Liquid assisted sintering of SiC powders by MW (2.45 GHz) heating

The feasibility of densifying alpha-silicon carbide powder compacts-based on a liquid assisted sintering approach-by the use of microwave powered furnaces, is examined. Despite the low penetration depth of GHz radiation, it is possible to obtain microwave sintering of SiC. Spatial uniformity of fired state density and warpage/cracking tendency are more dependent on size than in the case of conventional heating. Electromagnetic field intensity spatial variation-related to both the low penetration depth of the carbide and the inherent non-uniformity of the MW's distribution within the applicator-is one of the main factors which negatively affect densification uniformity. Nonetheless, fired state bulk density of 98% t.d. may be achieved in the case of small components. The phase composition of MWed and respectively conventionally sintered specimens is similar and so is the grain size distribution. A larger fraction of the oxide second phase is accumulated in triple points than in the case of resistive furnace firing. While MW sintering of SiC is feasible, it does not seem to generate practical advantages over conventional heating. (C) 2002 Elsevier Science Ltd. All rights reserved.