| 摘要 |
PURPOSE:To manufacture the titled iron oxide particle powder containing Co ions with excellent dispersibility by a method wherein the precipitates of a hydroxide containing Fe<2+>/Co<2+> in value not less than a specified ratio are oxidized under the existence of needle-shaped Fe3O4 particles and the surfaces of the particles are changed into a cooxide. CONSTITUTION:The precipitates of a hydroxide formed at rate of not less than 1.3 atom Fe<2+> to 1 atom Co<2+> are oxidized under the existence of Fe3O4 particles with 0.4-1.0mu length, which substantially display needle-shaped. Co ferrite with the composition of CoxFe3-xO4(X<=1.3) is formed to the surfaces and holes of needle-shaped, ferromagnetic Fe3O4 with the holes in an epitaxial shape. The needle- shaped particles are filtered from a liquid, washed by water, dehydrated and thermally treated at temperatures not more than 500 deg.C without approximately changing the form and size of the needle-shaped particles as starting substance. Thus, needle- shaped, ferromagnetic iron oxide particle powder is manufactured which contains not more than 0.11 atom Co ions to 1 atom Fe ions and has remarkably few internal holes. |
