JP2013004511A - Fuel cell separator and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid polymer fuel cell separator manufactured using a metal substrate excellent in corrosion resistance and low in contact resistance, and to provide a method for manufacturing the solid polymer fuel cell separator.SOLUTION: A laminated coat including a conductive carbon coat and a metal oxycarbide coat is deposited on at least one surface of a metal substrate of a fuel cell separator. A manufacturing method according to the present invention includes the steps of: placing a separator substrate in a plasma processing vessel and heating the separator substrate to 100-450°C in a non-oxidation gas atmosphere; performing plasma treatment on a surface of the separator substrate; forming a conductive carbon coat by means of discharge plasma CVD; and forming a coat mainly containing chromium oxycarbide on a surface of the conductive carbon coat.

Description

  The present invention relates to a solid polymer fuel cell separator that is excellent in corrosion resistance, has low contact electrical resistance with carbon paper, and is inexpensive, and a method for producing the same.

  In recent years, fuel cells have attracted attention as energy sources for solving global environmental problems and energy problems. In particular, since the polymer electrolyte fuel cell can be operated at a low temperature and can be reduced in size and weight, application to a household power source or a fuel cell vehicle is being studied.

  One of the important parts that constitute a general polymer electrolyte fuel cell is a separator. The properties required for this separator include excellent corrosion resistance in an acidic atmosphere, high mechanical strength against vibration, etc., low contact resistance with carbon paper serving as the anode and cathode electrodes, groove processing, etc. It is excellent in workability, light and inexpensive.

  Recently, a metal plate such as a stainless steel plate has been mainly studied as a base material for a separator that satisfies the above-mentioned various characteristics. Separators using metals such as stainless steel, titanium, and alloys thereof have good corrosion resistance by forming a passive film on the surface, but this passive film increases contact resistance with the anode and cathode electrodes. Therefore, it is known that the conductivity is hindered and the power generation efficiency of the fuel cell is lowered. In addition, aluminum or magnesium metal has been studied as an inexpensive separator base material. However, an insulating oxide film is easily formed on the surface of the base material, corrosion resistance is not sufficient, and eluted ions deteriorate catalyst characteristics. In order to reduce the ionic conductivity of the solid polymer membrane, it is known that the power generation characteristics of the fuel cell are deteriorated as a result.

  For this reason, a corrosion-resistant metal material, for example, a carbide-based or boride-based metal inclusion is deposited on the surface of stainless steel to remove the conductivity-inhibiting factor due to the passive film (see Patent Document 1). Studies have been made on those that form a film layer having amorphous carbon and a conductive portion (see Patent Document 2), and those that form a chromium oxycarbide film on the surface of a metal substrate (see Patent Document 3).

  Patent Document 1 discloses a technique for precipitating carbon or / and boron in stainless steel as fine particles of chromium carbide and chromium boride on the surface of the substrate by heat-treating stainless steel at 800 ° C. to 1200 ° C. for a long time. It is disclosed. These fine particles have a low resistivity and do not form a passive film on the surface thereof, so that the contact resistance can be sufficiently lowered. However, since the stainless steel substrate is exposed, metal ions are eluted in the electrolytic solution, and it is necessary to heat treat the stainless steel substrate at 800 ° C. to 1200 ° C. for a long time.

Patent Document 2 discloses a fuel cell separator technology having a coating layer composed of an amorphous carbon layer and a conductive portion on a metal substrate. The separator includes an amorphous carbon layer and a coating layer including a conductive portion composed of the amorphous carbon layer and graphite fine particles. Since amorphous carbon is an insulating film, the contact resistance is about 10 mΩ · cm ² , and there is a problem that it cannot be lowered sufficiently. Moreover, although the amorphous carbon coating layer is said to be excellent in corrosion resistance, there is a problem that the amorphous carbon coating layer at a potential of +1 V is dissolved in a sulfuric acid solution having a pH of 2.

