JP3935851B2 - Hydrogen separation membrane and method for producing the same - Google Patents

Description

【００２６】
【表２】

【００２７】
そして、上記により得られた実施例１〜１９の合金箔、及び比較例１〜８の合金箔について、以下の評価項目および測定方法により特性評価を行った。
表面状態；顕微鏡で観察し、表面の平滑性を評価した。
ピンホールの有無；油性赤色染料を溶媒に１ｇ／Ｌの濃度で溶解させた染料液を用意し、十分に換気されたドラフト内において吸取紙の上にサンプルを置き、サンプルの上にブラシで染料液を塗布した。５分経過後にサンプルを取り除いて吸取紙に染色点が形成されているか否かを確認した。
箔中の元素分布の偏析の有無；ＥＰＭＡ（表面元素分析）によって、箔中の元素分布の偏析の有無を調べた。
結晶構造；Ｘ線回析法により結晶構造を分析した。
水素透過性能；実施例７及び８の合金箔、比較例１及び５の合金箔については、各合金箔を気体透過測定セルに固定して４００℃に加熱し、その片側に水素ガスを流通させ、反対側に透過した水素のガス流量を測定した。
【００２８】
その結果、上記により得られた実施例１〜１９の合金箔はいずれも均一な厚みを有しており、表面状態も良好で、ピンホールも確認されなかった。その上、合金箔中の元素分布の偏析もなく、しかもその結晶構造はアモルファス（非晶質）であり、優れた水素透過性及び耐水素脆化性を有し、水素精製装置のメンブレンとして有用であることも確認された。
これに対し、比較例１〜８の合金箔については、比較例６及び８の場合、箔にすることができずアモルファスの箔帯とならない。又、比較例４及び７の場合、箔になるがアモルファスとならず、比較例１、２、３及び５の場合は、アモルファスの良好な箔帯となったが、水素透過量が著しく低かった（図３参照）。
又、図３に示した実施例７及び８の合金箔、比較例１及び５の合金箔についての水素透過性能のグラフから、測定温度４００℃において、Ｎｂ₂₈Ｎｉ₄₂Ｚｒ₃₀（実施例７）は１．３×１０^-8〔ｍｏｌ・ｍ^-1・ｓｅｃ^-1・Ｐａ^-1/2〕、Ｎｂ₃₂Ｎｉ₄₈Ｚｒ₂₀（実施例８）は６．４×１０^-9〔ｍｏｌ・ｍ^-1・ｓｅｃ^-1・Ｐａ^-1/2〕の高い水素透過係数をそれぞれ示し、本発明の水素透過膜は、比較例１及び５の合金箔よりも著しく優れた水素透過性能を有していることがわかった。
【００２９】
【発明の効果】
アモルファス結晶構造を有する本発明の水素透過膜は、水素のみを選択的に高い効率で透過する能力を有し、水素雰囲気中でも十分な強度及び安定性を有しており、燃料電池や半導体関連分野において使用される水素精製装置の水素透過膜として特に有用である。
また、本発明の製造方法を用いることによって、これまでの圧延法では加工が困難であった組成のニオブ合金箔が比較的簡単に製造でき、圧延法では水素透過性が低下するような組成（例えばＮｂに対するＮｉの割合が２０重量％を越える組成）の場合であっても、水素透過性の低下を起こすことなく、耐水素脆化性に優れた水素精製装置用の水素透過膜が得られる。
【図面の簡単な説明】
【図１】本発明のニオブ合金箔を製造する装置を示した図である。
【図２】本発明のニオブ合金箔を製造する装置を示した図である。
【図３】実施例７及び８で得られた本発明の水素分離膜と、比較例１及び５で得られた水素分離膜との水素透過性能の比較を示した図である。
【符号の説明】
１ 坩堝
２ ロール
３ スリット
４ 高周波誘導加熱器
５ ロール面
６ 箔
７ ガス加圧口
８ ロールの中心軸
９ ロール面上の第１の地点
１０ ロール面上の第２の地点
１１ 熔湯（溶融物）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a metal foil (niobium alloy foil) useful for a hydrogen permeable membrane (membrane) of a hydrogen purifier used in fuel cells and semiconductor-related fields, and a method for producing the metal foil.
[0002]
[Prior art]
In recent years, as one of the countermeasures against global warming, the practical application and popularization of a hydrogen purifier and a fuel cell using the same have been desired. Such a hydrogen purification apparatus has a first chamber and a second chamber, and the first chamber is isolated from the second chamber via a membrane. When a gas containing hydrogen flows into the first chamber, the membrane plays a role of substantially permeating hydrogen, and the gas enriched with hydrogen collects in the second chamber, and impurities (CO, CO _2, etc.) are collected. The contained gas remains in the first chamber. Thus, what is called hydrogen permeability is required for the membrane of the hydrogen purifier.
