High capacity easily activated ti-zr-pr-mn-cr-co-al system ab2 type hydrogen storage alloy and preparation method

Abstract

This invention belongs to the technical field of solid-state hydrogen storage alloy materials, and specifically provides a high-capacity, easily activated Ti-Zr-Pr-Mn-Cr-Co-Al AB2-type hydrogen storage alloy for various scenarios such as fuel cells, and its preparation method. The chemical formula of the hydrogen storage alloy is: (Ti 1‑x‑y Zr x Pr y ) 1.1 Mn 2‑z‑m Cr z Co m Al n In the formula, x, y, z, m, and n are atomic ratios, and 0.15 ≤ x ≤ 0.35, 0.01 ≤ y ≤ 0.05, 0.35 ≤ z ≤ 0.85, 0.1 ≤ m ≤ 0.3, and 0.05 ≤ n ≤ 0.15. Alloying with metallic elements Zr, Cr, Co, Al, and rare earth element Pr significantly improves the alloy's activation performance and plateau characteristics, significantly reduces plateau hysteresis, and ensures that the alloy's hydrogen absorption and desorption plateau pressure meets the application requirements of various scenarios such as fuel cells. In particular, the absence of precious metals such as V in the alloy significantly reduces the cost of raw materials. The addition of Pr significantly improves the alloy's room temperature activation performance and increases its reversible hydrogen storage capacity. The addition of Co and Al significantly improves the alloy's hydrogen absorption and desorption kinetics and activation performance, significantly enhances the alloy's resistance to pulverization, and improves the alloy's cycle stability.

Description

Technical Field

[0001] This invention belongs to the field of solid hydrogen storage alloy material technology, and in particular provides a high-capacity, easily activated Ti-Zr-Pr-Mn-Cr-Co-Al AB2 type hydrogen storage alloy for various scenarios such as fuel cells, and its preparation method. Background Technology

[0002] Hydrogen is an ideal energy source with wide availability, abundant reserves, diverse utilization methods, high calorific value, and pollution-free combustion products. Efficient and safe hydrogen storage is a crucial step in hydrogen energy utilization. Generally, increasing the storage pressure can increase hydrogen density, but this increases compression energy consumption and places higher demands on the pressure resistance of the storage container, leading to a sharp rise in costs. Cryogenic liquid hydrogen storage is a method of storing liquid hydrogen in insulated containers, offering high hydrogen density (greater than 50 kg H₂ m³). −3 While solid hydrogen storage offers advantages, its liquefaction process is energy-intensive, requires high-performance containers, and poses safety hazards due to hydrogen evaporation and leakage. Solid hydrogen storage utilizes materials to absorb hydrogen through physical or chemical absorption to form hydrides, thus achieving solid storage. Because hydrogen exists in the form of solid hydrides, solid hydrogen storage methods offer advantages such as high volumetric density (greater than 50 kg H₂ m³). −3 Solid-state hydrogen storage offers several advantages. Furthermore, it operates at lower pressures (less than 10 MPa) and produces hydrogen with higher purity. Therefore, solid-state hydrogen storage is an excellent choice for hydrogen energy applications. Since solid-state hydrogen storage technology largely depends on the hydrogen absorption and desorption performance of the storage materials, the research and development of high-performance hydrogen storage materials is a major focus in the development of solid-state hydrogen storage technology.

[0003] Among numerous hydrogen storage material systems, Ti-Mn-based AB2-type hydrogen storage alloys are among the few that can be practically applied. Ti-Mn-based AB2-type hydrogen storage alloys possess characteristics such as relatively high hydrogen storage capacity, easy activation, fast hydrogen absorption and desorption rates, a wide adjustable range of hydrogen absorption and desorption plateau pressures, and good cycle performance. They are a key research direction in the field of solid-state hydrogen storage. However, because the gravitational hydrogen storage density of Ti-Mn-based AB2-type hydrogen storage alloys is still relatively low for vehicle applications, they are more suitable for static scenarios. In fact, Ti-Mn-based AB2-type hydrogen storage alloys have shown good applications in high-density hydrogen storage and static compressed hydrogen. Hydrogen storage systems based on Ti-Mn-based AB2-type hydrogen alloys have been applied in renewable energy hydrogen production and integrated hydrogen storage and compression at hydrogen refueling stations. However, existing Ti-Mn-based AB2-type hydrogen storage alloys suffer from problems such as high activation conditions (i.e., difficult activation at room temperature), long activation cycles, poor plateau characteristics with significant hysteresis, unstable product performance, and high preparation costs.

[0004] To improve the overall hydrogen storage performance of TiMn-based AB2-type hydrogen storage alloys, reduce their hysteresis effect, and enhance their plateau characteristics, transition metal elements are typically used to partially replace elements on the A and B sides, and the proportions of these elements are adjusted to regulate the hydrogen storage performance of the Ti-Mn-based hydrogen storage alloys. For elements on the A side, Zr, Hf, Sc, etc., are generally used to replace some of the Ti elements in the alloy. Results show that Zr can change the affinity between hydrogen and the alloy, increase the lattice constant of the alloy crystal, thereby effectively reducing the hydrogen absorption and desorption plateau pressure, decreasing the plateau slope, and improving the hydrogen storage performance of the alloy. In particular, recent studies have shown that replacing Ti elements on the A side with trace amounts of rare earth elements (La, Ce, Y, Pr, Sm, etc.) can significantly improve the activation performance of the alloy, reduce the plateau pressure, and increase the hydrogen storage capacity of the alloy. For elements on the B side, transition metal elements such as Cr, Fe, V, Co, W, Ni, Cu, Mo, as well as other elements such as Si and Al, are typically used to partially replace Mn. Studies have found that Cr can effectively reduce the hysteresis effect of hydrogen absorption and dehydrogenation plateaus in Ti-Mn-based AB2 alloys, but the hydrogen absorption and dehydrogenation plateaus become shorter, resulting in a decrease in hydrogen absorption capacity. Appropriate substitution of Mn with other elements has a positive effect on improving the hydrogen storage performance of the alloy, particularly in terms of activation properties.

[0005] Studies have found that the hydrogen storage performance of alloys is closely related not only to their chemical composition but also to their phase structure, phase abundance, and microstructural parameters related to the alloy production process (such as particle morphology, chemical composition homogeneity, and grain size). To date, alloy smelting has been the most commonly used method for preparing hydrogen storage alloys in many studies. For ingots prepared using common methods such as arc melting and induction melting, segregation inevitably occurs during the solidification process, especially in alloys produced on a large scale, where compositional segregation is more pronounced. The traditional method involves prolonged high-temperature diffusion annealing of the cast alloy ingots to achieve compositional homogenization. While effective, this method is time-consuming, labor-intensive, and consumes a large amount of electricity, significantly increasing production costs. New processes with extremely rapid cooling rates, such as melt quenching and gas atomization, along with mechanical alloying methods, can produce ingots and powders with better chemical homogeneity and smaller grain size than those synthesized by traditional casting methods. This significantly improves the overall hydrogen storage performance of the alloys, particularly hydrogen absorption / desorption kinetics and cycle stability.

