JP4086241B2 - Hydrogen storage alloy powder - Google Patents

Description

  The present invention relates to a hydrogen storage alloy powder having a nanostructured surface and excellent initial activation performance and hydrogen storage performance.

  A hydrogen storage alloy capable of reversibly occluding or releasing hydrogen gas at around room temperature makes it possible to store or transport a large amount of hydrogen gas, which is an alternative energy, in a lightweight and safe manner. The hydrogen storage alloy also has a wide function of being able to convert hydrogen gas, which is an energy medium, into heat, chemical, mechanical and electrical energy when necessary using this reversible reaction.

  Various methods have been studied for producing this hydrogen storage alloy. As a typical production method, a raw material metal is introduced into a melting furnace to be melted, cast into a mold and solidified. A casting method in which the alloy ingot is mechanically pulverized with a crusher or the like to produce a hydrogen storage alloy powder, or a high energy mixing and stirring device such as a ball mill for two or more types of metal powder. A mechanical alloying method is widely known that uses a solid-phase reaction by repeating mixing and grinding of metal powder to produce uniform alloy particles in a solid state. In particular, the mechanical alloying method as a manufacturing method can alloy and powder two or more kinds of metal powders at a temperature lower than the melting point by utilizing mechanical energy. It is not necessary to provide a pulverization step for producing powder.

  By the way, the hydrogen occlusion reaction of the hydrogen occlusion alloy is such that after hydrogen molecules are physically adsorbed on the surface of the hydrogen occlusion alloy, the hydrogen molecules are dissociated into hydrogen atoms and chemically adsorbed on the surface of the alloy. Through the process of dissolving and diffusing in the alloy, hydrogen is occluded in the alloy. Therefore, as a hydrogen storage alloy, it is necessary to dissociate hydrogen molecules into hydrogen atoms and chemically adsorb them on the surface of the alloy and to efficiently dissolve and diffuse them inside the crystal structure alloy.

  As described above, the hydrogen storage alloy has an internal structure as a crystal structure and stores hydrogen in the gaps of the crystal structure. In such a crystal structure, hydrogen molecules are formed on the surface of the alloy. It was difficult to dissociate hydrogen into hydrogen atoms and to adsorb the hydrogen atoms. Further, in order to promote such dissociation of hydrogen molecules and occlusion / release of hydrogen, the hydrogen storage alloy has been required to have an initial activation process as a pretreatment.

  Such initial activation treatment is generally performed by repeating the operation of introducing and exhausting hydrogen under high pressure several times. However, these operations require complicated steps and operations and require a lot of time. There has been a demand for a hydrogen storage alloy with improved initial activation performance that can reduce the load caused by the activation treatment as much as possible. And the hydrogen storage alloy obtained by using mechanical alloying method with a ball mill etc. tends to improve the initial reactivity with hydrogen, while the maximum hydrogen storage amount of the hydrogen storage alloy is Compared with the one manufactured using, it was slightly inferior.

  On the other hand, in order to improve the initial activation performance and the maximum hydrogen storage amount, a third component layer is formed on the surface of the hydrogen storage alloy, or the surface of the hydrogen storage alloy is treated with a treatment solution or a buffer solution. Thus, means for modifying the surface of the hydrogen storage alloy is used.

  Examples of the former include a hydrogen storage alloy in which a layer of a hydride of an alloy having hydrogen storage performance is formed on at least a part of the surface of the mother alloy particles (for example, Patent Document 1). Further, when activating a hydrogen storage alloy containing Mg (magnesium), Ti (titanium) or V (vanadium), these metals and hexagonal boron nitride are mechanically mixed to produce the hexagonal nitriding. A hydrogen storage material in which the surface state is modified by refining boron has been proposed (for example, Patent Document 2). Moreover, as the latter, for example, a hydrogen storage alloy obtained by immersing and stirring in an alkali solution of a hydrogen storage alloy, then immersing and stirring in an acidic aqueous solution or acidic buffer, and then washing with water has been provided (for example, Patent Documents). 3).

