Metal porous body, nitrous oxide decomposition element, and nitrous oxide decomposition apparatus

Abstract

To provide a metal porous body having a large specific surface area, a nitrous oxide decomposition element composed of the metal porous body, and a nitrous oxide decomposition apparatus including the nitrous oxide decomposition element.SOLUTION: A metal porous body includes a framework having a three-dimensional mesh structure, wherein the framework includes a plurality of columnar supporting portions and a node portion that connects the plurality of columnar supporting portions, the framework is provided with a plurality of opening holes opened in a surface of the framework, and the framework contains at least one selected from the group consisting of nickel, cobalt, iron, tin, copper, and chromium.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present disclosure relates to a porous metal body, a nitrous oxide decomposition element, and a nitrous oxide decomposition device. [Background technology]

[0002] Nitrous oxide (N 2 O) is a greenhouse gas with a global warming potential lower than that of carbon dioxide (CO 2 ) and even a small amount is believed to have an impact on global warming.

[0003] Catalysts that decompose nitrous oxide are used to remove nitrous oxide contained in exhaust gases emitted from incinerators, chemical plants, automobiles, etc. Examples of such catalysts include oxides of nickel or cobalt.

[0004] Patent Document 1 discloses a method for removing nitrogen oxides from a fluid using a metal mesh-like structure as a substrate and a nitrogen oxide conversion catalyst disposed on the substrate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2003-512150 Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, a catalyst is applied onto a substrate having a metal mesh-like structure to obtain a nitrous oxide decomposition ability. On the other hand, when the metal porous body is made of a catalytic substance, the metal porous body itself may have the ability to decompose nitrous oxide. When the metal porous body itself is used as a nitrous oxide decomposition catalyst, it is effective to increase the specific surface area of ​​the metal porous body in order to improve the nitrous oxide decomposition ability.

[0007] Therefore, an object of the present disclosure is to provide a metal porous body having a large specific surface area, a nitrous oxide decomposition element made of the metal porous body, and a nitrous oxide decomposition device including the nitrous oxide decomposition element. [Means for solving the problem]

[0008] The metal porous body of the present disclosure is A metal porous body having a skeleton with a three-dimensional network structure, The skeleton is composed of a plurality of support parts and node parts connecting the plurality of support parts, The skeleton has a plurality of openings that open to a surface of the skeleton, The skeleton is a porous metal body containing at least one element selected from the group consisting of nickel, cobalt, iron, tin, copper and chromium. Effect of the Invention

[0009] According to the present disclosure, it is possible to provide a metal porous body having a large specific surface area, a nitrous oxide decomposition element made of the metal porous body, and a nitrous oxide decomposition device including the nitrous oxide decomposition element. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is an enlarged schematic view focusing on one of the cells in the skeleton having a three-dimensional network structure of the first embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing one embodiment of the shape of the cell portion. [Diagram 3] FIG. 3 is a schematic diagram showing another embodiment of the shape of the cell portion. [Figure 4] FIG. 4 is a schematic diagram showing another embodiment of the shape of the cell portion. [Diagram 5] FIG. 5 is a schematic diagram showing an embodiment of two joined cell parts. [Figure 6] FIG. 6 is a schematic diagram showing an embodiment of four joined cell parts. [Figure 7]FIG. 7 is a schematic diagram showing one embodiment of a skeleton having a three-dimensional network structure formed by bonding a plurality of cells. [Figure 8] FIG. 8 is a schematic diagram showing one aspect of the shape of the porous metal body of the first embodiment. [Figure 9] FIG. 9 is a diagram showing an example of an SEM image of the surface of the skeleton of the metallic porous body of the first embodiment. [Figure 10] FIG. 10 is a diagram showing an example of an SEM image of a cross section of the skeleton of the metallic porous body of the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be listed and described. (1) The metal porous body of the present disclosure is A metal porous body having a skeleton with a three-dimensional network structure, The skeleton is composed of a plurality of support parts and node parts connecting the plurality of support parts, The skeleton has a plurality of openings that open to a surface of the skeleton, The skeleton is a porous metal body containing at least one element selected from the group consisting of nickel, cobalt, iron, tin, copper, and chromium.

[0012] According to the present disclosure, it is possible to provide a metal porous body having a large specific surface area.

[0013] (2) In the above (1), the BET surface area of ​​the framework is 0.8 m 2 / g or more, which further increases the specific surface area of ​​the metal porous body.

[0014] (3) In the above (1) or (2), the average maximum diameter of the open pores of the skeleton may be 0.1 μm or more and 2 μm or less, thereby further increasing the specific surface area of ​​the porous metal body.

[0015] (4) In any one of the above (1) to (3), the number of the open holes per unit area on the surface of the skeleton is 1.6 / μm 2 More than 5 pieces / μm 2 This further increases the specific surface area of ​​the metal porous body.

