US3598568A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of preparing a magnetically stable powder mainly consisting of iron for magnetic recording
Assignee: US Philips Corp
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Filing: 1969-01-29
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Granted: 1971-08-10
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Expires: 1989-01-29
Abstract
Abstract A METHOD OF PREPARING MAGNETICALLY STABLE IRON POWDER SUITABLE FOR MAGNETIC RECORDING IN WHICH IRON OXIDE HYDRATE, A-FEOI(OH) IS PRECIPITATED FROM A STRONGLY REACTING ALKALINE SOLUTION OF FERROUS HYDROXIDE CONTAINING AT LEAST ONE COMPOUND OF AT LEAST ONE METAL SELECTED FROM THE GROUP CONSISTING OF GERMANIUM, TIN AND ALUMINUM IN SUCH A CONCENTRATION THAT THE ATOMIC RATION OF THE LATTER METAL TO FE IN THE SOLUTION IS A LEAST 0.005 WHILE PASSING AN OXIDIZING GAS THROUGH THE SOLUTION. THE PRECIPITATE IS THEREAFTER SEPARATED FROM THE LIQUID, WASHED, DRIED, AND REDUCED IN HYDROGEN AT 250* TO 500* C.
Inventors
- 👤 Cornelis Johannes Klomp
- 👤 Gerard Willem Van Oosterhout
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 13:55
CPC Classifications
H; H01; H01F; H01F1/00; H01F1/01; H01F1/03; H01F1/032; H01F1/04; H01F1/06; H01F1/065; G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70605; G11B5/70615; G11B5/70626; G11B5/70642; G11B5/70652; G11B5/70668
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) | 1974-08-09 | 1975-02-08 | 1975-08-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-08-09 | 1979-02-08 | 1979-08-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-08-09 | 1983-02-08 | 1983-08-10 | $7700.00 | Window Closed / Lapsed |