Hydrogen storage body, method for producing same, and hydrogen container

Abstract

A hydrogen storage body (1) is provided with a metal porous body (2) having pores (21), and hydrogen storage alloy particles (3) comprising a hydrogen storage alloy and held in the pores (21) of the metal porous body (2). The pores (2) have accommodation spaces (211) in which the hydrogen storage alloy particles (3) are accommodated. The average value of the ratio (Dopeningg / dMH) of the opening diameter (Dopening (unit: [mu] m) of the accommodation space (211) in which the hydrogen storage alloy particles (3) are accommodated, represented by the following formula, to the circumscribed circle equivalent diameter (dMH (unit: [mu] m)) of each hydrogen storage alloy particle (3) obtained by observing the surface of the hydrogen storage body (1), is greater than or equal to the cubic root of the volume expansion ratio when hydrogen is occluded in the hydrogen storage alloy particles (3). Dopen = (Dmax + Dmin) / 2, where Dmax is the diameter (unit: [mu] m) of the smallest circle among the circumscribed circles of the opening of the housing space (211), and Dmin is the diameter (unit: [mu] m) of the largest circle among the inscribed circles of the opening of the housing space (211).

Description

Technical Field

[0001] This invention relates to a hydrogen storage medium, a method for manufacturing the same, and a hydrogen container. Background Technology

[0002] In recent years, the environmental burden caused by the use of fossil fuels has become a cause for concern, and there is a growing expectation to utilize hydrogen, which has a lower environmental impact, as an energy source. To utilize hydrogen as an energy source, devices are sometimes used that include a hydrogen storage medium capable of reversibly absorbing and releasing hydrogen. For example, Patent Document 1 describes a hydrogen tank that uses a hydrogen storage medium to store hydrogen. Additionally, Patent Document 2 describes, for example, a hydrogen pressurization system that uses a hydrogen storage medium to pressurize hydrogen.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2007-309457

[0006] Patent Document 2: Japanese Patent Application Publication No. 2019-19884 Summary of the Invention

[0007] Powdered hydrogen storage alloys are commonly used as hydrogen storage media in hydrogen tanks and hydrogen pressurization systems. However, these alloys exhibit the characteristic of expanding when absorbing hydrogen and contracting when releasing it. Furthermore, if powdered hydrogen storage alloys are filled into containers such as hydrogen tanks and pressurization systems, the alloy is densely packed at the bottom, creating gaps at the top. This uneven distribution of the alloy within the container can lead to hydrogen absorption, raising concerns about high stress on the container due to the alloy's expansion.

[0008] To mitigate the problems caused by the expansion of the hydrogen storage alloy, a technique has been proposed that involves interposing resin between the particles of the hydrogen storage alloy, causing the resin to deform when the alloy expands, thereby alleviating stress on the container. However, due to the high thermal resistance of the resin, the temperature of the hydrogen storage alloy is difficult to change if the resin is interposed between the particles. Therefore, in this case, there is a problem that it is difficult to rapidly achieve hydrogen adsorption into the hydrogen storage alloy and hydrogen release from it.

[0009] The present invention was made in view of the above-mentioned problems, and its object is to provide a hydrogen storage body with small volume change and excellent thermal conductivity during hydrogen adsorption, a method for manufacturing the same, and a hydrogen container having the hydrogen storage body.

[0010] One aspect of the present invention is to provide a hydrogen storage medium having:

[0011] Porous metals, which possess micropores; and

[0012] Hydrogen storage alloy particles, which are composed of hydrogen storage alloy and are retained within the fine pores of the aforementioned metal porous body;

[0013] The aforementioned fine pores have a containing space for accommodating the aforementioned hydrogen storage alloy particles.

[0014] The opening diameter D of the containment space containing the hydrogen storage alloy particles is shown in equation (1) below. opening (Unit: μm) and the equivalent diameter d of the circumscribed circle of the hydrogen storage alloy particle obtained by observing the surface of the hydrogen storage body. MH (Unit: μm) ratio D opening / d MH The average value is the root of the cube of the volume expansion ratio when hydrogen is retained in the above-mentioned hydrogen storage alloy particles.

[0015] D opening = (D) max +D min ) / 2···(1)

[0016] Wherein, D in equation (1) above max D is the diameter (in μm) of the smallest circle tangent to the opening of the aforementioned containment space on the surface of the hydrogen storage body. min It is the diameter (unit: μm) of the largest circle among the circles tangent to the opening of the aforementioned containment space on the surface of the aforementioned hydrogen storage body.

[0017] The hydrogen storage alloy particles in the aforementioned hydrogen storage body are contained within the pores of the porous metal body. Furthermore, the opening diameter D of the containing space for the hydrogen storage alloy particles... opening (Unit: μm) Equivalent diameter d of the circumscribed circle of the above hydrogen storage alloy particles MH (Unit: μm) ratio D opening / d MH The average value is within the specific range mentioned above. In the aforementioned hydrogen storage medium, by making the aforementioned ratio D... opening / d MH Within the aforementioned specific range, the average value allows for the formation of sufficiently wide voids around the hydrogen storage alloy particles contained within the containment space. Furthermore, by creating voids around the hydrogen storage alloy particles, even when hydrogen is adsorbed within the particles and the particles expand within the containment space, it is easy to prevent the hydrogen storage alloy particles from compressing the porous metal body. Therefore, the aforementioned hydrogen storage body can reduce the amount of volume change when hydrogen is adsorbed.

[0018] Furthermore, the aforementioned porous metal has high thermal conductivity. Therefore, when the temperature of the hydrogen storage body is changed, the temperature of the hydrogen storage alloy particles contained within the porous metal can change rapidly. This allows for rapid hydrogen adsorption into and release from the hydrogen storage body.

[0019] As described above, a hydrogen storage medium with small volume change and excellent thermal conductivity can be provided according to the above method. Attached Figure Description

[0020] Figure 1 This is a partial cross-sectional view showing the main part of the hydrogen storage body in Embodiment 1.

[0021] Figure 2 This is a partial cross-sectional view showing the main part of the molded body of the mixture in the method for manufacturing the hydrogen storage body according to Embodiment 1.

[0022] Figure 3 This is a partial cross-sectional view showing the main part of the hydrogen storage body in Embodiment 2.

