JPS63310936A - Hydrogen storage alloy material and its production - Google Patents

Abstract

PURPOSE:To obtain the title hydrogen storage alloy material which is not damaged due to pulverization of the alloy even when the occlusion and release of hydrogen are repeated by coating the aggregate of the fine particles of the hydrogen storage alloy with a metal having higher malleability and ductility than the alloy, and compacting the aggregates into a compact. CONSTITUTION:The fine particles 2 of the alloy such as La-Ni are damped in water form a slurry (expressed by A hereunder). Meanwhile, the surface of the fine particle 6 of a metal such as Al having higher malleability and ductility than the alloy is subjected to oleophilic treatment by zinc stearate, etc., the fine particles 6 are dispersed in the org. solvent such a freon-based solvent incompatible with water and not damaging the oleophilic treatment to prepare a suspension (expressed by B hereunder). The A is finely dispersed in the B while agitating to form a W/O type emulsion, the emulsion is dried to obtain a body 7 covered with the aggregate 3 of the particles 2 of the storage alloy coated with the fine metal particles 6, and the bodies 7 are compacted to form the hydrogen storage alloy material 1.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to a hydrogen storage alloy material using a hydrogen storage alloy that absorbs and releases hydrogen, and a method for manufacturing the same.

"Prior Art" Conventionally, hydrogen storage alloys have been provided that have the function of storing hydrogen or releasing stored hydrogen by controlling temperature and pressure.

As for the use of this hydrogen storage alloy, in addition to hydrogen storage and hydrogen purification, research is being conducted into applications such as energy conversion using heat generation and heat absorption during hydrogen storage and release.

However, hydrogen storage alloys have the property of being easily disintegrated and powdered by repeated storage and release of hydrogen.Hydrogen storage alloys that have been powdered have the following problems. Ta.

■ Although the surface area of the hydrogen storage alloy increases due to pulverization, the thermal conductivity, which determines the absorption and release rate, decreases significantly, so the absorption and release rate slows down.

(2) Fine particles of the hydrogen storage alloy produced by powdering move with the flow of hydrogen, so when this alloy is used for hydrogen purification, the fine particles tend to get mixed into the purified hydrogen gas.

■When the hydrogen-absorbing alloy powder moves within the storage container and collects locally in the container, the powder expands locally while in a hydrogen-absorbing state, and a large stress is applied to the local portion of the container, causing the container to break.

Therefore, in order to solve the above problem, a method has been proposed in which hydrogen storage alloy powder is mixed with powder of a metal with better malleability, and the mixture is compression-molded using a powder compaction method to form a compact into a predetermined shape. is being attempted.

"Problems to be solved by the invention" The compression molded body of the above-mentioned hydrogen storage alloy powder and metal powder is
The hydrogen-absorbing alloy powder and the metal powder have almost the same particle size, and the metal powder simply acts as a binder between the hydrogen-absorbing alloy powders, so the hydrogen-absorbing alloy powder is exposed on the surface of the compact. Therefore, there was a problem in that fine particles of the hydrogen storage alloy were easily generated during hydrogen storage and release operations. Further, there was a problem that the molded body could not have sufficient strength.

The object of the present invention is to solve the above-mentioned problems and provide a hydrogen storage alloy material and a method for producing the same that do not cause harmful effects due to powderization of the storage alloy even after repeated storage and release of hydrogen. .

"Means for solving the problem" In this invention, a plurality of hydrogen storage alloy fine particles are aggregated to form an aggregate, and this aggregate is coated with a large number of fine particles of a metal that has better malleability than the hydrogen storage alloy. The solution to this problem was to create a covering body, and then compression mold a large number of these covering bodies to form a molded body.

Hereinafter, the first aspect of the present invention will be explained in detail with reference to the drawings. FIGS. 1 and 2 are diagrams showing an example of the hydrogen storage alloy material of the first aspect of the present invention.

In these figures, the symbol l represents a hydrogen storage alloy material (hereinafter abbreviated as storage alloy material). As shown in FIG. 1, this storage alloy material 1 is composed of aggregates 3.3 of a plurality of fine particles 2.2 of hydrogen storage alloys (hereinafter abbreviated as storage alloys). It is coated with a copper coating layer 4 to form a capsule-shaped coating, and a large number of these coatings are adhered to each other to form a disk-like shape as a whole.

