SiC/C Composite Sheets Produced from Polycarbosilane/Resin/Binder Mixtures

Abstract

Green sheets were made from polycarbosilane (PCS), phenol-formaldehyde resin or furfuryl alcohol resin by adding binder with the weight ratio of PCS to resin equal to 2/1 or 1/1. The two types of green sheets were heat-treated at 1200° to 1400°C under N₂ gas to form SiC/C composite sheets 0.4-0.6mm thick. The SiC/C composite sheets were highly amorphous, that is, the crystallite sizes of L₁₁₁ and L_C of SiC and C components in the SiC/C composites were below 34Å and 25Å, respectively. As another feature, it was recognized that amorphous SiO₂ was formed as a secondary product by the reaction of silicon in PCS and oxygen in resin during pyrolysis. Little difference was observed in bending strength and oxidation resistance between two SiC/C composite sheets. These features depend on the content of SiC in the composite sheet. The effective mixing ratio is PCS/resin≥2/1.