The present invention relates to iron oxide red pigments having improved color values, a process for producing these improved iron oxide red pigments by the Penniman red process using nitrate (also referred to as nitrate process or direct red process) and an apparatus for the production thereof.

The present invention relates to iron oxide red pigments having improved color values, a process for producing these improved iron oxide red pigments by the Penniman red process using nitrate (also referred to as nitrate process or direct red process) and an apparatus for the production thereof.

The invention relates to a class of electrochemical energy storage materials and a preparation method and application thereof. A porous metal oxide-based electrochemical energy storage material at least comprises a host metal oxide with a hierarchical pore structure; wherein, the host metal oxide is a single crystal, quasicrystal, or twin crystal structure with ordered atomic lattice arrangement, the crystal is rich in oxygen atom vacancy defects, the structural general formula is M.sub.xO.sub.y−z, wherein M is selected from one or more combinations of niobium element, molybdenum element, titanium element, vanadium element, manganese element, iron element, cobalt element, nickel element, copper element, zinc element, tungsten element, tantalum element, and zirconium element; and 1≤x≤2, 1≤y≤5, and 0.1≤z≤0.9, preferably Nb.sub.2O.sub.5−z.

A magnetoplumbite-type hexagonal ferrite powder containing a powder of a magnetoplumbite-type hexagonal ferrite represented by Formula (1) and a powder of a compound represented by Formula (2), in which a magnetic field strength Hα, which corresponds to 90% of a magnetization quantity obtained in a case where an external magnetic field of 50 kOe is applied, satisfies 19 kOe≤Hα≤28 kOe, a radio wave absorber, and a method of controlling resonance frequency of a magnetoplumbite-type hexagonal ferrite powder are provided. In Formula (1), A represents at least one metal element selected from the group consisting of Sr, Ba, Ca, and Pb, and x satisfies 1.5≤x≤8.0. In Formula (2), A.sup.a represents at least one metal element selected from the group consisting of Sr, Ba, Ca, and Pb.

AFe.sub.(12-x)Al.sub.xO.sub.19  Formula (1)

A.sup.aAl.sub.2O.sub.4  Formula (2)

A magnetoplumbite-type hexagonal ferrite powder containing a powder of a magnetoplumbite-type hexagonal ferrite represented by Formula (1) and a powder of a compound represented by Formula (2), in which a magnetic field strength Hα, which corresponds to 90% of a magnetization quantity obtained in a case where an external magnetic field of 50 kOe is applied, satisfies 19 kOe≤Hα≤28 kOe, a radio wave absorber, and a method of controlling resonance frequency of a magnetoplumbite-type hexagonal ferrite powder are provided. In Formula (1), A represents at least one metal element selected from the group consisting of Sr, Ba, Ca, and Pb, and x satisfies 1.5≤x≤8.0. In Formula (2), A.sup.a represents at least one metal element selected from the group consisting of Sr, Ba, Ca, and Pb.

AFe.sub.(12-x)Al.sub.xO.sub.19  Formula (1)

A.sup.aAl.sub.2O.sub.4  Formula (2)

A method of producing efficiently and stably core-shell type oxide particles, wherein the entire surface of the core oxide particles is uniformly coated with the shell oxide, includes at least two steps of: Step 1 of precipitating the core oxide particles in a mixed fluid prepared by mixing an oxide raw material liquid for core and an oxide precipitation solvent and Step 2 of coating the entire surface of the core oxide particles uniformly with the shell oxide by mixing the mixed fluid and an oxide raw material liquid for shell. (A) At least Steps 1 and 2 are performed continuously between at least two processing surfaces 1 and 2 which are capable of approaching to and separating from each other, at least one of which rotates relatively to the other; (B) after Step 1, Step 2 is completed within a prescribed time during which the core oxide particles do not aggregate in the mixed fluid; or (C) Step 1 and Step 2 are controlled so that the primary particle diameter of the core-shell type oxide particles is 190% or less relative to the primary particle diameter of the core oxide particles.

A method of producing efficiently and stably core-shell type oxide particles, wherein the entire surface of the core oxide particles is uniformly coated with the shell oxide, includes at least two steps of: Step 1 of precipitating the core oxide particles in a mixed fluid prepared by mixing an oxide raw material liquid for core and an oxide precipitation solvent and Step 2 of coating the entire surface of the core oxide particles uniformly with the shell oxide by mixing the mixed fluid and an oxide raw material liquid for shell. (A) At least Steps 1 and 2 are performed continuously between at least two processing surfaces 1 and 2 which are capable of approaching to and separating from each other, at least one of which rotates relatively to the other; (B) after Step 1, Step 2 is completed within a prescribed time during which the core oxide particles do not aggregate in the mixed fluid; or (C) Step 1 and Step 2 are controlled so that the primary particle diameter of the core-shell type oxide particles is 190% or less relative to the primary particle diameter of the core oxide particles.

Embodiments include a magnetic recording medium containing ε-type iron oxide particles and having excellent SNR, a manufacturing method of ε-type iron oxide particles, and a manufacturing method of a magnetic recording medium. High SNR is achieved by a magnetic recording medium containing ε-type iron oxide particles, in which a coefficient of variation of an aspect ratio of the ε-type iron oxide particles is equal to or smaller than 18%, and a squareness ratio of the magnetic recording medium measured in a longitudinal direction of the magnetic recording medium is higher than 0.3 and equal to or lower than 0.5. The object is also achieved by the application of the magnetic recording medium.

Embodiments include a magnetic recording medium containing ε-type iron oxide particles and having excellent SNR, a manufacturing method of ε-type iron oxide particles, and a manufacturing method of a magnetic recording medium. High SNR is achieved by a magnetic recording medium containing ε-type iron oxide particles, in which a coefficient of variation of an aspect ratio of the ε-type iron oxide particles is equal to or smaller than 18%, and a squareness ratio of the magnetic recording medium measured in a longitudinal direction of the magnetic recording medium is higher than 0.3 and equal to or lower than 0.5. The object is also achieved by the application of the magnetic recording medium.

A process disclosed herein is related to the isolation and purification of substantially pure chemicals, including silica gel, sodium silicate, aluminum silicate, iron oxide, and rare earth elements (or rare earth metals, REEs), from massive industrial waste coal ash. In one embodiment, the process includes a plurality of caustic extractions of coal ash at an elevated temperature, followed by an acidic treatment to dissolve aluminum silicate and REEs. The dissolved aluminum silicate is precipitated out by pH adjustment as a solid product while REEs remain in the solution. REEs are captured and enriched using an ion exchange column. Alternatively, the solution containing aluminum silicate and REEs is heated to produce silica gel, which is easily separated from the enriched REEs solution. REEs are then isolated and purified from the enriched solution to afford substantially pure individual REE by a ligand-assisted chromatography. Additionally, a simplified process using one caustic extraction and one acidic extraction with an ion exchange process was also investigated and optimized to afford a comparable efficiency.