  In Patent Document 3, a solid polymer type or phosphoric acid type fuel cell separator provided with a coating mainly composed of chromium oxycarbide or chromium oxycarbide on a fuel cell separator substrate, and a fuel cell separator substrate 300 as a manufacturing method thereof. A technique is disclosed in which chromium oxycarbide or a film containing chromium oxycarbide as a main component is formed on the substrate by chemical vapor deposition using hexacarbonylchromium as a raw material while being kept at a temperature of from 500 ° C to 500 ° C. However, when the chromium oxycarbide film is formed on an inexpensive metal substrate surface such as aluminum or magnesium in an atmosphere containing oxygen, an insulating oxide film is formed at the interface between the metal substrate and the chromium oxycarbide film, and the junction resistance There was a problem of increasing.

JP 2003-193206 A JP 2008-204876 A JP 2006-278040 A Japanese Patent Application No. 2008-184765

  The problem to be solved by the present invention is to provide a polymer electrolyte fuel cell separator having excellent corrosion resistance and low contact resistance at low cost, and to provide a method for producing the same. Another object of the present invention is to provide a fuel cell separator surface-treated and a polymer electrolyte fuel cell using the fuel cell separator at low cost.

  The present invention has been made to solve the above problems, and provides the following fuel cell separator and method for producing the fuel cell separator.

  The invention according to claim 1 is a fuel cell separator substrate made of iron, titanium, nickel, chromium, aluminum, magnesium, an alloy material of these metals, or a laminated material of metals selected from these groups, and at least One main surface is a fuel cell separator characterized in that it is coated with a laminated film of a conductive carbon film and a metal oxycarbide film.

  The invention according to claim 2 is the fuel cell separator according to claim 1, wherein the fuel cell separator substrate according to claim 1 is a laminated material in which aluminum is plated on the surface of an iron plate or an iron alloy plate. It is a separator.

  The invention according to claim 3 is the fuel cell separator, wherein the conductive carbon film according to claim 1 is a conductive diamond-like carbon film having a thickness of 0.03 μm to 1 μm. It is.

  According to a fourth aspect of the present invention, the metal oxycarbide coating according to any one of the first to third aspects is a coating layer containing chromium oxycarbide as a main component, and the thickness thereof is 0.03 μm to 3 μm. This is a fuel cell separator.

  The invention according to claim 5 includes a first step of installing the fuel cell separator substrate in a plasma processing vessel and heating the fuel cell separator substrate to 100 ° C. to 450 ° C. in a high vacuum or in a non-oxidizing gas atmosphere. A second step of supplying a high frequency power and a negative bias voltage to the fuel cell separator substrate in an inert gas or non-oxidizing gas atmosphere to generate discharge plasma, and irradiating the surface of the fuel cell separator substrate with ions; A discharge plasma is generated in a carbon film forming source gas atmosphere to form the conductive carbon film, and then the substrate is heated to 300 ° C. to 450 ° C. in a metal oxycarbide film forming source gas atmosphere. And a fourth step of forming a film mainly composed of chromium oxycarbide by chemical vapor deposition. It is a method of manufacturing the separator.

  According to a sixth aspect of the present invention, a plurality of the fuel cell separator substrates are arranged substantially in parallel and at equal intervals, and the odd-numbered separator substrates are electrically connected to form a first substrate electrode. A substrate is electrically connected to form a second substrate electrode, high-frequency power is fed using the first substrate electrode and the second substrate electrode as counter electrodes, and a negative bias voltage is alternately applied to both substrate electrodes. A method for producing a separator for a fuel cell, wherein the second step and the third step according to claim 5 are carried out by supplying power.

  The invention according to claim 7 is characterized in that the bias voltage is a negative pulse voltage or a negative pulsating voltage, and its peak value is 300V to 5000V. It is a manufacturing method of the separator for batteries.

  The invention according to claim 8 uses the fuel cell separator according to any one of claims 1 to 5 or the fuel cell separator manufactured by the manufacturing method according to any of claims 5 to 7. It was a solid polymer fuel cell.

  According to the present invention, a separator for a polymer electrolyte fuel cell having excellent corrosion resistance and low contact resistance can be provided at low cost, and a production method excellent in productivity can be provided. Moreover, the separator for fuel cells manufactured by this, and the polymer electrolyte fuel cell using the said separator for fuel cells can be provided at low cost.

