Titanium porous material and method for manufacturing a titanium porous material

Abstract

To provide a titanium porous body which is formed in a relatively thin sheet shape, is hardly broken in handling, and has at least one surface which is smooth, and a production method of the same.SOLUTION: There is provided a titanium porous body which has a sheet shape, whose thickness is 0.3 mm or smaller, whose breakage flexure strain is 0.005 or greater, and in a three-dimensional surface property on at least one surface, an arithmetical average height Sa is 2.5 μm or smaller, a maximum height Sz is 30 μm or smaller, an aspect ratio Str of the surface property is 0.93 or greater, and an arithmetical average curvature Spc of a crest is 4.8(1 / μm) or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a sheet-like porous titanium material and a method for manufacturing a porous titanium material. [Background technology]

[0002] Conventional titanium porous materials and methods for producing them include, for example, those described in Patent Documents 1 and 2.

[0003] Patent Document 1 discloses a "sintered metal sheet material for electrochemical components" characterized by being made of a metal sintered body obtained by sintering metal powder, having a plurality of voids dispersed inside, having a porosity of 10% by volume or more and 50% by volume or less, having an average pore diameter of 1 μm or more and 30 μm or less, and having a portion of the plurality of voids arranged to open to the surface, wherein "the metal sintered body is composed of Ti with a carbon content of 0.5% by mass or less and an oxygen content of 1% by mass or less." Patent Document 1 describes a method for manufacturing this "sintered metal sheet material for electrochemical components" which involves a "slurry preparation step," a "molding step," a "drying step," a "degreasing step," and a "sintering step." In the "slurry preparation step," it states that "a slurry is prepared by mixing titanium raw material powder with an organic binder, water, and a plasticizer as needed." Furthermore, regarding the "drying process," it is stated that "the temperature inside the drying tank 25 is adjusted to, for example, 40 to 90°C, and the slurry S, which has been formed into a thin plate shape, passes through the drying tank 25 over a period of, for example, 10 to 30 minutes."

[0004] Patent Document 2 proposes a method for producing a titanium powder sintered body, comprising the steps of: producing titanium secondary particles in which primary titanium particles are aggregated into a spherical shape; mixing the titanium secondary particles with a binder to form a slurry; processing the slurry into a plate-shaped molded body; drying the molded body; heating the dried molded body to remove the binder from the molded body; and sintering the molded body obtained after removing the binder. Regarding the "slurry," Patent Document 2 states that "the produced spherical titanium secondary particles are made into a slurry by mixing them with a solvent and a solvent-soluble binder," and that "there is no particular restriction on the type of solvent; commonly used solvents can be used in general mixing ratios, for example, water, various alcohols, various ketones, etc. can be widely used." Furthermore, Patent Document 2 states that "the prepared sintering raw material titanium powder was kneaded with 10% by weight of a water-soluble acrylic binder (Yuken Kogyo Co., Ltd., AP-2), 3.5% by weight of a plasticizer (Yuken Kogyo Co., Ltd., VL-A Test 1), and water to obtain a slurry." [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2011-99146 [Patent Document 2] International Publication No. 2007 / 138806 [Overview of the project] [Problems that the invention aims to solve]

[0006] Incidentally, porous titanium materials possess permeability or liquid permeability due to their numerous pores, as well as electrical conductivity, and also exhibit high corrosion resistance due to the formation of a passive film on their surface. For this reason, porous titanium materials are being considered for use as PTLs (Porous Transport Layers) in environments where corrosion may occur in PEM water electrolysis equipment.

[0007] For such applications, a thin, sheet-like titanium porous material is required, as it is less prone to damage during handling, such as during transport or installation on equipment, from the standpoint of miniaturizing the device and ease of handling.

[0008] Furthermore, in the above-mentioned PEM water electrolysis apparatus, the titanium porous material may be placed in close contact with other components such as the electrode layer. In this case, it is desirable that at least one surface of the titanium porous material be smooth in order to improve the adhesion between the titanium porous material and the other components.

[0009] Patent documents 1 and 2 do not address the issue of smoothing the surface of the titanium porous material. Furthermore, it has been newly discovered that adding water to the "slurry," as in the manufacturing methods described in patent documents 1 and 2, impairs the surface smoothness of the final titanium porous material.

