WO2017081950A1 - Alliage de titane, matériau au titane, séparateur, cellule et pile à combustible à polymère solide - Google Patents

Alliage de titane, matériau au titane, séparateur, cellule et pile à combustible à polymère solide Download PDF

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WO2017081950A1
WO2017081950A1 PCT/JP2016/078548 JP2016078548W WO2017081950A1 WO 2017081950 A1 WO2017081950 A1 WO 2017081950A1 JP 2016078548 W JP2016078548 W JP 2016078548W WO 2017081950 A1 WO2017081950 A1 WO 2017081950A1
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titanium
separator
fuel cell
contact resistance
platinum group
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PCT/JP2016/078548
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English (en)
Japanese (ja)
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西山　佳孝
淳子 今村
上仲　秀哉
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新日鐵住金株式会社
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Priority to JP2017518164A priority Critical patent/JP6308330B2/ja
Publication of WO2017081950A1 publication Critical patent/WO2017081950A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C14/00—Alloys based on titanium
    • 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
    • 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
    • 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
    • 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 invention relates to a titanium alloy, a titanium material including the titanium alloy, a solid polymer fuel cell separator including the titanium material, a cell including the separator, and a solid polymer fuel cell including the cell.
  • Fuel cells use the energy generated during the binding reaction between hydrogen and oxygen. Therefore, introduction and spread of fuel cells are expected from both aspects of energy saving and environmental measures.
  • fuel cells such as a solid electrolyte type, a molten carbonate type, a phosphoric acid type, and a solid polymer type.
  • the polymer electrolyte fuel cell has a high output density and can be miniaturized.
  • the polymer electrolyte fuel cell operates at a lower temperature than other types of fuel cells, and is easy to start and stop. Because of these advantages, the polymer electrolyte fuel cell is expected to be used for automobiles, small cogeneration for home use, and the like, and has attracted particular attention in recent years.
  • FIG. 1A is a perspective view of a polymer electrolyte fuel cell (hereinafter also simply referred to as “fuel cell”), and FIG. 1B is an exploded perspective view of a single cell used in the fuel cell.
  • fuel cell a polymer electrolyte fuel cell
  • the fuel cell 1 is an assembly (stack) of single cells.
  • an anode-side gas diffusion electrode membrane also referred to as “fuel electrode membrane”; hereinafter referred to as “anode”
  • anode anode-side gas diffusion electrode membrane
  • Cathode side gas diffusion electrode films also referred to as “oxidant electrode films”; hereinafter referred to as “cathodes”
  • Separators (bipolar plates) 5a and 5b are stacked on both sides of the laminate.
  • Some fuel cells are provided with a separator having a cooling water flow path between two adjacent single cells or every several single cells.
  • the present invention is also directed to a titanium material used for such a water-cooled fuel cell separator.
  • solid polymer electrolyte membrane 2 a fluorine-based proton conductive membrane having a hydrogen ion (proton) exchange group is mainly used.
  • the anode 3 and the cathode 4 are mainly composed of a carbon sheet in which conductive carbon fibers are formed into a sheet. Instead of the carbon sheet, carbon paper thinner than the carbon sheet, or thinner carbon cloth may be used.
  • the anode 3 and the cathode 4 may be provided with a catalyst layer made of a particulate platinum catalyst, graphite powder, and, if necessary, a fluorine resin having a hydrogen ion (proton) exchange group.
  • a groove-like flow path 6a is formed on the surface on the anode 3 side.
  • a fuel gas (hydrogen or hydrogen-containing gas) A flows through the flow path 6a, and hydrogen is supplied to the anode 3.
  • the separator 5b has a groove-like channel 6b formed on the surface on the cathode 4 side.
  • An oxidizing gas B such as air flows through the flow path 6 b and oxygen is supplied to the cathode 4. By supplying these gases, an electrochemical reaction occurs and DC power is generated.
  • a catalyst layer is provided on the anode 3 and the cathode 4, the fuel gas or oxidizing gas and the catalyst layer come into contact with each other to promote the reaction.
  • the main functions required for a separator of a polymer electrolyte fuel cell are as follows. (1) Function as a “flow path” for uniformly supplying fuel gas or oxidizing gas into the battery surface (2) Water generated on the cathode side together with a carrier gas such as air and oxygen after reaction, Function as a “flow path” for efficiently discharging from the fuel cell to the outside of the system (3) Contact with the electrode membrane (anode 3, cathode 4) to form an electrical path, and further, electricity between two adjacent single cells (4) Function as a “partition” between the anode chamber of one cell and the cathode chamber of the other cell between adjacent cells (5) In a water-cooled fuel cell, Function as a “partition wall” between adjacent cells
  • the base material of the separator used for the polymer electrolyte fuel cell needs to be able to fulfill such a function.
