CA2441578A1 - Inert electrode material in nanocrystalline powder form - Google Patents
Inert electrode material in nanocrystalline powder form Download PDFInfo
- Publication number
- CA2441578A1 CA2441578A1 CA002441578A CA2441578A CA2441578A1 CA 2441578 A1 CA2441578 A1 CA 2441578A1 CA 002441578 A CA002441578 A CA 002441578A CA 2441578 A CA2441578 A CA 2441578A CA 2441578 A1 CA2441578 A1 CA 2441578A1
- Authority
- CA
- Canada
- Prior art keywords
- group
- process according
- oxide
- carbide
- nitride
- 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.)
- Abandoned
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
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/002—Making metallic powder or suspensions thereof amorphous or microcrystalline
- B22F9/004—Making metallic powder or suspensions thereof amorphous or microcrystalline by diffusion, e.g. solid state reaction
- B22F9/005—Transformation into amorphous state by milling
-
- 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
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/07—Metallic powder characterised by particles having a nanoscale microstructure
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
- C04B35/26—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on ferrites
- C04B35/2666—Other ferrites containing nickel, copper or cobalt
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
- C04B35/453—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on zinc, tin, or bismuth oxides or solid solutions thereof with other oxides, e.g. zincates, stannates or bismuthates
-
- 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
- B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
- B22F2998/10—Processes characterised by the sequence of their steps
-
- 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
- B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy
Abstract
The invention relates to an inert electrode material in powder form comprising particles having an average particle size of 0.1 to 100 ~m and each formed of an agglomerate of grains of a ceramic material and grains of a metal or alloy with each grain of ceramic material comprising a nanocrystal of the ceramic material and each grain of metal or alloy comprising a nanocrystal of the metal or alloy. Alternatively, each particle can be formed of an agglomerate of grains with each grain comprising a nanocrystal of a single phase ceramic material, a metal or an alloy. The electrode material in powder form according to the invention is useful for the manufacture of inert electrodes having improved thermal shock and corrosion resistance properties.
Description
POWDER FORM
TECHNICAL FIELD
The present invention pertains to improvements in the field of electrodes for metal electrolysis. More particularly, the invention relates to an inert electrode material in nanocrystalline powder form for use in the manufacture of such electrodes.
BACKGROUND ART
Aluminum is produced conventionally in a Hall-Heroult reduction cell by the electrolysis of alumina dissolved in molten cryolite (Na3A1F6) at temperatures of up to about 950 °C. A Hall-Heroult cell typically has a steel shell provided with an insulating lining of refractory material, which in turn has a lining made of prebaked carbon blocks contacting the molten constituents of the electrolyte. The carbon lining acts as the cathode substrate and the molten aluminum pool acts as the cathode.
The anode is a consumable carbon electrode, usually prebaked carbon made by coke calcination. Typically, for each ton of aluminum produced, 0.5 ton of carbon anode is required.
During electrolysis in Hall-Heroult cells, the carbon anode is consumed leading to the evolution of greenhouse gases such as CO and C02. The anode has to be periodically changed and the erosion of the material modifies the anode-cathode distance, which increases the voltage due to the electrolyte resistance. On the cathode side, the carbon blocks are subjected to erosion and electrolyte penetration. A sodium intercalation in the graphitic structure occurs, which causes swelling and deformation of the cathode carbon blocks. The increase of voltage between the electrodes adversely affects the energy efficiency of the process.
Many attempts have been made to find a suitable material for inert anodes and a number of materials have been proposed and tested. The proposed materials include metals such as proposed in US Patent No. 6,162,334, ceramics such as proposed in US Patent Nos. 3,960,678 and 4,399,008, and cermets such as proposed in US Patent No. 5,865,980. In spite of intensive efforts of more than 20 years to produce inert anodes, to date, no fully acceptable inert anode materials have been found. Ceramics are generally brittle and do not resist to the thermal shocks during start-up and operation of a Hall-Heroult cell. Metal oxide ceramics are generally resistant to oxidation, but they are not good electrical conductors. Metals, however, are very good conductors but the corrosion rate of metallic anodes in cryolite is very high. Cermets, on the other hand, seem to be promising materials for anode applications. Cermets combine the good properties of metals (conductivity, toughness) with good properties of ceramics (corrosion resistance).
US Patent No. 5,865,980 describes a cermet comprising a ferrite, copper and silver which can be used as an inert anode. These cermet anodes exhibit a good corrosion resistance due to the ceramic part and a good electrical conductivity due to the metallic part. Fabrication process of such a cermet is complex and consists of several steps. At least two metal oxides, such as Ni0 and Fe203, are mixed and calcined at high temperatures (1300-1400 °C) for a relatively long period of time (12 h) in order to synthesize a nickel ferrite spinel with or without excess of NiO. The resulting material is grinded to reduce the average particle size to about 10 microns, mixed with a polymeric binder and water, spray dried, and mixed with copper and silver powder. The powder mixture thus obtained is then pressed and sintered at about° 1350 °C for 2-4 hours. The resulting cermet has ceramic phase portions and alloy phase portions.
Although the above-mentioned cermet seems to be a promising material for inert anode applications, several disadvantages are associated with its production and the characteristics of the final product.
The process is complex and requires several steps, which results in a product having a high cost. The sintering and densification rates of ceramic and metal powders having an average particle size of about 10 microns are slow so that it is very difficult to obtain a highly dense cermet. A small amount of porosity is present in the cermet obtained, resulting in a decrease of mechanical properties. Thus, an anode made of such a cermet is easily destroyed when subjected to repeated thermal shocks. In order to increase the final density, the sintering temperature must be increased. Using high sintering temperature results in an excessive grain growth and an increase in the final cost of the product.
Segregation is a serious problem when powders having a Iarge average particle size are mixed together. Segregation is more pronounced when the difference between the densities of the particles or their size is larger. Metal particles having a density greater than that of ceramic particles tend to segregate from the Iow-density ceramic particles.
This results in a non-homogeneous powder mixture and, consequently, in a non-homogeneous sintered anode. Since the conductivity of the ceramic phase is much lower than that of the metal phase, any non-homogeneity results in a non-homogeneous current density during use of the anode. On the other hand, the corrosion or erosion rates of the ceramic and metal phase portions of the cermet in cryolite are not the same. Therefore, any non-homogeneity results in an excessive local degradation of the anode.
The purpose of sintering is to obtain a solid product having maximum density and homogeneity. During sintering, two phenomena are particularly important: densification (pore elimination) and grain growth.
Higher sintering temperatures and longer sintering times generally lead to high densification but, on the other hand, favor grain growth. When powders having a large average particle size are used as starting material, densification is slow and in order to obtain higher densities, the sintering temperature and/or time must be increased. This results in a cermet with a coarse microstructure which decreases the thermal shock resistance of the cermet. Coarse structured cermets also exhibit low mechanical properties and non-homogeneous corrosion rates.
DISCLOSURE OF INVENTION
It is therefore an object of the invention to overcome the above drawbacks and to provide an electrode material in powder form for use in the manufacture of inert electrodes having improved thermal shock and corrosion resistance properties.
According to one aspect of the invention, there is provided an inert electrode material in powder form comprising particles having an average particle size of 0.1 to 100 ~,m and each formed of an agglomerate of grains of a ceramic material and grains of ~ a metal or alloy with each grain of ceramic material comprising a nanocrystal of the ceramic material and each grain of metal or alloy comprising a nanocrystal of the metal or alloy.
According to another aspect of the invention, there is provided an inert electrode material in powder form comprising particles having an average particle size of 0.1 to 100 ~,m and each formed of an agglomerate of grains with each grain comprising a nanocrystal of a single phase ceramic material.
According to a further aspect of the invention, there is provided an inert electrode material in powder form comprising particles having an average particle size of 0.1 to 100 ~,m and each formed of an agglomerate of grains with each grain comprising a nanocrystal of a metal.
According to still a further aspect of the invention, there is provided an inert electrode material in powder form comprising particles having an average particle size of 0.1 to 100 ~,m and each formed of an agglomerate of grains with each grain comprising a nanocrystal of an alloy.
The term "nanocrystal" as used herein refers to a crystal having a size of 100 nanometers or less. The nanocrystalline microstructure considerably favors densification, even without sintering aids, when the electrode material in powder form according to the invention is compacted and sintered to produce dense electrodes. Nanocrystalline powders also minimize grain growth ~ since sintering can be effected at lower temperatures. The sintering time is also much shorter than that required for densification of the conventional coarse-grained (about 10 ~.m) powder mixtures for a same densification level. Thus, the overall cost of the sintering process is considerably decreased.
Since the time and the temperature of the sintering are considerably low, the resulting electrode has a fine microstructure. The finer the microstructure, the higher the toughness and the resistance to thermal shock, and consequently the longer the electrode life time.
In the case where each particle is formed of an agglomerate of grains with each grain comprising a nanocrystal of a metal, the nanocrystalline metals are more resistant to corrosion than polycrystalline metals because of the growth of a passivation layer. This protective layer grows faster at the surface of a nanocrystalline metal than in a polycrystalline metal.
