WO2015068559A1 - チタン製燃料電池セパレータ材およびチタン製燃料電池セパレータ材の製造方法 - Google Patents
チタン製燃料電池セパレータ材およびチタン製燃料電池セパレータ材の製造方法 Download PDFInfo
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- WO2015068559A1 WO2015068559A1 PCT/JP2014/077848 JP2014077848W WO2015068559A1 WO 2015068559 A1 WO2015068559 A1 WO 2015068559A1 JP 2014077848 W JP2014077848 W JP 2014077848W WO 2015068559 A1 WO2015068559 A1 WO 2015068559A1
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- 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
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- 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
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- 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
- H01M8/0221—Organic resins; Organic polymers
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- 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
- H01M8/0258—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant
- H01M8/026—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant characterised by grooves, e.g. their pitch or depth
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- 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
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/1069—Polymeric electrolyte materials characterised by the manufacturing processes
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- 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
- H01M8/0213—Gas-impermeable carbon-containing materials
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- 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
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- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Definitions
- the present invention relates to a titanium fuel cell separator material used in a fuel cell and a method for producing a titanium fuel cell separator material.
- the fuel cell includes a polymer electrolyte fuel cell (PEFC), an alkaline electrolyte fuel cell (AFC), a phosphoric acid fuel cell (PAFC), a molten carbonate fuel cell (MCFC), and a solid oxide. It has been developed as a type fuel cell (SOFC) and biofuel cell.
- solid polymer fuel cells are being developed for use in fuel cell vehicles, home cogeneration systems, mobile devices such as mobile phones and personal computers.
- a polymer electrolyte fuel cell (hereinafter referred to as a fuel cell) is a single cell in which a polymer electrolyte membrane is sandwiched between an anode and a cathode, and a groove serving as a gas (hydrogen, oxygen, etc.) channel is formed.
- a plurality of the single cells are overlapped via a separator (also called a bipolar plate).
- the separator Since the separator is also a part for taking out the current generated in the fuel cell to the outside, a material having a low contact resistance (which means that a voltage drop occurs due to an interface phenomenon between the electrode and the separator surface). Applied.
- the separator is required to have high corrosion resistance because the inside of the fuel cell is in an acidic atmosphere with a pH of about 2 to 4, and the low contact resistance (conductivity) is maintained for a long time during use in this acidic atmosphere.
- the characteristic that Carbon is attracting attention as a material that satisfies these requirements, and the application of carbon to separators is being studied.
- a carbon powder separator for example, Patent Documents 1 to 3 formed from a graphite powder molded body, a mixture of graphite and resin, or a metal such as titanium or stainless steel.
- a separator in which carbon particles are adhered to a base material made of a material (for example, Patent Documents 4 to 7) or a carbon film is formed by a chemical vapor deposition (CVD) method or the like has been studied.
- Japanese Patent Laid-Open No. 10-3931 Japanese Patent No. 4075343 JP 2005-162550 A Japanese Patent No. 3904690 Japanese Patent No. 3904696 Japanese Patent No. 4886885 Japanese Patent No. 5108986
- Fuel cell separators may rub against each other when they are processed into separators or assembled into cells, and the conductive layer (carbon-based conductive layer) formed on the separator surface is scratched at this time. There are concerns about the occurrence.
- the separator surface is in contact with the carbon paper that constitutes the gas diffusion layer while being pressurized, but when used in in-vehicle applications, the conductive layer and carbon formed on the separator surface due to vibration associated with running. Friction may occur with the paper. If the conductive layer is easily worn at this time, the electrical resistance between the separator and the carbon paper increases as the usage time becomes longer, and the power generation performance of the fuel cell is lowered.
- the separator material of the fuel cell separator is required to have wear resistance as well as conductivity and durability (conductivity durability: property of maintaining conductivity for a long period of time).
- conductivity durability property of maintaining conductivity for a long period of time.
- the present invention has been made in view of the above-mentioned problems, and the problem is that the titanium fuel cell separator material and the titanium fuel cell separator material are excellent in conductivity and durability and also in wear resistance. It is to provide a method.
- the inventors formed a carbon-based conductive layer (carbon layer, conductive resin layer) having a two-layer structure on the base material surface of the titanium fuel cell separator material, and the coverage of the carbon layer
- the present invention has been found by making the resin of the conductive resin layer specified to be a predetermined value and having excellent conductivity and durability as well as excellent wear resistance.
- the inventors have performed a press molding process after the carbon layer forming process and the conductive resin layer forming process, or a conductive resin after the carbon layer forming process and the press molding process.
- a press molding process after the carbon layer forming process and the conductive resin layer forming process, or a conductive resin after the carbon layer forming process and the press molding process.
- a titanium fuel cell separator material is a titanium fuel cell separator material in which a carbon-based conductive layer is formed on a substrate surface made of pure titanium or a titanium alloy,
- the carbon-based conductive layer has a two-layer structure, and the layer close to the base material in the carbon-based conductive layer is a carbon layer, and the layer far from the base material is a conductive resin layer.
- the carbon layer contains graphite, the coverage of the carbon layer is 40% or more, the conductive resin layer contains carbon powder and a resin, and the resin is an acrylic resin, It is one or more resins selected from polyester resins, alkyd resins, urethane resins, silicone resins, phenol resins, epoxy resins, and fluororesins.
- the titanium fuel cell separator material according to the present invention includes the carbon-based conductive layer having a two-layer structure of the carbon layer and the conductive resin layer, the carbon-based conductive layer is a conductive material of the separator material. And durability can be improved. And since a conductive resin layer functions as a protective film, compared with a separator material provided with only one conductive layer, wear resistance can be improved.
- the carbon layer preferably has a coverage of 40% or more and 80% or less.
- the titanium fuel cell separator material according to the present invention has a carbon layer coverage on the base material of a predetermined value or less, after the press molding process for manufacturing the separator material is performed. Even if it exists, electroconductivity can naturally suppress the wear resistance and the fall of adhesiveness.
- an intermediate layer containing titanium carbide is preferably formed between the base material and the carbon layer.
- the titanium fuel cell separator material according to the present invention can improve the adhesion between the base material and the carbon layer by forming the intermediate layer between the base material and the carbon layer. . As a result, the possibility of peeling of the carbon-based conductive layer including the carbon layer can be reduced.
- the conductive resin layer preferably has a thickness of 0.1 to 20 ⁇ m.
- the titanium fuel cell separator material according to the present invention ensures the effect of improving the wear resistance by defining the thickness of the conductive resin layer within a predetermined range, A significant increase in the electrical resistance value can be prevented, and a suitable aspect can be obtained as a separator material.
- the method for producing a titanium fuel cell separator material according to the present invention includes a carbon layer forming step of forming a carbon layer containing graphite on a substrate surface made of pure titanium or a titanium alloy, and the carbon layer after the carbon layer forming step.
- the resin of the conductive resin layer is one or more resins selected from an acrylic resin, a polyester resin, an alkyd resin, a urethane resin, a silicone resin, a phenol resin, an epoxy resin, and a fluororesin.
- the manufacturing method of the titanium fuel cell separator material according to the present invention includes a carbon layer forming step and a conductive resin layer forming step, thereby forming a two-layer structure of the carbon layer and the conductive resin layer.
- the present carbon-based conductive layer can be formed on the substrate.
- a titanium fuel cell separator material with improved conductivity and durability can be produced by the carbon-based conductive layer.
- the conductive resin layer functions as a protective film, it is possible to manufacture a titanium fuel cell separator material with improved wear resistance compared to a separator material having only one conductive layer.
- the carbon layer preferably has a coverage of 40% or more and 80% or less.
- the titanium fuel cell separator material manufacturing method according to the present invention was subjected to a press molding process for manufacturing the separator material because the coverage of the carbon layer on the base material was not more than a predetermined value. Even later, it is possible to produce a titanium fuel cell separator material that is naturally conductive, and that also suppresses a decrease in wear resistance and adhesion.
- the method for producing a titanium fuel cell separator material according to the present invention preferably includes a heat treatment step of heat-treating the substrate at 200 to 550 ° C. after the conductive resin layer forming step.
- the manufacturing method of the titanium fuel cell separator material according to the present invention includes the heat treatment step after the conductive resin layer forming step, the resin on the outermost surface of the conductive resin layer may be partially decomposed and removed. Therefore, an increase in contact resistance due to a high resin ratio of the conductive resin layer can be suppressed. As a result, a titanium fuel cell separator material with further reduced contact resistance can be produced.
- the method for producing a titanium fuel cell separator according to the present invention includes a heat treatment in which the substrate is heat-treated at 300 to 850 ° C. in a non-oxidizing atmosphere between the carbon layer forming step and the conductive resin layer forming step. It is preferable to include a process.
- the manufacturing method of the titanium fuel cell separator material according to the present invention includes the heat treatment step between the carbon layer forming step and the conductive resin forming step, an intermediate between the base material and the carbon layer is provided. A layer can be formed, and the adhesion between the substrate and the carbon layer can be improved. As a result, it is possible to manufacture a titanium fuel cell separator material in which the possibility of peeling of the carbon-based conductive layer including the carbon layer is reduced.
- the method for producing a titanium fuel cell separator material according to the present invention includes a carbon layer forming step of forming a carbon layer containing graphite on a substrate surface made of pure titanium or a titanium alloy, and the carbon layer after the carbon layer forming step.
- the manufacturing method of the fuel cell separator material made from titanium which concerns on this invention performs a press molding process after a carbon layer formation process and a conductive resin layer formation process, a conductive resin layer is at the time of press molding. Since it plays the role of a protective layer, it is possible to avoid peeling and dropping of the carbon layer during press molding.
- the two layers of the carbon layer and the conductive resin layer formed on the base material improve conductivity and durability (conductivity durability: property of maintaining conductivity for a long time), and the conductive resin layer The possibility of peeling of the carbon-based conductive layer (carbon layer, conductive resin layer) during handling after press molding is reduced.
- the carbon layer preferably has a coverage of 40% or more and 80% or less.
- the titanium fuel cell separator material manufacturing method performs the press forming process when manufacturing the separator material because the coverage of the carbon layer on the substrate is not more than a predetermined value. Even after this, it is possible to produce a titanium fuel cell separator material that is naturally conductive, and that suppresses a decrease in wear resistance and adhesion.
- the method for producing a titanium fuel cell separator material according to the present invention preferably includes a heat treatment step of heat treating the substrate at 200 to 550 ° C. after the press molding step.
- the manufacturing method of the titanium fuel cell separator material according to the present invention performs the heat treatment step after the press molding step, the resin on the outermost surface of the conductive resin layer can be partially decomposed and removed. An increase in contact resistance due to the high resin ratio of the conductive resin layer can be suppressed. As a result, a titanium fuel cell separator material with further reduced contact resistance can be produced.
- the method for producing a titanium fuel cell separator according to the present invention includes a heat treatment in which the substrate is heat-treated at 300 to 850 ° C. in a non-oxidizing atmosphere between the carbon layer forming step and the conductive resin layer forming step. It is preferable to include a process.
