JP2006239528A - Hydrogen permeable membrane and production method for hydrogen permeable membrane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To further enhance an effect for suppressing metal diffusion in a hydrogen permeable membrane provided with an intermediate layer. <P>SOLUTION: The hydrogen permeable membrane 10 for selectively permeating hydrogen is provided with a metal base layer 12 containing a group V metal ; the intermediate layer 13, i.e. the metal layer formed on the metal base layer 12 and having a composition different from the metal base layer 12; and a metal covering layer 16 formed on the intermediate layer 13 and containing palladium (Pd). Here, the intermediate layer 13 has an amorphous layer 14, i.e., a low grain boundary density layer in which a density of a crystal grain boundary is formed lower than a crystalline metal layer 15, i.e., the other part at a part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hydrogen permeable membrane and a method for producing a hydrogen permeable membrane.

  In order to extract hydrogen from a hydrogen-containing gas, a hydrogen permeable membrane having a layer containing a hydrogen permeable metal has been conventionally used. For example, a hydrogen-permeable metal coating layer containing palladium (Pd) on both sides of a hydrogen-permeable metal base layer containing a Group 5 metal via a hydrogen-permeable intermediate layer containing nickel (Ni) or cobalt (Co) A hydrogen-permeable membrane having a five-layer structure provided with a film is known (see Patent Document 1). In such a hydrogen permeable membrane, by providing a hydrogen permeable intermediate layer, a decrease in hydrogen permeability due to diffusion of the metal constituting the metal coating layer into the metal base layer is prevented.

JP 2003-112020 A JP-A-7-185277 JP 2004-167379 A

  However, even if the intermediate layer is provided as described above, metal diffusion through the intermediate layer can proceed between the metal base layer and the metal coating layer, and thus further suppression of metal diffusion has been desired. When an intermediate layer is provided, the durability of the entire hydrogen permeable membrane may be insufficient due to the difference in expansion coefficient between the intermediate layer and other layers (difference in expansion coefficient due to hydrogen expansion and / or thermal expansion). There was sex.

  The present invention has been made to solve the above-described conventional problems, and an object thereof is to further enhance the effect of suppressing metal diffusion in a hydrogen permeable membrane including an intermediate layer.

To achieve the above object, the first hydrogen permeable membrane of the present invention is a hydrogen permeable membrane that selectively permeates hydrogen,
A metal base layer containing a Group 5 metal;
A part of the low grain boundary density layer formed on the metal base layer and having a composition different from that of the metal base layer and having a crystal grain boundary density lower than other parts. An intermediate layer having
And a metal coating layer containing palladium (Pd) and formed on the intermediate layer.

  According to the first hydrogen permeable membrane of the present invention configured as described above, since the intermediate layer is provided, metal diffusion between the metal base layer and the metal coating layer is suppressed, and the hydrogen permeable membrane resulting from metal diffusion is provided. It is possible to prevent performance degradation. Here, since the low grain boundary density layer is partially provided in the intermediate layer, the effect of preventing the metal diffusion between the metal base layer and the metal coating layer by the intermediate layer can be further enhanced.

In such a first hydrogen permeable membrane of the present invention,
The low grain boundary density layer of the intermediate layer is a layer formed of an amorphous metal,
The other part of the intermediate layer may be a metal layer having a crystal structure.

  Since an amorphous metal is a metal that does not have a crystal structure, the amorphous metal layer is a layer that does not have a crystal grain boundary that facilitates metal diffusion. Thus, by providing the intermediate layer with a layer made of amorphous metal having no crystal grain boundary as the low grain boundary density layer, the effect of preventing metal diffusion by the intermediate layer can be further enhanced.

In the first hydrogen permeable membrane of the present invention,
In the intermediate layer, the vicinity of one of the interfaces formed between adjacent layers is formed of amorphous metal as the low grain boundary density layer, and the vicinity of the other interface has a crystal structure. Formed by metal,
The intermediate layer may be a metal layer that gradually changes from an amorphous metal to a metal having a crystal structure between the vicinity of the one interface and the vicinity of the other interface.

  Even in such a case, by making a part of the intermediate layer an amorphous metal layer, the effect of preventing metal diffusion by the intermediate layer can be further enhanced.

The second hydrogen permeable membrane of the present invention is a hydrogen permeable membrane that selectively permeates hydrogen,
A metal base layer containing a Group 5 metal;
An intermediate layer formed on the metal base layer and having a composition different from that of the metal base layer, the intermediate layer being made of an amorphous metal;
And a metal coating layer containing palladium (Pd) and formed on the intermediate layer.

  According to the second hydrogen permeable membrane of the present invention configured as described above, since the intermediate layer is provided, metal diffusion between the metal base layer and the metal coating layer is suppressed, and the hydrogen permeable membrane caused by metal diffusion It is possible to prevent performance degradation. Moreover, since the intermediate layer is made of an amorphous metal, the effect of preventing metal diffusion between the metal base layer and the metal coating layer by the intermediate layer can be further enhanced.

In the first hydrogen permeable membrane of the present invention,
In the intermediate layer, the other part is formed of a metal having a higher melting point than the metal base layer and the metal coating layer, and the low grain boundary density layer has a melting point higher than that of the metal base layer and the metal coating layer. However, it may be formed of an amorphous alloy containing a high metal.

  With such a configuration, the effect of preventing metal diffusion can be enhanced by providing the intermediate layer by increasing the melting point of the constituent metal in the entire intermediate layer. At this time, in particular, in the other part that is not the low grain boundary density layer, the effect of suppressing metal diffusion can be significantly obtained due to the high melting point of the constituent metals.

Alternatively, in the second hydrogen permeable membrane of the present invention,
The intermediate layer may be formed of an alloy containing a metal having a higher melting point than the metal base layer and the metal coating layer.

  A metal having a higher melting point generally has a property that metal diffusion is less likely to occur. Therefore, with such a configuration, the effect of suppressing metal diffusion can be further enhanced by providing an intermediate layer.

  In the first or second hydrogen permeable membrane of the present invention, the intermediate layer includes tantalum (Ta) or niobium (Nb) as a metal having a melting point higher than that of the metal base layer and the metal coating layer. It's also good. The metal base layer may include vanadium (V) as a main metal of the metal base layer.

