Alloy, hydrogen extraction system, hydrogen storage material, and method for producing alloy

Abstract

To provide an alloy that can occlude hydrogen from the atmosphere at ordinary temperature and ordinary pressure.SOLUTION: The alloy (10) has a composition of AlxFe1-x(x=0.7 to 0.9), AlxCo1-x(x=0.7 to 0.9) or AlxMn1-x(x=0.7 to 0.9). The alloy (10) contains an amorphous structure, has a plurality of first regions (13) in which the density of the alloy (10) is smaller as compared with the other regions, and, in the cross section obtained when the alloy (10) is cut in a plane perpendicular to the surface of the alloy (10), has a distance between the neighboring first regions of 30 nm or less.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an alloy that can be used for hydrogen storage. [Background technology]

[0002] Hydrogen has been attracting attention as a fuel that does not emit carbon dioxide. However, hydrogen has a low energy density per volume, so a hydrogen storage material is required to increase the density of hydrogen when transporting or carrying it. For example, Patent Document 1 discloses a hydrogen storage material made of Al-Fe or Al-Mn. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-199640 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the hydrogen storage material disclosed in Patent Document 1 requires ultra-high pressure hydrogen of 70,000 atmospheres or more in order to store hydrogen, which results in high costs for storing hydrogen.

[0005] An object of one embodiment of the present invention is to provide an alloy capable of absorbing hydrogen from the air at room temperature and pressure. [Means for solving the problem]

[0006] In order to solve the above problems, an alloy according to one embodiment of the present invention comprises Al x Fe 1-x (x=0.7~0.9), Al x Co 1-x (x=0.7~0.9) or Al x Mn 1-xAn alloy having a composition of (x=0.7 to 0.9), the alloy having an amorphous structure and a plurality of first regions in which the density of the alloy is lower than that of other regions, and in a cross section of the alloy cut along a plane perpendicular to a surface of the alloy, the distance between adjacent first regions is 30 nm or less. Effect of the Invention

[0007] According to one aspect of the present invention, an alloy capable of absorbing hydrogen from the atmosphere at room temperature and pressure can be realized. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing the structure of an alloy according to one embodiment of the present invention. [Diagram 2] 1 is a SEM photograph of the surface of the alloy opposite to the substrate. [Diagram 3] This is a HAADF image of the above alloy by scanning TEM. [Figure 4] 1 is a block diagram showing a configuration of a hydrogen extraction system in one embodiment of the present invention. FIG. [Diagram 5] 1 is a cross-sectional TEM image of an alloy according to Example 1 of the present invention. [Figure 6] 1 is a cross-sectional TEM image of an alloy as Comparative Example 1 of the present invention. [Figure 7] 1 is a SEM photograph of the alloy of Comparative Example 1, showing the surface opposite to the substrate side. [Figure 8] 1 is an electron beam diffraction image of the alloy of Example 1 obtained using a TEM. [Figure 9] 1 is an electron beam diffraction image of Comparative Example 1 obtained using a TEM. [Figure 10] 1 is a graph showing the results of measuring the hydrogen distribution present inside the alloys of Example 1 and Comparative Example 1 after exposing the alloys to the atmosphere at room temperature and pressure. [Figure 11] 1 is a graph showing the amount of hydrogen released from an alloy of a modification of Example 1 that has absorbed hydrogen. [Figure 12] 1 is a cross-sectional TEM image of an alloy of Reference Example 1 of the present invention. [Figure 13] 1 is a graph showing the results of measuring the hydrogen distribution present inside the alloy of Reference Example 1 after exposing the alloy to the air at room temperature and pressure. [Figure 14] 1 is a HAADF image of the alloy of Reference Example 2 obtained by a scanning TEM method. [Figure 15] 15 is a graph created by calculating the contrast intensity on lines L1 and L2 shown in FIG. 14. [Figure 16] 1 is a cross-sectional TEM image of the alloy of Example 2 of the present invention. [Figure 17] 1 is an electron beam diffraction image of the alloy of Example 2 obtained using a TEM. [Figure 18] 11 is a graph showing the amount of hydrogen released from an alloy of a modified example of Example 2 that has absorbed hydrogen. [Figure 19] 1 is a cross-sectional TEM image of the alloy of Example 3 of the present invention. [Figure 20] 1 is a cross-sectional TEM image of an alloy of Comparative Example 2 of the present invention. [Figure 21] 1 is a SEM photograph of the alloy of Example 3, showing the surface opposite to the substrate side. [Figure 22] 1 is an SEM photograph of the alloy of Comparative Example 2, showing the surface opposite to the substrate side. [Diagram 23] 1 is an electron beam diffraction image of the alloy of Example 3 obtained using a TEM. [Figure 24] 1 is an electron beam diffraction image of Comparative Example 2 obtained using a TEM. [Diagram 25] 1 is a graph showing the results of measuring the hydrogen distribution present inside the alloys of Example 3 and Comparative Example 2 after exposing the alloys to the atmosphere at room temperature and pressure. [Figure 26] 13 is a graph showing the amount of hydrogen released from an alloy of a modified example of Example 3 that has absorbed hydrogen. [Figure 27] 1 is a cross-sectional TEM image of an alloy of Comparative Example 3 of the present invention. [Figure 28] 1 is an electron beam diffraction image of an alloy as Comparative Example 3 of the present invention, obtained using a TEM. [Figure 29] 1 is a graph showing the results of measuring the hydrogen distribution present inside the alloy of Comparative Example 3 after exposing the alloy to the atmosphere at room temperature and pressure. [Diagram 30] 13 is a graph showing the amount of hydrogen released from an alloy of a modified example of Comparative Example 3 that has absorbed hydrogen. [Diagram 31] 1 is a cross-sectional TEM image of the alloy of Example 4 of the present invention. [Diagram 32] 1 is an electron beam diffraction image of the alloy of Example 4 obtained using a TEM. [Diagram 33] 1 is a graph showing the results of measuring the hydrogen distribution present inside the alloy of Example 4 after exposing the alloy to the air at room temperature and pressure. [Diagram 34] 1 is a cross-sectional TEM image of the alloy of Example 5 of the present invention. [Diagram 35] 1 is an electron beam diffraction image of the alloy of Example 5 obtained using a TEM. [Diagram 36] 1 is a graph showing the results of measuring the hydrogen distribution present inside the alloy of Example 5 after exposing the alloy to the air at room temperature and pressure. [Figure 37] 13 is a graph showing the amount of hydrogen released from an alloy of a modified example of Example 5 that has absorbed hydrogen. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Embodiment 1] Hereinafter, one embodiment of the present invention will be described in detail.

