Process for producing cobalt- and iron-containing ferromagnetic powder
AssigneeFuji Photo Film Co., Ltd.
InventorsKoji Sasazawa, Shin-Ichiro Dezawa, Tatsuji Kitamoto
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Abstract
Co- and Fe-containing ferromagnetic iron oxide powder having a high coercive force and improved stability to heat and pressure is produced by adding an aqueous alkali solution, an aqueous solution containing Co.sup.+2 ions, and an aqueous solution containing not more than 1 equivalent, based on the Co.sup.+2 ions, of Fe.sup.+3 ions to a suspension of a ferromagnetic iron oxide, and heating the mixture at a temperature of at least about 80.degree. C, preferably 90.degree. to 105.degree. C. The ferromagnetic iron oxide powder is especially suitable for producing magnetic recording media.
Claims15
A process for producing a Co- and Fe- containing ferromagnetic iron oxide powder which comprises adding an aqueous alkali solution, an aqueous solution containing Co.sup.+2 ions and an aqueous solution of Fe.sup.+3 ions to a suspension of an acicular ferromagnetic iron oxide and heat-treating the resulting suspension, at a temperature of at least about 80.degree. C;
- said Co.sup.+2 ions being present in said aqueous solution containing Co.sup.+2 ions in an amount of 0.5 to about 10 atomic percent based on the iron present in the ferromagnetic iron oxide, said Fe.sup.+3 ions being added to the suspension in an amount of at least 0.1 equivalent but not more than 1 equivalent based on the Co.sup.+2 ions, and said alkali solution contains alkali in such an amount that after neutralization of the Co.sup.+2 and Fe.sup.+3 ions the hydroxyl ion concentration of the suspension is at least about 0.5 mol/liter.
Dependencies are inferred from the claim text.