[0010] The object of this invention is to provide a titanium porous body that is relatively thin, sheet-like, resistant to damage during handling, and has at least one smooth surface, as well as a method for manufacturing a titanium porous body. [Means for solving the problem]

[0011] As a result of diligent research, the inventors discovered that by adjusting the composition of the titanium powder and paste, as well as the drying temperature of the paste, a titanium porous body can be obtained that is less prone to breakage during handling, even in a relatively thin sheet form, and has at least one surface with the required smoothness. Specifically, using pulverized titanium powder with a hydrogen content of 0.1% by mass or less, a paste without water or a foaming agent is dried on a substrate at a temperature of 100°C or higher and 130°C or lower. This yields a molded body. Subsequently, organic matter in the molded body is volatilized, and the titanium powder is sintered. In this way, the above-mentioned titanium porous body is obtained.

[0012] The titanium porous material of this invention is in sheet form, has a thickness of 0.3 mm or less, a fracture bending strain of 0.005 or more, and for the three-dimensional surface properties of at least one surface, the arithmetic mean height Sa is 2.5 μm or less, the maximum height Sz is 30 μm or less, the aspect ratio Str of the surface properties is 0.93 or more, and the arithmetic mean curvature Spc of the peaks is 4.8 (1 / μm) or less.

[0013] The above-mentioned porous titanium material preferably has a porosity of 30% or more and 50% or less.

[0014] The above-mentioned titanium porous material may have a titanium content of 97% by mass or more.

[0015] The above-mentioned titanium porous material may have a carbon content of 0.01% by mass or more and 0.06% by mass or less.

[0016] The present invention relates to a method for producing a sheet-shaped titanium porous body, comprising: a drying step of applying a paste containing pulverized titanium powder with a hydrogen content of 0.1% by mass or less, an organic binder, and an organic solvent, without water or a foaming agent, onto a substrate, and then heating and drying the paste on the substrate at a temperature of 100°C or higher and 130°C or lower to obtain a sheet-shaped molded body; a preheating step of heating the molded body to volatilize the organic matter in the molded body; and a sintering step of heating the molded body after the preheating step to sinter the titanium powder in the molded body.

[0017] In the above manufacturing method, it is preferable to separate the molded body obtained in the drying step from the substrate and then perform the preheating step.

[0018] In the above manufacturing method, it is preferable that the 10% particle size D10 of the titanium powder in the paste used in the drying step is 5 μm or more and 15 μm or less, and the 90% particle size D90 is 15 μm or more and 25 μm or less.

[0019] In the drying step, it is preferable to use a paste in which the ratio (Ms / Mb) of the mass Ms of the organic solvent to the mass Mb of the organic binder is 2.0 or more and 9.0 or less as the paste.

Advantages of the Invention

[0020] The titanium porous body of this invention is in the form of a relatively thin sheet and is difficult to break during handling, and at least one of its surfaces is smooth. The method for manufacturing the titanium porous body of this invention is suitable for manufacturing such a titanium porous body.

Embodiments for Carrying Out the Invention

[0021] Hereinafter, embodiments of this invention will be described in detail. The titanium porous body according to one embodiment of this invention is in the form of a sheet having a thickness of 0.3 mm or less, a fracture bending strain of 0.005 or more, and at least one of its surfaces has a predetermined three-dimensional surface property (surface roughness). The predetermined three-dimensional surface property means that the arithmetic mean height Sa is 2.5 μm or less, the maximum height Sz is 30 μm or less, the aspect ratio Str of the surface property is 0.93 or more, and the arithmetic mean curvature Spc of the peaks is 4.8 (1 / μm) or less. It can be said that this titanium porous body is difficult to break during handling due to its large fracture bending strain, and the above surface has the required smoothness required for a predetermined application.

[0022] The method for manufacturing the above titanium porous body includes a drying step of heating and drying a paste containing titanium powder, an organic binder, and an organic solvent on a substrate at a temperature of 100°C or more and 130°C or less to obtain a sheet-shaped molded body, a preheating step of heating the molded body to volatilize the organic substances in the molded body, and a sintering step of heating the molded body after the preheating step to sinter the titanium powder in the molded body. This method may further include a paste preparation step of preparing the above paste and a paste coating step of coating the paste on a substrate before the drying step.

