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 metal particles which essentially consist of iron and carry, on their surface, from 0.02 to 0.6% by weight of boron in the form of a borate, by reducing an acicular iron oxide with a gaseous reducing agent at from 250° to 500° C., wherein a compound selected from the group comprising boron oxyacids and their inorganic salts is precipitated on the said iron oxide before reduction.

Manufacture of ferromagnetic metal particles essentially consisting of iron

A metal powder, suitable for magnetic recording, consisting essentially of iron, the individual particles being acicular and containing on average no more then 5 pores and consisting on average of no more than 2 metal cores is produced by precipitating and oxidizing an aqueous iron-(II)-salt solution to produce finely divided acicular iron-(III)-oxide-hydroxide, stabilizing it as by treatment with cadmium, lead, calcium, magnesium, zinc, aluminum, chromium, tungsten, a phosphorus oxide and/or a boron oxide, converting it into ferromagnetic iron oxide of low pore content, and reducing it to metallic iron with a gaseous reducing agent at about 300° to 600° C.

Ferromagnetic metal pigment essentially consisting of iron and a process for its production

A process for the manufacture of acicular ferromagnetic metal pigments containing iron, having a reduced field strength distribution and a steeper residual magnetization curve, by applying equivalent amounts of an alkaline earth metal cation and of a monobasic, dibasic or tribasic aliphatic carboxylic acid of up to 6 carbon atoms onto appropriate acicular iron oxides and then reducing the treated oxides.

Manufacture of ferromagnetic, acicular metallic iron particles by hydrogen reduction

A method of preparing iron powder for recording in which iron oxide hydrate powder is reduced by flowing hydrogen in intimate contact with the iron oxide hydrate powder, preferrably in a fluidized bed.

Method of preparing ferromagnetic material

A method of preparing a metal powder which consists mainly of iron by reduction of finely divided acicular iron oxide hydrate. The iron oxide hydrate particles are doped with a metal which is catalytic for hydrogen reactions (for example Co, Ni, Ru). The reduction to metal then occurs more rapidly.

J Wegener

Papers

Method of preparing iron powder suitable for magnetic recording