Hydrogen storage body, method for manufacturing the same, and hydrogen container

Abstract

To provide a hydrogen storage body that has high porosity, and excellent hydrogen storage properties and hydrogen release properties, a method for manufacturing the hydrogen storage body and a hydrogen container equipped with the hydrogen storage body.SOLUTION: A hydrogen storage body 1 has pores 11. The hydrogen storage body 1 has: hydrogen storage alloy particles 2; aggregate particles 3 which are made of metal having no hydrogen storage ability; and bonding parts 4 which bond the aggregate particles 3 to each other and also bond the hydrogen storage alloy particles 2 to the aggregate particles 3. At least a part of the hydrogen storage alloy particles 2 is exposed in the pores 11. The bonding parts 4 are composed of metal particles 41 having a smaller particle diameter than the aggregate particles 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hydrogen storage material, a method for producing the same, and a hydrogen container. [Background technology]

[0002] In recent years, there has been concern about the environmental impact of using fossil fuels, and the use of hydrogen, which has a lower environmental impact, as an energy source is expected. To use hydrogen as an energy source, devices containing hydrogen storage materials that can reversibly store and release hydrogen are sometimes used. Porous sintered bodies containing hydrogen storage alloys are sometimes used as this type of hydrogen storage material. For example, Patent Document 1 describes a hydrogen storage alloy compact obtained by filling a container made of a porous material with excellent thermal conductivity with a hydrogen storage alloy powder or a mixture of hydrogen storage alloy powder and a metal powder with excellent thermal conductivity, and then compacting the filled body under pressure. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-180901 Summary of the Invention [Problem to be solved by the invention]

[0004] In porous bodies containing hydrogen storage alloys, it is desirable to increase the porosity of the porous body in order to efficiently store and release hydrogen into and from the hydrogen storage alloy.

[0005] For example, when a porous sintered body is produced using a hydrogen storage alloy powder and a metal powder, the porosity of the sintered body can be increased by using hydrogen storage alloy powder or metal powder with a relatively large particle size. However, if the particle size of the hydrogen storage alloy powder or metal powder used to produce the sintered body is increased, the mixture of the hydrogen storage alloy powder and the metal powder must be heated and sintered at a high temperature to sufficiently bond these powders. Furthermore, if the heating temperature during sintering is too high, the hydrogen storage alloy powder is more likely to melt, which may result in a deterioration in the hydrogen absorption and desorption properties of the sintered body.

[0006] The present invention has been made in consideration of such problems, and aims to provide a hydrogen storage material that has high porosity and excellent hydrogen absorption and release properties, a method for manufacturing the same, and a hydrogen container equipped with the hydrogen storage material. [Means for solving the problem]

[0007] One aspect of the present invention is a hydrogen storage material having pores, hydrogen storage alloy particles; aggregate particles made of a metal that does not have hydrogen storage capacity; bonding portions that bond the aggregate particles to each other and to the hydrogen storage alloy particles and the aggregate particles; At least a portion of the hydrogen storage alloy particles is exposed to the pores, The joints are made of metal particles having a particle size smaller than that of the aggregate particles.

[0008] Another aspect of the present invention is a method for producing a hydrogen storage material according to the above aspect, comprising: forming composite particles by adhering metal particles to the aggregate particles; Then, the hydrogen storage alloy particles and the composite particles are mixed to prepare a mixture, The mixture is molded to produce a molded body; The hydrogen absorbing material is formed by sintering the molded body.

[0009] A further aspect of the present invention is a hydrogen container equipped with the hydrogen absorbing material of the above aspect. [Effects of the Invention]

[0010] In the hydrogen storage material, aggregate particles are bonded to each other and to hydrogen storage alloy particles via bonding sections. The bonding sections are made of metal particles with a smaller particle size than the aggregate particles. By using metal particles with a smaller particle size than the aggregate particles to bond the aggregate particles to each other and to the hydrogen storage alloy particles, bonding sections can be easily formed and the aggregate particles can be bonded to each other and to the hydrogen storage alloy particles even when the heating temperature during sintering is relatively low. Furthermore, by lowering the heating temperature during sintering, melting of the hydrogen storage alloy particles during sintering can be easily avoided.

[0011] Furthermore, in the hydrogen storage material, the metal particles are used to bond aggregate particles together or to bond aggregate particles to hydrogen storage alloy particles, which allows the particle size of the aggregate particles and hydrogen storage alloy particles to be increased. As a result, the porosity of the hydrogen storage material can be easily increased. Furthermore, since at least a portion of the hydrogen storage alloy particles in the hydrogen storage material are exposed to the pores, hydrogen can be efficiently absorbed into and released from the hydrogen storage alloy.