[0023] In the above manufacturing method, it is important that the paste contains pulverized titanium powder with a hydrogen content of 0.1% by mass or less, and does not contain water or a foaming agent, and that the paste is heated to a temperature of 100°C or higher and 130°C or lower during the drying process. When titanium powder with a relatively high hydrogen content is used, the hydrogen is removed during heating in sintering, causing shrinkage and reducing the surface smoothness of the titanium porous material. Furthermore, using pulverized titanium powder increases the fracture bending strain of the titanium porous material. When water is added to the paste in addition to an organic solvent, the difference in drying behavior between the organic solvent and water disrupts the mixing state of the titanium powder and organic binder in the paste, resulting in pinhole formation on the surface of the titanium porous material. These differences in drying behavior include the fact that the organic solvent volatilizes and is removed before water during drying, and that the affinity between the organic solvent and water for titanium powder and organic binders differs. Additionally, if the paste contains a foaming agent, large localized voids are formed in the titanium porous material due to the foaming agent, reducing surface smoothness and making it more prone to cracking during handling. If the drying temperature is too high, organic solvents in the paste tend to boil easily, causing roughness on the surface of the titanium porous material. On the other hand, if the drying temperature is too low, drying takes a long time, during which the liquid in the paste is unevenly distributed, disrupting the mixing state of the titanium powder and organic binder. This can lead to the formation of pinholes and other issues, resulting in a deterioration of the surface smoothness of the titanium porous material. In this embodiment of the manufacturing method, the occurrence of the problems described above is suppressed, making it possible to produce a good titanium porous body.

[0024] (composition) The titanium porous material is made of titanium. If made of titanium, a titanium porous material with high electrical conductivity at a certain relative density can be obtained. The titanium content of the titanium porous material is 97% by mass or more, preferably 98% by mass or more. A higher titanium content is desirable, but it may be 99.8% by mass or less, and may be 99% by mass or less.

[0025] The titanium porous material may contain Fe as an impurity, and the Fe content is, for example, 0.25% by mass or less. In addition, the titanium porous material may contain Ni, Cr, Al, Cu, Zn, and Sn as unavoidable impurities resulting from the manufacturing process. Preferably, the content of each of Ni, Cr, Al, Cu, Zn, and Sn is less than 0.10% by mass, and their total content is less than 0.30% by mass.

[0026] When the titanium porous body of this embodiment is manufactured using a paste containing titanium powder as described later, carbon from the organic matter contained in the paste may remain, resulting in a somewhat high carbon content. Specifically, the carbon content of the titanium porous body may be between 0.01% by mass and 0.06% by mass, and typically between 0.01% by mass and 0.04% by mass. The carbon content can be measured by combustion infrared absorption spectroscopy.

[0027] Furthermore, the purity of the titanium porous material may correspond to that of pure titanium grades 1 to 4, typically grades 1 to 2, according to JIS H 4600 (2012), excluding oxygen and nitrogen content.

[0028] (Thickness) The thickness of the sheet-like porous titanium material is 0.3 mm or less, preferably 0.02 mm or more and 0.3 mm or less, and more preferably 0.02 mm or more and 0.2 mm or less. Depending on the application, materials with such a thin thickness may be required. In reference to the porous titanium material, "sheet-like" means a plate-like or foil-like material with a small thickness relative to its dimensions in plan view, and the shape in plan view is not particularly limited.

[0029] The thickness is measured at five points: four points on the periphery and one point in the center of the porous titanium material. This measurement is taken using a digital thickness gauge with a flat probe of Φ10 mm and a measurement accuracy of 0.001 to 0.01 mm, such as a Mitutoyo digital thickness gauge (model 547-321). The average of these measurements is used as the thickness. If the sheet-like porous titanium material is rectangular in plan view, the four points on the periphery should be the four corner points.

[0030] (porosity) The porosity of the titanium porous material is preferably 30% or more and 50% or less, more preferably 35% or more and 50% or less. Within this range of porosity, it is possible to ensure the required air permeability or liquid permeability according to the application while suppressing damage during handling. When the porosity is 30% or more, good air permeability or liquid permeability is obtained. On the other hand, when the porosity is 50% or less, cracking during handling becomes less likely.

[0031] The porosity ε of a titanium porous material is calculated from the volume obtained from the width, length, and thickness of the titanium porous material, as well as the apparent density ρ' calculated from the mass, and the true density ρ (4.51 g / cm³) of the titanium constituting the titanium porous material. 3 Using ), it is calculated by the formula: ε = (1 - ρ' / ρ) × 100.

[0032] Furthermore, when a titanium porous body is manufactured using titanium powder as described later, the three-dimensional network structure that partitions the voids in the titanium porous body tends to become sponge-like. This sponge-like three-dimensional network structure is similar in shape to the sponge titanium manufactured by the Kroll method. On the other hand, when titanium fibers are used, the three-dimensional network structure that partitions the voids in the titanium porous body often becomes nonwoven fabric-like. In addition, in a method in which a paste containing titanium powder or an organic binder is used, and the paste is dried and then the titanium powder is sintered, if a foaming agent is added to the paste, the resulting titanium porous body is more prone to the formation of voids within its framework due to the effect of the foaming agent.

