The present invention relates to a method for obtaining calcium aluminates for metallurgical use from non-saline aluminum slags by means of reactive grinding and thermal treatment.

Disclosed is a method for manufacturing a hydraulic binder including a calcium aluminate, which involves: a) providing a composition including a lime C source compound and an alumina source compound, the composition including at most 95% lime C and alumina, and at least 23% alumina, by weight relative to the total weight of dry matter of the composition; b) placing the composition provided in step a) in a moisture-saturated environment, at a hydration temperature of between 40? C. and 150? C., so as to precipitate hydrated phases containing at least one aluminium oxide combined with a calcium oxide and with water; and c) subjecting the precipitates obtained in step b) to a baking temperature of between 200? C. and 1300? C., for at least 15 minutes.

Disclosed is a method for manufacturing a hydraulic binder including a calcium aluminate, which involves: a) providing a composition including a lime C source compound and an alumina source compound, the composition including at most 95% lime C and alumina, and at least 23% alumina, by weight relative to the total weight of dry matter of the composition; b) placing the composition provided in step a) in a moisture-saturated environment, at a hydration temperature of between 40? C. and 150? C., so as to precipitate hydrated phases containing at least one aluminium oxide combined with a calcium oxide and with water; and c) subjecting the precipitates obtained in step b) to a baking temperature of between 200? C. and 1300? C., for at least 15 minutes.

The invention related to a material that can stably hold an imide anion (NH.sup.2) therein even in the atmosphere or in a solvent, and a method for synthesizing the material and a use of the material. A mayenite-type compound into which imide anions are incorporated at a concentration of 110.sup.18 cm.sup.3 or more are provided. The mayenite-type compound can be produced by heating a mayenite-type compound including electrons or free oxygen ions in a cage thereof, in liquefied ammonia at 450 to 700 C. and at a pressure of 30 to 100 MPa. The compound has properties such that active imide anions can be easily incorporated into the compound and the active imide anions can be easily released in the form of ammonia from the compound, and the compound has chemical stability.

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.

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.

A process for preparing particles of a layered double hydroxide of the general formula

[M.sub.p.sup.z+M.sub.q.sup.y+(OH).sub.2].sup.a+(X.sup.n).sub.a/n.bH.sub.2O(I)

wherein M.sup.z+ and M.sup.y+ are metal cations or mixtures of metal cations, z=1 or 2; y=3 or 4; p+q=1; b=0 to 10, X.sup.n is an anion, n is 1 to 5 and a is determined by p, q, y and z such that a=zp+yq2, comprises (a) mixing, in aqueous solution, M.sup.z+ cations, M.sup.y+ cations and X.sup.n anions, with a base; and (b) allowing the layered double hydroxide of formula (I) to precipitate from the solution mixed in step (a).

Preferably, M is Li, Mg, Zn, Fe, Ni, Co, Cu, Ca, or a mixture of two or more. Preferably, y is 3, and M is Al, Ga, In, Fe or a mixture of two or more thereof. Also provided are particles obtainable by the process, especially wherein M is Ca, M is Al, and X.sup.n is NO.sub.3.sup.. Particles of a layered double hydroxide wherein the particles have a particle size of not greater than 2000 nm, preferably not greater than 300 nm and especially not greater than 100 nm, are also provided. The layered double hydroxides according to the invention are useful in certain applications, for example, as adsorbents, coatings and catalyst supports.

Objects of the present invention are to provide a mayenite compound which can induce electron donation reaction, H.sup. donation reaction, deoxygenation reaction, and dehydration reaction; a multifunctional agent which contains the mayenite compound which is not dissolved in a solvent, and which can induce electron donation reaction, H.sup. donation reaction, deoxygenation reaction, and dehydration reaction; and a method for producing a mayenite-compound-containing product. The invention provides a mayenite compound characterized by comprising enclosing electron and H.sup., a multifunctional agent characterized in that the agent contains at least one of the mayenite compound I and a mixture II of the mayenite compound enclosing electron and the mayenite compound enclosing H.sup., and exhibits radical scavenging activity, reducing property, deoxygenation performance, and dehydration performance; and a method for producing a mayenite-compound-containing product containing the aforementioned mayenite compound.

A production method of an electroconductive mayenite compound having an electron density greater than or equal to 510.sup.20 cm.sup.3 includes preparing an object of processing containing a mayenite compound or a precursor of a mayenite compound, placing aluminum foil on at least part of a surface of the object of processing, and retaining the object of processing at temperatures falling within the range of 1080 C. to 1450 C. in a low oxygen partial pressure atmosphere.

A method of manufacturing an electrically conductive mayenite compound, includes preparing a body to be processed including a mayenite compound; and placing the body to be processed in the presence of carbon monoxide gas and aluminum vapor supplied from an aluminum source without being in contact with the aluminum source and retaining the body to be processed at a temperature range of 1080 C. to 1450 C. under a reducing atmosphere.