Novel V-based ternary alloy material for hydrogen permeation and preparation method thereof

Abstract

The invention discloses a novel V-based ternary alloy material for hydrogen permeation and a preparation method thereof, and relates to the technical field of hydrogen separation and purification membranes. The chemical formula of the alloy is shown as V25Ti65Fe10. The preparation method comprises the following steps: firstly, cleaning, drying and accurately weighing a high-purity metal raw material; and then, the prepared raw materials are subjected to vacuum electric arc melting, and cast ingots with uniform structures are obtained. And carrying out surface grinding and polishing on the cast ingot after the cast ingot is linearly cut into a sample. And finally, evaporating a Pd catalyst layer on the polished alloy surface. The alloy prepared by the method has a body-centered cubic structure and good hydrogen embrittlement resistance. Meanwhile, the alloy keeps a high hydrogen permeation coefficient, the comprehensive hydrogen permeation performance of the alloy is superior to that of a traditional palladium-based hydrogen permeation material, and the alloy has wide application prospects in the field of hydrogen separation and purification.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen separation and purification membrane technology, specifically relating to a novel V-based ternary alloy material for hydrogen permeation and its preparation method. Background Technology

[0002] Hydrogen energy, as the most promising clean energy source of the 21st century, has become a key carrier for promoting energy transformation and achieving the goals of "carbon peaking and carbon neutrality" due to its green, low-carbon, efficient, and versatile characteristics. According to the China Hydrogen Energy Alliance, by 2060, my country's annual hydrogen demand will increase to 130 million tons, with hydrogen from fossil fuel reforming or industrial by-products accounting for the majority of the current supply. However, these feedstock gases often contain impurities such as CO, CO2, and H2O, requiring purification to meet the high-purity hydrogen (≥99.97%) requirements of fuel cells, semiconductors, and other fields. Existing hydrogen purification technologies include pressure swing adsorption, cryogenic separation, and metal hydride separation. Among these, membrane separation is particularly suitable for distributed hydrogen production scenarios due to its low energy consumption, flexible operation, and high device integration.

[0003] Among hydrogen separation membrane materials, palladium (Pd) and its alloy membranes are the most mature technologies, exhibiting excellent hydrogen selectivity and permeability. For example, Amandusson, Helena et al., in "Hydrogen permeation through surface-modified Pd and PdAg membranes," pointed out that PdAg alloy membranes can maintain stable hydrogen permeability even in environments containing impurity gases (such as O2). However, Pd is a precious metal, scarce and expensive, and also suffers from limitations such as hydrogen embrittlement and H2S poisoning, restricting its large-scale industrial application. Therefore, developing low-cost, high-performance non-palladium-based alternatives has become one of the key demands of the hydrogen energy industry.

[0004] Studies have shown that Group VB metals (V, Nb, Ta) and their alloys, due to their body-centered cubic structure and high hydrogen diffusion coefficient, exhibit superior hydrogen permeability compared to pure Pd, making them ideal alternative materials. However, pure Group VB metals are prone to forming hydrides during hydrogen dissolution, leading to hydrogen embrittlement and degradation of the membrane material's mechanical properties. To overcome this deficiency, researchers have designed dual-phase structures (solid solution phase and intermetallic compound phase) through multi-element alloying to control hydrogen solubility and diffusion pathways. For example, Thad M. Adams et al. from Savannah River National Laboratory reported in "Hydrogen permeability of multiphase V–Ti–Ni metallic membranes" that V-Ti-Ni dual-phase alloys have significantly higher hydrogen permeability at room temperature than pure Pd, and their microstructure may possess both high hydrogen diffusivity and resistance to hydrogen embrittlement. Such dual-phase alloys effectively suppress hydride formation by controlling hydrogen atom transport at phase boundaries, providing an important direction for the design of novel hydrogen separation membranes.

[0005] Currently, VB group alloy films still face the following technical challenges:

[0006] 1. Insufficient surface catalytic activity: The hydrogen molecule dissociation kinetics on the surface of group VB metals are slow, and noble metals (such as Pd) are often required as a catalytic layer, which increases the cost and process complexity;

[0007] 2. Poor high-temperature stability: Amorphous alloy films are prone to crystallization at high temperatures, while crystalline alloys may experience phase separation or element segregation during long-term cycling.

