DISCOID FERROMAGNETIC POWDER AND ITS PRODUCTION

摘要

PURPOSE:To obtain the titled magnetic powder excellent in the dispersion properties or the like by inducing discoid alpha-FeOOH which is obtained by subjecting the reaction product of ferric salt and alkali in the presence of oxyalkylamine to the hydrothermal treatment into gamma-Fe2O3 and providing a Co layer on the surface. CONSTITUTION:Ferric salt is allowed to react with alkali in an aq. medium in the presence of oxyalkylamine (e.g. monoethanolamine) to produce ferric hydroxide and discoid alpha-FeOOH is produced by subjecting the slurry of the obtained ferric hydroxide to the hydrothermal treatment. Then the discoid alpha-FeOOH is heat-treated in the nonreductive atmosphere to produce discoid alpha-Fe2O3 and it is reduced in the gaseous reductive atmosphere to produce discoid Fe3O4 and furthermore reoxidized to obtain discoid gamma-Fe2O3. Successively the discoid gamma-Fe2O3 powder is dispersed in a soln. contg. Co salt an alkali aq. soln. is added and the mixture is filtered and dried and thereby the discoid ferromagnetic powder having a Co-contg. layer on the surface of the grain is obtained.