| 摘要 |
PURPOSE:To provide a granular magnetite particle powder which is provided with a coercive force of 150 to 300Oe, whose heat-resisting property is excellent and whose coloring power is high and to provide a manufacturing method in which the granular magnetite particle powder can be obtained industrially. CONSTITUTION:In a granular magnetitie particle, the particle surface is covered with CoxFe2+yOz (where 0.4<=x<=1.0, x+y=1 and 4.0<=z<=4.3). A granular magnetite particle powder is featured in such a way that the amount of Co in the CoxFe2+yOz is 1 to 6mol% with reference to the total of Fe in the granular magnetite particle. A ferrous salt aqueous solution, a cobalt salt aqueous solution and a hydroxide alkali aqueous solution are added to, and mixed with, a water <dispersed liquid containing the granular magnetite particle powder, a gas containing oxygen is aerated at a temperature of 50 deg.C or higher, and the particle surface of the granular magnetite particle is covered. |