JP-A-9-143503 (Claim 1) JP 2003-321703 A (Claim 1, FIG. 1) Japanese Patent Laid-Open No. 10-158767 (Claim 2, FIG. 1)

  However, it is difficult to achieve both the initial activation performance and the maximum hydrogen storage capacity improvement in the hydrogen storage alloy. When the third component layer is formed on the surface of the hydrogen storage alloy, the surface reactivity is reduced. Although the effect on the initial activation performance was observed, the amount of hydrogen occlusion could not be improved. In addition, in the case where the hydrogen storage alloy is to be surface-treated with an acid or alkali treatment solution or a buffer solution, in addition to the above-described problems, there is a problem that the constituent components of the alloy are eluted. It was.

  Accordingly, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a hydrogen storage alloy powder that has good initial activation performance, reacts quickly with hydrogen, and is excellent in hydrogen storage performance.

In order to solve the above problems, the hydrogen storage alloy powder of the present invention is composed of Ti (titanium) and Fe (iron) with a blending ratio of 1: 1, and has a thickness from the surface of 0.005 to 0.01 μm. Is characterized by being nanostructured.

  Here, the “nanostructure” is composed of a crystalline region and an amorphous region (amorphous phase, metastable phase having short-range order), and these are several to several tens of nanometers (nanometer (nm)) : 10 −9 to the power of a meter) A structure composed of ultrafine regions on the scale.

  In the hydrogen storage alloy powder of the present invention, since the alloy surface is nanostructured, the alloy surface becomes reactive and the reactivity between the alloy powder and hydrogen is dramatically promoted. That is, hydrogen molecules can be physically adsorbed on the surface of the hydrogen storage alloy, and the hydrogen molecules can be easily dissociated into hydrogen atoms and chemically adsorbed on the alloy surface. Is reduced, and the hydrogen storage alloy powder has excellent initial activation performance.

  In addition, since the hydrogen storage alloy powder of the present invention maintains the crystal structure inside the alloy powder, hydrogen atoms are suitably dissolved and diffused inside the hydrogen storage alloy powder, and many hydrogen atoms are stored in the alloy. Therefore, the hydrogen storage alloy powder having a large hydrogen storage amount is obtained.

Hydrogen hydrogen absorbing alloy powder of the present invention, the thickness from the surface for up 0.005~0.01μm (5~10nm) is nanostructured, which combines good balance initial activation performance and hydrogen-absorbing performance It becomes a storage alloy powder.

Since the hydrogen storage alloy powder of the present invention has a hydrogen storage amount of 1.2% by mass or more, the hydrogen storage amount is excellent, and Ti-Fe such as a stationary hydrogen storage and utilization facility for storing a large amount of hydrogen. The hydrogen storage alloy powder of the system (titanium-iron system) can be applied to applications that require a large amount of hydrogen storage.

The hydrogen storage alloy powder of the present invention is composed of titanium (Ti) and iron (Fe) and the surface thereof is nanostructured. Ti (titanium) used as a raw material for the hydrogen storage alloy powder and the average particle diameter of the metal raw material powder composed of Fe (iron) may be about 1 to 500 [mu] m, about 10~100μm are preferred.

Further, as the metal raw material powder, a Ti—Fe-based (titanium-iron-based) alloy obtained by alloying titanium (Ti) and iron (Fe) is used . By making the metal raw material powder into such an alloy, the burden of alloying the metal raw material powder can be reduced or omitted in mechanical alloying, which can simplify the subsequent ball milling process and reduce the manufacturing cost. it can.

