Metal film, hydrogen permeation apparatus using the same, and hydrogen production method

Abstract

To provide a metal film capable of satisfactorily permeating hydrogen even when the pressure of a raw material gas is high and to provide a hydrogen permeation device using the metal film and a hydrogen production method.SOLUTION: In a metal film: a hydrogen-containing raw material gas is in contact at a pressure of 30 kPa or higher and hydrogen is permeated; a fifth group element is included; and an average crystal particle diameter is 1 mm or less and a thickness is 0.05 mm or more when the surface of the fifth group element is observed and measured by a combination of an electron field emission type scanning electron microscope and an electron backscatter diffraction.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a metal membrane for permeating hydrogen from a raw material gas, a hydrogen permeation apparatus using the same, and a hydrogen production method. [Background technology]

[0002] As hydrogen permeable membranes, vanadium (V) or its alloys, which are metals capable of selectively permeating hydrogen from the source gas, are used, often processed into thin films by rolling, plating, or other methods.

[0003] For example, Patent Document 1 describes a technique for producing a vanadium film with a particle size number of 20 and an average particle size d of 390 nm by applying high-pressure torsion (HPT) processing as a strong strain processing that imparts a huge strain of ε=10 or more to a thin vanadium metal film that can selectively permeate hydrogen from a raw material gas. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2017-177024 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, the technology described in Patent Document 1 has a problem in that increasing the pressure of the raw material gas causes the vanadium metal film to rupture, and the hydrogen gas pressure in the raw material gas (in the case of a raw material (mixed) gas containing hydrogen, this is the partial pressure of hydrogen, and in the case of pure hydrogen gas, this corresponds to the total pressure) can only be raised to about 20 kPa, thus limiting the amount of hydrogen permeation. Furthermore, this problem exists not only for vanadium but also for metal films containing so-called Group 5 elements (hereinafter, in this specification, such metal films may be simply referred to as "metal films").

[0006] The present invention aims to solve the above problems and provides a metal membrane that can effectively permeate hydrogen even when the pressure of the raw material gas is high, a hydrogen permeation apparatus using this metal membrane, and a hydrogen production method. [Means for solving the problem]

[0007] The present invention relates to a metal film that allows hydrogen to pass through by contacting a hydrogen-containing raw material gas at a pressure of 30 kPa or more, wherein the metal film contains a Group 5 element, the average crystal particle diameter measured by observing the surface of the metal film using a combination of a field emission scanning electron microscope and backscattered electron diffraction is 1 mm or less, and the thickness of the metal film is 0.05 mm or more.

[0008] Furthermore, in the present invention, it is preferable that the content of the Group 5 element in the metal film be 50 atomic percent or more.

[0009] Furthermore, in the present invention, it is preferable that the Group 5 element is at least one selected from the group consisting of vanadium, niobium, or tantalum.

[0010] Furthermore, in this invention, the Vickers hardness of the metal film is 120 HV / kg / mm 2 It is preferable to keep the above in place.

[0011] Furthermore, in the present invention, it is preferable to set the hydrogen concentration in the raw material gas to 70% or less.

[0012] Furthermore, the present invention relates to a hydrogen permeation device characterized by using the above-mentioned metal film for hydrogen permeation.

[0013] Furthermore, the present invention relates to a hydrogen production method characterized by extracting hydrogen from the raw material gas by bringing a raw material gas containing hydrogen at a pressure of 30 kPa or higher into contact with the above-mentioned metal film and recovering the hydrogen that permeates the metal film. [Effects of the Invention]

[0014] Even when the pressure of the raw material gas containing hydrogen is increased, the metal film of the present invention can allow hydrogen to permeate well without the film being broken or the like. Further, according to the hydrogen permeation device of the present invention, since the above metal film is used, hydrogen can be preferably and selectively separated or permeated from the raw material gas. Furthermore, according to the hydrogen production method of the present invention, since the above metal film is used, a hydrogen production method capable of preferably and selectively separating or permeating hydrogen from the raw material gas is provided.