[0008] Third, the large-scale preparation process is not mature: existing research is mostly concentrated on the laboratory scale, and breakthroughs are still needed in alloy composition optimization, thin film forming process and membrane module integration technology.

[0009] In summary, developing a low-cost, highly hydrogen-permeable, hydrogen-embrittled, and long-term stable VB-group biphase alloy hydrogen separation membrane is of significant practical importance for promoting the large-scale application of hydrogen energy. This invention, based on the V-Ti-Ni system, optimizes the phase composition and hydrogen transport pathway by introducing rare earth elements, aiming to achieve the preparation and industrial application of a high-performance hydrogen separation membrane. Summary of the Invention

[0010] The purpose of this invention is to provide a novel V-based ternary alloy material for hydrogen permeation and its preparation method for areas not covered by existing technologies. The alloy microstructure consists of a single BCC phase and exhibits excellent hydrogen permeation performance and resistance to hydrogen embrittlement at high temperatures.

[0011] The present invention provides a ternary alloy, wherein the alloy composition is V. 25 Ti 65 Fe 10 .

[0012] A method for preparing an alloy according to the present invention includes the following steps:

[0013] Step 1: Select high-purity vanadium (V), titanium (Ti), and iron (Fe) metals with a purity exceeding 99% as raw materials. First, use anhydrous ethanol as the cleaning medium and ultrasonically clean the raw materials in an ultrasonic cleaner for 10-15 minutes to thoroughly remove surface organic matter and oxide layers. After cleaning, dry them in a vacuum drying oven at 80°C for later use.

[0014] Step 2: Accurately weigh the cleaned raw materials according to the calculated proportions. To avoid the volatilization of low-melting-point metals, place them in the water-cooled copper crucible of the vacuum arc melting furnace in the order of Fe, Ti, and V, ensuring that the high-melting-point metals are in the lower layer to promote uniform melting.

[0015] Step 3: Before melting, evacuate the sample chamber to a vacuum level ≤ 5 × 10⁻⁶. -3 Pa, high-purity argon gas is refilled as a protective atmosphere, and the argon gas pressure is maintained at -0.05 to -0.03 MPa; when igniting the arc, the arc gun is 3–5 mm away from the surface of the raw material, the initial current is set to 25A, and after the arc stabilizes, it is gradually increased to 250A to fully melt the raw material; after the alloy is completely liquefied, the melting is maintained for 2 minutes to ensure initial homogenization, then the current is cut off, and the ingot is turned over after cooling to room temperature with the furnace.

[0016] Step 4: To eliminate compositional segregation, the initial ingot is repeatedly melted. Each remelting process involves holding the alloy at a constant temperature for 2 minutes after complete melting, and controlling the cooling rate by slowly reducing the current to minimize internal stress. The remelting process is repeated at least 10 times until no unmelted particles or heterogeneous phases remain in the liquid alloy, achieving the required macroscopic structural uniformity.

[0017] Step 5: The homogenized metal ingot is processed into a standard hydrogen permeation sample with a size of Φ=16mm and a thickness of t=0.7mm using wire electrical discharge machining.

[0018] Step Six: The sample is successively ground with silicon carbide sandpaper ranging from 80 to 2000 grit, and then polished with diamond polishing paste on a polishing machine until the surface has a mirror finish and no visible scratches. After polishing, it is ultrasonically cleaned with anhydrous ethanol for 5 minutes to remove residual abrasive from the surface.

[0019] Step 7: Place the polished sample in a vacuum evaporation equipment and evacuate to a vacuum level of ≤5×10⁻⁶. -3 After Pa, the high-purity Pd material is placed in a vapor deposition tank. The vapor deposition current is controlled at 50–60 A, and the time is 30–40 seconds to form a continuous Pd catalyst layer with a thickness of approximately 250 nm on the alloy surface. This layer is used to promote the dissociation of hydrogen molecules and prevent surface oxidation.

[0020] Preferably, in step one, the molar ratio of metals Fe, Ti, and V is 5:13:2.

[0021] Preferably, in step one, the total mass of each raw material metal is accurately weighed to be 20g.

