| 摘要 |
PROBLEM TO BE SOLVED: To industrially produce powder of spherical hematite particles having 0.40-1.10g/cm3 bulk density and excellent in dispersibility. SOLUTION: An aq. ferrous salt soln. is allowed to react with 0.80-0.99 equiv. alkali hydroxide based on the amt. of Fe<2+> in the soln. at >=75 deg.C and oxygen- contg. gas is blown into the resultant soln. contg. colloidal ferrous hydroxide under heating at 70-100 deg.C to oxidize the ferrous hydroxide. Spherical magnetite particles are then formed by adding >=1.00 equiv. alkali hydroxide based on the amt. of Fe<2+> remaining in the mother liquor under the same conditions as the oxidation conditions. The formed particles are washed, separated by filtration and dried as usual and they are oxidized under heating at 450-700 deg.C in air to obtain the objective spherical hematite particles. |
