Coating iron oxide particles for magnetic recording

US4400432A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Gunter Buxbaum · Krefeld, DE
• Ingo Pflugmacher · Meerbusch, DE
• Franz Hund · Krefeld, DE
• Volker Hahnkamm · Krefeld, DE
• Peter Woditsch · Krefeld, DE

Key dates

• Filing date: Sep 24, 1981
• Grant date: Aug 23, 1983
• Expiry date: Sep 24, 2001

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10T428/2991
• WIPO field: Audio-visual technology
• WIPO sector: Electrical engineering

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.