A hydrogen storage alloy and its preparation method

Abstract

This invention discloses a hydrogen storage alloy and its preparation method, belonging to the technical field of hydrogen storage alloy materials. It solves the problems of decreased hydrogen storage performance of TiFe as its activation performance improves, and the poor surface condition of the alloy. The hydrogen storage alloy contains multiple rare earth elements Gd and Nd, transition metals Mn, Cu, and Zn, and its chemical formula is: Ti 1.2‑x‑y Gd x Nd y Fe 0.85 Mn 0.25‑z‑m Zn z Cu m In the chemical formula, x, y, z, and m are atomic ratios, where 0.01 ≤ x ≤ 0.05, 0.01 ≤ y ≤ 0.05, 0.02 ≤ z ≤ 0.08, and 0.02 ≤ m ≤ 0.1. This invention employs a combination of elemental substitution and short-time ball milling to obtain TiFe alloys with good activation properties and hydrogen absorption / desorption kinetics.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen storage alloy materials technology, and specifically relates to a hydrogen storage alloy and its preparation method. Background Technology

[0002] Metal hydrides are currently the most commonly used hydrogen storage method due to their advantages such as long hydrogen absorption / desorption cycle life, high energy density, good reversibility, and good environmental compatibility. TiFe alloys possess excellent cycle performance, high hydrogenation capacity, a low room temperature equilibrium plateau (0.41 MPa H2), and low cost, making them one of the most promising hydrogen storage alloys. However, TiFe alloys are highly sensitive to air and moisture. Due to the formation of a stable surface oxide layer (TiO2 and / or Fe2O3) during synthesis or handling in air, the initial hydrogen absorption process (so-called activation) is extremely slow. The formed oxide layer inhibits electron exchange between the metal and hydrogen (MH), thus disrupting hydrogen dissociation and absorption. Therefore, the activation step of TiFe alloys typically requires high temperature and high hydrogen pressure, which poses an obstacle to practical applications.

[0003] Current research involves forming a Ti-rich phase. 1+x Methods such as Fe, surface modification, and the addition of transition metals improve the activation process. In Ti-rich alloys, the hydrogenation of the β-Ti phase precedes the formation of the TiFe hydrogenated phase, which helps to lower the activation barrier of the first hydrogenation reaction. Furthermore, surface modification of TiFe alloys using methods such as ball milling, ion implantation, high-pressure torsion, cold rolling, and Pd doping improves kinetic properties. Replacing Fe and / or Ti with transition metals such as Mn, Co, Cu, Cr, Zr, Ni, and Al improves the activation kinetics of TiFe alloys. In most cases, transition metals help to alter the microstructure of the alloy, thereby improving the activation process. Among these methods, replacing Fe with transition metals is considered the most economical and effective solution. However, as the activation performance of TiFe improves, other hydrogen storage properties of TiFe generally deteriorate.

[0004] Mechanical alloying (MA) is one possible approach to improve the hydrogen adsorption / desorption properties of alloys. This method has a positive impact on the activation properties of TiFe alloys, such as reducing particle size and creating new, clean surfaces.

[0005] Ordinary TiFe alloys, after activation treatment, will lose their activity and hydrogen absorption capacity if exposed to air, even for a very short time. This obviously cannot meet the requirements of practical applications and large-scale production. Summary of the Invention

[0006] Based on the above analysis, this invention aims to provide a hydrogen storage alloy and its preparation method to solve at least one of the following technical problems existing in the prior art: (1) the hydrogen storage performance of TiFe deteriorates as the activation performance of TiFe increases after the addition of other metal elements; (2) the alloy has poor surface condition; and (3) the performance deteriorates after prolonged exposure to air after activation. This invention significantly improves the activation performance of the alloy and the surface condition of the alloy particles without significantly reducing the hydrogen storage capacity. The alloy's activation performance does not decrease significantly after being placed in air for 3 months.