The present invention also provides, in a further aspect thereof, a process for producing an inert electrode material in powder form as previously defined, wherein each particle is formed of an agglomerate of grains of a ceramic material and grains of a metal. The process of the invention comprises the steps of a) subj ecting at least one metal oxide, nitride or carbide to high-energy ball milling to form a first powder comprising particles having an average particle size of 0.1 to 100 ~,m and each formed of an agglomerate of grains of a ceramic material;
b) subjecting a metal to high-energy ball milling to form a second powder comprising particles having an average particle size of 0.1 to 100 ~,m and each formed of an agglomerate of grains with each grain comprising a nanocrystal of the metal;
_7_ c) mixing the first and second powders to form a powder mixture; and d) subjecting the powder mixture obtained in step (c) to high-energy ball milling to form a nanocrystalline powder comprising particles having an average particle size of 0.1 to 100 ~.m and each formed of an agglomerate of grains of the ceramic material and g~'ains of the metal, wherein each grain of ceramic material comprises a nanocrystal of the ceramic material and each grain of metal comprises a nanocrystal of the metal.
According to still a further aspect of the invention, there is provided a process for producing an inert electrode material as previously defined, wherein each particle is formed of an agglomerate of grains of a ceramic material and grains of an alloy. The process of the invention comprises the steps of:
a) subjecting ~at least one metal oxide, nitride or carbide to high-energy ball milling to form a first powder comprising particles having an average particle size of 0.1 to 100 ~,m and each formed of an agglomerate of grains of a ceramic material;
b) subjecting at least two metals to high-energy ball milling to form a second powder comprising particles having an average particle size of 0.1 to 100 ~m and each formed of an agglomerate of grains with each grain comprising a nanocrystal of an alloy of the metals;
c) mixing the first and second powders to form a powder mixture; and d) subjecting the powder mixture obtained in step (c) to high-energy ball milling to form a nanocrystalline powder comprising particles having an average particle size of 0.1 to 100 ~,m and each formed of an _$_ agglomerate of grains of the ceramic material and grains of the alloy, wherein each grain of ceramic material comprises a nanocrystal of the ceramic material and each grain of alloy comprises a nanocrystal of the alloy.
According to another aspect of the invention, there is provided a process for producing an inert electrode material in powder form as previously defined, wherein each particle is formed of an agglomerate of grains each comprising a nanocrystal of a single phase ceramic material.
The process of the invention comprises subjecting a metal oxide, nitride or carbide to high-energy ball milling to form a nanocrystalline powder comprising particles having an average particle size of 0.1 to 100 ~m and each formed of an agglomerate of grains with each grain comprising a nanocrystal of a single phase ceramic material.
According to yet another aspect of the invention, there is provided a process for producing an inert electrode material in powder form as previously defined, wherein each particle is formed of an agglomerate of grains each comprising a nanocrystal of a metal. The process of the invention comprises subjecting a metal to high-energy ball milling to form a nanocrystalline powder comprising particles having an average particle size of 0.1 to 100 ~.m and each formed of an agglomerate of grains with each grain comprising a nanocrystal of the metal.
According to still another aspect of the invention, there is provided a process for producing an inert electrode material in powder form as previously defined, wherein each particle is formed of an agglomerate of grains each comprising a nanocrystal of an alloy. The process of the invention comprises subjecting at least two metals to high-energy ball milling to form a nanocrystalline powder comprising particles having an average particle size of 0.1 to 100 ~,m and each formed of an agglomerate of grains with each grain comprising a nanocrystal of an alloy of the metals.
The expression "high-energy ball milling" as used herein refers to a ball milling process capable of forming the aforesaid particles within a period of time of about 40 hours. In the aforementioned step (d), the high-energy ball milling is carried out for a period of time sufficient to break the agglomerates formed in steps (a) and (b), and to form new agglomerates comprising nanocrystalline grains of the ceramic material and nanocrystalline grains of the metal or alloy. Generally, such a period of time is about one hour.
MODES FOR CARRYING OUT THE INVENTION
Examples of suitable ceramic materials include oxides, nitrides and carbides of transition metals such as Ag, Co, Cu, Cr, Fe, Ir, Mo, Mn, Nb, Ni, Ru, Ta, Ti, V, W, Y, Zn and Zr, p-group metals such as Al, Ge, In, Pd, Sb, Si and Sn, rare earth metals such as Ce, La and Th, and alkaline earth metals such as Ca, Mg and Sr.
In the case where each particle is formed of an agglomerate of grains of ceramic material and grains of metal, the metal can be for example chromium, cobalt, copper, gold, iridium, iron, nickel, niobium, palladium, platinum, rubidium, ruthenium, silicon, silver, titanium, yttrium or zirconium. On the other hand, in the case where each particle is formed of an agglomerate of grains of ceramic material and grains of alloy, the alloy can be for example a Cu-Ag, Cu-Ag-Ni, Cu-Ni, Cu-Ni-Fe, Cu-Pd, Cu-Pt or Ni-Fe alloy. When these particles are sintered, they will form a cermet material having ceramic phase portions and .metal or alloy phase portions.
In the case where each particle is formed of an agglomerate of grains with each grain comprising a nanocrystal of a single phase ceramic material, the ceramic material advantageously includes a dopant for improving the sinterability of the powder and/or for increasing the conductivity of the electrode eventually made from the ceramic powder.
Examples of suitable dopants include those comprising an element selected from the group of Al, Co, Cr, Cu, Fe, Mo, Nb, Ni, Sb, Si, Sn, Ti, V, W, Y, Zn and Zr. The dopant is generally present in an amount of about 0.002 to about 1 wt.%, preferably between about 0.005 and about 0.05 wt.%. Since the corrosion, erosion and thermal expansion of a single phase ceramic material are uniform, electrodes produced from the nanocrystalline powder according to the invention, comprising such a material, have a longer life time.
In the case where each particle is formed of an agglomerate of grains with each grain comprising a nanocrystal of a metal, the metal can be for example chromium, cobalt, copper, gold, iridium, iron, nickel, niobium, palladium, platinum, rubidium, ruthenium, silicon, silver, titanium, yttrium or zirconium. Copper is preferred. On the other hand, in the case where each particle is formed of an agglomerate of grains with each grain comprising a nanocrystal of an alloy, the alloy can be for example a Cu-Ag, Cu-Ag-Ni, Cu-Ni, Cu-Ni-Fe, Cu-Pd, Cu-Pt or Ni-Fe alloy. When these particles are sintered, they form a dense metallic material.
According to a preferred embodiment of the process of the invention, the high-energy ball milling is carned out in a vibratory ball mill operated at a frequency of ~ to 25 Hz, preferably about 17 Hz. It is also possible to carry out such a ball milling in a rotary ball mill operated at a speed of 100 to 2000 r.p.m., preferably about 1200 r.p.m.
According to another preferred embodiment, the high-energy ball milling is carried out under an inert gas atmosphere such as a gas atmosphere comprising argon or helium. An atmosphere of argon is preferred.
The electrode material in powder form according to the invention can be used to produce dense electrode by powder metallurgy. The expression "powder metallurgy" as used herein refers to a technique in which the bulk powders are transformed into preforms of a desired shape by compaction or shaping followed by a sintering step. Compaction refers to techniques where pressure is applied to the powder, as, for example, cold uniaxial pressing, cold isostatic pressing or hot isostatic pressing. Shaping refers to techniques executed without the application of external pressure such as powder filling or slurry casting. The dense electrodes thus obtained have improved thermal shock and corrosion resistance properties.
The electrode material in powder form according to the invention can also be used to produce electrodes by thermal deposition applications. The expression "thermal deposition" as used herein refers to a technique in which powder particles are injected in a torch and sprayed on a conductive substrate such as graphite or copper, to form thereon a highly dense coating. The particles acquire a high velocity and are partially or totally melted during the flight path. The coating is built by the solidification of the droplets on the substrate surface. Examples of such techniques include plasma spray, arc spray and high velocity oxy-fuel.
Since the electrodes produced from the nanocrystalline powder according to the invention have a high density, the electrolyte does not penetrate into the electrode via pores and, consequently, the degradation of the electrode is minimized.
The following non-limiting examples illustrate the invention.
A NiFe204 spinal powder was produced by ball milling 51.7 wt.% Ni0 and 48.3 wt.% Fe203 in a tungsten carbide crucible with a ball-to-powder mass ratio of 15:1 using a SPEX 8000 (trademark) vibratory ball mill operated at a frequency of about 17 Hz. The operation was performed under a controlled argon atmosphere. The crucible was closed and sealed with a rubber O-ring. After 10 hours of high-energy ball milling, a nanocrystalline structure comprising a NiFe204 spinal with excess Ni0 was formed. The particle size varied between 0.1 and 5 ~.m and the crystallite size, measured by X-ray diffraction, was about 30 nm.
A Cu-Ag alloy powder was also produced by ball milling 69.5 wt.% Cu and 29.5 wt.% Ag in a tungsten carbide crucible with a ball-to-powder mass ratio of 10:1 using a SPEX 8000 vibratory ball mill operated at a frequency of about 17 Hz. The operation was performed under a controlled argon atmosphere. 1 wt.% of stearic acid was added as a lubricant. After 10 hours of high-energy ball milling, a nanocrystalline structure comprising an alloy of copper and silver was formed. The particle size varied between 10 and 30 ~m and.the crystallite size, measured by X-ray diffraction, was about 40 nm.
80 wt.% of the NiFea04 spinet powder and 20 wt.% of the Cu-Ag alloy powder produced above were mixed and the resulting powder mixture and the resulting powder mixture was ball milled in a tungsten carbide crucible with a ball-to-powder mass ratio of 10:1 using a SPEX
8000 vibratory ball mill operated at a frequency of about 17 Hz. After one hour of high-energy ball milling, a nanocrystalline powder comprising particles each formed of an agglomerate of grains comprising nanocrystals of the NiFe204 spinet and nanocrystals of the Cu-Ag alloy was obtained.
