Rheological properties of nanometer tetragonal polycrystal zirconia slurries for aqueous gel tape casting process

The aim of the present work was to identify the conditions for the preparation of stable zirconia slurries with high solids content for the production of aqueous gel tape casting objects with improved properties. Influences of the powder and dispersant on the rheological properties were investigated. High stable low-viscosity nanoparticles zirconia suspensions were achieved. Nanometer-sized tetragonal polycrystal zirconia powder was synthesized by a new low-temperature environment-benign method. The oxide powders were confirmed to be 3Y-TZP single phase with tetragonal structure measured by X-ray diffraction analysis. Acryl amide (AM) and N,N' -methylene bisacrylamide (MBAM) have been used as organic monomer and cross-linker of the process, respectively. NH(4)PAA (M=5000-8000) has been used as polyelectrolyte dispersant. The electrokinetic behavior of nanometer-sized zirconia suspensions stabilized by various dispersant contents was studied. The result indicated the dispersant concentration greatly affected the surface charge of nanometer tetragonal zirconia powder. The isoelectric point (IEP) obviously changed from 8.1 to about 4.7 because of the addition of polyelectrolyte dispersant. To acquire stable low-viscosity slurries, the influences of several parameters on rheological behavior of nanosized tetragonal zirconia suspensions were investigated. It was found that for each factor, there exists an optimum range in which low viscosity was achieved for a slurry with high solid loading. For the slurry of 77 wt.% powder concentration with about 1.0 wt.% polyelectrolyte (based on the powder), the viscosity was 350 mPa s at the shear rate of 110 s(-1). The slurry at the optimum conditions met the demands of aqueous gel tape casting process. (C) 2002 Elsevier Science B.V. All rights reserved.