Method for producing titanium molded body, method for producing titanium porous body, and titanium porous body

Abstract

This method for producing a titanium molded body is a method for producing a sheet-like titanium molded body, and comprises a bonding step for bonding a plurality of sheet-like dried bodies obtained by drying a paste containing a titanium powder, an organic binder, and an organic solvent, while pressing the sheet-like dried bodies at a pressure of 0.1 N / cm2 or more in the thickness direction, and bonding the sheet-like dried bodies to form a sheet-like titanium molded body. And heating to a temperature of 70 DEG C to 200 DEG C (inclusive) while heating.

Description

Technical Field

[0001] This invention relates to a method for manufacturing sheet-like titanium molded bodies, a method for manufacturing porous titanium bodies, and porous titanium bodies. Background Technology

[0002] Porous titanium bodies manufactured by sintering titanium powder possess air permeability, liquid permeability, and electrical conductivity achieved through micropores. Furthermore, they exhibit high corrosion resistance through the formation of passivation films on their surfaces.

[0003] Regarding porous titanium materials with such properties, studies have been conducted on porous transport layers (PTLs) used in water electrolysis devices containing polymer-electrolyte membranes (PEMs) in potentially corrosive environments. In particular, hydrogen produced using PEM-type water electrolysis devices, powered by electricity derived from renewable energy sources, is known as "green hydrogen" and has been highly anticipated in recent years as efforts accelerate towards a decarbonized society.

[0004] As a technology related to porous titanium bodies, for example, Patent Document 1 describes "a method for manufacturing a porous metal laminate, characterized in that the porous metal laminate is composed of multiple layers including a porous layer, wherein multiple polyhedral voids formed by the skeleton of a sintered metal body in the porous layer are formed in a continuous state, and the method for manufacturing the porous metal laminate includes: a lamination step of laminating the porous layer with an adjacent layer formed of metal; and a melting step of fusing the porous layer and the adjacent layer in the laminated state to a desired shape using a laser, wherein in the melting step, the porous layer and the adjacent layer are melted and solidified by using the laser, thereby forming a fused bonding layer on the side of the porous layer and the adjacent layer to bond the porous layer and the adjacent layer.

[0005] Furthermore, Patent Document 2 describes "a composite material comprising: a first region formed of a metal foam having a conductive metal component with an electrical conductivity of 8 MS / m or more at 20°C; and a second region formed of a metal foam having a soft magnetic metal component."

[0006] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2011-106023 Patent Document 2: Japanese Patent Publication No. 2021-529891 Summary of the Invention

[0007] The problem that the invention aims to solve When using porous titanium as a porous transport layer in a PEM-type water electrolysis device, the porous titanium is sometimes pressed onto the electrolyte membrane for assembly. In this case, if the pores on the surface of the porous titanium are large, the electrolyte membrane pressed by the porous titanium will partially enter the pores, causing significant deformation near the pores, which may lead to damage to the electrolyte membrane.

[0008] Therefore, from the perspective of suppressing damage to the electrolyte membrane, ideally, the surface openings of the titanium porous body on the electrolyte membrane side should be small. Even if the surface pores are small, as long as there are many of them, they can still provide a certain degree of aeration or liquid permeability.

[0009] However, when the pores in a titanium porous body are small not only on the surface but also throughout, even with a large number of pores, the required aeration or fluid permeability may not always be achieved, depending on the desired level. To address this issue, it is considered that by stacking multiple porous layers, a porous layer with small pores is provided on one side of the surface to suppress damage to the electrolyte membrane, and a titanium porous body with a high overall porosity is formed, so as to achieve good aeration or fluid permeability.

[0010] When manufacturing a porous titanium body with multiple porous layers, if multiple sintered titanium bodies to be formed into porous layers are stacked and heated to bond, each porous layer constituting the porous titanium body will undergo two relatively high-temperature heating processes: the heating used for sintering during the formation of the titanium sintered bodies and the heating used for bonding. As a result, the porous titanium body obtained by bonding multiple sintered titanium bodies generally has small pores, and sometimes the desired level of excellent air permeability or liquid permeability cannot be obtained. This situation exists not only in the manufacture of porous titanium bodies with multiple porous layers having different pore sizes and numbers, but also in the manufacture of porous titanium bodies with multiple porous layers having the same pore size and number.

[0011] The purpose of this invention is to provide a method for manufacturing a titanium molded body, a method for manufacturing a porous titanium body, and a porous titanium body. The method for manufacturing the titanium molded body can manufacture a titanium molded body, and the titanium molded body can be used to manufacture a porous titanium body with multiple porous layers and a high porosity.

[0012] Solution for solving the problem The inventors conducted in-depth research and proposed a method of stacking multiple sheet-like dried bodies obtained by drying a paste of titanium powder, and then bonding them under specified conditions. By debinding and sintering the resulting titanium molded body, the number of high-temperature heating cycles can be reduced compared to bonding pre-sintered objects. As a result, the final manufactured porous titanium body has a high porosity.

[0013] The method for manufacturing titanium molded bodies of the present invention is a method for manufacturing sheet-like titanium molded bodies, comprising a bonding step, wherein the bonding step involves drying a paste containing titanium powder, an organic binder, and an organic solvent, thereby stacking multiple dried sheet-like bodies while increasing the thickness by 0.1 N / cm. 2 The pressure is increased while heating to a temperature above 70°C and below 200°C.

[0014] The above-described method for manufacturing titanium molded bodies may include a drying step prior to the joining step, in which the paste is dried to obtain a sheet-like dried body.

[0015] In the drying process, the paste can be heated to a temperature above 90°C and below 165°C.

[0016] The drying of the paste in the drying process can be carried out on a resin substrate.

[0017] In the joining process, pressure and heat can be applied while multiple stacked sheet-like dried bodies are clamped by forming molds from both sides in the thickness direction.

