INVESTIGATION OF THE POWDER CHARACTERISTICS AND MICROSTRUCTURES ALUMINA-ZIRCONIA COMPOSITES

The electrokinetic properties of selected commercial ZrO2 and Al2O3 po wders in aqueous suspensions were analysed. The relationship between t he colloidal interactions in heteroparticulate powder mixtures and the rheological behaviour of appropriately concentrated real ceramic susp ensions was examined, and related to the homogeneity of distribution o f alumina and zirconia grains in the sintered microstructures. The ZrO 2 powder grades investigated, although of nominally the same chemical and phase composition, differed not only in their specific surface are a but also in their electrokinetic properties in aqueous suspensions. It is presumed that these differences result from the presence of acti ve groups on the powder surface due to different powder calcination te mperatures. Since the preferential adsorption of foreign ions contribu tes substantially to the powder surface properties of ZrO2 as measured by microelectrophoresis, the zeta potential vs. pH behaviour of these zirconia powders cannot be used to predict the colloidal compatibilit y with alumina in mixed concentrated suspensions.