| 摘要 |
PURPOSE:To reduce extremely the deterioration of the magnetic characteristics of needlelike magnetic metallic iron powder due to oxidation in the air by doping iron oxyhydroxide with a metal having relatively high weather resistance other than Fe while providing a concn. gradient. CONSTITUTION:Iron oxyhydroxide is doped with one or more among Cr, Mn, Co, Ni, Cu and Zn while providing a concn. gradient so that the amount of the metals contained in the particles of the iron oxyhydroxide is increased from the centers toward the outsides, and the doped iron oxyhydroxide is reduced at 300-600 deg.C as a starting material. A very small amount of said metals is added in the early stage of a reaction for forming iron oxyhydroxide, and the amount is increased in accordance with the growth of iron oxyhydroxide crystals. Iron oxyhydroxide having a high length/width ratio can be manufactured without making the particles excessively fine. |
