The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 06, 1982
Filed:
Mar. 19, 1979
Gunter Buxbaum, Krefeld, DE;
Ingo Pflugmacher, Meerbusch, DE;
Franz Hund, Krefeld, DE;
Volker Hahnkamm, Krefeld, DE;
Peter Woditsch, Krefeld, DE;
Bayer Aktiengesellschaft, Leverkusen, DE;
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.