EP0695371A1 - Micropyretically-produced components of aluminium production cells - Google Patents
Micropyretically-produced components of aluminium production cellsInfo
- Publication number
- EP0695371A1 EP0695371A1 EP93910631A EP93910631A EP0695371A1 EP 0695371 A1 EP0695371 A1 EP 0695371A1 EP 93910631 A EP93910631 A EP 93910631A EP 93910631 A EP93910631 A EP 93910631A EP 0695371 A1 EP0695371 A1 EP 0695371A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- cerium
- nickel
- aluminium
- weight
- particulate
- 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
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/23—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces involving a self-propagating high-temperature synthesis or reaction sintering step
-
- 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
- C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
- C25C3/08—Cell construction, e.g. bottoms, walls, cathodes
-
- 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
- C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
- C25C3/08—Cell construction, e.g. bottoms, walls, cathodes
- C25C3/12—Anodes
Definitions
- This invention relates to components of aluminiu production cells made of composite materials comprisin ordered aluminide compounds of nickel, iron and/or titanium, for use in particular as anodes and cathodes and cel linings in aluminium production cells containing a fluoride based molten electrolyte containing dissolved alumina an cerium species.
- the invention is more particularly concerned with th production of components of aluminium production cells mad of composite materials comprising ordered aluminid compounds of nickel, iron and/or titanium, by th micropyretic reaction of a mixture of reactive powders, which reaction mixture when ignited undergoes a micropyreti reaction to produce a net-shaped reaction product, it bein understood that the reaction product may be used directly a an anode or cathode, or as substrate carrying an oute protective coating, or as a cell component.
- US Patent N° 4,614,569 describes anodes for aluminium production coated with a protective coating of ceriu oxyfluoride, formed in-sit u in the cell or pre-applied, thi coating being maintained by the addition of cerium to th molten cryolite electrolyte.
- cerium in th substrate was proposed to promote formation of the ceriu oxyfluoride coating and enhance its properties, but so fa no practical way was found ' to effectively implement this.
- US Patent N° 4,948,676 describes a ceramic/metal composite material for use as an anode for aluminium production particularly when coated with a protective cerium oxyfluoride based coating, comprising mixed oxides of cerium and one or more of aluminium, nickel, iron and copper in the form of a skeleton of interconnected ceramic oxide grains interwoven with a metallic network of an alloy or an intermetallic compound of cerium and one or more of aluminium, nickel, iron and copper.
- the production methods included reactive sintering, reactive hot-pressing and reactive plasma spraying of a metal powder mix optionally including some oxides.
- the described process conditions led to a complex porous microstructure which through dissolution and redeposition of cerium provided a self-healing effect when the anode is first used. However, difficulties were encountered in controlling the porosity of this microstructure .
- US Patent N° 4,909,842 discloses the production of dense, finely grained composite materials with ceramic and metallic phases by self-propagating high temperature synthesis (SHS) with the application of mechanical pressure during or immediately after the SHS reaction.
- the ceramic phase may be carbides or borides of titanium, zirconium, hafnium, tantalum or niobium, silicon carbide or boron carbide.
- the intermetallic phase may be aluminides of nickel, titanium or copper, titanium nickelides, titanium ferrites or cobalt titanides, ' and the metallic phase may include aluminium, copper, nickel, iron or cobalt.
- the final product which has ceramic grains in an intermetallic and/or metallic matrix, has a density of at least about 95% of the theoretical density obtained by the application of pressure. Interconnected porosity is not obtained, nor does the process control porosity. Because the pressure is applied uniaxially, it is not possible to produce a net-shaped article, i.e. whose final shape and dimensions may be largely or even completely achieved in the manufacturing process, and for which no or only minor post manufacturing processing such as grinding are required. Also, the required application of pressure prevents high production rates. Moreover, materials produced by the described method but without the application of pressure are weak and have a porosity of about 45 to 48%, which makes them unsuitable as electrodes for aluminium production.
- PCT patent application WO/13977 describes the production of ceramic or ceramic-metal electrodes for electrochemical processes, in particular for aluminium production, by combustion synthesis of particulate or fibrous reactants with particulate or fibrous fillers and binders .
- the reactants included aluminium usually with titanium and boron; the binders included copper and aluminium; the fillers included various oxides, nitrides, borides, carbides and suicides.
- the described composites included copper/aluminium oxide-titanium diboride etc. This method has prospects of improved process control leading to a better microstructure, but the compositions are still in need of improvement .