Brief Description of the Drawings

[0015] [Figure 1] Schematic diagram of the hydrogen permeation device of the present invention [Figure 2] Vickers hardness measurement results at 0.2mmHPS-V, 0.3mmHPS-V, 0.5mmHPS-V and 0.7mmHPS-V [Figure 3] Observation results of the crystal structure of 0.2mmHPS-V [Figure 4] Observation results of the crystal structure of 0.3mmHPS-V [Figure 5] Observation results of the crystal structure of 0.5mmHPS-V [Figure 6] Observation results of the crystal structure of 0.7mmHPS-V [Figure 7] Graph showing the results of the hydrogen permeation test [Figure 8] Graph showing the results of the hydrogen permeation test

Embodiments for Carrying Out the Invention

[0016] Hereinafter, preferred embodiments for carrying out the present invention will be described. Note that the following embodiments do not limit the invention according to each claim, and not all combinations of features described in the embodiments are essential for the solution means of the invention.

[0017] [Metal film] The present invention relates to a metal film that allows hydrogen to pass through by contacting it with a hydrogen-containing raw material gas at a pressure of 30 kPa or more, wherein the metal film contains a Group 5 element, the average crystal particle diameter measured by observing the surface of the metal film using a combination of a field emission scanning electron microscope and backscattered electron diffraction is 1 mm or less, and the thickness of the metal film is 0.05 mm or more.

[0018] Metal films containing Group 5 elements possess the excellent property of selectively separating and permeating hydrogen from source gases. By utilizing this property, metal films containing Group 5 elements can be applied to increasing the purity of hydrogen used as a raw material for fuel cells, and to reusing energy by separating and extracting hydrogen from by-product gases emitted from power plants, chemical plants, steel mills, etc., and are expected to make a significant contribution to achieving carbon neutrality.

[0019] However, metal films containing Group 5 elements have insufficient mechanical strength, making them prone to rupture when attempting to selectively extract hydrogen from the source gas. This aspect needed improvement. Furthermore, there was a need to further increase the hydrogen permeation efficiency to increase the amount of hydrogen that could be separated or extracted per unit time.

[0020] As a result of diligent research, the inventors of this invention have found that by using vanadium as an example of a Group 5 element and applying strain to a vanadium-containing metal film to reduce the size of the crystal particles in the metal film, the hydrogen permeation efficiency can be increased. This suggests that the crystal grain boundaries function as diffusion pathways for hydrogen atoms, and it is considered that by reducing the size of the crystal particles in the metal film and increasing the number of crystal grain boundaries, the diffusion pathways for hydrogen atoms increase, resulting in an increase in hydrogen permeability. However, even in this case, there is still room for improvement in the mechanical strength of the vanadium-containing metal film when considering practical application, and there was a problem that the metal film would break when the pressure of the hydrogen-containing raw material gas was increased. As a result, the actual situation was that the pressure of the raw material gas could only be increased to about 20 kPa.

[0021] As a result of further investigation by the inventors, it was found that in order to ensure the mechanical strength of a metal film containing Group 5 elements against the raw material gas, in other words, to improve its resistance to rupture during hydrogen permeation, how strain is applied to the untreated (simply industrially rolled to manufacture a thin film) metal film containing Group 5 elements is a crucial factor. Specifically, it was found that by constraining the untreated metal film containing Group 5 elements to be strained, applying pressure to both sides of the metal film, and applying strain while minimizing changes in the thickness of the metal film, it is possible to refine the crystal grains and improve the mechanical strength of the metal film. Furthermore, it was found that by introducing shear strain to the metal film in addition to pressure from above and below, the crystal grains can be further refined while maintaining the above mechanical strength, and this may lead to even greater advantages in terms of hydrogen permeation.

[0022] Here, while the untreated metal film containing a group 5 element to be strained is constrained as described above, various methods can be appropriately employed for applying pressure or shear strain to both sides of the metal film without changing its thickness as much as possible. One example is the High-Pressure Sliding (HPS) method. In the HPS method, the untreated metal film is sandwiched between two molds, one above the other, to constrain the top, bottom, and periphery of the metal film. Then, strain is applied by applying pressure from above and below the metal film. By applying this pressure from above and below, the average crystal grain size in the metal film (measurement method will be explained later) can be refined from several millimeters to several tens of millimeters in the untreated metal film to typically 1 mm or less, preferably 100 μm or less, more preferably 50 μm or less, particularly preferably 10 μm or less, most preferably 5 μm or less, and usually 100 nm or more.