  Group 5 metals such as V, Ta, and Nb have excellent hydrogen permeation performance. Among them, Ta and Nb exhibit a higher melting point than V and Pd. Therefore, when the intermediate layer is formed of Ta or Nb and the metal base layer is further formed of V, a hydrogen permeable membrane having excellent hydrogen permeation performance and durability can be obtained. At this time, the metal base layer may be a layer made of V alone or a layer made of a V alloy.

The first method for producing a hydrogen permeable membrane of the present invention is a method for producing a hydrogen permeable membrane that selectively permeates hydrogen,
(A) preparing a metal base layer containing a Group 5 metal;
(B) On the metal base layer, a metal layer having a composition different from that of the metal base layer, wherein a low grain boundary density layer is formed in which the density of crystal grain boundaries is lower than other parts. Forming an intermediate layer having;
And (c) forming a metal coating layer containing palladium (Pd) on the intermediate layer.

  According to the manufacturing method of the first hydrogen permeable membrane of the present invention configured as described above, the first hydrogen permeable membrane of the present invention can be manufactured. An effect is obtained.

In the first method for producing a hydrogen permeable membrane of the present invention,
The step (b)
(B-1) forming a metal layer having a composition different from that of the metal base layer on the metal base layer;
(B-2) It is good also as providing the process which heat-processes with respect to the surface of the said metal layer, and lowers the density of the crystal grain boundary in a part including the said surface in the said metal layer.

  With such a configuration, a low grain boundary density layer constituting a part of the intermediate layer can be formed by a simple process called heat treatment. At this time, since the heat treatment is performed on the surface of the metal layer, the temperature rise of the metal base layer can be suppressed during the heat treatment. Therefore, the diffusion of the metal constituting the metal base layer accompanying the heat treatment can be suppressed.

In the first method for producing a hydrogen permeable membrane of the present invention,
The step (b)
(B-1) forming an amorphous metal layer having a composition different from that of the metal base layer;
(B-2) forming a metal layer having a crystal structure having a composition different from that of the metal base layer.

  With such a configuration, it is possible to manufacture a hydrogen permeable membrane including an intermediate layer in which a low grain boundary density layer made of amorphous metal is formed as a part of the intermediate layer.

Alternatively, in the first method for producing a hydrogen permeable membrane of the present invention,
The step (b) is a step of forming a metal layer that gradually changes from an amorphous metal to a metal having a crystal structure between the vicinity of the interface with the metal base layer and the interface with the metal coating layer. It's also good.

  With such a configuration, the vicinity of one interface is formed of an amorphous metal, the vicinity of the other interface is formed of a metal having a crystal structure, and an amorphous region is formed between one interface vicinity and the other interface vicinity. A hydrogen permeable membrane having an intermediate layer that gradually changes from a metal to a metal having a crystal structure can be produced.

The second method for producing a hydrogen permeable membrane of the present invention is a method for producing a hydrogen permeable membrane that selectively permeates hydrogen,
(A) preparing a metal base layer containing a Group 5 metal;
(B) forming on the metal base layer an intermediate layer having a composition different from that of the metal base layer and entirely composed of amorphous metal;
And (c) forming a metal coating layer containing palladium (Pd) on the intermediate layer.

  According to the manufacturing method of the second hydrogen permeable membrane of the present invention configured as described above, the second hydrogen permeable membrane of the present invention can be manufactured. An effect is obtained.

The third method for producing a hydrogen permeable membrane of the present invention is a method for producing a hydrogen permeable membrane that selectively permeates hydrogen,
(A) preparing a metal base layer containing a Group 5 metal;
(B) forming a metal layer having a composition different from that of the metal base layer on the metal base layer;
(C) reducing the density of at least some of the crystal grain boundaries of the metal layer by performing a heat treatment on the surface of the metal layer;
And (d) forming a metal coating layer containing palladium (Pd) on the metal layer.

  According to the third method for manufacturing a hydrogen permeable membrane of the present invention configured as described above, the density of crystal grain boundaries can be lowered in at least a part of the intermediate layer by a simple process such as heat treatment. At this time, since the heat treatment is performed on the surface of the metal layer, the temperature rise of the metal base layer can be suppressed during the heat treatment. Therefore, the diffusion of the metal constituting the metal base layer accompanying the heat treatment can be suppressed.

  The present invention can be realized in various forms other than those described above. For example, the present invention can be realized in the form of a hydrogen extraction device using a hydrogen permeable membrane, a fuel cell, or the like.

Next, embodiments of the present invention will be described in the following order based on examples.
A. Configuration of hydrogen permeable membrane:
B. Manufacturing method of hydrogen permeable membrane:
C. Modification of the first embodiment:
D. Second embodiment:
E. Third embodiment:
F. Use of hydrogen permeable membrane:
G. Variations:

A. Configuration of hydrogen permeable membrane:
FIG. 1 is a schematic cross-sectional view showing the outline of the configuration of a hydrogen permeable membrane 10 according to the first embodiment of the present invention. The hydrogen permeable membrane 10 includes a metal base layer 12, an intermediate layer 13 formed on both surfaces of the metal base layer, and a metal coating layer 16 formed on each intermediate layer 13. Here, the intermediate layer 13 includes an amorphous layer 14 provided in a region including an interface in contact with the metal base layer 12, and a crystalline metal provided in another region including an interface in contact with the metal coating layer 16. Layer 15. That is, the hydrogen permeable membrane 10 has a seven-layer structure as a whole.

  The metal base layer 12 is formed of a metal containing V, such as vanadium (V) or a vanadium alloy containing V as a main component in a proportion exceeding 50%, and is a metal layer that exhibits excellent hydrogen permeability. is there.

  The metal coating layer 16 is made of a metal containing Pd, and is made of, for example, palladium (Pd) or a palladium alloy containing Pd as a main component in a proportion exceeding 50%. The metal coating layer 16 is a layer that functions as a catalyst layer having an activity of promoting the dissociation reaction of hydrogen molecules on the surface of the hydrogen permeable membrane or the binding reaction to hydrogen molecules.