[0016] (5) In any one of the above (1) to (4), the porosity of the skeleton may be 20% or more and 40% or less. This further increases the specific surface area of ​​the metal porous body. In addition, the skeleton has sufficient strength and is easy to handle.

[0017] (6) In any one of the above (1) to (5), the metal porous body may contain potassium, which improves the nitrous oxide decomposition ability of the metal porous body.

[0018] (7) A nitrous oxide decomposition element of the present disclosure is a nitrous oxide decomposition element made of the metal porous body according to any one of (1) to (6) above.

[0019] According to the present disclosure, it is possible to provide a nitrous oxide decomposition element having excellent nitrous oxide decomposition ability.

[0020] (8) A nitrous oxide decomposition device according to the present disclosure is a nitrous oxide decomposition device including the nitrous oxide decomposition element described in (7) above.

[0021] According to the present disclosure, it is possible to provide a nitrous oxide decomposition device having excellent nitrous oxide decomposition ability.

[0022] [Details of the embodiment of the present disclosure] Specific examples of the metal porous body, nitrous oxide decomposition element, and nitrous oxide decomposition device of the present disclosure will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference symbols represent the same or corresponding parts. Furthermore, dimensional relationships such as length, width, thickness, and depth have been appropriately changed to clarify and simplify the drawings, and do not necessarily represent actual dimensional relationships.

[0023] In this specification, the expression "A to B" means the upper and lower limits of a range (i.e., A or more and B or less). When no unit is specified for A and a unit is specified only for B, the unit of A and the unit of B are the same.

[0024] In the present specification, when a compound or the like is represented by a chemical formula, unless the atomic ratio is particularly limited, it is understood to include any conventionally known atomic ratio, and is not necessarily limited to only those within the stoichiometric range.

[0025] In the present disclosure, when one or more numerical values ​​are described as the lower limit and the upper limit of a numerical range, a combination of any one numerical value described as the lower limit and any one numerical value described as the upper limit is also disclosed. For example, when a1 or more, b1 or more, and c1 or more are described as the lower limit, and a2 or less, b2 or less, and c2 or less are described as the upper limit, a1 or more and a2 or less, a1 or more and b2 or less, a1 or more and c2 or less, b1 or more and a2 or less, b1 or more and b2 or less, b1 or more and c2 or less, c1 or more and a2 or less, c1 or more and b2 or less, and c1 or more and c2 or less are disclosed.

[0026] [Embodiment 1: Porous metal body] A metal porous body according to one embodiment of the present disclosure (hereinafter also referred to as "embodiment 1"), A metal porous body having a skeleton with a three-dimensional network structure, The skeleton is composed of a plurality of support parts and node parts connecting the plurality of support parts, The skeleton has a plurality of openings that open to a surface of the skeleton, The skeleton is a porous metal body containing at least one element selected from the group consisting of nickel, cobalt, iron, tin, copper and chromium.

[0027] <Structure of porous metal body> In the first embodiment, the metal porous body has a skeleton having a three-dimensional mesh structure. In the present disclosure, the three-dimensional mesh structure means a structure in which the constituent solid components are spread three-dimensionally in a mesh shape. Here, the solid components are metals, etc.

[0028] In the following, for ease of understanding of the three-dimensional mesh structure, a constituent unit of the three-dimensional mesh structure will be described as a cell portion 20. Fig. 1 is an enlarged schematic view of one cell portion constituting the three-dimensional mesh structure in embodiment 1. As shown in Fig. 7, a three-dimensional mesh structure 30 is formed by joining a plurality of cell portions.

[0029] As shown in FIG. 1 and FIG. 2, the cell portion 20, which is a constituent unit of the three-dimensional mesh structure, is composed of a plurality of support portions 5 and a node portion 6 connecting the plurality of support portions 5. Therefore, the skeleton having the three-dimensional mesh structure can be expressed as being composed of a plurality of support portions 5 and a node portion 6 connecting the plurality of support portions 5. In the following, the support portions 5 and the node portions 6 are described separately, but there is no clear boundary between them, and the plurality of support portions 5 and the plurality of node portions 6 are integrated to form a skeleton having a three-dimensional mesh structure. In the following, for ease of understanding, the shape of the cell portion in FIG. 1 is described as a regular dodecahedron shown in FIG. 2.

[0030] The plurality of support members 5 and the plurality of node members 6 form a frame member 10 that is a planar polygonal structure. Here, a planar polygonal structure means a polygonal shape when viewed in a plane. In FIG. 2, the planar polygonal structure is a regular pentagon, but the shape of the planar polygonal structure is not limited to a regular pentagon. The planar polygonal structure may be another polygon, such as a triangle, a rectangle, or a hexagon. The frame member 10 forms a planar polygonal hole by the plurality of support members 5 and the plurality of node members 6.