[0012] In the manufacturing method, metal particles are first attached to the surfaces of aggregate particles to form composite particles. These composite particles are then mixed with hydrogen storage alloy particles, molded into a desired shape, and sintered. By attaching the metal particles used to form the joints to the surfaces of the aggregate particles in this way, it is possible to easily prevent the surfaces of the hydrogen storage alloy particles from being covered with metal particles. Therefore, the manufacturing method makes it easy to obtain a hydrogen storage material in which at least a portion of the hydrogen storage alloy particles are exposed to the pores.

[0013] As described above, according to the above-described aspects, it is possible to provide a hydrogen absorbing material having high porosity and excellent hydrogen absorbing and releasing properties, a method for manufacturing the same, and a hydrogen container equipped with the hydrogen absorbing material. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a partial cross-sectional view showing a main part of a hydrogen absorbing material according to the first embodiment. [Figure 2] FIG. 2 is a partial cross-sectional view showing a main part of a compact in the method for producing a hydrogen absorbing material according to the first embodiment. [Figure 3] FIG. 3 is an SEM image of the surface of the hydrogen absorbing material in Experimental Example 1. As shown in FIG. [Figure 4] FIG. 4 is an enlarged SEM image of the pore opening in FIG. [Figure 5] FIG. 5 is an SEM image of the surface of the hydrogen storage material in Experimental Example 2. [Figure 6] FIG. 6 is an enlarged SEM image of the pore opening in FIG. [Figure 7] FIG. 7 is a partial cross-sectional view showing the main part of the hydrogen container in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] (Embodiment 1) An embodiment of the hydrogen storage material will be described with reference to Figs. 1 and 2. As shown in Fig. 1, the hydrogen storage material 1 of this embodiment is porous and has pores 11. The hydrogen storage material 1 has hydrogen storage alloy particles 2, aggregate particles 3 made of a metal that does not have hydrogen storage capacity, and bonding portions 4 that bond the aggregate particles 3 to each other and to the hydrogen storage alloy particles 2 and the aggregate particles 3. At least a portion of the hydrogen storage alloy particles 2 is exposed to the pores 11. The bonding portions 4 are made of metal particles 41 that are smaller in diameter than the aggregate particles 3.

[0016] [Hydrogen storage material 1] The hydrogen storage material 1 of this embodiment is a porous body having a skeleton of aggregate particles 3, hydrogen storage alloy particles 2, and joints 4. The pores 11 of the hydrogen storage material 1 have a continuous pore structure in which gaps between the aggregate particles 3 and gaps between the aggregate particles 3 and the hydrogen storage alloy particles 2 are connected. Therefore, the hydrogen storage material 1 can guide hydrogen supplied from the outside to the hydrogen storage alloy particles 2 in the pores 11, allowing the hydrogen to be absorbed by the hydrogen storage alloy particles 2. The hydrogen storage material 1 can also guide hydrogen released from the hydrogen storage alloy particles 2 to the outside of the hydrogen storage material 1 through the pores 11.

[0017] The porosity of the hydrogen storage material 1 is preferably 9% or more. In this case, sufficient gaps are formed around the hydrogen storage alloy particles 2, and even when the hydrogen storage alloy particles 2 expand as they absorb hydrogen, gaps are more likely to be formed between the hydrogen storage alloy particles 2 and the particles surrounding the hydrogen storage alloy particles. As a result, deformation of the hydrogen storage material 1 when hydrogen is absorbed can be more easily suppressed. From the viewpoint of more reliably achieving this effect, the porosity of the hydrogen storage material 1 is more preferably 20% or more, even more preferably 40% or more, and sometimes preferably 60% or more. On the other hand, from the viewpoint of ensuring sufficient strength of the hydrogen storage material 1 and further improving handleability, the porosity of the hydrogen storage material 1 is preferably 80% or less.

[0018] The porosity of the hydrogen absorbing material 1 can be measured, for example, as follows: First, the hydrogen absorbing material 1 is sealed in a vacuum pack with a known volume and mass, and the total volume of the vacuum pack and the hydrogen absorbing material 1 is measured by an underwater displacement method. The volume of the vacuum pack is subtracted from the total volume thus obtained to calculate the bulk volume of the hydrogen absorbing material 1 sealed in the vacuum pack.

[0019] Separately, the volume ratio of the hydrogen storage alloy particles 2, aggregate particles 3, and metal particles 41 within the hydrogen storage material 1 is calculated using the respective densities and mass ratios of the hydrogen storage alloy particles 2, aggregate particles 3, and metal particles 41 that make up the hydrogen storage material 1, and the mass of the hydrogen storage material 1. The porosity can then be calculated by subtracting the volumes of the hydrogen storage alloy particles 2, aggregate particles 3, and metal particles 41 from the bulk volume of the hydrogen storage material 1, i.e., the value obtained by multiplying the bulk volume of the hydrogen storage material 1 by the volume ratio.

