| 摘要 |
PURPOSE:To obtain ferromagnetic iron powder of high quality for magnetic recording by calcining the hematite obtained by dehydrating goethite under a specific condition. CONSTITUTION:The hematite obtained by dehydrating acicular crystal goethite at a temperature below 500 deg.C is calcined in the atmosphere of water vapor concentration of less than 5vol% and at a temperature above 500 deg.C. The acicular crystal goethite is obtained, for example, by mixing ferrous sulfate with surplus caustic soda solution and the blowing oxygen-containing gas. It is more effective to use the acicular crystal goethite which contains accessory constituents synthesized by blowing oxygen-containing gas after adding Cr, Zn, Ni, Si, Mo, Co, etc., constituent except iron, to water solution or ferrous salt of alkaline water solution, in synthesizing goethite. |