[0010] [Hydrogen storage material] As a result of intensive research, the present inventors have found that Al x Fe 1-x (x=0.7~0.9) alloy, Al x Co 1-x (x=0.7~0.9) or Al x Mn 1-xIt has been found that, in hydrogen storage materials including alloys having a composition of (x=0.7-0.9), alloys having the following configuration absorb hydrogen in the atmosphere at room temperature and pressure. In this specification, "room temperature" refers to a temperature of 15°C to 30°C, and "normal pressure" refers to atmospheric pressure, i.e., 1 atmosphere (1013 hPa). Note that, even though it is atmospheric pressure, there are differences in low and high pressure depending on the weather, so here, "normal pressure" means a pressure near atmospheric pressure (970 hPa to 1030 hPa). First, the structure of the hydrogen storage material will be described in detail.

[0011] 1 is a schematic diagram showing the structure of an alloy 10 according to one embodiment of the present invention. The alloy 10 is formed as a thin film on a substrate 1 by, for example, a sputtering method. The substrate 1 of this embodiment is made of Si (silicon).

[0012] Alloy 10 is Al x Fe 1-x (x=0.7~0.9), Al x Co 1-x (x=0.7~0.9), or Al x Mn 1-x (x=0.7-0.9). Alloy 10 has a non-crystalline (amorphous) structure. However, Alloy 10 may contain microcrystals with a crystal grain size of several nm or less. In other words, Alloy 10 may have a structure including an amorphous structure region and a microcrystal region. Here, "microcrystals" refers to "tiny crystal grains having a crystalline structure."

[0013] Alloy 10 has regions with a lower density than other regions at intervals of 30 nm or less on any straight line in a plane parallel to the surface. This will be explained with reference to Figures 2 and 3.

[0014] FIG. 2 is a scanning electron microscope (SEM) photograph of the surface of alloy 10 opposite to the substrate 1 (i.e., the surface of alloy 10). FIG. 3 is a high-angle annular dark field (HAADF) image of alloy 10 by a transmission electron microscope (TEM). The HAADF image shown in FIG. 3 is a HAADF image of alloy 10 cut along a plane parallel to the direction in which alloy 10 is layered on substrate 1 (in other words, the thickness direction of alloy 10). The alloy 10 shown in FIG. 2 and FIG. 3 is a film formed on substrate 1 at room temperature using a target having a composition of Al:Fe=76:24 in atomic ratio. The details of the manufacturing method of alloy 10 will be described later.

[0015] As shown in Figs. 2 and 3, the alloy 10 is composed of a collection of columnar structures 11 (first columnar structures) with a diameter of 30 nm or less, which extend along the thickness direction of the alloy 10 (in other words, the direction perpendicular to the surface of the alloy 10). In the SEM photograph of Fig. 2, the region that appears to be approximately circular, including a perfect circle, corresponds to the longitudinal end of the columnar structures 11. As shown in Fig. 3, the columnar structures 11 are composed of a collection of multiple tiny columnar structures 12 (second columnar structures). More specifically, the columnar structures 11 include multiple columnar structures 12 adjacent to each other via a second region 14 in which the density of the alloy 10 is lower than that of other regions in the columnar structures 11.

