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EP0253841B1 - 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 Download PDF

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Publication number
EP0253841B1
EP0253841B1 EP87900658A EP87900658A EP0253841B1 EP 0253841 B1 EP0253841 B1 EP 0253841B1 EP 87900658 A EP87900658 A EP 87900658A EP 87900658 A EP87900658 A EP 87900658A EP 0253841 B1 EP0253841 B1 EP 0253841B1
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Prior art keywords
metal
bath
electrolysis
process according
voltage
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German (de)
French (fr)
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EP0253841A1 (en
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Marcel Armand
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Pechiney SA
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Pechiney SA
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    • CCHEMISTRY; METALLURGY
    • C25ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25CPROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C5/00Electrolytic production, recovery or refining of metal powders or porous metal masses
    • C25C5/04Electrolytic 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.
  • 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.
  • the fluorine / metal ratio is between 3 and 20. However, preferably, the best results are obtained with the range of values between 6 and 12.
  • 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 supply 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.
  • the easiest to reduce of the alkali 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 which meet the following analysis in ppm:
  • the electrical efficiency is greater than 90%.
  • the electrical efficiency is greater than 85%.
  • 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 1.0 A / cm 2
  • the deposition voltage of Hafnium is 2.2 V. and deposits are obtained in the form of relatively massive dendrites ( cauliflower appearance) with an electrical efficiency greater than 95%.
  • F- ions are introduced into the bath by means of the addition of sodium fluoride for example, so that the fluorine / Hafnium molecular ratio is equal to 12, under the same electrolysis conditions, the voltage of Hafnium deposit goes to 2.90 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:

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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

The disclosed process is characterized in that the electrolysis is conducted in such a way that the voltage of deposition of said transition metal is lower by 0,1 - 0,4 volt than that of the alkaline or alkaline earth metal which is the easiest to reduce. The process may be applied to the production of powders whose sizes range from a few fractions of microns to 200 microns approximately of metals pertaining to the columns IVb, Vb, VIb of the periodic classification such as for example titanium, zirconium, hafnium.

Description

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:

  • 1. on entend par métaux de transition, tout métal appartenant aux collones IVa, Va, Via de la classification périodique des éléments.
  • 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.
In what follows:
  • 1. transition metals are understood to mean any metal belonging to the columns IVa, Va, Via of the periodic table.
  • 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 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.The methods currently used for this purpose are diverse.

On peut citer:

  • à partir des métaux massifs:
  • 1. le procédé par hydruration, broyage et déshydruration.
  • 2. les procédés par fusion à l'arc ou au faisceau d'électrons et pulvérisation par centrifugation. à partir d'un oxyde ou d'un sel:
We can cite:
  • from solid metals:
  • 1. the hydriding, grinding and dehydrating process.
  • 2. the processes by arc or electron beam fusion and sputtering by centrifugation. 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 purété, soit du point de vue granulométrie ou forme des grains.the process by reduction by hydrogen at very high temperature. These processes generally require large, complex and costly 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.

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.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.

En général, dans le bain, le rapport fluor/métal est compris entre 3 et 20. Mais, de préférence, les meilleurs résultats sont obtenus avec la fourchette de valeurs comprise entre 6 et 12.In general, in the bath, the fluorine / metal ratio is between 3 and 20. However, preferably, the best results are obtained with the range of values between 6 and 12.

Les exemples suivants ilustrent l'application du procédé suivant les deux modes décrits ci-dessus.The following examples illustrate the application of the method according to the two modes described above.

Exemple 1Example 1

Cet exemple est relatif au Titane. Dans ce cas, le dispositif anodique comporte en outre un diaphragme qui sépare le bain en deux compartiemnts, un compartiment anodique qui ne contient que des traces 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 supply device.

Le bain est constitué par un mélange équimoléculaire de chlorures de potassium et de sodium fondu à 750°C.The bath consists of an equimolecular mixture of potassium chlorides and sodium molten at 750 ° C.

