Sheet-shaped titanium porous body and producing method thereof

Abstract

To provide a method capable of producing a sheet-shaped titanium porous body at high efficiency and with good yield.SOLUTION: This producing method comprises: placing a mother sheet containing a titanium porous body on a jig, which includes at least one stage having at least one through hole, a frame surrounding the at least one stage and distanced from the at least one stage, and at least one coupling part connecting the at least one stage and the frame to each other, in such a way 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 laser light emitted from a fiber laser over the mother sheet along the gap.SELECTED DRAWING: Figure 6B

Description

[Technical Field]

[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. [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 supports, and the like. Depending on the application, the sheet-shaped porous metal bodies are cut using a laser, a blade, or the like before use (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 opposing blades. Patent Document 2 discloses that laser cutting of 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 exerting an anchor effect. In other words, this cutting method actively forms burrs. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 039693 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-106023 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 high 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 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. [Brief explanation of the drawings]

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

[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. Manufacturing method for sheet-shaped porous titanium body 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, making it useful 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)-type water electrolysis system.

[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 sheet-shaped porous titanium are essentially made of pure titanium, also known as commercially pure titanium, and their purity corresponds, for example, to pure titanium types 1 to 4, typically types 1 to 2, as specified in JIS H 4600 (2012). More specifically, the titanium content in the mother sheet and the sheet-shaped porous titanium 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. Note that, depending on the manufacturing conditions of the sheet-shaped porous titanium, the oxygen content may be higher than that of commercially pure titanium. For example, the paste method described below tends to produce a sheet-shaped porous titanium with a higher oxygen content than the dry method.

[0016] (1) Preparation of mother sheet There are no limitations on the method for producing the mother sheet, and it can 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 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 produce 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 on it. 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 Figure 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 is 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 produced 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 larger than that of the front surface, and exceeds 10 μm, for example. 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 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, 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 AA', BB', and CC' 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 surrounding 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. 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 laser light 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 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 FIGS. 2A to 3C , the stage 104 is provided with at least one through-hole 104a that penetrates the stage 104 in a direction perpendicular to its upper surface. The at least one through-hole 104a may include multiple through-holes 104a. The multiple 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) 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 104a may also be determined appropriately. For example, if the through-hole 104a is circular, its diameter may be selected from the range of 10 mm to 30 mm. If the through-hole 104a is polygonal, its area may be equal to the area of the circular through-hole 104a 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 maintain a stable 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 therebetween. Alternatively, as shown in FIG. 2A , multiple pairs of connecting portions 106 may be provided in intersecting directions so as to sandwich the stage 104 therebetween. 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 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 that protrude from the peripheral edge toward one main surface, although the main surface opposite the protrusion direction is flat or almost 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 that the connecting portion 106 blocks) 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, it is possible to prevent contact between the connecting portion 106 and 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 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] 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 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 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 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 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 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 104a and gaps 108, and the mother sheet 130 is sucked and fixed to the jig 100.

[0035] Then, the mother sheet 130 is 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 the surface of the mother sheet 130 or nearby (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 environment in which the mother sheet 130 is cut is entirely or partially 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 then 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 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 scanning path 142 of the laser beam, 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 the frame 102, the laser beam is irradiated while the mother sheet 130 is in contact with the connecting portions 106. However, by setting the output power and / or scanning speed of the laser beam within the above-mentioned range, damage to the connecting portions 106 can be prevented. This allows the jig 100 to be used 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 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 a well-known method for cutting porous metal sheets. However, because this method uses abrasives, if the cutting process is not properly cleaned, the abrasives may remain on the porous titanium sheet. 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 at the cut surface. Burrs with a height (or length) of approximately 100 μm or less can usually be physically removed using a spatula, but burrs larger than this size are difficult to remove. Large burrs on the cut surface affect the properties of the porous metal sheet and the characteristics and reliability of various devices that use it. For example, when porous titanium sheets are used as porous transport layers in PEM water electrolysis systems, they can cause damage to adjacent ion exchange membranes.

[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 the narrow gap 108 between the stage 104 and frame 102 that constitute the jig 100. Therefore, the mother sheet 130 does not bend significantly in the gap 108, and the mother sheet 130 can be cut while it is fixed to the jig 100. 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, which can 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. Modified form 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 the stages 104. 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 appropriately determined 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 then 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 porous titanium sheet The properties of the sheet-shaped porous titanium body 132 produced according to the above-described production method will be described below.

