Porous metal plate and method for producing same

Abstract

This porous metal plate is composed of a connected structure of alloy particle parts including Cr and Fe, and has a porosity of 50-80%. The average value of the maximum diameter measured from the general shape of the alloy particle parts is preferably 1-20 μm. This method for producing a porous metal plate comprises, in the stated order, a molded body production step for subjecting a powder comprising a composition containing a pore-forming material and alloy particles including Cr and Fe to pressure molding to produce a thin-walled molded body, and a heat treatment step for subjecting the obtained thin-walled molded body to a heat treatment at a temperature at which the pore-forming material is thermally decomposed and the alloy particles are sintered.

Description

Porous metal plate and its manufacturing method

[0001] The present invention relates to a porous metal plate to be bonded to an anode of an electrochemical cell having an air cathode, a solid electrolyte layer, and an anode in this order, and to a method for manufacturing the same.

[0002] Known solid oxide electrochemical cells include solid oxide fuel cells and solid oxide electrolysis cells. Of these, solid oxide fuel cells include a three-layer power generation cell consisting of a solid electrolyte layer containing an oxygen-ion conductive solid oxide and a fuel electrode and a cathode arranged opposite each other on either side of the electrolyte layer. A fuel gas such as hydrogen is supplied to the fuel electrode, and an oxidizing gas such as air is supplied to the cathode, generating DC power based on an electrochemical reaction.

[0003] Among such fuel cells, metal-supported cell type solid oxide fuel cells have recently become known, in which a power generating cell is supported via an anode by a gas-permeable and electrically conductive metal support portion.

[0004] Patent Document 1 discloses a support structure for a metal support cell, which includes a metal support cell in which an electrolyte layer is fixed to a metal support layer via an electrode layer, and a metal frame surrounding the periphery of the metal support cell, wherein the electrolyte layer has compressive residual stress along the surface direction, the metal frame is sinter-bonded to the electrolyte layer, and the linear expansion coefficient of the metal frame is approximately the same as the linear expansion coefficient of the metal support layer.

[0005] Patent Document 2 discloses a metal support having a plurality of through holes that penetrate from the front side to the back side, the through holes being formed in a plate shape as a whole and having an electrode layer provided thereon, the through holes being inclined through holes whose central axes are inclined with respect to the thickness direction. Furthermore, as a method for manufacturing such a metal support, a method is disclosed in which a plurality of through holes that penetrate from the front side to the back side are formed in a metal material plate by laser processing, punching processing, etching processing, or a combination of these.

[0006] Patent Document 3 discloses an electrochemical cell having a metal support, a cell unit including a solid electrolyte layer having oxygen ion conductivity, a first electrode laminated on one side of the solid electrolyte layer, and a second electrode laminated on the other side of the solid electrolyte layer, and a bonding layer bonding the metal support and the first electrode of the cell unit, wherein the bonding layer includes at least one of an alloy containing a metal support constituent element that is at least one metal element constituting the metal support and a first electrode constituent element that is at least one metal element constituting the first electrode, and a metal oxide containing the metal support constituent element and the first electrode constituent element.

[0007] Also, for example, known methods for forming a fuel electrode on a metal support include a baking method (e.g., a wet method in which baking treatment is applied at about 1100°C), a spray coating method (thermal spraying, aerosol deposition, aerosol gas deposition, powder jet deposition, particle jet deposition, cold spray, etc.), a PVD method (sputtering, pulsed laser deposition, etc.), a CVD method, etc.

[0008] JP 2020-21646 A JP 2021-163655 A JP 2023-3622 A

[0009] When a load body made using a breathable metal plate as a manufacturing material for a metal-supported cell type solid oxide electrochemical cell is heat-treated (co-sintered), it may shrink. Therefore, from the viewpoint of the power generation efficiency and structural stability of the resulting metal-supported cell type solid oxide fuel cell, it is preferable to form a breathable metal support part with a porosity of 25% or more.

