JP3749952B1 - Crystalline double-phase hydrogen permeable alloy membrane and crystalline double-phase hydrogen permeable alloy membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crystalline multiphase hydrogen permeable alloy having hydrogen permeability and resistance to hydrogen embrittlement and usable at 473K or more.
The composite phase comprises a eutectic (CoTi + TiNb) structure of a CoTi phase in which Nb is dissolved and a TiNb phase in which Co is dissolved, and the TiNb phase generated as an initial phase is the composite phase. A structure surrounded by a eutectic or a structure where the CoTi phase generated as an initial phase is surrounded by the eutectic, and Co _x Ti _y Nb _(100−xy) (where 20 <x It is a multiphase Co—Ti—Nb-based crystalline double phase hydrogen permeable alloy having a composition of <50 atomic%, 10 <y <60 atomic%.
[Selection] Figure 1

Description

  The present invention relates to a crystalline double phase hydrogen permeable alloy and a crystalline double phase hydrogen permeable alloy film.

  High-purity hydrogen is used in the manufacture of semiconductors, optical fibers, chemicals, etc., and the amount of use is increasing year by year. Recently, hydrogen has attracted attention as a fuel for fuel cells, and if fuel cells are to be used in earnest in the future, a large amount of high-purity hydrogen is required. Therefore, development of a method capable of producing high-purity hydrogen in large quantities at low cost is desired.

  As a method for mass production of hydrogen, there are (1) a method by electrolysis of water using non-fossil resources and (2) a method by reforming hydrocarbons using fossil resources. In the electrolysis method (1), water electrolysis using electricity obtained by photovoltaic power generation as a power source has been studied, but practical application is difficult at the current technical level. Therefore, for the time being, it is realistic to produce hydrogen by (2) steam reforming of hydrocarbons.

As described above, hydrocarbon reforming is suitable for mass production of hydrogen. For example, in a reaction system in which H ₂ O is added to CH ₄ , a large amount of hydrogen is generated according to the following reaction formulas (1) to (3).

    (Chemical formula 1)

CH ₄ + H ₂ O⇔CO + 3H ₂ [gasification reaction (endothermic reaction)] (1)

    (Chemical formula 2)

CO + H ₂ O⇔CO ₂ + H ₂ [shift reaction (exothermic reaction)] (2)

      (1) + (2) = (3)

    (Chemical formula 3)

CH ₄ + 2H ₂ O⇔CO ₂ + 4H ₂ [endothermic reaction] (3)

The reaction takes place according to Chemical Formula 1 and Chemical Formula 2, and finally, the reaction of Chemical Formula 3 occurs. The reaction system contains impurities such as CO, CO ₂ , H ₂ O, and CH ₄ in addition to a large amount of hydrogen. In order to use hydrogen as a fuel cell feedstock, it must be separated and purified from these impurities. Further, unless the CO content in the purified hydrogen is 10 ppm or less, the Pt electrode of the fuel cell is damaged. In other words, in order to use hydrogen in a fuel cell, it is necessary to purify and purify it.

  Hydrogen purification methods include an absorption method, a cryogenic separation method, an adsorption method, and a membrane separation method. Among these, the membrane separation method has been put into practical use. The membrane separation method uses the difference in the speed of gas passing through the membrane, and a polymer membrane or a metal membrane is used as the membrane.

  In the membrane separation method using a polymer membrane, hydrogen is separated and purified from the difference in diffusion rate of gas molecules passing through pores. In this membrane separation method, high-purity hydrogen cannot be obtained, but the system can be enlarged.

On the other hand, in the metal film, there are no pores in the polymer film, and the hydrogen permeation mechanism is as follows. When there is a hydrogen pressure difference across the metal film, on the high pressure side, hydrogen molecules (H ₂ ) dissociate into atoms (H) on the metal surface and dissolve in the metal, and enter and diffuse. The hydrogen atoms permeate the metal film, recombine with H ₂ on the low pressure side surface, and jump out. As a result, the hydrogen is purified. The purification of hydrogen using a metal membrane is characterized by extremely large influences of the separation coefficient and permeation coefficient. In the purification of hydrogen using a metal film, for example, about 99% of hydrogen can be purified to about 99.99999%. Therefore, it can be said that a membrane separation method using a metal membrane is suitable for purification of high purity hydrogen for fuel cells.

  As a hydrogen permeable metal film used for the hydrogen permeable film, an alloy mainly composed of Pd, such as a Pd—Ag alloy, a Pd—Ti alloy, or the like is known (for example, see Patent Document 1).

  By the way, at present, a Pd—Ag alloy film has been put into practical use as a hydrogen permeable metal film. However, if the use of fuel cells becomes full-scale and a large amount of hydrogen is required, the demand for Pd—Ag alloys as hydrogen permeable metal films will increase accordingly. In such a case, Pd, which is expensive and less resource-intensive, is considered to be a limitation, and it is assumed that the Pd—Ag alloy film cannot cope with it, and material development of a metal film to replace it is urgently required.

It is indispensable that the hydrogen permeable alloy has the property of “occluding hydrogen” in the same manner as the hydrogen storage alloy. However, the material properties required for each material are completely different as shown in Table 1, and cannot be realized based on the development guidelines for hydrogen storage alloys.

  A hydrogen storage alloy is an alloy that can easily store and release hydrogen repeatedly. The principle is that the hydrogen pressure remains constant even when the hydrogen storage amount increases, that is, a pressure plateau occurs. As explained by Gibbs' phase law, the pressure plateau occurs when hydrogen is in solid solution (hereinafter referred to as hydrogen solid solution) and hydride coexists. If a hydride is not generated, a pressure plateau is not generated, and therefore it cannot be used efficiently as a hydrogen storage alloy.

  Although hydrides are brittle without exception, it is not an obstacle to hydrogen storage alloys, but rather an advantage. For example, there is no problem even if the alloy before hydrogen storage is brittle. This is because the alloy is easily self-pulverized by hydrogen storage, and the hydrogen storage / release rate is increased by increasing the specific surface area that reacts with hydrogen, which is advantageous as a hydrogen storage alloy.

  The hydrogen storage alloy is used in a powder form and is not used in a plate form or a film form. When the operating temperature rises or the hydrogen pressure decreases, hydride formation becomes difficult and the properties as a hydrogen storage alloy deteriorate. Therefore, it is required to use at temperatures from room temperature to 150 ° C and under hydrogen of 0.5 MPa or more. It has been.

On the other hand, the hydrogen permeable alloy is the same as the hydrogen occluding alloy until the hydrogen molecules (H ₂ ) dissociate into hydrogen atoms (H) on the metal surface and enter the metal to be occluded.

  However, in hydrogen permeable alloys, hydrogen containing impurities is on the high pressure side, and hydrogen purified through the metal film is on the low pressure side, creating a pressure difference, that is, a hydrogen concentration gradient on both sides of the alloy, The driving force for transmission is used. Since it is essential to make a pressure difference on both sides of the alloy, it cannot be used in a powder state and is used as a plate or a film.

  The material generally has a property of becoming brittle when hydrogen is occluded. The hydrogen solid solution does not become so brittle, but when hydride is formed, it becomes brittle and self-pulverization occurs. Therefore, the formation of hydride must be avoided in hydrogen permeable alloys. In addition, when the temperature is lowered or the hydrogen pressure is increased, hydride formation is facilitated. Therefore, the hydrogen permeable alloy is used at a temperature of 200 ° C. (473 K) or more and under 0.5 MPa of hydrogen.

