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US 4,394,160 AGranted
Making magnetic powders
AssigneeSperry Corporation
InventorsWalter O. Freitag, Victor V. Suchodolski
Life of this patent
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Abstract
Magnetic powders for use in the manufacture of magnetic recording media are produced by a borohydride process in which aqueous solutions of ferrous sulfate and sodium borohydride are mixed in a magnetic field. The coercive force of the magnetic powder produced as a result of this method is controlled by controlling the temperature of the reactant solutions prior to mixing thereof.
Claims7
A method of producing magnetic powders having a coercive force in the range of from about 300 Oe to 700 Oe for use in the manufacture of magnetic recording media which comprises:
- (a) pre-determining the desired coercive force of said magnetic powders,
- (b) preparing a solution of metal salt capable of forming a ferromagnetic material,
- (c) maintaining the solution of Step (b) at a pre-selected temperature which is functionally determinate of the desired coercive force, said pre-selected temperature being within a range of from about 0.degree. C. to 50.degree. C.,
- (d) preparing a solution of a borohydride reducing agent,
- (e) maintaining the solution of Step (d) at a pre-selected temperature which is functionally determinate of the desired coercive force, said pre-selected temperature being within a range of from about 0.degree. C. to 50.degree. C.,
- (f) mixing the solutions of Steps (c) and (e) together while applying a magnetic field of a selected magnitude to said mixture during the reducing reaction between said solutions, the temperatures of said reactant solutions of Steps (c) and (e) prior to the mixing being pre-selected so as to control the coercive force of the magnetic powder produced from the mixture of Step (f).
3 more elements
Dependencies are inferred from the claim text.