PatentDe  


Dokumentenidentifikation EP1399937 29.12.2005
EP-Veröffentlichungsnummer 0001399937
Titel VERFAHREN ZUR HERSTELLUNG EINER METALLELEKTRODE
Anmelder Cerel (Ceramic Technologies) Ltd., Tirat HaCarmel, IL
Erfinder COHEN, Nissim, 26307 Kiryat Haim, IL;
SCHUSTER, Israel, 36090 Kiryat Tivon, IL;
CHERNIAK, Ludmila, 33176 Haifa, IL;
PELED, Tali, 32767 Haifa, IL
Vertreter derzeit kein Vertreter bestellt
DE-Aktenzeichen 60207557
Vertragsstaaten AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LI, LU, MC, NL, PT, SE, TR
Sprache des Dokument EN
EP-Anmeldetag 13.06.2002
EP-Aktenzeichen 027385848
WO-Anmeldetag 13.06.2002
PCT-Aktenzeichen PCT/IL02/00458
WO-Veröffentlichungsnummer 0002103728
WO-Veröffentlichungsdatum 27.12.2002
EP-Offenlegungsdatum 24.03.2004
EP date of grant 23.11.2005
Veröffentlichungstag im Patentblatt 29.12.2005
IPC-Hauptklasse H01G 9/052

Beschreibung[en]
Field of the Invention

The present invention provides a porous metal electrode, wherein the porosity degree is in the range of 30 to 50% and the metal is capable of forming a stable, uniform, oxide layer having a dielectric constant equal to or greater than 20 (ε ≥20), preferably selected from the group consisting of tantalum and niobium, comprising a substantially uniform porous layer of deposited said metal particles thereon. The present invention further provides a process for manufacturing the same metal electrode for applying in a dry electrolytic capacitor. The term "metal" in this application referred to any metal that capable of forming a stable oxide layer having a dielectric constant equal to or greater than 20 (ε ≥20). Ta and Nb are typical representatives of such metals. The process of present invention provides a substantially uniform porous layer of deposited said metal particles thereon. The present invention further relates to a stable suspension for electrophoretically homogeneously deposition of said metal.

Background of the Invention

The production of a metal capacitor, wherein the metal is capable of forming a stable oxide layer having a dielectric constant equal to or greater than 20 (ε ≥20), preferably selected from the group consisting of tantalum and niobium, comprises some common general steps. Just for the sake of simplicity, the description hereunder relates to tantalum: (a) mechanical pressing of tantalum powder around tantalum wire, thus forming a tantalum anode element; (b) sintering the pressed powder at high temperatures (1400-2000°C) to form a sponge-like structure; (c) anodizing the sintered tantalum-coated tantalum conductor of step (b), thereby yielding Ta2O5 on the surface of particles and the anode (dielectric formation); (d) forming a MnO2 conductive layer (manganzing) on the formed Ta2O5; (e) dipping the element into a graphite dispersion and completing the cathode formation process by dipping into a silver dispersion. This is a rather cumbersome process that frequently yields a non-homogeneous, tantalum and niobium layer. Furthermore, the thickness of a metal particles layer formed by mechanical pressure is generally limited to over 800 microns. A thinner layer is not producible using conventional mechanical pressing procedures.

In order to improve this process and makes it more economical and technologically rational, the present invention is directed to providing a stable suspension for performing an electrophoretic step intended for replacing the above mentioned mechanical pressing step (a). The major advantage of applying an electrophoretic deposition (EPD) step in this particular case lies in the possibility of controlling the homogeneity and the thickness of the metal layer formed in step (a).

EPD allows obtaining a thickness of deposit layers in the range from 10 microns to few millimeters. In contradiction, the conventional mechanical pressing procedure cannot provide a metal particles layer of less than about 800 microns. Consequently, the EPD procedure according to the present invention reduces the capacitor overall size and the effective equivalent serial resistance (ESR).

Electrophoretic deposition processes are well known and are described, inter alia, in the US Patents 5,919,347, 6,069,949 and 6,127,283.

However, of the known prior art neither teaches how to obtain homogenously dispersed porous metal electrode applicable in a capacitor, wherein the porosity degree is in the range of 30 to 50% and the metal is capable of forming a stable, uniform, oxide layer having a dielectric constant greater than 20 (k ≥20), preferably tantalum or niobium layer, with required thickness of about 20 - 500 micron, nor they teach how to obtain the required stable suspension for carrying out the electrophoretic process.

USP 4,067,735 discloses a method of making bulk porous anodes for electrolytic capacitors, which comprises preparing a suspension of tantalum or niobium powder and a binding material, and subjecting the suspension to an electric field established by a voltage applied to electrodes, whereby the metal powder and the binder deposit forming bulk porous bodies, which are then sintered at temperatures from 1600 to 2000°C, to produce bulk porous anodes. This process, however, does not permit to control the porosity of the final anodes nor to impart to them desired shapes without high temperature treatments, combined with shape controlling means. The bulk structure, also, is not optimal, and it would be desirable to control the shape of the final electrode without treatments in addition to the electrophoretic deposition.

Thus, there is a need for, and it is an aim of the present invention to provide a stable metal suspension, wherein said metal is capable of forming a stable oxide layer having a dielectric constant greater than 20 (k ≥20), preferably selected from the group consisting of tantalum and niobium, for producing uniform deposition of metal particles in said metal layer, having a controllable range of layer thickness and porosity. It is a further aim of the present invention to provide such a process in which it is possible to control over the layer thickness within a desired range.