  • Substrate materials are roughly classified into metal materials and carbon materials.
  • the carbon-based material has an advantage that the weight of the separator can be reduced due to its small specific gravity, but has a problem that it has gas permeability and a low mechanical strength.
  • a separator made of a metal material is obtained by molding a metal material by press working or the like. Metallic materials are excellent in workability as a characteristic property of metals.
  • a separator made of a metal-based material has an advantage that the thickness can be reduced and the weight of the separator can be reduced.
  • the electrical conductivity of the separator decreases due to oxidation of the separator surface, and the contact resistance between the separator and the electrode film can increase. The following measures have been proposed for this problem.
  • Patent Document 1 in order to improve corrosion resistance (oxidation resistance), a passive film is removed from a surface in contact with an electrode in a titanium separator, and then the surface is plated with a noble metal such as gold (Au). It has been proposed to form a thin film layer consisting of However, the use of a large amount of precious metals such as gold in mobile fuel cells or stationary fuel cells such as automobiles is problematic from the viewpoints of economy and the amount of resources. For this reason, the titanium separator proposed in Patent Document 1 is not widespread.
  • Patent Document 2 attempts to increase the corrosion resistance (oxidation resistance) of a titanium separator without using a noble metal such as gold. Specifically, Patent Document 2 proposes a titanium separator having a conductive contact layer made of carbon formed on its surface. The conductive contact layer is formed by vapor deposition. However, since it takes a long time to form such a conductive contact layer by vapor deposition, productivity is lowered. Moreover, since a special apparatus is required for vapor deposition, the equipment cost increases. For this reason, the titanium separator proposed in Patent Document 2 is not actively employed at present.
  • Patent Document 3 proposes to reduce an increase in contact resistance due to surface oxidation by forming a metal film in which conductive ceramics are dispersed on the surface of a titanium separator.
  • a metal film in which conductive ceramics are dispersed on the surface of a titanium separator may hinder molding, and cracks or through holes may occur in the plate material during processing. .
  • ceramics wear the press die, it is necessary to change the press die to an expensive material such as a cemented carbide. For this reason, the titanium separator proposed in Patent Document 3 has not been put into practical use.
  • Patent Document 4 a titanium alloy base material containing a platinum group element is immersed in a solution containing a non-oxidizing acid and an oxidizing acid and pickled, thereby concentrating the platinum group element on its surface, Thereafter, a method of manufacturing a separator titanium material by a process of performing a heat treatment in a low oxygen concentration atmosphere is disclosed. By this process, a mixed layer of a platinum group element and titanium oxide is formed on the surface of the separator titanium material. With this mixed layer, the contact resistance of the titanium material when a current of 7.4 mA is passed with a load of 5 kgf / cm 2 (4.9 ⁇ 10 5 Pa) applied to the titanium material is 10 m ⁇ ⁇ cm 2. It is supposed to be lower as follows. This technique is also described in Non-Patent Document 1.
  • Patent Document 5 a titanium alloy substrate containing a platinum group element is immersed in an acid containing a non-oxidizing acid and pickled to form a separator in which a layer enriched with the platinum group element is formed on the surface thereof. Titanium materials have been proposed. In patent document 5, the time which immerses a base material in a solution for pickling is all made into 5 minutes or more in the Example. For this reason, it is difficult to perform pickling continuously, and it is necessary to perform it by a batch type.
  • Patent Document 5 a heat treatment is performed by heating to 350 to 600 ° C. in a vacuum atmosphere (low oxygen concentration atmosphere) for the purpose of improving the adhesion between the platinum group element components concentrated on the surface after pickling and the matrix. Is preferred.
  • the titanium material for a separator proposed in Patent Document 5 requires time for pickling, and it takes time to adjust the heat treatment atmosphere so as to satisfy a predetermined condition. Is difficult and reduces productivity.
  • Patent Document 6 discloses a titanium material for a separator of a polymer electrolyte fuel cell, which contains a platinum group element and a rare earth element. Since this titanium material contains rare earth elements, platinum group elements are concentrated on the surface by a short pickling treatment, and the initial titanium material can be obtained without heat treatment in a vacuum (low oxygen concentration atmosphere). It is said that the contact resistance is reduced. Further, in this titanium material, even when the platinum group element content is as small as 0.005 mass%, the effect of reducing the initial contact resistance by concentrating the platinum group element on the surface by pickling can be obtained. Has been.