The particle size varied between 5 and 10 ~,m. This nanocrystalline powder was then pressed uniaxially at a pressure of 400 MPa. The compacted powder was then sintered at a temperature of 950°C for one hour to produce a dense electrode having excellent thermal shock and corrosion resistance properties.
A NiFea04 ferrite powder was produced by ball milling 51.7 wt.% of Ni0 and 48.3 wt.% Fe203 in a steel crucible with a ball-to-powder mass ratio of 10:1 using a SIMOLOYER (trademark) rotary ball mill operated at a speed of 1200 r.p.m.. The operation was performed under a controlled argon atmosphere by continously flushing the crucible with argon. After 5 hours of high-energy ball milling, an amorphous NiFe204 spinet was .~ ~~ . , , ,~ ~ , ~CA02Q0SJ
hPt'lt~t~t1 30 46 ~O3 ~ESCI="AMD
produced with an excess of nanocrystalline NiO. The particle size varied between 0.1 and 5 ~,m.
- A Cu-Ag alloy powder was also produced by ball milling 98 wt.%
Cu and 2 wt.% Ag in a steel crucible with a ball-to-powder mass ratio of 10:1 using a SIMOLOYER rotary ball mill operated at a speed of 1200 r.p.m. The operation was performed under a controlled argon atmosphere. 1 wt.% stearic acid was added as a lubricant. After 5 hours of high-energy ball milling, a nanocrystalline structure comprising an alloy of copper and silver was formed. The particle size varied between 5 to 30 ~,m and the crystallite size, measured by X-ray diffraction, was about 20 nm.
81.3 wt.% of the above NiFea04 spinal powder, 16.6 wt.% of the above Cu-Ag alloy powder and 2 wt.% of CAPLUBE G (trademark) acting as a lubricant arid binder were mixed and the resulting powder mixture was ball milled in a steel crucible with a ball-to-powder mass ratio of 10:1 using a SIMOLOYER rotary ball mill operated at 800 r.p.m.. After 1 S minutes of high-energy ball milling, a nanocrystalline powder comprising particles each formed of an agglomerate of grains comprising nanocrystals of the NiFe20a spinal and nanocrystals of the Cu-Ag alloy was obtained. The particle size varied between 5 and 10 p,m. This nanocrystalline powder was then cold isostatically pressed at 138 Mpa. The compacted powder was then sintered at a temperature of 1050°C for one hour to produce a dense electrode having excellent thermal shock and corrosion resistance properties.
1 °,' RECTIFIED SHEET (RULE 91 ) i~~~ a~.,~00~
' CA 02441578 2003-09-19 Pr~r'lte~ ,~30 06 20t~~ DESGI='.~1M~:! . CRO~t?Q395 A NiFe204 ferrite powder was produced by ball milling 51.7 wt.% of Ni0 and 48.3 wt.% Fe20~ in a steel crucible with a ball-to-powder mass ratio of 10:1 using a SIMOLOYER rotary ball mill operated at a speed of 1200 r.p.m.. The operation was performed under a controlled argon atmosphere by continously flushing the crucible with argon. After 5 hours of high-energy ball milling, an amorphous NiFe204 spinet was produced with an excess of nanocrystalline NiO. The particle size varied between 0.1 and S wm.
A Cu-Ag alloy powder was also produced by ball milling 98 wt.% Cu and 2 wt.% Ag in a steel crucible with a ball-to-powder mass ratio of 10:1 using a SIMOLO'YER rotary ball mill operated at a speed of 1200 r.p.m.. The operation was performed under a controlled argon atmosphere. 1 wt.% stearic acid was added as a lubricant. After 5 hours of high-energy ball milling, a nanocrystalline structure comprising an alloy of copper and silver was formed. The particle size varied between 5 to 30 ~,m and the crystallite size, measured by X-ray diffraction, was about 20 nm.
81.3 wt.% of the above NiFe20~ spinet powder, 16.6 wt.% of the above Cu-Ag alloy powder produced above and 2 wt.% of CAPLUBE G
acting as a lubricant and binder were mixed and the resulting powder mixture was ball milled in a steel crucible with a ball-to-powder mass ratio of 5:1 using a SPEX 8000 vibratory ball mill operated at 17 Hz. After 15 minutes of high-energy ball milling, a nanocrystalline powder comprising particles each formed of an agglomerate of grains comprising nanocrystals of the NiFe204 spinet and nanocrystals of the Cu-Ag alloy was obtained.
2r RECTIFIED SHEET (RULE 91 ) 45 (l6-2002 ' CA 02441578 2003-09-19 ~'rlnted 30 00 20U3V! ~=DAESCPAM~Y: ~C~t~~0t139 The particle size varied between 5 and 10 ~.m. This nanocrystaIline powder was then uniaxially pressed at 138 Mpa. The compacted powder was then sintered at a temperature of lOSO°C for one hour to produce a dense ' electrode having excellent thermal shock and corrosion resistance properties.
A coarse-grained Zn0 powder (99.9% pure) having an average grain size of 1 ~,m and a specific surface area of 3 m~/g was used as starting material. 0.008 wt.% A1z03 and ~ wt.% PVA were added as dopant and binder, respectively. The powder mixture was ball milled in a tungsten carbide crucible using a SPEX 8000 vibratory ball mill operated at a frequency of about 17 Hz. After I S hours of high-energy ball milling, a nanocrystalline Zn0 powder having a particle size between I and 5 ~,m and .
an average grain size smaller than I00 nm was obtained. The specific surface area of the nanocrystalline grains was 40 m2/g. This nanocrystalline powder was then pressed uniaxially at a pressure of 400 MPa. The compacted powder was then sintered at a temperature of 1250°C for one hour to produce a dense electrode having excellent thermal shock and corrosion resistance properties.
A nanocrystalline Cu-Ni alloy powder was produced by ball milling 70 wt.% Cu and 30 wt.% Ni in a steel crucible with a ball-to-powder mass ratio of 10:1 using a SIMOLOYER rotary ball mill operated at a speed of 1200 r.p.m.. 1 wt.% stearic acid was added as a lubricant.
~'' RECTIFIED SHEET (RULE 91) ,p~TO,Or~O(~~
' CA 02441578 2003-09-19 ~Pr~t~t~C~ ~30 06 20E~3I ? C?ESt'rPAM~~G~tt?,'~G0039~"J
TECHNICAL FIELD
The present invention pertains to improvements in the field of electrodes for metal electrolysis. More particularly, the invention relates to an inert electrode material in nanocrystalline powder form for use in the manufacture of such electrodes.
BACKGROUND ART
Aluminum is produced conventionally in a Hall-Heroult reduction cell by the electrolysis of alumina dissolved in molten cryolite (Na3A1F6) at temperatures of up to about 950 °C. A Hall-Heroult cell typically has a steel shell provided with an insulating lining of refractory material, which in turn has a lining made of prebaked carbon blocks contacting the molten constituents of the electrolyte. The carbon lining acts as the cathode substrate and the molten aluminum pool acts as the cathode.
The anode is a consumable carbon electrode, usually prebaked carbon made by coke calcination. Typically, for each ton of aluminum produced, 0.5 ton of carbon anode is required.
During electrolysis in Hall-Heroult cells, the carbon anode is consumed leading to the evolution of greenhouse gases such as CO and C02. The anode has to be periodically changed and the erosion of the material modifies the anode-cathode distance, which increases the voltage due to the electrolyte resistance. On the cathode side, the carbon blocks are subjected to erosion and electrolyte penetration. A sodium intercalation in the graphitic structure occurs, which causes swelling and deformation of the cathode carbon blocks. The increase of voltage between the electrodes adversely affects the energy efficiency of the process.
Many attempts have been made to find a suitable material for inert anodes and a number of materials have been proposed and tested. The proposed materials include metals such as proposed in US Patent No. 6,162,334, ceramics such as proposed in US Patent Nos. 3,960,678 and 4,399,008, and cermets such as proposed in US Patent No. 5,865,980. In spite of intensive efforts of more than 20 years to produce inert anodes, to date, no fully acceptable inert anode materials have been found. Ceramics are generally brittle and do not resist to the thermal shocks during start-up and operation of a Hall-Heroult cell. Metal oxide ceramics are generally resistant to oxidation, but they are not good electrical conductors. Metals, however, are very good conductors but the corrosion rate of metallic anodes in cryolite is very high. Cermets, on the other hand, seem to be promising materials for anode applications. Cermets combine the good properties of metals (conductivity, toughness) with good properties of ceramics (corrosion resistance).
US Patent No. 5,865,980 describes a cermet comprising a ferrite, copper and silver which can be used as an inert anode. These cermet anodes exhibit a good corrosion resistance due to the ceramic part and a good electrical conductivity due to the metallic part. Fabrication process of such a cermet is complex and consists of several steps. At least two metal oxides, such as Ni0 and Fe203, are mixed and calcined at high temperatures (1300-1400 °C) for a relatively long period of time (12 h) in order to synthesize a nickel ferrite spinel with or without excess of NiO. The resulting material is grinded to reduce the average particle size to about 10 microns, mixed with a polymeric binder and water, spray dried, and mixed with copper and silver powder. The powder mixture thus obtained is then pressed and sintered at about° 1350 °C for 2-4 hours. The resulting cermet has ceramic phase portions and alloy phase portions.
