Preparation of acicular cobalt-containing magnetic iron oxide

Details Preparation of acicular cobalt-containing magnetic iron oxide Preparation of acicular cobalt-containing magnetic iron oxide

1994-08-16

1996-01-16

Beck, Shrive

Coating processes

Particles, flakes, or granules coated or encapsulated

Inorganic base

427214, 427216, 427127, 427128, 148105, 75349, B05D 700

Patent

active

054846285

ABSTRACT:
Acicular cobalt-containing magnetic iron oxides having a high coercive force and a core/shell structure and hence low temperature dependence of the coercive force are prepared by a process in which, in a first stage, surface activation is effected by means of iron(II) and cobalt ions under alkaline conditions on the iron oxide core under an inert gas atmosphere and thereafter, in a second stage, an epitactic coating of cobalt ferrite is applied, which coating is formed oxidatively from iron (II) and cobalt (II) hydroxide, likewise under alkaline reaction conditions. The total amount of cobalt ions used for doping remains unchanged compared with the known doped iron oxides or is even smaller. In the second process stage, the achievable coercive force can be controlled by the proportion of air in the gas mixture during the formation of the epitactic coating.

REFERENCES:
patent: 3573980 (1971-04-01), Haller
patent: 4122216 (1978-10-01), Okazoe
patent: 4770903 (1988-09-01), Schwab et al.

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