JP5507496B2 - Manufacturing method of fuel cell separator - Google Patents

Description

  The present invention relates to a method for producing a fuel cell separator used in a fuel cell.

  Unlike primary batteries such as dry batteries and secondary batteries such as lead-acid batteries, fuel cells that can continuously extract power by continuing to supply fuel such as hydrogen and oxidants such as oxygen have high power generation efficiency. It is expected to be an energy source that covers a wide range of applications and scales because it is not significantly affected by the size of the system and has little noise and vibration. Specifically, 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. In particular, solid polymer fuel cells are being developed for mobile devices such as fuel cell vehicles, household fuel cells (household cogeneration systems), mobile phones and personal computers.

  A polymer electrolyte fuel cell (hereinafter referred to as a fuel cell) is a single cell in which a solid polymer electrolyte membrane is sandwiched between an anode electrode and a cathode electrode, and a groove serving as a gas (hydrogen, oxygen, etc.) flow path. Is formed as a stack in which a plurality of the single cells are overlapped with each other through an electrode called a separator (also called a bipolar plate). The output of the fuel cell can be increased by increasing the number of cells per stack.

  Since the separator for a fuel cell is also a component for taking out the generated current to the outside of the fuel cell, the material has a contact resistance (a voltage drop occurs due to an interfacial phenomenon between the electrode and the separator surface). Is required to be maintained for a long time during use as a separator. Furthermore, since the inside of the fuel cell is in an acidic atmosphere, the separator is also required to have high corrosion resistance.

  In order to satisfy these requirements, various separators have been proposed which are formed by cutting a graphite powder molded body or a mixture of graphite and resin mixture. Although these have excellent corrosion resistance, they are inferior in strength and toughness, and therefore may be damaged when subjected to vibration or impact. Therefore, various separators based on metal materials have been proposed and variously proposed.

  Examples of the metal material having both corrosion resistance and conductivity include Au and Pt. Conventionally, a metal material such as an aluminum alloy, stainless steel, nickel alloy, titanium alloy, etc., which can be thinned and has excellent workability and high strength, is coated with a noble metal such as Au or Pt. A separator imparted with corrosion resistance and conductivity has been studied. However, these noble metal materials are very expensive and therefore expensive.

In order to solve such a problem, a method of manufacturing a metal separator that does not use a noble metal material has been proposed.
For example, a method of pressure bonding graphite powder to the surface of a stainless steel base material (Patent Document 1), or a method of coating a stainless steel base material with a paint in which carbon powder is dispersed and then disassembling and eliminating the paint by heat treatment (Patent Document 2) has been proposed.

  In addition, a method of dispersing and fixing graphite powder on the surface and inside of a substrate by mixing and sintering titanium powder and graphite powder has been proposed (Patent Document 3).

Japanese Patent No. 3904690 Japanese Patent No. 3904696 JP 2006-269256 A

  However, the techniques disclosed in Patent Documents 1 and 2 merely attach granular carbon powder to the surface of the base material, and the adhesion between the carbon powder and the base material is insufficient, resulting in deterioration of conductivity. There are concerns. In addition, since the base material is made of stainless steel, elution of iron ions may occur and the solid polymer film may be deteriorated, and the carbon layer formed on the surface of the base material is porous and has poor environmental barrier properties. The surface of the material is likely to be oxidized and the conductivity may be deteriorated.

  In addition, since the technique disclosed in Patent Document 3 uses a mixed sintering method of metal powder and carbon powder, it is difficult to make the separator thin, and it is easy to break during press working, so that the flow path is formed. Is difficult to process.

  The present invention has been made in view of the above-mentioned problems, and the problem is to manufacture a fuel cell separator that can maintain high conductivity for a long time even in a high temperature / acid atmosphere inside the fuel cell and is excellent in workability. It is to provide a method.

  The present inventors can produce a separator that can maintain high conductivity for a long time and is excellent in workability by forming a mixed layer containing metal powder and carbon powder on the surface of the substrate and rolling it. And found the present invention.

  In order to solve the above problems, a method for manufacturing a fuel cell separator according to the present invention is a method for manufacturing a fuel cell separator in which a mixed layer is formed on a surface of a base material, wherein metal powder and carbon are formed on the surface of the base material. A mixed layer forming step of forming the mixed layer containing powder; and a rolling step of rolling the base material on which the mixed layer is formed after the mixed layer forming step. .

