| 摘要 |
PURPOSE:To obtain magnetic iron oxide powder composed of spindle shaped maghemite particle containing Co-modified and excellent in coercive force or the like by converting a Si-containing spindle shaped goethite particle into a maghemite particle and modifying with Co. CONSTITUTION:An aq. solution containing FeCO3 is prepared by allowing a ferrous salt aq. solution to react with an alkali carbonate. Next, the Si containing spindle shaped goethite particle is formed by adding a 0.87-7.7atom% water soluble silicate expressed in terms of Si for Fe into the aq. solution and oxidizing it by passing a oxygen-containing gas. Next, the spindle shaped maghemite particle is obtained by heating and reducing the particle in a reducing gas and furthermore oxidizing. Next, the particle is used as a precursor particle, is dispersed into an alkali suspension solution containing cobalt hydroxide so as to contain 0.5-15atom% Co for Fe in the particle and is heat treated at 50-100 deg.C. As a result, the magnetic iron oxide particle powder composed of the Co-modified Si containing spindle shaped maghemite particle is obtained. |