- the manufacturing method of the titanium fuel cell separator material according to the present invention includes the heat treatment step between the carbon layer forming step and the conductive resin layer forming step, the method is performed between the base material and the carbon layer.
- An intermediate layer containing titanium carbide can be formed.
- the method for producing a titanium fuel cell separator material according to the present invention includes a carbon layer forming step of forming a carbon layer containing graphite on a substrate surface made of pure titanium or a titanium alloy, and the carbon layer after the carbon layer forming step. Press forming the base material on which the layer is formed to form a gas flow path, and after the press forming step, carbon powder and resin are formed on the base material on which the carbon layer is formed and press formed.
- the manufacturing method of the fuel cell separator material made from titanium which concerns on this invention has performed the conductive resin layer formation process after the press molding process, a carbon layer is with respect to the deformation
- the two layers of the carbon layer and the conductive resin layer formed on the base material improve conductivity and durability (conductivity durability: property of maintaining conductivity for a long time), and the conductive resin layer The possibility of peeling of the carbon-based conductive layer (carbon layer, conductive resin layer) during handling after press molding is reduced.
- the carbon layer preferably has a coverage of 40% or more and 80% or less.
- the titanium fuel cell separator material manufacturing method performs the press forming process when manufacturing the separator material because the coverage of the carbon layer on the substrate is not more than a predetermined value. Even after this, it is possible to produce a titanium fuel cell separator material that is naturally conductive, and that suppresses a decrease in wear resistance and adhesion.
- the method for producing a titanium fuel cell separator material according to the present invention preferably includes a heat treatment step of heat-treating the substrate at 200 to 550 ° C. after the conductive resin layer forming step.
- the manufacturing method of the titanium fuel cell separator material according to the present invention includes the heat treatment step after the conductive resin layer forming step, the resin on the outermost surface of the conductive resin layer may be partially decomposed and removed. Therefore, an increase in contact resistance due to a high resin ratio of the conductive resin layer can be suppressed. As a result, a titanium fuel cell separator material with further reduced contact resistance can be produced.
- the method for producing a titanium fuel cell separator according to the present invention includes a heat treatment step of heat-treating the base material at 300 to 850 ° C. in a non-oxidizing atmosphere between the carbon layer forming step and the press molding step. It is preferable.
- the manufacturing method of the titanium fuel cell separator material according to the present invention includes the heat treatment step between the carbon layer forming step and the press molding step, titanium carbide is provided between the base material and the carbon layer. An intermediate layer can be formed. As a result, it is possible to manufacture a titanium fuel cell separator material in which the adhesion between the base material and the carbon layer is improved and the possibility of peeling of the carbon layer and the conductive resin layer is reduced.
- the titanium fuel cell separator material according to the present invention includes a carbon-based conductive layer having a two-layer structure of a carbon layer and a conductive resin layer, the carbon-based conductive layer provides the conductivity and durability of the separator material. Can be improved. And since a conductive resin layer functions as a protective film, compared with a separator material provided with only one conductive layer, wear resistance can be improved. Therefore, the titanium fuel cell separator material according to the present invention is excellent in conductivity and durability (conductivity durability: property of maintaining conductivity for a long period of time) and also in wear resistance.
- the method for producing a titanium fuel cell separator according to the present invention includes a carbon-based conductive material having a two-layer structure of a carbon layer and a conductive resin layer by including a carbon layer forming step and a conductive resin layer forming step. A layer can be formed on a substrate. As a result, a titanium fuel cell separator material with improved conductivity and durability can be produced by the carbon-based conductive layer. Since the conductive resin layer functions as a protective film, it is possible to manufacture a titanium fuel cell separator material with improved wear resistance compared to a separator material having only one conductive layer.
- a titanium fuel cell separator material according to the present invention, it is excellent in conductivity and durability (conductivity durability: the property of maintaining conductivity for a long period of time) and also in wear resistance.
- a fuel cell separator material can be manufactured.
- Example 1 It is the schematic of the contact resistance measuring apparatus used in the evaluation of the electroconductivity, durability, and abrasion resistance in Example 1,2. It is the schematic of the contact resistance measuring apparatus used in the evaluation of the electroconductivity, durability, and abrasion resistance in Example 3, 4. It is typical sectional drawing of the fuel cell separator which concerns on the Example of this invention.
- a titanium fuel cell separator material according to the present invention (hereinafter, appropriately referred to as a separator material) and a mode for carrying out the method for manufacturing the separator material will be described in detail.
- a separator 10 (10 a) includes a base 1 made of pure titanium or a titanium alloy, and a carbon-based conductive layer formed on the surface (one side or both sides) of the base 1. 2 is provided. And as shown in FIG. 2, the separator material 10 (10b) which concerns on this embodiment may be provided with the intermediate
- separator material 10 may be exhibiting plate shape, as shown in FIG. 3, as the gas flow path 13 is formed in the surface, you may exhibit uneven
- the separator material 10 is provided between the cell 14 and the cell 14 formed by stacking the gas diffusion layers 11 and 11 and the electrolyte membrane 12. 3 is an enlarged cross-sectional view corresponding to the cross-sectional views of FIGS.
- the base material 1, the carbon-based conductive layer 2, and the intermediate layer 3 of the separator material 10 will be described.
- the base material of the separator material according to the present embodiment is a metal base material from the viewpoint of workability, gas barrier property, conductivity and thermal conductivity required to form a groove serving as a gas flow path.
- pure titanium or a titanium alloy is very preferable because it is lightweight, excellent in corrosion resistance, and excellent in strength and toughness.
- the base material may be prepared by a conventionally known method, for example, a method of melting and casting pure titanium or a titanium alloy to form an ingot, hot rolling, and then cold rolling. Further, the base material is preferably annealed, but the finished state is not limited, and for example, in any finished state such as “annealing + pickling finish”, “vacuum heat treatment finish”, “bright annealing finish”, etc. It does not matter.
- the base material is not limited to pure titanium or titanium alloy having a specific composition, but when a base material made of pure titanium or titanium alloy is used, cold rolling of the titanium material (base material) is performed. From the viewpoint of ease (cold rolling with a total rolling reduction of 35% or more can be performed without intermediate annealing) and subsequent press formability securing, for example, 1 to 4 types of pure titanium specified in JIS H 4600, Ti alloys such as Ti—Al, Ti—Ta, Ti-6Al-4V, and Ti—Pd can be applied. Among these, pure titanium that is particularly suitable for thinning is preferable.
- O 1500 ppm or less (more preferably 1000 ppm or less)
- Fe 1500 ppm or less (more preferably 1000 ppm or less)
- C 800 ppm or less
- N 300 ppm or less
- H 130 ppm or less
- Ti titanium ppm or less
- the strength and toughness of the separator material are improved, and since it is lightweight, it is particularly easy to use as an automotive application.
- the substrate thickness is preferably 0.05 to 1.0 mm. If the plate thickness is less than 0.05 mm, the strength required for the substrate cannot be ensured. On the other hand, if it exceeds 1.0 mm, it becomes difficult to perform fine processing of the gas flow path through which hydrogen or air passes. It is.
- the carbon-based conductive layer has a two-layer structure. As shown in FIGS. 1 and 2, the carbon-based conductive layer 2 includes a carbon layer 21 formed on the side close to the substrate 1 and a conductive resin layer 22 formed on the side far from the substrate 1. Composed.
- the carbon layer includes graphite and is provided so as to cover the base material. And since the graphite contained in the carbon layer has high crystallinity and excellent conductivity, it imparts conductivity to the separator material and also has durability to maintain conductivity even in the fuel cell internal environment (high temperature, acidic atmosphere). Give.
- the graphite contained in the carbon layer is preferably configured to include at least one of scaly graphite powder, scaly graphite powder, expanded graphite powder, and pyrolytic graphite powder.
- the carbon layer substantially does not contain a resin (binder resin).
- “substantially free of resin” means that, in the carbon layer, the mass ratio of the solid component of the resin and graphite (the mass of resin solids in the carbon layer / the mass of carbon powder in the carbon layer) is 0.1 or less.
- the carbon layer is preferably coated on the entire surface of the substrate from the viewpoint of conductivity, but it is not always necessary to cover the entire surface, and in order to ensure conductivity and corrosion resistance, 40% of the surface is required. What is necessary is just to coat
- the material elongation occurs due to the processing.
- the coverage of the carbon layer on the substrate exceeds 80%, the elongation of the carbon layer cannot follow the portion where the elongation of the substrate at the time of processing is large, and separation occurs between the substrate and the carbon layer.
- the wear resistance and adhesion of the carbon-based conductive layer may be reduced.
- the coverage of the carbon layer on the substrate is 80% or less, it is possible to suppress a decrease in wear resistance and adhesion of the carbon-based conductive layer even in a portion where the elongation of the substrate occurs due to processing.
- the lower limit of the coverage of the carbon layer is preferably 40% or more, more preferably Is 45% or more, particularly preferably 50% or more, and the upper limit is preferably 80% or less, more preferably 75% or less, and particularly preferably 70% or less.
- the coverage of the carbon layer can be determined by observing the separator surface on which the carbon layer is formed with an optical microscope or a scanning microscope. For example, the surface of the separator on which the carbon layer is formed is observed using a scanning electron microscope at a magnification of 200 ⁇ and a range of 550 ⁇ 400 ⁇ m, and the reflected electron image is taken.
- the backscattered electron image is binarized into a portion where the carbon layer is covered by image processing and a portion where the carbon layer is not covered and the base material is exposed, and the area ratio occupied by the carbon layer is calculated and covered. It is a method of obtaining the rate.
- the above method may be performed after dissolving and removing the conductive resin layer with an organic solvent or an alkaline solution.
- the adhesion amount of the carbon layer is not particularly limited, but is preferably 2 to 1000 ⁇ g / cm 2 . If the amount is less than 2 ⁇ g / cm 2 , the amount of adhesion is small and the conductivity and corrosion resistance cannot be ensured. If the amount exceeds 1000 ⁇ g / cm 2 , the effects of conductivity and corrosion resistance are saturated and workability is reduced. Because. And the adhesion amount of a carbon layer becomes like this. More preferably, it is 5 microgram / cm ⁇ 2 > or more, More preferably, it is 10 microgram / cm ⁇ 2 > or more. In addition, the coverage and adhesion amount of the carbon layer can be controlled by the amount of graphite powder applied to the substrate in the graphite powder application step described later.
- the conductive resin layer includes carbon powder and resin, and functions as a protective film having both conductivity and wear resistance.
- the carbon powder contained in the conductive resin layer is preferably carbon black powder, acetylene black powder, graphite powder or a mixed powder thereof. These powders are excellent in conductivity and corrosion resistance, and are inexpensive because they are inexpensive materials.
