Highly magnetic iron oxide powder
US4822509A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 6, 1986 |
| Grant date | Apr 18, 1989 |
| Priority date | — |
| Expiry date | Nov 6, 2006 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC01P2006/42
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A highly magnetic isotropic iron oxide powder with a uniform particle size distribution and particle size in the range from 0.005 to 0.2 micrometer consists of a mixed iron oxide exhibiting gamma (Fe.sub.2 O.sub.3) and ferrite (Fe.sub.3 O.sub.4) structure, having the empirical formula Fe.sub.72-x O.sub.96, where x has a value between 2 to 7, an aspect ratio of at most 2:1 and a temperature coefficient of coercivity of less than -0.7% per degree Celcius. The mixed oxide is optionally a cobalt-modified mixed iron oxide containing 2-6% by weight of cobalt and is obtained by heating ultrafine, ferrite particles in a controlled, oxidizing atmosphere at a temperature of 240.degree. C. to 320.degree. C. for a period of one to three hours.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.