  The intermediate layer 13 is a layer made of a hydrogen permeable metal having a composition different from that of the metal base layer 12 and the metal coating layer 16, in order to prevent metal diffusion between the metal base layer 12 and the metal coating layer 16. It is a layer to be provided. Of the intermediate layer 13, the crystalline metal layer 15 is made of tantalum (Ta). The amorphous layer 14 is made of an alloy containing Ta, and specifically, a Ta—Cu alloy containing 64% Ta and 36% copper (Cu) (hereinafter referred to as Ta64Cu36 alloy). Formed by.

B. Manufacturing method of hydrogen permeable membrane:
FIG. 2 is a process diagram showing a method for manufacturing the hydrogen permeable membrane 10. When manufacturing the hydrogen permeable membrane 10, first, a metal layer containing V to be the metal base layer 12 is prepared (step S100). The metal layer prepared in step S100 can be produced, for example, by repeating the rolling and annealing processes on the metal ingot containing V as a main constituent, and by such a process, an extremely dense crystalline material is produced. A metal layer consisting of can be obtained. In step S100, the surface of the prepared metal layer is etched with an alkaline solution to remove impurities such as an oxide film formed on the surface.

  Following step S100, the amorphous layer 14 made of the Ta—Cu alloy described above is formed on each of both surfaces of the prepared metal base layer 12 (step S110). The amorphous layer 14 can be formed by, for example, the PVD method or the CVD method. Examples of the PVD method include sputtering, ion plating, and vacuum deposition. A film-forming material corresponding to the composition of the amorphous layer 14 to be formed is prepared, and the amount of energy supplied to the film-forming material at the time of film formation is sufficiently reduced to suppress crystallization, thereby having no crystal structure. An amorphous layer 14 can be formed. The amount of energy supplied to the film formation material can be adjusted by the temperature at the time of film formation of the metal base layer 12 that is the film formation substrate and the input energy when the film formation material collides with the substrate. The input energy when the film forming material collides with the substrate can be reduced by increasing the film forming speed, for example. In addition, when an amorphous layer is formed by sputtering or ion plating, the gas pressure of argon (Ar) gas filling the chamber is increased during film formation of the amorphous layer, so that more Ar is formed in the film formation material. It is good also as making it collide. Alternatively, when ion plating is performed, the input energy when the film forming material collides with the substrate can be reduced by setting the bias voltage applied to the substrate lower when the amorphous layer is formed. it can. Note that, since the crystallization starts when the amorphous layer 14 is heated to a temperature equal to or higher than the crystallization temperature, it is necessary to control the temperature so that the amorphous layer 14 is not heated to a temperature higher than the crystallization temperature in the processes after Step S110. . Specifically, in the film forming process after step S110, the substrate temperature for film formation may be controlled to be lower than the crystallization temperature of the alloy constituting the amorphous layer 14. In the Ta64Cu36 alloy of this example, the crystallization temperature is 656 ° C.

  Once the amorphous layer 14 is formed, a crystalline metal layer 15 made of Ta is then formed on the amorphous layer 14 (step S120). The crystalline metal layer 15 can be formed by, for example, a PVD method, a CVD method, or a plating process (for example, electroless plating or electrolytic plating).

  When the crystalline metal layer 15 is formed in step S120, the metal coating layer 16 containing Pd is formed on the crystalline metal layer 15 (step S130), and the hydrogen permeable membrane 10 is completed. The metal coating layer 16 can be formed by, for example, a PVD method, a CVD method, or a plating process.

  When the hydrogen permeable membrane 10 is manufactured, the thickness of each layer may be set according to the hydrogen permeation performance and strength required based on the application. For example, the metal base layer 12 can be 10 to 100 μm. The metal coating layer 16 can be 0.1 to 1.0 μm. Since the metal coating layer 16 is a layer that functions as a catalyst layer as described above, it can be made thinner than the metal base layer 12. The intermediate layer 13 is desirably formed thicker in order to prevent metal diffusion between the metal base layer 12 and the metal coating layer 16, but if it is interposed between the two, the intermediate layer 13 is a predetermined one that prevents metal diffusion. Therefore, it may be formed thinner than the metal coating layer 16. Therefore, for example, the thickness can be about 0.01 to 10 μm.

  According to the hydrogen permeable membrane 10 of the first embodiment configured as described above, since the amorphous layer 14 is provided in the intermediate layer 13, the metal diffusion between the metal base layer 12 and the metal coating layer 16 is intermediate. The effect prevented by the layer 13 can be further enhanced. Here, since the amorphous amorphous layer 14 does not have a crystal structure, it does not have a crystal grain boundary which is one of main fields where metal diffusion proceeds. Thus, by providing the intermediate layer 13 with the amorphous layer 14 that does not have a crystal grain boundary where metal diffusion is likely to proceed (in a broad sense, the density of the crystal grain boundary is lower), the metal diffusion can be performed. The effect to prevent can be heightened more. That is, the effect of preventing metal diffusion between the metal base layer 12 and the metal coating layer 16 can be further enhanced as compared with the case where the entire intermediate layer 13 is formed as a layer having a crystal structure by PVD or CVD. In particular, when the metal diffused into the metal coating layer 16 reaches the surface of the metal coating layer 16, the catalytic activity for dissociating hydrogen molecules to be permeated through the membrane on the surface of the hydrogen permeable membrane is hindered. By suppressing the metal diffusion as described above, it is possible to prevent such a decrease in the hydrogen permeation performance of the hydrogen permeable membrane 10.

  Further, when the hydrogen permeable membrane 10 is used, stress is generated between the adjacent metal layers due to a difference in expansion coefficient due to thermal expansion and hydrogen expansion. In this embodiment, by providing the amorphous layer 14, The influence of stress can be reduced by increasing the strength of the entire hydrogen permeable membrane 10. That is, the stress generated in the metal layer is generally concentrated on the crystal grain boundary in the crystalline metal layer, but in the amorphous layer 14 having no crystal grain boundary, the stress is dispersed throughout the amorphous layer 14 and the stress is reduced. There is no local concentration. Thus, it can be said that the amorphous layer 14 which does not have a grain boundary where stress is concentrated is a layer having excellent strength as compared with a layer having a crystal structure. Therefore, by providing the amorphous layer 14 with excellent strength, the occurrence of damage in the hydrogen permeable membrane 10 due to the difference in expansion coefficient between adjacent layers is suppressed, and the durability of the entire hydrogen permeable membrane 10 is improved. be able to.

