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.

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.

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.

A Mg-doped alumina aerogel and a manufacturing method thereof are provided. The Mg-doped alumina aerogel is a three-dimensional cross-linked network structure including a plurality of magnesium atoms, a plurality of aluminum atoms, a plurality of oxygen atoms, and a plurality of hydrogen atoms. The three-dimensional cross-linked network structure has a MgOAl bond at least on the main chain.

The invention provides ballistic-resistant transparent objects of complex shapes consisting of magnesium aluminate spinel. The invention also provides a cost-effective industrial process for making the objects, including slip casting and sintering.

The present invention relates to a method for the production of a support material for a nitrogen oxide storage component that is applicable in catalysts for treating exhaust gases from lean-burn engines and a support material made according to said process that is stable against the reaction with a Barium compound to form BaAl.sub.2O.sub.4.

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.

In an embodiment, an abrasive particle comprises a body including alumina, the alumina including a plurality of crystallites having an average crystallite size of not greater than 0.18 microns. In other embodiments, the body further comprises magnesium and zirconia. The abrasive particle has at least one of an average strength of not greater than 1000 MPa or a relative friability of at least 105%.

The invention provides for a method of making a magnesium aluminate spinel including an alumina compound and a magnesium compound, the method including the steps of; dispersing the alumina compound by dispersing it in a aqueous solution, to form an alumina dispersion, the aqueous solution having a pH of between 2 and 5; preferably between 2 and 4, flocculating the alumina by increasing the pH of the alumina dispersion to a pH of between 8 and 10 by adding a base; adding the alumina dispersion to an aqueous dispersion of the magnesium compound to form a slurry; drying the slurry to produce a dried spinel precursor; and calcining the dried spinel precursor to produce the magnesium aluminate spinel. Dispersing at such a low pH results in a conversion to spinel as well as allows for the control of the surface area of the spinel.