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EP0253841A1 - Process for producing transition metal powders by electrolysis in baths of molten salts. - Google Patents

Process for producing transition metal powders by electrolysis in baths of molten salts.

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Publication number
EP0253841A1
EP0253841A1 EP87900658A EP87900658A EP0253841A1 EP 0253841 A1 EP0253841 A1 EP 0253841A1 EP 87900658 A EP87900658 A EP 87900658A EP 87900658 A EP87900658 A EP 87900658A EP 0253841 A1 EP0253841 A1 EP 0253841A1
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EP
European Patent Office
Prior art keywords
metal
electrolysis
bath
transition metal
baths
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP87900658A
Other languages
German (de)
French (fr)
Other versions
EP0253841B1 (en
Inventor
Marcel Armand
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Pechiney SA
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Pechiney SA
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Publication of EP0253841A1 publication Critical patent/EP0253841A1/en
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Expired - Lifetime legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C5/00—Electrolytic production, recovery or refining of metal powders or porous metal masses
    • C25C5/04—Electrolytic production, recovery or refining of metal powders or porous metal masses from melts

Definitions

  • the present invention relates to the preparation of powders of transition metals by electrolysis of their halides in baths of molten salts.
  • transition metals means any metal belonging to columns IVb, Vb, VIb of the periodic table.
  • powder means a solid substance, finely divided and containing grains ranging in size from a few micron fractions to about 200 microns.
  • the process which is the subject of the present invention consists in an electrolysis of a halide of the metal, in particular of its chloride, dissolved in a bath of molten salts based on alkali and / or alkaline earth halides, carried out under conditions particular.
  • the electrolytic processes, known for these metals lead in fact to deposits of excellent quality from the point of view of purity which are in the form of more or less massive or dendrltic crystals directly usable for melting, but unsuitable for metallurgy powders.
  • the method is characterized in that the electrolysis is carried out so that the deposition voltage of the metal to be obtained in powder form is 0.1 to 0.4 volt lower than that of the easiest alkali or alkaline earth metal to reduce and preferably less than 0.2 to 0.3 volts.
  • E 0 is the normal potential
  • R the constant of ideal gases
  • T the temperature in ° K
  • n the number of electrons exchanged
  • F the number of FARADAY
  • a the activity of metal ions in the solution.
  • Example 1 illustrates the application of the method according to the two modes described above.
  • Example 1 illustrates the application of the method according to the two modes described above.
  • the anode device further comprises a diaphragm which separates the bath into two compartments, an anode compartment which contains only traces of Titanium in solution, and a cathode compartment in which the content of dissolved Titanium is kept constant by a continuous feeding device.
  • the bath consists of an equimolecular mixture of potassium chlorides and sodium molten at 750 ° C.
  • the halide introduced is titanium tetrachloride.
  • the content of titanium dissolved in the bath is 4%.
  • the deposition voltage of titanium measured by drawing the voltage / current curve is 2.15 V., that of the alkali the easiest to reduce, in this case, the sodium is 3.2 V.
  • the deposits collected on the cathode are in the form of well crystallized dendrites which can reach several centimeters and meet the following analysis in ppm
  • the electrical efficiency is greater than 90%.
  • This example relates to Hafnium.
  • the halide introduced this time being hafnium tetrachloride, at the content of 25%, under normal conditions.
  • electrolysis i.e. with a current density of 1.0A / cm2
  • the Hafnium deposition voltage is 2.2 V. and deposits are obtained in the form of relatively massive dendrites (aspect of cauliflower) with an electrical efficiency greater than 95%.
  • the ratio here is equal to 12 but that with other metals with values of this ratio between 3 and 20 can be used; preferably the best results are obtained in the range of values between 6 and 12.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electrolytic Production Of Metals (AREA)
  • Length Measuring Devices By Optical Means (AREA)

