Abstract
Submicron grinding of low-soda alumina was studied with a ball mill using alumina balls from 30mm to 0.75mm in diameter. Low-soda alumina powder was of commercial grade and its average particle size was 1.64μm. The average particle size was calculated from the specific surface area measured by BET method, and the characteristics of alumina were determined by X-ray pH, DTA and TG. The results obtained are summerized as follows.
(1) It was demonstrated that submicron grinding of alumina powder was possible in a short time by using balls of several mmφ in diameter.
(2) The maximum grinding speed was achieved with balls of 2mmφ.
(3) The following experimental relation was obtained,
ln(Sw)=-0.399lnr3-0.482/r+0.503lnt+1.043
where Sw is the specific surface area, r is the ball radius and t is time. The multiple correlation coefficient R was found to be 0.952 when calculated by a computer.
(4) A part of alumina transformed to gibbsite with a mechano-chemical reaction.
(5) With decreasing particle size, pH of slurry became high. As a result, the viscosity of slurry became low, and the grinding speed showed no tendency to slow down.
