A method for recovering alkali and aluminum during treatment of Bayer red mud using a calcification-carbonation method, including steps of mixing the Bayer red mud with calcium aluminate or with calcium aluminate and lime, performing calcification dealkalization conversion in a high-concentration alkaline liquor, and carbonizing the calcified residues produced during dealkalization to obtain carbonized residues; and then performing low-temperature aluminum dissolution, aluminum precipitation and the like to obtain calcium aluminate products, which is returned to the calcification dealkalization conversion of the red mud for recycling. Part of an alkali-containing and aluminum-containing liquid phase after calcification dealkalization conversion can be used as supplementary alkali in the Bayer production course for recycling. The method is energy-saving and environmentally-friendly, and allows recovering alkali and aluminum from the red mud and harmless treatment of the Bayer red mud.

A method for recovering alkali and aluminum during treatment of Bayer red mud using a calcification-carbonation method, including steps of mixing the Bayer red mud with calcium aluminate or with calcium aluminate and lime, performing calcification dealkalization conversion in a high-concentration alkaline liquor, and carbonizing the calcified residues produced during dealkalization to obtain carbonized residues; and then performing low-temperature aluminum dissolution, aluminum precipitation and the like to obtain calcium aluminate products, which is returned to the calcification dealkalization conversion of the red mud for recycling. Part of an alkali-containing and aluminum-containing liquid phase after calcification dealkalization conversion can be used as supplementary alkali in the Bayer production course for recycling. The method is energy-saving and environmentally-friendly, and allows recovering alkali and aluminum from the red mud and harmless treatment of the Bayer red mud.

Spinel has conventionally been used as mentioned above in applications, such as gems, catalyst carriers, adsorbents, photocatalysts, optical materials, and heat-resistant insulating materials, and is not expected to be used in an application of an inorganic filler having thermal conductive properties. Accordingly, an object of the present invention is to provide spinel particles having excellent thermal conductive properties. A spinel particle having spinel containing a magnesium atom, an aluminum atom, and an oxygen atom, and molybdenum being existed on the surface of and/or in the inside of the spinel, wherein the crystallite diameter of the spinel at the [311] plane is 100 nm or more.

Spinel has conventionally been used as mentioned above in applications, such as gems, catalyst carriers, adsorbents, photocatalysts, optical materials, and heat-resistant insulating materials, and is not expected to be used in an application of an inorganic filler having thermal conductive properties. Accordingly, an object of the present invention is to provide spinel particles having excellent thermal conductive properties. A spinel particle having spinel containing a magnesium atom, an aluminum atom, and an oxygen atom, and molybdenum being existed on the surface of and/or in the inside of the spinel, wherein the crystallite diameter of the spinel at the [311] plane is 100 nm or more.

The present invention relates to a method for the passivation of MgAl.sub.2O.sub.4 (Mg-spinel) powders against hydrolysis exhibiting in aqueous media by coating the surfaces with Al.sub.2O.sub.3 during the synthesis via flame pyrolysis technique. Stable aqueous suspensions with high solid loading and low viscosity can be prepared from coated powders with a core/shell structure of MgO.nAl.sub.2O.sub.3 (0.65<n<4.10)/Al.sub.2O.sub.3. Such suspensions might not only ensure production of high quality granules, but also enable production of green bodies with high density and homogeneity through wet forming methods. Accordingly, precise microstructural control can be ensured during sintering. Al.sub.2O.sub.3 shell re-dissolves within the core during sintering at variable temperatures depending on the core stoichiometry (n value). The final stoichiometry might be altered by controlling the n value of the core, the shell thickness and particle size distribution.

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.

Provided are a new phosphor having emission characteristics different from the conventional nitride or oxynitride phosphor, a manufacturing method, and a light-emitting device. In an embodiment, the phosphor may include inorganic substance having crystal represented by A.sub.26(D, E).sub.51X.sub.86 including at least A, D, X (A is at least one kind of element selected from Mg, Ca, Sr, and Ba; and D is Si, and X is at least one kind of element selected from O, N, and F); and further includes, if necessary, E (E is at least one kind of element selected from B, Al, Ga, and In) wherein the crystal further includes M (M is at least one kind of element selected from Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, and Yb). Upon irradiation of excitation source, the maximum value of emission peak in a wavelength range from 630 nm to 850 nm may occur.

Provided are a new phosphor having emission characteristics different from the conventional nitride or oxynitride phosphor, a manufacturing method, and a light-emitting device. In an embodiment, the phosphor may include inorganic substance having crystal represented by A.sub.26(D, E).sub.51X.sub.86 including at least A, D, X (A is at least one kind of element selected from Mg, Ca, Sr, and Ba; and D is Si, and X is at least one kind of element selected from O, N, and F); and further includes, if necessary, E (E is at least one kind of element selected from B, Al, Ga, and In) wherein the crystal further includes M (M is at least one kind of element selected from Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, and Yb). Upon irradiation of excitation source, the maximum value of emission peak in a wavelength range from 630 nm to 850 nm may occur.

A particulate material having a body including a first phase having at least about 70 wt % alumina for a total weight of the first phase, and a second phase comprising phosphorus, wherein the body includes at least about 0.1 wt % of the second phase for the total weight of the body, and wherein the second phase has an average grain size of not greater than about 1 micron.