| 摘要 |
PURPOSE:To facilitate controlling the diameter of fine particles of a ferromagnetic substance and to improve their dispersion properties independently by a method wherein an amount to be added of a surface-active agent in a first adsorption process is set to be less than 100% of a covering rate on the surface of the fine particle of the ferromagnetic substance and a surface-active agent in a second adsorption process is added in an aqueous phase. CONSTITUTION:A first ionic surface-active agent whose dispersion property is lower than that of a second surface-active agent is used intentionally; alternatively, when the first ionic surface-active agent whose dispersion property is equal to that of the second surface-active agent is used, an amount to be added is reduced and a covering rate is lowered. In addition, when the second ionic surface-active agent is used in an aqueous phase, the ionic surface-active agent is not adsorbed simply physically to the surface of a fine particle of a ferromagnetic substance in a part which has not been covered with the first surface-active agent; polar radicals of both agents can be bonded firmly and irreversibly. By this setup, a control operation of the fine particle of the ferromagnetic substance can be executed easily and independently of an enhancement of the dispersion property. |
