| 摘要 |
PURPOSE:To obtain spherical magnetite granular powder having a high saturation magnetic flux density in a low magnetic field and excellent in dispersibility by adding iron(II) chloride and iron(III) chloride in a specific manner to a mixture solution containing an alkali metal hydroxide, an alkali metal carbonate and Si. CONSTITUTION:The first mixture solution containing an alkali metal hydroxide, an alkali metal carbonate and further silicon in an amount of 0.1-3.0 atomic % to the total iron to be used in a reaction is prepared. The second mixture solution containing iron(II) chloride in an amount of 0.1-5.0 to the total amount of iron(II) salts to be used in molar ratio and an iron(III) chloride in an amount of 1.0-0.5 to the total amount of iron(II) salt in molar ratio is prepared. The second mixture solution is added to the first mixture solution to form seed crystals of magnetite. Thereafter, a solution containing iron(II) chloride in an amount of 0.5-0.95 to the total amount of iron(II) salt to be used in molar ratio is added to the seed solution and pH of the reaction system is adjusted to 9.0-12.5. An oxidizing gas is introduced into this solution, which is heated at 80-100 deg.C, to produce magnetite particles. The objective granular powder is obtained by filtering the magnetite particles, washing with water, drying and pulverizing. |
