Patent US4144325A successfully refreshed from Google Patents.
US4698140A
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Techniques for preparing magnetic particles having utility in recording media
Assignee: Olin Corp
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Filing: 1986-12-29
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Granted: 1987-10-06
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Expires: 2006-12-29
Abstract
Abstract The present invention relates to techniques for producing magnetic particles for use in recording media. The process of the present invention generally 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 throughout a surrounding matrix; and dissolving the matrix to leave the magnetic particles. The dissolution of the matrix is done electrochemically using a pyrophosphate solution.
Inventors
- 👤 Jacob Crane
- 👤 George J. Muench
- 👤 Yousef Saleh
- 👤 Lifun Lin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 14:29
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: 15
Claim 1
Independent Claim
63 words
A process for forming passivated free magnetic particles, said process comprising: forming a plurality of magnetic particles, providing an electrolytic cell containing two electrodes and an aqueous pyrophosphate solution electrolyte; immersing said particles in said electrolyte, and applying a current having a current density in the range of from about 10 mA/cm 2 to about 30 mA/cm 2 to form said passivated particles.
Claim 2
Dependent Claim
63 words
A process for forming passivated free magnetic particles, said process comprising: forming a plurality of magnetic particles, providing an electrolytic cell containing two electrodes and an aqueous pyrophosphate solution electrolyte; immersing said particles in said electrolyte, and applying a current having a current density in the range of from about 10 mA/cm 2 to about 30 mA/cm 2 to form said passivated particles.
Claim 3
Dependent Claim
35 words
The process of claim 1 wherein: said particle forming step comprises forming a magnetic precipitate comprising a plurality of magnetic particles dispersed in a matrix; and said current applying step causing dissolution of said matrix.
Claim 4
Dependent Claim
69 words
The process of claim 1 wherein said immersing step comprises immersing said particles in an aqueous solution having a pH greater than about 8, a pyrophosphate ion concentration in a range of from about 0.5M to about 1.5M, a copper concentration in a range of from an effective amount up to about 0.75M, and a nickel concentration in a range of from an effective amount up to about 0.75M.
Claim 5
Dependent Claim
71 words
The process of claim 1 wherein said immersing step comprises immersing said particles in an aqueous solution having a pH in a range of from about 8 to about 9, a pyrophosphate ion concentration in a range of from about 1.0M to about 1.4M, a copper concentration in a range of from about 0.2M to about 0.5M, and a nickel concentration in a range of from about 0.2M to about 0.5M.
Claim 6
Dependent Claim
25 words
The process of claim 1 further comprising: maintaining said electrolyte at a temperature in the range of from about room temperature to about 50° C.
Claim 7
Dependent Claim
41 words
The process of claim 2 wherein said magnetic precipitate and matrix forming step comprises: providing a metallic material capable of forming a magnetic precipitate by aging; and thermally aging said metallic material to form said magnetic particles dispersed in said matrix.
Claim 8
Dependent Claim
20 words
The process of claim 6 further comprising: solution heat treating and quenching said metallic material prior to said aging step.
Claim 9
Dependent Claim
34 words
The process of claim 6 further comprising: working said material up to a reduction of about 99% prior to said aging step to affect particle morphology and size and/or assist in said material processing.
Claim 10
Dependent Claim
28 words
The process of claim 8 wherein said working step comprises cold rolling said material and obtaining a reduction in a range of from about 50% to about 95%.
Claim 11
Dependent Claim
18 words
The process of claim 6 wherein said metallic material providing step comprises providing said material in strip form.
Claim 12
Dependent Claim
18 words
The process of claim 6 wherein said metallic material providing step comprises providing said material in rod form.
Claim 13
Dependent Claim
62 words
The process of claim 6 wherein: said metallic material providing step comprises providing a copper-base alloy; and said aging step comprises heating said copper-base alloy to a temperature in the range of from about 500° C. to about 800° C. for a time period up to about 48 hours and forming a plurality of acicular ferromagnetic particles surrounded by a copper-rich matrix.
Claim 14
Dependent Claim
44 words
The process of claim 12 wherein said aging step comprises heating said copper-base alloy to a temperature in the range of from about 500° C. to about 700° C. for a time period in the range of from about 1 to about 8 hours.
Claim 15
Dependent Claim
18 words
Free magnetic particles having utility in recording media, said particles being produced by the process of claim 1.
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) | 1990-10-05 | 1991-04-06 | 1991-10-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-10-05 | 1995-04-06 | 1995-10-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-10-05 | 1999-04-06 | 1999-10-06 | $7700.00 | Window Closed / Lapsed |