With an aim to provide an oxide particle with controlled color characteristics, the present invention provides a method for producing an oxide particle, wherein the color characteristics of the oxide particle are controlled by controlling a M-OH bond/M-O bond ratio, which is a ratio of a M-OH bond between an element (M) and a hydroxide group (OH) to a ratio of an M-O bond between the element (M) and oxygen (O), where the element (M) is one or plural different elements other than oxygen or hydrogen included in the oxide particle selected from metal oxide particles and semi-metal oxide particles. According to the present invention, by controlling the M-OH bond/M-O bond ratio of the metal oxide particle or the semi-metal oxide particle, the oxide particle with controlled color characteristics of any of reflectance, transmittance, molar absorption coefficient, hue, and saturation can be provided.

Reaction mixtures, gel compositions that are a polymerized product of the reaction mixtures, shaped gel articles that are formed within a mold cavity and that retain the size and shape of the mold cavity upon removal from the mold cavity, and sintered articles prepared from the shaped gel articles are provided. The sintered article has a shape identical to the mold cavity (except in regions where the mold cavity was overfilled) and to the shaped articles but reduced in size proportional to the amount of isotropic shrinkage. Methods of forming the sintered articles also are provided.

Reaction mixtures, gel compositions that are a polymerized product of the reaction mixtures, shaped gel articles that are formed within a mold cavity and that retain the size and shape of the mold cavity upon removal from the mold cavity, and sintered articles prepared from the shaped gel articles are provided. The sintered article has a shape identical to the mold cavity (except in regions where the mold cavity was overfilled) and to the shaped articles but reduced in size proportional to the amount of isotropic shrinkage. Methods of forming the sintered articles also are provided.

The invention relates to a method for producing a scandium-containing concentrate from the wastes of alumina production and extracting high-purity scandium oxide from the same. Provided is a method for producing a scandium-containing concentrate from a red mud, wherein the Sc.sub.2O.sub.3 content therein is least of 15 wt. %, the TiO.sub.2 content not more than 3 wt. %, the ZrO.sub.2 content not more than 15 wt. %, and wherein scandium in the concentrate is in form of a mixture of Sc(OH).sub.3 hydroxide with ScOHCO.sub.3.4H.sub.2O. Also provided is a method for producing high-purity scandium oxide, with a purity of approximately 99 wt. %.

The invention relates to a method for producing a scandium-containing concentrate from the wastes of alumina production and extracting high-purity scandium oxide from the same. Provided is a method for producing a scandium-containing concentrate from a red mud, wherein the Sc.sub.2O.sub.3 content therein is least of 15 wt. %, the TiO.sub.2 content not more than 3 wt. %, the ZrO.sub.2 content not more than 15 wt. %, and wherein scandium in the concentrate is in form of a mixture of Sc(OH).sub.3 hydroxide with ScOHCO.sub.3.4H.sub.2O. Also provided is a method for producing high-purity scandium oxide, with a purity of approximately 99 wt. %.

A method for purifying uranium includes forming primary uranyl peroxide precipitates (UO.sub.2O.sub.2.4H.sub.2O). Forming the primary uranyl peroxide precipitates includes obtaining impure uranium dissolved in an acidic solution, evaporating the acidic solution to increase uranium concentration and to form a concentrated solution, mixing a hydrogen peroxide (H.sub.2O.sub.2) solution with the concentrated solution in a first container, and forming uranyl peroxide precipitates in the first container. The method includes collecting the uranyl peroxide precipitates and washing and drying the uranyl peroxide precipitates. The method also includes converting the washed and dried uranyl peroxide precipitates into triuranium octoxide (U.sub.3O.sub.8).

A method for purifying uranium includes forming primary uranyl peroxide precipitates (UO.sub.2O.sub.2.4H.sub.2O). Forming the primary uranyl peroxide precipitates includes obtaining impure uranium dissolved in an acidic solution, evaporating the acidic solution to increase uranium concentration and to form a concentrated solution, mixing a hydrogen peroxide (H.sub.2O.sub.2) solution with the concentrated solution in a first container, and forming uranyl peroxide precipitates in the first container. The method includes collecting the uranyl peroxide precipitates and washing and drying the uranyl peroxide precipitates. The method also includes converting the washed and dried uranyl peroxide precipitates into triuranium octoxide (U.sub.3O.sub.8).

The present invention relates to silicon-compound-coated fine metal particles, with which surfaces of fine metal particles, composed of at least one type of metal element or metalloid element, are at least partially coated with a silicon compound and a ratio of Si—OH bonds contained in the silicon-compound-coated fine metal particles is controlled to be 0.1% or more and 70% or less. By the present invention, silicon-compound-coated fine metal particles that are controlled in dispersibility and other properties can be provided by controlling the ratio of Si—OH bonds or the ratio of Si—OH bonds/Si—O bonds contained in the silicon-compound-coated fine metal particles. By controlling the ratio of Si—OH bonds or the ratio of Si—OH bonds/Si—O bonds, a composition that is more appropriate for diversifying applications and targeted properties of silicon-compound-coated fine metal particles than was conventionally possible can be designed easily.

The present invention relates to silicon-compound-coated fine metal particles, with which surfaces of fine metal particles, composed of at least one type of metal element or metalloid element, are at least partially coated with a silicon compound and a ratio of Si—OH bonds contained in the silicon-compound-coated fine metal particles is controlled to be 0.1% or more and 70% or less. By the present invention, silicon-compound-coated fine metal particles that are controlled in dispersibility and other properties can be provided by controlling the ratio of Si—OH bonds or the ratio of Si—OH bonds/Si—O bonds contained in the silicon-compound-coated fine metal particles. By controlling the ratio of Si—OH bonds or the ratio of Si—OH bonds/Si—O bonds, a composition that is more appropriate for diversifying applications and targeted properties of silicon-compound-coated fine metal particles than was conventionally possible can be designed easily.

A powder of melted particles, more than 95% by number of the particles exhibiting a circularity of greater than or equal to 0.85. The powder including more than 99.8% of a rare earth metal oxide and/or of hafnium oxide and/or of an aluminum oxide, as percentage by mass based on the oxides. The powder has a median particle size D.sub.50 of less than 15 μm, a 90 percentile of the particle sizes, D.sub.90, of less than 30 μm, and a size dispersion index (D.sub.90−D.sub.10)/D.sub.10 of less than 2, and a relative density of greater than 90%. The D.sub.n percentiles of the powder are the particle sizes corresponding to the percentages, by number, of n%, on the cumulative distribution curve of the size of the particles in the powder and the particle sizes are classified by increasing order.