Alloy components, electrochemical modules, solid oxide fuel cells, solid oxide electrolytic cells, electrochemical devices, energy systems, and methods for manufacturing alloy components.

Abstract

To provide an alloy member capable of suppressing phosphorus poisoning to a member on the side to be joined.SOLUTION: An alloy member 11 contains Fe and Cr, and an oxide film 11a is formed on the surface of a part joined to another member, and an average thickness of the oxide film 11a is 0.3 μm or more and 0.7 μm or less.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to alloy members, electrochemical modules, solid oxide fuel cells, solid oxide electrolytic cells, electrochemical devices, energy systems, and methods for manufacturing alloy members. [Background technology]

[0002] Solid oxide fuel cells (hereinafter referred to as "SOFCs" as appropriate) are composed of single cells having an air electrode and a fuel electrode, and alloy members such as inter-cell connecting members provided between these single cells. Such alloy members are made from stainless steel, which has excellent electronic conductivity and heat resistance.

[0003] In SOFCs and similar devices, phosphorus volatilized from the stainless steel constituting the inter-cell connection material can react with Ni, the main component of the fuel electrode in a single cell, potentially causing degradation such as the volatilization of Ni from the fuel electrode. For example, under high-temperature operating conditions, Ni used in fuel electrodes reacts with impurities such as phosphorus, generally increasing its vapor pressure relative to metallic Ni. As a result, Ni volatilizes from the fuel electrode material (mainly a cermet of Ni and an oxide of the electrolyte material), disrupting the Ni metal network in the fuel electrode, reducing electronic conductivity, and leading to a decrease in cell performance (degradation).

[0004] One possible source of phosphorus that can degrade fuel electrodes is phosphorus contained in the stainless steel used in the alloy components to which they are joined. In this case, the phosphorus in the stainless steel may be at a low concentration, for example, a few hundred ppm, but it has been reported to cause degradation of fuel electrodes.

[0005] Patent Document 1 describes a method for manufacturing ultra-low phosphorus stainless steel. By using stainless steel manufactured using this method in alloy components, it may be possible to suppress the deterioration of the fuel electrode as described above. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 3855043 [Overview of the project] [Problems that the invention aims to solve]

[0007] As described in Patent Document 1, a method for producing stainless steel with a low phosphorus concentration has been proposed, but using such stainless steel presents the problem of increased costs for alloy components.

[0008] The present invention has been made in view of the above-mentioned problems, and its objective is to provide an alloy member capable of suppressing phosphorus poisoning of the member being joined, an electrochemical module, a solid oxide fuel cell, a solid oxide electrolytic cell, an electrochemical device, an energy system, and a method for manufacturing the alloy member. [Means for solving the problem]

[0009] To achieve the above objective, the characteristic configuration of the alloy member according to the present invention is that it contains Fe, Cr, and phosphorus, an oxide film is formed on the surface of the portion that is joined with other members, the average thickness of the oxide film is 0.3 μm or more and 0.7 μm or less, and in the portion where the oxide film is formed from inside The surface Towards The point is that the phosphorus concentration has decreased. Here, the oxide film may contain an oxide of Cr.

[0010] According to the above characteristic configuration, an oxide film with an average thickness of 0.3 μm or more and 0.7 μm or less is formed on the surface of the alloy member, and in the portion where the oxide film is formed from inside surface Towards Because the phosphorus concentration is reduced, even if the alloy component is joined to, for example, the fuel electrode of a solid oxide fuel cell and placed in that environment, the release of phosphorus from the alloy component is suppressed. In other words, other components joined to the alloy component are not poisoned due to the presence of phosphorus. Therefore, it is possible to provide an alloy member that can suppress phosphorus poisoning of the member being joined.

[0011] A key feature of the electrochemical module according to the present invention, which achieves the above objective, is that it is constructed by joining the alloy member and an electrochemical element having a single cell in which an electrolyte layer is sandwiched between an electrode layer and a counter electrode layer.

[0012] According to the above characteristic configuration, phosphorus poisoning of the electrode layer or counter electrode layer constituting the electrochemical element, which is joined to the alloy member, can be suppressed.

[0013] Another characteristic configuration of the electrochemical module according to the present invention is that it comprises a plurality of electrochemical elements, and the plurality of electrochemical elements are electrically connected to each other by the alloy member.

[0014] According to the above-described configuration, since multiple electrochemical elements are arranged in a cluster, even if the capacity of a single electrochemical element constituting the electrochemical module is low, the capacity of the electrochemical module, which is a combination of multiple such elements, can be increased.

[0015] Another characteristic feature of the electrochemical module according to the present invention is that a protective film composed of a metal oxide containing at least one of Co, Mn, Cu, and Ni is provided on the oxide film of the alloy member on the side that is joined to the electrochemical element.

[0016] According to the above-described configuration, poisoning of the electrochemical element can be prevented, and the electrical resistance between the electrochemical element and the alloy member can be maintained at a good level.

[0017] The characteristic configuration of the solid oxide fuel cell according to the present invention for achieving the above objective is that it includes the electrochemical module described above and generates a power generation reaction in the single cell.

[0018] According to the above characteristic configuration, since it is possible to perform a power generation reaction as a solid oxide fuel cell equipped with an electrochemical module excellent in durability, reliability, and performance, it is possible to obtain a highly durable and high-performance solid oxide fuel cell.