[0020] The bending strength of the hydrogen storage material 1 is preferably 3.3 MPa or more. In this case, even if the hydrogen storage alloy particles 2 expand as they absorb hydrogen and come into contact with particles surrounding the hydrogen storage alloy particles 2, deformation of the hydrogen storage material 1 can be more easily suppressed. The bending strength of the hydrogen storage material 1 is measured by a four-point bending test.

[0021] The hydrogen storage alloy particles 2 are made of a hydrogen storage alloy and are bonded to the aggregate particles 3 via bonding portions 4. At least a portion of the hydrogen storage alloy particles 2 is exposed in the pores 11 of the hydrogen storage material 1. By retaining the hydrogen storage alloy particles 2 in the pores 11 in this way, the pores 11 are less likely to be expanded even when the hydrogen storage alloy particles 2 expand as they absorb hydrogen. As a result, deformation of the hydrogen storage material 1 when hydrogen is absorbed can be more easily suppressed.

[0022] There are no particular limitations on the composition of the hydrogen storage alloy constituting the hydrogen storage alloy particles 2. Examples of hydrogen storage alloys that can be used to form the hydrogen storage alloy particles 2 include AB5-type rare earth alloys such as LaNi5 and mischmetal-nickel alloys, AB2-type Laves phase alloys such as MgZn2 and ZrNi2, AB-type titanium alloys such as TiFe and TiCo, A2B-type magnesium alloys such as Mg2Ni and Mg2Cu, and solid solution BCC alloys such as Ti-V alloys and Ti-Cr alloys.

[0023] There are no particular limitations on the particle size of the hydrogen storage alloy particles 2. For example, the volume-based median size of the hydrogen storage alloy particles 2 can be appropriately set within the range of 1 μm to 200 μm.

[0024] The mass ratio of the hydrogen storage alloy particles 2 in the hydrogen storage material 1 is preferably 20 mass% or more and 50 mass% or less. By making the mass ratio of the hydrogen storage alloy particles 2 in the hydrogen storage material 1 preferably 20 mass% or more, more preferably 25 mass% or more, and even more preferably 30 mass% or more, the amount of hydrogen that can be absorbed in the hydrogen storage material 1 can be increased.

[0025] On the other hand, if the mass ratio of the hydrogen storage alloy particles 2 is excessively high, when hydrogen is absorbed, the expansion of the hydrogen storage alloy particles 2 may easily cause the entire hydrogen storage material 1 to expand. By setting the mass ratio of the hydrogen storage alloy particles 2 in the hydrogen storage material 1 to preferably 50 mass% or less, more preferably 45 mass% or less, and even more preferably 40 mass% or less, this problem can be more easily avoided.

[0026] The aggregate particles 3 are composed of a metal that does not have hydrogen storage capacity, such as iron, iron alloy, copper, copper alloy, aluminum, aluminum alloy, nickel, or nickel alloy. By using a metal that does not have hydrogen storage capacity, i.e., the ability to reversibly store and release hydrogen, for the aggregate particles 3, deformation of the hydrogen storage material 1 when hydrogen is stored can be easily suppressed. Furthermore, by using aggregate particles 3 made of a metal, the thermal conductivity of the hydrogen storage material 1 can be increased, allowing hydrogen to be quickly stored in the hydrogen storage alloy particles 2 and released from the hydrogen storage alloy to the outside.

[0027] The aggregate particles 3 are preferably made of stainless steel. Stainless steel has the property of being less susceptible to hydrogen embrittlement when it comes into contact with hydrogen. Therefore, by using aggregate particles 3 made of stainless steel, the shape and strength of the hydrogen storage material 1 can be easily maintained even when hydrogen is repeatedly absorbed and released.

[0028] The volumetric median diameter of the aggregate particles 3 can be appropriately set, for example, within the range of 1 μm or more and 200 μm or less. From the viewpoint of further increasing the porosity of the hydrogen storage material 1, the volumetric median diameter of the aggregate particles 3 is preferably 10 μm or more, more preferably 30 μm or more, even more preferably 50 μm or more, and particularly preferably 70 μm or more. Note that the volumetric median diameter of the aggregate particles 3 can be measured using, for example, a laser diffraction / scattering particle size distribution analyzer.

[0029] The joints 4 are composed of metal particles 41 having a smaller particle size than the aggregate particles 3 and the hydrogen storage alloy particles 2. More specifically, the joints 4 are formed by the mutual bonding of a plurality of metal particles 41 that gather in the gaps between the aggregate particles 3 and in the gaps between the aggregate particles 3 and the hydrogen storage alloy particles 2. The joints 4 have, for example, a mass-like structure in which a large number of metal particles 41 are aggregated, and adjacent metal particles 41 are bonded to each other by solid-state diffusion. The particle size of the metal particles 41 in the joints 4 generally reflects the particle size of the metal particles 41 used to produce the hydrogen storage material 1.

