Freeze Casting of Ceramic Components Using Ice Cores and Ice Moulds

A novel shaping technique for advanced ceramic components is presented which allows manufacturing of complex ceramic components with enclosed cavities by using ice moulds or ice cores. Different suspensions of alumina and zirconia powders have been developed for this special freeze casting technique. The suspensions must meet following requirements: high solid content, the capability of flow, a freezing point between -10 and -2 °C, and a casting temperature below 0 °C. After the casting process the moulds and cores could be easily removed by sublimation. The suspension liquid was removed in the frozen state simultaneously. In this way very complicated hollow or filled structures such as metallic or ceramic components encapsulated in ceramic shells could be produced. No de-moulding was necessary, no solid core must be removed, and no liquid phase appeared as known from other lost-mould techniques. Ice mould casting is a very environmental-friendly shaping technique. Furthermore, the influence of dispersing agents, anti-freeze agents and of the freezing speed on the pore structure of the ceramic components has been investigated.