[0031] A plurality of frame parts 10 are combined to form a cell part 20, which is a three-dimensional polyhedral structure. One support part 5 and one node part 6 are shared by a plurality of frame parts 10. The shape of the node part 6 may be a sharp-edged shape having vertices, a flat shape having chamfered vertices, or a curved shape having rounded vertices. In FIG. 2, the three-dimensional polyhedral structure is a dodecahedron, but it may be another polyhedron such as a cube, an icosahedron (FIG. 3), or a truncated icosahedron (FIG. 4). The cell part 20 forms a three-dimensional space surrounded by a virtual plane A defined by each of the plurality of frame parts 10.

[0032] As shown in Figs. 5, 6 and 7, a skeleton 11 having a three-dimensional mesh structure 30 is formed by combining a plurality of cell portions 20. The frame portion 10 is shared by a plurality of cell portions 20. The frame portion 10 may be shared by two cell portions 20. The skeleton 11 having the three-dimensional mesh structure 30 can also be expressed as being made up of a plurality of frame portions 10. The skeleton 11 having the three-dimensional mesh structure 30 can also be expressed as being made up of a plurality of cell portions 20. Since the metal porous body of the present disclosure includes a skeleton 11 having a three-dimensional mesh structure 30, it can have interconnected pores.

[0033] The metal porous body of the present disclosure has planar polygonal holes formed by the frame portion and three-dimensional spaces formed by the cell portion. The metal porous body of the present disclosure can be clearly distinguished from two-dimensional mesh structures such as punching metals and grills that have only planar holes. The skeleton of the metal porous body of the present disclosure is a three-dimensional mesh structure formed by a plurality of support parts and a plurality of node parts being integrated together. Therefore, it can be clearly distinguished from structures such as nonwoven fabrics formed by intertwining fibers that are constituent units.

[0034] The three-dimensional mesh structure of the present disclosure is not limited to the above-mentioned structure. For example, the cell portion 20 may be formed by a plurality of frame portions 10 each having a different size and planar shape. The three-dimensional mesh structure may be formed by a plurality of cell portions 20 each having a different size and three-dimensional shape. The three-dimensional mesh structure may include a frame portion 10 in which no planar polygonal holes are formed, or may include a cell portion 20 in which no three-dimensional space is formed and the inside is solid.

[0035] The porosity of the metal porous body (hereinafter also referred to as "first porosity") may be 30% or more and 98% or less, 40% or more and 97% or less, or 50% or more and 96% or less. When the first porosity of the metal porous body is 30% or more, the metal porous body can be made very lightweight and the surface area of ​​the metal porous body can be increased. When the first porosity of the metal porous body is 98% or less, the strength of the metal porous body can be made sufficient.

[0036] In the present disclosure, the first porosity of the metal porous body is defined by the following formula. First porosity [%] = (pore volume of metal porous body [cm 3 ] / Volume of porous metal [cm 3 ])×100 In the above formula, the volume of the porous metal body is the volume of the external shape of the porous metal body.

[0037] The method for measuring the pore volume of the porous metal body and the volume of the porous metal body is as follows. Three-dimensional data of the porous metal body is obtained by X-ray CT, and the pore volume of the porous metal body and the volume of the porous metal body are calculated based on the three-dimensional data. The volume of the entire measurement area of ​​the X-ray CT corresponds to the volume of the porous metal body in the above formula. The size of the measurement area of ​​the X-ray CT is 2 mm 3 The size of the measurement region can be set appropriately depending on the size of the measurement target.

[0038] The first porosity of the porous metal body is calculated by substituting the obtained pore volume of the porous metal body and the volume of the porous metal body into the above formula. Three measurement regions that do not overlap with each other are set for one porous metal body to be measured. In each of the three measurement regions, the pore volume of the porous metal body and the volume of the porous metal body are obtained to calculate the porosity of the porous metal body. The average of the porosities of the porous metal body in the three measurement regions is calculated. In the present disclosure, the average of the porosities of the porous metal body in the three measurement regions corresponds to the first porosity of the porous metal body.

[0039] The average pore diameter of the metal porous body (hereinafter also referred to as "first average pore diameter") may be 250 μm or more and 3500 μm or less, 250 μm or more and 1000 μm or less, or 250 μm or more and 850 μm or less. The pore diameter of the metal porous body means the pore diameter of the three-dimensional space defined by the outer surface of the skeleton. When the first average pore diameter of the metal porous body is 250 μm or more, the strength of the metal porous body can be increased. When the first average pore diameter of the metal porous body is 3500 μm or less, the bendability of the metal porous body can be increased. When the first average pore diameter of the metal porous body is 250 μm or more and 1000 μm or less, the nitrous oxide decomposition ability is improved.

