EP0548498B1 - Procédé d'électrolyse de composés de néodyme en milieu fondu - Google Patents

Procédé d'électrolyse de composés de néodyme en milieu fondu Download PDF

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Publication number
EP0548498B1
EP0548498B1 EP92118082A EP92118082A EP0548498B1 EP 0548498 B1 EP0548498 B1 EP 0548498B1 EP 92118082 A EP92118082 A EP 92118082A EP 92118082 A EP92118082 A EP 92118082A EP 0548498 B1 EP0548498 B1 EP 0548498B1
Authority
EP
European Patent Office
Prior art keywords
weight
fluoride
neodymium
melt
magnetite
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.)
Expired - Lifetime
Application number
EP92118082A
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German (de)
English (en)
Other versions
EP0548498A1 (fr
Inventor
Ulrich Dr. Ströder
Jean-Jacques Duruz
Jean-Louis Jorda
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.)
De Nora Deutschland GmbH
Moltech Invent SA
Original Assignee
Heraeus Elektrochemie GmbH
Moltech Invent SA
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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
    • C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
    • C25C3/34—Electrolytic production, recovery or refining of metals by electrolysis of melts of metals not provided for in groups C25C3/02 - C25C3/32

Definitions

  • the invention relates to a process for the electrolysis of a melt containing neodymium oxide, neodymium fluoride, alkali metal fluoride and optionally alkaline earth metal fluoride with one or more anodes immersed in the melt.
  • Both metallic neodymium and neodymium-iron master alloys which are becoming increasingly important as materials for the production of permanent magnet materials, such as neodymium-iron-boron alloys (DE-A1 37 29 361), can be produced by electrolytic ones Reduction of molten salts containing neodymium compounds can be produced, it being possible for the neodymium-iron alloys to be obtained using iron cathodes.
  • JP 2-4994 A1 (Chemical Abstracts Vol.112, 1990, 225539) describes the electrolysis of melts from 65.9% by weight (20 mol%) neodymium fluoride and 34.1% by weight (80 mol%) lithium fluoride or from 2% by weight of neodymium oxide, 64.6% by weight (20 mol%) of neodymium fluoride and 33.4% by weight (80 mol%) of lithium fluoride with carbon anodes and carbon or iron cathodes. To remove the carbon that accumulates on the surface of the molten bath during electrolysis, the melt is electrolyzed in an oxygen-containing atmosphere.
  • EP 0 177 233 B1 also relates to the production of neodymium-iron alloys by melt flow electrolysis.
  • a bath consisting of a melt of 35-76% by weight of neodymium fluoride, 20-60% by weight of lithium fluoride, 0-40% by weight of barium fluoride and 0-20% by weight of calcium fluoride is made under protective gas with at least one carbon anode and at least one Iron cathode is electrolyzed, the neodymium which deposits on the iron cathode reacts with the iron to form an alloy, and the neodymium-iron alloy which is liquid at the bath temperature drips from the cathode into a container underneath.
  • the electrolysis takes place at 770 ° - 950 ° C by applying a direct current to the anode with a current density of 0.05 - 0.60 A / cm2 and to the iron cathode with a current density of 0.50 - 55 A / cm2.
  • the carbon anodes used in these known processes are consumed by oxidation, so that they have to be constantly readjusted and frequently replaced.
  • the consumption of the anodes also enriches both the molten baths and the neodymium-iron alloys that are formed with carbon and the impurities present in the anode material, and oxides and fluorides of the carbon get into the atmosphere surrounding the electrolysis cell.
  • the process is intended to obtain high-purity neodymium and neodymium-iron alloys, as are required for the production of permanent magnet materials.
  • the method which achieves the object is characterized in that magnetite is used as the anode material.
  • the anode material can be applied as a coating on an electrically conductive carrier material, for example iron (EP 0 443 730 A1).
  • anodes made entirely of magnetite can equally well be used.
  • the anodes can be both in compact form and as hollow bodies.
  • the latter proves to be favorable if a possible decomposition or the conversion of the magnetite into less conductive iron oxides is to be prevented.
  • a protective gas can be pressed through the hollow body or - in the case of dense, non-porous magnetite material - a negative or positive pressure can be generated within the hollow body.
  • a protective gas is also used to generate the excess pressure.
  • the process has proven particularly useful when the electrolysis is carried out at a melt temperature between 750 ° C and 1100 ° C and under a protective gas.
  • protective gases which form an inert protective atmosphere and thus prevent undesired reactions of the melt and the electrodes, especially with the atmospheric oxygen.
  • Protective gases suitable for the process according to the invention are, for example, helium, argon and nitrogen.
  • Salt melts suitable for the process consist in particular of 2-5% by weight of neodymium oxide 35-92% by weight of neodymium fluoride, 6-60% by weight of lithium fluoride, 0-40% by weight of barium fluoride and 0-20% by weight of calcium fluoride.
  • Salt melts of 2-4% by weight of neodymium oxide, 78-90% by weight of neodymium fluoride and 8-20% by weight of lithium fluoride are preferred, especially those of 2% by weight of neodymium oxide, 80% by weight of neodymium fluoride and 18% by weight of lithium fluoride.
  • the method can be carried out in electrolysis cells as are known per se for the electrolysis of molten salts containing neodymium compounds, for example in the cells described by E. Morrice et al and in EP 0 177 233 B1.
  • Insoluble cathodes made of heat-resistant (refractory) metals, preferably made of tungsten or molybdenum, or - to obtain the neodymium-iron alloys - consuming cathodes made of iron are suitable for the process.
  • One or more cathodes can be present, which either dip into the melt or are arranged horizontally on the bottom of the electrolytic cell and are then completely covered by the melt.
  • the advantages of the method according to the invention characterized by the use of magnetite instead of the carbon which is consumed as anode material are a simpler mode of operation and a longer operating time since the anodes have to be readjusted less frequently and replaced less frequently.
  • the impurities caused by the carbon anodes are avoided both in the melt and in the alloys obtained and in the exhaust air. Because of their purity, the neodymium-iron alloys produced by the process according to the invention are very well suited for the production of permanent magnet materials.
  • a melt of 2% by weight neodymium oxide, 80% by weight neodymium fluoride and 18% by weight lithium fluoride is prepared and at 980 ° C. under argon at an anode electrolyzed from magnetite and an iron cathode.
  • the current is 55 A, the cell voltage 29 V, the anodic current density 0.8 A / dm2, the cathodic current density 7 A / dm2 and the duration of the electrolysis 2 hours.
  • the alloy dripping from the iron cathode into the container underneath consists of 72% by weight neodymium and 28% by weight iron.