[0019] The characteristic configuration of the solid oxide electrolysis cell according to the present invention for achieving the above object is that it includes the above electrochemical module and causes an electrolysis reaction to occur in the single cell.

[0020] According to the above characteristic configuration, since it is possible to generate a gas by an electrolysis reaction as a solid oxide electrolysis cell equipped with an electrochemical module excellent in durability, reliability, and performance, it is possible to obtain a highly durable and high-performance solid oxide electrolysis cell.

[0021] The characteristic configuration of the electrochemical device according to the present invention for achieving the above object is that it includes at least the above electrochemical module and a fuel converter that circulates a gas containing a reducing component to the electrochemical module, or a fuel converter that converts a gas containing a reducing component generated by the electrochemical module.

[0022] According to the above characteristic configuration, it has an electrochemical module and a fuel converter that circulates a gas containing a reducing component to the electrochemical module. Therefore, when the electrochemical module is operated as a fuel cell, if it is configured to generate hydrogen from natural gas or the like supplied using an existing primary fuel supply infrastructure such as city gas by a fuel converter such as a reformer and circulate it to the fuel cell, it is possible to realize an electrochemical device equipped with an electrochemical module excellent in durability, reliability, and performance.

[0023] Furthermore, according to the above characteristic configuration, the device includes an electrochemical module and a fuel converter that converts the gas containing reducing components generated by the electrochemical module. Therefore, when the electrochemical module is operated as an electrolytic cell, for example, it can be used as an electrochemical device that converts hydrogen generated by the electrolytic reaction of water into methane by reacting it with carbon monoxide or carbon dioxide in the fuel converter. With such a configuration, it is possible to realize an electrochemical device equipped with an electrochemical module that is excellent in durability, reliability, and performance.

[0024] Another characteristic configuration of the electrochemical apparatus according to the present invention is that it comprises at least the above-mentioned electrochemical module and a power converter that extracts power from the electrochemical module or supplies power to the electrochemical module.

[0025] According to the above characteristic configuration, the power converter extracts the electricity generated by the electrochemical module or supplies electricity to the electrochemical module. As a result, the electrochemical module acts as a fuel cell or an electrolytic cell. Therefore, according to the above characteristic configuration, it is possible to provide an electrochemical module that can improve the efficiency of converting chemical energy such as fuel into electrical energy, or electrical energy into chemical energy such as fuel. For example, when an inverter is used as the power converter, it is preferable because the electrical output obtained from an electrochemical module with excellent durability, reliability, and performance can be boosted by the inverter or converted from DC to AC, making it easier to utilize the electrical output obtained from the electrochemical module.

[0026] The characteristic configuration of the energy system according to the present invention for achieving the above objective is that it includes the electrochemical apparatus and a waste heat utilization unit that reuses the heat discharged from the electrochemical apparatus.

[0027] According to the above characteristic configuration, since it has an electrochemical device and a waste heat utilization unit that reuses the heat discharged from the electrochemical device, it is possible to realize an energy system that is excellent in durability, reliability and performance, as well as energy efficiency. It can also be combined with a power generation system that generates electricity using the combustion heat of unused fuel gas discharged from the electrochemical device to realize an energy-efficient hybrid system.

[0028] The characteristic configuration of the method for manufacturing an alloy member according to the present invention, which achieves the above objective, is joined with other members. ,the above A method for manufacturing alloy members, Contains Fe, Cr, and 250 ppm to 350 ppm of phosphorus. Before joining the alloy member to other members using a bonding agent, the alloy member is heat-treated in a reducing atmosphere at a temperature range of 800°C to 1000°C. Then, an oxide film with an average thickness of 0.3 μm or more and 0.7 μm or less is formed on the surface of the alloy member in the portion that is joined with the other member, and the phosphorus concentration on the surface of the alloy member in the portion where the oxide film is formed is reduced. The key point is the heat treatment process.

[0029] According to the above characteristic configuration, by performing a heat treatment process in which the alloy member is heat-treated in a reducing atmosphere at a temperature range of 800°C to 1000°C, the release of phosphorus from the alloy member is promoted during this process. The phosphorus concentration on the surface of the alloy member where the oxide film is formed is reduced. and, The average thickness of the alloy member surface in the part that is joined to other members is between 0.3 μm and 0.7 μm. An oxide film is formed. As a result, even if the resulting alloy member is joined to, for example, the fuel electrode of a solid oxide fuel cell and placed in that environment, the release of phosphorus from the alloy member is suppressed. In other words, other members joined to the alloy member are not poisoned by the presence of phosphorus. [Brief explanation of the drawing]

[0030] [Figure 1] This is a schematic diagram of a solid oxide fuel cell. [Figure 2] This is an explanatory diagram of the reaction during the operation of a solid oxide fuel cell. [Figure 3] This is a cross-sectional view showing the structure of an inter-cell connecting member having an alloy component. [Figure 4] This graph shows the results of the GD-OES analysis for the examples and comparative examples. [Figure 5] This is an SEM image showing a cross-section of an alloy component. [Figure 6] This is the result of elemental analysis of the oxide film on the alloy component. [Figure 7] This is an SEM image showing a cross-section of an alloy component. [Figure 8] This is the result of elemental analysis of the oxide film on the alloy component. [Figure 9] This is an SEM image showing a cross-section of an alloy component. [Figure 10] This is the result of elemental analysis of the oxide film on the alloy component. [Figure 11] This diagram shows the configuration of an energy system and an electrochemical apparatus. [Figure 12] This diagram shows the configuration of an energy system and an electrochemical apparatus. [Modes for carrying out the invention]