[0023] Figure 4 This is a partial cross-sectional view showing the main part of the resin foam in the method for manufacturing the hydrogen storage body according to Embodiment 2.

[0024] Figure 5 This is a SEM image of the surface of the hydrogen storage body in Experiment Example 1.

[0025] Figure 6 It is Figure 5 The magnified SEM image of the opening of the fine pores in the image.

[0026] Figure 7 This is a magnified SEM image of the fine pores on the surface of the hydrogen storage body in Experiment Example 2.

[0027] Figure 8 This is a partial cross-sectional view showing the main part of the hydrogen container in Embodiment 3. Detailed Implementation

[0028] (Implementation Method 1)

[0029] Reference Figures 1-2 The embodiments of the above-described hydrogen storage medium will be described. For example... Figure 1 As shown, the hydrogen storage body 1 of this method has: a metal porous body 2 with fine pores 21, and hydrogen storage alloy particles 3 made of hydrogen storage alloy and held in the fine pores 21 of the metal porous body 2.

[0030] [Porous metal body 2]

[0031] The porous metal 2 is composed of metal and has fine pores 21 for retaining hydrogen storage alloy particles 3. For example... Figure 1 As shown, the pores 21 of the porous metal body 2 have receiving spaces 211 for accommodating hydrogen storage alloy particles 3. The shape of the receiving spaces 211 is not particularly limited and can take various shapes. When the hydrogen storage body 1 is made using a pore-forming material as described later, sometimes the receiving spaces 211 formed by spherical spaces are formed in the porous metal body 2. It should be noted that the "spherical" shape mentioned above includes not only the geometrically defined sphere, but also shapes that are generally considered to be spherical, such as those with concave and convex shapes on the inner surface of the sphere, or shapes obtained by deforming the sphere by rotating an ellipsoid.

[0032] like Figure 6 As shown in the example, the receiving space 211 containing the hydrogen storage alloy particles 3 opens on the surface of the hydrogen storage body 1. The opening diameter D of the receiving space 211 containing the hydrogen storage alloy particles 3 is shown in the following formula (1). opening (Unit: μm) and the equivalent diameter d of the circumscribed circle of each hydrogen storage alloy particle 3 obtained by observing the surface of the hydrogen storage body 1. MH (Unit: μm) ratio D opening / d MH The average value is the cube root of the volume expansion ratio when hydrogen is retained in the hydrogen storage alloy particle 3.

[0033] D opening = (D) max +D min ) / 2···(1)

[0034] Wherein, D in equation (1) above max D is the diameter (in μm) of the smallest circle tangent to the surface of the hydrogen storage body 1 and the opening of the containing space 211. min It is the diameter (unit: μm) of the largest circle among the circles inscribed in the surface of the hydrogen storage body 1 and the opening of the containment space 211.

[0035] In addition, the equivalent diameter d of the circumscribed circle of the hydrogen storage alloy particle 3 MH (Unit: μm) is the diameter of the smallest circle (unit: μm) circumscribed on the surface of the hydrogen storage body 1 and the hydrogen storage alloy particle 3. Moreover, specifically, the volume expansion ratio when hydrogen is retained in the hydrogen storage alloy particle 3 is the ratio of the volume of the hydrogen storage alloy particle 3 in the fully hydrogenated state to the volume of the hydrogen storage alloy particle 3 in the state without hydrogen retention.

[0036] In the hydrogen storage medium 1, if hydrogen is adsorbed into the hydrogen storage alloy particles 3, the hydrogen storage alloy particles 3 will expand as described above. Furthermore, the volume of the expanded hydrogen storage alloy particles 3 is the volume of the unadsorbed hydrogen particles multiplied by the aforementioned expansion ratio. Here, it is assumed that the expansion of the hydrogen storage alloy particles 3 occurs isotropically; therefore, it is assumed that the particle size of the hydrogen storage alloy particles 3 in the hydrogen-adsorbed state is approximately the cube root of the particle size of the unadsorbed hydrogen storage alloy particles 3 multiplied by the expansion ratio of the hydrogen storage alloy particles 3.

[0037] On the other hand, the opening diameter D of the receiving space 211 shown in the above formula (1) is... opening This represents the average size of the opening of the receiving space 211 that opens onto the surface of the hydrogen storage body 1. Furthermore, the internal size of this receiving space 211 is always equal to the opening diameter D of the receiving space 211. opening The values ​​above.

[0038] Therefore, in hydrogen storage 1, by making the above ratio D opening / d MH The average value is greater than the cube root of the expansion ratio of the hydrogen storage alloy particles 3, which can form a sufficiently wide void around the hydrogen storage alloy particles 3 contained in the containment space 211. As a result, when the hydrogen storage alloy particles 3 expand in the containment space 211, it is easy to avoid the hydrogen storage alloy particles 3 squeezing the metal porous body 2, and reduce the amount of volume change of the hydrogen storage body 1 under the condition of hydrogen adsorption.

[0039] From the perspective of obtaining the above effects more reliably, the above is better than D. opening / d MH The average value is preferably 1.05 or higher, and more preferably 1.10 or higher.

[0040] It should be noted that the above is compared to D. opening / d MH The average value is calculated, for example, using the following method. First, the surface of the hydrogen storage body 1 is observed using a scanning electron microscope (i.e., SEM), and magnified photographs of multiple containment spaces 211 are obtained. Next, based on the magnified photographs of each containment space 211, the equivalent diameter d of the circumscribed circle of the hydrogen storage alloy particles 3 contained in the containment space 211 is measured. MH (Unit: μm) The diameter D of the smallest circle among the circles circumscribed outside the opening of the receiving space 211. max (Unit: μm) and the diameter D of the largest of the circles tangent to the opening of the containment space 211. min (Unit: μm). Then, using these values, the aforementioned ratio D of each containment space 211 is calculated. opening / d MH Then, for multiple containment spaces 211, the obtained ratio D is... opening / dMH The above ratio D can be obtained by taking the arithmetic mean of the values. opening / d MH The average value.

[0041] Used to calculate the above ratio D opening / d MH The number of average-valued containment spaces 211 is not particularly limited, and is calculated by increasing the number of spaces used to calculate the above ratio D. opening / d MH The average number of containment spaces 211 allows for a more accurate calculation of the aforementioned ratio D. opening / d MH The average value. Used to calculate the above ratio D. opening / d MH The average number of containment spaces 211 is, for example, only 5 or more.

