JP2021080128A - Core-shell composite and its manufacturing method - Google Patents

Abstract

To provide: a core-shell composite capable of maintaining a desired hydrogen-absorbing-and-releasing capability or the like to thermal hysteresis; and its manufacturing method.SOLUTION: A core-shell composite 1 includes: a core part 10 having rigidity and containing a refractory material made of inorganic oxide, ceramics, ore and the like; and at least one layer of shell parts 20 surrounding the core part 10 and containing a hydrogen-absorbing-and-releasing metal. The refractory material contained in the core part has a melting point higher than the most highest one among the hydrogen absorbing and releasing metal contained in the shell parts. The shell part 20 has a lamination part formed by laminating a plurality of multi-metal layers 21, 23, 25, and 27 containing a plurality of metals (Ni, Al) that constitutes the hydrogen-absorbing-and-releasing metal. A manufacturing method of the core-shell composite coats the shell part on the core part by depositing under non-presence of oxygen, when manufacturing such a core-shell composite.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a core-shell complex and a method for producing the same, and more specifically, the desired performance is unlikely to deteriorate with respect to the heat history, the number of hydrogen absorption / release sites increases, and excellent hydrogen absorption / release ability can be exhibited. The present invention relates to a core-shell complex and a method for producing the same.

Conventionally, hydrogen storage alloys that reversibly absorb and release hydrogen have been known, and applications to hydrogen gas storage devices, hydrogen gas generators, various secondary batteries, and the like have been proposed.
Such a hydrogen storage alloy easily disintegrates into powder or granular material by repeating absorption and release of hydrogen, and the generated fine powder or granular material easily moves along with the flow of absorbed and released hydrogen. Therefore, not only is it difficult to obtain pure hydrogen gas, but there is a possibility that these fine powders and granules accompanying the flow may be mixed into a device or the like to which hydrogen is supplied, causing a problem.

On the other hand, conventionally, an agglomerate of hydrogen storage alloy particles is coated with metal fine particles having good malleability, and the obtained coating is further compression-molded. Specifically, a plate-shaped hydrogen storage alloy material ( A compression molded product) was obtained (see, for example, Patent Document 1).
In the hydrogen storage alloy material thus obtained, the ductile metal fine particles are pressure-bonded to each other to form a porous film during compression molding, so that the hydrogen storage alloy is capable of absorbing and releasing hydrogen. Particle decay is suppressed.

Japanese Unexamined Patent Publication No. 63-310936

However, in the above-mentioned conventional technique, it is not a technique for improving the physical properties of the powder or granular material of the hydrogen storage alloy itself.
Therefore, there is still room for study on the properties and performance of the powder-granular hydrogen storage alloy, and as a result of the study by the present inventor, such a powder-grain hydrogen storage alloy is repeatedly used at a high temperature. Then, it was found that it causes performance deterioration.

The present disclosure has been made in view of the above findings, and the purpose of the present disclosure is to maintain the initial shape with respect to the thermal history so that the intended hydrogen absorption / release ability and the like are unlikely to deteriorate. The present invention is to provide at least one of a core-shell composite and a method for producing the same, which can improve the hydrogen absorption / release ability as compared with the prior art.

In the present disclosure, the above object can be achieved by combining a predetermined core portion having heat resistance and a shell portion having hydrogen absorption / release ability, and a core-shell composite having a multi-layer containing a predetermined plurality of metals in the shell portion. I found it.

That is, the core-shell composite of the present disclosure encloses a rigid core portion containing at least one heat-resistant material selected from the group consisting of inorganic oxides, ceramics and minerals, and all or a part of the core portion. A core-shell complex having a shell portion containing a hydrogen-absorbing / releasing metal.
The heat-resistant material contained in the core portion has a melting point higher than the melting point of the highest hydrogen absorbing / releasing metal contained in the shell portion.
The shell portion is characterized by including a multi-metal layer containing a plurality of types of metals constituting the hydrogen absorbing / releasing metal.
Further, a preferable form of the core-shell composite of the present disclosure comprises a laminated portion formed by laminating a plurality of the above-mentioned multi-metal layers.

Further, in the preferred form of the core-shell composite of the present disclosure, the outermost surface of the laminated portion has irregularities.

Furthermore, another preferred form of the core-shell complex of the present disclosure has a channel in which the laminate extends along its stacking direction.

Furthermore, in yet another preferred form of the core-shell composite of the present disclosure, the hydrogen absorbing / releasing metal comprises a hydrogen storage alloy.

Further, in another preferred form of the core-shell complex of the present disclosure, the shell portion further has a monometal layer containing a single type of metal, and the monometal layer is inside the multi-metal layer with respect to the core portion and Located on at least one of the outside.

