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US4303699A
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Method of manufacturing magnetic powder
Assignee: Sony Corp
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Filing: 1980-05-06
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Granted: 1981-12-01
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Expires: 2000-05-06
Abstract
Abstract A method of manufacturing magnetic power is disclosed which includes the steps of mixing acicular magnetic iron oxide powders and metallic cobalt in aqueous solution containing an alkali hydroxide and keeping the solution at an elevated temperature during the mixing step to cause deposition of cobalt and/or a cobalt compound on the surface of the iron oxide powders.
Inventors
- 👤 Hideo Tamura
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 16:23
CPC Classifications
C; C21; C21D; C21D1/00; C21D1/04; B; B22; B22F; B22F1/00; B22F1/18; G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70652; G11B5/70668; G11B5/70673; H; H01; H01F; H01F1/00; H01F1/01; H01F1/03; H01F1/12; H01F1/14
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
68 words
Method of manufacturing magnetic powder, consisting of: (a) forming a mixture consisting essentially of acicular magnetic iron oxide powder and metallic cobalt in an aqueous solution of an alkali hydroxide having a concentration of 0.1 mol/l to 10 mol/l under agitation, and (b) keeping said solution at an elevated temperature during said agitation to cause deposition of cobalt and/or cobalt compound on surface of said iron oxide powder.
Claim 2
Dependent Claim
68 words
Method of manufacturing magnetic powder, consisting of: (a) forming a mixture consisting essentially of acicular magnetic iron oxide powder and metallic cobalt in an aqueous solution of an alkali hydroxide having a concentration of 0.1 mol/l to 10 mol/l under agitation, and (b) keeping said solution at an elevated temperature during said agitation to cause deposition of cobalt and/or cobalt compound on surface of said iron oxide powder.
Claim 3
Dependent Claim
17 words
Method according to claim 1, wherein said alkali hydroxide is sodium hydroxide, potassium hydroxide or lithium hydroxide.
Claim 4
Dependent Claim
16 words
Method according to claim 1, wherein said concentration is selected at 1 mol/l to 7 mol/l.
Claim 5
Dependent Claim
15 words
Method according to claim 1, wherein said elevated temperature is between 60° and 150° C.
Claim 6
Dependent Claim
16 words
Method according to claim 1, wherein said metallic cobalt is in a form of fine powder.
Claim 7
Dependent Claim
36 words
Method according to claim 1, wherein said iron oxide is gamma-ferric oxide, magnetite, intermediate iron oxide having a ratio of ferrous to ferric ions greater than 0 but less than 0.5, or cobalt containing iron oxide.
Claim 8
Dependent Claim
13 words
Method according to claim 6, wherein said iron oxide is gamma ferric oxide.
Claim 9
Dependent Claim
34 words
Method according to claim 1, wherein a gas introduced into said solution during keeping said solution at an elevated temperature to control the ratio of ferrous to ferric ions of the resulting magnetic powder.
Claim 10
Dependent Claim
10 words
Method according to claim 8, wherein said gas is air.
Claim 11
Dependent Claim
10 words
Method according to claim 8, wherein said gas is nitrogen.
References Cited (Backward Citations)
US4125474A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-11-30 | 1985-06-01 | 1985-12-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-11-30 | 1989-06-01 | 1989-12-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-11-30 | 1993-06-01 | 1993-12-01 | $7700.00 | Window Closed / Lapsed |