The storage alloy fine particles 2.2... are made into fine particles with a particle size of 50 μm or less by mechanically crushing the storage alloy material or repeating hydrogen absorption and desorption operations, and the storage alloy material is L a -Ni-based alloy, Ti-Mn
alloy, Ti-Ni alloy, Fe-Ti alloy, MIl
L (mitshu metal) alloys and the like are preferably used.

The aggregate 3 is made up of a plurality of storage alloy fine particles 2.2...
* is in an agglomerated state, and the particle size is 300 μm or less. Binder 5.5 is attached to fine particles 2.2 of the storage alloy in an agglomerated state. This binder 5.5... is made up of storage alloy fine particles 2.2...
colloidal silica,
Particulate inorganic substances such as titanium dioxide and alumina, polyvinyl alcohol, fluororesin, and silicone resin are used.

The steel coating layer 4 is in the form of a porous film and covers the aggregate 3, so that hydrogen permeates into the interior of the storage alloy material 1. This copper coating layer 4 has a grain size of several μm.
When producing the storage alloy material 1 by attaching a large number of copper fine particles of about 100 mL to the surface of the aggregate 3 to cover the aggregate 3, and compression molding the thus obtained large number of coated bodies, the copper particles are removed by compression. Fine particles are pressed together to form a porous membrane. The surface of the storage alloy material 1 is covered with this copper coating layer 4, and the storage alloy fine particles 2.2 are not exposed.

The storage alloy material 1 described above can repeatedly store and release hydrogen by controlling the temperature and pressure. When storing hydrogen, hydrogen passes through the copper coating layer 4 and penetrates into the interior of the storage alloy material 1, and the fine particles 2.2 of the storage alloy absorb hydrogen. During this occlusion, the fine particles 2.2... expand, but because they are covered with the copper coating layer 4, they do not collapse. On the other hand, when releasing the stored hydrogen, the fine particles of the storage alloy 2.2
The hydrogen released from... passes through the copper coating layer 4 and is released from the storage alloy material l. In addition, this storage alloy material has extremely good thermal conductivity even though the contact surface area between the storage alloy and hydrogen is large because the storage alloy fine particles 2.2... are coated with copper. It is. Therefore, temperature control in each occlusion/desorption process can be easily controlled, and a delay in the occlusion/desorption rate due to a decrease in thermal conductivity can be prevented.

Note that the storage alloy material 1 described above contains fine particles 2.2 of the storage alloy.
Copper was used as the material for covering the aggregates 3, but any other material may be used as long as it has better malleability than the storage alloy; for example, aluminum can also be suitably used.

Next, the second aspect of the present invention will be explained in detail.

The storage alloys used in the method for producing the storage alloy material of the second invention include La-Ni alloys, Ti-Mn alloys, Ti-Ni alloys, Fe-Ti alloys, Mm (mitshu metal) alloys, etc. is preferably used. Usually one type of storage alloy is used, but a mixture of two or more types may be used. This adsorbed alloy is powdered into fine particles 2.2... having a particle size of 20 μm or less, preferably several μm or less.

This pulverization can be easily carried out by mechanical pulverization or repeated hydrogen absorption and release. The obtained fine particles 2.2... are made into a slurry (hereinafter referred to as A) by adding water.

On the other hand, the surfaces of the fine metal particles 6.6, which have better malleability than the storage alloys mentioned above, are modified to be lipophilic with a rust preventive agent or a wax or fatty acid metal salt that is generally used as a lubricant in compression molding. For example, when using fine metal particles 6.6... and copper powder, it can be easily treated by contacting it with a solution of a rust preventive agent such as benzotriazole, and in particular, it can be treated with a volatile rust preventive agent. This is preferred because it can be easily removed by heating later. In the case of electrolytic copper powder, there are many products on the market that have already been subjected to anti-corrosion treatment by manufacturers, and there is no need to perform anti-rust treatment again for such powders. In addition, when using fine metal particles 6.6... and aluminum powder, it is possible to make it lipophilic by mixing it with a lubricant such as zinc stearate or aluminum stearate in a rotary vane type stirring mixer. can. Further, the surface of the powder may be subjected to lipophilic treatment using another lipophilic treatment agent, such as a silicone water repellent.

