Hydrogen permeation structure and manufacturing method of the same

Abstract

To provide a hydrogen permeation structure and a manufacturing method of the same which suppresses deterioration of strength.SOLUTION: A hydrogen permeation structure 10 comprises: a hydrogen permeable membrane 20 which dissociates hydrogen; a metal oxide membrane 30 which is connected with the hydrogen permeable membrane 20 in a membrane thickness direction DT and through which the dissociated hydrogen passes; and a base material 40 in which the metal oxide membrane 30 is sandwiched between the hydrogen permeable membrane 20 and the base material. The metal oxide membrane 30 is formed through ALD from metal oxide of amorphous. A through hole 45 is formed in the base material 40 and extends in the membrane thickness direction DT in which the hydrogen passed through the metal oxide membrane 30 is recoupled and the recoupled hydrogen passes through the through hole. The through hole 45 is formed by use of etching.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a hydrogen-permeable structure and a method for manufacturing the hydrogen-permeable structure. [Background technology]

[0002] As described in Patent Document 1, a metal composite hydrogen-permeable membrane has been known, which includes a hydrogen-permeable metal membrane, a porous Ni-plated film, and a diffusion barrier layer. The porous Ni-plated film is formed by electrolytic plating using a plating bath containing a surfactant, and then burning off the surfactant in the Ni-plated film. The diffusion barrier layer is provided at the interface between the hydrogen-permeable metal membrane and the porous Ni-plated film. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-39083 Summary of the Invention [Problem to be solved by the invention]

[0004] In the metal composite hydrogen-permeable membrane described in Patent Document 1, a porous Ni plating film is formed by plating as a substrate supporting the hydrogen-permeable metal membrane. Because it is difficult to form a film with a relatively large thickness by plating, the thickness of the porous Ni plating film is relatively small. As a result, the strength of the metal composite hydrogen-permeable membrane is relatively low.

[0005] An object of the present disclosure is to provide a hydrogen-permeable structure that suppresses a decrease in strength and a method for manufacturing the hydrogen-permeable structure. [Means for solving the problem]

[0006] The invention described in claim 1 is a hydrogen-permeable structure comprising a hydrogen-permeable membrane (20) that dissociates hydrogen, a metal oxide membrane (30) that is connected to the hydrogen-permeable membrane in the thickness direction (DT) of the hydrogen-permeable membrane and through which the dissociated hydrogen passes, and a substrate (40) that sandwiches the metal oxide membrane with the hydrogen-permeable membrane, wherein the metal oxide membrane contains amorphous metal oxide, and the substrate has through-holes (45) that extend in the thickness direction of the membrane, and wherein hydrogen that has passed through the metal oxide membrane recombines and the recombined hydrogen passes through the through-holes.

[0007] The invention described in claim 6 is a method for manufacturing a hydrogen-permeable structure, which comprises forming a hydrogen-permeable membrane (20) that dissociates hydrogen, a metal oxide membrane (30) that is connected to the hydrogen-permeable membrane in the thickness direction (DT) of the hydrogen-permeable membrane and through which the dissociated hydrogen passes, and a substrate (40) that sandwiches the metal oxide membrane between the hydrogen-permeable membrane and the metal oxide membrane; forming the metal oxide membrane from amorphous metal oxide using ALD; forming through-holes (45) in the substrate that extend in the thickness direction and through which hydrogen that has passed through the metal oxide membrane recombines and the recombined hydrogen passes; and forming the through-holes using etching.

[0008] Because the metal oxide film contains amorphous metal oxide, the metal oxide film has relatively few grain boundaries and cracks. This metal oxide film prevents the etching solution and etching gas from coming into contact with the hydrogen-permeable film when through-holes in the substrate are formed by etching rather than plating. Furthermore, etching allows the formation of through-holes regardless of the thickness of the substrate. Therefore, the substrate can be sufficiently thick, preventing a decrease in the strength of the hydrogen-permeable structure.

[0009] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and the specific components described in the embodiments described below. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a cross-sectional view of an embodiment of a hydrogen-permeable structure. [Figure 2] 4 is a flowchart showing a method for manufacturing a hydrogen-permeable structure. [Figure 3] 1 is a diagram showing the relationship between the metal oxide film, the thickness of the metal oxide film, and the ratio of the hydrogen permeability coefficient in Examples 1-3 and Comparative Examples 1-2. [Figure 4] 1 is a graph summarizing the relationship between the film thickness of the metal oxide film and the ratio of the hydrogen permeability coefficient in Examples 1-2 and Comparative Example 1. [Figure 5] 10 is a graph summarizing the relationship between the thickness of the metal oxide film and the ratio of the hydrogen permeability coefficient in Example 3 and Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments will be described with reference to the drawings. In the following embodiments, identical or equivalent parts will be denoted by the same reference numerals, and description thereof will be omitted.