[0007] The objective of this invention is mainly achieved through the following technical solutions:

[0008] On one hand, the present invention provides a hydrogen storage alloy comprising multiple rare earth elements Gd and Nd, transition metals Mn, Cu, and Zn, and its chemical formula is: Ti 1.2-x-y Gd x Nd y Fe 0.85 Mn 0.25-z-m Zn z Cu m In the chemical formula, x, y, z and m are atomic ratios, where 0.01≤x≤0.05, 0.01≤y≤0.05, 0.02≤z≤0.08, and 0.02≤m≤0.1.

[0009] Furthermore, the values ​​are 0.02≤x≤0.05, 0.02≤y≤0.05, 0.03≤z≤0.08, and 0.04≤m≤0.1.

[0010] Furthermore, the atomic ratio in the chemical formula is: x:y:z:m = 0.9-1.1:0.9-1.1:1.1-1.4:1.4-1.6.

[0011] Furthermore, the microstructure of the hydrogen storage alloy is a nanocrystalline structure.

[0012] Furthermore, the hydrogen storage alloy has refined grains with an average grain size of ≤25nm and no obvious agglomeration.

[0013] Furthermore, the hydrogen storage alloy is prepared by adding multiple rare earth elements Gd and Nd, transition metals Mn, Cu and Zn, and combining it with mechanical ball milling.

[0014] On the other hand, the present invention provides a method for preparing a hydrogen storage alloy, wherein the raw materials are induction heated and melted under an inert atmosphere to obtain an alloy ingot, and then mechanically ball-milled to obtain a hydrogen storage alloy.

[0015] Furthermore, the preparation method involves induction heating and melting of raw materials under an inert atmosphere to obtain an alloy ingot, followed by mechanical ball milling to obtain a hydrogen storage alloy.

[0016] Furthermore, the preparation method includes:

[0017] Step 1: According to the chemical formula Ti 1.2-x-y Gd x Nd y Fe 0.85 Mn 0.25-z-m Zn z Cu m Prepare the ingredients;

[0018] Step 2: Under an argon atmosphere, all elements are melted by induction heating to obtain a molten alloy;

[0019] Step 3: Pour the molten alloy into a copper mold to obtain a cast master alloy ingot;

[0020] Step 4: The as-cast master alloy ingot is mechanically crushed, vacuumed and filled with high-purity argon gas, and then mechanically ball-milled to obtain the hydrogen storage alloy.

[0021] Furthermore, in step 1, the prepared raw materials are placed in the zirconium oxide crucible in sequence, the pure iron rod is placed vertically along the crucible wall, and the other metal raw materials are added in the following order: blocky rare earth Gd and Nd are placed at the bottom of the crucible, sponge Ti is placed above rare earth Gd and Nd, electrolytic Mn is placed on top of sponge Ti, and finally electrolytic Cu and Zn are added.

[0022] Furthermore, in step 1, the proportion of Gd, Nd, Mn and Zn in the chemical formula is increased by 5%-10% to reduce the burn-off, and the metal purity of the raw materials is ≥99.5%.

[0023] Furthermore, in step 2, the conditions for induction heating melting are: evacuation, filling with 0.01-0.1 MPa of pure argon gas, and melting temperature of 1500-1650℃.

[0024] Furthermore, in step 2, the vacuum is evacuated to 1×10⁻⁶. -2 -5×10 -5 Pa.

[0025] Furthermore, in step 3, the alloy is kept at a molten state for 3-5 minutes before being poured into a copper mold.

[0026] Furthermore, in step 4, the as-cast master alloy ingot is mechanically crushed, passed through a 200-mesh sieve, and then loaded into a stainless steel ball mill jar along with stainless steel grinding balls for ball milling.

[0027] Furthermore, the ball milling conditions are as follows: ball milling for 0.5-2 hours in an all-around planetary high-energy ball mill, with a ball-to-material ratio of 1:20 and a rotation speed of 300-400 r / min.

