12 - Mechanical Properties of Dry Ceramic Powders and Wet Ceramic Suspensions

Abstract

This chapter discuses the fundamentals of suspension rheology from dilute suspensions to concentrated suspensions. The rheological properties are used with the Cauchy equation of motion to predict the velocity profiles, wall shear stress, and the pressure distribution in the mold. The rheological properties are used with the Cauchy equation of motion. The rheology of concentrated ceramic suspensions is very important for good mold filling. For concentrated suspensions that are colloidally stable (by steric means, giving a hard sphere model), there is a particle volume fraction where the particles come into contact, giving a random close packed network. The mechanical properties of dry ceramic powders have been discussed in terms of the Coulomb yield criterion, which gives the stress necessary for flow (or deformation) of the powder. The mechanical properties of dry ceramic powders and wet ceramic suspensions must be controlled to have dry powders that flow into molds for dry pressing and deform during pressing, suspensions that flow into slip cast molds, and pastes that can be stamped into objects, extruded into shapes, or injection molded.