Freeze Casting of Aqueous Alumina Slurries with Glycerol

Freeze-drying concepts were utilized in the shape forming of alumina parts by pressureless slip molding using aqueous slurries. A water solidification modifier, glycerol, was utilized to eliminate the defects associated with the expansion and ceramic particle rejection of water during freezing. Castable alumina slurries with solids loading up to 60 vol% were prepared and characterized using viscosity and zeta-potential measurements with and without glycerol additions. Frozen parts were dried under vacuum by sublimation of ice to obtain net-shape green bodies. The combined effects of high-solids-loading slurries, >57.5 vol%, and glycerol additions were essential for freeze casting to achieve highly dense alumina bodies with a uniform microstructure.