Surface-modified zirconia powders with 20% to 100% of the particle surface area covered with stearic acid was blended with 50 vol% of an organic wax vehicle for rheological study. These fractions of surface coverage gave rise to different degrees of powder agglomeration. A further adsorption of the wax on partially modified particle surfaces was examined, which was likely to exhibit different degrees of solid surface-wax affinity depending upon whether the particle surfaces were `bare' or `premodified.' The rheological behavior of the suspensions revealed that the shear viscosity as well as the yield stress increased appreciably with decreased fractions (or surface coverage) of the pre-adsorption. The observed suspension rheology due to incomplete surface modification can be accounted for by the formation of agglomerates which suppress suspension flowability to a significant extent. The formation of the agglomerates alters the suspension structure by reduction of the maximum solid concentration (πmax) that is attainable for a given powder. This change in suspension structure (decrease in πmax) leads to a restriction of particle mobility, reflected as a linear function of the yield stress of the suspensions.
|Number of pages||6|
|Journal||Journal of the American Ceramic Society|
|State||Published - 1 Oct 1999|