Although the above-mentioned cermet seems to be a promising material for inert anode applications, several disadvantages are associated with its production and the characteristics of the final product.
The process is complex and requires several steps, which results in a product having a high cost. The sintering and densification rates of ceramic and metal powders having an average particle size of about 10 microns are slow so that it is very difficult to obtain a highly dense cermet. A small amount of porosity is present in the cermet obtained, resulting in a decrease of mechanical properties. Thus, an anode made of such a cermet is easily destroyed when subjected to repeated thermal shocks. In order to increase the final density, the sintering temperature must be increased. Using high sintering temperature results in an excessive grain growth and an increase in the final cost of the product.
Segregation is a serious problem when powders having a Iarge average particle size are mixed together. Segregation is more pronounced when the difference between the densities of the particles or their size is larger. Metal particles having a density greater than that of ceramic particles tend to segregate from the Iow-density ceramic particles.
This results in a non-homogeneous powder mixture and, consequently, in a non-homogeneous sintered anode. Since the conductivity of the ceramic phase is much lower than that of the metal phase, any non-homogeneity results in a non-homogeneous current density during use of the anode. On the other hand, the corrosion or erosion rates of the ceramic and metal phase portions of the cermet in cryolite are not the same. Therefore, any non-homogeneity results in an excessive local degradation of the anode.
The purpose of sintering is to obtain a solid product having maximum density and homogeneity. During sintering, two phenomena are particularly important: densification (pore elimination) and grain growth.
Higher sintering temperatures and longer sintering times generally lead to high densification but, on the other hand, favor grain growth. When powders having a large average particle size are used as starting material, densification is slow and in order to obtain higher densities, the sintering temperature and/or time must be increased. This results in a cermet with a coarse microstructure which decreases the thermal shock resistance of the cermet. Coarse structured cermets also exhibit low mechanical properties and non-homogeneous corrosion rates.
DISCLOSURE OF INVENTION
It is therefore an object of the invention to overcome the above drawbacks and to provide an electrode material in powder form for use in the manufacture of inert electrodes having improved thermal shock and corrosion resistance properties.
According to one aspect of the invention, there is provided an inert electrode material in powder form comprising particles having an average particle size of 0.1 to 100 ~,m and each formed of an agglomerate of grains of a ceramic material and grains of ~ a metal or alloy with each grain of ceramic material comprising a nanocrystal of the ceramic material and each grain of metal or alloy comprising a nanocrystal of the metal or alloy.
According to another aspect of the invention, there is provided an inert electrode material in powder form comprising particles having an average particle size of 0.1 to 100 ~,m and each formed of an agglomerate of grains with each grain comprising a nanocrystal of a single phase ceramic material.
According to a further aspect of the invention, there is provided an inert electrode material in powder form comprising particles having an average particle size of 0.1 to 100 ~,m and each formed of an agglomerate of grains with each grain comprising a nanocrystal of a metal.
According to still a further aspect of the invention, there is provided an inert electrode material in powder form comprising particles having an average particle size of 0.1 to 100 ~,m and each formed of an agglomerate of grains with each grain comprising a nanocrystal of an alloy.
The term "nanocrystal" as used herein refers to a crystal having a size of 100 nanometers or less. The nanocrystalline microstructure considerably favors densification, even without sintering aids, when the electrode material in powder form according to the invention is compacted and sintered to produce dense electrodes. Nanocrystalline powders also minimize grain growth ~ since sintering can be effected at lower temperatures. The sintering time is also much shorter than that required for densification of the conventional coarse-grained (about 10 ~.m) powder mixtures for a same densification level. Thus, the overall cost of the sintering process is considerably decreased.
Since the time and the temperature of the sintering are considerably low, the resulting electrode has a fine microstructure. The finer the microstructure, the higher the toughness and the resistance to thermal shock, and consequently the longer the electrode life time.
In the case where each particle is formed of an agglomerate of grains with each grain comprising a nanocrystal of a metal, the nanocrystalline metals are more resistant to corrosion than polycrystalline metals because of the growth of a passivation layer. This protective layer grows faster at the surface of a nanocrystalline metal than in a polycrystalline metal.
The present invention also provides, in a further aspect thereof, a process for producing an inert electrode material in powder form as previously defined, wherein each particle is formed of an agglomerate of grains of a ceramic material and grains of a metal. The process of the invention comprises the steps of a) subj ecting at least one metal oxide, nitride or carbide to high-energy ball milling to form a first powder comprising particles having an average particle size of 0.1 to 100 ~,m and each formed of an agglomerate of grains of a ceramic material;
b) subjecting a metal to high-energy ball milling to form a second powder comprising particles having an average particle size of 0.1 to 100 ~,m and each formed of an agglomerate of grains with each grain comprising a nanocrystal of the metal;
_7_ c) mixing the first and second powders to form a powder mixture; and d) subjecting the powder mixture obtained in step (c) to high-energy ball milling to form a nanocrystalline powder comprising particles having an average particle size of 0.1 to 100 ~.m and each formed of an agglomerate of grains of the ceramic material and g~'ains of the metal, wherein each grain of ceramic material comprises a nanocrystal of the ceramic material and each grain of metal comprises a nanocrystal of the metal.
According to still a further aspect of the invention, there is provided a process for producing an inert electrode material as previously defined, wherein each particle is formed of an agglomerate of grains of a ceramic material and grains of an alloy. The process of the invention comprises the steps of:
a) subjecting ~at least one metal oxide, nitride or carbide to high-energy ball milling to form a first powder comprising particles having an average particle size of 0.1 to 100 ~,m and each formed of an agglomerate of grains of a ceramic material;
b) subjecting at least two metals to high-energy ball milling to form a second powder comprising particles having an average particle size of 0.1 to 100 ~m and each formed of an agglomerate of grains with each grain comprising a nanocrystal of an alloy of the metals;
c) mixing the first and second powders to form a powder mixture; and d) subjecting the powder mixture obtained in step (c) to high-energy ball milling to form a nanocrystalline powder comprising particles having an average particle size of 0.1 to 100 ~,m and each formed of an _$_ agglomerate of grains of the ceramic material and grains of the alloy, wherein each grain of ceramic material comprises a nanocrystal of the ceramic material and each grain of alloy comprises a nanocrystal of the alloy.
According to another aspect of the invention, there is provided a process for producing an inert electrode material in powder form as previously defined, wherein each particle is formed of an agglomerate of grains each comprising a nanocrystal of a single phase ceramic material.
The process of the invention comprises subjecting a metal oxide, nitride or carbide to high-energy ball milling to form a nanocrystalline powder comprising particles having an average particle size of 0.1 to 100 ~m and each formed of an agglomerate of grains with each grain comprising a nanocrystal of a single phase ceramic material.
According to yet another aspect of the invention, there is provided a process for producing an inert electrode material in powder form as previously defined, wherein each particle is formed of an agglomerate of grains each comprising a nanocrystal of a metal. The process of the invention comprises subjecting a metal to high-energy ball milling to form a nanocrystalline powder comprising particles having an average particle size of 0.1 to 100 ~.m and each formed of an agglomerate of grains with each grain comprising a nanocrystal of the metal.
According to still another aspect of the invention, there is provided a process for producing an inert electrode material in powder form as previously defined, wherein each particle is formed of an agglomerate of grains each comprising a nanocrystal of an alloy. The process of the invention comprises subjecting at least two metals to high-energy ball milling to form a nanocrystalline powder comprising particles having an average particle size of 0.1 to 100 ~,m and each formed of an agglomerate of grains with each grain comprising a nanocrystal of an alloy of the metals.
The expression "high-energy ball milling" as used herein refers to a ball milling process capable of forming the aforesaid particles within a period of time of about 40 hours. In the aforementioned step (d), the high-energy ball milling is carried out for a period of time sufficient to break the agglomerates formed in steps (a) and (b), and to form new agglomerates comprising nanocrystalline grains of the ceramic material and nanocrystalline grains of the metal or alloy. Generally, such a period of time is about one hour.
MODES FOR CARRYING OUT THE INVENTION
Examples of suitable ceramic materials include oxides, nitrides and carbides of transition metals such as Ag, Co, Cu, Cr, Fe, Ir, Mo, Mn, Nb, Ni, Ru, Ta, Ti, V, W, Y, Zn and Zr, p-group metals such as Al, Ge, In, Pd, Sb, Si and Sn, rare earth metals such as Ce, La and Th, and alkaline earth metals such as Ca, Mg and Sr.
In the case where each particle is formed of an agglomerate of grains of ceramic material and grains of metal, the metal can be for example chromium, cobalt, copper, gold, iridium, iron, nickel, niobium, palladium, platinum, rubidium, ruthenium, silicon, silver, titanium, yttrium or zirconium. On the other hand, in the case where each particle is formed of an agglomerate of grains of ceramic material and grains of alloy, the alloy can be for example a Cu-Ag, Cu-Ag-Ni, Cu-Ni, Cu-Ni-Fe, Cu-Pd, Cu-Pt or Ni-Fe alloy. When these particles are sintered, they will form a cermet material having ceramic phase portions and .metal or alloy phase portions.
In the case where each particle is formed of an agglomerate of grains with each grain comprising a nanocrystal of a single phase ceramic material, the ceramic material advantageously includes a dopant for improving the sinterability of the powder and/or for increasing the conductivity of the electrode eventually made from the ceramic powder.