  As described above, the concept of alloy design of both materials is 180 degrees different, and it is impossible to use a hydrogen storage alloy as a hydrogen permeable alloy, and vice versa. A hydrogen permeable alloy must exhibit ductility before hydrogen storage and must not generate hydride before hydrogen storage.

In general, the hydrogen permeable material is used in a region where a hydrogen solid solution is formed. In such a case, hydrogen amount J (molH ₂ m ⁻² s ⁻¹ ) and hydrogen permeating the alloy film per unit time and unit area are used. There is a relationship represented by the following equation with the transmission coefficient Φ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ).

    (Equation 1)

J = Φ (P _u ^0.5 −P _d ^0.5 ) / L

In the above formula, P _u and P _d (Pa) are the hydrogen pressures on the upstream side and the downstream side, respectively, and L is the thickness (m) of the hydrogen permeable alloy film.

  In order to increase the hydrogen permeation amount J, in addition to using an alloy having a large hydrogen permeation coefficient Φ, a thin membrane may be used with a higher pressure difference. Therefore, it is essential that the mechanical properties of the alloy film are excellent. This is because a material having a high hydrogen permeability coefficient cannot be realized as a hydrogen-permeable alloy film if it is destroyed by hydrogen embrittlement. The reason why pure Nb having a hydrogen permeability coefficient 100 times higher than that of pure Pd is not used as a hydrogen permeable alloy film is that Nb has low hydrogen embrittlement resistance. Currently, the biggest development issue for hydrogen permeable alloys is how to suppress hydrogen embrittlement.

  As the hydrogen permeable alloy film, for example, it is known that an alloy of V, Nb, Ta and Ti, Zr, Ni, Co is suitable (see, for example, Patent Document 2). The alloy design guideline in this document is to make a hydrogen permeable alloy from Ti, Zr, Hf having hydrogen storage ability in V, Nb, Ta excellent in hydrogen permeability and Ni, Co having catalytic action. is there. However, this document does not describe hydrogen embrittlement as well as hydrogen permeability. Further, even if an alloy is produced based on such guidelines, the alloy is broken by hydrogen embrittlement and cannot be used as a hydrogen permeable alloy.

  A similar document (see Patent Document 3) also describes an Nb-based hydrogen permeable alloy, but its hydrogen permeability is lower than that of Pd. These alloys assume a single phase, but it is difficult for the single phase to have contradictory properties of hydrogen permeability and hydrogen embrittlement resistance. If it is going to suppress hydrogen embrittlement with these alloys, the amount of hydrogen solid solution must be reduced, which causes a decrease in hydrogen permeability.

  Furthermore, in order to suppress hydrogen embrittlement, it is known to make an alloy structure amorphous (see, for example, Patent Document 4). However, since the diffusion coefficient of hydrogen in an amorphous alloy is generally lower than that in a crystalline material, high hydrogen permeability cannot be obtained. Further, since the amorphous material is crystallized when the temperature is increased, the use temperature is restricted. In particular, since an amorphous alloy produced for hydrogen permeation contains an element having a high binding force with hydrogen, crystallization occurs in hydrogen at a lower temperature.

In order to solve such a problem, it has been proposed that the alloy is effective in making a double phase (see, for example, Non-Patent Document 1). The material properties are strongly influenced by the structure of the alloy, but the structure is strongly dependent on the alloy composition. Therefore, when discussing the characteristics of the material, it is meaningless unless the relationship between the alloy composition, structure, and characteristics is clearly indicated. However, this document does not specify the alloy composition. Further, there is no mention of the relationship between the alloy composition, the structure, and the properties, and it cannot be implemented.
JP-A-8-215551 (paragraph 0006) Japanese Patent Laid-Open No. 11-276866 (paragraph 0014) JP 2000-159503 A (paragraph 0006) Japanese Patent Laying-Open No. 2004-042017 (paragraphs 0005 and 0009) Kunihiko Hashi et al., “Hydrogen Permeation Properties of Co—Ti—Nb Alloy”, Outline of the Japan Institute of Metals, VOL133, P.A. 427

  Therefore, the relationship between the alloy composition, structure, and hydrogen permeability is clarified, and the hydrogen permeability and hydrogen embrittlement resistance are assigned to different phases. There is a demand for realization of alloys.

  Accordingly, an object of the present invention is to provide a crystalline multi-phase hydrogen permeable alloy and a crystalline multi-phase hydrogen permeable alloy film that have hydrogen permeability and hydrogen embrittlement resistance and can be used at 473 K or higher. To do.

  The above problem is that the present inventors have a role of hydrogen permeability and hydrogen embrittlement resistance in the alloy, a composite of a phase responsible for hydrogen permeability and a phase responsible for hydrogen embrittlement resistance, that is, a multiphase alloy. It was solved by finding that it can be solved.

  Double phase Co-Ti-Nb crystalline double phase hydrogen permeable alloy, double phase Ni-Zr-Nb crystalline double phase hydrogen permeable alloy and double phase Co-Zr-Nb crystalline double phase hydrogen permeable alloy of the present invention Is characterized by comprising a composite phase of a phase responsible for hydrogen permeability and a phase responsible for hydrogen embrittlement resistance.

  In a multiphase Co—Ti—Nb alloy, a eutectic (CoTi + TiNb) structure of a TiNb phase in which Co is dissolved (hereinafter referred to as TiNb phase) and a CoTi phase in which Nb is dissolved (hereinafter referred to as CoTi phase). The TiNb phase generated as the initial phase is surrounded by the eutectic, or the CoTi phase generated as the initial phase is surrounded by the eutectic. This makes it possible to produce a hydrogen permeable alloy that has both hydrogen permeability and hydrogen embrittlement resistance, and can efficiently permeate hydrogen.

The Co—Ti—Nb-based alloy is made of Co _x Ti _y Nb _(100-xy) (where 20 <x <50 atomic%, 10 <y <60 atomic%). When x is 20 atomic% or less, hydrogen embrittlement is remarkable and it is not suitable as a hydrogen permeable alloy. Further, if x is 50 atomic% or more, the hydrogen permeation coefficient is extremely small or brittleness is exhibited in the cast state, so that it is not suitable as a hydrogen permeation alloy. On the other hand, if y is out of the above range, it is brittle in the cast state and cannot be used as a hydrogen permeable alloy. Preferably, in the Co-Ti-Nb ternary phase diagram, Co ₅₀ Ti ₅₀ , Co ₅₀ Ti ₁₀ Nb ₄₀ , Co ₂₀ Ti ₁₀ Nb ₇₀ , Co ₂₀ Ti ₆₀ Nb ₂₀ and Co ₄₀ Ti ₆₀ (where the alloy composition is All alloys in the region surrounded by atomic%).

  Further, in a Ni—Zr—Nb alloy, a eutectic (NiZr + ZrNb) structure of a ZrNb phase in which Ni is dissolved (hereinafter referred to as a ZrNb phase) and a NiZr phase in which Nb is dissolved (hereinafter referred to as a NiZr phase). The ZrNb phase generated as the initial phase is surrounded by the eutectic, or the NiZr phase generated as the initial phase is surrounded by the eutectic. This makes it possible to produce a hydrogen permeable alloy that has both hydrogen permeability and hydrogen embrittlement resistance, and can efficiently permeate hydrogen.

The Ni—Zr—Nb-based alloy is made of Ni _x Zr _y Nb _(100-xy) (where 20 <x <55 atomic% and 20 <y <55 atomic%). If x and y are out of the above ranges, they cannot be used as hydrogen permeable alloys because they show brittleness in the cast state or hydrogen embrittlement becomes significant. Preferably, on the Ni-Zr-Nb ternary phase diagram, it is surrounded by Ni ₄₅ Zr ₅₅ , Ni ₅₅ Zr ₄₅ , Ni ₃₀ Zr ₂₀ Nb ₅₀ and Ni ₂₀ Zr ₃₀ Nb ₅₀ (all alloy compositions are atomic%). Alloy in the region.