  In general, a high-purity metal has a property that it is difficult to become amorphous. Therefore, in order to form the amorphous layer 14, it is easy to make amorphous with respect to a metal element (Ta) having hydrogen permeability. It is necessary to add elements. Here, as the element that facilitates amorphization, for example, when the obtained alloy has a eutectic reaction in the phase diagram, an element having a property of lowering the melting point near the eutectic composition is selected. be able to. Or it is good also as selecting the element from which atomic radius remarkably differs with respect to Ta. In this embodiment, Cu is selected as an element that facilitates amorphization, and a Ta—Cu alloy (Ta64Cu36 alloy) is used. However, the present invention is not limited to this. When an amorphous layer is formed from a Ta—Cu alloy as in the example, the Cu content should be 25 to 60% in order to facilitate the formation of the amorphous layer while maintaining hydrogen permeation performance. desirable.

  Here, the metal generally has the property that the higher the melting point, the less likely it is to cause metal diffusion. However, Ta contained in the entire intermediate layer 13 is a metal constituting the metal base layer 12 and the metal coating layer 16. Compared to high melting point metals. In the present embodiment, as described above, since the amorphous layer 14 is an alloy of Ta and Cu, the melting point is lower than that of Ta. However, since the crystalline metal layer 15 is formed of Ta, The melting point is higher than that of the base layer 12 or the metal coating layer 16. Therefore, the hydrogen permeable membrane 10 of the present embodiment can further enhance the effect of suppressing metal diffusion in the hydrogen permeable membrane 10 by providing such a crystalline metal layer 15.

C. Modification of the first embodiment:
C1. Modification 1:
Although the crystalline metal layer 15 of the first embodiment is composed of Ta, it may be composed of an alloy containing Ta, for example, a Ta-Cu alloy having a lower Cu content than the amorphous layer 14. good. Even in such a configuration, if the melting point of the Ta—Cu alloy constituting the crystalline metal layer 15 is higher than that of the metal constituting the metal base layer 12 and the metal coating layer 16, the same as in the embodiment. An effect is obtained. In other words, the effect of suppressing metal diffusion by making part of the intermediate layer an amorphous layer without crystal grain boundaries, and the metal diffusion being suppressed by making part of the intermediate layer a layer made of a metal having a higher melting point Both effects can be obtained.

C2. Modification 2:
In the first embodiment, the amorphous layer 14 is provided on the interface side with the metal base layer 12, and the crystalline metal layer 15 is provided on the interface side with the metal coating layer 16, but these arrangements may be reversed. Is possible. That is, the crystalline metal layer 15 may be provided on the interface side with the metal base layer 12, and the amorphous layer 14 may be provided on the interface side with the metal coating layer 16. Thus, when the interface side with the metal coating layer 16 is the amorphous layer 14, the metal coating is provided on the amorphous layer 14 having no grain boundary step (step generated at the boundary of the metal crystal) or crystal structure defect on the surface. Layer 16 will be deposited. Therefore, no defect in the crystal structure occurs in the metal coating layer 16 provided on the upper side due to the above-described grain boundary step or the defect in the crystal structure. When defects in the crystal structure occur in the metal coating layer 16, metal diffusion tends to proceed in the metal coating layer 16 through such defects, but hydrogen permeation performance resulting from metal diffusion is suppressed by suppressing the occurrence of defects. Can be prevented.

C3. Modification 3:
The amorphous layer 14 may be provided not in the vicinity of the interface between the intermediate layer 13 and the layer adjacent to the intermediate layer 13 but in the middle of the intermediate layer 13. FIG. 3 shows a configuration of a hydrogen permeable film 110 which is an example of such a hydrogen permeable film. The hydrogen permeable film 110 includes an intermediate layer 113 in which the amorphous layer 14 is sandwiched between the crystalline metal layers 15 from above and below, instead of the intermediate layer 13 of the hydrogen permeable film 10.

  Alternatively, the intermediate layer may be formed by alternately laminating a plurality of amorphous layers 14 and crystalline metal layers 15. FIG. 4 shows the configuration of a hydrogen permeable membrane 210 which is an example of such a hydrogen permeable membrane. The hydrogen permeable membrane 210 shown in FIG. 4 has an intermediate layer 213 in which three sets of laminated structures of the amorphous layer 14 and the crystalline metal layer 15 are laminated.

  With such a configuration, the amorphous layer 14 having no crystal grain boundary is provided to suppress the metal diffusion and secure the strength, and the crystalline metal layer 15 having a high content of Ta which is a refractory metal. It is possible to further enhance the effect of suppressing metal diffusion.

C4. Modification 4:
Further, the entire intermediate layer may be formed of an amorphous layer. By making at least a part of the intermediate layer an amorphous layer having no crystal grain boundary, it is possible to obtain the same effect of suppressing the metal diffusion and securing the strength by the intermediate layer. Furthermore, in this case, the intermediate layer is formed of an amorphous alloy containing a metal (for example, Ta) having a melting point higher than that of the metal constituting the metal base layer 12 or the metal coating layer 16, so that the intermediate layer can diffuse the metal. The suppression effect can be enhanced. In particular, if the melting point of the amorphous metal constituting the intermediate layer is higher than the melting point of the metal constituting the metal base layer 12 or the metal coating layer 16, the effect of suppressing metal diffusion by the intermediate layer can be further enhanced.

D. Second embodiment:
FIG. 5 is an explanatory diagram showing an outline of the configuration of the hydrogen permeable membrane 310 of the second embodiment. Since the hydrogen permeable membrane 310 of the second embodiment has a configuration similar to that of the hydrogen permeable membrane 10 of the first embodiment, portions common to the hydrogen permeable membrane 10 will be described below with the same reference numerals. .