Examples of suitable dopants include those comprising an element selected from the group of Al, Co, Cr, Cu, Fe, Mo, Nb, Ni, Sb, Si, Sn, Ti, V, W, Y, Zn and Zr. The dopant is generally present in an amount of about 0.002 to about 1 wt.%, preferably between about 0.005 and about 0.05 wt.%. Since the corrosion, erosion and thermal expansion of a single phase ceramic material are uniform, electrodes produced from the nanocrystalline powder according to the invention, comprising such a material, have a longer life time.
In the case where each particle is formed of an agglomerate of grains with each grain comprising a nanocrystal of a metal, the metal can be for example chromium, cobalt, copper, gold, iridium, iron, nickel, niobium, palladium, platinum, rubidium, ruthenium, silicon, silver, titanium, yttrium or zirconium. Copper is preferred. On the other hand, in the case where each particle is formed of an agglomerate of grains with each grain comprising a nanocrystal of an alloy, the alloy can be for example a Cu-Ag, Cu-Ag-Ni, Cu-Ni, Cu-Ni-Fe, Cu-Pd, Cu-Pt or Ni-Fe alloy. When these particles are sintered, they form a dense metallic material.
According to a preferred embodiment of the process of the invention, the high-energy ball milling is carned out in a vibratory ball mill operated at a frequency of ~ to 25 Hz, preferably about 17 Hz. It is also possible to carry out such a ball milling in a rotary ball mill operated at a speed of 100 to 2000 r.p.m., preferably about 1200 r.p.m.
According to another preferred embodiment, the high-energy ball milling is carried out under an inert gas atmosphere such as a gas atmosphere comprising argon or helium. An atmosphere of argon is preferred.
The electrode material in powder form according to the invention can be used to produce dense electrode by powder metallurgy. The expression "powder metallurgy" as used herein refers to a technique in which the bulk powders are transformed into preforms of a desired shape by compaction or shaping followed by a sintering step. Compaction refers to techniques where pressure is applied to the powder, as, for example, cold uniaxial pressing, cold isostatic pressing or hot isostatic pressing. Shaping refers to techniques executed without the application of external pressure such as powder filling or slurry casting. The dense electrodes thus obtained have improved thermal shock and corrosion resistance properties.
The electrode material in powder form according to the invention can also be used to produce electrodes by thermal deposition applications. The expression "thermal deposition" as used herein refers to a technique in which powder particles are injected in a torch and sprayed on a conductive substrate such as graphite or copper, to form thereon a highly dense coating. The particles acquire a high velocity and are partially or totally melted during the flight path. The coating is built by the solidification of the droplets on the substrate surface. Examples of such techniques include plasma spray, arc spray and high velocity oxy-fuel.
Since the electrodes produced from the nanocrystalline powder according to the invention have a high density, the electrolyte does not penetrate into the electrode via pores and, consequently, the degradation of the electrode is minimized.
The following non-limiting examples illustrate the invention.
A NiFe204 spinal powder was produced by ball milling 51.7 wt.% Ni0 and 48.3 wt.% Fe203 in a tungsten carbide crucible with a ball-to-powder mass ratio of 15:1 using a SPEX 8000 (trademark) vibratory ball mill operated at a frequency of about 17 Hz. The operation was performed under a controlled argon atmosphere. The crucible was closed and sealed with a rubber O-ring. After 10 hours of high-energy ball milling, a nanocrystalline structure comprising a NiFe204 spinal with excess Ni0 was formed. The particle size varied between 0.1 and 5 ~.m and the crystallite size, measured by X-ray diffraction, was about 30 nm.
A Cu-Ag alloy powder was also produced by ball milling 69.5 wt.% Cu and 29.5 wt.% Ag in a tungsten carbide crucible with a ball-to-powder mass ratio of 10:1 using a SPEX 8000 vibratory ball mill operated at a frequency of about 17 Hz. The operation was performed under a controlled argon atmosphere. 1 wt.% of stearic acid was added as a lubricant. After 10 hours of high-energy ball milling, a nanocrystalline structure comprising an alloy of copper and silver was formed. The particle size varied between 10 and 30 ~m and.the crystallite size, measured by X-ray diffraction, was about 40 nm.
80 wt.% of the NiFea04 spinet powder and 20 wt.% of the Cu-Ag alloy powder produced above were mixed and the resulting powder mixture and the resulting powder mixture was ball milled in a tungsten carbide crucible with a ball-to-powder mass ratio of 10:1 using a SPEX
8000 vibratory ball mill operated at a frequency of about 17 Hz. After one hour of high-energy ball milling, a nanocrystalline powder comprising particles each formed of an agglomerate of grains comprising nanocrystals of the NiFe204 spinet and nanocrystals of the Cu-Ag alloy was obtained.
The particle size varied between 5 and 10 ~,m. This nanocrystalline powder was then pressed uniaxially at a pressure of 400 MPa. The compacted powder was then sintered at a temperature of 950°C for one hour to produce a dense electrode having excellent thermal shock and corrosion resistance properties.
A NiFea04 ferrite powder was produced by ball milling 51.7 wt.% of Ni0 and 48.3 wt.% Fe203 in a steel crucible with a ball-to-powder mass ratio of 10:1 using a SIMOLOYER (trademark) rotary ball mill operated at a speed of 1200 r.p.m.. The operation was performed under a controlled argon atmosphere by continously flushing the crucible with argon. After 5 hours of high-energy ball milling, an amorphous NiFe204 spinet was .~ ~~ . , , ,~ ~ , ~CA02Q0SJ
hPt'lt~t~t1 30 46 ~O3 ~ESCI="AMD
produced with an excess of nanocrystalline NiO. The particle size varied between 0.1 and 5 ~,m.
- A Cu-Ag alloy powder was also produced by ball milling 98 wt.%
Cu and 2 wt.% Ag in a steel crucible with a ball-to-powder mass ratio of 10:1 using a SIMOLOYER rotary ball mill operated at a speed of 1200 r.p.m. The operation was performed under a controlled argon atmosphere. 1 wt.% stearic acid was added as a lubricant. After 5 hours of high-energy ball milling, a nanocrystalline structure comprising an alloy of copper and silver was formed. The particle size varied between 5 to 30 ~,m and the crystallite size, measured by X-ray diffraction, was about 20 nm.
81.3 wt.% of the above NiFea04 spinal powder, 16.6 wt.% of the above Cu-Ag alloy powder and 2 wt.% of CAPLUBE G (trademark) acting as a lubricant arid binder were mixed and the resulting powder mixture was ball milled in a steel crucible with a ball-to-powder mass ratio of 10:1 using a SIMOLOYER rotary ball mill operated at 800 r.p.m.. After 1 S minutes of high-energy ball milling, a nanocrystalline powder comprising particles each formed of an agglomerate of grains comprising nanocrystals of the NiFe20a spinal and nanocrystals of the Cu-Ag alloy was obtained. The particle size varied between 5 and 10 p,m. This nanocrystalline powder was then cold isostatically pressed at 138 Mpa. The compacted powder was then sintered at a temperature of 1050°C for one hour to produce a dense electrode having excellent thermal shock and corrosion resistance properties.
1 °,' RECTIFIED SHEET (RULE 91 ) i~~~ a~.,~00~
' CA 02441578 2003-09-19 Pr~r'lte~ ,~30 06 20t~~ DESGI='.~1M~:! . CRO~t?Q395 A NiFe204 ferrite powder was produced by ball milling 51.7 wt.% of Ni0 and 48.3 wt.% Fe20~ in a steel crucible with a ball-to-powder mass ratio of 10:1 using a SIMOLOYER rotary ball mill operated at a speed of 1200 r.p.m.. The operation was performed under a controlled argon atmosphere by continously flushing the crucible with argon. After 5 hours of high-energy ball milling, an amorphous NiFe204 spinet was produced with an excess of nanocrystalline NiO. The particle size varied between 0.1 and S wm.
A Cu-Ag alloy powder was also produced by ball milling 98 wt.% Cu and 2 wt.% Ag in a steel crucible with a ball-to-powder mass ratio of 10:1 using a SIMOLO'YER rotary ball mill operated at a speed of 1200 r.p.m.. The operation was performed under a controlled argon atmosphere. 1 wt.% stearic acid was added as a lubricant. After 5 hours of high-energy ball milling, a nanocrystalline structure comprising an alloy of copper and silver was formed. The particle size varied between 5 to 30 ~,m and the crystallite size, measured by X-ray diffraction, was about 20 nm.
81.3 wt.% of the above NiFe20~ spinet powder, 16.6 wt.% of the above Cu-Ag alloy powder produced above and 2 wt.% of CAPLUBE G
acting as a lubricant and binder were mixed and the resulting powder mixture was ball milled in a steel crucible with a ball-to-powder mass ratio of 5:1 using a SPEX 8000 vibratory ball mill operated at 17 Hz. After 15 minutes of high-energy ball milling, a nanocrystalline powder comprising particles each formed of an agglomerate of grains comprising nanocrystals of the NiFe204 spinet and nanocrystals of the Cu-Ag alloy was obtained.
