Sheet-form titanium porous body, method for producing same, and use thereof

Abstract

Provided is a sheet-form titanium porous body. The sheet-form titanium porous body has a thickness of 40-500 μm and a porosity of 30-50%. The surface roughness of a first main surface of the sheet-form titanium porous body is lower than the surface roughness of a second main surface opposite the first main surface. The number of first protrusions protruding at a height of 30 μm or greater from the first main surface at a peripheral edge part of the sheet-form titanium porous body is equal to or less than the number of second protrusions protruding at a height of 30 μm or greater from the second main surface at the peripheral edge part.

Description

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

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

[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 used after being cut using a laser or a blade depending on the application (see Patent Documents 1 and 2). Patent Document 1 discloses that a pair of opposing blades can be used to cut a long sheet-shaped porous metal body extending in a specific direction. Patent Document 2 discloses that laser cutting a laminate of a sheet-shaped porous metal body and an adjacent layer bonds the sides of the sheet-shaped porous metal body and the adjacent layer at the laser cut locations, forming a laminate of the sheet-shaped porous metal body and the adjacent layer. In this method, icicle-like burrs are formed at the laser cut locations to firmly bond the sheet-shaped porous metal body and the adjacent layer, thereby exhibiting an anchor effect. In other words, this cutting method actively forms burrs.

[0003] International Publication No. 2020 / 039693 Japanese Patent Application Laid-Open No. 2011-106023

[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 high yield, and a jig for implementing this method.

[0005] One embodiment of the present invention is a sheet-shaped porous titanium body. The thickness of this 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 the first main surface of the porous titanium sheet is lower than the surface roughness of the second main surface opposite the first main surface. At the peripheral portion of the porous titanium sheet, 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 porous titanium sheet 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 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. This method includes: placing a mother sheet containing porous titanium on a jig that includes at least one stage having at least one through-hole, a frame that surrounds and is spaced apart from the at least one stage, and at least one connecting portion that connects 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; sucking 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, which includes 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 to the frame.

[0010] FIG. 1 is a schematic diagram showing a method for producing a porous titanium sheet according to one embodiment of the present invention. FIG. 2 is a schematic top view of a jig according to one embodiment of the present invention. FIG. 3 is a schematic side view of a jig according to one embodiment of the present invention. FIG. 4 is a schematic end view of a jig according to one embodiment of the present invention. FIG. 5 is a schematic end view of a jig according to one embodiment of the present invention. FIG. 6 is a schematic end view of a jig according to one embodiment of the present invention. FIG. 7 is a schematic side view including a jig according to one embodiment of the present invention. FIG. 8 is a schematic top view of an airflow adjustment table used in a jig according to one embodiment of the present invention. FIG. 9 is a schematic top view of a method for producing a porous titanium sheet according to one embodiment of the present invention. FIG. 10 is a schematic end view of a porous titanium sheet according to one embodiment of the present invention. FIG. 11 is a schematic end view of a porous titanium sheet according to one embodiment of the present invention. FIG. 12 is a schematic top view of a jig according to one embodiment of the present invention. FIG. 13 is a schematic perspective view of a porous titanium sheet according to one embodiment of the present invention. Schematic side view of a sheet-shaped porous titanium body according to one embodiment of the present invention. Schematic perspective view of a sheet-shaped porous titanium body according to one embodiment of the present invention. Schematic side view of a sheet-shaped porous titanium body according to one embodiment of the present invention. Photograph of a mother sheet produced in an example. Photograph of a sheet-shaped porous titanium body produced in an example.

[0011] 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 by this method, will be described below 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 schematically 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 function as elements explained in the previous drawings may be assigned the same reference numerals, and duplicate explanations may be omitted.

