| 摘要 |
PURPOSE:To obtain maghemite magnetic powder having improved electromagnetic transduction characteristics, by adding a phosphorus compound and a solvent therefor to a needlelike iron oxyhydroxide, removing the solvent while kneading the resultant mixture under heating, dehydrating the needlelike iron oxyhydroxide, and reducing and oxidizing the resultant dehydrated iron oxyhydroxide. CONSTITUTION:A phosphorus compound and a solvent for dissolving the phosphorus compound are added to a needlelike iron oxyhyroxide, and the solvent is then removed while kneading the resultant mixture under heating to incorporate the phosphorus compound in the needlelike iron oxyhydroxide. The resultant needlelike iron oxyhydroxide is then dehydrated, reduced and oxidized to produce maghemite magnetic powder. alpha-FeOOH, beta-FeOOH, gamma-FeOOH, etc. may be cited as the needlelike iron oxyhydroxide. Among them, alpha-FeOOH, having 0.1-0.5mum grain length (major axis) and 10-20 aspect (axial) ratio, and obtained by reacting an aqueous solution of ferrous sulfate with an aqueous solution of sodium hydroxide, blowing an oxidizing gas, e.g. air, thereinto, and filtering and washing the resultant grown crystals is particularly preferably used. |
