| 摘要 |
PURPOSE: To obtain nonmagnetic iron oxide having low light transmissivity and satisfactory electric conductivity and fit for the nonmagnetic layer of a coating type magnetic recording medium by limiting production conditions. CONSTITUTION: This nonmagnetic iron oxide contains 5-45wt.% Mn atoms and has <=0.05μm minor axis size and an acicularity ratio (major axis size/minor axis size) of 2/1 to 15/1. It is produced as follows; a prescribed amt. of an aq. Mn salt soln. is added at the time when 5-100% of Fe (II) is oxidized to Fe (III) when goethite is produced, the oxidation reaction is allowed to proceed further and the resultant aq. goethite slurry is neutralized by adding an alkali equiv. to Mn optionally after a prescribed amt. of an aq. Mn salt soln. is added to the slurry. The formed goethite is then separated by filtration, washed, dried and fired at 250-900 deg.C. |