[0013] 1. Method for Producing a Porous Titanium Sheet A method for producing a porous titanium sheet according to one embodiment of the present invention is described below. Porous titanium has high liquid permeability, air permeability, electrical conductivity, and excellent corrosion resistance, and is therefore used as an electrode material or filter that can be used in highly corrosive environments. In particular, porous titanium sheet having a thickness of several tens to several hundreds of micrometers is useful as a porous transport layer (PTL) in a polymer electrolyte membrane (PEM) water electrolysis device.

[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 then cut appropriately to produce a porous titanium sheet of 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 porous titanium sheet are essentially made of pure titanium, also known as commercially pure titanium, and their purity corresponds to, for example, pure titanium types 1 to 4, typically types 1 to 2, specified in JIS H 4600 (2012). More specifically, the titanium content in the mother sheet and the porous titanium sheet 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 non-metallic components such as oxygen from 100% by mass. Depending on the manufacturing conditions of the porous titanium sheet, the oxygen content may be higher than that of commercially pure titanium. For example, the paste method described below tends to produce porous titanium sheets with a higher oxygen content than the dry method.

[0016] (1) Preparation of Mother Sheet There are no limitations on the method for preparing the mother sheet, and it may be prepared 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 higher are deposited on a setter, then scraped to form a sheet, and then heated and sintered at a high temperature (e.g., 950°C or higher) to obtain a mother sheet. To facilitate separation from the setter, it is preferable to coat the setter with a release agent such as boron nitride or titanium boride and then deposit the titanium fine particles or titanium fibers thereon. The titanium fine particles may be spherical, but using a shape that deviates from a sphere, such as titanium fine particles (HDH powder) produced by a hydrogenation-dehydrogenation method, increases the number of junctions between the titanium fine particles. As a result, a mother sheet with a three-dimensional network structure containing numerous internal pores can be obtained. When titanium fine particles are used, a mother sheet with a sponge-like three-dimensional network structure can be obtained. On the other hand, when titanium fibers are used, a mother sheet with a nonwoven three-dimensional network structure can be obtained.

[0017] In the paste method, a paste containing titanium fine particles or titanium fibers, a binder, and a solvent is first 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 antifoaming agents, dispersants, leveling agents, and plasticizers. However, it is preferable that the paste does not contain foaming agents or water. As shown in FIG. 1, this paste 134 is applied to a substrate 150, and the solvent is evaporated at room temperature or under heated conditions (e.g., 80°C to 160°C) to obtain a sheet-like green body 136.

[0018] The green body 136 is peeled off from the substrate and placed on a setter 152, which serves as a support 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 of the setter 152 (see FIG. 1). The green body 136 placed on the setter 152 is then heated in an oxygen-containing atmosphere, such as the air, to perform debinding. Debinding can be performed, for example, by heating at a temperature of 300°C to 450°C for 3 to 20 hours. This thermally decomposes or volatilizes the binder and additives, resulting in a sheet-like brown body 138 made essentially of titanium.

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

[0020] The size of the mother sheet 130 is not limited, as long as it is larger than the titanium porous body to be finally produced. For example, the mother sheet 130 may have a rectangular shape with sides of 200 mm to 2000 mm. The thickness of the mother sheet 130 can also be determined arbitrarily, for example, from 10 μm to 3000 μm, 40 μm to 1000 μm, or 40 μm to 500 μm, and is typically 40 μm to 300 μm. The porosity of the mother sheet 130 is also not limited, but is preferably 30% to 50%. A titanium porous body with a smooth surface tends to have a relatively small porosity. Furthermore, in the cells of a (PEM)-type water electrolysis device, the ion exchange membrane and the titanium porous body are sometimes arranged in a compressed state, and a smooth surface of the titanium porous body can effectively prevent damage to the ion exchange membrane.

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

[0022] A. Jig A schematic top view of jig 100 is shown in Fig. 2A, and schematic end views along chain lines A-A', B-B', and C-C' in Fig. 2A are shown in Figs. 3A to 3C, respectively. As shown in Fig. 2A, jig 100 includes at least one stage 104 and a frame 102 that surrounds stage 104. As shown in Fig. 2B, a suction table 110 is disposed below jig 100. The thicknesses of stage 104 and frame 102 may be determined appropriately depending on their size, and are, for example, 1 mm to 10 mm.