  The hydrogen permeable membrane 310 includes an intermediate layer 313 between the metal base layer 12 and the metal coating layer 16. In the intermediate layer 313, the region including the interface with the metal base layer 12 is formed of an amorphous alloy that is a Ta—Cu alloy, and the content ratio of Ta gradually increases toward the interface with the metal coating layer 16 and the crystal structure. The vicinity of the interface with the metal coating layer 16 is made of Ta. Thus, in the intermediate layer 313, an amorphous layer 314 formed of a Ta-Cu alloy is formed in a region including the interface with the metal base layer 12, and in a region including the interface with the metal coating layer 16, A crystalline metal layer 315 made of Ta having a crystal structure is formed. However, in the second embodiment, the interface between the amorphous layer 314 and the crystalline metal layer 315 is not a clear interface like the hydrogen permeable film 10 of the first embodiment, but the composition and crystal structure over a predetermined thickness. Is a gradually changing layer (hereinafter referred to as an inclined interface).

  FIG. 6 is a process diagram showing a method for manufacturing the hydrogen permeable membrane 310 of the second embodiment. When manufacturing the hydrogen permeable membrane 310, first, the metal base layer 12 is prepared in the same manner as in Step S100 of FIG. 2 (Step S200). Thereafter, an intermediate layer 313 that gradually changes from an amorphous layer composed of a Ta—Cu alloy to a crystalline metal layer composed of Ta is formed on both surfaces of the metal base layer 12 prepared in step S200. (Step S210).

  Here, the intermediate layer 313 is formed by using, for example, a Ta alloy having a high Cu content ratio as a film forming material in a predetermined region including the interface with the metal base layer 12 when the film is formed by the PVD method. The film may be formed while supplying less energy to the film forming material. An amorphous metal layer can be formed by sufficiently reducing the amount of energy supplied to the film forming material in a state where the content of an element that facilitates amorphization such as Cu is large. Further, as the distance from the interface increases, the amount of energy supplied to the film forming material may be gradually increased while the ratio of Cu in the film forming material is decreased to increase the ratio of Ta. Thus, by gradually increasing the amount of energy supplied to the film forming material, the film forming material can obtain energy required for crystallization, and a film having a crystal structure can be formed. As described above, the amount of energy supplied to the film forming material can be adjusted by the temperature of the metal base layer 12 that is the film forming substrate and the input energy when the film forming material collides with the substrate.

  After forming the intermediate layer 313 in step S210, the metal coating layer 16 is formed on the intermediate layer 313 in the same manner as in step S130 of FIG. 2 (step S220), thereby completing the hydrogen permeable membrane 310.

  Also in the hydrogen permeable membrane 310 of the second embodiment configured as described above, the same effect as that of the first embodiment can be obtained by making a part of the intermediate layer 313 an amorphous layer 314 having no crystal grain boundary. Obtainable. In particular, in the second embodiment, since the inclined interface is formed between the amorphous layer 314 and the crystalline metal layer 315, it is caused by the difference in lattice constant between the two and the difference in expansion coefficient during hydrogen expansion or thermal expansion. Generation of defects (point defects or dislocations) in the crystal structure in the intermediate layer 313 can be prevented. Therefore, metal diffusion into the intermediate layer 313 through the defects of the crystal structure can be effectively suppressed.

  In the second embodiment, various modifications can be made as in the first embodiment. For example, the vicinity of the interface between the crystalline metal layer 315 and the metal coating layer 16 may be composed of Ta—Cu alloy having a high Ta content ratio instead of Ta. Alternatively, the arrangement of the amorphous layer 314 and the crystalline metal layer 315 may be reversed upside down.

E. Third embodiment:
In the first and second embodiments, an amorphous layer is provided as a layer having a lower density of crystal grain boundaries, but a different configuration may be used. FIG. 7 is an explanatory diagram showing an outline of the configuration of the hydrogen permeable film 410 of the third embodiment having a crystalline metal layer in which crystal grains are grown and densified as a layer having a lower density of crystal grain boundaries. Since the hydrogen permeable membrane 410 of the third embodiment has a configuration similar to that of the hydrogen permeable membrane 10 of the first embodiment, portions common to the hydrogen permeable membrane 10 will be described below with the same reference numerals. .

  Instead of the intermediate layer 13 of the hydrogen permeable membrane 10, the hydrogen permeable membrane 410 is a dense metal layer 415 provided on the interface side with the metal base layer 12 and a dense layer provided on the interface side with the metal coating layer 16. An intermediate layer 413 including a crystallized crystalline layer 414 is provided. FIG. 8 is a process diagram showing a method for manufacturing the hydrogen permeable membrane 410.

  When manufacturing the hydrogen permeable membrane 410, first, the metal base layer 12 is prepared in the same manner as in step S100 of FIG. 2 (step S300). Thereafter, Ta layers having a crystal structure are formed on both surfaces of the metal base layer 12 prepared in step S300 (step S310). The Ta layer may be formed in the same manner as the step of forming the crystalline metal layer 15 in step S120 of FIG.

  Thereafter, heat treatment (annealing) is performed on the surface of the Ta layer, and crystal grains are grown in the vicinity of the surface of the Ta layer to form a densified crystalline layer 414 (step S320). In the Ta layer, the region including the interface with the metal base layer 12 and the region where the crystal grains are not grown becomes the crystalline metal layer 415. Here, the heat treatment can be performed, for example, by irradiating the Ta layer with a pulse laser. By locally heating the Ta layer surface in this manner and applying energy, crystal grains of metal crystals grow near the surface of the Ta layer, and the crystal grain size increases. The growth of crystal grains means that defects in the crystal structure are eliminated and the grain boundary density is reduced.

  The heat treatment method is not limited to the pulse laser, and any method can be used as long as crystal grains can be grown and the surface of the Ta layer can be heated to a predetermined high temperature lower than the melting temperature of Ta. However, when the temperature of the metal base layer 12 rises, metal diffusion from the metal base layer 12 to the Ta layer proceeds. To suppress such metal diffusion, the temperature rise of the metal base layer 12 is suppressed. It is desirable to select a heating method that can be used. As a heat treatment method that makes it possible to control the heating state of the Ta layer surface so as to suppress the temperature rise of the metal base layer 12, heating by a pulse laser is an excellent method.

