US3062727A

US3062727A - Manufacture of niobium by fusion electrolysis

Info

Publication number: US3062727A
Application number: US857254A
Authority: US
Inventors: Pokorny Ernst Adalbert
Original assignee: Societe Generale Metallurgique de Hoboken SA
Current assignee: Societe Generale Metallurgique de Hoboken SA
Priority date: 1958-12-10
Filing date: 1959-12-04
Publication date: 1962-11-06
Anticipated expiration: 1979-11-06

Description

United tates Patent l 3,062,727 MANUFACTURE OF NIOBIUM BY FUSION ELECTROLYSIS Ernst Adalbert Pokorny, London, England, assignor to Societe Generale Metallurgique de Hoboken, Hobokenlez-Anvers, Belgium, a limited company of Belgium No Drawing. Filed Dec. 4, 1959, Ser. No. 857,254 Claims priority, application Great Britain Dec. 10, 1958 3 Claims. (Cl. 204-64) The electrolysis of niobium with fused electrolyte carried out with electrolytes consisting for instance of the double fluoride of potassium and niobium in a mixture with alkali fluorides and chlorides presents great dfliculties in that the cathodic deposit of the metal may contain lower oxides of niobium, and in order to obtain metallic niobium, the electrolytic product has to be substituted to a separate reduction operation, which is rather uneconomical.

It is already known to use alkali metals as additions to the electrolyte in the fusion electrolysis of uranium and other rare metals to prevent oxidation of the metal which is deposited on the cathode in powder or sponge form. The alkali metals are not added to the electrolyte as such but in the forms of their halides, forming during the electrolysis clouds or a fog of metallic alkali within the electrolyte. The alkali metals do not form alloys with the uranium.

The present invention applies to niobium and uses as additions strongly reactive metals, capable of forming an alloy with the niobium, at least to a certain extent. Such metals are chosen in a class consisting of: calcium, magnesium, aluminium, zinc, and rare earth metals. One or several such metals may be used. The additions can be made either in the form of metals, or of their alloys as such, or in the form of those of their compounds which are decomposed during the electrolysis. The additions may be made either before or during or immediately after the end of the electrolysis.

The electrolyte normally used for the electrolysis of niobium has a specific gravity of between 2.3 and 2.7 and therefore the mentioned light metals cannot be easily brought into contact with the niobium in the electrolytic cell. They may be introduced in the form of their alloys with the heavier metals, such as zinc and/or the rare earth metals. It is also possible to add their halides to the electrolyte, the metals being formed by electrolytical decomposition during the electrolysis of the niobium.

The rare earth metals and their alloys are particularly suitable for the purpose because of their high density. Furthermore, they are to a certain limited extent absorbed by the niobium, forming an alloy of improved Patented Nov. 6, 1962 properties, above all of greater resistance to oxidation during subsequent manufacture.

The fusion electrolysis of the rare earth metals is effected under working conditions very similar to those of the fusion electrolysis of niobium, i.e. at 8-12 volts and at a temperature of about 700-900 C. Therefore, instead of adding the rare earth metals as such to the electrolysis, they can be added to the electrolyte in the form of their halides. The rare earth metals are thus deposited electrolytically on the cathode at the same time as the nobium and they react with the cathodic deposit of niobium, in order to reduce the oxides to metal form, at the same time becoming alloyed with the niobium and improving the properties of the latter in various respects.

This can to a certain extent be achieved also with calcium and/or magnesium and/or aluminium as such or in the form of their alloys with heavier metals.

The oxygen-containing reaction products of the rare earth metals or the other metals mentioned, with the oxides of niobium are partly dissolved in the electrolyte, and partly collected at the boundaries between the niobium deposit and the electrolyte. They can be separated from the niobium metal powder by any known chemical method or mechanically by any known ore dressing method.

The following approximate quantities of the various metals added maybe used: for each 100 grams niobium oxide introduced in any form into the electrolyte, an addition of 25.5 g. aluminium is made, or 36 g. magnesium or g. calcium or g. zinc or g. rare earth metals (misch metal) or a proportioned mixture of these metals.

What I claim is:

1. Method for the preparation of metallic niobium which comprises passing a direct electric current through a fused electrolyte bath of a double fluoride of niobium and an alkali metal, said bath containing a member selected from the group consisting of a rare earth metal, a rare earth metal alloy, and a rare earth metal halide, and recovering an alloy of niobium and rare earth metal.

2. The method of claim 1 in which the bath temperaaure is about 700900 C.

3. The method of claim 1 in which the bath contains misch metal.

References Cited in the file of this patent UNITED STATES PATENTS 2,777,809 Kolodney Jan. 15, 1957 2,899,369 Slatin Aug. 11, 1959 2,947,672 Ervin et al. Aug. 2, 1960

Claims

1. METHOD FOR THE PREPARATION OF METALLIC NIOBIUM WHICH COMPRISES PASSING A DIRECT ELECTRIC CURRENT THROUGH A FUSED ELECTROLYTE BATH OF A DOUBLE FLUORIDE OF NIOBIUMIUM AND AN ALKALI METAL, SAID BATH CONTAINING A MEMBER SELECTED FROM THE GROUP CONSISTING OF A RARE EARTH METAL, A RARE EARTH METAL ALLOY, AND A RARE EARTH METAL HALIDE, AND RECOVERING AN ALLOY OF NIOBIUM AND RARE EARTH METAL.