  • JP 2003-105523 A Japanese Patent No. 4367062 Japanese Patent Laid-Open No. 11-162479 Japanese Patent No. 4032068 JP 2006-190643 A JP 2013-109981 A
  • the titanium material of Patent Document 6 for example, has a low initial contact resistance measured by applying a load of 20 kgf / cm 2 (1.96 ⁇ 10 6 Pa). The problem arises that the resistance increases.
  • the titanium material of Patent Document 6 is liable to cause rough skin (increase in surface roughness) during molding.
  • the surface of the titanium material needs to be flat.
  • an object of the present invention is to provide a titanium material having a low contact resistance after repeated load application and excellent formability while maintaining the effects (1) to (3).
  • Another object of the present invention is to provide a titanium alloy from which the titanium material can be easily obtained by pickling.
  • Still another object of the present invention is to provide a polymer electrolyte fuel cell separator including the titanium material, a cell including the separator, and a polymer electrolyte fuel cell including the cell.
  • the titanium alloy of the embodiment of the present invention is % By mass Platinum group elements: 0.005% to 0.15%, Rare earth element: 0.0005% or more, less than 0.002%, Ni: 0 to 1.0%, Mo: 0 to 0.5%, V: 0 to 0.5% Cr: 0 to 0.5%, and W: 0 to 0.5% And the balance consists of Ti and impurities,
  • the average crystal grain size of the ⁇ phase is more than 25 ⁇ m and not more than 300 ⁇ m.
  • the titanium material of the embodiment of the present invention is A base material made of the above titanium alloy; A film formed on the surface of the base material and mainly composed of titanium oxide and a platinum group element and having a thickness of 50 nm or less is provided.
  • a separator for a polymer electrolyte fuel cell according to an embodiment of the present invention includes the titanium material.
  • a cell for a polymer electrolyte fuel cell according to an embodiment of the present invention includes the separator.
  • a polymer electrolyte fuel cell according to an embodiment of the present invention includes the cell.
  • the initial contact resistance is low and the increase in contact resistance due to repeated load is small. For this reason, the contact resistance after repeatedly applying a load is low. Moreover, since this titanium material is provided with the above-described film, the contact resistance is low. Since the coating is excellent in corrosion resistance, the contact resistance of the titanium material is kept low in the environment inside the polymer electrolyte fuel cell. Furthermore, the formability of the titanium material of the present embodiment is good, and rough skin hardly occurs on the surface of the titanium material at the time of molding. For this reason, when this titanium material is applied to a separator of a polymer electrolyte fuel cell, it has good adhesion to other members such as an anode and a cathode.
  • the titanium alloy of the present embodiment can be pickled under appropriate conditions to concentrate the platinum group element on the surface in a short time and form the film. That is, the titanium material can be easily obtained by pickling the titanium alloy under appropriate conditions.
  • the separator of the present embodiment includes the titanium material of the present embodiment, and the cell and the polymer electrolyte fuel cell of the present invention include this separator. Therefore, in these separator, cell, and polymer electrolyte fuel cell, The said effect by the said titanium material is acquired.
  • FIG. 1A is a perspective view schematically showing a structure of a polymer electrolyte fuel cell.
  • FIG. 1B is an exploded perspective view showing the structure of a single cell constituting the solid polymer fuel cell.
  • FIG. 2 is a diagram for explaining a method of measuring contact resistance.
  • Patent Document 6 the present inventors have confirmed that when a platinum group element and a rare earth element are contained in a titanium alloy, the platinum group element can be concentrated on the surface in a short time and at a high concentration.
  • the titanium material thus obtained has a low initial contact resistance, but it has been found that the contact resistance increases when a repeated load is applied.
  • the crystal grain size of the titanium ⁇ phase also affects the contact resistance. Specifically, the larger the crystal grain size, the smaller the contact resistance. This is presumably because the crystal grain boundaries lower the mobility of electrons.
  • % for chemical composition means mass%.
  • Platinum group element means Ru, Rh, Pd, Os, Ir, and Pt.
  • the platinum group element is an element having an electric resistivity lower than that of Ti, and does not cause oxidation and corrosion in the operating environment of the polymer electrolyte fuel cell and does not increase the electric resistivity.
  • the titanium alloy contains one or more of the above platinum group elements.
  • the platinum group element content of the titanium alloy is 0.005 to 0.15%.
  • the “platinum group element content” refers to the content when the base material contains substantially only one type of platinum group element, and the base material contains two or more types of platinum group elements. When it contains, it shall mean the sum total of the content rate of each platinum group element.