[0010] An object of the present invention is to provide a porous metal plate used to form an air-permeable metal support part that constitutes a metal-supported cell-type solid oxide electrochemical cell, typified by a metal-supported cell-type solid oxide fuel cell and a metal-supported cell-type solid oxide electrolysis cell, and which can form an air-permeable metal support part that provides a metal-supported cell-type solid oxide electrochemical cell having a porosity of about 25 to 50% and excellent structural stability even if there is some shrinkage when a slurry for forming an anode and a slurry for forming an electrolyte layer are sequentially applied to the surface of the porous metal plate and then subjected to co-sintering, and a method for producing the same.

[0011] The present inventors have found that the above-mentioned problems can be solved by a porous metal plate obtained by utilizing powder metallurgy technology, pressure-molding a composition containing alloy particles containing Cr and Fe and a pore-forming agent, and sintering the resulting thin-walled molded body, the porous metal plate being made of a connected structure of alloy particles and having a porosity of 50 to 80%.

[0012] The present invention provides the following: (1) A porous metal plate comprising a connected structure of alloy particle portions containing Cr and Fe, and having a porosity of 50 to 80%. (2) The porous metal plate according to (1) above, wherein the average maximum diameter of the alloy particle portions, measured from the general shape of the alloy particle portions, is 1 to 20 μm. (3) The porous metal plate according to (1) or (2) above, which is to be bonded to the anode of an electrochemical cell comprising an air electrode, a solid electrolyte layer, and an anode in this order. (4) A method for producing the porous metal plate according to any one of (1) to (3) above, comprising, in order, a compact-forming step of producing a thin-walled compact by pressure-molding a powder made of a composition containing particles made of an alloy containing Cr and Fe and a pore-forming agent, and a heat-treating step of heat-treating the thin-walled compact at a temperature at which the pore-forming agent thermally decomposes and the alloy particles sinter. (5) The method for producing a porous metal plate according to (4) above, wherein the alloy particles have an average particle size of 1 to 20 μm.

[0013] The porous metal plate of the present invention is suitable as a material for manufacturing the gas-permeable metal support portion of a metal-supported cell type solid oxide electrochemical cell (including half cells). When manufacturing these electrochemical cell products using a porous metal plate, a method may be employed in which an anode-forming slurry containing stabilized zirconia, an electrolyte layer-forming slurry, etc. are sequentially applied to the surface of the porous metal plate, followed by co-sintering. During this co-sintering, the porous metal plate may shrink somewhat along with the formed anode and electrolyte layer. However, the resulting gas-permeable metal support portion has a porosity of approximately 25 to 50%, providing excellent structural stability. The interior of the gas-permeable metal support portion does not have a single through-hole flow path, but rather the voids formed between the alloy particles form multiple interconnecting pores, providing excellent gas diffusivity. This structure is expected to enable the suitable manufacture of metal-supported cell type solid oxide electrochemical cell products with excellent electrochemical cell performance. In this specification, "stabilized zirconia" refers to zirconia in which a rare earth element oxide is solid-solved, and also includes partially stabilized zirconia.

[0014] 1 is a schematic cross-sectional view showing an example of a metal-supported cell type solid oxide electrochemical cell obtained using the porous metal plate of the present invention. It is a schematic diagram showing an example of a connection structure of a plurality of alloy particle portions constituting the porous metal plate of the present invention, and is an explanatory diagram showing a method for measuring the maximum diameter of each alloy particle portion. It is an SEM image of the surface of the porous metal plate R1 obtained in Example 1. It is an enlarged image of FIG. 3. It is an SEM image of the surface of the porous metal plate R2 obtained in Example 2. It is an enlarged image of FIG. 5. It is an SEM image of the surface of the porous metal plate R3 obtained in Example 3. It is an enlarged image of FIG. 7. It is an SEM image of the surface of the porous metal plate R4 obtained in Example 4. It is an enlarged image of FIG. 9. It is an SEM image of the surface of the porous metal plate R5 obtained in Example 5. It is an enlarged image of FIG. 11. It is an SEM image of the surface of the porous metal plate R6 obtained in Example 6. It is an enlarged image of FIG. 13. It is an SEM image of the surface (rear surface) of the breathable metal support portion constituting the metal-supported cell type solid oxide electrochemical cell obtained using the porous metal plate R2 in a reference example. It is an enlarged image of FIG. 15.

