| 摘要 |
PURPOSE:To obtain magnetic powder wherein acicular properties are excellent, coercive force and magnetic saturaion are large, and performance is superior by a method wherein, in the state that geothite is sufficiently diffused, water- containing aluminum hydroxide is deposited from the inside of a system uniformly and very slowly. CONSTITUTION:When aluminum compound as inhibitor for sintering is stuck on the surface of geothite as the material of magnetic powder for magnetic recording, aluminate ion aqueous solution is added to geothite suspension under the ammoniacal state of pH12 or more, then ammonia is evaporated, and pH is reduced to 9; thus the aluminum compound is deposited on the surface of the geothite. Then filtering and drying are performed; in the air atmosphere, annealing is performed at 300-800 deg.C; further reduction treatment is performed in a reducing atmosphere at 400-600 deg.C. Thereby the grain surface of geothite is stuck uniformly and densely. This coating film maintains grain shape, and high coercive force is obtained. |
