TiCrNbV high-entropy hydrogen storage alloy with bcc structure and preparation method thereof

Abstract

This invention discloses a TiCrNbV high-entropy hydrogen storage alloy with a BCC structure. The general formula for the composition of the high-entropy hydrogen storage alloy is (TiCr). x (NbV) y In the general formula, 5 ≤ x / 2 ≤ 40 at.%, 5 ≤ y / 2 ≤ 40 at.%, and x + y = 100 at.%, and the atomic ratios of Ti and Cr are the same, while the atomic ratios of Nb and V are also the same; the valence electron concentration of the TiCrNbV high-entropy hydrogen storage alloy is always 5; the lattice distortion of the TiCrNbV high-entropy hydrogen storage alloy is 4% ≤ δ ≤ 5.5%; the high-entropy hydrogen storage alloy has a single-phase BCC structure before hydrogen absorption and can still revert to a single-phase BCC structure after hydrogen release. Its preparation method includes the following steps: first, arc melting is performed to obtain a TiCrNbV high-entropy hydrogen storage alloy ingot; then, mechanical crushing and sieving are performed to obtain alloy powder; finally, the alloy powder is activated. Within the hydrogen absorption / desorption temperature range of 30-70℃, the maximum hydrogen absorption capacity reaches 1.9-2.1H / M, and the maximum hydrogen desorption capacity reaches 1.4-1.7H / M; the hydrogen absorption plateau pressure reaches 10-40 bar, and the hydrogen desorption plateau pressure reaches 0.03-1 bar.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen storage alloy technology, specifically relating to a TiCrNbV high-entropy hydrogen storage alloy with a BCC structure and its preparation method. Background Technology

[0002] Body-centered cubic (BCC) hydrogen storage alloys possess advantages such as high hydrogen storage capacity, mild hydrogenation reaction conditions, and good hydrogen absorption kinetics due to the hydrogen-to-metal atomic ratio (H / M) reaching 2. However, traditional BCC hydrogen storage alloys, represented by vanadium-based alloys, suffer from low reversible hydrogen storage capacity, low hydrogen release plateau pressure, and expensive raw materials.

[0003] To improve the hydrogen storage performance of BCC hydrogen storage alloys, elements such as Ti, Cr, Fe, and Mn can be added. For example, existing literature 1 (Huang Z, Li C, Chu Y, et al. Potential and challenges for V-based solid solution hydrogen storage alloys. Energy, 2025:134574.) shows that the hydrogen release rate at room temperature can be significantly improved by adding Ti and Cr in combination, thus improving the hydrogen release performance of BCC alloys. However, this technique is difficult to activate because an oxide film easily forms on the alloy surface, hindering the penetration and diffusion of hydrogen atoms into the alloy interior. At the same time, the hydrogen storage capacity of the alloy is reduced because the added elements have a weak affinity for hydrogen. In addition, there is the problem of forming other hydrides with higher thermal stability after hydrogen absorption, i.e., disproportionation reaction, which leads to a sharp drop in the alloy's cycle performance.

[0004] To address the aforementioned technical challenges, three common solutions exist: introducing multiple principal elements to form a high-entropy hydrogen storage alloy, adjusting the valence electron concentration to modify hydrogen storage performance, and adding alloying elements to catalyze the hydrogen release process.

[0005] Among these methods, by introducing multiple principal components (i.e., when the number of principal components is greater than or equal to 3), high-entropy hydrogen storage alloys can be obtained, thereby improving the hydrogen storage performance of BCC hydrogen storage alloys. The principle is that the components of high-entropy alloys are composed of equal or near-equal atomic ratios; therefore, the high-entropy effect present in high-entropy alloys can cause the alloy to tend to form single-phase solid solutions rather than intermetallic compounds. For example, existing literature 2 (Ek G, MM, Pavan AF, et al. Inorganic Chemistry, 2020, 60(2): 1124-1132) selected five components, V, Ti, Zr, Nb, and Hf, to prepare a single-phase BCC high-entropy hydrogen storage alloy. The high-entropy hydrogen storage alloy obtained by this technical scheme transforms into a single-phase hydride after absorbing hydrogen, that is, no disproportionation reaction occurs, and the hydrogen storage capacity H / M reaches 1.82-2.0. However, the technical problem with this technical scheme is that the hydrogen release temperature of the obtained high-entropy hydrogen storage alloy is as high as 265-540℃. The reason is that the components of this technical scheme have a strong affinity for hydrogen, and the binding force between metal atoms and hydrogen is strong. It is necessary to destroy the structure of the hydride at a high temperature so that the hydrogen atoms can be separated from the metal atoms.

[0006] In addition, technical solutions for regulating valence electron concentration include existing literature 3 ( MM, Ek G, Karlsson D, et al. Acta Materialia, 2019, 175: 121-129) proposed adjusting the thermal stability of hydrides by controlling the valence electron concentration of BCC high-entropy hydrogen storage alloys, thereby reducing the hydrogen release temperature. Specifically, when the valence electron concentration is equal to 5, the BCC high-entropy hydrogen storage alloy exhibits the best overall performance in terms of hydrogen storage capacity and hydrogen release temperature. At the same atomic ratio, the hydrogen storage capacity H / M of the TiVNbCr high-entropy hydrogen storage alloy is close to 2, and the hydrogen release temperature is below 70℃. However, according to the experimental results provided in this existing literature, under the condition of a hydrogen release temperature below 70℃, the hydrogen release amount of the TiVNbCr high-entropy hydrogen storage alloy is less than 66.6% of the hydrogen absorption amount, indicating that this technical solution has the problem of high hydrogen release temperature requirements.