[0015] The porous metal plate of the present invention is preferably an article obtained by powder metallurgy using alloy particles containing Cr and Fe as one of the manufacturing raw materials, and is composed of a connected structure of alloy particles with a porosity of 50 to 80%. The porous metal plate is preferably a manufacturing material for forming, by co-sintering, a gas-permeable metal support part to be disposed on the anode side of a solid oxide electrochemical cell half-cell (not shown) comprising an anode and a solid electrolyte layer, or a manufacturing material for forming, by co-sintering, a gas-permeable metal support part 2 to be disposed on the anode side of a metal-supported cell type solid oxide electrochemical cell 1 (see FIG. 1 ) comprising, in order, an anode 4, a solid electrolyte layer 6, and an air electrode 8.

[0016] The alloy particle portion constituting the porous metal plate of the present invention is made of an alloy containing Cr and Fe, and this alloy may further contain Mn, Ni, Ti, Cu, Zr, Si, Al, Mo, etc. in addition to Cr and Fe. The alloy is preferably ferritic stainless steel (SUS 430, etc.). Various stabilized zirconias are widely used in electrolyte layers of solid oxide electrochemical cells, and among stainless steels, the thermal expansion coefficient of ferritic stainless steel is close to that of stabilized zirconia. Therefore, when co-sintering is performed to bond an anode and an electrolyte layer containing stabilized zirconia to the porous metal plate, problems such as thermal shock are suppressed.

[0017] The shape of the porous metal plate of the present invention is not particularly limited, and may be either a flat plate or a curved plate. From the viewpoints of productivity of the metal-supported cell type solid oxide electrochemical cell and structural stability of the formed metal-supported cell type solid oxide electrochemical cell, the lower limit of the thickness is usually 0.1 mm and the upper limit is usually 1.5 mm, preferably 1.2 mm.

[0018] The porous metal plate of the present invention preferably has a plurality of nonlinear interconnecting holes extending from one side to the other side, making it breathable. Its surface is shown, for example, in Figures 3 to 15. The enlarged views of typical examples shown in Figures 4, 6, 8, 10, 12, and 14 show that not all alloy particle portions are the same size, but alloy particle portions of various sizes form a connected structure, and the alloy particle portions are connected together, typically with a maximum diameter of 1 μm or more measured from their overall shape. The present invention is not limited to this embodiment, and all alloy particle portions may be the same size. Furthermore, the connection between adjacent alloy particle portions may be either regular or irregular, but as can be seen from these typical examples, it is usually irregular. As described above, when the alloy particle portions are small in size, the connection between adjacent alloy particle portions is irregular, and the thickness is 0.1 mm or more, the number of alloy particle portions in the thickness direction is large, and the porous metal plate of the present invention can have more suitable voids between adjacent alloy particle portions. The porosity of the porous metal plate of the present invention is 50 to 80%, preferably 60 to 80%, and more preferably 70 to 80%, because when a slurry for forming an anode and a slurry for forming an electrolyte layer are applied to the surface of the porous metal plate in this order and then co-sintered, a gas-permeable metal support part having suitable pores can be formed, and an integrated body consisting of the gas-permeable metal support part, the anode, and the solid electrolyte layer can be efficiently formed. Note that this porosity can be measured in accordance with JIS Z 2501.

[0019] In the porous metal plate of the present invention, for example, when the thickness is 0.1 mm or more, the above-mentioned porosity can be ensured if the average value of the maximum diameter of the alloy particle portions measured from the outlines of at least 20 alloy particle portions is preferably 1 to 20 μm, more preferably 1 to 10 μm.