[0023] The stage 104 and the frame 102 are not in direct contact with each other but are spaced apart 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 will be 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 to cut the mother sheet 130 and cut out a sheet-shaped porous titanium body. Therefore, the shape of the gap 108 essentially 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. For example, it may be a polygon including a rectangle, a circle, an ellipse, or a shape defined by an outline composed of curves and straight lines.

[0024] The stage 104, frame 102, and connecting portion 106 each contain, for example, a metal. Preferably, they all contain titanium, and more preferably, they are made of commercially pure titanium, which is 99% by mass or more. By containing high-purity titanium in the stage 104, frame 102, and connecting portion 106, contamination during cutting of the mother sheet 130 can be prevented. As a result, impurities can be prevented from being mixed into the sheet-shaped porous titanium.

[0025] Alternatively, at least one of the stage 104, the frame 102, and the connecting portion 106 may contain 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 weight of the jig 100 can be reduced.

[0026] As shown in FIGS. 2A to 3C , the stage 104 is provided with at least one through-hole 104 a penetrating the stage 104 in a direction perpendicular to its upper surface. The at least one through-hole 104 a may include multiple through-holes 104 a. The multiple through-holes 104 a are preferably arranged at a uniform density, i.e., at a constant pitch. The pitch of the through-holes 104 a may be set, for example, in the range of 30 mm to 70 mm. The shape of the through-hole 104 a (the shape on the upper surface of the stage 104) may be, for example, circular or polygonal. In the latter case, the corners may be rounded. The size of the at least one through-hole 104 a may also be determined appropriately. For example, if the through-hole 104 a is circular, its diameter may be selected from the range of 10 mm to 30 mm. If the through-hole 104 a is polygonal, its area may be equal to the area of ​​the circular through-hole 104 a described above. The plurality of 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 periphery of the frame (the outline of the upper surface of the frame 102 facing the stage 104) is substantially similar to the outer periphery of the stage 104. The shape of the inner periphery 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 will be described later, the mother sheet 130 is adsorbed onto the frame 102 and the stage 104 while being disposed so as to cover the gap 108. By setting the width of the gap 108 within 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 multiple connecting portions 106. The connecting portions 106 are provided so as to block a portion of the gap 108. Therefore, typically, the number of connecting portions 106 is the same as the number of gaps 108. The positions of the connecting portions 106 may be determined appropriately 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 on the jig 100 so as to sandwich the stage 104. Alternatively, as shown in FIG. 2A , multiple pairs of connecting portions 106 may be provided so as 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. In other words, the shape of the gaps 108, which essentially determines the shape of the sheet-like porous body obtained by cutting the mother sheet 130, can be fixed. As a result, sheet-like porous bodies having a consistent 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. Generally, when cutting a sheet-shaped porous metal body, protrusions called burrs (protrusions protruding from the peripheral edge toward one main surface, although the main surface opposite the protruding direction is 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) be 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-holes 104a extend) 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 surfaces of the stage 104 or the frame 102. In other words, the upper surface of the connecting portion 106 is located lower than the upper surfaces 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 surfaces of the stage 104 or the frame 102, contact between the connecting portion 106 and the mother sheet 130 can be prevented, and as a result, the occurrence of burrs can be more effectively suppressed. 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 will be described later, during 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 sucked 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 schematically 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) or arrangement of the through holes 120a, but it is preferable to arrange the hexagonal through holes 120a in a honeycomb pattern so that the through holes 120a can be arranged at high density. By providing the airflow adjusting table 120, the airflow created by the suction table 110 can be made uniform, so that the mother sheet 130 can be sucked onto the jig 100 with a uniform force over the entire mother sheet 130.

