JP2005334828A - Hydrogen-permeable membrane and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prepare a hydrogen-permeable membrane which is highly flexible and easily processable. <P>SOLUTION: The hydrogen-permeable membrane 1 is composed a hydrogen-permeable metal membrane 2 and a porous thin metal film 3a or 3b applied to at least either surface of the membrane 2. The porous thin metal film 3a or 3b is desirably one formed by electrolytic plating. The hydrogen-permeable metal membrane 2 is desirably made from an amorphous hydrogen storage alloy. The hydrogen-permeable metal membrane 1 is produced by forming the porous thin metal film 3b on a carrier foil 11 by electrolytic plating, forming the hydrogen-permeable metal membrane 2 on the porous thin metal film 3b by a thin-film formation means, and thereafter separating the carrier foil 11 from the resulting assemblage. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hydrogen permeable membrane having high flexibility and easy processing, and a method for manufacturing the same.

  Conventionally, palladium has been mainly studied as a hydrogen permeable membrane. However, palladium needs to be heated to 300 ° C. or higher for hydrogen permeation, and since palladium itself is expensive, it cannot be used for industrial hydrogen purification. Accordingly, it has been proposed to reduce the amount of palladium used to reduce the amount of palladium used, and to compensate for the decrease in strength with a porous support (see, for example, Patent Documents 1 and 2). However, in these proposals, a sintered body of a metal powder that is a rigid body, a stainless steel porous body that is perforated by etching, or a ceramic porous body is used as the porous support. Therefore, flexibility is low and processability is inferior.

It has also been proposed to use an intermetallic compound such as LaNi ₅ known as a hydrogen storage alloy as a hydrogen permeable membrane. However, since this material is brittle and easily cracks, it is difficult to use it as a hydrogen permeable membrane. It is conceivable to make the material amorphous as one means for increasing the strength of the material. However, if the film thickness of the amorphous film is increased in order to increase the strength, the amorphous is crystallized by the heat generated at that time, and consequently the strength cannot be increased. In particular, when an amorphous film of a hydrogen storage alloy is formed on a ceramic porous film by sputtering, the heat generated by sputtering does not escape due to the low thermal conductivity of the ceramic, and amorphous crystallization is likely to be promoted. .

JP-A-11-267477 Japanese Patent Laid-Open No. 2000-5580

  Accordingly, it is an object of the present invention to provide a hydrogen permeable membrane and a method for manufacturing the same that can eliminate the various disadvantages of the above-described prior art.

  The present invention achieves the above object by providing a hydrogen permeable membrane characterized in that a porous metal thin film is disposed on at least one surface of the hydrogen permeable metal membrane.

  According to the present invention, as a preferred method for producing the hydrogen permeable film, the porous metal thin film is formed on a carrier foil by electrolytic plating, and then the hydrogen permeable metal film is formed on the porous metal thin film by a thin film forming means. Then, after that, the carrier foil is peeled and separated, and a method for producing a hydrogen permeable membrane is provided.

  According to the present invention, a hydrogen permeable membrane having high flexibility and easy processing can be obtained. Further, according to the present invention, even if the hydrogen-permeable metal film made of an expensive material such as palladium is thinned to reduce the amount of use, sufficient strength is maintained by the porous metal thin film.

  The present invention will be described below based on preferred embodiments with reference to the drawings. FIG. 1 schematically shows the structure of a preferred embodiment of the hydrogen permeable membrane of the present invention. The hydrogen permeable membrane 1 of this embodiment is configured by arranging porous metal thin films 3 a and 3 b on each surface of a hydrogen permeable metal membrane 2.

  The hydrogen permeable metal film 2 is not particularly limited as long as it is made of a material having hydrogen permeability. For example, palladium or an alloy thereof can be used. The hydrogen permeable metal film 2 made of these materials can be formed by various thin film forming means such as sputtering, ion plating, and electrolytic plating.