[0007] Furthermore, as indicated in existing literature 4 (Cheng B, Kong L, Cai H, et al. Exploring microstructure variations and hydrogen storage characteristics in TiVNbCrNi high-entropy alloys with different Ni incorporation. International Journal of Hydrogen Energy, 2024, 72: 29-40), Ti can also be improved by adding catalytically active Ni elements. 25 V 30 Nb 10 Cr 35 The activation and incubation time of the high-entropy hydrogen storage alloy was shortened from 3185 seconds to 22 seconds, accelerating the hydrogen absorption and desorption rate. However, in order to achieve the above technical effects, this technical solution reduced the hydrogen storage capacity from 1.86 H / M to 1.27 H / M.

[0008] Therefore, existing technologies cannot simultaneously achieve both high hydrogen release rates and low hydrogen release temperatures. Furthermore, current BCC high-entropy hydrogen storage alloy preparation technologies require high-temperature heat treatment of the high-entropy hydrogen storage alloy prepared by arc melting. For example, the TiNbCrMo high-entropy hydrogen storage alloy described in existing literature 5 (A high-capacity, long-life BCC-type high-entropy hydrogen storage alloy and its preparation method: 202411620676.0.2025-02-11.) was obtained by arc melting and then crushed into powder for direct hydrogen absorption and desorption performance testing. The hydrogen release was only 51.1% of the hydrogen absorption. Through multi-stage high-temperature heat treatment, namely, heating the ingot from room temperature to 1000℃ at a heating rate of 10℃ / min, then heating it to 1200℃ at a heating rate of 1℃ / min and holding it for 9 min; then heating it to 1300℃ at a heating rate of 1℃ / min and holding it for 9 min; then heating it to 1400℃ at a heating rate of 1℃ / min and holding it for 30 min; and finally quenching it with nitrogen, the hydrogen release can reach 71.5% of the hydrogen absorption.

[0009] Similarly, existing literature 6 (Jiangxi Rare Earth Research Institute, Chinese Academy of Sciences, Shenzhen Guoke Hydrogen Source Technology Co., Ltd. A high-entropy hydrogen storage alloy and its preparation method: 202310501531.8.2024-10-25) describes a high-entropy hydrogen storage alloy with the general formula Ti. a Cr b V c Mn d Mo e Ce f Where 0.3≤a≤0.5, 0.05≤b≤0.2, 0.2≤c≤0.3, 0.25≤d≤0.4, 0.05≤e≤0.1, and 0.01≤f≤0.03. The high-entropy hydrogen storage alloy ingot of this scheme requires heat treatment at 1350-1450℃ to improve compositional uniformity, thereby reducing the inclination of the hydrogen absorption / desorption plateau and enhancing hydrogen storage performance.

[0010] As can be seen from existing references 5 and 6, high-temperature heat treatment can improve the hydrogen storage performance of BCC high-entropy hydrogen storage alloys. This is because high-temperature heat treatment can eliminate dendritic segregation in the casting structure, improve compositional uniformity, and obtain a smooth hydrogen absorption / desorption plateau. Therefore, conventional preparation methods in the prior art include high-temperature heat treatment as an essential technical feature. However, according to the inventors' research based on the present invention, high-temperature heat treatment leads to two new technical problems:

[0011] 1. Causes oxidation of BCC high-entropy hydrogen storage alloy;

[0012] 2. Increase the complexity of the production process, which in turn increases production costs. Summary of the Invention

[0013] The technical problem to be solved by this invention is to provide a BCC high-entropy hydrogen storage alloy based on lattice distortion control and its preparation method. This invention calculates and determines the required composition of a TiCrNbV high-entropy hydrogen storage alloy by reducing lattice distortion, thereby minimizing the differences in shape and size between hydrogen storage gaps. This narrows the bond length distribution range between hydrogen atoms in the system, shortens the average bond length, and causes more hydrogen atoms to become unstable due to Coulomb repulsion exceeding the critical threshold, making them easier to desorb. This results in a high-entropy hydrogen storage alloy with high hydrogen release capacity within a temperature range of 30-70℃.

[0014] The lattice distortion δ is calculated using the following formula:

[0015]

[0016] In the formula, n is the number of components, and c i and c j These are the atomic percentages of components i and j, respectively, and r i and r j These are the atomic radii of components i and j, respectively; specifically, in this invention, the atomic radii of Ti, Cr, Nb, and V are 0.1462 nm, 0.1249 nm, 0.1429 nm, and 0.1316 nm, respectively.

[0017] To achieve the above objectives, the present invention provides the following technical solution:

[0018] A TiCrNbV high-entropy hydrogen storage alloy with a BCC structure, wherein the general formula for high-entropy hydrogen storage alloys is (TiCr). x (NbV) y In the general formula, 5≤x / 2≤40at.%, 5≤y / 2≤40at.%, and x+y=100at.%, and the atomic ratios of Ti and Cr are the same, while the atomic ratios of Nb and V are kept the same;

[0019] The valence electron concentration of TiCrNbV high-entropy hydrogen storage alloy is always 5, that is, 10x + 10y = 5;

[0020] The lattice distortion of TiCrNbV high-entropy hydrogen storage alloy is 4% ≤ δ ≤ 5.5%;

[0021] The high-entropy hydrogen storage alloy has a single-phase BCC structure before hydrogen absorption and can revert to a single-phase BCC structure after hydrogen release.

