JP2007005120A - Metallic separator for fuel cell, manufacturing method of metallic separator for fuel cell, and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metallic separator for a fuel cell having sufficient corrosion resistance, facilitating manufacturing, and lowering contact resistance on a surface. <P>SOLUTION: Each of the separators 10a, 10b for the fuel cell has a plate-shaped body part comprising a nickel base amorphous metal material having a crystallization temperature of 500°C or higher and a glass transition temperature on the lower temperature side than the crystallization temperature, and an Au-alloying layer formed by diffusing and alloying an Au component in the nickel base amorphous metal material forming the body so as to have an Au content of 10-60 atomic% and covering the surface of the body, and a recess forming a gas diffusion layer between an electrode layer and a plate surface when the plate surface on one side is put on the electrode layer covering a polymer electrolyte membrane of the fuel cell is formed on the plate surface. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

TECHNICAL FIELD OF THE INVENTION

  The present invention relates to a metal member for a fuel cell, a manufacturing method thereof, and a fuel cell.

JP 2001-68129 A JP 2000-021418 A JP-A-10-228914 JP 2002-373673 A JP 2004-273314 A JP-A-10-228914 JP 2000-21418 A JP 2001-68129 A

  Conventionally, various fuel cells such as a polymer electrolyte fuel cell, a phosphoric acid fuel cell, and a molten carbonate fuel cell have been proposed. Among these, the polymer electrolyte fuel cell uses a polymer solid electrolyte membrane and can be operated at a low temperature, and can be easily reduced in size and weight. Yes. Specifically, a unit cell is formed by sandwiching a solid polymer electrolyte membrane for transporting protons between a pair of electrode layers, and a fuel gas (hydrogen gas) or an oxidant gas (air) is formed on the surface of the electrode layer. A separator for forming a diffusion layer is laminated. On the plate surface of the separator, a recess for forming a gas diffusion layer is formed between the electrode layer and the electrode layer. Further, since the separator also serves as a conductive path for taking out the output from the electrode layer of the unit cell, the separator needs to be entirely made of a conductive material. Specifically, various fuel cell structures in which a separator is formed of metal have been proposed in order to achieve both workability, conductivity, and strength (for example, Patent Documents 1 to 4).

  In a fuel cell using a polymer solid electrolyte membrane, a polymer material having a functional group exhibiting strong acidity such as a sulfonic acid group is used as a polymer solid electrolyte exhibiting proton conductivity, and the polymer material is impregnated. There is a problem that an acidic component oozes out together with the moisture, and the separator is subjected to an acid attack. The metal separators exemplified in the above-mentioned patent documents, for example, disclosed in Patent Documents 1 to 3 use stainless steel such as SUS316, and are not sufficiently resistant to corrosion in a strongly acidic environment, particularly in a sulfuric acid acidic environment. There is a problem that the internal resistance tends to increase with time as the corrosion of the separator progresses. In the above Patent Documents 1 to 3, the stainless steel plate material is further plated with a precious metal such as Au to make up for corrosion resistance. However, the effect is not always sufficient, and of course, only the plating process is necessary. There is a difficulty that the manufacturing cost is likely to rise. On the other hand, although the metal separator disclosed in Patent Document 4 is composed of a Mo plate, it is difficult to process, and the corrosion resistance is insufficient with a single Mo plate, so it is essential to form a Mo nitride film on the surface. It is difficult to avoid complication of the structure and soaring manufacturing costs.

  Therefore, the present inventors made a metal separator for a fuel cell using a Ni-based amorphous metal material having a crystallization temperature of 500 ° C. or higher and a glass transition temperature Tg on the lower temperature side than the crystallization temperature Tx. It was proposed to configure (Patent Document 5). Amorphous materials are generally considered to be unsuitable for plastic working because of their high deformation resistance at room temperature and poor ductility. However, if the Ni-based amorphous metal material is used, the deformation resistance of the material is greatly reduced in the temperature region (supercooled liquid region) between the glass transition temperature Tg and the crystallization temperature Tx, and the plastic fluidity is good. It becomes. As a result, even a metal separator for a fuel cell that is a thin plate and has a complicated uneven shape can be manufactured very efficiently by plastic working.

  Ni-based amorphous alloys exhibit very good corrosion resistance due to the passive film formed on the surface. In addition, since there are no crystal grain boundaries in the amorphous alloy, there are few surface defects, and the passive film is denser and more stable, which is another reason for the high corrosion resistance. However, as the passive film becomes denser and stronger, the insulation of the film becomes more remarkable, and the electrical conductivity becomes significantly worse. Therefore, when applied to the metal separator of a fuel cell as described above, there is a problem that the contact resistance between the electrode layer and the metal separator becomes high, and the internal resistance of the battery tends to increase.

