Direct observation of the deformation behavior of agglomerates in a highly concentrated slurry under startup shear flow

Dispersibility and agglomeration of particles in a highly concentrated slurry are important factors in ceramic colloidal processing. In this study, the particles in a transparent slurry, prepared using silica particles and glycerol solution as a model, and their deflocculation under an applied startup shear flow were directly observed using a confocal laser scanning fluorescent microscope. The dispersibility of the particles was changed using additives and was evaluated by studying the rheology and measuring the interaction force between two particles using a scanning probe microscope. A slurry concentrated with polyacrylic ammonium exhibited a shear-thinning behavior, i.e., the gradual transformation of agglomerates into linear chain-like structures on the application of shear-stress, and weak repulsive forces were observed between the particles. The results of this study can enhance the homogeneity of ceramic colloids, powder compacts, and ceramics.