1 is a schematic cross-sectional view of a fuel cell separator according to the present invention. It is a schematic drawing which shows the principal part structure of the plasma processing apparatus which concerns on this invention.

The fuel cell separator according to the present invention is characterized in that a conductive carbon film and a metal oxycarbide film are laminated on the surface of an inexpensive metal separator substrate. The carbon coating may be conductive diamond-like carbon (hereinafter also referred to as conductive DLC) having a resistivity of 10 Ω · cm or less. Ordinary diamond-like carbon (hereinafter also referred to as DLC) is insulative and cannot be used. However, if a conductive DLC film having a resistivity of 10 Ω · cm or less is formed, a 1 μm-thick film is formed per square centimeter. The film resistance is 1 mΩ or less, and can be used practically without any problem. However, in order to reduce the contact resistance to 10 mΩ · cm ² or less, it is desirable that the resistivity of the conductive DLC film be 0.1 Ω · cm or less. According to the production method of the present invention, a conductive DLC film having a resistivity of 10 mΩ · cm can be obtained (see Patent Document 4).

  On the other hand, a normal DLC film is excellent in chemical resistance and is not affected by an acidic solution or an alkaline solution, but a conductive DLC film at a natural potential of +1 V is in a pH 2 sulfuric acid solution. Dissolve with. This invention solves the said subject by laminating | stacking the metal oxycarbide film which has corrosion resistance also on a sulfuric acid solution on the said electroconductive DLC film. FIG. 1 is a schematic sectional view of a fuel cell separator according to the present invention.

  The present invention in which a conductive DLC film and a film mainly composed of chromium oxycarbide are laminated on the surface of the fuel cell separator substrate is a metal substrate that is easily oxidized other than a stainless steel substrate, such as iron, titanium, magnesium, aluminum, and the like. The present invention can also be applied to an inexpensive substrate material such as an alloy material or a laminated material of a metal selected from these groups.

  However, in the step of forming a conductive DLC film and a film mainly composed of chromium oxycarbide on the separator substrate surface, a high-resistance oxide film is likely to be generated on the separator substrate surface. A conductive metal nitride layer containing a nitrogen element having a stoichiometric composition or less is formed in advance on the outermost surface of the metal separator substrate surface that is easily oxidized. The conductive nitride layer can be formed by irradiating the separator substrate surface with nitrogen ions.

  In particular, in the case of an aluminum separator substrate, aluminum nitride is the most stable oxide material among nitrides, and the aluminum separator is used in the conductive DLC film forming step and the film forming step mainly comprising chromium oxycarbide. Oxidation of the substrate surface can be suppressed, and the junction resistance between the separator substrate and the conductive DLC film can be significantly reduced.

  According to the present invention, the conductive aluminum nitride layer has a thickness of 0.01 μm to 0.1 μm and exhibits its effect. The conductive DLC film has a thickness of 3 μm or less, preferably 0.03 μm to 1 μm. The resistivity of the chromium oxycarbide is about 0.2 mΩ · cm, and the thickness of the film mainly composed of the chromium oxycarbide is not specified, but it is preferably 5 μm or less in consideration of productivity. Is 0.03 μm to 3 μm.

  The method for manufacturing a separator for a fuel cell according to the present invention includes a first step of installing a separator substrate in a plasma processing vessel and heating the separator substrate to 100 ° C. to 450 ° C. in a non-oxidizing gas atmosphere; A second step of plasma-treating the substrate surface; a third step of forming a conductive carbon coating by a discharge plasma CVD method; and a fourth step of forming a coating composed mainly of chromium oxycarbide on the surface of the conductive carbon coating. It consists of. The present invention has a feature that can be implemented by switching the source gas from the first step to the fourth step in the same plasma processing apparatus.

