Preparation of crucibles from special refractories by slip-casting

Abstract

The slip-casting process, which is widely used in ceramics, has not been generally applied to the preparation of crucibles from special refractories, which lack the property of plasticity. However, enough plasticity to make slip-casting feasible can be developed in some of the special r efractories by fine grinding and treatment with acid. Thin-walled crucibles of alumina, beryllia, zircon, zirconia, and electrically fused thoria were cast from aqueous slips, and bricks 5 cm thick were made by a modified process . Magnesia crucibles could not be cast from aqueous slips but wer e formed s uccessfully from a suspension of fin ely ground magnesia in absolute alcohol.

Colloidal processing: enabling complex shaped ceramics with unique multiscale structures

“…During the 1930s research on the processing side of casting and forming ceramics for more advanced applications was carried out. Slip casting was seen as a viable method in producing ceramic crucibles for use in casting refractories . The surface finish associated with the traditional forming methods such as pressing or tamping produced a degree of roughness that would lead to premature fractures.…”

“…The surface finish associated with the traditional forming methods such as pressing or tamping produced a degree of roughness that would lead to premature fractures. For this reason, Thompson and Mallett applied the slip casting process to produce thin walled crucibles along with thick cross‐section bricks of Al 2 O 3 , beryllia (BeO), zircon (ZrSiO 4 ), ZrO 2 , and electrically fused ThO 2 —all of which were cast from aqueous colloidal suspensions. The authors drew on Hall's review of slip casting clays that highlighted aspects such as controlling suspension impurities, found in both the solid materials and in the solution.…”

“…Slip casting was seen as a viable method in producing ceramic crucibles for use in casting refractories. 29 The surface finish associated with the traditional forming methods such as pressing or tamping produced a degree of roughness that would lead to premature FRANKS ET AL. | 459 fractures.…”

The Behavior of the Alumina-Water System.

“…Further, other workers (6) have shown that this method of treatment may be applied to other non-plastic materials than that used in this investigation. This is to be expected, since the fundamental basis of the process is the development of colloidal properties in the material used.…”

Better ceramics through colloid chemistry

“…Similar acid treatments were used for alumina (23,24) and other refractory oxides such as ZrO2, ThO2, BeO, etc (25,26) in the 30s, as well as the use of alkaline deflocculants.…”