[0012] The hydrogen-permeable structure and its manufacturing method of this embodiment prevent a decrease in the strength of the hydrogen-permeable structure. Specifically, as shown in Figure 1, a hydrogen-permeable structure 10 includes a hydrogen-permeable membrane 20, a metal oxide membrane 30, and a substrate 40.

[0013] The hydrogen-permeable membrane 20 is made of Pd or a Pd alloy. Due to the properties of Pd, the hydrogen-permeable membrane 20 dissociates hydrogen when it comes into contact with hydrogen contained in a gas mixture. Therefore, the hydrogen-permeable membrane 20 selectively separates only hydrogen from the gas mixture. The thickness of the hydrogen-permeable membrane 20 is set to 20 nm or more and 100 nm or less. Pd is palladium. Furthermore, hereinafter, the thickness direction of the hydrogen-permeable membrane 20 will be simply referred to as the thickness direction DT.

[0014] The metal oxide film 30 is connected to the hydrogen-permeable film 20 in the thickness direction DT. Dissociated hydrogen passes through the metal oxide film 30. The metal oxide film 30 also contains amorphous metal oxide. Examples of metal oxide include Al2O3 and TiO2. The thickness of the metal oxide film 30 is 10 nm or more and 160 nm or less. Al2O3 is aluminum oxide. TiO2 is titanium oxide. Amorphous refers to a substance that does not have a crystalline structure and is also called non-crystalline. Whether the microstructure of the film is amorphous can be detected using, for example, a TEM. TEM stands for Transmission Electron Microscope.

[0015] The substrate 40 is connected to the metal oxide film 30 on the side opposite to the hydrogen-permeable film 20 in the film thickness direction DT. Thus, the metal oxide film 30 is sandwiched between the substrate 40 and the hydrogen-permeable film 20. The substrate 40 is formed into a plate shape from metal, resin, ceramics, or the like. For example, the substrate 40 is formed from stainless steel. The substrate 40 also has through-holes 45.

[0016] The through holes 45 extend in the film thickness direction DT. Furthermore, a plurality of the through holes 45 are arranged at intervals in a direction perpendicular to the film thickness direction DT. Therefore, the substrate 40 is porous. Furthermore, the through holes 45 penetrate the surface of the substrate 40 that is connected to the metal oxide film 30 and the surface opposite to that surface. Furthermore, hydrogen that has passed through the metal oxide film 30 recombines, and the recombined hydrogen passes through the through holes 45. Therefore, the hydrogen-permeable structure 10 selectively allows hydrogen to permeate.

[0017] The hydrogen-permeable structure 10 of this embodiment is configured as described above. This hydrogen-permeable structure 10 is used, for example, for hydrogen separation in a hydrogen engine. Next, a method for manufacturing the hydrogen-permeable structure 10 will be described with reference to the flowchart in FIG.

[0018] In step S100, a plate-shaped substrate 40 is prepared. Subsequently, in step S102, an amorphous metal oxide film 30 is formed on the substrate 40 prepared in step S100 by ALD. Note that ALD is an abbreviation for atomic layer deposition.

[0019] For example, if the metal oxide film 30 is Al2O3, TMA and H2O, which are the raw materials for Al2O3, are alternately introduced and exhausted at a predetermined temperature, and this introduction and exhaust is repeated. Then, atomic layers are deposited one by one. At this time, by setting the formation temperature to 500°C or less, the Al2O3 does not have a crystalline structure, i.e., it is made amorphous. TMA is trimethylaluminum.

[0020] For example, when the metal oxide film 30 is made of TiO2, TiCl4 and H2O, which are the raw materials for TiO2, are alternately introduced and exhausted at a predetermined temperature, and this introduction and exhaust is repeated. Then, atomic layers are deposited one by one. At this time, by setting the formation temperature to 400°C or less, the TiO2 does not have a crystalline structure, i.e., it is made amorphous. TiCl4 is titanium chloride.

[0021] Next, in step S104, a Pd-containing hydrogen-permeable film 20 is formed on the metal oxide film 30 formed in step S102 using PVD or CVD. Note that PVD stands for Physical Vapor Deposition, and CVD stands for Chemical Vapor Deposition.