[0040] The method for measuring the first average pore diameter of the metal porous body is as follows. Three-dimensional data of the metal porous body is obtained by X-ray CT. The size of the measurement area of ​​the X-ray CT is 2 mm 3 The above is the case. The size of the measurement area can be appropriately set according to the size of the measurement target. The pore diameters of all the metal porous bodies in the measurement area are determined based on the three-dimensional data. Here, the pore diameter of the metal porous body means the equivalent diameter of the pores in an equal volume sphere. If a part of the pore is located outside the measurement area, the pore is excluded from the measurement. The average of the average pore diameters of all the pores in the measurement area (hereinafter also referred to as the "1A average pore diameter") is calculated.

[0041] The above measurement is carried out in any three measurement regions set in the metal porous body. The first A average pore diameter is calculated in each of the three measurement regions, and the first average pore diameter, which is the average of these, is calculated. In the present disclosure, the first average pore diameter corresponds to the average pore diameter of the metal porous body.

[0042] As long as measurements are taken on the same porous metal body, it has been confirmed that there is almost no variation in the measurement results even if the positions of the three measurement regions are arbitrarily selected and measurements are taken multiple times.

[0043] In the first embodiment, the shape of the metal porous body is not particularly limited and can be appropriately selected depending on the application. For example, as shown in FIG. 8, the shape of the metal porous body 1 may be sheet-like. The shape of the metal porous body may be chip-like or block-like. A plurality of sheet-like metal porous bodies may be stacked, or may be folded, rolled, compressed, or cut according to the application.

[0044] The average thickness of the metal porous body is not particularly limited and may be 0.1 mm or more and 10 mm or less, 0.5 mm or more and 3 mm or less, 0.1 mm or more and 2.2 mm or less, or 0.1 mm or more and 1 mm or less.

[0045] The average thickness of the metal porous body is measured by a digital thickness gauge. The thickness is measured at three points arbitrarily set within an area 2 mm or more away from the outer edge of the metal porous body. The average of the thicknesses at the three points is calculated. In the present disclosure, the average of the thicknesses at the three points corresponds to the average thickness of the metal porous body.

[0046] <Skeletal opening> In the metal porous body of embodiment 1, the skeleton has a plurality of open pores that open to the surface of the skeleton. The presence of the open pores on the surface of the skeleton is confirmed by observing the surface of the skeleton with a scanning electron microscope (SEM). The magnification of the SEM observation can be 3,000 to 10,000 times.

[0047] Fig. 9 shows an example of an SEM image of the surface of the skeleton of the metal porous body of embodiment 1. As shown in Fig. 9, the skeleton of the metal porous body of embodiment 1 has a plurality of open pores 12 that open to the surface of the skeleton.

[0048] In the metal porous body of the first embodiment, the average maximum diameter of the open pores of the skeleton may be 0.1 μm or more and 2 μm or less, 0.2 μm or more and 1.5 μm or less, or 0.3 μm or more and 1.0 μm or less. When the average maximum diameter of the open pores is 0.1 μm or more, the fluid can easily enter and exit the inside of the open pores. When the average maximum diameter of the open pores is 2 μm or less, the specific surface area of ​​the metal porous body increases.

[0049] The method for measuring the average maximum diameter of the open pores of the skeleton is as follows. An SEM image of the surface of the skeleton of the metal porous body is obtained. The magnification of the SEM observation is 10,000 times. A rectangular measurement area of ​​5 μm × 5 μm is set in the SEM image. The position of the measurement area in the SEM image can be set arbitrarily as long as the entire measurement area is set inside the skeleton part. The maximum diameter is measured for each of all the open pores in the measurement area. The open pores whose entire outer edges are located within the measurement area are measured. If an open pore straddles the inside and outside of the measurement area, the open pore is not measured.

[0050] The maximum diameter of the opening hole is the maximum diameter across the opening hole, which corresponds to the maximum distance between two points on the outer edge of the opening hole. There is no particular limitation on the method of measuring the maximum diameter of each opening hole. For example, the SEM image may be printed and measured with a ruler, or the SEM image may be imported into a computer and measured using Excel, PowerPoint, or image processing software.

[0051] The arithmetic mean of the maximum diameter of all open pores within the measurement area is calculated.

[0052] The above measurement is performed in a measurement area set in each of three SEM images acquired in non-overlapping areas. In each of the three measurement areas, the arithmetic mean of the maximum diameter of all open pores in the measurement area (hereinafter referred to as the "first arithmetic mean") is calculated. In the present disclosure, the average of the three first arithmetic means corresponds to the average of the maximum diameter of the open pores of the skeleton.

[0053] As long as measurements are taken of the same porous metal body, it has been confirmed that there is almost no variation in the measurement results even if the position from which the SEM image is taken and the position of the measurement area in the SEM image are set arbitrarily.