[0018] In this case, it is preferable that, during the bonding process, pressure and heat are applied while the resin substrate is sandwiched between the sheet-like dried body and the molding die.

[0019] Preferably, the average particle size of the titanium powder in at least one of the sheet-like dried bodies is 10 μm or more and 20 μm or less.

[0020] Preferably, in the sheet-like dried body, the difference between the average particle size of the titanium powder in one of the sheet-like dried bodies and the average particle size of the titanium powder in at least one other sheet-like dried body is 5 μm or more.

[0021] Preferably, the paste used to make the sheet-like dried body does not contain a foaming agent.

[0022] The method for manufacturing porous titanium material of the present invention is a method for manufacturing sheet-like porous titanium material, comprising: a debinding step, wherein the titanium molded body manufactured by any of the above-described methods for manufacturing titanium molded bodies is heated to volatilize the organic binder in the titanium molded body; and a sintering step, wherein the titanium molded body after the debinding step is heated to sinter the titanium powder in the titanium molded body.

[0023] The titanium porous body of the present invention is a sheet-like titanium porous body, which comprises multiple layers of porous titanium. These multiple layers of porous titanium are stacked with adjacent titanium bonding surfaces in the thickness direction, each having pores that allow gas and / or liquid to permeate. In the multiple porous layers, the average area of ​​the pores opening on the surface of the porous layer forming one of the layers is 5 μm. 2 Above and 15μm 2 Hereinafter, the standard deviation of the area of ​​the hole is 35 μm. 2 Below, in an area of ​​22000μm 2 Furthermore, the number of pores present in the rectangular area with an aspect ratio of 4:3 is more than 256, and the overall porosity of the multi-layered porous material is more than 40% and less than 60%.

[0024] Preferably, the average area of ​​the openings on the other surface located on the back side of the surface of one of the surfaces is more than 1.5 times the average area of ​​the openings on the surface of the one of the surfaces.

[0025] Preferably, the total thickness is 200 μm or more and 3000 μm or less.

[0026] Preferably, the thickness of the porous layer constituting the surface side of one side is less than 30% of the total thickness.

[0027] Invention Effects According to the method for manufacturing titanium molded articles of the present invention, titanium molded articles can be manufactured, which can be used to manufacture titanium porous articles having multiple porous layers and high porosity. Attached Figure Description

[0028] Figure 1 middle, Figure 1 (a) and Figure 1 (b) are cross-sectional views along the thickness direction of a sheet-like dried body that can be used in a method for manufacturing a titanium molded body according to one embodiment of the present invention.

[0029] Figure 2 middle, Figure 2 (a) to (d) indicate that... Figure 1 A cross-sectional view of an example of the order in which the sheet-like dried bodies are joined. Detailed Implementation

[0030] The embodiments of the present invention will be described in detail below.

[0031] In one embodiment of the present invention, a method for manufacturing a titanium molded body includes a joining step of stacking and joining multiple sheet-like dried bodies.

[0032] To obtain the sheet-like dried bodies, the following steps can be performed: a paste preparation step, in which titanium powder, an organic binder, and an organic solvent are mixed; and a drying step, in which the paste is formed into sheets and dried. In the bonding step, while multiple sheet-like dried bodies are stacked, the sheets are bonded at a rate of 0.1 N / cm along their thickness direction. 2 The pressure is increased while the material is heated to a temperature between 70°C and 200°C. This causes multiple sheet-like dried bodies to bond together, forming a titanium molded body.

[0033] The aforementioned titanium molded body is sequentially fed into the debinding process and the sintering process to become a titanium porous body. The titanium porous body is formed by stacking multiple sheet-like dried bodies during its manufacturing process, resulting in a porous titanium layer that serves as the sintered body of each sheet-like dried body. By appropriately setting the particle size of the titanium powder used in forming the sheet-like dried bodies and other conditions, the titanium porous body can be manufactured such that, for example, in the case of using it as a porous transport layer in a PEM-type water electrolysis device, the pores on the surface of the side where the electrolyte membrane is pressed are small, but the overall porosity is large.

[0034] The porous titanium body manufactured as described above undergoes fewer high-temperature heating cycles during sintering compared to a porous titanium body manufactured by bonding sintered titanium bodies, thus resulting in a higher porosity. In other words, if multiple sheet-like dried bodies are separately debonded and sintered, and the resulting multiple sintered titanium bodies are then heated and bonded, at least two high-temperature heating cycles occur during sintering and bonding. As a result, the sintering of the titanium powder intensifies, and the porosity decreases. In contrast, the embodiment described herein reduces the number of high-temperature heating cycles, thus enabling the manufacture of porous titanium bodies with high porosity, for example.

[0035] (Paste preparation process) In the paste-making process, raw materials containing titanium powder, organic binders, and organic solvents are mixed using a mixer with a stirrer, a rotary mixer, or a three-roll mill to produce a paste. Alternatively, a vibratory mill, a bead mill, or other pulverizing and mixing equipment can be used for pulverization.

[0036] As titanium powder, pulverized powders such as hydrogenated dehydrogenated titanium powder and hydrogenated titanium powder, as well as spherical powders such as atomized powder, can be used. For example, when using fine titanium powder with an average particle size of 10 μm or more and 20 μm or less, the porous layer obtained by sintering the sheet-like dried body has small pores. On the other hand, when using coarse titanium powder with an average particle size of more than 20 μm, the porous layer after sintering has large pores and high porosity.

[0037] From the viewpoint of manufacturing a porous titanium body with small pores but high overall porosity on one side of its surface, among multiple sheet-like dried bodies, the difference between the average particle size of the titanium powder used to make a porous layer on one side of the surface and the average particle size of the titanium powder used to make at least one other sheet-like dried body is preferably 5 μm or more, and more preferably 10 μm or more. However, if the above-mentioned difference in average particle size is too large, the difference in sintering shrinkage of each sheet-like dried body becomes too large, and the porous titanium layer may peel off. Therefore, considering this situation, it is sometimes set to 100 μm or less, and more preferably 50 μm or less.

