Application of dry grinding to reduction in transformation temperature of aluminum hydroxides

Dry grinding of gibbsite (alpha-Al(OH)(3)) and pseudo (p)-boehmite (gamma-AlO(OH)) powder samples separately, with and without fine a-alumina powder as a seed, was conducted using a planetary ball mill to investigate effects of grinding and addition of the seed on their transformation temperatures to or-phase during heating. The transformation temperatures of both samples reduced to below 1000 degrees C with increasing grinding time as well as the amount of seed. The transformation temperatures depend on the grinding time and the amount of seed, and the minimum temperatures are about 910 degrees C for gibbsite and about 950 degrees C for p-boehmite when they are ground for more than 60 min with an equivalent amount of the seed powder. Combination of grinding with addition of the seed would be an effective operation for the reduction in the transformation temperature of bath compounds to a-phase. (C) 2000 Elsevier Science B.V. All rights reserved.