JP2005171349A - Method of producing hydrogen storage body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a hydrogen storage body for obtaining a good deposition state even when the quantity of second particles is small when the second particles are deposited. <P>SOLUTION: The method of producing the hydrogen storage body including first particles serving for the occlusion and release of hydrogen and the second particles combined to the first particles is provided with: a mixing process of obtaining a mixture composed of the first particles and second particles; and a combining process of repeating the processing of passing the mixture through a prescribed gap formed by a rigid body a plurality of times. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a hydrogen storage body, and particularly to a hydrogen storage body composed of a plurality of different types of particles.

At present, there are concerns about acid rain caused by NOx (nitrogen oxide) that increases due to the use of fossil fuels and global warming due to CO ₂ , and these environmental destructions have become serious problems. Among them, the practical application of hydrogen energy as clean energy has attracted worldwide attention. Hydrogen is an inexhaustible constituent element of water on the earth. It can be produced using various primary energies, and there is no concern about environmental destruction because the only by-product is water. In addition, it has excellent characteristics such as relatively easy storage compared to electric power.

For this reason, in recent years, research and development and practical application studies of hydrogen storage alloys have been actively carried out as storage and transport media for these hydrogen. A hydrogen storage alloy is an alloy that can absorb and release hydrogen under suitable conditions. By using this alloy, it is possible to store hydrogen at a low pressure and at a high density compared to conventional hydrogen gas cylinders. The volume density is almost equal to or higher than that of liquid hydrogen or solid hydrogen, and the safety in handling is remarkably excellent.
As these hydrogen storage alloys, AB5 type alloys such as LaNi ₅ or AB2 type alloys such as TiMn ₂ have been put into practical use. However, since the hydrogen storage amount is at most about 1.4 mass%, the hydrogen release amount is also insufficient at 1.4 mass% or less. Therefore, a hydrogen storage alloy having a larger hydrogen release amount has been demanded, and in recent years, Mg having a high hydrogen release amount of 7.6 mass% has attracted attention.

By the way, when a hydrogen storage alloy is used as a hydrogen storage body, it is important not only to have a large hydrogen storage / release amount, but also to be able to absorb / release hydrogen at 200 ° C. or less, preferably near room temperature. Although the above-mentioned Mg metal has a high hydrogen release amount, its hydride (MgH ₂ ) is thermodynamically stable, so the hydrogen release temperature is as high as 300 ° C. or higher. Such a defect in temperature characteristics is an obstacle to the practical use of Mg for hydrogen storage. In view of such a current situation, many studies have been made to improve the defect of the temperature characteristic of Mg. For example, Non-Patent Document 1 reports that a release amount of about 2 mass% can be obtained at 150 ° C. by using an Mg ₈₆ Ni ₁₀ Nd ₄ (at%) alloy produced by melt span. Non-Patent Document 2 reports that an Mg _1.0 Ni _1.02 H _2.2 (at%) alloy produced by a method using high-pressure technology releases 2.6 mass% of hydrogen between room temperature and 200 ° C. Has been. Furthermore, in Non-Patent Document 3, it was shown that the (Mg _0.5 Y _0.5 ) Ni ₂ (at%) alloy releases hydrogen at 40 ° C., but the released amount is as small as about 1 mass%.
Thus, although the hydrogen storage alloys according to Non-Patent Documents 1 to 3 are effective in improving the temperature characteristics of Mg, the hydrogen release amount is insufficient compared to the hydrogen release amount inherent in Mg. It is.

JP-A-5-317679 Mater Tran, Jim (vol.43 No.7 p1732-1736, 2002) J. Am. Chem. Soc. 2002, 123, p6193-6194 17th “University and Science” Public Symposium World of Hydrogen that Opens the 21st Century Proceedings p44-46, 2002 "Mechano-Fusion" Page 23 Nikkan Kogyo Shimbun June 1989

On the other hand, studies have been conducted to deposit and complex second particles such as Ni, Cr, LaNi ₅ , TiFe, Ti, C, BN, and Pd around the first particles made of Mg. Some results have been achieved by lowering the release temperature. However, when the atomic weight of the second particles is large, there is also a negative effect of reducing the hydrogen storage amount per unit weight. Therefore, it is necessary to suppress the use of the second particles as little as possible. However, no effective method has been found for depositing the first particles with the second particles uniformly dispersed when the amount of the second particles is small.

  Therefore, the present invention has been made based on such a technical problem, and when the second particles are deposited, even when the amount of the second particles is small, a good deposition state can be obtained. It is an object of the present invention to provide a method for producing a hydrogen storage body that can be used.

The present invention relates to a method for producing a hydrogen storage body including first particles responsible for occlusion and release of hydrogen and second particles combined with the first particles, wherein a mixture of the first particles and the second particles is obtained. The above-mentioned problem can be solved by a method for producing a hydrogen storage body, comprising: a mixing step to be obtained; and a joining step in which a process of passing the mixture through a predetermined gap formed by a rigid body is repeated a plurality of times. .
The hydrogen reservoir obtained by the present invention includes several forms. One of them is a form in which the second particles cover the first particles. In the case of this form, the second particles need to have a smaller diameter than the first particles, and specifically, the particle size of the second particles is desirably 1/50 or less of the particle size of the first particles.