2r RECTIFIED SHEET (RULE 91 ) 45 (l6-2002 ' CA 02441578 2003-09-19 ~'rlnted 30 00 20U3V! ~=DAESCPAM~Y: ~C~t~~0t139 The particle size varied between 5 and 10 ~.m. This nanocrystaIline powder was then uniaxially pressed at 138 Mpa. The compacted powder was then sintered at a temperature of lOSO°C for one hour to produce a dense ' electrode having excellent thermal shock and corrosion resistance properties.
A coarse-grained Zn0 powder (99.9% pure) having an average grain size of 1 ~,m and a specific surface area of 3 m~/g was used as starting material. 0.008 wt.% A1z03 and ~ wt.% PVA were added as dopant and binder, respectively. The powder mixture was ball milled in a tungsten carbide crucible using a SPEX 8000 vibratory ball mill operated at a frequency of about 17 Hz. After I S hours of high-energy ball milling, a nanocrystalline Zn0 powder having a particle size between I and 5 ~,m and .
an average grain size smaller than I00 nm was obtained. The specific surface area of the nanocrystalline grains was 40 m2/g. This nanocrystalline powder was then pressed uniaxially at a pressure of 400 MPa. The compacted powder was then sintered at a temperature of 1250°C for one hour to produce a dense electrode having excellent thermal shock and corrosion resistance properties.
A nanocrystalline Cu-Ni alloy powder was produced by ball milling 70 wt.% Cu and 30 wt.% Ni in a steel crucible with a ball-to-powder mass ratio of 10:1 using a SIMOLOYER rotary ball mill operated at a speed of 1200 r.p.m.. 1 wt.% stearic acid was added as a lubricant.
~'' RECTIFIED SHEET (RULE 91) ,p~TO,Or~O(~~
' CA 02441578 2003-09-19 ~Pr~t~t~C~ ~30 06 20E~3I ? C?ESt'rPAM~~G~tt?,'~G0039~"J
7 _ After 5 hours of high-energy ball milling, a nanocrystalline powder comprising particles each formed of an agglomerate of grains comprising nanocrystals of an alloy of copper and nickel was obtained. The particle ' size varied between 5 to 30 ~m and the crystallite size, measured by X-ray diffraction, was about 20 nm. This nanocrystalline powder was mixed with 2 wt.% of CAPLUBE G and uniaxially pressed at 300 Mpa. The compacted powder was then sintered at a temperature of 1000°C for one hour to produce a dense electrode.
4, RECTIFIED SHEET (RULE 91) p~ a0.~~p0
4, RECTIFIED SHEET (RULE 91) p~ a0.~~p0
Claims (107)
1. An inert electrode material in powder form comprising particles having an average particle size of 0.1 to 100 µm and each formed of an agglomerate of grains of a ceramic material and grains of a metal or alloy with each grain of ceramic material comprising a nanocrystal of said ceramic material and each grain of metal or alloy comprising a nanocrystal of said metal or alloy.
2. An inert electrode material according to claim 1, wherein each said particle is formed of an agglomerate of said grains of ceramic material and said grains of metal.
3. An inert electrode material according to claim 2, wherein said ceramic material comprises an oxide, nitride or carbide of a metal selected from the group consisting of transition metals, p-group metals, rare earth metals and alkaline earth metals.
4. An inert electrode material according to claim 3, wherein said ceramic material comprises an oxide, nitride or carbide of a transition metal selected from the group consisting of Ag, Co, Cu, Cr, Fe, Ir, Mo, Mn, Nb, Ni, Ru, Ta, Ti, V, W, Y, Zn and Zr.
5. An inert electrode material according to claim 3, wherein said ceramic material comprises an oxide, nitride or carbide of a p-group metal selected from the group consisting of Al, Ge, In, Pb, Sb, Si and Sn.
6. An inert electrode material according to claim 3, wherein said ceramic material comprises an oxide, nitride or carbide of a rare earth metal selected from the group consisting of Ce, La and Th.
7. An inert electrode material according to claim 3, wherein said ceramic material comprises an oxide, nitride or carbide of an alkaline earth metal selected from the group consisting of Ca, Mg and Sr.
8. An inert electrode material according to claim 2, wherein said metal is selected from the group consisting of chromium, cobalt, copper, gold, iridium, iron, nickel, niobium, palladium, platinum, rubidium, ruthenium, silicon, silver, titanium, yttrium and zirconium.
9. An inert electrode material according to claim 1, wherein each said particle is formed of an agglomerate of said grains of ceramic material and said grains of alloy.
10. An inert electrode material according to claim 9, wherein said ceramic material comprises an oxide, nitride or carbide of a metal selected from the group consisting of transition metals, p-group metals, rare earth metals and alkaline earth metals.
11. An inert electrode material according to claim 10, wherein said ceramic material comprises an oxide, nitride or carbide of a transition metal selected from the group consisting of Ag, Co, Cu, Cr, Fe, Ir, Mo, Mn, Nb, Ni, Ru, Ta, Ti, V, W, Y, Zn and Zr.
12. An inert electrode material according to claim 10, wherein said ceramic material comprises an oxide, nitride or carbide of a p-group metal selected from the group consisting of Al, Ge, In, Pb, Sb, Si and Sn.
13. An inert electrode material according to claim 10, wherein said ceramic material comprises an oxide, nitride or carbide of a rare earth metal selected from the group consisting of Ce, La and Th.
14. An inert electrode material according to claim 10, wherein said ceramic material comprises an oxide, nitride or carbide of an alkaline earth metal selected from the group consisting of Ca, Mg and Sr.
15. An inert electrode material according to claim 9, wherein said alloy is selected from the group consisting of Cu-Ag, Cu-Ag-Ni, Cu-Ni, Cu-Ni-Fe, Cu-Pd, Cu-Pt and Ni-Fe alloys.
16. An inert electrode material according to claim 15, wherein said alloy is a Cu-Ag alloy.
17. An inert electrode material according to claim 16, wherein said ceramic material comprises a NiFe2O4 spinel.
18. An inert electrode material in powder form comprising particles having an average particle size of 0.1 to 100 µm and each formed of an agglomerate of grains with each grain comprising a nanocrystal of a single phase ceramic material, wherein ceramic materials selected from the group consisting of CeO2, SiC, WC and carbides, nitrides and borides of Nb, Ti, V
and Zr are excluded.
and Zr are excluded.
19. An inert electrode material according to claim 18, wherein said ceramic material comprises an oxide of a transition metal selected from the group consisting of Ag, Co, Cu, Cr, Fe, Ir, Mo, Mn, Nb, Ni, Ru, Ta, Ti, V, W, Y, Zn and Zr.
20. An inert electrode material according to claim 18, wherein said ceramic material comprises a nitride or carbide of a transition metal selected from the group consisting of Ag, Co, Cu, Cr, Fe, Ir, Mo, Mn, Ni, Ru, Ta, Y and Zn.
21. An inert electrode material according to claim 18, wherein said ceramic material comprises an oxide or nitride of a p-group metal selected from the group consisting of Al, Ge, In, Pb, Sb, Si and Sn.
22. An inert electrode material according to claim 18, wherein said ceramic material comprises a carbide of a p-group metal selected from the group consisting of Al, Ge, In, Pb, Sb and Sn.
23. An inert electrode material according to claim 18, wherein said ceramic material comprises an oxide of a rare earth metal selected from the group consisting of La and Th.
24. An inert electrode material according to claim 18, wherein said ceramic material comprises a nitride or carbide of a rare earth metal selected from the group consisting of Ce, La and Th.
25. An inert electrode material according to claim 18, wherein said ceramic material comprises an oxide, nitride or carbide of an alkaline earth metal selected from the group consisting of Ca, Mg and Sr.
26. An inert electrode material according to claim 18, wherein said ceramic material is zinc oxide.
27. An inert electrode material according to claim 18, wherein said ceramic material includes at least one dopant comprising an element selected from the group consisting of Al, Co, Cr, Cu, Fe, Mo, Nb, Ni, Sb, Si, Sn, Ti, V, W, Y, Zn and Zr.
28. An inert electrode material according to claim 27, wherein said dopant is present in an amount of about 0.002 to about 1 wt.%.
29. An inert electrode material according to claim 28, wherein the amount of dopant ranges from about 0.005 to about 0.05 wt.%.
30. An inert electrode material according to claim 29, wherein the amount of dopant is about 0.008 wt.%.
31. An inert electrode material according to claim 27, wherein said ceramic material comprises zinc oxide doped with aluminum oxide.
32. An inert electrode material according to claim 31, wherein the aluminum oxide is present in an amount of about 0.008 wt.%.
33. An inert electrode material in powder form comprising particles having an average particle size of 0.1 to 100 µm and each formed of an agglomerate of grains with each grain comprising a nanocrystal of a metal.
34. An inert electrode material according to claim 33, wherein said metal is selected from the group consisting of chromium, cobalt, copper, gold, iridium, iron, nickel, niobium, palladium, platinum, rubidium, ruthenium, silicon, silver, titanium, yttrium and zirconium.
35. An inert electrode material according to claim 34, wherein said metal is copper.
36. An inert electrode material according to claim 1, 9, 18 or 33, wherein said average particle size ranges from 1 to 10 µm.
37. An inert electrode material in powder form, for use in electrolytic production of a metal by electrolytic reduction of a metal compound, comprising particles having an average particle size of 1 to 30 µm and each formed of an agglomerate of grains with each grain comprising a nanocrystal of an alloy, wherein alloys selected from the group consisting of Cr2Nb, CrSi2, NbSi2 and alloys of formula (Mg1-x A x)D y in which A is an element selected from the group consisting of Li, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, V, Zr, Nb, Mo, In, Sn, O, Si, B, C and F, D is a metal selected from the group consisting of Fe, Co, Ni, Ru, Rh, Pd, Ir and Pt, x is a number ranging from 0 to 0.3 and y is a number ranging from 0 to 0.15, are excluded.
