JP2007103072A - Fuel cell system, component parts of fuel cell system, and piping of fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of enduring a long-period operation as well as component parts and a piping for the same. <P>SOLUTION: In the fuel cell system provided with a fuel cell obtaining electromotive force at least with the supply of fuel gas, a fuel supply means consisting of a supply piping for sending fuel gas at one end part to the fuel cell at the other end and one or more supply means component parts arranged on the supply piping, and a fuel exhaust means consisting of an exhaust piping for sending the fuel gas coming out of the fuel cell arranged at one end to the other end and one or more exhaust means component parts arranged on the exhaust piping, at least a part of the supply piping, supply means component parts, exhaust piping and exhaust means component parts consists of a base material 1 and a corrosion-resistant coating 2 fixed on the surface of the base material and made of amorphous carbon with an area ratio occupied by a plurality of defects A penetrating in a thickness direction of 10<SP>-2</SP>% or less, as well as of a corrosion-resistant member 3 with an electric resistivity of 10<SP>8</SP>Ω or more. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system that can withstand long-term operation, and its components and piping.

  A fuel cell is known as a device that directly converts chemical energy (free energy change of combustion reaction) of fuel into electric energy. A fuel cell uses a fuel gas such as hydrogen or hydrocarbon as a negative electrode and an oxidant gas such as oxygen or air as a positive electrode as a battery active material, and sequentially removes water (product water) generated by the reaction. Thus, an electromotive force can be obtained continuously. In recent years, fuel cells are being used in fuel cell systems such as vehicle power supplies mounted on vehicles such as large-scale power plants and electric vehicles.

  Since water generated by power generation in the fuel cell system may be acidic, metal ions may be slightly eluted from the metal parts such as pipes that are components of the fuel cell system (corrosion phenomenon). . The eluted metal ions flow into the fuel cell through the circulation path of the fuel cell system, and are adsorbed by the solid polymer electrolyte constituting the fuel cell, thereby reducing the performance of the fuel cell. Even if the elution of the metal ions is small, there is a concern that the fuel cell will deteriorate due to long-term use and the life thereof will be shortened. Therefore, measures to prevent elution are taken. For example, Patent Document 1 proposes a method of removing metal ions using an ion exchange resin.

  The fuel cell system is mounted on a vehicle because the energy conversion efficiency does not decrease even if the fuel cell system is downsized. When mounted on a vehicle, it is also desired to be lightweight. Therefore, it is desirable to use a light metal that is lighter than stainless steel, but there is a problem that the amount of metal ions to be eluted increases.

  Incidentally, it is known that a coating film (amorphous carbon film) made of amorphous carbon (diamond-like carbon) not only has excellent sliding characteristics but also has high corrosion resistance. However, defects in the amorphous carbon film during film formation and cracks and peeling off in the amorphous carbon film after film formation cause the various characteristics of amorphous carbon to be exhibited well. There is a problem that it is not. In particular, when an amorphous carbon film is used as a corrosion-resistant film, damage to the film greatly affects.

  With respect to the above problems, Patent Document 2 discloses a coating member having corrosion resistance, which includes a base material and an amorphous carbon film containing a metal and / or metal carbide formed on the surface of the base material. ing. Patent Document 3 discloses a base material having a carbon diffusion layer made of an austenitic metal and formed in a surface layer portion by performing fluorination treatment and carburization treatment, and an amorphous carbon film laminated on the carbon diffusion layer. And a metal product having corrosion resistance is disclosed.

  However, in Patent Documents 2 and 3, it is conceivable that the desired corrosion resistance cannot be obtained if the corrosion resistance of the metal contained in the amorphous carbon film or the carbon diffusion layer is low. Further, since the defects of the amorphous carbon film generated during the film formation are not reduced, the corrosion still proceeds from the defect as a starting point. Furthermore, corrosion progresses to the interface between the base material and the amorphous carbon film, and the amorphous carbon film peels off from the interface, so that the corrosion resistance cannot be maintained.

As another method, it is conceivable to reduce corrosion caused by defects in the amorphous carbon film by coating the substrate with high corrosion resistance with the amorphous carbon film to ensure the corrosion resistance. However, the types of base materials that can be used are limited, and when the base material does not have the same corrosion resistance as amorphous carbon, the performance as a corrosion-resistant member is inferior.
JP 2002-313404 A JP 2003-231203 A JP 2004-307894 A

  In view of the above-described problems, the present invention prevents elution of metal ions by using an excellent corrosion-resistant member that sufficiently exhibits the inherent corrosion resistance of amorphous carbon, and can withstand long-term operation. And it aims at providing the component and piping.

The fuel cell system of the present invention includes at least a fuel cell that receives an supply of fuel gas to obtain an electromotive force, a supply pipe that sends the fuel gas to the fuel cell, and one or more supply means disposed on the supply pipe A fuel cell comprising: a fuel supply means comprising component parts; a fuel discharge means comprising a discharge pipe for discharging exhaust gas from the fuel cell; and one or more discharge means component parts disposed on the discharge pipe. In the system,
At least a part of the supply pipe, the supply means component, the discharge pipe, and the discharge means component is a base material and an area occupied by a plurality of defects that are fixed to the surface of the base material and penetrate in the thickness direction. And a corrosion-resistant film made of amorphous carbon having a rate of 10 ⁻² % or less, and a corrosion-resistant member having an electrical resistivity of 10 ⁸ Ω · cm or more.

In addition, the fuel cell system component of the present invention includes a supply pipe for sending fuel gas to a fuel cell that receives the supply of the fuel gas and obtains an electromotive force, or a discharge pipe for discharging exhaust gas from the fuel cell. A component of a fuel cell system disposed on the top,
An electrical resistivity comprising: a base material; and a corrosion-resistant film made of amorphous carbon that is fixed to the surface of the base material and has an area ratio occupied by a plurality of defects penetrating in the thickness direction of 10 ⁻² % or less. Is made of a corrosion-resistant member having 10 ⁸ Ω · cm or more.