In this case, as in Patent Documents 6 to 8, it is conceivable that Au having excellent corrosion resistance and electrical conductivity is formed by plating or the like to reduce the surface resistance. However, Au is expensive, and the upper limit of the formation layer thickness that can be established economically is about 20 to 30 nm. In this case, the following two points are serious problems.
(1) When a metal material on which a passive film is densely formed is used as a base, in the case of chemical plating, it becomes difficult to form an Au layer itself, and on the other hand, it is formed using a physical vapor deposition method such as sputtering. The Au layer has a problem of poor adhesion to the passive film and very easy to peel off.
(2) When heat treatment is performed in order to improve the adhesion between the underlayer and the Au layer, the thickness of the Au layer is very small, so that a normal material instantly diffuses into the underlayer, and the surface layer portion A sufficient Au layer does not remain, and the surface resistance improvement effect is impaired.

  An object of the present invention is to provide a metal separator for a fuel cell that has sufficient corrosion resistance, can be easily manufactured, and can keep the surface contact resistance low, a method for manufacturing the same, and a fuel cell using the same. It is in.

Means for Solving the Problems and Effects of the Invention

In order to solve the above problems, the fuel cell metal separator of the present invention is
A crystallization temperature of 500 ° C. or higher, a plate-like main body made of a Ni-based amorphous metal material having a glass transition temperature lower than the crystallization temperature, a surface of the main body, and an Au A polymer solid electrolyte for a fuel cell, comprising an Au alloyed layer obtained by diffusion-alloying an Au component in a Ni-based amorphous metal material forming a main body so that the content is 10 atomic% to 60 atomic% When a plate surface on one side is laminated on the electrode layer covering the film, a concave portion for forming a gas diffusion layer is formed between the electrode layer and the electrode layer.

The fuel cell of the present invention is
The polymer solid electrolyte membrane, the first electrode layer covering the first main surface, the second electrode layer covering the second main surface, and the metal separator for a fuel cell of the present invention, the first electrode layer A first separator that forms a gas diffusion layer for fuel gas by a recess and a metal separator for a fuel cell according to the present invention, and is stacked on the second electrode layer and And a second separator that forms a gas diffusion layer for the oxidant gas.

Furthermore, the manufacturing method of the metal separator for fuel cells of the present invention includes:
A metal material formed in a plate shape by a Ni-based amorphous metal material having a crystallization temperature of 500 ° C. or higher and having a glass transition temperature lower than the crystallization temperature is not lower than the glass transition temperature and is crystallized. Gas diffusion between the electrode layers when the plate surface on one side is laminated on the electrode layer covering the polymer solid electrolyte membrane of the fuel cell by performing plastic working in the supercooled liquid temperature range lower than the conversion temperature A temperature increasing process for forming a concave portion for forming a layer on the plate surface of the metal material;
An Au layer forming step of forming an Au layer on the surface of the metal material;
By increasing the temperature of a metal material made of an Ni-based amorphous metal material with an Au layer up to the crystallization temperature, the Ni-based amorphous metal material that forms the surface layer of the Au material is used as a diffusion alloy. A diffusion alloying step of forming an Au alloying layer in which an Au component is diffusion-alloyed in a Ni-based amorphous metal material so that the Au content is 10 atomic% or more and 60 atomic% or less. It is characterized by including.

  In the present invention, “Ni-based amorphous metal material” means that the metal element having the highest weight content is Ni, and the proportion of the amorphous phase in the material structure is 50% by volume or more. A certain material. Furthermore, the glass transition temperature is based on the first endothermic peak appearing in the heating curve obtained by differential scanning calorimetry (DSC, heating rate: 40 ° C./min) specified in JIS: H7101, and the crystallization temperature is Similarly, the first exothermic peak is determined as the intersection of the DSC curve base line extension obtained by measurement and the peak maximum slope line extension, respectively.

  According to the present invention, a metal separator for a fuel cell is made of a Ni-based amorphous metal material having a metal crystallization temperature of 500 ° C. or higher and a glass transition temperature Tg on the lower temperature side than the crystallization temperature Tx. It forms in plate shape with the Ni group amorphous metal material in which the matrix was formed. Ni-based amorphous metal materials are generally considered to be unsuitable for plastic working because of their high deformation resistance at room temperature and poor ductility. However, the Ni-based amorphous metal material employed in the present invention has a relatively high crystallization temperature of the matrix of 500 ° C. or higher, and the glass transition temperature Tg exists in a lower temperature range than the crystallization temperature. In a temperature range between Tg and the crystallization temperature Tx (hereinafter referred to as a supercooled liquid region), the deformation resistance of the material is greatly reduced, and the plastic fluidity is improved. As a result, even a metal separator for a fuel cell that is a thin plate and has a complicated uneven shape can be manufactured very efficiently by plastic working such as die pressing.

  The reason why the deformation resistance of the Ni-based amorphous metal material is reduced in the supercooled liquid region is that, in the supercooled liquid region, the bonding between metal atoms is loosened as a precursor phenomenon for the material to move to the crystalline phase, It is considered that the viscosity of the crystalline phase decreases. And in this invention, since such an amorphous metal material is comprised as Ni base material, compared with the conventional stainless steel (for example, JIS: SUS316) and Mo type | system | group metal material, corrosion resistance is also very favorable, especially sulfuric acid. Since corrosion does not proceed easily even under acidic conditions, the durability of the separator is improved, and the increase in battery internal resistance over time can be effectively suppressed.

