Porous metal plate and method for manufacturing the same

Abstract

To provide a porous metal plate that is used for forming an air permeable metal support part of a metal support cell type solid oxide electrochemical cell, which enables formation of an air permeable metal support part for giving a metal support cell type solid oxide electrochemical cell that has porosity of approximately of 25 to 50% and is excellent in structural stability, even if there is contraction to some extent, when a slurry for forming a fuel electrode and a slurry for forming an electrolyte layer are sequentially applied on its surface, and the metal plate is subjected to co-sintering, and a method for manufacturing the same.SOLUTION: A porous metal plate is composed of a connection structure of an alloy particle part containing Cr and Fe, and has porosity of 50 to 80%. An average value of a maximum diameter measured from the outline of the alloy particle part is preferably 1 to 20 μm.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] As solid oxide type electrochemical cells, solid oxide type fuel cells and solid oxide type electrolytic cells are known. Among these, a solid oxide type fuel cell includes a three-layer power generation cell composed of a solid electrolyte layer containing an oxygen ion conductive solid oxide, and a fuel electrode and an air electrode disposed on both sides of the electrolyte layer so as to face each other. A fuel gas such as hydrogen is supplied to the fuel electrode, and an oxidizing gas such as air is supplied to the air electrode to generate DC power based on an electrochemical reaction.

[0003] In such a fuel cell, in recent years, a metal-supported cell type solid oxide fuel cell in which a power generation cell is supported by a metal support part (metal support part) having gas permeability and electrical conductivity through a fuel electrode is known.

[0004] Patent Document 1 discloses a support structure of a metal support cell having 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. The electrolyte layer has a compressive residual stress along the plane direction, the metal frame is sintered and bonded to the electrolyte layer, and the linear expansion rate of the metal frame is about the same as the linear expansion rate of the metal support layer.

[0005] Patent Document 2 discloses a metal support that is formed in a plate shape as a whole and has a plurality of through-holes penetrating from the front surface provided with the electrode layer to the back surface, and as the through-holes, a metal support having inclined through-holes whose central axis is inclined with respect to the thickness direction is disclosed. Further, as a method for manufacturing such a metal support, a method of forming a plurality of through-holes penetrating from the front side to the back side on a metal material plate by any one of laser processing, punching processing, etching processing, or a combination thereof is disclosed.

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

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

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

[0009] When a carrier produced using a metal plate having air permeability 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 viewpoints of the power generation efficiency and structural stability of the resulting metal-supported cell type solid oxide fuel cell, it is considered preferable that an air-permeable metal support part having a porosity of 25% or more is formed.

[0010] An object of the present invention is to provide a porous metal plate used for forming an air-permeable metal support part constituting 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. When a fuel electrode forming slurry and an electrolyte layer forming slurry are sequentially applied to the surface thereof and then subjected to co-sintering, even if there is some shrinkage, the porosity is about 25 to 50%, and a metal-supported cell type solid oxide electrochemical cell excellent in structural stability can be provided. It is to provide a porous metal plate capable of forming an air-permeable metal support part and a method for manufacturing the same. MEANS FOR SOLVING THE PROBLEMS

[0011] The present inventors have found that the above problems can be solved by using powder metallurgy technology to subject a composition containing alloy particles containing Cr and Fe and a pore former to pressure molding and sintering the obtained thin molded body, which is a porous metal plate composed of a connected structure of alloy particles and has a porosity of 50 to 80%.

[0012] The present invention is shown below. (1) A porous metal plate characterized by comprising a connected structure of alloy particle parts containing Cr and Fe and having a porosity of 50 to 80%. (2) The porous metal plate according to (1) above, wherein the average value of the maximum diameter of the alloy particle portion measured from the general shape of the alloy particle portion is 1 to 20 μm. (3) The porous metal plate according to (1) above, which is to be joined to the fuel electrode of an electrochemical cell including an air electrode, a solid electrolyte layer, and a fuel electrode in this order. (4) A method for manufacturing the porous metal plate according to (1) above, comprising a compact manufacturing step of subjecting a powder composed of a composition containing particles made of an alloy containing Cr and Fe and a pore-forming material to pressure molding to produce a thin compact, and a heat treatment step of heat-treating the thin compact at a temperature at which the pore-forming material thermally decomposes and the alloy particles sinter, in sequence. A method for manufacturing a porous metal plate, characterized by comprising the above steps. (5) The method for manufacturing a porous metal plate according to (4) above, wherein the average particle diameter of the alloy particles is 1 to 20 μm.