[0038] The average particle size mentioned above refers to the particle size that constitutes 50% of the cumulative distribution of the volume reference in the particle size distribution obtained by laser diffraction scattering method.

[0039] As the organic binder for the paste, various organic binders can be appropriately selected, such as methylcellulose-based, polyvinyl alcohol-based, ethylcellulose-based, acrylic-based, and polyvinyl butyral-based binders. Hydrophobic organic binders are preferred. However, they are not limited to the organic binders listed herein. Organic solvents, for example, include alcohols (ethanol, isopropanol, terpineol, butylcarbidol, etc.). As an example, polyvinyl butyral may be used as the organic binder, and isopropanol as the organic solvent. The paste may further contain plasticizers (glycerol, ethylene glycol, etc.), surfactants (alkylbenzene sulfonates, etc.), etc.

[0040] The paste is preferably a water-free paste. More preferably, the paste is also free of foaming agents. It should be noted that the paste only needs to be free of water as a solvent; the presence of water that may accidentally mix into the paste due to hygroscopic properties is permissible. If a paste containing water and / or a foaming agent is used to manufacture the titanium porous body, large pores may form during the manufacturing process, making it impossible to achieve the desired pore size. In the case of a titanium porous body with large pore sizes manufactured due to the inclusion of water and / or a foaming agent in the paste, it will result in a titanium porous body with poor surface smoothness that can easily damage the electrolyte membrane surface of a solid polymer-type water electrolysis device.

[0041] (Drying process) In the drying process, the above-mentioned paste is thinly coated into a sheet and heated. As a result, the organic solvent in the paste evaporates, resulting in a dried sheet.

[0042] The paste can be applied to a flat surface, preferably to a resin substrate. The resin substrate for paste application can be placed on a molding die (described later), but is not limited to this. It should be noted that if the paste is applied directly to a graphite molding die, carbon from the molding die may mix into the paste and the sheet-like dried body during the drying process, sometimes causing discoloration of the porous titanium material after the sintering process. Resin substrates are relatively inexpensive and flexible, making them easy to handle. Specific materials for resin substrates include, for example, polyesters such as PET (polyethylene terephthalate) and PEN (polyethylene naphthalate), polyethylene, polypropylene, polystyrene, and polyvinyl alcohol. PET resin substrates are particularly inexpensive and allow for easy separation of the sheet-like dried body from the resin substrate after the drying process.

[0043] A release layer can be applied to the resin substrate as needed. When applying a release layer, a silicone coating or similar material can be used. For example, a release layer can be applied to a substrate pre-coated with a material such as Cerapeel (registered trademark) manufactured by Toray Corporation. By applying a release layer to the substrate, the thin, sheet-like molded body obtained after the drying process can be easily separated from the substrate.

[0044] The heating temperature during drying can be set between 90°C and 165°C. Drying the paste at this temperature range suppresses boiling of components such as organic solvents and allows drying to complete in a shorter time. The drying time is not particularly limited, but can be appropriately determined; for example, it can be set between 5 minutes and 300 minutes. Drying is preferably carried out in an oxygen-containing atmosphere, such as atmospheric air. This helps to prevent increases in manufacturing costs.

[0045] In the case of manufacturing a porous titanium body with multiple porous layers of varying thicknesses, the coating thickness of the paste can be adjusted according to the thickness of the porous layers when making each sheet-like dried body.

[0046] For example in Figure 1 (a) and Figure 1 In (b) of each, by adjusting the coating thickness of the paste placed on the resin substrates 2 and 12 on the molding molds 1 and 11 and drying them respectively, sheet-like dried body 3 with thickness Ta and sheet-like dried body 13 with thickness Tb thinner than thickness Ta were obtained.

[0047] To improve the overall porosity of the titanium porous body, the relatively thick sheet-like dried body 3 of thickness Ta sometimes uses titanium powder with a relatively large average particle size. Conversely, the relatively thin sheet-like dried body 13 of thickness Tb is used to form a porous layer on the surface of the side where the electrolyte membrane is pressed in a PEM-type water electrolysis device, and titanium powder with a relatively small average particle size can be used.

[0048] As molding dies 1 and 11, they only need to have the required heat resistance and a flat surface that contacts the resin substrate 2 and 12 or the paste or sheet-like dried body 3 and 13, and ideally, excellent heat transfer properties are desirable. Specifically, a graphite sintering plate can be cited as an example of a molding die 1 or 11. Here, molding dies 1 and 11 are used as an example, but titanium molded bodies can be manufactured even without them. Furthermore, the paste coating can be performed using various known techniques. For example, although not shown in the diagram, it can be done by continuously coating the resin substrate with a paste from between rollers while conveying a long strip of resin substrate with a roller (the so-called comma coating method). Alternatively, although not shown in the diagram, a doctor blade method can be used.

[0049] (Jointing process) In the bonding process, multiple sheet-like dried bodies are stacked and bonded by applying pressure and heating simultaneously in their thickness direction. This yields a titanium molded body.

[0050] At this point, the pressure acting along the thickness direction on the multiple stacked sheet-like dried bodies is set to 0.1 N / cm. 2 The preferred value is 0.2 N / cm. 2 Above and 5.0 N / cm 2 The heating temperature is set to 70°C or higher and 200°C or lower, preferably 100°C or higher and 180°C or lower.