As described above, the method for producing a fuel cell separator according to the present invention includes forming a mixed layer containing metal powder and carbon powder on the surface of the base material, and then rolling the metal powder to each other and between the metal powder and the base material. Join. As a result, the mixed layer has a structure in which the carbon powder is taken in between the bonded metals, whereby the carbon powder is firmly fixed to the base material. Therefore, it is possible to manufacture a fuel cell separator that can maintain high conductivity for a long time even under a high temperature / acid atmosphere inside the fuel cell.
In addition, since the rolling is performed after the mixed layer is formed, a fuel cell separator excellent in workability can be manufactured as compared with the case where the mixed layer is formed using a sintering method.

  In the method for producing a fuel cell separator according to the present invention, the base material and the metal powder are preferably made of pure titanium or a titanium alloy.

  Thus, when a base material and metal powder consist of pure titanium or a titanium alloy, while being able to reduce a weight of a separator, corrosion resistance can be improved. Further, since elution of metal ions from the separator does not occur, there is no possibility of deteriorating the solid polymer film. In addition, the strength and toughness of the substrate can be improved.

  In the method for producing a fuel cell separator according to the present invention, the carbon powder is preferably graphite powder.

  Graphite has good conductivity and durability in an acidic atmosphere. For this reason, when the carbon of the graphite structure covers the surface of the base material with a certain area ratio or more, the environmental shielding property (performance for shielding the base material from the environment in the cell of the fuel cell) is improved, and the base material and the mixed layer (carbon powder) ), A reaction that causes a decrease in conductivity such as oxidation is less likely to occur. Therefore, according to the method for manufacturing a fuel cell separator according to the present invention, since the carbon powder to be used is graphite powder, a fuel cell separator capable of maintaining high conductivity for a long time can be manufactured.

  The method for producing a fuel cell separator according to the present invention preferably includes a heat treatment step of heat-treating the substrate after the rolling step.

  Thus, by heat-treating the base material on which the mixed layer is formed, the sintering of the metals (metal powders or metal powder and base material) proceeds and the bond between the metals becomes stronger. When the base material and the metal powder are pure titanium or a titanium alloy, a titanium carbide layer is formed at the interface (contact portion) between the metal powder and the base material and the carbon powder, so that the conductivity and adhesion are excellent. A fuel cell separator can be manufactured.

  In the fuel cell separator manufacturing method according to the present invention, the heat treatment in the heat treatment step is preferably performed at a temperature of 500 to 950 ° C. in a non-oxidizing atmosphere.

  Thus, by performing heat treatment at a predetermined temperature in a predetermined atmosphere, the metals can be appropriately sintered, so that a fuel cell separator with improved adhesion can be manufactured.

The manufacturing method of the fuel cell separator according to the present invention is a separator that can maintain high conductivity for a long time and is excellent in workability by forming and rolling a mixed layer containing metal powder and carbon powder on the surface of the substrate. Can be manufactured.
Moreover, the manufacturing method of the fuel cell separator which concerns on this invention can manufacture the separator with which corrosion resistance improved, when a base material and metal powder consist of pure titanium or a titanium alloy.
In addition, the method for producing a fuel cell separator according to the present invention can produce a separator that can maintain high electrical conductivity for a longer time because the carbon powder is graphite powder.
Furthermore, the method for producing a fuel cell separator according to the present invention can produce a fuel cell separator in which the adhesion of the mixed layer is further improved by performing a heat treatment at a predetermined temperature in a predetermined atmosphere.

It is a flowchart which shows the manufacturing process of the fuel cell separator which concerns on embodiment. It is a figure which shows order for a separator in a manufacturing process of a fuel cell separator concerning an embodiment later. It is the schematic of the contact resistance measurement apparatus used in the contact resistance measurement in an Example, and adhesive evaluation.

  Hereinafter, an embodiment for carrying out a method for producing a fuel cell separator according to the present invention will be described in detail with reference to the drawings as appropriate.