The piping of the fuel cell system of the present invention is arranged at one end to send the fuel gas at one end to the fuel cell that receives the supply of the fuel gas to obtain an electromotive force. A fuel cell system pipe for sending fuel gas exiting the fuel cell to the other end,
A pipe base material, and a corrosion-resistant film made of amorphous carbon that is fixed to the inner surface of the pipe base material and has a plurality of defects penetrating in the thickness direction and having an area ratio of 10 ⁻² % or less. The resistivity is 10 ⁸ Ω · cm or more.

  Here, the “electrical resistivity” is the electrical resistivity of the corrosion-resistant member (pipe) itself, and is the resistivity when a voltage is applied in the thickness direction of the corrosion-resistant coating.

In the fuel cell system of the present invention, and its components and piping, the corrosion-resistant coating film preferably has an area of each defect of 100 μm ² or less.

  Moreover, it is desirable that the corrosion-resistant film has a thickness of 0.5 to 100 μm. The amorphous carbon is preferably silicon-containing amorphous carbon containing carbon as a main component and containing silicon. Further, the amorphous carbon contains 0.1 at% to 10 at% of silicon and 35 at% to 50 at% of hydrogen. % Or less is desirable.

  The base material (pipe base material) is preferably made of a conductive material having conductivity in at least the surface layer portion or a metal material. In this case, the metal material is preferably a light metal, particularly an aluminum-based material mainly composed of aluminum.

In the present invention, the fuel cell system includes components (supply means component parts, discharge means component parts) and pipes (supply pipes, supply pipes, etc.) using a corrosion-resistant member in which a corrosion-resistant coating made of amorphous carbon is fixed on the surface of the substrate. Corrosion resistance is imparted by using the discharge pipe. In particular, if the area ratio (defect area ratio) occupied by a plurality of defects penetrating in the thickness direction of the corrosion-resistant film is 10 ⁻² % or less and the electrical resistivity of the corrosion-resistant member is 10 ⁸ Ω · cm or more, Since the corrosion resistance of crystalline carbon is exhibited well, a fuel cell system having excellent corrosion resistance is configured. In addition, since the corrosion-resistant film made of amorphous carbon is excellent in heat resistance, the above-mentioned corrosion-resistant member is also suitable for a fuel cell system that becomes high temperature during operation.

Furthermore, if the area of each defect of the corrosion-resistant film is 100 μm ² or less, the reliability as a fuel cell system is enhanced in terms of corrosion prevention.

  Moreover, if the film thickness of a corrosion-resistant film is 0.5-100 micrometers, since a desired defect area rate and electrical resistivity are obtained, a component and piping show the outstanding corrosion resistance. In addition, when the silicon content of amorphous carbon is 0.1 at% or more and 10 at% or less, and the hydrogen content is 35 at% or more and 50 at% or less, even if the corrosion resistant film is thickened (for example, 12 μm or more), it occurs in the film. Therefore, a corrosion-resistant member having a desired defect area ratio and electrical resistivity can be obtained.

  If the substrate is made of a light metal, a lightweight fuel cell system can be obtained.In particular, if the substrate is made of an aluminum-based material, it has excellent adhesion with an anticorrosion coating made of amorphous carbon, so the corrosion resistance is good. Retained.

  The components of the fuel cell system of the present invention (that is, the supply device component and the discharge device component) include a valve body that opens and closes the supply pipe or the discharge pipe, and a gas-liquid separation that separates moisture from the fuel gas. Part, a hydrogen pump for circulating the fuel gas, and a temperature sensor.

  The best mode for carrying out the fuel cell system of the present invention and its components and piping will be described below.

  FIG. 9 is a diagram schematically showing the configuration of the main part of the fuel cell system of the present invention. The fuel cell system 90 of the present invention mainly includes a fuel cell 91, a fuel supply means 92 that supplies fuel gas to the fuel cell, and a fuel discharge means 93 that discharges the fuel gas exiting the fuel cell.

  The fuel cell 91 usually has a pair of electrodes that sandwich a matrix layer impregnated with an electrolyte. An electromotive force is generated by a chemical reaction between the fuel gas supplied to one electrode (negative electrode) and the air in contact with the other electrode (positive electrode). The fuel cell 91 may be any fuel cell such as a solid polymer type, a phosphoric acid type, a molten salt carbonate type, and an alkaline type. In particular, if the fuel cell 91 is a solid polymer type, by preventing the elution of metal ions, the adsorption of metal ions to the solid polymer film is reduced, and the deterioration of the performance of the fuel cell can be satisfactorily prevented. Is preferable.

  The fuel supply means 92 mainly includes a supply pipe 92d for sending fuel gas to the fuel cell 91, and one or more supply means components 92X and 92Y disposed on the supply pipe 92d. The fuel discharge means 93 mainly includes a discharge pipe 93d for discharging exhaust gas from the fuel cell 91, and one or more discharge means components 93X to 93Z disposed on the discharge pipe 93d.

  The fuel supply means 92 and the fuel discharge means 93 send at least a part of the exhaust gas (including the fuel gas) of the discharge pipe 93 d exiting the fuel cell 91 to the supply pipe 92 d and circulate the fuel gas in the fuel cell system 90. A fuel circulation means 95 may be provided. Normally, the fuel circulation means 95 has a circulation pipe 95d for sending fuel gas from one end branched from a part of the discharge pipe 92d to the other end branched from a part of the supply pipe 93d. The fuel circulation means 95 may include one or more circulation means component parts 95X and 95Y disposed on the circulation pipe 95d as the component parts.