[0031] Hereinafter, with reference to the drawings, an alloy member 11 used in a solid oxide fuel cell (SOFC) according to an embodiment of the present invention and a method for manufacturing the same will be described. Figure 1 is a schematic diagram of a solid oxide fuel cell equipped with an electrochemical module M. Figure 2 is an explanatory diagram of the reaction during operation of the solid oxide fuel cell. Figure 3 is a diagram showing the configuration of the inter-cell connecting member 1 having an alloy member 11. As shown in Figures 1 to 3, the electrochemical module M is constructed by joining an inter-cell connecting member 1 having an alloy member 11 with an electrochemical element having a single cell 3 in which an electrolyte layer 30 is sandwiched between a fuel electrode 32 as an electrode layer and an air electrode 31 as a counter electrode layer. Specifically, the single cell 3 is formed by joining an air electrode 31 made of a porous material that conducts oxygen ions and electrons to one side of an electrolyte layer 30 made of a dense solid oxide that conducts oxygen ions, and joining a fuel electrode 32 made of a porous material that conducts electrons to the other side of the same electrolyte layer 30.

[0032] The electrochemical module M has a structure in which a single cell 3, which serves as an electrochemical element, is sandwiched between a pair of electronically conductive inter-cell connecting members 1, each having grooves 2 formed therein for transferring electrons to and from an air electrode 31 or a fuel electrode 32, and for supplying air and hydrogen, with a gas seal body appropriately held at its outer edge. When the air electrode 31 and the inter-cell connecting member 1 are in close contact, the groove 2 on the air electrode 31 side functions as an air passage 2a for supplying air to the air electrode 31. When the fuel electrode 32 and the inter-cell connecting member 1 are in close contact, the groove 2 on the fuel electrode 32 side functions as a fuel passage 2b for supplying hydrogen to the fuel electrode 32.

[0033] To elaborate on the common materials used in each element constituting the single cell 3 described above, for example, as the material for the air electrode 31, a perovskite-type oxide of (La,AE)MO3 can be used, in which some of the La in LaMO3 (e.g., M=Mn,Fe,Co,Ni) is replaced with alkaline earth metal AE (AE=Sr,Ca). As the material for the fuel electrode 32, for example, a cermet of Ni and yttria-stabilized zirconia (YSZ) can be used, and as the material for the electrolyte layer 30, for example, yttria-stabilized zirconia (YSZ) can be used.

[0034] Then, multiple single cells 3 are electrically connected to each other by inter-cell connecting members 1 having alloy members 11, that is, multiple single cells 3 are stacked with inter-cell connecting members 1 in between, and are held together by applying pressure in the stacking direction with multiple bolts and nuts to form a cell stack. In this cell stack, the inter-cell connecting members 1 located at both ends in the stacking direction only need to have either a fuel passage 2b or an air passage 2a formed on them, and the other inter-cell connecting members 1 located in the middle can have a fuel passage 2b formed on one side and an air passage 2a formed on the other side. In such a stacked cell stack, the inter-cell connecting members 1 may be called separators, interconnectors, etc.

[0035] The cell stack is attached to the manifold that supplies the fuel gas (hydrogen) using an adhesive such as a glass sealant. Crystallized glass is used as the glass sealant. The glass sealant is used not only for bonding the manifold but also in places where sealing is required, such as between the single cell 3 and the inter-cell connecting member 1. A solid oxide fuel cell having such a cell stack structure is generally called a planar solid oxide fuel cell. In this embodiment, a planar solid oxide fuel cell is described as an example, but the present invention is also applicable to solid oxide fuel cells with other structures.

[0036] When a solid oxide fuel cell (cell stack) equipped with such an electrochemical module M and generating electricity in a single cell 3 is in operation, as shown in Figure 2, air is supplied to the air electrode 31 via the air channel 2a formed in the adjacent inter-cell connecting member 1, and hydrogen is supplied to the fuel electrode 32 via the fuel channel 2b formed in the adjacent inter-cell connecting member 1, and it operates at an operating temperature of, for example, about 800°C. Then, at the air electrode 31, oxygen molecules O2 emit electrons e - It reacts with oxygen ions O 2- O is generated, and 2- The oxygen moves through the electrolyte layer 30 to the fuel electrode 32, and the H2 supplied to the fuel electrode 32 is its oxygen. 2- It reacts with H2O and e - As a result of this generation, an electromotive force E is generated between the pair of cell-to-cell connecting members 1, and this electromotive force E can be extracted and used externally.

[0037] <Inter-cell connecting member 1> As shown in Figure 3, the inter-cell connecting member 1 comprises an alloy member 11 made of, for example, stainless steel containing Fe and Cr, and a protective film 12 formed on the surface of the alloy member 11 that is joined to the air electrode 31 of the single cell 3. The inter-cell connecting member 1 also has an air passage 2a for supplying air to the air electrode 31 of the single cell 3 and a fuel passage 2b for supplying fuel gas.