[0033] (Fracture bending strain) The fracture bending strain of a porous titanium material is 0.005 or greater. A larger fracture bending strain indicates that the material is less prone to breakage and has excellent handling properties. As described later in the Examples section, a porous titanium material may not fracture during the fracture bending strain test. Such a porous titanium material is less prone to breakage and has excellent handling properties. Therefore, there is no particular preferred upper limit for the fracture bending strain. However, depending on the application, there may be a preferred upper limit for the fracture bending strain.

[0034] The fracture bending strain of a porous titanium material is measured by a three-point bending test. The specimen dimensions are 60 mm in length and 15 mm in width, with a support distance of 22.5 mm, an indenter diameter and support diameter of R5 mm, and a test speed of 2 mm / min. Other conditions follow JIS K 7171 (Method for determining the bending properties of plastics). If the deflection is s (mm), the specimen thickness is h (mm), and the support distance is L (mm), then the bending strain is ε. f is, formula: ε f =6sh / L 2 The fracture bending strain is determined by the following method. The fracture bending strain is the bending strain at the time the specimen fractures. For example, the Miyabeya Techno Graph TG-1KN can be used as the measuring device.

[0035] (Three-dimensional surface texture) The arithmetic mean height Sa of the surface roughness on at least one surface of the titanium porous material is 2.5 μm or less. The arithmetic mean height Sa represents the average of the absolute values ​​of the heights from the average plane of the surface. If the arithmetic mean roughness Sa is 2.5 μm or less, the smoothness of the surface is ensured. As a result, it becomes less likely to damage adjacent members placed adjacent to the titanium porous material in a PEM water electrolysis device or the like. From this viewpoint, the arithmetic mean height Sa of at least one surface of the titanium porous material is preferably 2.0 μm or less. The arithmetic mean height Sa of at least one surface of the titanium porous material may be, for example, 1.0 μm or more and 2.5 μm or less, or for example, 1.0 μm or more and 2.0 μm or less.

[0036] The maximum surface roughness height Sz on at least one surface of the titanium porous material is 30 μm or less. The maximum height Sz refers to the distance from the highest point to the lowest point on the surface. A maximum height Sz of 30 μm or less ensures surface smoothness, making it less likely to damage adjacent members. Preferably, the maximum surface roughness Sz on at least one surface of the titanium porous material is 25 μm or less. The maximum surface roughness Sz on at least one surface of the titanium porous material may be, for example, 18 μm or more and 30 μm or less, or 18 μm or more and 25 μm or less.

[0037] The aspect ratio Str of the surface roughness of at least one surface of the titanium porous material is 0.93 or higher. The aspect ratio Str of the surface roughness represents isotropy or anisotropy on a horizontal plane (a plane parallel to the surface). The aspect ratio Str of the surface roughness can be a value between 0 and 1. A value close to 0 means that there is anisotropy such as a streaky pattern, while a value close to 1 means that it is isotropic regardless of direction. If the aspect ratio Str of the surface roughness is 0.93 or higher, it is isotropic, and fluid diffusion can be made more uniform. Also, because of the high isotropy, it is less likely to damage adjacent members of the titanium porous material. The aspect ratio Str of the surface roughness is preferably 0.95 or higher. The aspect ratio Str of the surface roughness of at least one surface of the titanium porous material may be 0.99 or lower. The aspect ratio Str of the surface roughness of at least one surface may be, for example, 0.93 or higher and 0.99 or lower, or for example, 0.95 or higher and 0.99 or lower.

[0038] The arithmetic mean curvature Spc of the peaks of the surface roughness on at least one surface of the titanium porous material is 4.8 (1 / μm) or less. The arithmetic mean curvature Spc of the peaks refers to the mean curvature (average sharpness) of the tip of the peak. When the arithmetic mean curvature Spc of the peaks is 4.8 (1 / μm) or less, the tip of the peak is gentle and less likely to damage adjacent members. The arithmetic mean curvature Spc of the peaks of at least one surface of the titanium porous material is preferably 4.0 (1 / μm) or less, and more preferably 3.6 (1 / μm) or less. The arithmetic mean curvature Spc of the peaks of at least one surface of the titanium porous material may be, for example, 2.0 (1 / μm) or more and 4.8 (1 / μm) or less, or for example, 2.0 (1 / μm) or more and 4.0 (1 / μm) or less, or for example, 2.0 (1 / μm) or more and 3.6 (1 / μm) or less.