It is another object of present invention to provide a process for producing a porous metal electrode, wherein said metal is capable of forming a stable oxide layer having a dielectric constant equal to or greater than 20 (ε ≥20), preferably selected from the group consisting of tantalum and niobium, comprising the step of electrophoretic uniform deposition of metal particles onto a substrate comprising said metal conductor.

It is a further object of present invention to provide a stable suspension for electrophoretic homogeneous deposition of said metal, preferably tantalum or niobium particles. A major aspect of the present invention is the use of such stable suspension in the electrophoretic deposition process for obtaining homogeneously dispersed tantalum or niobium particles in a substantially uniform thickness layer. This layer may have a wide range of thickness, from a few microns to millimeters, and may be obtained in several minutes.

It is an additional object of present invention to provide a metal electrode, preferably tantalum or niobium anode for use in capacitors, wherein such an electrode comprises uniformly dispersed tantalum or niobium particles within said tantalum or niobium layer thereof.

Summary of the Invention

According to present invention there is provided a porous metal electrode as defined by the features of claim 1. A suspension defined by the features of claim 22 and an electrophoretic process, defined by the features of claim 4, for producing said porous metal electrode are provided, as well.

Description of the Invention

The present invention relates to a process for the production of a porous electrode comprising a homogeneous deposited metal layer, wherein the metal is capable of forming a stable, uniform, oxide layer having a dielectric constant equal to or greater than 20 (ε ≥20), preferably selected from the group consisting of tantalum and niobium, on the surface of said metal conductor. The process comprises the use of a stable suspension comprising uniformly dispersed said metal particles. For the sake of simplicity, the description of the process hereunder relates to tantalum:

  • (a) preparation of a homogenous suspension of tantalum particles, comprising tantalum particles, preferably in size range of 1 to 10 microns, in a polar solvent. If so desired, the larger particles are removed from the suspension by conventional means (decantation, filtration, etc.). The concentration of the metal particles in the suspension is dependent on the desired thickness of the deposit layer;
  • (b) electrophoretic deposition of tantalum particles from said suspension onto the surface of tantalum conductor to form a tantalum layer on the surface of the tantalum conductor;
  • (c) sintering the deposited tantalum layer. The process further optionally comprises the steps:
  • (d) anodization of the sintered deposited tantalum layer of step (c) to produce Ta2O5 on the surface;
  • (e) dipping the layer formed in step (d) into an aqueous solution of manganese nitrate for producing a MnO2 layer, thus forming the cathode.

Step (b) of the above process, i.e., the electrophoretic deposition of tantalum, includes the sub-steps of:

  • (I) adding an additive (a) charging agent such as, for example, acetyl acetone (AcAc)+Emphose® (phosphate ester), AlCl3, Poly-diallyldimethylammonium chloride (PDADMAC), ortan-850E (polyacrylic acid potassium salt) etc. and optionally a dispersant (such as, for example, ketones, polyethyleneglycols, copolymer organic pigments and TiO2 etc.) to the suspension of step (a), wherein the polar solvent is preferably n-butanol for depositing tantalum and ethanol for depositing niobium;
  • (II) passing a direct electrical current through the suspension, by means of a deposition electrode and counter electrode therein. A tantalum conductor in the form of a foil on which it is desired to deposit the layer of tantalum, is used as the said deposition electrode. The counter electrode may include an inert electrode made from rhodium, platinum palladium, or anodically dissolved electrode made from tantalum or niobium.

The preferred polar solvent in step (a) is n-butanol for tantalum suspension and ethanol for niobium suspension. However, other polar organic solvents and mixtures of water and polar organic solvents are applicable, as well. According to a preferred embodiment of the present invention, the tantalum or niobium particles in the suspension are positively charged, and consequently they are deposited on the cathode. However, they may be negatively charged, using for example, polyacrilic acid as an additive, in which case they are deposited on the anode.

The electrode, onto which the charged tantalum or niobium particles are deposited, is referred herein as "deposition electrode".

To impose de-agglomeration of the charged tantalum or niobium particles, the suspension is subjected to ultrasound treatment at 20 kHz and a power level of up to about 550 watts, for 5 - 15 minutes with pulses (on and off, every 2 - 8 seconds), prior the step (b). Additives such as pH and conductivity adjustment agents, charging agents, dispersants and binders may be added to the suspension. Some additives, such as, for example, Emphos may act as charging agent and buffer (i.e. pH and conductivity adjustment agent, simultaneously). The preferred charging agents for tantalum or niobium are Emphos (phosphate ester); AlCl3 and PDADMAC serving as pH and conductivity adjustment agents. These additives allow to charge tantalum or niobium particles positively and control the pH and conductivity of the tantalum or niobium suspensions to provide desired conditions for electrophoretic deposition of tantalum or niobium particles. The preferred dispersant is acetylacetone, which has been found to allow the electrophoretic deposition of tantalum or niobium particles to form a homogenous, smooth, uniform layer.

The selected counter electrode materials should be electrically conductive, optionally inert under the conditions of the present process and they should eliminate the possibility of contamination of the formed Ta or Nb deposition layer with dissolved other metal particles like Ni, Fe, Cr. In the case of organic additives, an anode made from inert materials, such as rhodium, platinum or palladium is preferred. In the case of inorganic additives, such as AlCl3 non-inert anodes, made from tantalum (for Ta deposition) or niobium (for Nb deposition) may be used. Consequently, in an electric field this anode dissolves anodically in the suspension to provides ions (Ta3+, Ta5+, Nb3+, Nb5+ etc.), which are known to play a role in charging the particles in the suspension and thereby increase particles mobility.