Further, yet another preferred form of the core-shell complex of the present disclosure is provided with a heat-resistant hydrogen-permeable shell layer having both hydrogen gas permeability and heat resistance outside the outermost layer of the layers constituting the shell portion. ..

Furthermore, in another preferred form of the core-shell complex of the present disclosure, the heat-resistant hydrogen-permeable shell layer is contained in an oxide of any metal constituting the hydrogen-absorbing / releasing metal of the shell portion and the core portion. Consists of at least one of the heat resistant materials.

Further, in a preferable form of the core-shell composite of the present disclosure, unevenness having a pitch of 2 μm or less is present on the surface of the core portion.

Furthermore, in another preferred form of the core-shell composite of the present disclosure, the metals constituting the hydrogen absorbing / releasing metal are titanium (Ti), manganese (Mn), zirconium (Zr), nickel (Ni), and vanadium (V). ), Lantern (La), Palladium (Pd), Magnesium (Mg), Calcium (Ca), Cobalt (Co), Copper (Cu), Iron (Fe), Silver (Ag), Rhodium (Rh), and Aluminum ( It is at least one selected from the group consisting of Al).

On the other hand, the method for producing a core-shell complex of the present disclosure is characterized in that, in producing the core-shell complex as described above, the shell portion is coated on the core portion by vapor deposition in a non-oxidizing atmosphere.

Further, in a preferred embodiment of the method for producing a core-shell composite of the present disclosure, the shell portion uses sputtering using an alloy target composed of a plurality of types of metals contained in the multi-metal layer, and the plurality of types of metals themselves are simultaneously used. It is formed by at least one of the sputterings used as a target.

Further, another preferred embodiment of the method for producing a core-shell complex of the present disclosure is that the core-shell complex is a heat-resistant hydrogen-permeable shell layer having both hydrogen gas permeability and heat resistance on the outside of the shell portion of the outermost layer. With
After forming the shell portion to be the outermost layer of this heat-resistant hydrogen permeable shell layer,
Sputtering using a target made of heat-resistant material contained in the core part,
And at least either in the presence of oxygen or by sputtering using an oxide target.

Furthermore, in yet another preferred embodiment of the method for producing a core-shell complex of the present disclosure, the core-shell complex is a heat-resistant hydrogen permeation having both hydrogen gas permeability and heat resistance on the outside of the shell portion of the outermost layer. With a shell layer,
This heat-resistant hydrogen permeable shell layer is formed by coating a non-aqueous solution containing the raw material of the heat-resistant hydrogen permeable shell layer after the shell portion to be the outermost layer is formed.

According to the present disclosure, a predetermined core portion having heat resistance and a shell portion having hydrogen absorption / release ability are combined to form a core-shell complex having a multi-metal layer containing a predetermined plurality of metals in the shell portion. On the other hand, since there is no change from the initial shape, the intended hydrogen absorption / release ability is less likely to deteriorate, and at least one of the core-shell complex and its production method capable of improving the hydrogen absorption / release ability as compared with the prior art. Can be provided.

It is sectional drawing which shows one Embodiment of the core-shell complex of this disclosure. It is a partially enlarged sectional view of the core-shell complex shown in FIG. It is sectional drawing which shows the other embodiment of the core-shell complex of this disclosure. FIG. 5 is a cross-sectional view showing still another embodiment of the core-shell complex of the present disclosure. It is an SEM photograph of the core-shell complex of Example 1. It is a partially enlarged SEM photograph of the core-shell complex of Example 1. It is a schematic diagram which shows the method of TEM observation. It is a TEM photograph of the core-shell complex of Example 1. It is a partially enlarged TEM photograph of the core-shell complex of Example 1. It is a partially enlarged TEM photograph of the core-shell complex of Example 1.

Hereinafter, the core-shell complex of the present disclosure will be described.
As described above, the core-shell complex of the present disclosure is a core-shell complex including a core portion and a shell portion surrounding all or a part of the core portion.
In this core-shell composite, a heat-resistant material is contained in the core portion and a hydrogen absorbing / releasing metal is contained in the shell portion, but the melting point of the above-mentioned heat-resistant material is among the hydrogen absorbing / releasing metals contained in the shell portion. Higher than the melting point of the highest of.