- the resin (binder resin) for forming the conductive resin layer is one or more resins selected from acrylic resin, polyester resin, alkyd resin, urethane resin, silicone resin, phenol resin, epoxy resin, and fluororesin. . When two or more resins are included, the resins may react with each other or may simply be mixed. However, this resin is preferably a resin that can be made into a paint. Furthermore, it is more preferable to select from a urethane resin, a silicone resin, a phenol resin, an epoxy resin, or a fluororesin that is stable even in a high temperature (80 to 100 ° C.) and acidic (pH 2 to 4) atmosphere in the fuel cell.
- the conductive resin layer is formed by applying a conductive resin paint prepared by mixing a resin and carbon powder, but the mass ratio of the solid component of the resin and the carbon powder in the paint (resin solids in the paint).
- the mass / mass of carbon powder in the paint is preferably 0.5-10. If the mass ratio is less than 0.5, the ratio of the resin component when the conductive resin layer is formed becomes small, so that the strength as the layer is insufficient and the intended wear resistance cannot be obtained. On the other hand, if this mass ratio exceeds 10, the ratio of the carbon powder when it becomes a conductive resin layer becomes small and the electrical resistance as a layer increases, which is not preferable in terms of the characteristics of the separator material. A more preferable range of the mass ratio is 0.8 to 8.
- the thickness of the conductive resin layer is preferably 0.1 to 20 ⁇ m. If the thickness of the conductive resin layer is less than 0.1 ⁇ m, the conductive resin layer is broken by slight friction, resulting in insufficient wear resistance. On the other hand, if the thickness of the conductive resin layer exceeds 20 ⁇ m, the electrical resistance as the layer increases, which is not preferable in terms of the characteristics of the separator material. A more preferable thickness of the conductive resin layer is 0.3 to 19 ⁇ m.
- the coverage of a carbon layer does not necessarily need to be 100%, and should just be 40% or more.
- the coverage of the carbon layer is smaller than 100%, a part of the surface of the carbon layer has a portion where the surface of the titanium or titanium alloy is exposed. It will be in the state where the conductive resin layer is formed.
- the carbon-based conductive layer has a two-layer structure, so that sufficient conductivity and durability can be obtained macroscopically.
- the coverage of the conductive resin layer is preferably 100%, but may be 70% or more in order to ensure wear resistance and conductivity.
- the coverage of the conductive resin layer can be determined by observing the separator surface on which the conductive resin layer is formed with an optical microscope or a scanning microscope.
- the surface of the separator on which the conductive resin layer is formed is observed with a scanning electron microscope at a magnification of 200 ⁇ at a magnification of 550 ⁇ 400 ⁇ m, and the reflected electron image is taken. Then, the reflected electron image is binarized into a portion where the conductive resin layer is coated by image processing and a portion where the conductive resin layer is not covered and the base material (or carbon layer) is exposed, and the conductive image is conductive. In this method, the area ratio occupied by the conductive resin layer is calculated to obtain the coverage.
- the coverage of the carbon layer on the substrate is 80% or less, in other words, the conductive resin layer is formed in direct contact with the substrate.
- the portion is present in an area ratio of 20% or more, a decrease in wear resistance and adhesion of the carbon-based conductive layer can be suppressed even in a portion where the base material has been stretched by press molding. Therefore, in order to achieve both the conductivity of the separator produced by press-molding the separator material and the wear resistance and adhesion of the carbon-based conductive layer, for the lower limit of the coverage of the carbon layer on the substrate,
- the upper limit is preferably 40% or more, more preferably 45% or more, and particularly preferably 50% or more.
- the upper limit is preferably 80% or less, more preferably 75% or less, and particularly preferably 70% or less.
- the intermediate layer 3 of the separator material 10 is formed at the interface between the base material 1 and the carbon layer 21.
- the intermediate layer includes titanium carbide (titanium carbide, TiC) generated by reaction between C and Ti diffusing at the interface between the base material and the carbon layer, and further includes carbon solid solution titanium (C solid solution Ti). ) May be included.
- titanium carbide titanium carbide has electroconductivity, the electrical resistance in the interface of a base material and a carbon layer becomes small. Therefore, by providing the intermediate layer containing titanium carbide, the conductivity of the separator material is further improved.
- the intermediate layer containing titanium carbide is formed by the reaction between the base material and the carbon layer, the adhesion between the base material and the carbon layer is improved.
- the intermediate layer is formed by heat treatment at a predetermined temperature in a non-oxidizing atmosphere as will be described later, it has one aspect that a natural oxide film existing on the surface of the base material is modified and formed. . Therefore, the separator material in which the intermediate layer is formed at the interface between the base material and the carbon layer is different from the separator material in which the intermediate layer is not formed at the interface, and the natural oxide film is hardly present at the interface. Yes. Therefore, the separator material in which the intermediate layer is formed at the interface between the base material and the carbon layer can avoid a decrease in contact resistance due to the natural oxide film, and as described above, is extremely effective in terms of improving conductivity. .
- the method for manufacturing a separator material according to the present invention includes a carbon layer forming step S ⁇ b> 1 and a conductive resin layer forming step S ⁇ b> 3.
- the manufacturing method of the separator material which concerns on this invention includes heat processing process S2 between carbon layer formation process S1 and conductive resin layer formation process S3, and after conductive resin layer formation process S3, It is preferable to include the heat treatment step S4, and a base material manufacturing step may be included before the carbon layer forming step S1.
- the manufacturing method of the separator material which concerns on this invention has carbon layer formation process S1, conductive resin layer formation process S3, Press forming step S5. And it is preferable that the manufacturing method of the separator material which concerns on this invention includes heat processing process S2 after carbon layer formation process S1, and heat processing process after press molding process S5 (or conductive resin layer formation process S3). Preferably, S4 is included. Moreover, the base-material manufacturing process may be included before carbon layer formation process S1. Hereinafter, each process will be described in detail.
- the base material production process refers to casting or hot rolling the above pure titanium or titanium alloy by a known method, performing annealing / pickling treatment, etc. as needed, and cold rolling to a desired thickness. It is a process of rolling a sheet to produce a plate (strip) material. It does not matter whether there is an annealing finish after cold rolling, but when performing the press forming process in manufacturing separator materials, annealing is performed after cold rolling in order to ensure the workability required during press forming processing. Preferably it is done. In addition, the presence or absence of the pickling after cold rolling (+ after annealing) does not matter.
- the carbon layer forming step S1 is a step of forming a carbon layer containing graphite on the substrate surface.
- graphite powder is applied to the surface (one side or both sides) of the base material (graphite powder applying step).
- the application method is not particularly limited, but a slurry in which graphite powder is directly adhered to a base material in a powder form or graphite powder is dispersed in a paint containing an aqueous solution such as methylcellulose or a binder such as a resin is used. It may be applied to the surface of the material.
- the graphite powder to be applied to the surface of the substrate is preferably 0.5 to 100.0 ⁇ m in diameter.
- the diameter is less than 0.5 ⁇ m, the force with which the powder is pressed against the base material during the rolling process described later becomes small and it is difficult to adhere to the base material.
- the diameter exceeds 100.0 ⁇ m, it is difficult to adhere to the surface of the base material in the graphite powder application step and the pressure bonding step described later.
- the method of applying the slurry in which the graphite powder is dispersed to the substrate is not particularly limited, but the slurry may be applied to the substrate using a bar coater, roll coater, gravure coater, dip coater, spray coater or the like. That's fine.
- the method for adhering the graphite powder on the substrate is not limited to the above method, and the following method is also used. For example, a method of sticking a graphite powder-containing film prepared by kneading graphite powder and a resin onto a substrate, a method of driving graphite powder onto the substrate surface by shot blasting, and supporting it on the substrate surface are conceivable. .
- the graphite powder is applied to the surface of the base material by cold rolling after applying the graphite powder (crimping step).
- the graphite powder is pressure bonded to the substrate surface as a carbon layer.
- the carbon powder adhering to the substrate surface also serves as a lubricant, the lubricant does not have to be used when performing cold rolling.
- the graphite powder is not granular, and is attached in a thin layer on the substrate to cover the substrate surface.
- the carbon layer in order for the carbon layer to be crimped to the substrate with good adhesion, it is preferable to perform rolling at a total rolling reduction of 0.1% or more.
- the heat treatment step S2 is a step of heat-treating the substrate on which the carbon layer is formed in a non-oxidizing atmosphere. Specifically, in the heat treatment step S2, the intermediate layer containing titanium carbide formed by the reaction between the base material and the carbon layer is formed at the interface between the base material and the carbon layer. This is a step of performing heat treatment in a non-oxidizing atmosphere after the crimping step. In addition, a base material is annealed by heat processing process S2, and the workability at the time of a press molding process is also securable.
- the range of the heat treatment temperature in the heat treatment step S2 is preferably 300 to 850 ° C.
- the heat treatment temperature is less than 300 ° C.
- the reaction between graphite (carbon layer) and the substrate hardly occurs, and the adhesion is difficult to improve.
- the heat treatment temperature exceeds 850 ° C.
- phase transformation of the base material (titanium) may occur, and mechanical properties may be deteriorated.
- the range of the heat treatment temperature in the heat treatment step S2 is more preferably 400 to 800 ° C., and further preferably 450 to 780 ° C.
- the heat treatment time in the heat treatment step S2 is preferably 0.5 minutes to 10 hours. Then, it is preferable to appropriately adjust the time depending on the temperature, such as a long-time treatment when the temperature is low and a short-time treatment when the temperature is high. Further, the heat treatment temperature and time can be appropriately adjusted depending on the state of the material, such as heat treatment in a roll-to-roll or sheet shape, or heat treatment in a coiled state.
- the resin component (binder resin component) and solvent contained in the slurry in which the graphite powder is dispersed are carbonized by this heat treatment to become almost inorganic, so that the resin component is substantially contained in this carbon layer. And good conductivity can be obtained.
- the heat treatment step S2 is performed in a non-oxidizing atmosphere such as a vacuum or an Ar gas atmosphere.
- the non-oxidizing atmosphere in the heat treatment step S2 is an atmosphere having a low oxygen partial pressure, and preferably an atmosphere having an oxygen partial pressure of 10 Pa or less. If it exceeds 10 Pa, graphite reacts with oxygen in the atmosphere to become carbon dioxide (causes a combustion reaction), and the base material is oxidized to deteriorate the conductivity. is there.
- the conductive resin layer forming step S3 is a step of forming a conductive resin layer containing carbon powder and resin on the base material on which the carbon layer is formed.
- a conductive resin coating is laminated and applied to the surface of the carbon layer formed on the substrate.
- This conductive resin paint is prepared by using the above-described carbon powder in a paint containing the above-described resin (binder resin) by dispersing it so that the mass ratio of the resin solid content to the carbon powder falls within the above range. Good.
- it does not specifically limit about the solvent of a conductive resin coating material, What is necessary is just to use a well-known organic solvent.
- the method of applying the conductive resin paint in which the carbon powder is dispersed to the base material is not particularly limited, but it is conductive on the carbon layer using a bar coater, roll coater, gravure coater, dip coater, spray coater or the like. What is necessary is just to apply a functional resin paint.
