| abstract |
PURPOSE: To industrially produce needle-like iron oxide particle powder having uniform particle size, a large axial ratio (major axis/minor axis) and excellent coercive force distribution, not containing dendritic particles. n CONSTITUTION: An oxygen-containing gas is introduced into an aqueous reactional solution of ferrous salt and <equivalent an alkali aqueous solution less than equivalent thereto to form needle-like goethite nuclear particles. Then the ferrous salt reactional solution containing the needle-like goethite nuclear particles is mixed with ≥equivalent, based on Fe 2- in the ferrous salt reaction solution, of an aqueous solution of alkali carbonate, an oxygen-containing gas is introduced into the solution and the nuclear particles are grown to form needle-like goethite particles. Then the needle-like goethie particles are reduced to give magnetite particles or, optionally further, the magnetite particles are oxidized to give needle-like maghemite particles or optionally both the particles are modified with Co to give the objective needle-like iron oxide particle powder. n COPYRIGHT: (C)1992,JPO&Japio |