[0023] Furthermore, by shifting all or part of the upper and lower molds to the left or right while pressure is applied to the metal film containing the Group 5 element in the upper and lower molds, shear strain can be introduced into the metal film. This introduction of shear strain makes it easier to further refine the crystal grains. Specifically, by introducing shear strain, the average crystal grain diameter in the metal film containing the Group 5 element can be made to typically 1 μm or less, preferably 700 nm or less, more preferably 500 nm or less, and typically 1 nm or more.

[0024] In this invention, the method for measuring the average crystal particle size in a metal film containing a Group 5 element involves observing the surface of the metal film using a combination of field emission scanning electron microscope (FE-SEM) and backscattered electron diffraction (EBSD), performing image processing of the observed image, and then measuring the average crystal particle size.

[0025] For the field emission scanning electron microscope, the JEOL Ltd. JSM-7100F can be used. Using this device, the observation conditions were set as follows: 9.5 × 10⁻⁶ -5 A metal film sample (which has been mirror-polished with alumina or colloidal silica suspension before observation, if necessary) is placed in an electron microscope sample chamber (chamber) where a vacuum of Pa or higher is achieved. An electron beam accelerated at 10, 15, or 20 kV is irradiated onto the top surface of the film, and secondary electron images or backscattered electron images at 500x, 15,000x, or 20,000x magnification are acquired. During observation, the electron probe is scanned two-dimensionally, and secondary electrons and backscattered electrons are detected and combined into a single image to observe the surface irregularities and compositional contrast of the sample.

[0026] Furthermore, backscatter electron diffraction (EBSD) was used for crystal analysis in metal films containing Group 5 elements. This method allows for the analysis of crystal orientation and grain size by projecting the diffraction pattern (Kikuchi line) of electrons emitted as backscattered electrons from the sample (metal film) onto the detector surface. The EBSD detector attached to the JSM-7100F was a Nordlys from Oxford Instruments Ltd. The analysis was performed using the company's HKL CHANNEL5 mapping software (Tango). The EBSD conditions were set as follows: 9.5 × 10⁻¹⁰ -5 A metal film sample (which has been mirror-polished with alumina or colloidal silica suspension before observation, if necessary) is placed in an electron microscope sample chamber (chamber) where a vacuum of Pa or higher has been achieved. The sample is tilted at 70°, and an electron beam accelerated at 10, 15, or 20 kV, focused on the tilted surface, is irradiated onto it. The diffraction pattern of the EBSD is captured as image data at 500x, 15,000x, or 20,000x magnification by a camera (detector) positioned at approximately 90° to the electron beam. After data processing, the crystal planes are indexed and their orientations are determined. In addition, grain (crystal particle) analysis can be performed by measuring and listing grain size (crystal particle size) and shape from the EBSD data. Therefore, it is possible to analyze changes in crystal orientation and average crystal particle diameter due to differences in processing conditions.

[0027] The metal film of the present invention contains a Group 5 element. The content of the Group 5 element is usually 30 atomic% or more, preferably 50 atomic% or more, more preferably 70 atomic% or more, even more preferably 90 atomic% or more, and particularly preferably 95 atomic% or more. On the other hand, the upper limit of the content of the Group 5 element in the metal film may be 100% (pure Group 5 element), but it is usually 99.9999 atomic% or less. By setting the content of the Group 5 element in the metal film within the above range, it becomes easier to improve hydrogen permeability. In particular, by setting the content of the Group 5 element to 50 atomic% or more and making the Group 5 element the main element in the metal film, it becomes easier to improve the hydrogen permeability characteristics. Furthermore, by setting the content of the Group 5 element within the above range, even when the hydrogen concentration in the raw material gas is 70% or less, and the hydrogen content in the raw material gas is small, it becomes easier to separate hydrogen well from this raw material gas.

