Manufacture of Refractory Articles from Pure Oxides of High Melting Point
JSGT_1936_V20_T200_T217
The manufacture is described of crucibles, rods and tubing from the pure refractory oxides Al2O3, MgO, BeO, ThO2, and ZrO2, and a general account given of the production of highly refractory articles by fusion casting, slip casting, and by the use of temporary bonding agents. Spacers of high electrical resistance for wireless valves are produced by moulding Al2O3 and MgO under pressure, to tolerances of ±0·5%. Wet paste and slip casting processes are employed for the production of crucibles. For the extrusion of rod or tubing a plasticising agent of flour containing NH4OH is used for alumina, and a cellulose composition for magnesia. The particle size must be graded to suit the diameter of the extruded shape. The extent of the firing shrinkage is controlled by particle size grading, the ratio of plasticiser to material, and by the use of material pre-calcined at different temperatures. Data are given on the chemical, thermal, and electrical properties of the materials produced.
J.H. Partridge & J.R. Lait
