PROCESS FOR PRODUCING COBALT-CONTAINING FERROMAGNETIC IRON OXIDE POWDER

摘要

F-2-19084/78 A process for producing a cobalt-containing ferromagnetic iron oxide powder suitable for magnetic recording which comprises (a) mixing cobalt ion, ferrous ion and an alkali with an aqueous dispersion of acicular ferromagnetic iron oxide nuclei under non-oxidizing conditions at a temperature of about 50.degree.C or less; (b) heating the dispersion to a temperature of at least about 60.degree.C but below the boiling point of the dispersion under non-oxidizing conditions to cause a reaction; and (c) treating the dispersion at a temperature of at least about 60.degree.C but below the boiling point of the dispersion under the following conditions: (1) initially treating the dispersion under nonoxidizing conditions for about 5 minutes or more; (2) subsequentially treating the dispersion under oxidizing conditions for about 5 minutes or more prior to the termination of the reaction; and (3) a total treating time under non-oxidizing conditions and oxidizing conditions of at least about 30 minutes.