Here, as the Ti-Fe alloy, titanium (Ti) and iron (Fe) raw materials melted in a vacuum melting furnace were cast into a mold and solidified to mechanically pulverize the Ti-Fe alloy ingot. An atomized powder of Ti and Fe obtained by alloying titanium (Ti) and iron (Fe) by atomization can be used.
Atomizing treatment includes, for example, a high pressure gas atomizing treatment in which high pressure gas is blown onto molten metal to form an alloy or fine powder, or a method in which molten metal or the like is dropped onto a disk rotating at a high speed of several thousand to several tens of thousands of revolutions / minute and blown off. Well-known means such as a rotating disk atomizing process for alloying and pulverizing can be used. The average particle diameter when such atomized powder is used as the metal raw material powder may be about 1 to 500 μm, and preferably about 10 to 250 μm.

  Moreover, what is necessary is just to set the compounding ratio of both in metal raw material powder to Ti: Fe = 40: 60-60: 40, and it is preferable to set it as 45: 55-55: 45. If the ratio of Ti is higher than the above blend ratio, it may be difficult to release even if hydrogen is absorbed. Conversely, if the ratio of Ti is low, it may be difficult to absorb hydrogen. .

  In addition to Ti and Fe described above, the metal raw material powder of the hydrogen storage alloy obtained by the production method of the present invention includes Pd, Mn, Al, Co, as long as the objects and effects of the present invention are not affected. One or more metal powders selected from the group consisting of V, Cr, Mo, Ni, Zr, Nb, and Be can be added.

  In the production method of the present invention, pretreatment such as heat treatment, surface treatment, and pickling treatment may be performed on the metal raw material powder as long as the object and effect of the present invention are not affected.

Then, the hydrogen storage alloy powder of the present invention is such that the metal raw material powder containing Ti and Fe is processed by ball milling to have a nanostructured surface.
Here, the nanostructured portion of the hydrogen storage alloy powder of the present invention is preferably nanostructured 0.005 μm (5 nm) or more from the surface of the alloy powder, for example, 0.005 to 0.01 μm. It is particularly preferred that (5-10 nm) is nanostructured. It is preferable that the nanostructured portion be in such a range because a hydrogen storage alloy powder having a good balance between initial activation performance and hydrogen storage performance is obtained.
In the hydrogen storage alloy powder of the present invention, the entire surface of the alloy powder is preferably nanostructured, but a part of the surface may be nanostructured.

  Ball milling generally refers to a technique in which metal raw material powder is mixed and pulverized by a ball mill or the like, and ball milling of metal raw material powder containing two or more kinds of metal elements, particularly mechanical alloying ( MA) or mechanical gliding (MG).

This mechanical alloying method (hereinafter sometimes abbreviated as “MA method”) is a method of using a high-energy mixing stirrer or the like for a metal raw material powder containing two or more kinds of metal elements. Is a method of producing a uniform alloy particle in a solid state by solid-phase reaction by ball milling by repeated mixing and grinding.
In the present invention, the “mechanical alloying method” includes the meaning of “mechanical gliding (MG) method” exclusively for the purpose of mixing and pulverizing the components and pulverization.

  In the case of producing the hydrogen storage alloy of the present invention, when a mixed powder of Ti powder and Fe powder is used as the metal raw material powder, the treatment by the MA method as ball milling is mainly performed by the hydrogen storage alloy powder. It plays the role of surface nanostructuring, alloying treatment, and grinding / pulverization treatment. On the other hand, when Ti—Fe-based alloy powder is used as the metal raw material powder, the treatment by the MA method mainly plays the role of nano-structuring the surface of the hydrogen storage alloy powder and grinding / pulverization treatment. .

  Examples of the ball milling method (ball mill method) include a rotating ball mill method, a vibration ball mill method, a planetary ball mill method, and a stirring ball mill method (also referred to as an attritor). In the production method of the present invention, It is preferable to use the vibration ball mill method and the planetary ball mill method, and it is particularly preferable to use the rotating ball mill method and the vibration ball mill method.

  In the rotating ball mill method, a container containing metal raw material powder and a ball for mixing and grinding (hereinafter sometimes simply referred to as “ball”) is rotated, and the collision between the raw material powder and the container and the ball causes In this method, the metal raw material powder is mechanically mixed and ground in a high energy state to be alloyed or pulverized.

