| 摘要 |
PURPOSE:To produce acicular ferromagnetic iron oxide powder excellent in coercive force, saturation magnetization, temp. dependency and pressurized demagnetization, etc., by calcining acicular iron oxyhydroxide grain deposited with fine Co-ferrite grain on the surface. CONSTITUTION:Both aq. suspension of acicular iron oxyhydroxide grain (e.g. goethite) and aq. suspension of fine Co-ferrite grain which is obtained by dissolving ferric sulfate and cobalt sulfate in water in stoichiometric amount and heating the mixture at <=100 deg.C in alkalinity and stirring it are mixed and stirred at room temp. for several ten minutes, and thereby a mixture deposited with fine Co-ferrite grain on the surface of acicular iron oxyhydroxide grain is obtained. Then after washing this mixture with water, filtering and drying it, it is hydrated at 300-350 deg.C and reduced at 300-450 deg.C and thereafter calcined at 200-300 deg.C in oxygen-contg. atmosphere to reoxidize it. |
