RHEOLOCY OF AQUEOUS DISPERSIONS OF ALUMINA, TITANIA AND MIXTURE OF ALUMINA AND TITANIA POWDERS

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Abstract
The electrophoretic mobility and rheology of alumina, titania and alumina / titania powder mixtures ( ratio of alumina : titania 1 : 2 and 2 : 1 ) were investigated in aqueous suspensions in the pH range 3 - 10. The results suggest that the electrophoretic mobility of the individual powders is independent of the particle concentration, but the electrokinetic behavior of the powder mixture depends upon the concentration of the individual constituents. The rheology of all the suspensions is charge related and while alumina and alumina / titania ( ratio 2 : 1 ) flocculate at pH 9.0 both titania and alumina / titania ( ratio 1 : 2 ) form low viscous dispersions. Similarly while later dispersions flocculate at pH 5.6, the former dispersions behave as Newtonian type fluids. Better correlation between the slip rheology and the electrokinetic behavior of suspensions containing both alumina and titania powders can be obtained provided the experimental results are evaluated based upon the total surface area of the individual powders but not the particle concentration.