  In order to suppress metal diffusion from the metal base layer 12 to the Ta layer side during the heat treatment, for example, the metal base layer 12 is set so as to have a temperature equal to or lower than the Tamman temperature of the metal constituting the metal base layer 12. What is necessary is just to control the temperature. The Tamman temperature is a temperature at which self-diffusion starts in a solid, and is a temperature showing a certain relationship with the melting point. In this way, while maintaining the metal base layer 12 at a temperature lower than the Tamman temperature of the constituent metal, for example, 500 ° C. or lower, by performing heat treatment on the Ta layer, while suppressing metal diffusion from the metal base layer 12, It is possible to reduce the grain boundary density near the surface of the Ta layer. It is desirable to control the temperature of the metal base layer 12 in the same manner not only during the heat treatment of the Ta layer surface but also when forming the Ta layer and when forming the metal coating layer 16.

  After forming the densified crystalline layer 414 in step S310, the metal coating layer 16 is formed on the densified crystalline layer 414 in the same manner as in step S130 of FIG. 2 (step S330), and the hydrogen permeable membrane 410 is formed. To complete.

  According to the hydrogen permeable membrane 410 of the third embodiment configured as described above, an effect of suppressing metal diffusion through the intermediate layer 413 by forming a part of the intermediate layer 413 as the densified crystalline layer 414. Is obtained. Such an effect is obtained because defects in the crystal structure and grain boundaries where metal diffusion tends to proceed are reduced by heat treatment. As a result, the metal constituting the metal base layer 12 is prevented from diffusing into the metal coating layer 16 and reaching the surface of the metal coating layer 16, thereby preventing the performance of the hydrogen permeable membrane from being deteriorated.

  Further, in the hydrogen permeable film 410 of the third embodiment, since the densified crystalline layer 414, which is a layer having a lower grain boundary density, is made of Ta, an amorphous layer made of an alloy as a layer having a lower grain boundary density. Compared with the case of providing, the melting point in the layer having a lower grain boundary density can be increased. Therefore, in the densified crystalline layer 414, in addition to the effect of suppressing metal diffusion due to the low grain boundary density, the effect of suppressing metal diffusion due to the high melting point can also be obtained. Note that the metal layer provided in step S310 to form the densified crystalline layer 414 and the crystalline metal layer 415 may be a layer other than Ta, for example, a Ta alloy, but in this case also, the metal base layer It is desirable to use a metal having a higher melting point than the constituent metals of 12 and the metal coating layer 16.

  In the third embodiment, the crystalline metal layer 15 is provided on the metal base layer 12 side and the densified crystalline layer 414 is provided on the metal coating layer 16 side. However, the reverse arrangement is also possible. That is, after the Ta layer is formed on the metal base layer 12, the Ta layer is heat-treated to reduce the grain boundary density in the entire Ta layer to form the densified crystalline layer 414, and then the crystalline metal is formed thereon. A Ta layer may be further formed as the layer 15 by PVD or CVD. However, in order to prevent metal diffusion due to the temperature rise of the metal base layer 12 during the heat treatment, it is desirable to heat only the region away from the metal base layer 12 as shown in the third embodiment.

  Alternatively, by heating from the surface of the Ta layer provided on the metal base layer 12, the grain boundary density of the entire Ta layer is reduced, and the metal coating layer 16 is formed thereon, and the entire intermediate layer is densely formed. It can also be constituted by the crystallized crystalline layer 414. By lowering the grain boundary density of at least a portion of the intermediate layer, the effect of suppressing metal diffusion by the intermediate layer can be enhanced.

  In the third embodiment, the Ta layer once formed by PVD or CVD is heat-treated to reduce the grain boundary density of a part of the intermediate layer. The intermediate layer having can also be formed by adjusting the amount of energy applied to the film formation material during film formation. As described above, the amount of energy supplied to the film forming material can be adjusted by the temperature of the film forming substrate at the time of film formation and the input energy when the film forming material collides with the substrate. Therefore, when a part of the intermediate layer is formed, by increasing the amount of energy supplied, it is possible to form a metal layer with fewer crystal structure defects and a lower grain boundary density compared to other regions. it can. However, since the hydrogen permeable film 410 of the third embodiment performs the heat treatment for lowering the grain boundary density separately from the film forming process, compared to the case of controlling only the energy amount during film formation, The grain boundary density of the densified crystalline layer 414 can be further lowered to enhance the effect of preventing metal diffusion.

F. Use of hydrogen permeable membrane:
F-1. Hydrogen extraction equipment:
FIG. 9 is a schematic cross-sectional view showing the configuration of a hydrogen extraction apparatus 20 using the hydrogen permeable membrane 10 of the embodiment (hereinafter, the hydrogen permeable membranes of the first to third embodiments are collectively referred to as the hydrogen permeable membrane 10). FIG. The hydrogen extraction apparatus 20 has a structure in which a plurality of hydrogen permeable membranes 10 are stacked, and FIG. In the hydrogen extraction device 20, a support portion 22 that is joined to the outer peripheral portion of the hydrogen permeable membrane 10 is disposed between the stacked hydrogen permeable membranes 10. A predetermined portion is provided between the hydrogen permeable membranes 10 by the support portion 22. A space is formed. The support portion 22 may be bonded to the hydrogen permeable membrane 10 and has sufficient rigidity. For example, by forming with a metal material such as stainless steel (SUS), it is possible to easily join the hydrogen permeable membrane 10 which is a metal layer.

  The predetermined spaces formed between the hydrogen permeable membranes 10 alternately form hydrogen-containing gas paths 24 and purge gas paths 26. A hydrogen-containing gas to be subjected to hydrogen extraction is supplied to each hydrogen-containing gas passage 24 from a hydrogen-containing gas supply unit (not shown). A purge gas having a sufficiently low hydrogen concentration is supplied to each purge gas passage 26 from a purge gas supply unit (not shown). Hydrogen in the gas supplied to the hydrogen-containing gas passage 24 is extracted from the hydrogen-containing gas by permeating the hydrogen permeable membrane 10 toward the purge gas passage 26 according to the hydrogen concentration difference.

