A centrifugal compaction process applying a 10-20kG centrifugal force to a slip of ceramic powder in a die has been developed. The slip was prepared by dispersing a submicron(0.22μm) high purity alumina powder in 22-28mass % of ion-exchanged water with a ball mill. The coefficient of viscosity of the slip is 80-2000mP⋅sec.
The compaction process is as follows: 1) when the centrifugal force acts, the alumina particles are sedimented in the bottom part of the die cavity, leaving upper clear water in the top part of the cavity; 2) the centrifugal machine is stopped, and the upper clear water is removed; 3) the bottom of the die is replaced by a porous bottom so as to reduce the moisture in the sediment by about 2 mass % with a 10-20kG centrifugal force applied again to the sediment; 4) after dehydration, the bottom is removed and the compact is stripped from the die.
This process has the following merits;
1) preparing and regulating the slip is easy, because the influence of the slip's concentration and viscosity is small.
2) neither a vacuum unaerating process nor unaerating agents are necessary.
3) compacts with a relative green density level above 60% can be obtained in a short time.
4) there is no contamination from the plaster mold.
5) the time for drying and sintering compacts can be shortened.