Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C26/00—Coating not provided for in groups C23C2/00 - C23C24/00
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B15/00—Layered products comprising a layer of metal
  • B32B15/01—Layered products comprising a layer of metal all layers being exclusively metallic
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B15/00—Layered products comprising a layer of metal
  • B32B15/18—Layered products comprising a layer of metal comprising iron or steel
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
  • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
  • C23C28/32—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer
  • C23C28/321—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer with at least one metal alloy layer
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
  • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
  • C23C28/32—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer
  • C23C28/322—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer only coatings of metal elements only
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
  • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
  • C23C28/34—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates
  • C23C28/345—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates with at least one oxide layer
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
  • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
  • C23C28/34—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates
  • C23C28/345—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates with at least one oxide layer
  • C23C28/3455—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates with at least one oxide layer with a refractory ceramic layer, e.g. refractory metal oxide, ZrO2, rare earth oxides or a thermal barrier system comprising at least one refractory oxide layer
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C30/00—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C8/02—Pretreatment of the material to be coated
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
  • H01M4/88—Processes of manufacture
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/02—Details
  • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
  • H01M8/0204—Non-porous and characterised by the material
  • H01M8/0206—Metals or alloys
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/02—Details
  • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
  • H01M8/0204—Non-porous and characterised by the material
  • H01M8/0206—Metals or alloys
  • H01M8/0208—Alloys
  • H01M8/021—Alloys based on iron
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/02—Details
  • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
  • H01M8/0204—Non-porous and characterised by the material
  • H01M8/0215—Glass; Ceramic materials
  • H01M8/0217—Complex oxides, optionally doped, of the type AMO3, A being an alkaline earth metal or rare earth metal and M being a metal, e.g. perovskites
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/02—Details
  • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
  • H01M8/0204—Non-porous and characterised by the material
  • H01M8/0215—Glass; Ceramic materials
  • H01M8/0217—Complex oxides, optionally doped, of the type AMO3, A being an alkaline earth metal or rare earth metal and M being a metal, e.g. perovskites
  • H01M8/0219—Chromium complex oxides
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/02—Details
  • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
  • H01M8/0204—Non-porous and characterised by the material
  • H01M8/0223—Composites
  • H01M8/0228—Composites in the form of layered or coated products
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/10—Fuel cells with solid electrolytes
  • H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/50—Fuel cells