[0051] If the heating temperature is too low or the pressure is too low, there is a concern that the multiple sheet-like dried bodies may not bond sufficiently. In such cases, even after the bonding process and the debonding process described later, the sheet-like dried bodies of the titanium molded body may partially peel off from each other. It can be considered that if the temperature is increased to a certain extent and a specified pressure is applied, the organic adhesive of each sheet-like dried body will soften and be compressed, thus achieving good bonding. On the other hand, by keeping the pressure from being too high, the size and shape disorder of the sheet-like dried bodies caused by compression during pressurization can be well suppressed. In addition, at high heating temperatures, there is a tendency for the bonding of multiple sheet-like dried bodies to end in a short time. However, if the heating temperature is too high, there are concerns that the titanium molded body may be over-dried and cracked, or that the titanium molded body may deform due to the deformation of the resin substrate.

[0052] The pressurization and heating in the joining process can be performed while multiple stacked sheet-like dried bodies are clamped in place by a forming mold from both sides in the thickness direction. This ensures the flatness of the titanium molded body. Preferably, the state of clamping with the forming mold is maintained after heating until cooling to room temperature. The forming mold can be the same as the forming mold used in the drying process described above, but is not limited to it. Furthermore, the forming mold only needs to have a flat surface on the sheet-like dried body side to allow the titanium molded body described later to be formed into a sheet; the shape of other parts is not particularly limited. When a forming mold is used in the joining process, the pressure exerted by the weight of the forming mold is considered, and the aforementioned pressure is applied to the sheet-like dried body. That is, the pressure acting on the sheet-like dried body includes the pressure exerted by the weight of the forming mold.

[0053] When using a molding die in the joining process, in order to suppress contamination of the sheet-like dried body from the molding die during heating during joining, it is preferable to apply pressure and heat while the resin substrate is sandwiched between the sheet-like dried body and the molding die. This resin substrate may be the same as the resin substrate used in the drying process described above, or a different resin substrate may be used.

[0054] like Figure 1 As shown, the sheet-like dried bodies tend to have a surface roughness of Sa1 and Sb1 on the resin substrate 2 and 12 side of the sheet-like dried bodies 3 and 13 that is smaller than the surface roughness of Sa2 and Sb2 on their back (opposite) side during the drying process. Therefore, the sheet-like dried body 13 used to form a porous layer on one side of the surface of the electrolyte membrane pressed by the titanium porous body is preferably joined to the sheet-like dried body 3 with the surface Sb1 on the resin substrate 12 side facing outward in the thickness direction of the titanium molded body.

[0055] In contrast, sometimes even if it is desired to align the back surface Sa2 of the sheet-like dried body 3, which is the surface Sa1 on the resin substrate 2 side, with the back surface Sb2 of the sheet-like dried body 13 to form the porous layer on the other side of the titanium porous body, and to bond it to the surface Sb2, the surface roughness of both surfaces Sa2 and Sb2 is rough, so the bonding cannot be sufficiently firm. Therefore, it is preferable to bond the surface Sa1 of the sheet-like dried body 3, which is the surface Sa1 on the resin substrate 2 side, with the back surface Sb2 of the sheet-like dried body 13.

[0056] Figure 2 The diagram illustrates an example of stacking and joining sheet-like dried bodies 3 and 13. Here, firstly, the sheet-like dried body 3, after the drying process, is temporarily peeled from the molding die 1 along with the resin substrate. Then, as... Figure 2As shown in (a), another resin substrate 32 is laid on the molding die 1, and the sheet-like drying body 3 is arranged on the resin substrate 32 with its back side surface Sa2, which is located on the side of the resin substrate 2, in contact with the resin substrate 32. That is, as Figure 2 As shown by the arrow in (a), the sheet-like dried body 3, which is bonded to the resin substrate 2, is flipped over and placed on another resin substrate 32.

[0057] Next, as Figure 2 As shown in (b), the resin substrate 2 used in the drying process is peeled off from the sheet dryer 3, exposing the surface Sa1 of the sheet dryer 3 located on the side of the resin substrate 2.

[0058] After that, as Figure 2 As shown in (c), the sheet-like dried body 13, along with the resin substrate 12 and the molding die 11, is arranged on the sheet-like dried body 3 with the back surface Sb2 of the resin substrate 12 side of the sheet-like dried body 13 facing the exposed surface Sa1 of the sheet-like dried body 3 located on the resin substrate 2 side. It should be noted that the resin substrate 12 is mostly not bonded to the molding die 11. In this case, the sheet-like dried body 13 and the resin substrate 12 can be arranged on the sheet-like dried body 3 first, and then the molding die 11 can be placed on it, thereby producing... Figure 2 The configuration shown in (c) is as follows. In this case, the molding die 11 can also be replaced with a different molding die than the one used in the drying process. In this state, the sheet-like dried bodies 3 and 13 are as follows... Figure 2 As indicated by the arrow in (c), pressure and heat are applied to join them together. Thus, as... Figure 2 As shown in (d), a titanium molded body 31 with sheet-like dried body 3 and sheet-like dried body 13 joined together is obtained.

[0059] If so Figure 2 If the bonding process is performed as shown in (a) to (d), for example, the surface Sb1 of the resin substrate 12 side with the smallest surface roughness of the sheet-like dried body 13 using fine titanium powder becomes one surface of the titanium molded body 31. The back surface Sa2 of the sheet-like dried body 3 using coarse titanium powder with the largest surface roughness is located on the other surface of the titanium molded body 31. Since the back surface Sb2 of the sheet-like dried body 13 is in contact with the surface Sa1 of the resin substrate 2 side of the sheet-like dried body 3 with a less large surface roughness, the sheet-like dried body 3 and the sheet-like dried body 13 can be firmly bonded.

[0060] It should be noted that, although the illustrations are omitted, titanium molded bodies can also be manufactured by stacking and joining three or more sheet-like dried bodies. Furthermore, an example is given here where the resin substrate 2 used in the drying process and a resin substrate 32 of the same material as that used in the joining process are also used; however, resin substrates of different materials can also be used in the drying and joining processes. As for the properties required of the resin substrate in the drying process, examples include: the paste should not detach from the resin substrate during coating, and the dried sheet-like dried body should be easily separated from the resin substrate. On the other hand, in the joining process, a resin substrate that allows for easy separation of the titanium molded body and has heat resistance to a specified temperature is required.

