SiC/C composites prepared from wood-based carbons by pulse current sintering with SiO2: Electrical and thermal properties

A powder mix of wood charcoal and SiO2 was sintered into a SiC/C composite. The heat treatment temperatures were 1400-1800 degreesC, the SiO2 concentration 0, 10, 30 and 50 wt.% with respect to the dry weight of wood charcoal. The microstructure, electrical resistance and thermal conductivity were studied. SEM and EDX confirmed that a 1 mum thick layer of beta-SiC was formed on the surface of the wood charcoal pieces. The bulk density did increase only slightly with temperature and SiC contents. The electrical resistance decreased slightly with temperature but increased with SiO2 contents. The thermal conductivity did increase both with temperature and SiC contents. By coating the wood charcoal in this rather natural way by such a ceramic layer we can use the SiC/C composite at least up to 1800 degreesC, far beyond the carbon oxidation limit of 500 degreesC. (C) 2004 Elsevier Ltd. All rights reserved.