[0042] Furthermore, the expansion ratio of the hydrogen storage alloy particles 3 described above can be calculated, for example, based on the volume expansion rate of the hydrogen storage alloy during hydrogen absorption as recorded in various documents. More specifically, when the volume expansion rate of the hydrogen storage alloy constituting the hydrogen storage alloy particles 3 is expressed as k (unit: %), the expansion ratio of the hydrogen storage alloy particles 3 is expressed by the following formula (2). In addition, the volume expansion rate of the hydrogen storage alloy during hydrogen absorption can be determined, for example, by comparing the volume of a unit lattice obtained by X-ray diffraction.

[0043] Expansion ratio = (k + 100) / 100 ... (2)

[0044] The size of the containment space 211 can be controlled, for example, in the manufacturing method described later, by adjusting the amount of pore-forming material and pore-forming aid attached to the hydrogen storage alloy particles 3. More specifically, for example, if a wider containment space 211 is desired, more pore-forming material and / or pore-forming aid can be attached to the hydrogen storage alloy particles 3, or pore-forming material with a larger particle size can be attached to the hydrogen storage alloy particles 3.

[0045] like Figure 1As shown, the pores 21 of the porous metal body 2, in addition to the receiving space 211, may also have connecting spaces 212. These connecting spaces 212 connect the receiving space 211 to adjacent receiving spaces and to the outside of the porous metal body 2. For example, the porous metal body 2 in this embodiment is composed of a sintered metal powder 22, and the gaps between the metal particles 221 constituting the metal powder 22 form the connecting spaces 212 of the pores 21. Thus, by providing the connecting spaces 212 in the porous metal body 2, hydrogen supplied from the outside of the porous metal body 2 can be introduced into the hydrogen storage alloy particles 3 through the connecting spaces 212 and the receiving space 211 of the pores 21, causing it to be retained in the hydrogen storage alloy particles 3. Furthermore, the hydrogen storage body 1 can introduce hydrogen released from the hydrogen storage alloy particles 3 to the outside of the porous metal body 2 through the receiving spaces 211 and the connecting spaces 212 of the pores 21.

[0046] On the surface of the hydrogen storage body 1, the diameter of the largest circle among the circles inscribed within the opening of the connecting space 212 is preferably smaller than the median particle size of the hydrogen storage alloy particles 3 based on volume. In this case, the hydrogen storage alloy particles 3 are less likely to pass through the connecting space 212, thus making it easier to prevent the hydrogen storage alloy particles 3 from falling out of the housing space 211.

[0047] When the porous metal body 2 is composed of a sintered metal powder 22, the median particle size of the metal particles 221 constituting the metal powder 22 is preferably smaller than the median particle size of the hydrogen storage alloy particles 3. In this case, the metal powder 22 can be sintered at a lower temperature during the manufacturing process of the hydrogen storage body 1. Therefore, the porous metal body 2 can be formed while suppressing the deterioration of the hydrogen storage alloy particles 3 caused by heating during sintering. From the viewpoint of more reliably obtaining the above-mentioned effects, the average particle size of the metal particles 221 constituting the metal powder 22 is preferably less than 1 / 2 times the average particle size of the hydrogen storage alloy particles 3, more preferably less than 1 / 5 times, and even more preferably less than 1 / 10 times.

[0048] It should be noted that the average particle size of the metal particles 221 and the median particle size of the hydrogen storage alloy particles 3, as defined above, are the cumulative 50% particle sizes determined based on the particle size distribution of the volume reference. The particle size distribution of the volume reference can be obtained, for example, using a laser diffraction / scattering particle size analyzer.

[0049] In the hydrogen storage 1 of this method, the average particle size of the metal particles 221 constituting the metal powder 22 can be appropriately set, for example, from a range of 0.1 μm to 20 μm.

[0050] The pores 21 of the metal porous body 2 preferably have a continuous pore structure, that is, each pore 21 is connected to other pores 21. In this case, hydrogen can more easily flow throughout the hydrogen storage body 1, thus enabling a greater amount of hydrogen to be absorbed in the hydrogen storage body 1.

[0051] The metal constituting the porous metal 2 can be any metal other than a hydrogen storage alloy, i.e., a metal that cannot reversibly absorb and release hydrogen. More specifically, the metal constituting the porous metal 2 can be iron, iron alloys, copper, copper alloys, aluminum, aluminum alloys, nickel, and nickel alloys, etc.

[0052] The metal constituting the porous metal 2 preferably has a melting point lower than that of the hydrogen storage alloy. In this case, when manufacturing the hydrogen storage body 1, the porous metal 2 can be formed while suppressing the deterioration of the hydrogen storage alloy particles 3 caused by heating.

[0053] [Hydrogen storage alloy particles 3]

[0054] The hydrogen storage alloy particles 3 are made of a hydrogen storage alloy and are held within the receiving space 211 of the fine pores 21 of the metal porous body 2. A portion of the surface of the hydrogen storage alloy particles 3 is preferably separated from the metal porous body 2. Thus, by providing a gap between the hydrogen storage alloy particles 3 and the metal porous body 2, it is easier to prevent the hydrogen storage alloy particles 3 from expanding to the outer edge of the receiving space 211 of the metal porous body 2, thereby preventing deformation of the metal porous body 2, when hydrogen is absorbed. Therefore, in this case, it is easier to suppress the expansion of the hydrogen storage body 1 during hydrogen absorption.

[0055] The hydrogen storage alloy particles 3 can be fixed to the inner surface of the porous metal body 2, or they can be kept movable within the pores 21 of the porous metal body 2. In either case, by housing the hydrogen storage alloy particles 3 within the housing space 211, it is easier to prevent the hydrogen storage alloy particles 3 from expanding to the outer side of the pores 21 of the porous metal body 2 when absorbing hydrogen. As a result, it is easier to suppress the expansion of the hydrogen storage body 1 when absorbing hydrogen.

[0056] From the viewpoint of further reducing the thermal resistance between the hydrogen storage alloy particles 3 and the metal porous body 2 and further improving the thermal conductivity of the hydrogen storage body 1, it is preferable to join a portion of the surface of the hydrogen storage alloy particles 3 to the metal porous body 2.