[0016] The alloy 10 is mostly composed of a plurality of columnar structures 11. In the HAADF image shown in FIG. 3, the region between one columnar structure 11 and the columnar structure 11 adjacent thereto (hereinafter also referred to as the first region 13) is darker than the columnar structures 11. In the alloy 10, the first region 13 is continuously formed from one surface to the other surface of the alloy 10 in a cross section obtained by cutting the alloy 10 along a plane perpendicular to the surface of the alloy 10. In the HAADF image, when the composition is the same, the higher the density, the brighter the image appears. Therefore, the first region 13 has a lower density than the columnar structures 11. That is, in the alloy 10, the distance between adjacent first regions 13 is 30 nm or less. With the above configuration, the alloy 10 has a structure in which, on any straight line on a plane parallel to the surface of the alloy 10 inside the alloy 10, there are regions with a lower density than other regions at intervals of 30 nm or less. In other words, alloy 10 has a plurality of first regions 13 in which the density of alloy 10 is lower than other regions, and the distance between adjacent first regions 13 is 30 nm or less in a cross section of alloy 10 cut along a plane perpendicular to the surface of alloy 10. In this specification, the distance between adjacent first regions 13 refers to the distance between the point of lowest density in first region 13 and the point of lowest density in a first region adjacent to said first region 13.

[0017] The inventors' intensive research has revealed that, due to this structure, alloy 10 can absorb hydrogen from the atmosphere at room temperature and pressure, although the detailed mechanism is not clear. Therefore, alloy 10 can be suitably used as a hydrogen storage material. It is considered that alloy 10 absorbs hydrogen from water molecules or hydrogen molecules contained in the atmosphere.

[0018] 2, the regions that appear to be approximately circular, including perfect circles, correspond to the longitudinal ends of columnar structures 11. That is, in the cross section of alloy 10 cut along a plane parallel to the surface of alloy 10, the distance between adjacent first regions is 30 nm or less.

[0019] In the present embodiment, the alloy 10 is constituted by a collection of columnar structures 11, and has a structure having regions with a lower density than other regions at intervals of 30 nm or less, but the alloy of the present invention is not limited to this. The alloy of the present invention may have other configurations as long as it has a structure having regions with a lower density than other regions at intervals of 30 nm or less, and may have, for example, a particulate or layered structure.

[0020] As mentioned above, Alloy 10 is made of Al x Fe 1-x (x=0.7~0.9) alloy, Al x Co 1-x (x=0.7~0.9) or Al x Mn 1-x (x=0.7-0.9). Thus, when alloy 10 is produced by the manufacturing method described below, alloy 10 having the above configuration can be obtained. If x is less than 0.7, the alloy produced will have a crystalline structure rather than an amorphous structure, resulting in a reduced hydrogen storage capacity. If x exceeds 0.9, the alloy will have a crystalline structure, resulting in a reduced hydrogen storage capacity.

[0021] In this embodiment, alloy 10 releases hydrogen by heating the hydrogen it absorbs. Specifically, when alloy 10 is heated, it gradually releases hydrogen from about 100° C., and the amount of hydrogen released increases as the temperature rises to about 150° C. The heating rate is preferably 10° C. / min.

[0022] The alloy 10 in this embodiment is composed only of Al and Fe, Co or Mn. These substances are inexpensive metals and can be produced more inexpensively than existing hydrogen storage alloys.

[0023] [Method of manufacturing hydrogen storage material] The alloy 10 can be produced, for example, by a sputtering method. More specifically, the alloy 10 having the above-mentioned structure can be produced by carrying out a sputtering process (alloy lamination process) while maintaining the temperature of the base material 1 at less than 200°C, preferably 100°C or less, and more preferably at room temperature (specifically, 15°C to 30°C).

[0024] The substrate 1 is not particularly limited, but may be made of, for example, metals such as Si, Al, and stainless steel, heat-resistant polymeric substances such as polyimide, and ceramics such as SiC and alumina. In the sputtering process, a substrate having the same composition as the alloy to be produced (i.e., Al x Fe 1-x (x=0.7~0.9), Al x Co 1-x (x=0.7~0.9), or Al x Mn 1-x A sintered body of a mixed powder having a composition of (x=0.7 to 0.9) is used as a target. The sputtering process can be performed in an inert gas atmosphere (for example, an Ar atmosphere).

[0025] When the temperature of the substrate 1 is higher than room temperature, the substrate 1 does not have a structure having regions with a lower density than other regions at intervals of 30 nm or less on any straight line on a plane parallel to the surface. For example, when the temperature of the substrate 1 is 200° C., the interval between regions with a lower density than other regions on any straight line on a plane parallel to the surface becomes larger than 30 nm. Furthermore, when the temperature of the substrate 1 is 300° C. or higher, the substrate 1 becomes an alloy with a crystalline structure rather than an amorphous structure, and the hydrogen storage capacity becomes small.

[0026] The above-mentioned method for producing the hydrogen storage material is one example of a method for producing alloy 10. Alloy 10 can be produced by forming a film while maintaining the temperature of substrate 1 at room temperature, for example, by physical vapor deposition such as vacuum deposition, thermal spraying, and laser deposition. Alloy 10 can also be produced by mechanical alloying using a ball milling device.

[0027] [Application example of Alloy 10] As described above, the alloy 10 can absorb hydrogen from the atmosphere at room temperature and pressure. Therefore, the alloy 10 can be suitably applied to a hydrogen extraction system that extracts hydrogen from the atmosphere. Here, an example of the hydrogen extraction system will be described.