[0022] Next, in step S106, through-holes 45 are formed in the substrate 40 by etching. Specifically, a portion of the surface of the substrate 40 opposite the metal oxide film 30 is masked. If the material of the substrate 40 is a material suitable for wet etching, for example, a metal, an etching solution is applied to the surface of the substrate 40 opposite the metal oxide film 30, thereby removing the unmasked portion of the substrate 40 from the surface of the substrate 40. This forms the through-holes 45 in the substrate 40. Alternatively, if the material of the substrate 40 is a material suitable for dry etching, for example, a resin, an etching gas or the like is brought into contact with the surface of the substrate 40 opposite the metal oxide film 30, thereby removing the unmasked portion of the substrate 40 from the surface of the substrate 40. This forms the through-holes 45 in the substrate 40. Then, once the formation of the through-holes 45 by etching is completed, the hydrogen-permeable structure 10 is completed.

[0023] As described above, the hydrogen-permeable structure 10 is manufactured. Next, examples of the hydrogen-permeable structure 10 having the above configuration will be described in comparison with comparative examples.

[0024] First, a stainless steel plate having a thickness of approximately 100 μm is prepared as the substrate 40. The hydrogen-permeable structure 10 is formed from the substrate 40 made of this stainless steel using the manufacturing method described above. At this time, the thickness of the hydrogen-permeable membrane 20 is set to 20 nm. Furthermore, countless through-holes 45 are formed.

[0025] FIG. 3 shows the ratio of the hydrogen permeability coefficient to that of a comparative example, calculated from the measurement results of the hydrogen permeability coefficient when the material and film thickness of the metal oxide film 30 are changed to form the hydrogen-permeable structure 10. The hydrogen permeability coefficient was evaluated using a measurement method based on JIS K 7126-1 of the JIS standard. Specifically, using a device capable of controlling the pressure in the spaces above and below the sample to be evaluated, hydrogen gas is introduced into the upper space while controlling the space pressure, creating a reduced pressure state near vacuum in the lower space, and the amount of hydrogen permeated from the upper space to the lower space is measured. Under these conditions, the hydrogen permeability coefficient is calculated by multiplying the amount of hydrogen permeated by the thickness of the hydrogen-permeable structure 10.

[0026] 3, the hydrogen permeability coefficient was measured and the ratio of the hydrogen permeability coefficient was calculated for Comparative Example 1, in which the metal oxide film 30 was formed of amorphous Al2O3 with a film thickness of 320 nm. Here, Comparative Example 1 is used as a comparison standard for cases in which the metal oxide film 30 is formed of amorphous Al2O3, and therefore the ratio of the hydrogen permeability coefficient of Comparative Example 1 is 1.00.

[0027] Furthermore, for Comparative Example 2, the hydrogen permeability coefficient was measured and the ratio of the hydrogen permeability coefficient was calculated for a case in which the metal oxide film 30 was formed of amorphous TiO2 with a film thickness of 320 nm. Here, Comparative Example 2 is used as a comparison standard for cases in which the metal oxide film 30 is formed of amorphous TiO2, and therefore the ratio of the hydrogen permeability coefficient of Comparative Example 2 is 1.00.

[0028] In addition, the hydrogen permeability coefficient was measured and the ratio of the hydrogen permeability coefficient was calculated for Example 1, where the metal oxide film 30 was formed of amorphous Al2O3 with a film thickness of 160 nm. As a result, the ratio of the hydrogen permeability coefficient of Example 1 to that of Comparative Example 1 was 9.50.

[0029] Furthermore, in Example 2, the hydrogen permeability coefficient was measured and the ratio of the hydrogen permeability coefficient was calculated for a metal oxide film 30 formed of amorphous Al2O3 with a film thickness of 600 nm. As a result, the ratio of the hydrogen permeability coefficient of Example 2 to that of Comparative Example 1 was 0.89.

[0030] In Example 3, the hydrogen permeability coefficient was measured and the ratio of the hydrogen permeability coefficient was calculated for a metal oxide film 30 formed of amorphous TiO2 with a film thickness of 160 nm. As a result, the ratio of the hydrogen permeability coefficient of Example 3 to that of Comparative Example 2 was 3.00.

[0031] Here, the hydrogen permeability coefficient is a coefficient that indicates how much hydrogen permeates. Therefore, a higher ratio of the hydrogen permeability coefficient indicates a higher hydrogen permeability coefficient and a higher hydrogen permeability.