[0061] The sheet-like dried body used in the joining process, especially the sheet-like dried body on the surface of the one that becomes the titanium molded body (in Figure 2 The sheet-like dried body (corresponding to the sheet-like dried body 13) has its surface Sb2 bonded (in Figure 2 The surface roughness Ra of the surface Sa1 (corresponding to the sheet-like dried body 3) is preferably 3.0 μm or less, and more preferably 0.1 μm or more and 3.0 μm or less, and more preferably 0.2 μm or more and 2.0 μm or less. If the surface roughness Ra is within this range, the surface Sa1 of the sheet-like dried body 3 is smooth, which allows for more bonding areas with the sheet-like dried body 13 and enables good bonding between the sheet-like dried bodies. The surface roughness Ra refers to the arithmetic mean roughness, which is measured according to ISO 4287-1997. This measurement can be performed using a roughness measuring machine (model: SJ-210) manufactured by Mitutoyo Co., Ltd.

[0062] (Adhesive removal process) In the case of manufacturing porous titanium bodies, the aforementioned titanium molded body can be supplied to a debonding process. In the debonding process, for example, the resin substrate used in the aforementioned bonding process is removed, and the titanium molded body is heated while placed on a molding die, as appropriate, to volatilize the main organic binder in the titanium molded body. When the debonding process is performed on the molding die, for example... Figure 2 The titanium molded body 31 obtained in (d) can be placed on either of the molding dies 1 and 11 for the debonding process, in which case the other molding die may not be used. The debonding process does not require the titanium molded body to be clamped by the molding die as in the joining process.

[0063] In the debinding process, the titanium molded body is preferably heated to a temperature of 300°C or higher and 450°C or lower. This suppresses the sintering of the titanium powder caused by heating and removes the organic binder.

[0064] There is no particular limitation on the heating time; it is sometimes set to a time of 3 to 20 hours, and sometimes to a time of 3 to 12 hours. The heating atmosphere can be an atmospheric atmosphere or an oxygen-containing atmosphere. Using an oxygen-containing atmosphere helps to prevent the cost increases that would occur with meticulous atmosphere control.

[0065] (Sintering process) Then, the titanium molded body that has undergone the debinding process is subjected to a sintering process to sinter the titanium powder in the molded body. After the sintering process, a porous titanium body is obtained as the sintered body.

[0066] In the sintering process, the titanium molded body after the debinding process can be heated to a temperature, for example, above 700°C and below 1100°C, typically above 825°C and below 950°C. This temperature is sometimes maintained for more than one hour and less than four hours. The sintering atmosphere can be, for example, 1.0 × 10⁻⁶ m³ / h. -2 Vacuum or reduced pressure atmosphere below Pa, or inert gas atmosphere of Ar or He.

[0067] (Porous titanium material) The sheet-like porous titanium body manufactured by the above-described manufacturing method comprises multiple layers of porous titanium formed after debinding and sintering of the aforementioned multi-layered dried sheet-like bodies. The multiple porous layers are stacked with adjacent titanium bonding surfaces in the thickness direction, each having pores that allow gas and / or liquid to permeate.

[0068] When manufacturing a porous titanium body using the method described above, titanium powders located on adjacent surfaces of each sheet-like dried body are sintered to form mutually bonded titanium bonding surfaces. When adjacent sheet-like dried bodies are manufactured using titanium powders with different average particle sizes, in the sheet-like porous titanium body obtained after the sintering process, when viewed from the side, there are portions where the size of the skeleton formed by the bonded titanium powders varies in the thickness direction; the aforementioned titanium bonding surfaces can be identified as located in these portions. From the perspective of achieving the required high conductivity at low cost, it is preferable that the titanium bonding surfaces of the multi-layer porous material do not substantially contain metals other than titanium, titanium-free compounds, etc. It should be noted that the porous titanium body used as the porous transport layer in a PEM-type water electrolysis device can be a porous titanium body that allows gas and / or liquid to permeate in other directions, such as the thickness direction or a direction perpendicular to the thickness direction.

[0069] Each porous layer has titanium powder bonded together to form a framework, and the bonded titanium powders form a sponge-like three-dimensional mesh structure with pores.

[0070] One surface of the titanium porous body is formed by a porous layer (also called the "porous layer on one side") that constitutes the surface side of that one side. That is, the surface of one side corresponds to the surface of the porous layer on one side.

[0071] The average area of ​​the pores opening on one side of the titanium porous material is 5 μm. 2 Above and 15μm 2 The following applies. As long as the pores on such a surface have a small area, the surface can be made roughly smooth, which can effectively suppress damage to the electrolyte membrane in a PEM-type water electrolysis device.

[0072] From this perspective, the average area of ​​the pores on one side of the surface is preferably 7 μm. 2 Above and 13μm 2 The following applies. If the average area of ​​the pores on one surface is too small, the aeration or liquid permeability may decrease. Furthermore, if the average area of ​​the pores on one surface is too large, the electrolyte membrane may partially enter the pores, causing significant deformation near the pores and potentially damaging the electrolyte membrane.

[0073] Furthermore, from the same perspective, the standard deviation of the area of ​​the pores on this surface is preferably 35 μm. 2 Hereinafter, 3μm is further preferred. 2 ~25μm 2 Especially preferred is 5μm 2 ~17μm 2 A small standard deviation value means that most of the holes on one side of the surface are the required fine holes.

[0074] Furthermore, the surface area on one side is 22000 μm. 2 Furthermore, the number of holes within a rectangular area with an aspect ratio of length:width = 4:3 is 256 or more, preferably 290 or more, and even more preferably 400 or more. By having a large number of fine holes as described above on one side of the surface, smoothness can be achieved and the required air permeability or liquid permeability can be ensured. The number of holes within this rectangular area on one side of the surface is not limited to this; for example, sometimes it is 700 or less, and sometimes it is 550 or less.

