Milling alpha alumina powder with sol-gelled alpha alumina milling media

摘要

A process for milling alpha alumina powder in a bead mill (eg. a rotating/tumbling mill) primarily involves making the associated alpha alumina milling means by a seeded sol-gel process so as to provide randomly shaped alumina particles consisting of alpha alumina crystals having an average diameter in the range of 0.1 to 1.0 microns. The sol-gel process which provides a uniform crystalline structure, involves the steps of seeding boehmite sol with material which is iso-structural with alpha alumina (eg. alpha alumina itself), so as to promote the formation of alpha alumina when sufficiently heated. The sol produced is uniformly seeded and is then gelled, dried and calcined so as to remove water and produce an intermediate precursor. The precursor is ten sintered (to at least 100{C) to form alpha alumina having a preferred Vickers hardness of 21 GPa. Use of such alpha alumina in the milling of alpha alumina powder is considered favourable as it prevents/reduces contamination/ineffectiveness by previously used milling media such as steel, zirconia and pure and impure alpha alumina.