[0032] 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 Figs. 5B and 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 Figures 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 gaps 108. At this time, the mother sheet 130 is placed on the jig 100 so that the back surface 130b is in contact with 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 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 104 a 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, negative pressure is created within the through-holes 104 a and the gaps 108, and the mother sheet 130 is sucked and fixed to the jig 100.

[0035] The mother sheet 130 is then cut using a fiber laser. Specifically, as shown in FIG. 6A , laser light 140 emitted from the fiber laser is irradiated onto the mother sheet 130 from the opposite side of the jig 100. That is, the laser light 140 is irradiated from the surface 130a side. A fiber laser is a type of solid-state laser that uses an optical fiber as an amplification medium. For example, a core at the center of an optical fiber is doped with a rare earth element such as ytterbium, and one or more cladding layers with a lower refractive index than the core are formed to surround the core. The wavelength of the laser light is, for example, 1000 nm or more and 1200 nm or less, and its output is adjusted to, for example, 50 W or more and 800 W or less. The laser light is pulsed, and its 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 or near the surface of the mother sheet 130 (for example, within ±5 mm from the surface). The diameter of the laser beam on the mother sheet 130 is adjusted to 40 μm or more and 200 μm or less. The scanning speed of the laser beam can be adjusted appropriately depending on the thickness and number of mother sheets 130, for example, to 1,000 mm / min or more and 10,000 mm / min or less. During laser beam irradiation, the entire or part of the environment in which the mother sheet 130 is cut is set to an inert gas atmosphere such as nitrogen or argon, preferably an argon atmosphere, to prevent discoloration due to nitriding of the cut surface. For example, in an air atmosphere, an inert gas may be sprayed as a shielding gas toward the laser beam irradiation position. Alternatively, the entire jig 100 may be placed in an inert gas atmosphere and irradiated with the laser beam. This allows the laser beam to be scanned in an inert gas atmosphere, thereby suppressing oxidation and nitridation of the mother sheet 130 and the resulting contamination and discoloration.

[0036] The laser beam is scanned on the mother sheet 130 along the gaps 108. By scanning the laser beam from the laser beam irradiation start position over the gaps 108 and the connecting portions 106 and then irradiating the laser beam again to the irradiation start position, the mother sheet 130 is cut along the laser beam scanning path 142, as shown in FIG. 6B , and a sheet-shaped porous titanium body 132 having a shape that reflects the shape of the gaps 108 can be cut out. If the upper surface of the connecting portions 106 is flush with the upper surface of the stage 104 or frame 102, the laser beam is irradiated while the mother sheet 130 is in contact with the connecting portions 106. However, by setting the laser beam output and / or scanning speed within the above-mentioned ranges, damage to the connecting portions 106 can be prevented. This allows the jig 100 to be reused repeatedly.

[0037] When irradiating the laser light, the scanning direction turns 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, resulting in a sheet-shaped porous titanium body 132 with arc-shaped corners ( FIG. 6B ). The chamfering radius r can also be set arbitrarily; for example, the chamfering radius r may be set appropriately in the range of 1 mm to 15 mm.

[0038] The water jet method is known as a method for cutting sheet-shaped porous metal bodies. However, because the water jet method uses abrasives, if the cutting is not performed properly, the abrasives may remain on the porous titanium sheet body. Furthermore, when cutting porous metal sheets using a carbon dioxide laser, it is difficult to avoid the generation of burrs during the melting and solidification process on the cut surface. Burrs with a height (or length) of approximately 100 μm or less can usually be physically removed using a spatula or the like, but burrs larger than this size cannot be easily removed. The generation of large burrs on the cut surface affects the properties of the porous metal sheet body and the properties and reliability of various devices that use it. For example, when porous titanium sheets are used as porous transport layers in PEM-type water electrolysis systems, they may induce damage to adjacent ion exchange membranes.