  FIG. 2 shows a schematic diagram of the main configuration of the plasma processing apparatus according to the present invention. A plurality of separator substrates 10 are arranged substantially in parallel and at equal intervals, the odd-numbered separator substrates are electrically connected to form the first substrate electrode 22a, and the even-numbered separator substrates are electrically connected to the second. The first substrate electrode 22a and the second substrate electrode 22b are used as a pair of substrate electrodes 24, and a high frequency power is fed from a high frequency power supply 25 through an impedance matching device 26 and a capacitor 27 to discharge the substrate electrode 22b. Plasma is generated, and negative bias voltage is alternately supplied from the bias power source 28 to the both substrate electrodes via the low-pass filter 32, so that the second to third steps are performed.

  In the first step, heating means (not shown) installed in the plasma processing apparatus in a high vacuum obtained by evacuating the plasma processing chamber 21 or in a non-oxidizing gas atmosphere such as argon gas or nitrogen gas. To heat the separator substrate to a predetermined temperature. In this step, while suppressing the oxidation reaction on the separator substrate surface, the substrate substrate is heated to 100 ° C. or more to sufficiently outgas, and at the same time, heated to a substrate temperature of 250 ° C. to 450 ° C. for forming a conductive DLC film in the third step It is preferable.

  In the second step, an inert gas, for example, a non-oxidizing gas such as argon gas or a mixed gas of argon gas and hydrogen is introduced into the plasma processing vessel 21, and high frequency power is applied to the pair of substrate electrodes 22a and 22b. Electric power is supplied to generate discharge plasma, and at the same time, a negative bias voltage is applied to irradiate both surfaces of the separator substrate with ions to remove oxide films and deposits on the substrate surface. As the high frequency power source 5, for example, one having a frequency of 13.56 MHz and an output of 300 W to 3 kW can be used.

  Further, it is necessary to alternately apply a negative pulsating voltage or a negative pulse voltage having a peak value of 300 V to 5 kV to the pair of substrate electrodes as a bias voltage. For this purpose, as shown in FIG. 2, the output voltage of the AC voltage generator 29 is fed to the primary side of the transformer 30, and the secondary output voltage is rectified by a diode 31 to generate a negative pulsating voltage. The pulsating voltage can be alternately supplied to the pair of substrate electrodes 24 through the low-pass filter 32. The frequency of the AC voltage is not specified, but is preferably 50 Hz to 200 kHz. Furthermore, it is preferably 1 kHz to 100 kHz.

  In this step, if necessary, nitrogen gas or the like is mixed with the argon gas and nitrogen ions are implanted into the surface of the separator substrate to form a nitride layer. The nitrogen content ratio of the nitride layer can be controlled by the mixing ratio of argon gas and nitrogen gas. For example, in the case of an aluminum separator substrate, aluminum nitride is insulative, but conductive nitridation is achieved by forming an aluminum layer containing nitrogen elements with a nitrogen content of less than 50 atomic percent, preferably 25 to 45 atomic percent. An aluminum layer can be formed.

  In the third step, the separator substrate 10 installed in the plasma processing vessel 21 is heated to 250 ° C. to 450 ° C., and a hydrocarbon gas such as methane, acetylene, toluene gas and a hydrogen gas as necessary are used as a raw material gas. Then, high frequency power is supplied to the pair of substrate electrodes 22a and 22b to generate discharge plasma. A conductive DLC film can be formed on both sides of the separator substrate by applying a negative bias voltage superimposed on the high frequency power.

  For the formation of the conductive DLC film, it is essential that the temperature of the separator substrate is 250 ° C. or higher and a predetermined amount of ion irradiation. The conductive DLC film 11 can be applied to the surface of the separator substrate by alternately applying a negative bias voltage to the first substrate electrode 22a and the second substrate electrode 22b which are the opposing separator substrates. . A pulsating voltage having a peak value of 300 V to 5000 V or a pulse voltage can be applied as the negative bias voltage.

  According to another embodiment of the present invention, the high frequency power is supplementarily used for generating the discharge plasma of the raw material gas, and the discharge plasma is maintained by the pulsating voltage from the bias power supply 28 to obtain a desired conductive DLC. A film can also be formed. Furthermore, it is possible to form a desired conductive DLC film only by supplying the bias voltage. A method for forming these conductive DLC films is also included in the present invention.