  • the platinum group element content is less than 0.005%, the corrosion resistance cannot be increased and the contact resistance cannot be sufficiently reduced. On the other hand, when the platinum group element content is larger than 0.15%, the raw material cost becomes large. Considering the balance between economy and corrosion resistance, the platinum group element content is preferably 0.01 to 0.05%.
  • platinum group element is not particularly limited, but Pd, Ru, and Ir are preferable because they are less expensive and have a larger effect of reducing contact resistance per unit content than other platinum group elements. On the other hand, since Rh, Os and Pt are very expensive, they are not preferable from the viewpoint of economy.
  • the rare earth element refers to Sc, Y, and Ln group (La to Lu).
  • the platinum group element is concentrated on the surface of the base material by pickling to reduce the contact resistance of the titanium material. can do.
  • two or more kinds of rare earth elements are contained in the base material, such as mixed rare earth elements (Misch metal; hereinafter referred to as “Mm”) before separation and purification, and didymium alloys (alloys composed of Nd and Pr) Mixtures or alloys of rare earth elements can be used.
  • Mm and didymium alloys can be used as materials for the titanium alloy of the present invention as long as they are commercially available. In this case, the kind of rare earth elements contained in Mm and the didymium alloy and the content ratio of each rare earth element in the Mm and didymium alloy are not limited.
  • the rare earth element content of the titanium alloy of the present invention is 0.0005% or more and less than 0.002%.
  • the “rare earth element content” refers to the rare earth element content when the titanium alloy substantially contains only one kind of rare earth element, and the titanium alloy contains two or more kinds of rare earth elements. When it contains, it shall mean the sum total of the content rate of each rare earth element.
  • the titanium alloy contains a platinum group element and a rare earth element
  • Ti and the rare earth element are simultaneously dissolved in an aqueous solution containing a non-oxidizing acid in the active state region of the titanium alloy, and the platinum group element on the titanium alloy surface is obtained. Precipitation can be promoted. This effect is sufficiently obtained when the rare earth element content is 0.0005% or more.
  • the rare earth element When a titanium alloy containing a rare earth element is repeatedly subjected to a load, the rare earth element becomes an oxide with poor conductivity. If the rare earth element content is too high, an increase in contact resistance due to this oxide cannot be ignored. On the other hand, if the rare earth element content is too high, this oxide deteriorates the formability such as roughening or cracking during processing. This tendency becomes prominent when the average crystal grain size of the ⁇ phase described later exceeds 25 ⁇ m. When the rare earth element content is less than 0.002%, it is possible to suppress an increase in the contact resistance of the titanium material due to a repeated load and to improve the moldability. The effect of suppressing an increase in contact resistance due to repeated load and improving the moldability is significantly obtained when the Ln group is used among the rare earth elements. Therefore, it is preferable to use the Ln group as the rare earth element.
  • the lower limit of the rare earth element content is preferably 0.0006%, and more preferably 0.0008%.
  • the upper limit of the rare earth element content is preferably 0.0019%, more preferably 0.0018%. preferable.
  • the titanium alloy may contain one or more selected from the group consisting of Ni, Mo, V, Cr and W.
  • a platinum group element can be concentrated on the surface of the titanium alloy by a synergistic effect with the rare earth elements. Thereby, a titanium material having excellent crevice corrosion resistance can be obtained.
  • the contents are Ni: 1.0% or less, Mo: 0.5% or less, V: 0.5% or less, Cr: 0.5% or less, W: 0.5 % Or less.
  • a preferable upper limit of the Ni content is 0.7%, and a preferable lower limit of the Ni content is 0.001%.
  • a preferable upper limit of the Mo content is 0.4%, and a preferable lower limit of the Mo content is 0.001%.
  • a preferable upper limit of the V content is 0.4%, and a preferable lower limit of the V content is 0.001%.
  • a preferable upper limit of the Cr content is 0.4%, and a preferable lower limit of the Cr content is 0.001%.
  • a preferable upper limit of the W content is 0.4%, and a preferable lower limit of the W content is 0.001%.
  • the impurity elements of titanium alloys include raw materials, melting electrodes, and Fe, O, C, H, N, etc. introduced from the environment, and scraps as raw materials. Al, Zr, Nb, Si, Sn, Mn, Cu and the like introduced from the above. These impurity elements may be contained in the titanium alloy as long as the content does not hinder the effects of the present invention.