[0020] 2 is an explanatory diagram showing a method for measuring the maximum diameter of a plurality of connected alloy particle portions 10. The method involves photographing the surface or interior of a porous metal plate with an electron microscope, drawing an outline of each alloy particle portion from the obtained image, and measuring its maximum diameter. FIG. 2 shows that the maximum diameters of four alloy particle portions 10 are r1, r2, r3, and r4, respectively. Using this measurement method, for example, the maximum diameters of 20 or more alloy particle portions are measured, and then the average value is calculated. If the average value is within the above-mentioned preferred average value range, the resulting product will have strength suitable for manufacturing a metal-supported solid oxide electrochemical cell.

[0021] The flexural strength of the porous metal plate of the present invention is preferably 1.5 to 15 MPa, more preferably 2 to 5 MPa, when measured in accordance with JIS Z 2511. Since the flexural strength is within this range, there are no problems such as deformation or breakage even when, for example, screen printing is used as a method for applying an anode-forming slurry to the surface of the porous metal plate when producing a metal-supported cell-type solid oxide electrochemical cell.

[0022] The method for producing a porous metal plate of the present invention sequentially comprises a compact production step of press-molding a powder of a composition containing particles (alloy particles) of an alloy containing Cr and Fe and a pore-forming agent to produce a thin-walled compact, and a heat treatment step of heat-treating the obtained thin-walled compact at a temperature at which the pore-forming agent is thermally decomposed and the alloy particles are sintered. The method for producing a porous metal plate of the present invention can include other steps (described below) after the heat treatment step, as necessary.

[0023] The compact preparation step is a step of preparing a thin-walled compact to be used in the heat treatment step. In this compact preparation step, the composition constituting the powder used for pressure molding (hereinafter referred to as the "solid component composition") contains alloy particles and a pore-forming material, and may also contain other components (described below) as necessary.

[0024] The alloy particles contained in the solid component composition may be made of any of the alloys exemplified as the constituent materials of the alloy particle portion, with particles made of ferritic stainless steel being preferred. A single alloy particle may be made of only one type of alloy, or may be made of two or more types of alloys. The solid component composition may also contain a combination of alloy particles made of one material and alloy particles made of another material. From the viewpoint of the porosity and strength of the resulting porous metal plate, the average particle size of the alloy particles is preferably 1 to 20 μm, more preferably 1 to 10 μm. The average particle size is determined by the D measured by a laser diffraction scattering method. ５０ (median diameter).

[0025] The pore-forming material contained in the solid component composition is not particularly limited, and any known pore-forming material can be used that can decompose to form voids when a molded body containing sinterable inorganic particles and a pore-forming material is heated to a temperature at which the inorganic particles sinter. In the present invention, since the heating temperature used in the heat treatment step is usually 350°C or higher, a material that decomposes at this temperature is preferred, specifically solid or hollow resin particles made of acrylic resin, phenolic resin, styrene-based resin, etc. The average particle size of the pore-forming material is preferably 1 to 50 μm from the viewpoint of the porosity and strength of the resulting porous metal plate.

[0026] The content of the pore-forming material in the solid component composition is preferably 10 to 40 mass %, more preferably 15 to 35 mass %, assuming that the total of the alloy particles and the pore-forming material is 100 mass %.

[0027] As described above, the solid component composition may contain other components. For example, an adhesive may be included to efficiently produce a thin-walled molded body with excellent shape stability by adhering the alloy particles and the pore-forming material. This adhesive preferably contains a polymer, and more preferably a water-soluble polymer. Examples of water-soluble polymers include polyvinyl alcohol, polyvinylpyrrolidone, vinyl acetate-acrylamide copolymer, polyacrylamide derivatives, and cellulose derivatives (hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, etc.). The adhesive may contain one or more types of polymers.

[0028] In the present invention, the solid component composition preferably contains an adhesive. In this case, from the viewpoint of formability of the thin-walled molded body, the contents of the alloy particles, the pore-forming material, and the adhesive are preferably 55 to 90 mass%, 9 to 40 mass%, and 1 to 5 mass%, respectively, and more preferably 60 to 75 mass%, 23 to 35 mass%, and 1.9 to 4.8 mass%, when the total of these is taken as 100 mass%.