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

[0040] Furthermore, because the mother sheet 130 is cut using a laser beam, the porous titanium sheet 132 can be cut out in a short time of approximately several tens of seconds. Furthermore, 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 effectively suppresses the generation of burrs, preventing the generation of burrs that could affect the properties of the porous titanium sheet 132 and the properties of the device in which it is used. These features contribute to improving the manufacturing efficiency and yield of the porous titanium sheet.

[0041] C. Modification 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 frames 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 are no restrictions on the number of stages 104 provided in one jig 100, and the number may be determined appropriately within the 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 using such a jig 100, multiple mother sheets 130 can be positioned and cut simultaneously. Alternatively, multiple porous titanium sheets 132 can be produced from a single mother sheet 130 by positioning one mother sheet 130 so that it covers all of the stages 104 and the gaps 108 and then scanning the gaps 108 with a laser beam. Since it typically takes several hours to several days to produce a single mother sheet 130, the production time per porous titanium sheet 132 increases when a single porous titanium sheet 132 is produced from a single mother sheet 130. In contrast, by producing a large mother sheet 130 and cutting multiple porous titanium sheets 132 from it, the production time per porous titanium sheet 132 can be significantly reduced. Therefore, by applying one of the embodiments of the present invention, it is possible to provide porous titanium sheets 132 at low cost.

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

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

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

[0046] Due to the cutting process described above, the structure of the peripheral edge of the porous titanium sheet 132 differs from that of the mother sheet 130 before cutting. Specifically, the bending of the peripheral edge of the porous titanium sheet 132 is small. As shown in Figures 8A and 8B, a curved portion may occur at the peripheral edge of the mother sheet 130 after sintering due to the bending. Specifically, a protrusion 146 protruding from one side of the peripheral edge, and a recess 148 present at a position corresponding to the protrusion 146 and recessed on the other side, may occur. The height of the curved portion, i.e., the height h of the protrusion 146, １ The height of the protrusions 146 (based on the flat portion of the surface on which the protrusions 146 are present) is approximately 1 mm to 2 mm. However, because the peripheral edges where warping may occur can be removed by cutting the mother sheet 130 (see FIG. 6B), there are no curved portions at the peripheral edges 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] Furthermore, although the sheet-shaped porous titanium body 132 is obtained by cutting the mother sheet 130, there are very few burrs at the periphery and the size (height) of the burrs is also extremely small. Specifically, as shown in Figures 9A and 9B, the height h ２The number of burrs 144 with a height of 30 μm or more (based on the flat portion of the first main surface 132 a) is equal to or less than the number of burrs 144 protruding toward the surface 132 b (hereinafter, the second main surface) of the sheet-shaped porous titanium body 132 originating from the back surface 130 b. Burrs 144 protruding toward the first main surface 132 a are absent (i.e., the probability of burrs 144 being present per any length of the peripheral edge is 0), or the probability of their presence is less than 0.1 per 100 mm of peripheral edge length. Therefore, it is possible to omit the step of physically removing burrs 144 protruding toward the first main surface 132 a. As described above, the smoothness of the front surface 130 a of the mother sheet 130 fabricated using the paste method is higher than that of the back surface 130 b. Therefore, the first main surface 132a of the sheet-shaped porous titanium body 132 is not only highly smooth but also has few burrs, and the ion exchange membrane is not easily 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 extremely small, ranging from 0.0 to 3.0 per 100 mm of peripheral length. 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, no burrs exceeding 100 μm exist. Therefore, even if burrs 144 occur, almost all of them can be physically removed using a spatula or the like. Even if burrs 144 exist, they 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 occur. This is thought to be because no shear force is applied to the mother sheet 130, unlike the method of producing the sheet-shaped porous titanium 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. Because there are no burrs 144 with thick bases in the direction parallel to the first main surface 132 a or the second main surface 132 b, it is possible to suppress gouging and damage to the sheet-shaped porous titanium body 132 during the burr removal work.