[0028] Compared with the prior art, the present invention can achieve at least one of the following technical effects:

[0029] 1) This invention significantly increases the activation performance of the alloy by adding small amounts of multi-element rare earth elements and transition metals. The alloying process utilizes multi-element rare earth elements Gd and Nd, and transition metals Mn, Zn, and Cu. Through compositional design, this invention reduces the activation conditions and shortens the activation cycle of the TiFe alloy.

[0030] 2) By subjecting the as-cast master alloy ingot to short-term mechanical ball milling, and through scientific composition design and reasonable mechanical ball milling treatment, the alloy can obtain a special microstructure. Without forming an amorphous phase, the grain size of the alloy can be significantly reduced, with an average grain size ≤25nm. This forms nanocrystals with high defect density, increases the nucleation sites and diffusion channels for hydrogen, further reduces the thermal stability of the alloy, and improves its hydrogen absorption and desorption kinetics, thus obtaining a hydrogen storage material with excellent hydrogen absorption and desorption kinetics.

[0031] 3) In the hydrogen storage alloy of this invention, rare earth elements Gd and Nd are added in a near 1:1 ratio, which reduces segregation and ensures uniform dispersion of elements in the alloy matrix. The GdH3 and NdH3 nanocrystals generated after hydrogen absorption not only significantly increase grain boundaries and phase boundaries in the alloy but also serve as catalytic active centers. The CuZn phase generated after the addition of Zn and Cu helps improve the alloy's oxidation resistance and activation performance. The added Mn can react with Ti to form the TiMn2 phase, which not only increases the alloy's hydrogen absorption capacity but also improves the hydrogen diffusion rate within the alloy.

[0032] 4) The activated alloy obtained by this invention does not show significant degradation in its activation performance after being exposed to air at room temperature and pressure for three months, and can fully meet the needs of practical applications.

[0033] 5) The alloy surface of the present invention introduces high-density crystal defects, thus maintaining the activation performance of the alloy prepared by the present invention. Studies have shown that the grain size of TiFe is closely related to its hydrogen absorption activation performance; under the premise of maintaining a low degree of amorphization, the smaller the grain size, the better the activation performance.

[0034] Other features and advantages of the invention will be set forth in the following description, and in part will be obvious from the description or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0035] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0036] Figure 1 The XRD diffraction patterns of the as-cast alloys in Examples 1-6 are shown below.

[0037] Figure 2 The SEM morphology of the ball-milled powders of Examples 1-5 and Comparative Example 2 is shown.

[0038] Figure 3 The XRD patterns of the ball-milled alloys in Examples 1-6 are shown below.

[0039] Figure 4 The HRTEM morphology of the ball-milled alloys in Examples 1-5 and Comparative Example 2 is shown. Detailed Implementation

[0040] The following detailed description of a hydrogen storage alloy and its preparation method, with reference to specific embodiments, is provided. These embodiments are for comparative and illustrative purposes only, and the present invention is not limited to these embodiments.

[0041] This invention provides a hydrogen storage alloy, the chemical formula of which is: Ti 1.2-x- y Gd x Nd y Fe 0.85 Mn 0.25-z-m Zn z Cu m In the chemical formula, x, y, z and m are atomic ratios, where 0.01≤x≤0.05, 0.01≤y≤0.05, 0.02≤z≤0.08, and 0.02≤m≤0.1.

[0042] The following details the function and dosage selection of the components contained in this invention:

[0043] In the hydrogen storage alloy of this invention, rare earth elements Gd and Nd are added in a near 1:1 ratio, allowing them to be uniformly dispersed in the alloy matrix. The GdH3 and NdH3 nanocrystals generated after hydrogen absorption not only significantly increase grain boundaries and phase boundaries in the alloy but also serve as catalytic active centers. The CuZn phase generated after the addition of Zn and Cu helps improve the alloy's oxidation resistance and activation performance. The added Mn can react with Ti to form the TiMn2 phase, which not only increases the alloy's hydrogen absorption capacity but also improves the hydrogen diffusion rate within the alloy.