[0054] In the metal porous body of embodiment 1, the number of open pores per unit area on the surface of the skeleton is 1.6 pores / μm 2 More than 5 pieces / μm 2 Less than 1.8 particles / μm is acceptable. 2 More than 4 pieces / μm 2 or less, or 2 pieces / μm 2 More than 3 pieces / μm 2 The number of openings per unit area may be 1.6 / μm or less. 2 When the number of open pores per unit area is 5 / μm or more, the specific surface area of ​​the metal porous body is further increased. 2 If it is equal to or less than this, the strength of the skeleton is sufficient and the metal porous body is easy to handle.

[0055] The method for measuring the number of open holes per unit area on the surface of the skeleton is as follows. An SEM image of the surface of the skeleton of the metal porous body is obtained. The magnification of the SEM observation is 10,000 times. A rectangular measurement area of ​​5 μm × 5 μm is set in the SEM image. The position of the measurement area in the SEM image can be set arbitrarily as long as the entire measurement area is set inside the skeleton part. The number of all open holes in the measurement area is measured. Open holes whose entire outer edges are located within the measurement area are measured. If an open hole straddles the inside and outside of the measurement area, the open hole is not measured.

[0056] There is no particular limitation on the method for measuring the number of open pores. For example, the SEM images may be printed and counted visually, or the SEM images may be imported into a personal computer and counted using image processing software.

[0057] The number of open holes per unit area is calculated based on the number of open holes in the measurement region and the area of ​​the measurement region.

[0058] The above measurement is performed in the measurement area set in each of the three SEM images obtained in non-overlapping areas. In each of the three measurement areas, the number of open holes per unit area is measured. In the present disclosure, the average number of open holes per unit area in the three measurement areas corresponds to the number of open holes per unit area on the surface of the scaffold.

[0059] As long as measurements are taken of the same porous metal body, it has been confirmed that there is almost no variation in the measurement results even if the position from which the SEM image is taken and the position of the measurement area in the SEM image are set arbitrarily.

[0060] <Skeletal Composition> In the metal porous body of embodiment 1, the skeleton contains at least one selected from the group consisting of nickel, cobalt, iron, tin, copper, and chromium. The skeleton may have a composition of at least one selected from the group consisting of nickel, nickel-chromium alloy, nickel-cobalt alloy, nickel-tin alloy, nickel-iron alloy, nickel-copper alloy, cobalt, cobalt-chromium alloy, cobalt-tin alloy, cobalt-iron alloy, cobalt-copper alloy, or copper.

[0061] The total content of nickel, cobalt, iron, tin, copper, and chromium in the skeleton may be 80% by mass or more and 100% by mass or less, 83% by mass or more and 99% by mass or less, or 85% by mass or more and 98% by mass or less.

[0062] The skeleton may be made of at least one selected from the group consisting of nickel, cobalt, iron, tin, copper, and chromium. The skeleton may be made of at least one selected from the group consisting of nickel, cobalt, iron, tin, copper, and chromium, and impurities. Examples of impurities include carbon, phosphorus, sulfur, oxygen, and chlorine. The content of impurities in the skeleton may be 20% by mass or less, or 15% by mass or less.

[0063] The composition of the skeleton is identified by the following procedure. The metal porous body is embedded in a resin (e.g., epoxy resin), the resin is hardened, and then the surface is processed using a grinder and a cross-section polisher to expose the cross section of the skeleton. The cross section of the skeleton is subjected to surface analysis using SEM-EDX to identify the composition. The condition for SEM-EDX is an acceleration voltage of 15 keV.

[0064] <BET surface area of ​​the skeleton> In the metal porous body of embodiment 1, the BET surface area of ​​the skeleton is 0.8 m from the viewpoint of increasing the specific surface area of ​​the metal porous body. 2 / g or more, 1.5m 2 / g or more, or 5m 2 The upper limit of the BET surface area of ​​the skeleton is not particularly limited, but from the viewpoint of production, it is preferably 30 m 2 The BET surface area of ​​the framework may be less than 0.8 m 2 / g or more 30m 2 / g or less is acceptable, and 1.5m 2 / g or more 25m 2 / g or less, or 5m 2 / g or more 20m 2 / g or less.

[0065] The BET surface area of ​​the skeleton is measured using a specific surface area / pore distribution measuring device (MicrotracBEL Corp.'s "BELSORP mini" (trademark)). As a pretreatment, the metal porous body is dried using a vacuum dryer. The drying conditions are 120°C for 12 hours or more. The adsorption gas during the measurement is nitrogen, and the adsorption temperature is 77K.