[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 after washing the titanium sheet porous body 132 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 sheet-shaped porous titanium 132 differs from that of the mother sheet 130 before cutting. Specifically, the bending of the peripheral edge of the sheet-shaped porous titanium 132 is small. As shown in FIGS. 8A and 8B, a curved portion may occur at the peripheral edge of the sintered mother sheet 130 due to the bending. Specifically, a protrusion 146 protruding from one surface of the peripheral edge and a recess 148 present at a position corresponding to the protrusion 146 and recessed on the other surface may occur. The height of the curved portion, i.e., the height h1 of the protrusion 146 (the height of the protrusion 146 relative to the flat portion of the surface on which the protrusion 146 is present) is approximately 1 to 2 mm. However, since the peripheral portion where warping may occur can be removed by cutting the mother sheet 130 (see Figure 6B), there are no curved portions at the peripheral portion of the sheet-shaped titanium porous body 132, as shown in Figure 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 peripheral edge, and the size (height) of the burrs is also extremely small. Specifically, as shown in Figures 9A and 9B, the number of burrs 144 having a height h2 (the height of the burrs 144 relative to the flat portion of the first main surface 132a) of 30 μm or more that originate from the front surface 130a (see Figure 1) of the mother sheet 130 and protrude toward the surface 132a of the sheet-shaped porous titanium body 132 (hereinafter referred to as the first main surface) is less than the number of burrs 144 that originate from the back surface 130b and protrude toward the surface 132b of the sheet-shaped porous titanium body 132 (hereinafter referred to as the second main surface). Burrs 144 that protrude toward the first main surface 132a are absent (i.e., the probability of burrs 144 existing along any length of the peripheral edge is 0), or the probability of their existence is less than 0.1 per 100 mm of the peripheral edge length. 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 porous titanium 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 it in 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 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. 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 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 porous titanium sheet To reiterate, the porous titanium sheet 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 porous titanium sheet 132 as a porous transport layer in a polymer electrolyte membrane water electrolysis system. In this case, it is preferable to arrange the porous titanium sheet 132 so that the component (e.g., an ion exchange membrane) in contact with the porous titanium sheet 132 is in contact with the first main surface 132a of the porous titanium sheet 132. However, the uses of the porous titanium sheet 132 are not limited thereto, and the porous titanium sheet 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 porous titanium sheet 132 in a PEM water electrolysis system to produce hydrogen and oxygen. [Example]

[0053] 1. Example 1 A mother sheet was fabricated using a paste method. The mother sheet 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 attached to the jig 100 by suction using a suction table 110 via an aluminum airflow adjustment table 120.

[0054] In this state, a fiber laser (manufactured by Amada Corporation, 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. 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 cut in approximately 15 seconds. Observation of the cut surface revealed no burrs with a maximum height from the surface exceeding 10 μm. 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 observed, and no coloring was observed at the peripheral edge of the resulting 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 by removing the warped portion due to cutting, a sheet-shaped porous titanium body without warping along the entire peripheral edge can be obtained. 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 without 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 difference in height 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. The mother sheet was cut in the same manner as in Example 1 using argon gas as the shielding gas. As a result, no burrs with a maximum height from the surface exceeding 10 μm were observed, and no coloring 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 × 70 mm. 240 mm of the side surface of each of the two resulting sheet-shaped titanium porous 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] [Table 1]

[0060] As shown in Table 1, burrs greater than 30 μm in height were extremely rare, and no burrs protruding toward the first principal surface 132a (see FIG. 9A) were observed. These results confirmed that the probability of burrs greater than 30 μm in height protruding toward the first principal surface 132a was 0, and the probability of burrs greater than 30 μm in height protruding toward the second principal surface 132b was 3.0 or less per 100 mm of peripheral length. These results demonstrate that applying an embodiment of the present invention can effectively suppress burr formation and completely prevent burrs protruding toward one surface (here, the first principal surface 132a). The burrs on the second principal surface 132b of Samples A and B could be easily removed using a titanium metal spatula. By removing the burrs, a sheet-shaped porous titanium body without burrs on the first principal surface 132a and second principal surface 132b was obtained.

[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. [Explanation of symbols]

[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, 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 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.

2. a mother sheet including a porous titanium 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 step of cutting the mother sheet along the gaps by scanning a laser beam emitted from a fiber laser over the mother sheet.

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