[0022] A method for preparing a TiCrNbV high-entropy hydrogen storage alloy includes the following steps: First, Ti, Cr, Nb, and V are electrically arc-melted in a certain molar ratio. After melting, the molten alloy is poured into a water-cooled copper mold to obtain a TiCrNbV high-entropy hydrogen storage alloy ingot. Then, the ingot is mechanically crushed and sieved to obtain alloy powder. Finally, the alloy powder is activated to obtain the TiCrNbV high-entropy hydrogen storage alloy for hydrogen storage.

[0023] The conditions for arc melting are as follows: high-purity argon is used as the protective gas; electromagnetic stirring is performed during melting; the melting current is 200-450A; the melting time is 10-100s / cycle; the number of melting cycles is 5; and the melting is turned over after each cooling cycle. The conditions for sieving are as follows: the particle size requirement is 50-300 mesh.

[0024] The activation conditions are as follows: a two-step activation method is adopted. The conditions for the first step of activation are: activation temperature of 20-50℃, activation hydrogen pressure of 1-20 bar, and activation time of 0.15-2h.

[0025] The conditions for the second step of activation are: activation temperature 300-600℃, activation hydrogen pressure 0.0005-0.005 bar, and activation time 0.5-4 h.

[0026] The obtained TiCrNbV high-entropy hydrogen storage alloy exhibits a maximum hydrogen absorption capacity of 1.9-2.1 H / M and a maximum hydrogen release capacity of 1.4-1.7 H / M within a hydrogen absorption / desorption temperature range of 30-70℃; the hydrogen absorption plateau pressure reaches 10-40 bar, and the hydrogen release plateau pressure reaches 0.03-1 bar.

[0027] The technical effects of this invention were tested experimentally as follows:

[0028] EDS testing showed that the actual composition of the TiCrNbV high-entropy hydrogen storage alloy was not substantially different from the nominal composition, which is consistent with the composition characteristics of high-entropy alloys, and the elements were evenly distributed.

[0029] XRD analysis revealed that the TiCrNbV high-entropy hydrogen storage alloy exhibits a single-phase BCC structure with a lattice distortion δ ranging from 5.1% to 6.3%. Reducing the lattice distortion δ can suppress the disproportionation reaction, which is beneficial for the alloy to maintain its single-phase structure.

[0030] SEM testing revealed that the TiCrNbV high-entropy hydrogen storage alloy has a single-phase structure.

[0031] Hydrogen absorption and desorption performance tests showed that, within the hydrogen absorption / desorption temperature range of 30-70℃, as the lattice distortion δ decreased from 6.3% to 5.1%, the hydrogen absorption capacity of the TiCrNbV high-entropy hydrogen storage alloy remained at 2.0 H / M, while the hydrogen desorption capacity increased, and the hydrogen absorption / desorption plateau pressure rose. Specifically, at a hydrogen absorption / desorption temperature of 30℃, the maximum hydrogen desorption capacity was 1.58 H / M.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] 1. This invention designs alloy composition by controlling lattice distortion, resulting in (TiCr) 20 (NbV) 80 The high-entropy hydrogen storage alloy exhibits excellent and stable hydrogen absorption and desorption performance at operating temperatures of 30℃-70℃, with a hydrogen absorption capacity (H / M) of 2.00-2.08 and a hydrogen release capacity (H / M) of 1.55-1.58. It also has a hydrogen desorption rate of 75.7-77.4%, making it suitable for application in vehicle-mounted hydrogen storage.

[0034] 2. The preparation method of the present invention has simple steps, and the resulting ingot does not require high-temperature heat treatment, making it easy to achieve controllable preparation of the alloy;

[0035] 3. This invention can reduce the solid solution strengthening effect of high-entropy hydrogen storage alloy by reducing lattice distortion, thereby reducing its strength or hardness and making it easier to break in the future, thus reducing the difficulty of preparation.

[0036] 4. Based on the empirical parameter method to calculate the lattice distortion δ, this invention successfully designed a high-entropy hydrogen storage alloy with a high hydrogen release capacity at an operating temperature of 30℃-70℃. Attached Figure Description

[0037] Figure 1 The lattice distortion values ​​(δ) of the high-entropy hydrogen storage alloys of Example 1, Comparative Example 1, Comparative Example 3 and Comparative Example 4 are shown.

[0038] Figure 2 This is a SEM image of TCNV-2 / 8 prepared in Example 1;

[0039] Figure 3 These are the XRD patterns of the high-entropy hydrogen storage alloys of Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 after activation;

[0040] Figure 4 The PCT curve of TCNV-2 / 8 prepared in Example 1;

[0041] Figure 5 These are the XRD patterns of the high-entropy hydrogen storage alloys of Example 1, Comparative Example 1, Comparative Example 3 and Comparative Example 4 after hydrogen desorption at 30°C.

[0042] Figure 6The image shows the SEM image of TCNV-5 / 5 prepared in Comparative Example 1.

[0043] Figure 7 The PCT curves of TCNV-5 / 5 prepared in Comparative Example 1 are shown.

[0044] Figure 8 The image shows the SEM image of TCNV-3 / 7 prepared in Comparative Example 3.

