Sheet-shaped titanium porous body, its manufacturing method and use

Abstract

A sheet-shaped porous titanium body is disclosed. The thickness of the sheet-shaped porous titanium body is 40 μm or more and 500 μm or less, and the porosity is 30% or more and 50% or less. The surface roughness of a first main surface of the sheet-shaped porous titanium body is lower than the surface roughness of a second main surface opposite the first main surface. In the peripheral portion of the sheet-shaped porous titanium body, the number of first protrusions having a height of 30 μm or more protruding from the first main surface is equal to or less than the number of second protrusions having a height of 30 μm or more protruding from the second main surface in the peripheral portion.

Description

[Technical field]

[0001] One embodiment of the present invention relates to a sheet-shaped porous titanium body, a production method and use thereof, and a jig for implementing the above-mentioned production method. [Background technology]

[0002] Sheet-shaped porous metal bodies containing metals (zero-valent metals) are widely used in filters, secondary battery electrodes, solid polymer fuel cell current collectors, catalyst carriers, and the like. The sheet-shaped porous metal bodies are cut using a laser or a blade depending on the application and then used (see Patent Documents 1 and 2). Patent Document 1 discloses that a long sheet-shaped porous metal body extending in a specific direction can be cut using a pair of blades facing each other. Patent Document 2 discloses that a laminate of a sheet-shaped porous metal body and an adjacent layer is laser-cut, and the sides of the sheet-shaped porous metal body and the adjacent layer are bonded to each other at the laser cut points, so to speak, forming a laminate of a sheet-shaped porous metal body and an adjacent layer. In this method, icicle-like burrs are formed at the laser cut points to firmly bond the sheet-shaped porous metal body and the adjacent layer, thereby exerting an anchor effect. In other words, it can be said that this is a cutting method that actively forms burrs. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 039693 [Patent Document 2] JP 2011-106023 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of one embodiment of the present invention is to provide a sheet-shaped porous metal body containing titanium, i.e., a sheet-shaped porous titanium body and its use. Alternatively, an object of one embodiment of the present invention is to provide a method for producing a sheet-shaped porous titanium body with high efficiency and good yield, and a jig for implementing this method. [Means for solving the problem]

[0005] One embodiment of the present invention is a sheet-shaped porous titanium body. The thickness of this sheet-shaped porous titanium body is 40 μm or more and 500 μm or less, and the porosity is 30% or more and 50% or less. The surface roughness of a first main surface of the sheet-shaped porous titanium body is lower than the surface roughness of a second main surface opposite to the first main surface. At the peripheral portion of the sheet-shaped porous titanium body, the number of first protrusions having a height of 30 μm or more protruding toward the first main surface is equal to or less than the number of second protrusions having a height of 30 μm or more protruding toward the second main surface at the peripheral portion.

[0006] One embodiment of the present invention is the use of the above-mentioned sheet-shaped porous titanium body as a porous transport layer in a polymer electrolyte membrane water electrolysis device.

[0007] One embodiment of the present invention is a method for producing hydrogen by using the above-mentioned porous titanium sheet in a polymer electrolyte membrane water electrolysis device.

[0008] One embodiment of the present invention is a method for producing a sheet-shaped porous titanium body, which includes the steps of: placing a mother sheet containing a porous titanium body on a jig including at least one stage having at least one through-hole, a frame surrounding the at least one stage and spaced apart from the at least one stage, and at least one connecting portion connecting the at least one stage and the frame to each other, so as to cover the at least one through-hole and a gap between the at least one stage and the frame, adsorbing the mother sheet onto the jig, and cutting the mother sheet by scanning a laser beam emitted from a fiber laser over the mother sheet along the gap.

[0009] One embodiment of the present invention is a jig for producing a sheet-shaped porous titanium body, the jig comprising at least one stage having at least one through hole, a frame surrounding and spaced apart from the at least one stage, and at least one connecting part connecting the at least one stage and the frame to each other. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic diagram showing a method for producing a sheet-shaped porous titanium body according to one embodiment of the present invention. [Figure 2A] FIG. 2 is a schematic top view of a jig according to an embodiment of the present invention. [Figure 2B] FIG. 2 is a schematic side view of a jig according to one embodiment of the present invention. [Figure 3A] FIG. 2 is a schematic end view of a jig according to one embodiment of the present invention. [Figure 3B] FIG. 2 is a schematic end view of a jig according to one embodiment of the present invention. [Figure 3C] FIG. 2 is a schematic end view of a jig according to one embodiment of the present invention. [Figure 3D] FIG. 2 is a schematic end view of a jig according to one embodiment of the present invention. [Figure 4A] FIG. 2 is a schematic side view including a jig according to one embodiment of the present invention. [Figure 4B] FIG. 4 is a schematic top view of an airflow adjustment table used in a jig according to one embodiment of the present invention. [Figure 5A] FIG. 2 is a schematic top view showing a method for producing a sheet-shaped porous titanium body according to one embodiment of the present invention. [Figure 5B] FIG. 2 is a schematic end view showing a method for producing a sheet-shaped porous titanium body according to one embodiment of the present invention. [Figure 6A] FIG. 2 is a schematic end view showing a method for producing a sheet-shaped porous titanium body according to one embodiment of the present invention. [Figure 6B]FIG. 2 is a schematic top view showing a method for producing a sheet-shaped porous titanium body according to one embodiment of the present invention. [Figure 7] FIG. 2 is a schematic top view of a jig according to an embodiment of the present invention. [Figure 8A] FIG. 1 is a schematic perspective view of a sheet-shaped porous titanium body according to one embodiment of the present invention. [Figure 8B] FIG. 1 is a schematic side view of a sheet-shaped porous titanium body according to one embodiment of the present invention. [Figure 9A] FIG. 1 is a schematic perspective view of a sheet-shaped porous titanium body according to one embodiment of the present invention. [Figure 9B] FIG. 1 is a schematic side view of a sheet-shaped porous titanium body according to one embodiment of the present invention. [Figure 10A] Photograph of a mother sheet produced in an embodiment. [Figure 10B] Photograph of a sheet-shaped porous titanium body produced in an example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, a method for producing a sheet-shaped porous titanium body according to an embodiment of the present invention, and a sheet-shaped porous titanium body produced according to this production method will be described with reference to the drawings, etc. However, the present invention can be embodied in various forms without departing from the gist of the invention, and should not be construed as being limited to the description of the embodiment exemplified below.