[0022] Preferably, in step one, anhydrous ethanol is used as the cleaning medium to perform ultrasonic cleaning on the raw material for 25 minutes, and the anhydrous ethanol must completely submerge the raw material during cleaning.

[0023] Preferably, after the ultrasonic cleaning in step one is completed, the raw material is dried using hot air.

[0024] Preferably, in step two, the initial melting current gradually increases from 25A to 220A.

[0025] Preferably, in step two, the ingot is turned over in the same direction each time it is cooled.

[0026] This invention has the following superior effects:

[0027] The alloy designed in this invention is a single-phase BCC solid solution structure based on group VB metals. This structure is widely considered an ideal channel for hydrogen atom transport, thus theoretically possessing both excellent hydrogen diffusion and hydrogen dissolution capabilities, which is beneficial for achieving efficient hydrogen separation. Furthermore, the raw materials selected in this invention are all commercially available high-purity metals, resulting in low cost, simple preparation process, and ease of large-scale production. Compared with existing technologies, this invention not only possesses an ideal hydrogen transport channel, providing excellent hydrogen permeation performance, but also enhances the material's resistance to hydrogen embrittlement through rational composition design, thereby significantly improving the membrane material's service life and operational stability. While achieving a significant cost reduction, it also improves overall performance, showing promising application prospects in the field of hydrogen separation and purification. Attached Figure Description

[0028] Figure 1 V is the embodiment of the present invention. 25 Ti 65 Fe 10 XRD pattern of the alloy film.

[0029] Figure 2 V is the embodiment of the present invention. 25 Ti 65 Fe 10 SEM images of the alloy film.

[0030] Figure 3 V is the embodiment of the present invention. 25 Ti 65 Fe 10 Elemental distribution of the alloy film in EDS.

[0031] Figure 4 V is the embodiment of the present invention. 25 Ti 65 Fe 10 The relationship between the hydrogen solubility (wt.%) of the alloy film and the equilibrium pressure (MPa).

[0032] Figure 5 V is the embodiment of the present invention. 25 Ti 65 Fe 10 Hydrogen permeation flow rate of the alloy membrane at temperatures ranging from 523K to 673K.

[0033] Figure 6 V is the embodiment of the present invention. 25 Ti 65 Fe 10 The relationship between the alloy film at various temperatures (J×L) and the hydrogen pressure difference (ΔP0.5).

[0034] Figure 7 V is the embodiment of the present invention. 25 Ti 65 Fe 10 Tafel polarization curves of the alloy film.

[0035] Specific embodiments are provided to illustrate the present invention in order to help people understand its technical content, but are not intended to limit the scope of the invention. Detailed Implementation

[0036] I. High-purity vanadium (V), titanium (Ti), and iron (Fe) metals with a purity exceeding 99% are selected as raw materials. First, anhydrous ethanol is used as the cleaning medium, and the raw materials are ultrasonically cleaned for 10-15 minutes in an ultrasonic cleaner to thoroughly remove surface organic matter and oxide layers. After cleaning, they are dried in a vacuum drying oven at 80℃ for later use.

[0037] 2. Weigh the cleaned raw materials precisely according to the calculated proportions. To avoid the volatilization of low-melting-point metals, place them in the water-cooled copper crucible of the vacuum arc melting furnace in the order of Fe, Ti, and V, ensuring that the high-melting-point metals are in the lower layer to promote uniform melting.

[0038] 3. Before melting, the sample chamber should be evacuated to a vacuum level of ≤5×10. -3 Pa, high-purity argon gas is refilled as a protective atmosphere, and the argon gas pressure is maintained at -0.05 to -0.03 MPa; when igniting the arc, the arc gun is 3–5 mm away from the surface of the raw material, the initial current is set to 25A, and after the arc stabilizes, it is gradually increased to 250A to fully melt the raw material; after the alloy is completely liquefied, the melting is maintained for 2 minutes to ensure initial homogenization, then the current is cut off, and the ingot is turned over after cooling to room temperature with the furnace.

[0039] IV. To eliminate compositional segregation, the initial smelting ingot is repeatedly melted. Each remelting involves holding the alloy at room temperature for 2 minutes after complete melting, and controlling the cooling rate by slowly reducing the current to minimize internal stress. The remelting process is repeated at least 10 times until no unmelted particles or heterogeneous phases remain in the liquid alloy, achieving the required macroscopic structural uniformity.

