Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Patent
1981-09-24
1983-08-23
Robinson, Ellis P.
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
252 6258, 252 6257, 252 6256, 252 6259, 427127, 427128, 428323, 428329, 428333, 428694, 428900, B32B 516, B22F 102, G11B 562, C01G 4902
Patent
active
044004320
ABSTRACT:
In the preparation of highly orientatable needle-shaped ferrimagnetic iron oxide particles by the reduction and reoxidation of needle-shaped particles of hydrated oxide of iron which have been surface treated against sintering the improvement which comprises effecting the surface treatment by applying to the particles of hydrated oxide of iron one layer of oxygen-containing anions and a further layer of polyvalent cations, each layer weighing about 0.02 to 2% by weight of the particle. Advantageously, the polyvalent cation-containing layer is applied between two oxygen-containing anion layers, the oxygen-containing anions used are selected from the group consisting of silicate, phosphate, borate, vanadate, molybdate and tungstate, the polyvalent cations used are selected from the group consisting of aluminum, chromium, manganese, iron and gallium, each layer weighs about 0.1 to 1% of the weight of the particles and before the reduction and reoxidation the surface treated particles of hydrated oxide of iron are tempered at a temperature of about 600.degree. to 900.degree. C.
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Bruce et al., IBM Tech. Bull., vol. 20(5), Oct. 1977, pp. 1971-1972.
Buxbaum Gunter
Hahnkamm Volker
Hund Franz
Pflugmacher Ingo
Woditsch Peter
Bayer Aktiengesellschaft
Robinson Ellis P.
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