Dilatant Behavior of TiO₂ (Rutile) -Water Suspensions

Abstract

The dilatant behavior of TiO₂ (Rutile)-in-water suspensions stabilized with various amounts of sodium pyrophosphate was studied using a caplillary viscometer for a wide variety of solid concentrations, colloidal stabilities, shear histories and capillary dimensions. The onset of dilatancy was observed at lower shear rates, and the extent of dilatancy was found to increase, respectively, with an increase in (a) the solid concentration, (b) the degree of flocculation varied by the dispersing agent (colloidal stability) and the shear stress previously imposed (history of shear), and (c) the length of capillary. In the dilatant region, the apparent viscosity increased not only with increasing shear rate but with shearing time, i. e., resident time of suspension in a capillary at a constant shear rate. Based on these results, it was concluded that the dilatancy observed in this study can be attributed to the progressive flocculation induced by shear. Additionally, there is a discussion of the mechanism of the pseudo-plastic flow observed at the lower and higher shear-rate ends of the dilatant recrion.