38. An inert electrode material according to claim 37, wherein said alloy is selected from the group consisting of Cu-Ag, Cu-Ag-Ni, Cu-Ni, Cu-Ni-Fe, Cu-Pd, Cu-Pt and Ni-Fe alloys.
39. An inert electrode material according to claim 38, wherein said alloy is a Cu-Ni alloy.
40. A process for producing an inert electrode material in powder form as defined in claim 2, which comprises the steps of:
a) subjecting at least one metal oxide, nitride or carbide to high-energy ball milling to form a first powder comprising particles having an average particle size of 0.1 to 100 µm and each formed of an agglomerate of grains of a ceramic material;
b) subjecting a metal to high-energy ball milling to form a second powder comprising particles having an average particle size of 0.1 to 100 µm and each formed of an agglomerate of grains with each grain comprising a nanocrystal of said metal;
c) mixing said first and second powders to form a powder mixture; and d) subjecting the powder mixture obtained in step (c) to high-energy ball milling to form a nanocrystalline powder comprising particles having an average particle size of 0.1 to 100 µm and each formed of an agglomerate of grains of said ceramic material and grains of said metal, wherein each grain of ceramic material comprises a nanocrystal of said ceramic material and each grain of metal comprises a nanocrystal of said metal.
a) subjecting at least one metal oxide, nitride or carbide to high-energy ball milling to form a first powder comprising particles having an average particle size of 0.1 to 100 µm and each formed of an agglomerate of grains of a ceramic material;
b) subjecting a metal to high-energy ball milling to form a second powder comprising particles having an average particle size of 0.1 to 100 µm and each formed of an agglomerate of grains with each grain comprising a nanocrystal of said metal;
c) mixing said first and second powders to form a powder mixture; and d) subjecting the powder mixture obtained in step (c) to high-energy ball milling to form a nanocrystalline powder comprising particles having an average particle size of 0.1 to 100 µm and each formed of an agglomerate of grains of said ceramic material and grains of said metal, wherein each grain of ceramic material comprises a nanocrystal of said ceramic material and each grain of metal comprises a nanocrystal of said metal.
41. A process according to claim 40, wherein said metal oxide, nitride or carbide is an oxide, nitride or carbide of a metal selected from the group consisting of transition metals, p-group metals, rare earth metals and alkaline earth metals.
42. A process according to claim 41, wherein said metal oxide, nitride or carbide is an oxide, nitride or carbide of a transition metal selected from the group consisting of Ag, Co, Cu, Cr, Fe, Ir, Mo, Mn, Nb, Ni, Ru, Ta, Ti, V, W, Y, Zn and Zr.
43. A process according to claim 41, wherein said metal oxide, nitride or carbide is an oxide, nitride or carbide of a p-group metal selected from the group consisting of Al, Ge, In, Pb, Sb, Si and Sn.
44. A process according to claim 41, wherein said metal oxide, nitride or carbide is an oxide, nitride or carbide of a rare earth metal selected from the group consisting of Ce, La and Th.
45. A process according to claim 41, wherein said metal oxide, nitride or carbide is an oxide, nitride or carbide of an alkaline earth metal selected from the group consisting of Ca, Mg and Sr.
46. A process according to claim 40, wherein said metal is selected from the group consisting of chromium, cobalt, copper, gold, iridium, iron, nickel, niobium, palladium, platinum, rubidium, ruthenium, silicon, silver, titanium, yttrium and zirconium.
47. A process according to claim 40, wherein steps (a), (b) and (d) are carried out in a vibratory ball mill operated at a frequency of 5 to 40 Hz.
48. A process according to claim 47, wherein said vibratory ball null is operated at a frequency of about 17 Hz.
49. A process according to claim 40, wherein steps (a), (b) and (d) are carried out in a rotary ball mill operated at a speed of 100 to 2000 r.p.m.
50. A process according to claim 49, wherein said rotary ball mill is operated at a speed of about 1200 r.p.m.
51. A process according to claim 40, wherein steps (a) and (b) are carried out under an inert gas atmosphere.
52. A process according to claim 51, wherein said inert gas atmosphere comprises argon.
53. A process according to claim 40, wherein steps (a) and (b) are carried out for a period of time of about 5 to 10 hours.
54. A process for producing an inert electrode material in powder form as defined in claim 9, which comprises the steps of:
a) subjecting at least one metal oxide, nitride or carbide to high-energy ball milling to form a first powder comprising particles having an average particle size of 0.1 to 100 µm and each formed of an agglomerate of grains of a ceramic material;
b) subjecting at least two metals to high-energy ball milling to form a second powder comprising particles having an average particle size of 0.1 to 100 µm and each formed of an agglomerate of grains with each grain comprising a nanocrystal of an alloy of said metals;
c) mixing said first and second powders to form a powder mixture; and d) subjecting the powder mixture obtained in step (c) to high-energy ball milling to form a nanocrystalline powder comprising particles having an average particle size of 0.1 to 100 µm and each formed of an agglomerate of grains of said ceramic material and grains of said alloy, wherein each grain of ceramic material comprises a nanocrystal of said ceramic material and each grain of alloy comprises a nanocrystal of said alloy.
a) subjecting at least one metal oxide, nitride or carbide to high-energy ball milling to form a first powder comprising particles having an average particle size of 0.1 to 100 µm and each formed of an agglomerate of grains of a ceramic material;
b) subjecting at least two metals to high-energy ball milling to form a second powder comprising particles having an average particle size of 0.1 to 100 µm and each formed of an agglomerate of grains with each grain comprising a nanocrystal of an alloy of said metals;
c) mixing said first and second powders to form a powder mixture; and d) subjecting the powder mixture obtained in step (c) to high-energy ball milling to form a nanocrystalline powder comprising particles having an average particle size of 0.1 to 100 µm and each formed of an agglomerate of grains of said ceramic material and grains of said alloy, wherein each grain of ceramic material comprises a nanocrystal of said ceramic material and each grain of alloy comprises a nanocrystal of said alloy.
55. A process according to claim 54, wherein said metal oxide, nitride or carbide is an oxide, nitride or carbide of a metal selected from the group consisting of transition metals, p-group metals, rare earth metals and alkaline earth metals.
56. A process according to claim 55, wherein said metal oxide, nitride or carbide is an oxide, nitride or carbide of a transition metal selected from the group consisting of Ag, Co, Cu, Cr, Fe, Ir, Mo, Mn, Nb, Ni, Ru, Ta, Ti, V, W, Y, Zn and Zr.
57. A process according to claim 55, wherein said metal oxide, nitride or carbide is an oxide, nitride or carbide of a p-group metal selected from the group consisting of Al, Ge, In, Pb, Sb, Si and Sn.
58. A process according to claim 55, wherein said metal oxide, nitride or carbide is an oxide, nitride or carbide of a rare earth metal selected from the group consisting of Ce, La and Th.
59. A process according to claim 55, wherein said metal oxide, nitride or carbide is an oxide, nitride or carbide of an alkaline earth metal selected from the group consisting of Ca, Mg and Sr.
60. A process according to claim 54, wherein said metals are selected from the group consisting of chromium, cobalt, copper, gold, iridium, iron, nickel, niobium, palladium, platinum, rubidium, ruthenium, silicon, silver, titanium, yttrium and zirconium.
61. A process according to claim 54, wherein ferric oxide and nickel oxide are subjected to said high-energy ball milling in step (a), whereby said first powder comprises particles having an average particle size of 0.1 to 100 µm and each formed of an agglomerate of grains of a NiFe2O4 spinet.
62. A process according to claim 61, wherein copper and silver are subjected to said high-energy ball milling in step (b), whereby said second powder comprises particles having an average particle size of 0.1 to 100 µm and each formed of an agglomerate of grains with each grain comprising a nanocrystal of a Cu-Ag alloy.
63. A process according to claim 54, wherein steps (a), (b) and (d) are carried out in a vibratory ball mill operated at a frequency of 5 to 40 Hz.
64. A process according to claim 63, wherein said vibratory ball mill is operated at a frequency of about 17 Hz.
65. A process according to claim 54, wherein steps (a), (b) and (d) are carried out in a rotary ball mill operated at a speed of 100 to 2000 r.p.m.
66. A process according to claim 65, wherein said rotary ball mill is operated at a speed of about 1200 r.p.m.
67. A process according to claim 54, wherein steps (a) and (b) are carried out under an inert gas atmosphere.
68. A process according to claim 67, wherein said inert gas atmosphere comprises argon.
69. A process according to claim 54, wherein steps (a) and (b) are carried out for a period of time of about 5 to 10 hours.
70. A process according to claim 54, wherein step (b) is carried out in the presence of a lubricant.
71. A process according to claim 70, wherein said lubricant is stearic acid.
72. A process for producing an inert electrode material in powder form, which comprises subjecting a starting material consisting of a metal oxide, nitride or carbide to high-energy ball milling to form a nanocrystalline powder comprising particles having an average particle size of 0.1 to 100 µm and each formed of an agglomerate of grains with each grain comprising a nanocrystal of a single phase ceramic material, wherein starting materials selected from the group consisting of WC and carbides, nitrides and borides of Nb, Ti, V and Zr are excluded.
