| 摘要 |
PURPOSE:To produce fusiform or rod-like alpha-ferric oxide particle free from void and suitable as magnetic powder, etc., by heating an alkaline aqueous solution of amorphous ferric hydroxide in the presence of an organic phosphonic acid or hydroxycarboxylic acid. CONSTITUTION:An aqueous suspension of amorphous ferric hydroxide is alkalinized with an alkali, added with 10<-5>-5X10<-3>mol (based on 1g-atom of Fe) of an additive selected from an organic phosphonic acid [e.g. aminotri (methylenephosphonic acid), methylenediphosphonic acid, etc.] and a hydroxycarboxylic acid (e.g. citric acid, tartaric acid, etc.), and heated at about 100-250 deg.C. The produced red precipitate is separated by filtration, washed with water, and dried to obtain fusiform or rod-like alpha-ferric oxide particle having an aspect ratio of 1-3 and a major diameter of <=1mum, and free from void. |