[0028] In the present invention, the metal film contains a Group 5 element, and it is preferable to use at least one selected from the group consisting of vanadium, niobium, or tantalum as the Group 5 element, with vanadium being even more preferable. Group 5 elements, represented by vanadium, and especially the so-called vanadium group elements, have very similar chemical properties, and since vanadium has the property of permeating hydrogen, other Group 5 elements, especially the vanadium group elements, also have similar properties. Furthermore, in the present invention, a Group 5 element is used in the metal film, but as mentioned above, Group 5 elements have very similar chemical properties, so they may be used in combination. For example, vanadium may be used in combination with niobium or tantalum, or as an alloy thereof.

[0029] Furthermore, the metal film may contain elements other than Group 5 elements. Including such elements makes it easier to impart various properties to the metal film. Examples of such elements include iron (Fe), ruthenium (Ru), aluminum (Al), tungsten (W), molybdenum (Mo), chromium (Cr), and cobalt (Co). Using these alloying elements makes it easier to impart rigidity to the hydrogen separation film, suppressing the hydrogen solid solubility (also called hydrogen solubility) in the alloy even when the applied hydrogen pressure is increased, thus contributing to improved hydrogen embrittlement resistance. The content of elements other than Group 5 elements is usually 0.1 atomic% or more, preferably 1 atomic% or more for each element. This range makes it easier to impart the properties described above to the metal film. On the other hand, the content of elements other than Group 5 elements is usually 25 atomic% or less, preferably 11 atomic% or less for each element. This range makes it easier to impart the necessary properties without diminishing the advantages of using Group 5 elements.

[0030] The content of Group 5 elements and other elements in a metal film can be analyzed by the following method: By using a scanning electron microscope (SEM / EDS / WDS) or field emission scanning electron microscope (FE-SEM / EDS / WDS) equipped with EDS or WDS, and setting appropriate analytical conditions, the types and composition of the contained elements can be analyzed.

[0031] In this invention, the thickness of the metal film containing a Group 5 element is set to 0.05 mm or more. Generally, the thicker the metal film, the easier it is to increase its mechanical strength, making it less prone to breakage and allowing for good hydrogen permeation over a long period of time. On the other hand, increasing the thickness of the metal film tends to decrease the amount of hydrogen that can be permeated per unit time. For this reason, the thickness of the metal film needs to be controlled to an appropriate level. From this viewpoint, the thickness of the metal film is preferably 0.1 mm or more, more preferably 0.2 mm or more, even more preferably 0.3 mm or more, particularly preferably 0.5 mm or more, while normally 1 cm or less, preferably 5 mm or less, and more preferably 1 mm or less. A noteworthy finding in this invention is that when strain is applied to an untreated metal film containing a Group 5 element (e.g., vanadium) using the method described above, a good hydrogen permeability can be achieved despite the relatively high thickness. The thickness of the metal film containing a Group 5 element can be measured using known measuring devices such as a square, caliper, micrometer, or 3D shape measuring machine, depending on the thickness.

[0032] In this invention, the Vickers hardness of the metal film is set to 120 HV / kg / mm². 2 The above is preferable. The Vickers hardness is preferably 130 HV / kg / mm 2 More preferably 150 HV / kg / mm 2 This concludes the explanation. From the viewpoint of ensuring the mechanical strength of the metal film, a higher Vickers hardness is preferable. However, due to the material limitations of the metal film containing Group 5 elements (as mentioned above, the chemical properties of Group 5 elements, especially vanadium elements, are very similar), the Vickers hardness is generally 500 HV / kg / mm. 2 Below, usually 300HV / kg / mm 2 The following applies: Vickers hardness can be measured using a commercially available Vickers hardness tester (for example, a micro-Vickers hardness tester).

[0033] [Surface treatment of metal films] It is preferable to have palladium or a palladium-based alloy on one or both surfaces of the metal film. By having palladium or a palladium-based alloy on the surface, they function as a hydrogen dissociation catalyst, making it easier to efficiently permeate hydrogen into the metal film. Examples of palladium-based alloys include alloys of palladium with at least one element from silver, copper, and gold. By using an alloy of palladium with these elements, it becomes easier to lower the hydride formation temperature in the Pd-H binary system and to improve the durability of the metal film. When using a palladium alloy, the content of elements other than palladium is usually 1 mol% or more, preferably 5 mol% or more, more preferably 10 mol% or more, while the content of elements other than palladium is usually 50 mol% or less, preferably 40 mol% or less, more preferably 30 mol% or less, from the viewpoint of improving hydrogen permeation performance. In this specification, mol% is used synonymously with atomic%. The type and composition ratio of palladium or palladium alloy present on the metal film surface can be analyzed by the following method. In other words, by using a scanning electron microscope (SEM / EDS / WDS) or field emission scanning electron microscope (FE-SEM / EDS / WDS) equipped with EDS or WDS, and setting appropriate analytical conditions, the types and composition of contained elements can be analyzed.