  In addition, the vibration ball mill method means that a cylindrical container containing a metal raw material powder and a ball for mixing and grinding is subjected to high-speed circular vibration, and the simultaneous action of intense shock and friction between the raw material powder and the inner wall of the container and the raw material powder. This is a method of pulverizing in a short time, mixing and pulverizing the metal raw material powder in the container in a mechanically high energy state, and alloying or pulverizing. In the production method of the present invention, the vibration ball mill method can be used for both dry and wet processes.

  In the planetary ball mill method, a container containing metal raw material powder and a ball for mixing and grinding is placed on a gantry and the container is rotated (rotated), and the gantry on which the container is placed is rotated (revolved). ), And the metal raw material powder in the container is mechanically mixed and pulverized in a high energy state to be alloyed or pulverized by collision of the raw material powder with the container and the ball for mixing and pulverizing. Is the method.

When using the ball mill method, the metal raw material powder, which is the raw material used, is mixed and ground in a container (pot) together with the ball for mixing and grinding, and the metal raw material powder is mixed and ground using means such as rotating the container. A hydrogen storage alloy powder is prepared by the following means.
In the case of producing the hydrogen storage alloy powder of the present invention, the shape of the container used can be various shapes such as a cylindrical shape and a rectangular tube shape, but it is preferable to use a cylindrical shape. .

The capacity of the container is appropriately determined depending on the amount of the metal raw material powder used, the size and number of balls for mixing and grinding, etc., but generally may be about 80 to 500 ml.
Further, the material of the container can be stainless steel, chromium, tungsten, alumina, zirconia, etc., and stainless steel is particularly preferable.

  Similarly, the material of the balls for mixing and grinding used for carrying out the ball mill method can be stainless steel, chromium, tungsten, alumina, zirconia, etc., and particularly preferably stainless steel.

The size of the ball for mixing and pulverizing is appropriately determined depending on the capacity of the container to be used as described above. Generally, when producing hydrogen storage alloy powder having a nanostructured surface, the diameter is generally φ10 mm. It is preferable to use one having a diameter of about ~ 30 mm.
In the MA method, a plurality of mixed and pulverized balls are usually used. However, when producing the hydrogen storage alloy powder of the present invention, all the balls have the same size. Alternatively, different sizes may be used.

  Also, the number of balls for mixing and grinding is preferably 1 to 5 in order to produce hydrogen storage alloy powder having a nanostructured surface. By setting the relationship between the capacity of the container and the size and quantity of the balls for mixing and grinding as described above, a hydrogen storage alloy powder having a nanostructured surface can be preferably produced.

  In producing the hydrogen storage alloy powder of the present invention, the relationship between the volume of the container and the size of the ball for mixing and grinding, and the weight ratio between the metal raw material powder to be used and the total weight of the ball for mixing and grinding, What is necessary is just to determine suitably according to the quantity of the hydrogen storage alloy powder to manufacture, the grade of the nanostructured part of the alloy powder surface required, etc.

  When producing the hydrogen storage alloy powder of the present invention, when performing ball milling, the rotational speed of the container (in addition to the planetary ball mill method, in addition to the mount on which the container is placed) is determined by the planetary ball mill method as the ball mill method. When using, it is preferable that the rotation speed (autorotation rotation speed) of a container shall be 200-1050 rpm. Moreover, it is preferable that the rotation speed (revolution rotation speed) of the gantry is 200 to 700 rpm (and the rotation speed of the container: the rotation speed of the gantry = 1.5: 1 to 1: 1). When the rotational speed is within these ranges, the hydrogen storage alloy powder can be alloyed or pulverized / pulverized and the nanostructure of the surface can proceed efficiently, and the hydrogen storage performance combines initial activation performance and hydrogen storage performance. Since alloy powder can be obtained suitably, it is preferable.

