SPINDLE-LIKE HEMATITE PARTICLE AND ITS PRODUCTION AND SPINDLE-LIKE METAL MAGNETIC PARTICLE CONTAINING IRON AS MAIN COMPONENT AND OBTAINED FROM THE HEMATITE PARTICLE AS STARTING RAM MATERIAL AND ITS PRODUCTION

摘要

PROBLEM TO BE SOLVED: To obtain a spindle-like metal magnetic particles from hematite particles as a starting raw material. ;SOLUTION: The spindle-like hematite particles have an average major axis diameter of 0.05-1.0μm and an X-ray crystal particle diameter ratio D₁₀₄/D₁₁₀ of 0.20-0.65. The spindle-like hematite particles are obtained by reacting a ferrous salt aqueous solution with a mixed alkali aqueous solution comprising an alkali carbonate and an alkali hydroxide, aging the obtained aqueous suspension containing the ferrous salt-containing precipitates, aerating the suspension to produce seed crystal particles, adding the mixed alkali solution and the ferrous salt aqueous solution, mixing, aerating to grow the surfaces of the seed crystal particles, treating the produced spindle-like geothite particles with a sintering-preventing agent, and subsequently thermally dehydrating the treated particles. Therein, Co and Al are added in amounts of 0.5-25 atom % and 0.5-15 atom % in the production reaction time and in the growth reaction time, respectively, and a rate earth element as the sintering-preventing agent is added in an amount of 0.5-15 atom %. The thermal dehydration is carried out at 400-850°C.;COPYRIGHT: (C)1998,JPO