The present invention can include an energy application step of obtaining an aggregate in which the processed objects are combined by applying mechanical energy to the processed products obtained by the combining step. By applying this mechanical energy, the crystals of the first particles constituting the processed product can be oriented. This mechanical energy application is realized by the collision of the media. When the first particles are made of a material having high ductility, typically Mg or Mg alloy, the first particles are spread by applying mechanical energy, and the first particles are bonded to each other to be flat. To form an aggregate. This aggregate can be used as it is as a hydrogen storage body, but a crushed aggregate can also be used as a hydrogen storage body.
In the present invention, crystal orientation can be performed in advance. That is, according to the present invention, mechanical energy is applied to predetermined particles to produce an aggregate in which the first particles are bonded to each other, and the particles obtained by pulverizing the aggregate are used as the first particles. Allow to obtain a mixture with the particles.

  In the present invention, the metal constituting the first particle and the second particle is not particularly limited, but Mg or Mg alloy is used as the first particle, and a Ti—Cr alloy known as a hydrogen rapidly increasing alloy is used as the second particle. Is desirable.

Mg (dense hexagonal crystal structure) ionically bonds with hydrogen to generate a stable hydride phase (rutile tetragonal crystal structure β-MgH ₂ ). The hydride generation enthalpy at this time was −74.6 kJ / mol H ₂ , and the temperature at which the dehydrogenation reaction proceeds was 300 ° C. or higher. Further, it is said that one of the factors that slows the hydrogen release rate of MgH ₂ is that the catalytic action of dissociating hydrogen molecules such as those possessed by transition metals into hydrogen atoms is extremely weak.
However, the present inventors have confirmed that Mg to which predetermined mechanical energy is applied releases hydrogen at a temperature of 300 ° C. or lower. This is extremely significant when compared with the fact that hydrogen release at 300 ° C. or lower can be realized only by a Mg alloy having a predetermined composition obtained by a special manufacturing method. The matters confirmed by the present inventors can be applied universally not only to Mg but also to Mg alloys (sometimes referred to as Mg metal), and the high hydrogen storage capacity that is characteristic of Mg metal. This is because the features can be used effectively.

  The present inventors have found that Mg metal crystals subjected to a predetermined mechanical impact are oriented, specifically, oriented in the c-axis direction. Although the specific reason is unknown, it is understood that the orientation as described above is the cause of hydrogen release of Mg metal at 300 ° C. or lower. Further, the Mg metal in the crystal orientation could exhibit other effects such as an improvement in the hydrogen release rate.

  The present invention provides two production methods based on the above findings. One of them is a method for producing a hydrogen storage body capable of occluding and releasing hydrogen, in which Ti-Cr alloy particles are deposited around Mg metal particles responsible for occluding and releasing hydrogen. And a step of performing an orientation treatment on the Mg metal particles in the adherend to be treated. The other one is a method for producing a hydrogen storage body capable of occluding and releasing hydrogen, and a step of obtaining an alignment treatment product by performing an alignment process on Mg metal particles responsible for the storage and release of hydrogen. And a deposition process step of depositing Ti—Cr-based alloy particles around the alignment processed product. In the above two manufacturing methods, it is desirable to deposit Ti—Cr-based alloy particles around the Mg metal particles or the alignment treatment product by repeating a process of passing through a predetermined gap formed by a rigid body a plurality of times. .

  According to the present invention, since the process of passing the mixture of the first particles and the second particles through the predetermined gap formed by the rigid body is repeated a plurality of times, even if the amount of the second particles is small, the surface of the first particles The second particles can be uniformly dispersed and deposited.

The hydrogen storage body according to the present invention is a hydrogen storage body including first particles responsible for occlusion and release of hydrogen and second particles bonded to the first particles and mechanochemically.
<First particle: Mg>
The first particles can be composed of Mg or Mg alloy.
Mg intends Mg as a pure metal, but allows the presence of impurities inevitably mixed by industrial production. As described above, Mg has a hydrogen storage / release amount of 7 mass% or more, but there is a problem that hydrogen cannot be released unless the temperature is 300 ° C. or more. However, according to the present invention, hydrogen can be released from Mg at a temperature of 300 ° C. or lower.
Mg alloys widely include known ones. For example, an Mg—RE alloy (RE: rare earth element), an Mg—Ni alloy, an Mg—Ni—RE alloy, or the like can be employed. Specifically, there are Mg ₂ Ni alloy, La—Mg—Nix (x = 3 to 3.5) alloy, La ₂ MgNi ₉ alloy, LaMgNi alloy, LaMgNi ₁₄ alloy and the like. By applying the present invention to these alloys, it is possible to enjoy the effect of the present invention that lowers the hydrogen release temperature of each alloy.