[0029] Here, a method for preparing a solid component composition containing a water-soluble polymer as an adhesive and a method for producing a thin-walled molded body, which are preferred embodiments of the present invention, are described. Alloy particles, a pore-forming material, and an aqueous solution of the water-soluble polymer are mixed so that the alloy particles, the pore-forming material, and the water-soluble polymer (adhesive) are contained in the preferred proportions described above, and the resulting aqueous mixture is thoroughly dried. The resulting dried product is then pulverized and sieved to recover a powder (solid component composition) of a predetermined size (particle size). This powder is then placed in a mold and subjected to pressure molding, roll-rolling, or other known molding methods to obtain a thin-walled molded body. Using a thin-walled molded body containing a powder with small particle size variation in the heat treatment process allows for efficient production of a porous metal plate with small void variation.

[0030] The thickness of the thin-walled molded body is not particularly limited, but is preferably 0.1 to 1.5 mm.

[0031] Next, the heat treatment step is a step of performing heat treatment at a temperature at which the pore-forming material contained in the thin-walled molded body is thermally decomposed and the alloy particles are sintered. If the thin-walled molded body contains a pore-forming material made of resin particles and is made of a powder with small particle size variation, when the thin-walled molded body is heated to the sintering temperature of the alloy particles, the alloy particles are sintered to form a connected structure of the alloy particles, and the pore-forming material is decomposed, resulting in a porous metal plate with uniformly distributed pores.

[0032] The sintering temperature in the heat treatment step is set appropriately depending on the type of alloy contained in the thin-walled compact, but is usually 850°C or higher. When the alloy particles contain SUS 430, the sintering temperature is preferably 850°C to 1100°C, more preferably 900°C to 1050°C. This heat treatment is preferably carried out in a reducing atmosphere or under reduced pressure. Furthermore, when the thin-walled compact is heat-treated, it may be carried out under pressurized conditions. The heat treatment time is set appropriately depending on the size of the thin-walled compact, and is not particularly limited.

[0033] As described above, the method for manufacturing a porous metal plate of the present invention may include other steps after the heat treatment step. For example, the porous metal plate may be subjected to a surface treatment (such as plating).

[0034] When a metal-supported cell type solid oxide electrochemical cell product is manufactured using the porous metal plate of the present invention, the following method is preferably applied: (1) a fuel electrode-forming slurry is applied (by screen printing or the like) to the surface of the porous metal plate and dried to form a fuel electrode film, and then an electrolyte layer-forming slurry is applied to the surface of the fuel electrode film and dried to form a film made of a solid electrolyte layer-forming material, and then this stack is co-sintered; or (2) a fuel electrode film prepared in advance using a fuel electrode-forming slurry or the like is placed on the surface of the porous metal plate, and then an electrolyte layer-forming slurry is applied to the surface of the fuel electrode film and dried to form a film made of a solid electrolyte layer-forming material, and then this stack is co-sintered. During this co-sintering, some shrinkage may occur in the porous metal plate along with the formed anode and electrolyte layer, but because the porous metal plate is made of a specific alloy, the porosity of the formed permeable metal support portion can be set to about 25 to 50%, making it possible to efficiently produce a metal-supported cell type solid oxide electrochemical cell product with excellent structural stability, i.e., a stable layer structure with excellent mechanical strength. The anode-forming slurry preferably contains stabilized zirconia, nickel oxide, etc.

[0035] The present invention will be explained in more detail below by way of examples, but the present invention is not limited to these examples.

[0036] 1. Production and Evaluation of Porous Metal Plates Porous metal plates were produced using the following raw materials.