[0028] 4 is a block diagram showing the configuration of the hydrogen extraction system 100 in this embodiment. As shown in FIG. 4, the hydrogen extraction system 100 includes a hydrogen absorbing section 110 and a hydrogen releasing section 120.

[0029] The hydrogen absorbing unit 110 absorbs hydrogen using alloy 10 as a hydrogen absorbing material. The hydrogen absorbing unit 110 may be, for example, a container coated with alloy 10. Since the hydrogen absorbing unit 110 includes alloy 10, it is possible to cause the hydrogen absorbing unit 110 to absorb hydrogen by exposing the hydrogen absorbing unit 110 to the atmosphere.

[0030] The hydrogen releasing section 120 heats the hydrogen absorbing section 110 that has absorbed hydrogen, thereby releasing hydrogen from the hydrogen absorbing section 110. Specifically, the hydrogen releasing section 120 heats the hydrogen absorbing section 110 to 150° C. or higher, which is the temperature at which the alloy 10 releases the hydrogen stored therein.

[0031] In the hydrogen extraction system 100 having the above configuration, hydrogen in the atmosphere can be absorbed in the hydrogen absorption section 110 at room temperature and pressure, and hydrogen can be extracted at a desired timing simply by heating the hydrogen absorption section 110 that has absorbed hydrogen.

[0032] An embodiment of the present invention will be described below. Fig. 5 is a cross-sectional TEM image of an alloy as Example 1 of the present invention. Fig. 6 is a cross-sectional TEM image of an alloy as Comparative Example 1 of the present invention. Fig. 7 is an SEM photograph of the alloy of Comparative Example 1, in which the surface opposite the substrate side is observed. The SEM photograph of the alloy of Example 1, in which the surface opposite the substrate side is observed, is the SEM photograph shown in Fig. 2.

[0033] The alloy of Example 1 was prepared by magnetron sputtering using Si as a substrate. More specifically, the sputtering was performed using a mixed powder sintered body having a molar ratio of Al:Fe=76:24 as a target, with an Ar gas pressure of 0.183 Pa and a substrate temperature maintained at 25° C. The alloy of Example 1 was deposited at a deposition rate of 5.4 nm / min to a thickness of about 250 nm.

[0034] The alloy of Comparative Example 1 was produced in the same manner as in Example 1, except that the temperature at which the substrate was held during the sputtering treatment was 200°C.

[0035] As shown in Figs. 5 and 6, the alloy of Example 1 had more white lines extending along the thickness direction of the alloy than the alloy of Comparative Example 1. Specifically, in the alloy of Example 1, white lines were observed at intervals of 30 nm or less on any straight line on a plane parallel to the surface. On the other hand, in the alloy of Comparative Example 1, white lines were observed at intervals longer than 30 nm (for example, 50 nm) on any straight line on a plane parallel to the surface. As described later, the white lines are regions with a lower density than the black regions. Therefore, the alloy of Example 1 had a structure having regions with a lower density than other regions at intervals of 30 nm or less on any straight line on a plane parallel to the surface. The black regions in the photographs shown in Figs. 5 and 6 are columnar structures. In the SEM photographs of Figs. 2 and 7, the regions that appear to be approximately circular correspond to the longitudinal ends of the columnar structures.

[0036] FIG. 8 is an electron beam diffraction image of the alloy of Example 1 using a TEM. FIG. 9 is an electron beam diffraction image of Comparative Example 1 using a TEM. As shown in FIG. 8, the electron beam diffraction image of the alloy of Example 1 has a structure close to a halo shape, and no spots due to the crystal structure were confirmed. Here, the halo shape means a halo. That is, it can be seen that the alloy of Example 1 has a non-crystalline (amorphous) structure. However, as shown in FIG. 8, the electron beam diffraction image of the alloy of Example 1 is not a complete halo shape, and a ring-shaped image is observed, so it is considered that there is a possibility that it contains microcrystals with a crystal grain size of less than several nm (specifically, less than 5 nm). Note that, usually, when crystals with a crystal grain size of several nm exist, they can be confirmed in a TEM image, but in the TEM image of Example 1, crystals with a crystal grain size of several nm could not be observed.

[0037] In addition, as shown in FIG. 9, the alloy of Comparative Example 1 also had an electron beam diffraction pattern similar to that of the alloy of Example 1, and had an amorphous structure.

[0038] 10 is a graph showing the results of measuring the hydrogen distribution inside the alloy of Example 1 and the alloy of Comparative Example 1 after exposing them to the atmosphere at room temperature and pressure. 4 He + The measurement was performed by a recoil particle detection method using the analysis beam as the recoil particle detection method. In the graph shown in Figure 10, the horizontal axis of the channel number corresponds to the distance from the substrate, and the vertical axis of the normalized yield corresponds to the amount of hydrogen.