[0044] To further improve the overall performance of the aforementioned hydrogen storage alloy, its composition can be further adjusted. For example, in the chemical formula, 0.02≤x≤0.05, 0.02≤y≤0.05, 0.03≤z≤0.08, and 0.04≤m≤0.1.

[0045] Alloys within this range are more likely to form phases with small and uniform particle size, which is beneficial for improving the kinetic properties of the alloy.

[0046] The atomic ratio in the chemical formula is: x:y:z:m = 0.9-1.1:0.9-1.1:1.1-1.4:1.4-1.6. Alloys with this ratio are more likely to form a uniform multiphase structure during the smelting process, resulting in smaller grain size and more uniform grain distribution.

[0047] The hydrogen storage alloy has a nanocrystalline structure. This composition design facilitates the formation of fine and uniform phase distribution within the alloy. Further ball milling breaks down the grains, generating even finer nanocrystals.

[0048] The hydrogen storage alloy exhibits refined grains with an average grain size ≤25nm and no obvious agglomeration. This is determined by the composition design and ball milling parameters. The composition design and ball milling facilitate the formation of nanocrystals in the alloy, while limiting the ball milling time and speed effectively controls particle agglomeration and reduces the degree of amorphization.

[0049] Compared with existing technologies, this invention utilizes abundant and inexpensive Ti and Fe elements, facilitating large-scale industrial application. Multi-element alloying significantly improves the activation performance of TiFe alloys, especially with the addition of small amounts of rare earth elements, which significantly enhances activation performance, shortens incubation time, and noticeably increases hydrogen storage capacity. This is because rare earth elements readily react with hydrogen atoms to form highly stable rare earth hydrides GdH3 and NdH3, becoming the catalytic active centers of the alloy. The alloy possesses a multiphase structure, containing various intermetallic compounds in addition to the main TiFe phase. Ti and Mn form the TiMn2 phase, and Cu and Zn form the CuZn phase. These intermetallic compounds significantly enhance activation ability and increase hydrogen storage capacity because the TiMn2 phase itself can absorb a large amount of hydrogen.

[0050] This invention also provides a method for preparing a hydrogen storage alloy, comprising:

[0051] Step 1: According to the chemical formula Ti 1.2-x-y Gd x Nd y Fe 0.85 Mn 0.25-z-m Zn z Cu m Prepare the ingredients;

[0052] Step 2: Under an argon atmosphere, all elements are melted by induction heating to obtain a molten alloy;

[0053] Step 3: Pour the molten alloy into a copper mold to obtain a cast master alloy ingot;

[0054] Step 4: The as-cast master alloy ingot is mechanically crushed, vacuumed and filled with high-purity argon gas, and then mechanically ball-milled to obtain the hydrogen storage alloy.

[0055] Specifically, in step 1, rare earth metals Gd and Nd, sponge Ti, high-purity Fe, electrolytic Mn, Cu, and Zn are selected according to the chemical formulas of each embodiment. The purity of the selected raw materials is all higher than 99.5%. The surface oxide layer of the high-purity iron rod is removed by sanding. The rare earth metals Gd and Nd and electrolytic Mn and Zn are increased by 5 wt.% for burn-off during the preparation process to reduce the compositional fluctuation of the alloy.

[0056] Specifically, in step 2, the conditions for induction heating melting are: the vacuum induction melting furnace is evacuated to 1×10⁻⁶ before heating. -2 -5×10 -5 Pa; then, 0.01-0.1 MPa of inert argon gas is introduced into the furnace as a protective gas; the melting temperature is 1500-1650℃; the liquid master alloy is held at the molten state for 3-5 minutes.

[0057] Compared with existing technologies, this invention can prepare cast alloys with accurate composition and uniform element distribution by controlling parameters such as vacuum degree, argon gas pressure, melting temperature and holding time. This makes it easier to form alloy powders with small particle size and uniform distribution during subsequent ball milling, which is beneficial to improving the hydrogen storage performance of the alloy.

[0058] Specifically, in step 3, the molten alloy is poured into a copper mold to obtain a cast master alloy ingot.