[0057] The composition of the hydrogen storage alloy constituting the hydrogen storage alloy particle 3 is not particularly limited. For example, the hydrogen storage alloy constituting the hydrogen storage alloy particle 3 can be an AB5 type rare earth alloy such as LaNi5 and mixed rare earth-nickel alloy, an AB2 type Laves phase alloy such as MgZn2 and ZrNi2, an AB type titanium alloy such as TiFe and TiCo, an A2B type magnesium alloy such as Mg2Ni and Mg2Cu, or a solid solution type BCC alloy such as Ti-V alloy and Ti-Cr alloy.

[0058] The average particle size of the hydrogen storage alloy particles 3 can be appropriately set, for example, in the range of 1 μm to 200 μm.

[0059] [Method for manufacturing hydrogen storage 1]

[0060] In manufacturing the hydrogen storage body 1 according to this method, for example, simply attaching the pore-forming material 213 to the surface of the hydrogen storage alloy particles 3,

[0061] Then, the hydrogen storage alloy particles 3 are mixed with the metal powder 22, which becomes a porous metal body 2, to prepare a mixture.

[0062] Made by shaping the mixture Figure 2 The molded body 10 shown,

[0063] The porous metal body 2 is formed by heating the molded body 10, removing the pore-forming material 213, and sintering the metal powder 22.

[0064] Thus, the hydrogen storage alloy particles 3, pre-attached with pore-forming material 213, are heated together with metal powder 22 to remove the pore-forming material 213. This creates a containment space 211 around the hydrogen storage alloy particles 3, and connecting spaces 211 formed between the containment spaces 211, each consisting of a gap narrower than the containment space 211. The containment space 211 formed in this way has a cage-like shape to contain the hydrogen storage alloy particles 3. Therefore, according to the above manufacturing method, the hydrogen storage alloy particles 3 can be held within the containment space 211 of the fine pores 21 of the metal porous body 2.

[0065] In this manufacturing method, firstly, a pore-forming material 213 is attached to the surface of the hydrogen storage alloy particles 3. The pore-forming material 213 can be a substance capable of thermal decomposition at a temperature below the melting point of the hydrogen storage alloy particles 3. More specifically, organic polymers such as acrylic resin, styrene-based resin, and urethane resin can be used as the pore-forming material 213. From the viewpoint of more reliably forming voids around the hydrogen storage alloy particles 3, the thermal decomposition temperature of the pore-forming material 213 is preferably lower than the sintering temperature of the metal powder 22.

[0066] The morphology of the pore-forming material 213 is not particularly limited. For example, the pore-forming material 213 can be in the form of a film or particles. Furthermore, the pore-forming material 213 can be bonded to the surface of the hydrogen storage alloy particles 3 via a pore-forming aid composed of an organic material. For example, an adhesive organic polymer such as polyvinyl acetate can be used as the pore-forming aid. The thermal decomposition temperature of the pore-forming aid is preferably lower than the sintering temperature of the metal powder 22.

[0067] The amount of pore-forming material 213 attached relative to 100 parts by mass of hydrogen storage alloy particles 3 is preferably 1 to 50 parts by mass, more preferably 3 to 40 parts by mass, further preferably 5 to 30 parts by mass, and particularly preferably 7 to 20 parts by mass.

[0068] By ensuring that the amount of pore-forming material 213 attached is preferably 1 part by mass or more, more preferably 3 parts by mass or more, further preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more, relative to 100 parts by mass of hydrogen storage alloy particles 3, the voids formed around the hydrogen storage alloy particles 3 can be appropriately enlarged. Furthermore, by ensuring that the amount of pore-forming material 213 attached is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, further preferably 30 parts by mass or less, and particularly preferably 20 parts by mass or less, relative to 100 parts by mass of hydrogen storage alloy particles 3, a greater amount of hydrogen storage alloy particles 3 can be retained in the hydrogen storage body 1, resulting in a greater amount of hydrogen that can be adsorbed into the hydrogen storage body 1. In addition, in this case, it is easier to avoid an excessively high volume ratio of the fine pores 21 in the metal porous body 2. As a result, it is easier to avoid a decrease in the strength of the metal porous body 2.

[0069] Next, the hydrogen storage alloy particles 3 with the pore-forming material 213 attached are mixed with the metal powder 22, which becomes a metal porous body 2, to prepare a mixture. The content of the hydrogen storage alloy particles 3 in the mixture relative to the total mass of the hydrogen storage alloy particles 3 and the metal powder 22 is preferably 40% to 90% by mass, more preferably 45% to 85% by mass, further preferably 50% to 80% by mass, and particularly preferably 55% to 75% by mass.

[0070] By making the content of hydrogen storage alloy particles 3 in the mixture preferably 40% by mass or more, more preferably 45% by mass or more, further preferably 50% by mass or more, and particularly preferably 55% by mass or more, the amount of hydrogen storage alloy particles 3 retained in the hydrogen storage body 1 can be increased, and the amount of hydrogen that can be retained in the hydrogen storage body 1 can be increased.

[0071] Furthermore, by ensuring that the content of hydrogen storage alloy particles 3 in the mixture is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, and particularly preferably 75% by mass or less, relative to the total mass of the hydrogen storage alloy particles 3 and the metal powder 22, it is easy to avoid an excessively high volume ratio of the fine pores 21 in the porous metal body 2. As a result, it is easier to avoid a decrease in the strength of the porous metal body 2.

[0072] To the mixture, a liquid dispersion medium for dispersing the hydrogen storage alloy particles 3 and the metal powder 22 can be added as needed. By dispersing the hydrogen storage alloy particles 3 and the metal powder 22 in the liquid dispersion medium, the mixture is made into a liquid state, making it easier to shape the mixture into the desired form. As a result, a hydrogen storage body 1 of the desired shape can be obtained.

[0073] As a liquid dispersion medium, liquid organic polymers such as polyoxyalkylene or polyvinyl alcohol, or solutions containing these organic polymers, can be used.