- the heat treatment step S4 is a step of heat-treating the base material on which the carbon layer and the conductive resin layer (and the intermediate layer) are formed at a predetermined temperature.
- heat treatment is performed in the range of 200 to 550 ° C. in order to further reduce the contact resistance of the conductive resin layer. If the resin component ratio in the conductive resin layer is high, the contact resistance may be slightly high. In such a case, the outermost surface of the conductive resin layer is reduced by performing heat treatment in the range of 200 to 550 ° C. A part of the covering resin film is decomposed and removed, so that the added carbon powder is exposed, and the conductivity in this part is increased.
- the heat treatment temperature is lower than 200 ° C., the effect of reducing contact resistance is weak, so it takes a long time to reduce the target contact resistance. On the other hand, if the temperature exceeds 550 ° C., the effect of reducing the contact resistance is saturated, and further, the decomposition of the conductive resin layer may proceed excessively, and the target wear resistance may not be obtained.
- the range of the heat treatment temperature in the heat treatment step S4 is preferably in the range of 250 to 500 ° C, more preferably in the range of 270 to 450 ° C.
- the heat treatment atmosphere of heat treatment process S4 can be implemented in the atmosphere containing oxygen like air atmosphere, for example.
- the press forming step S5 is a step of forming a gas channel by forming a base material.
- the base material in the press molding step S5 may be molded by a known press molding apparatus using a molding die.
- the presence or absence of the use of the lubricant during press molding may be appropriately determined according to the complexity of the target shape, etc., and when performing press molding using the lubricant, a process for removing the lubricant, What is necessary is just to carry out as a part of press molding process.
- the manufacturing method of the separator material which concerns on this invention is a conductive resin layer formation process.
- S3 ⁇ press molding step S5 ⁇ heat treatment step S4 and a case of press molding step S5 ⁇ conductive resin layer forming step S3 ⁇ heat treatment step S4 as shown in FIG.
- the conductive resin layer forming step S3 is performed before the press molding step S5, the conductive resin layer of the protective layer at the time of press molding is subjected to the press molding on the base material. Since it plays a role, it is possible to avoid peeling and dropping of the carbon layer during press molding. In addition, although it is anticipated that a crack will generate
- the conductive resin layer forming step S3 is performed after the press molding step S5.
- the carbon layer cannot follow the deformation of the base material at the time of press molding, and the carbon layer is broken. Even then, by forming a conductive resin layer so as to be laminated, the layer covers and protects the cracked portion of the carbon layer. As a result, the possibility of peeling and dropping of the carbon layer from the substrate can be reduced.
- the titanium fuel cell separator material according to the present invention will be specifically described by comparing an example satisfying the requirements of the present invention with a comparative example not satisfying the requirements of the present invention.
- ⁇ Preparation of test specimen ⁇ [Base material]
- a JIS type 1 titanium substrate was used as the substrate.
- the chemical composition of the titanium substrate (cold rolling finish) is O: 450 ppm, Fe: 250 ppm, N: 40 ppm, the balance being Ti and inevitable impurities.
- board thickness of the titanium base material was 0.1 mm, and the size was 50x150 mm.
- the titanium substrate is obtained by subjecting a titanium raw material to a conventionally known melting step, casting step, hot rolling step, and cold rolling step.
- graphite powder expanded graphite powder (manufactured by SEC Carbon, SNE-6G, average particle size 7 ⁇ m, purity 99.9%) is used so that the graphite powder becomes 8 wt% in a 0.8 wt% carboxymethyl cellulose aqueous solution.
- a slurry was prepared by dispersing. And the slurry was apply
- the work roll is not coated with lubricating oil.
- the material forming the carbon layer was heat-treated at a temperature of 650 ° C. for 5 minutes in a vacuum atmosphere of 6.7 ⁇ 10 ⁇ 3 Pa.
- Samples No. 1-2 to 1-4 were prepared using the No. 10 bar coater, and those No. 1-5 to 1- 1 were prepared using the No. 7 bar coater.
- Nos. 1-9 to 1-13 were prepared using a No. 5 bar coater.
- the conductive resin paints are phenol resin (Arakawa Chemical Industries, Tamanol 2800), acrylic resin (Toray Fine Chemical, Cotax LH681), epoxy resin (Cemedine, EP106), polyester resin (Arakawa Chemical Industries). Made of 7005N) and silicone resin (manufactured by Shin-Etsu Silicone Co., Ltd., KR251), and carbon powder was dispersed in each paint.
- carbon powder carbon black powder (manufactured by Cabot, Vulcan XC72, average particle size 40 nm, purity 99.2%), graphite powder (manufactured by Ito Graphite Co., Ltd., Z-5F, average particle size 4 ⁇ m, purity 98.9%) ) was used.
- the concentration was adjusted so that the ratio of the powder to the graphite powder was 10: 1, and the paint was applied onto the material on which the carbon layer was formed using a bar coater and dried.
- the conductive resin layer was formed on both surfaces of the substrate.
- the test body which changed the thickness of the conductive resin layer by changing the count of the bar coater used at this time was produced.
- Heat treatment after forming conductive resin layer Some of the specimens obtained by forming the conductive resin layer on the carbon layer were subjected to heat treatment. Then, the heat treatment was carried out by appropriately adjusting the treatment time under the condition of 200 to 400 ° C. in an air atmosphere.
- contact resistance was measured using the contact resistance measuring apparatus shown in FIG. Specifically, both sides of the specimen are sandwiched between two carbon papers, and the outside is sandwiched between two copper electrodes with a contact area of 1 cm 2 and pressurized with a load of 10 kgf, and 7.4 mA is applied using a direct current power source. A current was applied, and a voltage applied between the carbon papers was measured with a voltmeter to obtain a contact resistance (initial contact resistance). The conductivity was good when the initial contact resistance was 12 m ⁇ ⁇ cm 2 or less, and the conductivity was poor when the initial contact resistance exceeded 12 m ⁇ ⁇ cm 2 .
- durability evaluation (durability test) was performed on the test body in which the initial contact resistance was determined to be acceptable. That is, after the specimen was immersed in an 80 ° C. sulfuric acid aqueous solution (pH 2) having a specific liquid volume of 10 ml / cm 2 for 500 hours, the specimen was taken out from the sulfuric acid aqueous solution, washed and dried, and The contact resistance was measured by the same method. When the contact resistance after the durability test was 15 m ⁇ ⁇ cm 2 or less, the durability passed, and when the contact resistance exceeded 15 m ⁇ ⁇ cm 2 , the durability was rejected.
- Evaluation criteria for adhesion are ⁇ when the adhesive of the tape remains on the surface of the carbon-based conductive layer, ⁇ when the carbon-based conductive layer is slightly transferred to the tape side, ⁇ in the carbon-based conductive layer
- delta the case where it peeled was set to (triangle
- x the case where a carbon-type conductive layer peeled from the interface with a base material was set as x, and (circle) or more was set as the pass.
- the wear resistance of the carbon-based conductive layer was evaluated using the contact resistance measuring device (see FIG. 7) used for measuring the contact resistance.
- the contact area of the copper electrode was 1 cm 2 , but in this evaluation, a copper electrode having a contact area of 4 cm 2 was used.
- the prepared specimen is sandwiched between two carbon cloths from both sides, and the outside is pressurized to a contact load of 40 kgf with a copper electrode having a contact area of 4 cm 2 , and the specimen is held while being pressed from both sides. Drawing in the surface direction (pull-out test).
- the sliding region on the surface of the test body was observed with an optical microscope, and the remaining state of the conductive layer, that is, the degree of exposure of the base material was evaluated.
- Judgment criteria for abrasion resistance are ⁇ when the substrate surface is not exposed at all on the specimen surface, ⁇ when the ratio of the exposed area of the substrate to the specimen surface is less than 30%, ⁇ specimen surface
- the case where the ratio of the exposed area of the base material was less than 50% was evaluated as ⁇
- the case where the ratio of the exposed area of the base material was 50% or more was evaluated as x
- the case where ⁇ or higher was determined as acceptable was determined as acceptable.
- Test body No. 1-3 with a carbon layer coverage of 100%
- “Test body No. 1-10” with 60% A test piece of ⁇ 65 mm was prepared, and after using this to perform a tensile process simulating a material stretched part during press molding, the wear resistance and adhesion of the carbon-based conductive layer in the stretched part were evaluated. .
- ⁇ Preparation of test specimen ⁇ [Base material]
- a JIS type 1 titanium substrate was used as the substrate.
- the chemical composition of the titanium substrate (cold rolling finish) is O: 450 ppm, Fe: 250 ppm, N: 40 ppm, the balance being Ti and inevitable impurities.
- board thickness of the titanium base material was 0.1 mm, and the size was 80x160 mm.
- the titanium substrate is obtained by subjecting a titanium raw material to a conventionally known melting step, casting step, hot rolling step, and cold rolling step.
- graphite powder expanded graphite powder (manufactured by SEC Carbon Co., SNE-6G, average particle size 7 ⁇ m, purity 99.9%) is used, and the graphite powder is 7 wt% in a 0.7 wt% carboxymethyl cellulose aqueous solution.
- a slurry was prepared by dispersing. And the slurry was apply
- the work roll is not coated with lubricating oil.
- the material forming the carbon layer was heat-treated at a temperature of 650 ° C. for 5 minutes in a vacuum atmosphere of 6.7 ⁇ 10 ⁇ 3 Pa. In addition, the coverage of the carbon layer of the test body obtained by this method was approximately 60%.
- the conductive resin paints are phenol resin (Arakawa Chemical Industries, Tamanol 2800), acrylic resin (Toray Fine Chemical, Cotax LH681), epoxy resin (Cemedine, EP106), polyester resin (Arakawa Chemical Industries). Made of 7005N) and silicone resin (manufactured by Shin-Etsu Silicone Co., Ltd., KR251), and carbon powder was dispersed in each paint.
- carbon powder carbon black powder (manufactured by Cabot, Vulcan XC72, average particle size 40 nm, purity 99.2%), graphite powder (manufactured by Ito Graphite Co., Ltd., Z-5F, average particle size 4 ⁇ m, purity 98.9%) ) was used.
- the concentration was adjusted so that the ratio of the powder to the graphite powder was 10: 1, and the paint was applied onto the material on which the carbon layer was formed using a bar coater and dried.
- the conductive resin layer was formed on both surfaces of the substrate.
- the test body which changed the thickness of the conductive resin layer by changing the count of the bar coater used at this time was produced.
- a substrate having a carbon layer and a conductive resin layer formed on the surface was cut out to 50 mm ⁇ 50 mm, and then press-molded with a mold to obtain a shape as shown in FIG.
- Heat treatment after forming conductive resin layer Some of the specimens obtained by press molding after forming the conductive resin layer were subjected to heat treatment. Then, the heat treatment was performed under the conditions of 300 to 400 ° C. in an air atmosphere with the treatment time adjusted appropriately.
