorphous solid black mass. On heating to 1400 and 1600 degrees C, it exhibits presence of crystalline SiC. In organic-inorganic gel system, the pyrolysed mass exhibits phase stability up to much higher temperatures. XRD studies show that pyrolysed materials obtained from BD-TEOS system contain higher amorphous component even after heat treatment to 1600 degrees C in contrast to FFA-TEOS system. Carbon fiber reinforced composites have been prepared with above matrixes using prepreg lay-up, consolidation and pyrolysis technique. At heat treatment temperature of around 1400 degrees C, though consolidation of the matrix is observed to be maximum, no reaction between fibers and matrix is observed and the fibers are not damaged. The composites exhibit non-catastrophic fracture.