  In the fourth step, a metal hexacarbonyl gas is additionally introduced as a source gas, and the substrate temperature is maintained at 300 ° C. to 450 ° C. in an atmosphere containing the metal hexacarbonyl gas, and a metal oxycarbide film is formed by chemical vapor deposition. . In this step, the metal oxycarbide film can be formed not only by the plasma CVD method but also by the thermal CVD method. In the case of plasma CVD, generation of a metal oxycarbide coating on the substrate surface can be assisted by generating discharge plasma by supplying high-frequency power to the pair of substrate electrodes 22a and 22b, which are separator substrates. The chemical vapor deposition method in the present invention refers to a thermal CVD method using a metal hexacarbonyl gas as a raw material, a plasma CVD method, a reactive ion plating method, or the like.

  As shown in FIG. 2, six aluminum substrates obtained by hot-plating aluminum on the surface of an A6 size iron plate in the plasma processing vessel are locked in parallel with an insulator support at intervals of about 4 cm, and the odd-numbered three pieces are attached. The first electrode substrate 22a was electrically connected, and the even-numbered three substrates were electrically connected to form the second electrode substrate 22b, thereby forming a pair of counter electrode plates 24. The power supply terminal of the first electrode substrate 22 a was connected to the output terminal of the high frequency power supply 25 via an impedance matching device 26 and a capacitor 27, and the ground terminal of the second electrode substrate 22 b was grounded via the capacitor 27. The power supply terminal and the ground terminal of the pair of counter electrode plates 24 are connected to a bias power source 28 through a low-pass filter 32. In this example, for comparison, a sample in which only the DLC film 11 was deposited on the SUS substrate surface and a sample in which only the DLC film 11 was deposited on the aluminum substrate 10 were prepared.

  In the first step, the inside of the plasma processing chamber 1 is evacuated to a high vacuum in advance and sufficiently discharged, and then a mixed gas of nitrogen gas 80% and hydrogen gas 20% is introduced as a non-oxidizing gas and the pressure is reduced to about The pair of counter electrode plates was heated to 300 ° C. by a heating means held at 100 Pa and installed along the inner wall surface of the plasma processing vessel via a heat shielding material.

  In the second step, a mixed gas of 80% argon gas and 20% hydrogen gas is introduced as a substrate surface cleaning gas into the plasma processing apparatus and maintained at a pressure of about 1 Pa, and a frequency of 13 is applied to the pair of counter electrode plates 24. A high frequency power of .56 MHz and an output of 500 W is supplied to generate discharge plasma, and a pulsating voltage with a frequency of 33 kHz and −800 V is alternately applied to the pair of counter electrode plates 24 through the low-pass filter 32 to form a separator base material. The surface was cleaned. The natural oxide film and contaminants on the substrate surface were removed by a cleaning process for 20 minutes.

  In the third step, the separator substrate temperature is maintained at 300 ° C., a mixed gas of acetylene gas 80% and hydrogen gas 20% is introduced as a conductive DLC film forming gas, and the pressure is maintained at about 5 Pa. A high-frequency power having a frequency of 13.56 MHz and an output of 700 W is supplied to the counter electrode plate 24 to generate discharge plasma, and a pulsating voltage having a frequency of 33 kHz and −800 V is alternately applied to the pair of counter electrode plates through the low-pass filter 32. This was applied to form a conductive DLC film. A conductive DLC film having a thickness of 150 nm was obtained by film formation for 15 minutes.

  In the fourth step, the separator substrate temperature was maintained at 350 ° C., and hexacarbonyl chromium and water vapor were introduced into the vacuum vessel using acetylene gas and hydrogen as carrier gases to adjust the pressure to about 100 Pa. The partial pressure ratio of hexacarbonylchromium to hydrogen was about 0.01. In this embodiment, discharge plasma was generated by supplying high frequency power of 13.56 MHz and 300 W to the pair of substrate electrodes 22a and 22b which are separator substrates. A bias voltage was not applied, and a chromium oxycarbide coating 12 having a thickness of 260 nm was laminated by film formation for 10 minutes.