[0034] There are no particular restrictions on the method of surface treatment of the metal film, but it is preferable to deposit palladium or a palladium-based alloy onto the surface of the metal film using a sputtering method (more specifically, an RF sputtering method). However, methods other than sputtering may be used to deposit palladium or a palladium-based alloy onto the surface of the metal film. For example, means of dispersing a catalyst in a coating solution and applying it, or means of uniformly forming a thin film by vacuum deposition can be employed. The palladium or palladium-based alloy may be formed in island-like formations on the surface of the metal film, may exist as particulate aggregates (in a form like a row of Go stones), or may exist as a film covering the entire surface.

[0035] [Raw material gas] The metal film of the present invention, when brought into contact with a raw material gas, allows hydrogen present in the raw material gas to selectively permeate the metal film, thereby enabling the extraction of hydrogen from the raw material gas. Here, the higher the hydrogen concentration in the raw material gas, the greater the amount of hydrogen that can be permeated and separated. However, even considering only by-product gases discharged from power plants, chemical plants, steel mills, etc., there are various types and compositions, and they are not always high in hydrogen concentration. The advantage of the metal film of the present invention is that it can effectively extract hydrogen from raw material gases with low hydrogen concentration (e.g., by-product gases). Specifically, the metal film of the present invention can be applied even if the hydrogen concentration in the raw material gas is 70% or less. Note that "hydrogen concentration" in the raw material gas refers to the amount of hydrogen contained in the composition of the raw material gas, and the hydrogen concentration can be determined by separating and quantifying each compound in the raw material gas using a gas analyzer such as a gas chromatograph (GC) analyzer.

[0036] Another feature of the present invention is that it allows for an increase in the pressure of the raw material gas. The hydrogen permeation using the metal film of the present invention is thought to occur through the following mechanism: the raw material gas is sealed at a constant pressure on the primary side (upstream side) with the metal film in between; hydrogen molecules in the raw material gas dissociate into two hydrogen atoms at the surface of the metal film; these hydrogen atoms permeate through the metal film to the secondary side (downstream side); and then recombine to form hydrogen molecules. Therefore, the higher the pressure of the raw material gas, the higher the probability that hydrogen molecules will adhere to the surface of the metal film on the primary side (upstream side), and as a result, the hydrogen permeability and hydrogen permeation rate can be increased.

[0037] However, until now, it was not possible to raise the pressure of the raw material gas above 30 kPa due to its relationship with mechanical strength. By applying a huge strain to the metal film containing Group 5 elements using the method described above, it has become possible to raise the pressure of the raw material gas above 30 kPa. The higher the pressure of the raw material gas, the greater the hydrogen permeability, so it is preferably 50 kPa or higher, more preferably 100 kPa or higher, and particularly preferably 150 kPa or higher. On the other hand, from the viewpoint of the mechanical properties of the metal film, it is usually kept below 500 kPa. In the above, the pressure of the raw material gas represents the partial pressure of pure hydrogen (in the case of pure hydrogen gas, it is 100%, and the pressure of the raw material gas is the same as the pressure of pure hydrogen gas), and the total pressure of the raw material gas should be less than 1 MPa.

[0038] [Hydrogen permeation device] The hydrogen permeation apparatus of the present invention uses the metal film described above. As stated above, the hydrogen permeation of the metal film containing a group 5 element in the present invention is thought to occur through the following mechanism: a raw material gas is sealed at a constant pressure on the primary side (upstream side) with the metal film described above in between; hydrogen molecules in the raw material gas dissociate into two hydrogen atoms on the surface of the metal film; these hydrogen atoms permeate through the metal film to the secondary side (downstream side); and then recombine to form hydrogen molecules. Therefore, the higher the pressure of the raw material gas, the higher the probability that hydrogen molecules will adhere to the metal film surface on the primary side (upstream side), and as a result, the hydrogen permeability and hydrogen permeation rate can be increased.

