Nd-Mg-based hydrogen storage alloy based on electromagnetic-current composite field regulation microstructure and preparation method

Abstract

The application relates to a Nd-Mg-based hydrogen storage alloy based on electromagnetic-current composite field regulation and control of microstructure and a preparation method, which comprises the following steps: S1, raw materials are weighed and mixed according to atomic percentage to obtain raw materials; S2, the raw materials are completely melted under a protective atmosphere, electromagnetic stirring is carried out in the melting process, and a homogeneous melt is obtained; S3, the melt is cast into a boron nitride mold, and current stimulation is carried out in the solidification process to obtain a cast alloy; S4, the cast alloy is polished to remove the oxide skin and mechanically broken to obtain alloy particles; and S5, the alloy particles are mechanically ball milled to obtain hydrogen storage alloy ball milling powder. The hydrogen storage capacity of the alloy reaches 6.68-6.73 wt.%, complete dehydrogenation is achieved at 375 DEG C for 8-13 minutes, the process is simple, the cost is low, and the problems of capacity decline and poor kinetic performance caused by too many doped elements and uneven melting structure of traditional magnesium-based alloys are solved.

Description

Technical Field

[0001] This invention relates to the field of solid-state hydrogen storage, specifically to an Nd-Mg-based hydrogen storage alloy and its preparation method based on electromagnetic-current composite field-controlled microstructure. Background Technology

[0002] Hydrogen energy, as a readily available, zero-carbon, and high-energy-density secondary energy source, is crucial for achieving energy transition, mitigating environmental pollution, and promoting the realization of "dual-carbon" goals. Among the three stages of the hydrogen energy industry chain—preparation, storage, transportation, and application—safe and efficient solid-state hydrogen storage technology is the core for realizing large-scale hydrogen energy applications.

[0003] Magnesium-based materials stand out due to their high hydrogen storage density, but their commercialization is hampered by their inherent thermodynamic and kinetic properties. Microscopically, the strong Mg-H bonds create a high barrier, leading to sluggish desorption kinetics. The introduction of large amounts of catalysts or alloying elements to improve dehydrogenation performance often significantly increases system weight, resulting in a substantial decrease in effective hydrogen storage capacity. During smelting, the density difference and melting point deviation between rare earth elements and the magnesium matrix easily lead to gravity segregation, causing uneven alloy composition distribution. Furthermore, magnesium's chemical reactivity means that mechanical stirring in traditional smelting easily introduces impurities and oxide inclusions. Simply relying on mechanical crushing is insufficient to control lattice defect formation during solidification, causing irreversible degradation of hydrogen storage capacity. To overcome these bottlenecks in balancing kinetic rates and hydrogen storage capacity, current research focuses on various modification strategies and multi-element synergistic design for magnesium-based hydrogen storage alloys. Therefore, this study investigates a Nd-Mg-based hydrogen storage alloy and its preparation method based on electromagnetic-current composite field-controlled microstructure, aiming to improve hydrogen carrier materials for future hydrogen energy applications, achieve large-scale preparation, and promote the practical application of magnesium-based materials in hydrogen energy systems. Summary of the Invention

[0004] Purpose of the invention The purpose of this invention is to solve the problems of reduced hydrogen storage capacity and poor kinetic performance caused by excessive doping elements and uneven microstructure during melting in magnesium-based hydrogen storage alloys. This invention proposes an Nd-Mg-based hydrogen storage alloy and its preparation method based on electromagnetic-current composite field-controlled microstructure.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing an Nd-Mg-based hydrogen storage alloy with microstructure controlled by an electromagnetic-current composite field, wherein the Nd-Mg-based hydrogen storage alloy is composed of Mg and Nd, and the atomic percentage formula of the Nd-Mg-based hydrogen storage alloy is Mg 100-x Nd x , where x ranges from 0.4 to 1.6.

[0006] A method for preparing the above-mentioned Nd-Mg-based hydrogen storage alloy based on electromagnetic-current composite field-controlled microstructure includes the following steps: S1: According to the above Mg 100-x Nd x Weigh and mix the raw materials according to the atomic percentage ratio to obtain the raw materials; S2: The raw materials of step S1 are completely melted in a protective atmosphere at 750-850°C. During the melting process, a low-turn induction coil coated with MgO is used to perform electromagnetic stirring in the melt for 2-3 seconds to obtain a homogeneous melt. S3: The melt obtained in step S2 is poured into a boron nitride mold containing a pair of Ni electrode plates, and current stimulation is applied during solidification to obtain a cast alloy. S4: Grind the as-cast alloy obtained in step S3 to remove oxide scale and mechanically crush it to obtain alloy particles; S5: The alloy particles obtained in step S4 are mechanically ball-milled to obtain Mg. 100-x Nd x Hydrogen storage alloy ball milled powder.