  Furthermore, an oxidant gas supply means (not shown) for supplying an oxidant gas such as air or oxygen to the fuel cell 91 may be provided. It is preferable that the oxidant gas supply means mainly comprises an infeed pipe for sending the oxidant gas to the fuel cell, and one or more infeed means components arranged on the infeed pipe.

  Fuel cell system configurations such as the above-mentioned supply piping, discharge piping, circulation piping, and delivery piping, and fuel cell system configurations such as supply means components, discharge means components, circulation means components, and delivery means components As described above, since the component comes into contact with the generated water (acidic), it may cause elution of metal ions. Therefore, some anti-corrosion measures are necessary. Specific examples of components are given below.

  It is desirable that at least one of the components is a valve body that opens and closes a supply pipe or a discharge pipe. The valve body includes an open / close valve that opens and closes the flow path of the fuel gas supplied to the fuel cell, a drain valve that discharges the generated water separated from the exhaust gas to the outside, and a check valve that prevents backflow in the piping. And an exhaust valve for controlling the exhaust from the fuel cell system.

  Moreover, it is desirable that at least one of the components is a gas-liquid separator that separates generated water from the exhaust gas exiting the fuel cell, or a hydrogen pump that circulates hydrogen gas. Further, at least one of the components may be a temperature sensor that detects the temperature of the fuel gas or the oxidant gas in order to suitably control the operation of the fuel cell.

  And any component should just consist of a corrosion-resistant member at least the part which contacts production | generation water.

  Each component described above is arranged on the pipes 92d, 93d, and 95d in FIG. Specifically, the fuel gas (here, hydrogen gas) accumulated in the fuel tank or the like is adjusted to a specified pressure by the pressure regulating valve 92X of the supply pipe 92d, passes through the on-off valve 92Y, and is supplied to the fuel cell 91. Is done. Hydrogen gas containing moisture after reaction in the fuel cell 91 passes through the on-off valve 93X of the discharge pipe 93d, and is separated into hydrogen gas and water by the gas-liquid separator 93Y. The separated water is discharged to the outside from the drain valve 93Y '. The hydrogen gas is pumped out to the supply pipe 92d side by the hydrogen pump 95X of the circulation pipe 95d and supplied again to the fuel cell 91. A check valve 95Y for preventing a backflow from the supply pipe 92d is disposed behind the hydrogen pump 95X. Since the circulated gas has a nitrogen concentration increased by diffusion of nitrogen from the air, it is appropriately discharged into the atmosphere via the exhaust valve 93Z.

[Corrosion resistant material]
The corrosion-resistant member mainly includes a base material and a corrosion-resistant film made of amorphous carbon fixed on the surface of the base material. The corrosion-resistant coating film only needs to be fixed to a surface that requires at least corrosion resistance, that is, a surface that may come into contact with generated water. Specifically, if the corrosion-resistant member is the above pipe, it is the inner surface of the pipe base material.

  There is no particular limitation on the shape and material of the base material, and if the base material is inferior in corrosion resistance to amorphous carbon, the base material has good corrosion resistance by forming a corrosion-resistant film made of amorphous carbon. Is granted. In particular, when the corrosion-resistant film is formed by a direct current plasma CVD method described later, the base material is a base material made of a metal material or a base material made of a conductive material having conductivity at least on the surface layer portion. preferable. Examples of the metal material and the conductive material include an aluminum-based material mainly composed of aluminum, an iron-based material mainly composed of iron, and a copper-based material mainly composed of copper, and metals and conductive resins. In addition to a substrate made entirely of a conductive material, a substrate having a conductive coating on the surface of an insulator may be used. Among these, the aluminum-based material is excellent in adhesion with a corrosion-resistant film made of amorphous carbon. Therefore, the corrosion of the base material generated from the portion where the corrosion-resistant film is peeled off can be prevented. Moreover, it is easy to form a corrosion-resistant film with few defects on the surface of a substrate with high adhesion.

  In particular, the use of a light metal such as an aluminum-based material as the base material leads to weight reduction of the fuel cell system, which is advantageous when the fuel cell system is mounted on a vehicle.

  By the way, the defects present in the coating greatly affect the corrosion resistance of the corrosion-resistant coating made of amorphous carbon. There are roughly two types of defects. One is a defect (defect A) penetrating in the thickness direction of the corrosion-resistant film. Since the surface of the base material is exposed from the defects having such a shape, the base material is easily corroded, and when corrosion starting from the defect A progresses to the interface between the base material and the corrosion-resistant coating, the coating is peeled off. . Therefore, the defect A has a great influence on the corrosion resistance of the corrosion resistant member. The other is a defect (defect B) that does not penetrate the corrosion resistant coating. Even if the defect does not penetrate the coating, the film thickness of the defective portion is thinner than the other portions. FIG. 1 is a cross-sectional view of the corrosion-resistant member cut in the thickness direction of the corrosion-resistant film, and schematically shows the cross-sectional shapes of the defect A and the defect B.

Therefore, in the corrosion-resistant member used in the present invention, the area ratio (hereinafter referred to as “defect area ratio”) occupied by a plurality of defects (defect A) penetrating in the thickness direction of the corrosion-resistant film is set to 10 ⁻² % or less. If the defect area ratio in the corrosion-resistant coating is 10 ⁻² % or less, the corrosion of the base material proceeding from the defects is reduced. The defect area ratio can be measured, for example, by using an electrochemical method described in detail in the “Example” section described later.