The deposition electrode is tantalum or niobium foil, whereas the preferred counter electrode is either rhodium, platinum, palladium or tantalum, in the case of AlCl3, as additive.

In step (II) the cathode and anode are immersed into the tantalum or niobium suspension, and a direct electrical current is passed between the electrodes. Deposition of tantalum or niobium from the suspension according to step (b) can be carried out either at a substantially constant current (the preferred range of current densities being between about 0.1 mA/cm2 and about 5 mA/cm2) or at a substantially constant voltage. The voltage range is between about 30 volts to about 500 volts, depending on the additive-solvent-solid load system. Deposition times may range from a few minutes to over 15 minutes, preferably 60-90 seconds, depending on the desired thickness of the formed tantalum or niobium layer. The deposition quality depend on type and concentration, of dispersed materials, type of solvent, type and concentration of additives, deposition conditions, etc. and on required deposit properties, such as thickness, density, uniformity, etc. Preferably, before the metal suspension, wherein the metal is selected from the group consisting of tantalum and niobium, is used for uniformly deposition of, for example, tantalum particles onto a tantalum deposition electrode (step (b)), a "pre-processing" initiating step is required for "starting up" the suspension. The charging mechanism of the tantalum particles in the suspension has not been yet studied in full. As known, metal and non-oxide materials (such as carbides and nitrides), unlike oxides, demand some initiating step of EPD process. An electric field is needed in order to charge the particles.

For running the pre-processing step a temporary cathode, such as, for example, tantalum foil is used as a deposition electrode and a temporary counter electrode, may be, for example, Pt. A direct electrical current having a constant current density of about 3 (or 0.1-5) mA/cm2 is passed between the electrodes for about 30-60 minutes (electrification). The constant conductivity is maintained at 0.1-3µS/cm in organic solvents and 10-300µS/cm in water. The high values are typical for water. Following this pre-processing step, the temporary tantalum (or niobium) electrode is removed (this electrode can be recycled) and another Ta (or Nb) foil onto which it is desired to deposited the tantalum (or niobium) layer is inserted into the suspension as a deposition electrode. For processing step (b), a direct electrical current having a constant current density of about 3 (0.1-5) mA/cm2 is passed between the electrodes for about 15 minutes.

As an alternative to the above described pre-processing charging step the metal particles may be charged by stirring the suspension for about 12 hours, followed by ultrasonic treatment.

Etching or sandblasting of the deposition electrode surface before deposition (step (b)), provides high adhesion of the deposited tantalum or niobium.

The subsequent sintering of the obtained tantalum- or niobium-coated tantalum (or niobium) foil conductor (step (c)) is carried out in a furnace.

The following examples are provided merely to illustrate the invention and are not intended to limit the scope of the invention in any manner.

Example 1

A suspension was prepared by dispersing 25 g tantalum powder in 100 ml of n-butanol. The suspension was cooled to about 10°C and subjected to ultrasonic treatment at 20 KHz and a power level of up to 550 Watts for 5 minutes at pulse regime ("on" 8 secons and "off" 8 seconds). 1000µl Pure (100%) Emphose (phosphate ester) and 250µl acetyl acetone (AcAc) were added to the suspension to adjust the pH to about 4 and conductivity of the suspension to about 1µS. In the pre-processing step, a direct electrical current having a constant current density of about 3mA/cm2 was passed between the electrodes tantalum foil and Pt for about 30-60 minutes. The constant conductivity was maintained at 1µS. Following this pre-processing step, the temporary tantalum foil electrode was removed and another Ta foil was inserted into the suspension as a deposition electrode onto which it is desired to deposit the tantalum layer. A direct electrical current having a constant current density of about 3mA/cm2 was passed between the electrodes for about 15 minutes. The constant conductivity was maintained at 1µS.

The tantalum - coated Ta foil was removed from the suspension, and dried in open air for a few minutes. The electrophoretic process provided a uniform tantalum coating with a thickness of about 200 µm. The coating thickness was evaluated using optical means. The green density was about 35% with about 5µ roughness.

Example 2

A suspension was prepared by dispersing 25 g tantalum powder in 100 ml of n-butanol. The suspension was cooled to 10°C and subjected to ultrasonic treatment at 20 KHz and a power level of up to 550 Watts for 5 minutes ("on" 8 and "off" 8 seconds). 300µl AlCl3 (0.01M in ethanol) were added to the suspension to adjust the conductivity to about 1 µS and pH to about 5. For the pre-processing step tantalum foil was used as deposition electrode and Ta was used as counter electrode. A direct electrical current having a constant current density of about 3mA/cm2 was passed between the electrodes for about 30-60 minutes. Following this pre-processing step, the temporary tantalum foil electrode was removed and another Ta foil was inserted into the suspension as a deposition electrode onto which it is desired to deposit the tantalum layer. Ni was used as counter electrode. A direct electrical current having a constant current density of about 3mA/cm2 was passed between the electrodes for about 15 minutes. The constant conductivity was maintained at 1µS, by adding AlCl3.

The tantalum - coated Ta foil was removed from the suspension, and dried for a few minutes. The electrophoretic process provided a uniform tantalum coating with a thickness of about 200 µm. The coating thickness was evaluated by optical means. The green density was about 35% with about 10µ roughness.