[0039] To measure the arithmetic mean height Sa, maximum height Sz, surface texture aspect ratio Str, and peak curvature Spc, a laser microscope is used. Specifically, the Keyence VK-X1000 / 1050 shape analysis laser microscope can be used. In surface shape measurement mode, a region measuring 500 μm vertically and 750 μm horizontally is measured at a magnification of 50x. This measurement is performed at five locations per sample, and the average value of the five measurements for Sa, Sz, Str, and Spc must satisfy the predetermined numerical criteria mentioned above. That is, for at least one surface of the titanium porous body, the average value of the arithmetic mean height Sa at five locations is 2.5 μm or less, the average value of the maximum height Sz at five locations is 30 μm or less, the average value of the surface texture aspect ratio Str at five locations is 0.93 or more, and the average value of the peak curvature Spc at five locations is 4.8 (1 / μm) or less. When using the VK-X1000 / 1050, Sa, Sz, Str, and Spc are parameters that are calculated as standard without any special setting changes, so their detailed calculation formulas are omitted. However, Sa represents the average value of the absolute height from the average plane of the surface, Sz represents the distance from the highest point to the lowest point of the surface, and is standardized by ISO 25178. Str represents the aspect ratio of the surface texture and is the shortest lateral distance r at which the autocorrelation value decays to 0.2.min and the longest distance r max The ratio (r min / r max Spc is calculated as follows: Spc represents the average sharpness of the peak tip. For peaks where the curvature is higher than 5% of the maximum amplitude of the contour surface, the curvature of the peak is determined, and the arithmetic mean of these curvatures is taken as Spc.

[0040] A titanium porous body having the aforementioned three-dimensional surface properties on at least one surface, when used in a PEM water electrolysis device, for example, is expected to exhibit excellent adhesion to adjacent components such as electrolyte membranes, as well as reduce cell resistance and prevent damage to the electrode layer. In addition, its stable surface properties contribute to the stabilization of electrolysis performance.

[0041] Furthermore, the sheet-like titanium porous material may have the three-dimensional surface properties described above on both its surface and the other surface on its reverse side. However, if at least one surface of the titanium porous material has the three-dimensional surface properties, then by arranging it in a PEM water electrolysis device, etc., so that its surface faces the electrode layer or other components, effects such as improved adhesion with those other components can be obtained.

[0042] (Manufacturing method) The titanium porous material described above may be manufactured, for example, as described below.

[0043] First, in the paste preparation process, a paste containing titanium powder, an organic binder, and an organic solvent is prepared.

[0044] Here, titanium powder with a hydrogen content of 0.1% by mass or less is prepared and incorporated into the paste. If the hydrogen content of the titanium powder is higher than 0.1% by mass, a large amount of hydrogen will be released during the sintering process, causing significant shrinkage. This can lead to the formation of pinholes and make it impossible to ensure the required smoothness of the titanium porous body's surface. Note that the hydrogen content of the titanium powder may be 50 ppm by mass or more. High-purity titanium powder is preferable, and pure titanium powder can be used. The titanium content of the titanium powder may be 99% by mass or more.

[0045] Furthermore, the titanium powder is in the form of pulverized powder. Using pulverized titanium powder is preferable because it increases the number of contact points between the particles constituting the pulverized powder, resulting in a larger fracture bending strain value. Pulverized powder is powder produced by pulverizing lumps or the like. An example of such pulverized powder is hydrogenated dehydrogenated titanium powder (so-called HDH powder), which is obtained by hydrogenating and pulverizing sponge titanium, and then dehydrogenating it. Hydrogenated dehydrogenated titanium powder tends to have a sufficiently low hydrogen content, which is another reason why it is particularly preferable. However, when atomized titanium powder is used, there are concerns that problems may arise, such as a smaller fracture bending strain value when the same porosity is maintained, or that sintering at higher temperatures will increase waviness and make it impossible to maintain the sheet shape.

[0046] The titanium powder preferably has a 10% particle size D10 of 5 μm or more and 15 μm or less. Furthermore, the 90% particle size D90 of the titanium powder is preferably 15 μm or more and 25 μm or less. If the 10% particle size D10 and 90% particle size D90 of the titanium powder are within the above ranges, the titanium powder is fine enough that a thin sheet-shaped titanium porous body with a large fracture bending strain can be manufactured.

[0047] The paste shall not contain water or foaming agents. This is to suppress the formation of pinholes on the surface of the titanium porous material due to the difference in drying behavior between organic solvents and water when the paste contains water. Furthermore, by not including foaming agents in the paste, large localized voids caused by the foaming of the foaming agent will not be formed in the titanium porous material. As a result, the three-dimensional surface properties of the titanium porous material will be smoother, and cracking will be less likely to occur during handling.