[0006] This invention employs an A-side stoichiometric design, partially replacing Ti on the A-side with Zr and Pr, and partially replacing Mn on the B-side with Cr, Co, and Al. The most prominent feature of the alloy composition is the absence of the precious metal V. By adding trace amounts of rare earth Pr and the metallic elements Co and Al, the hydrogen storage performance of the alloy is improved, achieving the expected experimental results. In terms of preparation technology, a vacuum induction melting-rapid quenching integrated technology is applied, avoiding compositional segregation during the solidification process and obtaining a microstructure with ultrafine grains. This significantly improves the overall hydrogen storage performance of the alloy, meeting the requirements of various application scenarios, especially vehicle fuel cells. A key finding of this invention is that the combination of multi-element joint substitution and rapid quenching processes can more effectively improve the activation performance of Ti-Mn-based AB2 alloys, regulate their plateau pressure, improve plateau characteristics, and enhance the alloy's hydrogen absorption and desorption kinetics and cycle stability. Compared with traditional V-containing alloys, the raw material cost of the alloy is significantly reduced, demonstrating a clear competitive advantage in the field of solid-state hydrogen storage. Summary of the Invention

[0007] The present invention aims to provide a high-capacity, easily activated Ti-Zr-Pr-Mn-Cr-Co-Al AB2-type hydrogen storage alloy and its preparation method, in order to solve the problems of existing Ti-Mn-based AB2-type hydrogen storage alloys, such as high activation conditions (i.e., difficult to activate at room temperature), long activation cycle, poor plateau characteristics and large hysteresis, unstable product performance and high preparation cost.

[0008] To improve the overall hydrogen storage performance of TiMn-based AB2-type hydrogen storage alloys, reduce their hysteresis effect, and enhance their plateau characteristics, transition metal elements are used to partially replace elements on the A and B sides, and the proportions of these elements are adjusted to regulate the hydrogen storage performance of the Ti-Mn-based hydrogen storage alloys. For elements on the A side, Zr, Hf, Sc, etc., are generally used to replace some of the Ti elements in the alloy. Results show that Zr can alter the affinity between hydrogen and the alloy, increase the lattice constant of the alloy crystal, thereby effectively reducing the hydrogen absorption and desorption plateau pressure, decreasing the plateau slope, and improving the hydrogen storage performance of the alloy. In particular, recent studies have shown that replacing Ti elements on the A side with trace amounts of rare earth elements (La, Ce, Y, Pr, Sm, etc.) can significantly improve the activation performance of the alloy, reduce the plateau pressure, and increase the hydrogen storage capacity. For elements on the B side, transition metal elements such as Cr, Fe, V, Co, W, Ni, Cu, Mo, as well as other elements such as Si and Al, are typically used to partially replace Mn. Studies have found that Cr can effectively reduce the hysteresis effect of hydrogen absorption and dehydrogenation plateaus in Ti-Mn-based AB2 alloys, but the hydrogen absorption and dehydrogenation plateaus become shorter, resulting in a decrease in hydrogen absorption capacity. Appropriate substitution of Mn with other elements has a positive effect on improving the hydrogen storage performance of the alloy, particularly in terms of activation properties.

[0009] The inventors discovered that the hydrogen storage performance of an alloy is closely related not only to its chemical composition but also to its phase structure, phase abundance, and microstructural parameters related to the alloy production process (such as particle morphology, chemical composition homogeneity, and grain size). In many studies, alloy smelting has been the most commonly used method for preparing hydrogen storage alloys. For ingots prepared using common methods such as arc melting and induction melting, segregation inevitably occurs during the solidification process, especially in alloys produced on a large scale, where compositional segregation is more pronounced. The traditional method involves prolonged high-temperature diffusion annealing of the cast alloy ingot to achieve compositional homogenization. While effective, this method is time-consuming, labor-intensive, and consumes a large amount of electricity, significantly increasing production costs. New processes with extremely rapid cooling rates, such as melt quenching and gas atomization, along with mechanical alloying methods, can produce ingots and powders with better chemical homogeneity and smaller grain size than those synthesized by traditional casting methods. This significantly improves the overall hydrogen storage performance of the alloy, particularly its hydrogen absorption / desorption kinetics and cycle stability.

[0010] This invention employs an A-side stoichiometric design, partially replacing Ti on the A-side with Zr and Pr, and partially replacing Mn on the B-side with Cr, Co, and Al. The most prominent feature of the alloy composition is the absence of the precious metal V. By adding trace amounts of rare earth Pr and the metallic elements Co and Al, the hydrogen storage performance of the alloy is improved, achieving the expected experimental results. In terms of preparation technology, a vacuum induction melting-rapid quenching integrated technology is applied, avoiding compositional segregation during the solidification process and obtaining a microstructure with ultrafine grains. This significantly improves the overall hydrogen storage performance of the alloy, meeting the requirements of various application scenarios, especially vehicle fuel cells. A key finding of this invention is that the combination of multi-element joint substitution and rapid quenching processes can more effectively improve the activation performance of Ti-Mn-based AB2 alloys, regulate their plateau pressure, improve plateau characteristics, and enhance the alloy's hydrogen absorption and desorption kinetics and cycle stability. Compared with traditional V-containing alloys, the raw material cost of the alloy is significantly reduced, demonstrating a clear competitive advantage in the field of solid-state hydrogen storage.

[0011] Therefore, the first aspect of this invention provides a high-capacity, easily activated Ti-Zr-Pr-Mn-Cr-Co-Al type AB2 hydrogen storage alloy, wherein the chemical formula of the hydrogen storage alloy is: (Ti 1-x-y Zr x Pr y ) 1.1 Mn 2-z-m Cr z Co m Al nIn the formula, x, y, z, m, and n are atomic ratios, and 0.15 ≤ x ≤ 0.35, 0.01 ≤ y ≤ 0.05, 0.35 ≤ z ≤ 0.85, 0.1 ≤ m ≤ 0.3, and 0.05 ≤ n ≤ 0.15. The preferred ratio of x, y, z, and m is x: y: z: m: n = 0.25: 0.03: 0.75: 0.15: 0.1.

[0012] Specifically, the hydrogen storage alloy has a nanocrystalline structure with an average grain size of 50-200 nm. The hydrogen storage alloy has a single-phase structure containing a C14-type Laves phase and exhibiting a MgZn2 structure. C14 is a Strukturbericht (structure report) classification symbol, proposed by a German crystallographer in the 1930s for systematically naming crystal structure types. The letter C represents a binary compound (AB2 type). The number 14 represents the 14th specific variant of this type of structure. The Laves phase is named after Fritz Laves's foundational research on the AB2 close-packed structure. He first systematically studied the crystal geometry of AB2-type intermetallic compounds in the 1930s–1940s. In honor of his pioneering work, this type of structure is collectively referred to as Laves Phases. The C14 Laves phase is a hexagonal intermetallic compound, typically represented by MgZn2, and is therefore also called the MgZn2-type structure. The general chemical formula is AB2, where A atoms are larger metal atoms (such as Mg, Ti, Zr, V), and B atoms are smaller metal atoms (such as Zn, Mn, Cr, Fe). Its crystal structure is as follows: Crystal system: Hexagonal; Space group: P63 / mmc; Cell parameters: A typical cell contains 12 atoms (4 A atoms + 8 B atoms). A atoms occupy the vertices and center of the bottom face of the hexagonal lattice, with a coordination number of 16 (surrounded by 16 B atoms). B atoms form a twisted tetrahedral network, with a coordination number of 12 (6 A atoms + 6 B atoms). The atomic layers are stacked in a specific sequence (such as ABACABAC...), exhibiting characteristics derived from hexagonal close-packed (HCP).

[0013] The second invention also provides a method for preparing the hydrogen storage alloy, specifically including the following steps:

[0014] S1: The dosage is calculated according to the chemical formula composition and the ingredients are prepared, with appropriate amounts of Mn and Pr added for burn-off.

[0015] S2: Place the prepared raw materials in an Al2O3 crucible, cover the furnace, evacuate to the preset vacuum level, and then fill with high-purity Ar gas at a certain pressure as a protective gas. Heat the raw materials to a molten state using a medium-frequency induction heating method. After holding the temperature for a period of time, obtain a liquid master alloy with uniform composition.