- PCT patent application WO/92/22682 describes an improvement of the just mentioned production method with specific fillers.
- the described reactants included an aluminium nickel mixture, and the binder could be a metal mixture including aluminium, nickel and up to 5 weight% copper.
- the many combinations covered is a combination of 85-90 weight% nickel-aluminium-copper with 10-15 weight% of cerium oxide.
- such combinations are very reactive and the described method does not provide details as to how to control the microstructure.
- Co-pending application SN 07/861,513 discloses the production of a protective refractory coating on carbonaceous and other substrates by applying to the substrate a micropyretic reaction layer from a slurry containing particulate reactants in a colloidal carrier, and initiating a micropyretic reaction.
- This application is H specially concerned with the production of refractory borides coatings suitable for cathodic applications.
- the invention provides a method of manufacturing components of aluminium production cells made of composite materials comprising ordered aluminide compounds of nickel, iron and/or titanium, for use in particular as anodes and cathodes and cell linings in aluminium production cells containing a fluoride-based molten electrolyte containing dissolved alumina and cerium species, by micropyretic reaction of a reaction mixture comprising reactants which react to produce the aluminide-based composite material, which reaction mixture when ignited undergoes a micropyretic reaction.
- the reaction mixture is mixed with a cerium-based colloidal carrier, dried and compacted into a reaction body bonded by the cerium-based colloid, and the colloid-bonded reaction body is ignited to initiate the micropyretic reaction.
- a cerium- based colloidal carrier usually colloidal ceria or cerium acetate, usually in an aqueous medium - has been found to assist bonding of the reaction mixture to form the reaction body, and contributes to moderating the micropyretic reaction as well as considerably improving the properties of the reaction product.
- Comparable reaction mixtures without X the cerium-based colloidal carrier are difficult to bond, react poorly and do not produce a satisfactory product .
- the cerium-based colloid improves the reaction product , in particular when it is to be used as an anode for aluminium production coated with a protective cerium oxyfluoride coating .
- the colloid-originating cerium in the anode promotes initial cerium oxyfluoride formation and improves the impermeability of the cerium oxyfluoride coating by its dissolution and re- deposition, which provides a self-healing effect .
- These ef fect s are enhanced when the composite material of the anode also contains copper oxide .
- the colloid-originating cer ium in the compos it e material also improves its performance when used as cathode or cell lining in an aluminium production cell with a cerium-containing fluoride- based electrolyte .
- the cerium-based col loidal carrier may comprise colloidal ceria , colloidal cerium acetate or mixtures thereof .
- These cerium-based colloids may also include some co lloidal s ilica , alumina , yttria , thoria , zirconia , magnesia, lithia or monoaluminium phosphate, and hydroxides , acetates and formates thereof as well as oxides and hydroxides of other metals , cationic species and mixtures thereof .
- Some part iculate ceria can be included in the colloidal ceria .
- the cerium-based colloid may be derived from colloid precursors and reagents which are solutions of at least one salt such as chlorides , sulfates , nitrates , chlorates , perchlorates or metal organic compounds such as alkoxides , formates , acetates
- the aforementioned solutions of metal organic compounds may be of the general formula M (OR) z where M is a metal or complex cation, R is an alkyl chain and z is a number usually from 1 to 12 .
- the dry colloid content of the cerium-based colloidal carrier usually corresponds to 10 - 30 weight% of the colloidal carrier, preferably 10 - 20 weight%, but may account for up to 40 weight% or even 50 weight% of the colloidal carrier, there being preferably from 10 to 20 ml of the colloidal carrier per 100 grams of the powder mixture .
- the colloid-originating cerium usually amounts to 0.2 to 10% by weight of the composite material.
- the reaction mixture usually comprises particulate metals from the group of aluminium, nickel, iron, titanium, copper, chromium, manganese, vanadium, molybdenum, zirconium, niobium and cerium, and/or compounds of these metals, and mixtures thereof.
- a typical reaction mixture comprises 50 to 100 parts by weight of particulate nickel, iron and/or titanium and 2 to 50 parts by weight of particulate aluminium. There may also be a further 1 to 30 parts by weight of particulate additives selected from copper, chromium, manganese, vanadium, molybdenum, zirconium, niobium and cerium and compounds thereof, as well as compounds of aluminium, nickel, iron and titanium.
- One preferred reaction mixture comprises 50 to 100 parts by weight of particulate nickel, 2 to 50 parts by weight of particulate aluminium and 1 to 25 parts by weight of particulate copper.
