The Influence of Carbon on the Structure of Preceramic Polymer Derived SiC

The microstructure of SiC produced from allyl-hydridopolycarbosilane (AHPCS) was studied after thermal treatments at temperatures up to 1600 C. SiC samples were prepared in contact with pyrocarbon, carbon fiber, carbon felt, carbon powder, and graphite. Each of these configurations was examined using optical, scanning electron, and transmission electron microscopy. The resultant microstructure of the SiC in the vicinity of the carbon/graphite source was different for each sample. In some cases the grains were uniform, equiaxed and about the same size as SiC grains derived from neat AHPCS. Other samples exhibited accelerated grain growth in the vicinity of the carbon, and occasionally appeared to mimic the original carbon structure. Understanding and controlling such behavior will facilitate the fabrication of polymer derived stoichiometric SiC, and also has significant implications for the fabrication of SiC/SiC composites with a pyrocarbon interface and polymer derived matrix.