| 摘要 |
PURPOSE:To improve the coercive force, inverse magnetic field distribution, aspect ratio, orientational property, magnetic flux density and dispersibility to an org. binder of the above iron oxide by reducing iron oxyhydroxide deposited with an Si compd. and phosphorus compd. on the surface. CONSTITUTION:A suspension contg. the iron oxyhydroxide nucleic crystal obtd. by adding an alkali of the amt. necessary to settle Fe ions by 5 to 50% to a ferrous salt soln. of 30 to 100g/l to partially neutralize the same, then oxidizing the soln. is oxidized wile the alkali is added thereto to allow the nucleic crystal to grow; thereafter, the suspension is filtered to obtain the iron oxyhydroxide. After this iron oxyhydroxide is suspended in water, the pH thereof is adjusted to >=6 and thereafter, water soluble silicate is added at 0.05 to 2wt.% in terms of S, to adjust the pH to <=7 and to deposit the Si compd. thereon. Water soluble phosphoric acid (salt) is then added at 0.05 to 2wt.% in terms of P thereto to deposit the P thereon, following which the suspension is filtered, washed, dried and pulverized to obtain the iron oxyhydroxide powder. This powder is dehydrated at 300 to 800 deg.C in the air and is reduced at 300 to 500 deg.C in hydrogen. |