Conventionally, as such a membrane, a palladium alloy (Pd-Ag or the like) foil having hydrogen storage properties has been used. Palladium alloy foils have excellent hydrogen permeability, but palladium is relatively expensive, so there is a need for alternative products made of materials that are less expensive than palladium alloy foils.
And the vanadium alloy and the niobium alloy have been examined as an alternative material of a palladium alloy (for example, refer patent documents 1-4).
[0003]
[Patent Document 1]
JP-A-1-262,924 [Patent Document 2]
JP-A-4-29,728 [Patent Document 3]
Japanese Patent Laid-Open No. 11-276,866 [Patent Document 4]
Japanese Patent Laid-Open No. 2000-159,503
However, all of the alloys described in Patent Documents 1 to 4 are poor in rollability, and when it is attempted to produce an alloy foil by rolling, special rolling conditions and repeated annealing steps are required, resulting in an increase in production cost. . Moreover, when annealing is repeated when producing a foil, the element distribution in the foil may be segregated. Further, such work must be performed in an inert gas atmosphere in order to prevent oxidation of the alloy. However, if the rolling process or annealing process is performed in an inert gas atmosphere, the apparatus becomes large. Moreover, the roll-formed vanadium alloy foil and niobium alloy foil have low toughness and poor workability and durability.
As for niobium alloy foils, it has been known so far to add Ta, Co, Mo, Ni, etc. in order to enhance hydrogen embrittlement resistance (see Patent Document 4 above). In this case, when manufacturing a niobium alloy foil by the cold rolling method, there is a problem that hydrogen permeability is remarkably lowered when the ratio of Ni to niobium exceeds 10 to 20% by weight.
[0005]
[Problems to be solved by the invention]
Accordingly, the present invention provides a niobium alloy foil that is excellent in hydrogen embrittlement resistance, hydrogen permeability and workability, can avoid segregation of element distribution in the foil, and is useful as a membrane for a hydrogen purifier, and a method for producing the same. The issue is to provide.
[0006]
[Means for Solving the Problems]
As a result of repeated studies to solve the above-mentioned problems, the inventor of the present application is able to achieve the above-described problems by using a hydrogen separation membrane composed mainly of a non-Pd element, which is made of an amorphous crystal structure niobium alloy having a specific alloy composition. I found that it can be solved.
The present invention is described in further detail below.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The hydrogen separation membrane of the present invention includes 5 to 65 atomic% of at least one selected from the group consisting of Ni, Co and Mo as the first additive element, and V, Ti, Zr, At least one selected from the group consisting of Ta and Hf is made of an amorphous niobium alloy consisting of 0.1 to 60 atomic% and the balance Nb as an essential constituent element. Such a niobium alloy has good hydrogen embrittlement resistance and hydrogen permeability, and is useful as a membrane for a hydrogen purifier.
[0008]
In the present invention, the total amount of Ni, Co and Mo as the first additive elements blended in the niobium alloy is 5 to 65 atomic%, preferably 10 to 50 atomic%, particularly preferably 20 to 40 atomic%. Within such a range, a niobium alloy containing Ni, Co and Mo exhibits good hydrogen embrittlement resistance. In the present invention, when the first additive element is Ni, the composition ratio is preferably 20 to 40 atomic%.
[0009]
Moreover, in this invention, the total amount of V, Ti, Zr, Ta, and Hf mix | blended in a niobium alloy as a 2nd addition element is 0.1-60 atomic%, 10-50 atomic% is preferable, and 20-20 is preferable. 40 atomic percent is particularly preferred. By adding at least one of these additive elements to the niobium alloy within the above range, the hydrogen permeability of the resulting niobium alloy foil can be increased.
[0010]
Furthermore, in this invention, you may mix | blend Al and / or Cu in a niobium alloy as a 3rd addition element, and hydrogen embrittlement resistance can be improved further by adding these elements, These metals are preferable. The composition ratio is 0.01 to 20 atomic%, and 0.1 to 5% by weight is particularly preferable.
[0011]
The hydrogen separation membrane of the present invention contains Nb as an essential constituent element in addition to the above-described additive elements. The composition ratio of Nb in the alloy is preferably 15 to 70 atomic%, and preferably 25 to 50 atomic%. Particularly preferred.
