Magnetic iron oxide pigments and a process for their preparation

Details Magnetic iron oxide pigments and a process for their preparation Magnetic iron oxide pigments and a process for their preparation

1987-08-31

1990-06-12

Yarbrough, Amelia Burgess

Compositions: coating or plastic

Materials or ingredients

Pigment, filler, or aggregate compositions, e.g., stone,...

106480, 428403, C09C 122

Patent

active

049330144

ABSTRACT:
Magnetic iron oxide pigments useful in magnetic signal recordings having a dependence of coercivity on temperature in the temperature range of from 76K to 298K of less than 0.13 kA/mK and having a coercivity on powder compressed to 0.9 g/cm.sup.3 of greater than 51 kA/m are prepared by coating a magnetic iron oxide core material having the composition FeO.sub.x where x is a number from 1.33 to 1.5 in a first step with a compound containing divalent and trivalent iron having a ratio of Fe(III): Fe(II) from 0.01 to less than 2, and then in a second step coating the pre-coated core with a second coating of a cobalt compound.

REFERENCES:
patent: 3931025 (1974-08-01), Woditsch et al.
patent: 4200680 (1975-06-01), Sasazawa et al.
patent: 4267207 (1979-05-01), Sasazawa et al.
patent: 4297395 (1980-01-01), Buxbaum et al.
patent: 4371567 (1983-02-01), Chamard et al.
patent: 4414245 (1982-06-01), Timberlake et al.
patent: 4594267 (1986-06-01), Honma et al.

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