Enhanced grain growth in porous materials from α- and β-SiC powder mixtures

alpha- and beta-SiC powders and their powder mixtures with 0.3 mass% of AIB(2) additive were sintered at 2200degreesC. Porous materials having approximately 55-57% theoretical density were obtained from the powders. Grains in the porous material prepared from alpha-SiC powder grew into round-sbaped grains with a 4 mum size, and those prepared from beta-SiC powder grew into plate-shaped grains with the same size. Grain growth was considerably enhanced in the powder mixtures forming a locking structure with plate-shaped grains. The mean grain sizes of the porous materials from the powder mixtures were 5.6-8.2 mum. beta(3C)-SiC in the powder mixtures was transformed completely to alpha, that is, 6H and small amounts of 4H and 15R. An energy difference accompanied by beta-to-alpha transformation enhanced grain growth. The strength of the porous materials prepared from the mixtures was 70-83 MPa.