In addition, preferred Nb alloy compositions in the present invention include Nb—Ni—Zr, Nb—Ni—Zr—Al, Nb—Ni—Ti—Zr, Nb—Ni—Ti—Zr—Co, Nb— Ni-Ti-Zr-Co-Cu system, Nb-Co-Zr system, etc. are mentioned, but it is not limited to these.
In the present invention, the preferred Nb: Ni ratio (atomic% ratio) can be selected as appropriate, but is preferably 1: 0.8 to 1.2, particularly preferably around 1: 1.
[0012]
Next, a method for producing the hydrogen separation membrane of the present invention will be described. In the production method of the present invention, first, Nb that is an essential constituent element, the first additive element, the second additive element, and the third additive element as necessary are prepared at the above composition ratio, and these constituent metals are prepared. A metal compound composed of the above is melted by heating to a temperature higher than the melting point in an inert gas, and this melt is processed into a film (foil) using a liquid quenching method. At this time, as a method of processing into a foil shape, a crucible having a slit at the bottom thereof is used to prepare a melt of niobium alloy having the above-described composition, which is made of a cylindrical body, and its central axis is parallel to the slit. Rotate the roll placed on the roll, the melt is ejected from the slit toward the roll surface of the rotating roll, the melt ejected from the slit is rapidly cooled and solidified on the roll surface A method in which the niobium alloy is continuously peeled from the roll surface to obtain a foil is preferred.
[0013]
FIG. 1 is a preferred specific example of an apparatus used in producing the hydrogen separation membrane of the present invention, but this apparatus is conceptually shown and is not limited thereto.
The crucible 1 in the apparatus (alloy foil manufacturing apparatus) shown in FIG. 1 includes a concave portion and a lid portion, and the inside thereof can be sealed. The material of the crucible 1 is not particularly limited. The crucible 1 is made of a material that can withstand a high temperature that melts the niobium alloy charged in the recess and does not chemically react with the melt (molten metal). The A suitable material for the crucible 1 is, for example, boron nitride ceramic.
[0014]
A heating means for heating the inside of the crucible is provided around the crucible 1. The heating means is not particularly limited as long as the inside of the crucible can be heated to the melting point of the niobium alloy or higher. In the apparatus shown in FIG. 1, a high frequency induction heater 4 composed of a high frequency coil is provided as a heating means. According to the high frequency induction heater 4, the melt in the crucible is convected and stirred, so that the niobium alloy can be rapidly melted while maintaining a uniform temperature distribution. If a thermocouple is placed in the crucible, the temperature of the niobium alloy melt in the crucible can be confirmed.
[0015]
According to the invention, the crucible 1 is provided with a gas inlet 7. When the niobium alloy charged in the crucible is completely melted, gas is injected from the injection port 7 so that the inside of the crucible is pressurized.
The gas injected from the injection port 7 is inert, and oxidation of the molten niobium alloy is prevented. Particularly suitable inert gases include, for example, nitrogen, helium, argon, and hydrogen. Among these, argon gas is particularly preferred.
Here, the pressure in the crucible when gas is injected into the crucible is not particularly limited, but the pressure in the crucible is preferably 0.01 to 0.1 MPa.
[0016]
According to the invention, a slit 3 is provided at the bottom of the crucible. The slit 3 can blow the melt in the crucible toward the roll surface 5 of the rotating roll 2 described later. This slit is normally closed until the niobium alloy charged in the crucible is completely melted. The means for closing the slit is not particularly limited. In the present invention, the slit does not necessarily have to have a shape protruding like a nozzle from the bottom of the crucible as shown in FIG.
The width of the slit 3 is not particularly limited, but the slit preferably has a width of 0.1 to 0.6 mm, more preferably 0.2 to 0.5 mm, and most preferably 0.3 to 0.4 mm. . Thereby, a foil having a desired thickness can be obtained. On the other hand, the length of the slit 3 is not particularly limited, and the length of the slit can be appropriately changed according to the dimensions of the roll.
[0017]
As shown in FIG. 1, according to the present invention, a cylindrical roll 2 is disposed below the slit. The roll 2 is arranged so that its central axis 8 is parallel to the crucible slit 3, and the roll is attached so as to rotate about the central axis 8. The melt (molten metal) 11 ejected from the slit 3 is sprayed toward the rotating roll surface 5. That is, the melt ejected from the slit comes into contact with the roll surface at the first point 9 on the roll surface and is rapidly cooled to form a foil layer on the roll surface. The roll is rotating at a constant rotational speed, and the foil layer is continuously peeled off at the second point 10 on the roll surface to obtain the foil 6. The peeled foil is collected in a chamber (not shown).
