Study On Zirconia-Toughened Alumina Ceramics Prepared By Gelcasting

Gelcasting process is a novel in-situ forming technology combining traditional forming process with macromolecule chemical reaction. In this paper, an in-depth study on gelcasting process, microstructure and properties of zirconia-toughened alumina (ZTA) composites was preceded based on a comprehensive review on research progress in gelcasting process and ZTA composites.Firstly, the work was performed with respect to the key technology in gelcasting process, namely, the preparation of suspensions with low viscosity and high solid volume fraction. The influences of mass fraction of dispersant, solid volume fraction, powder composition and milling time on the rheological properties of Al₂O₃, ZrO₂ and ZTA suspensions were investigated by the characterization of zeta potential, sedimentation volume fraction and rheological behaviors, etc. The results show that the viscosity of Al₂O₃,ZrO₂ and ZTA suspensions increases with the increase of their respective solid volume fraction. The optimum mass fraction of dispersant and the viscosity of ZTA suspension increase with the increase of mass fraction of ZrO₂. ZTA suspension with good stability can be prepared by adjusting the addition of dispersant for the case with a relatively high mass fraction of ZrO₂. The Al₂O₃,ZrO₂ and ZTA suspensions exhibit the lowest viscosity when the milling time is 4h in the experiments.Then the optimum gelling conditions of green body were studied. When monomer concentration is 14wt%, gelling temperature is 20～30℃ and initiator addition is less than 1.58wt%, the green body with excellent performance was prepared. It is found that solid volume fraction and powder composition affect the properties of green body significantly. Suspensions with low viscosity and high solid volume fraction favor to increase the density and reduce the shrinkage of the dried green body, which results in fewer faults in it. The density of the dried green body increases with the increase of mass fraction of ZrO₂, however, the shrinkage also increases simultaneously.