| 摘要 |
PURPOSE:To obtain the subject grain powder useful as a starting raw material for magnetic grain powder used in magnetic recording by adding spindle-shaped goethite grains which are seed crystals and a prescribed amount of an Si compound to a suspension of ferrous hydroxide and passing an oxygen-containing gas therethrough. CONSTITUTION:Goethite grains assuming a spindle shape having an axial ratio 6:1 as seed crystals are added to a suspension at pH>=11, containing ferrous hydroxide and obtained by reacting a ferrous salt (e.g. ferrous sulfate) with an aqueous alkaline solution. An Si compound (e.g. water glass No. 3) in an amount of 0.2-5.0 atomic % expressed in terms of Si/Fe based on the whole iron are then added, stirred and mixed. An oxygen-containing gas (e.g. air) is subsequently passed therethrough to afford peedlelike goethite grains having a homogeneous grain size, a high axial ratio and a high density of crystallinity without any mixed dendritic grains. |