[0039] The hydrogen permeation apparatus of the present invention is not particularly limited as long as it has a structure that can realize the above mechanism. A specific example of such a hydrogen permeation apparatus is shown in Figure 1. Figure 1 is a schematic diagram including an enlarged portion of the hydrogen permeation apparatus for fixing a metal film containing a group 5 element of the present invention.

[0040] In the enlarged view at the top of Figure 1, "Sample" indicates a metal film containing the Group 5 element of the present invention. This metal film is fixed using a VCR Gasket (VCR surface seal joint) with a cap nut (primary side, upstream side) and a male nut (secondary side, downstream side). The raw material gas is brought into contact with the Sample (metal film) from the primary side, and a portion of it is returned to the system side. However, a system that recovers a portion of the raw material gas while bringing it into contact with the Sample is not essential. Another feature of the present invention is that by improving the metal film containing the Group 5 element, the primary side pressure can be increased to 30 kPa or more. At this pressure, the raw material gas is brought into contact with the metal film, allowing hydrogen to permeate through the metal film, and hydrogen is extracted to the secondary side. At that time, the metal film is heated in the Electric furnace shown in Figure 1 to ensure good hydrogen permeation. The leak test port is used to check whether the source gas or the permeated hydrogen is leaking outside the hydrogen permeator during hydrogen permeation. If a leak occurs, the contact between the VCR Gasket and the Sample (metal film) should be adjusted to eliminate the leak.

[0041] The lower part of Figure 1 shows an example of an overall diagram of the hydrogen permeation system. This system is constructed using valve fittings and various types of valves in a piping configuration. The inlet for the hydrogen-containing raw material gas is connected to the primary side (P1) of the VCR Gasket (VCR face seal fitting), and the hydrogen outlet is connected to the secondary side (P2). This allows for stable hydrogen permeation under controlled pressure by operating the valves in the piping system. Furthermore, a mass flow meter incorporated into the secondary side of the piping allows for on-site measurement of the permeation flow rate.

[0042] [Hydrogen production methods] The present invention relates to a hydrogen production method or hydrogen extraction method, which involves contacting a raw material gas containing hydrogen at a pressure of 30 kPa or higher with a metal film containing a Group 5 element of the present invention, and recovering the hydrogen that permeates through the metal film to extract hydrogen from the raw material gas. This production method can be realized using the hydrogen permeation apparatus described above.

[0043] The present invention will be described in more detail below using examples, but the present invention is not limited to the following examples. [Examples]

[0044] [Preparation of a metal film containing a Group 5 element (vanadium)] As the untreated metal film, pure V (99.9% purity) virgin material (hereinafter sometimes referred to as "virgin material" or "Virgin-V") was used. This virgin material was processed to a width of 10 mm, a length of 100 mm, and a thickness of 0.2 mm, 0.3 mm, 0.5 mm, and 0.7 mm. While constraining its periphery, HPS processing was performed at room temperature under the conditions of an applied pressure of 1.5 GPa, a processing speed of 1.0 mm / sec, and slide amounts x = 0 mm, 3 mm, 5 mm, 10 mm, and 15 mm. The vanadium-containing metal film samples obtained in this manner were designated as follows: "0.2mmHPS-V" for a thickness of 0.2mm, "0.3mmHPS-V" for a thickness of 0.3mm, "0.5mmHPS-V" for a thickness of 0.5mm, and "0.7mmHPS-V" for a thickness of 0.7mm. Samples for subsequent measurements were then cut from each of these vanadium-containing metal film samples. At that time, the surface of the samples was wet-polished or otherwise used as needed to obtain a smooth, mirror-like surface.