Abstract

Ce procédé est caractérisé en ce que l'on conduit l'électrolyse de telle sorte que la tension de dépôt dudit métal de transition soit inférieure de 0,1 à 0,4 volt à celle du métal alcalin ou alcalino-terreux le plus facile à réduire. Il trouve son application dans l'élaboration de poudres de dimensions comprises entre quelques fractions de microns à 200 microns environ de métaux appartenant aux colonnes IVb, Vb, VIb de la classification périodique tels que par exemple le titane, le zirconium, l'hafnium.This process is characterized in that the electrolysis is carried out in such a way that the deposition voltage of said transition metal is 0.1 to 0.4 volts lower than that of the alkali or alkaline earth metal that is easiest to deposit. reduce. It finds its application in the production of powders with dimensions ranging from a few fractions of microns to approximately 200 microns of metals belonging to columns IVb, Vb, VIb of the periodic classification such as for example titanium, zirconium, hafnium.

Description

PROCEDE D'ELABORATION DE POUDRES DE METAUX DE TRANSITION PAR ELECTROLTSE EN BAINS DE SELS FONDUSPROCESS FOR THE PREPARATION OF POWDERS OF TRANSITION METALS BY MELTING SALT BATHS
La présente invention est relative à l'élaboration de poudres des métaux de transition par électrolyse de leurs halogénures en bains de sels fondus.The present invention relates to the preparation of powders of transition metals by electrolysis of their halides in baths of molten salts.
Dans ce qui va suivre:In what follows:
1. on entend par métaux de transition, tout métal appartenant aux colonnes IVb, Vb, VIb de la classification périodique des éléments.1. transition metals means any metal belonging to columns IVb, Vb, VIb of the periodic table.
2. on entend par poudre, une substance solide, finement divisée et comportant des grains de dimension allant de quelques fractions de micron à 200 microns environ.2. powder means a solid substance, finely divided and containing grains ranging in size from a few micron fractions to about 200 microns.
L'application des méthodes de mise en forme de la métallurgie des poudres, en raison des importantes économies de matières qu'elles permettent, suscite le plus haut intérêt pour des métaux coûteux tels que les métaux de transition. La difficulté principale rencontrée pour cette application est celle de l'élaboration de poudres de qualité convenable.The application of powder metallurgy shaping methods, because of the significant material savings which they allow, arouses the greatest interest in expensive metals such as transition metals. The main difficulty encountered for this application is that of developing powders of suitable quality.
Les procédés utilisés actuellement dans ce but sont divers. On peut citer :The methods currently used for this purpose are diverse. We can cite :
- à partir des métaux massifs: 1. le procédé par hydruration, broyage et déshydruration.- from solid metals: 1. the hydriding, grinding and dehydrating process.
2. les procédés par fusion à l'arc ou au faisceau d'électrons et pulvérisation par centrifugation.2. the processes by arc or electron beam fusion and sputtering by centrifugation.
- à partir d'un oxyde ou d'un sel :- from an oxide or a salt:
. le procédé par réduction par hydrogène à très haute température. Ces procédés nécessitent, en général, des installations importantes, complexes et coûteuses: par ailleurs, ils ne conduisent pas toujours à des poudres convenables, soit du point de vue pureté, soit du point de vue granulométrie ou forme des grains. Le procédé, objet de la présente invention, consiste en une électrolyse d'un halogénure du métal, en particulier de son chlorure, dissous dans un bain de sels fondus à base d'halogénures alcalins et/ou alcalino-terreux, effectuée dans des conditions particulières. Les procédés électrolytiques, connus pour ces métaux, conduisent en effet à des dépôts d'excellente qualité du point de vue pureté qui se présentent sous forme de cristaux plus ou moins massifs ou dendrltiques directement utilisables en vue de la fusion, mais impropres à la métallurgie des poudres. On a proposé d'obtenir des formes plus divisées, en augmentant fortement la densité de courant sur les cathodes de dépôt, nais dans ces conditions, l'adhérence du métal sur les cathodes est très mauvaise sinon nulle, et les produits obtenus se détachent et se dispersent dans le bains où ils perturbent la marche de l'électrolyse et sont difficiles è récupérer. Le demandeur a découvert qu'il était possible d'éviter cet écueil, tout en utilisant des densités de courant classiques (0,3-1,0 A/cm2) et d'obtenir des dépôts pulvérulents et suffisaαnent adhérents pour pouvoir être extraits avec les cathodes. Le procédé est caractérisé en ce que l'on conduit l'électrolyse de sorte que la tension de dépôt du métal à obtenir en poudre soit inférieure de 0,1 à 0,4 volt à celle du métal alcalin ou alcalino-terreux le plus facile à réduire et de préférence inférieure de 0,2 à 0,3 volt. On sait que le potentiel de dépôt E d'un métal à partir