[0059] Specifically, in step 4, the ingot alloy is mechanically crushed and passed through a 200-mesh sieve, with a particle size of approximately 75 μm. The alloy powder is then loaded into a stainless steel ball mill jar along with stainless steel grinding balls and milled in an all-around planetary high-energy ball mill for 0.5-2 hours at a ball-to-material ratio of 1:20 and a rotation speed of 350 r / min to obtain the alloy powder described in this invention.

[0060] To prevent the alloy powder from overheating, the ball mill is stopped for 10 minutes every 0.5 hours of operation, and then ball milling is carried out for another 0.5 hours. This process is repeated until the ball milling time reaches the specified value.

[0061] Compared with the prior art, in terms of alloy preparation, the present invention significantly reduces the grain size of the alloy and controls the particle size of the alloy powder by mechanical ball milling. At the same time, by limiting the ball milling time and speed, the density of grain boundaries and defects in the alloy is greatly increased. This provides a channel for the rapid diffusion of hydrogen atoms inside the alloy. Therefore, while improving the activation performance, the hydrogen absorption / desorption kinetics of the alloy are significantly improved.

[0062] The hydrogen storage alloy prepared by the above method has a nanocrystalline structure, with refined grains, an average grain size ≤25nm, and no obvious agglomeration. Figure 4 As shown, nanocrystals with high defect density are formed, resulting in a hydrogen storage material with excellent hydrogen absorption and desorption kinetics.

[0063] The phase structure of the as-cast and ball-milled powders was determined by XRD. The morphology and microstructure of the ball-milled alloy particles were observed by high-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM), and the crystal state of the alloy was determined by selected area electron diffraction (SAED). The hydrogen absorption activation performance, hydrogen storage capacity, and hydrogen absorption and desorption kinetics of the alloy powder were tested using a semi-automatic Sieverts system. The hydrogen absorption temperature was 30℃, and the initial hydrogen pressure was 3 MPa; the hydrogen desorption temperature was 30℃, and the hydrogen desorption rate was 1 × 10⁻⁶ MPa. -4 The test was conducted at a pressure of MPa.

[0064] The advantages of precise control of the composition and process parameters of the hydrogen storage alloy of the present invention will be demonstrated below with specific embodiments and comparative examples.

[0065] Example 1: Ti 1.12 Gd 0.04 Nd 0.04 Fe 0.85 Mn 0.14 Zn 0.05 Cu 0.06 (Ball milling for 0.5 hours);

[0066] The preparation method is as follows:

[0067] According to the chemical formula Ti 1.12 Gd 0.04 Nd 0.04 Fe 0.85 Mn 0.14 Zn 0.05 Cu 0.06Bulk rare earth metals Gd and Nd, sponge Ti, high-purity Fe, electrolytic Mn, metallic Cu, and Zn were selected. These metals had a purity of 99.5% and were weighed according to stoichiometric ratios. The weights were: sponge Ti 419.1 g, pure Fe 371.1 g, rare earth Gd 51.6 g, rare earth Nd 47.4 g, electrolytic Mn 63.1 g, metallic Cu 29.8 g, and metallic Zn 26.8 g. The weighed bulk metals were placed in a zirconia crucible within a medium-frequency induction furnace according to the designed process. A pure iron rod was placed vertically along the crucible wall. Bulk rare earth Gd and Nd were placed at the bottom of the crucible, sponge Ti was placed above the rare earth Gd and Nd, electrolytic Mn was placed on top of the sponge Ti, and finally Cu and Zn were added.

[0068] Then cover the furnace and evacuate for approximately 30 minutes until the vacuum level reaches 5×10⁻⁶. -2 Above Pa, high-purity argon protective gas is then introduced until the pressure reaches 0.04 MPa. The heating temperature is adjusted to about 1650℃ to melt all the raw material metals. The molten liquid metal is kept at this temperature for 5 minutes to ensure uniformity.