  • the contents not inhibiting the effects of the present invention include Fe: 0.3% or less, O: 0.35% or less, C: 0.18% or less, H: 0.015% or less, N : 0.03% or less, Al: 0.3% or less, Zr: 0.2% or less, Nb: 0.2% or less, Si: 0.02% or less, Sn: 0.2% or less, Mn: 0 0.01% or less, Cu: 0.1% or less, and the total content of these elements is 0.6% or less.
  • Average crystal grain size of the ⁇ phase The larger the crystal grain size of the ⁇ phase (parent phase) of the titanium alloy, the higher the conductivity of the titanium alloy. When the average crystal grain size of the ⁇ phase exceeds 25 ⁇ m, the conductivity can be sufficiently increased. On the other hand, if the average crystal grain size of the ⁇ phase exceeds 300 ⁇ m, even if the rare earth element content is optimized, the ductility of the titanium material containing the titanium alloy is lowered, and it becomes easy to crack during press molding. For this reason, the average crystal grain size of the ⁇ phase is more than 25 ⁇ m and not more than 300 ⁇ m, preferably 26 to 200 ⁇ m, and more preferably 30 to 120 ⁇ m.
  • the average crystal grain size of the ⁇ phase can be controlled by heat treatment (annealing) conditions and the like.
  • the average crystal grain size of the ⁇ phase is measured by a method defined in JIS-G 0551 (2013 edition) without polishing the surface of the titanium alloy after annealing.
  • the average crystal grain size of the ⁇ phase may be measured on the cut surface of the titanium alloy (titanium material). Even in this case, substantially the same value as that obtained when the surface of the titanium alloy after annealing is measured without polishing is obtained.
  • the ⁇ phase and the ⁇ phase coexist, the ⁇ phase is excluded from the measurement target and the average crystal grain size is obtained.
  • Titanium material The titanium material of the present invention includes a base material made of the titanium alloy and a film formed on the surface of the base material.
  • the film is mainly composed of titanium oxide and a platinum group element.
  • “mainly composed of titanium oxide and platinum group element” means that the ratio of titanium oxide and platinum group element in the film is 90% by mass or more. It is considered that the platinum group element in the film exists as a metal and forms an energization path between the base material and the surface of the film.
  • the thickness of the film exceeds 50 nm, many corrosion products such as oxides (including oxides of platinum group elements) are formed in the environment inside the polymer electrolyte fuel cell, and the surface contact resistance is low. May decrease. For this reason, the thickness of the film is 50 nm or less, preferably 20 nm or less, more preferably 10 nm or less. On the other hand, if the film is too thin, the corrosion resistance may decrease. For this reason, the thickness of the film is set to 0.1 nm or more, preferably 0.15 nm or more, and more preferably 0.2 nm or more.
  • the film thickness is determined as follows. First, the titanium material is cut in the thickness direction. The cut surface is observed with an electron microscope (for example, TEM), and the thickness (the distance from the boundary between the base material and the coating to the surface of the coating) is measured at any 10 locations. The measured values are averaged to obtain the film thickness. The film can be distinguished from the base material by contrast in the electron microscope image.
  • an electron microscope for example, TEM
  • a titanium material having a desired shape can be obtained by carrying out processes such as melting, casting, hot rolling, cold rolling, annealing, and pickling.
  • the method for forming the film is not particularly limited, but for example, the film can be formed by pickling or electrolytically treating the base material with a non-oxidizing acid and concentrating the platinum group element on the surface of the base material.
  • the platinum group elements are concentrated by eluting from the base material and reprecipitating on the surface of the base material.
  • the non-oxidizing acid for example, hydrochloric acid, sulfuric acid and the like can be employed.
  • hydrofluoric acid is a non-oxidizing acid, it has a strong dissolving power in the base material, and the reprecipitation efficiency of the platinum group element is inferior to hydrochloric acid, sulfuric acid and the like.
  • hydrofluoric acid when used, the amount of hydrogen generated during pickling is large, and hydrogen is easily absorbed by the base material. For this reason, when pickling using hydrofluoric acid, it is necessary to sufficiently control the concentration of hydrofluoric acid, the treatment time, the treatment temperature, and the like.
  • a plurality of types of acids such as hydrochloric acid, sulfuric acid, hydrofluoric acid, and sulfamic acid may be mixed and used.
  • the conditions for the electrolytic treatment are not particularly limited, but, for example, by treating the current density in the range of 0.1 to 30 mA / cm 2 , the platinum group element can be uniformly concentrated on the surface of the base material.
