Process for the preparation of acicular .alpha.-FeOOH for magnet

Details Process for the preparation of acicular .alpha.-FeOOH for magnet Process for the preparation of acicular .alpha.-FeOOH for magnet

1984-12-10

1985-12-24

Cooper, Jack

Chemistry of inorganic compounds

With additive

For stabilizing crystal size or shape

423633, 423634, C01G 4906

Patent

active

045605440

ABSTRACT:
A process for preparing acicular .alpha.-FeOOH by partially neutralizing and then oxidizing a ferrous salt solution in the presence of phosphoric acid or a salt thereof to form seed crystals of .alpha.-FeOOH and optionally further oxidizing said solution while neutralizing said solution with an alkali to grow said seed crystals, wherein pyrophosphoric acid or a salt thereof is used as said phosphoric acid and the seed crystals of .alpha.-FeOOH are formed at a temperature of 50.degree. to 100.degree. C. The .alpha.-FeOOH obtained according to the process of this invention is composed of fine particles and appreciably improved in acicularity and particle size distribution. Also, a magnetic recording medium made from the magnetic iron oxides derived therefrom in a usual way have a low noise characteristic and, are excellent in coercivity and other magnetic properties.

REFERENCES:
patent: 4400432 (1983-08-01), Buxbaum et al.
Richards et al.: "The Relationship of Switching Distribution to Tape Digital Output", J. Appl. Phys., vol. 49(3), 1978, pp. 1819-1820.
Koester et al.: "Switching Field Distribution and A.C. Bias Recording Parameters", IEEE Trans. on Magnetics, vol. MAG-17, No. 6, Nov. 1981, pp. 2505-2552.
Wilson: "Effect of Switching Field Distributions and Coercivity on Magnetic Recording Properties", IEEE Trans. on Mag., vol. MAG-11, No. 5, Sep. 1975, pp. 1200-1202.

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