[0016] S3: Liquid master alloy is directly injected into an tundish with NB nozzles embedded at the bottom. The liquid alloy is continuously sprayed from the narrow slits of the NB nozzles at the bottom of the tundish onto the surface of a rotating water-cooled copper roller, resulting in a uniform alloy strip. This method enables rapid solidification of liquid metal or alloy; therefore, in the metallurgical industry, this process is called rapid solidification or rapid quenching, and the surface linear velocity of the rotating copper roller is called the quenching rate.

[0017] Furthermore, in step S1, the amount of Mn and Pr added is 3%-5% of the calculated dosage.

[0018] Furthermore, the placement and specific operations of each raw material in step S2 are as follows: All raw materials Ti, Zr, Pr, Mn, Cr, Co, and Al are cleaned with specialized raw material surface cleaning equipment to remove surface impurities and oxide scale. The crucible must be cleaned with high-purity Fe before melting the alloy to remove surface impurities. All raw materials are placed in the Al2O3 crucible in sequence, with rare earth Pr placed at the bottom, sponge Ti and Zr mixed and placed on top of the rare earth Pr, Cr and Co placed on top of the sponge Ti and Zr, and electrolytic Mn and Al placed on top.

[0019] Furthermore, in step S2, the smelting process employs a power-incrementing melting and refining process. Specifically, the power is increased by 5 kW every 5 minutes after melting for approximately 10 minutes at a power of 10 kW, until a power of 40 kW is reached. After all raw materials have melted, the mixture is held at approximately 1550°C in a molten state for 3-5 minutes to ensure complete homogenization of the liquid alloy composition. This power-incrementing method creates varying electromagnetic stirring forces within the molten raw materials, enhancing the electromagnetic stirring effect, improving smelting efficiency, promoting alloy composition homogenization, and most importantly, significantly increasing the yield of the smelted alloy.

[0020] Further, the rapid quenching operation in step S3 is as follows: Adjust the power supply of the melting furnace to approximately 30 kW, maintain the liquid alloy temperature at approximately 1450°C, and directly inject the liquid master alloy into the tundish with NB nozzles embedded at the bottom. Under the action of gravity, the liquid alloy is continuously sprayed from the narrow slit of the NB nozzles at the bottom of the tundish onto the surface of the rotating water-cooled copper roller. The linear velocity of the rapid quenching roller surface is 3–15 m / s. The water inlet flow rate of the copper roller is ≥20 m³ / s. 3The process involves cooling the alloy to room temperature at a rate of 100–300 μm to obtain rapidly quenched alloy sheets. Determining the appropriate quenching rate (linear velocity of the copper roller surface) is a key technical parameter. A suitable quenching rate ensures that the rapidly quenched alloy strip has an almost complete nanocrystalline structure with a grain size between 50 and 200 nm.

[0021] Beneficial effects:

[0022] The advantages of this invention lie in its A-side overstoichiometry composition design, which significantly improves the hydrogen absorption capacity and activation performance of the alloy. Alloying with metallic elements Zr, Cr, Co, Al, and rare earth element Pr significantly improves the alloy's activation performance and plateau characteristics, significantly reduces plateau hysteresis, and ensures that the alloy's hydrogen absorption / desorption plateau pressure meets the application requirements of various scenarios such as fuel cells. In particular, the absence of precious metals such as V in the alloy significantly reduces the cost of raw materials. The addition of Pr significantly improves the alloy's room temperature activation performance and increases its reversible hydrogen storage capacity. The addition of Co and Al significantly improves the alloy's hydrogen absorption / desorption kinetics and activation performance, significantly enhances its resistance to pulverization, and improves its cycle stability. Furthermore, the addition of Co significantly improves the alloy's plateau characteristics.

[0023] In terms of preparation technology, an integrated vacuum induction melting-rapid quenching technology is adopted. The advantage of this technology is that melting and rapid quenching are completed in one step, completely suppressing component segregation during solidification. Simultaneously, rapid quenching generates an internal stress state and reduces microscopic crystal defects conducive to activation, significantly improving the alloy's hydrogen storage performance. This eliminates the complex processes of alloy melting, casting, and annealing, significantly improving the alloy's yield and performance stability, and substantially reducing preparation costs. Attached Figure Description

[0024] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0025] In the attached diagram:

[0026] Figure 1 Seven sets of phase diagrams for different binary alloy systems are used primarily to aid in alloy composition design. (a) Ti-Mn system; (b) Ti-Zr system; (c) Zr-Mn system; (d) Pr-H system; (e) Ti-Cr system; (f) Zr-Cr system; (g) Zr-Co system;

[0027] Figure 2 This is a rapidly quenched alloy sheet from Example 1.

[0028] Figure 3The XRD diffraction patterns of the rapidly quenched alloys in Examples 1-6 are shown.

[0029] Figure 4 The SEM morphology of the horizontal and longitudinal sections of the rapid quenching thin strip in Example 1 is shown.

[0030] Figure 5 The following are the SEM morphology, EDS elemental distribution map, and energy spectrum of the rapidly quenched thin strip in Example 1: (a) Morphology of the rapidly quenched strip; (bi) EDS elemental distribution map; (jk) EDS energy spectrum of different regions. Detailed Implementation

[0031] It should be noted that the above-mentioned technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of the present invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of the present invention can be realized and obtained from the content particularly pointed out in the description and drawings.

[0032] The design concept and mechanism of the present invention will be described in further detail below to make the technical solution of the present invention clearer.

[0033] Ti-Mn-based AB2 alloys possess higher capacity (≈2%) than rare-earth AB5 alloys, better room-temperature hydrogen storage performance and kinetics than magnesium-based alloys, and better activation performance than Ti-Fe-based alloys. Therefore, they are considered the most promising solid-state hydrogen storage materials. However, some problems still exist in the practical application of Ti-Mn-based AB2 alloys. These mainly include difficulties in alloy activation, significant plateau tilt, and large hysteresis. Traditional preparation methods tend to result in Ti enrichment, poor compositional uniformity, and low yield in large-scale preparations.

[0034] Studies have found that the difficulty in activating the alloy is mainly due to the presence of highly reactive titanium (Ti), which, upon contact with air during the preparation process, forms a titanium oxide film on the alloy surface. The activation process includes: 1) removal of the protective oxide film, 2) dissociation of hydrogen molecules on the metal surface, and 3) diffusion of dissociated hydrogen atoms into the alloy interior through the surface and their interaction with the metal to form hydrides. Among these steps, the dissolution and removal of the oxide film are usually the most difficult, generally requiring prolonged exposure to high-pressure hydrogen and / or high temperatures. Research has revealed that the activation process of Ti-Mn-based AB2 alloys is a hydrogen-induced cracking process. These alloys are generally brittle materials. Introducing Zr and Pr on side A and Cr, Co, and Al on side B increases microcracks and lattice stress in the Ti-Mn-based alloy. Under internal stress and a certain hydrogen pressure, these cracks provide deep diffusion channels, ensuring initial dissociation and adsorption of hydrogen on the relatively fresh surface at the crack tip. This leads to lattice expansion of the material at the crack tip, subsequently generating new cracks and creating a burst of fresh surfaces. Hydrogen diffuses more rapidly through these new channels, then dissociates and adsorbs further into the crack surface deeper within the alloy. Room-temperature activation performance is influenced by the reactivity between hydrogen molecules and the surface oxide layer, and this reactivity varies depending on the composition of the oxide layer. The study found that partial substitution of Ti and Cr with trace amounts of rare earth elements Pr and Zr, and partial substitution of Mn with Co and Al, alters the composition of the surface oxide layer, promoting the reaction between hydrogen molecules and the oxide layer, accelerating the dissolution and removal of the surface oxide layer, thereby improving the activation performance of the alloy at room temperature. In terms of composition design, the addition of trace amounts of rare earth element Pr can significantly improve the activation performance of the alloy, reduce plateau pressure, and enhance plateau characteristics. Since rare earth Pr is itself a hydrogen-absorbing element, its addition is beneficial for increasing the alloy's hydrogen storage capacity. Another prominent role of rare earth Pr is its ability to suppress Ti segregation during alloy solidification, improving the alloy's compositional uniformity and overall hydrogen storage performance. The synergistic effect of Co and Al significantly improves the alloy's plateau characteristics and reduces hysteresis. Furthermore, the addition of Co significantly reduces the dissociation energy of hydrogen molecules decomposing into hydrogen atoms on the alloy surface, improving the alloy's hydrogen absorption kinetics. Simultaneously, the use of vacuum induction melting-rapid quenching integrated technology to prepare the alloy yields a unique microstructure, enabling the alloy to possess activation performance and plateau characteristics suitable for various applications such as automotive fuel cells. Because rapid quenching generates significant lattice stress within the alloy, it accelerates fracture during activation, promoting the formation of numerous fresh surfaces and thus significantly improving its activation performance.