Effects of the Invention

[0013] The porous metal plate of the present invention is suitable as a manufacturing material for the air-permeable metal support portion of a metal-supported cell type solid oxide type electrochemical cell (including a half cell). When manufacturing these electrochemical cell products using the porous metal plate, a method may be applied in which a slurry for forming a fuel electrode containing stabilized zirconia, a slurry for forming an electrolyte layer, etc. are sequentially applied to the surface of the porous metal plate and then co-sintered. During this co-sintering, some shrinkage may occur in the porous metal plate together with the formed fuel electrode and electrolyte layer, but the porosity of the obtained air-permeable metal support portion can be about 25 to 50% and excellent in structural stability. Inside the air-permeable metal support portion, instead of through-holes with a single flow path, void portions formed between the alloy particle portions form through-holes with multiple paths and have a structure excellent in gas diffusibility. Therefore, it is expected to suitably manufacture a metal-supported cell type solid oxide type electrochemical cell product excellent in electrochemical cell performance. In this specification, "stabilized zirconia" means zirconia in which a rare earth element oxide is solid-solved, and includes partially stabilized zirconia.

Brief Description of the Drawings

[0014]

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MODE FOR CARRYING OUT THE INVENTION

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

[0016] The alloy particle part constituting the porous metal plate of the present invention is made of an alloy containing Cr and Fe. This alloy may further contain Mn, Ni, Ti, Cu, Zr, Si, Al, Mo, etc. in addition to Cr and Fe. The above alloy is preferably a ferritic stainless steel (such as SUS 430). Various stabilized zirconias are widely used for the electrolyte layer of solid oxide type electrochemical cells. Among stainless steels, the thermal expansion coefficient of ferritic stainless steel is close to that of stabilized zirconia. Therefore, when co-sintering to join a fuel electrode 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 it may be either a flat plate or a curved plate. From the viewpoints of the productivity of the metal-supported cell type solid oxide type electrochemical cell and the structural stability of the formed metal-supported cell type solid oxide type 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 non-linear communication holes from one surface side to the other surface side and has air permeability, and its surface is shown in, for example, FIGS. 3 to 15. According to the enlarged views of typical examples, FIGS. 4, 6, 8, 10, 12, and 14, not all alloy particle portions have the same size, and alloy particle portions of various sizes form a connected structure, and alloy particle portions having a maximum diameter measured from its general shape usually of 1 μm or more are connected. The present invention is not limited to this aspect, and all of the alloy particle portions may have the same size. Further, the connection state of adjacent alloy particle portions may be either regular or irregular, but as can be seen from these typical example figures, it is usually irregular. As described above, while the size of the alloy particle portions is small, the connection of adjacent alloy particle portions is irregular, and when the thickness is 0.1 mm or more, the number of alloy particle portions in the thickness direction becomes large, and the porous metal plate of the present invention can have suitable voids formed by adjacent alloy particle portions. The porosity of the porous metal plate of the present invention is such that when a slurry for forming a fuel electrode, a slurry for forming an electrolyte layer, etc. are sequentially applied to the surface of the porous metal plate and then co-sintered, a breathable metal support portion having suitable voids can be formed, and an integrated product composed of the breathable metal support portion, the fuel electrode, and the solid electrolyte layer can be efficiently formed, so it is 50 to 80%, preferably 60 to 80%, more preferably 70 to 80%. Incidentally, this porosity can be measured according to JIS Z 2501.

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

[0020] FIG. 2 is an explanatory diagram showing a method for measuring the maximum diameter of a plurality of connected alloy particle portions 10. It shows a method of photographing the surface or inside of a porous metal plate with an electron microscope, drawing a schematic line for each alloy particle portion from the obtained image, and measuring its maximum diameter. FIG. 2 shows that the maximum diameters of the four alloy particle portions 10 were r1, r2, r3, and r4, respectively. Based on this measurement method, for example, after measuring the maximum diameters of 20 or more alloy particle portions, an average value is calculated, and if it is within the above-mentioned preferable average value range, it will have a suitable strength for manufacturing a metal-supported cell type solid oxide electrochemical cell.

