Production method for metal oxide particles, metal oxide powder, and magnetic recording medium

Patent metadata

Field	Value
Publication number	US-10734144-B2
Application number	US-201715627636-A
Country	US
Kind code	B2
Filing date	Jun 20, 2017
Priority date	Sep 30, 2013
Publication date	Aug 4, 2020
Grant date	Aug 4, 2020

Abstract

A production method for metal oxide particles includes: obtaining precursor particles of a metal oxide by performing a synthesis reaction of the precursor particles in the presence of an organic compound; and converting the obtained precursor particles into metal oxide particles by heating an aqueous solution containing the precursor particles to 300° C. or higher and pressurizing the aqueous solution at a pressure of 20 MPa or higher.

First claim

What is claimed is:

1. A production method for metal oxide particles comprising:
synthesizing precursor particles of a metal oxide by a synthesis reaction in which the precursor particles are formed in the presence of an organic compound during the synthesis reaction; and
converting the precursor particles into metal oxide particles by heating an aqueous solution containing said precursor particles to 300° C. or higher and pressurizing the aqueous solution at a pressure of 20 MPa or higher,
wherein the synthesis reaction is performed in an aqueous reaction solution in a pH range of 5 to 14.

2. The production method for metal oxide particles according to claim 1 ,
wherein the heating and pressurizing is performed while continuously feeding the aqueous solution.

3. The production method for metal oxide particles according to claim 1 ,
wherein an average particle size of the precursor particles is 25 nm or less.

4. The production method for metal oxide particles according to claim 2 ,
wherein an average particle size of the precursor particles is 25 nm or less.

5. The production method for metal oxide particles according to claim 1 ,
wherein a coefficient of variation in the particle size of the precursor particles is 5% to 40%.

6. The production method for metal oxide particles according to claim 1 ,
wherein, in the synthesis reaction, an iron salt, an alkali earth metal salt, and the organic compound are mixed with each other in an aqueous solution so as to cause precursor particles of hexagonal ferrite to precipitate.

7. The production method for metal oxide particles according to claim 1 ,
wherein the conversion of the precursor particles into metal oxide particles is performed through the following steps including:
adding a precursor particle solution containing the precursor particles, which are obtained in the synthesis reaction, to a liquid feeding path to which water, which is heated to 300° C. or higher and is pressurized at a pressure of 20 MPa or higher, is continuously fed; and
converting the precursor particles into metal oxide particles by continuously feeding a mixed solution containing water and the precursor particle solution to the liquid feeding path while heating the mixed solution to 300° C. or higher and pressurizing the mixed solution at a pressure of 20 MPa or higher.

8. The production method for metal oxide particles according to claim 1 ,
wherein the metal oxide particles are hexagonal ferrite particles selected from the group consisting of barium ferrite, strontium ferrite, and a mixed crystal of barium ferrite and strontium ferrite.

9. The production method for metal oxide particles according to claim 1 ,
wherein the organic compound is selected from the group consisting of a carboxylic acid, a carboxylate, an anionic surfactant, and a water-soluble polymer.

10. The production method for metal oxide particles according to claim 1 ,
wherein the precursor particles of a metal oxide are obtained by performing a reaction of two or more starting material compounds in the presence of an organic compound, the reaction being one in which the organic compound is added to a reaction solvent to dissolve or suspend the organic compound therein, and then the two or more starting material compounds are added to the reaction solvent, to perform the reaction.

Assignees

• Fujifilm Corp

Inventors

• Shirata Masashi
• Hosoya Yoichi

Classifications

• G11B5/70678 Primary

  Ferrites · CPC title

• H01F1/113 Primary

  in a bonding agent · CPC title

• C01P2006/12

  Surface area · CPC title

• C01G49/0036 Primary

  containing one alkaline earth metal, magnesium or lead · CPC title

• C01P2004/64

  Nanometer sized, i.e. from 1-100 nanometer · CPC title