<First particle ... Ti-Cr>
As the first particles, in addition to the above Mg or Mg alloy, a Ti—Cr alloy can be used. According to the Ti—Cr alloy, the plateau pressure (release plateau pressure) of the Ti—Cr alloy can be set to an arbitrary value by appropriately setting the molar ratio of Cr to Ti (Cr / Ti). There is also an advantage of being able to do it.
In the Ti—Cr alloy, the molar ratio of Cr to Ti (Cr / Ti) is preferably 0.3 to 4.0. When the molar ratio of Cr and Ti is less than 0.3, hydrogen is occluded but it is difficult to release hydrogen. On the other hand, when the molar ratio of Cr and Ti exceeds 4.0, hydrogen is not occluded, which is not preferable. A desirable molar ratio of Cr and Ti is 0.5 to 3.0, and a more desirable molar ratio of Cr and Ti is 0.8 to 2.5.

Here, in the case of a Ti—Cr binary system, when Cr / Ti> 1.5, it is difficult to become a bcc main phase even if a quenching process described later is performed. Therefore, particularly when Cr / Ti> 1.5, it is desirable that the total amount of Ti and Cr is 10 to 99 at% and at least one of Ru, V, Mo, and W is contained.
Ru can be obtained just have high bcc phase forming ability, deleterious C ₁₄ type, contains almost no Laves phase C ₁₅ type, etc. bcc single phase alloy is contained in a trace amount in the Ti-Cr-based alloy. When Ru is contained in the Ti—Cr alloy, a desirable content is 0.5 to 10 at%, a further desirable content is 0.5 to 8 at%, and a more desirable content is 0.5 to 5 at%.
On the other hand, by including at least one of V, Mo, and W in the Ti—Cr alloy, bcc is the main phase, and the alloy cost and the hydrogen storage amount per unit weight are balanced and have high practicality. A Ti—Cr alloy can be obtained.

When V is contained in the Ti—Cr alloy, a desirable content is 3 to 90 at%, a more desirable content is 3 to 50 at%, and a more desirable content is 3 to 40 at%.
When Mo is contained in the Ti—Cr alloy, a desirable content is 1 to 25 at%, a further desirable content is 2 to 15 at%, and a more desirable content is 2 to 10 at%.
When W is contained in the Ti—Cr alloy, a desirable content is 1 to 20 at%, a further desirable content is 1 to 15 at%, and a more desirable content is 1 to 10 at%.
Even when Cr / Ti ≦ 1.5, addition of Ru, V, Mo, W or the like is preferable for bcc phase stabilization.

By adopting the above composition, it is possible to make the Ti—Cr alloy have the bcc phase as the main phase. Whether or not the Ti—Cr alloy has the bcc phase as the main phase can be determined by X-ray diffraction. When the ratio (%) according to the following equation (1) based on the integrated intensity of the diffraction line is 50% or more, the bcc phase is regarded as the main phase alloy.
bcc (110) / [bcc (110) + {C14Laves (201) + C15Laves (311)} × 2]
... Formula (1)
In the above Ti—Cr alloy, the phase that can exist in addition to the bcc phase is the Laves phase.
In the above, Mg, Mg alloy, and Ti—Cr alloy are described as desirable metals constituting the first particles. However, the present invention is not limited to this, and it is allowed to use other metals such as V and V alloys. .
As the first particles, in addition to the above-mentioned Mg, Mg metal, Ti—Cr alloy, alkali metal hydride (for example, NaAlH ₄ or a partially substituted product thereof, LiBH ₄ or a partially substituted product thereof), A lithium compound (for example, Li ₃ N or a partially substituted product thereof) can be used.

<Second particle>
The second particles in the present invention are Ni, V, V alloy, LaNi ₅ alloy, Ti—Cr alloy, Ti—Fe alloy, Pd, Pt, C (carbon material such as graphite and carbon nanotube), BN group. It can comprise from 1 type, or 2 or more types chosen from. Of these, Ti—Cr alloys are most desirable. As the Ti—Cr alloy, the alloy described for the first particles can be used. In addition, as the second particles for the above-described NaAlH ₄ and partially substituted products thereof, LiBH ₄ and partially substituted products thereof, and Li ₃ N and partially substituted products thereof, metals such as Ni, Fe, Co, Ti, and Pd are used. Fine particles, TiCl ₃ , and TiCl ₄ can be used as a catalyst.

<About MCB>
The manufacturing method of the hydrogen storage body of this invention exists in the point which repeats the process which makes the mixture containing a 1st particle and a 2nd particle forcibly pass through the predetermined | prescribed clearance gap formed with the rigid body several times. By this treatment, at least the first particles and the second particles are bonded by mechanochemical action. At this time, the first particles or the second particles may naturally be bonded by a mechanochemical action. In the present specification, this process is sometimes referred to as mechanochemical bonding (sometimes referred to as MCB).

