Synthesis of silicon carbide foams from polymeric precursors and their blends

Several polysilanes with different overall functionalities have been synthe sized and pyrolyzed to produce porous silicon carbide. The polysilanes and their ceramic products have been characterized using gel permeation chromat ography, Fourier transform-infrared spectroscopy, thermogravimetry, X-ray d iffractometry and microscopy. Some products were foams while others were mi cro-porous ceramics, The effect of the final pyrolytic yield on the type of ceramic produced, its pore structure and shape retention are discussed. Tw o polysilanes were blended in various ratios to control the pyrolysis proce ss more precisely. This allowed the type, shape and pore-structure of the s ilicon carbide produced to be controlled more efficiently. There exists a r elationship between the composition and structure of the precursors and the ir final pyrolytic yield and this determines the type, shape retainability and pore structure of the ceramics produced. In this work, precursors or th eir blends which gave a final pyrolytic yield of 50-60 wt % produced the be st silicon carbide foams. (C) 1999 Kluwer Academic Publishers.