  • an oxidizing acid When an oxidizing acid is used for pickling, hydrogen generated by pickling can be prevented from entering the base material and being absorbed. On the other hand, when an oxidizing acid is used for pickling, a thick oxide layer is formed on the surface layer of the base material, making it difficult to form a film. For this reason, even if it is a case where an oxidizing acid is used for pickling for the purpose of preventing the absorption of hydrogen into the base material, it is preferable to use the oxidizing acid at the lowest possible concentration.
  • the film After forming the film, it is preferable to perform heat treatment in order to improve the adhesion between the base material and the film. Since the film is mainly composed of titanium oxide and a platinum group element, even when this titanium material is heat-treated in an oxidizing atmosphere, the oxidation of the surface layer hardly proceeds. Therefore, heat treatment in a vacuum (low oxygen concentration atmosphere) can be omitted when manufacturing the titanium material of the present embodiment.
  • a vacuum low oxygen concentration atmosphere
  • the heat treatment for example, an on-line bright annealing facility or a batch annealing furnace can be used.
  • the crystal grain size of the ⁇ phase can be in the range of more than 25 ⁇ m and 300 ⁇ m or less.
  • a light pickling for example, pickling within 10 minutes with an aqueous solution of pH 2 to 3 for the purpose of washing the surface as necessary. Light pickling does not affect the contact resistance and formability of the titanium material.
  • the polymer electrolyte fuel cell separator includes the titanium material described above.
  • a cell for a polymer electrolyte fuel cell (unit battery) includes the separator described above.
  • the polymer electrolyte fuel cell includes the above-described cell. Each cell has a solid polymer electrolyte membrane, an anode (fuel electrode membrane) superimposed on one surface of the solid polymer electrolyte membrane, and a cathode (oxidant electrode membrane) superimposed on the other surface of the solid polymer electrolyte membrane. Can be included.
  • the polymer electrolyte fuel cell may include a plurality of cells stacked via separators. The polymer electrolyte fuel cell generates DC power by supplying a fuel gas and an oxidant gas to the anode and cathode of each cell, respectively.
  • the titanium material of the present invention suppresses an increase in contact resistance due to repeated loads. Therefore, in the polymer electrolyte fuel cell of the present invention, an increase in contact resistance between the separator, the anode, and the cathode is suppressed.
  • the titanium material of the present invention has good moldability as described above, rough skin hardly occurs when it is formed into a separator shape. Therefore, in the polymer electrolyte fuel cell of the present invention, the adhesion between the separator and other members (for example, the anode and the cathode) can be increased.
  • the separator using this titanium material has low initial contact resistance and excellent corrosion resistance in the environment inside the polymer electrolyte fuel cell. Therefore, the low contact resistance of this separator is maintained in the polymer electrolyte fuel cell. Therefore, the polymer electrolyte fuel cell using this separator has a high initial voltage and a small voltage drop with time.
  • Titanium material sample was prepared and evaluated by the following method. 1. Production of Titanium Material A titanium ingot was prepared as a titanium material. Table 1 shows the chemical composition of the titanium ingot (material). These titanium ingots were obtained by melting and solidifying the raw material at the laboratory level. Material 1 contained substantially no platinum group elements and rare earth elements. The rare earth element content of the material 2 was lower than the range defined as the base material of the present invention. The rare earth element contents of the materials 3, 5, 8, 10, 11, 15, and 52 were higher than the range defined as the base material of the present invention. The platinum group element content of the material 51 was lower than the range defined as the base material of the present invention. In these respects, the raw materials 1 to 3, 5, 8, 10, 11, 15, 51, and 52 did not satisfy the chemical composition requirements of the base material of the present invention. Materials 4, 6, 7, 9, 12-14 and 53-60 met the chemical composition requirements of the matrix of the present invention.
  • pickling was performed by immersing the titanium plate in an aqueous solution of any one of the following (a) to (d) as an acid solution.
  • d An aqueous solution having a sulfuric acid concentration of 25% by mass and a hydrofluoric acid concentration of 0.1% by mass.
  • the temperature of the acid solution was 45 to 70 ° C., and the immersion time of the titanium plate in the acid solution was 0.3 to 20 minutes.
  • an oxide film was formed on the surface of the titanium plate. It was confirmed by analyzing with TEM-EDX that this oxide film was mainly composed of titanium oxide and a platinum group element (film in the titanium material of the present invention).
  • film simply refers to this oxide film.
  • the thickness of this oxide film was calculated
  • a groove-like gas flow path having a width of 2 mm and a depth of 1 mm is formed on both surfaces of the titanium plate (corresponding to the anode side and the cathode side of the separators 5a and 5b in FIG. 1B) and used as a separator. In a form that can be.