[0066] <Porosity of the skeleton> In the metal porous body of embodiment 1, the skeleton can contain pores. Fig. 10 is a diagram showing an example of an SEM image of a cross section of the skeleton of the metal porous body of embodiment 1. As shown in Fig. 10, there are a plurality of small black regions inside the skeleton 11 itself, which correspond to pores present inside the skeleton. Note that although the region surrounded by the skeleton 11 is hollow, the hollows are not pores of the skeleton.

[0067] In the metal porous body of embodiment 1, the porosity of the skeleton may be 20% or more and 40% or less, 25% or more and 38% or less, or 30% or more and 35% or less. When the porosity of the skeleton is 20% or more, the specific surface area of ​​the metal porous body is further increased. When the porosity of the skeleton is 40% or less, the skeleton has sufficient strength and is easy to handle.

[0068] The porosity of the skeleton is measured as follows. The metal porous body is embedded in resin (e.g., epoxy resin), and after the resin has hardened, the surface is processed using a grinder and a cross-section polisher to expose the cross section of the skeleton. An SEM image of the cross section of the skeleton is obtained. The observation magnification with the SEM is 5,000 times. A rectangular measurement area of ​​5 μm x 5 μm is set inside the skeleton part of the SEM image. The position of the measurement area in the SEM image can be set arbitrarily as long as the entire measurement area is set inside the skeleton part. The SEM image is imported into a PC and binarized using image processing software. In the binarized image, the metal parts of the skeleton are shown in white, and the pores present inside the skeleton are shown in black.

[0069] The percentage of the pore area relative to the total area of ​​the measurement region is calculated.

[0070] The above measurement is performed in a measurement area set in each of three SEM images acquired in non-overlapping areas. In each of the three measurement areas, the percentage of the pore area relative to the total area of ​​the measurement area is calculated. In the present disclosure, the average of the percentages of the three pore areas corresponds to the porosity of the skeleton.

[0071] As long as measurements are taken of the same porous metal body, it has been confirmed that there is almost no variation in the measurement results even if the position from which the SEM image is taken and the position of the measurement area in the SEM image are set arbitrarily.

[0072] <Potassium> The metal porous body of embodiment 1 may contain potassium. In the metal porous body, the ratio of the number of moles of potassium to the total number of moles of nickel, cobalt, iron, tin, copper, and chromium (hereinafter also referred to as the "molar ratio of potassium") may be 0.001 or more and 0.1 or less, 0.002 or more and 0.01 or less, or 0.003 or more and 0.008 or less, from the viewpoint of improving the nitrous oxide decomposition ability.

[0073] The molar ratio of potassium in the metal porous body is measured by X-ray fluorescence (XRF) analysis. Specifically, it is measured by irradiating the skeleton surface with X-rays using an energy dispersive X-ray fluorescence analyzer (JEOL Ltd. "JSX-3100R II" (trademark)).

[0074] <Method of manufacturing porous metal body> The manufacturing method of the metal porous body of embodiment 1 can include a step of preparing a metal porous body precursor, an oxidation treatment step of performing an oxidation treatment on the metal porous body precursor, and a reduction treatment step of performing a reduction treatment on the metal porous body precursor after the oxidation treatment.

[0075] <Step of preparing a metal porous body precursor> A porous metal precursor may be prepared, for example, Celmet (registered trademark) manufactured by Sumitomo Electric Industries, Ltd.

[0076] When the metal porous body precursor is not available on the market, the metal porous body precursor may be manufactured by the following method. A sheet of a resin molded body having a three-dimensional mesh structure is prepared. As the resin molded body, a polyurethane resin, a melamine resin, or the like can be used. Then, a conductive treatment step is performed to form a conductive layer on the surface of the resin molded body. The conductive treatment can be performed, for example, by applying a conductive paint containing conductive particles such as carbon and conductive ceramic, forming a layer of a conductive metal such as nickel and copper by an electroless plating method, or forming a layer of a conductive metal by a vapor deposition method or a sputtering method. Then, a plating step is performed to electroplate a metal such as nickel using the resin molded body with a conductive layer formed on its surface as a substrate. The electroplating may be performed by a known method.

[0077] Finally, a removal step is carried out by heat treatment or the like to remove the resin molded body used as the substrate, thereby obtaining a metal porous body precursor having a skeleton with a three-dimensional network structure.

[0078] <Oxidation treatment process> Next, the metal porous body precursor is subjected to an oxidation treatment, for example, by heating the metal porous body precursor in a muffle furnace in the atmosphere at 1000° C. to 1600° C. for 0.1 to 24 hours.

[0079] <Reduction treatment process> Next, the metal porous body after the oxidation treatment is subjected to a reduction treatment, whereby the metal porous body of the first embodiment can be obtained.

