PREPARATION OF PARTIALLY STABILIZED ZIRCONIA CERAMIC BY AQUEOUS GELCASTING

A partially stabilized zirconia (PSZ) ceramic was prepared by aqueous gelcasting. The effects of the zeta potentials, solid loading, dispersant content and milling time on the PSZ suspension were studied. The dispersant content has a remarkable effect on the rheological properties of the suspension. The appropriate dispersant mass fraction for PSZ aqueous slurry with the solid loading of 55% in volume is 0.4%. All suspensions (50%?56% solid loading) exhibit a shear-thinning behavior and relatively low viscosity (less than 50 mPa?s, at a shear rate of 10 s-1), which is suitable for casting. The degree of shear thinning and the viscosity at high shear rates increase with the increasing of volume fraction of solid phase. As the milling time is prolonged, the viscosity of the suspension de-creases first, and then a plateau appears and the average diameter remains unchanged. When the milling time is shorter than 20 h, the viscosity of the slurry decreases gradually as the time of milling is increased. After 20 h milling, the viscosity of the slurry tends to be consistent. Therefore, the ball milling time should be equal to or more than 20 h in order to obtain a stable suspension at equilibrium. The appropriate time for casting the slurry (idle time) can be controlled by the amounts of initiator and catalyst added to the slurry as well as by the processing temperature. According to micrographs, the gelcasting green body is homogeneous.