PURPOSE: To provide a magnetic material with superior dispersibility, magnetic field orientation properties, etc. by adding an alkali to a slurry contg. ferric hydroxide, citric acid (salt) and an alkali cpd. to adjust the slurry to a specified pH value followed by heating at a specified temp.
CONSTITUTION: An alkali such as NaOH is added to a slurry contg. a predetermined amt. of ferric hydroxide, citric acid or its slat, and an alkali cpd. such as NaOH so that the slurry is adjusted to pH10W13 at 25°C. The pH-adjusted slurry is heated to a treatment temp. of 100W250°C and agitated to form needlelike α-Fe2O3, which is then separated by heat reduction or other method to obtain magnetite taking over the needle form of α-Fe2O3. The magnetite may be reoxidized to give γ-Fe2O3 taking over the needle form. The magnetic material for recording obtd. by this method has no pore in the particles and high density, is free from branching, and exhibits superior magnetic characteristics.
GOGURE TADASHI
FUKAI KIYOSHI
NAKATANI SHINYA
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