  Furthermore, in the Co—Zr—Nb alloy, the composite phase is a eutectic of a ZrNb phase in which Co is dissolved (hereinafter referred to as ZrNb phase) and a CoZr phase in which Nb is dissolved (hereinafter referred to as CoZr phase). CoZr + ZrNb) structure, a structure in which the ZrNb phase generated as an initial phase is surrounded by the eutectic, or a structure in which the CoZr phase generated as an initial phase is surrounded by the eutectic. This makes it possible to produce a hydrogen permeable alloy that has both hydrogen permeability and hydrogen embrittlement resistance, and can efficiently permeate hydrogen.

The Co—Zr—Nb-based alloy is made of Co _x Zr _y Nb _(100-xy) (where 20 <x <55 atomic% and 15 <y <50 atomic%). If x and y are out of the above ranges, they cannot be used as hydrogen permeable alloys because they show brittleness in the cast state or hydrogen embrittlement becomes significant. Preferably, on the Co-Zr-Nb ternary phase diagram, Co ₄₀ Zr ₅₀ Nb ₁₀ , Co ₅₅ Zr ₃₅ Nb ₁₀ , Co ₃₅ Zr ₁₅ Nb ₅₀ and Co ₂₀ Zr ₃₀ Nb ₅₀ (wherein the alloy composition is all atomic%) ) In the region surrounded by

  The metal film (alloy film) produced from the alloy of the present invention has a thickness of 0.01 to 3 mm. When the thickness exceeds 3 mm, the hydrogen permeation flux (amount) becomes small, and the hydrogen permeation efficiency is deteriorated. On the other hand, if the thickness is less than 0.01 mm, the mechanical strength becomes weak and impractical.

  A Pd film or a Pd alloy film is further formed on both sides of the surface of the metal film on which the raw material to be treated is supplied and on the side from which purified hydrogen is extracted, and the thickness of the Pd film or Pd alloy film is 50 to 400 nm. It is characterized by. If a Pd film or a Pd alloy film having a predetermined thickness is formed on both sides of the raw material gas side (upstream, high-pressure side) and the purified hydrogen side (downstream, low-pressure hydrogen side) with the alloy material sandwiched in this way, Thus, oxidation, nitridation, and the like of the alloy film can be prevented, and hydrogen can be easily dissociated and recombined. Outside this range, the Pd film or Pd alloy film peels off when it is thin, and becomes uneconomical when it is thick.

  According to the present study, a multiphase alloy of a phase responsible for hydrogen permeability and a phase responsible for hydrogen embrittlement resistance, for example, a Co—Ti—Nb based multiphase alloy having a specific composition, a Ni—Zr—Nb based composite. By using the phase alloy and the Co—Zr—Nb-based multiphase alloy, it is possible to achieve both excellent hydrogen permeability and hydrogen embrittlement resistance at 473 K or higher.

  Hereinafter, the best mode for carrying out the present invention will be described more specifically with reference to the drawings. Here, in the accompanying drawings, the same reference numerals are given to the same members, and duplicate descriptions are omitted. In addition, since description here is the best form by which this invention is implemented, this invention is not limited to the said form.

  As a result of various investigations on ternary phase diagrams of a large number of metals, the present inventors have found that Co—Ti—Nb, Ni—Zr—Nb, and Co—Zr—Nb alloys are multiphase alloys. The possibility of being useful as a metal membrane for hydrogen permeation was found and confirmed by hydrogen permeation experiments.

  According to the embodiment of the present invention, a film made of a Co—Ti—Nb-based alloy is used as the hydrogen permeable metal film, and this metal film is responsible for the hydrogen permeable phase and the hydrogen embrittlement resistance. It consists of a double phase alloy which has a composite phase with a phase.

That is, the composition of the Co—Ti—Nb alloy material is represented by Co ₅₀ Ti ₅₀ , Co ₅₀ Ti ₁₀ Nb ₄₀ , Co ₂₀ Ti ₁₀ Nb ₇₀ , Co ₂₀ Ti ₆₀ Nb ₂₀ on the Co—Ti—Nb ternary phase diagram. A multiphase alloy material composed of a eutectic (CoTi + TiNb) of a CoTi phase and a TiNb phase by adopting an alloy composition in a region surrounded by Co ₄₀ Ti ₆₀ (all alloy compositions are atomic%), A multiphase alloy material composed of eutectic and primary phase TiNb or a multiphase alloy material composed of this eutectic and primary crystal CoTi can be provided, and a metal film is provided from, for example, a cast alloy material of this multiphase alloy material it can.

  This multiphase alloy material is excellent in both properties of hydrogen permeability and hydrogen embrittlement resistance, and is suitable for forming a metal film for hydrogen permeation. Although the hydrogen permeability coefficient of this multiphase alloy varies depending on the composition, it exhibits a hydrogen permeability equal to or higher than that of a Pd alloy film currently in practical use as a metal film for hydrogen purification.

  The present invention also uses a film made of a Ni—Zr—Nb alloy as the hydrogen permeable metal film, and this metal film is a composite phase of a phase responsible for hydrogen permeability and a phase responsible for hydrogen embrittlement resistance. It consists of a dual phase alloy having

That is, the composition of the Ni-Zr-Nb-based alloy material is expressed as Ni ₄₅ Zr ₅₅ , Ni ₅₅ Zr ₄₅ , Ni ₃₀ Zr ₂₀ Nb ₅₀ and Ni ₂₀ Zr ₃₀ Nb ₅₀ on the Ni-Zr-Nb ternary phase diagram. All the alloy compositions are in the region surrounded by the atomic%), so that a multi-phase alloy material composed of a eutectic of NiZr phase and ZrNb phase (NiZr + ZrNb), the eutectic and the initial phase ZrNb, Or a multiphase alloy material composed of this eutectic and primary crystal NiZr, and a metal film can be provided from, for example, a cast alloy material of the multiphase alloy material.

  This multiphase alloy material is excellent in both properties of hydrogen permeability and hydrogen embrittlement resistance, and is suitable for forming a metal film for hydrogen permeation. Although the hydrogen permeability coefficient of this multiphase alloy varies depending on the composition, it exhibits hydrogen permeability higher than that of a Pd alloy film currently in practical use as a metal film for hydrogen purification.

  Furthermore, the present invention uses a film made of a Co—Zr—Nb alloy as the hydrogen permeable metal film, and this metal film is a composite phase of a phase responsible for hydrogen permeability and a phase responsible for hydrogen embrittlement resistance. It consists of a dual phase alloy having

That is, on the Co-Zr-Nb ternary phase diagram, the composition of the Co-Zr-Nb alloy material is Co ₄₀ Zr ₅₀ Nb ₁₀ , Co ₅₅ Zr ₃₅ Nb ₁₀ , Co ₃₅ Zr ₁₅ Nb ₅₀ and Co ₂₀ Zr ₃₀ Nb. ₅₀ (however, the alloy composition is all in atomic%), a multiphase alloy material composed of a eutectic (CoZr + ZrNb) of a CoZr phase and a ZrNb phase, A multiphase alloy material composed of primary phase ZrNb or a multiphase alloy material composed of this eutectic and primary crystal CoZr can be provided, and a metal film can be provided from, for example, a cast alloy material of this multiphase alloy material.