L'halogénure introduit est le tétrachlorure de titane.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. The easiest to reduce of the alkali , 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 ppm:

Figure imgb0001
The deposits collected on the cathode are in the form of well crystallized dendrites which can reach several centimeters and which meet the following analysis in ppm:
Figure imgb0001

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:

Figure imgb0002
If the titanium content in the cathode compartment is lowered to 0.1%, under the same current density conditions, the deposition voltage of titanium drops to 2.9 V, that of the alkali remains equal to 3 , 2 V and a sort of gray felt is collected at the cathode made up of fine intertwined dendrites which finally gives, 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:
Figure imgb0002

Le rendement électrique est supérieure à 85%.The electrical efficiency is greater than 85%.

Exemple 2Example 2 Cet exemple est relatif au Hafnium.This example relates to Hafnium.

Dans la même cellule que dans l'exemple 1, mais sans diaphragme anodique, toujours avec le bain NaCI/KCI 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-dire avec une densité de courant de 1,0 A/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 un rendement électrique supérieur à 95%.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 1.0 A / cm 2 , the deposition voltage of Hafnium is 2.2 V. and deposits are obtained in the form of relatively massive dendrites ( cauliflower appearance) with an electrical efficiency greater than 95%.

L'analyse de ces dépôts donne les résultats suivants en ppm:

Figure imgb0003
Analysis of these deposits gives the following results in ppm:
Figure imgb0003

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 moléculaire fluor/Hafnium soit égal à 12, dans les mêmes conditions d'électrolyse, la tension de dépôt du Hafnium passe à 2,90 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 ppm:

Figure imgb0004
If F- ions are introduced into the bath by means of the addition of sodium fluoride for example, so that the fluorine / Hafnium molecular ratio is equal to 12, under the same electrolysis conditions, the voltage of Hafnium deposit goes to 2.90 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:
Figure imgb0004

Claims (6)

1. A process for producing powders comprising grains of dimensions of less than 200 pm of transition metals belonging to groups IVa, Va and Via by electrolysis of their halides dissolved in a bath of molten salts based on alkali metal and/or alkaline earth halides, using current densities of between 0.3 and 1.0 A/cm2, characterised by carrying out the electrolysis operation in such a way that the deposit voltage of said transition metal is 0.1 to 0.4 volt below that of the alkali metal or alkaline earth metal which is the easiest to reduce.
2. A process according to claim 1 characterised in that the deposit voltage is 0.2 to 0.3 volt below that of the alkali metal or alkaline earth metal which is the easiest to reduce.
3. A process according to claim 1 characterised in that said voltage is obtained by lowering the amount of metal dissolved in the cathodic bath.
4. A process according to claim 1 characterised in that said voltage is obtained by modifying the complexing of the dissolved metal ions.
5. A process according to claims 1 and 4 characterised in that the bath of salts used is an equimolecular NaCI/KCI mixture which is molten at 750°C, the halide of the metal to be deposited is a chloride, and the complexing agent is fluorine which is introduced into the bath in the form of NaF in an amount such that the fluorine/metal molecular ratio is between 3 and 20.
6. A process according to claim 5 characterised in that the fluorine/metal 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

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

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EP (1) EP0253841B1 (en)
JP (1) JPS63500187A (en)
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DE (1) DE3762890D1 (en)
FR (1) FR2592664B1 (en)
WO (1) WO1987004193A1 (en)

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WO1991001942A1 (en) * 1989-08-01 1991-02-21 Australian Copper Company Pty. Ltd. Production of copper compounds
GB2376241B (en) * 2000-02-22 2004-03-03 Qinetiq Ltd Method for the manufacture of metal foams by electrolytic reduction of porous oxidic preforms
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
US10400305B2 (en) 2016-09-14 2019-09-03 Universal Achemetal Titanium, Llc Method for producing titanium-aluminum-vanadium alloy
RU2763465C2 (en) 2017-01-13 2021-12-29 ЮНИВЕРСАЛ АКЕМЕТАЛ ТИТАНИУМ, ЭлЭлСи TITANIUM LIGATURE FOR ALLOYS BASED ON Ti-Al

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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

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WO1987004193A1 (en) 1987-07-16
EP0253841A1 (en) 1988-01-27
DE3762890D1 (en) 1990-06-28
CA1287814C (en) 1991-08-20
JPH0312156B2 (en) 1991-02-19
JPS63500187A (en) 1988-01-21
US4770750A (en) 1988-09-13
FR2592664B1 (en) 1990-03-30
FR2592664A1 (en) 1987-07-10

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