As the hydrogen permeable metal film 2, a material known as a hydrogen storage alloy can also be used. Examples thereof include an AB ₅ type alloy having a CaCu ₅ type crystal structure and an AB ₂ type alloy having a Laves phase structure typified by ZrV _0.4 Ni _1.5 . Also, AB type alloys and A ₂ B type alloys such as Mg ₂ Ni can be used. Specifically, for example, LaNi ₅ , MmNi ₅ (Mm represents Misch metal), and a part of Ni in MmNi ₅ are selected from Al, Mn, Co, Ti, Cu, Zn, Zr, Cr, and B, A multi-element alloy substituted with an element containing at least Al, Co, and Mn can be used. Among them, general formula MmNi _a Mn _b Al _c Co _d (where Mm represents Misch metal, 4.0 ≦ a ≦ 4.7, 0.3 ≦ b ≦ 0.65, 0.2 ≦ c ≦). 0.5, 0 <d ≦ 0.35, 5.2 ≦ a + b + c + d ≦ 5.5) is preferably used.

  When a hydrogen storage alloy is used as the hydrogen permeable metal film 2, the hydrogen storage alloy is preferably amorphous. This is because an amorphous hydrogen storage alloy has a smaller volume change during hydrogen storage and higher durability than a crystalline hydrogen storage alloy. The amorphous hydrogen storage alloy can be formed by sputtering, for example.

  Although there is no restriction | limiting in particular in the thickness of the hydrogen-permeable metal film 2, It is preferable from an economical point of view that the function as a film | membrane is not impaired and it makes it as thin as intensity | strength permits. When the hydrogen permeable metal film 2 is made of, for example, palladium or an alloy thereof, the film 2 is preferably a thin layer of about 1 to 10 μm, particularly about 1 to 3 μm. On the other hand, when the hydrogen permeable metal film is made of, for example, a hydrogen storage alloy, the thickness of the film is preferably 3 to 50 μm, particularly 3 to 15 μm.

  The porous metal thin films 3a and 3b sandwiching the hydrogen permeable metal film 2 from both sides are used for supporting the hydrogen permeable metal film 2 and imparting strength to the hydrogen permeable film 1. Further, it is used to prevent the metal film 2 from being poisoned by covering the surface of the hydrogen permeable metal film 2. The porous metal thin films 3a and 3b are formed with a large number of fine holes through which hydrogen can easily pass through. There are no particular restrictions on the size of the fine holes, but if it is too large, the thickness of the hydrogen permeable metal film 2 must be increased in order to close the holes with the hydrogen permeable metal film 2. Accordingly, the size of the micropores is preferably about 0.01 to 30 μm, particularly about 0.01 to 5 μm. The size of the micropores in each porous metal thin film 3a, 3b may be the same or different.

The micropores are formed substantially uniformly over the entire area of the porous metal thin films 3a and 3b. Any part of the porous metal thin film has 30 to 5000 fine pores in an area of 1 mm ² , especially 30 to 2000, which means that hydrogen is sufficiently transmitted through the porous metal thin films 3a and 3b. This is preferable. For the same reason, the ratio of the total area of the micropores to the area of the porous metal thin films 3a and 3b is preferably 1 to 15%, particularly 1 to 7%. These values may be the same or different in each porous metal thin film 3a, 3b.

  One feature of the hydrogen permeable membrane 1 of the present embodiment is that the thickness of the porous metal thin films 3a and 3b can be reduced, thereby providing the hydrogen permeable membrane 1 with flexibility. The thickness of each of the porous metal thin films 3a and 3b can be freely controlled within a range of about 1 to 50 μm, preferably about 2 to 10 μm, particularly about 2 to 5 μm. Such a thin porous metal thin film can be easily formed by, for example, electrolytic plating. This thickness may be the same or different in each porous metal thin film 3a, 3b.

  There are no particular restrictions on the material that forms the porous metal thin films 3a and 3b, but it is preferable that the material be made of a material that exhibits sufficient strength even when the porous metal thin films 3a and 3b are thinned. Examples of such a material include nickel, iron, copper, and alloys thereof. In particular, nickel is preferably used because it has a catalytic action for dissociation of hydrogen molecules. The material which comprises each porous metal thin film 3a, 3b may be the same, or may differ.