  This multiphase alloy material is excellent in both properties of hydrogen permeability and hydrogen embrittlement resistance, and is suitable for forming a metal film for hydrogen permeation. Although the hydrogen permeability coefficient of this multiphase alloy varies depending on the composition, it exhibits hydrogen permeability equivalent to that of a Pd alloy film currently in practical use as a metal film for hydrogen purification.

  The metal film made of the multi-phase alloy of the present invention is low in cost because it can be produced at a cost of 1/4 to 1/8 of that of the Pd alloy film. It can be said that it is a material that can be applied as an alternative.

  The method for producing the alloy material of the present invention is not particularly limited, but after blending the raw metal so as to have a predetermined composition, arc melting in an inert gas atmosphere such as Ar, or in an inert gas atmosphere such as Ar or in vacuum These are prepared by melting methods such as high-frequency induction heating melting, melting in an inert gas atmosphere such as Ar or in an electric furnace in vacuum, electron beam melting in vacuum, or laser heating melting.

  Or, after pulverizing an alloy prepared by the above melting method, alloy powder subjected to mechanical grinding in an inert gas atmosphere such as Ar, or after blending each raw metal powder to have a predetermined composition, Ar or the like It is produced by a powder metallurgy method for solidifying and molding a powder subjected to mechanical alloying in an inert gas atmosphere.

  From the experimental results for a number of compositions, the Co—Ti—Nb-based alloys within the broken lines surrounded by points A, B, C, D and E shown in FIG. 1 are useful. As for the Ni—Zr—Nb alloy, those within a broken line surrounded by points A, B, C and D shown in FIG. 2 are useful. As for the Co—Zr—Nb alloy, those within the broken line surrounded by points A, B, C and D shown in FIG. 3 are useful. 1 to 3 indicate embrittlement in the cast state, ♦ indicates embrittlement during hydrogen permeation measurement, and Δ mark outside the broken line area indicates excellent ductility but hydrogen permeability coefficient Are small, and these are all not suitable for hydrogen permeable alloy films.

  The thinner the metal membrane for hydrogen permeation, the greater the hydrogen permeation flux (amount) and the better the hydrogen permeation efficiency. However, as the thickness of the metal film is reduced, the mechanical strength is reduced. Therefore, in the case of these alloy systems, the thickness of the alloy film is preferably 0.01 to 3 mm.

  In order to use these alloy materials as metal membranes for hydrogen permeation, both sides of the raw material gas side (upstream, high-pressure hydrogen side) and purified hydrogen side (downstream, low-pressure hydrogen side) are sandwiched between the alloy materials. In order to dissociate and recombine hydrogen, it is necessary to further form a Pd film or a Pd alloy film. The thickness is generally 50 to 400 nm, preferably 100 to 200 nm.

  The method of forming Pd or Pd alloy film on both sides of these alloy films for hydrogen dissociation and recombination is not particularly limited. For example, vacuum deposition, spuck ring, ion plating, electrolytic plating, electroless plating, etc. Any of these may be used.

  Hereinafter, examples and comparative examples of the present study will be described.

  (Example 1)

Co (purity 99.9%), Ti (purity 99.5%) so that the composition of the Co _x Ti _y Nb _(100-xy) alloy material is x = 35 atomic% and y = 35 atomic%. A predetermined amount of Nb (99.9%) was blended. This blend was loaded into an arc melting furnace and evacuated. The evacuation was performed to 1.3 × 10 ⁻³ Pa or less using an oil rotary pump and an oil diffusion pump. After completion of evacuation, arc melting was performed by introducing 36 mmHg argon gas. In order to produce a uniform alloy, the ingot after melting was inverted and remelted. The inversion-remelting of the ingot was performed 6 times. A disk having a diameter of 12 mm and a thickness of 0.6 mm was cut out from the ingot thus obtained by electric discharge machining to obtain a measurement sample.

  After polishing both sides of the sample with a paper file, buff, and then α-alumina with a diameter of 0.5 μm, a scanning electron microscope (SEM) is used to observe the microstructure of the sample, and an X-ray diffractometer (XRD) is used to analyze the crystal structure. Was used. The chemical composition was determined by an energy dispersive X-ray analyzer (EDS). The volume occupancy of the phase was calculated with a Macintosh computer using the public domain NIH image program.

The sample polished with α-alumina was washed with acetone and then set in a high-frequency magnetron sputtering apparatus. Vacuum drawing was performed to 4 × 10 ⁻³ Pa using an oil rotary pump and a cryopump. Thereafter, reverse sputtering was performed for 10 minutes using an RF power source in order to remove the oxide film and the like adhering to the sample surface. Next, the sample was heated to 350 ° C. in the sputtering apparatus, and Pd sputtering was performed using a DC power source for 5 minutes. The thickness of the Pd film coated under these conditions is 190 nm.

Hydrogen permeation measurement was carried out by the following flow rate method. First, the Pd-coated disc sample was sealed with a Cu gasket. Next, both sides of the disk were evacuated with an oil diffusion pump to a pressure of 3 × 10 ⁻³ Pa or less, and then the disk was heated to 673 K and held for 30 minutes. Then, hydrogen gas (purity: 99.99999%) was introduced into the downstream side and the upstream side, respectively, at 0.1 and 0.2 MPa, and then hydrogen permeation measurement was performed. The upstream hydrogen pressure was increased from 0.2 MPa to 0.97 MPa, and the temperature was decreased stepwise from 673 K to 523 K at 50 K intervals. After maintaining at a constant temperature for 30 minutes, the hydrogen permeation test was started. The hydrogen permeation flux J (molH ₂ m ⁻² s ⁻¹ ) was measured using a mass flow meter.

As shown in Equation 1, the hydrogen permeation coefficient Φ is obtained from the slope of the J × L vs. (Pu ^0.5 −Pd ^0.5 ) plot.

The temperature dependence of the hydrogen permeability coefficient Φ calculated from the slope of the J × L vs. (Pu ^0.5 -Pd ^0.5 ) plot for the Co ₃₅ Ti ₃₅ Nb ₃₀ alloy material obtained as described above is the Arrhenius plot. This is shown in FIG. FIG. 4 also shows the result of pure Pd for comparison. In both samples, the hydrogen permeability coefficient decreased with decreasing temperature. As for the reduction method, the Co ₃₅ Ti ₃₅ Nb ₃₀ alloy material was larger than pure Pd. However, the hydrogen permeation coefficient of the Co ₃₅ Ti ₃₅ Nb ₃₀ alloy material at 673 K is 2.64 × 10 ⁻⁸ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ), which is 1 of that of pure Pd. About 6 times.

From the X-ray diffraction pattern analysis of the cast Co ₃₅ Ti ₃₅ Nb ₃₀ alloy material, this alloy material was composed of B2 type-CoTi and bcc-TiNb.

FIG. 5 shows a SEM photograph of the Co ₃₅ Ti ₃₅ Nb ₃₀ alloy material in the cast state. It can be seen that this alloy is composed of eutectic (CoTi + TiNb).

  As described above, it was found that the multiphase alloy composed of the eutectic exhibited an excellent hydrogen permeation coefficient, that is, hydrogen permeation characteristics, and could be used as a metal film for hydrogen permeation.

  (Example 2)

The production of the Co—Ti—Nb alloy was carried out in the same manner as in Example 1. However, the composition was such that x = 30 atomic% and y = 30 atomic%. FIG. 6 shows an SEM photograph of the obtained Co ₃₀ Ti ₃₀ Nb ₄₀ alloy material in a cast state. It can be seen that this alloy material is mainly composed of primary TiNb and eutectic (CoTi + TiNb). The primary phase TiNb, which is a white phase, is surrounded by a eutectic, and the volume ratio is 21% by volume. From the result of EDS analysis, the composition of the primary TiNb phase was Co ₄ Ti ₁₄ Nb ₈₂ . This alloy material had a hydrogen permeation coefficient at 673 K of 1.89 × 10 ⁻⁸ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ), and could be used as a hydrogen permeable metal film.