[0048] Various organic binders and organic solvents can be appropriately selected and used in the paste. For example, examples of organic binders include methylcellulose-based, polyvinyl alcohol-based, ethylcellulose-based, acrylic-based, and polyvinyl butyral-based binders. Hydrophobic organic binders are preferred. As for organic solvents, alcohols (ethanol, isopropanol, terpineol, butyl carbitol, etc.), toluene, cyclohexane, methyl ethyl ketone, etc. can be used, but are not limited to those listed here. As an example, polyvinyl butyral may be used as the organic binder and isopropyl alcohol as the organic solvent. The paste may also contain plasticizers (glycerin, ethylene glycol, etc.) and surfactants (alkylbenzene sulfonates, etc.).

[0049] The mass ratio of the organic binder to the organic solvent in the paste is preferably 2.0 or more and 9.0 or less (Ms / Mb). By setting the mass ratio of the organic solvent to the organic binder (Ms / Mb) to 2.0 or more and 9.0 or less, the paste will have an appropriate viscosity, allowing for the production of a smooth sheet of a predetermined thickness, and the porosity of the sintered titanium porous body will be within a preferred range of 30% or more and 50% or less. Furthermore, this mass ratio (Ms / Mb) is more preferably 2.5 or more and 6.0 or less, and even more preferably 3.0 or more and 5.0 or less. In the paste, for example, the content may be 5 g or more and 15 g or less of organic binder and 25 g or more and 45 g or less of organic solvent per 100 g of titanium powder.

[0050] The paste can be prepared by mixing the titanium powder, organic binder, and organic solvent as described above, for example, using a mixer with a stirrer, a rotary mixer, or a three-roll mill. At this time, grinding may also be done using a vibratory mill, a bead mill, or other grinding mixer.

[0051] In the paste application process, the paste described above is applied relatively thinly to the substrate. A release layer can be provided on the substrate beforehand. In this case, the paste is applied to the substrate via the release layer. When a release layer is provided on the substrate, it becomes easier to separate the molded body obtained after the paste dries from the substrate after the drying process.

[0052] As a base material, a resin base material is preferable because it can be obtained relatively inexpensively. Furthermore, resin base materials have the advantage of being easy to handle due to their flexibility. Specific examples of resin base materials include polyesters such as PET (polyethylene terephthalate) and PEN (polyethylene naphthalate), and polyvinyls such as polyethylene, polypropylene, polystyrene, and polyvinyl alcohol. Among these, PET is preferable because it is inexpensive and allows for easy separation of the molded product from the base material after the drying process described later.

[0053] Providing a release layer on the substrate is optional, but if a release layer is provided, a silicone coating or the like can be used as the release layer. For example, by selecting a substrate that has such a material, such as Toray's Therapyel (registered trademark), pre-coated, a release layer can be provided on the substrate. By providing a release layer on the substrate, the thin sheet-like molded body obtained after the drying process can be easily separated from the substrate.

[0054] In the drying process, the paste is dried on the substrate, for example, in a furnace or dryer. This causes the organic solvent in the paste to evaporate, and a sheet-like molded body is obtained on the substrate.

[0055] The drying temperature should be between 100°C and 130°C. By heating and drying the paste within this temperature range, boiling of organic solvents and other components in the paste can be suppressed, and drying can be completed in a relatively short time. In other words, if the drying temperature is higher than 130°C, there is a risk that the organic solvents in the paste will boil, which will lead to the occurrence of numerous localized roughnesses on the surface of the titanium porous material, especially on the side facing the substrate. In other words, the smoothness of the titanium porous material's surface will be impaired. On the other hand, if the drying temperature is lower than 100°C, it will be necessary to heat and dry the paste for a relatively long time. In this case, pinholes are more likely to form in the titanium porous material, and the smoothness of the titanium porous material's surface will deteriorate.

[0056] The drying time is not particularly limited and can be determined as appropriate; for example, it can be 5 minutes or more and 20 minutes or less. From the viewpoint of effectively removing organic solvents from the paste, it is desirable to perform drying while exhausting gas from the furnace or dryer. When exhausting from the furnace or dryer, the furnace or dryer can be kept under reduced pressure, or the pressure can be made equivalent to the outside pressure by supplying a gas such as air.