  • FIG. 2 is a diagram for explaining a contact resistance measurement method.
  • a titanium material (hereinafter referred to as “separator”) 21 processed into a separator shape is sandwiched between a pair of carbon papers (TGP-H-90 manufactured by Toray Industries, Inc.) 22 and this is plated with a pair of gold. It was sandwiched between electrodes 23.
  • the carbon paper 22 was used for the gas diffusion layer (the anode 3 and the cathode 4 in FIG. 1B), and the area thereof was 1 cm 2 .
  • a load is applied between the pair of gold-plated electrodes 23, and in this state, a constant current is passed between the pair of gold-plated electrodes 23.
  • the voltage drop was measured and the resistance value was determined based on this result.
  • the load was 20 kgf / cm 2 (1.96 ⁇ 10 6 Pa). Since the obtained resistance value is a sum of the contact resistances on both sides of the separator 21, this is divided by 2 to obtain a contact resistance value (initial contact resistance) per one side of the separator 21.
  • FC50-MEA which is a standard MEA for PFEC manufactured by Toyo Corporation, as a membrane electrode assembly (MEA) including a solid polymer electrolyte membrane (Nafion (registered trademark) -1135 as an ion exchange membrane) ) was used.
  • MEA membrane electrode assembly
  • a load was applied as a clamping pressure between the separator and the anode and the cathode. The contact resistance after operation of this fuel cell was measured.
  • the fuel cell operated by incorporating a separator was not a multi-cell fuel cell in which single cells were stacked. The reason is that in the state where the single cells are stacked, the difference in the stacked state is reflected in the evaluation result, and the reproducibility of the measured value is lowered.
  • hydrogen gas having a purity of 99.9999% was flowed as the anode side fuel gas, and air was flowed as the cathode side gas.
  • the gas pressure for introducing hydrogen gas and air into the fuel cell was 0.04 to 0.20 bar (4000 to 20000 Pa).
  • the temperature of the fuel cell main body was kept at 70 ⁇ 2 ° C., and the humidity control inside the fuel cell was adjusted by setting the inlet dew point to 70 ° C.
  • the pressure inside the battery was about 1 atmosphere (about 1.01 ⁇ 10 5 Pa).
  • This fuel cell was operated at a constant current density of 0.5 A / cm 2 .
  • the output voltage was highest in 20 to 50 hours from the start of operation. After reaching this highest voltage, the operation was continued for 250 hours, and then the operation of the fuel cell was temporarily stopped. Thereafter, the load, that is, the tightening pressure was removed and the load was applied again to restart the operation of the fuel cell. Then, after reaching the highest voltage, the operation was continued for 250 hours. Thereafter, the cell was disassembled, the separator was taken out, and the contact resistance was measured by the method described above to obtain the contact resistance after the power generation operation.
  • a digital multimeter (KEITLEY 2001 manufactured by Toyo Technica Co., Ltd.) was used for measurement of contact resistance and measurement of current and voltage during operation of the fuel cell.
  • the titanium plate to be evaluated (a titanium plate that has been pickled and a titanium plate that has not been intentionally pickled) is referred to as a “titanium material”.
  • the Eriksen test specified in JIS Z 2247 2006 edition
  • the side surface of the titanium material is magnified 50 times to confirm the presence or absence of wrinkles (unevenness). did.
  • Evaluation Results Table 2A and Table 2B show the above evaluation results together with the average crystal grain size of the base material, pickling conditions, and the thickness of the oxide film (film).
  • the titanium alloys (base materials) used for the titanium materials 6 and 7 satisfied the requirements of the titanium alloy of the present invention, but the titanium materials 6 and 7 did not satisfy the requirements of the titanium material of the present invention. For this reason, in the column of Table 2A and Table 2B, the titanium materials 6 and 7 are described as “reference examples”.
  • the contact resistance of the titanium material of the present invention (titanium materials 4, 9 to 11, 14, 18 to 20, 51, 53, 56, and 58 to 65) is initially, after repeatedly applying a load, and after operation of the fuel cell. All of these were sufficiently low at 10 m ⁇ ⁇ cm 2 or less.
  • the contact resistance was large at the initial stage, after repeatedly applying a load and after the power generation operation.
  • the contact resistance of the titanium material 1 was large because the base material contained substantially neither a platinum group element nor a rare earth element. This is thought to be due to the formation of
  • the reason why the contact resistance of the titanium material 2 was large is considered to be that a film in which the platinum group element was sufficiently concentrated on the surface was not formed by pickling because the rare earth element content of the base material was low.
