Methods for preparation of surfactant-free ultra-small spinel ternary metal oxide nanoparticles are provided. A method comprises dissolving first and second metal salts in deionized water in a specific mole ratio to form a solution comprising two different metal ions, applying a coprecipitation method and adding an alkaline solution to the solution to form a colloidal suspension, wherein a colloid of the colloidal suspension is a metal hydroxide, adjusting the amount and the addition rate of the alkaline solution to form a specific structure of metal hydroxide precipitate; washing and drying the metal hydroxide to form a structured metal hydroxide powder, and applying a calcination method to the structured metal hydroxide powder to form a surfactant-free spinel-type (AB.sub.2O.sub.4) ternary metal oxide, wherein A and B each respectively comprise a metal element.

An electron transport includes a metal co-doped zinc oxide compound having a formula Mn.sub.xCo.sub.0.015Zn.sub.1−xO, wherein x has a value in a range of 0.001 to 0.014. The electron transport material of the present disclosure may be used in a perovskite solar cell.

The present invention generally relates to a method for preparing metal oxide nanosheets. In a preferred embodiment, graphene oxide (GO) or graphite oxide is employed as a template or structure directing agent for the formation of the metal oxide nanosheets, wherein the template is mixed with metal oxide precursor to form a metal oxide precursor-bonded template. Subsequently, the metal oxide precursor-bonded template is calcined to form the metal oxide nanosheets. The present invention also relates to a lithium-ion battery anode comprising the metal oxide nanosheets. In a further preferred embodiment, the battery anode may comprising reduced template, which is reduced graphene oxide (rGO) or reduced graphite oxide.

[Problem] To provide a method for producing iron based oxide magnetic powder that has a narrow particle size distribution and a small content of fine particles that do not contribute to the magnetic recording characteristics, and consequently has a narrow coercive force distribution and is suitable for the enhancement of the recording density of the magnetic recording medium. [Solution] ε-Type iron based oxide magnetic powder is obtained by a wet method, then a tetraalkylammonium salt as a surface modifier is added to a slurry containing the magnetic powder to make a concentration of 0.009 mol/kg or more and 1.0 mol/kg or less, and simultaneously to make pH of 11 or more and 14 or less, and the slurry is subjected to a dispersion treatment and then classified, so as to provide iron based oxide magnetic powder having a narrow particle size distribution and a narrow coercive force distribution.

A substitution-type ε-iron oxide magnetic particle powder having a reduced content of a non-magnetic α-type iron-based oxide and Fe sites of ε-Fe.sub.2O.sub.3 partially substituted by another metal element is obtained by neutralizing an acidic aqueous solution containing a trivalent iron ion and an ion of a metal that partially substitutes Fe sites to a pH of 2.0 or higher and 7.0 or lower. A silicon compound having a hydrolyzable group is added to a dispersion liquid containing an iron oxyhydroxide having a substituent metal element or a mixture of an iron oxyhydroxide and a hydroxide of a substituent metal element. The dispersion liquid is neutralized to a pH of 8.0 or higher and the iron oxyhydroxide having a substituent metal element or the mixture of the iron oxyhydroxide and the hydroxide of a substituent metal element is coated with a chemical reaction product of the silicon compound and then heated.

[Problem] To provide a method for producing iron based oxide magnetic powder that has a narrow particle size distribution and a small content of fine particles that do not contribute to the magnetic recording characteristics, and consequently has a narrow coercive force distribution and is suitable for the enhancement of the recording density of the magnetic recording medium. [Solution] ε-Type iron based oxide magnetic powder is obtained by a wet method, then a tetraalkylammonium salt as a surface modifier is added to a slurry containing the magnetic powder to make a concentration of 0.009 mol/kg or more and 1.0 mol/kg or less, and simultaneously to make pH of 11 or more and 14 or less, and the slurry is subjected to a dispersion treatment and then classified, so as to provide iron based oxide magnetic powder having a narrow particle size distribution and a narrow coercive force distribution.

A surface-modified iron-based oxide magnetic particle powder has good solid-liquid separation property in the production process, has good dispersibility in a coating material for forming a coating-type magnetic recording medium, has good orientation property, and has a small elution amount of a water-soluble alkali metal, and to provide a method for producing the surface-modified iron-based oxide magnetic particle powder. The surface-modified iron-based oxide magnetic particle powder can be obtained by neutralizing a solution containing dissolved therein a trivalent iron ion and an ion of the metal, by which the part of Fe sites is to be substituted, with an alkali aqueous solution, so as to provide a precursor, coating a silicon oxide on the precursor, heating the precursor to provide e-type iron-based oxide magnetic powder, and adhering a hydroxide or a hydrous oxide of one kind or two kinds of Al and Y thereto.

A method for producing oxide particles with controlled color characteristics and to provide oxide particles with controlled color characteristics includes controlling color characteristics of the oxide particles by controlling the ratio of M-OH bonds, the binding of one or more different elements (M) other than oxygen or hydrogen with hydroxyl group (OH), in oxide particles selected from metal oxide particles and metalloid oxide particles. Oxide particles having controlled color characteristics of any one of reflectance, transmittance, molar absorption coefficient, hue, or color saturation can be provided by controlling the percentage of the M-OH bonds contained in metal oxide particles or metalloid oxide particles.

An anode material for a secondary battery is provided. The anode material for the secondary battery includes a metal oxide containing four or more than four elements, or an oxide mixture containing four or more than four elements. The metal oxide includes cobalt-copper-tin oxide, silicon-tin-iron oxide, copper-manganese-silicon oxide, tin-manganese-nickel oxide, manganese-copper-nickel oxide, or nickel-copper-tin oxide. The oxide mixture includes the oxide mixture containing cobalt, copper and tin, the oxide mixture containing silicon, tin and iron, the oxide mixture containing copper, manganese and silicon, the oxide mixture containing tin, manganese and nickel, the oxide mixture containing manganese, copper and nickel, or the oxide mixture containing nickel, copper and tin.

Methods for preparation of surfactant-free ultra-small spinel ternary metal oxide nanoparticles are provided. A method comprises dissolving first and second metal salts in deionized water in a specific mole ratio to form a solution comprising two different metal ions, applying a coprecipitation method and adding an alkaline solution to the solution to form a colloidal suspension, wherein a colloid of the colloidal suspension is a metal hydroxide, adjusting the amount and the addition rate of the alkaline solution to form a specific structure of metal hydroxide precipitate; washing and drying the metal hydroxide to form a structured metal hydroxide powder, and applying a calcination method to the structured metal hydroxide powder to form a surfactant-free spinel-type (AB.sub.2O.sub.4) ternary metal oxide, wherein A and B each respectively comprise a metal element.