≪Fuel cell separator≫
First, a fuel cell separator 10 (hereinafter, appropriately referred to as a separator) manufactured by a method for manufacturing a fuel cell separator according to an embodiment will be described.
The separator 10 is comprised from the base material 1 and the mixed layer 2 formed in the surface (both surfaces or single side | surface) of the said base material 1, as shown in FIG. 2 (figure after rolling process S2). In addition, as shown in FIG. 2 (the figure after heat processing step S3), what is comprised from the mixed layer 2 'and the base material 1 which metal powder 2a couple | bonded firmly by heat processing (separator 10') ) Is preferable.
2 shows the separator 10 (or the separator 10 ′) in which the mixed layer 2 (or the mixed layer 2 ′) is formed on both surfaces of the substrate 1, but the mixed layer is formed only on one surface of the substrate 1. 2 (or mixed layer 2 ') may be formed.
Hereinafter, the substrate 1 and the mixed layer 2 (mixed layer 2 ′) constituting the separator 10 will be described.

<Base material>
The substrate 1 of the separator 10 is preferably made of pure titanium, a titanium alloy or stainless steel from the viewpoint of corrosion resistance under the environment inside the fuel cell, but more preferably made of pure titanium or a titanium alloy. When the substrate 1 is made of pure titanium or a titanium alloy, the substrate 1 is lighter than the case of using stainless steel or the like and has excellent corrosion resistance. Moreover, since elution of metal ions from the separator does not occur, there is no possibility of deteriorating the solid polymer film.

  And the base material 1 is produced by a conventionally well-known method, for example, the method of melt | dissolving and casting pure titanium, a titanium alloy, or stainless steel, making it an ingot, hot rolling, and then cold rolling. is there. The base material 1 is preferably annealed, but the finished state is not limited, and any finished state such as “annealing + pickling finish”, “vacuum heat treatment finish”, “bright annealing finish”, etc. It does not matter.

  In addition, although the base material 1 is not limited to pure titanium, a titanium alloy, or stainless steel of a specific composition, when using the base material 1 which consists of titanium, the ease of carrying out the cold rolling of a titanium raw material, From the standpoint of ensuring the subsequent press formability, 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 And the balance is preferably Ti and inevitable impurities. As the base material 1, for example, a JIS type 1 cold-rolled plate can be used.

  The plate thickness of the substrate 1 is preferably 0.05 to 1.0 mm. This is because if the plate thickness is less than 0.05 mm, the strength required for the substrate 1 cannot be ensured, while if it exceeds 1.0 mm, the workability decreases.

<Mixed layer>
The mixed layer 2 of the separator 10 contains metal powder 2a and carbon powder 2b.
The state of the metal powder 2a and the carbon powder 2b in the mixed layer 2 is not particularly limited, but the metal powder 2a is deformed and bonded to each other by a rolling step S2 described later, and a three-dimensional network-like (network-like) shape. It is preferable to have a structure in which the carbon powder 2b is incorporated therein. This is because the carbon powder 2b having conductivity and corrosion resistance can be extremely firmly fixed in the mixed layer 2 by being in such a state.

Moreover, it is preferable that the metal powder 2a and the carbon particles 2b are not in a single layer but in a state where two or more layers are formed in the thickness direction of the mixed layer 2 to form a layer. Therefore, the average thickness of the mixed layer 2 is preferably 1 to 50 μm. When the average thickness of the mixed layer 2 is less than 1 μm, sufficient conductivity and corrosion resistance cannot be obtained, and when the average thickness of the mixed layer 2 exceeds 50 μm, the workability deteriorates.
In addition, what is necessary is just to determine preferable average thickness for the average thickness of the mixed layer 2 with the relationship between the average particle diameter of the metal powder 2a, and the average particle diameter of the carbon powder 2b. When the average particle size of each powder is small, even if the mixed layer 2 is thin, the metal powder 2a and the carbon particles 2b are formed to overlap two or more layers to form a layer, so that conductivity and corrosion resistance can be ensured. On the other hand, when the average particle size of each powder is large, it is preferable to make the mixed layer 2 thick in order to make the metal powder 2a and the carbon particles 2b two or more layers and to ensure conductivity and corrosion resistance.

  The average thickness of the mixed layer 2 can measure the cross section of the base material 1 and the mixed layer 2 using a transmission electron microscope (TEM) or the like. Here, the average thickness is, for example, the average thickness of the mixed layer 2 in the range of a width of 500 nm when a cross section is observed with a TEM.

