| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide magnetite particles having sufficiently high electric resistance, excellent in dispersibility and fluidity, excellent in environmental resistance, and excellent especially in the stability of the electric resistance and the like, and to provide a manufacturing method for the magnetite particles. <P>SOLUTION: The residual amount of alkali metals on the surfaces of the magnetite particles is made to be 10-50 ppm to the the whole of the particles. The magnetite particles are manufactured by a wet oxidation method of ferrous hydroxide wherein the ferrous hydroxide is obtained by the neutralization by an alkali hydroxide, and are subjected to a coating treatment wherein the particles are coated with an oxide, a hydroxide or a hydrous oxide of one kind selected from silicon and aluminum or combination thereof, or with a mixture of these oxides. In the manufacturing method, when subjecting the slurry containing the coated magnetite particles to solid-liquid separation and to washing, a treatment using an emulsification disperser is conducted. <P>COPYRIGHT: (C)2004,JPO&NCIPI |
