Equilibrium-State Density Profiles of Centrifuged Cakes

ACKING-DENSITY variations in a powder compact often P result in nonuniform shrinkages andor cracking during subsequent drying and sintering. In case of dry-pressed compacts, the effect of consolidation conditions on density variations has been sufficiently detailed by theoretical models.' However, although recent trends have favored the use of colloidal consolidation methods in order to attain a higher degree of uniformity in packing densities, the effect of the forming methods on density variations in colloidally consolidated compacts is still poorly understood. A variety of colloidal processing methods are now utilized in shape forming. These methods can be grouped into two categories, depending on whether the starting suspension is in a dispersed or flocculated A thorough discussion on the benefits of these two methods has been provided by Lange! Since, in both methods, a central issue is the minimization of packing density variations, the goal of this paper is to provide a theoretical model for the variation of packing density in flocculated suspensions when the flocculated network is subjected to a nonuniform pressure field. In prior studies, Schilling et aL5 used y-ray densitometry to study the density variation in a sedimentation cake and showed