[0012] In order to clarify the description, the drawings may show the width, thickness, shape, etc. of each part in a schematic manner compared to the actual embodiment, but these are merely examples and do not limit the interpretation of the present invention. In this specification and each drawing, elements having the same functions as elements explained in the previous drawings may be given the same reference numerals, and duplicate explanations may be omitted.

[0013] 1. Manufacturing method of sheet-shaped porous titanium Hereinafter, a method for producing a sheet-shaped porous titanium body according to one embodiment of the present invention will be described. Since porous titanium bodies have high liquid permeability, air permeability, electrical conductivity, and excellent corrosion resistance, they are used as electrode materials and filters that can be used in highly corrosive environments. In particular, sheet-shaped porous titanium bodies having a thickness of several tens of μm to several hundreds of μm are useful as porous transport layers (PTLs) in polymer electrolyte membrane (PEM)-type water electrolysis devices.

[0014] In this manufacturing method, a large porous titanium sheet having a larger area than the final porous titanium sheet is produced, and this is cut appropriately to produce a porous titanium sheet having the desired size and shape. Hereinafter, this large porous titanium sheet will be referred to as the "mother sheet."

[0015] The mother sheet and the sheet-shaped titanium porous body are essentially made of pure titanium, also called industrially pure titanium, and the purity of the titanium is, for example, equivalent to pure titanium type 1 to type 4, typically type 1 to type 2, of JIS H 4600 (2012). More specifically, the titanium content in the mother sheet and the sheet-shaped titanium porous body is 97% by mass or more or 98% by mass or more. The upper limit of the titanium content is 99.8% by mass or less or 99% by mass or less. The titanium content is calculated by subtracting the total content of metal components other than titanium and nonmetallic components such as oxygen from 100% by mass. Depending on the manufacturing conditions of the sheet-shaped titanium porous body, the oxygen content may be higher than that of industrially pure titanium. For example, in the paste method described later, the oxygen content of the sheet-shaped titanium porous body manufactured tends to be higher than that of the dry method.

[0016] (1) Preparation of the mother sheet There is no restriction on the method of producing the mother sheet, and it may be produced by, for example, a dry method or a paste method. In the dry method, for example, titanium fine particles or titanium fibers with a purity of 99% or more are deposited on a setter, then scraped to form a sheet, and then heated and sintered at a high temperature (for example, 950°C or higher) to obtain a mother sheet. At this time, in order to facilitate separation from the setter, it is preferable to apply a release agent such as boron nitride or titanium boride to the setter and deposit the titanium fine particles or titanium fibers on it. The shape of the titanium fine particles may be spherical, but by using a shape that deviates from a sphere, for example, titanium fine particles (HDH powder) produced by a hydrogenation-dehydrogenation method, the number of junctions between the titanium fine particles increases. As a result, a mother sheet having a three-dimensional mesh structure with many pores inside can be obtained. When titanium fine particles are used, a mother sheet having a sponge-like three-dimensional mesh structure can be obtained. On the other hand, when titanium fibers are used, a mother sheet having a nonwoven three-dimensional mesh structure can be obtained.

[0017] In the paste method, first, a paste containing titanium fine particles or titanium fibers, a binder, and a solvent is prepared. Examples of binders include cellulose, polyvinyl alcohol resin, acrylic resin, and polyvinyl butyral resin. Examples of solvents include alcohols such as ethanol and isopropanol, aromatic solvents such as toluene and xylene, hydrocarbons such as cyclohexane, and ketones such as methyl ethyl ketone. The paste may further contain additives such as a defoaming agent, a dispersing agent, a leveling agent, and a plasticizer. However, it is preferable that the paste does not contain a foaming agent and water. As shown in FIG. 1, the paste 134 is applied onto a substrate 150, and the solvent is removed at room temperature or under heating conditions (for example, 80° C. to 160° C.) to obtain a sheet-shaped green body 136.

[0018] The green body 136 is peeled off from the substrate and placed on a setter 152, which is a supporting substrate. At this time, it is preferable to place the green body 136 so that the surface 136a of the green body 136 that was in contact with the substrate 150 is located on the opposite side to the setter 152 (see FIG. 1). Thereafter, the green body 136 placed on the setter 152 is heated in an oxygen-containing atmosphere such as air, thereby performing debinding. The debinding may be performed, for example, by heating at a temperature of 300° C. to 450° C. for 3 hours to 20 hours. As a result, the binder and additives are thermally decomposed or volatilized, and a sheet-like brown body 138 substantially made of titanium is obtained.

[0019] Furthermore, after the binder is removed, the brown body 138 placed on the setter 152 is sintered at a high temperature of about 750°C to 1100°C to obtain the mother sheet 130. Even when the paste method is used, the mother sheet 130 having a sponge-like or nonwoven fabric-like three-dimensional mesh structure can be obtained, as in the dry method. When the paste does not contain water and a foaming agent, the surface smoothness of the mother sheet 130 produced tends to be excellent, and in particular, the surface 130a of the mother sheet 130 originating from the surface 136a of the green body 136 that was in contact with the substrate 150 (hereinafter, the surface 130a for convenience) has a smaller surface roughness than the surface 130b opposite to the surface 130a (hereinafter, the back surface for convenience). For example, the maximum height Rz, which is an index of the surface roughness of the surface 130a, is 1.0 μm or more and 10 μm or less, or 1.0 μm or more and 7 μm or less, or 1.0 μm or more and 5 μm or less. On the other hand, the maximum height Rz of the rear surface 130b is larger than that of the front surface, and exceeds, for example, 10 μm. The maximum surface height Rz may be determined in accordance with ISO (International Organization for Standardization) 4287-1997.