  (Example 3)

The production of the Co—Ti—Nb alloy was carried out in the same manner as in Example 1. However, the composition was such that x = 40 atomic% and y = 40 atomic%. The obtained Co ₄₀ Ti ₄₀ Nb ₂₀ alloy material in a cast state was composed of primary crystal CoTi and eutectic (CoTi + TiNb). This alloy material had a hydrogen permeation coefficient at 673 K of 1.20 × 10 ⁻⁸ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ), and could be used as a hydrogen permeable metal film.

From Examples 1 to 3, the hydrogen permeation mechanism and the hydrogen embrittlement resistance mechanism in the Co—Ti—Nb alloy material are estimated as follows. It is considered that the hydrogen permeation path in the Co ₃₀ Ti ₃₀ Nb ₄₀ alloy material is realized by eutectic. In other words, it can be said that the eutectic (CoTi + TiNb) mainly contributes to hydrogen permeation of the present multiphase alloy. Therefore, it is considered that the highest hydrogen permeation coefficient was obtained with the Co ₃₅ Ti ₃₅ Nb ₃₀ alloy composed only of eutectic. Moreover, even if a CoTi phase that does not transmit hydrogen exists in the eutectic, hydrogen can be transmitted. The Co ₄ Ti ₁₄ Nb ₈₂ alloy having the same composition as the primary TiNb becomes brittle and collapses when hydrogenated, but the Co ₃₀ Ti ₃₀ Nb ₄₀ alloy material has an initial shape even after being hydrogenated. Is preserved. This is presumably because the eutectic structure suppressed the volume expansion of TiNb and consequently prevented hydrogen embrittlement of TiNb. That is, the eutectic structure also plays a main role in suppressing hydrogen embrittlement in the Co ₃₀ Ti ₃₀ Nb ₄₀ alloy material.

  From the above, it can be concluded that the eutectic shows a role of hydrogen permeation in the ternary Co—Ti—Nb alloy material, reduces hydrogen embrittlement of the TiNb phase, and retains mechanical properties.

  (Example 4)

The production of the Co—Ti—Nb alloy was carried out in the same manner as in Example 1. However, the composition was such that x = 30 atomic% and y = 40 atomic%. The obtained cast Co ₃₀ Ti ₄₀ Nb ₃₀ alloy material was composed of primary TiNb and eutectic (CoTi + TiNb). This alloy material had a hydrogen permeation coefficient at 673 K of 2.54 × 10 ⁻⁸ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ), and could be used as a hydrogen permeable metal film.

  (Example 5)

The production of the Co—Ti—Nb alloy was carried out in the same manner as in Example 1. However, the composition was such that x = 30 atomic% and y = 35 atomic%. The obtained cast Co ₃₀ Ti ₃₅ Nb ₃₅ alloy material was composed of primary TiNb and eutectic (CoTi + TiNb). This alloy material had a hydrogen permeation coefficient at 673 K of 2.22 × 10 ⁻⁸ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ), and could be used as a hydrogen permeable metal film.

  (Example 6)

The production of the Co—Ti—Nb alloy was carried out in the same manner as in Example 1. However, the composition was such that x = 30 atomic% and y = 20 atomic%. The obtained cast Co ₃₀ Ti ₂₀ Nb ₅₀ alloy material was composed of primary TiNb and eutectic (CoTi + TiNb). This alloy material had a hydrogen permeation coefficient at 673 K of 1.54 × 10 ⁻⁸ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ), and could be used as a hydrogen permeable metal film.

  (Example 7)

The production of the Co—Ti—Nb alloy was carried out in the same manner as in Example 1. However, the composition was such that x = 40 atomic% and y = 30 atomic%. The obtained cast Co ₄₀ Ti ₃₀ Nb ₃₀ alloy material was composed of primary crystal CoTi and eutectic (CoTi + TiNb). This alloy material had a hydrogen permeation coefficient at 673 K of 1.29 × 10 ⁻⁸ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ) and could be used as a metal film for hydrogen permeation.

  (Example 8)

The production of the Co—Ti—Nb alloy was carried out in the same manner as in Example 1. However, the composition was such that x = 30 atomic% and y = 50 atomic%. The obtained cast Co ₃₀ Ti ₅₀ Nb ₂₀ alloy material was composed of primary crystal CoTi and eutectic (CoTi + TiNb). This alloy material had a hydrogen permeation coefficient at 673 K of 2.14 × 10 ⁻⁸ (molH ₂ (m ⁻¹ s ⁻¹ Pa ^−0.5 )) and could be used as a metal film for hydrogen permeation.

  Example 9

The production of the Co—Ti—Nb alloy was carried out in the same manner as in Example 1. However, the composition was such that x = 40 atomic% and y = 50 atomic%. The obtained cast Co ₄₀ Ti ₅₀ Nb ₁₀ alloy material was composed of primary crystal CoTi and eutectic (CoTi + TiNb). This alloy material had a hydrogen permeation coefficient at 673 K of 0.45 × 10 ⁻⁸ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ), and could be used as a hydrogen permeable metal film.

  The composition of the cast Co—Ti—Nb alloy material and the measurement results of the hydrogen permeation coefficient at 673 K for the above Examples 1 to 9 are summarized as points A, B, and C shown in FIG. , And a numerical value described below the ◯ mark shown in the broken line region surrounded by D and E (that is, in the hydrogen-permeable Co—Ti—Nb alloy forming region). A eutectic state of the CoTi phase and the TiNb phase appears with the composition in the broken line region, and good hydrogen permeation characteristics and hydrogen embrittlement resistance can be obtained regardless of whether the primary crystal is a CoTi phase or a TiNb phase.

  (Example 10)

The Ni _x Zr _y Nb _(100-xy) alloy material was blended with predetermined amounts of Ni (purity 99.9%), Zr (purity 99.5%), and Nb (99.9%). An alloy sample was prepared in the same manner as in Example 1. However, x = 45 atomic% and y = 45 atomic% were set. An SEM photograph of the obtained Ni ₄₅ Zr ₄₅ Nb ₁₀ alloy material in a cast state is shown in FIG. It can be seen that this alloy material is mainly composed of primary crystal NiZr and eutectic (NiZr + ZrNb). The primary crystal NiZr which is a dark gray phase is surrounded by eutectic, and the volume ratio thereof is 16% by volume. This alloy material had a hydrogen permeation coefficient at 673 K of 2.35 × 10 ⁻⁸ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ) and could be used as a metal film for hydrogen permeation.

  (Example 11)

The Ni—Zr—Nb alloy was produced in the same manner as in Example 10. However, x = 40 atomic% and y = 40 atomic% were set. The obtained cast Ni ₄₀ Zr ₄₀ Nb ₂₀ alloy material was composed of primary crystal ZrNb and eutectic (NiZr + ZrNb), and the volume ratio thereof was 18% by volume. This alloy material had a hydrogen permeation coefficient at 673 K of 2.73 × 10 ⁻⁸ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ), and could be used as a hydrogen permeable metal film.

  Example 12

The Ni—Zr—Nb alloy was produced in the same manner as in Example 10. However, x = 35 atomic% and y = 35 atomic% were set. The obtained cast Ni ₃₅ Zr ₃₅ Nb ₃₀ alloy material was composed of primary crystal ZrNb and eutectic (NiZr + ZrNb), and the volume ratio was 27% by volume. This alloy material had a hydrogen permeation coefficient at 673 K of 3.59 × 10 ⁻⁸ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ) and could be used as a hydrogen permeable metal film.