- Another comprises 50 to 90 parts by weight of particulate nickel, 5 to 30 parts by weight of particulate aluminium, 5 to 25 parts by weight of particulate copper and 0 to 15 parts by weight of additives selected from chromium, manganese, vanadium, molybdenum, zirconium, niobium and cerium and compounds thereof, as well as compounds of aluminium, nickel, iron, titanium and copper.
- the reaction mixture includes one or more oxides of at least one metal from the group of aluminium, nickel, copper, chromium, manganese and cerium.
- the reaction mixture may comprise at least one boride of at least one metal from the group titanium, chromium, vanadium, molybdenum, zirconium, niobium and cerium, or precursors that react to form said borides .
- the micropyretic reaction (also called self-propagating high temperature synthesis) can be initiated by applying local heat to one or more points of the reaction body by a convenient heat source such as an electric arc, electric spark, flame, welding electrode, microwaves or laser, in which case the reaction propagates through the reaction body along a reaction front which may be self-propagating or assisted by a heat source. Reaction may also be initiated by heating the entire body to initiate reaction throughout the body in a thermal explosion mode. In either case, the reaction proceeds without supplying further heat as in a furnace.
- the reaction atmosphere is not critical, and reaction can take place in ambient conditions without the application of pressure.
- a coating may be applied to the component produced by micropyretic reaction, the composition of this coating depending on the intended use.
- Such coatings may in general contain the same components as the additives listed above.
- a preferred coating for aluminium-production anodes is cerium oxyfluoride according to US Patent No 4,614,569, formed i n-si t ⁇ in the cell or pre-applied.
- the cerium oxyfluoride may optionally contain additives such as compounds of tantalum, niobium, yttrium, tantalum, praesodymium and other rare earth elements, this coating being maintained by the addition of cerium and possibly other elements to the molten cryolite electrolyte.
- the anode substrate preferably includes cerium or cerium oxide as an additive in the composite material, in addition to the % cerium from the colloidal carrier. Production of such a coating i ⁇ -si t u leads to dense and homogeneous cerium oxyfluoride. The presence of copper oxide in the anode surface is believed to enhance the cerium oxyfluoride coating.
- a cathode according to the invention can also be coated with a protective refractory coating, typically containing an aluminium-wettable Refractory Hard Metal compound such as the borides and carbides of metals of Group IVB (titanium, zirconium, hafnium) and Group VB (vanadium, niobium, tantalum) . Boride-containing coatings are preferred.
- Such a protective coating may be formed by applying to the cathode a micropyretic reaction layer from a slurry containing particulate reactants in a colloidal carrier, and initiating a micropyretic reaction as described in co- pending application SN 07/861,513, the contents whereof are incorporated herein by way of reference.
- a micropyretic slurry comprises particulate micropyretic reactants in combination with optional particulate or fibrous non- reactant fillers or moderators in a carrier of colloidal materials or other fluids such as water or other aqueous solutions, organic carriers such as acetone, urethanes, etc., or inorganic carriers such as colloidal metal oxides.
- the cathode When the cathode is coated with a refractory coating forming a cathodic surface in contact with the cathodically- produced aluminium, it can be used as a drained cathode, the refractory coating forming the cathodic surface on which the aluminium is deposited cathodically, and the component being arranged usually upright or at a slope for the aluminium to drain from the cathodic surface.
- the operative surface of the cell component is conditioned by impregnating it with colloidal ceria or .
- cerium acetate or other colloids such as colloidal silica, alumina, yttria, thoria, zirconia, magnesia or lithia followed by drying the colloid- impregnated electrode, these impregnation/drying steps being repeated preferably until the electrode surface is saturated with the colloid.
- Impregnation of the component should be followed by a heat treatment and is preferably also preceded by a heat treatment . For anodes used in molten salt electrolysis, coated or not with cerium oxyfluoride, this impregnation preferably takes place with colloidal ceria or cerium acetate.
- the invention also pertains to a cell component of an aluminium production cell, made of a composite material comprising at least one ordered aluminide compound of at least one of nickel, iron and titanium.
- the cell component is produced by micropyretic reaction of a dried reaction mixture comprising compacted particulate reactants which react to produce the composite material, bonded by a cerium- based colloidal carrier. Cerium from the colloid is dispersed in the aluminide compound forming the cell component. Usually, the colloid-originating cerium amounts to 0.2 to 10% by weight of the composite material.