[0020] There is no restriction on the size of the mother sheet 130, and it is sufficient that it is larger than the titanium porous body finally produced. For example, the mother sheet 130 may have a rectangular shape with one side of 200 mm to 2000 mm. The thickness of the mother sheet 130 can also be determined arbitrarily, and can be selected from the range of, for example, 10 μm to 3000 μm, 40 μm to 1000 μm, or 40 μm to 500 μm, and is typically 40 μm to 300 μm. There is no restriction on the porosity of the mother sheet 130, but it is preferably 30% to 50%. A sheet-shaped titanium porous body with a smooth surface tends to have a small porosity to some extent. In addition, in the cells of the (PEM) type water electrolysis device, the ion exchange membrane and the sheet-shaped titanium porous body may be arranged in a pressed state, and if the surface of the sheet-shaped titanium porous body is smooth, damage to the ion exchange membrane can be effectively suppressed.

[0021] (2) Cutting the mother sheet The following describes a method for cutting the mother sheet 130. The sheet-shaped porous titanium body is produced by appropriately cutting the mother sheet 130 using a jig that will be described in detail below.

[0022] A Jig A schematic top view of the jig 100 is shown in Fig. 2A, and schematic views of the end faces along the dashed lines AA', BB', and CC' in Fig. 2A are shown in Figs. 3A to 3C, respectively. As shown in Fig. 2A, the jig 100 includes at least one stage 104 and a frame 102 surrounding the stage 104. As shown in Fig. 2B, a suction table 110 is disposed below the jig 100. The thicknesses of the stage 104 and the frame 102 may be appropriately determined depending on their sizes, and are, for example, 1 mm or more and 10 mm or less.

[0023] The stage 104 and the frame 102 are not in direct contact with each other and are separated from each other. However, the stage 104 and the frame 102 are connected by at least one connecting portion 106. Therefore, a gap (groove) 108 is formed between the stage 104 and the frame 102 (see Figs. 2A and 3B). As described later, a mother sheet 130 is arranged so as to overlap the gap 108, and a laser beam is irradiated along the gap 108, whereby the mother sheet 130 is cut and a sheet-shaped porous titanium body is cut out. Therefore, the shape of the gap 108 substantially determines the shape of the sheet-shaped porous titanium body. The shape of the gap 108 is determined by the outer peripheral shape of the stage 104. In other words, the outer peripheral shape of the stage 104 may be appropriately selected depending on the shape of the sheet-shaped porous titanium body to be manufactured, and may be, for example, a polygon including a rectangle, a circle or an ellipse, or a shape defined by an outline composed of curves and straight lines.

[0024] The stage 104, the frame 102, and the connecting parts 106 include, for example, a metal. Preferably, all of them include titanium, and more preferably, they are made of titanium with a purity of 99% or more by mass, which is called industrially pure titanium. By including high-purity titanium in the stage 104, the frame 102, and the connecting parts 106, contamination during cutting of the mother sheet 130 can be prevented. As a result, the incorporation of impurities into the sheet-shaped porous titanium can be prevented.

[0025] Alternatively, at least one of the stage 104, the frame 102, and the connecting portion 106 may include resin or wood. Examples of resin include polypropylene, polycarbonate, acrylic resin, and engineering plastics such as polyether ether ketone, polytetrafluoroethylene, polyamide, polyacetal, modified polyphenylene ether, polybutylene terephthalate, and polyphenylene sulfide. By using resin or wood, the jig 100 can be made lighter.

[0026] As shown in FIG. 2A to FIG. 3C, the stage 104 is provided with at least one through hole 104a penetrating the stage 104 in a direction perpendicular to the upper surface thereof. The at least one through hole 104a may include a plurality of through holes 104a. The plurality of through holes 104a are preferably arranged at a uniform density, i.e., at a constant pitch. The pitch of the through holes 104a may be set, for example, in the range of 30 mm to 70 mm. The shape of the through hole 104a (the shape on the upper surface of the stage 104) is, for example, a circle or a polygon. In the latter case, each corner may be rounded. The size of the at least one through hole 104a may also be appropriately determined. For example, when the shape of the through hole 104a is a circle, the diameter may be appropriately selected from the range of 10 mm to 30 mm. When the shape of the through hole 104a is a polygon, the area of ​​the through hole 104a may be equal to the area of ​​the circular through hole 104a described above. The through holes 104a may be arranged in a matrix, or may be arranged so as to occupy the vertices of a honeycomb structure.

[0027] As described above, the frame 102 surrounds the stage 104. Therefore, the shape of the inner circumference of the frame (the outline of the upper surface of the frame 102 on the side of the stage 104) is substantially similar to the outer circumference of the stage 104. The inner circumference of the frame 102 is preferably set so that the width of the gap 108 between the frame 102 and the stage 104 is 1 mm or more and 10 mm or less, typically 3 mm or more and 6 mm or less. As described later, the mother sheet 130 is sucked onto the frame 102 and the stage 104 in a state in which it is arranged to cover the gap 108, and by making the gap 108 have a width in the above range, it is possible to suppress bending of the mother sheet 130 above the gap 108, thereby enabling precise cutting.