73. A process according to claim 72, wherein said starting material is an oxide of a transition metal selected from the group consisting of Ag, Co, Cu, Cr, Fe, Ir, Mo, Mn, Nb, Ni, Ru, Ta, Ti, V, W, Y, Zn and Zr.
74. A process according to claim 72, wherein said starting material is a nitride or carbide of a transition metal selected from the group consisting of Ag, Co, Cu, Cr, Fe, Ir, Mo, Mn, Ni, Ru, Ta, Y and Zn.
75. A process according to claim 72, wherein said starting material is an oxide, nitride or carbide of a p-group metal selected from the group consisting of Al, Ge, In, Pb, Sb, Si and Sn.
76. A process according to claim 72, wherein said starting material is an oxide, nitride or carbide of a rare earth metal selected from the group consisting of Ce, La and Th.
77. A process according to claim 72, wherein said starting material is an oxide, nitride or carbide of an alkaline earth metal selected from the group consisting of Ca, Mg and Sr.
78. A process according to claim 72, wherein zinc oxide is subjected to said high-energy ball milling.
79. A process according to claim 72, wherein at least one dopant comprising an element selected from the group consisting of Al, Co, Cr, Cu, Fe, Mo, Nb, Ni, Sb, Si, Sn, Ti, V, W, Y, Zn and Zr is admixed with starting material prior to ball milling.
80. A process according to claim 79, wherein said dopant is used in an amount of about 0.002 to about 1 wt.%.
81. A process according to claim 80, wherein the amount of dopant ranges from about 0.005 to about 0.05 wt.%.
82. A process according to claim 79, wherein said metal oxide is zinc oxide and said dopant is aluminum oxide.
83. A process according to claim 82, wherein said dopant is used in an amount of about 0.008 wt.%.
84. A process according to claim 72, wherein said high-energy ball milling is carried in a vibratory ball mill operated at a frequency of 5 to 40 Hz.
85. A process according to claim 84, wherein said vibratory ball mill is operated at a frequency of about 17 Hz.
86. A process according to claim 72, wherein said high-energy ball milling is carried out in a rotary ball mill operated at a speed of 100 to r.p.m.
87. A process according to claim 86, wherein said rotary ball mill is operated at a speed of about 1200 r.p.m.
88. A process according to claim 72, wherein said high-energy ball milling is carried out under an inert gas atmosphere.
89. A process according to claim 88, wherein said inert gas atmosphere comprises argon.
90. A process far producing an inert electrode material in powder form as defined in claim 33, which comprises subjecting a metal to high-energy ball milling to form a nanocrystalline powder comprising particles having an average particle size of 0.1 to 100 µm and each formed of an agglomerate of grains with each grain comprising a nanocrystal of said metal.
91. A process according to claim 90, wherein said metal is selected from the group consisting of chromium, cobalt, copper, gold, iridium, iron, nickel, niobium, palladium, platinum, rubidium, ruthenium, silicon, silver, titanium, yttrium and zirconium.
92. A process according to claim 91, wherein said metal is copper.
93. A process according to claim 90, wherein said high-energy ball milling is carried in a vibratory ball mill operated at a frequency of 5 to 40 Hz.
94. A process according to claim 93, wherein said vibratory ball mill is operated at a frequency of about 17 Hz.
95. A process according to claim 90, wherein said high-energy ball milling is carried out in a rotary ball mill operated at a speed of 100 to r.p.m.
96. A process according to claim 95, wherein said rotary ball mill is operated at a speed of about 1200 r.p.m.
97. A process according to claim 90, wherein said high-energy ball milling is carried out under an inert gas atmosphere.
98. A process according to claim 97, wherein said inert gas atmosphere comprises argon.
99. A process for producing an inert electrode material in powder form as defined in claim 37, which comprises subjecting at least two metals to high-energy ball milling to form a nanocrystalline powder comprising particles having an average particle of 1 to 30 µm and each formed of an agglomerate of grains with each grain comprising a nanocrystal of an alloy of the metals, wherein alloys selected from the group consisting of Cr2Nb, CrSi2, NbSi2 and alloys of formula (Mg1-x A x)D y in which A is an element selected from the group consisting of Li, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Y, Zr, Nb, Mo, In, Sn, O, Si, B, C and F, D is a metal selected from the group consisting of Fe, Co, Ni, Ru, Rh, Pd, Ir and Pt, x is a number ranging from 0 to 0.3 and y is a number ranging from 0 to 0.15, are excluded.
100. A process according to claim 99, wherein said metals are selected from the group consisting of chromium, cobalt, copper, gold, iridium, iron, nickel, niobium, palladium, platinum, rubidium, ruthenium, silicon, silver, titanium, yttrium and zirconium.
101. A process according to claim 100, wherein copper and nickel are subjected to said high-energy ball milling, whereby said nanocrystalline powder comprises particles having an average particle size of 1 to 30 µm and each formed of an agglomerate of grains with each grain comprising a nanocrystal of a Cu-Ni alloy.
102. A process according to claim 99, wherein said high-energy ball milling is carried in a vibratory ball mill operated at a frequency of 5 to 40 Hz.
103. A process according to claim 102, wherein said vibratory ball mill is operated at a frequency of about 17 Hz.
104. A process according to claim 99, wherein said high-energy ball milling is carried out in a rotary ball mill operated at a speed of 100 to r.p.m.
105. A process according to claim 104, wherein said rotary ball mill is operated at a speed of about 1200 r.p.m.
106. A process according to claim 99, wherein said high-energy ball milling is carried out under an inert gas atmosphere.
107. A process according to claim 106, wherein said inert gas atmosphere comprises argon.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002441578A CA2441578A1 (en) | 2001-03-20 | 2002-03-20 | Inert electrode material in nanocrystalline powder form |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002341779A CA2341779A1 (en) | 2001-03-20 | 2001-03-20 | Inert electrode material in nanocrystalline powder form |
| CA2,341,779 | 2001-03-20 | ||
| CA002441578A CA2441578A1 (en) | 2001-03-20 | 2002-03-20 | Inert electrode material in nanocrystalline powder form |
| PCT/CA2002/000395 WO2002075023A2 (en) | 2001-03-20 | 2002-03-20 | Inert electrode material in nanocrystalline powder form |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2441578A1 true CA2441578A1 (en) | 2002-09-26 |
Family
ID=30001272
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002441578A Abandoned CA2441578A1 (en) | 2001-03-20 | 2002-03-20 | Inert electrode material in nanocrystalline powder form |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2441578A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2419354A (en) * | 2004-10-21 | 2006-04-26 | Psimedica Ltd | Silicon-metal nanocrystalline structure |
| US9119906B2 (en) | 2008-09-24 | 2015-09-01 | Integran Technologies, Inc. | In-vivo biodegradable medical implant |
-
2002
- 2002-03-20 CA CA002441578A patent/CA2441578A1/en not_active Abandoned
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2419354A (en) * | 2004-10-21 | 2006-04-26 | Psimedica Ltd | Silicon-metal nanocrystalline structure |
| US9119906B2 (en) | 2008-09-24 | 2015-09-01 | Integran Technologies, Inc. | In-vivo biodegradable medical implant |
| US10286120B2 (en) | 2008-09-24 | 2019-05-14 | Integran Technologies, Inc. | In-vivo biodegradable medical implant comprising a microstructure engineered metallic material |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US20040045402A1 (en) | Inert electrode material in nanocrystalline powder form | |
| CA2388206C (en) | Inert anode containing oxides of nickel, iron and cobalt useful for the electrolytic production of metals | |
| CN113880580B (en) | High-entropy carbide ultra-high temperature ceramic powder and preparation method thereof | |
| CA1235001A (en) | Reaction sintered cermet | |
| AU2002338623A1 (en) | Electrolytic production of high purity aluminum using ceramic inert anodes | |
| WO2002083992A2 (en) | Electrolytic production of high purity aluminum using ceramic inert anodes | |
| NZ518796A (en) | Electrolytic production of high purity aluminum using inert anodes | |
| KR20020091046A (en) | Cermet inert anode for use in the electrolytic production of metals | |
| EP1230437B1 (en) | Inert anode containing oxides of nickel, iron and zinc useful for the electrolytic production of metal | |
| JPS6025511B2 (en) | Electrode for molten salt electrolysis with electrocatalytic coating layer | |
| AU2004222545B2 (en) | Method for the manufacture of an inert anode for the production of aluminium by means of fusion electrolysis | |
| ZA200604572B (en) | Stable anodes including iron oxide and use of such anodes in metal production cells | |
| CA2330352A1 (en) | Refractory hard metals in powder form for use in the manufacture of electrodes | |
| US7033469B2 (en) | Stable inert anodes including an oxide of nickel, iron and aluminum | |
| CA2441578A1 (en) | Inert electrode material in nanocrystalline powder form | |
| AU2002240764A1 (en) | Inert electrode material in nanocrystalline powder form | |
| RU2352690C2 (en) | Inert anode designed for aluminium electrowinning in fused salts, and method for making same | |
| AU2007221833B2 (en) | Stable anodes including iron oxide and use of such anodes in metal production cells | |
| ZA200602351B (en) | Inert anode for producing aluminium by igneous electrolyse and method for producing said anode | |
| AU2002218924A1 (en) | Refractory hard metals in powder form for use in the manufacture of electrodes |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |