JP2006339045A - Metal separator for fuel cell, manufacturing method of the same, and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal separator for a fuel cell having sufficient corrosion resistant property, easy to manufacture, capable of maintaining low surface contact resistance. <P>SOLUTION: Crystallization temperature of the metal separator for the fuel cell 10a, 10b is 500°C or higher. Indented parts 21, formed into plate-shape by using composite amorphous material made of Ni base amorphous phase with glass transition temperature of lower than crystallization temperature, having a constitution of dispersing TiN particles in a matrix, forming a gas diffusion layer between electrode layers when the plate face at one side is laminated on an electrode layer covering a polymeric solid electrolyte film of the fuel cell, is formed on the electrode layer. The metal separator for the fuel cell 10a, 10b are assembled in the fuel cell in a state of contacting the electrode layer. The TiN particles in the matrix reduce the contact resistance between the electrode layer and itself. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  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

  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 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.

  The Ni-based amorphous alloy exhibits very good corrosion resistance due to the passive oxide 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 one of the reasons why the high corrosion resistance is good. However, the denser and stronger the passive oxide film is, the more insulative the film is, and the electrical conductivity is remarkably deteriorated. 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.

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

Means and actions / effects for solving the problem

In order to solve the above problems, the fuel cell metal separator of the present invention is
A composite amorphous material having a structure in which TiN particles are dispersed in a matrix composed of a Ni-based amorphous phase having a crystallization temperature of 500 ° C. or higher and a glass transition temperature lower than the crystallization temperature. When a plate surface on one side is laminated on the electrode layer that covers the polymer solid electrolyte membrane of the fuel cell, a recess for forming a gas diffusion layer is formed between the electrode layer and the electrode layer. It is characterized by.

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 composite amorphous material having a structure in which TiN particles are dispersed in a matrix composed of a Ni-based amorphous phase having a crystallization temperature of 500 ° C. or higher and a glass transition temperature lower than the crystallization temperature. The electrode layer that covers the polymer solid electrolyte membrane of the fuel cell by subjecting the metal material formed in a plate shape to plastic processing in a supercooled liquid temperature range that is higher than the glass transition temperature and lower than the crystallization temperature. When the plate surface on one side is laminated on top, a recess for forming a gas diffusion layer between the electrode layers is formed on the plate surface of the material.

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

  According to the present invention, a metal separator for a fuel cell is matrixed with a Ni-based amorphous phase 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 is formed in a plate shape by the composite amorphous material formed. The Ni-based amorphous phase generally has high deformation resistance at room temperature and is poor in ductility, and thus is considered unsuitable for plastic working. However, the composite amorphous material adopted in the present invention has a relatively high matrix crystallization temperature 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 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. Furthermore, since TiN particles are dispersed in the matrix, the metal separator made of the composite amorphous material can reduce the contact resistance with the electrode layer and suppress the increase in the internal resistance of the battery. Even when the load increases, the output voltage is less likely to decrease.

  The reason why the deformation resistance of the Ni-based amorphous phase 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, and the amorphous phase is amorphous. It is considered that the viscosity of the mass phase decreases. In the present invention, since the amorphous phase that forms the matrix of the material is composed of Ni, the corrosion resistance is extremely good as compared with conventional stainless steel (for example, JIS: SUS316) and Mo-based metal materials. Since corrosion does not easily proceed even under acidic conditions, the durability of the separator is improved, and the increase in internal resistance of the battery over time can be effectively suppressed. Further, the TiN particles are uniformly dispersed in the matrix, so that those existing in the outermost layer portion of the material penetrate the surface passive oxide film and are exposed on the material surface. The TiN particles have good conductivity, and the TiN particles that have broken through the passive oxide film function as a conduction path between the electrode layer disposed in contact with the separator and the metal matrix inside the separator. As a result, it is considered that the contact resistance is reduced.

  Next, in the production method of the present invention, the metal material formed into a plate shape by the composite amorphous material is a kind of supercooled liquid temperature range that is higher than the glass transition temperature and lower than the crystallization temperature. Warm plastic working. 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 the separator is formed by forming the recesses based on the bending in the thickness direction of the plate material made of the composite amorphous material, the above-described die press processing is performed on the material plate material obtained as a quenched ribbon or the like. It can be easily manufactured by applying forging or molten metal forging.

  Further, since the matrix of the constituent material of the separator of the present invention is made of a Ni-based amorphous phase, it has higher strength than a conventional separator made of carbon, and can be easily processed to be thinner than a separator made of carbon. . In this case, the plate thickness of the plate used for the separator is desirably 0.02 mm or more and 0.2 mm or less. If the plate thickness is less than 0.02 mm, the gas barrier function of the separator may be insufficient due to the occurrence of pinholes, etc. If a thickness exceeding 0.2 mm is used, the material cost will increase, and the cost In terms of reduction, the advantages over existing technologies (for example, conventional carbon separators) may be poor.

  Next, it is desirable to use a composite amorphous material (nickel-based matrix phase) employed in the present invention in which the difference between the crystallization temperature and the glass transition temperature is 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 phase, the present inventors have found that if the processing temperature is set at least 20 ° C. or more (preferably 30 ° C. or more) lower than the crystallization temperature in the supercooled liquid temperature range, crystallization will occur. Thus, the low-viscosity amorphous phase suitable for processing can be secured with sufficient margin until the processing is completed. Further, 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 obtained material must also be in the form of a ribbon or flake (for example, less than 50 μm thick), and in the first place 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.

Specifically, the composite amorphous material constituting the metal separator for fuel cells 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,
Ti content is 10 atomic% or more and 30 atomic% or less,
N content is 0.05 atomic% or more and 5 atomic% or less,
The total content of the optional metal component M composed of one or more selected from Zr, Co, Cu, Al, Fe, Si and Cr is 0 atomic% or more and 20 atomic% or less,
And what is made into the total content rate of Nb, Ti, N, 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 and Ti form the basis of subcomponents with respect to Ni, and by containing these elements, the supercooled liquid region can be set sufficiently large, and a stable Ni-based amorphous phase can be formed into a separator plate material. Can be obtained in a suitable bulk. 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.

  Ti is not only indispensable for expanding the supercooled liquid region and, in turn, stable formation of the amorphous phase, but also functions as an essential constituent element of TiN, which is a basic phase responsible for reducing the surface resistance of the metal separator. . In other words, Ti contained for the purpose of expanding the supercooled liquid region is used for another purpose of reducing the surface resistance. If the Ti content 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 Ti content is more preferably 13 atomic% or more and 25 atomic% or less.

  N combines with Ti and is dispersedly formed in the matrix in the form of TiN, contributing to the reduction of surface resistance. Further, when the TiN particles are finely dispersed in the matrix, the strength of the composite amorphous material may be improved. In the alloy composition in which N is not positively added, nothing is observed in the matrix, and there is no crystal grain boundary and a soft structure is shown. The N content at this time is about 0.015 atomic% to 0.025 atomic%. More than this, the addition of N clearly reveals TiN particles in the matrix. When the N content is less than 0.05 atomic%, the amount of TiN particles formed becomes insufficient, and the surface resistance of the resulting separator may not be sufficiently reduced. On the other hand, if the N content exceeds 5 atomic%, the amount of TiN particles formed becomes excessive, making it difficult to produce the composite amorphous material, and the workability of the composite amorphous material is also deteriorated to obtain a desired separator shape. It becomes difficult.

  Further, in order to form TiN particles without excess or deficiency, it is desirable that the Ti content in the composite amorphous material is 3 to 100 times the N content. If the Ti content is less than 3 times the N content or exceeds 100 times, the amount of TiN particles formed may be insufficient.

The average particle size of the TiN particles formed in the matrix (the particle size is represented by the diameter of a circle having the same area as the particles converted in the tissue cross section) is desirably 10 μm or less. When the average particle diameter of TiN particles exceeds 10 μm, TiN particles may not be uniformly distributed in the structure, the effect of reducing surface resistance may be reduced, and the workability of the composite amorphous material may be deteriorated. . On the other hand, the lower limit of the average particle size of TiN particles is technically about 1 μm. The area ratio of TiN particles observed in the structure is desirably 3% or more and 30% or less. If the area ratio is less than 3%, the effect of reducing the surface resistance may be diminished, and if it exceeds 30%, the above-described problem occurs when the TiN particle formation amount becomes excessive. Further, when the average particle size of TiN particles is adjusted to 1 μm or more and 10 μm or less as described above, the number formation density of TiN particles having a particle size of 1 μm or more and 10 μm or less observed in the structure observation field is 500 particles / mm ² or more. It is good that it is 3000 pieces / mm ² or less. When the number formation density is less than 500 / mm ² , the effect of reducing the surface resistance may be reduced. When the number formation density exceeds 3000 / mm ² , the above-described problem occurs when the TiN particle formation amount becomes excessive.

  Moreover, the arbitrary metal component M which consists of 1 type (s) or 2 or more types chosen from Zr, Co, Cu, Al, Fe, Si, and Cr has the effect which improves the amorphous formation ability of a Ni-Nb type alloy more ( However, it is 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, N, 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.

The composite amorphous material used in the present invention can obtain a plate-like (strip-like) material from a molten state by a known single roll method or twin roll method. In this case, the cooling rate is desirably set in the range of, for example, about 10 ⁴ ° C / second to 10 ⁶ ° C / second, and is well-known depending on the cooling capacity of the roll (water-cooled copper roll is particularly desirable) and the rotation speed. 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 composite amorphous material having the above composition has very good corrosion resistance in a sulfuric acid atmosphere, and is applied to a metal separator. In addition, an increase in internal resistance over time due to corrosion is sufficiently suppressed, and a good power generation capacity 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 have a structure in which TiN particles are dispersed in a matrix made of a Ni-based amorphous phase having a crystallization temperature of 500 ° C. or higher and a glass transition temperature lower than the crystallization temperature. The composite amorphous material is formed into a plate shape. The recess 21 for forming the gas diffusion layer between the electrode layers 2 and 4 is formed based on the bending in the thickness direction of the plate material made of the composite amorphous 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 composite amorphous material used for the separators 10a and 10b is such that the difference between the crystallization temperature and the glass transition temperature is 30 ° C. or higher. For example, the Ni content is 40 atomic% or more and 60 atomic% or less. Nb content is 15 atomic% to 25 atomic%, Ti content is 10 atomic% to 30 atomic%, N content is 0.05 atomic% to 5 atomic%, Zr, Co, Cu, Al, The total content of one or more arbitrary metal components M selected from Fe, Si and Cr is 0 atomic% or more and 20 atomic% or less, and the total content of Nb, Ti, N and M is What is made into 40 atomic% or more and 60 atomic% or less is employable.

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 cooled and solidified to form a ribbon 45 made of a composite amorphous material. (Single roll method: 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.

  Next, as shown in FIG. 4, the obtained ribbon 45 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 lower than the crystallization temperature Tx by 30 ° C. or more. After cutting at 53, it is transferred to a press apparatus having press dies 51, 51 to perform warm press work. 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. Then, as shown in step 3, the separators 10a (10b) can be obtained by separating the pressing dies 51, 51 from each other. 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 whose plastic flow becomes extremely good by heating to the supercooled liquid temperature range 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.

  Moreover, FIG. 6 is an example in the case of employing a molten metal forging process. In this case, as shown in step 1, the molten metal 42 is poured into a female die 61f of a forging die having a cavity 61a corresponding to the unevenness to be formed. Then, the male die 61m is immediately approached and forging is performed. The molten metal 42 is rapidly solidified by contact with the female mold 61f and the male mold 61m, and becomes amorphous. Further, while the temperature of the amorphous material after solidification is in the supercooled liquid temperature range, the molten metal 42 is formed by the female mold 61f and the male mold 61m. If the pressurization is continued (step 2), a separator 10a (10b) having irregularities having a shape corresponding to the cavity 61a is obtained (step 3).