[0038] While ferritic stainless steel is often used as the alloy member 11 for the inter-cell connecting member 1, austenitic stainless steel such as Fe-Cr-Ni alloy, which has superior heat resistance, or nickel-based alloy such as Ni-Cr alloy may also be used. The stainless steel that makes up the alloy member 11 generally contains about 250 ppm to 350 ppm of phosphorus.

[0039] In this embodiment, before joining the alloy member 11 to other members using the joining material 4, a heat treatment step is performed in which the alloy member 11 is heat-treated in a reducing atmosphere at a temperature range of 800°C to 1000°C. This heat treatment step forms an oxide film 11a on the surface of the portion of the alloy member 11 that will be joined to the other members. The average thickness of this oxide film 11a is 0.3 μm to 0.7 μm. A reducing atmosphere is an atmosphere containing gases such as hydrogen and ammonia that exhibit reducing properties.

[0040] Figure 4 shows the results of GD-OES analysis of a sample from the example that underwent the heat treatment process of this embodiment and a sample from the comparative example that did not undergo the heat treatment process, i.e., was untreated. As shown in Figure 4, in the comparative example sample, the phosphorus concentration in the alloy member 11 is almost constant in the depth direction from the surface. In comparison, in the example sample, the phosphorus concentration decreases from the inside towards the surface. This result is thought to be because, during the heat treatment process, phosphorus volatilizes from the surface of the alloy member 11, and at the same time, phosphorus diffuses from the inside of the alloy member 11 towards the surface. However, since the rate of phosphorus volatilization on the surface side of the alloy member 11 is faster than the rate of phosphorus diffusion from the inside of the alloy member 11 towards the surface, it is thought that the phosphorus concentration distribution shown in Figure 4 is formed. Thus, in the heat treatment process... An oxide film 11a as described above is formed on the surface of the alloy member 11. By significantly reducing the phosphorus concentration on the surface of the alloy member 11, it is expected that during the operation of the solid oxide fuel cell, phosphorus will diffuse from the inside of the alloy member 11 to the surface at a slow diffusion rate, but very little phosphorus will volatilize from the surface of the alloy member 11.

[0041] <Protective film 12> A protective film 12 is formed on the oxide film 11a of the alloy member 11 on the side that is joined to the single cell 3 as an electrochemical element. The protective film 12 is composed of a metal oxide containing at least one of Co, Mn, Cu, and Ni. In this embodiment, a protective film formation step is performed to form the protective film 12 on at least the surface of the alloy member 11 that is joined to the air electrode 31 of the single cell 3, after the heat treatment step has been performed. As a result, the protective film 12 is formed on the surface of the alloy member 11 that is joined to the air electrode 31 of the single cell 3. The protective film 12 can be formed by depositing a protective film forming material containing the metal oxide onto the alloy member 11 and then firing it.

[0042] The following are examples of methods for forming protective film materials. For example, it can be formed by a wet coating method or a dry coating method. Examples of wet coating methods include screen printing, doctor blade method, spray coating, inkjet method, spin coating, dip coating, electroplating, electroless plating, and electrodeposition coating. Examples of dry coating methods include vapor deposition, sputtering, ion plating, chemical vapor deposition (CVD), electrochemical vapor deposition (EVD), ion beam, laser ablation, atmospheric pressure plasma deposition, reduced pressure plasma deposition, and thermal spraying.

[0043] However, dry coating methods such as CVD / EVD and thermal spraying have drawbacks, including the complexity of the protective film formation process and the instability of the protective film 12's composition. Therefore, laser ablation is also being considered as an alternative to these methods for forming the protective film 12. Furthermore, since laser ablation is more expensive to manufacture than CVD / EVD or thermal spraying, wet coating is often adopted in practice as a technology that can produce the protective film 12 at a low cost. Examples of such wet coating methods include screen printing, doctor blade, spray coating, inkjet, spin coating, dip coating, electroplating, electroless plating, and electrodeposition coating.

[0044] For example, by applying the electrodeposition coating method, the protective film 12 can be formed using the following technique. Electrodeposition coating was performed using a mixture containing metal oxide fine particles dispersed at a concentration of 100 g per liter of electrodeposition solution and an anionic resin such as polyacrylic acid. Here, the ratio of (metal oxide fine particles:anionic resin) was set to (1:1) (mass ratio). By applying current using the mixture with the alloy member 11 as the positive polarity and the SUS304 electrode plate as the counter electrode as the negative polarity, an uncured electrodeposited coating film is formed on the surface of the alloy member 11 that is joined to the air electrode 31 of the single cell 3. Electrodeposition coating is carried out according to known methods, for example, by completely or partially immersing the alloy member 11 in an energizing tank filled with the mixture to make it the anode and applying current. The electrodeposition coating conditions are not particularly limited and can be appropriately selected from a wide range depending on various conditions such as the type of metal of the alloy member 11, the type of mixed liquid, the size and shape of the energizing bath, and the intended use of the resulting alloy member 11. However, typically, the bath temperature (mixed liquid temperature) should be around 10 to 40°C, the applied voltage around 10V to 450V, the voltage application time around 1 to 10 minutes, and the liquid temperature of the mixed liquid around 10 to 40°C. The thickness of the electrodeposited coating can be controlled by changing the electrodeposition voltage and electrodeposition time. Various pretreatments can also be performed on the alloy member 11. By heat treatment of the alloy member 11 on which this uncured electrodeposited coating has been formed, a hardened electrodeposited coating is formed on the surface of the alloy member 11. The heat treatment includes pre-drying to dry the electrodeposited coating and hardening heating to harden the electrodeposited coating, with hardening heating performed after pre-drying. Subsequently, the alloy member 11 on which the protective film-forming material was formed was fired in an electric furnace at 1000°C for 2 hours, and then slowly cooled to obtain an alloy member 11 on which a protective film 12 was formed on the surface.