[0075] The other surface of a titanium porous body refers to the surface located on the back or opposite side of the surface of one side, which is formed by a porous layer (also called the "porous layer on the other side") that constitutes part of the surface side of the other side. In other words, the other surface corresponds to the surface of the porous layer on the other side.

[0076] To improve the air permeability or liquid permeability of the titanium porous body, the average area of ​​the pores opening on the other surface is preferably at least 1.5 times the average area of ​​the pores on the other surface, and more preferably at least 3 times. By forming the other surface side with a porous layer of large pores in this way, gas and liquid can easily flow inside the titanium porous body. The upper limit of the average area of ​​the pores opening on the other surface is not particularly limited, for example, provided that it has the required strength for use in a PEM-type water electrolysis device; sometimes it is set to less than 10 times the average area of ​​the pores on the other surface, sometimes less than 7 times, and sometimes less than 5 times.

[0077] The average and standard deviation of the area of ​​the openings on the surface, as well as the number of openings within a specified rectangular area, were measured using a scanning electron microscope (Keyence VHX-D510 ultra-depth-of-field multi-angle lens, manufactured by Keyence Co., Ltd.). More specifically, for both one side of the surface and the other side, the area on each surface was 22000 μm. 2 SEM images of rectangular regions with an aspect ratio of 4:3 were acquired at 2000x magnification. Then, a scanning electron microscope was used to analyze the SEM images. A threshold was set at half the maximum detected brightness value, and closed regions with brightness between 0 and the threshold were considered as holes. Binarization of the SEM images could be performed as needed. After binarization, particle removal was performed on closed regions smaller than 50 pixels (processing of the binarized black pixels), followed by hole filling (processing of the binarized white pixels). The number and area of ​​each hole were calculated, and the standard deviation, which is the square root of the variance, was determined. SEM images of five rectangular regions, at least a portion of the surface, were analyzed. The average area and average number of holes in these rectangular regions were set as the average area and standard deviation of the surface's holes, and the number of holes within the rectangular regions, respectively. In the case of a rectangular surface that appears as a square or rectangle when viewed from above, the above-mentioned 5 rectangular areas are defined as the 5 rectangular areas at the center and the four corners.

[0078] The thickness of the sheet-like porous titanium material (including the total thickness of all porous layers) is sometimes set to be 200 μm or more and 3000 μm or less. For example, such a relatively thick porous titanium material may be required for the porous material transport layer of a PEM-type water electrolysis device. On the other hand, if the thickness is too thick, it may lead to the large-scale development of PEM-type water electrolysis devices. The thickness of the porous titanium material is sometimes set to be 200 μm or more, sometimes to be 1000 μm or less, and sometimes to be 500 μm or less.

[0079] The thickness of the porous titanium body is measured at five points: four points at the periphery and one point at the center. This is achieved using a flat-type digital thickness gauge (model 547-321) with a Φ10mm probe and a measurement accuracy of 0.01mm, manufactured by Mitutoyo Corporation. The average of these measurements is then recorded. If the sheet-like porous titanium body appears rectangular when viewed from above, the four points at the periphery are designated as the four corner points.

[0080] The thickness of the porous layer on one side is sometimes set to be 20 μm or more and 120 μm or less, and sometimes 35 μm or more and 100 μm or less. Furthermore, the thickness of the porous layer on one side is sometimes set to less than 30% of the total thickness mentioned above, sometimes less than 20%, and sometimes further less than 15%. Since the porous layer on one side is composed of porous layers with small pores, its thickness is too thick, thus reducing the overall air permeability or liquid permeability of the titanium porous body. On the other hand, by increasing the thickness of the porous layer on one side to a certain extent, the required strength is ensured after sintering when producing the corresponding porous material, and this porous layer is less likely to break when pressed together with other porous layers onto the electrolyte membrane. The porous layer on one side preferably has the thinnest thickness among the multiple porous layers. By making the thickness of the porous layer on the one side, where the pores are small and gas or liquid is not easily permeable, the air permeability or liquid permeability of the titanium porous body can be significantly improved.

[0081] The thickness of the porous layer on the other side is preferably 100 μm to 2900 μm, more preferably 100 to 1000 μm, and even more preferably 200 μm to 600 μm. By increasing the thickness of the porous layer on the other side to a certain extent, the air permeability or liquid permeability can be further improved. In addition, by not making it too thick, the water electrolysis device can be miniaturized, and the electrolysis efficiency per unit area can be improved.

[0082] Regarding the thickness of each porous layer, the thickness of five points in a cross-section along the thickness direction of the titanium porous body after resin filling and grinding was observed and measured using SEM, and the average value was used. Since the required functions of each porous layer of the sheet-like titanium porous body in this embodiment differ, portions with different sizes of the framework formed by the titanium powder bonding observed in the stacking direction were identified, and the thickness of each porous layer was determined by SEM observation of these portions.

[0083] The surface area of ​​a sheet-like porous titanium body, when viewed from above, can be appropriately determined based on various conditions and is therefore not particularly limited; for example, it is sometimes set to 70 mm². 2 Above and 600,000 mm 2 Below, and sometimes 10000mm 2 Above and 600,000 mm 2Below. The term "sheet-like" as used above refers to a plate-like or foil-like shape that is thinner than its size when viewed from above; there are no particular limitations on the shape when viewed from above.

[0084] It should be noted that the titanium porous body can be composed of a double-layer porous body formed by directly bonding a porous layer on one side and a porous layer on the other side through their titanium bonding surface. Alternatively, it can be made into a titanium porous body with one or more porous layers as intermediate layers between the porous layers on one side and the porous layer on the other side. In this case, the pore size within the titanium porous body can be gradually increased to control the flow of gas and liquid to a certain extent.