[0080] The reduction treatment is carried out, for example, by subjecting the metal porous body precursor to a muffle furnace in a 4% to 100% H 2 The reaction is carried out by heating in an Ar-balanced atmosphere at 400° C. to 800° C. for 0.1 to 10 hours.

[0081] The present inventors have found that by subjecting a metal porous body precursor to the above-mentioned oxidation and reduction treatments, a plurality of open pores that open to the outer surface can be formed on the surface of the skeleton.

[0082] <Potassium loading process> The method for producing a metal porous body according to the first embodiment may further include a potassium supporting step after the reduction treatment step, thereby obtaining a metal porous body containing potassium.

[0083] The potassium loading process can be carried out by the following procedure. A 5 mol / L KOH aqueous solution is prepared, and the metal porous body is immersed in it. After 30 minutes of 120 kHz ultrasound is applied, the body is left to stand overnight at room temperature. Washing is carried out about five times with distilled water. The pH of the solution after the fifth and subsequent washes is adjusted to 9 or higher. After washing, the body is dried. This allows a metal porous body containing potassium to be obtained.

[0084] <Applications of porous metal bodies> The metal porous body of the first embodiment is used in alkaline water electrolysis devices and CO 2 It can be used as an electrode for electrolysis devices, and as a substrate for supporting substances such as amines and catalysts.

[0085] [Embodiment 2: Nitrous oxide decomposition element] A nitrous oxide decomposition element according to one embodiment of the present disclosure (hereinafter also referred to as "embodiment 2") is made of the porous metal body of embodiment 1. The porous metal body of embodiment 1 has an increased specific surface area. Therefore, the nitrous oxide decomposition element made of the porous metal body can have excellent nitrous oxide decomposition ability.

[0086] In the second embodiment, the metal porous body may have a composition of nickel, cobalt, or a nickel-cobalt alloy, which further improves the ability to decompose nitrous oxide.

[0087] [Embodiment 3: Nitrous oxide decomposition device] A nitrous oxide decomposition device according to one embodiment of the present disclosure (hereinafter also referred to as "embodiment 3") includes the nitrous oxide decomposition element of embodiment 2. The nitrous oxide decomposition element of embodiment 2 has excellent nitrous oxide decomposition ability. Therefore, the nitrous oxide decomposition device of embodiment 3 can also have excellent nitrous oxide decomposition ability. EXAMPLES

[0088] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0089] [Preparation of porous metal bodies] <Sample 1 to Sample 3> <Step of preparing a metal porous body precursor> As a precursor of the metal porous body, "Nickel Celmet" (trademark) manufactured by Sumitomo Electric Industries, Ltd. (product number #8, average pore size 0.45 mm, thickness 1.2 mm, basis weight 315 g / m) was used. 2 A porosity of 97% was prepared.

[0090] <Oxidation treatment process> Next, the porous metal precursor was subjected to an oxidation treatment by heating the porous metal precursor in a muffle furnace in the atmosphere at 1200° C. for 2 hours.

[0091] <Reduction treatment process> Next, the metal porous body after the oxidation treatment was subjected to a reduction treatment. The reduction treatment was carried out by subjecting the metal porous body precursor to a muffle furnace in an atmosphere of 10% by volume of H 2 The heating was carried out at 600° C. for 1 hour under an Ar balanced atmosphere. As a result, a metal porous body of Sample 1 was obtained.

[0092] <Potassium loading process> For samples 2 and 3, a potassium loading step was further carried out. A 5 mol / L KOH aqueous solution was prepared and the metal porous bodies were immersed in it. After 30 minutes of irradiation with 120 kHz ultrasound, the bodies were left to stand overnight at room temperature. Sample 2 was washed six times with distilled water. Sample 3 was washed five times with distilled water. For samples 2 and 3, the solutions after the fifth and subsequent washes had a pH of 9 or higher. After washing, the bodies were dried. In this way, the metal porous bodies of samples 2 and 3 were obtained.

[0093] <Sample 4> In Sample 4, the same porous metal body precursor as in Samples 1 to 3 was used as the porous metal body.

[0094] <Sample 5> For Sample 5, a porous metal body was obtained by carrying out the same potassium supporting step as for Sample 3 on the same porous metal body precursor as for Samples 1 to 3. For Sample 5, the oxidation treatment step and the reduction treatment step were not carried out.

[0095] [Measurement of porous metal bodies] The composition of the skeleton of each sample of the porous metal body was measured by SEM-EDX. The specific measurement method is as described in embodiment 1. It was confirmed that the skeleton of all samples contained 85 mass % or more of nickel.

[0096] For each sample of the porous metal body, the presence or absence of open pores on the surface of the skeleton, the porosity of the skeleton, the maximum diameter of the open pores in the skeleton, and the number of open pores per unit area on the surface of the skeleton were measured using a SEM. The specific measurement method is as described in embodiment 1. The results are shown in the "Open pores on the surface", "Porosity", "Average maximum diameter of open pores", and "Number of open pores" columns of "Skeleton" in Table 1.

