VISCOSITY AND YIELD STRESS OF ALUMINA SLURRIES CONTAINING LARGE CONCENTRATIONS OF ELECTROLYTE

Viscosity and yield stress measurements of Al2O3 slurries containing h igh concentrations of electrolyte are reported. Contrary to what is ex pected from DLVO theory, the particles in coagulated slurries produced in this way are held together by weaker forces than particles in slur ries brought to the isoelectric point by changing the pH. In both case s an attractive, connective particle network is present. However, the network at the isoelectric point is stronger, as indicated by its much higher yield stress and by its higher viscosity at stresses above the yield point. An additional short-range repulsive force that appears a t low pH and high electrolyte concentrations is believed to be respons ible. This force prevents the particles from reaching the primary mini mum associated with particle contact. The effects of solids loading, e lectrolyte concentration and type, and particle size have been investi gated.