Study On Ultrafine Zirconia Green Body Prepared With Gelcasting

The demands of ceramic parts of complex shape increase as excellent characteristic function ceramics develop its practical use, which could not be satisfied by processes such as dry pressing, die pressing, slip casting, injection molding. Gelcasting was a product of colloid chemistry, preparation technique of ceramics and polymer chemistry. At present, gelcasting had become an important shaping method for its incessant improving and gradual becoming perfection.Combination with researchful state and process and the relative theories of gelcasting, the key technology for preparing low viscosity and concentrated ultrafine zirconia slurry in gelcasting, the new drying method of biscuit, and the eliminating of the malformations due to the release of residual stresses were investigated.The key technology for preparing low viscosity and concentrated zirconia slurry in gelcasting was investigated in detail. Effects of pH value, dispersant, milling time and solid loading on zirconia slurry were discussed in detail. Results show that pH value and contents of dispersant have obvious effects on rheological property of suspension. When pH value is 10~11 and content of dispersant is 1.5vol%~ 2vol% and milling time is 20h~24h, the dispersive effect is the best. The slurry that solid loading utmost to 58vol% was prepared; whose viscosity was only 655mPa·s could fully satisfy the demands of gelcasting.Conventional methods in drying ceramic parts, that use dry air or gas with particular conditions of humidity and temperature, are usually confronted with many difficulties. Non-uniform drying in various regions due to the solvent gradient, induces structural and residual stresses, which cause defects, such as cracking, warpage, bending and the other malformations. These malformations can be minimised or even eliminated due to the release of residual stresses. Experiments were conducted on gelcast parts with solid loading of 50vol%, 52vol%, 54vol% and 58vol% separately, the data indicated that lower solid loading in the gel and higher liquid desiccant concentration, increase the drying rate.