- contact resistance was measured using the contact resistance measuring apparatus shown in FIG. Specifically, both sides of the test body are sandwiched between two carbon papers, and the outside is sandwiched between two copper electrodes with a contact area of 4 cm 2 and pressurized with a load of 40 kgf, and 7.4 mA is applied using a direct current power source. A current was applied, and a voltage applied between the carbon papers was measured with a voltmeter, and a contact resistance (initial contact resistance) was obtained assuming that the contact area was 2/5 of a flat plate. The conductivity was good when the initial contact resistance was 12 m ⁇ ⁇ cm 2 or less, and the conductivity was poor when the initial contact resistance exceeded 12 m ⁇ ⁇ cm 2 .
- durability evaluation (durability test) was performed on the test body in which the initial contact resistance was determined to be acceptable. That is, after the specimen was immersed in an 80 ° C. sulfuric acid aqueous solution (pH 2) having a specific liquid volume of 10 ml / cm 2 for 500 hours, the specimen was taken out from the sulfuric acid aqueous solution, washed and dried, and The contact resistance was measured by the same method. When the contact resistance after the durability test was 15 m ⁇ ⁇ cm 2 or less, the durability passed, and when the contact resistance exceeded 15 m ⁇ ⁇ cm 2 , the durability was rejected.
- the wear resistance of the carbon-based conductive layer was evaluated using the contact resistance measuring device (see FIG. 8) used for measuring the contact resistance.
- the prepared specimen is sandwiched between two carbon cloths from both sides, and the outside is pressurized to a contact load of 40 kgf with a copper electrode having a contact area of 4 cm 2 , and the specimen is held while being pressed from both sides.
- Drawing was performed in a direction parallel to the direction of the groove (pull-out test). After the pull-out test, the sliding region on the surface of the test body was observed with an optical microscope, and the remaining state of the carbon-based conductive layer, that is, the degree of exposure of the base material was evaluated.
- Judgment criteria for abrasion resistance is ⁇ , where no exposure of the base material is seen on the surface of the convex region of the groove of the test specimen (planar portion 4 on the outer surface of the gas flow path) and no exposure is seen in the R section. No exposure of the substrate is seen on the surface of the groove convex area, but a slight exposure of the base material is seen in the R part, ⁇ , the ratio of the exposed area of the base material on the surface of the specimen groove convex area When the ratio is less than 50%, ⁇ , and when the ratio of the exposed area of the base material is 50% or more, ⁇ , and ⁇ or more is determined as acceptable.
- Table 3 shows the resin type and thickness of the conductive resin layer, the heat treatment conditions after forming the conductive resin layer, the contact resistance after the initial and endurance tests, and the abrasion resistance evaluation results.
- Specimen No. 2-1 is only a carbon layer, and the initial conductivity is excellent, but the durability is within the acceptable range, but the contact resistance value is significantly increased and the wear resistance is insufficient. As a result.
- the specimen No. Nos. 2-2 to 2-9 were produced by the method defined in the present invention, and all the conductivity, durability and wear resistance were acceptable after press molding.
- the specimen No. 1 was heat-treated after forming the conductive resin layer. It was found that 2-3, 2-4, 2-7, and 2-9 are preferable because of low contact resistance and good durability.
- a carbon layer having a coverage of about 60% is formed on a pure titanium base material by the same method and material as in Example 3, heat-treated, press-molded on the material, and then conductive on both sides by the following method.
- a functional resin layer was formed.
- the conductive resin paints are phenol resin (Arakawa Chemical Industries, Tamanol 2800), acrylic resin (Toray Fine Chemical, Cotax LH681), epoxy resin (Cemedine, EP106), polyester resin (Arakawa Chemical Industries). Made of 7005N) and silicone resin (manufactured by Shin-Etsu Silicone Co., Ltd., KR251), and carbon powder was dispersed in each paint.
- carbon powder carbon black powder (manufactured by Cabot, Vulcan XC72, average particle size 40 nm, purity 99.2%), graphite powder (manufactured by Ito Graphite Co., Ltd., Z-5F, average particle size 4 ⁇ m, purity 98.9%) ) was used.
- the concentration was adjusted so that the ratio of the powder to the graphite powder was 4: 1, and the paint was spray-coated on the material after press molding and dried.
- various test bodies were produced by forming conductive layers on both sides of the material after press molding.
- Example 3 Evaluation of initial contact resistance, durability, and abrasion resistance was carried out in the same manner as in Example 3.
- the thickness of the conductive resin layer after applying the conductive resin paint spray is the place that seems to be average in the field of view by performing cross-sectional processing after filling a part of the material with resin and performing SEM observation from the cross-section. The resin layer thickness at was measured. Cross-sectional observation was performed for 3 fields per specimen, and the average value of 3 fields was calculated.
- Table 4 shows the resin type and thickness of the conductive resin layer, the heat treatment conditions after forming the conductive resin layer, the contact resistance after the initial and endurance tests, and the abrasion resistance evaluation results.