  About the content rate of the metal powder 2a and the carbon powder 2b in the mixed layer 2, it is contained so that the metal powder 2a may be 5-90 wt% with respect to the quantity which added the metal powder 2a and the carbon powder 2b. preferable. If the metal powder 2a is less than 5 wt%, the metal powder 2a is hardly bonded in the rolling step S2, and the carbon powder 2b is not sufficiently fixed. On the other hand, if the metal powder 2a exceeds 90 wt%, the content of the carbon powder 2b having conductivity and corrosion resistance decreases, and the conductivity and corrosion resistance of the separator 10 cannot be sufficiently improved.

  The carbon state of the mixed layer 2 is not particularly limited, and may be any of an amorphous carbon state, a crystalline graphite state, and a state where both are mixed. However, the carbon preferably contains crystalline graphite. Due to the environmental shielding property of graphite (the ability to shield the base material 1 from the environment inside the cell of the fuel cell), the conductivity of the base material 1 and the interface (contact portion) between the metal powder 2a and the carbon powder 2b is reduced. This is because the induced reaction is less likely to occur, and as a result, the conductivity of the separator 10 can be maintained for a long time.

  The mixed layer 2 is preferably coated on the entire surface of the substrate 1, but is not necessarily coated on the entire surface, and in order to ensure conductivity and corrosion resistance, 40% or more of the surface, Preferably, 50% or more may be covered.

The mixed layer 2 is in a state (mixed layer 2 ′) in which the metal powders 2a are firmly bonded to each other by performing a heat treatment step S3 described later (the separator 10 ′ after the heat treatment step S3 in FIG. 2).
In addition, when the metal powder 2a is made of titanium, a titanium carbide layer is formed at the interface (contact portion) between the metal powder 2a and the carbon powder 2b by the reaction of the titanium of the metal powder 2a and the carbon of the carbon powder 2b. Is done. In addition, when the substrate 1 is made of titanium, a titanium carbide layer is also formed at the interface between the substrate 1 and the carbon powder 2b. Since this titanium carbide has conductivity, the electrical resistance at the interface between the substrate 1 and the metal powder 2a and the carbon powder 2b is reduced, and the conductivity of the separator 10 'is improved. In addition, since titanium carbide is formed by the reaction of the base material 1 and the metal powder 2a and the carbon powder 2b, the adhesion between the base material 1 and the mixed layer 2 'is improved.

Next, the metal powder 2a and the carbon powder 2b constituting the mixed layer 2 will be described.
<Metal powder>
Since the metal powder 2a is firmly bonded to the substrate 1 by the rolling step S2 (or the rolling step S1 and the heat treatment step S2) after forming the mixed layer 2 including the metal powder 2a and the carbon powder 2b, It is preferable to use the same material type as the material 1. For example, if the substrate 1 is made of titanium, titanium powder may be used as the metal powder 2a.
In particular, if the metal powder 2 is made of pure titanium or a titanium alloy, a titanium carbide layer can be formed at the interface (contact portion) between the metal powder 2a and the carbon powder 2b in the heat treatment step S2. preferable.

  The particle size of the metal powder 2a is preferably 1 to 50 μm. If the particle size is too small, the stress applied to the metal powder 2a during rolling is small and it is difficult to obtain a binding force to the substrate 1, and if the particle size is too large, it is difficult to collapse during rolling and the substrate 1 may be deformed. Because.

<Carbon powder>
The carbon powder 2b may be any of carbon powder (amorphous carbon powder), graphite powder (crystalline carbon powder), and mixed powders thereof, but the graphite powder having a high content ratio in terms of conductivity and corrosion resistance. Is preferred.

  The particle size of the carbon powder 2b is preferably 0.02 to 50 μm. This is because if the particle size is too small, the stress applied to the carbon powder 2b during rolling is small, so that it is difficult to obtain a bonding force with the base material 1 or the metal powder 2a, and if the particle size is too large, it is difficult to collapse during rolling.

  Although the separator 10 has been described above, the paint, resin, and the like used in the mixed layer forming step S <b> 1 to be described later may remain in the mixed layer 2.

