A process for producing a magnesium aluminate spinel comprising the steps of: i) preparing a magnesium suspension containing a magnesium compound; ii) preparing an aluminum suspension containing an aluminum compound; iii) feeding the magnesium suspension and aluminum suspension independently into a spray dryer nozzle to form a mixed magnesium, aluminum suspension; iv) feeding the mixed magnesium, aluminium suspension from the spray dryer nozzle into a spray dryer to form a mixed magnesium and aluminum compound; and v) calcining the mixed magnesium and aluminum compound to generate a magnesium aluminate spinel.

This invention relates to a supported catalyst for synthesizing ammonia (NH.sub.3) from nitrogen gas (N.sub.2) and hydrogen gas (H.sub.2), method of making the support, and methods of decorating the support with the catalyst.

This invention relates to a supported catalyst for synthesizing ammonia (NH.sub.3) from nitrogen gas (N.sub.2) and hydrogen gas (H.sub.2), method of making the support, and methods of decorating the support with the catalyst.

A fused grain is essentially composed of a matrix of a magnesium aluminum oxide of MgAl.sub.2O.sub.4 spinel structure and/or of the MgOMgAl.sub.2O.sub.4 eutectic structure, and of inclusions essentially composed of magnesium oxide. The grain has the following overall chemical composition, as percentages by weight, expressed in the form of oxides: more than 5.0% and less than 19.9% of Al.sub.2O.sub.3, Al.sub.2O.sub.3 and MgO together represent more than 95.0% of the weight of the grain. The cumulative content of CaO and of ZrO.sub.2 is less than 4000 ppm, by weight.

Disclosed is a method for manufacturing calcium aluminates in an industrial furnace, according to which, continuously, into a tank made of refractory material containing a molten pool that is constantly heated, fine particles are introduced of a raw material source of alumina and/or of aluminium and of a raw material source of calcium oxide and/or of calcium having a median diameter d50 less than or equal to 6,000 m in order to melt the fine particles of raw material, and, continuously, at the outlet of the tank a mass of liquid calcium aluminates is recovered.

A method of purifying a spinel powder includes contacting a spinel powder with an acid solution to form an acid-washed spinel composition and contacting the acid-washed spinel composition with a basic solution to form a purified composition. The purified powder is suited to formation of low-absorption shaped bodies, such as windows for high intensity laser devices.

An object of the present invention is to provide a method for producing conductive mayenite, with which a reaction is completed in a short time, an operation can be simplified, the reaction is easily controlled, and the cost of energy can be reduced. The present invention is a method for producing conductive mayenite, characterized by mixing a mayenite type compound with a carbon component, placing the resulting mixture in an airtight container, and irradiating the mixture with a microwave in an inert gas atmosphere or in a vacuum atmosphere to heat the mixture.

Provided is a magnesium oxide-containing spinel powder capable of producing a ceramic sintered body having high strength and excellent strength stability. In the magnesium oxide-containing spinel powder, a 50% particle diameter (D50) is 0.30 to 10.00 m, a ratio (D90-D50)/(D50-D10) of a difference between a 90% particle diameter (D90) and the 50% particle diameter (D50) and a difference between the 50% particle diameter (D50) and a 10% particle diameter (D10) is 1.0 to 5.0, and a composition ratio of Mg and Al in terms of an oxide equivalent content is 50 to 90% by weight of MgO and 10 to 50% by weight of Al.sub.2O.sub.3.

Provided is a magnesium oxide-containing spinel powder capable of producing a ceramic sintered body having high strength and excellent strength stability. In the magnesium oxide-containing spinel powder, a 50% particle diameter (D50) is 0.30 to 10.00 m, a ratio (D90-D50)/(D50-D10) of a difference between a 90% particle diameter (D90) and the 50% particle diameter (D50) and a difference between the 50% particle diameter (D50) and a 10% particle diameter (D10) is 1.0 to 5.0, and a composition ratio of Mg and Al in terms of an oxide equivalent content is 50 to 90% by weight of MgO and 10 to 50% by weight of Al.sub.2O.sub.3.

Disclosed is a method for manufacturing crystals of aluminates of one or more element(s) other than aluminium, referred to as A. The method includes: placing starting reagents, including at least one aluminium element source and a source of the element(s) A that has a degree of oxidation of between 1 and 6, in suspension in a liquid medium, forming a suspension referred to as the starting suspension; milling the starting suspension at 50 C., in a three-dimensional liquid medium ball mill for 5 minutes; recovering, at the outlet of the three-dimensional ball mill, a suspension referred to as the end suspension including the starting reagents in activated form or crystals of aluminate of the element(s) A generally in hydrated form; if required, calcination of the end suspension when it includes the starting reagents in activated form, to obtain generally non-hydrated crystals of aluminate of the element(s) A.