  On the other hand, the above amorphous metal material has a strong passive film formed on the surface, and even if an Au layer is formed, the adhesion is not good as it is. However, as a result of investigation by the present inventor, by raising the temperature up to the upper limit of the crystallization temperature of the Ni-based amorphous metal material, the Au component of the Au layer is transferred to the bulk of the Ni-based amorphous metal material that forms the surface layer portion of the metal material. The diffusion reaction proceeds more slowly than other metal materials. As a result, an Au alloyed layer in which the Au component is diffusion-alloyed so that the Au content is 10 atomic% or more and 60 atomic% or less can be easily formed on the surface of the main body portion made of a Ni-based amorphous metal material. Can do. The reason for this is thought to be that the passive film formed strongly on the surface of the Ni-based amorphous metal material gives an appropriate rate-determining rate to Au diffusion from the Au layer formed thereon.

  And since the above Au alloying layer is formed in the surface of a main-body part, the surface resistance of a metal separator can be reduced and corrosion resistance can be ensured still more favorably. When the Au content in the Au alloying layer is less than 10 atomic%, the effect of reducing the surface resistance of the metal separator and the effect of improving the corrosion resistance are not significant. On the other hand, when the Au content of the Au alloyed layer exceeds 60 atomic%, the adhesion between the Au alloyed layer and the main body portion made of the Ni-based amorphous metal material forming the base becomes insufficient.

  The Au layer formed in the Au layer forming step may be entirely composed of only Au. However, as long as the surface resistance reduction effect and the corrosion resistance improvement effect are not significantly impaired, the 10 atoms If it is up to about%, it may be substituted with an appropriate dilution component (for example, Ni, Ag, Cu, etc.). In addition, the formation thickness of the Au layer in the Au layer formation step is suitably 5 nm or more and 20 nm or less. If the formation thickness of the Au layer is less than 5 nm, the Au alloying layer cannot be formed to a sufficient thickness, and the surface resistance reduction effect and the corrosion resistance improvement effect are insufficient. If the formation thickness exceeds 20 nm, the manufacturing cost of the metal separator increases. Invite. In addition, if the surface of the main body part made of Ni-based amorphous metal material is 50% or more in terms of area ratio, it can be configured to be partially covered with an Au alloying layer, reducing surface resistance and corrosion resistance. Certain effects can be obtained with respect to improvement.

  Next, in the production method of the present invention, in the supercooled liquid temperature range that is higher than the glass transition temperature and lower than the crystallization temperature, the metal material formed into a plate shape by the Ni-based amorphous metal material, A kind of warm plastic working is performed. Examples of the processing form include a method of performing die press processing on a plate-shaped solid material. As another method, the molten metal is poured into a forging die, and the molten metal is rapidly solidified by contact with the die to become amorphous, while the amorphous phase after solidification is in the supercooled liquid temperature range. In addition, it is possible to apply a molten metal forging process in which a forging process is performed on the spot to obtain a desired separator shape. In any case, since the removal process such as cutting is not involved, the material yield is high, and the material having increased fluidity in the cooling liquid temperature range can be made to follow the mold surface shape well. As a result, processing defects due to stress concentration are less likely to occur when forming deep irregularities, and by smoothing the mold surface, the material has been rough at the stage of the plate material. However, there is also an advantage that a smooth processed surface can be easily obtained without troublesome post-treatment such as polishing. In this case, the smooth surface is a surface having an arithmetic average roughness Ra of 1 μm or less measured by a method defined in JIS: B0601, for example.

  In particular, if a configuration of a separator in which the concave portion is formed based on bending in the thickness direction of the plate material made of the Ni-based amorphous metal material is used, the above-described mold is applied to the material plate material obtained as a quenching ribbon or the like. It can be easily manufactured by performing press working or melt forging.

  Next, as the Ni-based amorphous metal material (nickel-based matrix phase) employed in the present invention, it is desirable to use a material having a difference between the crystallization temperature and the glass transition temperature of 30 ° C. or more. Moreover, when manufacturing a separator by plastic working using this, it is desirable to carry out the plastic working at a temperature that is at least 20 ° C. lower than the crystallization temperature in the supercooled liquid temperature region.

  The amorphous phase is a liquid structure at high temperature that can be maintained at room temperature by rapid cooling, but the structure is metastable to the end, especially in the supercooled liquid temperature range. Is maintained at a certain temperature in the supercooled liquid temperature range, it undergoes a transition to a stable crystalline phase after a certain incubation period. This incubation period becomes shorter as the temperature approaches the crystallization temperature. Therefore, when performing warm processing in the supercooled liquid temperature range, if the processing temperature is too close to the crystallization temperature, the material will crystallize before the necessary processing is completed, increasing the deformation resistance or reducing the ductility. Or cause defects such as processing cracks and cracks.