[0085] The overall porosity of titanium porous materials, comprising multiple porous layers, is 40% to 60%, preferably 45% to 55%. Within this range of porosity, the material possesses the required air or liquid permeability for its intended application, making it suitable for use as a porous transport layer in solid polymer-type water electrolysis devices. If the porosity is too high, the mechanical strength of the titanium porous material is insufficient, and undesirable compressive deformation may easily occur.

[0086] The porosity ε of the titanium porous body is calculated using the apparent density ρ´ derived from the volume and mass obtained from the external dimensions of the titanium porous body, such as its width, length, and thickness, and the true density ρ of the titanium constituting the titanium sintered body (4.51 g / cm³). 3 The value is calculated according to the formula: ε=(1-ρ´ / ρ)×100.

[0087] The titanium porous body is made of titanium. If it is made of titanium, it can be said that the titanium porous body has high electrical conductivity at a certain relative density. The titanium content of the titanium porous body (and thus each porous layer) is preferably 97% by mass or more, and more preferably 98% by mass or more. The upper limit of the titanium content is not limited to this; for example, it is sometimes 99.8% by mass or less, and sometimes 99% by mass or less. This titanium content refers to the purity of titanium, taking into account not only metallic impurities but also gaseous impurities such as oxygen. Therefore, the titanium content is calculated by subtracting the total content of impurities, including both metallic and gaseous components, from 100% by mass.

[0088] Besides oxygen content, porous titanium materials sometimes have a purity corresponding to 1 to 4 types of pure titanium as defined in JIS H 4600 (2012), typically 1 to 2 types. The oxygen content of porous titanium materials can be determined by inert gas melting-infrared absorption method.

[0089] Example Next, the method for manufacturing the titanium molded body and the method for manufacturing the titanium porous body of the present invention were experimentally implemented to produce a prototype titanium porous body, and therefore, will be described below. However, the description herein is for illustrative purposes only and is not intended to be limiting.

[0090] (Example 1) As shown in Table 1, titanium powder with an average particle size of 14 μm (hydrogenated dehydrogenated titanium powder) and titanium powder with an average particle size of 21 μm were mixed with an organic solvent (isopropanol) and an organic binder (polyvinyl butyral) to prepare pastes containing these materials. It should be noted that the pastes did not contain water or foaming agents. Each paste was coated onto a PET resin substrate as a sheet and dried at 150°C for 90 minutes to obtain dried sheet bodies. It should be noted that the PET resin substrate had an organosilicon coating as a release layer.

[0091] Next, as Figure 2 As shown, the sheet-like dried body for the porous layer on the other side is flipped over together with the resin substrate and placed on another resin substrate laid on a molding die. Then, the resin substrate on the upper side is peeled off, and the sheet-like dried body for the porous layer on one side is flipped over together with the resin substrate on top. The molding die is then placed on top, and in this state, heating and pressurization are performed at the temperature, pressure, and time shown in Table 1. It should be noted that the pressure applied to the sheet-like dried body is achieved by placing a weight on the molding die on the upper side. Thus, the sheet-like dried bodies are joined together to obtain a titanium molded body.

[0092] Next, the titanium molded body was heated at 380°C in an atmospheric atmosphere for the time shown in Table 1 to separate the organic binder and perform debinding. Then, the debinded titanium molded body was heated under vacuum at the temperature shown in Table 1 for 1 hour. As a result, the titanium powder in the titanium molded body was sintered, yielding a porous titanium body.

[0093] (Example 2) As shown in Table 2, the bonding conditions of the sheet-like dried body were changed, but otherwise, a titanium porous body was manufactured in the same manner as in Example 1.

[0094] (Example 3) As shown in Table 3, three sheet-like dried bodies with a specified surface roughness Ra were prepared. In their respective preparation, titanium powder with an average particle size of 21 μm was used. Otherwise, titanium porous bodies were prepared in the same manner as in Example 1.

[0095] (Example 4) As shown in Table 4, titanium powder with an average particle size of 28 μm was used in the fabrication of the sheet-like dried body for the porous layer on the other side, and the sheet-like dried body was made with a specified surface roughness Ra and the heating time and sintering temperature for debinding were changed. Otherwise, the titanium porous body was manufactured in the same manner as in Example 1.

[0096] (Comparative Example 1) When bonding the sheet-like dried body, the pressure was set to zero (no pressure applied). Otherwise, when trying to manufacture a titanium porous body in the same way as in Example 1, the porous layers of the titanium porous body were easily peeled off by hand, so the titanium porous body could not be manufactured.

[0097] (Comparative Example 2) When bonding the sheet-like dried bodies, pressure was applied but heating was not performed and the temperature was set to room temperature. Otherwise, when attempting to manufacture a porous titanium body in the same manner as in Example 1, the sheet-like dried bodies were not bonded, and subsequent processes could not be carried out.

[0098] (evaluate) For each titanium porous body in Examples 1-4, the total thickness, the thickness of each porous layer (layer thickness), the average area of ​​the pores opening on each surface of one and the other (average pore area of ​​the surface), and the standard deviation of the pore area (standard deviation of the pore area of ​​the surface) were measured according to the method described above. 2 The number of holes (number of holes on the surface) and the overall porosity within a rectangular area with an aspect ratio of 4:3 are also considered. The results are shown in Tables 1-4.

[0099] In addition, the conductivity (layer conductivity) of one and the other surfaces of each titanium porous body was measured separately. Conductivity was measured using a MITSUBISHI ANALYTECH LORESTA GP MCP-T610 low resistivity meter, employing a four-probe method with the surface of the object being measured positioned on the upper side. An MCP-T610RMH112 probe inspection instrument was used. The results are also shown in Table 1. It is believed that if the titanium bonding surfaces of the porous titanium layers are sufficiently bonded together, the conductivity increases. Furthermore, it is speculated that with high conductivity, the gas-liquid permeable layers are firmly bonded, thus resulting in excellent mechanical strength. It should be noted that in Tables 1-4, the unit of conductivity is recorded as "E+3S / cm", which refers to "10"... 3 "×S / cm". For example, the value "4.1" in the "Laminated Conductivity" column of Table 1 refers to 4100 S / cm.