[0032] 4, when comparing Example 1 with Comparative Example 1, both of which have amorphous Al2O3 metal oxide films 30, the ratio of the hydrogen permeability coefficient of Example 1 to that of Comparative Example 1 is greater than 1.00. Therefore, the hydrogen-permeable structure 10 of Example 1 exhibited high hydrogen permeability.

[0033] 5, when comparing Comparative Example 2 and Example 3, both of which had amorphous TiO2 metal oxide films 30, the ratio of the hydrogen permeability coefficient of Example 3 to that of Comparative Example 2 was greater than 1.00. Thus, the hydrogen-permeable structure 10 of Example 3 exhibited high hydrogen permeability.

[0034] As described above, it can be said that it is preferable to set the thickness of the metal oxide film 30 to 160 nm or less, regardless of the material of the metal oxide film 30. Next, the suppression of strength reduction by the hydrogen-permeable structure 10 of this embodiment will be described.

[0035] In the metal composite hydrogen-permeable membrane described in Patent Document 1, a porous Ni plating film is formed by plating as a substrate supporting the hydrogen-permeable metal membrane. Because it is difficult to form a film with a relatively large thickness by plating, the thickness of the porous Ni plating film is relatively small. As a result, the strength of the metal composite hydrogen-permeable membrane is relatively low.

[0036] In contrast, the hydrogen-permeable structure 10 of this embodiment includes a hydrogen-permeable membrane 20, a metal oxide membrane 30, and a substrate 40 having through-holes 45. The metal oxide membrane 30 is sandwiched between the hydrogen-permeable membrane 20 and the substrate 40, and contains amorphous metal oxide. The metal oxide membrane 30 preferably contains amorphous Al2O3. Alternatively, the metal oxide membrane 30 preferably contains amorphous TiO2.

[0037] Because the metal oxide film 30 contains amorphous metal oxide, the metal oxide film 30 has relatively few grain boundaries and cracks. This metal oxide film 30 prevents the etching solution or etching gas from coming into contact with the hydrogen-permeable membrane 20 when the through-holes 45 in the substrate 40 are formed by etching rather than plating. Furthermore, when etching is used, the through-holes 45 can be formed regardless of the thickness of the substrate 40. Therefore, a sufficient thickness of the substrate 40 can be ensured, and a decrease in the strength of the hydrogen-permeable structure 10 is prevented.

[0038] The hydrogen-permeable structure 10 of this embodiment also provides the following effects.

[0039] [1] The metal oxide film 30 is formed using ALD. By using ALD, the metal oxide film 30 is more likely to be pinhole-free than when it is formed by a method other than ALD, such as PVD or CVD. If the metal oxide film 30 is pinhole-free, contact of the etching solution or etching gas with the hydrogen-permeable membrane 20 is suppressed. Therefore, through-holes 45 can be easily formed using etching, regardless of the thickness of the substrate 40. Therefore, a sufficient thickness of the substrate 40 can be ensured, and a decrease in the strength of the hydrogen-permeable structure 10 is suppressed.

[0040] [2] When the thickness of the metal oxide film 30 is less than 10 nm, the metal oxide film 30 is relatively thin, so gases other than hydrogen that flow from the hydrogen-permeable membrane 20 side and pass through the hydrogen-permeable membrane 20 easily pass through the metal oxide film 30. This reduces the ability of the hydrogen-permeable structure 10 to selectively allow hydrogen to pass through. Furthermore, when the thickness of the metal oxide film 30 is greater than 160 nm, the metal oxide film 30 is relatively thick, so it becomes difficult for hydrogen dissociated by the hydrogen-permeable membrane 20 to move, reducing the hydrogen permeability of the hydrogen-permeable structure 10.

[0041] In contrast, in the hydrogen-permeable structure 10 of this embodiment, the thickness of the metal oxide film 30 is preferably 10 nm or more and 160 nm or less.

[0042] This prevents the thickness of the metal oxide film 30 from being too small, thereby preventing a decrease in the hydrogen-permeable structure 10's ability to selectively allow hydrogen to pass through. Furthermore, because the thickness of the metal oxide film 30 is not too large, the hydrogen dissociated by the hydrogen-permeable film 20 can move more easily. This prevents a decrease in the hydrogen permeability of the hydrogen-permeable structure 10.

[0043] [3] Furthermore, when the thickness of the hydrogen-permeable membrane 20 is less than 20 nm, the hydrogen-permeable membrane 20 is relatively thin, making it difficult for hydrogen to dissociate. Therefore, the ability of the hydrogen-permeable structure 10 to selectively allow hydrogen to pass through is likely to be impaired. Furthermore, the material of the hydrogen-permeable membrane 20 is Pd, etc., which is relatively expensive. Therefore, when the thickness of the hydrogen-permeable membrane 20 is greater than 100 nm, the cost of the hydrogen-permeable membrane 20 increases, and therefore the cost of the hydrogen-permeable structure 10 increases.