[0030] The joints 4 may be made of any metal, but from the viewpoint of suppressing galvanic corrosion, it is preferable that the joints 4 be made of the same metal as the aggregate particles 3. Furthermore, from the viewpoint of suppressing hydrogen embrittlement, it is preferable that the joints 4 be made of stainless steel.

[0031] The volume-based median diameter of the metal particles 41 is preferably 1 / 20 or less of the volume-based median diameter of the aggregate particles 3. In this case, the surfaces of the aggregate particles 3 can be easily coated with the metal particles 41 during the manufacturing process of the hydrogen absorbing material 1. As a result, the hydrogen absorbing material 1 can be easily obtained. Note that the volume-based median diameter of the metal particles 41 can be measured using, for example, a laser diffraction / scattering particle size distribution analyzer.

[0032] [Method for manufacturing hydrogen storage material 1] In manufacturing the hydrogen absorbing material 1 of this embodiment, for example, the metal particles 41 are attached to the aggregate particles 3 to prepare the composite particles 30, Thereafter, the hydrogen storage alloy particles 2 and the composite particles 30 are mixed to prepare a mixture, The mixture is molded to produce a molded body 100 shown in FIG. The compact 100 may be heated to sinter the compact 100, thereby forming the hydrogen storage material 1.

[0033] In the manufacturing method of this example, metal particles 41 having a smaller particle size than the aggregate particles 3 are used to bond the aggregate particles 3 together and to bond the aggregate particles 3 to the hydrogen storage alloy particles 2. This allows the compact 100 to be sintered at a relatively low temperature. Furthermore, because the metal particles 41 are used to bond the aggregate particles 3 together and the aggregate particles 3 to the hydrogen storage alloy particles 2, the particle sizes of the aggregate particles 3 and the hydrogen storage alloy particles 2 can be increased, and the porosity of the hydrogen storage material 1 can be easily increased.

[0034] In the manufacturing method of this embodiment, first, the metal particles 41 are attached to the surfaces of the aggregate particles 3 to prepare the composite particles 30. In this way, after the metal particles 41 are attached to the surfaces of the aggregate particles 3, the composite particles 30 are mixed with the hydrogen storage alloy particles 2 and sintered, which makes it possible to easily prevent the surfaces of the hydrogen storage alloy particles 2 from being covered with the metal particles 41.

[0035] There is no particular limitation on the method for adhering the metal particles 41 to the surfaces of the aggregate particles 3. For example, after applying a binder (not shown) to the surfaces of the aggregate particles 3, the metal particles 41 can be adhered to the surfaces of the aggregate particles 3 by adhering the metal particles 41 to the binder. As the binder, an organic polymer having adhesive properties such as polyvinyl acetate can be used.

[0036] Next, the hydrogen storage alloy particles 2 and the composite particles 30 are mixed to prepare a mixture. If necessary, a liquid dispersion medium for dispersing the composite particles 30 and the hydrogen storage alloy particles 2 may be added to the mixture. By dispersing the composite particles 30 and the hydrogen storage alloy particles 2 in the liquid dispersion medium and liquefying the mixture, the mixture can be more easily formed into a desired shape. As a result, a hydrogen storage material 1 having a desired shape can be more easily obtained.

[0037] As the liquid dispersion medium, for example, a liquid organic polymer such as polyalkylene oxide or polyvinyl alcohol, or a solution containing such an organic polymer, can be used.

[0038] Furthermore, before mixing the hydrogen storage alloy particles 2 with the composite particles 30, a pore-forming material may be attached to the surface of the hydrogen storage alloy particles 2, if necessary. By using hydrogen storage alloy particles 2 with a pore-forming material attached, it is expected that voids will be more easily formed around the hydrogen storage alloy particles 2 in the hydrogen storage material 1.

[0039] The pore-forming material can be a substance that can be thermally decomposed at a temperature lower than the melting point of the hydrogen storage alloy particles 2. More specifically, the pore-forming material can be an organic polymer such as an acrylic resin, a styrene-based resin, or a urethane resin. From the viewpoint of more reliably forming voids around the hydrogen storage alloy particles 2, it is preferable that the thermal decomposition temperature of the pore-forming material be lower than the sintering temperature of the metal particles 41.

[0040] The form of the pore-forming material is not particularly limited. For example, the pore-forming material may be in the form of a film or particles. The pore-forming material may also be adhered to the surface of the hydrogen storage alloy particles 2 via a pore-forming aid made of an organic substance. As the pore-forming aid, for example, an organic polymer having adhesive properties such as polyvinyl acetate can be used. The thermal decomposition temperature of the pore-forming aid is preferably lower than the sintering temperature of the metal particles 41.