[0039] As shown in FIG. 10, the alloy of Example 1 contained more hydrogen than the alloy of Comparative Example 1. In other words, it was shown that the alloy of Example 1 had a higher hydrogen storage capacity than the alloy of Comparative Example 1. Calculations made from the graph shown in FIG. 10 showed that the alloy of Example 1 had absorbed 1.3 wt% of hydrogen relative to the weight of the alloy. This value was obtained by comparing the hydrogen storage capacity of LaNi 5This is about the same as the amount of hydrogen absorbed when TiFe or the like is made to absorb hydrogen using high-concentration hydrogen gas. In other words, the alloy of Example 1 absorbed hydrogen to the same extent as a conventional hydrogen storage material simply by being exposed to the air at room temperature and pressure.

[0040] FIG. 11 is a graph showing the amount of hydrogen released from an alloy as a modification in which hydrogen was absorbed from the alloy of Example 1, in which the substrate was changed to Al and the film thickness of the alloy was changed to about 1 μm. In FIG. 11, the ion current on the left vertical axis corresponds to the amount of hydrogen released from the alloy. The graph shown in FIG. 11 was created based on the results of measurements using a thermobalance-mass spectrometer. Specifically, the sample was heated from room temperature to 350° C. at a heating rate of 10° C. / min under He flow conditions, and the weight change and the amount of hydrogen released from the sample were measured.

[0041] As shown in FIG. 11, when the temperature of the alloy of the modified example of Example 1 was increased, hydrogen was gradually released from about 100°C, and the amount of released hydrogen increased as the temperature increased to about 150°C. Also, as shown in FIG. 11, the weight of the alloy decreased as the amount of released hydrogen increased. Hydrogen release was observed up to about 250°C. From this result, it can be seen that the absorbed hydrogen can be sufficiently released by heating the alloy of the modified example of Example 1 to 250°C at a temperature increase rate of 10°C / min. Second Example

[0042] Next, an alloy as Reference Example 1 of the present invention will be described. The alloy of Reference Example 1 is made of Al with respect to Si as a base material. 76 Fe 24 Alloy, Al, Al 76 Fe 24 Except for laminating the alloys in this order, the alloys were produced in the same manner as in Example 1. Fig. 12 is a cross-sectional TEM image of the alloy of Reference Example 1. Fig. 13 is a graph showing the results of measuring the hydrogen distribution present inside the alloy of Reference Example 1 after exposing it to the air at room temperature and pressure.

[0043] As shown in FIG. 13, in the alloy of Reference Example 1, Al present near the surface 76 Fe 24The amount of hydrogen in the layer is smaller than that in the Al layer, which is closer to the substrate. 76 Fe 24 The amount of hydrogen present in the Al film was greater than that present in the Al film. The Al film does not absorb hydrogen. This shows that the hydrogen absorbed in the alloy of Reference Example 1 is not hydrogen absorbed in the alloy during the sputtering process, but hydrogen absorbed in the alloy by exposure to the atmosphere after film formation.

[0044] Next, an alloy as Reference Example 2 of the present invention will be described. The alloy of Reference Example 2 is a first Al alloy with a Si substrate, a substrate holding temperature of 200° C., and a second Al alloy with a Si substrate. 76 Fe 24 After the alloy layer 10a is formed, the substrate is held at a temperature of 25° C. and the second Al 76 Fe 24 Except for forming the alloy layer 10b, the alloy was produced in the same manner as in Example 1. Fig. 14 is a HAADF image by a scanning TEM method of the alloy of Reference Example 2. Fig. 15 is a graph produced by calculating the contrast intensity at the line L1 and the line L2 shown in Fig. 14.

[0045] As shown in FIG. 14, the dark lines indicating a relatively low density are the first Al 76 Fe 24 The second Al is higher than the alloy layer 10a. 76 Fe 24 More specifically, as shown in FIG. 76 Fe 24 In the alloy layer 10b, regions with relatively low density exist at intervals of 30 nm or less, whereas in the first Al 76 Fe 24 It can be seen that in the alloy layer 10a, regions of relatively low density exist at intervals longer than 30 nm.

[0046] Next, an alloy of the present invention will be described as Example 2. The alloy of Example 2 was produced in the same manner as the alloy of Example 1, except that a mixed powder sintered body having a composition of Al:Fe=80:20 in molar ratio was used as a target.

[0047] Fig. 16 is a cross-sectional TEM image of the alloy of Example 2. As shown in Fig. 16, the alloy of Example 2, like the alloy of Example 1, had white lines at intervals of 30 nm or less on any straight line on a plane parallel to the surface. That is, the alloy of Example 2 had a structure having regions with a lower density than other regions at intervals of 30 nm or less on any straight line on a plane parallel to the surface.

[0048] FIG. 17 is an electron beam diffraction image of the alloy of Example 2 using a TEM. As shown in FIG. 17, the alloy of Example 2, like the alloy of Example 1, has a structure close to a halo shape, and no spots due to a crystal structure were confirmed. In other words, it is understood that the alloy of Example 2 has a non-crystalline (amorphous) structure. However, as shown in FIG. 17, the electron beam diffraction image of the alloy of Example 2 does not have a complete halo shape, and a ring-shaped image is observed, so it is considered that it may contain microcrystals with a crystal grain size of less than several nm (specifically, less than 5 nm).