  FIG. 1 is a diagram showing a basic configuration of a processing apparatus 1 capable of performing MCB (Non-Patent Document 4). As shown in FIG. 1, the processing apparatus 1 includes a rotating casing 2 that rotates at high speed and a chip 3 that is fixed to the inner wall 2 a of the rotating casing 2 with a predetermined interval. Both the rotating casing 2 and the tip 3 are members that can be regarded as rigid bodies. The workpiece P (a mixture of the first particles and the second particles in the present invention) is consolidated to the inner wall 2a by the centrifugal force accompanying the rotation of the rotating casing 2, while the inner wall 2a of the rotating casing 2 and the chip 3 are Pass through the gap between them. During this passage, the workpiece P undergoes strong compression and friction. When the workpiece P is a metal particle, the metal particles are bonded by a mechanochemical action by being subjected to compression and friction.

  As an apparatus capable of performing MCB, an apparatus disclosed in Japanese Patent Laid-Open No. 5-317679 (Patent Document 1) can be used. The main configuration of this apparatus is shown in FIG. In this apparatus, the tip 3 has an inclined surface formed such that the gap between the rotary casing 2 and the rotary casing 2 becomes narrower toward the rotation direction, and the rake 4 has a gap between the rotary casing 2 and the rotary casing 2. 2 is formed in a wedge shape or a comb-like shape that becomes wider toward the rotation direction side and its action surface gradually becomes wider, and the rotary casing 2 and the tip 3 and the rake 4 are opposed to each other to compress and compress the tip 3. Shearing and stirring and mixing by the rake 4 are performed on the workpiece P pressed against the inner wall 2a of the rotating casing 2. In short, the rotating casing 2 is rotated at high speed, the workpiece P is pressed against the inner wall 2a by centrifugal force, and the tip 3 that rotates relative to the rotating casing 2 is formed on the layer made of the workpiece P formed by the pressing. The rake 4 is allowed to act so that the workpiece P can be compressed and sheared by the tip 3 and stirred and mixed by the rake 4.

<Method category>
In the method for producing a hydrogen storage body of the present invention, a processed product obtained by repeating MCB a plurality of times can be used as it is as a hydrogen storage body. Hereinafter, this is referred to as a first method. Furthermore, other processing can be performed. As another treatment, for example, an alignment treatment performed using a ball mill is effective for a treatment obtained by MCB. This is called the second method. In the present invention, particles that have been subjected to orientation treatment can be used as the first particles. This is called the third method. Hereinafter, the first method to the third method will be described in order.

<First method>
The first method in which the processed product obtained by repeating MCB a plurality of times is used as a hydrogen storage as it is, is applied to obtain a hydrogen storage in a form in which the second particles are coated around the first particles. be able to. In this case, the second particle needs to have a smaller diameter than the first particle, and specifically, the particle size of the second particle is 1/50 or less, for example, 1/100 of the particle size of the first particle. It is desirable. When the particle size of the first particles is about 1 to 15 μm, the second particles may have a particle size of 10 to 100 nm.
FIG. 3 shows a state in which the second particles 6 are coated around the first particles 5 by treating the mixture of the first particles 5 and the second particles 6 with MCB. As shown in FIG. 3, the second particles 6 may cover the entire periphery of the first particles 5, or may be a partial coating. Here, the finer the second particles 6 are, the more easily they are aggregated. However, the aggregation is released during the MCB process, and the second particles 6 are dispersed. By controlling the mixing amount of the second particles 6, the degree of coating on the first particles 5 can be controlled. If MCB is used, the uniformity of the coating | covering to the 1st particle | grains 5 can be ensured, reducing the quantity of the 2nd particle | grains 6. FIG.
In the present invention, the case where the particle diameters of the first particles 5 and the second particles 6 are equal is not excluded. Further, in the present invention, it is allowed to include the third particles, the fourth particles,.

<Second method>
In the second method, as described above, the alignment treatment is performed on the processed product obtained by the first method. This alignment process is performed by applying mechanical energy to the processed object. The mechanical impact can be applied using, for example, a ball mill. Usually, a ball mill is used for pulverizing powder, but in the present invention, pulverization is not the primary purpose. When the first particles 5 are made of Mg metal having a relatively high ductility, the particles are spread in preference to the pulverization even if they are processed by a ball mill. For this reason, the treatment by the ball mill, that is, the particles subjected to mechanical impact form an aggregate.
FIG. 4 is a diagram schematically showing the procedure of the second method. In the following description, it is assumed that Mg particles 7 are used as the first particles 5 and Ti—Cr alloy particles 8 are used as the second particles 6. As shown in FIG. 4A, Mg particles 7 and Ti—Cr alloy particles 8 are mixed to obtain a mixed powder containing Mg particles 7 and Ti—Cr alloy particles 8. At the mixed powder stage, the fine Ti—Cr alloy particles 8 tend to aggregate. When the mixed powder is subjected to MCB treatment, Ti—Cr-based alloy particles 8 are bonded around the Mg particles 7. At this time, Mg particles 7 or Ti—Cr alloy particles 8 may also be bonded. This bond is due to a mechanochemical action.