[0021] When the flexural strength of the porous metal plate of the present invention is measured according to JIS Z 2511, it is preferably 1.5 to 15 MPa, more preferably 2 to 5 MPa. Since the flexural strength is within this range, when manufacturing a metal-supported cell type solid oxide electrochemical cell, as a method of applying a slurry for forming a fuel electrode on the surface of the porous metal plate, for example, even if screen printing is applied, there are no problems such as deformation and breakage.

[0022] The method for manufacturing a porous metal plate of the present invention comprises a compact manufacturing step of subjecting a powder composed of a composition containing particles (alloy particles) made of an alloy containing Cr and Fe and a pore former to pressure molding to produce a thin compact, and a heat treatment step of heat-treating the obtained thin compact at a temperature at which the pore former thermally decomposes and the alloy particles sinter, sequentially. The method for manufacturing a porous metal plate of the present invention can include other steps (described later) as necessary after the heat treatment step.

[0023] The compact manufacturing step is a step of manufacturing a thin compact used in the heat treatment step. In this compact manufacturing step, the composition (hereinafter referred to as "solid component composition") constituting the powder used for pressure molding contains alloy particles and a pore former, but may contain other components (described later) as necessary.

[0024] The alloy particles contained in the solid component composition can be composed of the alloys exemplified as the constituent materials of the above alloy particle portion, and particles made of ferritic stainless steel are preferred. In addition, one alloy particle may be a particle of an alloy composed of only one type, or a particle composed of two or more alloys. Further, the solid component composition may contain a combination of alloy particles made of one material and alloy particles made of another material. From the viewpoints of the porosity and strength of the resulting porous metal plate, the average particle diameter of the alloy particles is preferably 1 to 20 μm, more preferably 1 to 10 μm. The average particle diameter is D 50 (median diameter).

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

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

[0027] As described above, the solid component composition can contain other components. For example, in order to efficiently produce a thin-walled molded body with excellent shape stability by adhering alloy particles and a pore former, an adhesive can be contained. This adhesive preferably contains a polymer, and preferably contains a water-soluble polymer. Examples of the water-soluble polymer include polyvinyl alcohol, polyvinyl pyrrolidone, vinyl acetate-acrylamide copolymer, polyacrylamide derivative, cellulose derivative (hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, etc.). The polymer contained in the adhesive may be only one kind or two or more kinds.

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

[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 in the present invention, will be described. The alloy particles, the pore former, and the aqueous solution of the water-soluble polymer (adhesive) are mixed so that they have the above-mentioned preferred content ratios, and this water-containing mixture is sufficiently dried. Next, the obtained dried product is pulverized and sieved, etc., to recover a powder (solid component composition) having a predetermined size (particle size). Thereafter, the powder is put into a mold and subjected to a known molding method such as pressure molding by roll rolling, whereby a thin-walled molded body can be obtained. In the heat treatment step, when a thin-walled molded body containing a powder with a small variation in particle size is used, a porous metal plate with a small variation in voids can be efficiently obtained.

[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 formed body thermally decomposes and the alloy particles sinter. When the thin-walled formed body contains a pore-forming material made of resin particles and is made of powder with a small variation in particle size, when this thin-walled formed body is heated to the sintering temperature of the alloy particles, the alloy particles are sintered to form a connected structure of the alloy particle portions, and the pore-forming material decomposes to obtain a porous metal plate in which voids are uniformly distributed.

[0032] The sintering temperature in the heat treatment step is appropriately set according to the type of alloy contained in the thin-walled formed body, 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 performed under a reducing atmosphere or under reduced pressure conditions. Also, when heat-treating the thin-walled formed body, it may be performed under pressure conditions. In addition, the heat treatment time is appropriately set according to the size of the thin-walled formed body and the like, and is not particularly limited.

