Minnesota Mining and Manufacturing Company

Gerald G Endres

Albena V Blagev

Jean A Lown

Spindle-shaped goethite particles are produced by oxidizing a ferrous carbonate intermediate in the presence of a growth modifier, or alternatively by changing the flowrate of oxidizing gas during oxidation. The goethite particles thus produced have a narrow size distribution, high aspect ratio and are substantially dendrite-free. These properties make the inventive goethite particles suitable for use in preparation of high density magnetic recording media.

Process for making goethite

This invention provides a method of producing goethite particles comprising the steps of a) reacting, in aqueous solution, less than a stoichiometric amount of an alkali compound with an iron (II) salt to form a precipitated complex intermediate, b) oxidizing iron (II) in the complex intermediate to iron (III) at an average rate less than 10 g iron(III)/l/hr to form goethite seed particles until 20 to 70% of iron (II) in the precipitated complex intermediate has been converted to iron (III), and c) after 20 to 70% of iron (II) in the precipitated complex intermediate has been convened to iron (III), increasing the average oxidation rate to greater than 10 g iron(III)/l/hr.

Growing community of inventors

Hastings, MN, United States of America

Gerald G Endres