  • the initial contact resistance was small, but the contact resistance after repeated load application and after power generation operation was large. This is presumably because the rare earth element content in the base material was high, so that the rare earth element was oxidized by repeated loading and fuel cell operation. Further, the titanium material 3 was roughened by processing. This is probably because the rare earth element promoted non-uniform deformation due to the high rare earth element content of the base material.
  • the initial contact resistance was small, but the contact resistance after repeated load application and after power generation operation was large. Further, the initial contact resistance of these titanium materials was larger than the average initial contact resistance of the titanium materials of the present invention examples. This is considered to be related to the fact that in the titanium materials 5 and 57, the average crystal grain size of the ⁇ phase of the base material was as small as 25 ⁇ m or less.
  • the contact resistance was high at the initial stage, after repeatedly applying a load, and after the power generation operation. This is probably because the titanium material 6 was not subjected to the pickling treatment, and therefore no film was formed.
  • the contact resistance was large at the initial stage, after repeatedly applying a load, and after the power generation operation. This is probably because the titanium material 7 has an increased contact resistance as a result of the film thickness obtained by the pickling treatment being too thick.
  • the contact resistance was sufficiently low at 10 m ⁇ ⁇ cm 2 at the initial stage, after repeated load application, and after power generation operation.
  • the titanium materials 8, 12, 15 to 17, 21, and 55 were roughened by processing. This is probably because the rare earth element promoted non-uniform deformation due to the high rare earth element content of the base material.
  • the initial contact resistance was small, but the contact resistance after repeated load application and after power generation operation was large. Moreover, the initial contact resistance of the titanium material 13 was larger than the average initial contact resistance of the titanium material of the present invention example. This is considered to be related to the fact that in the titanium material 13, the average crystal grain size of the ⁇ phase of the base material was as small as 25 ⁇ m or less. Further, the titanium material 13 was roughened by processing. This is probably because the rare earth element promoted non-uniform deformation due to the high rare earth element content of the base material.
  • rough skin was caused by processing. This is presumably because, in the titanium material 52, the ductility was remarkably reduced because the average crystal grain size of the ⁇ phase of the base material exceeded 300 ⁇ m.
  • the contact resistance was large both in the initial stage, after repeatedly applying a load, and after the power generation operation. This is presumably because, in the titanium material 54, the platinum group element content of the base material was low, so that a film in which the platinum group element was sufficiently concentrated on the surface was not formed by pickling.

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Abstract

L'invention concerne un matériau au titane qui comprend un matériau de base et un film de revêtement formé sur la surface du matériau de base. Le matériau de base contient, en % en masse, de 0,005 % à 0,15 % d'un élément du groupe du platine, 0,0005 % ou plus mais moins de 0,002 % d'une terre rare, de 0 à 1,0 % de Ni, de 0 à 0,5 % de Mo, de 0 à 0,5 % de V, de 0 à 0,5 % de Cr et de 0 à 0,5 % de W, le reste étant constitué de Ti et d'impuretés. La phase alpha du matériau de base présente une granulométrie cristalline moyenne supérieure à 25 µm, mais inférieure ou égale à 300 μm. Le film de revêtement est composé principalement d'oxyde de titane et d'un élément du groupe du platine, et il a une épaisseur inférieure ou égale à 50 nm. Ce matériau au titane présente une faible résistance de contact après l'application répétée d'une charge, tout en présentant une excellente aptitude au moulage.
PCT/JP2016/078548 2015-11-10 2016-09-28 Alliage de titane, matériau au titane, séparateur, cellule et pile à combustible à polymère solide WO2017081950A1 (fr)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013109891A (ja) * 2011-11-18 2013-06-06 Nippon Steel & Sumitomo Metal 固体高分子型燃料電池セパレータ用チタン材並びにその製造方法およびそれを用いた固体高分子型燃料電池
JP5660253B2 (ja) * 2013-01-25 2015-01-28 新日鐵住金株式会社 臭素イオンを含む環境での耐食性に優れたチタン合金

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JP2017088931A (ja) * 2015-11-05 2017-05-25 新日鐵住金株式会社 固体高分子型燃料電池用チタン合金、それを用いたチタン材、およびそれを用いた固体高分子型燃料電池

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013109891A (ja) * 2011-11-18 2013-06-06 Nippon Steel & Sumitomo Metal 固体高分子型燃料電池セパレータ用チタン材並びにその製造方法およびそれを用いた固体高分子型燃料電池
JP5660253B2 (ja) * 2013-01-25 2015-01-28 新日鐵住金株式会社 臭素イオンを含む環境での耐食性に優れたチタン合金

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