Aqueous synthesis and processing of nanosized yttria tetragonally stabilized zirconia

The goal of this study is the production of bulk ceramics from well-dispersed nanosized aqueous ceramic suspensions via wet processing routes. In order to obtain this goal, yttria tetragonally stabilized zirconia (Y-TZP) was used as a model system to develop an understanding of and ability to manipulate the solution chemistry parameters of solution pH, solid loading, zeta potential and complexation chemistry in order to accomplish synthesis and processing of nanosized doped metal oxide powders in an aqueous environment.; The objective of the aqueous degradation study was to establish the mechanism(s) controlling degradation of 3Y-TZP powder in aqueous suspensions at room temperature and determine the effect of this degradation on the aqueous physical chemistry of 3Y-TZP. This objective was accomplished by performing experiments on commercially available 3Y-TZP powder placed in aqueous suspensions at 25°C. It was determined that the mechanism of aqueous degradation of 3Y-TZP at room temperature was yttrium leaching. Furthermore, it was determined that the addition of oxalic acid to the aqueous suspension of 3Y-TZP impeded the aqueous degradation by interaction with the 3Y-TZP powder surface.; The objective of the synthesis study was to produce well-dispersed nanosized yttria tetragonally stabilized zirconia (Y-TZP) powder in aqueous suspension.; Once the nominally 7 to 8 nanometer hydrothermally prepared 1.7 Y-TZP powder was produced, experiments were begun to disperse, recover and concentrate by washing the powder via centrifugation. Centrifugation without irreversible aggregate formation was possible by taking advantage of a protective colloid formation. Protection was provided after synthesis by bicine, the synthesis complexation agent. The change in the surface chemistry of the 1.7Y-TZP powder as a function of washing was monitored by diffuse reflectance infrared Fourier transformed spectroscopy (DRIFTS) and solution chemistry analysis for metal ions in solution as a function of washing was determined by direct couple plasma spectroscopy (DCP). Well-dispersed aqueous suspensions of 1.7Y-TZP with an average agglomeration number of 3 or less were produced by washing the as-synthesized powder using centrifugation.; Finally, the well-dispersed 1.7Y-TZP aqueous suspensions were used to produce bulk ceramic pellets via the wet processing techniques of slip casting and filter pressing. Filter pressing was determined to be the more efficient method of pellet formation. The 1.7Y-TZP pellets formed by filter pressing were then thermally analyzed using thermal gravimetric analysis (TGA), differential thermal analysis (DTA), thermal mechanical analysis (TMA) and cyclic dilatometry. The thermal analysis data was then used to determine a sintering scheme to attempt to produce fully dense bodies. (Abstract shortened by UMI.)...