[0041] The amount of pore-forming material attached is preferably 1 part by mass or more and 50 parts by mass or less per 100 parts by mass of hydrogen storage alloy particles 2, more preferably 3 parts by mass or more and 40 parts by mass or less, even more preferably 5 parts by mass or more and 30 parts by mass or less, and particularly preferably 7 parts by mass or more and 20 parts by mass or less.

[0042] By setting the amount of the pore-forming material to be preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more per 100 parts by mass of the hydrogen storage alloy particles 2, voids can be more easily formed around the hydrogen storage alloy particles 2. On the other hand, if the amount of the pore-forming material is too large, the volume ratio of pores in the hydrogen storage material 1 may become excessively high. To more easily avoid such problems, the amount of the pore-forming material to be attached is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, even more preferably 30 parts by mass or less, and particularly preferably 20 parts by mass or less per 100 parts by mass of the hydrogen storage alloy particles 2.

[0043] After preparing the mixture, the mixture is molded into a desired shape to obtain a molded body 100. The molded body 100 thus obtained has a structure in which hydrogen storage alloy particles 2 are uniformly dispersed in composite particles 30, as shown in Fig. 2. The method for molding the mixture is not particularly limited, and an appropriate method may be selected from known methods such as press molding, injection molding, powder rolling, and gelation freezing, depending on the properties of the mixture.

[0044] The compact 100 thus produced is heated to sinter it. When the compact 100 is heated, the metal particles 41 present on the surface of the composite particles 30 and the particles in contact with the metal particles 41 are bonded to each other by solid-phase diffusion. As a result, joints 4 are formed between the aggregate particles 3 and between the aggregate particles 3 and the hydrogen storage alloy particles 2. As a result of the above, a porous hydrogen storage material 1 having a skeleton of the hydrogen storage alloy particles 2, the aggregate particles 3, and the joints 4 can be obtained.

[0045] In the above-described manufacturing method, when sintering the compact 100, it is preferable to heat the compact 100 at a temperature of 950°C or less. In this case, melting of the hydrogen storage alloy particles 2 during sintering and clogging of the pores 11 due to excessive heating can be more easily avoided, and a hydrogen storage material 1 with high porosity can be more easily obtained. The heating time when sintering the compact 100 can be appropriately set depending on the temperature at which the aggregate particles 3, metal particles 41, and hydrogen storage alloy particles 2 melt, the desired sintered state, and the like.

[0046] In the hydrogen storage material 1 of this embodiment, aggregate particles 3 are bonded to each other, and aggregate particles 3 and hydrogen storage alloy particles 2 are bonded to each other via bonding portions 4. The bonding portions 4 are made of metal particles 41 having a smaller particle size than the aggregate particles. Therefore, when the compact 100 is sintered in the manufacturing process of the hydrogen storage material 1, the metal particles 41 present around the aggregate particles 3 begin to bond at a relatively low heating temperature. The metal particles 41 then bond to each other, or to the aggregate particles 3, thereby forming bonding portions 4. Therefore, by making the particle size of the metal particles 41 that make up the bonding portions 4 at least smaller than the particle size of the aggregate particles 3, the bonding portions 4 can be easily formed even when the heating temperature during sintering is low.

[0047] In addition, by lowering the heating temperature during sintering, it is possible to easily prevent the hydrogen storage alloy particles 2 from melting during sintering. Furthermore, by using aggregate particles 3 and hydrogen storage alloy particles 2 with relatively large particle sizes, the porosity of the hydrogen storage material 1 can be easily increased.

[0048] In the manufacturing method of this embodiment, first, metal particles 41 are attached to the surfaces of aggregate particles 3 to form composite particles 30. These composite particles 30 are mixed with hydrogen storage alloy particles 2, and then molded into a desired shape and sintered. By attaching the metal particles 41 used to form the joints 4 to the surfaces of the aggregate particles 3 in this manner, it is possible to easily prevent the surfaces of the hydrogen storage alloy particles 2 from being covered with the metal particles 41. Therefore, according to the manufacturing method of this embodiment, it is possible to easily obtain a hydrogen storage material 1 in which at least a portion of the hydrogen storage alloy particles 2 is exposed to the pores 11.

[0049] (Experimental Example 1) In this example, a hydrogen storage material 102 was produced using hydrogen storage alloy particles 2 and composite particles of aggregate particles 3 and metal particles 41. The hydrogen storage alloy particles 2 used in this example were made of LaNi5 and had a particle size in the range of 45 μm to 100 μm. The aggregate particles 3 and metal particles 41 were both made of stainless steel. The volumetric median diameter of the aggregate particles 3 was 100 μm, and the volumetric median diameter of the metal particles 41 was 3 μm. Note that, among the symbols used in the following experimental examples and embodiments, the same symbols as those used in the previously described embodiments represent the same components as those in the previously described embodiments, unless otherwise specified.