Furthermore, the revolution radius in the case of using the planetary ball mill method may be about 30 to 300 cm, and preferably about 50 to 100 cm.

On the other hand, when the rotating ball mill method is used as the ball mill method in producing the hydrogen storage alloy powder of the present invention, the rotational speed of the container is preferably 200 to 1050 rpm. When the rotational speed is within these ranges, as in the planetary ball mill method described above,
Alloying or crushing / pulverization and surface nano-structuring of the hydrogen storage alloy powder proceed efficiently, and a hydrogen storage alloy powder having both initial activation performance and hydrogen storage performance can be suitably obtained.

Milling time in the case of producing a hydrogen-absorbing alloy powder of the present invention, the type of ball mill method to be used, the amount of metal raw material powder, the size and number of mixing and grinding balls is suitably determined by the capacity of the container or the like, as metallic material powder, in the case of using a Ti-Fe-based alloy powder may be set to about two hours 1.5. If ball milling is performed within this range, alloying or pulverization / pulverization of the hydrogen storage alloy powder and nano-structure of the surface proceed efficiently, and hydrogen storage that combines initial activation performance and hydrogen storage performance. Since alloy powder can be obtained suitably, it is preferable.

  On the other hand, when the milling time is shorter than the above-mentioned range, the nanostructure of the surface of the alloy powder does not progress, and the initial activation performance may not be good, resulting in a hydrogen storage alloy powder. However, when the above range is exceeded, nanostructuring may proceed excessively from the surface to the inside, which may adversely affect the hydrogen storage performance of the alloy powder.

  In producing the hydrogen storage alloy powder of the present invention, the atmosphere in the container described above is preferably an inert gas atmosphere such as argon, nitrogen, helium or the like, or a hydrogen gas atmosphere, and particularly an argon gas atmosphere. It is preferable. By setting the atmosphere in the container to such a state, oxidation of the metal raw material powder can be prevented.

The average particle diameter of the hydrogen storage alloy powder of the present invention is about 1 to 500 μm. Here, the average particle size of the hydrogen storage alloy powder is greatly related to the hydrogen storage performance and production cost of the alloy. That is, since the hydrogen gas storage or release reaction occurs on the surface of the hydrogen storage alloy powder, by reducing the average particle size of the hydrogen storage alloy, the surface area per unit weight is increased to facilitate the reaction. It is possible to increase the reaction rate. In addition, since the average particle size is small, it is difficult to pulverize, so there is an advantage that it is effective for repeated use. On the other hand, in order to reduce the average particle size, a very large mechanical energy is required at the time of manufacture, which increases the manufacturing cost, and if the average particle size is small, the particle size distribution becomes large. In some cases, a process is required, which also increases the manufacturing cost.
On the other hand, since the hydrogen storage alloy powder of the present invention has an average particle diameter of about 1 to 500 μm as described above, it becomes a hydrogen storage alloy powder having a good balance between hydrogen storage performance and manufacturing cost.

  The hydrogen storage alloy powder of the present invention obtained as described above has a nanostructured alloy surface, so that the alloy surface becomes reactive and the reactivity between the alloy powder and hydrogen is greatly accelerated. Is done. That is, hydrogen molecules can be physically adsorbed on the surface of the hydrogen storage alloy powder, and the hydrogen molecules can be easily dissociated into hydrogen atoms and chemically adsorbed on the alloy surface. Therefore, the load in initial activation is reduced, and the hydrogen storage alloy powder is excellent in initial activation performance.

  In addition, since this hydrogen storage alloy powder maintains the crystal structure inside the alloy powder, it is possible to suitably dissolve and diffuse hydrogen atoms in the hydrogen storage alloy powder, and to store many hydrogen atoms in the alloy. Therefore, a hydrogen storage alloy powder having a large hydrogen storage capacity is obtained.

