Suspension characteristics and rheological properties of aqueous alumina/zirconia freeze casting slurries

The dispersion and rheological behavior of aqueous alumina, zirconia, and mixed alumina/ zirconia slurries have been studied in terms of solid loading and the incorporated multiple processing additives. Darvan-C, Dynol 604, Glycerol, and PVA were used as the dispersant, surfactant, cryoprotectant, and binder, respectively. Sedimentation density increased significantly on adding the dispersant; its effectiveness was similar for both the alumina and zirconia suspensions. With further addition of binder, the sedimentation density decreased. The suspension viscosity generally behaved in an opposite manner to the sedimentation density, i.e., low sedimentation density gave high low-shear viscosity, indicative of high order structure formation in the suspended particles. Shear rate theology of suspensions with high dispersant content showed a shear thinning but with low dispersant content (<= 2 wt.%), however, it showed a shear thickening at high shear rate (> 600 s(-1)).