Stabilized ferromagnetic chromium dioxide and process for obtaining same
US4244932A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 16, 1979 |
| Grant date | Jan 13, 1981 |
| Priority date | — |
| Expiry date | Jul 16, 1999 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T428/2991
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A ferromagnetic chromium dioxide stabilized by coating the particles thereof with a stabilizing substance is disclosed, wherein the stabilizing substance consists essentially of an equimolecular mixture of Fe.sub.2 O.sub.3 and MnO or of a mixture of ferrite MeFe.sub.2 O.sub.4 with oxides Fe.sub.2 O.sub.3 and MeO, wherein Me represents Cu, Co, Zn or Mg and wherein the molar ratio Fe.sub.2 O.sub.3 /MeO is equal to 1, the quantity of the ferrite in the mixture being such as results from calcining, at temperature between 250.degree. and 350.degree. C., equimolecular quantities of Fe.sub.2 O.sub.3 and MeO. A process for obtaining the stabilized CrO.sub.2 is also disclosed wherein the CrO.sub.2 is dispersed in water and on it are co-precipitated Fe(OH).sub.3 and Mn(OH).sub.2 or Me(OH).sub.2 in stoichiometric quantities with respect to each other; after which the CrO.sub.2, in admixture with the hydroxides, is separated from the water, dried at a temperature not exceeding 100.degree. C. and then calcined at temperatures between 250.degree. and 350.degree. C.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.