| 摘要 |
PURPOSE: To prepare a magnetic iron oxide pigment, having a film containing cobalt by coating the pigment with a layer of cobalt ferrite or bertholide com pound containing cobalt of specific composition. CONSTITUTION: A magnetic iron oxide core material with a composition of FeOx (here 1.33<x<=1.5) is coated with a compound with composition of COx FII1-x (OH)2 (here, 0<x<=1) by precipitation in alkali metal hydroxide. Then the material is coated with a cobalt compound (II), and further coated with a certain quantity of a cobalt compound (III). A third coating is performed under oxidizing conditions, and a first coating is performed using iron (II) and (III) salts containing 0-67% of Fe (III) content and cobalt salt. The initial coating is performed under oxidizing or inactivating conditions. Therefore, immediately after the second coating or a certain time interval, cobalt (III) is added. The time interval can be extended to the end of this method by slowly and continuously adding cobalt during the third coating. |
