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-A lO(OH)) powder samples separately, with and without fine a-alumina powder a s a seed, was conducted using a planetary ball mill to investigate effects of grinding and addition of the seed on their transformation temperatures t o or-phase during heating. The transformation temperatures of both samples reduced to below 1000 degrees C with increasing grinding time as well as th e amount of seed. The transformation temperatures depend on the grinding ti me and the amount of seed, and the minimum temperatures are about 910 degre es C for gibbsite and about 950 degrees C for p-boehmite when they are grou nd for more than 60 min with an equivalent amount of the seed powder. Combi nation of grinding with addition of the seed would be an effective operatio n for the reduction in the transformation temperature of bath compounds to a-phase. (C) 2000 Elsevier Science B.V. All rights reserved.