Next, a method for manufacturing the fuel cell separator 10 according to the embodiment will be described.
≪Method for manufacturing fuel cell separator≫
The manufacturing method of the fuel cell separator 10 includes a mixed layer forming step S1 and a rolling step S2. In addition, it is preferable to perform heat processing process S3 after rolling process S2.
Hereinafter, the manufacturing method of the fuel cell separator 10 is demonstrated for every process.

<Mixed layer forming step>
The mixed layer forming step S1 is a step of forming the mixed layer 2 including the metal powder 2a and the carbon powder 2b on at least a part of the surface of the substrate 1.

The method for forming the mixed layer 2 is not particularly limited as long as it can form the mixed layer 2 on the surface of the base material 1, and the following methods may be mentioned.
For example, the metal powder 2a and the carbon powder 2b are mixed with a paint (paint containing methylcellulose, phenol resin, etc.) to prepare a slurry, and the slurry is applied to the surface of the substrate 1, or the metal powder 2a and carbon In this method, a film prepared by kneading the powder 2b in a resin (polyester resin or the like) is attached to the surface of the substrate 1.

  In addition, a method in which a mixture of metal powder 2a and carbon powder 2b is sprayed onto the surface of the substrate 1 (the material is melted or softened by heating, accelerated into fine particles and collided with the surface of the object to be coated), metal Alternatively, the powder 2a may be sprayed onto the surface of the base material 1 and then the carbon powder 2b may be sprayed or applied into the irregularities on the surface of the base material 1 formed of the metal powder 2a.

  That is, as a formation method of the mixed layer 2, a method of simultaneously forming a mixture of the metal powder 2a and the carbon powder 2b on the base material 1 or after forming the metal powder 2a on the base material 1 may be used. The method of forming the carbon powder 2b may be used. Moreover, after forming the carbon powder 2b in the base material 1, the method of forming the metal powder 2a may be used.

<Rolling process>
The rolling step S2 is a step of rolling the base material 1 on which the mixed layer 2 is formed after the mixed layer forming step S1, thereby bringing the metal powder 2a and the carbon powder 2b in the mixed layer 2 onto the surface of the base material 1. This is a step of pressure bonding.

  Due to the stress generated at the interface (contact portion) between the metal powder 2a and the base material 1 in the rolling step S2, the oxide film on the surface of the base material 1 is broken and the metal powder 2a and the base material 1 come into contact with each other, and further pressure is applied To join directly. Moreover, the metal powder 2a couple | bonds together by the same phenomenon generate | occur | producing also between the metal powder 2a. As a result, the carbon powder 2b can be firmly fixed in the mixed layer 2 by having a structure in which the carbon powder 2b is taken in between the bonded metals.

In the rolling step S2, in order to firmly adhere the mixed layer 2 to the surface of the substrate 1, the rolling reduction is preferably 5% or more.
The rolling reduction is a value calculated from the change in thickness of the base material 1 before and after the rolling step S2, and “rolling rate = (t0−t1) / t0 × 100” (t0: initial stage after the mixed layer forming step S1) (Plate thickness, t1: plate thickness after rolling).

  The rolling in the rolling step S2 may be performed using a conventionally known rolling device. In addition, since the carbon powder 2b in the mixed layer 2 also serves as a lubricant, it is not necessary to use a lubricant when rolling.

<Heat treatment process>
In the heat treatment step S3, the metal powder 2a in the mixed layer 2 and the metal powder 2a and the base material 1 are sintered by heat-treating the base material 1 on which the mixed layer 2 is formed after the rolling step S2. This is a step of making the bond between metals more robust.

  When the metal powder 2a is made of titanium, a titanium carbide layer is formed at the interface (contact portion) between the metal powder 2a and the carbon powder 2b by the reaction between the titanium of the metal powder 2a and the carbon of the carbon powder 2b. . In addition, when the substrate 1 is made of titanium, a titanium carbide layer is also formed at the interface between the substrate 1 and the carbon powder 2b. Since this titanium carbide has conductivity, the electrical resistance at the interface between the substrate 1 and the metal powder 2a and the carbon powder 2b is reduced, and the conductivity of the separator 10 'is improved. In addition, the bondability between the metal powder 2a and the carbon powder 2b is improved, and the carbon powder 2b is difficult to drop off.