[0045] Figure 9 The PCT curves of TCNV-3 / 7 prepared in Comparative Example 3 are shown.

[0046] Figure 10 The image shows the SEM image of TCNV-4 / 6 prepared in Comparative Example 4.

[0047] Figure 11 The PCT curves of TCNV-4 / 6 prepared in Comparative Example 4 are shown.

[0048] Figure 12 This is a comparison of the hydrogen release amount of the high-entropy hydrogen storage alloys in Example 1, Comparative Example 1, Comparative Example 3 and Comparative Example 4 at 30°C. Detailed Implementation

[0049] The present invention will be further described in detail through embodiments and with reference to the accompanying drawings. These embodiments are for comparative and illustrative purposes only, and the present invention is not limited to these embodiments.

[0050] To facilitate differentiation of the various alloys and their basic information involved in the embodiments and comparative examples, a description is provided first. Specifically, in the embodiments and comparative examples, the general chemical formula of the TiCrNbV high-entropy hydrogen storage alloy satisfies (TiCr). x (NbV) y Where x+y=100, x=20,30,40,50, and the valence electron concentration of TiCrNbV high-entropy hydrogen storage alloy is always 5.

[0051] The principle of the general chemical formula is to maintain the same atomic ratio of Ti and Cr, abbreviated as (Ti+Cr), and simultaneously maintain the same atomic ratio of Nb and V, abbreviated as (Nb+V). Then, the ratios of (Ti+Cr) and (Nb+V) are changed to adjust the lattice distortion δ of the TiCrNbV high-entropy hydrogen storage alloy. Specifically, the lattice distortion δ of the TiCrNbV high-entropy hydrogen storage alloy is calculated, and the results are as follows: Figure 1 As shown in Table 1.

[0052] Table 1. Chemical formula and lattice distortion of TiCrNbV high-entropy hydrogen storage alloy

[0053] Example 1 <![CDATA[(TiCr) 20 (NbV) 80 ]]> TCNV-2 / 8 5.1 Comparative Example 3 <![CDATA[(TiCr) 30 (NbV) 70 ]]> TCNV-3 / 7 5.5 Comparative Example 4 <![CDATA[(TiCr) 40 (NbV) 60 ]]> TCNV-4 / 6 5.9 Comparative Example 1 <![CDATA[(TiCr) 50 (NbV) 50 ]]> TCNV-5 / 5 6.3

[0054] Example 1

[0055] A method for preparing a TiCrNbV high-entropy hydrogen storage alloy with a lattice distortion δ = 5.1% includes the following steps: First, Ti, Cr, Nb, and V are electrically arc-melted in a certain molar ratio. After melting, the molten alloy is poured into a water-cooled copper mold to obtain a TiCrNbV high-entropy hydrogen storage alloy ingot. Then, the alloy ingot is mechanically crushed and sieved to obtain alloy powder. Finally, the alloy powder is activated to obtain the TiCrNbV high-entropy hydrogen storage alloy. Furthermore, based on the compositional characteristics, the TiCrNbV high-entropy hydrogen storage alloy obtained in Example 1 is (TiCr). 20 (NbV) 80 High-entropy hydrogen storage alloy, therefore, is simply referred to as TCNV-2 / 8.

[0056] The molar ratio of Ti, Cr, Nb, and V is 10:10:40:40, that is, the molar ratio of (Ti+Cr) to (Nb+V) is 20:80.

[0057] The conditions for arc melting are as follows: high-purity argon is used as the protective gas, electromagnetic stirring is performed during melting, the melting current is 350A, the melting time is 60s / time, the number of melting times is 5, and the melting is turned over after each cooling.

[0058] The sieving conditions are that the particle size requirement is 100 mesh;

[0059] The activation conditions for TCNV-2 / 8 are as follows: First, activation is carried out at an activation temperature of 30°C, an activation hydrogen pressure of 10 bar, and an activation time of 0.5 h. Then, activation is carried out at an activation temperature of 400°C, an activation hydrogen pressure of 0.0005 bar, and an activation time of 2 h.

[0060] To verify the component content of TCNV-2 / 8, i.e., to prove that the actual component matches the nominal component, EDS testing was conducted. The test results are as follows: Figure 2 As shown in Table 2, the atomic percentages of Ti, Cr, Nb, and V are 10.3 at.%, 9.7 at.%, 38.0 at.%, and 42.0 at.%, respectively, which are not substantially different from the nominal composition. The test results indicate that TCNV-2 / 8 conforms to the compositional characteristics of a high-entropy alloy.

[0061] Table 2. Actual composition of TiCrNbV high-entropy hydrogen storage alloy

[0062] Example 1 10.3 9.7 38.0 42.0 Comparative Example 3 15.2 15.0 32.9 36.9 Comparative Example 4 20.3 20.0 28.2 31.4 Comparative Example 1 25.3 25.1 23.2 26.4

[0063] To confirm the crystal structure of TCNV-2 / 8, XRD analysis was performed. The test results are as follows: Figure 3 As shown, TCNV-2 / 8 exhibits only one characteristic peak of the BCC structure, with a lattice constant of [value missing]. Test results show that TCNV-2 / 8 is a single-phase BCC structure.

[0064] To further confirm that TCNV-2 / 8 is a single-phase structure, SEM testing was performed. The test results are as follows: Figure 2 As shown, TCNV-2 / 8 does not have a second phase, i.e., it has a single-phase structure. Combined with the EDS test results, it can be seen that TCNV-2 / 8 does not have obvious elemental segregation.