[0074] After preparing the mixture, it is molded into the desired shape to obtain molded body 10. For example... Figure 2 As shown, the molded body 10 obtained in this manner has a structure in which hydrogen storage alloy particles 3 with attached pore-forming material 213 are embedded in metal powder 22. The molding method for the mixture is not particularly limited; any appropriate method can be selected from known methods such as compression molding, injection molding, powder rolling, and gelation freezing, depending on the properties of the mixture.

[0075] The molded body 10 obtained in this manner is heated at a temperature higher than the thermal decomposition temperature of the pore-forming material 213 and the sintering temperature of the metal powder 22, but lower than the melting point of the hydrogen storage alloy particles 3. When the molded body 10 is heated at this temperature, the pore-forming material 213 adhering to the hydrogen storage alloy particles 3 disappears due to thermal decomposition, forming a containment space 211 around the hydrogen storage alloy particles 3. Furthermore, the metal powder 22 present around the hydrogen storage alloy particles 3 integrates, becoming a metal porous body 2. Therefore, by heating the molded body 10 at the aforementioned temperature, a hydrogen storage body 1 can be obtained.

[0076] like Figure 1 As shown, in this embodiment, the hydrogen storage alloy particles 3 in the hydrogen storage body 1 are held within the receiving space 211 in the fine pores 21 of the metal porous body 2. Furthermore, the opening diameter D of the receiving space 211 containing the hydrogen storage alloy particles 3 is... opening (Unit: μm) Equivalent diameter d of the circumscribed circle of hydrogen storage alloy particle 3 MH (Unit: μm) ratio D opening / d MHThe average value is greater than or equal to the cube root of the volume expansion ratio when hydrogen is retained in the aforementioned hydrogen storage alloy particles. Therefore, even when hydrogen is retained in the hydrogen storage alloy particles 3 and the hydrogen storage alloy particles 3 expand within the containing space 211, it is easy to prevent the hydrogen storage alloy particles from compressing the porous metal body 2. Therefore, the hydrogen storage body 1 can reduce the amount of volume change when hydrogen is retained.

[0077] Furthermore, the porous metal body 2 of this method has high thermal conductivity. Therefore, when the temperature of the hydrogen storage body 1 is changed, the temperature of the hydrogen storage alloy particles 3 held in the containment space 211 of the porous metal body 2 can be changed rapidly. As a result, the adsorption of hydrogen into the hydrogen storage body 1 and the release of hydrogen from the hydrogen storage body 1 can be carried out rapidly.

[0078] Therefore, the hydrogen storage body 1 of this method exhibits small volume change during hydrogen adsorption and excellent thermal conductivity.

[0079] (Implementation Method 2)

[0080] In this embodiment, examples of other types of hydrogen storage bodies will be described. It should be noted that, unless otherwise specified, any symbols used in this embodiment that are identical to those used in previously described embodiments represent the same constituent elements as those in previously described embodiments.

[0081] like Figure 3 As illustrated in the example, the metal porous body 202 in the hydrogen storage body 102 of this embodiment has a three-dimensional network structure comprising columnar supports 23 and a central core 24 formed by an assembly of multiple supports 23. The voids surrounding the supports 23 and the central core 24 constitute fine pores 21. The fine pores 21 in the metal porous body 202... Figure 3 The parts not shown are interconnected. In other words, the metal porous body 202 has a continuous porous structure.

[0082] Hydrogen storage alloy particles 3 are maintained within the three-dimensional network structure of the metal porous body 202. Voids are formed between the metal porous body 202 and the hydrogen storage alloy particles 3, and the voids surrounding the hydrogen storage alloy particles 3 in the fine pores 21 constitute a receiving space 211. Furthermore, the portion of the fine pores 21 excluding the receiving space 211 constitutes a connecting space 212.

[0083] When manufacturing the hydrogen storage body 102 according to this method,

[0084] As long as the pore-forming material 213 is attached to the surface of the hydrogen storage alloy particles 3,

[0085] Then, make Figure 4 The resin foam 4 shown contains hydrogen storage alloy particles 3 and has a continuous porous structure.

[0086] A metal film, forming a metal porous body 202, is formed on the surface of the bubble wall 42 of the resin foam 4.

[0087] Then, by heating the resin foam 4, the pore-forming material 213 is removed, and the bubble wall 42 is removed to form a metal porous body 202.

[0088] In this manufacturing method, firstly, the pore-forming material 213 is attached to the surface of the hydrogen storage alloy particle 3. The composition of the hydrogen storage alloy particle 3, the composition of the pore-forming material 213, and the amount of pore-forming material 213 attached in this manufacturing method are the same as those in Embodiment 1.

[0089] Next, the hydrogen storage alloy particles 3 with the pore-forming material 213 attached are mixed with a foaming resin, and the foaming resin is foamed to produce a resin foam 4 containing the hydrogen storage alloy particles 3. The bubbles 41 of the resin foam 4 obtained in this way have a continuous pore structure, that is, a structure in which multiple bubbles are interconnected. In addition, for example, Figure 4 As shown, the bubble wall 42 of the resin foam 4 has a three-dimensional network structure with columnar supports 421 and a central hub 422 formed by multiple supports 421. Furthermore, the hydrogen storage alloy particles 3 are held within the bubble wall 42 of the resin foam 4.

[0090] The foaming resin used to make the resin foam 4 is not particularly limited, and any known foaming resin capable of forming a continuous pore structure can be used. For example, the resin constituting the resin foam 4 can be polyurethane, polyethylene, polystyrene, etc. Furthermore, the method for foaming the foaming resin is not particularly limited, and known foaming methods can be used.

[0091] The content of hydrogen storage alloy particles 3 in the resin foam 4 is preferably in the range of 1% to 55% relative to the apparent volume of the resin foam 4, i.e., the volume of the resin foam 4 including the bubbles 41.

[0092] By making the content of hydrogen storage alloy particles 3 in the resin foam 4 preferably 10% by volume or more, more preferably 20% by volume or more, and even more preferably 30% by volume or more relative to the apparent volume of the resin foam 4, it is possible to increase the amount of hydrogen storage alloy particles 3 retained in the hydrogen storage body 102 and increase the amount of hydrogen that can be retained in the hydrogen storage body 102.

[0093] It should be noted that the content of hydrogen storage alloy particles 3 in the resin foam 4 can be adjusted by the mixing ratio of foaming resin and hydrogen storage alloy particles 3 and the foaming ratio of foaming resin.