- Specimen No. Nos. 2-10 to 2-16 were produced by the method defined in the present invention, and all the conductivity, durability and wear resistance were acceptable after press molding. In addition, the thing which formed the conductive resin layer after press molding obtained the very favorable result about abrasion resistance.
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Abstract
Description
これらの要求を満足する材料としてカーボンが注目されており、セパレータへのカーボンの適用が検討されている。具体的には、黒鉛粉末の成形体を削り出して製造されたり、黒鉛と樹脂の混合物成形体で形成されるカーボン製のセパレータ(例えば特許文献1~3)や、チタンやステンレス鋼等の金属材料からなる基材に、カーボン粒子を付着させたり(例えば特許文献4~7)、化学気相成長(CVD)法等で炭素膜を成膜したセパレータが検討されている。
このため、燃料電池セパレータのセパレータ材には、導電性や耐久性(導電耐久性:導電性を長期間維持する性質)とともに、耐摩耗性も求められる。
しかしながら、特許文献1~7に開示された技術は、前記した実情を考慮した技術でないことから、耐摩耗性等に関するニーズには十分に対応することはできず、改善の余地が存在する。
したがって、本発明に係るチタン製燃料電池セパレータ材は、導電性および耐久性(導電耐久性:導電性を長期間維持する性質)に優れるとともに、耐摩耗性にも優れる。
したがって、本発明に係るチタン製燃料電池セパレータ材の製造方法によれば、導電性および耐久性(導電耐久性:導電性を長期間維持する性質)に優れるとともに、耐摩耗性にも優れるチタン製燃料電池セパレータ材を製造することができる。
図1に示すように、本実施形態に係るセパレータ材10(10a)は、純チタンまたはチタン合金からなる基材1と、基材1の表面(片面または両面)に形成された炭素系導電層2と、を備える。そして、図2に示すように、本実施形態に係るセパレータ材10(10b)は、基材1と炭素系導電層2との間に中間層3を備えていてもよい。
なお、図1、2では、基材1の片面にのみ炭素系導電層2(および中間層3)が形成されているセパレータ材10を表しているが、基材1の両面に炭素系導電層2(および中間層3)が形成されていてもよい。
以下、セパレータ材10の基材1、炭素系導電層2および中間層3について説明する。
本実施形態に係るセパレータ材の基材は、ガスの流路となる溝を形成するために必要となる加工性の点、ガスバリア性の点、導電性や熱伝導性の点から、金属基材を用いるのが好ましく、特に純チタンやチタン合金は、軽量で耐食性に優れ、強度、靭性にも優れていることから非常に好ましい。
炭素系導電層は、2層構造を呈する。そして、図1、2に示すように、炭素系導電層2は、基材1に近い側に形成される炭素層21と、基材1に遠い側に形成される導電性樹脂層22とから構成される。
炭素層は、黒鉛を含んで構成されるとともに、基材を被覆するように設けられる。そして、炭素層に含まれる黒鉛は、結晶性が高く導電性に優れることから、セパレータ材に導電性を付与するとともに、燃料電池内部環境(高温、酸性雰囲気)でも導電性を維持する耐久性も付与する。
なお、炭素層に含まれる黒鉛は、好ましくは鱗状黒鉛粉、鱗片状黒鉛粉、膨張化黒鉛粉、及び熱分解黒鉛粉のうちの少なくとも1つを含んで構成される。
よって、導電性だけではなく、プレス成形加工後の炭素系導電層の耐摩耗性や密着性を両立させることを考慮すると、炭素層の被覆率の下限については、好ましくは40%以上、より好ましくは45%以上、特に好ましくは50%以上であり、上限については、好ましくは80%以下、より好ましくは75%以下、特に好ましくは70%以下である。
ここで、炭素層の被覆率については、炭素層を形成したセパレータ表面を、光学顕微鏡や走査型顕微鏡で観察することにより求めることができる。例えば、炭素層を形成したセパレータ表面について走査型電子顕微鏡を用いて、200倍の観察倍率で550×400μmの範囲を観察し、その反射電子像を撮影する。そして、反射電子像を画像処理により炭素層が被覆している部分と、炭素層が被覆せず基材が露出する部分と、に分けて二値化し、炭素層が占める面積率を計算し被覆率を求めるという方法である。なお、既に炭素層の上に導電性樹脂層が形成されている場合は、有機溶媒もしくはアルカリ溶液で導電性樹脂層を溶解除去した後、前記の方法を行えばよい。
なお、炭素層の被覆率および付着量は、後記する黒鉛粉塗布工程において基材に塗布する黒鉛粉の量により制御することができる。
導電性樹脂層は、炭素粉と樹脂とを含んで構成され、導電性と耐摩耗性を併せ持つ保護膜としての働きを持つ。
導電性樹脂層に含まれる炭素粉としては、カーボンブラック粉、アセチレンブラック粉、黒鉛粉又はこれらの混合粉であるのが好ましい。これらの粉末は導電性と耐食性に優れるとともに、安価な材料であるため生産上好都合である。
炭素層上に導電性樹脂層を形成したときに、導電性樹脂層に添加した黒鉛粉が当該層よりわずかに突出した状態であると、その部分が良好な導電パスとなり導電性樹脂層の電気抵抗が低減するため非常に好ましい。
そして、炭素層の被覆率は、前記のとおり、必ずしも100%でなくてもよく、40%以上であればよい。ここで、炭素層の被覆率が100%より小さい場合、炭素層表面の一部には基材のチタン、チタン合金の表面が露出している箇所があり、この部分では基材上に直接導電性樹脂層が形成されている状態になる。言い換えると、基材上に2層の炭素系導電層が形成されている部分と、1層の導電性樹脂層のみが形成されている部分が混在する状態となる。1層の導電性樹脂層でも導電性が得られるが、2層の炭素系導電層が形成されている部分では導電性が特に良好となって、当該部分が良好な導電パスとなる。つまり、本発明では、炭素系導電層が2層構造を呈することにより、マクロ的にも十分な導電性および耐久性が得られる。
なお、導電性樹脂層の被覆率は、好ましくは100%であるが、耐摩耗性および導電性を確保するために、70%以上であればよい。
ここで、導電性樹脂層の被覆率は、導電性樹脂層を形成したセパレータ表面を、光学顕微鏡や走査型顕微鏡で観察することにより求めることができる。例えば、導電性樹脂層を形成したセパレータ表面について走査型電子顕微鏡を用いて、200倍の観察倍率で550×400μmの範囲を観察し、その反射電子像を撮影する。そして、反射電子像を画像処理により導電性樹脂層が被覆している部分と、導電性樹脂層が被覆せず基材(または炭素層)が露出する部分と、に分けて二値化し、導電性樹脂層が占める面積率を計算し被覆率を求めるという方法である。
よって、セパレータ材をプレス成形加工して製造するセパレータの導電性と、炭素系導電層の耐摩耗性、密着性とを両立するには、基材上の炭素層の被覆率の下限については、好ましくは40%以上、より好ましくは45%以上、特に好ましくは50%以上であり、上限については、好ましくは80%以下、より好ましくは75%以下、特に好ましくは70%以下である。
図2に示すように、本実施形態に係るセパレータ材10の中間層3は、基材1と炭素層21との界面に形成される。そして、中間層は、基材と炭素層との界面でC、Tiが互いに拡散することにより反応して生成したチタンカーバイド(炭化チタン、TiC)を含み、さらに炭素固溶チタン(C固溶Ti)を含んでいてもよい。
そして、チタンカーバイドは導電性を有するため、基材と炭素層との界面における電気抵抗が小さくなる。よって、チタンカーバイドを含む中間層を備えることによりセパレータ材の導電性はさらに向上する。加えて、チタンカーバイドを含む中間層は、基材と炭素層とが反応して形成されたものであるため、基材と炭素層との密着性が向上する。
次に、本発明に係るチタン製燃料電池セパレータ材の製造方法について説明する。
図4に示すように、本発明に係るセパレータ材の製造方法は、炭素層形成工程S1と、導電性樹脂層形成工程S3と、を含む。そして、本発明に係るセパレータ材の製造方法は、炭素層形成工程S1と導電性樹脂層形成工程S3との間に、熱処理工程S2を含むことが好ましく、導電性樹脂層形成工程S3の後に、熱処理工程S4を含むことが好ましく、また、炭素層形成工程S1の前に、基材製造工程を含んでいてもよい。
以下、各工程を詳細に説明する。
基材製造工程とは、前記した純チタンまたはチタン合金を公知の方法で鋳造、熱間圧延し、必要に応じて間に焼鈍・酸洗処理等を行って、冷間圧延にて所望の厚さまで圧延して、板(条)材を製造する工程である。なお、冷間圧延後の焼鈍仕上げの有無は問わないが、セパレータ材を製造するにあたりプレス成形工程を行う場合は、プレス成形加工時に必要となる加工性を確保するために冷間圧延後に焼鈍を行うことが好ましい。その他、冷間圧延後(+焼鈍後)の酸洗の有無は問わない。
炭素層形成工程S1とは、基材表面に黒鉛を含む炭素層を形成する工程である。
この炭素層形成工程S1では、まず、基材の表面(片面または両面)に黒鉛粉を塗布する(黒鉛粉塗布工程)。塗布方法については、特に限定されないが、黒鉛粉を基材上に粉末状のまま直接付着させたり、黒鉛粉をメチルセルロース等の水溶液や樹脂等のバインダを含む塗料中に分散させたスラリーを、基材の表面に塗布したりすればよい。
黒鉛粉を基材上に付着させる方法は上記の方法に限定されず、次のような方法によっても実施される。例えば、黒鉛粉と樹脂とを混練して作製した黒鉛粉含有フィルムを基材上に貼り付ける方法や、ショットブラストにより黒鉛粉を基材表面に打ち込み、基材表面に担持させる方法等が考えられる。
なお、圧下率は、冷間圧延前後の炭素層を含めた材料厚さの変化から算出した値であり、「圧下率=(t0-t1)/t0×100」(t0:黒鉛粉塗布工程後の初期材料厚さ、t1:圧延後の材料厚さ)により算出する。
熱処理工程S2とは、炭素層が形成された基材を非酸化雰囲気下で熱処理する工程である。詳細には、熱処理工程S2とは、基材と炭素層との界面に、基材と炭素層とが反応して形成されたチタンカーバイドを含む中間層を形成させるため、炭素層形成工程S1における圧着工程後に、非酸化性雰囲気において熱処理を行う工程である。なお、熱処理工程S2により、基材が焼鈍され、プレス成形加工時の加工性も確保できる。
熱処理工程S2における熱処理温度の範囲は、より好ましくは400~800℃であり、さらに好ましくは、450~780℃である。
なお、黒鉛粉を分散させたスラリー中に含まれる樹脂成分(バインダ樹脂成分)や溶剤は、この熱処理によって炭化してほぼ無機物となるため、本炭素層中には実質的に樹脂成分は含まれなくなり、良好な導電性が得られる。
導電性樹脂層形成工程S3とは、炭素層が形成された基材に炭素粉と樹脂とを含む導電性樹脂層を形成する工程である。この導電性樹脂層形成工程S3では、具体的には、基材に形成された炭素層表面に導電性樹脂塗料を積層塗布する。
この導電性樹脂塗料は、前記した樹脂(バインダ樹脂)を含む塗料中に前記した炭素粉を、樹脂固形分と炭素粉との質量比率が前記範囲になるように分散させて調製して用いればよい。
なお、導電性樹脂塗料の溶剤については、特に限定されず、公知の有機溶剤等を用いればよい。
熱処理工程S4とは、炭素層と導電性樹脂層(および中間層)が形成された基材を所定温度で熱処理する工程である。
熱処理工程S4では、導電性樹脂層の接触抵抗を更に下げるために200~550℃の範囲での熱処理を行う。導電性樹脂層中の樹脂成分比率が高いと接触抵抗がやや高くなる場合があるが、このような場合に200~550℃の範囲での熱処理を行うことにより、導電性樹脂層の最表面を覆う樹脂膜の一部が分解除去されて添加した炭素粉が露出する状態となり、この部分での導電性が高まる。
熱処理工程S4における熱処理温度の範囲は、好ましくは250~500℃の範囲、より好ましくは270~450℃の範囲である。
そして、熱処理工程S4の熱処理雰囲気は、例えば大気雰囲気のような酸素を含む雰囲気で実施することができる。
プレス成形工程S5とは、基材を成形しガス流路を形成させる工程である。
プレス成形工程S5における基材の成形は、成形用の金型を用い、公知のプレス成形装置により行えばよい。なお、プレス成形時における潤滑剤の使用の有無は、狙う形状の複雑さ等に応じて適宜判断すればよく、潤滑剤を用いてプレス成形する場合は、潤滑剤を除去するための処理を、プレス成形工程の一部として行えばよい。
本発明に係るチタン製燃料電池セパレータ材の製造方法における前記した各工程の順について詳細に説明する。
なお、プレス成形工程S5の程度によっては導電性樹脂層に割れが発生することが予想されるが、このような場合にはプレス成形工程S5の後に再度、導電性樹脂層形成工程S3を行ってもよい。
[基材]
基材には、JIS 1種のチタン基材を使用した。