de la solution d'un de ses sels est donné par la loi de NERNST : dans laquelle E0 est le potentiel normal, R: la constante des gaz parfaits, T: la température en °K, n: le nombre d'électrons échangés, F: le nombre de FARADAY et a:l'activité des ions du métal dans la solution.. the process by reduction by hydrogen at very high temperature. These processes generally require large, complex and expensive installations: moreover, they do not always lead to suitable powders, either from the purity point of view, or from the particle size or grain form point of view. The process which is the subject of the present invention consists in an electrolysis of a halide of the metal, in particular of its chloride, dissolved in a bath of molten salts based on alkali and / or alkaline earth halides, carried out under conditions particular. The electrolytic processes, known for these metals, lead in fact to deposits of excellent quality from the point of view of purity which are in the form of more or less massive or dendrltic crystals directly usable for melting, but unsuitable for metallurgy powders. It has been proposed to obtain more divided forms, by greatly increasing the current density on the deposition cathodes, born under these conditions, the adhesion of the metal to the cathodes is very poor if not zero, and the products obtained detach and disperse in the bath where they disturb the progress of electrolysis and are difficult to recover. The applicant has discovered that it was possible to avoid this pitfall, while using conventional current densities (0.3-1.0 A / cm2) and to obtain pulverulent and sufficiently adherent deposits to be able to be extracted with cathodes. The method is characterized in that the electrolysis is carried out so that the deposition voltage of the metal to be obtained in powder form is 0.1 to 0.4 volt lower than that of the easiest alkali or alkaline earth metal to reduce and preferably less than 0.2 to 0.3 volts. We know that the deposit potential E of a metal from the solution of one of its salts is given by NERNST's law: in which E 0 is the normal potential, R: the constant of ideal gases, T: the temperature in ° K, n: the number of electrons exchanged, F: the number of FARADAY and a: the activity of metal ions in the solution.
On voit clairement sur cette relation qu'il y adeux façons de modifier E, soit en agissant sur a, c'est-à-dire sur la concentration, soit en agisssant sur E0 en modifiant l'état de complexation des ions Les études entreprises pour la mise au point de l'invention ont été effectuées dans une cellule comportant, d'une part une cuve métallique contenant le bain fondu, d'autre part un couvercle également métallique assurant l'étanchéité du système et présentant divers orifices permettant, entre autre, le passage étanche et isolé des dispositifs anodiques et cathodiques plongeant dans le bain, l'alimentation de ce bain en halogénure du métal à produire et l'extraction de l'halogène dégagé à l'anode.We can clearly see on this relation that there are two ways to modify E, either by acting on a, that is to say on the concentration, or by acting on E 0 by modifying the state of complexation of the ions. The studies undertaken for the development of the invention were carried out in a cell comprising, on the one hand a metal tank containing the molten bath, on the other hand a also metallic cover ensuring the sealing of the system and having various orifices allowing, among other things, the sealed and isolated passage of the anode and cathode devices immersed in the bath, the supply of this bath with the halide of the metal to be produced and the extraction of the halogen released at the anode.
Les exemples suivants illustrent l'application dû procédé suivant les deux modes décrits ci-dessus. Exemple 1.The following examples illustrate the application of the method according to the two modes described above. Example 1.
Cet exemple est relatif au Titane. Dans ce cas, le dispositif anodique comporte en outre un diaphragme qui sépare le bain en deux compartiments, un compartiment anodique qui ne contient que des tracés de Titane en solution, et un compartiment cathodique dans lequel la teneur en Titane dissous est maintenue constante grâce à un dispositif d'alimentation continue.This example relates to Titanium. In this case, the anode device further comprises a diaphragm which separates the bath into two compartments, an anode compartment which contains only traces of Titanium in solution, and a cathode compartment in which the content of dissolved Titanium is kept constant by a continuous feeding device.
Le bain est constitué par un mélange équimoléculaire de chlorures de potassium et de sodium fondu à 750°C. L'halogénure introduit est le tétrachlorure de titane.The bath consists of an equimolecular mixture of potassium chlorides and sodium molten at 750 ° C. The halide introduced is titanium tetrachloride.
Dans les conditions habituelles d'électrolyse, la teneur en titane dissous dans le bain est de 4%.Under the usual electrolysis conditions, the content of titanium dissolved in the bath is 4%.
