US4137342A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Cobalt-doped acicular hyper-magnetite particles
Assignee: 3M Co
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Filing: 1976-10-29
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Granted: 1979-01-30
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Expires: 1996-10-29
Abstract
Abstract Acicular hyper-magnetite particles, that is, acicular particles of (FeO).sub.x Fe.sub.2 O.sub.3 where x is greater than one and not greater than 1.5, are provided with coatings of a cobalt compound, the cobalt providing 1% to 10% of the total weight of the particles. The particles provide superior magnetic recording media.
Inventors
- 👤 Thomas M. Kanten
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 15:42
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70678; G11B5/70684; G11B5/70694; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/29; Y10T428/2982; Y10T428/2991
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
99 words
Process for making acicular particles useful for magnetic recording media consisting essentially of the steps of (1) heating acicular alpha-FeOOH particles of submicron size in an inert atmosphere in the presence of a reducing agent at 300°-600° C to produce acicular hyper-magnetite particles, (2) depositing a cobalt-containing material onto the surfaces of the hyper-magnetite particles in an amount such that after step (3) the cobalt in the surface layer provides 1-10% by weight of the particles, and (3) heating in an inert atmosphere at 80°-200° C to fix the surface deposit without unduly diffusing the cobalt into the particles.
Claim 2
Dependent Claim
99 words
Process for making acicular particles useful for magnetic recording media consisting essentially of the steps of (1) heating acicular alpha-FeOOH particles of submicron size in an inert atmosphere in the presence of a reducing agent at 300°-600° C to produce acicular hyper-magnetite particles, (2) depositing a cobalt-containing material onto the surfaces of the hyper-magnetite particles in an amount such that after step (3) the cobalt in the surface layer provides 1-10% by weight of the particles, and (3) heating in an inert atmosphere at 80°-200° C to fix the surface deposit without unduly diffusing the cobalt into the particles.
Claim 3
Dependent Claim
30 words
Process for making acicular particles as defined in claim 1 wherein step (1) involves heating in an inert atmosphere in the presence of an organic reducing agent at 400°-600° C.
Claim 4
Dependent Claim
18 words
Process for making acicular particles as defined in claim 2 wherein the organic reducing agent is a glyceride.
Claim 5
Dependent Claim
21 words
Process for making acicular particles as defined in claim 3 wherein the glyceride is one or more long-chain fatty acid glycerides.
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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) | 1982-01-29 | 1982-07-31 | 1983-01-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-01-29 | 1986-07-31 | 1987-01-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-01-29 | 1990-07-31 | 1991-01-30 | $7700.00 | Window Closed / Lapsed |