In this way, metal fine particles 6.6.
A suspension (hereinafter referred to as B) is prepared by dispersing .

Next, add A into B while stirring as shown in FIG. The lipophilic-treated metal particles 6.6 do not mix with A, but are dispersed around the droplets of A, and are stabilized to prevent the droplets of A, which have been atomized by stirring, from coalescing. Form a water-in-oil (W/O) emulsion. The particle size of the droplets of A in the emulsion can be adjusted by the amount of water used in preparing A, the amount of organic solvent B, and the stirring method, but it is preferably about 30 to 300 microns.

If the particle size is 300 microns or more, the heat conduction of the molded product after compression molding of the microcapsules will be inhibited, and if the particle size is 300 microns or more,
If the particle size is less than a micron, it becomes difficult to uniformly coat the metal particles 6.6.

The resulting emulsion is then dried. As a result of this drying, as shown in Fig. 4, fine particles 2.2 of the storage alloy...
The agglomerates 3.3... are aggregated into metal fine particles 6.6.
Microcapsules 7, 7... coated with... are obtained. This drying is preferably carried out in an inert gas atmosphere or in vacuum to prevent oxidation of the storage alloy. At this time, activation of the storage alloy and removal of the lipophilic surface treatment agent (or rust preventive agent) can be performed simultaneously by setting the temperature. Rapid drying is necessary to increase the productivity of the storage alloy material, but if the moisture in A rapidly evaporates, the aggregates 3 often break. To prevent this, it is effective to add to A something that has a binder effect. The binder must be hydrophilic, have heat resistance that will not melt or decompose at the temperature at which the storage alloy is used, and will not deteriorate over a long period of time.
Several μ of colloidal silica, titanium dioxide, alumina, etc.
Polymer suspension water, exemplified by suspensions of microparticulate inorganic substances of m or less in size, water-soluble polymers such as polyvinyl alcohol, fluororesins, and silicone resins in water, can be used.

Furthermore, if it is desired to prevent the hydrogen storage alloy from being oxidized by water as much as possible, the coating may be manufactured using a non-aqueous emulsion. That is, a suspension (hereinafter referred to as C) is prepared by dispersing fine particles of a hydrogen storage alloy of 20 μm or less in an organic solvent in which a polymer serving as a binder is dissolved. Further, a material (hereinafter referred to as D) is prepared by dispersing fine metal particles having better malleability than a hydrogen storage alloy in an organic solvent in which the polymer C is difficult to dissolve. Next, by adding C to D without stirring, the polymer in C acts as a binder and prevents the fine particles of the hydrogen storage alloy from migrating to D.

On the other hand, the metal fine particles D surround the droplets of C and prevent the droplets of C, which have been once atomized by stirring, from coalescing again. Therefore, a stable C/D non-aqueous emulsion is formed. The particle size of the droplets of C can be adjusted by the amount of polymer of C, the molecular weight, the viscosity of the organic solvent of C, the amount of the organic solvent of D, and the stirring method, but it is preferably about 30 to 300 μm. Unlike the W/O emulsion, the metal fine particles of D do not require lipophilic treatment.

The combination of polymers C and D and organic solvents is a combination of a polymer that has heat resistance that does not melt or decompose at the temperature at which the storage alloy is used and does not deteriorate over a long period of time, and an organic solvent that exhibits high solubility for the polymer. Select a low organic solvent. For example, when liquid silicone rubber is used as the polymer, as the organic solvent, a fluorocarbon solvent can be used for C, and methanol can be used for D.

The resulting emulsion is then dried. Further, at this time, the polymer used as the binder can also be crosslinked.

Microcapsules obtained by the above procedure 7.7...
When ・ is molded into a predetermined shape by compression as shown in FIG. 5, the fine metal particles 6.6 with excellent malleability are pressed against each other, forming a porous membrane and forming an aggregate 3.3 of the storage alloy.・・・
A molded body surrounding ・ is obtained. The load pressure for compression molding is preferably 1-/O ton/cm.During this compression molding, it is a problem to heat the storage alloy to a temperature that does not cause alloying of the storage alloy and fine metal particles and significantly change the composition of the storage alloy. In addition, compression molding using HIP or CIP is particularly suitable because it allows uniform pressure to be applied and it also allows molding of complex shapes.