In the present invention, the relative positional relationship between the slit 3 and the roll 2 is not particularly limited, and the slit 3 and the central axis of the roll are parallel to each other, and the roll surface is positioned in the ejection direction of the slit. If you do.
[0018]
The present invention is not limited to the case where an apparatus (single roll type apparatus) composed of one roll 2 is used as shown in FIG. 1, and two rolls 5 ′ and 5 ″ are provided as shown in FIG. An equipped device (a twin roll type device) may be used.
In the case of the apparatus shown in FIG. 2, the first roll 2 ′ is arranged in parallel with the second roll 2 ″, and the first roll 2 ′ and the second roll 2 ″ are inward of each other downward. It is rotating. When the melt in the crucible is ejected from the slit 3 between the first roll and the second roll, the melt is either the first roll 2 ′ or the second roll 2 ″. It cools rapidly in contact with one or both, thereby forming a foil layer on the roll surfaces 5 ', 5 ". The foil layer formed on the roll surface is continuously peeled to obtain a foil.
[0019]
According to the present invention, the rolls 2, 2 ′ and 2 ″ need to be made of a material having high thermal conductivity such as copper because it is necessary to rapidly cool the melt ejected from the slit 3. It should be noted that a hole for passing a coolant such as water may be formed inside the roll.
[0020]
According to the present invention, the roll surface 5 needs to be continuous. Moreover, the roll surface has sufficient smoothness, and the foil layer formed on the roll surface can be easily peeled off.
[0021]
In the present invention, the rotation speed of the roll 2 is not particularly limited, but the roll 2 is preferably rotated so that the roll surface 5 moves at 450 to 3000 m / min. Thereby, the melt ejected from the slit can be rapidly cooled, and a favorable foil having an amorphous crystal structure can be produced.
[0022]
According to the present invention, the thickness of the obtained niobium alloy foil can be freely changed by adjusting the amount of the melt blown, the width of the slit, the rotational speed of the roll, and the like. In the present invention, the thickness of the obtained niobium alloy foil is not particularly limited, but is 5 to 1000 μm. In particular, when the thickness of the niobium alloy foil obtained in the present invention is 5 to 40 μm, the niobium alloy constituting this foil becomes amorphous. Amorphous niobium alloy foils are particularly useful as membranes for hydrogen purification equipment.
[0023]
According to the present invention, the apparatus including the crucible and the roll is disposed in an inert gas such as argon, and thereby the oxidation of the obtained niobium alloy foil can be prevented.
[0024]
【Example】
Using a single roll type alloy foil manufacturing apparatus having the structure illustrated in FIG. 1, a niobium alloy foil was produced.
The crucible 1 was made of boron nitride ceramic and had a slit with a width of 0.4 mm and a length of 30 mm. Roll 2 was made of copper and had a diameter of 300 mm and a length of 80 mm. The distance between the roll surface 5 and the slit 3 was 0.5 mm. The roll was cooled with water. The number of rotations of the roll was set to 1500 rpm.
A 50Nb-40Ni-10Zr (atomic%) niobium alloy was charged into the crucible. The inside of the crucible was heated to 1750 ° C. to completely melt the niobium alloy. Thereafter, argon gas is injected into the crucible, the melt is ejected from the slit to form a foil layer on the roll surface, and the foil layer is continuously peeled from the roll to form a niobium alloy having a thickness of 0.03 mm. A foil (Example 1) was obtained. The pressure in the crucible was 0.05 MPa.
Similarly, alloy foils of Examples 2 to 19 according to the present invention were produced according to the alloy compositions shown in Table 1 below.
On the other hand, as comparative examples, alloy foils of Comparative Examples 1 to 8 were produced with the alloy compositions shown in Table 2 below.
[0025]
[Table 1]

[0026]
[Table 2]

[0027]
And about the alloy foil of Examples 1-19 obtained by the above, and the alloy foil of Comparative Examples 1-8, characteristic evaluation was performed with the following evaluation items and measuring methods.
Surface condition: Observed with a microscope to evaluate surface smoothness.
Presence / absence of pinholes: Prepare a dye solution prepared by dissolving oily red dye in a solvent at a concentration of 1 g / L, place the sample on blotting paper in a well-ventilated draft, and dye the sample with a brush on the sample The liquid was applied. After 5 minutes, the sample was removed and it was confirmed whether dyed spots were formed on the blotting paper.
Presence or absence of segregation of element distribution in foil: Presence or absence of segregation of element distribution in foil was examined by EPMA (surface element analysis).
Crystal structure: The crystal structure was analyzed by X-ray diffraction.
