Whisker Growth and Composite Fabrication in the SisN4-C System

Silicon carbide whiskers were synthesized by carbothermal reduction of silicon nitride. The whisker microstructural study reveals that the whiskers may grow in two stages, core lengthening first followed by whisker thickening. Observations show that the possibility of root growth of the whisker core can not be excluded. Whisker growth via the VLS mechanism in the Si3N4C system was also studied, it is noted that diffusion along the liquid alloy droplet surface may be an important mass-transport path. Partial carbothermal reduction of silicon nitride results in a mixture of Si3N4 powders and SiC whiskers which can be used for making silicon nitride matrix reinforced with silicon carbide whisker composites. The properties of the composites can be improved by optimising both the whisker synthesizing and composite fabricating processes.