[0028] At least one connecting portion 106 connecting the stage 104 and the frame 102 may include a plurality of connecting portions 106. The connecting portions 106 are provided so as to block a portion of the gaps 108. Therefore, the number of connecting portions 106 and the number of gaps 108 are usually the same. The positions of the connecting portions 106 may be appropriately determined so as to stably maintain the positional relationship between the stage 104 and the frame 102. Preferably, a pair of connecting portions 106 is provided in the jig 100 so as to sandwich the stage 104. Also, as shown in FIG. 2A, a plurality of pairs of connecting portions 106 may be provided to sandwich the stage 104 in mutually intersecting directions. By connecting the stage 104 and the frame 102 with the connecting portions 106, the positional relationship between the stage 104 and the frame 102 is fixed. That is, the shape of the gaps 108, which substantially determines the shape of the sheet-like porous body obtained by cutting the mother sheet 130, can be fixed. As a result, a sheet-like porous body having a constant shape can be efficiently mass-produced. The width of the connecting portion 106 (the length in the direction perpendicular to the side surfaces of the stage 104 and the frame 102) corresponds to the width of the gap 108. Therefore, the width of the connecting portion may be set to 1 mm or more and 10 mm or less, typically 3 mm or more and 6 mm or less. In general, when cutting a sheet-shaped porous metal body, protrusions called burrs (protrusions protruding from the peripheral portion toward one main surface side, with the main surface opposite to the protruding direction being flat or nearly flat) may occur on the cut surface. From the viewpoint of suppressing the occurrence of burrs in the sheet-shaped porous titanium body during cutting, it is preferable that the length of the connecting portion 106 (the length in the extension direction of the gap 108 blocked by the connecting portion 106) is relatively short, for example, 0.5 mm or more and 50 mm or less.

[0029] The thickness of the connecting portion 106 (the length in the direction in which the through-hole 104a extends) may be the same as the thickness of the stage 104 or the frame 102, or may be smaller than the thickness of the stage 104 or the frame 102 as shown in FIG. 3D. In the former case, the upper surface of the connecting portion 106 is flush with the upper surfaces of the stage 104 and the frame 102. In the latter case, the height of the upper surface of the connecting portion 106 is lower than the upper surface of the stage 104 or the frame 102. In other words, the upper surface of the connecting portion 106 is located on the lower surface side of the stage 104 and the frame 102 compared to the upper surface of the stage 104 or the frame 102. By setting the height of the upper surface of the connecting portion 106 lower than the upper surface of the stage 104 or the frame 102, it is possible to prevent the connecting portion 106 from contacting the mother sheet 130, and as a result, it is possible to more effectively suppress the occurrence of burrs. Although not shown, the lower surface of the connecting portion 106 may be located closer to the upper surface of the stage 104 and the frame 102 than the lower surface of the stage 104 or the frame 102 .

[0030] The suction table 110 is connected to an exhaust device (not shown) and configured to create a negative pressure on the suction table 110. As described later, at the time of cutting, the mother sheet 130 is placed on the jig 100. Therefore, by using the exhaust device, gas present in the through holes 104a and gaps 108 of the jig 100 is sucked through the suction table 110 (see the arrows in FIG. 2B ), and as a result, the mother sheet 130 is adsorbed onto the jig 100.

[0031] As shown in FIG. 4A, the airflow adjustment table 120 may be disposed between the jig 100 and the suction table 110. Alternatively, the suction table 110 may be integrated with the airflow adjustment table 120. As shown in FIG. 4B, the airflow adjustment table 120 is a support table having a shape smaller than the through-holes 104a of the stage 104 and having a greater number of through-holes 120a than the through-holes 104a. The through-holes 120a extend in a direction perpendicular to the upper surface of the airflow adjustment table 120. There are no restrictions on the shape (shape on the upper surface of the airflow adjustment table 120) and arrangement of the through-holes 120a, but it is preferable to arrange the through-holes 120a having a hexagonal shape in a honeycomb shape so that the through-holes 120a can be arranged at high density. By providing airflow adjustment table 120, the airflow created by suction table 110 can be made uniform, so that mother sheet 130 can be sucked to jig 100 with a uniform force over the entire mother sheet 130.

[0032] B. Cutting the mother sheet 5A to 6B, cutting of the mother sheet 130 using the jig 100 will be described. Fig. 5A is a schematic top view corresponding to Fig. 2A, and Fig. 5B and Fig. 6A are schematic end views corresponding to Fig. 3A.

[0033] First, the mother sheet 130 is placed on the jig 100. At this time, as shown in FIGS. 5A and 5B, the mother sheet 130 is placed on the jig 100 so as to entirely overlap all of the through holes 104a and the gaps 108. At this time, the mother sheet 130 is placed on the jig 100 so that the back surface 130b contacts the stage 104. The mother sheet 130 is also placed so as to entirely or at least partially cover the frame 102. Therefore, all of the through holes 104a and the gaps 108 are covered by the mother sheet 130.

[0034] Subsequently, suction by the exhaust device is started (see the solid arrow in FIG. 5B). When suction is started via the suction table 110, the gas in the through holes 104a and the gaps 108 is sucked into the suction table 110 directly or via the airflow adjustment table 120 (see the dotted arrow in FIG. 5B). As a result, the pressure in the through holes 104a and the gaps 108 becomes negative, and the mother sheet 130 is adsorbed and fixed to the jig 100.

[0035] Then, the mother sheet 130 is cut using a fiber laser. Specifically, as shown in FIG. 6A, the mother sheet 130 is irradiated with laser light 140 emitted from the fiber laser from the opposite side of the jig 100. That is, the laser light 140 is irradiated from the surface 130a side. The fiber laser is a type of solid-state laser that uses an optical fiber as an amplification medium. For example, a rare earth element such as ytterbium is doped into the core at the center of the optical fiber, and one or more cladding layers having a lower refractive index than the core are formed so as to surround the core. The wavelength of the laser light is, for example, 1000 nm or more and 1200 nm or less, and the output is adjusted to, for example, 50 W or more and 800 W or less. The laser light is pulsed, and the pulse frequency may be appropriately selected from the range of 400 Hz to 1200 Hz. The laser light is irradiated so that its focal point is located on the surface of the mother sheet 130 or in its vicinity (for example, ±5 mm or less from the surface). The diameter of the laser light on the mother sheet 130 is adjusted to 40 μm or more and 200 μm or less. The scanning speed of the laser light may be appropriately adjusted according to the thickness and number of the mother sheet 130, and may be, for example, 1000 mm / min or more and 10000 mm / min or less. During the irradiation of the laser light, the whole or part of the environment in which the mother sheet 130 is cut is set to an atmosphere of an inert gas such as nitrogen or argon, preferably an argon atmosphere from the viewpoint of preventing coloring due to nitriding of the cut surface. For example, in an air atmosphere, an inert gas may be sprayed as a shield gas against the irradiation position of the laser light. Alternatively, the entire jig 100 may be placed in an inert gas atmosphere and irradiated with the laser light. This allows the scanning of the laser light to be performed in an inert gas atmosphere, and it is possible to suppress oxidation and nitridation of the mother sheet 130, and contamination and discoloration caused by these.

