Effect of the Interparticle Pair Potential on the Rheological Behavior of Zirconia Powders: I, Electrostatic Double Layer Approach

Aqueous slurries containing 20 vol% ZrO₂ powder doped with 3 mol% Y₂O₃ were prepared by first dispersing the powder at pH 11, then adding 0.1 M to 1.0 M tetramethylammonium chloride (TMACl), or 1.0 M of TPACl, CsCl, and LiCl to produce different, weakly attractive particle networks. The particle pair potentials in the slurries were investigated by viscosity versus shear rate measurements. Slurries exhibited increasing viscosities (at a given shear rate) with increasing salt concentration and decreasing (unhydrated) counterion size. The viscosities for these weakly attractive networks were intermediate to dispersed (pH 11 without added salt) and flocced (isoelectric point, pH 7.5) slurries. Cylindrical bodies were consolidated from these slurries by pressure filtration at different applied pressures. The bodies consolidated from slurries formulated with TMACl had the highest packing densities relative to those consolidated from a flocculated slurry, but the relative densities were much lower than those achieved from bodies consolidated from a dispersed slurry. The plastic or brittle nature of these bodies was determined in uniaxial compression. Powder compacts consolidated from flocced slurries and slurries coagulated with 1 M TMACl, CsCl, and LiCl showed plastic behavior for filtration pressures ≤7.5 MPa. Results for ZrO₂ will be compared with those previously obtained for Al₂O₃, which produces plastic, consolidated bodies over a much broader range of slurry conditions.