[0069] The uniformly mixed liquid metal is then poured into a cylindrical copper mold with a diameter of 30 mm and a depth of 80 mm. After cooling to room temperature in a furnace, it is removed to obtain a master alloy ingot.

[0070] Ti alloy 1.12 Gd 0.04 Nd 0.04 Fe 0.85 Mn 0.14 Zn 0.05 Cu 0.06 After the ingot is mechanically crushed and passed through a 200-mesh sieve, 20 grams of the sieved alloy powder and 400 grams of stainless steel grinding balls are weighed and placed together in a 250 ml stainless steel ball mill jar. The jar is then evacuated, filled with high-purity argon, and sealed. The jar is then ball-milled in an all-around planetary high-energy ball mill for 0.5 hours.

[0071] Example 2: Ti 1.14 Gd 0.03 Nd 0.03 Fe 0.85 Mn 0.14 Zn 0.05 Cu 0.06 (Ball milling for 1.0 h);

[0072] The preparation method of Example 2 is similar to that of Example 1, except that the quality of each raw material is adjusted according to the different alloy composition, and the ball milling time is also adjusted to 1.0 h. To prevent the alloy powder from overheating, the ball mill is stopped for 10 min every 0.5 h of operation, and then ball milling is carried out for another 0.5 h. This process is repeated until the ball milling time reaches the specified value.

[0073] Example 3: Ti1.16 Gd 0.02 Nd 0.02 Fe 0.85 Mn 0.14 Zn 0.05 Cu 0.06 (Ball milling for 1.5 hours);

[0074] The preparation method of Example 3 is similar to that of Example 1, except that the quality of each raw material is adjusted according to the different alloy compositions, and the ball milling time is also adjusted to 1.5 hours. To prevent the alloy powder from overheating, the ball mill is stopped for 10 minutes every 0.5 hours of operation, and then ball milling is carried out for another 0.5 hours. This process is repeated until the ball milling time reaches the specified value.

[0075] Example 4: Ti 1.1 Gd 0.05 Nd 0.05 Fe 0.85 Mn 0.14 Zn 0.05 Cu 0.06 (Ball milling for 2.0 hours);

[0076] The preparation method of Example 4 is similar to that of Example 1, except that the quality of each raw material is adjusted according to the different alloy composition, and the ball milling time is adjusted to 2.0 h. To prevent the alloy powder from overheating, the ball mill is stopped for 10 min every 0.5 h of operation, and then ball milling is carried out for another 0.5 h. This process is repeated until the ball milling time reaches the specified value.

[0077] Example 5: Ti 1.12 Gd 0.04 Nd 0.04 Fe 0.85 Mn 0.21 Zn 0.03 Cu 0.1 (Ball milling for 0.5 hours + exposure for 3 months);

[0078] The preparation method of Example 5 is similar to that of Example 1, except that the quality of each raw material is adjusted according to the different alloy composition. The ball milling time is 0.5 h. The ball-milled alloy powder is activated (by performing one hydrogen absorption and desorption cycle at 30 °C using a semi-automatic Siefts device). Finally, it is exposed to air for 3 months to obtain Example 5.

[0079] Example 6: Ti 1.12 Gd 0.04 Nd 0.04 Fe 0.85 Mn 0.13 Zn 0.08 Cu 0.04 (Ball milling for 1.5 hours + exposure for 3 months);

[0080] The preparation method of Example 6 is similar to that of Example 1, except that the quality of each raw material is adjusted according to the different alloy composition. The ball milling time is 1.5 hours. The ball-milled alloy powder is activated (by performing one hydrogen absorption and desorption cycle at 30°C using a semi-automatic Siefts device). Finally, it is exposed to air for 3 months to obtain Example 6.

[0081] Comparative Example 1: Ti 1.2 Fe 0.8 Mn 0.2 (As-cast state);

[0082] According to the chemical formula Ti 1.2 Fe 0.8 Mn 0.2 Sponge Ti, high-purity Fe, and electrolytic Mn were selected. These metals had a purity of 99.5% and were weighed according to their stoichiometric ratios. The weights were: 419.1 g of sponge Ti, 371.1 g of pure Fe, and 63.1 g of electrolytic Mn. The weighed bulk metals were placed in a zirconia crucible in a medium-frequency induction furnace according to the designed process. A pure iron rod was placed vertically along the crucible wall, the sponge Ti was placed at the bottom of the crucible, and the electrolytic Mn was placed on top of the sponge Ti.

