Process for producing ferromagnetic powder
AssigneeFuji Photo Film Co., Ltd.
InventorsShin-ichiro Dezawa, Koji Sasazawa, Tatsuji Kitamoto
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Abstract
In a process for producing ferromagnetic powder which comprises adding an aqueous solution containing Co.sup.+2 ions, with or without another cation or cations, and an alkali solution to a suspension of ferromagnetic iron oxide, and heating the mixture to produce ferromagnetic iron oxide containing the metal provided by such an ion (s), the improvement wherein the heating is carried out in the presence of an oxidizing agent.
Claims22
A process for producing a cobalt containing ferromagnetic iron oxide which consists essentially of adding an aqueous solution containing Co.sup.+2 ions, an alkali solution, and an oxidizing agent to a suspension of ferromagnetic iron oxide and heating the resultant mixture at 80.degree. to 150.degree. C to form said cobalt containing ferromagnetic iron oxide;
- the amount of Co.sup.+2 ions in said Co.sup.+2 ion containing aqueous solution being 0.5 to 10 atomic percent based on the iron present in the ferromagnetic iron oxide;
- the amount of alkali present in said alkali solution being such that after neutralization of the Co.sup.+2 ions, the hydroxyl concentration of said mixture is at least 0.5 N;
- the amount of oxidizing agent, when it is a liquid or solid, being at least about 0.1 equivalent based on the Co.sup.+2 ions and when it is a gas, said oxidizing agent being added at a rate of at least 0.1/min per liter of said resultant mixture.
A process for producing a cobalt containing ferromagnetic iron oxide which consists essentially of adding an aqueous solution containing Co.sup.+2 ions and at least one cation selected from the group consisting of Cr.sup.+3, Cr.sup.+6, Mn.sup.+2, Ni.sup.+2 and Zn.sup.+2 ;
- an alkali solution;
- and an oxidizing agent to a suspension of ferromagnetic iron oxide and heating the resulant mixture at 80.degree. to 150.degree. C to form said cobalt containing ferromagnetic iron oxide;
- the amount of Co.sup.+2 ions and said cation in Co.sup.+2 and cation containing solution being 0.5 to 10 atomic percent based on the iron present in the ferromagnetic iron oxide and the ratio of Co.sup.+2 ion to said catioin being such that at last 1/3 of said 0.5 to 10 atomic percent is Co.sup.+2 ion, the amount of alkali in said alkali solution being such that after neutralization of the Co.sup.+2 ions and aid cation the hydroxyl ion concentration is at least 0.5 N;
- the amount of oxidizing agent when it is a liquid or solid is at least 0.1 equivalent based on said Co.sup.+2 ions and when it is a gas it is added at a rate of at least about 0.1 l./min per liter of said resulant mixture.
Dependencies are inferred from the claim text.