[0036] The laser light is scanned on the mother sheet 130 along the gap 108. By scanning the laser light from the irradiation start position of the laser light on the gap 108 and the connecting portion 106 and irradiating the laser light again to the irradiation start position, the mother sheet 130 is cut along the scanning path 142 of the laser light as shown in FIG. 6B, and the sheet-shaped titanium porous body 132 having a shape reflecting the shape of the gap 108 can be cut out. When the upper surface of the connecting portion 106 is flush with the upper surface of the stage 104 or the frame 102, the laser light is irradiated with the mother sheet 130 in contact with the connecting portion 106, but by setting the output and / or scanning speed of the laser light within the above-mentioned range, damage to the connecting portion 106 can be prevented. Therefore, the jig 100 can be used repeatedly.

[0037] When irradiating the laser light, the scanning direction is turned by 90° at the corner of the gap 108. At this time, the laser light may be irradiated so that the scanning path of the laser light forms an arc at the corner of the gap 108. This allows the corners of the sheet-shaped porous titanium body 132 to be chamfered, thereby obtaining a sheet-shaped porous titanium body 132 having arc-shaped corners (FIG. 6B). The chamfer radius r can also be set arbitrarily, and may be set, for example, appropriately in the range of 1 mm or more and 15 mm or less.

[0038] The water jet method is known as a method for cutting a sheet-shaped porous metal body, but since an abrasive is used in the water jet method, if cleaning after cutting is insufficient, the abrasive may remain on the sheet-shaped porous titanium body. In addition, in the method of cutting a sheet-shaped porous metal body using a carbon dioxide laser, it is difficult to avoid the generation of burrs during the process of melting and solidifying the cut surface. Normally, burrs with a height (or length) of about 100 μm or less can be physically removed using a spatula, but burrs larger than this size cannot be easily removed. If large burrs are generated on the cut surface, they affect the characteristics of the sheet-shaped porous metal body and the characteristics and reliability of various devices using it. For example, when a sheet-shaped porous titanium body is used as a porous transport layer in a PEM type water electrolysis device, they may induce damage to the adjacent ion exchange membrane.

[0039] On the other hand, as described above, in a method for producing a sheet-shaped porous titanium body according to one embodiment of the present invention, the mother sheet 130 is adsorbed onto the jig 100, and the mother sheet 130 is cut by scanning a laser beam along a narrow gap 108 between the stage 104 and the frame 102 that constitute the jig 100. Therefore, the mother sheet 130 can be cut while fixed to the jig 100 without being significantly deflected in the gap 108. Therefore, the mother sheet 130 can be cut with high precision to produce a sheet-shaped porous titanium body 132 having any desired shape.

[0040] In addition, because the mother sheet 130 is cut using a laser beam, the sheet-shaped porous titanium body 132 can be cut out in a short time of about several tens of seconds, and further, the cleaning and drying processes are unnecessary or can be simplified, thereby reducing the workload. Furthermore, as shown in the examples, the use of a fiber laser can effectively suppress the generation of burrs, preventing the generation of burrs that can affect the properties of the sheet-shaped porous titanium body 132 and the properties of the device in which it is used. These features contribute to improving the manufacturing efficiency and yield of the sheet-shaped porous titanium body.

[0041] C. Modified version In the jig 100 described above, one stage 104 is surrounded by one frame 102. The configuration of the jig 100 is not limited to this, and as shown in FIG. 7, the jig 100 may have multiple stages 104 and a frame 102 surrounding them. Each of the multiple stages 104 is fixed to the frame 102 by at least one connecting portion 106, preferably one or more pairs of connecting portions 106. There is no restriction on the number of stages 104 provided in one jig 100, and it may be appropriately determined within a range of, for example, 2 to 20. In the example shown in FIG. 7, three stages 104-1, 104-2, and 104-3 are surrounded by the frame 102, and gaps 108 are formed between each stage 104 and the frame 102.

[0042] When such a jig 100 is used, a plurality of mother sheets 130 can be arranged and cut at the same time. Alternatively, a single mother sheet 130 can be arranged so as to cover all the stages 104 and the gaps 108, and then a laser beam can be scanned along the gaps 108 to produce a plurality of sheet-shaped porous titanium bodies 132 from the single mother sheet 130. Since it usually takes several hours to several days to produce a single mother sheet 130, when a single sheet-shaped porous titanium body 132 is produced from a single mother sheet 130, the production time per sheet of porous titanium body 132 increases relatively. In contrast, by producing a large mother sheet 130 and cutting out a plurality of porous titanium bodies 132 from it, the production time per sheet of porous titanium body 132 can be significantly reduced. Therefore, by applying one of the embodiments of the present invention, it is possible to provide the sheet-shaped porous titanium body 132 at low cost.

[0043] 2. Characteristics of porous titanium sheet The characteristics of the sheet-shaped porous titanium body 132 produced according to the above-mentioned production method will now be described.