  As a result of intensive studies on the Ni-based amorphous metal material, the present inventors have found that if the processing temperature is set at least 20 ° C. or higher (preferably 30 ° C. or higher) lower than the crystallization temperature in the supercooled liquid temperature range, The latent period leading to the conversion becomes sufficiently long, and a low-viscosity amorphous phase suitable for processing can be secured with sufficient margin until the processing is completed. In addition, the material having an excessively narrow temperature range of the supercooled liquid eventually leads to an amorphous phase that cannot be stably obtained unless the cooling rate at the time of rapid cooling is set to be considerably large. In order to set the cooling rate to extremely high, the resulting material must also be in the form of a ribbon or flake (for example, less than 50 μm in thickness), and a bulk metal plate suitable for a fuel cell metal separator can be obtained in the first place. Can not be. From the above viewpoint, it is desirable to secure a difference of 30 ° C. or more between the crystallization temperature and the glass transition temperature in consideration of an error in temperature control of material heating. This temperature difference varies depending on the Ni-based amorphous metal material, but the upper limit is about 80 ° C.

Next, in the temperature raising process for forming the Au alloying layer, the Au layer forming process is performed after the temperature raising process, and then the diffusion alloying process is performed separately from the temperature raising process. You can also. However, it is more advantageous in the following points if the temperature raising process is performed also as the diffusion alloying process after the Au layer forming process.
(1) Since the diffusion alloying process is also used as the temperature raising process, it contributes to simplification of the manufacturing process of the metal separator.
(2) Since the temperature is raised while applying the processing pressure, the adhesion of the Au alloying layer to be formed is further enhanced.
(3) During processing, since the material is held in a relatively high supercooled liquid temperature range of 550 ° C. or higher and 600 ° C. or lower, diffusion alloying of the Au component proceeds at an appropriate rate, and Au in the Au alloying layer It is also easy to adjust the content to be 10 atomic% or more and 60 atomic% or less.

Specifically, the Ni-based amorphous metal material constituting the fuel cell metal separator is:
Ni content is 40 atomic% or more and 60 atomic% or less,
Nb content is 15 atomic% or more and 25 atomic% or less,
The total content of Ti and Zr is 10 atomic% or more and 30 atomic% or less,
The total content of the optional metal component M composed of one or more selected from Co, Cu, Al, Fe, Si and Cr is 0 atomic% to 20 atomic%,
And what is made into the sum total content rate of Nb, Ti, Zr, and M being 40 atomic% or more and 60 atomic% or less is employable. The alloy has excellent corrosion resistance in a strong acid atmosphere, particularly in a sulfuric acid atmosphere, and is extremely suitable as a separator material for a fuel cell.

  In the above materials, Nb, Ti, and Zr form the basis of subcomponents with respect to Ni. By containing these elements, a supercooled liquid region can be set sufficiently large, and a stable Ni-based amorphous metal material can be used for a separator. It can be obtained in a bulk suitable for forming a plate material. Among these, Nb is an element that greatly affects the corrosion resistance. If the Nb content is less than 15 atomic%, the corrosion resistance may not be sufficiently secured. On the other hand, when the Nb content exceeds 25 atomic%, the above-described supercooled liquid region becomes too narrow (for example, the width cannot be secured at 30 ° C. or more), and the stability of the amorphous phase may deteriorate. The Nb content is more preferably 15 atomic% or more and 20 atomic% or less.

  Further, Ti and Zr are indispensable for enlarging the supercooled liquid region, and thus stable formation of the amorphous phase, and either one of them must be contained (both may be contained). . When the total content of Ti and Zr is less than 10 atomic% or exceeds 30 atomic%, the supercooled liquid region becomes too narrow, and the stability of the amorphous phase may deteriorate. The total content of Ti and Zr is more preferably 13 atomic percent or more and 25 atomic percent or less.

  Further, the optional metal component M composed of one or more selected from Co, Cu, Al, Fe, Si and Cr has an effect of further improving the amorphous forming ability of the Ni—Nb alloy (however, Not an essential ingredient). However, if the total content of these optional metal components M exceeds 20 atomic%, the amorphous forming ability may be lowered, and the width of the supercooled liquid region may be insufficient.

  The total content of Nb, Ti, Zr, and M is preferably 40 atomic percent or more and 60 atomic percent or less. When the total content exceeds 60 atomic%, a supercooled liquid temperature range of 30 ° C. or higher cannot be obtained, and it may be difficult to form a complex shaped separator for a fuel cell by warm plastic working. . On the other hand, if the total content is less than 40 atomic%, amorphous formation may be difficult.

  When the Ni-based amorphous metal material having the above composition is adopted, since the passive film is very strong, it is difficult to form the Au layer by chemical plating in the Au layer forming step. It is desirable to form by vapor phase film-forming methods such as discharge sputtering or high-frequency sputtering) or vacuum deposition.

