US3748270A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of preparing cobalt doped magnetic iron oxide particles
Assignee: Ampex Media Corp
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Filing: 1971-10-27
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Granted: 1973-07-24
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Expires: 1991-10-27
Abstract
Abstract HIGH COERCIVITY COBALT DOPED MAGNETIC IRON OXIDE PARTICLES ARE MADE BY DOPING AN IRON OXIDE WITH COBALT, CONVERTING THE MATERIAL TO A COBALT DOPED GAMMA FERRIC OXIDE CONTAINING A SMALL AMOUNT OF DIVALENT IRON AT A HIGH TEMPERATURE AND SLOW COOLING THE HOT MATERIAL IN AN INERT ATMOSPHERE.
Inventors
- 👤 P Hwang
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 19:29
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70652; G11B5/70668; G11B5/70673
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 |