In addition, when a voltage is applied to a substrate on which a corrosion-resistant film made of amorphous carbon is formed, current leaks from the defective portion when the defect area ratio of the corrosion-resistant film is high, so the electrical resistance of the corrosion-resistant member is low. Become. Even if the defect area ratio is low, if there is a thin part such as defect B, the thin part is destroyed by an applied voltage of 50 V or more, current leaks and the electrical resistance decreases. . That is, when many defects A and B exist in the corrosion-resistant film, the original electrical resistivity (about 10 ¹¹ to 10 ¹² Ω · cm) of amorphous carbon does not appear. Therefore, the corrosion resistance member used in the present invention has an electrical resistivity of 10 ⁸ Ω · cm or more. If the electrical resistivity of the corrosion-resistant member is 10 ⁸ Ω · cm or more, the number of defects is small and the corrosion resistance of amorphous carbon can be satisfactorily exhibited, so that the corrosion resistance is excellent. In addition, the electrical resistivity of a corrosion-resistant member can be measured by the method explained in full detail in the below-mentioned [Example] column.

Further, the corrosion-resistant film preferably has an area of each defect A of 100 μm ² or less. When the area of one defect A is large, the base material is easily corroded from the defective portion, and furthermore, corrosion progresses quickly at the interface between the coating film and the base material. Cheap. If the area of each defect A is 100 μm ² or less, the corrosion from the defective portion is reduced, so that the corrosion-resistant member is more reliable. The area of each defect A is measured by, for example, observing the surface of the corrosion-resistant film with a scanning electron microscope (SEM) and analyzing the image, as described in detail in the section of [Example]. can do.

The corrosion-resistant film is preferably 0.5 to 100 μm in thickness although it depends on the composition of amorphous carbon. When the film thickness is less than 0.5 μm, since the film thickness is too thin, the probability of defects penetrating in the thickness direction increases, so that the defect area ratio of the corrosion-resistant film is 10 ⁻² % or less and the electric resistivity is 10 The characteristic of ⁸ Ω · cm or more may not be maintained. On the other hand, if the thickness exceeds 100 μm, the internal stress and strain of the coating increase, which may be undesirable because the coating may be broken or the release from the substrate may be promoted.

  The corrosion-resistant film is a film made of amorphous carbon, that is, an amorphous carbon film. In particular, amorphous carbon (silicon-containing amorphous carbon) containing carbon (C) as a main component and containing silicon (Si) is excellent when formed as an amorphous carbon film on the surface of a substrate. Shows adhesion. That is, since the corrosion-resistant film made of silicon-containing amorphous carbon is difficult to peel from the substrate, the corrosion resistance is maintained for a long time.

  Here, FIG. 7 is a graph showing the defect area ratio with respect to the Si amount of amorphous carbon. The numbers in the graph indicate the corrosion-resistant member No. described in the column of [Example]. It corresponds to. No. with extremely different film thickness It can be seen from FIG. 7 that, except for 1, 6, 7, and 10, the defect area ratio tends to decrease as the Si amount decreases. This is because when the amount of Si is large, the coating becomes hard, and internal stress and strain increase in the coating, damage and peeling of the coating are promoted, and the defect area ratio is likely to increase. Therefore, the Si amount of amorphous carbon is preferably 10 at% or less, more preferably 7 at% or less. However, if the amount of Si is extremely small, the amorphous carbon film is granulated depending on the film forming conditions, and a uniform film cannot be obtained, leading to the generation of defects. Therefore, the Si amount of amorphous carbon is preferably 0.1 at% or more, and more preferably 2 at% or more.

  FIG. 8 is a graph showing the defect area ratio with respect to the H content of amorphous carbon. The numbers in the graph indicate the corrosion-resistant member No. described in the column of [Example]. It corresponds to. No. with extremely different film thickness It can be seen from FIG. 8 that the defect area ratio tends to decrease as the amount of H increases except for 1, 6, 7, and 10. This is because when the amount of H is large, the coating becomes soft and internal stress and strain are alleviated, thereby reducing peeling and damage of the coating. Therefore, the H content of amorphous carbon is preferably 35 at% or more, more preferably 40 at% or more. However, it is difficult to synthesize amorphous carbon containing H exceeding 50 at%, and many defects are formed. Therefore, the amount of H of amorphous carbon is preferably 50 at% or less, more preferably 45 at% or less, and a film with few defects can be obtained.

  In general, a corrosion-resistant film made of amorphous carbon has a high hardness, so when the film is formed thick, cracks occur due to internal stress and strain, and further, corrosion from the cracks and peeling of the film occur, resulting in a defect area ratio. Urge the rise. Moreover, it takes a long time to form a thick film. Therefore, the film thickness of the corrosion resistant coating is preferably 0.5 μm or more and less than 18 μm, more preferably 0.5 μm or more and less than 16 μm, and further preferably 6 μm or more and less than 12 μm. On the other hand, in order to maintain the function and durability as a protective film, a certain thickness is required. If the corrosion-resistant film is made of amorphous carbon containing Si at 0.1 at% or more and 10 at% or less and H at 35 at% or more and 50 at% or less, even if the film thickness is 12 μm or more, 16 μm or more, further 18 μm or more, Internal stress and strain are alleviated and cracks generated in the coating can be reduced. More preferably, Si is 2 at% or more and 7 at% or less, and H is 40 at% or more and 45 at% or less. Note that even a corrosion-resistant film having a film thickness of less than 18 μm, less than 16 μm, or less than 12 μm is further excellent in corrosion resistance if it is a corrosion-resistant film made of amorphous carbon containing Si or H in the above range.

  The method for forming the corrosion-resistant film (amorphous carbon film) is not particularly limited, but is preferably formed by a general CVD (Chemical Vapor Deposition) method such as a plasma CVD method. It is desirable to form the film by plasma CVD. In the direct current plasma CVD method, a plurality of base materials are arranged in a state where the base materials face each other on a base material holder arranged in a film forming furnace and connected to the negative electrode, and two adjacent base materials When the processing gas pressure and the plasma power source are operated so that the negative glows overlap each other, a dense amorphous carbon film with few defects can be obtained. Glow discharge is generated by applying electric power between the two electrodes, the positive electrode and the negative electrode. Using this glow discharge, the processing gas introduced between the electrodes is activated to deposit an amorphous carbon film on the negative potential side electrode (base material). FIG. 2 shows an example of a film forming apparatus used in the DC plasma CVD method.