[0044] In contrast, in the hydrogen-permeable structure 10 of this embodiment, the thickness of the hydrogen-permeable membrane 20 is preferably 20 nm or more and 100 nm or less.

[0045] This prevents the thickness of the hydrogen-permeable membrane 20 from being too small, thereby preventing a decrease in the function of the hydrogen-permeable structure 10 to selectively allow hydrogen to pass through. Furthermore, because the thickness of the hydrogen-permeable membrane 20 is not too large, an increase in the cost of the hydrogen-permeable membrane 20 is prevented, thereby preventing an increase in the cost of the hydrogen-permeable structure 10.

[0046] (Other embodiments) The present disclosure is not limited to the above-described embodiments, and appropriate modifications can be made to the above-described embodiments. Furthermore, it goes without saying that the elements constituting the embodiments in the above-described embodiments are not necessarily essential unless they are specifically stated as essential or are considered to be clearly essential in principle.

[0047] In the above embodiment, the hydrogen-permeable membrane 20 is made of Pd or a Pd alloy. However, the hydrogen-permeable membrane 20 is not limited to being made of Pd or a Pd alloy. The hydrogen-permeable membrane 20 may be made of, for example, V, Nb, Ta, or a V-Ti-Ni alloy, an Nb-Ti-Ni alloy, an Nb-Ti-Co alloy, or a Ta-Ti-Ni alloy, which are capable of selectively separating only hydrogen from a gas mixture. Note that V is vanadium, Ti is titanium, Ni is nickel, Nb is niobium, Co is cobalt, and Ta is tantalum.

[0048] In the above embodiment, the substrate 40 is masked when etching is performed in step S106. However, instead of masking the substrate 40, recesses and projections may be formed on the surface of the substrate 40 opposite the metal oxide film 30, and portions of the substrate 40 may be removed from the recesses using an etching solution or etching gas, thereby forming the through-holes 45 in the substrate 40.

[0049] In the above embodiment, the through-holes 45 are formed by etching in step S106. On the other hand, when the metal oxide film 30 is made of Al2O3 and the base material 40 is made of aluminum, the through-holes 45 may be formed by anodizing, which is an anodic oxidation process for aluminum. [Explanation of symbols]

[0050] 10 Hydrogen permeable structure 20 Hydrogen permeable membrane 30 Metal oxide film 40 Base material 45 through holes

Claims

1. A hydrogen-permeable structure, a hydrogen-permeable membrane (20) that dissociates hydrogen; a metal oxide film (30) connected to the hydrogen permeable membrane in a thickness direction (DT) of the hydrogen permeable membrane and through which dissociated hydrogen passes; a substrate (40) sandwiching the metal oxide film between the hydrogen-permeable film; Equipped with the metal oxide film includes an amorphous metal oxide; The substrate has a through hole (45) extending in the film thickness direction, The hydrogen permeable structure is one in which hydrogen that has passed through the metal oxide film recombines and the recombined hydrogen passes through the through-holes.

2. The metal oxide film is amorphous Al ２ O ３ The hydrogen-permeable structure according to claim 1, comprising:

3. The metal oxide film is amorphous TiO ２ The hydrogen-permeable structure according to claim 1, comprising:

4. 2. The hydrogen-permeable structure according to claim 1, wherein the metal oxide film has a thickness of 10 nm or more and 160 nm or less.

5. 5. The hydrogen-permeable structure according to claim 1, wherein the hydrogen-permeable film has a thickness of 20 nm or more and 100 nm or less.

6. A method for manufacturing a hydrogen-permeable structure, comprising: a hydrogen-permeable membrane (20) that dissociates hydrogen; a metal oxide film (30) connected to the hydrogen permeable membrane in a thickness direction (DT) of the hydrogen permeable membrane and through which dissociated hydrogen passes; a substrate (40) sandwiching the metal oxide film between the hydrogen-permeable film; Forming The metal oxide film is formed of amorphous metal oxide using ALD; forming through-holes (45) in the substrate, the through-holes extending in the film thickness direction, through which hydrogen that has passed through the metal oxide film recombines and through which the recombined hydrogen passes; The method for manufacturing a hydrogen-permeable structure includes forming the through-holes by etching.

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