[0057] When the drying process is complete, the molded body obtained from the dried paste can be separated from the substrate by peeling it off or other means before the preheating process. Separating the molded body from the substrate at this stage can suppress defects in the sheet shape of the titanium porous body due to deformation of the substrate, and contamination of the titanium porous body by the material of the substrate, which can occur if the subsequent preheating and sintering processes are carried out together with the substrate. When a resin substrate is used, separation of the molded body from the substrate becomes easier. When a metal substrate is used, it may be difficult to separate the molded body from the substrate.

[0058] Next, in the preheating step, the above-mentioned molded body is heated in a furnace to volatilize and remove organic substances such as the organic binder in the molded body. In the preheating step, for example, the molded body can be heated in an air atmosphere at a temperature of 300°C or higher and lower than 450°C for 3 hours or more and 12 hours or less. The heating temperature in the preheating step is preferably higher than 350°C and lower than 450°C.

[0059] Thereafter, a sintering step is performed on the molded body that has undergone the preheating step to sinter the titanium powder in the molded body. The sintering step is not particularly limited as long as the titanium powder in the molded body is sintered. For example, in the sintering step, the molded body may be heated at a temperature of 700°C or higher and 850°C or lower for 1 hour or more and 4 hours or less. Since the titanium porous body of this embodiment is relatively thin, sintering of the titanium powder can be appropriately performed with heating at a certain degree of low temperature and for a short time. The atmosphere during sintering can be, for example, a vacuum of 1.0×10 -2 Pa or less, or an inert atmosphere of Ar or He.

[0060] After the sintering step, a titanium porous body is obtained. This titanium porous body is in the form of a relatively thin sheet as described above, is difficult to break during handling, and has good smoothness on at least one surface.

Example

[0061] Next, a titanium porous body of this invention was prototyped and its performance was evaluated, which will be described below. However, the description here is for the purpose of mere exemplification and is not intended to be limited thereto.

[0062] As the titanium powder, HDH powder (crushed powder) was prepared in Examples 1 to 4 and Comparative Examples 1 to 4 and 6, and HDH powder (crushed powder) with a mild dehydrogenation treatment was prepared in Comparative Example 5. In Comparative Example 7, atomized powder was used. All the titanium powders had a titanium content of 99% by mass or more. The type of titanium powder, hydrogen content, 10% particle size D10, and 90% particle size D90 are shown in Table 1.

[0063] The above titanium powder was mixed with polyvinyl butyral as an organic binder and isopropyl alcohol as an organic solvent to prepare a paste. The paste contained the organic binder and organic solvent in the mass ratio (Ms / Mb) shown in Table 1. In Comparative Example 6, a paste containing water was used. More specifically, the paste of Comparative Example 6 contained 3% by mass of water, and the organic binder and organic solvent were reduced by 3% by mass compared to the other examples. The mass ratio (Ms / Mb) in Comparative Example 6 is shown in Table 1.

[0064] Next, the paste was applied to a substrate (Therapeel®, manufactured by Toray Industries), and the paste on the substrate was heated and dried at the temperatures shown in Table 1 to obtain a sheet-like molded body. The drying time was 10 minutes. After drying, the molded body was separated from the substrate. Although a detailed explanation is omitted here, when the paste was applied to a metal substrate instead of a PET resin substrate and dried, it was sometimes difficult to separate the molded body from the metal substrate after drying.

[0065] Next, as a preheating step, the molded body was heated to 360°C for 360 minutes under an atmospheric environment to volatilize organic substances such as organic binders. Afterward, the molded body was heated to 800°C for 1 hour to sinter the titanium powder within it, obtaining a sintered titanium porous body. The atmosphere during sintering was 1.0 × 10⁻⁶. -2 A vacuum of Pa or less was maintained. In Comparative Example 7, the sintering temperature was adjusted so that the porosity of the titanium porous material was approximately 40%. Since porosity affects the permeability and liquid permeability of the titanium porous material, the sintering temperature in Comparative Example 7 was adjusted so that the porosity was similar to that of the other examples.

[0066] The thickness, carbon content, porosity, and fracture bending strain of the titanium porous materials were confirmed using the methods described above and are shown in Table 1. All of the titanium porous materials had a titanium content of 98% by mass or more.

[0067] Furthermore, the presence or absence of pinholes was checked by holding the titanium porous material up to light using a Tritech A2-450 tracing table. The results are shown in Table 1. A pinhole is a hole that can be seen with the naked eye through which light passes.

