Specialized metallurgical processes – compositions for use therei – Processes – Electrothermic processes
Patent
1983-07-25
1984-06-26
Lewis, Michael L.
Specialized metallurgical processes, compositions for use therei
Processes
Electrothermic processes
75 05BA, 148105, H01F 106
Patent
active
044564759
ABSTRACT:
A process for preparing ferromagnetic particles comprising metallic iron as the major component by oxidizing Fe(OH).sub.2 in an aqueous medium adjusted to a pH of not less than 11 with gaseous oxygen to produce particles of .alpha.-FeOOH, optionally followed by dehydration of the .alpha.-FeOOH particles under heating to produce particles of .alpha.-Fe.sub.2 O.sub.3, and reducing the .alpha.-FeOOH or .alpha.-Fe.sub.2 O.sub.3 particles under heating, characterized in that (1) the aqueous medium at the oxidation step comprises at least one metal compound chosen from compounds of alkaline earth metals, zinc and aluminum and (2) the coating of a silicon compound is applied to the .alpha.-FeOOH or .alpha.-Fe.sub.2 O.sub.3 particles before the reduction step, whereby the ferromagnetic particles of metallic iron having enhanced magnetic characteristics are obtained.
REFERENCES:
patent: 4056410 (1977-11-01), Corradi et al.
patent: 4115106 (1978-09-01), Snavely et al.
patent: 4133677 (1979-01-01), Matsuij et al.
patent: 4290799 (1981-09-01), Schroeder et al.
Amemiya Masahiro
Hirai Shigeo
Sueyoshi Toshinobu
Hitachi Maxell Ltd.
Lewis Michael L.
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