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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)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)

Claims (16)

  1. Procédé pour l'électrolyse d'une masse fondue contenant de l'oxyde de néodyme, du fluorure de néodyme, du fluorure de métal alcalin et éventuellement du fluorure de métal alcalino-terreux avec une ou plusieurs anodes plongeant dans la masse fondue, caractérisé en ce qu'on utilise comme matériau d'anode de la magnétite.
  2. Procédé selon la revendication 1, caractérisé en ce qu'on effectue l'électrolyse à une température de la masse fondue comprise entre 750°C et 1100°C.
  3. Procédé selon la revendication 1 ou 2, caractérisé en ce qu'on effectue l'électrolyse sous un gaz inerte.
  4. Procédé selon l'une quelconque des revendications 1 à 3, caractérisé en ce que la magnétite forme une couverture sur un matériau porteur électriquement conducteur.
  5. Procédé selon l'une quelconque des revendications 1 à 3, caractérisé en ce qu'on utilise une ou plusieurs anodes constituées entièrement de magnétite.
  6. Procédé selon la revendication 5, caractérisé en ce que les anodes en magnétite sont formées comme des corps creux.
  7. Procédé selon la revendication 6, caractérisé en ce qu'on utilise des corps creux en magnétite poreuse.
  8. Procédé selon la revendication 7, caractérisé en ce qu'on comprime un gaz inerte à travers le corps creux.
  9. Procédé selon la revendication 6, caractérisé en ce qu'on utilise des corps creux en magnétite dense, sans porosité.
  10. Procédé selon la revendication 9, caractérisé en ce qu'on produit une dépression dans les corps creux.
  11. Procédé selon la revendication 9, caractérisé en ce qu'on produit dans les corps creux une supression de gaz inerte.
  12. Procédé selon l'une quelconque des revendications 1 à 11, caractérisé en ce qu'on utilise une ou plusieurs cathodes constituées de tungstène ou de molybdène.
  13. Procédé selon l'une quelconque des revendications 1 à 11, caractérisé en ce qu'on utilise une ou plusieurs cathodes en fer plongeant dans la masse fondue.
  14. Procédé selon l'une quelconque des revendications 1 à 13, caractérisé en ce qu'on électrolyse une masse fondue constituée de 2-5 % en poids d'oxyde de néodyme, de 35-92 % en poids de fluorure de néodyme, de 6-60 % en poids de fluorure de lithium, de 0-40 % en poids de fluorure de baryum et de 0-20 % en poids de fluorure de calcium.
  15. Procédé selon la revendication 14, caractérisé en ce qu'on électrolyse une masse fondue constituée de 2-4 % en poids d'oxyde de néodyme, de 78-90 % en poids de fluorure de néodyme et de 8-20 % en poids de fluorure de lithium.
  16. Procédé selon la revendication 15, caractérisé en ce qu'on électrolyse une masse fondue constituée de 2 % en poids d'oxyde de néodyme, de 80 % en poids de fluorure de néodyme et de 18 % en poids de fluorure de lithium.
EP92118082A 1991-12-20 1992-10-22 Procédé d'électrolyse de composés de néodyme en milieu fondu Expired - Lifetime EP0548498B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4142160 1991-12-20
DE4142160A DE4142160C1 (fr) 1991-12-20 1991-12-20