Definitions

• the present disclosure relates to a fuel cell component, especially for use at high temperatures and in corrosive environments.
• the fuel cell component consists of a metallic substrate, such as stainless steel, and a coating, which in turn comprises at least one metallic layer and one reactive layer.
• the fuel cell component is produced by depositing the different layers and thereafter oxidising the coating to accomplish a conductive surface layer comprising at least one complex metal oxide such as a perovskite and/or a spinel.
• a fuel cell component which is used at high temperatures and in a corrosive environment, is an interconnect for fuel cells, especially for Solid Oxide Fuel Cells (SOFC).
• SOFC Solid Oxide Fuel Cells
• the interconnect material used in fuel cells should work as both separator plate between the fuel side and the oxygen/air side, and current collector of the fuel cell.
• separator plate For an interconnect material to be a good separator plate the material has to be dense to avoid gas diffusion through the material and in order to be a good current collector the interconnect material has to be electrically conducting and should not form insulating oxide scales on its surfaces.
• Interconnects can be made of for example graphite, ceramics or metals, often stainless steel.
• ferritic chromium steels are used as interconnect material in SOFC, which the two following articles are examples of: "Evaluation of Ferrite
• the thermal expansion of the interconnect material must not deviate greatly from the thermal expansion of the electro-active ceramic materials used as anode, electrolyte and cathode in the fuel cell stack.
• Ferritic chromium steels are highly suitable materials for this application, since the thermal expansion coefficients (TEC) of ferritic steels are close to the TECs of the electro-active ceramic materials used in the fuel cell.
• An interconnect in a fuel cell will be exposed to oxidation during operation. Especially in the case of SOFC, this oxidation may be detrimental for the fuel cell efficiency and the lifetime of the fuel cell.
• the oxide scale formed on the surface of the interconnect material may grow thick and may even flake off or crack due to thermal cycling. Therefore, the oxide scale should have a good adhesion to the interconnect material.
• the formed oxide scale should also have good electrical conductivity and not grow too thick, since thicker oxide scales will lead to an increased internal resistance.
• the formed oxide scale should also be chemically resistant to the gases used as fuels in a SOFC, i.e., no volatile metal-containing species such as chromium oxyhydroxides should be formed.
• Volatile compounds such as chromium oxyhydroxide will contaminate the electro-active ceramic materials in a SOFC stack, which in turn will lead to a decrease in the efficiency of the fuel cell. Furthermore, in the case the interconnect is made out of stainless steel, there is a risk for chromium depletion of the steel during the lifetime of the fuel cell due to diffusion of chromium from the centre of the steel to the formed chromium oxide scale at the surface.
• ferritic chromium steel as interconnect in SOFC is that they usually are alloyed with small amounts of aluminium and/or silicon, which will form AI 2 O3 and SiO 2 , respectively, at the working temperature of the SOFC. These oxides are insulating, thereby leading to an increase of electrical resistance of the cell, and as a consequence thereof decreasing the efficiency of the fuel cell.
• ferritic steels as interconnect material for SOFC is the use of ferritic steels with very low amounts of Si and Al in order to avoid the formation of insulating oxide layers. These steels are usually also alloyed with manganese and rare earth metals such as La.
• a super alloy defined as an austenitic stainless steel, an alloy of nickel and chromium, a nickel based alloy or a cobalt based alloy, is first coated with either Mn, Mg or Zn and then with a thick layer, 25 to 125 ⁇ m of an additional metal from the group Cu, Fe, Ni, Ag, Au, Pt, Pd, Ir or Rh.
• the coating of a thick second layer of an expensive metal such as Ni, Ag or Au is not a cost productive way of protecting already relatively expensive base materials such as super alloys.
• US2004/0058205 describes metal alloys, used as electrical contacts, which when oxidised forms a highly conductive surface. These alloys can be applied onto a substrate, such as steel. The conducting surface is accomplished by doping of one metal, such as Ti, with another metal, such as Nb or Ta. Furthermore, the alloys according to US2004/0058205 are applied onto the surface in one step and thereafter oxidised.
• a bipolar plate is disclosed in DE 195 47 699 Al having a part of the surface coated with metal or metal oxide which forms a mixed oxide layer of high conductivity with Cr from the substrate.
• the invention in DE 195 47 699 Al also relates to a plate consisting of a chromium oxide forming alloy with cobalt, nickel or iron enrichment layers in the region of the electrode contact surface.
• DE 103 06 649 Al is disclosed a Cr-oxide forming substrate, to be used as interconnect in a SOFC, having a layer comprising an element which may form a spinel. None of the cited prior art provides a satisfactory fuel cell component material for use in corrosive environments and/or at high temperatures which is produced in a cost- effective manner and with a high possibility of controlling the quality of the conductive surface.
• Another object is to provide a fuel cell component material, which will maintain its properties during operation for long service lives.
• a further object is to provide fuel cell component material that has a good mechanical strength even at high temperatures.
• Another object is to provide a cost-effective material for fuel cell components.
• a strip substrate of a metallic material preferably stainless steel, more preferably a ferritic chromium steel, is provided with a coating comprising at least one layer of a metallic material and at least one reactive layer.
• a reactive layer is considered to mean a layer, which consists of at least one element or compound which forms at least one complex metal oxide, such as a spinel and/or a perovskite, with the metallic material of the first layer when oxidised.
• the strip substrate may be provided with a coating by any method resulting in a dense and adherent coating.
• a coating method is vapour deposition, such as PVD, in a continuous roll-to-roll process.
