US4052326A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Manufacture of γ-iron(III) oxide
Assignee: BASF SE
•
Filing: 1976-08-30
•
Granted: 1977-10-04
•
Expires: 1996-08-30
Abstract
Abstract A process for the manufacture of acicular γ-iron(III) oxide of improved crystallinity and high coercive force by heating goethite or acicular alpha-iron(III) oxide particles at temperatures of from 500° to 800° C, reduction of the resulting product at temperatures of from 280° to 600° C and subsequent oxidation of the magnetite to γ-iron(III) oxide of improved crystallinity and high coercive force.
Inventors
- 👤 Eduard Schoenafinger
- 👤 Bernd Leutner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 02:52
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70652; C; C01; C01G; C01G49/00; C01G49/02; C01G49/06; G11B5/70647; C01P; C01P2002/00; C01P2002/50; C01P2002/52; C01P2002/54; C01P2004/00; C01P2004/10; C01P2006/00; C01P2006/42
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
87 words
In a process for the manufacture of acicular γ-iron(III) oxide of improved crystallinity and high coercive force by heating goethite or acicular γ-iron(III) oxide at a temperature of from 500° to 800° C, reducing the resulting product to magnetite at a temperature of from 280° to 600° C and subsequently oxidizing the magnetite to γ-iron(III) oxide, the improvement which comprises adding heat to the magnetite in an inert gas atmosphere to maintain a temperature of from 400° to 600° C after the reduction step has been completed.
Claim 2
Dependent Claim
87 words
In a process for the manufacture of acicular γ-iron(III) oxide of improved crystallinity and high coercive force by heating goethite or acicular γ-iron(III) oxide at a temperature of from 500° to 800° C, reducing the resulting product to magnetite at a temperature of from 280° to 600° C and subsequently oxidizing the magnetite to γ-iron(III) oxide, the improvement which comprises adding heat to the magnetite in an inert gas atmosphere to maintain a temperature of from 400° to 600° C after the reduction step has been completed.
Claim 3
Dependent Claim
30 words
A process as claimed in claim 1 wherein the goethite or the acicular γ-iron(III) oxide is modified with 0.5 to 25 percent by weight of cobalt, based on iron(III) oxide.
Claim 4
Dependent Claim
16 words
A process as claimed in claim 1 wherein the inert gas atmosphere is a nitrogen atmosphere.
Claim 5
Dependent Claim
22 words
A process as claimed in claim 1 wherein the reduction temperature is not less than 300° and not more than 370° C.
References Cited (Backward Citations)
US3897354A
Cited
US3974246A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-10-03 | 1981-04-04 | 1981-10-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-10-03 | 1985-04-04 | 1985-10-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-10-03 | 1989-04-04 | 1989-10-04 | $7700.00 | Window Closed / Lapsed |