[0083] Then cover the furnace and evacuate for approximately 30 minutes until the vacuum level reaches 5×10⁻⁶. -2 Above Pa, high-purity argon protective gas is then introduced until the pressure reaches 0.04 MPa. The heating temperature is adjusted to about 1650℃ to melt all the raw material metals. The molten liquid metal is kept at this temperature for 5 minutes to ensure uniformity.

[0084] The uniformly mixed liquid metal is then poured into a cylindrical copper mold with a diameter of 30 mm and a depth of 80 mm. After cooling to room temperature in a furnace, it is removed to obtain a master alloy ingot.

[0085] Comparative Example 2: Ti 1.12 Gd 0.04 Nd 0.04 Fe 0.85 Mn 0.14 Zn 0.05 Cu 0.06 (Ball milling for 10 hours);

[0086] Ti is prepared according to the method in Example 1. 1.12 Gd 0.04 Nd 0.04 Fe 0.85 Mn 0.14 Zn 0.05 Cu 0.06After ball milling the alloy powder for 0.5 hours, the mill was not stopped to remove the material, and ball milling continued for 9.5 hours. During the ball milling process, the ball mill was stopped for 10 minutes every 0.5 hours, and then ball milled for another 0.5 hours to prevent the alloy powder from overheating. This process was repeated until the total ball milling time reached 10 hours, thus obtaining Comparative Example 2.

[0087] Figure 1 The XRD patterns of the as-cast alloys in Examples 1-6 show that alloying with rare earth elements Gd, Nd, Mn, Cu, and Zn results in a multiphase structure. Besides the main TiFe phase, various intermetallic compounds, including TiMn2 and CuZn phases, are present. The increased number of phases leads to the formation of more grain boundaries and phase boundaries, while Gd and Nd absorb hydrogen and form nanocrystals in situ. These nanocrystals not only serve as catalytic active centers but also act as pinning agents, limiting grain growth. All of these factors contribute to improving the activation performance of the alloy.

[0088] Figure 2 The SEM morphology of the ball-milled alloys in Examples 1-5 and Comparative Example 2 shows that the alloy particles with ball-milling times of 0.5-2 hours exhibited good dispersion and no obvious agglomeration, which is clearly related to the shorter ball-milling time. However, the alloy powder of Comparative Example 2, with a long ball-milling time (10 hours), showed obvious agglomeration, which is detrimental to alloy activation. Therefore, the ball-milling scheme in this invention, while ensuring sufficiently fine particle size, can effectively prevent grain agglomeration, thereby effectively improving the activation performance of the alloy, saving costs, and reducing preparation difficulty.

[0089] Figure 3 The XRD patterns of the ball-milled alloys in Examples 1-6 show that ball milling significantly broadens the diffraction peaks of the alloys. This is clearly due to the lattice stress and grain refinement generated after ball milling, which has a positive effect on improving the activation performance of the alloys.

[0090] Figure 4 The HRTEM morphology of the ball-milled alloys in Examples 1-5 and Comparative Example 2 shows that the alloys ball-milled for 0.5-2 hours have a nanocrystalline structure and contain numerous grain boundaries and phase boundaries, which are beneficial for improving the activation performance of the alloy. However, prolonged ball milling (10 hours) will cause the appearance of an amorphous phase in the alloy, reducing its activation performance and hydrogen storage capacity.

[0091] The average particle size of the alloy powder was measured using a HELOS & RODOS laser particle size analyzer. The hydrogen absorption activation performance, hydrogen absorption and release capacity, and kinetics of the alloy powder were tested using a fully automated Siefverts system. The results are shown in Table 1.