[0065] To demonstrate the hydrogen storage performance of TCNV-2 / 8, a hydrogen absorption and desorption thermodynamic (PCT) test was conducted, and the mass hydrogen storage capacity was converted into the hydrogen-to-metal atomic ratio (H / M). The test results are as follows: Figure 4 As shown in Table 3,

[0066] At a hydrogen absorption / desorption temperature of 30℃, the hydrogen absorption rate is 2.08 H / M, the hydrogen desorption rate is 1.58 H / M, the hydrogen absorption plateau pressure is 10.98 bar, and the hydrogen desorption plateau pressure is 0.07 bar.

[0067] At a hydrogen absorption / desorption temperature of 50℃, the hydrogen absorption rate is 2.0 H / M, the hydrogen desorption rate is 1.55 H / M, and the hydrogen absorption plateau pressure is 12.56 bar and the hydrogen desorption plateau pressure is 0.24 bar.

[0068] At a hydrogen absorption / desorption temperature of 70°C, the hydrogen absorption rate is 2.04 H / M, the hydrogen desorption rate is 1.58 H / M, the hydrogen absorption plateau pressure is 30.53 bar, and the hydrogen desorption plateau pressure is 0.64 bar.

[0069] Test results show that within the hydrogen absorption / desorption temperature range of 30-70℃, temperature has no significant effect on the amount of hydrogen absorbed and desorbed. However, increasing the temperature can increase the hydrogen absorption plateau pressure and the hydrogen desorption plateau pressure.

[0070] Note: The TiCrNbV high-entropy hydrogen storage alloy after hydrogen absorption / desorption is abbreviated as TCNV-D, and the TCNV-D obtained in Specific Example 1 is abbreviated as TCNV-2 / 8-D.

[0071] To demonstrate the effect of hydrogen absorption / desorption on the crystal structure, XRD tests were performed on TCNV-2 / 8-D. The test results are as follows: Figure 5 As shown, TCNV-2 / 8-D exhibits characteristic peaks for only one type of BCC structure. Test results indicate that TCNV-2 / 8-D has a single-phase BCC structure. Comparison with the XRD results of TCNV-2 / 8 shows that TCNV-2 / 8 can revert to its single-phase BCC structure after hydrogen absorption / desorption, meaning that the hydrogen absorption / desorption process does not affect the crystal structure of TCNV-2 / 8.

[0072] Table 3 Hydrogen absorption / desorption properties and crystal structure after hydrogen desorption of TiCrNbV high-entropy hydrogen storage alloy at 30℃

[0073]

[0074] To further demonstrate the influence of lattice distortion on the hydrogen storage performance of TiCrNbV high-entropy hydrogen storage alloy, a comparative reference is provided, as shown in Table 4.

[0075] Table 4. Comparison of hydrogen release of TCNV-2 / 8 at 30℃ and other alloys at room temperature.

[0076]

[0077] 1. Cheng B, Kong L, Cai H, et al. Exploring microstructure variations and hydrogen storage characteristics in TiVNbCrNi high-entropy alloys with different Ni incorporation. International Journal of Hydrogen Energy. 2024; 60:282-292.

[0078] 2. Cheng B, Kong L, Cai H, et al. Pushing the Boundaries of solid-statehydrogen storage: A Refined study on TiVNbCrMo high-entropyalloys. International Journal of Hydrogen Energy. 2024; 60:282-292.

[0079] 3. Wu Z, Yang C, Yan Y, et al. Effect of dehydrogenation depth on cyclichydrogen desorption properties of V40Ti25.5Cr26.5Fe8 alloy. Journal of Alloysand Compounds, 2023,955:170036.

[0080] 4. Zhang X, Liu Y, Hu H, et al. Development of high-performance and low-cost BCC type hydrogen storage alloys from FeV80 master alloy refined bycerium. Journal of Rare Earths, 2025.

[0081] According to existing reference 1, in the high-entropy hydrogen storage alloy TiVNbCrNi system, the Ni content, i.e., the Cr / Ni ratio, has a negligible effect on lattice distortion; however, the hydrogen release rate varies significantly. That is, those skilled in the art can conclude from existing reference 1-1 that "the increase in hydrogen release rate is unrelated to lattice distortion."

[0082] According to existing reference 2, in the high-entropy hydrogen storage alloy TiCrNbVMo system, the content of Mo, i.e., the Cr / Mo ratio, can change the lattice distortion. However, although the hydrogen release amount changes, the change in hydrogen release amount is not regular. That is, those skilled in the art cannot obtain technical inspiration regarding "hydrogen release amount and lattice distortion" from existing references 1-2.

[0083] Based on a comparison of references 3 and 4, those skilled in the art can initially conclude that "increasing lattice distortion can improve the hydrogen release of BCC high-entropy hydrogen storage alloys"; however, further analysis of Embodiment 1 of the present invention shows that the above conclusion is not valid.

[0084] Therefore, based on the above analysis of existing technologies, it can be seen that current technologies cannot determine the relationship between the hydrogen release and lattice distortion of high-entropy hydrogen storage alloys, and thus cannot provide any technological insights.

[0085] To demonstrate the effect of a conventional high-entropy hydrogen storage alloy, i.e., the molar ratio of Ti, Cr, Nb, and V being 1:1:1:1, on the hydrogen storage performance of the TiCrNbV high-entropy hydrogen storage alloy, Comparative Example 1 is provided.

