PREPARATION OF FERROMAGNETIC IRON OXIDE CONTAINING COBALT

• Main Authors: ISHIKAWA TSUNEO, HIRAI MASAHARU, NAKADA KAZUO, AMANO MASATOSHI, HONMA ICHIROU
• Format: Patent
• Language: English
• Published: 08.07.1983
• Subjects: BASIC ELECTRIC ELEMENTS; CHEMISTRY; COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSESC01D OR C01F; ELECTRICITY; INDUCTANCES; INORGANIC CHEMISTRY; MAGNETS; METALLURGY; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES; TRANSFORMERS

PURPOSE:To prepare magnetic iron oxide, containing cobalt, and having improved coercive force as a magnetic recording medium, by applying a metallic compound containing the cobalt to the surface of a magnetic iron oxide powder, filtering the resultant slurry, washing the filtered cake with water, dispersing the washed cake in water, and heating the resultant slurry under pressure. CONSTITUTION:A magnetic iron oxide powder, e.g. gamma-Fe2O3 or Fe3O4, is dispersed in water to form a slurry, which is then mixed with an aqueous solution containing a Co salt, e.g. cobalt chloride, cobalt sulfate or cobalt acetate, dissolved therein and agitated. An aqueous solution of an alkali, e.g. NaOH, is then added to the slurry and agitated to apply the Co salt to the surface of the iron oxide particles. The resultant slurry is then filtered, and the cake is washed with water and introduced into an autoclave. The air in the autoclave is expelled and replaced with a nonoxidizing atmosphere, e.g. nitrogen, and the resultant cake is then dispersed in water in the autoclave to give a slurry, which is then heated at the boiling point or above under pressure, e.g. 105-200 deg.C while pressurized at 1.1-20 atm. The slurry is then filtered, and the resultant cake is washed with water and dried in the air to give the aimed magnetic iron oxide, coated with 1-10%, based on the magnetic iron oxide, Co, and having a great coercive force.