[0037] 1-1. Alloy particles (1) SUS 430 powder (alloy particles P1) Average particle size: 10 μm (2) SUS 430 powder (alloy particles P2) Average particle size: 17 μm (3) SUS XM27 powder (alloy particles P3) Average particle size: 7.4 μm

[0038] 1-2. Pore-forming material: Acrylic fine particles with an average particle size of 20 μm

[0039] 1-3. Adhesive: 10% by weight aqueous solution of polyvinyl alcohol

[0040] Example 1 Alloy particles P1, a pore-forming material, and an aqueous polyvinyl alcohol solution were kneaded to produce a raw material composition having solid contents of 88 mass % of alloy particles P1, 10 mass % of pore-forming material, and 2 mass % of polyvinyl alcohol, respectively. This raw material composition was then dried, pulverized, and sieved to recover powder with particle sizes of 50 to 300 μm. Approximately 2.5 grams of this powder was then subjected to press molding (pressure: 100 MPa) to obtain a circular thin-walled compact with a thickness of approximately 1.2 mm. This thin-walled compact was then heat-treated at 920°C under reduced pressure for 1 hour to obtain a porous metal plate (hereinafter referred to as "porous metal plate R1") measuring 32 mm (diameter) x 1.192 mm (thickness).

[0041] The porosity of the obtained porous metal plate R1 was measured in accordance with JIS Z 2501 and was found to be 61.8%. In addition, the flexural strength (strength per unit thickness; the same applies hereinafter) was measured in accordance with JIS Z 2511 using a single column material testing machine "STB-1225S" (model name) manufactured by A&D Co., Ltd. and was found to be 4.1 MPa. These results are shown in Table 1.

[0042] Furthermore, the surface of the porous metal plate R1 was observed with a scanning electron microscope, and Figure 3 and its enlarged image, Figure 4, were obtained. These figures show that the porous metal plate R1 is a connected structure of alloy particles. The maximum diameters of 20 alloy particles were measured from a total of four images, including Figure 4, according to Figure 2, and the average value was calculated to be 7.28 μm (see Table 1). The minimum and maximum values ​​were 1.95 μm and 27.15 μm, respectively.

[0043] Example 2 Alloy particles P1, a pore-forming material, and an aqueous polyvinyl alcohol solution were mixed to produce a raw material composition in which the solid contents of the alloy particles P1, the pore-forming material, and the polyvinyl alcohol were 68 mass%, 30 mass%, and 2 mass%, respectively. The same procedure as in Example 1 was then carried out to produce a thin-walled molded body. The resulting thin-walled molded body was heat-treated at 920 ° C. under reduced pressure for 1 hour to obtain a 28 mm (diameter) × 1.173 mm (thickness) porous metal plate (hereinafter referred to as "porous metal plate R2"). The porosity and flexural strength of the porous metal plate R2 were then measured, and were found to be 71.0% and 2.2 MPa, respectively.

[0044] Furthermore, when the surface of the porous metal plate R2 was observed with a scanning electron microscope, Figure 5 and its enlarged image, Figure 6, were obtained. These figures show that the porous metal plate R2 is a connected structure of alloy particles. Then, from a total of four images, including Figure 6, the maximum diameters of 20 alloy particles were measured according to Figure 2, and the average value was calculated to be 8.32 μm (see Table 1). The minimum and maximum values ​​were 1.98 μm and 27.37 μm, respectively.

[0045] Example 3 Alloy particles P1, a pore-forming material, and an aqueous polyvinyl alcohol solution were mixed to produce a raw material composition in which the solid contents of the alloy particles P1, the pore-forming material, and the polyvinyl alcohol were 88 mass%, 10 mass%, and 2 mass%, respectively. The same procedure as in Example 1 was then carried out to produce a thin-walled molded body. The resulting thin-walled molded body was heat-treated at 940 ° C. under reduced pressure for 1 hour to obtain a 31 mm (diameter) × 0.857 mm (thickness) porous metal plate (hereinafter referred to as "porous metal plate R3"). The porosity and flexural strength of the porous metal plate R3 were then measured, and were found to be 58.8% and 8.7 MPa, respectively.

[0046] Furthermore, when the surface of the porous metal plate R3 was observed with a scanning electron microscope, Figure 7 and its enlarged image, Figure 8, were obtained. These figures show that the porous metal plate R3 is a connected structure of alloy particles. The maximum diameters of 20 alloy particles were measured from a total of four images, including Figure 8, according to Figure 2, and the average value was calculated to be 8.56 μm (see Table 1). The minimum and maximum values ​​were 2.99 μm and 21.12 μm, respectively.

