Particles containing iron carbide
US5437805A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 12, 1993 |
| Grant date | Aug 1, 1995 |
| Priority date | — |
| Expiry date | Oct 12, 2013 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC01P2006/80
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
The present invention provides acicular particles (A) containing an iron carbide, which have (a) a free carbon content of at most 20 wt. %, and (b) and Fe.sub.5 C.sub.2 ratio(x) of at least 70% and a coercive force of 3.times.+300 to 7.times.+270 Oe, the ratio(x) being expressed by ##EQU1## where S1 is the X-ray diffraction strength of Fe.sub.5 C.sub.2, and S2 is the X-ray diffraction strength of Fe.sub.3 O.sub.4. The invention further provides particles (B) containing nickel and an iron carbide. The invention further provides acicular particles containing an iron carbide which are obtained by heating an aqueous dispersion of ferric hydroxide in an alkaline system in the presence of a water-soluble compound capable of coordinating to iron to obtain acicular .alpha.-ferric oxide and contacting the product with a carbon-containing reducing-and-carburizing agent or with a mixture of the agent and a carbon-free reducing agent, with or without contacting the product with the carbon-free reducing agent. These particles (A) and (C) are controllable in coercive force and usable for magnetic record media of various standards.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.