  In the manufacturing method of the chromium oxycarbide coating 12 by the plasma assisted thermal CVD method, even if a minute defect such as a pinhole is present in the conductive DLC film 11 formed in the third step, the source gas is allowed to enter the minute defect. Since a chromium oxycarbide film is formed in the defects and sealed, the corrosion resistance can be remarkably improved.

Table 1 shows the evaluation results of the laminated film of the obtained conductive DLC film and chromium oxycarbide film. A corrosion acceleration test was performed on an effective surface area of 5.76 cm ² as an evaluation sample. In the accelerated corrosion test, an anodic polarization test was conducted by dipping in a sulfuric acid solution at a temperature of 90 ° C. and pH 2. The acceleration test was conducted for 24 hours with 800 ml of sulfuric acid solution and natural immersion potentials +0.8 V and +1 V (SHE). The contact resistance was measured by cutting a sample into an area of 4 cm ² , sandwiching carbon paper between copper electrodes, and applying a load of 40 kg. The measurement results are shown in Table 1.

As for the sample in which only the conductive DLC film was deposited on the SUS substrate, as a result of the accelerated corrosion test at a natural potential of 0.8 V, the DLC film was hardly dissolved even after 24 hours, and the metal ion elution from the SUS substrate was a trace amount. Changed little. The contact resistance, which was 2.7 mΩ · cm ² before immersion, increased to 6.3 mΩ · cm ² , but hardly changed. However, when the natural potential was +1 V, the DLC film was completely dissolved within 1 hour, and the metal ions of the SUS substrate were eluted. The contact resistance increased from 5.7 mΩ · cm ² to 1700 mΩ · cm ² before immersion. This is considered to be because the conductive DLC film was dissolved and a chromium oxide film was formed on the surface of the SUS substrate.

  Further, in the sample in which only the conductive DLC film was deposited on the aluminum substrate, the DLC film was completely peeled off in the accelerated corrosion test at a natural potential of 0.8V. This is thought to be due to the presence of minute defects such as pinholes in the DLC film and peeling due to the penetration of the corrosive liquid.

On the other hand, for the sample coated with the laminated film of the conductive DLC film 11 and the chromium oxycarbide film 12 according to the present invention, the ion elution amount was 0.01 mg or less which is the measurement limit. In addition, no change was observed in the visual evaluation of the sample surface after the acceleration test at a natural potential of +1 V. Although the contact resistance was 3.5 mΩ · cm ² before the acceleration test, it increased to 4.2 mΩ · cm ² after the acceleration test, but hardly changed. In an accelerated test at a natural potential of +1 V in a sulfuric acid solution at pH 2, no elution of metal ions was observed and no corrosion occurred.

"Effect of the embodiment"
According to this embodiment, a separator for a fuel cell having excellent corrosion resistance and extremely low contact resistance can be manufactured at low cost. Further, even if a minute pinhole or the like exists in the conductive DLC film, if the metal oxycarbide is laminated by the thermal CVD method, the pinhole part is also sealed, and the laminated film is peeled off due to the pinhole. And the elution of metal ions does not occur.

  Further, according to this embodiment, by adding 10% to 30% nitrogen gas to the mixed gas of argon and hydrogen as the substrate surface cleaning gas in the second step, the substrate surface is cleaned and simultaneously irradiated with nitrogen ions. A metal nitride layer that is difficult to be oxidized can be formed. In the case of a metal substrate, such as a titanium substrate or an aluminum substrate, in which a metal oxide film is likely to be generated by natural oxidation, a conductive metal nitride layer having a thickness of 5 nm to 50 nm is formed on the surface, thereby forming a conductive film to be deposited in the third step. This has the effect of significantly reducing the junction resistance with the conductive DLC film. When an insulating metal nitride layer is formed, the junction resistance can be reduced by injecting nitrogen having a stoichiometric composition or less.

"Other embodiments"
In the above embodiment, a laminated material obtained by plating the surface of the iron plate with aluminum is used as the separator substrate material, but the present invention is not limited to this, and iron, aluminum, titanium, magnesium, copper, nickel, and alloy materials thereof, or Needless to say, the present invention can also be applied to laminated materials of these metals. If necessary, molybdenum oxycarbide or tungsten oxycarbide can be added to the chromium oxycarbide coating as the metal oxycarbide coating.

