Microstructural Control of Complex-Shaped Ceramics Processed by Freeze Casting

Highly dense, essentially flawless, complex ceramic shapes were formed utilizing freeze casting and freeze drying concepts. Aqueous or non-aqueous ceramic slurries of high-solids-loading up to 60 vol % were cast into dense molds. Frozen parts were removed from the molds and dried under vacuum by sublimation of ice to obtain near net-shape green bodies. Freezing behavior of aqueous slurries was controlled by using hydrogen bond forming compounds, such as glycerol, to reduce the size of ice crystals during solidification of water. Preparation of castable slurries with high-solids-loading using a water solidification modifier led to highly dense sintered ceramics with a uniform microstructure. This paper provides an overview of the developments in complex-shape forming of ceramics by freeze casting