This heat treatment is preferably performed at a predetermined temperature in a vacuum or in a non-oxidizing atmosphere such as an Ar gas atmosphere. And as temperature of heat processing, it is preferable that it is 500-950 degreeC. When the temperature during the heat treatment is less than 500 ° C., diffusion reaction between metals hardly occurs and adhesion is difficult to improve, and when the metal powder 2a is made of titanium powder, titanium carbide at the interface at a temperature of 500 ° C. or higher. A layer is easily formed. On the other hand, when the temperature exceeds 950 ° C., there is a possibility that the mechanical properties of the substrate 1 are deteriorated.
Furthermore, a preferable temperature range is 550-900 degreeC, More preferably, it is 580-880 degreeC.

  The non-oxidizing atmosphere in the heat treatment is an atmosphere having a low oxygen partial pressure. In the case of an Ar gas or nitrogen gas atmosphere, the oxygen concentration in the gas is preferably 100 ppm or less, and in the case of a vacuum atmosphere, the degree of vacuum is 50 Pa or less. That is, an atmosphere having an oxygen partial pressure of 10 Pa or less is preferable. When the oxygen partial pressure exceeds 10 Pa, the carbon of the carbon powder 2b reacts with oxygen in the atmosphere to become carbon dioxide (causes a combustion reaction), and the amount of carbon that improves conductivity and corrosion resistance. This is because of the decrease. Moreover, since metal powder and the base-material surface are oxidized simultaneously, there exists a possibility that electroconductivity may fall.

  The heat treatment time is 0.5 to 60 minutes, and the time may be appropriately adjusted 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.

  The heat treatment in the intermediate layer forming step S2 can be performed in any heat treatment furnace such as an electric furnace or a gas furnace as long as the heat treatment can be performed at a heat treatment temperature of 500 to 950 ° C. and the atmosphere can be adjusted. Can do.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and the design can be appropriately changed without departing from the gist of the present invention described in the claims.
For example, you may perform the passive film removal process which removes the passive film of the base material 1 surface before adhesion process S1.

  Next, the fuel cell separator manufacturing method 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 specimen>
As a base material, JIS 1 type titanium base material (annealing pickling finish) was used. The chemical composition of the titanium base material is O: 450 ppm, Fe: 250 ppm, N: 40 ppm, the balance is Ti and inevitable impurities, and the plate thickness of the titanium base material is 0.3 mm.

A methylcellulose-based paint in which 15 wt% of pure titanium powder (average particle size 10 μm), 30 wt% of graphite powder (average particle size 10 μm) or 10 wt% of acetylene black powder (average particle size 50 nm) is prepared, The paint was applied on both sides and dried at 80 ° C. for 3 minutes to form a mixed layer having a thickness of about 30 μm. Then, after rolling at a predetermined rolling reduction (0 to 60%), heat treatment was performed to prepare No. 1 to 10 specimens.
In addition, a methylcellulose-based paint in which only 30% by weight of graphite powder (average particle size 10 μm) is dispersed is applied to both surfaces of the substrate, rolled at a rolling reduction of 10%, heat-treated, No. Eleven test specimens were produced.
The heat treatment is performed under a vacuum atmosphere of 6.7 × 10 ⁻³ Pa (under an oxygen partial pressure of 1.3 × 10 ⁻³ Pa) or under an Ar gas atmosphere with an oxygen concentration of 10 ppm (corresponding to an oxygen partial pressure of 1.0 Pa). ) Was performed at the predetermined temperature and time described in Table 1.

  The test specimens thus produced were subjected to contact resistance measurement, mixed layer adhesion evaluation, and durability evaluation by the following methods.

[Contact resistance measurement]
The contact resistance was measured using the contact resistance measurement device 30 shown in FIG. Specifically, both surfaces of the test body 31 are sandwiched between two carbon cloths 32 and 32, and the outside is sandwiched between two copper electrodes 33 and 33 having a contact area of 1 cm ² and pressurized with a load of 98 N (10 kgf). A 7.4 mA current was passed using a direct current power supply 34, and the voltage applied between the carbon cloths 32 and 32 was measured with a voltmeter 35 to determine the contact resistance.
When the contact resistance (shown as the initial contact resistance in Table 1) is 10 mΩ · cm ² or less, the conductivity is good, and when it exceeds 10 mΩ · cm ² , the conductivity is poor.