[0094] After obtaining the resin foam 4 containing hydrogen storage alloy particles 3 and having a continuous porous structure as described above, a metal film is formed on the surface of the bubble walls 42 in the resin foam 4. The method for forming the metal film on the surface of the bubble walls 42 is not particularly limited. From the viewpoint of uniformly forming a metal film throughout the resin foam 4, a plating method is preferred for forming the metal film on the surface of the bubble walls 42. Furthermore, the metal constituting the metal film can be any metal other than the hydrogen storage alloy, that is, a metal that cannot irreversibly absorb and release hydrogen and can be used to form a metal film by plating. Examples of metals constituting the metal film include iron alloys, copper, copper alloys, chromium, chromium alloys, nickel, and nickel alloys.

[0095] Then, the molded body is heated at a temperature higher than the thermal decomposition temperature of the pore-forming material 213 and the thermal decomposition temperature of the bubble walls 42 in the resin foam 4 (i.e., the thermal decomposition temperature of the resin constituting the resin foam 4) but lower than the melting point of the hydrogen storage alloy particles 3. When the molded body is heated at such a temperature, the pore-forming material 213 adhering to the hydrogen storage alloy particles 3 disappears due to thermal decomposition, forming a containment space 211 around the hydrogen storage alloy particles 3. In addition, the bubble walls 42 in the resin foam 4 disappear due to thermal decomposition, and a metal film remains, forming a metal porous body 202 with a three-dimensional network structure reflecting the shape of the bubble walls 42 in the resin foam 4.

[0096] As described above, a hydrogen storage body 102 with the above-described structure can also be obtained by heating the resin foam 4 containing hydrogen storage alloy particles 3 to remove the pore-forming material 213 and the bubble wall 42 of the resin foam 4.

[0097] (Experimental Example 1)

[0098] In this example, an example of fabricating the hydrogen storage body in Embodiment 1 using hydrogen storage alloy particles composed of LaNi5 with a particle size of 100 μm and metal powder composed of stainless steel with an average particle size of 3 μm will be described.

[0099] In this example, firstly, polyvinyl acetate, used as a pore-forming aid, is dissolved in acetone to prepare a 5% by mass pore-forming aid solution. Next, 50 parts by mass of the pore-forming aid solution are added to 100 parts by mass of hydrogen storage alloy particles, mixed thoroughly, and then dried, thereby allowing the pore-forming aid to adhere to the surface of the hydrogen storage alloy particles.

[0100] Next, a pore-forming material is added to the hydrogen storage alloy particles and thoroughly mixed, thereby allowing the pore-forming material to adhere to the surface of the hydrogen storage alloy particles. It should be noted that the pore-forming material is spherical resin particles (manufactured by AICA Industries, Ltd., "GANZPEARL (registered trademark) GM-1001") composed of polymethyl methacrylate and having an average particle size of 10 μm. Furthermore, the amount of pore-forming material is 10 parts by mass relative to 100 parts by mass of the hydrogen storage alloy particles before the pore-forming agent is applied.

[0101] In addition, unlike the preparation of hydrogen storage alloy particles, a dispersion medium with a polyvinyl alcohol concentration of 10% by mass is prepared by dissolving polyvinyl alcohol in distilled water.

[0102] A slurry-like mixture is prepared by mixing hydrogen storage alloy particles, metal powder, and a dispersion medium obtained in this manner. The amount of metal powder in the mixture is 66 parts by mass relative to 100 parts by mass of the hydrogen storage alloy particles before the pore-forming material is attached. Additionally, the amount of binder solution in the mixture is 59 parts by mass relative to 100 parts by mass of the hydrogen storage alloy particles before the pore-forming material is attached.

[0103] The mixture obtained above is injected into a rectangular molding die with a length of 50 mm, a width of 10 mm, and a thickness of 5 mm, and then cooled at a temperature below -18°C. This gels the mixture within the container to obtain a molded body. After drying the molded body to remove distilled water, it is heated at 500°C for 2 hours in an inert gas atmosphere, thereby thermally decomposing the pore-forming material, pore-forming aid, and polyvinyl alcohol in the molded body. Then, the molded body is heated at 750°C for 3 hours, thereby sintering the metal powder to form a porous metal body. Through the above operations, a hydrogen storage body is obtained.

[0104] Figure 5 and Figure 6 The image shown is an example of a SEM image of the surface of hydrogen storage 103 obtained by observing the surface of the hydrogen storage body using a scanning electron microscope. Figure 5 As shown, the hydrogen storage body 103 can be understood to have a porous metal body 2 with multiple fine pores 21, the fine pores 21 opening on the surface of the porous metal body 2. In addition, it can be understood that hydrogen storage alloy particles 3, which are brighter in color than the metal powder 22 constituting the porous metal body 2, are present in the porous metal body 2.

[0105] If the opening on the surface of the hydrogen storage body 103 is further enlarged, then as... Figure 6As shown, the fine pores 21 can be understood to have a receiving space 211 and a connecting space 212. Furthermore, it can be understood that hydrogen storage alloy particles 3 are held within the receiving space 211, and voids are formed between the hydrogen storage alloy particles 3 and the porous metal body 2. Moreover, it can be understood that the porous metal body 2 is composed of a sintered body of metal powder 22, and connecting spaces 212 are formed between the metal particles constituting the metal powder 22.

[0106] based on Figure 6 The equivalent diameter d of the circumscribed circle of the hydrogen storage alloy particle 3 contained in the containment space 211 was measured. MH The diameter D of the smallest circle tangent to the opening of the receiving space 211 is 102 μm. max The diameter D of the largest circle among the circles tangent to the opening of the receiving space 211 is 223 μm. min The value is 120 μm. Therefore, the opening diameter D of the containment space 211 containing the hydrogen storage alloy particle 3 is calculated based on these values. opening Equivalent diameter d of the circumscribed circle of hydrogen storage alloy particle 3 MH The ratio of D opening / d MH The value is 1.68.