[0035] The excessively high hydrogen absorption plateau pressure of Ti-Mn-based AB2 alloys is another drawback hindering their widespread application. It is well known that hydrogen absorption is an exothermic process; the maximum hydrogen absorption capacity of the alloy decreases with increasing temperature, while the hydrogen absorption / desorption plateau pressure increases with temperature. This is because during the formation of the hydrogen solid solution, the 1s orbital electrons of hydrogen interact with the electrons in the transition metal's d orbitals. When the valence electron concentration increases, the number of vacancies in the orbitals decreases, increasing the energy consumption for hydrogen 1s electrons to occupy unoccupied sites, thus raising the plateau pressure. This invention partially replaces the Ti element on the A-side with Zr and Pr. Since the atomic radii and hydrogen affinity of Zr and Pr are much greater than those of Ti, the addition of Zr and Pr increases the alloy's lattice constant, thereby reducing the plateau pressure and significantly improving the alloy's hydrogen storage performance. The increased cell volume also reduces the volume expansion and contraction during hydrogen absorption / desorption cycles, thus improving the alloy's cycle stability. Replacing Mn elements on the B side with Co and Al can reduce the plateau pressure of Ti-Mn alloys and effectively improve plateau characteristics, reducing hydrogen absorption and desorption plateau hysteresis.

[0036] When the atomic ratio A / B between sides A and B deviates from 1:2, it is called a non-stoichiometric ratio. Studies have found that when the A / B atomic ratio varies within an appropriate range, the alloy can still achieve a single Laves phase structure. Compared with stoichiometric alloys, non-stoichiometric alloys have a significant advantage in hydrogen storage capacity. As the non-stoichiometric ratio A / B value increases, the hydrogen storage capacity of the alloy increases, the cell volume increases, the plateau pressure and tilt decrease, and the activation performance is significantly improved. This is due to the change in the interstitial chemical environment and the increase in the atomic proportions of hydrogen-absorbing elements Ti and Zr.

[0037] The advantages of rapid quenching lie in obtaining ultrafine grains and generating numerous grain boundaries, providing channels for hydrogen atom diffusion and significantly improving the hydrogen absorption and desorption kinetics of the alloy. Due to its extremely rapid cooling rate (>1000℃ / s), rapid quenching suppresses compositional segregation during solidification and cooling, thus improving hydrogen storage performance. Simultaneously, rapid quenching increases the cell volume of the alloy, increases plateau length, reduces hydrogen absorption and desorption plateau pressure, and decreases plateau hysteresis. Furthermore, the increased internal stress within the alloy lattice due to rapid quenching enhances the alloy's activation properties.

[0038] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0039] This invention discloses a Ti-Zr-Pr-Mn-Cr-Co-Al type AB2 hydrogen storage alloy, wherein the alloy has the following specific composition: (Ti 1-x-y Zr x Pr y )1.1 Mn 2-z-m Cr z Co m Al n Where x, y, z, m, and n are atomic ratios, and 0.15 ≤ x ≤ 0.35, 0.01 ≤ y ≤ 0.05, 0.35 ≤ z ≤ 0.85, 0.1 ≤ m ≤ 0.3, and 0.05 ≤ n ≤ 0.15. Preferably, x: y: z: m: n = 0.25: 0.03: 0.75: 0.15: 0.1.

[0040] The roles, contents, and atomic ratios of each component / element are determined based on the following:

[0041] The content of element A is determined as follows:

[0042] The elements on side A include Ti, Zr, and Pr. Among them,

[0043] Ti: In Ti-Mn alloys, Ti is the main alloying element, and the mass ratio of Ti to Mn has a decisive influence on the hydrogen storage performance of Ti-Mn AB2 type alloys. Studies have found that when Ti-Mn alloys possess a single C14 type Laves phase, the alloy exhibits better overall hydrogen storage performance. From the Ti-Mn binary phase diagram (... Figure 1 a) It can be observed that although the Ti / Mn atomic ratio can form a C14-type Laves structure over a relatively wide range, excessively high or low Ti content drastically reduces the hydrogen storage performance of the alloy. Studies show that when the Ti content is below 36 mol%, Ti-Mn alloys hardly absorb hydrogen. Only when the Ti content is above 36 mol% does the alloy begin to absorb hydrogen. While alloys with higher Ti content can react with hydrogen at room temperature without activation treatment, excessively high Ti content will form α-TiMn phase or even β-Ti phase, significantly reducing the alloy's activation performance.

[0044] Zr: To improve the hydrogen storage performance of AB2-type alloys and optimize for superior hydrogen storage, Zr is used to partially replace Ti in the alloy. Excessive plateau pressure is a major obstacle to the practical application of TiMn2 alloys, and Zr is considered the most effective and preferred element for adjusting the plateau pressure of Ti-Mn AB2-type alloys. From the Ti-Zr binary phase diagram (... Figure 1(b) It can be seen that Ti-Zr can be infinitely dissolved, and the substitution of Ti and Zr in any ratio will not change the AB2 Laves phase. Partial substitution of Ti by Zr can change the binding force between hydrogen and metal, thereby improving the hydrogen storage capacity of Ti-Mn AB2-type alloys. Adjusting the Ti / Zr ratio in the alloy can control the hydrogen absorption / desorption plateau pressure to meet the plateau pressure requirements of the application scenario. As the Zr content in the alloy increases, the Ti / Zr ratio decreases, the hydrogen absorption / desorption plateau pressure decreases significantly, and the hydrogen storage capacity increases. This is because the atomic radius of Zr is larger than that of Ti, and the partial substitution of Ti by Zr increases the unit cell volume. Furthermore, because Zr has a greater binding force on hydrogen than Ti, it can form more stable hydrides during hydrogen absorption, thus increasing the hydrogen absorption capacity of the alloy. It should be noted that from the binary phase diagram of the Zr-Mn alloy (… Figure 1 c) It can be seen that the Zr content in the alloy cannot be too high. Excessive Zr content will form the ZrMn2 phase with Mn in the alloy, reducing the alloy's reversible hydrogen storage performance, especially its activation performance. Furthermore, when the amount of Zr added is large, the plateau slope of the alloy increases significantly. This adverse effect of Zr can be eliminated by adding Co and Al elements.

