Synthesis of silicon carbide foams from polymeric precursors and their blends

Several polysilanes with different overall functionalities have been synthesized and pyrolyzed to produce porous silicon carbide. The polysilanes and their ceramic products have been characterized using gel permeation chromatography, Fourier transform-infrared spectroscopy, thermogravimetry, X-ray diffractometry and microscopy. Some products were foams while others were micro-porous ceramics, The effect of the final pyrolytic yield on the type of ceramic produced, its pore structure and shape retention are discussed. Two polysilanes were blended in various ratios to control the pyrolysis process more precisely. This allowed the type, shape and pore-structure of the silicon carbide produced to be controlled more efficiently. There exists a relationship between the composition and structure of the precursors and their final pyrolytic yield and this determines the type, shape retainability and pore structure of the ceramics produced. In this work, precursors or their blends which gave a final pyrolytic yield of 50-60 wt % produced the best silicon carbide foams. (C) 1999 Kluwer Academic Publishers.