  In addition, when the Ni-based amorphous metal material having the above composition is adopted, the following Au alloying layer can be obtained by performing the temperature rising process step in combination with the diffusion alloying step after the Au layer forming step. Can be obtained. That is, when the Au concentration distribution is analyzed in the depth direction from the outermost surface, the first Au enriched region in which the Au content is higher than the average Au content of the Au alloyed layer from the outermost surface side. An intermediate concentration region where the Au content is lower than that of the first Au concentrated layer, an Au content rate higher than the intermediate concentration region, and an Au content rate higher than the average Au content. The second Au enriched region is formed in this order. By forming an Au alloyed layer having such a structure, the adhesion of the Au alloyed layer can be increased, and the Au content can be easily optimized so as to be 10 atomic% or more and 60 atomic% or less. The passive film of the Ni-based amorphous metal material having the above composition has a kind of reverse segregation effect on Au diffusion, and a second Au concentration region in which the Au concentration is reversed and increased is formed on the deeper layer side. Therefore, it is speculated that the rate-limiting effect on Au diffusion from the first Au concentrated layer side may be enhanced. As a result, for example, as in conventional stainless steel, it is possible to effectively eliminate the problem that the Au layer rapidly bulk diffuses and disappears.

The Ni-based amorphous metal material used in the present invention can obtain a plate-like (thin strip-like) material from a molten state by a known single roll method or twin roll method. In this case, it is desirable to set the cooling rate in a range of, for example, about 10 ⁴ ° C / second to 10 ⁶ ° C / second. Adjustment is possible by the method. In addition, the above-mentioned molten metal forging method can also be used instead of obtaining the quenching ribbon.

  In the fuel cell of the present invention, it is desirable that the polymer solid electrolyte membrane is made of a polymer material having a sulfonic acid group in order to increase proton conductivity. In particular, from the viewpoint of improving the chemical resistance of the polymer solid electrolyte membrane itself, it is more desirable to employ a fluororesin having a sulfonic acid group. In this case, the sulfuric acid component derived from the sulfonic acid group is likely to elute together with moisture, but the Ni-based amorphous metal material having the above-mentioned composition has very good corrosion resistance in a sulfuric acid atmosphere and is applicable to a metal separator. In this case, an increase in internal resistance with time due to corrosion is sufficiently suppressed, and a good power generation capability can be maintained over a long period of time. As a polymer material having a sulfonic acid group, NAFION (trade name) can be exemplified as a representative if it is a commercial product, and JP-A No. 2002-313355, JP-A No. 10-40737 or JP-A No. The thing disclosed by 9-102322 can also be used.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 schematically illustrates an example of a fuel cell according to the present invention in a stacked form. The fuel cell 1 is a polymer electrolyte fuel cell employing a polymer solid electrolyte membrane 3. Specifically, the polymer solid electrolyte membrane 3 is formed of a fluororesin containing a sulfonic acid group, and has a pair of electrode layers 2 and 4 sandwiching the polymer resin electrolyte membrane 3. 4 has a unit battery body 5. Specifically, the first electrode layer 2 that covers the first main surface 3a of the polymer solid electrolyte membrane 3, the second electrode layer 4 that also covers the second main surface 3b, and the metal separator for a fuel cell of the present invention. And a first separator 10a that is stacked on the first electrode layer 2 and forms a gas diffusion layer for fuel gas by the recess 21; and a metal separator for a fuel cell of the present invention, and the second electrode layer 4, and a second separator 10 b that forms a gas diffusion layer for the oxidant gas by the recess 21. A gasket is disposed between the unit cell main body 5 and the separator 10 in order to prevent leakage of fuel gas and oxidant gas, but is omitted in FIG.

  FIG. 2 schematically shows the separators 10a and 10b. As shown to Fig.2 (a), the separators 10a and 10b are formed in plate shape, the unevenness | corrugation is formed in the main surface, and it has the form which the front end side of the convex part 14 contacts an electrode. On the other hand, the recess 21 forms a gas diffusion layer that also serves as a gas flow path between the electrode layers 2 and 4 (FIG. 1). In the present embodiment, the recess 21 is formed in two in the form of a meandering groove sandwiched between the protrusions 14, and both ends thereof serve as a gas inlet 22 and a gas outlet 23.

  Returning to FIG. 1, a unit cell body 5 and a separator 10 are used as a unit cell U, and a plurality of unit cells U are stacked via a cooling water circulation substrate 11 made of a conductor such as carbon. Is done. About 50 to 400 unit cells U are stacked, for example, and conductive sheets 9, current collecting plates 8, insulating sheets 7 and clamping plates 6 are arranged on both ends of the stacked body from the side in contact with the unit cells U, respectively. Thus, the fuel cell stack 1 is obtained. The current collector plate 8 and the plurality of separators 10 are connected in series, and currents from the plurality of unit battery bodies 5 are collected.

