Stock material or miscellaneous articles – Composite – Of inorganic material
Patent
1988-01-05
1989-08-15
Pianalto, Bernard
Stock material or miscellaneous articles
Composite
Of inorganic material
427127, 427128, 428403, 428688, 428900, 252 6254, 252 6256, G11B 566
Patent
active
048574171
ABSTRACT:
Cobalt-containing iron oxide magnetic particles having a high coercive force and a small surface electrical resistance which are useful as a recording element for a magnetic recording medium, and a method for the preparation of the same comprising reducing acicular .gamma.-Fe.sub.2 O.sub.3 particles in a reducing gas or liquid until the iron oxide reaches an intermediate oxidation state between .gamma.-Fe.sub.2 O.sub.3 and Fe.sub.3 O.sub.4, dispersing the resulting iron oxide particles into an aqueous solution containing a cobalt salt and optionally a ferrous salt and an alkali of one equivalent or more to the metal salt(s), and heating the mixture at a temperature of higher than room temperature up to a boiling point of the mixture under an atmospheric condition such that the divalent iron is substantially not oxidized. The cobalt is thereby predominantly incorporated into the most outer layer of the acicular iron oxide particles.
REFERENCES:
patent: 3725126 (1973-04-01), Haller et al.
patent: 4002804 (1977-01-01), Akashi et al.
patent: 4015030 (1977-03-01), Sasazawa et al.
Andoh Haruo
Hirata Junichi
Kitaoka Susumu
Hitachi Maxell Ltd.
Pianalto Bernard
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