• fuel cell components are formed of the coated strip by any conventional forming method, such as punching, stamping or the like.
• the fuel cell component, consisting of a coated strip may be oxidised before assembling the fuel cell or fuel cell stack, or may be oxidised during operation.
• Figure 2 GIXRD diffractogram of oxidised samples with and without coating.
• a surface provided with a layer is intended to be a result of an active action.
• a complex metal oxide structure can be formed on the surface instead of a "traditional" oxide on metal substrates used as fuel cell components.
• the purpose of the complex oxide is to accomplish a surface with high electrical conductivity in order to have a surface with a low contact resistance.
• a complex metal oxide is any metal oxide consisting of, but not limited to, include at least two different metal ions in the structure.
• oxide structures are spinel and perovskite type structures.
• a coated strip material is produced by providing a metallic substrate, such as stainless steel, preferably a ferritic chromium steel with a chromium content of 15-30 % by weight.
• the strip material substrate is thereafter provided with a coating consisting of at least two separate layers.
• One layer is a metallic layer based on a metal or metal alloy selected from the group consisting of Al, Cr, Co, Mo, Ni, Ta, W, Zr or an alloy based on any one of these elements, preferably Cr, Co, Mo or alloys based on any one of these elements.
• based on means that the element/alloy constitutes the main component of the composition, preferably constitutes at least 50 % by weight of the composition.
• the other layer is a reactive layer consisting of at least one element or compound, which forms a complex metal oxide structure with the element/elements of the metallic layer when oxidised.
• the precise composition of the coating can be tailor-made to achieve the formation of the wanted complex metal oxide structure which could be a spinel, perovskite and/or any other ternary or quartery metal oxide upon oxidisation with the desired properties, for example good conductivity and good corrosion resistance.
• the main reason for by providing a coating with two separate layers is that it is easier to control the amount of the different elements in the mixed oxide, i.e. tailor make the desired composition in order to achieve the desired result.
• an excellent adhesion of the coating to the substrate can be accomplished, thereby improving the properties of fuel cell component and improving the efficiency and prolonging life time of the fuel cell and the fuel cell stack.
• the reactive layer may be located on either side of the layer of a metallic material; i.e. sandwiched between the substrate and the metallic layer or, on top of the first deposited metallic layer.
• the metallic material consists of essentially pure Cr or a Cr-based alloy.
• a compound with a formula OfMCrO 3 and/or MCr 2 O 4 is formed, wherein M is any of the previously mentioned elements/compounds from the reactive layer.
• the reactive layer may contain elements from Group 2 A or 3 A of the periodic system, REM or transition metals.
• the element M of the reactive layer preferably consists of any of the following elements: La, Y, Ce, Bi 5 Sr, Ba, Ca 5 Mg, Mn, Co, Ni, Fe or mixtures thereof, more preferably La, Y, Sr, Mn, Co and or mixtures thereof.
• One specific example of this embodiment is one layer of Cr and the other layer being Co.
• the reactive layer is obtained by preoxidation of the surface of the metallic base material according to another preferred embodiment.
• the metallic base material is a stainless steel
• a chromium oxide will be formed.
• Ni or Co is deposited on the formed oxide according to this preferred embodiment.
• the coating may also comprise further layers.
• the coating may comprise a first metallic layer, thereafter a reactive layer and finally another metallic layer. This embodiment will further ensure a good conductivity of the surface of the fuel cell component.
• the coating does not comprise more than separate 10 layers, preferably not more than 5 separate layers.
• the thickness of the different layers are usually less than 20 ⁇ m, preferably less than 10 ⁇ m, more preferably less than 5 ⁇ m, most preferably less than 1 ⁇ m.
• the thickness of the reactive layer is less than that of the metallic layer. This is especially important when the reactive layer comprises elements or compounds that upon oxidation themselves form non-conducting oxides. In this case it is important that essentially the whole reactive layer/layers are allowed to react and/or diffuse into the metallic layer at least during operation of the fuel cell, so that the conductivity of the component during operation is not affected negatively.
• the coated strip may be produced in a batch like process. However, for economical reasons, the strip may be produced-in a continuous roll-to-roll process.
• the coating may be provided onto the substrate by coating with the metallic layer and the reactive layer.
• the coating may also be provided by pre-oxidation of the substrate to an oxide thickness of at least 50 run and thereafter coating with the additional layer. The coating is thereafter oxidised further as to achieve the complex metal oxide structure.
• This alternative embodiment of providing the coating onto the base material is especially applicable when the base material is a ferritic chromium steel, such as the oxide formed on the surface is a chromium based oxide.
• the coating may be performed with any coating process that generates a thin dense coating with good adhesion to the underlying material, i.e. the substrate or an underlying coating layer.
• the surface of the strip has to be cleaned in a proper way before coating, for example to remove oil residues and/or the native oxide layer of the substrate.
• the coating is performed by the usage of PVD technique in a continuous roll-to-roll process, preferably electron beam evaporation which might be reactive of plasma activated if needed.
• the strip may be provided with a coating on one side or on both sides.
• the coating is provided on both surfaces of the strip, the composition of the different layers on each side of the strip may be the same but may also differ.
• the strip may be coated on both sides simultaneously or one side at a time.
• the coated strip is exposed to an intermediate homogenisation step as to mix the separate layers and accomplish a homogenous coating.
• the homogenisation can be achieved by any conventional heat treatment under appropriate atmosphere, which could be vacuum or a reducing atmosphere, such as hydrogen or mixtures of hydrogen gas and inert gas, such as nitrogen, argon or helium.