The processed material composed of the Mg particles 7 and the Ti—Cr alloy particles 8 subjected to the MCB treatment is then given mechanical energy. Mechanical energy can be applied by a ball mill. Since the processed material to which mechanical energy is applied has a relatively high ductility, the Mg particles 7 are spread, and the Mg particles 7 are bonded to each other. FIG. 4C schematically shows a cross section thereof. Thus, the flat aggregate 9 is formed. The Ti—Cr alloy particles 8 are present inside the aggregate 9 (between the Mg particles 7), and form a predetermined bonded state. A part of the Ti—Cr-based alloy particles 8 exists on the surface portion of the aggregate 9 and protrudes to the outside.
FIG. 4D schematically shows a cross section of particles obtained by pulverizing the aggregate 9 shown in FIG. Since the aggregate 9 is obtained through mixing and application of mechanical energy, as shown in FIG. 4D, the Mg particles 7 and the Ti—Cr alloy particles 8 are in a predetermined bonded state even in the pulverized particles. have. The pulverized particles can be used as the hydrogen storage body 10.

  By applying mechanical energy with a ball mill, the crystals of the first particles 5 can be oriented in the c-axis direction. The degree of orientation in the c-axis direction becomes higher as the processing time by the ball mill becomes longer. On the other hand, the higher the degree of orientation in the c-axis direction, the more remarkable the effects of the present invention, such as lowering the hydrogen release temperature. Therefore, it is necessary to make the mechanical energy application time as long as possible within a range that takes productivity into consideration. The ball mill is a means for realizing this orientation and is not a limiting factor of the present invention. Where the orientation in the c-axis direction is due to mechanical energy application, a mixer or pulverizer other than a ball mill can be used. Moreover, it cannot be overemphasized that the means which can provide mechanical energy other than rolling can also be employ | adopted. Whether or not the crystal of the particles is oriented in the c-axis direction can be determined by an electron diffraction image using a TEM (Transmission Electron Microscope). In other words, the orientation of the present invention corresponds to the case where the proportion of crystal grains showing an electron beam diffraction image from the c-axis direction occupies 50% or more. The proportion of crystal particles showing an electron diffraction pattern from the c-axis direction preferably occupies 60% or more, and more preferably 75% or more.

  When the treatment with the ball mill is performed, the aggregate 9 is formed. However, when the treatment with the ball mill is performed for a time sufficient to obtain sufficient orientation, the aggregate 9 grows into a plate-like body having a length of about 3 mm. . With such a size, hydrogen storage / release occurs only in the vicinity of the surface, so the amount of hydrogen storage / release with respect to the volume is inferior. Therefore, it is desirable to pulverize and use this aggregate 9. In order to pulverize the assembly 9, it is not necessary to involve a large mechanical impact. By simply applying a slight blow to the aggregate 9, the bonds between the particles (MCB processed products) that existed before the formation of the aggregate 9 can be released. The bond can also be released by rubbing the assembly 9 accommodated in the mortar with a pestle. Otherwise, new particles can be generated by cutting the aggregate 9. The hydrogen storage body 10 obtained as described above has a length and thickness of 300 μm or less, desirably 150 μm or less, and more desirably 100 μm or less.

In the hydrogen storage body 10 obtained as described above, the Ti—Cr-based alloy particles 8 capable of absorbing and releasing hydrogen impart mechanical energy to the Mg particles 7 and lower the hydrogen release temperature of the Mg particles 7. It can bear the function of letting In order to have such a function, the Ti—Cr alloy particles 8 have a body-centered cubic crystal structure (hereinafter referred to as “bcc phase” or “bcc”) as the main phase in a non-hydrogenated state. It is desirable to use one.
A Ti—Cr alloy having a bcc phase as a main phase (hereinafter, a Ti—Cr alloy having a bcc phase as a main phase is simply referred to as “Ti—Cr alloy”) is unidirectional (specifically) with movement of hydrogen atoms. Specifically, the expansion and contraction of the lattice in the c-axis direction is large, and mechanical energy can be imparted to the Mg particles 7 when hydrogen is absorbed and released in the hydrogen storage body 10 in a predetermined bonding state. Further, although not as much as Mg, a Ti—Cr alloy having a bcc phase as a main phase exhibits a hydrogen occlusion amount of 3.5 mass% or more by itself. Therefore, the amount of hydrogen occlusion as the whole hydrogen storage body 10 can be increased by using a Ti—Cr alloy having a bcc phase as a main phase.

  Here, as one form of “movement of hydrogen atoms”, hydrogen atoms penetrate into the hydrogen storage body 10, and hydrogen atoms that have entered the hydrogen storage body 10 are released to the outside of the hydrogen storage body 10. Includes both. Specifically, hydrogen atoms are occluded inside the Mg particles 7 or Ti—Cr alloy particles 8, and hydrogen atoms permeate (pass through) the Mg particles 7 or Ti—Cr alloy particles 8. In other words, hydrogen atoms are released from the inside of the Mg particles 7 or the Ti—Cr alloy particles 8 toward the outside of the hydrogen storage body 10.