[0107] Table 1 shows the contents of the openings present on the surface of the hydrogen storage body 103 in this example. Figure 6 The above-mentioned d was measured at five openings, including the opening shown. MH D max and D min The result is obtained based on the value of D. The above ratio D is calculated based on these values. opening / d MH The arithmetic mean of the values ​​is 1.69. On the other hand, it is known that the volume expansion rate of the LaNi5 constituting the hydrogen storage alloy particle 3 in this example is about 27% (e.g., Yasuaki Osumi, "Hydrogen Storage Alloys - Their Properties and Applications -", ​​AGNE Technology Center, New Edition, 3rd Printing, 2008, pp. 65-67). Therefore, the volume expansion ratio of the hydrogen storage alloy particle 3 is about 1.27, and its cube root is about 1.08.

[0108] [Table 1]

[0109]

[0110] (Experimental Example 2)

[0111] In this example, spherical resin particles (AICA Industrial Co., Ltd. "GANZPEARL GM-0205S") made of polymethyl methacrylate and having an average particle size of 3 μm were used as the pore-forming material. Except for this, the hydrogen storage body 104 was fabricated using the same method as in Experimental Example 1. Figure 7 The image shows an enlarged photograph of the opening on the surface of the hydrogen storage body 104. (See image for details.) Figure 7 As shown, the porous metal body 2 in the hydrogen storage body 104 of this example, like the hydrogen storage body 103 of Experimental Example 1, has fine pores 21 with a housing space 211 and a connecting space 212. Furthermore, hydrogen storage alloy particles 3 are held within the housing space 211, and voids are formed between the hydrogen storage alloy particles 3 and the porous metal body 2. Moreover, the porous metal body 2 is composed of a sintered body of metal powder 22, and connecting spaces 212 are formed between the metal particles constituting the metal powder 22.

[0112] based on Figure 7 The equivalent diameter d of the circumscribed circle of the hydrogen storage alloy particle 3 contained in the containment space 211 was measured. MH The diameter D of the smallest circle tangent to the opening of the receiving space 211 is 124 μm. max The diameter D of the largest circle among the circles tangent to the opening of the receiving space 211 is 306 μm. min The value is 163 μm. Therefore, the opening diameter D of the containment space 211 containing the hydrogen storage alloy particle 3 is calculated based on these values. opening Equivalent diameter d of the circumscribed circle of hydrogen storage alloy particle 3 MH The ratio of D opening / d MH The value is 1.89.

[0113] Table 2 shows the contents contained in the openings on the surface of the hydrogen storage body 104 present in this example. Figure 7 The above-mentioned d was measured at the six openings, including the opening shown. MH D max and D min The result is obtained based on the value of D. The above ratio D is calculated based on these values. opening / d MH The arithmetic mean of the values ​​is 2.75. On the other hand, the hydrogen storage alloy particle 3 in this example is also composed of LaNi5, just like the hydrogen storage alloy particle 3 in Experimental Example 1. Therefore, the volume expansion ratio when hydrogen is absorbed in the hydrogen storage alloy particle 3 is about 1.25, and its cube root is about 1.08.

[0114] [Table 2]

[0115]

[0116] As described above, according to the methods of Experimental Example 1 and Experimental Example 2, a hydrogen storage body can be obtained, comprising a porous metal body with fine pores and hydrogen storage alloy particles made of a hydrogen storage alloy and held in a receiving space within the fine pores, wherein the opening diameter D of the receiving space containing the hydrogen storage alloy particles is... opening Equivalent diameter d of the circumscribed circle of the hydrogen storage alloy particleMH The ratio of D opening / d MH The average value is the root of the cube of the volume expansion ratio when hydrogen is retained in the hydrogen storage alloy particles.

[0117] (Implementation Method 3)

[0118] In this embodiment, examples of the application of hydrogen storage body 1 are described. Hydrogen storage body 1 can be applied to hydrogen-related devices configured to reversibly perform hydrogen adsorption and release. For example, the hydrogen storage body 1 of this embodiment is used in… Figure 8 The configuration shown is a hydrogen container 5 capable of reversibly absorbing and releasing hydrogen.

[0119] The hydrogen container 5 has: a container body 51 having a storage space 511 for storing hydrogen, a hydrogen storage body 1 disposed in the storage space 511, and a temperature adjustment device 52 configured to change the temperature of the hydrogen storage body 1.

[0120] The container body 51 of the hydrogen container 5 is configured to retain hydrogen supplied from the outside of the hydrogen container 5 and hydrogen released from the hydrogen storage body 1 within the storage space 511. The container body 51 has at least one hydrogen port 53 configured to communicate between the outside of the hydrogen container 5 and the storage space 511. The hydrogen port 53 is configured to enable the supply of hydrogen from the outside of the hydrogen container 5 to the storage space 511 and / or the release of hydrogen from the hydrogen container 5 to the outside by communicating with the external space. The number of hydrogen ports 53 provided on the container body 51 can be one or more. For example, as shown... Figure 8 As shown, the container body 51 of this method is configured to have a hydrogen port 53, and the hydrogen port 53 can be used for both supplying hydrogen from the outside of the hydrogen container 5 to the storage space 511 and releasing hydrogen from the hydrogen container 5 to the outside.

[0121] The shape of the container body 51 is not particularly limited; it can take various forms such as cylindrical, spherical, or box-shaped. For example, Figure 8 As shown, the container body 51 of this method has a cylindrical shape.

[0122] The volume of the container body 51 is preferably 300m³. 3 The pressure variation when hydrogen is released from the hydrogen container 5 tends to increase as the volume of the container body 51 decreases. Therefore, by making the volume of the container body 51 300 m³... 3 The following measures can further enhance the effect of suppressing the pressure fluctuations during hydrogen release. Additionally, by making the volume of the container body 51 300m³... 3 The hydrogen container 5 can be easily miniaturized, reducing the limitations of the installation location.

[0123] Furthermore, the maximum internal pressure of the container body 51 is preferably 1 MPa (G) or less, measured by a gauge pressure gauge. This is in addition to ensuring that the volume of the container body 51 is 300 m³. 3 In addition to the above, by keeping the maximum internal pressure of the container body 51 below 1 MPa (G), the safety of the container body 51 can be improved and the maintenance of the container body 51 can be simplified.

[0124] A hydrogen storage body 1 is provided in the storage space 511 of the container body 51. The number, shape and arrangement of the hydrogen storage bodies 1 provided in the container body 51 are not particularly limited, and can be appropriately set according to the desired maximum hydrogen storage capacity, the pressure when hydrogen is released from the hydrogen container 5, etc.