The amount of metal fine particles used in B or D above varies depending on the specific gravity and particle size, but the amount of /O
It is desirable that the amount is 50 parts by weight. If the amount of metal fine particles is less than /O parts by weight, the strength of the molded product will be insufficient, and if it is more than 50 parts by weight, it will be uneconomical.

Even if the molded body thus obtained undergoes repeated storage and release of hydrogen, it will not collapse, although volumetric expansion and formation of fine racks will occur due to storage. Further, since the fine particles of the storage alloy in the compact are coated with metal such as copper, they have good thermal conductivity and can easily store and release hydrogen.

Examples of this invention will be shown below.

"Experimental Example 1" 1 part of MmNi5/O0, which has been powdered to a particle size of /Oμm by repeated absorption and desorption of hydrogen, is added with a particle size of 0.1μm.
Add 3 parts by weight of colloidal titanium dioxide shown below and further add 18 parts by weight of distilled water and knead to form a slurry (A).
made.

Next, electrolytic copper powder with an average particle size of 4 microns was immersed in a 1% aqueous solution of benzotriazole, and then dried in a nitrogen atmosphere. 33 parts by weight of this dried electrolytic copper powder was added to a fluorocarbon-based solvent (manufactured by Daikin Industries, Ltd., Guiflon Solvent 53).
) and dispersed in 120 parts by weight. Next, the entire amount of the above alloy water slurry was added little by little to the suspension of electrolytic copper powder in a fluorocarbon solvent in an emulsifier. The alloy water slurry is atomized by stirring in an emulsifier, and its surface is surrounded by lipophilic-treated copper powder together with a fluorocarbon solvent, making it possible to generate a stable W/O emulsion without coalescing. Ta.

Next, this emulsion was vacuum dried at 60° C. to evaporate water and chlorofluorocarbon solvent. Since colloidal titanium dioxide was added to the alloy water slurry, no collapse of the aggregates of storage alloy fine particles that had become agglomerated during drying was observed. By this drying, microcapsules having a particle size of 50 to 250 μm were obtained, in which aggregates of storage alloy fine particles were coated with copper powder.

These microcapsules were compressed at 2 tons/cm'' to create disc-shaped pellets with a diameter of 1 cm and a thickness of 2.5 w++++.The surface of this pellet had a copper luster, and when viewed in cross section, it was found that copper powder were combined into a network, and the fine particles of the storage alloy were packed inside.

After activating this pellet at 200°C under vacuum conditions,
When hydrogen storage and release were repeated /O0 times at a temperature and pressure of 40℃ and 14Kgf/Cm during storage, fine cracks appeared on the pellet surface and a volumetric expansion of about 30% occurred. However, no collapse occurred.

"Example 2" Colloidal silica with a particle size of 0.1 μm or less was used in place of the colloidal titanium dioxide with a particle size of 0.1 μm used in Example 1, and the lipophilic treatment used in Example 1 was used. Instead of electrolytic copper powder, use commercially available electrolytic copper powder that has been treated to prevent rust (
Average 4 μm, manufactured by Mitsui Kinzoku Aji Co., Ltd., product name M'F
-Di) was used. Example 1 except that this material is different.
Using the same materials and performing the same operations, microcapsules with a particle size of 50 to 250 μm were obtained, in which aggregates of storage alloy powder were coated with copper powder.

The storage alloy of the microcapsules was activated at 300° C. under vacuum conditions, and the rust preventive agent remaining on the copper powder was removed.

It was then packed into rubber molds in an argon atmosphere and compressed by cold isostatic pressing (CIP) at 5 tons/am' to a diameter of 3 cm.
It was molded into a cylinder with a length of ms/Ocm.

Using this molded body, repeated hydrogen absorption and desorption tests similar to those in Example 1 were conducted, and no collapse of the molded body occurred.

"Example 3" The same method as in Example 2 was used except that 18 parts by weight of water containing a 30% suspension of fluorocarbon resin was used in place of the colloidal silica with a particle size of 0.1 μm or less used in Example 2. operate,
Particle size 50-2. '50 μm microcapsules were obtained.

This was carried out under vacuum conditions at 300° C. to activate the storage alloy, bind the fluorocarbon resin, and remove the rust preventive agent from the copper powder.

This was then compressed at 5 tons/cm'' in an argon atmosphere and formed into a disk-shaped pellet with a diameter of 1 cm and a thickness of 2.5 am.