Example 3

A suspension was prepared by dispersing 10 g tantalum powder in 100 ml of n-butanol. The suspension was cooled to 10°C and subjected to ultrasonic treatment at 20 KHz and a power level of up to 550 Watts for 5 minutes (with 2 seconds pulses). 100µl of 20% by weight poly-diallyldimethylammonium chloride (PDADMAC) aqueous solution were added to the suspension followed by sonication for one additional minute to adjust the conductivity to about 2µS and pH to about 3.5. For the pre-processing step tantalum foil was used as deposition electrode and Pt was used as counter electrode. A direct electrical current having a constant current density of about 1 mA/cm2 was passed between the electrodes for about 30 minutes. Following this pre-processing step, the temporary tantalum foil electrode was removed and another Ta foil was inserted into the suspension as a deposition electrode onto which it is desired to deposit the tantalum layer. Pt or Ta was used as counter electrode. A direct electrical current having a constant current density of about 1mA/cm2 was passed between the electrodes for about up to 30 minutes. The constant conductivity was maintained at 2 µS, by adding PDADMAC solution.

The tantalum-coated Ta foil was removed from the suspension, and dried for a few minutes. The electrophoretic process provided a uniform tantalum coating with a thickness of about 300 µm. The coating thickness was evaluated by optical means. The green density was about 35% with about 10µ roughness.

The tantalum suspension for electrophoretic deposition prepared in the procedure as described in Example 3 found to be very stable at a room temperature for a period of at least 12 hours.

The procedure of Example 3 may be carried out applying various conditions - as follows:

  • (a) 5-1000µl PDADMAC; pH 3.2-3.9; conductivity (µS/cm) 0.1-1.5
  • (b) 5-1000µl PDADMAC; pH 6.4-6.5; conductivity (µS/cm) 0.1-1.3
  • (c) 5-1000µl PDADMAC; 5-200µl dispersant; pH 3.0-3.5; conductivity (µS/cm) 0.5-3.5. The dispersant may be selected from ketones (for example, acetylacetone), polyethyleneglycols (for example, PEG-400) and copolymer organic pigments and TiO2 (for example, Disperbyk serval types).
  • (d) 5-1000µl PDADMAC; 5-200µl dispersant; pH 6.3-6.4; conductivity (µS/cm) 0.5-3.5. The dispersant may be selected from ketones (for example, acetylacetone), polyethyleneglycols (for example, PEG-400) and copolymer organic pigments and TiO2 (for example, Disperbyk serval types).

Other nitrogen-containing compounds such as polymethyleneimine (PEI), copolymer-poly (dimethylamine-co-epichlorohydriné-co-ethylenediamine) and poly (acrylamide-co-diallyldimethyl-ammonium chloride may substitute PDADMAC.

Example 4

A suspension was prepared by dispersing 10 g niobium powder in 100 ml of ethanol-butanol. The suspension was cooled to 10°C and subjected to ultrasonic treatment at 20 KHz and a power level of up to 550 Watts for 5 minutes (with 2 seconds pulses). 100µl Emphos were added to the suspension followed by sonication for one additional minute to adjust the conductivity to about 3µS and pH to about 3.5. For the pre-processing step niobium foil was used as deposition electrode and Pt was used as counter electrode. A direct electrical current having a constant current density of about 1mA/cm2 was passed between the electrodes for about 30 minutes. Following this pre-processing step, the temporary niobium foil electrode was removed and another niobium foil was inserted into the suspension as a deposition electrode onto which it is desired to deposit the niobium layer. Pt was used as counter electrode. A direct electrical current having a constant current density of about 1 mA/cm2 was passed between the electrodes for about up to 30 minutes. The constant conductivity was maintained at 3µS, by adding Emphos solution. The niobium-coated niobium foil was removed from the suspension, and dried for a few minutes. The electrophoretic process provided a uniform niobium coating with a thickness of about 160 µm. The coating thickness was evaluated by optical means. The green density is 35% with about 5µ roughness.

The niobium suspension for electrophoretic deposition prepared in the procedure as described in Example 4 found to be very stable at a room temperature for a period of at least 12 hours.

The procedure of Example 4 was carried out with tantalum applying a mixture of 25% ethanol in water as a solvent. Acetylacetone and PDADMAC were used as dispersant and charging agent, respectively. The pH was adjusted to 6-6.3 and the conductivity to 68-245µS/cm. For preventing the release of H2 gas during the EPD process the voltage was kept low (for example, 10V) and the deposition time short (such as, for example, 3 minutes). The electrophoretic process provided a tantalum layer with a thickness of about 50µm. The green density was about 30% with about 5µ roughness.

Similarly, other solvents consisting of mixtures of water and organic polar solvents may be used for preparing the suspensions for electrophoretic deposition of metal particles according to the present invention.