[0125] The temperature adjustment device 52 can change the temperature of the hydrogen storage body 1, releasing hydrogen retained in the hydrogen storage body 1 from the hydrogen storage body 1 to the storage space 511, or causing hydrogen in the storage space 511 to be retained in the hydrogen storage body 1. The method for changing the temperature of the hydrogen storage body 1 in the temperature adjustment device 52 is not particularly limited and various methods can be used. For example, the temperature adjustment device 52 of this type is configured to change the temperature of the hydrogen storage body 1 by heating or cooling the entire container body 51. Therefore, for example, by using the temperature adjustment device 52 to raise the temperature of the hydrogen storage body 1, hydrogen can be released from the hydrogen storage body 1 to the storage space 511. Alternatively, for example, by lowering the temperature of the hydrogen storage body 1, hydrogen in the storage space 511 can be retained in the hydrogen storage body 1.

[0126] As described above, the hydrogen storage alloy particles 3 in the hydrogen storage body 1 are contained within the fine pores 21 of the metal porous body 2. Therefore, the hydrogen storage body 1 can reduce the amount of volume change when hydrogen is absorbed. Thus, as in this embodiment, by applying the hydrogen storage body 1 to the hydrogen container 5, it is easier to reduce the load applied to the container body 51 when hydrogen is absorbed in the hydrogen storage body 1, and strain is less likely to occur in the container body 51. Furthermore, in this case, hydrogen can be stored more efficiently within the hydrogen container 5.

[0127] The hydrogen storage body 1 for the hydrogen container 5 preferably comprises hydrogen storage alloy particles made of TiFe-based hydrogen storage alloys. Since TiFe-based hydrogen storage alloys are easy to handle, applying hydrogen storage alloy particles made of TiFe-based hydrogen storage alloys to the hydrogen storage body 1 of the hydrogen container 5 can further improve the safety of the hydrogen container 5. Furthermore, TiFe-based hydrogen storage alloys are relatively inexpensive among hydrogen storage alloys, thus further reducing the cost of the hydrogen container 5 is expected.

[0128] The aforementioned TiFe alloys include TiFe binary alloys and TiFe multi-element alloys obtained by replacing a portion of Ti and / or Fe in TiFe binary alloys with other elements. For example, a TiFe alloy can be a TiFeMn ternary alloy obtained by replacing a portion of Fe in a TiFe binary alloy with Mn. Alternatively, TiFe alloys can also be multi-element alloys obtained by further adding other metallic elements to a TiFeMn ternary alloy.

[0129] The above description of the hydrogen storage body and its manufacturing method is based on the embodiments and experimental examples. However, the specific embodiments and manufacturing methods of the hydrogen storage body and the present invention are not limited to the embodiments and experimental examples described above, and the configuration can be appropriately modified without departing from the spirit of the present invention.

Claims

1. A hydrogen storage medium having: Porous metals, which have fine pores, and Hydrogen storage alloy particles, which are composed of hydrogen storage alloy and are retained within the fine pores of the metal porous body; The fine pores have a receiving space for containing the hydrogen storage alloy particles. The opening diameter D of the containment space containing the hydrogen storage alloy particles is shown in equation (1) below. opening The equivalent diameter d of the circumscribed circle of each hydrogen storage alloy particle obtained by observing the surface of the hydrogen storage body. MH The ratio of D opening / d MH The average value is above the cube root of the volume expansion ratio when hydrogen is retained in the hydrogen storage alloy particles. D opening =(D max +D min ) / 2···(1) in, In the formula (1) D max D is the diameter of the smallest circle among the circles tangent to the opening of the containment space on the surface of the hydrogen storage body. min It is the diameter of the largest circle among the circles tangent to the opening of the containment space on the surface of the hydrogen storage body, and the unit of the diameter is μm.

2. The hydrogen storage medium according to claim 1, wherein, A portion of the surface of the hydrogen storage alloy particles is bonded to the porous metal body.

3. The hydrogen storage medium according to claim 1, wherein, The fine pore has a connecting space that connects the receiving space to adjacent receiving spaces and to the exterior of the metal porous body.

4. The hydrogen storage medium according to claim 3, wherein, On the surface of the hydrogen storage body, the diameter of the largest circle among the circles inscribed within the opening of the connecting space is smaller than the median particle size of the hydrogen storage alloy particles based on volume.

5. The hydrogen storage medium according to any one of claims 1 to 4, wherein, The porous metal body is a sintered product of metal powder.

6. The hydrogen storage medium according to claim 5, wherein, The median particle size of the metal powder constituting the metal powder is smaller than the median particle size of the hydrogen storage alloy particles.

7. The hydrogen storage medium according to any one of claims 1 to 4, wherein, The porous metal has a three-dimensional mesh structure consisting of columnar supports and a central hub composed of multiple such supports.

8. A method for manufacturing a hydrogen storage medium, which is the method for manufacturing a hydrogen storage medium according to claim 5. The pore-forming material is then attached to the surface of the hydrogen storage alloy particles. Then, the hydrogen storage alloy particles are mixed with metal powder that forms the metal porous body to prepare a mixture. The mixture is shaped to form a molded body. The pore-forming material is removed by heating the molded body, and the metal powder is sintered to form the metal porous body.

9. The method for manufacturing a hydrogen storage medium according to claim 8, wherein, The median particle size of the metal powder is smaller than the median particle size of the hydrogen storage alloy particles.

10. A method for manufacturing a hydrogen storage medium, which is the method for manufacturing a hydrogen storage medium according to claim 7. The pore-forming material is then attached to the surface of the hydrogen storage alloy particles. Then, a resin foam containing the hydrogen storage alloy particles and having a continuous porous structure is prepared. A metal film, forming the metal porous body, is formed on the surface of the bubble wall of the resin foam. Then, the pore-forming material is removed and the bubble walls are removed by heating the resin foam to form the metal porous body.

11. A hydrogen container comprising a hydrogen storage body according to any one of claims 1 to 4.

12. The hydrogen container according to claim 11, wherein, The hydrogen storage alloy particles in the hydrogen storage body are composed of TiFe-based hydrogen storage alloys.

Images