- a preferred composite material making up the cell component comprises nickel aluminide in solid solution with copper, and possibly also in solid solution with other metals and oxides.
- Another composite material comprises a major amount of Ni3Al and minor amounts of NiAl, nickel, a ternary nickel-aluminium-copper intermetallic compound and Ce ⁇ 2.
- composite materials comprise at least one intermetallic compound from the group AINi, AlNi3, Al3Fe, AlFe3, AITi and AlTi3 as well as ternary intermetallic compounds derived therefrom, and solid solutions and mixtures of at least one of said intermetallic compounds with at least one of the metals aluminium, nickel, iron, titanium, copper, chromium, manganese, vanadium, molybdenum, zirconium, niobium and cerium and oxides of said metals.
- Another composite material comprises an intimate mixture of at least one intermetallic compound of nickel- aluminium, at least one intermetallic compound of nickel- , . arguments,, /24321
- the component produced by the micropyretic reaction may comprise an intimate mixture of at least one intermetallic
- Ni3Al and Al3_-Ii nickel-aluminium
- intermetallic compound of nickel-aluminium-copper such as Al 7 3Ni ⁇ Cu 9
- copper oxide copper oxide
- this material and materials like it contain 0 non-stoichiometric conductive oxides wherein lattice vacancies are occupied by the metals or intermetallics, providing an outstanding conductivity while retaining the property of ceramic oxides to resist oxidation.
- the aforementioned nickel aluminide based materials and 5 nickel aluminide composites and solid solutions have been found to perform particularly well as dimensionally stable anodes for aluminium production.
- the cell component is advantageously impregnated with colloidal ceria, cerium 0 acetate, silica, alumina, yttria, thoria, zirconia, magnesia or lithia.
- Another aspect of the invention is a precursor of a component of an aluminium production cell which is ignitable to produce by micropyretic reaction a cell component made of 5 a composite material comprising at least one ordered aluminide compound of at least one of nickel, iron and titanium.
- This precursor is a body formed of a dried reaction mixture, as explained above, comprising compacted particulate reactants which react to produce the composite 0 material, mixed with and bonded by a cerium-based colloidal carrier. The properties of this precursor are substantially enhanced by the cerium-based colloid.
- Yet another aspect of the invention is a reaction mixture for producing a component of an aluminium production 5 cell, which component is made of a composite material // comprising at least one ordered aluminide compound of at least one of nickel, iron and titanium, by micropyretic reaction of the reaction mixture after drying and compacting.
- the reaction mixture comprises particulate reactants, as set out above, which react to produce the composite material, mixed with a cerium-based colloidal carrier in an amount of at least 5ml of colloid per 100 grams of the reaction mixture.
- a powder mixture was prepared from nickel powder, -100 mesh, aluminium powder, -325 mesh, and copper powder, -200 mesh. First the nickel and aluminium powders were mixed in a ratio Ni:Al 87:13 wt% . Then this mixture was mixed with copper powder in a ratio Ni/Al.Cu 90:10 wt% in 12ml of colloidal cerium acetate per 100 grams of the powder mixture .
- the mixture was compacted into samples by applying a pressure of about 170 MPa for 2-3 minutes, and allowed to dry in air for at least 3 hours. When the sample was almost dry, an exothermic reaction between the powders and cerium acetate occurred. To keep the samples cool and avoid cracking, cool air was blown on the samples by an air gun.
- the samples were then combusted in a furnace at 900°C to initiate a micropyretic reaction which swept through the ⁇ sample, and afterwards allowed to cool slowly to avoid cracking.
- Example 1 was repeated varying the proportion of Ni:Al, in the ratios 75:25; 86.6:13.4; 90:10; 92:8; 94:6 and 96:4.
- the weight ratio of Ni/Al:Cu was kept constant at 90:10.
- Colloidal cerium acetate was added to the different series of samples in amounts of 12ml, 24ml and 36ml per 100 grams of powder mixture. Compacting was carried out at approx. 170 MPa for 4 minutes. After drying, the samples were combusted in a furnace at 950°C. All samples underwent a micropyretic reaction.
- a sample prepared as in Example 1 was conditioned for use as an aluminium electrowinning anode by heating in air at 1000°C for 4 hours to oxidize its surface. After cooling, the sample was dipped in colloidal cerium acetate until no more is absorbed. The sample was then heated in an oven to dry it. After cooling the sample was again dipped in colloidal cerium acetate and dried. The dipping and drying steps were repeated until no more cerium acetate was absorbed.
