The magnetic characteristics of magnetic powder consisting mainly of iron are improved by pre-treating the starting material from which the magnetic powder is prepared by reductions, with an aqueous solution and/or suspension of one member selected from the group consisting of zinc, chromium and copper compounds and mixtures thereof.

Production of magnetic powder

A process for the manufacture of acicular ferromagnetic iron particles by heating a goethite, provided with a shape-stabilizing surface coating, at 250°-450° C. in an atmosphere containing water vapor at a partial pressure of not less than 30 mbar, to give alpha-iron(III) oxide, and reducing this material with hydrogen at 275°-425° C., and the use of the iron particles thus obtained as magnetic material in the production of magnetic recording media.

Manufacture of acicular ferromagnetic iron particles

Acicular metal particles consisting essentially of iron are prepared by reducing α-iron(III) oxide obtained--by dehydration--from acicular iron(III) oxide hydroxide prepared in the presence of phosphate ions and having a shape-stabilizing surface coating.

Preparation of acicular ferromagnetic metal particles consisting essentially of iron

A process for preparing a ferromagnetic alloy powder comprising reducing salts of ferromagnetic metals in an aqueous solution containing an acicular fine powder in the presence of hypophosphite ion is disclosed. The aqueous solution can be subjected to the action of a magnetic field or ultrasonic waves during the reaction if desired, and the rate of the reaction can be increased by the addition to the aqueous solution of a noble metal ion.

Process for preparing ferromagnetic alloy powder

Described is an improved process for producing acicular ferromagnetic metallic particles by the reduction of acicular particles of iron oxide or iron oxide hydrate with a gaseous reducing agent. More specifically, the process concerns the improvement wherein the iron oxide or iron oxide hydrate particles are treated with a specified amount of a phosphorus compound and a compound of cobalt, nickel and/or copper prior to the reduction step.

Process for producing ferromagnetic metallic particles

Iron powder suitable for use as a magnetic recording medium is prepared by first subjecting a finely divided iron oxide or oxyhydrate such as Alpha -Fe203, gamma -Fe203, Alpha -Fe00H, gamma -Fe00H or Fe304 to the action of a 0.002 to 1 molar solution in water of stannous chloride and thereafter reducing the iron oxide or oxyhydrate, preferably in hydrogen, followed by stabilizing the iron powder thus obtained.

Cornelis Johannes Klomp

Papers

Method of preparing a magnetically stable powder consisting mainly of iron for magnetic recording