Manufacture of acicular ferromagnetic iron particles

US4178171A · kind A · utility

Assignee

• BASF SE

Inventors

• Werner Steck · Ludwigshafen, DE
• Rudolf Brodt · Hirschberg, DE
• Wilhelm Sarnecki · Schifferstadt, DE
• Helmut Jakusch · Bischofswerda, DE
• Manfred Ohlinger · Bischofswerda, DE
• Eberhard Koester · Bischofswerda, DE

Key dates

• Filing date: Mar 20, 1978
• Grant date: Dec 11, 1979
• Expiry date: Mar 20, 1998

Classification

• Technology area (CPC G): Physics
• CPC primary: G11B5/714
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

A process for the manufacture of acicular ferromagnetic iron particles by reducing acicular iron(III) oxide hydroxides which consist of pure synthetic lepidocrocite or a mixture of synthetic goethite and at least 70% by weight of synthetic lepidocrocite. The iron(III) oxide hydroxides used carry, on their surface, an alkaline earth metal cation and an anion of a monobasic, dibasic or tribasic aliphatic carboxylic acid of up to 6 carbon atoms or an organic compound containing at least two groups capable of chelating the alkaline earth metal cation, and are produced in such a way that they consist of at least 70 percent by weight of lepidocrocite and have a length-to-width ratio of not less than 15:1. Reduction of such iron(III) oxide hydroxides gives iron particles with pronounced shape anisotropy, which exhibit both good magnetic properties and a narrow field strength distribution.