[0050] The specific method for producing the hydrogen absorbing material 102 of this example is as follows. First, polyvinyl acetate was dissolved in acetone to prepare a binder solution with a concentration of 5% by mass. Next, 50 parts by mass of the binder solution was added to 100 parts by mass of aggregate particles 3, and after thorough stirring, the mixture was dried to adhere polyvinyl acetate as a binder to the surfaces of the aggregate particles 3. Next, 7.5 parts by mass of metal particles 41 were added to 67.5 parts by mass of aggregate particles 3, and the mixture was thoroughly stirred to adhere the metal particles 41 to the surfaces of the aggregate particles 3. In this way, composite particles were obtained.

[0051] Separately from the preparation of the composite particles, polyvinyl alcohol was dissolved in distilled water to prepare a dispersion medium with a polyvinyl alcohol concentration of 10%.

[0052] Next, the composite particles, hydrogen storage alloy particles 2, and dispersion medium were mixed in a mass ratio of composite particles:hydrogen storage alloy particles 2:dispersion medium=50:25:25 to produce a slurry mixture containing the composite particles and the hydrogen storage alloy.

[0053] The mixture obtained as described above was poured into a rectangular parallelepiped mold measuring 50 mm in length, 10 mm in width, and 5 mm in thickness, and then cooled to a temperature of -18°C or below. This caused the mixture in the container to gel, resulting in a molded body. This molded body was dried to remove the distilled water, and then heated in an inert gas atmosphere at 500°C for 2 hours to pyrolyze the organic matter in the molded body. The molded body was then sintered by heating at 750°C for 3 hours to obtain hydrogen storage material 102. The porosity of hydrogen storage material 102 was 71.7%, and the bending strength obtained in a four-point bending test was 24 MPa.

[0054] 3 and 4 show examples of SEM images of the surface of the hydrogen storage material 102, obtained by observing the surface of the hydrogen storage material 102 with a scanning electron microscope. As shown in FIG. 3, aggregate particles 3, which are represented in a relatively dark tone, and hydrogen storage alloy particles 2, which are represented in a lighter tone than the aggregate particles 3, are exposed on the surface of the hydrogen storage material 102. As shown in FIG. 4, the hydrogen storage material 102 is a porous body having a skeletal structure consisting of aggregate particles 3, hydrogen storage alloy particles 2, and joints 4, and has pores 11 that include gaps between the aggregate particles 3 and gaps between the aggregate particles 3 and the hydrogen storage alloy particles 2. The pores 11 are open to the surface of the hydrogen storage material 102.

[0055] 4, hydrogen storage alloy particles 2 are exposed in pores 11 of the hydrogen storage material 102, and voids exist around the hydrogen storage alloy particles 2. Bonds 4 derived from metal particles 41 are formed between aggregate particles 3 and between the aggregate particles 3 and the hydrogen storage alloy particles 2, and these particles are bonded via the bonded parts 4.

[0056] The hydrogen absorbing material 102 of this example can achieve the same effects as the hydrogen absorbing material 1 of the first embodiment.

[0057] (Experimental Example 2) In this example, a hydrogen storage material 103 was produced using hydrogen storage alloy particles 2 to which a pore-forming material was attached and composite particles of aggregate particles 3 and metal particles 41. The hydrogen storage alloy particles 2 used in this example were made of LaNi5 and had a particle size in the range of 45 μm to 100 μm. The pore-forming material used was spherical resin particles made of polymethyl methacrylate and having an average particle size of 3 μm ("Ganzpearl (registered trademark) GM-0205S" manufactured by Aica Kogyo Co., Ltd.). The aggregate particles 3 and metal particles 41 were both made of stainless steel. The median diameter of the aggregate particles 3 on a volume basis was 100 μm, and the median diameter of the metal particles 41 on a volume basis was 3 μm.

[0058] The specific method for producing the hydrogen absorbing material 103 of this example is as follows: First, in the same manner as in Experimental Example 1, metal particles 41 were attached to the surfaces of aggregate particles 3 to produce composite particles.

[0059] Also, a pore-forming aid solution with a concentration of 5% by mass was prepared by dissolving polyvinyl acetate as a pore-forming aid in acetone. Next, 50 parts by mass of the pore-forming aid solution was added to 100 parts by mass of hydrogen storage alloy particles 2, and the mixture was thoroughly mixed and dried to adhere the pore-forming aid to the surfaces of the hydrogen storage alloy particles 2. Thereafter, 8 parts by mass of a pore-forming material was added to 100 parts by mass of hydrogen storage alloy particles 2, and the mixture was thoroughly mixed to adhere the pore-forming material to the surfaces of the hydrogen storage alloy particles 2.

