Preparation of high solids content nanozirconia suspensions

A new colloidal route leading to the production of similar to 99% dense 3-mol% yttria-stabilized zirconia nanostructured ceramics, while retaining a final average grain size of similar to 75 nm, has been developed. The process was based on the production of stable, homogeneous nanosuspensions with solids contents of up to 28 vol% (70 wt%), but viscosities < 0.05 Pa.s at any shear rate in the range of study were obtained. The suspensions were formed by the concentration and optimization of precursor, dilute (5.0 vol%) commercial nanosuspensions, the approach requiring a change of pH, from the 2.4 of the as-received suspension to 11.5, and the use of an appropriate anionic dispersant. Exposure of the nanosuspensions to ultrasound also helped to reduce the viscosity further, although it only worked when the dispersant was optimized. The nanosuspension was slip cast to form homogenous green bodies with densities of similar to 55% of the theoretical without agglomeration in the nanostructure; these were subsequently densified using a two-step sintering technique.