[0045] Pr: It has been confirmed that adding trace amounts of rare earth elements to AB2 and AB-type alloys can significantly improve their hydrogen storage activation performance. Since rare earth elements (including Pr) are all hydrogen-absorbing elements, their addition undoubtedly benefits the improvement of the alloy's hydrogen storage capacity. Some argue that the difference in electronegativity between alloying elements significantly affects the alloy's hydrogen storage performance. For Ti-Mn-based AB2-type alloys, when the electronegativity of the substituting element is lower than that of the substituted element, the overall formation energy of the alloy may decrease, thus improving hydrogen storage performance. The substitution of different elements on the A-side of the parent alloy by the rare earth element Sm, especially elements with higher electronegativity, is more beneficial to improving the overall performance of the alloy. This means that Sm substitution of Ti on the A-side produces a more significant improvement in hydrogen storage performance than substitution of Zr. The atomic radius of Pr (183 pm) is much larger than that of Ti (170 pm). Therefore, the addition of Pr significantly increases the cell volume and significantly improves the alloy's hydrogen storage capacity and hydrogen absorption / desorption plateau pressure. Since Pr itself is a hydrogen-absorbing element, its addition contributes to the improvement of the alloy's hydrogen storage capacity. Furthermore, the addition of appropriate amounts of Pr can significantly improve the activation performance and anti-poisoning properties of the alloy, and effectively suppress the segregation of elements, especially Ti, thereby significantly improving the activation performance of the alloy. Pr is considered a very effective catalyst that can significantly improve the hydrogen absorption and desorption kinetics of the alloy. This is mainly because during the hydrogen absorption process, Pr and H can form highly stable nano-hydrides, PrH, in situ. x (See Figure 1d) This provides a rapid diffusion channel for hydrogen atoms to enter the alloy matrix. It should be noted that due to the large atomic radius of Pr, its solid solubility in the alloy is very small. Excessive addition of Pr will increase the raw material cost of the alloy and introduce impurity phases, thereby affecting the hydrogen storage performance of the alloy. In addition, Pr has a much higher density than Ti, and excessive addition of Pr will have a significant negative impact on the mass hydrogen storage capacity of the alloy.

[0046] Determination of the content of element B:

[0047] The elements on side B include Mn, Cr, Co, and Al. Among them,

[0048] Mn: In Ti-Mn-based alloys, Mn's role is to shrink the cell volume of the C14-type Laves phase, significantly reducing the stability of the hydride phase. This satisfies the thermodynamic requirements for solid-state hydrogen storage, enabling the Ti-Mn-based AB2 alloy to reversibly absorb and desorb hydrogen at room temperature. Mn primarily acts as a catalyst in the AB2 alloy, similar to the role of Ni in the AB5 alloy, but its catalytic effect is much smaller. Sufficient Mn content ensures that the AB2 alloy possesses a single Laves phase. The Mn content must be strictly controlled; excessively high Mn content will lead to a significant decrease in the alloy's hydrogen storage performance, especially its hydrogen storage capacity. With increasing Mn content, the plateau pressure of the alloy rises significantly, and the hysteresis and tilt increase.

[0049] Cr: Research has found that partially replacing Mn on the boron side with transition metals can significantly improve the hydrogen storage performance of alloys, with Cr being the preferred replacement element. Cr's role is to improve the overall hydrogen storage performance of the alloy, significantly regulating the plateau pressure, particularly improving activation performance and reducing hysteresis. Cr is located between Ti and Mn in the periodic table, with an atomic radius of 124.9 pm, while Ti and Mn have atomic radii of 144.8 pm and 136.6 pm, respectively. After partially replacing Mn, Cr creates larger voids in the alloy lattice, facilitating the entry of hydrogen atoms. Cr replacement of Mn improves the hydrogen absorption and desorption performance of the alloy, shortening the activation incubation period, increasing the hydrogen absorption and desorption rate, and also increasing the amount of hydrogen released. After Cr partially replaces Mn, the hydrogen desorption plateau pressure of the alloy increases significantly with increasing Cr content, thus significantly reducing the hydrogen absorption and desorption hysteresis. By adjusting the amounts of Cr and Zr added to the alloy, the hydrogen absorption and desorption plateau pressures of the alloy can be effectively controlled, making the alloy suitable for applications in a wider range of scenarios. In alloy design, the amount of Cr added must be strictly controlled, from Ti-Cr (… Figure 1 e) and Zr-Cr( Figure 1f) The binary phase diagram reveals that excessive Cr may form the TiCr2 phase with Ti, reducing the alloy's hydrogen storage performance, especially its activation performance. Simultaneously, it causes a sharp increase in the alloy's plateau pressure, requiring very high hydrogen pressure for absorption, which is unsuitable for fuel cells. Excess Cr may also form the ZrCr2 phase with Zr, significantly increasing the stability of the alloy hydride and preventing hydrogen release under normal temperature and pressure conditions. Studies have found that the hydrogen storage performance of Ti-Mn based AB2 alloys is particularly sensitive to their composition, especially the amount of Cr added, which must be strictly matched with the content of Ti and Zr. Furthermore, it is important to note that Cr itself is not a hydrogen-absorbing element and has a high density; excessive Cr addition will significantly reduce the alloy's hydrogen storage capacity.

[0050] Co: Partial substitution of Mn on the B side with Co significantly improves the PCT curve plateau characteristics of the alloy, making the curve noticeably flatter. Co's atomic radius is slightly larger than Mn's, and Co substitution slightly lowers the plateau. The results show that among almost all non-hydrogen-absorbing metal elements, Co has the least negative impact on the alloy's hydrogen storage performance. Co has a similar effect to Ni, exhibiting a significant catalytic effect on hydrogen absorption and desorption in solid-state hydrogen storage materials, especially in rare-earth-based AB5 alloys. In Ti-Mn-based AB2 alloys, the main role of adding Co is to improve the alloy's activation performance, increase its hydrogen storage capacity, and enhance hydrogen absorption and desorption kinetics. The combined catalytic effect of Co with other metals, such as Ni, Cu, Al, and Fe, is even more significant. Studies have demonstrated that Co can significantly reduce the dissociation energy of hydrogen molecules on the alloy surface, accelerating the decomposition of hydrogen molecules into hydrogen atoms. This reaction can improve the hydrogen absorption kinetics of the alloy and increase the plateau length. Co has been shown to increase the structural stability of the alloy and is considered the most effective element for improving the alloy's resistance to capacity decay. It should be noted that the addition of excess Co will form various binary compounds with Zr (…). Figure 1 (g) While these compounds can absorb hydrogen, the hydrides they form are highly stable and do not decompose at room temperature, significantly affecting the hydrogen storage capacity of the alloy. Furthermore, Co is a precious metal, and excessive use of Co will significantly increase the raw material cost of the alloy.

[0051] Al: Partial substitution of Mn on the B side with Al significantly improves the PCT curve plateau performance of the alloy. Al addition lowers the plateau pressure, mainly due to the larger atomic radius of Al (143 pm) compared to Mn. Al addition enhances the alloy's resistance to pulverization and improves its hydrogen absorption / desorption cycle stability to some extent. Al addition reduces the alloy's hydrogen absorption capacity, which can be understood from the occupancy of Al in the interstitial spaces. It is well known that in the hexagonal AB2 Laves phase, hydrogen atoms mainly occupy two interstitial sites: [A2B2] and [AB3]. After Al substitution, the [A2B2] and [AB3] interstitial sites change from [Ti2Mn2] or [TiMn3] to [Ti2MnAl], [TiMn2Al], [TiMnAl2], [Ti2Al2], or [TiAl3]. Since Al does not have a strong affinity for hydrogen, these last two sites are hydrogen-free. Therefore, the amount of Al added must be carefully controlled.