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

[0034] When manufacturing a metal-supported cell type solid oxide electrochemical cell product using the porous metal plate of the present invention, (1) a fuel electrode forming slurry is applied (such as screen printing) and dried on the surface of the porous metal plate to form a fuel electrode film, and then an electrolyte layer forming slurry is applied and dried on the surface of the fuel electrode film 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 and dried on the surface of the fuel electrode film to form a film made of a solid electrolyte layer forming material, and then this stack is co-sintered. This method is preferably applied. During this co-sintering, although some shrinkage may occur in the porous metal plate together with the formed fuel electrode and electrolyte layer, since the porous metal plate is made of a specific alloy, the porosity of the formed breathable metal support part can be about 25 to 50%, and a metal-supported cell type solid oxide electrochemical cell product having excellent structural stability, that is, having an excellent mechanical strength and a stable layer structure can be efficiently manufactured. The fuel electrode forming slurry preferably contains stabilized zirconia, nickel oxide, etc.

Examples

[0035] Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

[0036] 1. Manufacture and evaluation of porous metal plate A porous metal plate was manufactured using the following raw materials.

[0037] 1-1. Alloy particles (1) SUS 430 powder (alloy particles P1) The average particle diameter is 10 μm. (2) SUS 430 powder (alloy particles P2) The average particle diameter is 17 μm. (3) SUS XM27 powder (alloy particles P3) The average particle diameter is 7.4 μm.

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

[0039] 1-3. Adhesive Aqueous polyvinyl alcohol solution with a concentration of 10% by mass

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

[0041] When the porosity of the obtained porous metal plate R1 was measured according to JIS Z 2501, it was 61.8%. Further, the flexural strength (strength per unit thickness; the same shall apply hereinafter) was measured according to JIS Z 2511 using a single column type material testing machine "STB-1225S" (model name) manufactured by A&D Company, Ltd., and it was 4.1 MPa. These results are shown in Table 1.

[0042] Furthermore, when the surface of the porous metal plate R1 was observed with a scanning electron microscope, FIGS. 3 and its enlarged image FIG. 4 were obtained. From these figures, it can be seen that the porous metal plate R1 is a connected structure of alloy particle portions. Then, from a total of 4 images including FIG. 4, according to FIG. 2, the maximum diameters of 20 alloy particle portions were measured, and the average value was calculated, which was 7.28 μm (see Table 1). Incidentally, the minimum value and the maximum value were 1.95 μm and 27.15 μm, respectively.

[0043] Example 2 The alloy particles P1, the pore former, and the aqueous polyvinyl alcohol solution were kneaded to produce a raw material composition in which the solid contents of the alloy particles P1, the pore former, and the polyvinyl alcohol were 68% by mass, 30% by mass, and 2% by mass, respectively. Thereafter, an operation as in Example 1 was performed to produce a thin-walled molded body, and the obtained thin-walled molded body was heat-treated at 920 °C for 1 hour under reduced pressure conditions to obtain a porous metal plate having a diameter of 28 mm and a thickness of 1.173 mm (hereinafter referred to as "porous metal plate R2"). Next, when the porosity and the flexural strength of the porous metal plate R2 were measured, they were 71.0% and 2.2 MPa, respectively.

[0044] Further, when the surface of the porous metal plate R2 was observed with a scanning electron microscope, FIGS. 5 and 6 which is an enlarged image thereof were obtained. From these figures, it can be seen that the porous metal plate R2 is a connected structure of alloy particle portions. Then, from a total of 4 images including FIG. 6, according to FIG. 2, the maximum diameters of 20 alloy particle portions were measured, and the average value thereof was calculated to be 8.32 μm (see Table 1). The minimum value and the maximum value were 1.98 μm and 27.37 μm, respectively.

[0045] Example 3 The alloy particles P1, the pore former, and the aqueous polyvinyl alcohol solution were kneaded to produce a raw material composition in which the solid contents of the alloy particles P1, the pore former, and the polyvinyl alcohol were 88% by mass, 10% by mass, and 2% by mass, respectively. Thereafter, an operation as in Example 1 was performed to produce a thin-walled molded body, and the obtained thin-walled molded body was heat-treated at 940 °C for 1 hour under reduced pressure conditions to obtain a porous metal plate having a diameter of 31 mm and a thickness of 0.857 mm (hereinafter referred to as "porous metal plate R3"). Next, when the porosity and the flexural strength of the porous metal plate R3 were measured, they were 58.8% and 8.7 MPa, respectively.

