| 摘要 |
PURPOSE:To provide acicular crystal alpha-FeOOH which yields a magnetic recording material having excellent magnetic characteristics by controlling the Na content of the alpha-FeOOH obtd. by crystallizing the same from an aq. ferrous salt soln. adjusted to an alkaline region and growing the same in a souring region. CONSTITUTION:An alkali is added to the aq. ferrous chloride soln. such as aq. FeSO4 soln. or aq. FeCl2 soln. to neutralize the soln. and thereafter the soln. is adjusted to the alkaline region. The soln. is heated at the same instant to bud out the crystal of the alpha-FeOOH. Air is then permeated through the aq. soln. to form the souring region and to grow the crystal, by which the acicular crystal alpha-FeOOH is obtd. The alpha-FeOOH is cleaned until the Na content decreases to <=0.1%. The resulted alpha-FeOOH is dried at the temp. at which the shape is retained without collapsion to form alpha-Fe2O3. After the alpha-Fe2O3 is reduced to Fe3O4 in a reducing gas, the crystal is gently oxidized in the air, by which the acicular crystal alpha-Fe2O3 having the excellent magnetic characteristics is obtd. |