[0045] Examples of metal oxide fine particles used as protective film-forming materials include cobalt manganese oxide, copper manganese oxide, or copper cobalt manganese oxide. In other words, the material of the protective film 12 is cobalt manganese oxide, copper manganese oxide, or copper cobalt manganese oxide.

[0046] <Adhesion and bonding using adhesives> A fuel cell stack is formed by sequentially joining the alloy member 11, on which the protective film 12 is formed as described above, and the single cell 3 in series. Specifically, the surface of the alloy member 11 on which the protective film 12 is formed, on the side facing the air electrode 31, is adhesively bonded to the air electrode 31 of the single cell 3 using a bonding material 4.

[0047] As the bonding material 4, for example, a material containing a metal oxide that contains at least two of Co, Mn, Cu, and Ni is used.

[0048] <Effects of performing the heat treatment process> The effects of performing the above heat treatment process on the alloy member 11 used in manufacturing the inter-cell connecting member 1 are described below.

[0049] [Verification Result 1] The samples of the heat treatment process in this embodiment were obtained by heat-treating general-purpose stainless steel (equivalent to SUS445J1) as the alloy member 11 at temperatures of 800°C (Example 1), 900°C (Example 2), and 1000°C (Example 3) for 1 hour in a dry atmosphere (reducing atmosphere) of a mixed gas of H2 (5%) and N2 (95%). The comparative example sample is an untreated alloy member 11 that has not undergone the heat treatment process of this embodiment. Each sample measures 8mm square and 0.3mm thick.

[0050] Table 1 shows the ICP analysis results for samples from Examples 1, 2, and 3 that underwent a heat treatment process, and for an untreated comparative example sample that did not undergo a heat treatment process. The results of an evaluation test simulating the operation of a solid oxide fuel cell are also shown. This evaluation test involved exposing each sample to a 900°C, hydrogen / water vapor atmosphere for 36 and 82 hours, simulating the environment of the alloy member 11 on the fuel electrode 32 side during solid oxide fuel cell operation. In other words, it was conducted to estimate how the phosphorus concentration in the alloy member 11 changes during solid oxide fuel cell operation. As can be seen from the results in Table 1, in the case of samples from Examples 1, 2, and 3, the phosphorus concentration did not decrease during exposure to an environment simulating the atmosphere on the fuel electrode 32 side during solid oxide fuel cell operation. This is because the phosphorus concentration did not decrease during the heat treatment process. An oxide film 11a as described above is formed on the surface of the alloy member 11. It is believed that by significantly reducing the phosphorus concentration on the surface of the alloy member 11, phosphorus diffusion occurred from the inside to the surface of the alloy member 11 at a slow diffusion rate during the operation of the solid oxide fuel cell, but there was almost no volatilization of phosphorus from the surface of the alloy member 11. Therefore, it can be said that when using an alloy member 11 that has undergone the same heat treatment process as the sample in the example, the fuel electrode 32 will hardly be poisoned with phosphorus. In contrast, in the case of the comparative example sample, when exposed to an environment simulating the atmosphere on the side of the fuel electrode 32 during the operation of a solid oxide fuel cell, the phosphorus concentration decreased significantly during that time. In other words, when using an alloy member 11 similar to the sample in the comparative example, the fuel electrode 32 may be poisoned with phosphorus.

[0051] [Table 1]

[0052] [Verification Result 2] Next, we will explain the results of our verification of whether the surface condition of the alloy member 11 changed as a result of the heat treatment process of this embodiment. In this example, stainless steel samples (8 mm square, 0.3 mm thick) were prepared by heat-treating them at 800°C to 1000°C in a dry atmosphere (reducing atmosphere) of a mixed gas of H2 (5%) and N2 (95%). In addition, untreated stainless steel samples (8 mm square, 0.3 mm thick) and stainless steel samples (8 mm square, 0.3 mm thick) that were heat-treated at 800°C to 1000°C in air were prepared. The surface resistance of each sample was then measured at room temperature using a tester.

[0053] The surface resistance of the sample in the example was 0Ω as measured by the tester. Similarly, the surface resistance of the untreated sample was also 0Ω as measured by the tester. The sample that underwent heat treatment in air showed "OL" as measured by the tester, indicating high resistance. Thus, as with the sample in the example, when heat treatment is performed in a reducing atmosphere as in the heat treatment process of this embodiment, the electrical resistance of the oxide film 11a formed on the surface of the alloy member 11 is low.