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

[0050] To improve the operational efficiency of PEM water electrolysis equipment, the surface of the porous titanium sheet is sometimes coated, and the coated porous titanium sheet is then brought into contact with an ion exchange membrane or the like. This coating is usually a thin film, and the surface smoothness of the porous titanium sheet 132 is maintained even after coating. Therefore, even when the porous titanium sheet is brought into contact with an ion exchange membrane or the like after coating, the porous titanium sheet can be considered to be in contact with an ion exchange membrane or the like.

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

[0052] 3. Use of the Titanium Sheet Porous Body To reiterate, the titanium sheet porous body 132 according to one embodiment of the present invention can be suitably used in a PEM water electrolysis system, and is particularly useful as a porous transport layer. Therefore, one embodiment of the present invention is to use the titanium sheet porous body 132 as a porous transport layer in a polymer electrolyte membrane water electrolysis system. In this case, it is preferable to arrange the titanium sheet porous body 132 so that the component (e.g., an ion exchange membrane) that comes into contact with the titanium sheet porous body 132 is in contact with the first main surface 132a of the titanium sheet porous body 132. However, the uses of the titanium sheet porous body 132 are not limited thereto, and the titanium sheet porous body 132 can be used for a variety of applications and devices, such as various filters, electrode components for batteries, catalyst carriers, and various composite materials. Another embodiment of the present invention is to use the titanium sheet porous body 132 in a PEM water electrolysis system to produce hydrogen and oxygen.

[0053] 1. Example 1 Using a paste method, a mother sheet was fabricated, which was a sintered body of titanium fine particles with a thickness ranging from 160 μm to 170 μm and a porosity of approximately 40%. The mother sheet measured 400 mm × 500 mm. This mother sheet was placed on the jig 100 shown in FIG. 2A so that it overlapped the entire stage 104 and gap 108, and also overlapped a portion of the frame 102. The stage 104, frame 102, and connecting portion 106 were all made of pure titanium equivalent to JIS Class 1. The top surface of the stage 104 measured 100 mm × 200 mm, and the width of the gap 108 was 3 mm. The thickness of the stage 104 and frame 102 was 1.5 mm. Subsequently, the mother sheet was adsorbed onto the jig 100 using a suction table 110 via an 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 along the gap 108 with laser light (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 in the linear portion. At this time, the laser light irradiation was performed while supplying nitrogen gas as a shielding gas to the laser light irradiation position. As a result, the mother sheet was able to be cut in approximately 15 seconds. When the cut surface was observed, no burrs with a maximum height from the surface exceeding 10 μm were confirmed. Even when the mother sheet was similarly cut using argon gas as a shielding gas, no burrs with a maximum height from the surface exceeding 10 μm were confirmed, and no coloring was observed at the peripheral edge of the obtained porous sheet.

[0055] Photographs of the mother sheet and the sheet-shaped porous titanium body obtained by cutting the mother sheet are shown in Figures 10A and 10B, respectively. As can be seen from Figure 10A, a portion of the peripheral edge of the mother sheet before cutting was warped, with the height of the warped portion being approximately 1 to 2 mm. On the other hand, it was found that removing the warped portion by cutting yielded a sheet-shaped porous titanium body that was free of warping along the entire peripheral edge. Note that applying pressure or heating to a warped mother sheet can cause the mother sheet to crack or reduce its porosity. This demonstrates that by applying an embodiment of the present invention, a sheet-shaped porous titanium body that is free of warping along the peripheral edge can be obtained without causing damage to the mother sheet or reducing its properties.

[0056] 2. Example 2 Using the jig 100 shown in FIG. 3D , the mother sheet was cut in the same manner as in Example 1. The height difference between the top surface of the connecting portion 106 and the top surface of the stage 104 was 1 mm. That is, the thickness of the connecting portion 106 was 0.5 mm. Using argon gas as the shielding gas, the mother sheet was cut in the same manner as in Example 1. As a result, no burrs with a maximum height from the surface exceeding 10 μm were observed, and no discoloration was observed at the peripheral edge 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 occasionally 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 even such small burrs could be almost completely prevented.

