N_IMIDAZOLYL DERIVATIVES AND MANUFACTURE

摘要

PURPOSE:To produce economically magnetic metallic powder for magnetic recording which has a high apparent density and is balanced in coercive force and magnetic flux density in a short time by covering the surface of needlelike iron oxide or iron oxyhydroxide with a compd. of B and Bi and reducing the same. CONSTITUTION:An aq. soln. prepd. by dissolving a boric acid and an aq. soln. contg. bismuth nitrate are added to the filtered cake of the pulverous powder of needlelike iron oxide or iron oxyhydroxide in such a way that the value of B/Fe attains 0.1-2.4% and the value of Bi/Fe attains 0.01-1.2% and the mixture is kneaded. The mixture is dried at 90-110 deg.C to remove moisture and thereafter the mixture is roughly ground and sized and the powder is charged into a reducing furnace. While reducing gas consisting essentially of H2 is passed through the powder, the powder is reduced at 300-600 deg.C, thereby producing the magnetic powder consisting of the needlelike Fe deposited with the compd. of B and Bi on the surface with the smaller amt. of the H2 to be used. The metallic powder for magnetic recording maintaining the needlelike state as it is and having the balanced coercive force and magnetic flux density is obtd.