[0054] [Verification Result 3] Next, the measurement results of the resistance values ​​of a sample in which a protective film 12 was formed on the surface of the alloy member 11 after the heat treatment process of this embodiment (Example) and a sample in which a protective film 12 was formed on the surface of an untreated alloy member 11 that had not undergone the heat treatment process (Comparative Example) are shown.

[0055] In the example, the sample was subjected to a heat treatment process at 800°C in a dry atmosphere (reducing atmosphere) of a mixed gas of H2 (5%) and N2 (95%), after which a protective film 12 was obtained by dip coating with Co2MnO4 as a protective film forming material and firing in the atmosphere at 1000°C (protective film formation process). In the comparative example, the sample was subjected to a dip coating with Co2MnO4 as a protective film forming material on an untreated alloy member 11 and firing in the atmosphere at 1000°C to obtain a protective film 12. The resistance values ​​between the alloy member 11 and the protective film 12, including the interface between the alloy member 11 and the protective film 12, were measured at 600°C, 650°C, 700°C, 750°C, and 800°C, simulating the operating environment of a solid oxide fuel cell.

[0056] As shown in Table 2 below, the sample of the example had low resistance, similar to the sample of the comparative example. In other words, even when a protective film 12 is formed on the surface of the alloy member 11 after the heat treatment process of this embodiment, it was found that the resistance value between the alloy member 11 and the protective film 12, including the interface between the alloy member 11 and the protective film 12, remains low. Therefore, it can be said that the electrical resistance of the oxide film 11a formed on the surface of the alloy member 11 after the heat treatment process of this embodiment is low.

[0057] [Table 2]

[0058] Next, the properties of the oxide film 11a formed on the surface of the alloy member 11 will be described with reference to Figures 5 to 10. Figures 5, 7, and 9 are SEM images showing cross-sections of the alloy member 11 when the heat treatment process was carried out at 800°C, 900°C, and 1000°C, respectively. Figures 6, 8, and 10 are the results of elemental analysis in the thickness direction of the alloy member 11 by EPMA when the heat treatment process was carried out at 800°C, 900°C, and 1000°C, respectively.

[0059] As shown in Figure 5, an oxide film 11a with an average thickness of 0.3 μm is formed on the surface of the alloy member 11 that has undergone a heat treatment process at 800°C. Elemental analysis results in Figure 6 show peaks indicating the presence of high concentrations of oxygen (O) and chromium (Cr) in the same depth region, indicating that the oxide film 11a is a chromium oxide. No characteristic distribution is observed for manganese (Mn).

[0060] As shown in Figure 7, an oxide film 11a with an average thickness of 0.5 μm is formed on the surface of the alloy member 11 that has undergone a heat treatment process at 900°C. Elemental analysis results in Figure 8 show peaks indicating the presence of high concentrations of oxygen (O) and chromium (Cr) in the same depth region, indicating that the oxide film 11a is a chromium oxide. A small amount of manganese (Mn) is also present in the same depth region. This is thought to be due to the diffusion of manganese that was present in the alloy member 11.

[0061] As shown in Figure 9, an oxide film 11a with an average thickness of 0.7 μm is formed on the surface of the alloy member 11 that has undergone a heat treatment process at 1000°C. Elemental analysis results in Figure 10 show peaks indicating the presence of high concentrations of oxygen (O) and chromium (Cr) in the same depth region, indicating that the oxide film 11a is a chromium oxide. Manganese (Mn) is also present in the same depth region.

[0062] As described above, the heat treatment process forms an oxide film 11a with an average thickness of 0.3 μm to 0.7 μm on the surface of the alloy member 11. Therefore, even if the alloy member 11 is joined to, for example, the fuel electrode of a solid oxide fuel cell and placed in that environment, the release of phosphorus from the alloy member 11 is suppressed. In other words, other members joined to the alloy member 11 are not poisoned due to the presence of phosphorus.

[0063] Figure 11 shows the configuration of energy system Z and electrochemical apparatus Y. The energy system Z includes an electrochemical device Y and a heat exchanger 53 which serves as a waste heat utilization unit for reusing the heat discharged from the electrochemical device Y. The electrochemical apparatus Y comprises at least an electrochemical module M and a reformer 34, which acts as a fuel converter through which a gas containing reducing components flows to the electrochemical module M. In addition, the electrochemical apparatus Y comprises the electrochemical module M and an inverter 38, which acts as a power converter for extracting power from the electrochemical module M. Furthermore, the fuel supply module of the electrochemical apparatus Y consists of a desulfurizer 20, a vaporizer 33, and a reformer 34, etc., and supplies fuel gas containing reducing components to the electrochemical module M.

[0064] In addition, the electrochemical apparatus Y includes a reformed water tank 21, a blower 35, a combustion unit 36, a control unit 39, a storage container 40, a booster pump 41, a reformed water pump 43, and the like.

[0065] The vaporizer 33, reformer 34, electrochemical module M, and combustion section 36 are housed in a storage container 40. The reformer 34 uses the heat of combustion generated by the combustion of reaction exhaust gas in the combustion section 36 to reform the raw fuel.

[0066] The raw fuel is supplied to the desulfurizer 20 through the raw fuel supply line 42 by the operation of the booster pump 41. The reformed water from the reformed water tank 21 is supplied to the vaporizer 33 through the reformed water supply line 44 by the operation of the reformed water pump 43. The raw fuel supply line 42 then merges with the reformed water supply line 44 downstream of the desulfurizer 20, and the reformed water and raw fuel, which have merged outside the storage container 40, are supplied to the vaporizer 33 located inside the storage container 40.