• the coated strip is thereafter oxidised at a temperature above room temperature, preferably above 100 0 C, more preferably above 300 0 C, so that a complex metal oxide is formed on the surface of the strip.
• the coating thickness will increase when the coating is oxidised due to the complex metal oxide formation.
• the oxidation may result in a total oxidation of the coating or a partially oxidation of the coating, depending on for example the thickness of the layers, if the coating is homogenised, and time and temperature of the oxidation. In either case, the different layers of the coating are allowed to at least partially react and/or diffuse into each other, if this is not done by an intermediate homogenisation step.
• the oxidation may be performed directly after coating, i.e. before the formation of the fuel cell component final shape, after formation to the shape of the final component, i.e. the manufacturing of the fuel cell component from the coated strip, or after the fuel cell or fuel cell assembly, has been assembled, i.e. during operation.
• the purpose of accomplishing a complex metal oxide structure on the surface of the strip is that the formed structure has a much lower electrical resistance compared to traditional oxides of the elements of the metallic layer. This will in turn lead to a lower contact resistance of the fuel cell component and therefore also a better efficiency of fuel cell.
• the resistivity OfCr 2 O 3 at 800 0 C is about 7800 ⁇ -cm while the resistivity of for example Lao. 85 Sro.i 5 Cr ⁇ 3 is several orders of magnitude lower, namely about 0,01 ⁇ -cm.
• the fuel cell component will have good mechanical strength and is less expensive to manufacture than for example fuel cell components made entirely from a complex metal oxide material.
• the chromium depletion of the substrate is inhibited since the metallic layer will oxidise long before chromium of the substrate, this is especially pronounced when the metallic layer is Cr or a Cr-based alloy. Therefore, the corrosion resistance of the substrate will not be reduced during operation.
• the coating by other processes, for example co-evaporation of the different components of the coating.
• a stainless steel substrate is coated with a coating consisting of a metallic layer and a reactive layer.
• the metallic layer is a Cr or a Cr-based alloy.
• the reactive layer in this case includes transition metals, such as Ni, Co, Mn and/or Fe, if the oxide should receive a spinel structure.
• the reactive layer contains elements from Group 2A or 3 A of the periodic system, or REM.
• the reactive layer contains Ba, Sr, Ca, Y, La and/or Ce.
• the reactive layer may contain elements from Group 2A or 3 A of the periodic system, or REM along with transition metals.
• Mn and/or REM are allowed to diffuse from the substrate.
• the coating is optionally homogenised and thereafter oxidised so as to form the desired structure on the surface. This results in a very low surface resistance of the strip substrate. Also, the Cr-oxides MCrO 3 and/or MCr 2 O 4 formed during oxidation are less volatile than pure Cr 2 O 3 at high temperatures. This results in a coated strip that is highly suitable to be used as interconnects in Solid Oxide Fuel Cells.
• a 0.2 mm thick strip substrate of a ferritic chromium stainless steel was coated.
• the coating was homogenised so as to achieve a CrM layer wherein M is a mixture of La and Mn.
• the concentration of Cr in the coating is approximately 35-55 wt%, while the concentration of Mn is approximately 30-60 wt% and the concentration of La is 3- 4 wt%.
• the surface was analysed by Glow Discharge Optical Emission Spectroscopy (GDOES). Using this technique, it is possible to study the chemical composition of the surface layer as a function of the distance from the surface. The method is very sensitive for small differences in concentration and has a depth resolution of a few nanometres. The result of the GDOES analysis of a 1.5 ⁇ m thick CrM surface alloying layer is shown in Figure 1.
• GDOES Glow Discharge Optical Emission Spectroscopy
• One of the samples was coated with a 0.1 ⁇ m thick cobalt layer and a 0.3 ⁇ m thick chromium layer. The samples were oxidised in air at 850 °C for 168 hours prior to the analysis.
• GIXRD Grazing Incidence X-Ray Diffraction
• the ratio of Eskolaite /spinel for the uncoated oxidised samples was 9.9 while for the coated sample the ratio was 1.0. This could be interpreted as a tenfold increase of spinel structure in the surface oxide scale formed.
• the (1) diffractogram is the uncoated sample oxidised in air for 168 hours at 850 °C and the (2) diffractogram is the coated sample oxidised in air for 168 hours at 850 0 C.
• Three samples of a ferritic chromium steel with the nominal composition, by weight max 0.050 % C; max 0.25 % Si; max 0.35 % Mn; 21-23% Cr; max 0,40 % Ni; 0.80- 1.2 % Mo; max 0.01 % Al; 0.60 - 0.90 % Nb; small addition of V, Ti and Zr and normally occurring impurities were manufactured.
• Two of the samples were pre- oxidised in air to get a 100 nm thick oxide scale.
• the pre-oxidised samples were thereafter coated with a metallic layer.
• the metallic layer on sample 2 was a 300 nm thick Ni layer and on sample 3 a 300 nm thick Co layer.
• GIXRD Grazing Incidence X-Ray Diffraction
• the ratio OfCr 2 O 3 /MCr 2 O 4 for the uncoated oxidised samples was 9.9 while for the pre-oxidised sample with the Ni layer the ratio was 1.26 and for the pre-oxidised sample with the Co layer the ratio was 0.98. This indicating an 8.5, respective 10 folded increase of spinel structure in the formed oxide scale.
• the nickel layer does not only form more spinel oxide in the scale but also NiO is formed when the sample has been oxidised (6).
• the (1) diffractogram is the uncoated sample oxidised in air for 168 hours at 850 °C
• the (2) diffractogram is the pre-oxidised sample with a Ni layer sample oxidised in air for 168 hours at 850 °C
• the (3) diffractogram is the pre-oxidised sample with a Co layer sample oxidised in air for 168 hours at 850 °C.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Organic Chemistry (AREA)
• Metallurgy (AREA)
• Electrochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Inorganic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Sustainable Development (AREA)
• Sustainable Energy (AREA)
• Ceramic Engineering (AREA)
• Composite Materials (AREA)
• Fuel Cell (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
• Chemical Treatment Of Metals (AREA)

