| 摘要 |
<p>Black ultrafine magnetite particles having an FeO content of 31 to 35 % and a particle diameter of not more than 0.1 νm; and a process for preparing the same by dispersing ultrafine magnetite particles having a diameter of not more than 0.1 νm in water containing ferrous hydroxyde, ripening the dispersion under the condition of a free alkali content of not less than 1 mol/l (M/l) at 90 to 100 °C, then adding sodium oleate or potassium oleate in an amount of 0.2 to 5 % based on the magnetite particles, and adjusting the pH of the mixture to 5 to 6 to coat the magnetite particles with oleic acid.</p> |