[0086] Comparative Example 1

[0087] A method for preparing a TiCrNbV high-entropy hydrogen storage alloy with a lattice distortion δ = 6.3% is described. Unless otherwise specified, the steps are the same as in Example 1, except that the molar ratio of Ti, Cr, Nb, and V is 25:25:25:25, which is 1:1:1:1, or the molar ratio of (Ti+Cr) to (Nb+V) is 50:50. This corresponds to a lattice distortion δ = 6.3%. Therefore, the obtained TiCrNbV high-entropy hydrogen storage alloy is (TiCr).50 (NbV) 50 High-entropy hydrogen storage alloy, abbreviated as TCNV-5 / 5, and the TCNV-5 / 5 obtained after hydrogen absorption / desorption is abbreviated as TCNV-5 / 5-D.

[0088] The EDS test results of TCNV-5 / 5 are shown in Table 2. The atomic percentages of Ti, Cr, Nb, and V are 25.3 at.%, 25.1 at.%, 23.2 at.%, and 26.4 at.%, respectively, which are not substantially different from the nominal composition. The test results indicate that TCNV-5 / 5 conforms to the compositional characteristics of a high-entropy alloy.

[0089] The XRD test results of TCNV-5 / 5 are as follows: Figure 3 As shown, TCNV-5 / 5 exhibits only one characteristic peak of the BCC structure, with a lattice constant of [value missing]. Test results show that TCNV-5 / 5 is a single-phase BCC structure.

[0090] The SEM test results of TCNV-5 / 5 are as follows: Figure 6 As shown, TCNV-5 / 5 does not have a second phase, i.e., it has a single-phase structure. Combined with the EDS test results, it can be seen that TCNV-5 / 5 does not show obvious elemental segregation.

[0091] The PCT test results of TCNV-5 / 5 are as follows: Figure 7 As shown in Table 3,

[0092] At a hydrogen absorption / desorption temperature of 30℃, the hydrogen absorption rate is 2.02 H / M, the hydrogen desorption rate is 0.57 H / M, and the hydrogen absorption plateau pressure is 1.52 bar and the hydrogen desorption plateau pressure is 0.01 bar.

[0093] At a hydrogen absorption / desorption temperature of 50°C, the hydrogen absorption rate is 2.03 H / M, the hydrogen desorption rate is 1.45 H / M, the hydrogen absorption plateau pressure is 1.83 bar, and the hydrogen desorption plateau pressure is 0.04 bar.

[0094] At a hydrogen absorption / desorption temperature of 70°C, the hydrogen absorption rate is 2.0 H / M, the hydrogen desorption rate is 1.56 H / M, the hydrogen absorption plateau pressure is 3.52 bar, and the hydrogen desorption plateau pressure is 0.12 bar.

[0095] Test results show that within the hydrogen absorption / desorption temperature range of 30-70℃, temperature has no significant effect on the amount of hydrogen absorbed, but increasing the temperature can increase the amount of hydrogen released, as well as the hydrogen absorption plateau pressure and the hydrogen release plateau pressure.

[0096] The XRD test results of TCNV-5 / 5-D are as follows: Figure 5As shown, TCNV-5 / 5-D exhibits characteristic peaks of both BCC and FCC hydrides, in addition to the characteristic peaks of the BCC structure. According to common knowledge in the field, the higher the thermal stability of a hydride, the more difficult it is to decompose hydrogen. This is because the binding force between metal atoms and hydrogen is strong, requiring higher temperatures to break down the hydride structure. Therefore, the XRD results indicate that TCNV-5 / 5 forms thermodynamically stable hydrides after absorbing hydrogen, resulting in some FCC hydrides failing to revert to the BCC alloy during subsequent hydrogen decomposition.

[0097] By comparing Comparative Example 1 and Example 1, it can be seen that when the molar ratio of (Ti+Cr) to (Nb+V) is 50:50, although a TiCrNbV high-entropy hydrogen storage alloy can also be obtained, compared with TCNV-2 / 8, TCNV-5 / 5 has some FCC hydrides that cannot be restored to BCC alloy after hydrogen absorption and desorption, so the hydrogen release is lower.

[0098] To demonstrate the effect of conventional high-entropy hydrogen storage alloy processing methods, i.e., heat treatment, on the hydrogen storage performance of TiCrNbV high-entropy hydrogen storage alloy, Comparative Example 2 is provided, which is a TiCrNbV high-entropy hydrogen storage alloy obtained by heat treating TCNV-5 / 5 of Comparative Example 1 before mechanical crushing.

[0099] Comparative Example 2

[0100] A method for preparing a heat-treated TiCrNbV high-entropy hydrogen storage alloy, wherein the steps not specifically described are the same as those in Comparative Example 1, except that the TCNV-5 / 5 ingot is heat-treated before mechanical crushing, and the resulting TiCrNbV high-entropy hydrogen storage alloy is referred to as TCNV-5 / 5-A.

[0101] The heat treatment conditions are as follows: heat treatment temperature is 1200℃, heat treatment time is 12h, argon pressure is 5bar, and water quenching is performed after heat treatment.

[0102] The XRD test results of TCNV-5 / 5-A are as follows: Figure 3 As shown, after heat treatment, TCNV-5 / 5-A exhibits characteristic peaks of the NbCr2 phase in addition to the BCC structure, indicating that it is not a single-phase BCC structure. Test results demonstrate that heat treatment leads to the formation of precipitated phases in the alloy.