Avec une densité de courant cathodique initiale de 1,0 A/cm2, la tension de dépôt du titane, mesurée par tracé de la courbe tension/ courant est de 2,15 V., celle de l'alcalin le plus facile à réduire, en l'occurence, le sodium, est de 3,2 V.With an initial cathodic current density of 1.0 A / cm 2, the deposition voltage of titanium, measured by drawing the voltage / current curve is 2.15 V., that of the alkali the easiest to reduce, in this case, the sodium is 3.2 V.
Les dépôts recueillis sur la cathode se présentent sous forme de dendrites bien cristallisées pouvant atteindre plusieurs centimètres et répondant à l'analyse suivante en ppmThe deposits collected on the cathode are in the form of well crystallized dendrites which can reach several centimeters and meet the following analysis in ppm
0 Al Fe Cu Mn Si Sn V Y Mo solde Ti 380 <50 77 <20 <50 <100 <100 <50 <50 <100 Al Fe Cu Mn Si Sn V Y Mo balance Ti 380 <50 77 <20 <50 <100 <100 <50 <50 <10
Le rendement électrique est supérieur à 90%.The electrical efficiency is greater than 90%.
Si l'on abaisse la teneur en titane dans le compartiment cathodique à 0,1%, dans les mêmes conditions de densité de courant, la tension de dépôt du titane passe à 2,9 V. celle de l'alcalin restant égale à 3,2 V. et l'on recueille à la cathode une sorte de feutre gris constitué de fines dendrites entremêlées qui donne finalement après lavage à l'eau une poudre passant pratiquement entièrement au tamis de 100 microns d'ouverture de maille et répondant à l'analyse suivante en ppm O Al Fe Cu Mn Si Sn V Y Mo Solde Ti 700 <50 130 <20 95 <100 <100<50 <50 <10 Le rendement électrique est supérieur à 85%. Exemple 2.If the titanium content in the cathode compartment is lowered to 0.1%, under the same current density conditions, the deposition voltage of titanium becomes 2.9 V. that of the alkali remaining equal to 3 , 2 V. and we collect at the cathode a kind of gray felt made up of fine intertwined dendrites which gives finally after washing with water a powder passing almost entirely through a sieve of 100 microns of mesh opening and responding to the following analysis in ppm O Al Fe Cu Mn Si Sn VY Mo Balance Ti 700 <50 130 <20 95 <100 < 100 <50 <50 <10 The electrical efficiency is greater than 85%. Example 2.
Cet exemple est relatif au Hafnium. Dans la même cellule que dans l'exemple 1, mais sans diaphragme anodique, toujours avec le bain NaCl/KCl équimoléculaire, l'halogénure introduit étant cette fois le tétrachlorure de hafnium, à la teneur de 25%, dans les conditions normales d'électrolyse, c'est-à-dice avec une densité de courant de 1,0A/cm2, la tension de dépôt du Hafnium est de 2,2 V. et l'on obtient des dépôts sous forme de dendrites relativement massives (aspect de chou-fleur) avec an rendement électrique supérieur à 95%.This example relates to Hafnium. In the same cell as in Example 1, but without an anode diaphragm, still with the equimolecular NaCl / KCl bath, the halide introduced this time being hafnium tetrachloride, at the content of 25%, under normal conditions. electrolysis, i.e. with a current density of 1.0A / cm2, the Hafnium deposition voltage is 2.2 V. and deposits are obtained in the form of relatively massive dendrites (aspect of cauliflower) with an electrical efficiency greater than 95%.
L'analyse de ces dépôts donne les résultats suivants en ppm C N O Al B Cr Cu Fe Mn Si Ti V W Solde Hf <10 <10 250 39 2,427 <10 <20 36 <25 <10 <10 <15The analysis of these deposits gives the following results in ppm C N O Al B Cr Cu Fe Mn Si Ti V W Balance Hf <10 <10 250 39 2,427 <10 <20 36 <25 <10 <10 <15
Si l'on introduit dans le bain des ions F- au moyen d'une addition de fluorure de sodium par exemple, de sorte que le rapport moléαulaire soit égal à 12, dans les mêmes conditions d'électrolyse, la tension de dépôt du Hafnium passe à 2,9 V. et l'on obtient après lavage du dépôt, une poudre passant pratiquement entièrement au tamis de 200 microns d'ouverture et répondant à l'analyse suivante en ppmIf F- ions are introduced into the bath by means of the addition of sodium fluoride for example, so that the molecular ratio is equal to 12, under the same electrolysis conditions, the Hafnium deposition voltage goes to 2.9 V. and after washing the deposit, a powder is obtained which passes almost entirely through a sieve of 200 microns opening and which meets the following analysis in ppm
C N O Al B Cr Cu Fe Mn Si Ti V W Solde HfC N O Al B Cr Cu Fe Mn Si Ti V W Balance Hf
12 <10 290 68 2,7 20 11 <20 16 <25 <10 <10 <1012 <10 290 68 2.7 20 11 <20 16 <25 <10 <10 <10
Il est à noter que le rapport est ici égal à 12 mais qu'avec d'autres métaux des valeurs de ce rapport comprises entre 3 et 20 peuvent être utilisées; de préférence les meilleurs résultats sont obtenus dans la fourchette de valeurs comprises entre 6 et 12. It should be noted that the ratio here is equal to 12 but that with other metals with values of this ratio between 3 and 20 can be used; preferably the best results are obtained in the range of values between 6 and 12.

