Colloidal Consolidation of Ceramic Nanoparticles by Pressure Filtration

Abstract

The applied pressure and suspension height during consolidation of an aqueous suspension of nanometer-sized particles (24 nm hydroxyapatite, 30 nm SiC, 68 nm 8 mol% yttria-stabilized zirconia, 150 nm Al2O3, and 800 nm SiC) were continuously recorded using a pressure filtration apparatus. The packing density decreased when the particle size was less than 70 nm. The final packing density of 150−800 nm particles at 19 MPa was strongly influenced by the surface charge. However, surface charge does not affect the packing density of particles less than 70 nm. The ratio of the energy applied to two particles during consolidation to the interaction energy between two particles in a suspension was correlated to the packing density. The low packing density of 20−30 nm particles was improved by steric stabilization. The estimated thickness of the dispersant layer adsorbed on the particle surfaces was less than 1 nm and nearly independent of the molecular weight of the dispersants. When the applied pressure was released, the height of the consolidated cake increased because of the release of the elastic strain stored in the dispersant layer.