Anspruch[de]
  1. Poröse Metallelektrode mit einem Porositätsgrad im Bereich von 30 bis 50 %, umfassend eine Folie aus einem Metall, das eine stabile einheitliche Oxidschicht bilden kann, die eine Dielektrizitätskonstante von gleich oder größer 20 aufweist, wobei die Elektrode weiterhin eine im Wesentlichen einheitliche poröse Schicht aus Teilchen des Metalls aufweist, die auf der Folie abgeschieden sind.
  2. Poröse Metallelektrode nach Anspruch 1, worin die abgeschiedene Metallschicht eine Dicke von 20 bis 500 Mikrometer aufweist.
  3. Poröse Metallelektrode nach Anspruch 1, worin das Metall ausgewählt ist aus der Gruppe, bestehend aus Tantal und Niob.
  4. Elektrophoretisches Verfahren zum Herstellen einer porösen Metallelektrode, worin der Porositätsgrad im Bereich von 30 bis 50 % liegt und das Metall in der Lage ist zum Bilden einer stabilen Oxidschicht mit einer Dielektrizitätskonstanten von gleich oder größer als 20, wobei das Metall ausgewählt wird aus der Gruppe, bestehend aus Tantal und Niob, umfassend eine im Wesentlichen einheitliche poröse Schicht aus den abgeschiedenen Metallteilchen darauf, umfassend die Schritte:
    • (a) Bereitstellen einer Metallsuspension in einem polaren Lösungsmittel,
    • (b) Durchführen eines Vorbearbeitungsschrittes durch Eintauchen einer temporären Abscheidungselektrode und einer temporären Gegenelektrode in die Suspension, worin die Abscheidungselektrode aus einer Metallfolie besteht und Anlegen eines geeigneten Gleichstroms an die Elektroden, um eine elektrophoretische homogene Abscheidung der Metallteilchen auf der Oberfläche der temporären Abscheidungselektrode zu bewirken; und
    • (c) Durchführen der einheitlichen Abscheidung der Metallteilchen auf der Oberfläche der temporären Abscheidungselektrode, nachfolgend auf eine Beladungsinkubationsperiode, nach welcher, und vor der einheitlichen Abscheidung des Metalls, ein Ersetzen der temporären Abscheidungselektrode durch eine neue erfolgt.
  5. Elektrophoretisches Verfahren nach Anspruch 4, worin das polare Lösungsmittel ausgewählt wird aus der Gruppe, bestehend aus einem organischen polaren Lösungsmittel, Wasser und einem Gemisch aus Wasser und polarem (polaren) organischem (organischen) Lösungsmittel(n).
  6. Elektrophoretisches Verfahren nach einem der Ansprüche 4 und 5, worin das Metall Tantal ist und das polare Lösungsmittel n-Butanol ist.
  7. Elektrophoretisches Verfahren nach einem der Ansprüche 4 und 5, worin das Metall Niob ist und das polare Lösungsmittel Ethanol ist.
  8. Elektrophoretisches Verfahren nach einem der Ansprüche 4 bis 7, worin die Metallsuspension mindestens ein Additiv enthält, ausgewählt aus der Gruppe, bestehend aus pH-Wert- und Leitfähigkeiteinstellungsmitteln zum Steuern des pH-Werts und der Leitfähigkeit der Metallsuspension.
  9. Elektrophoretisches Verfahren nach Anspruch 8, worin das Additiv Phosphatester umfasst.
  10. Elektrophoretisches Verfahren nach Anspruch 8, worin das Additiv AlCl3 umfasst.
  11. Elektrophoretisches Verfahren nach Anspruch 8, worin das Additiv Polydiallyldimethylammoniumchlorid (PDADMAC) umfasst.
  12. Elektrophoretisches Verfahren nach Anspruch 8, worin der pH-Wert und die Leitfähigkeit so gesteuert werden, dass sie im Bereich von 3-11 bzw. im Bereich von 0,1-250 µS/cm liegen.
  13. Elektrophoretisches Verfahren nach Anspruch 8, worin die Metallsuspension weiterhin mindestens ein Dispergiermittel umfasst.
  14. Elektrophoretisches Verfahren nach Anspruch 13, worin das Dispergiermittel Acetylaceton ist.
  15. Elektrophoretisches Verfahren nach Anspruch 13, worin das Additiv und das Dispergiermittel Phosphatester bzw. Acetylaceton sind.
  16. Elektrophoretisches Verfahren nach einem der Ansprüche 4 bis 15, worin die Gegenelektrode aus der Gruppe ausgewählt ist, bestehend aus Rhodium, Palladium, Platin, Tantal und Niob.
  17. Elektrophoretisches Verfahren nach einem der Ansprüche 15 und 16, worin die Metallsuspension Phosphatester und Acetylaceton enthält und die Gegenelektrode ausgewählt ist aus Rhodium, Palladium und Platin.
  18. Elektrophoretisches Verfahren nach einem der Ansprüche 10 und 16, worin die Metallsuspension AlCl3 enthält und die Gegenelektrode ein Metall umfasst, das aus Niob und Tantal ausgewählt ist.