[0103] PCT test results of TCNV-5 / 5-A show that, under the condition of hydrogen absorption / desorption temperature of 30℃, the hydrogen absorption capacity is 0.1H / M, the hydrogen desorption capacity is zero, and the hydrogen absorption plateau pressure is less than 0.05 bar, and the hydrogen desorption plateau pressure is less than 0.05 bar.

[0104] By comparing Comparative Example 2 and Example 1, it can be seen that the TiCrNbV high-entropy hydrogen storage alloy will form the NbCr2 phase after high-temperature heat treatment.

[0105] To further demonstrate the effect of the molar ratio of Ti, Cr, Nb, and V, i.e., lattice distortion, on the hydrogen storage performance of TiCrNbV high-entropy hydrogen storage alloy, Examples 2 and 3 are provided, with TiCrNbV high-entropy hydrogen storage alloys having lattice distortions of 5.5% and 5.9%, respectively.

[0106] Comparative Example 3

[0107] A method for preparing a TiCrNbV high-entropy hydrogen storage alloy with a lattice distortion δ = 5.5% is described. Unless otherwise specified, the steps are the same as in Example 1, except that the molar ratio of Ti, Cr, Nb, and V is 15:15:35:35, i.e., the molar ratio of (Ti+Cr) to (Nb+V) is 30:70, corresponding to a lattice distortion δ = 5.5%. Therefore, the obtained TiCrNbV high-entropy hydrogen storage alloy is (TiCr). 30 (NbV) 70 The high-entropy hydrogen storage alloy is abbreviated as TCNV-3 / 7, and the TCNV-3 / 7 obtained after hydrogen absorption / desorption is abbreviated as TCNV-3 / 7-D.

[0108] The EDS test results of TCNV-3 / 7 are shown in Table 2. The atomic percentages of Ti, Cr, Nb, and V are 15.2 at.%, 15.0 at.%, 32.9 at.%, and 36.9 at.%, respectively, which are not substantially different from the nominal composition. The test results indicate that TCNV-3 / 7 conforms to the compositional characteristics of high-entropy alloys.

[0109] The XRD test results of TCNV-3 / 7 are as follows: Figure 3 As shown, TCNV-3 / 7 exhibits only one characteristic peak of the BCC structure, with a lattice constant of [value missing]. Test results show that TCNV-3 / 7 is a single-phase BCC structure.

[0110] The SEM test results of TCNV-3 / 7 are as follows: Figure 8 As shown, TCNV-3 / 7 does not have a second phase, i.e., it has a single-phase structure. Combined with the EDS test results, it can be seen that TCNV-3 / 7 does not have obvious elemental segregation.

[0111] The PCT test results of TCNV-3 / 7 are as follows: Figure 9 As shown in Table 3,

[0112] At a hydrogen absorption / desorption temperature of 30℃, the hydrogen absorption rate is 2.08 H / M, the hydrogen desorption rate is 1.06 H / M, the hydrogen absorption plateau pressure is 3.81 bar, and the hydrogen desorption plateau pressure is 0.03 bar.

[0113] At a hydrogen absorption / desorption temperature of 50℃, the hydrogen absorption rate is 2.05 H / M, the hydrogen desorption rate is 1.54 H / M, and the hydrogen absorption plateau pressure is 6.49 bar and the hydrogen desorption plateau pressure is 0.11 bar.

[0114] At a hydrogen absorption / desorption temperature of 70°C, the hydrogen absorption rate is 1.99 H / M, the hydrogen desorption rate is 1.54 H / M, the hydrogen absorption plateau pressure is 17.0 bar, and the hydrogen desorption plateau pressure is 0.31 bar.

[0115] Test results show that within the hydrogen absorption / desorption temperature range of 30-70℃, temperature has no significant effect on the amount of hydrogen absorbed, but increasing the temperature can increase the amount of hydrogen released, as well as the hydrogen absorption plateau pressure and the hydrogen release plateau pressure.

[0116] The XRD test results of TCNV-3 / 7-D are as follows: Figure 5 As shown, TCNV-3 / 7-D exhibits characteristic peaks for only one type of BCC structure. Test results indicate that TCNV-3 / 7-D has a single-phase BCC structure. Comparison with the XRD results of TCNV-3 / 7 shows that TCNV-3 / 7 can revert to a single-phase BCC structure after hydrogen absorption / desorption.

[0117] By comparing Comparative Example 3 and Example 1, it can be seen that when the molar ratio of (Ti+Cr) to (Nb+V) is 30:70, a TiCrNbV high-entropy hydrogen storage alloy can be obtained.

[0118] Comparative Example 4

[0119] A method for preparing a TiCrNbV high-entropy hydrogen storage alloy with a lattice distortion δ = 5.9% is described. Unless otherwise specified, the steps are the same as in Example 1, except that the molar ratio of Ti, Cr, Nb, and V is 20:20:30:30, i.e., the molar ratio of (Ti+Cr) to (Nb+V) is 40:60, corresponding to a lattice distortion δ = 5.5%. Therefore, the obtained TiCrNbV high-entropy hydrogen storage alloy is (TiCr). 40 (NbV) 60 High-entropy hydrogen storage alloy, abbreviated as TCNV-4 / 6, and the TCNV-4 / 6 obtained after hydrogen absorption / desorption is abbreviated as TCNV-4 / 6-D.