[0052] After comparing the activation performance and kinetic properties of alloy materials with a series of parameters, the optimal ratio of x, y, z, m, n was determined to be x: y: z: m: n = 0.25: 0.03: 0.75: 0.15: 0.1. Specifically, the hydrogen storage alloy has a nanocrystalline structure with an average grain size of 50–200 nm. Numerous grain boundaries provide rapid channels for hydrogen diffusion and nucleation sites for hydrogen absorption and desorption reactions, thereby improving the alloy's activation performance and hydrogen absorption and desorption kinetics. Substitution of elements on the A and B sides with multiple metal elements, combined with a rapid quenching process, allows for the regulation of the hydrogen absorption and desorption plateau pressure.

[0053] Specifically, the Ti-Zr-Pr-Mn-Cr-Co-Al AB2-type hydrogen storage alloy provided by this invention exhibits excellent activation and hydrogen absorption / desorption performance, with a hydrogen storage capacity ≥1.83 wt.% and adjustable hydrogen absorption and desorption plateau pressures. The alloy demonstrates excellent activation performance, achieving activation in a single hydrogen absorption / desorption cycle at 20℃ and 3 MPa. Furthermore, the alloy exhibits excellent cycle stability, maintaining a capacity retention rate >98.4% after 200 hydrogen absorption / desorption cycles. It can be widely applied as a solid-state hydrogen storage material in various scenarios, including hydrogen fuel cells.

[0054] The present invention also provides a method for preparing the hydrogen storage alloy, specifically comprising the following steps:

[0055] S1: The ingredients are prepared according to the chemical formula composition calculation, with appropriate amounts of Mn and Pr added for loss on ignition;

[0056] S2: Place the prepared raw materials into the Al2O3 crucible in sequence, cover the furnace, evacuate to the preset vacuum level, and then fill with Ar gas at a certain pressure as a protective atmosphere. Use induction heating to heat the raw materials to the molten state and hold for a period of time to obtain a liquid master alloy with uniform composition.

[0057] S3: Liquid master alloy (approximately 1450 ℃) is directly injected into the tundish with NB nozzles embedded at the bottom. The liquid alloy is continuously sprayed from the narrow slits of the NB nozzles at the bottom of the tundish onto the surface of the rotating water-cooled copper roller. The rapidly cooled alloy strip is thrown out of the copper roller under the action of centrifugal force, thus obtaining the rapidly quenched alloy strip.

[0058] The Ti-Zr-Pr-Mn-Cr-Co-Al based AB2 hydrogen storage alloy and its preparation method provided by this invention achieve the corresponding technical effects through "composition design + vacuum rapid quenching". Scientific composition design combined with an appropriate rapid quenching process can obtain alloy ribbons with special structures, thus giving the alloy excellent activation performance. In particular, rapid quenching treatment suppresses compositional segregation during solidification, and the rapid cooling significantly reduces the grain size of the alloy, providing a good channel for the rapid diffusion of hydrogen atoms within the alloy. Therefore, while improving activation performance, it significantly improves the hydrogen absorption and desorption kinetics of the alloy. Furthermore, rapid quenching increases the cell volume of the alloy, changing the lattice stress state and facilitating the regulation of the hydrogen absorption and desorption plateau pressure. In terms of composition design, trace amounts of Pr are used to replace Ti, and Co and Al are used to replace Mn, eliminating the need for the precious metal V. In terms of preparation process, the complex traditional melting-casting-annealing process is eliminated, significantly improving the yield and stability of the alloy's performance, and significantly reducing the raw material and preparation costs.

[0059] Specifically, in step S1, the burn-off amount of Mn and Pr added is 3%-5% of the calculated amount. Since Mn and Pr are volatile, an appropriate amount of burn-off needs to be added to ensure that the final alloy composition reaches the design value. According to repeated experimental verification, the burn-off amount should be 3%-5% of the calculated amount.

[0060] Specifically, the order and operation of placing the raw materials in step S2 are as follows: The cleaned raw materials are mixed in proportion and placed sequentially in an Al2O3 crucible. Rare earth Pr is placed at the bottom of the crucible, followed by a mixture of sponge Ti and Zr on top of the rare earth Pr, then metals Cr and Co on top of the sponge Ti and Zr, and finally electrolytic Mn and Al on top. This arrangement is determined by the melting point and electromagnetic induction efficiency of the raw material metals. This material placement effectively improves metal smelting efficiency, makes the alloy composition more stable, the element distribution more uniform, and increases the yield of the finished product.

[0061] Specifically, the raw material smelting operation in step S2 is as follows: vacuuming to 5×10-2 Above Pa, high-purity argon gas at a pressure of 0.01-0.1 MPa is introduced as a protective gas, and the alloy is melted by medium-frequency induction heating to melt all raw materials. The temperature of the molten alloy is controlled at 1550℃ and held for 3-5 minutes to ensure that the alloy composition is completely homogenized.

[0062] Specifically, the rapid quenching operation in step S3 is as follows: the power of the melting furnace is adjusted to 30 kW, and liquid alloy at a temperature of approximately 1450℃ is directly injected into the tundish with a narrow nozzle (NB) embedded at the bottom. Under the action of its own gravity, the liquid alloy is continuously sprayed from the nozzle gap (0.3 mm width) at the bottom of the NB tundish onto the surface of the rotating water-cooled copper roller. The surface linear velocity of the copper roller is 1–15 m / s, and the water inlet flow rate is ≥10 m³ / s. 3 / h, water temperature 18~20 ℃. After the alloy cools to room temperature, a rapid quenching alloy strip is obtained, with a thickness of 100~300 μm and a grain size between 50~200 nm. The starting temperature of rapid quenching, the nozzle width, and the quenching rate are key factors in the rapid quenching process. 1) Rapid quenching starting temperature: Controlling the starting temperature of the liquid alloy for rapid quenching is crucial. If the temperature is much lower than 1450 ℃, the fluidity of the liquid alloy will be very poor. The flow rate of the liquid alloy through the nozzle will be too slow, or even solidification and nozzle blockage will occur, causing the rapid quenching to be interrupted. Another problem with the casting temperature being too low is that the liquid alloy has poor adhesion to the rapid quenching roller when in contact with it, which greatly reduces the cooling rate of the alloy, thus making it impossible to obtain an ultra-fine crystal structure. 2) Nozzle width: Selecting an appropriate nozzle slit width is a key technical parameter. If the nozzle slit is too large, it will reduce the cooling effect during the alloy solidification process and will not be able to obtain an ultra-fine columnar crystal structure. If the nozzle slit is too small, the liquid alloy will solidify at the nozzle, resulting in discontinuous rapid quenching. Furthermore, a nozzle that is too small will increase the rapid quenching time, reducing productivity. 3) Quenching rate: Determining a suitable rapid quenching rate is a key technical parameter to ensure that the rapidly quenched alloy strip has an almost completely nanocrystalline structure. Too high a quenching rate will result in more amorphous phases in the alloy, leading to a decrease in hydrogen storage capacity and activation performance; too low a quenching rate will cause significant grain coarsening, affecting the uniform distribution of alloy composition and reducing activation and hydrogen absorption / desorption kinetics. The flow rate and temperature of the cooling water inlet to the copper roller must also meet requirements; otherwise, the microstructure of the rapidly quenched strip will be affected, thus impacting the alloy's hydrogen storage performance.