  Here, the initial activation treatment for the hydrogen storage alloy powder is generally a treatment such as holding at a high temperature or high vacuum for a certain period of time, or holding in a high pressure hydrogen atmosphere for a long time at a temperature at which hydrogen is easily absorbed. However, in the hydrogen storage alloy powder of the present invention, for example, a heat treatment at about 300 ° C. may be performed for about 2 hours.

  In order to adsorb hydrogen to the hydrogen storage alloy powder of the present invention, for example, the hydrogen storage alloy powder may be held in a sealed container filled with a hydrogen atmosphere.

Further, the hydrogen storage alloy powder of the present invention obtained as described above will be further described with reference to FIGS.
FIG. 1 is a schematic view showing the structure of the hydrogen storage alloy powder of the present invention, and FIG. 2 is a schematic view showing the dissociation state of hydrogen molecules on the surface of the hydrogen storage alloy powder of FIG.
Here, in FIG.1 and FIG.2, 1 is hydrogen storage alloy powder, 2 is a surface part, 3 is an inside, 4 is a hydrogen atom, 5 is a hydrogen molecule.
The hydrogen storage alloy powder of the present invention is formed such that the surface portion 2 has a nanostructure and the interior 3 has a crystal structure. Moreover, the surface part 2 used as nanostructure is about 0.005-0.01 micrometer (5-10 nm) thickness, for example.

  Thus, the hydrogen storage alloy powder 1 of the present invention having the surface portion 2 having a nanostructure and the inside 3 having a crystal structure, as shown in FIG. 2, when hydrogen molecules 5 are physically adsorbed, The hydrogen molecules 5 are easily dissociated into hydrogen atoms 4, and chemical adsorption by the dissociated hydrogen atoms 4 easily occurs.

  This is because the surface portion 2 is composed of a nanostructure, that is, a crystalline region and an amorphous region, and these are composed of ultrafine regions on the order of several to several tens of nanometers. Specifically, the specific surface area of the surface portion 2 of the alloy powder 1 and the grain boundary can be increased by nano-structuring the crystal of the surface portion 2 of the alloy powder 1. In addition, these interfaces are in a chemically very active state, so that the hydrogen molecules 5 dissociate into hydrogen atoms 4 and easily enter the metal.

  On the other hand, the hydrogen atoms 4 chemically adsorbed on the surface of the alloy powder 1 are introduced into the interior 3 of the alloy powder 1, but since the interior 3 has a crystal structure, Diffusion is preferably performed. Since the hydrogen storage alloy powder 1 of the present invention has such a specific structure, dissociation of the hydrogen molecules 5 and storage / release of the hydrogen atoms 4 can be easily performed, and the initial activation performance and the hydrogen storage performance are improved. The hydrogen storage alloy powder 1 can be provided.

  And since the hydrogen storage alloy powder of this invention is the above structures, it can be set as 1.2-1.6 mass% or more hydrogen storage amount. Accordingly, such a hydrogen storage alloy powder having a large hydrogen storage amount is used for a stationary hydrogen storage and utilization facility for storing a large amount of hydrogen, etc., which requires a large hydrogen storage amount for the Ti-Fe-based hydrogen storage alloy powder. Also, it can be suitably used.

  EXAMPLES Next, although an Example and a comparative example are given and this invention is demonstrated in more detail, this invention is not restrict | limited at all by these Examples.

[Example 1: Production of hydrogen storage alloy powder]
(1) Preparation of metal raw material powder The raw material metal was charged into a vacuum melting furnace, melted, cast into a mold and solidified to obtain a Ti-Fe alloy ingot (mixing ratio of Ti and Fe / 1: 1). Thereafter, the alloy ingot was pulverized with a commercially available hammer to obtain a metal raw material powder (total amount 70 g) having a particle size of 5 mm or less.

(2) Ball milling process:
This metal raw material powder was used as a test apparatus using a planetary ball mill (product number: P-5) manufactured by Fritzche, Germany, in a 250 ml container (inner diameter: φ75 mm, external height 102 mm (internal height 70 mm)), φ25 mm. Four stainless steel balls for mixing and pulverization were placed, and the inside of the container was filled with an argon gas as an inert gas. The inside of the container was filled with an argon gas atmosphere, and then the container was covered and sealed.