[0044] As described above, the titanium sheet porous body 132 is manufactured by cutting the mother sheet 130 using the laser light 140 emitted from the fiber laser. Therefore, the composition, thickness, and porosity of the titanium sheet porous body 132 are the same as those of the mother sheet 130. The composition can be obtained by subtracting the content of metal elements and nonmetal elements other than titanium from the total amount (100%) of the titanium sheet porous body 132. The content of metal elements other than titanium can be measured, for example, using high-frequency inductively coupled plasma (ICP) atomic emission spectrometry. The content of nonmetal elements such as chlorine, oxygen, carbon, nitrogen, and hydrogen can be measured using the silver nitrate measurement method, the inert gas fusion-infrared absorption method, the high-frequency combustion-infrared absorption method, the inert gas fusion-thermal conductivity method, and the inert gas fusion-thermal conductivity method, respectively. The thickness can be measured using a thickness gauge, and the porosity can be calculated using the apparent density calculated from the volume and mass of the target object and the true density of titanium.

[0045] Furthermore, unlike the sheet-shaped titanium porous body obtained by cutting the mother sheet 130 with a water jet, the sheet-shaped titanium porous body 132 produced by the above method does not contain components derived from an abrasive. Specifically, it does not contain fine particles containing inorganic compounds used as an abrasive, such as silicon oxide, iron (III) oxide, aluminum oxide, magnesium oxide, calcium oxide, and manganese oxide. For example, the waste liquid discharged by washing the sheet-shaped titanium porous body 132 with water or the like does not contain fine particles that constitute an abrasive. Therefore, even if the sheet-shaped titanium porous body 132 is used in a PEM water electrolysis device, the elution of metal ions contained in the abrasive can be ignored, and contamination, deterioration, and damage to the PEM water electrolysis device caused by these metal ions can be prevented.

[0046] Due to the above-mentioned cutting process, the structure of the sheet-shaped porous titanium body 132 at the periphery is different from that of the mother sheet 130 before cutting. Specifically, the bending of the sheet-shaped porous titanium body 132 at the periphery is small. As shown in Figs. 8A and 8B, a curved portion may be generated at the periphery of the mother sheet 130 after sintering due to the bending. Specifically, a convex portion 146 protruding from one surface of the periphery, and a concave portion 148 existing at a position corresponding to the convex portion 146 and recessed on the other surface may be generated. The height of the curved portion, i.e., the height h1 of the convex portion 146 (the height of the convex portion 146 based on the flat portion of the surface on the side where the convex portion 146 exists) is about 1 mm to 2 mm. However, since the peripheral portions where bending may occur can be removed by cutting the mother sheet 130 (see FIG. 6B), there are no curved portions at the peripheral portions of the sheet-shaped porous titanium body 132, as shown in FIG. 8B, or even if there are curved portions, their height is extremely small (for example, 0.1 mm or less).

[0047] Although the sheet-shaped porous titanium body 132 is obtained by cutting the mother sheet 130, there are very few burrs in the peripheral portion, and the size (height) of the burrs is also extremely small. Specifically, as shown in Fig. 9A and Fig. 9B, the number of burrs 144 having a height h2 (height of the burrs 144 based on the flat portion of the first main surface 132a) of 30 μm or more protruding from the surface 130a (see Fig. 1) of the mother sheet 130 toward the surface (hereinafter, the first main surface) 132a of the sheet-shaped porous titanium body 132 is equal to or less than the number of burrs 144 protruding from the back surface 130b toward the surface (hereinafter, the second main surface) 132b of the sheet-shaped porous titanium body 132. There are no burrs 144 protruding toward the first main surface 132a (i.e., the probability of the existence of burrs 144 per any length of the peripheral portion is 0), or the probability of the existence is less than 0.1 per 100 mm of the length of the peripheral portion. Therefore, it is possible to omit the step of physically removing the burrs 144 protruding from the first main surface 132a. As described above, the front surface 130a of the mother sheet 130 produced using the paste method is smoother than the back surface 130b. Therefore, the first main surface 132a of the sheet-shaped titanium porous body 132 is not only highly smooth but also has few burrs, and the ion exchange membrane is less likely to be damaged even when pressed against the ion exchange membrane of a PEM water electrolysis device.

[0048] Furthermore, the number of burrs 144 protruding toward the second main surface 132b is also extremely small, being 0.0 or more and 3.0 or less per 100 mm of the length of the peripheral portion. Furthermore, the height of the burrs 144 protruding toward the first main surface 132a or the second main surface 132b is also suppressed, with a maximum height of 100 μm or less. In other words, there are no burrs exceeding 100 μm. Therefore, even if burrs 144 are generated, almost all of the burrs 144 can be physically removed using a spatula or the like. Even if burrs 144 are present, the burrs 144 do not protrude in a direction parallel to the first main surface 132a or the second main surface 132b. In other words, burrs 144 with a wider base width than the tip are unlikely to be generated. This is considered to be because no shear force is applied to the mother sheet 130, unlike the method of producing the sheet-shaped titanium porous body 132 by shearing the mother sheet 130 with a cutter or the like. As shown in the examples, the effect of suppressing the generation of such burrs 144 is due to the use of laser light emitted from a fiber laser to cut the mother sheet 130. Since there are no burrs 144 with thick bases in the direction parallel to the first main surface 132a or the second main surface 132b, it is possible to suppress the sheet-shaped porous titanium body 132 from being gouged out and damaged during the burr removal operation.

[0049] As described above, the sheet-shaped porous titanium body 132 has few burrs 144 on its peripheral edge, and in particular, there is no or substantially no burrs 144 protruding from the first main surface 132a side. Therefore, by arranging components (e.g., ion exchange membranes) used in contact with the sheet-shaped porous titanium body 132 in the PEM water electrolysis apparatus so that they are in contact with the first main surface 132a, damage to these components can be effectively prevented. This can significantly improve the life and reliability of the PEM water electrolysis apparatus.