  19. Elektrophoretisches Verfahren nach einem der Ansprüche 4, 6, 8 bis 18, worin das Metall Tantal ist und Tantalsuspension Phosphatester und Acetylaceton enthält und die Gegenelektrode ausgewählt ist aus Rhodium, Palladium und Platin.
  20. Elektrophoretisches Verfahren nach einem der Ansprüche 4, 6, 8 bis 19, worin das Metall Tantal ist und Tantalsuspension ein Additiv und/oder Dispergiermittel enthält, ausgewählt aus der Gruppe, bestehend aus Phosphatester, Acetylaceton, AlCl3 und PDADMAC, und worin die Gegenelektrode ausgewählt ist aus Rhodium, Palladium und Platin.
  21. Elektrophoretisches Verfahren nach einem der Ansprüche 4, 7 bis 19, worin das Metall Niob ist und die Niobsuspension Phosphatester enthält und die Gegenelektrode Pt, Pd oder Nb ist.
  22. Suspension zum Herstellen einer porösen Metallelektrode nach einem der Ansprüche 1 bis 3, worin der Porositätsgrad der Elektrode im Bereich von 30 bis 50 % ist, umfassend:
    • (a) Metallteilchen, bevorzugt in einem Größenbereich von 1 bis 10 µm, worin das Metall in der Lage ist zum Bilden einer stabilen, einheitlichen Oxidschicht mit einer Dielektrizitätskonstanten von gleich oder größer als 20, ausgewählt aus der Gruppe, bestehend aus Tantal und Niob;
    • (b) ein polares Lösungsmittel, worin Metallteilchen in dem polaren Lösungsmittel einer Ultraschallbehandlung unterzogen werden;
    • (c) mindestens ein Additiv zur Teilchenbeladung und zum Steuern des pH-Werts und der Leitfähigkeit; und optional
    • (d) mindestens ein Dispergiermittel.
  23. Suspension nach Anspruch 22, worin das polare Lösungsmittel ausgewählt ist aus der Gruppe, bestehend aus einem organischen polaren Lösungsmittel und einem Gemisch aus Wasser und polarem (polaren) organischem (organischen) Lösungsmittel(n).
  24. Suspension nach einem der Ansprüche 22 und 23, worin das polare Lösungsmittel n-Butanol ist.
  25. Suspension nach einem der Ansprüche 22 und 23, worin die Additive oder das Beladungsmittel und Dispergiermittel Phosphatester bzw. Acetylaceton sind.
  26. Suspension nach einem der Ansprüche 22 und 23, worin das Additiv AlCl3 ist.
  27. Suspension nach einem der Ansprüche 22 und 23, worin das Additiv PDADMAC ist.
  28. Suspension nach einem der Ansprüche 22 bis 27, worin der pH-Wert in dem Bereich von 3-5 ist und die Leitfähigkeit in dem Bereich von 0,5-3,0 µS/cm ist.
  29. Suspension nach einem der Ansprüche 22 und 28 zum Herstellen einer Tantalelektrode, umfassend eine im Wesentlichen einheitliche poröse Schicht aus darauf abgeschiedenen Tantalteilchen, worin der Porositätsgrad im Bereich von 30 bis 50 % ist.
  30. Zusammensetzung nach Anspruch 22, worin das polare Lösungsmittel Ethanol ist.
  31. Suspension nach einem der Ansprüche 22, 23, 28 und 30 zur Herstellung einer Niobelektrode, umfassend eine im Wesentlichen einheitliche poröse Schicht aus darauf abgeschiedenen Niobteilchen, worin der Porositätsgrad im Bereich von 30 bis 50 % ist.
Anspruch[en]
  1. A porous metal electrode, having a porosity degree is in the range of 30 to 50%, comprising a foil of a metal capable of forming a stable uniform oxide layer having a dielectric constant equal to or greater than 20, said electrode further comprising a substantially uniform porous layer of particles of said metal deposited on said foil.
  2. A porous metal electrode according to claim 1, wherein the deposited metal layer has a thickness of 20 - 500 microns.
  3. A porous metal electrode according to claim 1, wherein the metal is selected from the group consisting of tantalum and niobium.
  4. An electrophoretic process for producing a porous metal electrode, wherein the porosity degree is in the range of 30 to 50% and the metal is capable of forming a stable oxide layer having a dielectric constant equal to or greater than 20, the metal being selected from the group consisting of tantalum and niobium, comprising a substantially uniform porous layer of deposited said metal particles thereon, comprising the steps of:
    • (a) providing a metal suspension in a polar solvent,
    • (b) running a pre-processing step by immersing a temporary deposition electrode and a temporary counter electrode in said suspension, wherein said deposition electrode is constituted by a metal foil,