[0046] Further, when the surface of the porous metal plate R3 was observed with a scanning electron microscope, FIGS. 7 and its enlarged image FIG. 8 were obtained. From these figures, it can be seen that the porous metal plate R3 is a connected structure of alloy particle portions. Then, from a total of 4 images including FIG. 8, according to FIG. 2, the maximum diameters of 20 alloy particle portions were measured, and when their average value was calculated, it was 8.56 μm (see Table 1). Incidentally, the minimum value and the maximum value were 2.99 μm and 21.12 μm, respectively.

[0047] Example 4 Alloy particles P2, a pore former, and an aqueous polyvinyl alcohol solution were kneaded to produce a raw material composition in which the solid contents of the alloy particles P2, the pore former, and polyvinyl alcohol were 78% by mass, 20% by mass, and 2% by mass, respectively. Thereafter, an operation as in Example 1 was performed to produce a thin molded body, and the obtained thin molded body was heat-treated at 940 ° C. for 1 hour under reduced pressure conditions to obtain a porous metal plate having a diameter of 30 mm (diameter) × 1.115 mm (thickness) (hereinafter referred to as "porous metal plate R4"). Next, when the porosity and the flexural strength of the porous metal plate R4 were measured, they were 68.3% and 2.9 MPa, respectively.

[0048] Further, when the surface of the porous metal plate R4 was observed with a scanning electron microscope, FIGS. 9 and its enlarged image FIG. 10 were obtained. From these figures, it can be seen that the porous metal plate R4 is a connected structure of alloy particle portions. Then, from a total of 4 images including FIG. 10, according to FIG. 2, the maximum diameters of 20 alloy particle portions were measured, and when their average value was calculated, it was 12.02 μm (see Table 1). Incidentally, the minimum value and the maximum value were 3.05 μm and 39.31 μm, respectively.

[0049] Example 5 Alloy particles P3, a pore former, and an aqueous polyvinyl alcohol solution were kneaded to produce a raw material composition in which the solid contents of the alloy particles P3, the pore former, and polyvinyl alcohol were 68% by mass, 30% by mass, and 2% by mass, respectively. Subsequently, operations similar to those in Example 1 were performed to produce a thin-walled molded body. The obtained thin-walled molded body was heat-treated at 940°C for 1 hour under reduced pressure conditions to obtain a porous metal plate with a diameter of 30 mm and a thickness of 1.018 mm (hereinafter referred to as "porous metal plate R5"). Next, when the porosity and flexural strength of the porous metal plate R5 were measured, they were 74.5% and 2.2 MPa, respectively.

[0050] In addition, when the surface of the porous metal plate R5 was observed with a scanning electron microscope, FIGS. 11 and its enlarged image FIG. 12 were obtained. From these figures, it can be seen that the porous metal plate R5 is a connected structure of alloy particle portions. Then, from a total of 4 images including FIG. 12, according to FIG. 2, the maximum diameters of 20 alloy particle portions were measured, and their average value was calculated, which was 8.19 μm (see Table 1). The minimum value and the maximum value 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 kneaded to produce a raw material composition in which the solid contents of alloy particles P1, the pore-forming material, and polyvinyl alcohol were 88% by mass, 10% by mass, and 2% by mass, respectively. Subsequently, operations similar to those in Example 1 were performed to produce a thin-walled molded body. The obtained thin-walled molded body was heat-treated at 960°C for 1 hour under reduced pressure conditions to obtain a porous metal plate with a diameter of 30 mm and a thickness of 1.121 mm (hereinafter referred to as "porous metal plate R6"). Next, when the porosity and flexural strength of the porous metal plate R6 were measured, they were 55.3% and 11.8 MPa, respectively.