  In the above embodiment, high frequency power is supplied to the pair of counter electrode plates made of the separator substrate to excite discharge plasma, and negative pulsating voltage is alternately applied to clean the surface of the separator substrate. In addition, the manufacturing method for depositing the chromium oxycarbide coating has been described. However, the present invention is not limited to the above manufacturing method, and the bias voltage is applied while holding the separator substrate in the ICP plasma or ECR plasma atmosphere of the source gas. Thus, the second to fourth steps can be performed, and the conductive DLC film and the chromium oxycarbide film can be applied. Further, the conductive DLC film can be applied by a reactive sputtering method, a reactive ion plating method, or the like using a chromium target and carbon oxide gas as raw materials.

  In another embodiment, hexacarbonyl chromium gas is introduced after the conductive DLC film is deposited in the third step, and the separator substrate is held at 300 ° C. to 500 ° C., and chromium oxycarbide is formed by a thermal CVD method. A coating can be applied, or a chromium oxycarbide coating can be applied using a combination of discharge plasma and thermal CVD.

10: Separator substrate, 11: Conductive DLC coating, 12: Chromium oxycarbide coating, 21: Vacuum container, 22a, 22b: Substrate electrode, 25: High frequency power supply, 26: Impedance matching device, 27: Capacitor, 28: Bias power supply 29: AC voltage generator, 30: Transformer, 31: Diode, 32: Low-pass filter, 33: Feedthrough

Claims (8)

  A fuel cell separator substrate made of iron, titanium, nickel, chromium, aluminum, magnesium, or an alloy material of these metals, or a laminated material of metals selected from these groups, at least one main surface of which is conductive A fuel cell separator, wherein the separator is coated with a laminated film of a carbon film and a metal oxycarbide film.   2. The fuel cell separator according to claim 1, wherein the fuel cell separator substrate is a laminated material in which aluminum is plated on the surface of an iron plate or an iron alloy plate.   3. The fuel cell separator according to claim 1, wherein the conductive carbon film is a conductive diamond-like carbon film having a thickness of 0.03 μm to 1 μm.   4. The fuel cell according to claim 1, wherein the metal oxycarbide coating is a coating layer mainly composed of chromium oxycarbide and has a thickness of 0.03 μm to 3 μm. Separator.   A first step of placing the fuel cell separator substrate in a plasma processing container and heating the fuel cell separator substrate to 100 ° C. to 450 ° C. in a high vacuum or non-oxidizing gas atmosphere; and an inert gas or non-oxidizing gas A second step of supplying a high frequency power and a negative bias voltage to the fuel cell separator substrate in a gas atmosphere to generate discharge plasma, and irradiating the surface of the fuel cell separator substrate with ions; In a third step of generating a discharge plasma in order to form the conductive carbon film, and subsequently maintaining the substrate at 300 ° C. to 450 ° C. in a source gas atmosphere for forming a metal oxycarbide film, chromium is deposited by chemical vapor deposition. And a fourth step of forming a coating mainly composed of oxycarbide.   A plurality of the fuel cell separator substrates are arranged substantially in parallel and at equal intervals, the odd-numbered separator substrates are electrically connected to form a first substrate electrode, and the even-numbered separator substrates are electrically connected. 6. The high frequency power is supplied as a second substrate electrode, the first substrate electrode and the second substrate electrode as counter electrodes, and a negative bias voltage is alternately supplied to both substrate electrodes. The manufacturing method of the separator for fuel cells characterized by implementing the 2nd process and 3rd process of these.   The method for manufacturing a fuel cell separator according to claim 5 or 6, wherein the bias voltage is a negative pulse voltage or a negative pulsating voltage, and a peak value thereof is 300V to 5000V.   A solid polymer fuel cell using the fuel cell separator according to any one of claims 1 to 5 or the fuel cell separator produced by the production method according to any one of claims 5 to 7.

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