[0040] 5. The homogenized metal ingot is processed into standard hydrogen permeation sample size with dimensions Φ=16mm and thickness t=0.7mm using wire electrical discharge machining.

[0041] 6. The samples were successively ground with silicon carbide sandpaper ranging from 80 to 2000 grit, and then polished with diamond polishing paste on a polishing machine until the surface achieved a mirror finish and was free of visible scratches. After polishing, the samples were ultrasonically cleaned with anhydrous ethanol for 5 minutes to remove any residual abrasive.

[0042] 7. Place the polished sample in a vacuum evaporation equipment and evacuate to a vacuum level of ≤5×10. -3 After Pa, the high-purity Pd material is placed in a vapor deposition tank. The vapor deposition current is controlled at 50–60 A, and the time is 30–40 seconds to form a continuous Pd catalyst layer with a thickness of approximately 250 nm on the alloy surface. This layer is used to promote the dissociation of hydrogen molecules and prevent surface oxidation.

[0043] The beneficial effects of the present invention are verified through the following embodiments:

[0044] Example 1

[0045] (1) Raw material preparation: High-purity vanadium (V), titanium (Ti), and iron (Fe) metal blocks with a purity exceeding 99% were selected as raw materials. Based on the target composition V... 25 Ti 65 Fe 10 (at%), calculate the mass percentage of each element, and weigh accurately using an analytical balance. After weighing, the raw material is ultrasonically cleaned with anhydrous ethanol for 10 minutes to remove surface organic matter and oxides, and then dried in a vacuum drying oven at 80℃ for later use.

[0046] (2) Alloy melting: The cleaned raw materials are placed in a water-cooled copper crucible in a vacuum arc melting furnace in order of increasing melting point (Fe, Ti, V). Before melting, the furnace cavity is evacuated to ≤5×10⁻⁶. -3 Pa, high-purity argon is used as a protective atmosphere. During arc ignition, the arc gun is 3–5 mm from the material surface, with an initial current set at 25 A. Once the arc stabilizes, the current is gradually increased to 250 A to ensure complete melting of the material. After complete alloy liquefaction, it is held at that temperature for 2 minutes, then cooled to room temperature with the furnace. To eliminate compositional segregation, the alloy ingot is flipped and the above melting process is repeated at least 10 times until the alloy microstructure is macroscopically homogeneous.

[0047] (3) Sample cutting: The homogenized metal ingot was processed into standard hydrogen permeation samples with dimensions Φ=16mm and thickness t=0.7mm using wire electrical discharge machining. Deionized water was used as the coolant during the cutting process to avoid oxidation in the heat-affected zone.

[0048] (4) Sample polishing: The sample was successively polished with sandpaper ranging from 80 to 2000 grit. Each time the sandpaper was changed, the sample was rotated 90° to completely remove the scratches from the previous polishing pass. After polishing, diamond polishing compound was used on a polishing cloth for mirror polishing until there were no visible scratches on the surface. The polished sample was then ultrasonically cleaned with anhydrous ethanol for 25 minutes and finally dried for later use.

[0049] (5) Place the polished sample in a vacuum evaporation equipment and evacuate it to a vacuum level of ≤5×10. -4 After Pa, the high-purity Pd material is placed in a vapor deposition tank. The vapor deposition current is controlled at 50–60 A, and the time is 30–40 seconds to form a continuous Pd catalyst layer with a thickness of approximately 250 nm on the alloy surface. This layer is used to promote the dissociation of hydrogen molecules and prevent surface oxidation.

[0050] The following tests were performed on this embodiment:

[0051] (1) Alloy phase analysis

[0052] Circular alloy samples were prepared by wire electrical discharge machining (EDM). The samples were then progressively ground with silicon carbide sandpaper ranging from 80 to 2000 mesh to remove the surface cutting damage layer. After polishing with diamond polishing paste until there were no obvious scratches, the samples were immediately placed in anhydrous ethanol for ultrasonic cleaning. Phase analysis was performed on an X-ray diffractometer equipped with a Cu-Kα radiation source (operating voltage 40 kV, current 40 mA) using continuous scanning mode. The scanning range was (2θ) 20° to 90°, the step size was 0.02°, and the counting time per step was 0.01 seconds.