(Embodiment 1)
The core-shell complex of the present embodiment is a core-shell complex including a core portion and a shell portion. FIG. 1 is a cross-sectional view conceptually showing an embodiment of the core-shell complex of the present disclosure.
The core-shell complex 1 shown in the figure includes a core portion 10 and a shell portion 20, and the entire surface of the core portion 10 is surrounded by the shell portion 20. The shell portion 20 may surround a part of the core portion 10.
The size of the core-shell complex is not particularly limited, and the size ratios of the core portion and the shell portion can be appropriately determined. An example of the average particle size of this complex is about 1 μm to 10 mm, preferably 5 μm to 100 μm. When it is 1 μm or more, the surface area of this complex becomes appropriately large, and the shell portion (layer) can be formed by vapor deposition such as sputtering in a practical time. If it is 10 mm or less, collisions between powders and granules during the formation of the shell portion are suppressed, and damage in the film-forming layer is less likely to occur. Further, it is preferable that 95% or more of the core portion as a powder or granular material is 1 μm or more and 100 μm or less, preferably 5 μm or more and 50 μm or less.
In such a core-shell composite 1, the shell portion 20 has multi-metal layers 21, 23, 25 and 27 containing a plurality of types of metals nickel (Ni) and aluminum (Al), and these multi-metal layers are laminated. It consists of a laminated part. Ni and Al are metals constituting a hydrogen absorbing / releasing metal.

In the core-shell complex 1, the core portion 10 is composed of zirconia (ZrO ₂ ), the multi-metal layer 21 and the like are composed of Al and Ni, but their melting points are ZrO ₂ (about 2,715 ° C.) and Ni from the highest melting point. The order is (about 1,455 ° C.) and Al (about 660.3 ° C.).

In the core-shell complex 1, the core portion 10 contains a heat-resistant material (eg, zirconia), has heat resistance and rigidity, and enables the core-shell complex 1 to maintain a substantially constant shape with respect to thermal history. ing.
Specifically, the core portion 10 spontaneously bends and twists with heat resistance capable of maintaining its initial shape from near room temperature to near a desired temperature (for example, near a target processing temperature or reaction temperature). It has rigidity with a hardness that does not cause deformation such as.

On the other hand, the shell portion 20 is composed of the multi-metal layers 21, 23, 25 and 27 in the core-shell complex 1 according to the present embodiment. Further, the core-shell complex 1 according to the present embodiment is composed of a laminated portion formed by laminating these multi-metal layers. Ni and Al, which are multiple types of metals contained in each of these multi-metal layers, are hydrogen storage alloys (Ni—Al-based alloys), which are examples of hydrogen absorbing / releasing metals in which both metals are alloyed due to an increase in temperature or the like. Can be formed. As a result, the shell portion 20 can be further imparted with the ability to absorb and release hydrogen.
In the core-shell composite 1 of the present embodiment, Ni and Al are mixed in each of the multi-metal layers 21, 23, 25, and 27, so that many hydrogen storage alloy sites are formed due to the contact between the two metals. Exists. Therefore, the core-shell complex 1 of the present embodiment can be expected to have excellent hydrogen absorption / release ability.

FIG. 2 is a partially enlarged cross-sectional view of the core-shell complex 1 shown in FIG.
As shown in the figure, in the core-shell complex 1 of the present embodiment, the core portion 10 has irregularities on its surface, and the multi-metal layers 21, 23, 25 and 27 have irregularities on the surface of the core portion 10. Each surface has irregularities due to the above. As described above, the surfaces of the core portion 10, each multi-metal layer, and the shell portion are not smooth.
Due to the presence of these irregularities, a so-called anchor effect is exhibited, and the multi-metal layers such as between the core portion 10 and the multi-metal layer 21 and between the multi-metal layers 21 and 23 are firmly fixed. Therefore, the core-shell complex 1 of the present embodiment has excellent mechanical strength and can easily maintain the initial shape.
Furthermore, it is possible to increase the area of the portion involved in hydrogen absorption / release due to such unevenness, and it is also possible to improve the hydrogen absorption / release ability of the core-shell complex.

The unevenness on the surface of the core portion is preferably unevenness having a pitch of 2 μm or less. The shape of the unevenness is not particularly limited, and may be a substantially spherical shape, an indefinite shape, or other shapes different from each other between pitches.
The finer the unevenness pitch is 2 μm or less, the more effectively the hydrogen gas is diffused by utilizing the large number of recesses in the adjacent portions of the powder or granular materials in the powder or granular material aggregate composed of a large number of core-shell complexes. Further, when the uneven structure is formed at a random pitch and size, the possibility that the concave portion exists in the adjacent powder contact portion increases. If it exceeds 2 μm, for example, considering the diameter of the core-shell complex used in the examples of the present disclosure (core portion 30 μm + shell portion), only slight irregularities are formed, and the above-mentioned effect on hydrogen diffusion is small. is there.
In addition to the effect of hydrogen diffusion, it can be expected that stress relaxation will be promoted by forming a large number of irregularities at a pitch of 2 μm or less even when internal stress is present due to the film formation of the shell portion. ..

