# US 5,702,630 A · Fluid having both magnetic and electrorheological characteristics

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- Number: US 5,702,630 A
- Document ID: US5702630A
- Status: Granted
- Kind: A
- Application number: 08/821,570
- Filed: 1997-03-19
- Granted: 1997-12-30
- Earliest claimed: 1992-07-16
- Assignees: Nippon Oil Co., Ltd.
- Inventors: Makoto Sasaki; Hisatake Sato
- Web page: https://patentgrep.com/patent/US5702630A

## CPC

- C10M 171/001: {Electrorheological fluids; smart fluids}
- H01F 1/445: {the magnetic component being a compound, e.g. Fe3O4 (H01F1/447 takes precedence)}
- H01F 1/447: {characterised by magnetoviscosity, e.g. magnetorheological, magnetothixotropic, magnetodilatant liquids (electrorheological fluids C10M171/001)}
- C10M 2201/05: Metals; Alloys
- C10M 2209/084: Acrylate; Methacrylate
- C10M 2217/044: Polyamides
- C10M 2217/045: Polyureas; Polyurethanes
- C10N 2040/14: Electric or magnetic purposes
- C10N 2040/16: Dielectric; Insulating oil {or insulators}
- C10N 2040/17: {for electric contacts}
- C10N 2040/175: {Pantographs, i.e. printing devices}
- C10N 2040/18: in connection with recordings on magnetic tape or disc
- C10N 2040/185: {Magnetic fluids}
- C10M: LUBRICATING COMPOSITIONS (well drilling compositions C09K8/02); USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION (mould release, i.e. separating, agents for metals B22C3/00, for plastics or substances in a plastic state, in general B29C33/56, for glass C03B40/02; textile lubricating compositions D06M11/00, D06M13/00, D06M15/00; immersion oils for microscopy G02B21/33)
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- C10N: INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS

## Abstract

A fluid having both magnetic and electrorheological characteristics, which comprises composite particles of ferromagnetic particles and a metallic oxide prepared by a sol-gel reaction of a metal alkoxide in the presence of the ferromagnetic particles and a solvent and a process for producing the same.

## Claims

### Claim 1

A fluid having both magnetic and electrorheological characteristics, consisting essentially of an insulating liquid having stably dispersed therein ferromagnetic particles of manganese ferrite, barium ferrite, iron, nickel, permalloy or iron nitride, having a particle size of 0.003 to 200 .mu.m and coated with a metallic oxide, said metallic oxide having been prepared by a sol-gel reaction of 2-98 wt % of a metal alkoxide in the presence of 98-2 wt % of the ferromagnetic particles.

### Claim 2 (depends on 1)

A fluid having both magnetic and electrorheological characteristics according to claim 1, wherein the metal alkoxide is a silicon alkoxide or a titanium alkoxide.

### Claim 3

A process for producing a fluid having both magnetic and electrorheological characteristics, which comprises:
mixing an aqueous alcohol solution containing 2-98 wt % of a metal alkoxide with 98-2 wt % of ferromagnetic particles of magnetite, manganese ferrite, barium ferrite, iron, nickel, permalloy or iron nitride having a particle size of 0.003 to 200 .mu.m,
effecting a sol-gel reaction to change the metal alkoxide to a metallic oxide thereby coating the ferromagnetic particles with the metallic oxide,
separating the coated ferromagnetic particles from the solution,
degasifying and drying the coated ferromagnetic particles, and
dispersing the coated ferromagnetic particles in an insulating liquid.

### Claim 4 (depends on 3)

A process according to claim 3, wherein the metal alkoxide is a silicon alkoxide or a titanium alkoxide.