GB582091A - Ceramic abrasive or refractory material - Google Patents

Abstract

A dense, non-porous, ceramic, abrasive or refractory material is obtained by firing a compacted mixture containing relatively pure, precipitated, pigment grade, anatase titanium dioxide having an average particle radius ranging from 0.1 to 1.5 m , obtainable by the hydrolysis of a titanium salt solution, and a densification promoter at temperatures ranging from 600 DEG C. to 1,100 DEG C. thereby converting the anatase into rutile, thereafter shaping such calcined mixture under pressure, and sintering the resulting shape at a temperature below the melting point of rutile, and preferably not in excess if 1400 DEG C. The example includes a process in which 1 part of zinc oxide is added to a thick, viscous, aqueous slurry of 99 parts of uncalcined precipitated pigment grade anatase titanium dioxide of the particle size above defined and the dried mixture is calcined at 1000 DEG C., wet-ground, filtered and dried to obtain a mixture in which the titanium oxide is present as pure rutile. The mixture is then sintered in a muffle furnace at 1100 DEG C. Specifications 275,672 and 310,949, [both in Class 1 (iii)], are referred to.ALSO:A dense, non-porous, ceramic, abrasive or refractory material is obtained by firing a compacted mixture containing relatively pure, precipitated, pigment grade, anatase titanium dioxide having an average particle radius ranging from 0.1 to 1.5 m , obtainable by the hydrolysis of a titanium salt solution, and a densification promoter as herein defined at temperatures ranging from 600 DEG C. to 1,100 DEG C. thereby converting the anatase into rutile, thereafter shaping such calcined mixture under pressure, and sintering the resulting shape at a temperature below the melting point of rutile, and preferably not in excess of 1,400 DEG C. Advantageously, the titanium dioxide is a relatively pure, anatase titanium dioxide hydrolysate and the mixture of promoter and dioxide is calcined at temperatures ranging from 900 DEG C. to 1,000 DEG C.; after shaping such calcined mixture the resulting shape is sintered at temperatures ranging from 1,100 DEG C. to 1,200 DEG C. The promoter is preferably a compound non-volatile under the conditions of the reaction, e.g., an oxide, or compound which, under the conditions of firing, will convert to an oxide, of one or more of the following elements; zinc, lithium, manganese, copper, iron, cobalt, aluminium, antimony, barium, beryllium, chromium, sodium or silicon, and is incorporated in the mixture in an amount of from 0.2 to 2 per cent. calculated as the oxide by weight of the titanium dioxide. Specified residues are; sulphate, nitrate, acetate, hydroxide, oxalate, peroxide, sulphide, oxysulphide and carbonate. In an example, 1 part of zinc oxide is added to a thick viscous, aqueous slurry of 99 parts of uncalcined precipitated pigment grade anatase titanium dioxide of the particle size above defined and the dried mixture is calcined at 1,000 DEG C., wet-ground, filtered and dried to obtain pure rutile. Three separate compositions are then mixed thus: F. consisting of 88 parts of the rutile so prepared and 12 parts of water; G. consisting of 86 parts of zinc oxide-free calcined pigment grade rutile with 12 parts of water and 2 parts of zinc oxide; H. consisting of 88 parts of identical zinc oxide-free rutile with 12 parts of water. Bars made from the three compositions by the use of 12 tons per square inch pressure acting on steel dies, are sintered in a muffle furnace at a maximum temperature of 1,100 DEG C. to obtain products of which that derived from F exhibits superior density, porosity and water imperviousness. Specifications 275,672 and 310,949, [both in Class 1 (iii)], are referred to.