[0100] Furthermore, Tables 1-4 also show the thickness, monomer conductivity, stacked conductivity, and porosity of titanium sintered bodies (titanium sintered bodies corresponding to each porous layer) obtained by debinding and sintering the sheet-like dried bodies used to manufacture each titanium porous body without bonding them. The monomer conductivity is the value obtained by measuring the conductivity of two or three titanium sintered bodies without bonding them, while the stacked conductivity is the value obtained by measuring the conductivity of two or three titanium sintered bodies stacked together. The stacked conductivity, measured only with two or three titanium sintered bodies stacked together, tends to be smaller than the monomer conductivity due to the large resistance between them. Furthermore, since the sheet-like dried bodies are not bonded and are stacked, the stacked thickness tends to be inconsistent with the total thickness of each titanium sintered body. In Examples 1-4, as shown in Tables 1-4, porous titanium bodies can be manufactured by simultaneously pressurizing the sheet-like dried body at a specified pressure and heating it at a specified temperature. These porous titanium bodies have a high conductivity (monomer conductivity) similar to that of each titanium sintered body, therefore it is considered that the porous layers are fully bonded to each other at the titanium bonding surface.

[0101] Furthermore, the aforementioned porous titanium body comprises multiple porous layers, wherein adjacent titanium bonding surfaces in the thickness direction are bonded together and stacked, each having pores. The stacked conductivity of at least one surface on one side and the other side of any porous titanium body is approximately 1.5 times, or more than 1.5 times, greater than the stacked conductivity of the same surface of a sintered titanium body consisting only of stacked layers, indicating that the porous layers are sufficiently bonded together. Moreover, the average area of ​​the pores on one surface of any porous titanium body (the surface of the porous layer on one side), the standard deviation of the pore area, the number of pores, and the porosity are all predetermined ideal values.

[0102] Explanation of reference numerals in the attached figures 1, 11: Molding mold; 2, 12, 32: Resin substrate; 3, 13: Sheet-shaped dried body; 31: Titanium molded body; Sa1, Sb1: Surface of the resin substrate side; Sa2, Sb2: Surface of the back side; Ta, Tb: Thickness.

Claims

1. A method for manufacturing a titanium molded body, comprising a method for manufacturing a sheet-like titanium molded body. The method for manufacturing the titanium molded body includes a bonding process, wherein the bonding process involves drying a paste containing titanium powder, an organic binder, and an organic solvent, thereby stacking multiple sheet-like dried bodies while maintaining a thickness of 0.1 N / cm. 2 The pressure is increased while heating to a temperature above 70°C and below 200°C.

2. The method for manufacturing a titanium molded article according to claim 1, wherein, The process prior to the bonding step includes a drying step to dry the paste to obtain a sheet-like dried body.

3. The method for manufacturing a titanium molded article according to claim 2, wherein, In the drying process, the paste is heated to a temperature above 90°C and below 165°C.

4. The method for manufacturing a titanium molded article according to claim 2 or 3, wherein, The drying of the paste in the drying process is carried out on a resin substrate.

5. The method for manufacturing a titanium molded article according to any one of claims 1 to 4, wherein, In the joining process, multiple stacked sheet-like dried bodies are pressurized and heated while being clamped by forming molds from both sides in the thickness direction.

6. The method for manufacturing a titanium molded article according to claim 5, wherein, In the bonding process, pressure and heat are applied while the resin substrate is sandwiched between the sheet-like dried body and the molding die.

7. The method for manufacturing a titanium molded article according to any one of claims 1 to 6, wherein, The average particle size of the titanium powder in at least one of the sheet-like dried bodies is greater than 10 μm and less than 20 μm.

8. The method for manufacturing a titanium molded article according to any one of claims 1 to 7, wherein, In the sheet-like dried body, the average particle size of the titanium powder in one of the sheet-like dried bodies differs from the average particle size of the titanium powder in at least one other sheet-like dried body by more than 5 μm.

9. The method for manufacturing a titanium molded article according to any one of claims 1 to 8, wherein, The paste used to prepare the sheet-like dried body does not contain a foaming agent.

10. A method for manufacturing a porous titanium body, comprising: The adhesive removal process involves heating a titanium molded body manufactured by the method for manufacturing titanium molded bodies according to any one of claims 1 to 9 to volatilize the organic adhesive in the titanium molded body; and In the sintering process, the titanium molded body after the debinding process is heated to sinter the titanium powder in the titanium molded body.

11. A porous titanium material, wherein the porous titanium material is in the form of sheets. The titanium porous body comprises multiple layers of porous titanium, wherein adjacent titanium bonding surfaces in the thickness direction are bonded together and stacked, each having pores that allow gas and / or liquid to permeate. In the multilayer porous layer, the average area of ​​the pores at the surface openings of the porous layer forming one surface is 5 μm. 2 Above and 15μm 2 Hereinafter, the standard deviation of the area of ​​the hole is 35 μm. 2 Below, in an area of ​​22000μm 2 Furthermore, the number of holes present within a rectangular area with an aspect ratio of 4:3 is 256 or more. The overall porosity of the multi-layered porous material is above 40% and below 60%.

12. The porous titanium body according to claim 11, wherein, The average area of ​​the openings on the other surface located on the back side of the surface of one side is more than 1.5 times the average area of ​​the openings on the surface of one side.

13. The porous titanium body according to claim 11 or 12, wherein, The total thickness is above 200μm and below 3000μm.

14. The porous titanium body according to any one of claims 11 to 13, wherein, The thickness of the porous layer constituting the surface side of one side is less than 30% of the total thickness.

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