Improving the Chemical Purity of Fused Corundum by High-Temperature Roasting

Abstract

The chemical purity of fused corundum was demonstrated experimentally to improve after high-temperature (~1750°C) vacuum (~10^–5 mm Hg) roasting. Three industrial fused corundum samples with different particle-size and impurity profiles were heat treated, after which the impurity contents decreased by an order of magnitude. The samples were practically completely purified of Na, Mg, K, Mn, Cu, and Zn whereas the Fe content decreased by 8 – 10 times. Samples were found to consist of porous granules 16 – 60 μm in size that consisted of solid microparticles of characteristic size 0.4 – 0.7 μm. The specific surface area of the granules lay in the range 2.8 – 3.3 cm²/g.