  According to such a hydrogen extraction device 20, since the hydrogen permeable membrane 10 in which the performance deterioration due to metal diffusion is suppressed is used as the hydrogen permeable membrane, the hydrogen extraction performance of the entire hydrogen extraction device 20 is prevented from being deteriorated. be able to.

F-2. Fuel cell:
FIG. 10 is a schematic cross-sectional view showing an example of the configuration of a fuel cell using the hydrogen permeable membrane 10 of the example. FIG. 10 shows a single cell 30, but the fuel cell is formed by stacking a plurality of single cells 30.

  The unit cell 30 includes a hydrogen permeable membrane 10, an electrolyte layer 32 formed on one surface of the hydrogen permeable membrane 10, and a cathode electrode 34 formed on the electrolyte layer 32. 31 is provided. The single cell 30 further includes two gas separators 36 and 37 that sandwich the MEA 31 from both sides. Between the hydrogen permeable membrane 10 and the gas separator 36 adjacent thereto, a single-cell fuel gas flow path 38 through which a hydrogen-containing fuel gas passes is formed. In addition, between the cathode electrode 34 and the gas separator 37 adjacent thereto, an in-single cell oxidizing gas passage 39 through which an oxidizing gas containing oxygen passes is formed.

The electrolyte layer 32 is a layer made of a solid electrolyte having proton conductivity, for example, a BaCeO ₃ or SrCeO ₃ ceramic proton conductor. The electrolyte layer 32 can be formed by generating the solid oxide on the hydrogen permeable membrane 10 by a method such as PVD or CVD. Thus, by forming the electrolyte layer 32 on the hydrogen permeable membrane 10 which is a dense metal film, the electrolyte layer 32 can be made thinner, and the membrane resistance of the electrolyte layer 32 can be further reduced. Thereby, it becomes possible to generate electric power at about 200 to 600 ° C., which is lower than the operating temperature of the conventional solid oxide fuel cell.

  The cathode electrode 34 is a layer having catalytic activity that promotes an electrochemical reaction, and may be formed of, for example, a porous Pt layer made of noble metal Pt. In the single cell 30, a current collector having electrical conductivity and gas permeability may be further provided between the cathode electrode 34 and the gas separator 37 or between the hydrogen permeable membrane 10 and the gas separator 36.

  The gas separators 36 and 37 are gas-impermeable members formed of a conductive material such as carbon or metal. On the surfaces of the gas separators 36 and 37, a predetermined uneven shape for forming the single-cell fuel gas flow path 38 or the single-cell oxidizing gas flow path 39 is formed.

  According to such a fuel cell, since the hydrogen permeable membrane 10 in which the decrease in hydrogen permeation performance due to metal diffusion is suppressed is used as the hydrogen permeable membrane that is the substrate for forming the electrolyte layer, Performance degradation can be prevented.

  In the hydrogen permeable membrane provided in the fuel cell shown in FIG. 10, unlike the hydrogen permeable membrane 10 shown in FIG. 1, the metal coating layer 16 and the intermediate layer 13 are not provided on the surface in contact with the electrolyte layer 32. It is also possible to do.

G. Variations:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

G1. Modification 1:
Each layer constituting the hydrogen permeable membrane may be formed of a metal different from those in the first to third embodiments. For example, although the metal base layer 12 is formed of V or a V alloy in the embodiment, it may be formed of a metal (including a simple substance) containing another group 5 metal.

G2. Modification 2:
In the first embodiment, the amorphous layer 14 is formed of a Ta-Cu alloy (Ta64Cu36 alloy), but an amorphous layer having a different composition may be provided. For example, a Ta63Cu36B1 alloy which is an alloy further containing boron (B) may be used. Even in such a case, in order to facilitate the formation of the amorphous layer, the Cu content in the alloy is preferably 25 to 60%.

  In addition, as an alloy constituting the amorphous layer, a Ta—Ni alloy (for example, Ta60Ni40 alloy) or a Ta—silicon (Si) alloy (for example, Ta80Si20 alloy) may be used. Ta has excellent hydrogen permeability and a higher melting point than V and Pd. However, the Ta alloy used to form the amorphous layer also has a higher melting point than the metal base layer 12 and the metal coating layer 16. In some cases, similar effects can be obtained that further enhance the effect of suppressing metal diffusion.

  Further, in addition to Ta, the intermediate layer may be formed using niobium (Nb), which belongs to the group 5 metal like Ta and has a higher melting point than V and Pd. As in the case of using Ta, the amorphous layer can be easily formed by further mixing Cu, Ni, or Si with Nb. As such an alloy for forming an amorphous layer, an Nb-Si alloy (for example, an Nb80Si20 alloy) can be cited. In step S310 of the third embodiment, an Nb layer may be formed instead of the Ta layer.

  Alternatively, when the metal base layer 12 is formed of V or a V alloy, the entire intermediate layer (amorphous layer and crystalline metal layer, or a densified crystalline layer and crystalline metal layer), both Ta and Nb It is good also as forming with the alloy to contain. In addition, the amorphous layer or the densified crystalline layer may contain one of Ta and Nb, and the crystalline metal layer may be formed of an alloy containing the other or a simple substance. Alternatively, the metal base layer 12 may be a metal layer containing one of Ta and Nb, and the entire intermediate layer may be a metal layer containing the other.

  Further, the intermediate layer may not contain a Group 5 metal. Even if Ta or Nb is not used, an intermediate layer is formed of a hydrogen permeable metal having a melting point higher than that of the metal base layer 12 or the metal coating layer 16, and at least a part thereof has a lower grain boundary density. A similar effect can be obtained.

G3. Modification 3:
In the hydrogen permeable membranes of the first to third embodiments already described, the hydrogen permeable membrane is a self-supporting membrane of a metal thin film having hydrogen permeability, but the hydrogen permeable metal is formed on a porous substrate having gas permeability. A hydrogen permeable membrane may be formed by supporting. That is, a metal layer laminated in the order of a metal coating layer, an intermediate layer, a metal base layer, an intermediate layer, and a metal coating layer may be sequentially formed on the layered porous body to form a hydrogen permeable membrane. Thus, the hydrogen permeable membrane carry | supported on the porous base material can be used instead of the hydrogen permeable membrane 10 of an Example in the hydrogen extraction apparatus shown in FIG. 9, for example.

