Production of Yttria Ceramics by Gelcasting

The production of yttria ceramics by green-gelcasting technique was developed through: (1) optimization of aqueous yttria slurries; (2) optimization of the gelcasting process; (3) thermal treatments and characterization of the final microstructures. Different dispersants were tested. Zeta potential characterization of the dispersed state was performed. Dynamic light scattering (DLS) measurements on the suspensions showed a strong aging effect of polyacrylate dispersants. Rheological measurements identified the exact Tg temperatures of the gelling agent. The yttria suspensions were ball milled with the dispersant for 24 h and heated at 65 °C, while the gelling agent as added to the ceramic suspension after solubilization in a separate solvent at 90 °C. The resulting mixture was de-aired under vacuum and casted into PE or silicon moulds. The casted bodies were dewatered, debonded at 500 °C and sintered in air or under vacuum at 1,660-1,700 °C. The microstructure of the sintered bodies with final relative density between 90%-95% was analyzed by scanning electron microscope (SEM).