チタン基材(冷間圧延仕上げ)の化学組成は、O:450ppm、Fe:250ppm、N:40ppm、残部がTiおよび不可避的不純物である。そして、チタン基材の板厚は、0.1mmであり、サイズは50×150mmとした。当該チタン基材は、チタン原料に対して従来公知の溶解工程、鋳造工程、熱間圧延工程、冷間圧延工程を施して得られたものである。
黒鉛粉として、膨張化黒鉛粉(SECカーボン社製、SNE-6G、平均粒径7μm、純度99.9%)を用い、黒鉛粉を0.8wt%カルボキシメチルセルロース水溶液中に8wt%となるように分散させてスラリーを作製した。そして、当該スラリーを10番、7番、5番の番手のバーコーターを用いてチタン基材の両面にスラリーを塗布し、黒鉛粉塗工材料を作製した。
そして、ワークロール径200mmの2段圧延機を用いて、荷重2.5トンでロールプレスし、黒鉛粉を潰して基材上に密着させた。なお、ワークロールには潤滑油を塗布していない。
上記、炭素層を形成した材料を、6.7×10-3Paの真空雰囲気下において、650℃の温度で5分間の熱処理を施した。
なお、10番のバーコーターを用いて作製したものが試験体No.1-2~1-4であり、7番のバーコーターを用いて作製したものが試験体No. 1-5~1-8であり、5番のバーコーターを用いて作製したものが試験体No. 1-9~1-13である。
導電性樹脂塗料は、フェノール樹脂(荒川化学工業社製、タマノル2800)、アクリル樹脂(東レ・ファインケミカル社製、コータックスLH681)、エポキシ樹脂(セメダイン社製、EP106)、ポリエステル樹脂(荒川化学工業社製、7005N)、シリコーン樹脂(信越シリコーン社製、KR251)の塗料を用い、それぞれの塗料に炭素粉末を分散させて作製した。炭素粉末としては、カーボンブラック粉末(キャボット社製、バルカンXC72、平均粒径40nm、純度99.2%)、黒鉛粉末(伊藤黒鉛社製、Z-5F、平均粒径4μm、純度98.9%)を用いた。
各種樹脂系の塗料をそれぞれに適した有機溶媒を用いて、塗料中の固形分(樹脂成分+炭素粉末)の濃度(=((樹脂成分質量+炭素粉末質量)×100)/塗料質量)がおよそ18質量%となるように、固形分中の炭素粉末の質量濃度(=(炭素粉末質量×100)/(樹脂成分質量+炭素粉末質量))がおよそ25質量%となるように、カーボンブラック粉末と黒鉛粉末の比率が10:1となるように濃度調整し、当該塗料をバーコーターを用いて炭素層を形成した材料上に塗布して乾燥させた。このようにして基材の両面に導電性樹脂層を形成した。このとき使用するバーコーターの番手を変えることで導電性樹脂層の厚さを変えた試験体を作製した。
炭素層上に導電性樹脂層を形成して得た試験体のうち幾つかを熱処理に供した。そして、熱処理は、大気雰囲気下において200~400℃の条件で、処理時間を適宜調整して実施した。
[炭素層被覆率測定]
炭素層を形成した試験体の表面について走査型電子顕微鏡を用いて、200倍の観察倍率で550×400μmの範囲を観察し、その反射電子像を撮影した。その反射電子像を画像処理により炭素層が被覆している部分と、炭素層が被覆せず基材が露出する部分と、に分けて二値化し、炭素層が占める面積率を計算し被覆率を求めた。観察は1試験体あたり3視野行い、3視野の平均値を算出した。
炭素層を形成した試験体上に導電性樹脂層を形成する前後の材料厚さについてマイクロメーターを用いて測定し、前後の厚さの差より導電性樹脂層の厚さを算出した。厚さの測定は1試験体あたり3箇所で行い、3箇所の平均値を算出した。
得られた各試験体について、図7に示す接触抵抗測定装置を用いて、接触抵抗を測定した。詳細には、試験体の両面を2枚のカーボンペーパーで挟み、さらにその外側を接触面積1cm2の2枚の銅電極で挟んで荷重10kgfで加圧し、直流電流電源を用いて7.4mAの電流を通電し、カーボンペーパーの間に加わる電圧を電圧計で測定して、接触抵抗(初期接触抵抗)を求めた。
初期接触抵抗が12mΩ・cm2以下の場合を導電性が良好、12mΩ・cm2を超える場合を導電性が不良とした。
また、初期接触抵抗が合格判定となった試験体において、耐久性評価(耐久試験)を行った。すなわち、試験体を比液量が10ml/cm2である80℃の硫酸水溶液(pH2)に500時間の浸漬処理を行った後、試験体を硫酸水溶液から取り出し、洗浄、乾燥して、前記と同様の方法で接触抵抗を測定した。
耐久試験後の接触抵抗が15mΩ・cm2以下の場合を耐久性が合格、15mΩ・cm2を超える場合を耐久性が不合格とした。
試験体の炭素系導電層表面にテープ(住友3M製メンディングテープ 12mm幅)を貼り付けた後、テープを試験体表面に対して垂直方向に引き剥がして炭素系導電層の密着性評価を行った。
密着性の評価基準は、テープの粘着剤が炭素系導電層表面に残っている場合を◎、テープ側に炭素系導電層がわずかに転着する程度の場合を○、炭素系導電層中で剥離する場合を△、炭素系導電層が基材との界面より剥離する場合を×として、○以上を合格とした。
炭素系導電層の耐摩耗性を、接触抵抗の測定に用いた接触抵抗測定装置(図7参照)を流用して評価した。接触抵抗評価の際には銅電極の接触面積を1cm2としたが、本評価では接触面積が4cm2の銅電極を用いて行った。作製した試験体を、両面から2枚のカーボンクロスで挟み、さらにその外側を接触面積4cm2の銅電極で接触荷重40kgfに加圧し、両面から加圧された状態を保持したまま、試験体を面方向に引き抜いた(引抜き試験)。引抜き試験後、試験体表面における摺動領域を光学顕微鏡にて観察し、導電層の残存状態、すなわち基材の露出の程度で評価した。
耐摩耗性の判断基準は、試験体表面に基材の露出がまったく見られない場合を◎、試験体表面に対し基材の露出した面積の割合が30%未満のものを○、試験体表面に対し基材の露出した面積の割合が50%未満のものを△、基材の露出した面積の割合が50%以上の場合を×として、○以上を合格とした。
各試験体表層の断面をイオンビーム加工装置(日立集束イオンビーム加工観察装置 FB-2100)でサンプルを加工した後、透過型電子顕微鏡(TEM:日立電界放出形分析電子顕微鏡 HF-2200)にて750000倍の倍率で断面観察し、炭素層とチタン基材との界面において中間層の存在を確認し、中間層中の任意の箇所においてEDX分析および電子線回折分析を行い、チタンカーバイドが存在するか否かを判定した。
一方、試験体No. 1-3~1-13は本発明に規定する範囲内で炭素層上に導電性樹脂層が形成されたものであり、導電性、耐久性、密着性、耐摩耗性のいずれもが合格範囲であった。特に、導電性樹脂層を形成後に熱処理を行った試験体のうち、試験体No. 1-7、1-8、1-10、1-12、1-13は接触抵抗が低い値となり、導電性および耐久性に非常に優れることがわかった。
引張加工は小型の引張試験機を用いて行った。試験片の両端から20mmの部分に線を引き(線間距離25mm)、試験片の両端を試験機のチャックで固定し、引張速度5mm/分の速度で線間距離が31mm(平均材料伸び25%)となるまで加工して引張加工試験体を得た。その後、引張加工部の炭素系導電層の密着性および耐摩耗性を実施例1と同様の方法で評価し、同様の基準で◎、○、△、×の判定を行った。なお、本評価は実施例1の評価よりもより厳しい評価であることから、△以上を合格として評価し、その結果を表2に示した。
しかしながら、プレス成形加工による材料伸び部を想定した引張加工を行うと炭素層被覆率が100%である試験体No.1-3は密着性および耐摩耗性が低下する傾向が明確にみられた。一方、炭素層被覆率80%のNo.1-7は密着性がやや低下するが耐摩耗性には有意な低下は見られず、炭素層被覆率60%のNo.1-10は密着性、耐摩耗性ともに有意な低下は見られなかった。
[基材]
基材には、JIS 1種のチタン基材を使用した。
チタン基材(冷間圧延仕上げ)の化学組成は、O:450ppm、Fe:250ppm、N:40ppm、残部がTiおよび不可避的不純物である。そして、チタン基材の板厚は、0.1mmであり、サイズは80×160mmとした。当該チタン基材は、チタン原料に対して従来公知の溶解工程、鋳造工程、熱間圧延工程、冷間圧延工程を施して得られたものである。
黒鉛粉として、膨張化黒鉛粉(SECカーボン社製、SNE-6G、平均粒径7μm、純度99.9%)を用い、黒鉛粉を0.7wt%カルボキシメチルセルロース水溶液中に7wt%となるように分散させてスラリーを作製した。そして、当該スラリーを5番の番手のバーコーターを用いてチタン基材の両面にスラリーを塗布し、黒鉛粉塗工材料を作製した。
そして、ワークロール径200mmの2段圧延機を用いて、荷重2.5トンでロールプレスし、黒鉛粉を潰して基材上に密着させた。なお、ワークロールには潤滑油を塗布していない。
上記、炭素層を形成した材料を、6.7×10-3Paの真空雰囲気下において、650℃の温度で5分間の熱処理を施した。
なお、本方法により得られた試験体の炭素層の被覆率はおおよそ60%であった。
導電性樹脂塗料は、フェノール樹脂(荒川化学工業社製、タマノル2800)、アクリル樹脂(東レ・ファインケミカル社製、コータックスLH681)、エポキシ樹脂(セメダイン社製、EP106)、ポリエステル樹脂(荒川化学工業社製、7005N)、シリコーン樹脂(信越シリコーン社製、KR251)の塗料を用い、それぞれの塗料に炭素粉末を分散させて作製した。炭素粉末としては、カーボンブラック粉末(キャボット社製、バルカンXC72、平均粒径40nm、純度99.2%)、黒鉛粉末(伊藤黒鉛社製、Z-5F、平均粒径4μm、純度98.9%)を用いた。
各種樹脂系の塗料をそれぞれに適した有機溶媒を用いて、塗料中の固形分(樹脂成分+炭素粉末)の濃度(=((樹脂成分質量+炭素粉末質量)×100)/塗料質量)がおよそ18質量%となるように、固形分中の炭素粉末の質量濃度(=(炭素粉末質量×100)/(樹脂成分質量+炭素粉末質量))がおよそ25質量%となるように、カーボンブラック粉末と黒鉛粉末の比率が10:1となるように濃度調整し、当該塗料をバーコーターを用いて炭素層を形成した材料上に塗布して乾燥させた。このようにして基材の両面に導電性樹脂層を形成した。このとき使用するバーコーターの番手を変えることで導電性樹脂層の厚さを変えた試験体を作製した。
表面に炭素層および導電性樹脂層が形成された基材を50mm×50mmに切り出した後、金型でプレス成形を行い、図9のような形状とした。
導電性樹脂層を形成した後にプレス成形を行って得た試験体のうち幾つかを熱処理に供した。そして、熱処理は、大気雰囲気下において300~400℃の条件で、処理時間を適宜調整して実施した。
[炭素層被覆率測定]
炭素層を形成した試験体の表面について走査型電子顕微鏡を用いて、200倍の観察倍率で550×400μmの範囲を観察し、その反射電子像を撮影した。その反射電子像を画像処理により炭素層が被覆している部分と、炭素層が被覆せず基材が露出する部分と、に分けて二値化し、炭素層が占める面積率を計算し被覆率を求めた。観察は1試験体あたり3視野行い、3視野の平均値を算出した。
炭素層を形成した試験体上に導電性樹脂層を形成する前後の材料厚さについてマイクロメーターを用いて測定し、前後の厚さの差より導電性樹脂層の厚さを算出した。厚さの測定は1試験体あたり3箇所で行い、3箇所の平均値を算出した。
得られた各試験体について、図8に示す接触抵抗測定装置を用いて、接触抵抗を測定した。詳細には、試験体の両面を2枚のカーボンペーパーで挟み、さらにその外側を接触面積4cm2の2枚の銅電極で挟んで荷重40kgfで加圧し、直流電流電源を用いて7.4mAの電流を通電し、カーボンペーパーの間に加わる電圧を電圧計で測定して、接触面積を平板の場合の2/5であるとして接触抵抗(初期接触抵抗)を求めた。
初期接触抵抗が12mΩ・cm2以下の場合を導電性が良好、12mΩ・cm2を超える場合を導電性が不良とした。
また、初期接触抵抗が合格判定となった試験体において、耐久性評価(耐久試験)を行った。すなわち、試験体を比液量が10ml/cm2である80℃の硫酸水溶液(pH2)に500時間の浸漬処理を行った後、試験体を硫酸水溶液から取り出し、洗浄、乾燥して、前記と同様の方法で接触抵抗を測定した。
耐久試験後の接触抵抗が15mΩ・cm2以下の場合を耐久性が合格、15mΩ・cm2を超える場合を耐久性が不合格とした。
炭素系導電層の耐摩耗性を、接触抵抗の測定に用いた接触抵抗測定装置(図8参照)を流用して評価した。作製した試験体を、両面から2枚のカーボンクロスで挟み、さらにその外側を接触面積4cm2の銅電極で接触荷重40kgfに加圧し、両面から加圧された状態を保持したまま、試験体を溝の向きと平行の方向に引き抜いた(引抜き試験)。引抜き試験後、試験体表面における摺動領域を光学顕微鏡にて観察し、炭素系導電層の残存状態、すなわち基材の露出の程度で評価した。
耐摩耗性の判断基準は、試験体溝凸領域の表面(ガス流路外面の平面部4)に基材の露出がまったく見られずR部にも露出が見られない場合を◎、試験体溝凸領域の表面に基材の露出はまったく見られないが、R部に若干の基材の露出が見られた場合を○、試験体溝凸領域の表面において基材の露出した面積の割合が50%未満のものを△、基材の露出した面積の割合が50%以上の場合を×として、○以上を合格とした。