[Adhesion evaluation]
Adhesion evaluation was performed using the contact resistance measuring apparatus 30 shown in FIG. A state in which both sides of the test body 31 are sandwiched between two carbon cloths 32 and 32 and the outside is sandwiched between copper electrodes 33 and 33 having a contact area of 1 cm ² and pressurized to a load of 98 N (10 kgf). The test body 31 was pulled out in the in-plane direction while holding (pull-out test).
After the pull-out test, the non-friction surface and the friction surface were observed at a magnification of 100 times with SEM / EDX, and when the acceleration voltage was 15 kV and titanium (Ti) and carbon (C) were quantitatively analyzed, When the amount of carbon (atomic%) is 100% and the amount of carbon on the friction surface is 80% or more of the amount of carbon on the non-friction surface, ○ (very good), the amount of carbon on the friction surface △ (ordinary) when the amount of carbon on the non-friction surface is 50% or more and less than 80%, and × (defect) when the amount of carbon on the friction surface is less than 50% of carbon on the non-friction surface It was judged.

[Durability evaluation]
Durability evaluation (durability test) was performed on the test specimen prepared by the above method. That is, the test specimen was immersed in an 80 ° C. sulfuric acid aqueous solution (10 mmol / L) having a specific liquid volume of 20 ml / cm ² , and a potential of +600 mV was applied to the test specimen based on the saturated calomel electrode (SCE). After 200 hours of immersion treatment, the test specimen was taken out from the sulfuric acid aqueous solution, washed and dried, and contact resistance was measured by the same method as described above.
When the contact resistance after immersion (after the durability test) (shown as contact resistance after the durability test in Table 1) is 30 mΩ · cm ² or less, the durability is good, and when the contact resistance exceeds 30 mΩ · cm ² , the durability is poor. did.

  Table 1 shows the types of carbon powder, preparation conditions, mixed layer adhesion, and initial and endurance contact resistance measurement results for each test specimen.

Specimen No. 1-8, the mixed layer is within the range specified in this patent, and the base material is rolled after the mixed layer is formed, so the adhesion of the mixed layer is very good, The initial contact resistance was low (good conductivity), and the contact resistance value was within the acceptable range (good durability) even after the durability test.
On the other hand, the specimen No. 9 and no. Regarding No. 10, since the rolling was not performed after the mixed layer was formed, the adhesion of the mixed layer was poor and the initial contact resistance was high (conductivity was poor). Further, an increase in contact resistance (durability was poor) after the durability test was observed.
Specimen No. Regarding No. 11, although the initial contact resistance was low and the contact resistance after the durability test was within the acceptable range, the mixed layer contained no metal powder, and therefore the adhesion of the mixed layer was normal.

  From the results shown in Table 1, the fuel cell separator produced by rolling after forming a mixed layer containing metal powder and carbon powder on the surface of the base material was found to be adhesive and conductive between the base material and the mixed layer. It turned out to be excellent in terms of durability.

DESCRIPTION OF SYMBOLS 1 Base material 2, 2 'Mixed layer 2a Metal powder 2b Carbon powder 10, 10' Fuel cell separator (separator)
30 Contact Resistance Measuring Device 31 Specimen 32 Carbon Cloth 33 Copper Electrode 34 DC Current Power Supply 35 Voltmeter S1 Mixed Layer Formation Process S2 Rolling Process S3 Heat Treatment Process

Claims (5)

A method of manufacturing a fuel cell separator in which a mixed layer is formed on a substrate surface,
A mixed layer forming step of forming the mixed layer containing metal powder and carbon powder on the substrate surface;
A method for producing a fuel cell separator, comprising: a rolling step of rolling the base material on which the mixed layer is formed after the mixed layer forming step.   The method for producing a fuel cell separator according to claim 1, wherein the base material and the metal powder are made of pure titanium or a titanium alloy.   The method for producing a fuel cell separator according to claim 1 or 2, wherein the carbon powder is graphite powder.   The method for producing a fuel cell separator according to any one of claims 1 to 3, further comprising a heat treatment step of heat-treating the base material after the rolling step.   The method of manufacturing a fuel cell separator according to claim 4, wherein the heat treatment in the heat treatment step is performed at a temperature of 500 to 950 ° C. in a non-oxidizing atmosphere.

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