  The thickness of the entire hydrogen permeable membrane 1 is preferably about 10 to 80 μm, particularly about 10 to 30 μm, from the viewpoint of flexibility and workability. The hydrogen permeable membrane 1 having such a thickness can be easily processed into a free shape, and thus has a degree of freedom to be attached to various forms of hydrogen purifiers. Further, since the porous metal thin films 3a and 3b are provided, the porous metal thin films 3a and 3b have sufficient strength even though they are thin, so that they can sufficiently withstand the differential pressure during hydrogen purification.

  Next, the preferable manufacturing method of the hydrogen permeable film 1 of this embodiment is demonstrated, referring FIG. In this manufacturing method, first, the porous metal thin film 3b is formed on the carrier foil 11 (see FIG. 2 (b)), and then the hydrogen permeable metal film 2 is formed thereon (see FIG. 2 (c)). A porous metal thin film 3a is formed thereon (see FIG. 2D).

  First, a carrier foil 11 is prepared as shown in FIG. The carrier foil 11 is used as a support for manufacturing the hydrogen permeable membrane 1. Further, the manufactured hydrogen permeable membrane 1 is supported until immediately before its use, and is used for improving the handleability of the hydrogen permeable membrane 1. From these viewpoints, it is preferable that the carrier foil 11 has such strength that no twist or the like is generated in the manufacturing process of the hydrogen permeable membrane 1 and in the transport process and the assembly process after the manufacturing. Therefore, the carrier foil 11 preferably has a thickness of about 10 to 50 μm.

  It is preferable to use a conductive foil as the carrier foil 11. In this case, the carrier foil 11 may not be made of metal as long as it has conductivity. However, the use of the metal carrier foil 11 has an advantage that the carrier foil 11 can be melted and made after the hydrogen permeable membrane 1 and recycled. When the metal carrier foil 11 is used, the carrier foil 11 is configured to include at least one metal of Cu, Ni, Co, Fe, Cr, Sn, Zn, In, Ag, Au, Al, and Ti. It is preferable.

  From the viewpoint of forming a large number of fine holes in the porous metal thin film 3b, an aluminum foil or an aluminum alloy foil (hereinafter collectively referred to simply as an aluminum foil) is used as the carrier foil 11, and the porous metal thin film is formed by the method described below. Preferably 3b is formed. As the aluminum foil, it is preferable to use a JIS standard 1N30 Al alloy (Al> 99.30%, Fe + Si <0.7%). Note that the lower limit of the Fe + Si concentration is Fe + Si> 0.01%, particularly Fe + Si> 0.1%. This Al alloy is one in which Al is the main component in the alloy and Fe and Si are uniformly dispersed in Al as a dispersion precipitation portion.

Prior to forming the porous metal thin film 3b on the carrier foil 11 made of an aluminum foil, a degreasing / etching process is performed to etch the Al portion of the carrier foil 11 while degreasing the surface of the carrier foil 11. The composition of the treatment liquid and the treatment conditions are, for example, as follows. Since aluminum is an amphoteric metal, alkali degreasing and etching are simultaneously performed by using a treatment liquid having the following composition.
NaOH: 15-45 g / l
・ Rochelle salt; 25-65 g / l
・ Na ₂ CO ₃ ; 25-65 g / l
Liquid temperature: 20-60 ° C, preferably 30-50 ° C
Processing time: 10 to 300 seconds Degreasing Etching rate 1 to 1.5 μm / min

As the degreasing / etching progresses, the aluminum on the surface of the carrier foil 11 is removed, and minute protrusions containing impurities such as Fe and Si contained in the aluminum are exposed. The degreasing / etching process is performed until this protrusion is exposed. If the treatment time is too long, Al ₂ O ₃ is generated and interferes with the etching process, so care should be taken not to oversaturate the etching.