Further, as shown in FIG. 2, the core-shell composite of the present embodiment has channels C1 and C2 extending along the stacking direction of these multi-metal layers in a laminated portion composed of the multi-metal layers 21 and the like. May be good.
Here, the term "along the stacking direction" does not necessarily mean that the stacking direction of the multi-metal layer and the elongation direction of the channel are exactly the same, and it is sufficient if both directions are substantially the same or approximate. This means that at least 90 ° is not formed in both directions (that is, the stacking direction and the extension direction of the channel are not orthogonal to each other).
It is sufficient that this channel is formed in a part of the above-mentioned surface uneven structure, and it is not necessary that the channel is formed in the entire surface uneven structure.

Such channels C1 and C2 may connect at least one of the core portion 10-multi-metal layer 21 core portion-multi-metal layer and the multi-metal layer such as between layers 21-23. When designing a core-shell complex as a material, it can be used not only as a path / site for supplying / holding various gases and materials, but also as a function of relieving stress applied between the core part-multi-metal layer and each layer.

In the present embodiment, since the multi-metal layer 21 absorbs and releases hydrogen, the ability of one core-shell complex particle is improved as the thickness of each layer of the multi-metal layer is formed thicker than the size of the core portion. From the viewpoint of hydrogen absorption / release efficiency and residual stress in the layer, the thinner the thickness of each layer of the multi-metal layer is, the more preferable, and the thickness of 10 nm or more and 5 μm or less and the preferable thickness of 100 nm or more and 800 nm or less can be exemplified. Further, the thickness of the entire shell portion 20 is preferably sufficiently thin with respect to the diameter of the core portion, and examples thereof include a thickness of 10 nm or more and 10 μm or less, a suitable thickness of 50 nm or more and 5 μm or less, and an optimum thickness of 200 nm or more and 1 μm or less. ..

In the core-shell complex 1, _{the melting point of the heat-resistant material ZrO 2} contained in the core portion 10 is higher than the melting point of the above-mentioned constituent metals having a high melting point (Ni). Therefore, even if the multi-metal layer 21 or the like is partially melted, the core portion 10 maintains the initial shape, and as a result, the shape of the core-shell complex 1, especially the macroscopic shape, maintains the initial shape. Can be done.

By maintaining the initial shape and further maintaining the macro shape, it is possible to suppress the reduction of the surface area (specifically, the reaction surface area, etc.) in the core-shell complex, and the performance such as hydrogen absorption / release ability is deteriorated with respect to the thermal history. It can be suppressed. When the core-shell complex is in the form of powders and granules, the effect becomes remarkable.
When the powder or granular material-like core-shell complex is observed macroscopically as an aggregate of powder or granular material, the core-shell composite of the present embodiment provides a powder or granular material aggregate in which the change in particle size distribution is small with respect to the thermal history. And provide uniformity of repetitive effect in the processes and operations in which they are used.

(Embodiment 2)
Next, other embodiments of the core-shell complex of the present disclosure are shown.
As shown in FIG. 3, the core-shell complex 2 of the present embodiment has a structure in which the core portion 10 is surrounded by the shell portion 20 like the core-shell complex of the first embodiment, but the shell portion 20 is a mono. It differs from the core-shell complex of Embodiment 1 in that it has a metal layer, that is, a layer containing only one type of hydrogen absorbing / releasing metal.
As shown in the figure, in the present embodiment, the shell portion 20 is configured by laminating a multi-metal layer 21, a mono-metal layer 22, a multi-metal layer 23, and a multi-metal layer 25 in this order, and the multi-metal layer is formed. Whereas Ni and Al are contained, the monometal layer contains only Al. In FIG. 3, the metal contained in the multi-metal layer and the mono-metal layer is shown as at least one of Ni and Al, but the metal type may be different between the layers.

In the present embodiment, the monometal layer 22 is provided, but Ni constituting the monometal layer 22 has a higher melting point than Al as described above. Therefore, in a high temperature environment, not only the core portion 10 but also the monometal layer 22 contributes to maintaining the initial shape. Further, the monometal layer forms a hydrogen storage alloy at the interface with the multi-metal layer, specifically, the interface between the multi-metal layer 21 and the mono-metal layer 22 and the interface between the multi-metal layer 23 and the mono-metal layer 22. Therefore, the hydrogen absorption / release capacity is not significantly reduced.

