US4657583A
Expired / Lapsed
US
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Method of producing ferromagnetic particles
Assignee: Olin Corp
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Filing: 1985-12-02
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Granted: 1987-04-14
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Expires: 2005-12-02
Abstract
Abstract The present invention relates to a method for producing magnetic particles for use in recording media. The method comprises providing an alloy capable of forming a magnetic precipitate, aging the alloy to form a magnetic precipitate comprising a plurality of magnetic particles dispersed througout a surrounding matrix; and dissolving the matrix to leave the magnetic particles. Magnetic particles produced by the present method are characterized by a size in the range of about 100 ANGSTROM to about 2000 ANGSTROM , a single magnetic domain, an aspect ratio up to about 10:1, a relatively smooth surface, and a substantially uniform composition throughout.
Inventors
- 👤 Jacob Crane
- 👤 George J. Muench
- 👤 Yousef Saleh
- 👤 Lifun Lin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 06:51
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/712; B; B22; B22F; B22F1/00; B22F1/06; B22F1/062; B22F9/00; B22F9/16; G11B5/706; G11B5/70605; B22F2998/00; B22F2998/10
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
67 words
A method of producing free metallic magnetic particles, said method comprising: providing an alloy capable of forming a magnetic precipitate by aging; thermally aging said alloy to form said magnetic precipitate in a matrix, said precipitate comprising a plurality of acicular magnetic particles dispersed in said matrix; and dissolving said matrix to leave said magnetic particles and to form a passive layer about each said magnetic particle.
Claim 2
Independent Claim
67 words
A method of producing free metallic magnetic particles, said method comprising: providing an alloy capable of forming a magnetic precipitate by aging; thermally aging said alloy to form said magnetic precipitate in a matrix, said precipitate comprising a plurality of acicular magnetic particles dispersed in said matrix; and dissolving said matrix to leave said magnetic particles and to form a passive layer about each said magnetic particle.
Claim 3
Dependent Claim
19 words
The method of claim 1 further comprising: solution heat treating and quenching said alloy prior to said aging step.
Claim 4
Dependent Claim
26 words
The method of claim 1 further comprising: working said alloy prior to said aging step to affect particle morphology and size and/or assist in alloy processing.
Claim 5
Dependent Claim
14 words
The method of claim 3 wherein said working step comprises cold rolling said alloy.
Claim 6
Dependent Claim
21 words
The method of claim 1 wherein said aging step forms a plurality of discrete acicular magnetic particles dispersed throughout said matrix.
Claim 7
Dependent Claim
26 words
The method of claim 1 wherein said dissolving step comprises immersing said particles and said surrounding matrix in a chemical solution and chemically dissolving said matrix.
Claim 8
Dependent Claim
22 words
The method of claim 6 wherein said immersing step comprises immersing said particles and said matrix in an aqueous solution containing ammonia.
Claim 9
Dependent Claim
26 words
The method of claim 1 wherein said dissolving step comprises immersing said particles and said surrounding matrix in an electrolyte solution and electrochemically dissolving said matrix.
Claim 10
Dependent Claim
22 words
The method of claim 8 wherein said immersing step comprises immersing said particles and said surrounding matrix in an aqueous citrate solution.
Claim 11
Dependent Claim
10 words
The method of claim 1 further comprising collecting said particles.
Claim 12
Dependent Claim
22 words
The method of claim 1 wherein said dissolving step further comprises dissolving said matrix without any significant dissolution of said magnetic particles.
Claim 13
Independent Claim
51 words
A method of producing free metallic magnetic particles, said method comprising: providing a copper base alloy capable of forming a ferromagnetic precipitate by aging; thermally aging said alloy to form a plurality of acicular ferromagnetic particles surrounded by a copper-rich matrix; and dissolving said copper-rich matrix to leave said ferromagnetic particles.
Claim 14
Independent Claim
51 words
A method of producing free metallic magnetic particles, said method comprising: providing a copper base alloy capable of forming a ferromagnetic precipitate by aging; thermally aging said alloy to form a plurality of acicular ferromagnetic particles surrounded by a copper-rich matrix; and dissolving said copper-rich matrix to leave said ferromagnetic particles.
Claim 15
Dependent Claim
38 words
The method of claim 12 wherein said aging step comprises heating said copper base alloy to a temperature in the range of about 550° C. to about 800° C. for a time period up to about 48 hours.
Claim 16
Dependent Claim
43 words
The method of claim 12 wherein said aging step comprises heating said copper base alloy to a temperature in the range of about 600° C. to about 700° C. for a time period in the range of about 1 to about 8 hours.
Claim 17
Dependent Claim
35 words
The method of claim 12 wherein: said copper base alloy providing step comprises providing a copper-iron-nickel alloy in strip form; and said aging step comprises forming an iron-nickel magnetic precipitate in said copper rich matrix.
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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) | 1990-04-13 | 1990-10-13 | 1991-04-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-04-13 | 1994-10-13 | 1995-04-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-04-13 | 1998-10-13 | 1999-04-14 | $7700.00 | Window Closed / Lapsed |