When the degreasing / etching process is completed, the carrier foil 11 is washed with running water at room temperature to remove the degreasing / etching solution. Next, electrolytic plating is performed on the carrier foil 11. For example, when nickel plating is performed, a plating bath (Watt bath) having the following composition or a nickel sulfamate bath can be used.
NiSO ₄ .6H ₂ O; 150 to 300 g / l
NiCl ₂ .6H ₂ O; 50 to 250 g / l
_{· H 3 BO 3; 30~40g /} l

When copper plating is performed, a plating bath (CuSO ₄ bath) having the following composition or a copper pyrophosphate bath can be used.
CuSO ₄ .5H ₂ O; 150 to 350 g / l
・ H ₂ SO ₄ ; 50 to 250 g / l
In this case, the current density is preferably ^{2 to} 50 A / dm ² , particularly preferably 10 to 30 A / dm ² . It is preferable to use an insoluble electrode (DSE) for the anode. A DC power source is used as the power source.

  A porous metal thin film 3b having a predetermined thickness is formed on the carrier foil 11 by electrolytic plating (see FIG. 2B). The mechanism by which a large number of micropores are formed in the porous metal thin film 3b is as follows. In the initial stage of electroplating, electrodeposition occurs starting from the protrusions exposed on the surface of the carrier foil 11, and metal particles of plated metal are generated. Then, the generated metal particles grow, and the grown metal particles continue to grow further. During this growth, pores are created between the metal particles. These holes are filled with the growth of the metal particles, but microscopically there are fine holes between the metal particles. This fine hole penetrates the metal thin film 3b. In this way, the porous metal thin film 3b is formed on the carrier foil 11.

  When the porous metal thin film 3b is formed, the hydrogen permeable metal film 2 is formed thereon as shown in FIG. 2 (c). Various thin film forming means can be used for this formation. For example, when the hydrogen permeable metal film 2 is made of palladium or a palladium alloy, the hydrogen permeable metal film 2 can be formed by sputtering, ion plating, electrolytic plating, or the like. On the other hand, when the hydrogen permeable metal film 2 is made of a hydrogen storage alloy, sputtering can be used. An amorphous hydrogen storage alloy can be formed by controlling the film formation conditions of sputtering. In this case, the porous metal thin film 3b serving as the base is made of a metal material that is a material having high thermal conductivity, so that heat generated during sputtering can easily escape and the inconvenience of crystallization of the amorphous hydrogen storage alloy is avoided. can do.

  Next, a porous metal thin film 3a is formed on the hydrogen permeable metal film 2 (see FIG. 2D). Prior to this, a coating liquid containing a conductive polymer is applied on the hydrogen permeable metal film 2 and dried to form a coating film. This coating film is for forming a large number of micropores in the porous metal thin film 3a. The surface of the hydrogen permeable metal film 2 is not completely flat, but is microscopically uneven. When the coating liquid is applied to such a surface, the coating liquid tends to accumulate in the recesses. When the solvent volatilizes in this state, the thickness of the coating film becomes non-uniform. That is, the thickness of the coating film corresponding to the concave portion is large, and the thickness of the coating film corresponding to the convex portion is small. In this manufacturing method, a large number of fine voids are formed in the porous metal thin film 3a by utilizing the nonuniformity of the thickness of the coating film.

  There is no restriction | limiting in particular as a conductive polymer, A conventionally well-known thing can be used. Examples thereof include poly (vinylidene fluoride) (PVDf), polyethylene oxide (PEO), polyacrylonitrile (PAN), and polymethyl methacrylate (PMMA). In particular, the conductive polymer is preferably a fluorine-containing conductive polymer. This is because the fluorine-containing polymer has high thermal and chemical stability and excellent mechanical strength. Considering this, it is particularly preferable to use poly (vinylidene fluoride) which is a fluorine-containing polymer.

  The coating liquid containing a conductive polymer is obtained by dissolving a conductive polymer in a volatile organic solvent. As the organic solvent, for example, when polyvinylidene fluoride is used as the conductive polymer, N-methylpyrrolidinone or the like can be used.

