Precipitation processing to synthesize fine polycarbosilane particles for precursors of silicon carbide powders

Abstract

Liquid processing to form fine polycarbosilane nanoparticles based on the supersaturation in mixed solvents was investigated, in order to synthesize fine precursor powders for silicon carbide. Polycarbosilane solids were dissolved in n-hexane, followed by two kinds of mixing methods with ethanol. By the method of gradual mixing the polycarbosilane solution into stirred ethanol, fine precipitates were formed. On the other hand, precipitates gathered and formed a sticky lump by the method of gradual mixing ethanol into the polycarbosilane solution. The fine precipitation by the former method is attributed to the drastic reduction in solubility of the polymer in scattered droplets. The precipitates had fine primary particle size of less than 100 nm, although these particles were partially bonded. The results of FT-IR indicated that PCS can be dissolved and precipitated during the processing without change of the molecular structure. The dried precipitates were converted to amorphous Si-C (-O) powders by oxidative cure treatment and pyrolysis at 1000°C.