In addition, in this embodiment, the example in which the monometal layer is arranged outside the multi-metal layer with respect to the core portion 10 is not shown, but the mono-metal layer can be either outside or inside with respect to the multi-metal layer. It can also be placed on both sides.
Furthermore, it is also possible to form the monometal layer with Al. In this case, for example, the alloy composition of the multi-metal layer is slightly changed, and Al is required more than Al contained in the multi-metal layer. In this case, rather than preparing an alloy with an increased Al amount in advance to form a multi-metal layer, it is possible to obtain an effect that the Al amount can be adjusted by forming an Al layer on the outside, inside, or both sides of the multi-metal layer. Be done.

(Embodiment 3)
Next, still another embodiment of the core-shell complex of the present disclosure will be shown.
The core-shell complex of the present embodiment is a core-shell complex having the same structure as that of the first embodiment (or the second embodiment), and is heat-resistant hydrogen outside the outermost layer of the layers constituting the shell portion. It has a transparent shell layer.
FIG. 4 is a cross-sectional view conceptually showing the core-shell complex of the present embodiment. The core-shell complex 3 shown in the figure has the same structure as that of the first embodiment, but heat-resistant hydrogen permeates outside the multi-metal layer 27 corresponding to the outermost layer of the layers constituting the shell portion. It has a shell layer.

In the present embodiment, the heat-resistant hydrogen-permeable shell layer (hereinafter, also referred to as “shell layer”) has hydrogen gas permeability and its melting point is higher than the melting point of the outermost layer of the shell portion. Just do it.
In the core-shell complex 3, the shell layer 30 is made of alumina (Al ₂ O ₃ ) having a melting point of about 2,072 ° C., and has heat resistance and hydrogen gas permeability as described above. The melting point of the shell layer may be equal to or lower than the melting point of the core portion.

Since the core-shell complex 3 has the heat-resistant hydrogen permeable shell layer 30 as described above, it has sufficient heat resistance and rigidity even when the core-shell complex 3 is exposed to a temperature higher than the melting point of the shell portion 20. The shell portion is sandwiched and fixed between the core portion 10 and the shell layer 30. This action is considered to be one of the reasons why the initial shape of the core-shell complex 3 is difficult to change. Therefore, it is possible to obtain a better effect by maintaining the initial shape described above.

Further, since the shell layer 30 has hydrogen gas permeability, the functions of the Ni—Al-based hydrogen storage alloy produced in the shell portion 20, specifically, the multi-metal layer 21 and the like are not substantially impaired.
The thickness of the shell layer 30 may be any thickness as long as the shell layer exhibits hydrogen gas permeability, and examples thereof include 5 nm or more and 1 μm or less, preferably 50 nm or more and 300 nm or less.

Further, since the above-mentioned unevenness (not shown) exists on the surface of the multi-metal layer 27, it is preferable that the multi-metal layer 27 and the shell layer 30 are firmly fixed. As a result, the core-shell complex 3 of the present embodiment has more excellent mechanical strength.

<Material, shape, other structures, etc.>
Next, the materials and performance of the core portion and the shell portion constituting the core-shell complex described above will be described.

The core portion contains inorganic oxides, ceramics or minerals, and heat-resistant materials related to any combination thereof. Specifically, zirconia (ZrO ₂ ), alumina (Al ₂ O ₃ ), silica (SiO). ₂ ), silicon dioxide and zeolite, and the like, preferably one or more selected from the group consisting of zirconia, alumina, and silica, and more preferably at least one of zirconia and silica.
The zirconia contained in the core portion is preferably stabilized zirconia, and more preferably stabilized by one or more selected from the group consisting _{of yttria (Y 2} O ₃ ), ceria (CeO _{2) and magnesia (MgO).} Zirconia, more preferably yttria-stabilized zirconia.

From the viewpoint of improving the strength of the core portion, the yttria content of zirconia stabilized in yttria is 2 mol% or more and 6 mol% or less, preferably 2 mol% or more and 4 mol% or less as yttria with respect to the total of zirconia and yttria. The crystal phase of zirconia is preferably zirconia having a tetragonal crystal as the main phase.
From the viewpoint of operability, it can be exemplified that the core portion has a compression strength of 100 MPa or more and 1200 MPa or less, preferably 850 MPa or more and 1100 MPa or less.

The hydrogen absorbing / releasing metal contained in the shell portion means a metal (at least one of a simple substance and an alloy) capable of absorbing and releasing hydrogen gas, and typically corresponds to a so-called hydrogen storage alloy.