Publications (2)

Publication Number Publication Date
EP0548498A1 EP0548498A1 (fr) 1993-06-30
EP0548498B1 true EP0548498B1 (fr) 1995-09-06

Family

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Family Applications (1)

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EP92118082A Expired - Lifetime EP0548498B1 (fr) 1991-12-20 1992-10-22 Procédé d'électrolyse de composés de néodyme en milieu fondu

Country Status (6)

Country Link
US (1) US5346608A (fr)
EP (1) EP0548498B1 (fr)
JP (1) JP2577172B2 (fr)
AT (1) ATE127539T1 (fr)
AU (1) AU654419B2 (fr)
DE (2) DE4142160C1 (fr)

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4088548A (en) * 1973-05-15 1978-05-09 Townsend Douglas W Electrolytic method and apparatus for refractory metals using a hollow carbon electrode
US4684448A (en) * 1984-10-03 1987-08-04 Sumitomo Light Metal Industries, Ltd. Process of producing neodymium-iron alloy
JPS63166987A (ja) * 1986-12-27 1988-07-11 Asahi Chem Ind Co Ltd 希土類金属の製造方法
FR2614319B1 (fr) * 1987-04-21 1989-06-30 Pechiney Aluminium Procede de preparation d'alliages mere de fer et de neodyme par electrolyse de sels oxygenes en milieu fluorures fondus.
DE3729361A1 (de) * 1987-09-02 1989-03-16 Max Planck Gesellschaft Optimierung der gefuegestruktur des fe-nd-b-basis sintermagneten
GB8804859D0 (en) * 1988-03-01 1988-03-30 Ici Plc Electrode & construction thereof
JP2596976B2 (ja) * 1988-06-22 1997-04-02 昭和電工株式会社 ネオジム又はネオジム合金の製造方法
WO1990001078A1 (fr) * 1988-07-28 1990-02-08 Massachusetts Institute Of Technology Procede et appareil de production de metaux par electrolyse
JPH03229888A (ja) * 1990-02-05 1991-10-11 Tokai Carbon Co Ltd マグネタイト被覆電極の製造方法

Also Published As

Publication number Publication date
DE59203579D1 (de) 1995-10-12
AU3028892A (en) 1993-06-24
JP2577172B2 (ja) 1997-01-29
ATE127539T1 (de) 1995-09-15
DE4142160C1 (fr) 1993-03-11
AU654419B2 (en) 1994-11-03
US5346608A (en) 1994-09-13
EP0548498A1 (fr) 1993-06-30
JPH0688279A (ja) 1994-03-29

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