The effect of pitch-based carbon fiber microstructure and composition on the formation and growth of SiC whiskers via reaction of such fibers with silicon sources.

The formation and growth of silicon carbide whiskers (SiCw) have been investigated by reaction of silicon sources at 1400 ºC with pitch-based carbon fibers possessing various microstructures. Isotropic and anisotropic pitch-based carbon fibers treated at various temperatures were employed as carbon sources. Silicon sources include silicon powder and a mixture of silicon and silica powder. The reaction of 1000 ºC heat-treated carbon fibers containing a certain content of oxygen with silicon powders is also reported. A reasonable yield of monocrystalline and polycrystalline SiC whiskers can be achieved by the reaction of the isotropic and anisotropic pitch-based carbon fibers treated at 1000 and 2000 ºC with the mixture of silicon and silica. The critical factors for promoting the formation of SiC whiskers are that the carbon sources should possess turbostratically stacked graphite structure and appropriate grain size. The presence of SiO, which originated from the reaction of silicon with silica or with water vapor derived from pyrolysis of carbon fibers, is another necessary condition for formation of SiCw during these reaction processes.