  Then, this container is placed on the gantry of the planetary ball mill test device, the rotation speed (rotational speed) of the container is 430 rpm (rotation direction: right direction), and the rotation speed (revolution speed) of the gantry is 200 rpm (rotation direction: left direction) ), Ball milling was performed with a revolution radius of 30 cm and a milling time of 2 hours to produce a Ti—Fe-based hydrogen storage alloy powder having an average particle size of 10 μm.

[Test Example 1: Confirmation of nanostructure formation on alloy powder surface]
The hydrogen storage alloy powder obtained in Example 1 was observed to confirm the formation state of the surface nanostructures. When the thickness of the nanostructure from the surface of the hydrogen storage alloy powder was confirmed, it was 0.005-0.01 micrometer.

[Test Example 2: Evaluation of hydrogen storage performance]
After activating the hydrogen storage alloy powder obtained in Example 1 under the following conditions, hydrogen pressure was applied at a temperature of 20 ° C. and a pressure of 3.2 MPa to react with hydrogen to obtain an alloy powder. On the other hand, hydrogen was occluded, and the relationship between the pressurization time and the hydrogen occlusion amount, and the maximum hydrogen occlusion amount were compared and evaluated. Moreover, what carried out hydrogen pressurization with respect to what used the metal raw material powder used in above-mentioned Example 1 as it is ((2) thing which does not perform ball milling) Reference example, and the metal raw material powder of a reference example In the same manner, Comparative Example 1 was subjected to the activation treatment under the following conditions and then pressurized with hydrogen. A graph showing the relationship between the hydrogen pressurization time and the hydrogen storage amount is shown in FIG. 1, and the maximum hydrogen storage amount of each is shown in Table 1.

(Activation processing conditions)
The target hydrogen storage alloy powder was evacuated at room temperature, and then hydrogen gas was introduced at a temperature of 300 ° C. and a pressure of 0.5 MPa, followed by pressurization for 2 hours. After 2 hours, the pressurization was stopped, the air was cooled to room temperature, and then opened.

(Maximum hydrogen storage capacity)

As shown in FIG. 3, the hydrogen storage alloy powder of Example 1 showed a large hydrogen storage amount immediately after being pressurized with hydrogen, and the hydrogen storage amount was also large.
In addition, the alloy powder that was not ball milled on the metal raw material powder hardly absorbs hydrogen even after the activation treatment and hydrogen pressurization (Comparative Example 1). On the other hand, as-cast alloy powders that were not ball milled and not activated did not occlude hydrogen even when hydrogen pressure was applied (reference example).

  And when comparing the hydrogen storage amount, as shown in Table 1, the hydrogen storage alloy powder of Example 1 is superior to 1.2 mass%, and is used for stationary hydrogen storage for storing a large amount of hydrogen. The application of the Ti-Fe-based hydrogen storage alloy powder, such as equipment, can be expected for applications that require a large amount of hydrogen storage.

The hydrogen storage alloy powder of the present invention is effective, for example, as a hydrogen storage alloy powder used in stationary hydrogen storage and utilization facilities that store hydrogen in large quantities.

It is the schematic diagram which showed the structure of the hydrogen storage alloy powder of this invention. It is the schematic diagram which showed the dissociation state of the hydrogen molecule in the surface of the hydrogen storage alloy powder of this invention. It is the graph which showed the relationship between hydrogen pressurization time and hydrogen storage amount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Hydrogen storage alloy powder 2 ... Surface part 3 ... Inside 4 ... Hydrogen atom 5 ... Hydrogen molecule

Claims (1)

A hydrogen storage alloy powder characterized in that it is composed of Ti (titanium) and Fe (iron) with a blending ratio of 1: 1, and has a thickness of 0.005 to 0.01 μm from the surface and is nanostructured.

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