Next, the mechanism by which the Ti—Cr-based alloy particles 8 can apply stress to the Mg particles 7 will be described with reference to FIG. As will be described in detail later, the Mg particles 7 and the Ti—Cr-based alloy particles 8 are bonded by applying mechanical energy. This bonding state is relatively strong, and the movement of the Mg particles 7 and the Ti—Cr alloy particles 8 is restricted in the composite.
As shown in FIG. 5, when hydrogen atoms are occluded in the Ti—Cr alloy particles 8, the volume of the Ti—Cr alloy particles 8 expands. Here, as described above, the Ti—Cr alloy particles 8 having the bcc phase as the main phase have a large lattice expansion and contraction in the c-axis direction accompanying the movement of hydrogen atoms, and hydrogen atoms are contained in the Ti—Cr alloy particles 8. Is occluded, the volume of the Ti—Cr alloy particles 8 expands in the c-axis direction. However, the Ti—Cr alloy particles 8 are firmly bonded to the Mg particles 7 by mechanical energy, and their movement is restricted. For this reason, with the volume expansion of the Ti—Cr alloy particles 8, stress is applied to the Mg particles 7 located around the Ti—Cr alloy particles 8. Specifically, when the bonding surface (bonding surface) between the Ti—Cr alloy particles 8 and the Mg particles 7 and the c-axis of the Ti—Cr alloy particles 8 are parallel, the Ti—Cr alloy particles. Since 8 expands in volume in the horizontal direction, tensile stress is applied to the Mg particles 7. On the other hand, when the bonding surface and the c-axis of the Ti—Cr alloy particles 8 are perpendicular to each other, the Ti—Cr alloy particles 8 are volume-expanded in the vertical direction, so that compressive stress is applied to the Mg particles 7. The

When hydrogen atoms are released from the Ti—Cr alloy particles 8, the volume of the Ti—Cr alloy particles 8 contracts in the c-axis direction. With this volume shrinkage, compressive stress or tensile stress is applied to the Mg particles 7 located around the Ti—Cr alloy particles 8.
Thus, since the hydrogen present in the Mg particles 7 becomes unstable due to the stress applied from the Ti—Cr-based alloy particle 8 side to the Mg particle 7 side, the hydrogen remains even at a relatively low temperature of 200 ° C. or less. Is likely to be released.

<Third method>
In the second method, the first particles 5 (typically made of Mg) were oriented after the MCB treatment. However, the alignment process can be performed before the MCB process. That is, the first particles 5 can be subjected to the alignment treatment by the same method as described above, and then mixed with the second particles 6 to be subjected to the MCB treatment.
FIG. 6 is a diagram schematically showing the procedure of the third method. As shown in FIGS. 6A and 6B, a flat aggregate 11 in which the Mg particles 7 are bonded to each other is produced by applying mechanical energy to the Mg particles 7 by, for example, a ball mill.
Next, as shown in FIG. 6C, the aggregate 11 is pulverized, and Ti—Cr-based alloy particles 8 are mixed with the Mg particles 7 obtained by the pulverization. According to the third method, the Mg particles 7 at this stage have their crystals oriented in the c-axis direction. When the mixed powder including the Mg particles 7 and the Ti—Cr alloy particles 8 is subjected to MCB treatment, the Ti—Cr alloy particles 8 are bonded around the Mg particles 7 as shown in FIG. . At this time, Mg particles 7 or Ti—Cr alloy particles 8 may also be bonded. This bond is due to a mechanochemical action. Particles obtained by pulverization can be used as the hydrogen storage body 10.

Hereinafter, the present invention will be described based on specific examples.
A hydrogen storage body was prepared in the following manner.
(1) 400g of cutting powder was produced from Mg lump. Hydrogen powder was pulverized by repeatedly storing and releasing hydrogen into 400 g of cutting powder to obtain Mg powder. Note that this Mg powder does not contain hydrogen because hydrogen is finally released. The obtained Mg powder was classified using a sieve having an opening of 150 μm.
(2) An alloy having a composition of Mo ₄ Ti ₃₉ Cr ₅₇ (at%) was produced by arc melting. Ti-Cr alloy with bcc phase as main phase by heat-treating Mo ₅ Ti ₄₁ Cr ₅₄ alloy (at%) prepared by arc melting at 1400 ° C for 10 minutes and then immediately quenching in water Got. The obtained Ti—Cr alloy was pulverized with a ball mill (pulverization time: 2 hours) to obtain Ti—Cr alloy powder having an average particle diameter of 1 to 2 μm. This pulverization was performed in a state where hydrogen was occluded in the Ti—Cr alloy. The Ti—Cr-based alloy powder obtained after pulverization was held at 500 ° C. for 20 minutes under reduced pressure (10 ⁻² Pa or less) to perform dehydrogenation.

(3) The Mg powder obtained in (1) and the Ti—Cr alloy powder obtained in (2) were mixed at a weight ratio of 87:13. This mixed powder was processed by the MCB method described above. When the treated powder was observed with SEM and SEM-EDS, no aggregation was confirmed, and it was confirmed that a composite in which Ti—Cr alloy particles were uniformly dispersed and bonded around the Mg particles was obtained. It was.