      and applying a suitable direct current to the said electrodes, such as to cause electrophoretic homogeneous deposition of said metal particles onto the surface of said temporary deposition electrode; and
    • (c) performing the uniform deposition of said metal particles on the surface of the temporary deposition electrode following a charging incubation period after which, and before the uniform deposition of said metal, replacing the temporary deposition electrode with a new one.
  5. An electrophoretic process according to claim 4, wherein the polar solvent is selected from the group consisting of an organic polar solvent, water and a mixture of water and polar organic solvent(s).
  6. An electrophoretic process according to any of claims 4 and 5, wherein the metal is tantalum and said polar solvent is n-butanol.
  7. An electrophoretic process according to any of claims 4 and 5, wherein the metal is niobium and said polar solvent is ethanol.
  8. An electrophoretic process according to any one of claims 4 to 7, wherein the metal suspension contains at least one additive chosen from the group consisting of pH and conductivity adjustment agents for controlling the pH and conductivity of said metal suspension.
  9. An electrophoretic process according to claim 8, wherein said additive comprises phosphate ester.
  10. An electrophoretic process according to claim 8, wherein said additive comprises AlCl3.
  11. An electrophoretic process according to claim 8, wherein said additive comprises poly-diallyldimethylammonium chloride (PDADMAC).
  12. An electrophoretic process according to claim 8 wherein the pH and the conductivity are controlled to be in the range of 3-11 and in the range of 0.1-250 µS/cm respectively.
  13. An electrophoretic process according to claim 8, wherein the metal suspension further contains at least one dispersant.
  14. An electrophoretic process according to claim 13, wherein said dispersant is acetyl acetone.
  15. An electrophoretic process according to claim 13, wherein said additive and said dispersant are phosphate eater and acetyl acetone, respectively.
  16. An electrophoretic process according to any one of claims 4 to 15, wherein the counter electrode selected from the group consisting of rhodium, palladium, platinum, tantalum and niobium.
  17. An electrophoretic process according to any one of claims 15 and 16, wherein the metal suspension contains phosphate ester and acetyl acetone and the counter electrode is selected from rhodium, palladium and platinum.
  18. An electrophoretic process according to any one of claims 10 and 16, wherein the metal suspension contains AlCl3 and the counter electrode comprises a metal selected from niobium and tantalum.
  19. An electrophoretic process according to any one of claims 4, 6, 8 to 18, wherein the metal is tantalum, and tantalum suspension contains phosphate ester and acetyl acetone and the counter electrode is selected from rhodium, palladium and platinum.
  20. An electrophoretic process according to any one of claims 4, 6, 8 to 19, wherein the metal is tantalum, and tantalum suspension contains an additive and/or dispersant selected from the group consisting of phosphate ester, acetyl acetone, AlCl3 and PDADMAC and the counter electrode is selected from rhodium, palladium and platinum.
  21. An electrophoretic process according to any one of claims 4, 7 to 19, wherein the metal is niobium and niobium suspension contains phosphate ester, and the counter electrode is Pt, Pd or Nb.
  22. A suspension for producing a porous metal electrode according to one of claims 1 to 3, wherein the porosity degree of said electrode is in the range of 30 to 50%, which comprises:
    • (a) metal particles, preferably in the size range of 1 to 10µm, wherein the metal is capable of forming a stable, uniform, oxide layer having a dielectric constant equal to or greater than 20, selected from the group consisting of tantalum and niobium;
    • (b) a polar solvent; wherein the metal particles in the polar solvent are subjected to ultrasonic treatment;
    • (c) at least one additive for particles charging and for controlling the pH and the conductivity; and optionally
    • (d) at least one dispersant
  23. A suspension according to claim 22, wherein the polar solvent is selected from the group consisting of an organic polar solvent and a mixture of water and polar organic solvent(s).
  24. A suspension according to any one of claims 22 and 23, wherein the polar solvent is n-butanol.
  25. A suspension according to any one of claims 22 and 23, wherein the additives, or charging agent and dispersant, are phosphate ester and acetyl acetone, respectively.
  26. A suspension according to any one of claims 22 and 23, wherein the additive is a AlCl3.
  27. A suspension according to any one of claims 22 and 23, wherein the additive is PDADMAC.
  28. A suspension according to any one of claims 22 to 27, wherein the pH is in the range of 3-5 and the conductivity is in the range of 0.5-3.0 µS/cm
  29. A suspension according to any one of claims 22 to 28, for manufacturing a tantalum electrode comprising a substantially uniform porous layer of deposited tantalum particles thereon, wherein the porosity degree is in the range of 30 to 50%.
  30. A suspension according to claim 22, wherein the polar solvent is ethanol.
  31. A suspension according to any one of claims 22, 23, 28 and 30, for manufacturing a niobium electrode comprising a substantially uniform porous layer of deposited niobium particles thereon, wherein the porosity degree is in the range of 30 to 50%.
Anspruch[fr]
  1. Électrode métallique poreuse, ayant un degré de porosité dans la gamme de 30 à 50%, comprenant une feuille d'un métal capable de former une couche d'oxyde stable uniforme ayant une constante diélectrique égale ou supérieure à 20, ladite électrode comprenant en outre une couche poreuse sensiblement uniforme de particules dudit métal déposé sur ladite feuille.
  2. Électrode métallique poreuse selon la revendication 1, dans laquelle la couche de métal déposé a une épaisseur de 20 à 500 micromètres.
  3. Électrode métallique poreuse selon la revendication 1, dans laquelle le métal est choisi dans le groupe consistant en le tantale et le niobium.
  4. Procédé électrophorétique pour produire une électrode métallique poreuse, dans laquelle le degré de porosité est comprise dans la gamme de 30 à 50%, et le métal est capable de former une couche d'oxyde stable ayant une constante diélectrique égale ou supérieure à 20, le métal étant choisi dans le groupe consistant en le tantale et le niobium, comprenant une couche poreuse sensiblement uniforme de particules dudit métal déposé sur celle-ci, comprenant les étapes de :
    • (a) fourniture d'une suspension d'un métal dans un solvant polaire,
    • (b) exécution d'une étape de prétraitement en immergeant une électrode de déposition temporaire et une contre-électrode temporaire dans ladite suspension, dans laquelle ladite électrode de déposition est constituée d'une feuille de métal,