[0067] The desulfurizer 20 removes (desulfurizes) sulfur compounds contained in hydrocarbon raw fuels such as city gas. When sulfur compounds are present in the raw fuel, the desulfurizer 20 can suppress the impact of sulfur compounds on the reformer 34 or the single cell 3 that constitutes the electrochemical module M. The vaporizer 33 generates steam from reformed water supplied from the reformed water tank 21. The raw fuel containing the steam generated in the vaporizer 33 is supplied to the reformer 34 through the steam-containing raw fuel supply passage 45.

[0068] The reformer 34 uses the steam generated in the vaporizer 33 to steam reform the raw fuel that has been desulfurized in the desulfurizer 20, thereby producing a reformed gas containing hydrogen. The reformed gas produced in the reformer 34 is supplied to the gas manifold 17 of the electrochemical module M through the reformed gas supply line 46.

[0069] The individual cells 3 constituting the electrochemical module M are arranged in parallel, electrically connected to each other, and one end (lower end) of each individual cell 3 is fixed to the gas manifold 17. The reformed gas supplied to the gas manifold 17 is distributed to the multiple individual cells 3. The individual cells 3 constituting the electrochemical module M generate electricity by performing an electrochemical reaction using the reformed gas supplied from the reformer 34 and the air supplied from the blower 35. The reaction exhaust gas, which contains residual hydrogen gas not used in the reaction, is discharged from the upper end of the electrochemical module M to the combustion section 36. The combustion section 36 mixes the reaction exhaust gas discharged from the electrochemical module M with air and burns the combustible components in the reaction exhaust gas.

[0070] The reaction exhaust gas burned in the combustion section 36 becomes combustion exhaust gas and is discharged to the outside of the storage container 40 from the combustion exhaust gas outlet 50. A combustion catalyst section 51 (for example, a platinum-based catalyst) is placed at the combustion exhaust gas outlet 50 to burn and remove reducing components such as carbon monoxide and hydrogen contained in the combustion exhaust gas. The combustion exhaust gas discharged from the combustion exhaust gas outlet 50 is sent to the heat exchanger 53 via the combustion exhaust gas discharge passage 52.

[0071] The heat exchanger 53 exchanges heat between the combustion exhaust gas generated by combustion in the combustion section 36 and the supplied chilled water to produce hot water. In other words, the heat exchanger 53 operates as a waste heat utilization unit that reuses the heat discharged from the electrochemical apparatus Y.

[0072] Alternatively, instead of the waste heat utilization section, a reaction exhaust gas utilization section that utilizes the reaction exhaust gas discharged (without being burned) from the electrochemical module M may be provided. The reaction exhaust gas contains residual hydrogen gas that was not used in the reaction in the single cell 3 constituting the electrochemical module M. In the reaction exhaust gas utilization section, the residual hydrogen gas is utilized for heat utilization by combustion or power generation by a fuel cell or the like, thereby enabling effective utilization of energy.

[0073] The inverter 38 adjusts the output power of the electrochemical module M to have the same voltage and the same frequency as the power received from the commercial power system (not shown). The control unit 39 controls the operation of the electrochemical device Y and the energy system Z.

[0074] <Alternative Embodiment> <1> In the above embodiment, the structural example of the single cell 3 as the electrochemical element has been described, but the structure of the single cell 3 can be appropriately changed.

[0075] <2> In the above embodiment, an example of using the electrochemical module M in a solid oxide fuel cell has been described, but the electrochemical module M can also be used in a solid oxide electrolysis cell, an oxygen sensor using a solid oxide, or the like.

[0076] A case of realizing a solid oxide electrolysis cell that causes an electrolysis reaction in the single cell 3 constituting the electrochemical module M will be described. In the energy system Z shown in FIG. 12, when the single cell 3 constituting the electrochemical module M operates as an electrolysis cell, a gas containing water vapor or carbon dioxide is circulated through the fuel electrode 32 as the electrode layer, and a voltage is applied between the fuel electrode 32 and the air electrode 31 as the counter electrode layer. Then, at the fuel electrode 32, electrons e - react with water molecules H2O and carbon dioxide molecules CO2 to form hydrogen molecules H2 and carbon monoxide CO and oxygen ions O 2- becomes. The oxygen ions O 2- move through the electrolyte layer 30 to the air electrode 31. At the air electrode 31, the oxygen ions O 2-The electrons are released to form oxygen molecules (O2). Through the above reaction, water molecules (H2O) are electrolyzed into hydrogen (H2) and oxygen (O2), and if a gas containing carbon dioxide molecules (CO2) is passed through, it is electrolyzed into carbon monoxide (CO) and oxygen (O2).

[0077] When a gas containing water vapor and carbon dioxide molecules (CO2) is being circulated, a fuel converter 91 can be provided to synthesize various compounds such as hydrocarbons from hydrogen and carbon monoxide produced by the electrochemical module M through electrolysis. A fuel supply unit (not shown) can circulate the hydrocarbons produced by this fuel converter 91 to the electrochemical module M, or it can be taken out of this system / device and used separately as fuel or chemical raw material.