(4) The composite (50 g) obtained in (3) and a φ12 mm stainless steel media ball (2 kg) were charged into the pot, and then the pot was sealed. In addition, the above process was performed in the glove box substituted with Ar gas. Next, pressure reduction and Ar gas insertion were alternately repeated on the pot to replace the inside of the pot with Ar gas, and the pot was further evacuated (approximately 10 Pa or less) with a rotary pump.
Thereafter, the pot containing the composite and the stainless steel balls was rotated at 50 rpm on a frame constituting the ball mill for 300 hours.
(5) After rotating for 300 hours, the pot was opened and the composite was taken out. The composite was grown into plate-like particles having a width of about 3 mm and a thickness of about 100 μm. This treatment was also performed in a glove box substituted with Ar gas.

  The hydrogen absorption / release characteristics of the plate-like particles obtained above were evaluated. The evaluation procedure is as follows. The plate-like particles were put in a sample tube, heated to 400 ° C. under reduced pressure, and pressurized at that temperature so that the hydrogen pressure became 7 MPa. This decompression and pressurization were repeated three times. Thereafter, in a glove box substituted with Ar gas, the plate-like particles were put in a stainless mortar and pulverized lightly with a pestle. The obtained powder was passed through a 150 μm sieve to obtain a powder sample. The 0.7 g sample thus obtained was placed in a sample tube and decompressed at 400 ° C., and then the absorption / release characteristics at temperatures of 280 ° C., 240 ° C., and 200 ° C. were measured. The measurement results are shown in Table 1. In addition, the measurement was performed according to the pressure-composition isotherm (PCT line) by the vacuum origin method (JIS H7201). The results are shown in Table 1, and a high hydrogen release amount of 4.7 mass% was obtained even at 200 ° C. Therefore, it is speculated that a mechanochemical reaction occurs between the Mg particles and the Ti—Cr alloy particles.

A hydrogen storage body was prepared in the following manner.
(1) 400g of cutting powder was produced from Mg lump. After hydrotreating 400 g of cutting powder by repeatedly storing and releasing hydrogen, the powder was ground by a ball mill to obtain Mg powder. The grinding time is 4 hours. The obtained Mg powder was dehydrogenated by subjecting it to a reduced pressure treatment at 400 ° C. When the particle size of the Mg powder after the dehydrogenation treatment was measured, the average particle size was 3.3 μm.
(2) A spherical Pd powder having an average particle diameter of 20 nm was prepared, and the Mg powder obtained in (1) and the Pd powder were mixed at a weight ratio of 90:10. This mixed powder was processed by the MCB method described above. When the powder after the treatment was observed with TEM and TEM-EDS, it was confirmed that a composite in which the surface of Mg particles was covered with Pd particles was obtained. The thickness of the Pd particles covering the Mg particles was in the range of 20 to 70 nm. Further, the Pd particles covered about 1/2 of the surface of the Mg particles.
(3) The composite (50 g) obtained in (2) and a media ball (2 kg) made of φ12 mm stainless steel were put into the pot, and then the pot was sealed. In addition, the above process was performed in the glove box substituted with Ar gas. Next, pressure reduction and Ar gas insertion were alternately repeated on the pot to replace the inside of the pot with Ar gas, and the pot was further evacuated (approximately 10 Pa or less) with a rotary pump. Thereafter, the pot containing the composite and stainless steel balls was continuously rotated for 300 hours at 50 rpm on a frame constituting a ball mill.

(4) After rotating for 300 hours, the pot was opened and the complex was taken out. The composite was grown into plate-like particles having a width of about 3 mm and a thickness of about 100 μm. This treatment was also performed in a glove box substituted with Ar gas.

(5) The plate-like particles obtained in (4) were put in a sample tube, heated to 400 ° C. under reduced pressure, and pressurized at that temperature so that the hydrogen pressure became 7 MPa. This decompression and pressurization were repeated three times. Then, in the glove box substituted with Ar gas, the plate-like particles were put in a stainless mortar and crushed by lightly rubbing with a pestle.
When the powder was observed by SEM-EDS and TEM-EDS, the presence of Pd particles could be confirmed in almost all powders although the amount of Pd powder added was as small as 10% by weight. The Pd particles have a curved band shape and a thickness of 10 to 80 nm.

(6) The hydrogen absorption / release characteristics of the plate-like particles obtained in (4) were evaluated. The evaluation procedure is as follows. The plate-like particles were put in a sample tube, heated to 400 ° C. under reduced pressure, and pressurized at that temperature so that the hydrogen pressure became 7 MPa. This decompression and pressurization were repeated three times. Thereafter, in a glove box substituted with Ar gas, the plate-like particles were put in a stainless mortar and pulverized lightly with a pestle. The 0.7 g sample thus obtained was placed in a sample tube, depressurized at 400 ° C., and then cooled to room temperature while maintaining a hydrogen pressure of 7 MPa. After cooling, the hydrogen pressure was set to 0.2 MPa.
The sample was moved to the hydrogenation chamber without being exposed to the atmosphere, kept in vacuum for 12 hours, and then kept in an atmosphere of hydrogen gas pressure 0.1 MPa and 130 ° C. for 24 hours.

