# US 7,745,004 B2 · Polymer-coated magnetic particle and magnetic material for absorbing electromagnetic waves

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- Number: US 7,745,004 B2
- Document ID: US7745004B2
- Status: Granted
- Kind: B2
- Application number: 11/258,569
- Filed: 2005-10-25
- Published: 2006-03-23
- Granted: 2010-06-29
- Earliest claimed: 2001-09-18
- Assignees: Sony Corporation; Koichiro Inomata; Satoshi Sugimoto; Yoshihiro Kato
- Inventors: Katsumi Okayama; Kaoru Kobayashi; Koichiro Inomata; Satoshi Sugimoto; Yoshihiro Kato
- Web page: https://patentgrep.com/patent/US7745004B2

## CPC

- B22F 9/305: {of metal carbonyls}
- B22F 1/054: Nanosized particles
- B22F 1/10: Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
- B22F 9/24: starting from liquid metal compounds, e.g. solutions
- B82Y 25/00: Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
- B82Y 30/00: Nanotechnology for materials or surface science, e.g. nanocomposites
- B82Y 40/00: Manufacture or treatment of nanostructures
- H01F 1/0054: {Coated nanoparticles, e.g. nanoparticles coated with organic surfactant}
- H01F 41/30: for applying nanostructures, e.g. by molecular beam epitaxy [MBE]
- H01F 41/301: {for applying ultrathin or granular layers (ultrathin or granular layers H01F10/007)}
- B22F 2998/00: Supplementary information concerning processes or compositions relating to powder metallurgy
- Y10S 977/777: Metallic powder or flake
- Y10S 977/783: Organic host/matrix, e.g. lipid
- Y10T 428/12146: Nonmetal particles in a component
- Y10T 428/254: Polymeric or resinous material
- Y10T 428/256: Heavy metal or aluminum or compound thereof
- Y10T 428/257: Iron oxide or aluminum oxide
- Y10T 428/29: Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
- Y10T 428/2991: Coated
- Y10T 428/2998: including synthetic resin or polymer
- B22F: WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER (making alloys by powder metallurgy C22C); APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A method for producing a magnetic particle forming a magnetic material for absorbing electromagnetic waves comprises the steps of mixing an organometallic complex or a metal salt with a chain polymer and dissolving the mixture in a solvent (step S1); raising the temperature of the mixture to reaction temperature (step S2), carrying out a reaction at the reaction temperature (step S3); and forming the magnetic particle having a structure that the periphery of each fine particle formed from the organometallic complex or the metal salt is surrounded by the chain polymer and recovering the formed magnetic particle after the reaction (step S4). The magnetic particle has a nanogranular structure to become a magnetic material for absorbing electromagnetic waves. Such a magnetic particle is produced by a wet reaction. Thus, a larger amount of magnetic particle can be produced by one reaction.

## Claims

### Claim 1

Magnetic particles forming a magnetic material for absorbing electromagnetic waves, wherein the magnetic particles have a diameter located within a range of 1 nm to 50 nm; and
a chain polymer surrounding individual ones of the magnetic particles being formed to a thickness of 1 nm or less.

### Claim 2 (depends on 1)

The magnetic particles according to claim 1, wherein the magnetic particles are comprised of iron (Fe), cobalt (Co) or nickel (Ni).

### Claim 3 (depends on 1)

The magnetic particles according to claim 1, wherein the chain polymer is poly(N-vinyl-2-pyrrolidone).

### Claim 4 (depends on 1)

The magnetic particles according to claim 1, wherein the chain polymer is polyacrylic acid.

### Claim 5

A magnetic material for absorbing electromagnetic waves comprising: powder comprised of magnetic particles having a diameter of from 1 nm to 50 nm and the magnetic particles are each individually surrounded by a chain polymer that is formed to a thickness of 1 nm or less.

### Claim 6 (depends on 5)

The magnetic material according to claim 5, wherein the polymer material is a biodegradable material.

### Claim 7 (depends on 5)

The magnetic material according to claim 5, wherein the magnetic material is formed of a sheet type material having the thickness of 10 μm to 2 mm comprised of the magnetic particles each individually bonded with a chain polymer and surrounded by a further resin material.

### Claim 8

A magnetic material for absorbing electromagnetic waves formed by pressing a powder comprised of magnetic particles that are each individually surrounded by a chain polymer that is formed to a thickness of 1 nm or less.