[0049] FIG. 18 is a graph showing the amount of hydrogen released from the alloy of Example 2, which is a modified example in which the substrate of the alloy is changed to Al and the film thickness of the alloy is changed to about 1 μm, in which hydrogen is absorbed. Here, the sample was heated from room temperature to 200° C. at a heating rate of 10° C. / min, and then held at 200° C. for 5 minutes. As shown in FIG. 18, when the temperature of the alloy of the modified example of Example 2 is increased, hydrogen is gradually released from about 100° C., and the amount of hydrogen released increases as the temperature increases to about 150° C. Also, as shown in FIG. 18, the weight of the alloy decreases as the amount of hydrogen released increases. From this result, it can be seen that the absorbed hydrogen can be sufficiently released by heating the alloy of the modified example of Example 2 to 200° C. at a heating rate of 10° C. / min and holding it at 200° C. for 5 minutes. Fifth Example

[0050] Next, an alloy as Example 3 of the present invention and an alloy as Comparative Example 2 will be described.

[0051] The alloy of Example 3 was produced in the same manner as the alloy of Example 1, except that an alloy made of a mixed powder sintered body having a molar ratio of Al:Mn=76:24 was used as a target. The alloy of Comparative Example 2 was produced in the same manner as the alloy of Comparative Example 1, except that an alloy made of a mixed powder sintered body having a molar ratio of Al:Mn=76:24 was used as a target.

[0052] Fig. 19 is a cross-sectional TEM image of the alloy of Example 3. Fig. 20 is a cross-sectional TEM image of the alloy of Comparative Example 2. Fig. 21 is an SEM photograph of the alloy of Example 3, in which the surface opposite to the substrate side is observed. Fig. 22 is an SEM photograph of the alloy of Comparative Example 2, in which the surface opposite to the substrate side is observed.

[0053] As shown in Figs. 19 and 20, the alloy of Example 3 had more white lines extending along the thickness direction of the alloy than the alloy of Comparative Example 2. Specifically, in the alloy of Example 3, white lines were observed at intervals of 30 nm or less on any straight line on a plane parallel to the surface. On the other hand, in the alloy of Comparative Example 2, white lines were observed at intervals longer than 30 nm (for example, intervals of 50 nm) on any straight line on a plane parallel to the surface. That is, the alloy of Example 3 had a structure having regions with a lower density than other regions at intervals of 30 nm or less on any straight line on a plane parallel to the surface. The black regions in the photographs shown in Figs. 19 and 20 are columnar structures. In the SEM photographs of Figs. 21 and 22, the regions that appear to be approximately circular correspond to the longitudinal ends of the columnar structures.

[0054] FIG. 23 is an electron beam diffraction image of the alloy of Example 3 using a TEM. FIG. 24 is an electron beam diffraction image of Comparative Example 2 using a TEM. As shown in FIG. 23, the electron beam diffraction image of the alloy of Example 3 has a structure close to a halo shape, and no spots due to a crystal structure were confirmed. That is, it can be seen that the alloy of Example 3 has a non-crystalline (amorphous) structure. However, as shown in FIG. 23, the electron beam diffraction image of the alloy of Example 3 is not a complete halo shape, and a ring-shaped image is observed, so it is considered that there is a possibility that it contains microcrystals with a crystal grain size of less than several nm (specifically, less than 5 nm). In addition, as shown in FIG. 24, the alloy of Comparative Example 2 also has the same electron beam diffraction image as the alloy of Example 3, and has an amorphous structure.

[0055] Fig. 25 is a graph showing the results of measuring the hydrogen distribution present inside the alloy of Example 3 and the alloy of Comparative Example 2 after exposing them to the atmosphere at room temperature and pressure. As shown in Fig. 25, the alloy of Example 3 contained more hydrogen than the alloy of Comparative Example 2. In other words, it was shown that the alloy of Example 3 has a higher hydrogen absorption capacity than the alloy of Comparative Example 2. Calculations made from the graph shown in Fig. 25 showed that the alloy of Example 3 absorbed 0.5 wt% of hydrogen with respect to the weight of the alloy.

[0056] FIG. 26 is a graph showing the amount of hydrogen released from the alloy of Example 3, which is a modified example in which the substrate of the alloy is changed to Al and the film thickness of the alloy is changed to about 1 μm. Here, the sample was heated from room temperature to 200° C. at a heating rate of 10° C. / min, and then held at 200° C. for 5 minutes. As shown in FIG. 26, when the temperature of the alloy of the modified example of Example 3 is increased, hydrogen is gradually released from about 100° C., and the amount of hydrogen released increases as the temperature increases to about 150° C. Also, as shown in FIG. 26, the weight of the alloy decreases as the amount of hydrogen released increases. From this result, it can be seen that the hydrogen absorbed can be sufficiently released by heating the alloy of the modified example of Example 3 to 200° C. at a heating rate of 10° C. / min, and then holding it at 200° C. for 5 minutes. Sixth Example

[0057] Next, an alloy as Comparative Example 3 of the present invention will be described. The alloy of Comparative Example 3 was prepared by magnetron sputtering using Si as a substrate. More specifically, the sputtering was performed using a mixed powder sintered body having a molar ratio of Al:Fe=76:24 as a target, with an Ar gas pressure of 0.183 Pa and a substrate temperature maintained at 25°C. The alloy of Comparative Example 3 was deposited to a thickness of about 250 nm at a deposition rate of 49 nm / min.