[0053] like Figure 1 The X-ray diffraction results showed that diffraction peaks of BCC-(V,Ti) could be observed.

[0054] (2) Microstructure analysis of the alloy

[0055] Before testing, the circular samples prepared by wire electrical discharge machining were successively ground with silicon carbide sandpaper ranging from 80 mesh to 2000 mesh to remove the surface cutting damage layer, and then polished with diamond polishing paste until there were no obvious scratches on the surface. After polishing, the samples were immediately placed in anhydrous ethanol for ultrasonic cleaning to remove residual contaminants on the surface. Then, they were adhered to the SEM sample stage with conductive adhesive to ensure a stable contact and a flat bottom surface. Finally, the secondary electron imaging scanning mode was selected on the SEM instrument to carry out the test.

[0056] like Figure 2SEM results showed that the alloy microstructure consisted of only a single phase of BCC-(V,Ti), consistent with the results of the alloy phase analysis.

[0057] like Figure 3 The EDS results showed that V, Ti, and Fe were evenly distributed in the alloy.

[0058] (3) Relationship between hydrogen solubility and equilibrium pressure of alloy

[0059] To quantitatively assess V 25 Ti 65 Fe 10 The hydrogen transport performance of the alloy film was determined using a Sieverts static volumetric method testing system manufactured by the Beijing Research Institute of Nonferrous Metals. The pressure-composition-temperature (PCT) relationship was measured under isothermal conditions. Before testing, the oxide film on the surface of the alloy sample was removed by friction and the sample was pulverized to a particle size <2mm to increase the specific surface area. Then, two activation-dehydrogenation cycle pretreatments were performed (first time: the sample container was placed at 400℃ under high vacuum ≤10...). -3 Degassing at 8 MPa for 2 hours, cooling to room temperature, and then activating in 8 MPa high-purity hydrogen (≥99.999%) for 1 hour, followed by dehydrogenation again at 400℃ under high vacuum for 2 hours; after the first activation, the sample was ground into micro-powder with a particle size ≤100μm, and after precise weighing with an analytical balance, a second activation was performed using the same parameters; finally, hydrogen solubility was tested within the temperature range of 250–400℃ and hydrogen pressure range of 0.01–0.7MPa, and the saturated hydrogen adsorption capacity was calculated by recording the system pressure changes.

[0060] like Figure 4 The PCT test results show that the hydrogen solubility of the alloy first increases and then decreases with increasing temperature, with the maximum hydrogen absorption occurring between 573K and 623K.

[0061] (4) Hydrogen permeation properties of the alloy

[0062] The hydrogen permeation performance of the alloy was tested using a hydrogen permeation testing system based on the "pressure difference method". First, the alloy film wafer sample was sealed in the hydrogen permeation mold with an oxygen-free copper sealing ring. Then, the outside of the mold was reinforced with bolts, nuts and gaskets to ensure airtightness. Subsequently, the mold was purged multiple times to reduce the influence of air on the test. The test temperature was 523-673K (ΔT=50K). At each temperature, the test pressure on the upstream side of the membrane was 0.1-0.4MPa (ΔP=0.05MPa), and the downstream side was fixed at atmospheric pressure. The hydrogen flux was observed in ml / min using a gas mass flow meter.

[0063] Figure 5 The figure shown is V 25 Ti 65 Fe 10 The alloy film at four temperatures (J×L) versus hydrogen pressure difference (ΔP) 0.5The relationship between the two is shown in the figure. The solid line represents the fitting result, and its slope represents the hydrogen permeability Φ. The hydrogen permeability of this alloy film at 623K is 1.55 × 10⁻⁶. -9 molH2m -1 s -1 Pa -0.5 .

[0064] Figure 6 The figure shown is V 25 Ti 65 Fe 10 The hydrogen permeation flow rate versus time curves of the alloy film at four temperatures and at upstream pressures of 0.2–0.4 MPa show that the alloy did not undergo hydrogen embrittlement during the hydrogen permeation process, based on the stability of the flow rate curves at various temperatures and pressures.