  The film forming apparatus in FIG. 2 uses a cylindrical, stainless steel chamber 11 as a film forming furnace, and has an exhaust system 13 that communicates with the chamber 11 through an exhaust passage 12. The exhaust system 13 includes an oil rotary pump, a mechanical booster pump, an oil diffusion pump, and the like. The processing pressure in the chamber 11 can be adjusted by opening and closing an exhaust adjustment valve 15 disposed in the exhaust passage 12. In the chamber 11, a cathode 20 and a gas supply means 30 that are energized to the negative electrode of the plasma power source 16 are disposed.

  The cathode 20 includes a support base 21 connected to the negative electrode of the plasma power source 16 and a base material 1 on which an amorphous carbon film is formed. The support base 21 is a stainless steel disk and is fixed to the bottom of the chamber 11 coaxially with the cylindrical chamber 11. The base material 1 is arranged in parallel so as to be parallel to the thickness direction and in a laminated state by being fitted into grooves formed so as to be parallel to each other at equal intervals on the surface of the support base 21. Fixed.

  The film forming apparatus in FIG. 2 has a gas supply means 30. The gas supply means 30 supplies a mixed gas of source gas and dilution gas to the chamber 11 at an arbitrary flow rate ratio. The mixed gas is adjusted in flow rate by a mass flow controller (MFC) 33 and then supplied into the chamber 11 through a gas supply valve 34 and a gas supply pipe 35. The gas supply pipe 35 has a plurality of holes at equal intervals in the length direction. The gas supply pipe 35 is installed so as to be positioned at the center of the chamber 11, and the mixed gas is uniformly supplied to the substrate 1 held on the support base 21.

  The positive electrode of the plasma power source 16 is connected to the chamber 11 and the ground, and the wall surface of the chamber 11 is a ground electrode (anode).

In the plasma CVD method, the type of the substrate is not particularly limited as long as it is a substrate made of a conductive material having conductivity. The conductive material desirably has an electrical resistivity of 10 ⁶ Ω · cm or less. For example, if the base material is an aluminum-based material, the electrical resistivity is 2 × 10 ^{−6 to} 6 × 10 ⁻⁶ Ω · cm. Moreover, since there is no limitation in particular also in the shape of a base material, film-forming on various members is possible.

  The base material is fixed to a base material holder disposed in the film forming furnace and connected to the negative electrode. At this time, the arrangement of the substrates is not limited as long as the plurality of substrates are arranged in a state of facing each other, and the negative glow overlap is easily formed favorably between the opposed surfaces. In particular, if the substrate is plate-shaped, for example, as shown in FIG. 2, it is desirable that the plurality of substrates be arranged on the substrate holding member in parallel with the thickness direction and in a stacked state.

  The base material is fixed so that at least a part of the base material is in contact with the base material holder connected to the negative electrode. If a base material holder consists of an electroconductive material, there will be no limitation in the shape in particular. Therefore, the base material holder may have a shape having a fixture that can fix at least a part of the base material in addition to a flat plate shape on which the base material can be placed.

  The substrates arranged in a state of facing each other are sheathed by operating the processing gas pressure and the plasma power source so that the negative glows (24) of two adjacent substrates among the plurality of substrates overlap each other. The film forming process may be performed by adjusting the width of (25). The “sheath” is a “sheath” of plasma covering the cathode (base material) and refers to a region where light emission is weak from the cathode surface to the negative glow. In the negative glow overlapping portion (26), a low voltage and high current density discharge occurs. In a discharge at a low voltage and a high current density, ion bombardment is reduced, so that damage to the amorphous carbon film during film formation is reduced. Therefore, a corrosion-resistant film with few defects can be formed.

  In addition, the sheath width is not less than one quarter of the interval between the opposing surfaces of two adjacent substrates, and more than one-half, and is not more than the interval between the opposing surfaces of two adjacent substrates. For example, the sheath can perform uniform glow discharge along the outer surface of the base material, and adjacent negative glows overlap each other, so that favorable film formation is possible. Specifically, the plurality of base materials may be arranged in a range of 2 to 60 mm in the interval between the opposing surfaces of two adjacent base materials. When the distance is 2 mm or less, the overlap of the sheaths becomes strong, and the glow discharge may become locally strong or unstable depending on the film forming conditions. On the other hand, if the thickness is 60 mm or more, the overlapping portion of the negative glow may be reduced or may not be overlapped. Then, the range of the processing gas pressure is adjusted so that the sheath width is obtained. The processing gas pressure is preferably 13 to 1330 Pa.

  The film forming temperature is desirably 500 ° C. or lower. The film formation temperature is the temperature of the surface of the substrate during film formation. When the film formation temperature exceeds 500 ° C., ion bombardment increases, and damage to the amorphous carbon film during film formation increases, which is not desirable. Further, when the film forming temperature is low, a minute arc is likely to be generated, and stable glow discharge becomes difficult. Therefore, in order to form a corrosion-resistant film with few defects, it is desirable that the temperature is 250 to 400 ° C.

  Further, the processing gas is preferably composed of a hydrocarbon gas or a mixed gas of a hydrocarbon gas and a diluent gas containing at least one of hydrogen and a rare gas. When it is desired to obtain an amorphous carbon film containing silicon, it is composed of a source gas containing at least one of a hydrocarbon gas and an organic metal-containing gas containing at least silicon and a halogen compound. It is desirable to use a processing gas composed of a mixed gas of a source gas and a dilution gas containing at least one of hydrogen and a rare gas.