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

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

[0059]

[0060] ​As shown in Table 1, burrs of 30 μm or more in height were extremely rare, and no burrs protruding toward the first main surface 132a (see FIG. 9A) were observed. These results confirmed that the probability of burrs of 30 μm or more in height protruding toward the first main surface 132a was 0, and the probability of burrs of 30 μm or more in height protruding toward the second main surface 132b was 3.0 or less per 100 mm of peripheral length. These results demonstrate that application of the present invention effectively suppresses burr formation and completely prevents burrs protruding toward one surface (here, the first main surface 132a). The burrs on the second main surface 132b of Samples A and B were easily removed using a titanium metal spatula. Removal of the burrs resulted in a sheet-shaped porous titanium body free of burrs on both the first main surface 132a and the second main surface 132b.

[0061] The above results show that by applying one of the embodiments of the present invention, it is possible to efficiently cut a mother sheet in a short time while suppressing the generation of burrs, and to efficiently provide a sheet-shaped porous titanium body of any desired shape. Furthermore, while burrs of approximately 100 μm or less can be easily removed, physically removing burrs with a height of more than 100 μm removes not only the burr but also the surrounding area 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 of any desired planar shape without any burrs.

[0062] Based on the above-described embodiments of the present invention, those skilled in the art may add, delete, or modify components, or add, omit, or modify processes as appropriate, as long as they comply with the spirit of the present invention. Even if there are other effects and advantages different from those achieved by the aspects of the above-described embodiments, those that are clear from the description in this specification or that can be easily predicted by those skilled in the art are naturally considered to be achieved by the present invention.

[0063] 100: jig, 102: frame, 104: stage, 104-1: stage, 104-2: stage, 104-3: stage, 104a: through-hole, 106: connecting portion, 108: gap, 110: suction table, 120: airflow 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 portion, 148: concave portion, 150: substrate, 152: setter

Claims

1. A sheet-shaped porous titanium 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, wherein the surface roughness of a first main surface is lower than the surface roughness of a second main surface opposite said first main surface, and the number of first protrusions having a height of 30 μm or more protruding from the peripheral portion toward said 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 peripheral portion toward said second main surface.

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

4. A sheet-shaped porous titanium body according to any one of claims 1 to 3, wherein the first projections are not present.

5. A sheet-shaped porous titanium body according to any one of claims 1 to 4, wherein the corners are arc-shaped.

6. A sheet-shaped porous titanium body according to any one of claims 1 to 5, 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. A sheet-shaped porous titanium body according to any one of claims 1 to 6, wherein the sheet-shaped porous titanium body is produced by cutting a mother sheet having an area larger than that of the sheet-shaped porous titanium body using a fiber laser.

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

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

10. A method for producing hydrogen by using the porous titanium sheet according to any one of claims 1 to 7 in a polymer electrolyte membrane water electrolysis device.

11. A method for producing a sheet-like porous titanium body, comprising: placing a mother sheet containing porous titanium on a jig having at least one stage having at least one through hole, a frame surrounding said at least one stage and spaced apart from said at least one stage, and at least one connecting part connecting said at least one stage and said frame to each other; adsorbing said mother sheet onto said jig; and cutting said mother sheet along said gap by scanning laser light emitted from a fiber laser over said mother sheet.

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

13. The manufacturing method of claim 11 or 12, wherein the at least one stage and the frame comprise pure titanium.

14. The manufacturing method according to any one of claims 11 to 13, wherein the wavelength of the laser light is 1000 nm or more and 1200 nm or less.

15. The manufacturing method according to any one of claims 11 to 14, wherein the laser beam scanning is performed in an argon atmosphere.

16. A manufacturing method according to any one of claims 11 to 15, wherein the porosity of the mother sheet is 30% or more and 50% or less.

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