| 摘要 |
PURPOSE:To obtain ferromagnetic metallic powder for a magnetic recording medium with high coercive force and saturation magnetic flux density suitable especially for high density recording by treating beta- or gamma-FeOOH in an alkali soln. followed by filtration, washing drying and reduction. CONSTITUTION:In an alkali soln. such as a 1-20N aqueous soln. of NaOH beta- or gamma-FeOOH is treated at 30-100 deg.C. The treated material is filtered, washed, and dired. The resulting beta- or gamma-FeOOH is reduced at <=600 deg.C in a hydrongen atmosphere. A gaseous mixture consisting of 1% air and 99% N2 is fed to ferromagnetic metallic powder in the reducing vessel obtd. by the reduction, and the air content of the gaseous mixture is doubled at intervals of about 30min. After the passage 4-5hr the gaseous mixture is changed over to air, and magnetic iron powder is taken out of the reducing vessel. This magnetic iron powder is applicable to a megnetic tape and other magnetic recording medium. |