Priority Applications (9)

Applications Claiming Priority (2)

Publications (1)

Family

ID=33538431

Family Applications (1)

Country Status (11)

Cited By (15)

Families Citing this family (17)

Citations (5)

Family Cites Families (16)

• 2004
  • 2004-11-30 SE SE0402935A patent/SE528379C2/sv not_active IP Right Cessation
• 2005
  • 2005-11-21 KR KR1020077012250A patent/KR101323559B1/ko not_active Expired - Lifetime
  • 2005-11-21 AU AU2005310323A patent/AU2005310323B2/en not_active Ceased
  • 2005-11-21 US US11/665,972 patent/US20080299417A1/en not_active Abandoned
  • 2005-11-21 CN CN2005800410043A patent/CN101068678B/zh not_active Expired - Lifetime
  • 2005-11-21 CA CA2584355A patent/CA2584355C/en not_active Expired - Fee Related
  • 2005-11-21 ES ES05804297T patent/ES2413012T3/es not_active Expired - Lifetime
  • 2005-11-21 JP JP2007542977A patent/JP5133695B2/ja not_active Expired - Lifetime
  • 2005-11-21 DK DK05804297.9T patent/DK1819507T3/da active
  • 2005-11-21 EP EP05804297A patent/EP1819507B1/en not_active Expired - Lifetime
  • 2005-11-21 WO PCT/SE2005/001748 patent/WO2006059943A1/en not_active Ceased

Patent Citations (5)

Also Published As

Similar Documents

Legal Events