      et en appliquant un courant continu approprié auxdites électrodes, de manière à causer une déposition homogène électrophorétique desdites particules de métal sur la surface de ladite électrode de déposition temporaire ; et
    • (c) exécution de la déposition uniforme desdites particules de métal sur la surface de l'électrode de déposition temporaire suite à une période d'incubation de charge après laquelle, et avant la déposition uniforme dudit métal, remplacement de l'électrode de déposition temporaire par une nouvelle.
  5. Procédé électrophorétique selon la revendication 4, dans lequel le solvant polaire est choisi dans le groupe consistant en un solvant polaire organique, l'eau et un mélange d'eau et de solvant(s) organique(s) polaire(s).
  6. Procédé électrophorétique selon l'une quelconque des revendications 4 et 5, dans lequel le métal est le tantale et ledit solvant polaire est le n-butanol.
  7. Procédé électrophorétique selon l'une quelconque des revendications 4 et 5, dans lequel le métal est le niobium et ledit solvant polaire est l'éthanol.
  8. Procédé électrophorétique selon l'une quelconque des revendications 4 à 7, dans lequel la suspension de métal contient au moins un additif choisi dans le groupe consistant en les agents d'ajustement du pH et de la conductivité pour contrôler le pH et la conductivité de ladite suspension de métal.
  9. Procédé électrophorétique selon la revendication 8, dans lequel ledit additif comprend un ester de phosphate.
  10. Procédé électrophorétique selon la revendication 8, dans lequel ledit additif comprend AlCl3.
  11. Procédé électrophorétique selon la revendication 8, dans lequel ledit additif comprend du chlorure de poly-diallyldiméthylammonium (PDADMAC).
  12. Procédé électrophorétique selon la revendication 8, dans lequel le pH et la conductivité sont contrôlés pour être dans la gamme de 3 à 11 et dans la gamme de 0,1 à 250 µS/cm respectivement.
  13. Procédé électrophorétique selon la revendication 8, dans lequel la suspension de métal contient en outre au moins un dispersant.
  14. Procédé électrophorétique selon la revendication 13, dans lequel ledit dispersant est l'acétylacétone.
  15. Procédé électrophorétique selon la revendication 13, dans lequel ledit additif et ledit dispersant sont un ester de phosphate et l'acétylacétone respectivement.
  16. Procédé électrophorétique selon l'une quelconque des revendications 4 à 15, dans lequel la contre-électrode est choisie dans le groupe consistant en le rhodium, le palladium, le platine, le tantale et le niobium.
  17. Procédé électrophorétique selon l'une quelconque des revendications 15 et 16, dans lequel la suspension de métal contient un ester de phosphate et l'acétylacétone et la contre-électrode est choisie parmi le rhodium, le palladium et le platine.
  18. Procédé électrophorétique selon l'une quelconque des revendications 10 et 16, dans lequel la suspension de métal contient AlCl3 et la contre-électrode comprend un métal choisi parmi le niobium et le tantale.
  19. Procédé électrophorétique selon l'une quelconque des revendications 4, 6, 8 à 18, dans lequel le métal est le tantale, et la suspension de tantale contient un ester de phosphate et l'acétylacétone et la contre-électrode est choisie parmi le rhodium, le palladium et le platine.
  20. Procédé électrophorétique selon l'une quelconque des revendications 4, 6, 8 à 19, dans lequel le métal est le tantale, et la suspension de tantale contient un additif et/ou un dispersant choisis dans le groupe consistant en un ester de phosphate, l'acétylacétone, AlCl3 et le PDADMAC et la contre-électrode est choisie parmi le rhodium, le palladium et le platine.
  21. Procédé électrophorétique selon l'une quelconque des revendications 4, 7 à 19, dans lequel le métal est le niobium et la suspension de niobium contient un ester de phosphate et la contre-électrode est Pt, Pd ou Nb.
  22. Suspension pour produire une électrode métallique poreuse selon l'une des revendications 1 à 3, dans laquelle le degré de porosité de ladite électrode est dans la gamme de 30 à 50%, qui comprend :
    • (a) des particules de métal, préférablement dans la gamme de taille de 1 à 10 µm, dans lesquelles le métal est capable de former une couche d'oxyde stable uniforme ayant une constante diélectrique égale ou supérieure à 20, choisi dans le groupe consistant en le tantale et le niobium ;
    • (b) un solvant polaire ; dans laquelle les particules de métal dans le solvant polaire sont soumises à un traitement par ultrasons ;
    • (c) au moins un additif pour charger les particules et pour contrôler le pH et la conductivité ; et facultativement
    • (d) au moins un dispersant.
  23. Suspension selon la revendication 22, dans laquelle le solvant polaire est choisi dans le groupe consistant en un solvant polaire organique et un mélange d'eau et de solvant(s) organique(s) polaire(s).
  24. Suspension selon l'une quelconque des revendications 22 et 23, dans laquelle le solvant polaire est le n-butanol.
  25. Suspension selon l'une quelconque des revendications 22 et 23, dans laquelle les additifs, ou agent de charge et dispersant, sont un ester de phosphate et l'acétylacétone, respectivement.
  26. Suspension selon l'une quelconque des revendications 22 et 23, dans laquelle l'additif est AlCl3.
  27. Suspension selon l'une quelconque des revendications 22 et 23, dans laquelle l'additif est le PDADMAC.
  28. Suspension selon l'une quelconque des revendications 22 à 27, dans laquelle le pH est dans la gamme de 3 à 5 et la conductivité est dans la gamme de 0,5 à 3,0 µS/cm.
  29. Suspension selon l'une quelconque des revendications 22 à 28, pour fabriquer une électrode au tantale comprenant une couche poreuse sensiblement uniforme de particules de tantale déposé sur celle-ci, dans laquelle le degré de porosité est dans la gamme de 30 à 50%.
  30. Suspension selon la revendication 22, dans laquelle le solvant polaire est l'éthanol.
  31. Suspension selon l'une quelconque des revendications 22, 23, 28 et 30, pour fabriquer une électrode au niobium comprenant une couche poreuse sensiblement uniforme de particules de niobium déposé sur celle-ci, dans laquelle le degré de porosité est dans la gamme de 30 à 50%.






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