US3967986A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of preparing ferromagnetic material
Assignee: US Philips Corp
•
Filing: 1975-01-27
•
Granted: 1976-07-06
•
Expires: 1995-01-27
Abstract
Abstract A method of preparing iron powder for recording in which iron oxide hydrate powder is reduced by flowing hydrogen in intimate contact with the iron oxide hydrate powder, preferrably in a fluidized bed.
Inventors
- 👤 Hans Rau
- 👤 Karl-Georg Knauff
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 14:17
CPC Classifications
H; H01; H01F; H01F1/00; H01F1/01; H01F1/03; H01F1/032; H01F1/04; H01F1/06; H01F1/065
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
114 words
A method of preparing ferromagnetic material in the form of acicular particles consisting at least predominantly of iron, comprising the steps of reducing an iron oxide or iron oxide hydrate powder by intimately contacting the powder with a quantity of a gaseous reduction agent which predomimantly contains hydrogen flowing at a rate corresponding at least to the formula V = 0.4 × T -120, where V is the volume in liters of the quantity of gaseous reduction agent at 0°C and 1 atm. which flows per hour and per gram of Fe contents of the material to be reduced, and T is the reduction temperature in ° C, T being between 300° and 600°C.
Claim 2
Independent Claim
114 words
A method of preparing ferromagnetic material in the form of acicular particles consisting at least predominantly of iron, comprising the steps of reducing an iron oxide or iron oxide hydrate powder by intimately contacting the powder with a quantity of a gaseous reduction agent which predomimantly contains hydrogen flowing at a rate corresponding at least to the formula V = 0.4 × T -120, where V is the volume in liters of the quantity of gaseous reduction agent at 0°C and 1 atm. which flows per hour and per gram of Fe contents of the material to be reduced, and T is the reduction temperature in ° C, T being between 300° and 600°C.
Claim 3
Dependent Claim
24 words
A method as claimed in claim 1, wherein the reduction is carried out at temperatures between 300° and 400°C in a single-stage fluidised bed.
Claim 4
Dependent Claim
17 words
A method as claimed in claim 1, wherein the reduction is carried out in a tilting furnace.
Claim 5
Dependent Claim
40 words
A method as claimed in claim 1, wherein the powder is transported from the top to the bottom in counter current with the gaseous reduction agent, and deposited, after successively passing through a plurality of sieves, into a storage container.
Claim 6
Dependent Claim
18 words
A method as claimed in claim 4, wherein successive sieves move relative to each other in opposite directions.
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) | 1979-07-06 | 1980-01-05 | 1980-07-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-07-06 | 1984-01-05 | 1984-07-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-07-06 | 1988-01-05 | 1988-07-06 | $7700.00 | Window Closed / Lapsed |