Claims

REVENDICATIONS
1. Procédé d'élaboration de poudres de métaux de transition par électrolyse de leurs halogénures dissous dans un bain de sels fondus à base d'halogénures alcalins et/ou alcalino-terreux, caractérisé en ce que l'on conduit l'électrolyse de telle sorte que la tension de dépôt dudit métal de transition soit inférieure de 0,1 à 0,4 volt à celle du métal alcalin ou alcalino-terreux le plus facile à réduire1. Process for the preparation of transition metal powders by electrolysis of their halides dissolved in a bath of molten salts based on alkali and / or alkaline earth halides, characterized in that the electrolysis of such is carried out so that the deposition voltage of said transition metal is 0.1 to 0.4 volts lower than that of the easiest to reduce alkali or alkaline earth metal
2. Procédé selon la revendication 1, caractérisé en ce que la tension de dépôt est inférieure de 0,2 à 0,3 volt.2. Method according to claim 1, characterized in that the deposition voltage is 0.2 to 0.3 volts lower.
3. Procédé selon la revendication 1, caractérisé en ce que l'on obtient cette tension par abaissement de la teneur en métal dissous dans le bain cathodique.3. Method according to claim 1, characterized in that this voltage is obtained by lowering the content of dissolved metal in the cathode bath.
4. Procédé selon la revendication 1, caractérisé en ce que l'on obtient cette tension par modification de la complexation des ions du métal dissous.4. Method according to claim 1, characterized in that this tension is obtained by modification of the complexation of the ions of the dissolved metal.
5. Procédé selon les revendications 1 et 3, caractérisé en ce que le bain de sels utilisé est un mélange équimoléculaire NaCl/KCl fondu à 750º C et l'halogénure du métal à déposer est un chlorure.5. Method according to claims 1 and 3, characterized in that the salt bath used is an equimolecular mixture NaCl / KCl molten at 750º C and the halide of the metal to be deposited is a chloride.
6. Procédé selon les revendications 1 et 4, caractérisé en ce que le bain de sels utilisé est un mélange équimoléculaire NcCl/KCl fondu à 750° C, l'halogénure du métal à déposer est un chlorure, l'agent complexant est le fluor introduit dans le bain sous forme de NaF en quantité telle que le rapport moléculaire soit compris entre 6 et 12. 6. Method according to claims 1 and 4, characterized in that the salt bath used is an equimolecular mixture NcCl / KCl melted at 750 ° C, the halide of the metal to be deposited is a chloride, the complexing agent is fluorine introduced into the bath in the form of NaF in an amount such that the molecular ratio is between 6 and 12.
EP87900658A 1986-01-06 1987-01-05 Process for producing transition metal powders by electrolysis in baths of molten salts Expired - Lifetime EP0253841B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8600390A FR2592664B1 (en) 1986-01-06 1986-01-06 PROCESS FOR THE PREPARATION OF TRANSITION METAL POWDERS BY ELECTROLYSIS IN MOLTEN SALT BATHS
FR8600390 1986-01-06