Using the obtained pellets, repeated hydrogen absorption and desorption tests similar to those in Example 1 were conducted, and no disintegration of the pellets occurred.

"Example 4" Thermosetting liquid silicone rubber (manufactured by Toshiba Silicone Corporation, trade name TSE3221) is added to MmN is /O0 parts by weight that have been powdered to a particle size of /Oμm or less by repeated absorption and desorption of hydrogen. 0 parts by weight were added thereto, and further 0 parts by weight of a fluorocarbon solvent (manufactured by Daikin Industries, Ltd., trade name: Guiflon Solvent 53)/O was added and kneaded to prepare a supporting Lee C. Next, 33 parts by weight of aluminum powder having an average particle size of 8 μm was added to 150 parts by weight of methanol and dispersed to prepare slurry D. Next, D was placed in an emulsifying machine, and C was added little by little to the entire amount while emulsifying. C was atomized by stirring, the surface of which was surrounded by aluminum powder, and an emulsion could be produced.

Next, vacuum drying was performed at /O0°C to evaporate the solvent and crosslink the silicone rubber. In this way, aggregates of storage alloy fine particles were coated with aluminum powder with a particle diameter of 50 mm.
Microcapsules of ~250μ were obtained. This was compressed at 3 tons/am'' in an argon atmosphere to a diameter of 1 cm.
It was molded into a disk-shaped pellet with a thickness of 3.5+am.

Using the obtained pellets, repeated hydrogen absorption and release tests similar to those in Example 1 were conducted, and no disintegration of the pellets occurred.

"Effects of the Invention" As explained above, the hydrogen storage alloy material according to the present invention is obtained by compression molding an aggregate of fine particles of the hydrogen storage alloy covered with a metal that is more malleable than the hydrogen storage alloy. Therefore, the compact does not disintegrate even when hydrogen is absorbed and released repeatedly, and therefore, it is possible to prevent the harmful effects caused by the pulverization of the hydrogen-absorbing alloy, such as the generation of fine particles of the hydrogen-absorbing alloy and a decrease in thermal conductivity. , the rate of hydrogen storage and release can be improved.

[Brief explanation of the drawing]

1 and 2 are diagrams showing an example of the first invention of the present invention, in which FIG. 1 is an enlarged sectional view of a part of the hydrogen storage alloy material, and FIG. 2 is a perspective view of the hydrogen storage alloy material. 3 to 5 are diagrams showing an example of the second invention of the present invention, and are diagrams showing an outline of the manufacturing process of a hydrogen storage alloy material in the order of the steps. l... Hydrogen storage alloy material 2... Storage alloy fine particles 3... Aggregates 4... Covering layer 6... Metal fine particles 7... Microcapsules (coated bodies).

Claims (4)

[Claims] (1) An aggregate of a plurality of fine particles of a hydrogen storage alloy is coated with a large number of fine particles of a metal that is more malleable than the hydrogen storage alloy to form a coating, and these many coatings are compression molded. A hydrogen-absorbing alloy material made into a molded body. (2) Hydrogen storage alloy fine particles wetted with water to form a slurry (A) and metal fine particles whose surface is treated to be lipophilic and have better malleability than the hydrogen storage alloy, are not miscible in water and have the above lipophilic properties. Dispersed in an organic solvent that does not affect processing (B)
A is finely dispersed in B to form a W/O type emulsion, which is then dried to form a coating, and a number of these coatings are compression-molded to form a molded body. A manufacturing method for hydrogen-absorbing alloy materials. (3) A method for producing a hydrogen storage alloy material according to claim 2, characterized in that at least one of an inorganic colloid, a water-soluble polymer, and a polymer suspension water that has a binder effect is added to the above A. . (4) Hydrogen storage alloy fine particles are dispersed in an organic solvent in which a polymer that acts as a binder is dissolved to form a slurry (C), and an organic solvent that does not dissolve the polymer in C has better spreadability than the hydrogen storage alloy. Dispersed metal fine particles (
Using D), C is finely dispersed in D to form a non-aqueous emulsion, which is then dried or a polymer that acts as a binder is cured to form a coating, and a large number of these coatings are compression molded. A method for producing a hydrogen-absorbing alloy material, characterized in that it is made into a molded body.