Examples of the metal constituting the hydrogen absorbing / releasing metal include titanium (Ti), manganese (Mn), zirconium (Zr), nickel (Ni), vanadium (V), lanthanum (La), palladium (Pd), and magnesium. (Mg), calcium (Ca), cobalt (Co), copper (Cu), iron (Fe), silver (Ag), rhodium (Rh) or aluminum (Al), and any combination thereof, and the like. At least one of the alloys can be exemplified, preferably one or more selected from the group consisting of titanium, manganese, zirconium, nickel, magnesium, calcium, cobalt and aluminum, and more preferably the group consisting of nickel and aluminum. It is one or more selected from the above, and more preferably at least one of nickel and aluminum.
As the above hydrogen storage alloy, conventionally known alloys can be shown, and for example, an alloy containing one or more selected from the group consisting of calcium, palladium, magnesium, vanadium and titanium and iron can be exemplified. .. Further comprising a hexagonal or cubic, can be mentioned hydrogen absorbing alloy called AB ₂ type having AB ₅ type or Laves phase containing a rare earth element.

Examples of the material contained in the heat-resistant hydrogen permeable shell layer include oxides of at least one of the metals constituting the hydrogen absorbing / releasing metal in the shell portion, inorganic oxides similar to those in the core portion, ceramics and minerals. However, at least one of metal oxides and ceramics is preferable, and one or more selected from the group consisting of zirconia, alumina and silica is preferable, and at least one of zirconia and alumina is more preferable.

In the above-described embodiment, the shape of the individual core-shell complex has been described by exemplifying a spherical shape, but the shape of the core-shell complex, the core portion, the shell portion, and the like is not necessarily limited to a spherical shape or a hollow spherical shape. ..
In addition to the spherical shape, an elliptical spherical shape, a scaly shape, a columnar shape, a plate shape, a polyhedral shape, a disk shape, a cone shape, and the like can be exemplified. The selection of these shapes can be appropriately selected according to the intended processing and operation of the core-shell complex, the application of the core-shell complex, etc., and macroscopically, it is a powder or granular material in which these are aggregated. May be good. Further, it can be selected according to the packing density of the core-shell composite in the desired reaction, and the packing density can be exemplified ^{as 1 g / cm 3} or more and 8 g / cm ³ or less, preferably 2 g / cm ³ or more and 7 g / cm ^{3 or less.} ..

Further, as for the hydrogen absorbing / releasing metal contained in the shell portion, a plurality of types can be used. For example, two or more types of hydrogen storage alloys may be used so as to form a multi-metal layer of a separate layer. it can.
The content of the plurality of metals in the multi-metal layer can be changed, and for example, the metal content in each multi-metal layer can be changed.
Further, it is possible to provide a metal concentration gradient in the same layer, and for example, it is possible to increase the concentration of the hydrogen storage alloy at the core side interface and the core opposite side interface. In particular, by forming a hybrid layer containing the core portion material and the plurality of metals between the core portion and the multi-metal layer, the difference in thermal expansion between the core portion and the multi-metal layer (shell portion) is reduced. It is also possible to suppress destruction due to thermal history.
By implementing the above deformation, it becomes possible to design and adjust the hydrogen absorption / release capacity, heat resistance, mechanical strength, thermal expansion between layers, etc. in each layer, and a core-shell complex specialized for various applications is provided. It becomes easier to do.

Further, in the core-shell composite of the present disclosure, the shell portion surrounds a part of the core portion, and the multi-metal layer or the mono-metal layer contained in the shell portion surrounds the other multi-metal layer or a part of the other mono-metal layer. The effects of the present disclosure can be obtained even with such a structure.
In the above case, it is possible to adopt a so-called sea-island structure in which a multi-metal spot containing a plurality of types of metals and a mono-metal spot containing only a single metal type _{exist on the ZrO 2 core.}
In this case, the multi-metal spot and the mono-metal spot may have a height difference (unevenness, etc.), but _{the surface of the ZrO 2} core is covered with any metal, and _{the surface of the ZrO 2} core is exposed. It is preferable not to use it.

<Manufacturing method of core-shell complex>
Next, a method for producing the core-shell complex of the present disclosure will be described.
The method for producing a core-shell complex of the present disclosure is a method for producing a core-shell complex as described above. A core-shell composite is produced by coating the core portion with the core portion by thin-film deposition in a non-oxidizing atmosphere.
Although not particularly limited, if the core raw material, for example, zirconia beads, is preheated or agitated under reduced pressure during sputtering, a part of the zirconia beads may be aggregated due to unexpected adhesion of water or the like. Aggregation can be suppressed, and it becomes easy to obtain a core-shell composite (aggregate) having uniform particle size and uniform performance. Further, it is preferable that the vapor deposition is performed while applying vibration to the core raw material. As a result, the shell portion is likely to be efficiently formed on the entire surface of the core portion, and the multi-metal layer in the shell portion is likely to be laminated in a plurality of layers. The vibration may be any vibration applied so that the core raw material is not allowed to stand for at least a part of the period during vapor deposition, and is, for example, vacuum stirring, tapping, rotation, a chamber by a vibrator, or the like. It can be exemplified that the vibration is applied by a method such as the addition of vibration.