  In this manufacturing method, the mechanism by which many fine holes are formed in the metal thin film 3a is considered as follows. The conductive polymer constituting the coating film has electronic conductivity, although not as much as metal. Therefore, the coating film has different electron conductivity depending on its thickness. As a result, when a metal is deposited on the coating film containing a conductive polymer by electrolytic plating, a difference occurs in the deposition rate depending on the electron conductivity. Due to the difference in the deposition rate, a large number of fine holes are formed in the metal thin film 3a. That is, a portion where the electrodeposition rate is low, in other words, a portion where the coating film is thick, tends to be fine holes.

  The pore size and density of the fine pores can be controlled by the concentration of the conductive polymer contained in the coating liquid. For example, when the concentration of the conductive polymer is low, the pore diameter tends to be small and the existence density tends to be small. Conversely, when the concentration of the conductive polymer is high, the pore diameter tends to increase. The concentration of the conductive polymer in the coating liquid is also a dominant factor of the pore size and density of the fine pores. From this viewpoint, the concentration of the conductive polymer in the coating solution is preferably 0.05 to 5% by weight, particularly 1 to 3% by weight.

  The plating bath and plating conditions for forming the porous metal thin film 3a can be the same as those of the previously formed porous metal thin film 3b.

  Finally, as shown in FIG. 2 (d), the carrier foil 11 is peeled and separated from the porous metal thin film 3b. Thereby, the hydrogen permeable membrane 1 is obtained. The hydrogen permeable membrane 1 may be supported on the carrier foil 11 without being peeled off from the carrier foil 11 before use. In the case where an aluminum foil is used as the carrier foil 11, the surface of the foil is passivated and an oxide film is formed between the degreasing and etching processes and the formation of the porous metal thin film 3b. Since this oxide film acts as a peeling layer, the carrier foil 11 is successfully peeled from the porous metal thin film 3b.

  The hydrogen permeable membrane thus obtained can be applied to hydrogen permeable membrane electrodes and various sensors as well as being used as a hydrogen separation / purification membrane.

  The present invention is not limited to the embodiment. For example, in the embodiment shown in FIG. 1, the porous metal thin films 3a and 3b are formed on each surface of the hydrogen permeable metal film 2, but instead of this, the porous metal thin film is formed only on one surface of the hydrogen permeable metal film. A thin film may be formed.

  Further, in the method for producing the hydrogen permeable membrane shown in FIG. 2, as a method for forming the porous metal thin film 3b formed on the carrier foil 11, the hydrogen permeable metal membrane 2 is used in place of the degreasing / etching treatment of the aluminum foil. A coating solution containing a conductive polymer may be used in the same manner as in the method for forming the porous metal thin film 3a formed thereon.

It is a schematic diagram which shows the structure of the hydrogen permeable film of this invention. It is process drawing which shows the manufacturing method of the hydrogen permeable film shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hydrogen permeable film 2 Hydrogen permeable metal film 3a, 3b Porous metal thin film 11 Carrier foil

Claims (8)

  A hydrogen permeable membrane comprising a porous metal thin film disposed on at least one surface of a hydrogen permeable metal membrane.   The hydrogen permeable membrane according to claim 1, wherein the porous metal thin film is formed by electrolytic plating.   The hydrogen permeable membrane according to claim 1, wherein the hydrogen permeable metal membrane is made of palladium, a palladium alloy, or a hydrogen storage alloy.   The hydrogen permeable membrane according to claim 3, wherein the hydrogen permeable metal membrane is made of an amorphous hydrogen storage alloy.   The hydrogen permeable membrane according to claim 1, wherein the porous metal thin film has a thickness of 1 to 50 μm. A method for producing a hydrogen permeable membrane according to claim 2,
The porous metal thin film is formed by electrolytic plating on the carrier foil, and then the hydrogen permeable metal film is formed on the porous metal thin film by a thin film forming means, and then the carrier foil is peeled and separated. A method for producing a hydrogen permeable membrane.   The manufacturing method according to claim 6, wherein an aluminum foil is used as the carrier foil, and the porous metal thin film is formed by electrolytic plating after degreasing and etching the aluminum foil. The coating liquid containing a conductive polymer is applied on the hydrogen permeable metal film to form a coating film, and then a porous metal thin film is further formed on the coating film by electrolytic plating. Production method.

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