  The separators 10a and 10b are formed in a plate shape by a Ni-based amorphous metal material having a crystallization temperature of 500 ° C. or higher (upper limit is about 650 ° C.) and having a glass transition temperature lower than the crystallization temperature. A main body portion. As shown in FIG. 6, the surface of the main body 10M is formed by diffusion-alloying an Au component in the Ni-based amorphous metal material formed by the main body 10M so that the Au content is 10 atomic% or more and 60 atomic% or less. An Au alloying layer 10G is formed. The thickness of the Au alloying layer 10G is 10 nm or more and 80 nm or less.

  The recess 21 forming the gas diffusion layer between the electrode layers 2 and 4 is formed based on the bending in the plate thickness direction of the plate material made of the Ni-based amorphous metal material. The plate thickness of the plate material is 0.02 mm or more and 0.2 mm or less.

  In the present embodiment, the Ni-based amorphous metal material constituting the main body 10M of the separators 10a and 10b has a Ni content of 40 atomic% to 60 atomic%, an Nb content of 15 atomic% to 25 atomic%, Ti And the total content of Zr is 10 atomic% or more and 30 atomic% or less, and the total content of the optional metal component M consisting of one or more selected from Co, Cu, Al, Fe, Si and Cr is 0 atomic% The total content of Nb, Ti, Zr and M is 40 atomic% or more and 60 atomic% or less.

  As shown in FIG. 6, when the Au alloying layer 10G is analyzed for the Au concentration distribution in the depth direction from the outermost surface (the analysis method is Auger electron spectroscopy or X-ray photoelectron combined with depth direction etching). A first Au-enriched region 10d in which the Au content is higher than the average Au content of the Au alloyed layer from the outermost surface side, and the first Au-enriched layer An intermediate concentration region 10e having a lower Au content than 10d, a higher Au content than the intermediate concentration region 10e, and a higher Au content than the average Au content of the Au alloying layer 10G. The second Au enriched region 10f is formed in this order.

Hereinafter, the manufacturing method of separator 10a (10b) is demonstrated.
As shown in FIG. 3, alloy raw materials are blended so as to have the desired composition, and the raw material is melted in a melting furnace 40 such as a high-frequency induction melting furnace using a crucible 41 to obtain a molten metal 42. Next, as shown on the lower left side of FIG. 3, the molten metal 42 is directly jetted onto the rotating quenching roll 44 through the molten metal supply nozzle 43, and rapidly solidified to form a ribbon made of a Ni-based amorphous metal material. 45 (single roll method: the roll is made of Cu, for example). On the other hand, as shown on the lower right side of FIG. 3, a twin roll method may be employed in which the molten metal 42 is ejected into the gap between the two quenching rolls 44, 44 to obtain the ribbon 45.

  As shown in FIG. 6, an Au layer 10G ′ is formed on the surface of the thin ribbon 45 thus obtained by sputtering so as to have a thickness of 5 nm to 20 nm. Then, as shown in FIG. 4, the ribbon 45 formed with the Au layer 10G ′ is heated by the preheating furnace 50 to a supercooled liquid temperature range that is higher than the glass transition temperature Tg of the material and 30 ° C. lower than the crystallization temperature Tx. Then, after being cut by the cutter 53, it is transferred to a press apparatus having press dies 51, 51 to perform warm press working as plastic working. Pressing is performed as follows. First, as shown in step 1 of FIG. 5, the cut ribbon 45 is disposed between the press dies 51, 51 having the uneven pattern 51a to be transferred. Then, as shown in step 2, the molds 51 and 51 are moved relatively close to each other, and the ribbon 45 is pressed between the molds 51 and 51. The material has a low viscosity by being heated to the supercooled liquid temperature range, and the pressurization easily causes plastic flow along the concave / convex pattern 51a of the mold, thereby transferring the concave / convex pattern.

  At this time, as shown in FIG. 6, the Au layer 10G 'formed on the surface of the ribbon is diffusion-alloyed with the underlying Ni-based amorphous material to form an Au alloyed layer 10G. The surface of the ribbon is partially covered with the Au layer 10G ′, and then heated to the supercooled liquid temperature range as described above to perform plastic working, thereby forming an Au alloy as shown in FIG. It is also possible to obtain a structure in which the surface of the main body 10M is partially covered by the layer 10G.

  Returning to FIG. 5, after that, as shown in Step 3, the separators 10 a (10 b) can be obtained by separating the press dies 51, 51. Note that the surface of the rapidly cooled ribbon 45 may be roughened to an arithmetic average roughness Ra exceeding 1 μm, as shown in enlarged view in step 1. However, if the pressing surface of the mold 51 is smoothed to 1 μm or less with Ra, the surface of the ribbon 45 in which the plastic flow becomes extremely good by heating to the supercooled liquid temperature region also follows the mold surface. The surface of the separator 10a (10b) can be smoothed to 1 μm or less with an arithmetic average roughness Ra, as shown in FIG.