Here, the non-oxidizing atmosphere is an atmosphere in which oxidation does not substantially proceed for a long period of time, and specific examples thereof include a state in which oxygen is absent, that is, a state in which oxygen is substantially absent. The non-oxidizing atmosphere is preferably an inert atmosphere or a vacuum atmosphere, and more preferably a vacuum atmosphere. It ^{is more preferable that the pressure is reduced to around 10-7} Torr or that a small amount of an inert gas such as argon gas is injected. By applying the vapor deposition by such a dry process, it is possible to effectively prevent the mixing of oxygen and to perform a high-purity film formation.

Examples of the vapor deposition include CVD and PVD, preferably sputtering.
When sputtering is applied, it is preferable to perform sputtering using an alloy target composed of a plurality of types of metals contained in the multi-metal layer in the shell portion, or sputtering using the plurality of types of metals themselves as targets at the same time.
It is preferable that the target corresponding to each layer of the laminated portion is changed under a nitrogen stream, or reverse sputtering is performed before the start of sputtering after the target change.
By such treatment, oxidation can be suppressed, formation of an oxide film between the constituent metals of the multi-metal layer can be sufficiently suppressed, and even if an oxide film is formed, it can be effectively removed.

In the core-shell composite of the present disclosure, when a heat-resistant hydrogen permeable shell layer is provided outside the outermost layer of the shell portion, the heat-resistant hydrogen permeable shell layer is surface-treated and the hydrogen absorbing / releasing metal contained in the outermost layer is oxidized. It is possible to form an oxide film by plating or by plating.
A desired oxide film can be formed by adjusting the solution components and the like. Further, according to plating, it is easy to achieve a desired film thickness by adjusting the applied voltage and time.
The formation of such a heat-resistant hydrogen permeable shell layer can be performed by sputtering using a target made of a heat-resistant material contained in the core portion, sputtering in the presence of oxygen or using an oxide target, and sputtering using a carbide target. Can also be used.
The heat-resistant hydrogen permeable shell layer can also be formed by coating a non-aqueous solution in which the raw materials of the heat-resistant hydrogen permeable shell layer are dispersed after the shell portion to be the outermost layer is formed.

Hereinafter, the core-shell complex according to the present disclosure will be described in more detail with reference to Examples and Comparative Examples, but the present disclosure is not limited to these Examples.

(Example 1)
Zirconia beads (trade name TZ-B30) manufactured by Tosoh Co., Ltd. were used as a core, and a mixture target of Al (37.3% by mass) and Ni (remaining amount) was used while applying vibration to the core by stirring under reduced pressure. A multi-metal layer containing Al and Ni was coated by sputtering to obtain a core-shell composite of this example having a substantially spherical shape as shown in FIG.

The properties of the zirconia beads used are as follows.
Composition: 3 mol% Y ₂ O ₃ containing ZrO ₂ sintered body Compressive strength: 1050 MPa
Morphology: Spherical properties of zirconia beads as an aggregate (powder / granular material) are as follows.
Filling density: 3.50 g / cm ³
Particle size distribution: 95% or more is 20 to 38 μm

[SEM observation]
The surface of the obtained core-shell composite was observed at an acceleration voltage of 5 kV using a field emission electron microscope (device name: JMS-7600F, manufactured by JEOL Ltd.). The obtained SEM photographs are shown in FIGS. 5 and 6. FIG. 5 shows the whole surface, and FIG. 6 shows a partial surface.
As shown in FIG. 5, the core-shell complex of this embodiment is spherical with a diameter of 30 μm, and has a plurality of irregularities of about 1 to 1.5 μm on its surface. Further, from FIG. 6, it can be confirmed that the shapes of the unevenness are random shapes different from each other, and that the multi-metal layer having such unevenness is covered.

[TEM observation]
As shown in FIG. 7, two obtained core-shell complex particles were juxtaposed, and the region S between the particles was observed by TEM. TEM photographs are shown in FIGS. 8 to 10. Note that FIG. 8 shows a portion corresponding to the region S in FIG. 7, FIG. 9 shows a left enlarged portion in FIG. 8, and FIG. 10 shows a right enlarged portion in FIG.
As shown in FIGS. 8 to 10, in the core-shell composite of this embodiment, the shell portion has a laminated structure of a multi-metal layer containing Ni and Al, and the laminated direction (left-right direction in FIGS. 8 to 10). ) Can also be confirmed.
It can also be confirmed that the surface of the core portion has irregularities, and the irregularities caused by these irregularities are also formed on the outermost surface of the multi-metal layer.