  (Example 13)

The Ni—Zr—Nb alloy was produced in the same manner as in Example 10. However, x = 30 atomic% and y = 30 atomic%. An SEM photograph of the obtained Ni ₃₀ Zr ₃₀ Nb ₄₀ alloy material in a cast state is shown in FIG. This alloy material was found to be composed of primary crystal ZrNb and eutectic (NiZr + ZrNb), and the volume ratio was 40% by volume. FIG. 9 shows the temperature dependence of the hydrogen permeability coefficient Φ of this alloy in the form of an Arrhenius plot. FIG. 9 also shows the result of pure Pd for comparison. In both samples, the hydrogen permeability coefficient decreased with decreasing temperature. Regarding the reduction method, the Ni ₃₀ Zr ₃₀ Nb ₄₀ alloy material was larger than the pure Pd. The hydrogen permeation coefficient at 673 K of this alloy material was 4.64 × 10 ⁻⁸ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ), which was 2.9 times that of pure Pd.

  (Example 14)

The Ni—Zr—Nb alloy was produced in the same manner as in Example 10. However, x = 29 atomic% and y = 29 atomic%. The obtained cast Ni ₂₉ Zr ₂₉ Nb ₄₂ alloy material was composed of primary crystal ZrNb and eutectic (NiZr + ZrNb), and the volume ratio was 42% by volume. This alloy material had a hydrogen permeation coefficient at 673 K of 5.01 × 10 ⁻⁸ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ) and could be used as a hydrogen permeable metal film.

  (Example 15)

The Ni—Zr—Nb alloy was produced in the same manner as in Example 10. However, x = 28 atomic% and y = 28 atomic%. The obtained cast Ni ₂₈ Zr ₂₈ Nb ₄₄ alloy material was composed of primary crystal ZrNb and eutectic (NiZr + ZrNb), and the volume ratio was 45% by volume. This alloy material had a hydrogen permeation coefficient at 673 K of 5.21 × 10 ⁻⁸ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ), and could be used as a hydrogen permeable metal film.

  (Example 16)

The Ni—Zr—Nb alloy was produced in the same manner as in Example 10. However, x = 27 atomic% and y = 27 atomic%. The obtained cast Ni ₂₇ Zr ₂₇ Nb ₄₆ alloy material was composed of primary crystal ZrNb and eutectic (NiZr + ZrNb), and the volume ratio was 46% by volume. This alloy material had a hydrogen permeation coefficient at 673 K of 6.06 × 10 ⁻⁸ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ) and could be used as a hydrogen permeable metal film.

  From Examples 11 to 16, the hydrogen permeation mechanism in the Ni—Zr—Nb alloy material is presumed as follows. As the Nb concentration in the alloy increases, the volume ratio and hydrogen permeability coefficient of the primary ZrNb phase increase accordingly. Looking at the relationship between the volume fraction of the primary crystal ZrNb phase and the hydrogen permeability coefficient, it can be seen that the hydrogen permeability coefficient is proportional to the volume fraction of the primary crystal ZrNb phase, as shown in FIG. Therefore, it is considered that the primary crystal ZrNb phase contributes to hydrogen permeation of the alloy.

In the Ni ₄₅ Zr ₄₅ Nb ₁₀ alloy of Example 10, the NiZr phase was generated as the primary crystal. On the other hand, in the Ni ₄₀ Zr ₄₀ Nb ₂₀ alloy of Example 11, the ZrNb phase was generated as the primary crystal. In other words, the types of primary crystals produced are different between the two alloys. Therefore, there should be an alloy composition composed only of eutectic (NiZr + ZrNb) between these two types of alloy compositions, with no primary crystals formed. From the results of Examples 10 to 16, it is considered that the eutectic (NiZr + ZrNb) alloy can also permeate hydrogen. When the straight line in FIG. 10 is extrapolated so that the primary crystal ZrNb volume fraction becomes 0, 1.0 × 10 ⁻⁸ (molH ₂ m ⁻¹ ) even in a state where the primary crystal ZrNb phase does not exist, that is, in the eutectic (NiZr + ZrNb). It can be estimated that it has a hydrogen permeability of about s ⁻¹ Pa ^−0.5 ). Therefore, it can be said that eutectic also contributes to hydrogen permeation in this alloy system.

Ni ₅₀ Zr ₅₀ alloy, which is a NiZr single phase, is brittle in the cast state, but eutectic (NiZr + ZrNb) is formed in the Ni ₄₅ Zr ₄₅ Nb ₁₀ alloy shown in Example 10 and hydrogen permeation is possible. became. Further, the Ni ₃ Zr ₈ Nb ₈₉ alloy having the same composition as the primary crystal ZrNb of the Ni ₃₀ Zr ₃₀ Nb ₄₀ alloy shown in Example 13 is destroyed by hydrogen embrittlement, but a eutectic is formed in the ZrNb phase. Then, hydrogen embrittlement is suppressed and hydrogen permeation becomes possible. Therefore, it is considered that eutectic (NiZr + ZrNb) contributes to suppression of hydrogen embrittlement resistance of the alloy. If a eutectic is present, hydrogen permeation is possible regardless of whether the primary crystal is a NiZr phase or a ZrNb phase.

  The composition of the Ni—Zr—Nb alloy material in the cast state up to Examples 10 to 16 and the measurement results of the hydrogen permeability coefficient at 673 K are summarized as points A, B, and C shown in FIG. , And a numerical value described below the ◯ mark shown in the broken line region surrounded by D and D (that is, in the hydrogen-permeable Ni—Zr—Nb alloy forming region). The eutectic state of the NiZr phase and the ZrNb phase appears with the composition in the broken line region, and good hydrogen permeation characteristics and hydrogen embrittlement resistance can be obtained regardless of whether the primary crystal is the NiZr phase or the ZrNb phase.

  (Example 17)

Co _x Zr _y Nb _(100-xy) alloy material was blended with predetermined amounts of Co (purity 99.9%), Zr (purity 99.5%), and Nb (99.9%). In the same manner as in Example 1, an alloy sample was prepared. However, x = 30 atomic% and y = 30 atomic%. FIG. 11 shows an SEM photograph of the obtained cast Co ₃₀ Zr ₃₀ Nb ₄₀ alloy material. In this alloy material, it can be seen that the primary phase ZrNb which is a gray phase is surrounded by a eutectic (CoZr + ZrNb). This alloy material had a hydrogen permeation coefficient at 673 K of 1.39 × 10 ⁻⁸ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ), and could be used as a hydrogen permeable metal film.

  (Example 18)

The Co—Zr—Nb alloy was produced in the same manner as in Example 17. However, x = 35 atomic% and y = 35 atomic% were set. The obtained cast Co ₃₅ Zr ₃₅ Nb ₃₀ alloy material was composed of primary crystal ZrNb and eutectic (CoZr + ZrNb). This alloy material had a hydrogen permeation coefficient at 673 K of 1.03 × 10 ⁻⁸ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ), and could be used as a hydrogen permeable metal film.

  (Example 19)

The Co—Zr—Nb alloy was produced in the same manner as in Example 17. However, x = 40 atomic% and y = 30 atomic%. The obtained Co ₄₀ Zr ₃₀ Nb ₃₀ alloy material in a cast state was composed of primary crystal ZrNb and eutectic (CoZr + ZrNb). This alloy material had a hydrogen permeation coefficient at 673 K of 0.62 × 10 ⁻⁸ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ), and could be used as a hydrogen permeable metal film.

