Rheological behavior of titanium dioxide suspensions

The theological properties of titanium dioxide dispersed in water are measu red over a wide range of powder concentrations, temperatures, and pH values . The value of intrinsic viscosity of titanium dioxide measured with an Ubb elohde capillary viscometer is 3.55, which is useful for determining the sh ape and aggregation property of the particles. The yield stress and steady shear viscosity of titanium dioxide with broad and narrow particle size dis tributions were measured over a wide range of solid volume fractions on a B rabender rheometer. It is observed that the theological properties of the s uspensions are quite different due to the difference in particle size distr ibutions. Quemada, Casson, and Zhou's models were used to fit the experimen tal data and useful parameters were obtained. Calculated data are also in g ood agreement with the experimental data. As expected, the shear viscosity and yield stress decrease with increasing temperature. But when the tempera ture is around 50 degreesC, yield stress increases with increasing temperat ure while shear viscosity exhibits a complex behavior. The phenomena are ve ry interesting and special. The Peclet number was used to analyze the shear thickening behavior. Models were also used to describe the shear viscosity under different temperatures and the master plots of the reduced variables eta/eta (infinity), vs t(c)(gamma) over dot at different temperatures are superimposed, which means the agreement is fair and the models are suitable to describe the theological properties of titanium dioxide suspensions. pH effects were investigated on a Rheometrics RFS-II rheometer and it was fou nd that pH can change the surface charge of the particles, which also affec ts the theological behavior. The pH at which maximum shear viscosity and yi eld stress occur is in concordance with the isoelectric point, (C) 2001 Aca demic Press.