[0047] Example 4 Alloy particles P2, a pore-forming material, and an aqueous polyvinyl alcohol solution were mixed to produce a raw material composition in which the solid contents of the alloy particles P2, the pore-forming material, and the polyvinyl alcohol were 78 mass%, 20 mass%, and 2 mass%, respectively. The same procedure as in Example 1 was then carried out to produce a thin-walled molded body. The resulting thin-walled molded body was heat-treated at 940 ° C. under reduced pressure for 1 hour to obtain a 30 mm (diameter) × 1.115 mm (thickness) porous metal plate (hereinafter referred to as "porous metal plate R4"). The porosity and flexural strength of the porous metal plate R4 were then measured, and were found to be 68.3% and 2.9 MPa, respectively.

[0048] Furthermore, when the surface of the porous metal plate R4 was observed with a scanning electron microscope, Figure 9 and its enlarged image, Figure 10, were obtained. These figures show that the porous metal plate R4 is a connected structure of alloy particles. The maximum diameters of 20 alloy particles were measured from a total of four images, including Figure 10, according to Figure 2, and the average value was calculated to be 12.02 μm (see Table 1). The minimum and maximum values ​​were 3.05 μm and 39.31 μm, respectively.

[0049] Example 5 Alloy particles P3, a pore-forming material, and an aqueous polyvinyl alcohol solution were mixed to produce a raw material composition in which the solid contents of alloy particles P3, the pore-forming material, and the polyvinyl alcohol were 68 mass%, 30 mass%, and 2 mass%, respectively. The same procedure as in Example 1 was then carried out to produce a thin-walled molded body. The resulting thin-walled molded body was heat-treated at 940 ° C. under reduced pressure for 1 hour to obtain a 30 mm (diameter) × 1.018 mm (thickness) porous metal plate (hereinafter referred to as "porous metal plate R5"). The porosity and flexural strength of the porous metal plate R5 were then measured, and were found to be 74.5% and 2.2 MPa, respectively.

[0050] Furthermore, when the surface of the porous metal plate R5 was observed with a scanning electron microscope, Figure 11 and its enlarged image, Figure 12, were obtained. These figures show that the porous metal plate R5 is a connected structure of alloy particles. The maximum diameters of 20 alloy particles were measured from a total of four images, including Figure 12, according to Figure 2, and the average value was calculated to be 8.19 μm (see Table 1). The minimum and maximum values ​​were 1.98 μm and 27.37 μm, respectively.

[0051] Example 6 Alloy particles P1, a pore-forming material, and an aqueous polyvinyl alcohol solution were mixed to produce a raw material composition in which the solid contents of the alloy particles P1, the pore-forming material, and the polyvinyl alcohol were 88 mass%, 10 mass%, and 2 mass%, respectively. The same procedure as in Example 1 was then carried out to produce a thin-walled molded body. The resulting thin-walled molded body was heat-treated at 960 ° C. for 1 hour under reduced pressure to obtain a 30 mm (diameter) × 1.121 mm (thickness) porous metal plate (hereinafter referred to as "porous metal plate R6"). The porosity and flexural strength of the porous metal plate R6 were then measured, and were found to be 55.3% and 11.8 MPa, respectively.

[0052] Furthermore, when the surface of the porous metal plate R6 was observed with a scanning electron microscope, Figure 13 and its enlarged image, Figure 14, were obtained. These figures show that the porous metal plate R6 is a connected structure of alloy particles. The maximum diameters of 20 alloy particles were measured from a total of four images, including Figure 14, according to Figure 2, and the average value was calculated to be 8.94 μm (see Table 1). The minimum and maximum values ​​were 2.99 μm and 29.41 μm, respectively.

[0053]

[0054] As is clear from Table 1, it was found that porous metal plates with a porosity of 50 to 80% have a bending strength of 2.2 MPa or more.

[0055] 2. Production of a Metal-Supported Cell-Type Solid Oxide Electrochemical Cell Using the porous metal plate R2 obtained in Example 2, a metal-supported cell-type solid oxide electrochemical cell was produced.

