| 摘要 |
PURPOSE:To simplify operation control compared with an oxidation method using O2 and to form an oxidized film on a ferromagnetic metallic powder safely and in a short time by bringing said metallic powder into contact with gaseous mixture of inert gases and steam at a prescribed temp. CONSTITUTION:A ferromagnetic metallic powder which is obtd. by heat decomposition of org. acid salt of said ferromagnetic metal and reduction by reducing gas such as H2 is treated in a following way. Namely, said metallic powder is allowed to contact with a gas which is obtd. by mixing inert gas of >=1 kinds of N2, rare gas, CO2 with 500-5,000vol. ppm steam. In this case, contacting is performed by using bed, fluid bed or the like and its contact temp. is regulated to 150-300 deg.. As a result, formation time of oxidized film for the metallic powder is shortened remarkably to about 30min-6hr compared with a conventional method. Then danger of mixing O2 to H2 using is producing the magnetic metallic powder by erroneous operation is eliminated, and therefore this method is advantageous in prevention of disasters. |