[0058] FIG. 27 is a cross-sectional TEM image of the alloy of Comparative Example 3. FIG. 28 is an electron beam diffraction image of the alloy of Comparative Example 3 using a TEM. As shown in FIG. 28, the electron beam diffraction image of the alloy of Comparative Example 3 has a structure close to a halo shape, and no spots due to a crystalline structure were confirmed. In other words, it is understood that the alloy of Comparative Example 3 has a non-crystalline (amorphous) structure. Furthermore, as shown in FIG. 27, the columnar structures seen in the alloy of Example 1 shown in FIG. 5 could not be confirmed in the alloy of Comparative Example 3.

[0059] Fig. 29 is a graph showing the results of measuring the hydrogen distribution inside the alloy of Comparative Example 3 after exposing the alloy to the atmosphere at room temperature and pressure. As shown in Fig. 29, the amount of hydrogen stored inside the alloy of Comparative Example 3 was smaller than that of the alloy of Example 1 shown in Fig. 10.

[0060] FIG. 30 is a graph showing the amount of hydrogen released from a modified alloy in which hydrogen was absorbed, in which the substrate of the alloy in Comparative Example 3 was changed to Al and the film thickness of the alloy was changed to about 1 μm. In FIG. 30, the ion current on the vertical axis corresponds to the amount of hydrogen released from the alloy. The graph shown in FIG. 30 shows the measurement results obtained by heating the sample from room temperature to 450° C. at a heating rate of 10° C. / min under He flow conditions. As shown in FIG. 30, in the test using the above modified alloy of the alloy in Comparative Example 3, no hydrogen was released, or even if hydrogen was released, it was below the detection limit.

[0061] The above results show that the alloy of Comparative Example 3, which has an amorphous structure but does not have columnar structures, absorbs a small amount of hydrogen at room temperature and pressure and does not release hydrogen or releases very little hydrogen.

[0062] Next, an alloy of the present invention will be described as Example 4. The alloy of Example 4 was produced in the same manner as the alloy of Example 1, except that an alloy made of a mixed powder sintered body having a composition of Al:Fe=90:10 in molar ratio was used as a target.

[0063] FIG. 31 is a cross-sectional TEM image of the alloy of Example 4. As shown in FIG. 31, the alloy of Example 4, like the alloy of Example 1, had white lines at intervals of 30 nm or less on any straight line on a plane parallel to the surface. That is, the alloy of Example 4 had a structure having regions with a lower density than other regions at intervals of 30 nm or less on any straight line on a plane parallel to the surface. The black regions in the photograph shown in FIG. 31 are columnar structures.

[0064] FIG. 32 is an electron beam diffraction image of the alloy of Example 4 using a TEM. As shown in FIG. 32, the alloy of Example 4, like the alloy of Example 1, has a structure close to a halo shape, and no spots due to a crystal structure were confirmed. In other words, it is understood that the alloy of Example 4 has a non-crystalline (amorphous) structure. However, as shown in FIG. 32, the electron beam diffraction image of the alloy of Example 4 does not have a complete halo shape, and a ring-shaped image is observed, so it is considered that it may contain microcrystals with a crystal grain size of less than several nm (specifically, less than 5 nm).

[0065] FIG. 33 is a graph showing the results of measuring the hydrogen distribution present inside the alloy of Example 4 after exposing the alloy to the atmosphere at room temperature and pressure. As shown in FIG. 33, the alloy of Example 4 is similar to the data for the alloy of Example 1 in the graph shown in FIG. 10, and it is found that the alloy absorbs a large amount of hydrogen like the alloy of Example 1. Since the manner in which hydrogen is absorbed is similar to that of the alloy of Example 1, it is believed that the alloy of Example 4 also releases the absorbed hydrogen when heated. Eighth Example

[0066] Next, an alloy of the present invention will be described as Example 5. The alloy of Example 5 was produced in the same manner as the alloy of Example 1, except that an alloy made of a mixed powder sintered body having a composition of Al:Co=76:24 in molar ratio was used as a target.

[0067] FIG. 34 is a cross-sectional TEM image of the alloy of Example 5. As shown in FIG. 34, the alloy of Example 5, like the alloy of Example 1, had white lines at intervals of 30 nm or less on any straight line on a plane parallel to the surface. That is, the alloy of Example 5 had a structure having regions with a lower density than other regions at intervals of 30 nm or less on any straight line on a plane parallel to the surface. The black regions in the photograph shown in FIG. 34 are columnar structures.

[0068] FIG. 35 is an electron beam diffraction image of the alloy of Example 5 using a TEM. As shown in FIG. 35, the alloy of Example 5, like the alloy of Example 1, has a structure close to a halo shape, and no spots due to a crystal structure were confirmed. That is, it is understood that the alloy of Example 5 has a non-crystalline (amorphous) structure. However, as shown in FIG. 35, the electron beam diffraction image of the alloy of Example 5 does not have a complete halo shape, and a ring-shaped image is observed, so it is considered that it may contain microcrystals with a crystal grain size of less than several nm (specifically, less than 5 nm).