  (Example 20)

The Co—Zr—Nb alloy was produced in the same manner as in Example 17. However, x = 40 atomic% and y = 35 atomic% were set. The obtained cast Co ₄₀ Zr ₃₅ Nb ₂₅ alloy material was composed only of eutectic (CoZr + ZrNb). This alloy material had a hydrogen permeation coefficient at 673 K of 0.66 × 10 ⁻⁸ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ), and could be used as a hydrogen permeable metal film.

  (Example 21)

The Co—Zr—Nb alloy was produced in the same manner as in Example 17. However, x = 40 atomic% and y = 40 atomic% were set. The obtained cast Co ₄₀ Zr ₄₀ Nb ₂₀ alloy material was composed of primary crystal CoZr and eutectic (CoZr + ZrNb), and the volume ratio was 46% by volume. The hydrogen permeation coefficient at 673 K was 1.24 × 10 ⁻⁸ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ), and could be used as a hydrogen permeable metal film.

  (Example 22)

The Co—Zr—Nb alloy was produced in the same manner as in Example 17. However, x = 45 atomic% and y = 40 atomic% were set. The obtained Co ₄₅ Zr ₄₀ Nb ₁₅ alloy material in a cast state was composed of primary crystal CoZr and eutectic (CoZr + ZrNb). This alloy material had a hydrogen permeation coefficient at 673 K of 0.20 × 10 ⁻⁸ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ), and could be used as a hydrogen permeable metal film.

Also in the Co-Zr-Nb system, as shown in Example 20, the Co ₄₀ Zr ₃₅ Nb ₂₅ alloy composed only of the eutectic transmits hydrogen, so the eutectic contributes to hydrogen permeation. It can be said. If a eutectic is included, even if the ZrNb phase is generated as the primary crystal as shown in Example 17, the CoZr phase is generated as the primary crystal as shown in Example 21, In either case, hydrogen permeation is possible. However, as the amount of Nb in the alloy increases and the volume fraction of the ZrNb phase increases, the hydrogen permeability coefficient tends to increase. Therefore, in this alloy system, the ZrNb phase contributes to hydrogen permeation more than eutectic. it seems to do.

  The composition of the cast Co—Zr—Nb alloy material and the hydrogen permeation coefficient measurement results at 673 K for the above Examples 17 to 22 are summarized as points A, B, and C shown in FIG. , And the numerical values described below and indicated by a circle in the broken line area surrounded by D (that is, in the hydrogen-permeable Co—Zr—Nb alloy forming area). A eutectic state of the CoZr phase and the ZrNb phase appears with the composition in the broken line region, and good hydrogen permeation characteristics and hydrogen embrittlement resistance can be obtained regardless of whether the primary crystal is a NiZr phase or a ZrNb phase.

  (Comparative Example 1)

  The method for producing the Co—Ti—Nb alloy was the same as in Example 1. However, the composition is x = 30, y = 60; x = 50, y = 50; x = 50, y = 40; x = 50, y = 30; x = 50, y = 20 Five types of samples were prepared.

Each of the obtained Co—Ti—Nb alloy materials has a composition outside the hydrogen-permeable multiphase Co—Ti—Nb alloy formation region in FIG. 1 (region surrounded by points A, B, C, D, and E). The sample was capable of measuring hydrogen permeation. These five types of samples are indicated by Δ marks outside the same region in FIG. All of these samples had a hydrogen permeation coefficient at 673 K of about 10 ⁻¹⁰ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ), which was not suitable for a metal film for hydrogen permeation.

  (Comparative Example 2)

  The method for producing the Co—Ti—Nb alloy was the same as in Example 1. However, four types of samples were prepared such that the composition was x = 20, y = 60; x = 20, y = 50; x = 20, y = 40; x = 20, y = 30. . These four types of samples are indicated by asterisks in FIG.

Of the four cast Co-Ti-Nb alloy materials obtained, the Co ₂₀ Ti ₆₀ Nb ₃₀ alloy is composed of a TiNb phase and a CoTi phase, but is an example of embrittlement caused by hydrogen storage. . The amount of TiNb is about 40% by volume, and the amount of eutectic (CoTi + TiNb) is limited. Since the TiNb phase becomes brittle when a large amount of hydrogen is occluded, it has poor resistance to hydrogen embrittlement. Therefore, these alloy materials could not be used as hydrogen permeable metal films.

  From the above, it is necessary to reduce the amount of primary TiNb in order to suppress brittleness in the cast state and brittleness after hydrogen storage.

  (Comparative Example 3)

  The method for producing the Co—Ti—Nb alloy was the same as in Example 1. However, the composition is x = 30, y = 70; x = 40, y = 60; x = 60, y = 40; x = 70, y = 30; x = 60, y = 30; x = 60, Six samples were prepared so that y = 20. These six types of samples are indicated by ▪ in FIG.

Of the seven cast Co—Ti—Nb alloy materials obtained, the Co ₆₀ Ti ₂₀ Nb ₂₀ alloy is composed of primary crystal Co ₂ Nb and eutectic (Co ₂ Nb + CoTi), and is brittle in the cast state. This is an example. Even if it is the same primary crystal + eutectic as in Example 2, since it contains a large amount of brittle Co ₂ Nb, it was brittle in the cast state and could not be used as a metal film for hydrogen permeation. The other six types of Co—Ti—Nb alloys also contain many brittle Co ₂ Nb, Co ₂ Ti, or Co ₆ Nb ₇ intermetallic compounds, and are brittle in the cast state, so that hydrogen permeation measurement is impossible. Yes, it could not be used as a metal membrane for hydrogen purification.

  (Comparative Example 4)

  The method for producing the Ni—Zr—Nb alloy was the same as in Example 10. However, four types of samples were prepared such that the composition was x = 20, y = 30; x = 25, y = 25; x = 30, y = 20; x = 40, y = 30. . These four types of samples are indicated by ♦ in FIG.

The four cast Ni-Zr-Nb alloy materials thus obtained are examples in which embrittlement occurs due to hydrogen storage. These alloy materials could not be used as hydrogen permeable alloy films. In particular, the volume fraction of primary crystal ZrNb in the Ni ₂₅ Zr ₂₅ Nb ₅₀ alloy is 50% by volume, and the amount of eutectic (NiZr + ZrNb) is limited. Since the ZrNb phase becomes brittle when a large amount of hydrogen is occluded, it becomes poor in hydrogen embrittlement resistance. From the above, it is necessary to reduce the amount of primary crystal ZrNb in order to suppress brittleness after hydrogen storage.

  (Comparative Example 5)

  The method for producing the Ni—Zr—Nb alloy was the same as in Example 10. However, the composition is x = 20, y = 40; x = 30, y = 50; x = 30, y = 40; x = 40, y = 60; x = 40, y = 50; x = 40, Ten samples were prepared so that y = 20; x = 50, y = 50; x = 50, y = 40; x = 50, y = 30; x = 50, y = 20. These ten samples are indicated by the ▪ marks in FIG.

  The obtained 10 Ni-Zr-Nb alloy materials in the cast state are alloys showing brittleness in the cast state. Since these alloys produced a large amount of brittle intermetallic compounds in addition to the NiZr phase and the ZrNb phase, the hydrogen permeation test was impossible, and they could not be used as hydrogen permeable alloys.

  (Comparative Example 6)

  The method for producing the Co—Zr—Nb alloy was the same as in Example 17. However, two types of samples were prepared such that the composition was x = 50, y = 50; x = 50, y = 40.

Each of the obtained Co—Zr—Nb-based alloy materials has a composition outside the region for forming the hydrogen purification double-phase Co—Zr—Nb alloy in FIG. 3 (outside the region surrounded by points A, B, C, and D). However, it was a sample capable of measuring hydrogen permeation. These two types of samples are indicated by Δ marks outside the same region in FIG. All of these samples had a hydrogen permeation coefficient at 673 K of about 10 ⁻¹⁰ (molH ₂ m ⁻¹ s ⁻¹ Pa ^−0.5 ), which was not suitable for a metal film for hydrogen permeation.

