| 摘要 |
PURPOSE:To manufacture high coercive force magnetic powder with improved coercive force by dispersing ferromagnetic iron oxide powder in water at a weakly alkaline state, adding a Co ion-contg. aqueous soln. to the dispersion, and heating them after adjusting to a specified pH. CONSTITUTION:In a method of manufacturing magnetically stable high coercive force magnetic iron oxide powder by forming a Co-base compound on the surface layer of ferromagnetic iron oxide powder, the ferromagnetic iron oxide powder is dispersed in water at a weakly alkaline pH state such as 8pH. To this dispersion is added a Co ion-contg. aqueous soln., and they are heated after adjusting to >=12pH with an aqueous weak alkali soln. When the ferromagnetic iron oxide powder is dispersed in water, it is required to disperse the powder at a weakly alkaline pH state, and the purpose of this method is not attained at the acidic pH side. An alkaline state up to about 11 pH has the effect of enhancing the coercive force, yet the coercive force begins to lower at >=about 11pH, resulting in a reverse effect. |