[0045] [Measurement of Vickers hardness] For 0.2mmHPS-V, 0.3mmHPS-V, 0.5mmHPS-V and 0.7mmHPS-V, in order to evaluate the Vickers hardness and the hardness uniformity in the width direction according to the slide amount, using a micro Vickers hardness tester, micro hardness measurements were performed on the surface of the HPS-V material at intervals of 1 mm in the width direction. The load during the hardness measurement was set to 0.5 kgf. As the micro Vickers hardness tester, a micro Vickers hardness tester (model number: HM-102) manufactured by Mitutoyo Corporation was used. The Vickers hardness test was performed by pressing a pyramidal diamond indenter against the sample, observing the resulting indentation with a microscope and measuring the length of the diagonal to obtain the hardness. The Vickers hardness test is excellent for measuring the hardness of thin samples because the indentation is as small as about 0. several millimeters even at the maximum. Also, the measurement was carried out after polishing the measurement surface of the measurement sample. A graph of the Vickers hardness measurement results is shown in Figure 2. In any of 0.2mmHPS-V, 0.3mmHPS-V, 0.5mmHPS-V and 0.7mmHPS-V, although there are differences, an improvement in the Vickers hardness (120 HV / kg / mm 2 degree) compared to the virgin material was observed.

[0046] [Measurement of average crystal grain size] The surface of HPS-V was observed using FE-SEM and the attached EBSD, and the average crystal grain size was measured and the crystal orientation was analyzed from the crystal structure at each slide amount. The measurement of the average crystal grain size and the analysis of the crystal orientation were carried out by observing the surface of the metal film in combination with a field emission scanning electron microscope and backscattered electron diffraction. The conditions are as described above.

[0047] The measurement results are shown in Figures 3-6. For 0.2mm HPS-V, the average crystal grain size was 359nm at a slide length of 0mm, 241nm at a slide length of 3mm, 238nm at a slide length of 5mm, and 206nm at a slide length of 10mm. For 0.3mm HPS-V, the average crystal grain size was 128nm at a slide length of 0mm, 180nm at a slide length of 3mm, 181nm at a slide length of 5mm, and 182nm at a slide length of 10mm. For 0.5mm HPS-V, the average crystal grain size was 240nm at a slide length of 0mm, 201nm at a slide length of 3mm, 237nm at a slide length of 5mm, 239nm at a slide length of 10mm, and 245nm at a slide length of 15mm. For 0.7mm HPS-V, the average crystal grain size was 4.77 μm with a slide length of 0 mm, 497 nm with a slide length of 3 mm, 496 nm with a slide length of 5 mm, 443 nm with a slide length of 10 mm, and 483 nm with a slide length of 15 mm.

[0048] [Hydrogen permeation test] Both sides of each 0.5mm HPS-V and 0.7mm HPS-V sample were made mirror-finished using the method described above, and then cut from the plate-shaped sample into a 12mm diameter disc shape. RF sputtering was performed using an RF sputtering apparatus at a substrate temperature of 300°C for 6 minutes, and both sides of the film were coated with Pd-25mol%Ag to impart hydrogen dissociation catalytic properties. The reason for coating with Pd-25mol%Ag instead of pure Pd is to lower the hydride formation temperature in the Pd-H binary system by adding Ag, thereby improving the durability of the film. In addition, 25mol% Ag was added to improve hydrogen permeation performance. Then, using the hydrogen permeation apparatus shown in Figure 1, the entire apparatus was evacuated, and the primary side hydrogen pressure was set to a pressure greater than or equal to the secondary side hydrogen pressure. Permeation tests were performed by changing the primary side pressure as appropriate.

[0049] The procedure for the hydrogen permeation test is as follows: The membrane sample is installed inside the VCR surface seal fitting, 2 × 10 -1Vacuum was applied to Pa. Then, the film sample fixing section of the VCR surface seal joint was heated to 300°C in a tubular electric furnace. The pressure was increased to the point where the primary side hydrogen solid solution concentration was 0.1 H / M (5 kPa), and this state was maintained until hydrogen permeation occurred. After confirming that hydrogen had permeated, the pressure was maintained until the hydrogen permeation rate stabilized, and the hydrogen permeation coefficient was calculated by measuring the volume flow rate [sccm] in the secondary side piping using a mass flow meter installed in the pipeline. Subsequently, the primary side pressure was increased to 0.2 H / M (7 kPa), 0.3 H / M (9 kPa), 0.4 H / M (16 kPa), etc., but was varied so that the maximum pressure was 0.57 H / M (150 kPa). The volume flow rate of hydrogen at each pressure was measured, and the hydrogen permeation coefficient was calculated. The measurement results are shown in Figures 7 and 8. Here, "virgin material" refers to an untreated (HPS-processed) vanadium film coated with Pd-25 mol% Ag.

