The Limit of Grinding of Alumina Powder in Water by a Planetary Ball Mill.

The effects of mechanical grinding conditions on the limit of grinding of alumina powder in water was investigated using a planetary ball mill. The evaluation of ground particles was done based on the specific surface area by the BET method and by pore distribution with mercury porosimetry, as well as being based on particle size analysis by the laser scattering-diffraction method and by observation with a microscope.Negative grinding phenomena were confirmed also in the wet grinding of alumina, and its grinding equilibrium size was well correlated with the maximum force exerting on a single ball when the product fineness was evaluated by the laser scattering-diffraction method. However, a decrease in the specific surface area by the BET method was not obtained, though it approached a certain value independent of the mechanical grinding conditions. It was found that the grinding equilibrium size was hardly influenced at all by the feed size, but it was influenced by the solid concentration to some extent.