US3748119A
Expired / Lapsed
US
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Process of making acicular stable magnetic iron particles
Assignee: Ampex Media Corp
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Filing: 1971-12-30
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Granted: 1973-07-24
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Expires: 1991-12-30
Abstract
Abstract ACICULAR IRON PARTICLES ARE MADE BY DOPING AN ACICULAR FERRIC OXIDE WITH BISMUTH AND A WATER SOLUBLE OR DISPERSIBLE SILICON COMPOUND AND REDUCING THE THUS DOPED OXIDE TO IRON AT A RELATIVELY LOW TEMPERATURE. THE PARTICLES ARE STABILIZED BY REOXIDIZING THE SURFACE SLIGHTLY. THE USE OF SILICON IN ADDITION TO BISMUTH YIELDS IRON PARTICLES OF IMPROVED COERCIVITY AND ACICULARITY.
Inventors
- 👤 P Hwang
- 👤 P Alto
- 👤 E Arvin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 15:12
CPC Classifications
B; B22; B22F; B22F9/00; B22F9/16; B22F9/18; B22F9/20; B22F9/22; B22F1/00; B22F1/14; B22F1/145; H; H01; H01F; H01F1/00; H01F1/01; H01F1/03; H01F1/032; H01F1/04; H01F1/06; H01F1/061; H01F1/065
Claims Analysis
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References Cited (Backward Citations)
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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) | 1976-07-23 | 1977-01-22 | 1977-07-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-07-23 | 1981-01-22 | 1981-07-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-07-23 | 1985-01-22 | 1985-07-24 | $7700.00 | Window Closed / Lapsed |