Effect of Powder and Cold Isostatic Pressing on Densification ofAl₂O₃ Ceramics Molded by Gelcasting

Two kinds of Al₂O₃ powder with average grain size of 0.31, 0.77 μm (named as 1^# and 2^#, respectively) was molded by low solid content (volume fraction of 45%) gelcasting, and then was cold isostaticly pressed (CIP) and pressurelessly sintered to obtain Al₂O₃ ceramics. Effects of powder and CIP pressure on densification of Al₂O₃ green body and ceramics were studied. The results show that the Al₂O₃ powder with smaller grain size was more difficult to disperse, and required higher addition amount of polyacrylate ammonium dispersant; the obtained green body and sintered ceramics had lower relative density. With increasing CIP pressure, the relative densities of the two Al₂O₃ green bodies increased, and the pores decreased; the relative densities of the two sintered ceramics showed a trend of increase first, then decrease, and then being stable. When the CIP pressures were 350-400 MPa, the two ceramics had the maximum relative densities and less intercrystalline pores.