At this time, the hydrocarbon gas is preferably methane, ethylene, acetylene, hexane, benzene and other (C _m H _n ) hydrocarbon gases. The organic metal-containing gas is preferably tetramethylsilane (Si (CH ₃ ) ₄ : TMS) and silane. The halogen compound is preferably silicon tetrachloride. The dilution gas is preferably one having an atomic weight lighter than Ar, specifically, H, He, Ne or the like. When a diluting gas whose atomic weight is lighter than Ar is used, ion bombardment received by the film is reduced, so that damage to the film during film formation is reduced, and an amorphous carbon film with few defects can be formed. Therefore, the diluent gas is preferably only hydrogen gas or a mixed gas mainly composed of hydrogen and helium.

  The composition of amorphous carbon varies depending not only on the type of gas used, the mixing ratio, or the flow ratio, but also on other deposition conditions such as deposition temperature, spacing between opposing surfaces, and the degree of vacuum during deposition. To do. The film forming conditions may be appropriately selected so that the composition of the obtained amorphous carbon becomes a desired composition.

  The components of the fuel cell system according to the present invention are configured to discharge the exhaust gas discharged from the fuel cell 91 on the supply pipe 92d that sends the fuel gas to the fuel cell 91 that receives the supply of the fuel gas and obtains an electromotive force. It is a component of the fuel cell system arranged on the pipe 93d, and corresponds to the above-described supply means components 92X and 92Y and discharge means components 93X to 93Z of the fuel cell system of the present invention. That is, the component of the fuel cell system of the present invention may be the circulation means component 95X of the fuel circulation means 95 or each component of the oxidant gas supply means (not shown). Good.

  The piping of the fuel cell system according to the present invention is arranged such that the fuel gas at one end is sent to the fuel cell 91 which is provided at the other end and receives the supply of fuel gas to obtain an electromotive force, or is arranged at one end. A fuel cell system pipe that sends the fuel gas exiting the fuel cell 91 to the other end, and corresponds to the above-described supply pipe 92d and discharge pipe 93d of the fuel cell system of the present invention. That is, the pipe of the fuel cell system of the present invention may be the circulation pipe 95d of the fuel circulation means 95, or the pipe used for the oxidant gas supply means (not shown) is required to have corrosion resistance. Alternatively, a pipe used for the oxidant gas supply means may be used.

  As mentioned above, although embodiment of the fuel cell system of this invention, its component, and piping was described, this invention is not limited to the said embodiment. The fuel cell system of the present invention, and its constituent parts and piping can be implemented in various forms with modifications, improvements, etc. that can be made by those skilled in the art without departing from the gist of the component.

  Hereinafter, examples of the fuel cell system of the present invention, and its components and piping will be described together with comparative examples with reference to Table 1 and FIGS.

[Example 1]
The film forming apparatus of FIG. 2 was operated to form a corrosion-resistant film made of amorphous carbon on the surface of the substrate 1. In this example, four flat substrates (22 mm × 39 mm × 3 mm) made of aluminum alloy (A2017: electrical resistivity 3.4 × 10 ⁻⁶ Ω · cm) were used as the substrate 1. In addition, the two adjacent base materials 1 were arrange | positioned so that the space | interval D between opposing surfaces might be 10 mm, respectively.

Next, a film forming procedure will be described. First, the exhaust system 13 evacuated the chamber 11 to a final vacuum of 1 × 10 ⁻² Pa. Next, the gas supply valve 34 was opened, and the flow rate of hydrogen gas (dilution gas) was adjusted by the MFC 33 and supplied into the chamber 11. Thereafter, the opening degree of the exhaust adjustment valve 15 was adjusted, and the processing gas pressure in the chamber 11 was set to 400 Pa.

  A voltage was applied to the cathode 20 by the plasma power source 16 to generate glow discharge (24, 25) around the cathode 20. Next, the discharge power was adjusted to 50 W to form a negative glow overlap 26. The base material 1 was set to 300 ° C. by this glow discharge. In addition, the radiation thermometer was used for the measurement of the temperature of a base material. Thereafter, methane and TMS as source gases were supplied, and the flow rates of the respective gases were hexane: 10 sccm, TMS: 0.5 sccm, and hydrogen gas: 200 sccm. In this way, film formation was started at 300 ° C., and film formation was performed for 0.5 hour to obtain No. 1. 1 corrosion-resistant member was obtained.

[Example 2]
A film was formed for 1 hour in the same procedure as in Example 1 except that the flow rate of each gas was hexane: 20 sccm, TMS: 5 sccm, and hydrogen gas: 100 sccm. 2 corrosion-resistant members were obtained.

[Example 3]
A film was formed for 3 hours in the same procedure as in Example 1 except that the flow rate of each gas was hexane: 20 sccm, TMS: 2 sccm, and hydrogen gas: 100 sccm. 3 corrosion-resistant members were obtained.

[Example 4]
A film was formed for 6 hours in the same procedure as in Example 1 except that the flow rate of each gas was hexane: 20 sccm, TMS: 2 sccm, and hydrogen gas: 100 sccm. 4 corrosion-resistant members were obtained.

[Example 5]
A film was formed for 4 hours in the same procedure as in Example 1 except that the flow rate of each gas was hexane: 20 sccm, TMS: 10 sccm, and hydrogen gas: 100 sccm. 5 corrosion-resistant members were obtained.

[Example 6]
A film was formed for 5 hours in the same procedure as in Example 1 except that the flow rate of each gas was benzene: 20 sccm, TMS: 2 sccm, and hydrogen gas: 100 sccm. 6 corrosion-resistant members were obtained.

