| 摘要 |
PURPOSE:To prepare acicular goethite powder having sharp particle size distribution and free of branching, even by the direct hydrothermal treatment, by mixing ferrous or ferric hydroxide precipitate with aged ferric hydroxide precipitate, and subjecting the mixture to the hydrothermal treatment. CONSTITUTION:Precipitate of ferrous hydroxide or ferric hydroxide is mixed with aged precipitate of ferric hydroxide obtained by aging ferric hydroxide precipitate at room temperature - 70 deg.C for 5-30hr, and the mixture is subjected to the hydrothermal reaction at 100-250 deg.C. The amount of the aged precipitate is >=1/4 equivalent based on the precipitate to be treated hydrothermally. When precipitate of ferrous hydroxide is used as the starting material, it is necessary to carry out the reaction in the presence of an oxidizing agent such as NaClO3, NaNO3, etc. The aged ferric hydroxide precipitate acts as a seed to promote the conversion to goethite, and gives branch-free acicular goethite particles having sharp particle size distribution suitable as a raw material for the preparation of magnetic powder for magnetic recording use. |