Hydrogen permeation performance: For the alloy foils of Examples 7 and 8, and the alloy foils of Comparative Examples 1 and 5, each alloy foil was fixed to a gas permeation measurement cell and heated to 400 ° C., and hydrogen gas was allowed to flow on one side. The gas flow rate of hydrogen permeated to the opposite side was measured.
[0028]
As a result, the alloy foils of Examples 1 to 19 obtained as described above all had a uniform thickness, the surface state was good, and no pinholes were confirmed. In addition, there is no segregation of the element distribution in the alloy foil, and the crystal structure is amorphous, which has excellent hydrogen permeability and hydrogen embrittlement resistance, and is useful as a membrane for hydrogen purification equipment. It was also confirmed.
On the other hand, about the alloy foil of Comparative Examples 1-8, in the case of Comparative Examples 6 and 8, it cannot be made into a foil and does not become an amorphous foil strip. Further, in Comparative Examples 4 and 7, the foil was formed but was not amorphous. In Comparative Examples 1, 2, 3, and 5, the amorphous foil was good, but the hydrogen permeation amount was extremely low. (See FIG. 3).
From the graphs of hydrogen permeation performance of the alloy foils of Examples 7 and 8 shown in FIG. 3 and the alloy foils of Comparative Examples 1 and 5, Nb ₂₈ Ni ₄₂ Zr ₃₀ (Example 7) at a measurement temperature of 400 ° C. Is 1.3 × 10 ⁻⁸ [mol · m ⁻¹ · sec ⁻¹ · Pa ^−1/2 ], and Nb ₃₂ Ni ₄₈ Zr ₂₀ (Example 8) is 6.4 × 10 ⁻⁹ [mol · m ^{−. 1} · sec ⁻¹ · Pa ^−1/2 ] respectively, and the hydrogen permeable membrane of the present invention has a hydrogen permeation performance significantly superior to the alloy foils of Comparative Examples 1 and 5. I understood it.
[0029]
【The invention's effect】
The hydrogen permeable membrane of the present invention having an amorphous crystal structure has the ability to selectively permeate only hydrogen with high efficiency, has sufficient strength and stability even in a hydrogen atmosphere, and is related to fuel cells and semiconductors. It is particularly useful as a hydrogen permeable membrane of a hydrogen purifier used in
Further, by using the production method of the present invention, a niobium alloy foil having a composition that has been difficult to process by the conventional rolling method can be produced relatively easily, and the hydrogen permeability is lowered by the rolling method ( For example, even in the case of a composition in which the ratio of Ni to Nb exceeds 20% by weight, a hydrogen permeable membrane for a hydrogen purifier excellent in hydrogen embrittlement resistance can be obtained without causing a decrease in hydrogen permeability. .
[Brief description of the drawings]
FIG. 1 is a view showing an apparatus for producing a niobium alloy foil of the present invention.
FIG. 2 is a view showing an apparatus for producing the niobium alloy foil of the present invention.
3 is a graph showing a comparison of hydrogen permeation performance between the hydrogen separation membranes of the present invention obtained in Examples 7 and 8 and the hydrogen separation membranes obtained in Comparative Examples 1 and 5. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Crucible 2 Roll 3 Slit 4 High frequency induction heater 5 Roll surface 6 Foil 7 Gas pressurizing port 8 Center axis 9 of a roll 1st point 10 on a roll surface 2nd point 11 on a roll surface )

Claims (4)

A hydrogen separation membrane comprising a niobium alloy having an amorphous crystal structure, wherein the niobium alloy comprises at least one selected from the group consisting of Ni, Co and Mo as the first additive element in an amount of 5 to 65 atomic%. And 0.1 to 60 atomic% of at least one selected from the group consisting of V, Ti, Zr, Ta and Hf as the second additive element and the balance Nb as the essential constituent element A hydrogen separation membrane characterized by 2. The hydrogen separation membrane according to claim 1, wherein the niobium alloy further contains 0.01 to 20 atomic% of Al and / or Cu as a third additive element. A method for producing a hydrogen separation membrane made of an amorphous niobium alloy, wherein at least one selected from the group consisting of Ni, Co and Mo as a first additive element is 5-65 atomic%, It is obtained by blending at least one or more selected from the group consisting of V, Ti, Zr, Ta and Hf as additive elements with 0.1 to 60 atomic% and the balance Nb as an essential constituent element. A method for producing a hydrogen separation membrane, comprising: heating and melting a metal compound in an inert gas to a temperature equal to or higher than a melting point, and processing into a membrane using a liquid quenching method. The method for producing a hydrogen separation membrane according to claim 3, wherein 0.01 to 20 atomic% of Al and / or Cu is further blended as the third additive element in the metal blend.

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