Abstract: Spray-coating materials having a high heat-resistance and thermal conductivity for the surface protection of materials. The spray-coating material consists of 8-35 wt. % magnesium oxide MgO or calcium oxide CaO, 2-10 wt. % of beryllium oxide BeO and 55-90 wt. % of aluminum oxide Al.sub.2 O.sub.3, zirconium dioxide ZrO.sub.2, silicon dioxide SiO.sub.2, chromic oxide Cr.sub.2 O.sub.3 and titanium dioxide TiO.sub.2. The spray-coating material of the invention can be employed to advantage, for example, in the chemical industry and in metallurgy.

Abstract: A fused cast ceramic composition having superior corrosion and stoning resistance in the presence of E glass when compared with prior art compositions having comparable chromia content. The composition is a solidified fusion of from about 65 to about 98 weight percent Cr.sub.2 O.sub.3, from about 0.75 to about 4 weight percent MgO and from about 1 to about 34.25 weight percent alumina. The invention also comprises the method for manufacturing the composition by fusing the appropriate materials at the required concentrations.

Abstract: There is disclosed a material for hot or plasma spraying, especially a material based on oxide ceramics, and a process for the production thereof. The composition of the invention is a mixture of powdered oxides containing at least two fundamental oxides with high melting point, and at least one glass-forming oxide the melting point of which is lower. The invention also includes a process for the production of such composition by the melting and agglomeration of individual components in the oxidizing medium of a plasma stream, including the special treatment of the starting components.

Abstract: The gasification of coal can be accomplished more efficiently if it is operated at a temperature high enough so that the mineral constituents of the coal will form a molten slag which can be continuously removed from the gasifier during operation. Proper control of such a process requires careful temperature control, but the molten coal slag has been found to be corrosive to most thermocouple materials and to conventional refractory ceramics which are used as thermocouple protection tubes in other environments. It has now been found that magnesium chromite serves satisfactorily as a corrosion resistant refractory material in molten coal slags, and that thermocouple protection tubes of this material can be made by isostatic pressing of granular magnesium chromite and subsequent firing.

Abstract: A spinel containing slip-casting composition, method for preparing the spinel slip-casting composition and method for casting the slip into usable forms are described. The spinel employed to prepare the castable slips is a pre-calcined spinel and a calcined spinel each prepared in the manner of copending application Ser. No. 184,189, filed Sept. 4, 1980, which is ball-milled with water, then mixed with a deflocculant at pH 9 or below. The slurry or "slip" is cast into a mold porous to water until the desired thickness of solid has been obtained and the excess "slip" decanted or otherwise withdrawn from the mold. The green shape is retained in the mold until it gains green strength, 1 hour to 5 days, and thereafter placed in an oven wherein it is fired to above about 1400.degree. C. for from 1 to 20 hours until it has reached its maximum density of between about 50 and 99 percent of theoretical.

Abstract: A chromia-magnesia based refractory product made up of fused chromia-magnesia grains bonded by an in situ formed chromia-magnesia bond. The product is very dense and especially suitable when used to process molten materials which involve coal slag.

Abstract: Several methods are set forth for preparing polymetallic spinels by coprecipitating two or more metal compounds in a proportion to provide a total of eight positive valences when combined in the oxide form in the spinel crystal lattice. The methods disclosed require coprecipitation of the metals in the hydroxide form or convertible to the hydroxide-oxide form, calcining the coprecipitate, and finally sintering the calcined material at about one-half its melting point or greater, thereby forming a spinel which has a density of greater than 50 percent of the theoretical density of spinel crystal. Also disclosed are techniques for preparing spinels having more than two metals incorporated into the spinel lattice, as well as a separate oxide phase associated with the spinel crystallites, and slipcasting compositions.

Abstract: A spinel containing slip-casting composition, a method for preparing the spinel slip-casting composition and a method for casting the slip into usable forms are described. The spinel employed to prepare the castable slips is a pre-calcined spinel prepared in the manner of copending application Ser. No. 184,189, filed Sept. 4, 1980, which is ball-milled with water, then mixed with a deflocculant at pH 9 or below and optionally with a molding aid. The slurry or "slip" is cast into a mold porous to water until the desired thickness of solid has been obtained and the excess "slip" decanted or otherwise withdrawn from the mold i.e., drain cast method or the "slip" is solid cast and dried to produce a green solid casting. The green shape is retained in the mold until it gains green strength, 1 hour to 5 days, and thereafter placed in an oven wherein it is fired to above about 1400.degree. C. for from 1 to 20 hours until it has reached its maximum density of between about 55 and 99 percent of theoretical.

Abstract: Gunning mixes and other magnesia-based refractory compositions are disclosed which include up about to 10% by weight sulfamic acid as a binder. Sulfamic acid reacts readily with periclase grain and, when employed with boric acid and ceramic sintering aids forms an excellent binder system.

Abstract: This invention is a new process for producing refractory crystalline oxides having improved or unusual properties. The process comprises the steps of forming a doped-metal crystal of the oxide; exposing the doped crystal in a bomb to a reducing atmosphere at superatmospheric pressure and a temperature effecting precipitation of the dopant metal in the crystal lattice of the oxide but insufficient to effect net diffusion of the metal out of the lattice; and then cooling the crystal. Preferably, the cooling step is effected by quenching. The process forms colloidal precipitates of the metal in the oxide lattice. The process may be used, for example, to produce thermally stable black MgO crystalline bodies containing magnetic colloidal precipitates consisting of about 99% Ni. The Ni-containing bodies are solar-selective absorbers, having a room-temperature absorptivity of about 0.96 over virtually all of the solar-energy spectrum and exhibiting an absorption edge in the region of 2 .mu.m.

Abstract: Magnesium oxide, especially suitable for use in basic refractories, is produced from brine or bittern containing magnesium chloride by:(a) adding to the brine or bittern, as a source of MgO and/or CaO, MgO or Mg(OH).sub.2 or calcined magnesite or calcined dolomite or calcined calcite/limestone in such amount that in the case of MgO, Mg(OH).sub.2 or calcined magnesite, the molar ratio of MgO:MgCl.sub.2 is in the range of 1:1.5 to 1:15 (i.e. 0.66:1 to 0.066:1) or, in the case of calcined dolomite, the molar ratio of MgO+CaO:MgCl.sub.2 is in the range of 0.66:1 to 0.05:1, or, in the case of calcined calcite/limestone, the molar ratio of CaO:MgCl.sub.2 is in the range of 0.66:1 to 0.1:1;(b) keeping the mixture at a temperature below 90.degree. C. till a solid mass is formed; and(c) drying the said solid mass at a temperature up to 200.degree. C.The said mass may then be calcined at a maximum temperature of 1200.degree. C. and optionally then briquetted with a binder and fired at above 1400.degree. C.

Abstract: Refractory chrome-magnesia bricks and compositions composed of a granular fused material having a grain size of 12 mm or less, and a content of from 71 to 83 wt. % Cr.sub.2 O.sub.3 and from 17 to 29 wt. % MgO, the minimum content of Cr.sub.2 O.sub.3 and MgO being 94 wt. %.