  (Comparative Example 7)

  The method for producing the Co—Zr—Nb alloy was the same as in Example 17. However, four types of samples were prepared such that the composition was x = 20, y = 30; x = 30, y = 40; x = 30, y = 20; x = 40, y = 50. . These four types of samples are indicated by ♦ in FIG.

  The obtained four types of Co-Zr-Nb alloy materials in the cast state are those in which embrittlement occurs due to hydrogen occlusion. These alloy materials could not be used as hydrogen permeable metal films.

  (Comparative Example 8)

  The method for producing the Co—Zr—Nb alloy was the same as in Example 1. However, the composition is x = 20, y = 50; x = 20, y = 40; x = 30, y = 60; x = 30, y = 50; x = 40, y = 60; x = 40, y = 20; x = 50, y = 30; x = 50, y = 20; x = 60, y = 40; x = 60, y = 30; x = 60, y = 20, and 11 A seed sample was made. These 11 types of samples are indicated by ▪ in FIG.

  The 11 cast Co—Zr—Nb alloy materials obtained in the cast state were brittle in the cast state. Since these alloys produced a large amount of brittle intermetallic compounds in addition to the CoZr phase and the ZrNb phase, the hydrogen permeation test was impossible, and they could not be used as hydrogen permeable alloys.

  As described above, in any of the systems Co—Ti—Nb, Ni—Zr—Nb, and Co—Zr—Nb, hydrogen permeation can be obtained from an alloy composed only of a eutectic or an alloy in which a primary crystal and a eutectic coexist. It is possible to produce a hydrogen permeable alloy having both characteristics and hydrogen embrittlement resistance.

  According to the present invention, Co—Ti—Nb, Ni—Zr—Nb, and Co—Zr— having a specific composition that is a composite alloy of a phase responsible for hydrogen permeability and a phase responsible for hydrogen embrittlement resistance. By using the Nb-based crystalline double phase alloy, both excellent hydrogen permeability and resistance to hydrogen embrittlement can be achieved. Therefore, since hydrogen can be permeated with extremely high efficiency, the obtained high-purity hydrogen can be applied to the manufacturing fields of fuel for fuel cells, semiconductors, optical fibers, chemicals, and the like.

FIG. 4 is a ternary phase diagram showing a composition region for producing a hydrogen-permeable multiphase Co—Ti—Nb-based alloy of the present invention, and a circle in a broken line region surrounded by points A, B, C, D, and E The numerical value described below represents the hydrogen permeation coefficient of the alloy materials obtained in Examples 1-9. FIG. 3 is a ternary phase diagram showing a composition region for producing a hydrogen-permeable multiphase Ni—Zr—Nb-based alloy according to the present invention, under a circle in a broken line region surrounded by points A, B, C, and D. The numerical value described in represents the hydrogen permeation coefficient of the alloy material obtained in Examples 10-16. FIG. 3 is a ternary phase diagram showing a composition region for producing a hydrogen-permeable multiphase Co—Zr—Nb-based alloy of the present invention, under a circle in a broken line region surrounded by points A, B, C, and D The numerical value described in represents the hydrogen permeation coefficient of the alloy material obtained in Examples 17-22. Is a graph showing the temperature dependence of the hydrogen permeability coefficient of _Co 35 _Ti 35 _{Nb 30} alloy material and the comparative net Pd casting condition in the embodiment 1. 2 is a SEM photograph of a Co ₃₅ Ti ₃₅ Nb ₃₀ alloy material in a cast state in Example 1. 6 is a SEM photograph of a cast Co ₃₀ Ti ₃₀ Nb ₄₀ alloy material in Example 2. Is a SEM photograph of _Ni 45 _Zr 45 _{Nb 10} alloy casting condition in embodiment 10. Is a SEM photograph of _Ni 30 _Zr 30 _{Nb 40} alloy casting condition in embodiment 13. Is a graph showing the temperature dependence of the hydrogen permeability coefficient of _Ni 30 _Zr 30 _{Nb 40} alloy material and the comparative net Pd casting condition in embodiment 13. It is a graph which shows the relationship between the volume fraction of the primary-crystal ZrNb phase of the Ni-Zr-Nb alloy obtained in Examples 11-16, and hydrogen permeability. Is a SEM photograph of _Co 30 _Zr 30 _{Nb 40} alloy casting condition in embodiment 17.

Claims (5)

The composite phase comprises a eutectic (CoTi + TiNb) structure of a CoTi phase in which Nb is dissolved and a TiNb phase in which Co is dissolved, and the TiNb phase generated as the primary crystal is surrounded by the eutectic. Or a structure in which the CoTi phase generated as the primary crystal is surrounded by the eutectic , and Co ₅₀ Ti ₅₀ , Co ₅₀ Ti ₁₀ Nb ₄₀ , Co on the Co-Ti-Nb ternary phase diagram Multi-phase Co—Ti—Nb characterized by having an alloy composition in a region surrounded by ₂₀ Ti ₁₀ Nb ₇₀ , Co ₂₀ Ti ₆₀ Nb ₂₀ and Co ₄₀ Ti ₆₀ (all alloy compositions are atomic%) Crystalline double phase hydrogen permeable alloy. The composite phase comprises a eutectic (NiZr + ZrNb) structure of a NiZr phase in which Nb is dissolved and a ZrNb phase in which Ni is dissolved, and the ZrNb phase generated as a primary crystal is surrounded by the eutectic. Or a structure in which the NiZr phase generated as the primary crystal is surrounded by the eutectic, and in the Ni-Zr-Nb ternary phase diagram, Ni ₄₅ Zr ₅₅ , Ni ₅₅ Zr ₄₅ , Ni ₃₀ Zr Crystalline multiphase hydrogen of a multiphase Ni—Zr—Nb system characterized by having an alloy composition in a region surrounded by ₂₀ Nb ₅₀ and Ni ₂₀ Zr ₃₀ Nb ₅₀ (all alloy compositions are atomic%) Transparent alloy. The composite phase is composed of a eutectic (CoZr + ZrNb) structure of a CoZr phase in which Nb is dissolved and a ZrNb phase in which Co is dissolved, and the ZrNb phase generated as a primary crystal is surrounded by the eutectic. Or a structure in which the CoZr phase generated as the primary crystal is surrounded by the eutectic, and in the Co-Zr-Nb ternary phase diagram, Co ₄₀ Zr ₅₀ Nb ₁₀ , Co ₅₅ Zr ₃₅ Nb ₁₀ , Co ₃₅ Zr ₁₅ Nb ₅₀ And Co ₂₀ Zr ₃₀ Nb ₅₀ A multiphase Co—Zr—Nb-based crystalline multiphase hydrogen permeable alloy characterized by having an alloy composition in a region surrounded by (wherein the alloy composition is all atomic%). An alloy film using the crystalline multiphase hydrogen permeable alloy according to any one of claims 1 to 3 , wherein the alloy film has a thickness of 0.01 to 3 mm. Hydrogen permeable alloy membrane. 5. The crystalline multi-phase hydrogen permeable alloy film according to claim 4 , wherein a Pd film or a Pd alloy film is formed on both surfaces of the surface of the alloy film on which a hydrogen is flown and a side where the surface is taken out, and the Pd film or the Pd alloy film is formed. A crystalline multi-phase hydrogen permeable alloy membrane characterized by having a thickness of 50 to 400 nm.

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