GB429367A - Process for the production of wholly crystalline refractories from zircon by fusion - Google Patents

Abstract

Crystalline zirconia is obtained by fuzing zircon at a temperature of at least 2000 DEG C., and removing the vitreous silica from the cooled product by treatment with hydrofluoric acid. Alternatively the bulk of the silica may be removed as a soluble silicate, as by fritting the fusion product with an alkali carbonate and washing with water, and the last traces of silica be then removed by hydrofluoric acid. Crystalline refractories may be obtained by fuzing zircon with a metallic oxide such as alumina, lime, or magnesia to give a mixture of crystalline zirconia and a crystalline silicate of the added oxide. By adding zirconia or silica to the mixture to be fuzed the relative proportions of zirconia and silicate in the product may be varied. In one example, a refractory is obtained by fuzing 17,5 per cent of zircon with 82,5 per cent of bauxite containing 45 per cent of alumina and 40 per cent of silica. By fuzing 20--30 per cent of zircon with 80--70 per cent of alumina a body suitable as an abrasive or as a refractory is obtained, whilst the fusion product of 70 per cent zircon and 30 per cent alumina forms an electric insulator.ALSO:Crystalline refractories may be obtained by fusing zircon with a metallic oxide such as alumina, lime, or magnesia to give a mixture of crystalline zirconia and a crystalline silicate of the added oxide. By adding zirconia or silica to the mixture to be fused the relative proportions of zirconia and silicate in the product may be varied. In one example, 17,5 per cent of zircon is fused with 82,5 per cent of bauxite containing 45 per cent of alumina and 40 per cent of silica. In other examples 20-30 or 70 per cent of zircon is fused respectively with 80-70 or 30 per cent of alumina.