  The separator 10a (10b) obtained as described above has a structure in which the composite amorphous material constituting the separator 10a has a structure in which TiN particles are dispersed in a matrix, and the contact resistance with the electrode layers 2 and 4 (FIG. 1). Is reduced.

  In order to confirm the effect of the present invention, the following experiment was conducted. First, raw materials were weighed and blended so as to obtain each composition shown in Table 1 (stainless steel (SUS316L) of Comparative Example 7 uses a commercially available plate material) and dissolved in an Ar atmosphere in a button arc melting furnace. An ingot (about 10 mm × 40 mm, 50 g) was produced. Note that N was added in the form of TiN (reagent), and the remainder of the Ti composition minus the contribution from TiN was blended in the form of sponge Ti. 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 melting is about 1450 ° C., and the added TiN is completely dissolved in the molten metal.

  Using this ribbon, the corrosion resistance, hardness, toughness and surface resistance value were investigated. 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. 7 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. 8 is a cross-sectional observation image of the composite amorphous material according to Example 2 using an optical microscope (scale is shown in the figure). It can be seen that a large number of TiN particles are dispersed in a uniform matrix without grain boundaries. By configuring the metal separator with a composite amorphous material in which TiN particles are dispersed in a matrix, the contact resistance with the electrode layer is reduced, the increase in the internal resistance of the battery can be suppressed, and the battery load is increased. Even in this case, the output voltage is hardly lowered. According to the experimental results of Table 1, the adoption of the composite amorphous material of the example in which TiN is dispersed is favorable over the supercooled liquid temperature range, corrosion rate, hardness (strength), contact resistance value, and toughness. It turns out that the result is obtained.

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. Explanatory drawing which shows the 2nd example of the manufacturing process of the metal separator of this invention. The conceptual diagram of the measuring apparatus of contact resistance. The optical microscope observation image of the cross-sectional structure | tissue of the composite amorphous material of Example 2. FIG.

Explanation of symbols

1 Fuel Cell 2 First Electrode Layer 3 Polymer Solid Electrolyte Membrane 4 Second Electrode Layer 10a First Separator 10b Second Separator

Claims (6)

A composite amorphous material having a structure in which TiN particles are dispersed in a matrix composed of a Ni-based amorphous phase having a crystallization temperature of 500 ° C. or higher and a glass transition temperature lower than the crystallization temperature. When a plate surface on one side is laminated on the electrode layer that covers the polymer solid electrolyte membrane of the fuel cell, a recess that forms a gas diffusion layer is formed on the plate surface. A metal separator for a fuel cell. The fuel cell metal separator according to claim 1, wherein the composite amorphous material has a difference between the crystallization temperature and the glass transition temperature of 30 ° C. or more. The composite amorphous 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,
Ti content is 10 atomic% or more and 30 atomic% or less,
N content is 0.05 atomic% or more and 5 atomic% or less,
The total content of the optional metal component M composed of one or more selected from Zr, Co, Cu, Al, Fe, Si and Cr is 0 atomic% or more and 20 atomic% or less,
The metal separator for a fuel cell according to claim 2, wherein the total content of Nb, Ti, N and M is 40 atomic% or more and 60 atomic% or less. The metal separator for a fuel cell according to claim 3, wherein the composite amorphous material has a Ti content of 3 to 100 times the N content. A composite amorphous material having a structure in which TiN particles are dispersed in a matrix composed of a Ni-based amorphous phase having a crystallization temperature of 500 ° C. or higher and a glass transition temperature lower than the crystallization temperature. The metal material formed into a plate shape by the above is subjected to plastic working in a supercooled liquid temperature range that is higher than the glass transition temperature and lower than the crystallization temperature, thereby covering the polymer solid electrolyte membrane of the fuel cell Producing a metal separator for a fuel cell, wherein when a plate surface on one side is laminated on an electrode layer, a recess for forming a gas diffusion layer between the electrode layer is formed on the plate surface of the metal material. Method. 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:

Images