Patent EP0214644A2 successfully refreshed from Google Patents.
EP0214644A2
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EP
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Method of producing ferromagnetic particles
Assignee: Olin Corp
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Filing: 1986-09-08
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Granted: —
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Expires: 2006-09-08
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 throughout 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 100A to about 2000A, 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
EP
Data Source
google_patents
Last Synchronized
2026-11-08 20:47
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; B; B22; B22F; B22F1/00; B22F1/06; B22F1/062; B22F9/00; B22F9/16; G11B5/68; G11B5/70; G11B5/706; G11B5/70605; G11B5/712; B22F2998/00; B22F2998/10
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
68 words
A method of producing free magnetic particles, said method being characterized by: 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
68 words
A method of producing free magnetic particles, said method being characterized by: 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
21 words
The method of claim 1 further being characterized by: solution heat treating and quenching said alloy prior to said aging step.
Claim 4
Dependent Claim
30 words
The method of claim 1 or 2 further being characterized by: working said alloy prior to said aging step to affect particle morphology and size and/or assist in alloy processing.
Claim 5
Independent Claim
40 words
The method of any one of claims 1 to 3 further being characterized by: said alloy providing step comprising providing a copper base alloy; and said aging step forming a plurality of acicular ferromagnetic particles surrounded by a copper-rich matrix.
Claim 6
Dependent Claim
39 words
The method of claim 4 further being characterized by said aging step comprising 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 7
Independent Claim
43 words
The method of any one of claims 1 to 5 further being characterized by: said dissolving step comprising immersing said particles and said matrix in an aqueous solution containing free ammonia in a concentration in the range of about 0.5M to about 3.5M.
Claim 8
Independent Claim
62 words
The method of any one of claims 1 to 5 further being characterized by: said dissolving step comprising immersing said particles and said surrounding matrix in an aqueous citrate solution without significantly dissolving said magnetic particles, said aqueous citrate solution containing a citrate ion concentration in the range of from about 0.5M to about 3M and having a pH greater than 3.
Claim 9
Dependent Claim
34 words
The method of claim 7 further being characterized by: said dissolving step further comprising: providing at least two electrodes at least partially immersed in said solution; and applying an electrical current between said electrodes.
Claim 10
Dependent Claim
32 words
Free acicular magnetic particles characterized by being in an aged condition and having a length in the range of about 100A to about 2000A and an aspect ratio up to about 10:1.
Claim 11
Dependent Claim
32 words
Free acicular magnetic particles characterized by being in an aged condition and having a length in the range of about 100A to about 2000A and an aspect ratio up to about 10:1.
Claim 12
Dependent Claim
31 words
The magnetic particles of claim 9 further being characterized by: each particle having a relatively smooth surface, a substantially uniform composition throughout, a single magnetic domain, and a face-centered cubic structure.
Claim 13
Dependent Claim
39 words
The magnetic particles of claim 9 or 10 further being characterized by: « said length being in the range of about 300A to about 1500A; and said aspect ratio being in the range of about 1.5:1 to about 8:1.
Claim 14
Dependent Claim
38 words
The magnetic particles of any one of claims 9 to 11 further being charaterized by iron-nickel particles containing from about 35% to about 60% nickel, up to about 15% copper, and from about 35% to about 65% iron.
Claim 15
Dependent Claim
40 words
The particles of any one of claims 9 to 12 further being characterized by each particle having a saturation magnetization greater than about 80 EMU/g and a coercive field in the range of about 300 Oe to about 2000 Oe.
Claim 16
Dependent Claim
55 words
Recording media characterized by a plurality of acicular ferromagnetic particles in an aged condition; each said particle having a length in the range of about 100 Å to about 2000A, an aspect ratio up to about 10:1, a relatively smooth surface, a substantially uniform composition throughout, and a single magnetic domain; and a substrate material.
Claim 17
Dependent Claim
55 words
Recording media characterized by a plurality of acicular ferromagnetic particles in an aged condition; each said particle having a length in the range of about 100 Å to about 2000A, an aspect ratio up to about 10:1, a relatively smooth surface, a substantially uniform composition throughout, and a single magnetic domain; and a substrate material.
Claim 18
Dependent Claim
34 words
The recording media of claim 14 further being characterized by: a magnetic layer comprising a plurality of said magnetic particles dispersed in a binder material, said magnetic layer being coated upon said substrate material.
Claim 19
Dependent Claim
50 words
A solution for extracting magnetic particles from a surrounding matrix characterized by said solution comprising an aqueous citrate solution containing a citrate ion concentration in the range of about 0.5M to about 3M and having a pH greater than about 3 into which said particles and said matrix are immersed.
Claim 20
Dependent Claim
50 words
A solution for extracting magnetic particles from a surrounding matrix characterized by said solution comprising an aqueous citrate solution containing a citrate ion concentration in the range of about 0.5M to about 3M and having a pH greater than about 3 into which said particles and said matrix are immersed.
Claim 21
Dependent Claim
20 words
The solution of claim 16 further being characterized by said solution containing a concentration of copper greater than about 0.3M.
Claim 22
Dependent Claim
50 words
A solution for extracting magnetic particles from a surrounding matrix characterized by said solution comprising an aqueous solution containing free ammonia in a concentration in the range of about 0.5M to about 3.5M and having a pH greater than about 8 into which said particles and said matrix are immersed.
Claim 23
Dependent Claim
50 words
A solution for extracting magnetic particles from a surrounding matrix characterized by said solution comprising an aqueous solution containing free ammonia in a concentration in the range of about 0.5M to about 3.5M and having a pH greater than about 8 into which said particles and said matrix are immersed.
Claim 24
Dependent Claim
22 words
The solution of claim 18 further being characterized by said solution containing from about 10 g/1 to about 50 g/1 of copper.
References Cited (Backward Citations)
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