[0052] In addition, when the surface of the porous metal plate R6 was observed with a scanning electron microscope, FIGS. 13 and its enlarged image FIG. 14 were obtained. From these figures, it can be seen that the porous metal plate R6 is a connected structure of alloy particle portions. Then, from a total of 4 images including FIG. 14, according to FIG. 2, the maximum diameters of 20 alloy particle portions were measured, and their average value was calculated, which was 8.94 μm (see Table 1). The minimum value and the maximum value were 2.99 μm and 29.41 μm, respectively.

[0053]

Table 1

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

[0055] 2. Production of 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 at a mass ratio of 60:40, and the resulting mixed powder, dibutyl phthalate, an acrylic binder, and a mixed solvent of toluene and 2-propanol were mixed using a ball mill to prepare a slurry for forming a fuel electrode. Then, this slurry for forming a fuel electrode was subjected to sheet forming to produce a preliminary sheet for a fuel electrode. Thereafter, this preliminary sheet for a fuel electrode was placed on the surface of the porous metal plate R2, heated and pressed to be adhered. Thereafter, in an argon gas atmosphere, degreasing was performed at 850 °C for 0.5 hours to obtain an integrated product composed of the porous metal plate R2 and a degreased fuel electrode layer. Next, in order to adjust the thickness of the fuel electrode, a separately prepared slurry was screen-printed on the surface of the degreased fuel electrode layer to produce a film for a fuel electrode. This slurry for screen printing is a slurry obtained by mixing nickel oxide powder and scandia-stabilized zirconia powder at a mass ratio of 60:40 and mixing the resulting mixed powder with a mixed solution in which ethyl cellulose is diluted with terpineol using a ball mill. Thereafter, a slurry for forming an electrolyte layer was screen-printed on the surface of the film for a fuel electrode to form a film, and a cell precursor was obtained. This slurry for forming an electrolyte layer is a slurry obtained by mixing scandia-stabilized zirconia powder and a mixed solution in which ethyl cellulose is diluted with terpineol using a ball mill. Next, the cell precursor was heat-treated (co-sintered) at 1200°C for 1 hour in a hydrogen gas atmosphere and then at 1250°C for 3 hours in an argon gas atmosphere under reduced pressure conditions to bond the solid electrolyte layer to the fuel electrode, obtaining a metal-supported cell type solid oxide electrochemical cell composed of a breathable metal support part derived from the porous metal plate R2, a fuel electrode, and a solid electrolyte layer, having an excellent mechanical strength and a stable layer structure.

[0057] When the surface (back surface side) of the breathable metal support part of the obtained metal-supported cell type solid oxide electrochemical cell was observed with a scanning electron microscope, FIGS. 15 and its enlarged image FIG. 16 were obtained. From these figures, it can be seen that the breathable metal support part has smaller voids than the porous metal plate R2 (FIGS. 5 and 6). Since the breathable metal support part is bonded to the fuel electrode, the porosity of the breathable metal support part cannot be measured according to JIS Z 2501. The photographed image by an optical microscope was binarized, and the ratio of the area of the void part per a predetermined area was calculated with image software and taken as the porosity, which was 30%.

Industrial Applicability

[0058] The porous metal plate of the present invention is suitable as a manufacturing material for a metal-supported cell type solid oxide electrochemical cell half-cell sequentially including a breathable metal support part, a fuel electrode, and a solid electrolyte layer derived from this porous metal plate, or for a metal-supported cell type solid oxide electrochemical cell sequentially including a breathable metal support part, a fuel electrode, a solid electrolyte layer, and an air electrode derived from this porous metal plate.

Explanation of Symbols

[0059] 1: Metal-supported cell type solid oxide electrochemical cell 2: Breathable 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 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 Claim 1, wherein an average value of the 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 Claim 1, which is to be joined to the fuel electrode of an electrochemical cell including an air electrode, a solid electrolyte layer, and a fuel electrode in this order.

4. A method for manufacturing the porous metal plate according to Claim 1, comprising a compact manufacturing step of subjecting a powder composed of a composition containing alloy particles containing Cr and Fe and a pore-forming material to pressure molding to produce a thin compact, and a heat treatment step of heat-treating the thin compact at a temperature at which the pore-forming material thermally decomposes and the alloy particles sinter. The method for manufacturing a porous metal plate is characterized by sequentially including these steps.

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

Images