2 is a schematic cross-sectional view showing an outline of the configuration of the hydrogen permeable membrane 10. FIG. 3 is a process diagram illustrating a method for manufacturing the hydrogen permeable membrane 10. FIG. 2 is a schematic cross-sectional view illustrating an outline of a configuration of a hydrogen permeable membrane 110. FIG. 2 is a schematic cross-sectional view showing an outline of the configuration of a hydrogen permeable membrane 210. FIG. 2 is a schematic cross-sectional view illustrating an outline of a configuration of a hydrogen permeable membrane 310. FIG. 6 is a process diagram illustrating a method for manufacturing the hydrogen permeable membrane 310. FIG. 2 is a schematic cross-sectional view illustrating an outline of a configuration of a hydrogen permeable membrane 410. FIG. 5 is a process diagram illustrating a method for manufacturing the hydrogen permeable membrane 410. FIG. 3 is a schematic cross-sectional view showing a configuration of a hydrogen extraction device 20. FIG. 1 is a schematic cross-sectional view showing a configuration of a fuel cell using a hydrogen permeable membrane 10. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,110,210,310,410 ... Hydrogen permeable film 12 ... Metal base layer 13,113,213,313,413 ... Intermediate layer 14,314 ... Amorphous layer 15,315,415 ... Crystalline metal layer 16 ... Metal coating Layer 20 ... Hydrogen extraction device 22 ... Supporting portion 24 ... Hydrogen-containing gas passage 26 ... Purge gas passage 30 ... Single cell 31 ... MEA
32 ... Electrolyte layer 34 ... Cathode electrode 36, 37 ... Gas separator 38 ... Single-cell fuel gas flow path 39 ... Single-cell oxidizing gas flow path 414 ... Densified crystalline layer

Claims (15)

A hydrogen permeable membrane that selectively permeates hydrogen,
A metal base layer containing a Group 5 metal;
A part of the low grain boundary density layer formed on the metal base layer and having a composition different from that of the metal base layer and having a crystal grain boundary density lower than other parts. An intermediate layer having
A hydrogen permeable membrane formed on the intermediate layer and comprising a metal coating layer containing palladium (Pd). The hydrogen permeable membrane according to claim 1,
The low grain boundary density layer of the intermediate layer is a layer formed of an amorphous metal,
The other part of the intermediate layer is a metal layer having a crystal structure. The hydrogen permeable membrane according to claim 1,
In the intermediate layer, the vicinity of one of the interfaces formed between adjacent layers is formed of amorphous metal as the low grain boundary density layer, and the vicinity of the other interface has a crystal structure. Formed by metal,
The intermediate layer is a metal layer that gradually changes from an amorphous metal to a metal having a crystal structure between the vicinity of the one interface and the vicinity of the other interface. The hydrogen permeable membrane according to claim 2 or 3,
In the intermediate layer, the other part is formed of a metal having a higher melting point than the metal base layer and the metal coating layer, and the low grain boundary density layer has a melting point higher than that of the metal base layer and the metal coating layer. A hydrogen permeable membrane formed of an amorphous alloy containing a high metal. A hydrogen permeable membrane that selectively permeates hydrogen,
A metal base layer containing a Group 5 metal;
An intermediate layer formed on the metal base layer and having a composition different from that of the metal base layer, the intermediate layer being made of an amorphous metal;
A hydrogen permeable membrane formed on the intermediate layer and comprising a metal coating layer containing palladium (Pd). The hydrogen permeable membrane according to claim 5,
The intermediate layer is formed of an alloy containing a metal having a higher melting point than the metal base layer and the metal coating layer. The hydrogen permeable membrane according to claim 4 or 6,
The intermediate layer includes tantalum (Ta) or niobium (Nb) as a metal having a higher melting point than the metal base layer and the metal coating layer. The hydrogen permeable membrane according to any one of claims 1 to 7,
The metal base layer includes vanadium (V) as a main metal of the metal base layer. A method for producing a hydrogen permeable membrane that selectively permeates hydrogen,
(A) preparing a metal base layer containing a Group 5 metal;
(B) On the metal base layer, a metal layer having a composition different from that of the metal base layer, wherein a low grain boundary density layer is formed in which the density of crystal grain boundaries is lower than other parts. Forming an intermediate layer having;
(C) forming a metal coating layer containing palladium (Pd) on the intermediate layer. A method for producing a hydrogen permeable membrane according to claim 9,
The step (b)
(B-1) forming a metal layer having a composition different from that of the metal base layer on the metal base layer;
(B-2) A method of manufacturing a hydrogen permeable membrane, comprising: subjecting a surface of the metal layer to a heat treatment to reduce a density of crystal grain boundaries in a part of the metal layer including the surface. A method for producing a hydrogen permeable membrane according to claim 9,
The step (b)
(B-1) forming an amorphous metal layer having a composition different from that of the metal base layer;
(B-2) forming a metal layer having a crystal structure having a composition different from that of the metal base layer. A method for producing a hydrogen permeable membrane according to claim 9,
The step (b) is a step of forming a metal layer that gradually changes from an amorphous metal to a metal having a crystal structure between the vicinity of the interface with the metal base layer and the interface with the metal coating layer. A method for producing a hydrogen permeable membrane. A method for producing a hydrogen permeable membrane that selectively permeates hydrogen,
(A) preparing a metal base layer containing a Group 5 metal;
(B) forming on the metal base layer an intermediate layer having a composition different from that of the metal base layer and entirely composed of amorphous metal;
(C) forming a metal coating layer containing palladium (Pd) on the intermediate layer. A method for producing a hydrogen permeable membrane that selectively permeates hydrogen,
(A) preparing a metal base layer containing a Group 5 metal;
(B) forming a metal layer having a composition different from that of the metal base layer on the metal base layer;
(C) reducing the density of at least some of the crystal grain boundaries of the metal layer by performing a heat treatment on the surface of the metal layer;
(D) forming a metal coating layer containing palladium (Pd) on the metal layer. A hydrogen permeable membrane that selectively permeates hydrogen,
A hydrogen permeable membrane produced by the method for producing a hydrogen permeable membrane according to claim 10.

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