  The separator 10a (10b) obtained as described above can reduce the surface resistance of the metal separator because the Au alloying layer 10G as described above is formed on the surface of the main body 10M. In addition, the corrosion resistance can be further ensured. The Ni-based morphous metal material forming the main body 10M has a strong passive film formed on the surface, and even if an Au layer is formed, the adhesion is not good as it is. However, the adhesive force can be greatly improved by alloying the Au layer with the Ni-based amorphous metal material during processing after raising the temperature to the supercooled liquid temperature range. The Ni-based amorphous metal material having the above composition has a sufficient concentration of Au (at least 10 atomic% or more) because Au from the Au layer gently diffuses even though the temperature is raised to the supercooled liquid temperature range. The Au alloyed layer 10G can be left on the surface of the main body 10M in a state secured to 60 atomic% or less.

In order to confirm the effect of the present invention, the following experiment was conducted. First, raw materials are weighed and blended so that each composition shown in Table 1 (Ti in Comparative Example 8 and stainless steel in Comparative Example 8 (SUS316L) uses a commercially available plate material) is obtained in a button arc melting furnace. An ingot (about 10 mm × 40 mm, 50 g) was prepared by melting in an Ar atmosphere. A ribbon was produced from the ingot thus obtained by a single roll quenching apparatus. In the actual process, an ingot 50 g is put into a φ30 mm quartz nozzle with a slit of 0.3 × 20 mm at the tip, heated and melted by high frequency induction heating, and then rotated at a peripheral speed of 15 m / s from the slit portion. It was ejected onto a copper roll having a diameter of 400 mm and a width of 50 mm to produce a ribbon having a thickness of about 50 μm and a width of 20 mm. In addition, the molten metal temperature at the time of melt | dissolution is about 1450 degreeC. Thereafter, an Au layer is formed on the surface of the ribbon with various thicknesses by high-frequency sputtering, heated to 560 ° C. under vacuum, and applied with a pressure of 200 kg / cm ² to achieve plasticity in the supercooled liquid temperature range. Processed.

  Corrosion resistance, hardness, toughness, and surface resistance were investigated for the strips after plastic working. Corrosion resistance was evaluated based on the corrosion rate obtained by placing a material cut to a length of 100 mm in 400 ml of 1 mass% sulfuric acid aqueous solution, holding it in a boiling state for one week, and measuring the weight loss. The hardness of the material (which also serves as a measure for strength) was evaluated by the Vickers hardness measured at a 50 g load with a microhardness meter on the cross section of the ribbon. The evaluation of the toughness of the material was made by judging whether or not fracture occurred in the ribbon by a 180 ° bending test.

  Next, as for surface resistance, a thin ribbon is cut into a predetermined size (20 mm square shape), a carbon cloth is placed on the top and bottom, a gold foil is placed thereon, and a direct current is applied while applying a pressure of 1 MPa from the top. A current was applied, and the contact resistance value obtained from the voltage and current value was evaluated. FIG. 8 shows a schematic diagram of the measuring apparatus. In this method, the total resistance penetrating the material can be obtained, but since the contact resistance of the surface is much larger than the resistance of the material, the resistance of the material is ignored and the contact resistance value of the surface is taken. The results are shown in Table 1.

  FIG. 9 and FIG. 10 are depth direction analysis profiles of each component by Auger electron spectroscopy on the sample surfaces according to Example 1 and Example 2, respectively. In both cases, Au is localized at a concentration of almost 100 atomic% on the surface of the material before the temperature increasing process, whereas Au is alloyed with the underlying amorphous metal material after the temperature increasing process. I understand. Also, the Au concentration profile clearly shows that the first Au concentrated layer, the intermediate concentration layer, and the second Au concentrated layer are formed. And by configuring the metal separator with the materials of the examples in Table 1 (thickness of Au layer is 5 nm or more), the contact resistance with the electrode layer is reduced, and the increase in the internal resistance of the battery is suppressed. It can be seen that even when the battery load increases, the output voltage is less likely to decrease. It can also be seen that by adopting the Ni-based amorphous metal material, good results have been obtained in all of the supercooled liquid temperature range, corrosion rate, hardness (strength), contact resistance value, and toughness. In all of the samples of Examples 1 to 15, the Au layer was simply peeled off by a scratch test immediately after the Au layer was formed by sputtering. I couldn't. The Au layer formed by sputtering exhibited a golden color tone, but the golden color was lost in the alloyed state after processing.