[0050] To improve the operating efficiency of the PEM water electrolysis apparatus, a coating is applied to the surface of the sheet-shaped porous titanium body, and the coated sheet-shaped porous titanium body is sometimes brought into contact with an ion exchange membrane or the like. This coating is usually a thin film, and the smoothness of the surface of the sheet-shaped porous titanium body 132 is maintained even after coating. Therefore, even when the coated sheet-shaped porous titanium body is brought into contact with an ion exchange membrane or the like, it can be considered that the sheet-shaped porous titanium body has been brought into contact with an ion exchange membrane or the like.

[0051] The shape of the mother sheet 130 is substantially determined in the process of applying a paste containing titanium fine particles or titanium fibers onto the substrate 150. For this reason, it is difficult to precisely control the shape of the corners of the mother sheet 130, and the corners have a complex shape composed of one or more straight lines and / or one or more curved lines. However, as described above, it is possible to form an arc-shaped chamfered portion at the corners of the sheet-shaped porous titanium body 132 by scanning the laser light in an arc-like manner at the stage of forming the corners of the sheet-shaped porous titanium body 132 in the cutting process of the mother sheet 130. This prevents damage to the sheet-shaped porous titanium body 132 even if an external force is applied to the corners of the sheet-shaped porous titanium body 132, and also prevents damage to other components that come into contact with the corners of the sheet-shaped porous titanium body 132.

[0052] 3. Use of porous titanium sheet To repeat, the sheet-shaped porous titanium body 132 according to one embodiment of the present invention can be suitably used in a PEM water electrolysis device, and is particularly useful as a porous transport layer. For this reason, one embodiment of the present invention is to use the sheet-shaped porous titanium body 132 as a porous transport layer in a polymer electrolyte membrane water electrolysis device. In this case, it is preferable to arrange the sheet-shaped porous titanium body 132 so that a component (e.g., an ion exchange membrane) that contacts the sheet-shaped porous titanium body 132 contacts the first main surface 132a of the sheet-shaped porous titanium body 132. However, the use of the sheet-shaped porous titanium body 132 is not limited to this, and the sheet-shaped porous titanium body 132 can be used for various uses and devices such as various filters, electrode members for batteries, carriers for catalyst support, and various composite materials. In addition, the use of the sheet-shaped porous titanium body 132 in a PEM water electrolysis device to produce hydrogen and oxygen is also one embodiment of the present invention. EXAMPLES

[0053] 1. Example 1 A mother sheet was produced by using a paste method, which was a sintered body of titanium fine particles with a thickness in the range of 160 μm to 170 μm and a porosity of about 40%. The size of the mother sheet was 400 mm × 500 mm. This mother sheet was placed on the jig 100 shown in FIG. 2A so as to overlap the entire stage 104 and the gap 108, and also overlap a part of the frame 102. The stage 104, the frame 102, and the connecting part 106 were all made of pure titanium equivalent to JIS type 1, the shape of the upper surface of the stage 104 was 100 mm × 200 mm, and the width of the gap 108 was 3 mm. The thickness of the stage 104 and the frame 102 was 1.5 mm. Subsequently, the mother sheet was sucked onto the jig 100 using the suction table 110 via the aluminum airflow adjustment table 120.

[0054] In this state, a fiber laser (manufactured by Amada Co., Ltd., model number PRELAS1212AJ) was used to irradiate the mother sheet with a laser beam (output 180 W, laser diameter 40 μm, pulse frequency 600 Hz) having a wavelength in the range of 1050 nm to 1100 nm at a scanning speed of 5000 mm / min along the gap 108 in the straight line portion. At this time, the laser beam was irradiated while supplying nitrogen gas as a shielding gas to the irradiation position of the laser beam. As a result, the mother sheet could be cut in about 15 seconds. When the cut surface was observed, no burrs were observed whose maximum height from the surface exceeded 10 μm. Even when the mother sheet was cut in the same manner using argon gas as a shielding gas, no burrs were observed whose maximum height from the surface exceeded 10 μm, and no coloring was observed at the periphery of the obtained sheet-like porous body.

[0055] Photographs of the mother sheet and the sheet-shaped porous titanium body obtained by cutting the mother sheet are shown in Figs. 10A and 10B, respectively. As can be seen from Fig. 10A, a part of the periphery of the mother sheet before cutting was warped, and the height of the warped part was about 1 mm to 2 mm. On the other hand, it was found that a sheet-shaped porous titanium body without warping over the entire periphery can be obtained by removing the part where warping occurred due to cutting. Note that if pressure is applied to or heating is applied to a mother sheet where warping has occurred, the mother sheet may crack or the porosity may decrease. From this, it can be understood that by applying the embodiment of the present invention, a sheet-shaped porous titanium body without warping over the periphery can be obtained without causing damage to the mother sheet or deterioration of its properties.

[0056] 2. Example 2 The mother sheet was cut in the same manner as in Example 1 using the jig 100 shown in FIG. 3D. The height difference between the upper surface of the connecting portion 106 and the upper surface of the stage 104 was 1 mm. That is, the thickness of the connecting portion 106 was 0.5 mm. As a result of cutting the mother sheet in the same manner as in Example 1 using argon gas as the shielding gas, no burrs with a maximum height from the surface exceeding 10 μm were observed, and no coloring was observed at the periphery of the obtained sheet-like porous body. Note that in Example 1, some burrs with a maximum height from the surface of less than 10 μm were sometimes generated at the points where the connecting portion 106 and the mother sheet were in contact, but in Example 2, it was confirmed that the generation of such small burrs could be almost completely prevented.

[0057] 3. Comparative Example As a comparative example, a laser beam emitted from a carbon dioxide laser (manufactured by Amada Co., Ltd., model number FO-MII 2412NT) was used to cut a mother sheet in the same manner as in Examples 1 and 2. The wavelength of the laser beam was 11 μm, the laser diameter was 150 μm, and the scanning speed of the laser beam in the straight line portion was set to 5000 mm / min. Nitrogen gas was used as the shielding gas. As a result, the mother sheet could be cut in about 15 seconds. However, it was confirmed that burrs with a maximum height of 170 μm from the surface were generated on the peripheral portion of the obtained sheet-like titanium porous body.