Although the present disclosure has been described above with reference to a few embodiments and examples, the present disclosure is not limited thereto, and various modifications can be made within the scope of the gist of the present disclosure.
For example, in the embodiments and examples, the powder having a substantially spherical shape has been taken as an example, but it may be scaly or elliptical spherical. The core portion, the shell portion, the material of the outermost shell layer, the melting point thereof, and the like constituting the core-shell complex can be appropriately changed according to the desired reaction and treatment.

According to the present disclosure, since a hydrogen absorption / release material whose performance does not easily deteriorate with respect to thermal history is provided, the core-shell composite of the present disclosure is for fields and applications where durability is required, for example, automobiles and energy storage devices. Especially useful in power supplies.

1,2,3 core-shell complex
10 core part
20 Shell part 21, 23, 25, 27 Multi-metal layer
22 Monometal layer
30 Shell layer C1, C2 channels

Claims (14)

A rigid core portion containing at least one heat-resistant material selected from the group consisting of inorganic oxides, ceramics and minerals, and a shell portion surrounding all or part of this core portion and containing a hydrogen absorbing / releasing metal. It is a core-shell complex with
The heat-resistant material contained in the core portion has a melting point higher than the melting point of the highest hydrogen absorbing / releasing metal contained in the shell portion.
The shell portion is a core-shell complex comprising a multi-metal layer containing a plurality of types of metals constituting the hydrogen absorbing / releasing metal. The core-shell complex according to claim 1, wherein the multi-metal layer comprises a laminated portion formed by laminating a plurality of layers. The core-shell complex according to claim 1 or 2, wherein the core portion has irregularities on its surface, and due to the irregularities, the outermost surface of the laminated portion has irregularities. The core-shell complex according to any one of claims 1 to 3, wherein the laminated portion has a channel extending along the laminating direction. The core-shell composite according to any one of claims 1 to 4, wherein the hydrogen absorbing / releasing metal is made of a hydrogen storage alloy. Any one of claims 1 to 5, wherein the shell portion further has a monometal layer containing a single type of metal, and the monometal layer is located inside and / or outside the multimetal layer with respect to the core portion. The core-shell complex described in one section. The core-shell composite according to any one of claims 1 to 6, wherein a heat-resistant hydrogen-permeable shell layer having both hydrogen gas permeability and heat resistance is provided outside the outermost layer of the layers constituting the shell portion. body. The core-shell complex according to claim 7, wherein the heat-resistant hydrogen-permeable shell layer is made of an oxide of a metal constituting the hydrogen-absorbing / releasing metal of the shell portion or a heat-resistant material contained in the core portion. The core-shell complex according to any one of claims 1 to 8, wherein the surface of the core portion has irregularities having a pitch of 1 μm or less and a random size. The metals constituting the hydrogen absorbing / releasing metal are titanium (Ti), manganese (Mn), zirconium (Zr), nickel (Ni), vanadium (V), lanthanum (La), palladium (Pd), and magnesium (Mg). ), Calcium (Ca), Cobalt (Co), Copper (Cu), Iron (Fe), Silver (Ag), Rhodium (Rh), and Aluminum (Al). 9. The core-shell complex according to any one of the sections. In producing the core-shell complex according to any one of claims 1 to 10.
A method for producing a core-shell complex, which comprises coating the core portion with the core portion by vapor deposition in a non-oxidizing atmosphere. The eleventh aspect of claim 11, wherein the laminated portion of the shell portion is formed by sputtering using an alloy target composed of a plurality of types of metals contained in the multi-metal layer, or sputtering using the plurality of types of metals themselves as targets at the same time. A method for producing a core-shell composite. The core-shell complex is provided with a heat-resistant hydrogen-permeable shell layer having both hydrogen gas permeability and heat resistance on the outside of the shell portion of the outermost layer.
After forming the shell portion to be the outermost layer of this heat-resistant hydrogen permeable shell layer,
Sputtering using a target made of heat-resistant material contained in the core part,
The method for producing a core-shell complex according to claim 11 or 12, which is carried out in the presence of oxygen or by sputtering using an oxide target. The core-shell complex is provided with a heat-resistant hydrogen-permeable shell layer having both hydrogen gas permeability and heat resistance on the outside of the shell portion of the outermost layer.
The 11th or 12th claim, wherein the heat-resistant hydrogen permeable shell layer is formed by coating a non-aqueous solution in which the raw materials of the heat-resistant hydrogen permeable shell layer are dispersed after the shell portion to be the outermost layer is formed. A method for producing a core-shell complex.

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