[0060] In addition to these preparations, polyvinyl alcohol was dissolved in distilled water to prepare a dispersion medium with a polyvinyl alcohol concentration of 10%.

[0061] Next, the composite particles, the hydrogen storage alloy particles 2 with the pore-forming material attached, and the dispersion medium were mixed in a mass ratio of composite particles:hydrogen storage alloy particles 2:dispersion medium=48:27:25 to produce a slurry mixture containing the composite particles and the hydrogen storage alloy. A compact was produced using this mixture in the same manner as in Experimental Example 1, and the compact was further sintered to obtain the hydrogen storage material 103. The porosity of the hydrogen storage material 103 was 73.5%, and the bending strength measured in a four-point bending test was 20 MPa.

[0062] 5 and 6 show examples of SEM images of the surface of the hydrogen storage material 103 obtained by observing the surface of the hydrogen storage material 103 with a scanning electron microscope. As shown in FIG. 5, aggregate particles 3, which are shown in a relatively dark tone, and hydrogen storage alloy particles 2, which are shown in a lighter tone than the aggregate particles 3, are exposed on the surface of the hydrogen storage material 103. As shown in FIG. 6, the hydrogen storage material 103 is a porous body having a skeletal structure consisting of aggregate particles 3, hydrogen storage alloy particles 2, and joints 4, and has pores 11 that include gaps between the aggregate particles 3 and gaps between the aggregate particles 3 and the hydrogen storage alloy particles 2. The pores 11 are open to the surface of the hydrogen storage material 103.

[0063] 6, hydrogen storage alloy particles 2 are exposed in pores 11 of the hydrogen storage material 103, and voids exist around the hydrogen storage alloy particles 2. Bonds 4 derived from metal particles 41 are formed between aggregate particles 3 and between the aggregate particles 3 and the hydrogen storage alloy particles 2, and these particles are bonded via the bonded parts 4.

[0064] The hydrogen absorbing material 103 of this example can achieve the same effects as the hydrogen absorbing material 1 of the first embodiment.

[0065] (Embodiment 2) In this embodiment, an example of the application of the hydrogen absorbing material 1 will be described. The hydrogen absorbing material 1 may be applied to hydrogen-related equipment configured to be able to reversibly absorb and release hydrogen. For example, the hydrogen absorbing material 1 of this embodiment is used in a hydrogen container 5 configured to be able to reversibly absorb and release hydrogen, as shown in FIG. 7.

[0066] The hydrogen container 5 has a container body 51 with a storage space 511 for storing hydrogen gas, a hydrogen absorbing material 1 arranged in the storage space 511, and a temperature adjustment means 52 configured to change the temperature of the hydrogen absorbing material 1.

[0067] The container body 51 of the hydrogen container 5 is configured to be able to retain hydrogen supplied from outside the hydrogen container 5 and hydrogen released from the hydrogen absorbing material 1 in the storage space 511. The container body 51 has at least one hydrogen port 53 configured to connect the outside of the hydrogen container 5 to the storage space 511. The hydrogen port 53 is configured to connect the external space to the storage space 511, thereby allowing hydrogen to be supplied from outside the hydrogen container 5 to the storage space 511 and / or hydrogen to be released from the hydrogen container 5 to the outside. The number of hydrogen ports 53 provided in the container body 51 may be one or two or more. For example, as shown in FIG. 7 , the container body 51 of this embodiment has one hydrogen port 53, and is configured so that the hydrogen port 53 can be used both to supply hydrogen from outside the hydrogen container 5 to the storage space 511 and to release hydrogen from the hydrogen container 5 to the outside.

[0068] The shape of the container body 51 is not particularly limited, and various shapes such as a cylindrical shape, a spherical shape, a box shape, etc. For example, the container body 51 of this embodiment has a cylindrical shape as shown in FIG.

[0069] The hydrogen absorbing material 1 is provided in the storage space 511 of the container body 51. The number, shape, arrangement, etc. of the hydrogen absorbing materials 1 provided in the container body 51 are not particularly limited, and can be set appropriately depending on the desired maximum hydrogen storage amount, the pressure when releasing hydrogen from the hydrogen container 5, etc.

[0070] The temperature adjustment means 52 can change the temperature of the hydrogen absorbing material 1, thereby releasing hydrogen absorbed in the hydrogen absorbing material 1 from the hydrogen absorbing material 1 to the storage space 511, or storing hydrogen in the storage space 511 in the hydrogen absorbing material 1. The method for changing the temperature of the hydrogen absorbing material 1 in the temperature adjustment means 52 is not particularly limited and can take various forms. For example, the temperature adjustment means 52 in this embodiment is configured to change the temperature of the hydrogen absorbing material 1 by heating or cooling the entire container body 51. Therefore, for example, by increasing the temperature of the hydrogen absorbing material 1 with the temperature adjustment means 52, hydrogen can be released from the hydrogen absorbing material 1 to the storage space 511. Also, for example, by lowering the temperature of the hydrogen absorbing material 1, hydrogen in the storage space 511 can be stored in the hydrogen absorbing material 1.