[Comparative Example 1]
Except that the flow rate of each gas was methane: 10 sccm and hydrogen gas: 200 sccm, a film was formed for 0.5 hours in the same procedure as in Example 1, 7 corrosion-resistant members were obtained.

[Comparative Example 2]
A film was formed for 3 hours in the same procedure as in Example 1 except that the flow rate of each gas was methane: 50 sccm, TMS: 5 sccm, and hydrogen gas: 100 sccm. 8 corrosion-resistant members were obtained.

[Comparative Example 3]
A film was formed for 6 hours in the same procedure as in Example 1 except that the flow rate of each gas was methane: 50 sccm, TMS: 5 sccm, and hydrogen gas: 60 sccm. Nine corrosion-resistant members were obtained.

[Comparative Example 4]
Except that the flow rate of each gas was benzene: 20 sccm, TMS: 2 sccm, and hydrogen gas: 100 sccm, the film was formed for 8 hours in the same procedure as in Example 1, Ten corrosion-resistant members were obtained.

[Evaluation]
[Measurement of Si content and H content]
No. For each of the corrosion resistant members 1 to 10, the contents of silicon (Si) and hydrogen (H) in the corrosion resistant coating were measured. The Si amount was measured by EPMA (electron probe microanalyser), and the H amount was measured by elastic recoil detection method (ERDA). The measurement results are shown in Table 1.

[Measurement of defect area ratio]
No. About each 1-10 corrosion-resistant member, the defect area rate of the corrosion-resistant film was measured by the electrochemical test. A schematic diagram of the apparatus used for the electrochemical test is shown in FIG. This apparatus includes a counter electrode 81 using a platinum plate, a reference electrode 82 using a saturated calomel electrode (SCE), a sample electrode 83 made of a corrosion-resistant member 3, an electrolytic bath 80 for holding a test solution L, and a constant potential. And an electrolysis device (potentiostat) 85. As the sample electrode 83, an electrode covered with an insulating tape 84 was used after a lead wire was connected to the substrate, leaving a 1 cm ² measurement surface (coating side). The electrolytic bath 80 was filled with 20 ml of a 0.5 mol / L H ₂ SO ₄ aqueous solution as the test solution L. The test solution L was stirred by a stirrer 86 during the measurement. The sample electrode 83 was inserted into the sample solution L together with the counter electrode 81 and the reference electrode 82, and the measurement of the natural corrosion potential was started at room temperature. The above-described measurement of natural corrosion potential is a measurement method based on the method described in “JIS G 0580”. The corrosion current (i _corr ) was determined by Tafel extrapolation. Using the corrosion current in the following mathematical formula, the defect area ratio of the defect A in the corrosion-resistant film per 1 cm ² was calculated.

Here, i _corr (Al) is the corrosion current of the base material only, and i _corr (DLC / Al) is the corrosion current of the corrosion-resistant member. Table 1 shows the defect area ratio of each member.

[Measurement of electrical resistivity]
No. The electrical resistivity was investigated about each corrosion-resistant member of 1-10. A leak current was detected by applying a DC voltage in the thickness direction of the corrosion-resistant coating, and the electrical resistivity of each member was calculated. FIG. 4 is a schematic diagram of the measuring apparatus. On the surface of the corrosion-resistant coating 2, an electrode E having a diameter of 6 mm was prepared using a conductive paste. A DC voltage was applied from the electrode E, and a leak current was detected by the curve tracer T. Each corrosion-resistant member was measured by removing the corrosion-resistant film by polishing one side surface because a corrosion-resistant film was formed on both surfaces of the substrate. The measurement results are shown in Table 1.

[Measurement of maximum defect size]
The maximum defect size of defect A was measured for the corrosion-resistant film of each member. For measurement of the maximum defect size, an SEM image observed from the direction perpendicular to the surface of the corrosion-resistant coating was used. The area of the defect A was calculated | required by observing several places on the surface of a film, and image-analyzing the obtained SEM image. Table 1 shows the area of the largest defect A in each sample.

  Note that FIG. 5 is an SEM photograph in which the surface of 5 is observed. As observed by SEM, the defect A is a white portion and the defect B is a gray portion. Further, the portion where the coating is peeled and the base material is exposed also becomes white. Therefore, the defect size is the area of the white portion and corresponds to the range indicated by a in FIG.

[Measurement of corrosion rate]
In the fuel cell system of the present invention, particularly, corrosion resistance against acidic product water is required. Therefore, using an acidic aqueous solution, For 1-10 and the substrate (no coating), the corrosion rate was measured by an electrochemical test.

For measuring the corrosion rate, the measurement surface of the sample electrode 83 is set to 2.25 cm ² , the potentiostat 85 is changed to a corrosion meter (HK-103 manufactured by Hokuto Denko), and the electrolytic bath 80 is immersed in a water bath at 80 ° C. An apparatus similar to the above measurement of the defect area ratio was used except that the solution L was set to 80 ° C. In addition, the measurement of the above corrosion rate is a measuring method based on the method as described in “JIS G 0580”. The measurement results are shown in FIG. FIG. 6 is a graph showing the corrosion rate with respect to the test time (0 to 100 hours) of each sample. The vertical axis of the graph indicates the corrosion rate, and the greater the value, the greater the degree of corrosion progression.

From the measurement results of the corrosion rate, the corrosion resistance member has an electrical resistivity of 10 ⁸ Ω · cm or more and the corrosion resistance film has a defect area ratio of 10 ⁻² % or less. 1-No. It was found that the corrosion resistant member 6 was excellent in corrosion resistance from the measurement result of the corrosion rate (FIG. 6). In addition, No. whose maximum defect size was 100 μm ² or less. 3 and no. The corrosion-resistant member No. 5 has a large maximum defect size. Compared with the corrosion-resistant member of 6, the progress of corrosion was suppressed. In particular, No. 1 in which the corrosion-resistant film is relatively thin and the composition of amorphous carbon is within the preferred range. 3 and no. No. 4 maintained high corrosion resistance for a long time.