[0068] [Table 1]

[0069] Furthermore, the three-dimensional surface properties of the titanium porous material facing the substrate (substrate-side surface) were measured at five locations A to E on the substrate-side surface using the method described above, including the arithmetic mean height Sa, maximum height Sz, surface property aspect ratio Str, and arithmetic mean curvature Spc. The measurement results for each substrate-side surface A to E and their average values ​​are shown in Table 2.

[0070] Furthermore, since pinholes were formed in the titanium porous materials of Comparative Examples 3 to 6, they could not be considered to be good titanium porous materials, and therefore, the porosity, fracture bending strain, and three-dimensional surface properties were not checked. Possible reasons for the formation of pinholes include: in Comparative Examples 3 and 4, the drying temperature was too low, resulting in prolonged drying; in Comparative Example 5, the high hydrogen content of the titanium powder caused a large amount of hydrogen to be released during sintering, resulting in significant shrinkage; and in Comparative Example 6, the paste contained water, which caused it to behave differently from organic solvents during drying.

[0071] [Table 2]

[0072] In Examples 1-4, a paste was prepared using titanium powder with a low hydrogen content, without water or a foaming agent, and dried at a predetermined temperature. As a result, the arithmetic mean height Sa, maximum height Sz, surface aspect ratio Str, and arithmetic mean curvature Spc of the titanium porous body all reached desirable values. Furthermore, the fracture bending strain test results were also favorable in Examples 1-4.

[0073] In Comparative Examples 1 and 2, the high drying temperature resulted in undesirable values ​​for at least one of the surface roughness parameters of the titanium porous material: arithmetic mean height Sa, maximum height Sz, surface texture aspect ratio Str, and arithmetic mean curvature Spc at the peak. In particular, in Comparative Examples 1 and 2, for the four surface roughness parameters, there were both locations that met the criteria and locations that did not at the five measurement points, making it difficult to predict in advance which surface roughness parameters would result in undesirable values. On the other hand, checking the average value of the five locations is effective because it allows for the determination of whether the criteria are met. Furthermore, in Examples 1 to 4, not only the average value but also all of the measurement results from the five locations met the criteria, suggesting that good smoothness was achieved over a wide area.

[0074] Comparative Example 7 was manufactured using substantially the same paste composition and drying temperature as Example 3, except that the titanium powder was changed from pulverized powder to atomized powder. In Comparative Example 7, the sintering temperature was adjusted so that the porosity of the titanium porous body was approximately 40%. As a result, although the surface roughness of the titanium porous body of Comparative Example 7 was at the desired value, the fracture bending strain was small, and it was not possible to achieve both the desired porosity and fracture bending strain.

[0075] From the above, it has been found that this invention provides a titanium porous body that is relatively thin, sheet-like, less prone to damage during handling, and has at least one smooth surface.

Claims

1. A sheet-like porous titanium material, The thickness is 0.3 mm or less. The fracture bending strain is 0.005 or greater. A porous titanium body having, for the three-dimensional surface properties of at least one surface, an arithmetic mean height Sa of 2.5 μm or less, a maximum height Sz of 30 μm or less, an aspect ratio Str of the surface properties of 0.93 or more, and an arithmetic mean curvature Spc of the peaks of 4.8 (1 / μm) or less.

2. The titanium porous body according to claim 1, wherein the porosity is 30% or more and 50% or less.

3. A titanium porous body according to claim 1 or 2, wherein the titanium content is 97% by mass or more.

4. A method for producing a titanium porous body according to any one of claims 1 to 3, A drying step to obtain a sheet-like molded body by applying a paste containing pulverized titanium powder with a hydrogen content of 0.1% by mass or less, an organic binder, and an organic solvent, without water or a foaming agent, to a substrate, and then heating the paste on the substrate to a temperature of 100°C or higher and 130°C or lower to dry it. A preheating step in which the molded body is heated and organic matter in the molded body is volatilized, A sintering step in which the molded body after the preheating step is heated and the titanium powder in the molded body is sintered. Includes, A method for producing a titanium porous material having a thickness of 0.3 mm or less.

5. A method for producing a titanium porous body according to claim 4, wherein the molded body obtained in the drying step is separated from the substrate, and then the preheating step is performed.

6. A method for producing a porous titanium body according to claim 4 or 5, wherein the 10% particle size D10 of the titanium powder in the paste used in the drying step is 5 μm or more and 15 μm or less, and the 90% particle size D90 is 15 μm or more and 25 μm or less.

7. A method for producing a titanium porous body according to any one of claims 4 to 6, wherein in the drying step, a paste is used in which the ratio of the mass Ms of the organic solvent to the mass Mb of the organic binder (Ms / Mb) is 2.0 or more and 9.0 or less.

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