MANUFACTURE OF MAGNETIC FINE POWDER

摘要

PURPOSE:To manufacture gamma-ferric oxide particles with satisfactory dispersibility and high coercive force by coating gamma-ferric oxyhydroxide prticles with a specified amount of a specified compound and reducing and oxidizing the coated particles. CONSTITUTION:The surfaces of gamma-ferric oxyhydroxide particles are coated with <0.2wt% of at least 1 kind of compound selected from metallic salts of 6-12C carboxylic acids such as hexylic acid and actylic acid, org. titanium compounds such as diisopropoxy-bis(acetylacetone) titanate and org. boron compounds such as polyoxyethyleneglycerol borate. The coated particles are heated to about 300-430 deg.C in a reducing atmosphere and to about 230-280 deg.C in an oxidizing atmosphere in order. The gamma-ferric oxyhydroxide is preferably manufactured from a ferrous chloride soln. by wet oxidation, and the perferred shape is a needlelike shape having about 0.3-2.0mum length and >= about 6 ratio between length and width.