[0092] Table 1. Particle size and hydrogen storage performance of alloys from different embodiments and comparative examples.

[0093]

[0094] The above results indicate that alloy powders ball-milled for 0.5-2 hours have excellent activation properties and high hydrogen absorption capacity. In particular, their ability to maintain activation capacity even after prolonged exposure to air is an advantage not possessed by other alloys.

[0095] Compared with Comparative Example 1, which did not contain Gd, Nd, Zn and Mn, the average particle size of Examples 1-6 was significantly reduced, the activation temperature was significantly reduced (30°C), and the number of activations required was significantly reduced (1 time). This indicates that the composition design of the present invention is reasonable and can greatly improve the activation performance of TiFe alloys.

[0096] By comparing Comparative Example 2, which had a ball milling time of 10 hours, and Examples 1-6, it can be found that the average particle size of Comparative Example 2 increased slightly, the number of activations required increased (3 times), and the hydrogen storage capacity decreased significantly (1.51 wt.%). This is because the excessively long ball milling time caused the alloy particles to agglomerate, and a large number of amorphous phases appeared inside the alloy, resulting in a decrease in the activation performance and hydrogen storage capacity of the alloy.

[0097] Clearly, the alloy preparation process of this invention is simple and easy to operate, fully suitable for large-scale production, and its performance meets the requirements of various applications for hydrogen storage materials. Compared with similar alloys at home and abroad, the hydrogen storage performance of the alloy of this invention is significantly improved, exhibiting obvious advantages.

[0098] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A hydrogen storage alloy, characterized in that, The chemical formula of the hydrogen storage alloy is: Ti 1.2-x- y Gd x Nd y Fe 0.85 Mn 0.25-z-m Zn z Cu m In the chemical formula, x, y, z, and m are atomic ratios, wherein 0.01≤x≤0.05, 0.01≤y≤0.05, 0.02≤z≤0.08, and 0.02≤m≤0.1; the microstructure of the hydrogen storage alloy is a nanocrystalline structure, the grains of the hydrogen storage alloy are refined, the average grain size is ≤25nm, and there is no obvious agglomeration phenomenon; the hydrogen storage alloy is obtained by mechanically ball milling the alloy ingot for 0.5-2 hours.

2. The hydrogen storage alloy according to claim 1, characterized in that, The values ​​are 0.02≤x≤0.05, 0.02≤y≤0.05, 0.03≤z≤0.08, and 0.04≤m≤0.

1.

3. The hydrogen storage alloy according to claim 1, characterized in that, The atomic ratio in the chemical formula is: x:y:z:m = 0.9-1.1:0.9-1.1:1.1-1.4:1.4-1.

6.

4. A method for preparing a hydrogen storage alloy according to any one of claims 1-3, characterized in that, The preparation method involves induction heating and melting of raw materials under an inert atmosphere to obtain an alloy ingot, followed by mechanical ball milling to obtain a hydrogen storage alloy. The ball milling conditions are as follows: ball milling in an all-around planetary high-energy ball mill for 0.5-2 hours, with a ball-to-material ratio of 1:20 and a rotation speed of 300-400 r / min.

5. The method for preparing the hydrogen storage alloy according to claim 4, characterized in that, The preparation method includes: Step 1: According to the chemical formula Ti 1.2-x-y Gd x Nd y Fe 0.85 Mn 0.25-z-m Zn z Cu m Prepare the ingredients; Step 2: Under an argon atmosphere, all elements are melted by induction heating to obtain a molten alloy; Step 3: Pour the molten alloy into a copper mold to obtain a cast master alloy ingot; Step 4: The as-cast master alloy ingot is mechanically crushed, vacuumed and filled with high-purity argon gas, and then mechanically ball-milled to obtain the hydrogen storage alloy.

6. The method for preparing the hydrogen storage alloy according to claim 5, characterized in that, In step 2, the conditions for induction heating melting are: evacuation, filling with 0.01-0.1 MPa of pure argon gas, and melting temperature of 1500-1650℃.

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