[0063] Based on the above component design and preparation method, the specific components of the embodiments and comparative examples of this invention are as follows:

[0064] Example 1: (Ti 0.72 Zr 0.25 Pr 0.03 ) 1.1 Mn 1.0 Cr 0.75 Co 0.15Al 0.1

[0065] Example 2: (Ti) 0.82 Zr 0.15 Pr 0.03 ) 1.1 Mn 1.0 Cr 0.75 Co 0.15 Al 0.1

[0066] Example 3: (Ti) 0.62 Zr 0.35 Pr 0.03 ) 1.1 Mn 1.0 Cr 0.75 Co 0.15 Al 0.1

[0067] Example 4: (Ti 0.72 Zr 0.25 Pr 0.03 ) 1.1 Mn 1.4 Cr 0.35 Co 0.15 Al 0.1

[0068] Example 5: (Ti) 0.72 Zr 0.25 Pr 0.03 ) 1.1 Mn 0.85 Cr 0.75 Co 0.3 Al 0.1

[0069] Example 6: (Ti 0.72 Zr 0.25 Pr 0.03 ) 1.1 Mn 0.95 Cr 0.75 Co 0.15 Al 0.15

[0070] Example 7: (Ti 0.72 Zr 0.25 Pr 0.03 ) 1.1 Mn 1.0 Cr 0.75 Co 0.15 Al 0.1 (1 m / s rapid quenching)

[0071] Example 8: (Ti) 0.72 Zr 0.25 Pr0.03 ) 1.1 Mn 1.0 Cr 0.75 Co 0.15 Al 0.1 (9 m / s rapid quenching)

[0072] Example 9: (Ti) 0.72 Zr 0.25 Pr 0.03 ) 1.1 Mn 1.0 Cr 0.75 Co 0.15 Al 0.1 (12 m / s rapid quenching)

[0073] Example 10: (Ti 0.72 Zr 0.25 Pr 0.03 ) 1.1 Mn 1.0 Cr 0.75 Co 0.15 Al 0.1 (15 m / s rapid quenching)

[0074] Comparative Example 1: (Ti 0.72 Zr 0.25 Pr 0.03 ) 1.1 Mn 1.0 Cr 0.75 Co 0.15 Al 0.1 (Copper mold casting)

[0075] Comparative Example 2: (Ti 0.72 Zr 0.25 Pr 0.03 ) 1.1 Mn 1.0 Cr 0.75 Co 0.15 Al 0.1 (Copper mold casting + annealing at 1000℃ for 8 hours)

[0076] Comparative Example 3: (Ti 0.72 Zr 0.25 Pr 0.03 ) 1.1 Mn 1.0 Cr 0.75 Co 0.15 Al 0.1 (30 m / s rapid quenching)

[0077] According to the chemical composition of each embodiment, sponge Ti and Zr, rare earth Pr, metallic Cr and Co, and electrolytic Mn and Al are selected. A special raw material cleaning device is used to remove the oxide layer and impurities from the surface of the raw materials. The loss on ignition of Mn and Pr is increased by 3%–5% during batching. The technical parameters for each stage are as follows: the vacuum induction melting furnace is evacuated to 5 × 10⁻⁶ m³ / h before heating. -2 Pa; then, 0.01-0.1 MPa of inert gas Ar is introduced into the furnace as a protective gas; induction heating is used to bring the temperature of the liquid alloy to 1550℃; the liquid alloy is held in the molten state for 3-5 min to fully homogenize the alloy composition; the surface linear velocity of the rapidly quenched water-cooled copper roller is 1-15 m / s.

[0078] It should be emphasized that all process parameters can be appropriately selected within the above range to prepare the hydrogen storage alloy described in the patent. Therefore, although only one typical embodiment has been given in this invention, this embodiment is applicable to preparation methods with different parameters.

[0079] Process parameters for Example 1:

[0080] According to the chemical formula (Ti) 0.72 Zr 0.25 Pr 0.03 ) 1.1 Mn 1.0 Cr 0.75 Co 0.15 Al 0.1 Bulk Ti and Zr, rare earth Pr, metallic Cr and Co, and electrolytic Mn and Al were selected. These metals had a purity of ≥99.5% and were weighed according to stoichiometric ratios, with 5 kg of materials per furnace. The proportions were: 1095 g Ti, 724 g Zr, 141 g Pr, 1666 kg Mn, 1126 kg Cr, and 78 g Al. The weighed bulk metals were placed in an Al₂O₃ crucible in a medium-frequency induction furnace according to the designed process. Rare earth Pr was placed at the bottom, followed by a mixture of Ti and Zr, then Cr and Co, and finally the electrolytic Mn and Al on top. The furnace lid was then closed, and a vacuum was evacuated for approximately 30 minutes to a vacuum level of 5 × 10⁻⁶. -2Above Pa, high-purity Ar protective gas is then introduced until the pressure reaches -0.04 MPa. Medium-frequency induction heating is used to melt all raw materials. The temperature of the molten alloy is controlled at 1550℃ and held for 3-5 minutes to ensure complete homogenization of the alloy composition. After adjusting the power of the melting furnace to 30 kW, the liquid alloy (approximately 1450℃) is directly injected into the tundish with NB nozzles embedded at the bottom. The liquid alloy is continuously sprayed from the narrow slits of the NB nozzles at the bottom of the tundish (slit width 0.3 mm) onto the surface of a rotating (305 rpm) water-cooled copper roller at a linear speed of 6 m / s. After the alloy cools to room temperature, a rapidly quenched alloy sheet with an average thickness ranging from 297 to 302 μm and an average grain size of approximately 101 nm is obtained.

[0081] The raw materials in Examples 2-10 were weighed according to their chemical formulas, and other preparation process parameters were the same as in Example 1 unless otherwise specified.

[0082] The raw materials of Comparative Examples 1 to 3 were weighed according to their chemical formulas. Other preparation process parameters were basically the same as those of the Examples. The difference was that after the alloy of Comparative Example 1 was induction melted, it was cast into a copper mold without any treatment. Comparative Example 1 verified the effect of the rapid quenching process on the hydrogen storage performance of the alloy.

[0083] Comparative Example 2 involved casting the induction-melted copper mold and then vacuum annealing it at 1000℃ for 8 hours. The difference was that Comparative Example 2 subjected the as-cast alloy to high-temperature, long-duration diffusion annealing. Comparative Example 2 verified the effect of annealing on the hydrogen storage performance of the alloy.

[0084] Comparative Example 3 had the same composition as Examples 1 and 7-10, but its quenching rate far exceeded the optimal quenching rate range selected in this patent. This comparative example verified the relationship between the alloy's hydrogen storage performance and the quenching rate.

[0085] The phase structure and phase composition of the rapidly quenched alloy were tested by XRD. The morphology and microstructure of the cross-sections of the rapidly quenched alloy strips were observed by scanning electron microscopy (SEM). The elemental distribution and energy spectrum of the alloy were tested by SEM and EDS.

[0086] Figure 1 Seven binary phase diagrams for different alloy systems: Ti-Mn, Ti-Zr, Zr-Mn, Pr-H, Ti-Cr, Zr-Cr, and Zr-Co. These phase diagrams can be used to assist in alloy composition design and to identify potential new phases within the alloy.

[0087] Figure 2 The rapidly quenched alloy sheet of Example 1; the thickness of the randomly selected rapidly quenched sheet was tested and found to be in the range of 197-202 μm, which meets the design requirements.

[0088] Figure 3XRD diffraction patterns of rapidly quenched alloys in Examples 1-6. It can be observed that the rapidly quenched alloys possess a single-phase hexagonal C... 14 It is a single Laves phase with a MgZn2 structure. The crystal lattice contains only tetrahedral interstitials, and the resulting hydride is TiMn2H. 2.5 The substitution of Zr, Pr, Cr, Co, and Al did not form new phases, proving that the element substitutions did not exceed their solid solubility in the matrix alloy.