[0078] Thus, in the energy system Z shown in Figure 12, the electrochemical device Y comprises at least an electrochemical module M and a fuel converter 91 that converts the gas containing reducing components generated by the electrochemical module. Furthermore, the electrochemical device Y comprises at least an electrochemical module M and a power converter 93 that supplies electricity to the electrochemical module M.

[0079] The electrochemical module M comprises multiple single cells 3 as electrochemical elements, and gas manifolds 17 and 171. The multiple single cells 3 are arranged in parallel and electrically connected to each other. One end (lower end) of each single cell 3 is fixed to gas manifold 17, and the other end (upper end) is fixed to gas manifold 171. Gas manifold 17 at one end (lower end) of each single cell 3 receives a supply of water vapor and carbon dioxide. Hydrogen and carbon monoxide produced in the single cell 3 by the above-mentioned reaction are collected by gas manifold 171, which is connected to the other end (upper end) of each single cell 3.

[0080] By configuring the heat exchanger 90 in Figure 12 to operate as a waste heat utilization unit that exchanges heat between the reaction heat generated by the reaction occurring in the fuel converter 91 and water to vaporize it, and by configuring the heat exchanger 92 in Figure 12 to operate as a waste heat utilization unit that exchanges heat between the waste heat generated by the single cell 3 and water vapor and carbon dioxide to preheat it, energy efficiency can be increased. Furthermore, the power converter 93 supplies power to the single cell 3. As a result, the single cell 3 functions as an electrolytic cell, as described above.

[0081] <3> In the above embodiment, the protective film 12 may be formed on both the surface of the alloy member 11 after the heat treatment process, specifically on the side that is joined to the air electrode 31 of the single cell 3 and the surface that is joined to the fuel electrode 32.

[0082] <4> The configurations disclosed in the above embodiments (including other embodiments, the same applies hereinafter) can be applied in combination with configurations disclosed in other embodiments, provided that no inconsistencies arise. Furthermore, the embodiments disclosed herein are illustrative, and the embodiments of the present invention are not limited thereto and can be modified as appropriate without departing from the purpose of the present invention. [Industrial applicability]

[0083] The present invention can be used for alloy members capable of suppressing phosphorus poisoning of the member being joined, electrochemical modules, solid oxide fuel cells, solid oxide electrolytic cells, electrochemical devices, energy systems, and methods for manufacturing alloy members. [Explanation of symbols]

[0084] 3: Single cell 4: Bonding material 11: Alloy components 11a: Oxide film 12:Protective film 30: Electrolyte layer 38: Inverter (power converter) 91: Fuel Converter 93: Power Converter M: Electrochemical Module Y: Electrochemical apparatus Z: Energy System

Claims

1. An alloy member comprising Fe, Cr, and phosphorus, wherein an oxide film is formed on the surface of the portion joined to another member, the average thickness of the oxide film is 0.3 μm or more and 0.7 μm or less, and the phosphorus concentration decreases from the interior toward the surface in the portion where the oxide film is formed.

2. The alloy member according to claim 1, wherein the oxide film comprises an oxide of Cr.

3. An electrochemical module comprising an alloy member according to claim 1 or 2 and an electrochemical element having a single cell in which an electrolyte layer is sandwiched between an electrode layer and a counter electrode layer, joined together.

4. The electrochemical module according to claim 3, comprising a plurality of the electrochemical elements, wherein the plurality of electrochemical elements are electrically connected to each other by the alloy member.

5. The electrochemical module according to claim 3 or 4, further comprising a protective film made of a metal oxide containing at least one of Co, Mn, Cu, and Ni on the oxide film of the alloy member on the side joined to the electrochemical element.

6. A solid oxide fuel cell comprising an electrochemical module according to any one of claims 3 to 5, wherein a power generation reaction is generated in the single cell.

7. A solid oxide type electrolytic cell comprising an electrochemical module according to any one of claims 3 to 5, wherein an electrolytic reaction is generated in the single cell.

8. An electrochemical apparatus comprising at least an electrochemical module according to any one of claims 3 to 5, and a fuel converter through which a gas containing a reducing component flows to the electrochemical module, or a fuel converter that converts a gas containing a reducing component generated by the electrochemical module.

9. An electrochemical apparatus comprising at least an electrochemical module according to any one of claims 3 to 5, and a power converter for extracting power from the electrochemical module or for supplying power to the electrochemical module.

10. An energy system comprising an electrochemical apparatus according to claim 8 or 9, and a waste heat utilization unit for reusing heat discharged from the electrochemical apparatus.

11. A method for manufacturing an alloy member according to claim 1 or 2, which is joined to other members, A method for manufacturing an alloy member, comprising a heat treatment step to reduce the phosphorus concentration on the surface of the alloy member in the portion of the alloy member to be joined with the other member, by heat-treating the alloy member in a reducing atmosphere at a temperature range of 800°C to 1000°C before joining the alloy member to the other member using a bonding agent, thereby forming an oxide film with an average thickness of 0.3 μm to 0.7 μm on the surface of the alloy member in the portion of the alloy member to be joined with the other member, and reducing the phosphorus concentration on the surface in the portion of the alloy member in which the oxide film has been formed.

Images