[0050] Figure 7 shows an example of the results of the hydrogen permeation test. For each film sample of virgin material, 0.5 mm HPS-V (slide amounts of 3 mm and 5 mm), and 0.7 mm HPS-V (slide amounts of 3 mm and 5 mm), the primary side raw material gas (in this case, pure hydrogen) pressure is shown on the horizontal axis, and the hydrogen permeation coefficient obtained at that time is shown on the vertical axis. Compared to the virgin material, all metal films that underwent HPS processing showed a high hydrogen permeation coefficient in all pressure ranges tested, showing a 2 to 3 times improvement in hydrogen permeation coefficient with HPS and processing. Figure 8 shows a comparison of the actual hydrogen permeation amounts. In this figure, the values ​​in parentheses to the right of each condition for the HPS-V material mean, for example, "t=0.7×0" means 0.7 mm HPS-V, slide amount of 0 mm, and "(t=0.400 mm)" means that the thickness of the film sample after polishing, as measured with a micrometer, was 0.4 mm. The notation method for other numerical values ​​in the figure is the same. The thickness of the 0.5mm HPS-V processed material after polishing was 0.318mm for the sample with a slide amount of 5mm and 0.333mm for the sample with a slide amount of 0mm. The thickness of the 0.7mm HPS-V processed material after polishing was 0.400mm for the sample with a slide amount of 0mm, 0.448mm for the sample with a slide amount of 3mm, and 0.514mm for the sample with a slide amount of 5mm. Although the film thickness of each sample was reduced by polishing, all metal films treated with HPS processing showed high hydrogen permeability (hydrogen permeation flow rate (cc) per minute at standard conditions (20℃, 1atm)) in all the pressure ranges tested. Compared to virgin material, HPS-V processing resulted in a 2-3 times increase in hydrogen permeation flow rate, demonstrating the effect of controlling the metal structure by applying strain during hydrogen permeation. Furthermore, Figures 7 and 8 show that the materials did not rupture even when the pressure of the raw material gas was changed from 30 to 150kPa, and high hydrogen permeability was maintained.

[0051] [Differentiation] Although preferred embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the embodiments described above. Various modifications or improvements can be made to each of the above embodiments.

Claims

1. A metal film that allows hydrogen to permeate by contacting a hydrogen-containing source gas at a temperature of 300°C under a pressure of 30 kPa or more, The metal film contains a Group 5 element, The average crystal particle size measured by observing the surface of the metal film using a combination of field emission scanning electron microscopy and backscattered electron diffraction is 1 mm or less. Furthermore, the thickness of the metal film is 0.05 mm or more. The Vickers hardness of the aforementioned metal film is 120 HV / kg / mm ２ That's all. A metal film characterized by the following features.

2. The metal film according to claim 1, wherein the content of the Group 5 element in the metal film is 50 atomic percent or more.

3. The metal film according to claim 1 or 2, wherein the Group 5 element is at least one selected from the group consisting of vanadium, niobium, or tantalum.

4. The metal film according to any one of claims 1 to 3, wherein the hydrogen concentration in the raw material gas is 70% or less.

5. A hydrogen permeation apparatus characterized by using a metal film according to any one of claims 1 to 4.

6. A method for producing hydrogen, characterized by bringing a raw material gas containing hydrogen at a pressure of 30 kPa or higher into contact with a metal film described in any of claims 1 to 4, and recovering the hydrogen that permeates the metal film to extract hydrogen from the raw material gas.

7. A method for manufacturing a metal film containing a Group 5 element, The process involves applying pressure to the metal film from both sides while it is restrained, and also includes a strain processing step that introduces shear strain. The aforementioned distortion process, Average crystal grain diameter is 1 mm or less. Thickness of 0.05 mm or more, The Vickers hardness of the aforementioned metal film is 120 HV / kg / mm ２ The present invention relates to a method for producing a metal film, characterized by obtaining a metal film that allows hydrogen to permeate by contacting a hydrogen-containing raw material gas with a pressure of 30 kPa or more under a temperature of 300°C.

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