Yield Stress of Alumina‐Zirconia Suspensions

Abstract

The yield stress of concentrated suspensions of alumina, zirconia, and mixed alumina‐zirconia powders was measured by the vane technique as a function of solids loading, relative amounts of alumina and zirconia, and pH. At the isoelectric point (IEP), the yield stress varied as the fourth power of the solids loading. The relative ratio of alumina and zirconia particles was important in determining the yield stress of the suspension at the IEP. The yield stress of single and mixed suspensions showed a marked variation with pH. The maximum value occurred at or near the IEP of the suspension. The effect of electrical double‐layer forces on the yield stress can be described on the basis of the Derjaguin‐Landau‐Verwey‐Overbeek (DLVO) theory. A normalized yield stress—that is, the ratio of the yield stress at a given pH to the yield stress at the IEP predicted by this model—showed good correlation with experimental data.