[0058] 4. Example 3 In this example, the results of cutting a mother sheet produced in a batch different from that in Example 1 are described. The mother sheet was produced and cut in the same manner as in Example 1, but the shape of the upper surface of the stage 104 was 50 mm x 70 mm. The side surfaces of 240 mm of the two obtained sheet-like titanium porous bodies (hereinafter referred to as Samples A and B) were observed using an optical microscope, and the number and height of burrs were measured. The results are shown in Table 1.

[0059] [Table 1]

[0060] As shown in Table 1, there were very few burrs with a height of 30 μm or more, and no burrs were observed protruding from the first main surface 132a (see FIG. 9A). From these results, it was confirmed that the probability of burrs with a height of 30 μm or more protruding from the first main surface 132a side was 0, and the probability of burrs with a height of 30 μm or more protruding from the second main surface 132b side was 3.0 or less per 100 mm of the peripheral length. These results show that by applying the embodiment of the present invention, the occurrence of burrs can be effectively suppressed, and the occurrence of burrs protruding from one surface (here, the first main surface 132a) can be completely prevented. The burrs generated on the second main surface 132b side of sample A and sample B could be easily removed using a spatula made of metal titanium. By removing the burrs, a sheet-shaped titanium porous body without burrs was obtained on the first main surface 132a side and the second main surface 132b side.

[0061] The above results show that by applying one of the embodiments of the present invention, it is possible to efficiently provide a sheet-shaped porous titanium body having any shape by cutting the mother sheet in a short time while suppressing the generation of burrs. Furthermore, while burrs of about 100 μm or less can be easily removed, when burrs with a height of more than 100 μm are physically removed, not only the burrs but also the surrounding area are removed at the same time. Therefore, it can be said that the embodiment of the present invention makes it possible to produce a sheet-shaped porous titanium body having no burrs and a desired planar shape.

[0062] Based on the above-mentioned embodiments of the present invention, those in which a person skilled in the art appropriately adds, removes, or modifies components, or adds, omits, or modifies processes are also included in the scope of the present invention as long as they include the gist of the present invention. Even if there are other effects and advantages different from those provided by the aspects of the above-mentioned embodiments, those that are clear from the description in this specification or that can be easily predicted by a person skilled in the art are naturally considered to be provided by the present invention. [Explanation of symbols]

[0063] 100: jig, 102: frame, 104: stage, 104-1: stage, 104-2: stage, 104-3: stage, 104a: through hole, 106: connection part, 108: gap, 110: suction table, 120: air flow adjustment table, 120a: through hole, 130: mother sheet, 130a: front surface, 130b: back surface, 132: sheet-shaped titanium porous body, 132a: first main surface, 132b: second main surface, 134: paste, 136: green body, 136a: surface, 138: Brown body, 140: laser light, 142: scanning path, 144: burr, 146: convex part, 148: concave part, 150: substrate, 152: setter

Claims

1. A sheet-shaped titanium porous body having a thickness of 40 μm or more and 500 μm or less and a porosity of 30% or more and 50% or less, The surface roughness of the first main surface is lower than the surface roughness of the second main surface opposite to the first main surface; A sheet-shaped titanium porous body, wherein the number of first protrusions having a height of 30 μm or more protruding toward the first main surface at the peripheral portion is less than or equal to the number of second protrusions having a height of 30 μm or more protruding toward the second main surface at the peripheral portion.

2. 2. The sheet-shaped porous titanium body according to claim 1, wherein the maximum height of the first projections and the second projections is 100 μm or less.

3. 2. The sheet-shaped porous titanium body according to claim 1, wherein the number of said second projections is 3.0 or less per 100 mm of said peripheral edge portion.

4. 2. The sheet-shaped porous titanium body according to claim 1, wherein the first projections are not present.

5. 2. The sheet-shaped porous titanium body according to claim 1, wherein the corners are in the shape of circular arcs.

6. 2. The sheet-shaped porous titanium body according to claim 1, wherein the peripheral portion does not have a curved portion that is curved toward the first main surface side or the second main surface side and has a height of more than 0.1 m.

7. 13. Use of the sheet-shaped porous titanium body according to claim 1 as a porous transport layer in a polymer electrolyte membrane water electrolysis device.

8. The polymer electrolyte membrane water electrolysis device includes an ion exchange membrane, The use according to claim 7 , wherein the ion exchange membrane is disposed so as to be in contact with the first main surface of the sheet-shaped titanium porous body.

9. 7. A method for producing hydrogen, comprising using the porous titanium sheet according to claim 1 in a polymer electrolyte membrane water electrolysis device.

10. a mother sheet including a titanium porous body is placed on a jig including at least one stage having at least one through hole, a frame surrounding the at least one stage and spaced apart from the at least one stage, and at least one connecting portion connecting the at least one stage and the frame to each other, so as to cover the at least one through hole and a gap between the at least one stage and the frame; adsorbing the mother sheet onto the jig; and a laser beam emitted from a fiber laser is scanned along the gaps on the mother sheet to cut the mother sheet.

11. The manufacturing method according to claim 10 , wherein an upper surface of the at least one connecting portion is located on a lower surface side of the at least one stage and the frame with respect to upper surfaces of the at least one stage and the frame.

12. The method of claim 10 , wherein the at least one stage and the frame comprise pure titanium.

13. The method according to claim 10 , wherein the wavelength of the laser light is not less than 1000 nm and not more than 1200 nm.

14. The manufacturing method according to claim 10 , wherein the laser beam scanning is performed in an argon atmosphere.

15. The method according to claim 10, wherein the porosity of the mother sheet is 30% or more and 50% or less.

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