[0120] The EDS test results of TCNV-4 / 6 are shown in Table 2. The atomic percentages of Ti, Cr, Nb, and V are 20.3 at.%, 20.0 at.%, 28.2 at.%, and 31.4 at.%, respectively, which are not substantially different from the nominal composition. The test results indicate that TCNV-4 / 6 conforms to the compositional characteristics of high-entropy alloys.

[0121] The XRD test results of TCNV-4 / 6 are as follows: Figure 3 As shown, TCNV-4 / 6 exhibits only one characteristic peak of the BCC structure, with a lattice constant of [value missing]. Test results show that TCNV-4 / 6 is a single-phase BCC structure.

[0122] The SEM test results of TCNV-4 / 6 are as follows: Figure 10 As shown, TCNV-4 / 6 does not have a second phase, i.e., it has a single-phase structure. Combined with the EDS test results, it can be seen that TCNV-4 / 6 does not show obvious elemental segregation.

[0123] The PCT test results of TCNV-4 / 6 are as follows: Figure 11 As shown in Table 3,

[0124] At a hydrogen absorption / desorption temperature of 30℃, the hydrogen absorption rate is 2.05 H / M, the hydrogen desorption rate is 0.66 H / M, the hydrogen absorption plateau pressure is 2.29 bar, and the hydrogen desorption plateau pressure is 0.01 bar.

[0125] At a hydrogen absorption / desorption temperature of 50°C, the hydrogen absorption rate is 2.02 H / M, the hydrogen desorption rate is 1.48 H / M, the hydrogen absorption plateau pressure is 2.60 bar, and the hydrogen desorption plateau pressure is 0.06 bar.

[0126] At a hydrogen absorption / desorption temperature of 70°C, the hydrogen absorption rate is 2.02 H / M, the hydrogen desorption rate is 1.61 H / M, the hydrogen absorption plateau pressure is 6.08 bar, and the hydrogen desorption plateau pressure is 0.18 bar.

[0127] Test results show that within the hydrogen absorption / desorption temperature range of 30-70℃, temperature has no significant effect on the amount of hydrogen absorbed. However, increasing the temperature can increase the amount of hydrogen released, as well as the hydrogen absorption plateau pressure and the hydrogen release plateau pressure.

[0128] The XRD test results of TCNV-4 / 6-D are as follows: Figure 5 As shown, TCNV-4 / 6-D exhibits characteristic peaks for only one type of BCC structure. Test results indicate that TCNV-4 / 6-D has a single-phase BCC structure. Comparison with the XRD results of TCNV-4 / 6 shows that TCNV-4 / 6 can revert to a single-phase BCC structure after hydrogen absorption / desorption.

[0129] By comparing Comparative Example 4 and Example 1, it can be seen that when the molar ratio of (Ti+Cr) to (Nb+V) is 40:60, a TiCrNbV high-entropy hydrogen storage alloy can be obtained.

Claims

1. A TiCrNbV high-entropy hydrogen storage alloy with a BCC structure, characterized in that: A high-entropy hydrogen storage alloy has a general formula of (TiCr) x (NbV) y , wherein 5≤x / 2≤40 at.%, 5≤y / 2≤40 at.%, x+y=100 at.%, and the atomic ratio of Ti and Cr is the same, and the atomic ratio of Nb and V is the same. The valence electron concentration of the TiCrNbV high-entropy hydrogen storage alloy is constant at 5. The lattice distortion of TiCrNbV high-entropy hydrogen storage alloy is 4%≤δ<5.5%; The high-entropy hydrogen storage alloy has a single-phase BCC structure before hydrogen absorption and can revert to a single-phase BCC structure after hydrogen release.

2. The TiCrNbV high-entropy hydrogen storage alloy with a BCC structure according to claim 1, characterized in that: The preparation method includes the following steps: First, Ti, Cr, Nb, and V are electrically arc-melted in a certain molar ratio. After melting, the molten alloy is poured into a water-cooled copper mold to obtain a TiCrNbV high-entropy hydrogen storage alloy ingot. Then, the ingot is mechanically crushed and sieved to obtain alloy powder. Finally, the alloy powder is activated to obtain the TiCrNbV high-entropy hydrogen storage alloy for hydrogen storage. The conditions for arc melting are as follows: high-purity argon is used as the protective gas; electromagnetic stirring is performed during melting; the melting current is 200-450 A; the melting time is 10-100 s / time; the number of melting times is 5; and the melting is turned over after each cooling. The conditions for sieving are as follows: the particle size requirement is 50-300 mesh. The activation conditions are as follows: a two-step activation method is adopted. The conditions for the first step of activation are: activation temperature of 20-50℃, activation hydrogen pressure of 1-20 bar, and activation time of 0.15-2 h. The conditions for the second step of activation are: activation temperature 300-600℃, activation hydrogen pressure 0.0005-0.005 bar, and activation time 0.5-4 h.

3. The TiCrNbV high-entropy hydrogen storage alloy with a BCC structure according to claim 1, characterized in that: The obtained TiCrNbV high-entropy hydrogen storage alloy exhibits a maximum hydrogen absorption capacity of 1.9-2.1 H / M and a maximum hydrogen release capacity of 1.4-1.7 H / M within a hydrogen absorption / desorption temperature range of 30-70℃; the hydrogen absorption plateau pressure reaches 10-40 bar, and the hydrogen release plateau pressure reaches 0.03-1 bar.

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