[0069] Fig. 36 is a graph showing the results of measuring the hydrogen distribution inside the alloy of Example 5 after exposing the alloy to the atmosphere at room temperature and pressure. As shown in Fig. 36, the alloy of Example 5 is similar to the data for the alloy of Example 1 in the graph shown in Fig. 10, and it is found that the alloy of Example 5 absorbs a large amount of hydrogen like the alloy of Example 1.

[0070] FIG. 37 is a graph showing the amount of hydrogen released from the alloy of Example 5, which is a modified example in which the substrate of the alloy is changed to Al and the film thickness of the alloy is changed to about 1 μm. In FIG. 37, the ion current on the vertical axis corresponds to the amount of hydrogen released from the alloy. The graph shown in FIG. 37 shows the measurement results obtained by heating the sample from room temperature to 450° C. at a heating rate of 10° C. / min under He flow conditions. As shown in FIG. 37, when the temperature of the alloy of the modified example of Example 5 was increased, hydrogen was gradually released from about 100° C., and the amount of hydrogen released increased as the temperature increased to about 150° C.

[0071] <Additional Notes: At the time of filing this application, it is impossible or almost impractical to directly identify the "product" according to the present invention by its structure or characteristics> Because there is a limit to the ability of current science and technology to evaluate the amorphous state and hydrogen storage state of a microscopic region of a hydrogen storage material, it was technically impossible to analyze the structure or characteristics of the "substance" to the extent described in the current claims at the time of filing this application. In addition, in light of the need for speed, etc., due to the nature of patent applications, it would require significantly excessive economic expenditure or time to carry out the work of identifying the structure or characteristics of the substance. [Explanation of symbols]

[0072] 1 Base material 10 alloy 11 Column structure (first column) 12 Columnar structure (second columnar body) 13 First area 14 Second area 100 Hydrogen Extraction System 110 Hydrogen storage section 120 Hydrogen release section

Claims

1. A ｘ Fe １－ｘ (x=0.7~0.9), Al ｘ Co １－ｘ (x=0.7 to 0.9) or Al ｘ Mn １－ｘ An alloy having a composition of (x=0.7 to 0.9), The alloy is It is a thin film, Contains an amorphous structure, a plurality of first regions in which the alloy has a lower density than other regions; An alloy, wherein the distance between adjacent first regions is 30 nm or less in a cross section of the alloy cut along a plane perpendicular to a surface of the alloy.

2. The alloy of claim 1 , wherein in the cross section, the first region is formed continuously from one surface of the alloy to the other surface.

3. 3. The alloy according to claim 1, wherein in a cross section of the alloy cut along a plane parallel to a surface of the alloy, the distance between adjacent first regions is 30 nm or less.

4. the amorphous structure has a plurality of first columns adjacent to each other with the first region interposed therebetween, The alloy according to any one of claims 1 to 3, wherein the first columnar body includes a plurality of second columnar bodies adjacent to each other via a second region in which the density of the alloy is lower than that of other regions in the first columnar body.

5. A hydrogen storage part using the alloy according to claim 1 or 2 as a hydrogen storage material; a hydrogen release section that releases hydrogen from the hydrogen storage section by heating the hydrogen storage section in which hydrogen has been stored.

6. A hydrogen storage material for storing hydrogen, A ｘ Fe １－ｘ (x=0.7~0.9), Al ｘ Co １－ｘ (x=0.7 to 0.9) or Al ｘ Mn １－ｘ (x=0.7 to 0.9), The alloy is It is a thin film, Contains an amorphous structure, a plurality of first regions in which the alloy has a lower density than other regions; A hydrogen storage material, wherein the distance between adjacent first regions is 30 nm or less in a cross section of the alloy cut along a plane perpendicular to a surface of the alloy.

7. 7. The hydrogen storage material according to claim 6, wherein a distance between adjacent first regions in a cross section of the alloy cut along a plane parallel to a surface of the alloy is 30 nm or less.

8. the amorphous structure has a plurality of first columns adjacent to each other with the first region interposed therebetween, 8. The hydrogen storage material according to claim 6, wherein the first columnar body includes a plurality of second columnar bodies adjacent to each other via a second region in which the density of the alloy is lower than that of other regions of the first columnar body.

9. 1. A method for producing an alloy on a substrate, comprising the steps of: The method for producing an alloy includes an alloy laminating step of laminating an alloy on the base material held at a temperature of 15° C. or higher and lower than 200° C., using a target having a composition of Al:Fe=x:1-x (x=0.7 to 0.9) in a molar ratio, Al:Co=x:1-x (x=0.7 to 0.9) in a molar ratio, or Al:Mn=x:1-x (x=0.7 to 0.9) in a molar ratio.

10. An alloy produced by using a target having a composition of Al:Fe=x:1-x (x=0.7-0.9) in molar ratio, Al:Co=x:1-x (x=0.7-0.9) in molar ratio, or Al:Mn=x:1-x (x=0.7-0.9) in molar ratio, and laminating it on a substrate maintained at a temperature of 15°C or higher but lower than 200°C.

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