- a cylindrical piece of 25 mm diameter and 40 mm height was prepared using the micropyretic technique of Example 2, with the composition Ni:Al 86.6:13.4, mixed with colloidal cerium acetate in an amount of 24ml/100 grams of the powder mixture.
- the material was then submitted to a heat treatment in air at 1000°C for 10 hours.
- the weight uptake due to oxidation was about 6%.
- the oxidized material was impregnated by dipping into a colloidal solution of cerium acetate for 10 minutes and- drying at 250°C. This operation was repeated twice.
- the sample was then tested as an anode in a small electrolytic cell containing molten cryolite at 1000°C with 5% alumina and 1.5% cerium fluoride, at a IS current density of 0.3 A/cm 2 for 4 hours.
- the cell voltage remained stable at 4V during the test.
- the test anode was then cross-sectioned and no significant corrosion was observed.
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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)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Powder Metallurgy (AREA)
- Inert Electrodes (AREA)
- Manufacture Of Alloys Or Alloy Compounds (AREA)
- Medicines Containing Material From Animals Or Micro-Organisms (AREA)
Abstract
Description
Claims
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/US1993/003605 WO1994024321A1 (en) | 1993-04-19 | 1993-04-19 | Micropyretically-produced components of aluminium production cells |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0695371A1 true EP0695371A1 (en) | 1996-02-07 |
EP0695371B1 EP0695371B1 (en) | 1999-10-20 |
Family
ID=22236515
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP93910631A Expired - Lifetime EP0695371B1 (en) | 1993-04-19 | 1993-04-19 | Micropyretically-produced components of aluminium production cells |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP0695371B1 (en) |
AU (1) | AU685053B2 (en) |
DE (1) | DE69326843T2 (en) |
NO (1) | NO954158D0 (en) |
WO (1) | WO1994024321A1 (en) |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5510008A (en) * | 1994-10-21 | 1996-04-23 | Sekhar; Jainagesh A. | Stable anodes for aluminium production cells |
US5904828A (en) * | 1995-09-27 | 1999-05-18 | Moltech Invent S.A. | Stable anodes for aluminium production cells |
DE69708903T2 (en) * | 1996-09-23 | 2002-06-27 | Moltech Invent Sa | HIGH STABILITY ANODES FOR ALUMINUM PRODUCTION CELLS |
KR101813280B1 (en) | 2011-06-28 | 2017-12-28 | 삼성전기주식회사 | Vanadium oxide, method for preparing the same, dielectric composition comprising the same |
WO2015002733A2 (en) * | 2013-06-17 | 2015-01-08 | The Curators Of The University Of Missouri | Multifunctional cerium-based nanomaterials and methods for producing the same |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB8301001D0 (en) * | 1983-01-14 | 1983-02-16 | Eltech Syst Ltd | Molten salt electrowinning method |
US4948676A (en) * | 1986-08-21 | 1990-08-14 | Moltech Invent S.A. | Cermet material, cermet body and method of manufacture |
DE69019664T2 (en) * | 1989-03-07 | 1995-09-21 | Moltech Invent Sa | ANODE SUBSTRATE COATED WITH A RARE OXIDE COMPOUND. |
US5217583A (en) * | 1991-01-30 | 1993-06-08 | University Of Cincinnati | Composite electrode for electrochemical processing and method for using the same in an electrolytic process for producing metallic aluminum |
-
1993
- 1993-04-19 AU AU41056/93A patent/AU685053B2/en not_active Ceased
- 1993-04-19 DE DE69326843T patent/DE69326843T2/en not_active Expired - Fee Related
- 1993-04-19 EP EP93910631A patent/EP0695371B1/en not_active Expired - Lifetime
- 1993-04-19 WO PCT/US1993/003605 patent/WO1994024321A1/en active IP Right Grant
-
1995
- 1995-10-18 NO NO954158A patent/NO954158D0/en not_active Application Discontinuation
Non-Patent Citations (1)
Title |
---|
See references of WO9424321A1 * |
Also Published As
Publication number | Publication date |
---|---|
NO954158L (en) | 1995-10-18 |
AU685053B2 (en) | 1998-01-15 |
AU4105693A (en) | 1994-11-08 |
WO1994024321A1 (en) | 1994-10-27 |
NO954158D0 (en) | 1995-10-18 |
DE69326843D1 (en) | 1999-11-25 |
DE69326843T2 (en) | 2000-05-18 |
EP0695371B1 (en) | 1999-10-20 |
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