  Further, as the film thickness increases, the internal stress and strain of the film increase, and the film is easily damaged and peeled off. However, if the film thickness is 100 μm or less, the amount of Si and H contained in amorphous carbon By setting the value to an appropriate value, a member excellent in corrosion resistance could be obtained. Specifically, no. 4 and no. No. 8 has a film thickness of 12 μm, but No. 8 having a corrosion-resistant film made of amorphous carbon containing 7 at% Si and 43 at% H. The corrosion resistant member 4 exhibited excellent corrosion resistance.

It is sectional drawing of a corrosion-resistant member, Comprising: It is a schematic diagram which shows the defect (defect A) which has penetrated in the thickness direction of the corrosion-resistant film, and the defect (defect B) which has not penetrated the corrosion-resistant film. It is a schematic explanatory drawing which shows an example of the film-forming apparatus of a corrosion resistant film. It is the schematic of the apparatus used for an electrochemical test. It is the schematic of the apparatus which measures an electrical resistivity. No. 5 is an SEM photograph of the corrosion resistant coating surface of No. 5 corrosion resistant member observed from a direction perpendicular to the coating. No. It is a graph which shows the result of the electrochemical test of each corrosion-resistant member of 1-10, Comprising: The corrosion rate with respect to test time is shown. It is a graph which shows the corrosion-resistant film defect area rate with respect to Si amount of amorphous carbon. It is a graph which shows the corrosion-resistant film defect area rate with respect to H amount of amorphous carbon. It is the figure which showed typically the structure of the principal part of the fuel cell system of this invention.

Explanation of symbols

1: Substrate 2: Corrosion resistant coating 3: Corrosion resistant member 90: Fuel cell system 91: Fuel cell 92: Fuel supply means 92d: Supply pipe 92X: Pressure regulating valve 92Y: Open / close valve 93: Fuel discharge means 93d: Discharge pipe 93X: Open / close Valve 93Y: Gas-liquid separator 93Y ': Drain valve 93Z: Exhaust valve 95: Fuel circulation means 95d: Circulation piping 95X: Hydrogen pump 95Y: Check valve

Claims (15)

A fuel supply means comprising at least a fuel cell that receives an supply of fuel gas to obtain an electromotive force, a supply pipe for sending the fuel gas to the fuel cell, and one or more supply means components disposed on the supply pipe A fuel discharge system comprising: a discharge pipe for discharging exhaust gas from the fuel cell; and one or more discharge means components disposed on the discharge pipe.
At least a part of the supply pipe, the supply means component, the discharge pipe, and the discharge means component is a base material and an area occupied by a plurality of defects that are fixed to the surface of the base material and penetrate in the thickness direction. A fuel cell system comprising: a corrosion-resistant film made of amorphous carbon having a rate of 10 ⁻² % or less; and a corrosion-resistant member having an electrical resistivity of 10 ⁸ Ω · cm or more. ^2. The fuel cell system according to claim 1, wherein the corrosion-resistant film has an area of each of the defects of 100 μm ² or less.   The fuel cell system according to claim 1 or 2, wherein the corrosion-resistant film has a thickness of 0.5 to 100 µm.   The fuel cell system according to claim 1, wherein the amorphous carbon is silicon-containing amorphous carbon containing carbon as a main component and containing silicon.   5. The fuel cell system according to claim 4, wherein the silicon-containing amorphous carbon contains silicon at 0.1 at% to 10 at% and hydrogen at 35 at% to 50 at%.   The fuel cell system according to claim 1, wherein the base material is made of a conductive material having conductivity at least on a surface layer portion.   The fuel cell system according to claim 1, wherein the base material is made of a metal material.   The fuel cell system according to claim 7, wherein the metal material is a light metal.   The fuel cell system according to claim 8, wherein the light metal is an aluminum-based material containing aluminum as a main component.   3. The fuel cell system according to claim 1, wherein at least one of the supply unit component and the discharge unit component is a valve body that opens and closes the supply pipe or the discharge pipe.   3. The fuel cell system according to claim 1, wherein at least one of the discharge means components is a gas-liquid separation unit that separates moisture from the fuel gas exiting the fuel cell.   The fuel cell system according to claim 1 or 2, wherein at least one of the supply means component and the discharge means component is a hydrogen pump for circulating the fuel gas.   The fuel cell system according to claim 1 or 2, wherein at least one of the supply means component and the discharge means component is a temperature sensor. A component of a fuel cell system arranged on a supply pipe that sends fuel gas to a fuel cell that receives the supply of the fuel gas and obtains an electromotive force, or on a discharge pipe that discharges exhaust gas that exits the fuel cell. There,
An electrical resistivity comprising: a base material; and a corrosion-resistant film made of amorphous carbon that is fixed to the surface of the base material and has an area ratio occupied by a plurality of defects penetrating in the thickness direction of 10 ⁻² % or less. A component of a fuel cell system, characterized in that it is made of a corrosion-resistant member having 10 ⁸ Ω · cm or more. The fuel gas at one end is sent to a fuel cell that is arranged at the other end and receives the supply of the fuel gas to obtain an electromotive force, or the fuel gas that exits from the fuel cell arranged at one end is sent to the other end To the fuel cell system piping,
A pipe base material, and a corrosion-resistant film made of amorphous carbon, which is fixed to the inner surface of the pipe base material and has a plurality of defects penetrating in the thickness direction and having an area ratio of 10 ⁻² % or less. A fuel cell system pipe having a resistivity of 10 ⁸ Ω · cm or more.

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