US4113528A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of preventing deterioration of characteristics of ferromagnetic metal or alloy particles
Assignee: TDK Corp
•
Filing: 1976-11-22
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Granted: 1978-09-12
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Expires: 1996-11-22
Abstract
Abstract Ferromagnetic metal or alloy particles are prepared by reducing ferromagnetic metal ions in the solution with a reducing agent under a magnetic field to obtain a slurry of ferromagnetic metal or alloy particles and adding an oxidizing agent to an aqueous slurry containing the ferromagnetic metal or alloy particles to prevent deterioration of magnetic characteristics.
Inventors
- 👤 Yasumichi Tokuoka
- 👤 Kazumasa Fukuda
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 14:33
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70605; G11B5/70621; H; H01; H01F; H01F1/00; H01F1/01; H01F1/03; H01F1/032; H01F1/04; H01F1/06; H01F1/061
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
108 words
A process for preparing ferromagnetic metal or alloy particles which comprises reducing ferromagnetic metal ions in a solution with a reducing agent under a magnetic field to obtain a slurry of ferromagnetic metal or alloy particles; admixing with said slurry water in a volume quantity at least 30 times that of said slurry, and a quantity of air and at least one oxidizing agent selected from the group consisting of chromates, peroxides and permanganates sufficient to oxidize the surface of said ferromagnetic metal or alloy particles; adjusting the pH to range from about 6 to about 8; and recovering ferromagnetic metal or alloy particles having an oxidized surface.
Claim 2
Dependent Claim
108 words
A process for preparing ferromagnetic metal or alloy particles which comprises reducing ferromagnetic metal ions in a solution with a reducing agent under a magnetic field to obtain a slurry of ferromagnetic metal or alloy particles; admixing with said slurry water in a volume quantity at least 30 times that of said slurry, and a quantity of air and at least one oxidizing agent selected from the group consisting of chromates, peroxides and permanganates sufficient to oxidize the surface of said ferromagnetic metal or alloy particles; adjusting the pH to range from about 6 to about 8; and recovering ferromagnetic metal or alloy particles having an oxidized surface.
Claim 3
Dependent Claim
16 words
A process according to claim 1 wherein the oxidizing agent is added in a washing step.
Claim 4
Dependent Claim
14 words
A process according to claim 1 wherein air is introduced in a washing step.
Claim 5
Dependent Claim
18 words
A process according to claim 1 wherein pH is controlled by adding an alkali in the washing step.
References Cited (Backward Citations)
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Cited
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US3782706A
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US3837912A
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Cited
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-09-11 | 1982-03-13 | 1982-09-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-09-11 | 1986-03-13 | 1986-09-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-09-11 | 1990-03-13 | 1990-09-12 | $7700.00 | Window Closed / Lapsed |