一方、試験体No.2-2~2-9は本発明に規定する方法により製造されたものであり、プレス成形後も導電性、耐久性、耐摩耗性のいずれもが合格範囲であった。特に導電性樹脂層を形成後に熱処理を行った試験体No.2-3、2-4、2-7、2-9は接触抵抗が低い値となり、耐久性も良好であるため好ましいことがわかった。
実施例3と同様の方法および材料により、純チタン基材上に被覆率約60%の炭素層を形成し、熱処理を施し、その材料にプレス成形を行った後、以下の方法により両面に導電性樹脂層を形成した。
導電性樹脂塗料は、フェノール樹脂(荒川化学工業社製、タマノル2800)、アクリル樹脂(東レ・ファインケミカル社製、コータックスLH681)、エポキシ樹脂(セメダイン社製、EP106)、ポリエステル樹脂(荒川化学工業社製、7005N)、シリコーン樹脂(信越シリコーン社製、KR251)の塗料を用い、それぞれの塗料に炭素粉末を分散させて作製した。炭素粉末としては、カーボンブラック粉末(キャボット社製、バルカンXC72、平均粒径40nm、純度99.2%)、黒鉛粉末(伊藤黒鉛社製、Z-5F、平均粒径4μm、純度98.9%)を用いた。
各種樹脂系の塗料をそれぞれに適した有機溶媒を用いて、塗料中の固形分(樹脂成分+炭素粉末)の濃度(=((樹脂成分質量+炭素粉末質量)×100)/塗料質量)がおよそ18質量%となるように、固形分中の炭素粉末の質量濃度(=(炭素粉末質量×100)/(樹脂成分質量+炭素粉末質量))がおよそ40質量%となるように、カーボンブラック粉末と黒鉛粉末の比率が4:1となるように濃度調整し、当該塗料をプレス成形後の材料上にスプレー塗布して乾燥させた。このようにしてプレス成形後の材料の両面に導電層を形成して各種試験体を作製した。
プレス成形後に導電性樹脂層を形成して得た試験体のうち幾つかを熱処理に供した。大気熱処理を用い、400℃の条件で処理時間を適宜調整して実施した。
実施例3と同様の方法により、初期接触抵抗、耐久性、耐摩耗性の評価を実施した。
なお、導電性樹脂塗料スプレー塗布後の導電性樹脂層の厚さは、材料の一部を樹脂埋めした後断面加工を行い、断面からのSEM観察を行って視野中で平均的と思われる箇所での樹脂層厚さを計測した。断面観察は1試験体あたり3視野行い、3視野の平均値を算出した。
2 炭素系導電層
3 中間層
10、10a、10b チタン製燃料電池セパレータ材(セパレータ材)
21 炭素層
22 導電性樹脂層
S1 炭素層形成工程
S2 熱処理工程
S3 導電性樹脂層形成工程
S4 熱処理工程
S5 プレス成形工程
Claims (16)
- 純チタンまたはチタン合金からなる基材表面に炭素系導電層が形成されているチタン製燃料電池セパレータ材であって、
前記炭素系導電層は2層構造を呈しており、前記炭素系導電層のうち前記基材に近い側の層が、炭素層であり、前記基材に遠い側の層が、導電性樹脂層であり、
前記炭素層は、黒鉛を含むとともに、前記炭素層の被覆率は、40%以上であり、
前記導電性樹脂層は、炭素粉と樹脂とを含むとともに、前記樹脂は、アクリル樹脂、ポリエステル樹脂、アルキッド樹脂、ウレタン樹脂、シリコーン樹脂、フェノール樹脂、エポキシ樹脂、フッ素樹脂から選択される1つ以上の樹脂であることを特徴とするチタン製燃料電池セパレータ材。 - 前記炭素層の被覆率は、40%以上80%以下であることを特徴とする請求項1に記載のチタン製燃料電池セパレータ材。
- 前記基材と前記炭素層の間に、チタンカーバイドを含む中間層が形成されていることを特徴とする請求項1または請求項2に記載のチタン製燃料電池セパレータ材。
- 前記導電性樹脂層の厚さは0.1~20μmであることを特徴とする請求項3に記載のチタン製燃料電池セパレータ材。
- 純チタンまたはチタン合金からなる基材表面に黒鉛を含む炭素層を形成する炭素層形成工程と、
前記炭素層形成工程の後、前記炭素層が形成された前記基材に炭素粉と樹脂とを含む導電性樹脂層を形成する導電性樹脂層形成工程と、
を含み、
前記炭素層の被覆率は、40%以上であり、
前記導電性樹脂層の前記樹脂は、アクリル樹脂、ポリエステル樹脂、アルキッド樹脂、ウレタン樹脂、シリコーン樹脂、フェノール樹脂、エポキシ樹脂、フッ素樹脂から選択される1つ以上の樹脂であることを特徴とするチタン製燃料電池セパレータ材の製造方法。 - 前記炭素層の被覆率は、40%以上80%以下であることを特徴とする請求項5に記載のチタン製燃料電池セパレータ材の製造方法。
- 前記導電性樹脂層形成工程の後、前記基材を200~550℃で熱処理する熱処理工程を含むことを特徴とする請求項5または請求項6に記載のチタン製燃料電池セパレータ材の製造方法。
- 前記炭素層形成工程と前記導電性樹脂層形成工程との間に、前記基材を非酸化雰囲気下において300~850℃で熱処理する熱処理工程を含むことを特徴とする請求項7に記載のチタン製燃料電池セパレータ材の製造方法。
- 純チタンまたはチタン合金からなる基材表面に黒鉛を含む炭素層を形成する炭素層形成工程と、
前記炭素層形成工程の後、前記炭素層が形成された前記基材に炭素粉と樹脂とを含む導電性樹脂層を形成する導電性樹脂層形成工程と、
前記導電性樹脂層形成工程の後、前記炭素層および前記導電性樹脂層が形成された前記基材をプレス成形しガス流路を形成するプレス成形工程と、
を含み、
前記炭素層の被覆率は、40%以上であり、
前記導電性樹脂層の前記樹脂は、アクリル樹脂、ポリエステル樹脂、アルキッド樹脂、ウレタン樹脂、シリコーン樹脂、フェノール樹脂、エポキシ樹脂、フッ素樹脂から選択される1つ以上の樹脂であることを特徴とするチタン製燃料電池セパレータ材の製造方法。 - 前記炭素層の被覆率は、40%以上80%以下であることを特徴とする請求項9に記載のチタン製燃料電池セパレータ材の製造方法。
- 前記プレス成形工程の後、前記基材を200~550℃で熱処理する熱処理工程を含むことを特徴とする請求項9または請求項10に記載のチタン製燃料電池セパレータ材の製造方法。
- 前記炭素層形成工程と前記導電性樹脂層形成工程との間に、前記基材を非酸化雰囲気下において300~850℃で熱処理する熱処理工程を含むことを特徴とする請求項11に記載のチタン製燃料電池セパレータ材の製造方法。
- 純チタンまたはチタン合金からなる基材表面に黒鉛を含む炭素層を形成する炭素層形成工程と、
前記炭素層形成工程の後、前記炭素層が形成された前記基材をプレス成形しガス流路を形成するプレス成形工程と、
前記プレス成形工程の後、前記炭素層が形成され前記プレス成形された前記基材に炭素粉と樹脂とを含む導電性樹脂層を形成する導電性樹脂層形成工程と、
を含み、
前記炭素層の被覆率は、40%以上であり、
前記導電性樹脂層の前記樹脂は、アクリル樹脂、ポリエステル樹脂、アルキッド樹脂、ウレタン樹脂、シリコーン樹脂、フェノール樹脂、エポキシ樹脂、フッ素樹脂から選択される1つ以上の樹脂であることを特徴とするチタン製燃料電池セパレータ材の製造方法。 - 前記炭素層の被覆率は、40%以上80%以下であることを特徴とする請求項13に記載のチタン製燃料電池セパレータ材の製造方法。
- 前記導電性樹脂層形成工程の後、前記基材を200~550℃で熱処理する熱処理工程を含むことを特徴とする請求項13または請求項14に記載のチタン製燃料電池セパレータ材の製造方法。
- 前記炭素層形成工程と前記プレス成形工程との間に、前記基材を非酸化雰囲気下において300~850℃で熱処理する熱処理工程を含むことを特徴とする請求項15に記載のチタン製燃料電池セパレータ材の製造方法。
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KR1020167012098A KR20160067959A (ko) | 2013-11-11 | 2014-10-20 | 티타늄제 연료 전지 세퍼레이터재 및 티타늄제 연료 전지 세퍼레이터재의 제조 방법 |
CN201480061025.0A CN105706280A (zh) | 2013-11-11 | 2014-10-20 | 钛制燃料电池隔板材及钛制燃料电池隔板材的制造方法 |
DE112014005143.8T DE112014005143T5 (de) | 2013-11-11 | 2014-10-20 | Separatormaterial aus Titan für Brennstoffzellen und Verfahren zu dessen Herstellung |
US15/033,780 US20160268611A1 (en) | 2013-11-11 | 2014-10-20 | Titanium separator material for fuel cells, and method for producing titanium separator material for fuel cells |
KR1020187016116A KR20180067708A (ko) | 2013-11-11 | 2014-10-20 | 티타늄제 연료 전지 세퍼레이터재 및 티타늄제 연료 전지 세퍼레이터재의 제조 방법 |
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JP2013233076A JP5968857B2 (ja) | 2013-11-11 | 2013-11-11 | チタン製燃料電池セパレータの製造方法 |
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KR (2) | KR20160067959A (ja) |
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WO (1) | WO2015068559A1 (ja) |
Cited By (2)
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WO2019163851A1 (ja) | 2018-02-21 | 2019-08-29 | 日本製鉄株式会社 | チタン材、セパレータ、セル、および燃料電池 |
WO2019194112A1 (ja) * | 2018-04-02 | 2019-10-10 | 日鉄ケミカル&マテリアル株式会社 | 金属カーボン積層前駆体及び金属カーボン積層前駆体の製造方法 |
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JP6863129B2 (ja) | 2017-06-23 | 2021-04-21 | トヨタ自動車株式会社 | 燃料電池用セパレータの製造方法 |
JP6856012B2 (ja) | 2017-12-14 | 2021-04-07 | トヨタ自動車株式会社 | 燃料電池用のセパレータ |
JP6973029B2 (ja) * | 2017-12-20 | 2021-11-24 | トヨタ自動車株式会社 | 燃料電池用のセパレータの製造方法およびセパレータ素材 |
JP2019133838A (ja) * | 2018-01-31 | 2019-08-08 | トヨタ自動車株式会社 | 燃料電池用セパレータ |
JP7359124B2 (ja) * | 2020-10-12 | 2023-10-11 | トヨタ自動車株式会社 | 燃料電池用セパレータの製造方法 |
CN113675417A (zh) * | 2021-07-15 | 2021-11-19 | 国家电投集团氢能科技发展有限公司 | 燃料电池、燃料电池双极板及其制备方法 |
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- 2014-10-20 US US15/033,780 patent/US20160268611A1/en not_active Abandoned
- 2014-10-20 KR KR1020187016116A patent/KR20180067708A/ko not_active Application Discontinuation
- 2014-10-20 WO PCT/JP2014/077848 patent/WO2015068559A1/ja active Application Filing
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Also Published As
Publication number | Publication date |
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KR20180067708A (ko) | 2018-06-20 |
CN105706280A (zh) | 2016-06-22 |
KR20160067959A (ko) | 2016-06-14 |
US20160268611A1 (en) | 2016-09-15 |
DE112014005143T5 (de) | 2016-08-04 |
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