[0071] As described above, the hydrogen storage alloy particles 2 in the hydrogen storage material 1 are held within the pores 11 of the hydrogen storage material 1. Therefore, the hydrogen storage material 1 can reduce the amount of change in volume when hydrogen is absorbed. Therefore, by applying the hydrogen storage material 1 to the hydrogen container 5 as in this embodiment, the load applied to the container body 51 when hydrogen is absorbed into the hydrogen storage material 1 can be more easily reduced, making it less likely that distortion will occur in the container body 51. Furthermore, in this case, hydrogen can be stored more efficiently in the hydrogen container 5.

[0072] The hydrogen absorbing material 1 used in the hydrogen container 5 preferably has hydrogen storage alloy particles made of a TiFe-based hydrogen storage alloy. TiFe-based hydrogen storage alloys are easy to handle, so by applying hydrogen storage alloy particles made of a TiFe-based hydrogen storage alloy to the hydrogen absorbing material 1 of the hydrogen container 5, the safety of the hydrogen container 5 can be further improved. In addition, TiFe-based hydrogen storage alloys are relatively inexpensive among hydrogen storage alloys, so further cost reductions in the hydrogen container 5 can be expected.

[0073] The TiFe-based alloys mentioned above include TiFe binary alloys and TiFe-based multi-component alloys in which part of the Ti and / or Fe in the TiFe binary alloy is substituted with other elements. The TiFe-based alloy may be, for example, a TiFeMn ternary alloy in which part of the Fe in the TiFe binary alloy is substituted with Mn. The TiFe-based alloy may also be a multi-component alloy obtained by further adding other metal elements to the TiFeMn ternary alloy.

[0074] The above describes the hydrogen storage body, its manufacturing method, and hydrogen container based on embodiments 1 to 3, but the specific aspects of the hydrogen storage body, its manufacturing method, and hydrogen container of the present invention are not limited to the above embodiments and experimental examples, and the configuration can be changed as appropriate within the scope that does not deviate from the gist of the present invention. [Explanation of symbols]

[0075] 1, 102, 103 Hydrogen storage material 2. Hydrogen storage alloy particles 3 Aggregate particles 4 Joint 41 Metal particles

Claims

1. A hydrogen storage material having pores, hydrogen storage alloy particles; aggregate particles made of a metal that does not have hydrogen storage capacity; bonding portions that bond the aggregate particles to each other and to the hydrogen storage alloy particles and the aggregate particles; At least a portion of the hydrogen storage alloy particles is exposed to the pores, The hydrogen storage material, wherein the joints are made of metal particles having a particle size smaller than that of the aggregate particles.

2. 2. The hydrogen storage material according to claim 1, wherein the median diameter of the metal particles on a volume basis is 1 / 20 or less of the median diameter of the aggregate particles on a volume basis.

3. 2. The hydrogen storage material according to claim 1, wherein the porosity of the hydrogen storage material is 9% or more.

4. 2. The hydrogen storage material according to claim 1, wherein the bending strength of the hydrogen storage material is 3.3 MPa or more.

5. 2. The hydrogen absorbing material according to claim 1, wherein the mass ratio of the hydrogen absorbing alloy particles in the hydrogen absorbing material is 20 mass % or more and 50 mass % or less.

6. 2. The hydrogen storage material according to claim 1, wherein the aggregate particles are made of stainless steel.

7. 2. The hydrogen storage material according to claim 1, wherein the aggregate particles and the joints are made of the same metal.

8. A method for producing a hydrogen storage material according to any one of claims 1 to 7, forming composite particles by attaching metal particles to the aggregate particles; Then, the hydrogen storage alloy particles and the composite particles are mixed to prepare a mixture, The mixture is molded to produce a molded body; The hydrogen absorbing material is formed by sintering the compact.

9. The method for producing a hydrogen storage material according to claim 8, wherein the porosity of the molded body is 9% or more.

10. 9. The method for producing a hydrogen absorbing material according to claim 8, wherein the compact is heated at a temperature of 950° C. or less in sintering the compact.

11. 9. The method for producing a hydrogen storage material according to claim 8, wherein a pore-forming material is first attached to the surface of the hydrogen storage alloy particles, and then the hydrogen storage alloy particles to which the pore-forming material is attached are mixed with the composite particles to produce the mixture.

12. A hydrogen container comprising the hydrogen absorbing material according to any one of claims 1 to 7.

13. 13. The hydrogen container according to claim 12, wherein the hydrogen storage alloy particles in the hydrogen storage body are made of a TiFe-based hydrogen storage alloy.

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