| 摘要 |
PURPOSE:To eliminate the possibility of ignition during handling in the stage of forming a magnetic recording layer by suspending iron nitride powder into an org. solvent having no acidic group and blowing a gas contg. O2 thereto form an oxide layer on the powder surface. CONSTITUTION:The ferromagnetic powder consisting of Fe3N, Fe4N, etc. of about 0.3mu average grain size obtd. by heating, in a gaseous mixture of H2 and NH3, the-iron component reduced from alpha-Fe2O3 powder by heating in gaseous H2 flow is suspended in a solvent such as hydrocarbon, alcohol, ketone, ester or the like having no acidic group such as COOH, SO3H or the like and having the b.p. in a 40-250 deg.C range for easier drying of solvent after the treatment. The gas contg. O2 (air suffices) is blown thereto to oxideize the surface of the iron nitride powder. The temp. in the stage of blowing is about 10-110 deg.C and the powder is oxidized quickly as the temp. is higher. The surface oxide layer is nonuniform or too thick as the oxidation is too fast. The iron nitride power obtd. in such a way is filtered and vacuum-dried so that the possibility of ignition during handling for the purpose of forming the magnetic layer is eliminated and no adverse influence is given to the electromgnetic characteristics thereof.
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