[0089] Figure 4 SEM images of the horizontal and longitudinal sections of the rapidly quenched strip in Example 1 show that the horizontal section exhibits a relatively uniform equiaxed crystal structure, with an average grain diameter of approximately 101 nm as measured by the truncation method. The longitudinal section shows a roughly parallel columnar crystal structure, which is attributed to the temperature gradient along the strip thickness direction (from the contact roller surface to the back roller surface) during rapid quenching.

[0090] Figure 5 Example 1 shows the SEM morphology, EDS elemental distribution map, and energy dispersive spectroscopy of the rapidly quenched alloy strip. It can be seen that Ti, Zr, Pr, Mn, Cr, Co, and Al are uniformly distributed, indicating that rapid quenching can suppress component segregation during solidification and ensure uniform alloy composition. The elemental distribution in different regions of the rapidly quenched strip was tested, and the results showed no significant compositional changes between different regions, which is impossible to achieve with traditional casting processes. It is this uniformity of composition that ensures the alloy's excellent hydrogen storage performance.

[0091] The hydrogen absorption activation performance, hydrogen storage capacity, hydrogen absorption and desorption kinetics, and cycle stability of all examples and comparative alloys were tested using a fully automated Sieverts system. The hydrogen absorption temperature was 20°C, and the initial hydrogen pressure was 3 MPa; the hydrogen desorption temperature was 20°C, and the cycle stability was tested at 1×10⁻⁶ MPa. -4 The test was conducted at a pressure of MPa. Using S 200 S represents the capacity retention of the alloy after 200 charge-discharge cycles. 200 = C 200 / C max ×100%. C max - Saturated reversible hydrogen absorption capacity; C 200 - Reversible hydrogen uptake capacity after 200 charge-discharge cycles. The results are shown in Table 1.

[0092] Table 1. Solid-state hydrogen storage performance of different embodiments and comparative alloys

[0093]

[0094] The Ti-Zr-Pr-Mn-Cr-Co-Al AB2-type hydrogen storage alloy provided by this invention exhibits excellent activation performance, hydrogen absorption and desorption kinetics, and cycle stability, with a hydrogen storage capacity >1.83 wt.% and adjustable hydrogen absorption and desorption plateau pressures. Activation can be completed in a single hydrogen absorption and desorption cycle at 20°C and an initial hydrogen pressure of 3 MPa. After 200 hydrogen absorption and desorption cycles, the alloy retains a capacity S0. 200 >98.4%.

[0095] Examples 1-6 show that, with the smelting and rapid quenching processes unchanged, changes in the alloy composition cause significant changes in its hydrogen storage performance, indicating that the hydrogen storage performance of the material is closely related to the amount of chemical composition.

[0096] Examples 7-10 used the same master alloy composition as Example 1, but the quenching rate of the rapid quenching treatment was changed, which led to a significant change in the hydrogen storage performance of the alloy, showing that the quenching rate has a significant impact on the hydrogen storage performance of the alloy.

[0097] Comparative Example 1 had the same alloy composition as Example 1, but was not treated after casting. The results showed that the overall hydrogen storage performance of the as-cast alloy was significantly lower than that of the rapidly quenched alloy, indicating that rapid quenching treatment has a significant effect on improving the hydrogen storage performance of the alloy.

[0098] Comparative Example 2 involved subjecting the alloy of Comparative Example 1 to prolonged high-temperature diffusion annealing. The results showed that annealing significantly improved the hydrogen storage performance, particularly the activation performance. This indicates that the compositional uniformity of the alloy has a significant impact on its hydrogen storage performance.

[0099] Compared with Examples 1 and 7-10, Comparative Example 3 had the same alloy composition, but it used a quenching rate range much higher than the optimal range selected in the patent, showing that non-patented quenching at a fast rate would lead to a significant decrease in the hydrogen storage performance, especially the activation performance, of the alloy.

[0100] Based on the analysis of the above embodiments and comparative examples, the following conclusions can be drawn:

[0101] 1) Scientific composition design is the foundation for obtaining high-performance AB2-type Ti-Mn-based alloys. The synergistic effect of multiple elements is often more significant than the effect of a single element.

[0102] 2) Given a fixed chemical composition of the alloy, the microstructure and compositional uniformity of the alloy are the determining factors of the alloy's performance. Alloys with a uniform and consistent ultrafine microstructure exhibit excellent comprehensive hydrogen storage performance.

[0103] 3) The mainstream technologies for the mass production of Ti-Mn based AB2 alloys include casting, casting + annealing, and rapid quenching. Among these, alloys prepared by rapid quenching exhibit the best hydrogen storage performance.

[0104] The above results show that the rapidly quenched alloy possesses excellent comprehensive hydrogen storage performance. 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 such as fuel cells 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, and the cost is significantly reduced, giving it a clear competitive advantage in the solid-state hydrogen storage industry.

[0105] 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.

[0106] 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 high-capacity, easily activated Ti-Zr-Pr-Mn-Cr-Co-Al AB2-type hydrogen storage alloy, characterized in that: The specific composition of the alloy is (Ti) 1-x-y Zr x Pr y ) 1.1 Mn 2-z-m-n Cr z Co m Al n In the formula, x, y, z, m, n are atomic ratios, and 0.15≤x≤0.35, 0.01≤y≤0.05, 0.35≤z≤0.85, 0.1≤m≤0.3, 0.05≤n≤0.

15.

2. The alloy of claim 1 wherein, The atomic ratio of the chemical formula is x: y: z: m: n = 0.25: 0.03: 0.75: 0.15: 0.

1.

3. The hydrogen storage alloy according to claim 2, characterized by: The hydrogen storage alloy has a nanocrystalline structure with an average grain size of 50–200 nm.

4. The hydrogen storage alloy according to claim 2, characterized in that: The rapidly quenched alloy exhibits a columnar crystal structure with roughly parallel crystals along the thickness direction of the strip.

5. The hydrogen storage alloy according to claim 1, characterized in that: The alloy has a single C14-type Laves phase structure.

6. A method for preparing the hydrogen storage alloy according to any one of claims 1 to 5, characterized in that, Specifically, the following steps are included: S1: The ingredients are prepared according to the chemical formula composition calculation, with appropriate amounts of Mn and Pr added for loss on ignition; S2: Place the prepared raw materials in an Al2O3 crucible, cover the furnace, and after evacuating to the preset vacuum level, introduce high-purity Ar gas at a certain pressure as a protective gas. Use medium-frequency induction heating to heat all raw materials to a completely molten state and hold at that temperature for an appropriate time to obtain a liquid alloy with uniform composition; S3: Liquid alloy is directly injected into the intermediate ladle with NB nozzles embedded at the bottom. The liquid alloy (approximately 1450 ℃) is continuously sprayed from the nozzle slit onto the surface of a rotating water-cooled copper roller with a surface linear velocity of 1 to 15 m / s under its own gravity. The rapidly solidified alloy sheet flies away from the rapid quenching roller under the action of the centrifugal force of the copper roller, thus obtaining a rapid quenching alloy strip with a thickness between 100 and 300 μm.

7. The preparation method according to claim 6, characterized in that: In step S1, the amount of Mn and Pr added is 3% to 5% of the calculated dosage.

8. The preparation method according to claim 6, characterized in that: The order and specific operation of placing each raw material in step S2 are as follows: rare earth Pr is placed at the bottom of the crucible, sponge Ti and Zr are mixed and placed on top of rare earth Pr, metal Cr and Co are placed on top of sponge Ti and Zr, and electrolytic Mn and Al are placed on top.

9. The preparation method according to claim 6, characterized in that: The temperature of the liquid alloy should be 1450 °C at the start of the rapid quenching in step S3.

10. The preparation method according to claim 6, characterized in that: In step S3, the width of the NB nozzle seam at the bottom of the intermediate package is 0.29–0.33 mm, and the surface linear velocity is 1–15 m / s.

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