  Then, after holding the sample in vacuum, the temperature was raised from room temperature to 240 ° C., the hydrogen release temperature was confirmed by thermal temperature programmed desorption analysis (TDS), and the hydrogen release amount was measured by quadrupole mass spectrometry. . As a result, it was confirmed that the hydrogen release start temperature was 110 ° C. or lower and the hydrogen release peak temperature was 180 ° C. Further, the hydrogen release amount was 5.6 mass%. Thus, since there was a hydrogen release peak at a temperature of 200 ° C. or less and a high hydrogen release amount of 5.6 mass% was obtained, a mechanochemical reaction occurred between Mg particles and Pd particles. It is assumed that

Commercially available Mg powder was classified using a sieve having an opening of 150 μm. Moreover, Ni powder with an average particle diameter of 70 nm was prepared. The classified Mg powder and Ni powder were mixed at a weight ratio of 70:30. This mixed powder was processed by the grinding method of the present invention described above. When the powder after the treatment was observed with SEM-EDS, it was confirmed that it was a composite in which Ni particles covered 90% or more of the surface of Mg particles.
A pellet was prepared from 0.25 g of the obtained composite and 0.75 g of Cu powder, and an evaluation electrode was manufactured by holding the pellet with Ni wire. As a result of performing reduction for 50 hours at 40 mA / g using an evaluation battery in which this electrode is a negative electrode, a Ni plate is a positive electrode, and an electrolytic solution is a 6M KOH aqueous solution, the amount of oxidized electricity is measured at 8 mA / g. A large value of g was obtained.

It is a figure which shows the concept of MCB. An example of a device configuration capable of performing MCB is shown. It is a figure which shows the process of coat | covering 2nd particle | grains by MCB around 1st particle | grains. It is a figure which shows typically the manufacturing method of the hydrogen storage body by the 2nd method in this invention. It is a figure for demonstrating the stress state which generate | occur | produces by hydrogen absorption / release. It is a figure which shows typically the manufacturing method of the hydrogen storage body by the 3rd method in this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Processing apparatus, 2 ... Rotary casing, 2a ... Inner wall, 3 ... Chip, 4 ... Lake, 5 ... 1st particle, 6 ... 2nd particle, 7 ... Mg particle, 8 ... Ti-Cr type alloy particle, 9, 11 ... Aggregates, 10 ... Hydrogen storage bodies

Claims (12)

A method for producing a hydrogen storage body, comprising: first particles responsible for storing and releasing hydrogen; and second particles combined with the first particles,
A mixing step of obtaining a mixture of the first particles and the second particles;
A joining step of repeating the process of passing the mixture through a predetermined gap formed by a rigid body a plurality of times;
A method for producing a hydrogen storage body, comprising:   The method for producing a hydrogen storage body according to claim 1, wherein the second particles have a smaller diameter than the first particles.   The method for producing a hydrogen storage body according to claim 1 or 2, wherein the particle size of the second particles is 1/50 or less of the particle size of the first particles.   4. The method according to claim 1, further comprising an energy applying step of obtaining an aggregate in which the processed products are combined by applying mechanical energy to the processed products obtained by the combining step. The manufacturing method of the hydrogen storage body as described in any one of.   The method for producing a hydrogen storage body according to any one of claims 1 to 4, wherein the application of the mechanical energy is performed by a collision of media.   6. The method for producing a hydrogen storage body according to claim 4, wherein the first particles are spread and the first particles are bonded to each other to form the flat aggregate.   The method for producing a hydrogen storage body according to any one of claims 4 to 6, wherein the aggregate is pulverized.   By applying mechanical energy to predetermined particles, an aggregate in which the first particles are bonded to each other is produced, and particles obtained by pulverizing the aggregate are used as the first particles and the second particles. The method for producing a hydrogen storage body according to claim 1, wherein the mixture is obtained.   The said 1st particle | grain is comprised from Mg or Mg alloy, The manufacturing method of the hydrogen storage body in any one of Claims 1-8 characterized by the above-mentioned.   The method for producing a hydrogen storage body according to any one of claims 1 to 9, wherein the second particles are made of a Ti-Cr alloy. A method for producing a hydrogen storage body capable of storing and releasing hydrogen, comprising:
A step of obtaining a deposit treatment product in which Ti—Cr-based alloy particles are deposited around Mg metal particles responsible for storing and releasing hydrogen;
A step of performing an orientation treatment on the Mg metal particles in the coated product;
A method for producing a hydrogen storage body, comprising: A method for producing a hydrogen storage body capable of storing and releasing hydrogen, comprising:
A step of performing an alignment process on the Mg metal particles responsible for the storage and release of hydrogen to obtain an alignment processed product;
A deposition treatment step of depositing Ti-Cr-based alloy particles around the alignment treatment product;
A method for producing a hydrogen storage body, comprising:

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