FREEZE CASTING USING ALUMINA SLURRIES WITH GLYCEROL

Freeze-drying techniques were used by press less slip moulding using aqueous slurries to shape alumina pieces. Glycerol was used as a water solidification agent to remove the defects associated with expansion and ceramic surface rejection during freezing of water. Using viscosity and zeta-potential measurements with and without glycerol additions, castable alumina slurries with solids loading up to 60% were prepared and characterized. In order to obtain net shape green bodies, frozen pieces were dried under vacuum by ice sublimation .in order to achieve highly dense alumina bodies with a uniform microstructure, the combined effects of high solids loading slurries, less than 56.4 % volume and glycerol additions were essential for freeze casting. The feasibility of complex formation was demonstrated by using Freezing principles and aqueous alumina slurries with high mixing of solids. This led to freeze formed samples were processed with a uniform microstructure in the absence of ice formation related defects.