Publications (2)

Publication Number Publication Date
EP0253841A1 true EP0253841A1 (en) 1988-01-27
EP0253841B1 EP0253841B1 (en) 1990-05-23

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EP87900658A Expired - Lifetime EP0253841B1 (en) 1986-01-06 1987-01-05 Process for producing transition metal powders by electrolysis in baths of molten salts

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US (1) US4770750A (en)
EP (1) EP0253841B1 (en)
JP (1) JPS63500187A (en)
CA (1) CA1287814C (en)
DE (1) DE3762890D1 (en)
FR (1) FR2592664B1 (en)
WO (1) WO1987004193A1 (en)

Cited By (1)

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Publication number Priority date Publication date Assignee Title
WO1991001942A1 (en) * 1989-08-01 1991-02-21 Australian Copper Company Pty. Ltd. Production of copper compounds

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Publication number Priority date Publication date Assignee Title
DE60130322T2 (en) * 2000-02-22 2008-06-12 Metalysis Ltd., Wath-Upon-Dearne METHOD OF PREPARING METAL FOAM BY ELECTROLYTIC REDUCTION OF POROUS OXIDIC PREPARATIONS
WO2005111272A1 (en) * 2004-04-06 2005-11-24 Iox Co., Ltd. Process for producing microparticles by plasma-induced electrolysis
PL377451A1 (en) * 2005-10-05 2007-04-16 Instytut Wysokich Ciśnień PAN Methods of reaction leading, chemical reactor
EP2794943B8 (en) 2011-12-22 2019-07-10 Universal Achemetal Titanium, LLC A method for extraction and refining of titanium
WO2018125322A1 (en) 2016-09-14 2018-07-05 Universal Technical Resource Services, Inc. A method for producing titanium-aluminum-vanadium alloy
CA3049769C (en) 2017-01-13 2023-11-21 Universal Achemetal Titanium, Llc Titanium master alloy for titanium-aluminum based alloys

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US2951021A (en) * 1952-03-28 1960-08-30 Nat Res Corp Electrolytic production of titanium
GB736567A (en) * 1952-07-03 1955-09-07 Horizons Titanium Corp Improvements in production of metallic titanium
FR1265427A (en) * 1960-06-03 1961-06-30 Ciba Geigy Process for the electrolytic production of the metals niobium and tantalum

Non-Patent Citations (1)

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Title
See references of WO8704193A1 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1991001942A1 (en) * 1989-08-01 1991-02-21 Australian Copper Company Pty. Ltd. Production of copper compounds

Also Published As

Publication number Publication date
FR2592664A1 (en) 1987-07-10
CA1287814C (en) 1991-08-20
FR2592664B1 (en) 1990-03-30
US4770750A (en) 1988-09-13
DE3762890D1 (en) 1990-06-28
JPS63500187A (en) 1988-01-21
JPH0312156B2 (en) 1991-02-19
EP0253841B1 (en) 1990-05-23
WO1987004193A1 (en) 1987-07-16

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