[0097] The BET surface area of ​​the skeleton of each sample of the porous metal body was measured using a specific surface area / pore distribution measuring device. The specific measuring method is as described in embodiment 1. The results are shown in the "BET surface area" column of "skeleton" in Table 1.

[0098] The nickel and potassium contents of the metal porous bodies of each sample were measured by X-ray fluorescence analysis. The ratio of the number of moles of potassium to the number of moles of nickel is shown in the "K / Ni" column of "Metal Porous Body" in Table 1. Note that in all samples, the skeleton does not contain cobalt, iron, tin, copper, or chromium. Therefore, the value of "K / Ni" in Table 1 corresponds to the ratio of the number of moles of potassium to the total number of moles of nickel, cobalt, iron, tin, copper, and chromium described in embodiment 1.

[0099] [Table 1]

[0100] [Measurement of decomposition rate of nitrous oxide] The decomposition rate of nitrous oxide in each sample was measured by the following procedure: Each sample of porous metal was cut into a size of about 1 mm x 1 mm to prepare a chip-shaped test piece.

[0101] A quartz tube was prepared as the flow path tube. The diameter of the inner space of the quartz tube was 1 / 4 inch. A plurality of test pieces made of a porous metal were filled into the inner space of the flow path tube, with a total weight of 0.15 g. In order to fix the porous metal body in the flow path tube, glass wool was placed on both ends of the porous metal body. The quartz tube filled with the test pieces made of the porous metal body was set in a tubular furnace and heated at 600°C for 1 hour.

[0102] Nitrous oxide (N 2 O) content is 1% by volume, 2 A mixture of O and argon (Ar) gas was introduced into the flow tube 10 cm from one opening. 3 / min, and the decomposition rate of nitrous oxide at 450°C was measured.

[0103] The decomposition rate of nitrous oxide was calculated by measuring the composition of the gas after passing through the metal porous body using an online connected Q-mass. The results of the decomposition rate of nitrous oxide at 450°C are shown in Table 1 as "N 2 The results are shown in the "N O decomposition rate" column. 2The higher the "O decomposition rate," the higher the nitrous oxide decomposition ability of the porous metal material.

[0104] [Consideration] The metal porous bodies of Samples 1 to 3 correspond to Examples. The metal porous bodies of Samples 4 to 5 correspond to Comparative Examples. It was confirmed that the metal porous bodies of Samples 1 to 3 have a larger specific surface area and excellent nitrous oxide decomposition ability compared to the metal porous bodies of Samples 4 to 5. Therefore, the nitrous oxide decomposition elements made of the metal porous bodies of Samples 1 to 3 also have excellent nitrous oxide decomposition ability, and a nitrous oxide decomposition device including the nitrous oxide decomposition elements can also have excellent nitrous oxide decomposition ability.

[0105] Although the embodiments and examples of the present disclosure have been described above, it is intended from the outset that the configurations of the above-described embodiments and examples may be appropriately combined or modified in various ways. The embodiments and examples disclosed herein are illustrative in all respects and should not be considered as limiting. The scope of the present invention is indicated by the claims, not by the embodiments and examples described above, and is intended to include the meaning equivalent to the claims and all modifications within the scope. [Explanation of symbols]

[0106] 1. Porous metal 2. Nitrous oxide decomposition catalyst 5 Support section 6 Node section 10 Frame section 11 Skeleton 12 Opening hole 20 Cell Section 30 Three-dimensional mesh structure

Claims

1. A metal porous body having a skeleton with a three-dimensional network structure, The skeleton is composed of a plurality of support parts and node parts connecting the plurality of support parts, The skeleton has a plurality of openings that open to a surface of the skeleton, The skeleton of the porous metal body comprises at least one element selected from the group consisting of nickel, cobalt, iron, tin, copper, and chromium.

2. The BET surface area of ​​the framework is 0.8 m ２ The metal porous body according to claim 1, wherein the molecular weight is 1 / g or more.

3. 3. The metal porous body according to claim 1, wherein the average maximum diameter of the open pores in the skeleton is 0.1 μm or more and 2 μm or less.

4. The number of the open holes per unit area on the surface of the skeleton is 1.6 / μm ２ More than 5 pieces / μm ２ The metal porous body according to claim 1 or 2, wherein:

5. 3. The metal porous body according to claim 1, wherein the porosity of the skeleton is 20% or more and 40% or less.

6. The metal porous body according to claim 1 or 2, comprising potassium.

7. A nitrous oxide decomposition element comprising the metallic porous body according to claim 1 or 2.

8. A nitrous oxide decomposition device comprising the nitrous oxide decomposition element according to claim 7.

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