[0065] (5) Alloy mechanical property testing

[0066] To evaluate the mechanical properties of the as-cast alloy, the hardness was tested using an HVS-1000 micro Vickers hardness tester. Before testing, the samples were prepared according to standard metallographic processes to ensure that the surface finish met the requirements for accurate indentation measurement. The test was conducted in microhardness mode, with a test force of 0.3 kgf and an indentation holding time of 15-20 seconds to ensure sufficient material deformation. Each alloy sample was measured 6-7 times at different locations. After removing outliers, the arithmetic mean was taken as the Vickers hardness value to reduce random errors and reflect the statistical characteristics of the material's hardness.

[0067] After testing, V 25 Ti 65 Fe 10 The alloy film has a microhardness value of 348.72HV0.3, exhibiting excellent mechanical properties.

[0068] (6) Alloy corrosion resistance test

[0069] A standard three-electrode system was used to evaluate the corrosion resistance of the alloy in acidic media by measuring Tafel polarization curves. The test was conducted in a 0.5 mol / L H2SO4 solution, and the current response was scanned and recorded within a set potential range using an electrochemical workstation to obtain the corrosion potential and corrosion current density. A more positive corrosion potential indicates better corrosion resistance, while a lower corrosion current density indicates a slower corrosion rate and superior corrosion resistance.

[0070] Figure 7 For V 25 Ti 65 Fe 10 Tafel polarization curves of alloy film electrochemical corrosion test, V 25 Ti 65 Fe10 The alloy has a corrosion potential of -0.2512V and a corrosion current density of 4.5995Log(current / A), respectively, and exhibits excellent corrosion resistance.

[0071] As can be seen from the above, the present invention has successfully prepared V 25 Ti 65 Fe 10 Ternary separation alloys, with this composition, can ensure that while having a sufficiently high hydrogen permeability, they also have good hardness and excellent resistance to hydrogen embrittlement.

[0072] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art to which this invention pertains can make various modifications and refinements without departing from the spirit and scope of the invention.

Claims

1. A novel V-based ternary alloy material for hydrogen permeation, characterized in that, The alloy's composition, in atomic percentage, is V 25 at.%, Ti 65 at.%, Fe 10 at.%, and its chemical formula is V 25 Ti 65 Fe 10 .

2. A method for preparing a novel V-based ternary alloy material for hydrogen permeation as described in claim 1, characterized in that, Includes the following steps: Step 1: Raw material preparation and cleaning: Select metallic vanadium, metallic titanium, and metallic iron with a purity of higher than 99 wt.% as raw materials and clean them. Step 2, Batching and Initial Melting: Mix the cleaned raw materials according to V... 25 Ti 65 Fe 10 The target components are accurately weighed and placed in a water-cooled copper crucible in a vacuum arc melting furnace for initial melting. After melting, the ingot is cooled and flipped. Step 3, remelting and homogenization: The ingot obtained in Step 2 is remelted multiple times; Step 4: Complete the melting process: Repeat the melting process in Step 3 at least 10 times until a macroscopically uniform alloy ingot is obtained. Step 5: Sample cutting: Cut the smelted alloy ingot into samples of predetermined specifications; Step 6, Sample Grinding and Polishing: Grind and polish the cut sample to achieve a mirror finish on its surface; Step 7: Surface vapor deposition: A palladium catalyst layer is vapor deposited on the surface of the polished sample.

3. The preparation method according to claim 2, characterized in that, In step one, the molar ratio of metals Fe, Ti, and V is 5:13:

2.

4. The preparation method according to claim 2, characterized in that, In step one, the total mass of each raw material metal is accurately weighed to be 20g.

5. The preparation method according to claim 2, characterized in that, In step one, anhydrous ethanol is used as the cleaning medium to perform ultrasonic cleaning on the raw material for 25 minutes, and the anhydrous ethanol must completely submerge the raw material during cleaning.

6. The preparation method according to claim 5, characterized in that, After the ultrasonic cleaning in step one is completed, the raw material is dried with hot air.

7. The preparation method according to claim 2, characterized in that, In step two, the initial melting current gradually increases from 25A to 220A.

8. The preparation method according to claim 2, characterized in that, In step two, each time the ingot is turned over after cooling, it is turned over in the same direction.

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