The figure which shows the fuel cell of this invention typically in a lamination | stacking form. The top view and expanded sectional view which show embodiment of the metal separator of this invention used for the fuel cell of FIG. Explanatory drawing which shows the 1st example of the manufacturing process of the metal separator of this invention. Process explanatory drawing following FIG. Process explanatory drawing following FIG. The figure which illustrates typically a mode that Au layer alloyed with the Ni base amorphous metal material which makes the foundation | substrate. The schematic diagram which shows the example which formed Au alloying layer partially in the main-body part surface. The conceptual diagram of the measuring apparatus of contact resistance. The depth direction composition analysis profile of the sample which concerns on Example 1 by the Auger electron spectroscopy analysis of Au layer and Au alloying layer. The depth direction composition analysis profile of the sample which concerns on Example 2 by the Auger electron spectroscopy analysis of Au layer and Au alloying layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell 2 1st electrode layer 3 Polymer solid electrolyte membrane 4 2nd electrode layer 10a 1st separator 10b 2nd separator 10G 'Au layer 10G Au alloying layer 10M Main body layer

Claims (11)

A crystallization temperature of 500 ° C. or higher, a plate-like main body made of a Ni-based amorphous metal material having a glass transition temperature lower than the crystallization temperature, a surface of the main body, and an Au A fuel cell polymer comprising: an Au alloying layer obtained by diffusion-alloying an Au component in the Ni-based amorphous metal material forming the main body so that the content is 10 atomic% or more and 60 atomic% or less. A metal for a fuel cell, characterized in that when a plate surface on one side is laminated on an electrode layer covering a solid electrolyte membrane, a recess for forming a gas diffusion layer is formed between the electrode layer and the electrode layer. Separator. The metal separator for a fuel cell according to claim 1, wherein the thickness of the Au alloying layer is 10 nm or more and 80 nm or less. 3. The fuel cell metal separator according to claim 1, wherein the Ni-based amorphous metal material forming the main body has a difference between the crystallization temperature and the glass transition temperature of 30 ° C. or more. The Ni-based amorphous metal material forming the main body is:
Ni content is 40 atomic% or more and 60 atomic% or less,
Nb content is 15 atomic% or more and 25 atomic% or less,
The total content of Ti and Zr is 10 atomic% or more and 30 atomic% or less,
The total content of the optional metal component M composed of one or more selected from Co, Cu, Al, Fe, Si and Cr is 0 atomic% to 20 atomic%,
The metal separator for a fuel cell according to claim 3, wherein the total content of Nb, Ti, Zr, and M is 40 atom% or more and 60 atom% or less. The Au alloying layer has an Au content higher than the average Au content of the Au alloying layer from the outermost surface side when the Au concentration distribution is analyzed in the depth direction from the outermost surface. One Au-concentrated region, an intermediate concentration region where the Au content is lower than that of the first Au-concentrated layer, an Au content higher than the intermediate concentration region, and the average Au content The metal separator for a fuel cell according to claim 4, wherein the second Au enriched region having a higher Au content is formed in this order. A metal material formed in a plate shape with a Ni-based amorphous metal material having a crystallization temperature of 500 ° C. or higher and having a glass transition temperature lower than the crystallization temperature is equal to or higher than the glass transition temperature. When a plate surface on one side is laminated on the electrode layer covering the polymer solid electrolyte membrane of the fuel cell by performing plastic working in a supercooled liquid temperature range lower than the crystallization temperature, the gap between the electrode layer A temperature increasing step for forming a recess for forming a gas diffusion layer on the plate surface of the metal material;
An Au layer forming step of forming an Au layer on the surface of the metal material;
By raising the temperature of the metal material made of the Ni-based amorphous metal material on which the Au layer is formed with the crystallization temperature as an upper limit, the Au component of the Au-based layer forms the surface layer portion of the metal material. By subjecting the amorphous metal material to diffusion alloying, an Au alloying layer is formed in which the Au component is diffusion-alloyed in the Ni-based amorphous metal material so that the Au content is 10 atomic% to 60 atomic%. A diffusion alloying process;
The manufacturing method of the metal separator for fuel cells characterized by including these. The manufacturing method of the metal separator for fuel cells of Claim 6 which implements the said temperature rising process process also as the said diffusion alloying process after implementing the said Au layer formation process. The method for producing a metal separator for a fuel cell according to claim 6 or 7, wherein a formation thickness of the Au layer in the Au layer forming step is 5 nm or more and 20 nm or less. The Ni-based amorphous metal material is
Ni content is 40 atomic% or more and 60 atomic% or less,
Nb content is 15 atomic% or more and 25 atomic% or less,
The total content of Ti and Zr is 10 atomic% or more and 30 atomic% or less,
The total content of the optional metal component M composed of one or more selected from Co, Cu, Al, Fe, Si and Cr is 0 atomic% to 20 atomic%,
The method for producing a metal separator for a fuel cell according to any one of claims 6 to 8, wherein the total content of Nb, Ti, Zr and M is 40 atomic% or more and 60 atomic% or less. The method for producing a metal separator for a fuel cell according to claim 9, wherein the Au layer is formed by sputtering in the Au layer forming step. 5. The fuel cell according to claim 1, a polymer solid electrolyte membrane, a first electrode layer covering the first main surface, a second electrode layer covering the second main surface, and the fuel cell according to claim 1. 5. A first separator configured as a metal separator for a fuel cell, stacked on the first electrode layer, and forming a gas diffusion layer for fuel gas by the recess, 5. And a second separator that is laminated on the second electrode layer and forms a gas diffusion layer for an oxidant gas by the recess,
A fuel cell comprising:

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