Patent US3917716A successfully refreshed from Google Patents.
US3917716A
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Method for raising the curie point of ferromagnetic chromium dioxide
Assignee: Fujifilm Holdings Corp
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Filing: 1973-05-16
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Granted: 1975-11-04
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Expires: 1993-05-16
Abstract
Abstract The Curie point of ferromagnetic chromium dioxide is raised by heating ferromagnetic chromium dioxide powder in intimate contact with a reducing agent in the gaseous phase at a temperature above 60*C.
Inventors
- 👤 Shin-Ichiro Dezawa
- 👤 Tatsuji Kitamoto
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 07:34
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70636
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
84 words
A METHOD FOR RAISING THE CURIE POINT OF FERROMAGNETIC CHROMIUM DIOXIDE TO MORE THAN 120*C, WHICH COMPRISES HEATING FERROMAGNETIC CHROMIUM DIOXIDE POWDER HAVING A CURIE POINT LESS THAN 120*C TO A TEMPERATURE MORE THAN 60*C IN INTIMATE CONTACT WITH A REDUCING AGENT IN THE GASEOUS PHASE, WHEREIN SAID FERROMAGNETIC CHROMIUM DIOXIDE AFTER SAID HEATING HAS X-RAY DIFFRACTION PEAKS WHICH SHOW A SPACING AT AT LEAST ONE OF 3.217 $ 0.01A, 2.520 $ 0.004A AND 1.718 $ 0.002A AND A CURIE POINT MORE THAN 120*C.
Claim 2
Independent Claim
84 words
A METHOD FOR RAISING THE CURIE POINT OF FERROMAGNETIC CHROMIUM DIOXIDE TO MORE THAN 120*C, WHICH COMPRISES HEATING FERROMAGNETIC CHROMIUM DIOXIDE POWDER HAVING A CURIE POINT LESS THAN 120*C TO A TEMPERATURE MORE THAN 60*C IN INTIMATE CONTACT WITH A REDUCING AGENT IN THE GASEOUS PHASE, WHEREIN SAID FERROMAGNETIC CHROMIUM DIOXIDE AFTER SAID HEATING HAS X-RAY DIFFRACTION PEAKS WHICH SHOW A SPACING AT AT LEAST ONE OF 3.217 $ 0.01A, 2.520 $ 0.004A AND 1.718 $ 0.002A AND A CURIE POINT MORE THAN 120*C.
Claim 3
Dependent Claim
16 words
A method as claimed in claim 1 wherein said heating is to between 100*C and 200*C.
Claim 4
Dependent Claim
21 words
A method as claimed in claim 1 wherein said ferromagnetic chromium dioxide shows a spacing at 3.217 + or - 0.01A.
Claim 5
Dependent Claim
19 words
A method as claimed in claim 1 wherein said reducing agent is hydrogen gas or an organic solvent gas.
Claim 6
Dependent Claim
44 words
A method as claimed in claim 4 wherein said reducing agent is an organic solvent gas and said organic solvent gas is selected from the group consisting of alcohols, ethers, esters and aldehydes, and these organic solvents having from 1 to 10 carbon atoms.
Claim 7
Dependent Claim
22 words
A method as claimed in claim 4 wherein said organic solvent gas is a hydrocarbon having from 1 to 10 carbon atoms.
Claim 8
Dependent Claim
23 words
The method as claimed in claim 1 where the partial pressure of reducing agent is from about 1/1000 atm. to about 1 atm.
Claim 9
Dependent Claim
19 words
The method as claimed in claim 1 where the heating is for about 30 minutes to about 24 hours.
Claim 10
Dependent Claim
13 words
The method of claim 1 wherein said gaseous phase reducing agent is hydrogen.
Claim 11
Dependent Claim
15 words
The method of claim 1 wherein said gaseous phase reducing agent is an organic solvent.
Claim 12
Dependent Claim
46 words
The method of claim 1 wherein said ferromagnetic chromium dioxide, prior to said heating, exhibits a coercive force of 400-600 oersteds, has a length of 0.3 - 1.0 microns, an axial ratio of 3:1 - 10:1 and exhibits a saturization magnetization of greater than 70 emu/g.
Claim 13
Dependent Claim
74 words
Ferromagnetic chromium dioxide having a Curie point of greater than 120*C, and X-ray diffraction peaks showing a spacing at least one of 3.217 + or - 0.01A, 2.520 + or - 0.004A and 1.718 + or - 0.002A said ferromagnetic chromium dioxide obtained by heating a ferromagnetic chromium dioxide powder having a Curie point lower than 120*C to a temperature more than 60*C in intimate contact with a reducing agent in the gaseous phase.
Claim 14
Dependent Claim
74 words
Ferromagnetic chromium dioxide having a Curie point of greater than 120*C, and X-ray diffraction peaks showing a spacing at least one of 3.217 + or - 0.01A, 2.520 + or - 0.004A and 1.718 + or - 0.002A said ferromagnetic chromium dioxide obtained by heating a ferromagnetic chromium dioxide powder having a Curie point lower than 120*C to a temperature more than 60*C in intimate contact with a reducing agent in the gaseous phase.
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) | 1978-11-03 | 1979-05-05 | 1979-11-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-11-03 | 1983-05-05 | 1983-11-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-11-03 | 1987-05-05 | 1987-11-04 | $7700.00 | Window Closed / Lapsed |