[0056] Reference Example Nickel oxide powder and scandia-stabilized zirconia powder were mixed in a mass ratio of 60:40. The resulting mixed powder was mixed with dibutyl phthalate, an acrylic binder, and a mixed solvent of toluene and 2-propanol using a ball mill to prepare a slurry for forming an anode. This slurry for forming an anode was then subjected to sheet molding to produce a preliminary anode sheet. This preliminary anode sheet was then placed on the surface of a porous metal plate R2 and heat-pressed to bond it to the surface. This was then degreased in an argon gas atmosphere at 850°C for 0.5 hours to obtain an integrated product consisting of the porous metal plate R2 and the degreased anode layer. Next, to adjust the thickness of the anode, a separately prepared slurry was screen-printed on the surface of the degreased anode layer to produce a cathode film. The screen printing slurry was prepared by mixing nickel oxide powder and scandia-stabilized zirconia powder in a mass ratio of 60:40, and then mixing the resulting mixed powder with a mixed solution of ethyl cellulose diluted with terpineol using a ball mill. The electrolyte layer-forming slurry was then screen-printed onto the surface of the anode membrane to form a cell precursor. The electrolyte layer-forming slurry was prepared by mixing scandia-stabilized zirconia powder with a mixed solution of ethyl cellulose diluted with terpineol using a ball mill. The cell precursor was then heat-treated (co-sintered) in a hydrogen gas atmosphere at 1200°C for 1 hour, and then in an argon gas atmosphere under reduced pressure at 1250°C for 3 hours to bond the solid electrolyte layer to the anode. A metal-supported solid oxide electrochemical cell was obtained, consisting of a gas-permeable metal support portion derived from the porous metal plate R2, the anode, and the solid electrolyte layer, and having a stable layer structure with excellent mechanical strength.

[0057] The surface (rear surface) of the permeable metal support part of the obtained metal-supported cell-type solid oxide electrochemical cell was observed with a scanning electron microscope, and the results shown in Figure 15 and its enlarged image, Figure 16, were obtained. These figures show that the permeable metal support part has smaller voids than the porous metal plate R2 (Figures 5 and 6). Because the permeable metal support part is bonded to the anode, it was not possible to measure the porosity of the permeable metal support part in accordance with JIS Z 2501. Therefore, the image taken with the optical microscope was binarized, and the ratio of the void area per specified area was calculated using image software. The porosity was found to be 30%.

[0058] The porous metal plate of the present invention is suitable as a material for producing a metal-supported cell-type solid oxide electrochemical cell half-cell having, in order, a gas-permeable metal support part derived from the porous metal plate, an anode, and a solid electrolyte layer, or for producing a metal-supported cell-type solid oxide electrochemical cell having, in order, a gas-permeable metal support part derived from the porous metal plate, an anode, a solid electrolyte layer, and an air cathode.

[0059] 1: Metal-supported cell type solid oxide electrochemical cell 2: Permeable metal support part formed from a porous metal plate 4: Fuel electrode 6: Solid electrolyte layer 8: Air electrode 10: Alloy particle part

Claims

1. A porous metal plate characterized by being composed of a connected structure of alloy particles containing Cr and Fe and having a porosity of 50 to 80%.

2. The porous metal plate according to claim 1, wherein the average maximum diameter of the alloy particle portions as measured from the general shape of the alloy particle portions is 1 to 20 μm.

3. The porous metal plate according to claim 1 or 2, which is to be joined to the fuel electrode of an electrochemical cell comprising an air electrode, a solid electrolyte layer and a fuel electrode in this order.

4. A method for producing a porous metal plate according to any one of claims 1 to 3, comprising the steps of: a compact production step of subjecting a powder consisting of a composition containing alloy particles containing Cr and Fe and a pore-forming material to pressure molding to produce a thin-walled compact; and a heat treatment step of subjecting the thin-walled compact to a heat treatment at a temperature at which the pore-forming material is thermally decomposed and the alloy particles are sintered.

5. The method for manufacturing a porous metal plate according to claim 4, wherein the average particle size of the alloy particles is 1 to 20 μm.

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