US3620841A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for making continuous magnetite films
Assignee: International Business Machines Corp
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Filing: 1970-02-16
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Granted: 1971-11-16
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Expires: 1990-02-16
Abstract
Abstract A continuous magnetite film, suitable for magnetic recording, is prepared by forming a film of amorphous Fe2O3, heating the Fe2O3 until it is completely converted to the alpha crystalline phase, and then reducing it to magnetite.
Inventors
- 👤 Richard Lawrence Comstock
- 👤 Eugene B Moore
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 01:37
CPC Classifications
H; H01; H01F; H01F10/00; H01F10/08; H01F10/10; H01F10/18; H01F10/20
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
18 words
A process as claimed in claim 1 wherein the amorphous Fe203 film is less than 1 micron thick.
Claim 2
Dependent Claim
18 words
A process as claimed in claim 1 wherein the amorphous Fe203 film is formed by a spinning technique.
Claim 3
Dependent Claim
18 words
A process as claimed in claim 1 wherein the reduction is carried out by reaction with hydrogen gas.
Claim 4
Dependent Claim
18 words
A process as claimed in claim 4 wherein the temperature during reduction is between 325 and 400* C.
Claim 5
Dependent Claim
18 words
A process as claimed in claim 4 wherein the hydrogen gas contains a small amount of water vapor.
Claim 6
Dependent Claim
17 words
A process as claimed in claim 1 wherein the film is deposited upon a nonmagnetic metallic substrate.
Claim 7
Dependent Claim
16 words
A process as claimed in claim 1 wherein the film is deposited upon a titanium substrate.
Claim 8
Dependent Claim
16 words
A process as claimed in claim 1 wherein the film is deposited upon an aluminum substrate.
Claim 9
Dependent Claim
16 words
A process as claimed in claim 1 wherein the film is deposited upon a glass substrate.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-11-15 | 1975-05-17 | 1975-11-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-11-15 | 1979-05-17 | 1979-11-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-11-15 | 1983-05-17 | 1983-11-16 | $7700.00 | Window Closed / Lapsed |