[0007] As a further description of the above scheme, in step S1, the raw materials consist of pure Mg with a purity higher than 99.9 wt.% and Mg-30 wt.% Nd master alloy; by adjusting the proportions of pure Mg and Mg-30 wt.% Nd master alloy, the final prepared Mg 100-x Nd x In hydrogen storage alloys, the atomic percentage of Mg is 98.4-99.6%, and the atomic percentage of Nd is 0.4-1.6%.

[0008] As a further description of the above scheme, in step S2, the protective atmosphere is a mixture of CO2 and SF6, and the electromagnetic stirring current is 20-25A.

[0009] As a further description of the above scheme, in step S3, the boron nitride mold is a square boron nitride crucible, and nickel electrode plates are placed on the left and right sides inside the square boron nitride crucible, respectively. The preheating and drying temperature of the crucible and the electrode plates is 300°C.

[0010] As a further description of the above solution, in step S3, the current is 100-120mA, and the cooling rate is controlled at 10-50K / s. As a further description of the above scheme, in step S5, the mechanical ball milling adopts a planetary ball mill, the ball mill jar is filled with argon gas with a purity of 99.999%, and dry ice is fixed on the top of the ball mill jar for cooling during the ball milling process.

[0011] As a further description of the above scheme, in step S5, the ball-to-material ratio of the ball mill is 20:1, and the milling is carried out in stages. First, the milling is carried out at a speed of 100-110 rpm for 1-1.5 hours, and then at a speed of 160-170 rpm for 1-1.5 hours, for a total milling time of 2-3 hours. After milling, the mesh size of the hydrogen storage alloy ball mill powder is <200 mesh.

[0012] Advantages and effects of the present invention: 1. The rare earth element Nd doping in the magnesium-based hydrogen storage alloy of the present invention improves the hydrogen storage capacity, maintaining it above 6.7 wt.%, while also enhancing kinetic performance. This method involves the formation of Mg3Nd and Mg during the solidification process of the magnesium melt using Nd. 12 The Nd second phase, distributed at the grain boundaries, effectively suppresses grain coarsening during solidification and provides a rapid diffusion path. It features low cost and high hydrogen storage capacity, overcoming the drawback of reduced hydrogen storage capacity due to excessive alloying elements.

[0013] 2. The process of using a low-turn induction coil coated with MgO for electromagnetic stirring in this invention introduces electromagnetic stirring during resistance melting, avoiding the introduction of impurities by mechanical stirring. Simultaneously, it ensures atomic-level uniform distribution of Nd in the alloy, guaranteeing the consistency of the overall material properties and the uniformity of composition. The MgO coating prevents reaction between the coil metal and the molten magnesium, ensuring the purity of the melt, reducing oxide inclusions, and further improving the material's effective hydrogen storage capacity.

[0014] 3. The current composite field control process of the present invention uses a square boron nitride mold to ensure the high purity of the melt. An electric field is introduced during the solidification process, and a current is applied instantaneously through the Ni plate electrode. The Joule heating effect and electromagnetic pressure generated by the current will change the supercooling of the melt, increase the nucleation rate, and the current stimulation can break up the coarse dendrites to refine the grains, further shortening the hydrogen diffusion distance. The large number of lattice defects introduced by the current become heterogeneous nucleation sites for hydrides, which significantly improves the dehydrogenation rate and reduces the activation energy of the dehydrogenation reaction.

[0015] 4. In the ball milling process of this invention, dry ice is fixed on top of the ball mill jar for cooling during the ball milling process. The low temperature environment provided by the dry ice can effectively counteract the heat generated by the conversion of mechanical energy, maintaining the reaction at a low temperature. The finer the grains, the shorter the diffusion path during hydrogen release, and the better the kinetic performance. This solves the chain problem of "heating-grain growth-powder sticking to the jar" in magnesium alloy ball milling, thereby preparing Mg-Nd hydrogen storage alloy powder with extremely fine grains, abundant defects, and high chemical activity.

[0016] 5. The Mg of the present invention 100-x Nd xThe alloy utilizes the solid solution strengthening and "hydrogen pump" catalytic effect of Nd to significantly reduce the hydrogen desorption temperature and reaction energy barrier of MgH2, forming NdH during the hydrogen absorption and desorption process. x Rare earth catalytic phases are formed and dispersed in situ within the alloy, providing more highly dispersed active sites for hydrogen diffusion. Mg 98.4 Nd 1.6 The alloy absorbs 6.73 wt.% H2 within 60 minutes and releases it completely within 8 minutes, significantly improving the high capacity and dehydrogenation rate of the magnesium-based hydrogen storage alloy. The alloy preparation method and process of this invention are simple, have a short cycle, and are low in cost, making it a magnesium-based hydrogen storage alloy with hydrogen storage potential. Attached Figure Description

[0017] Figure 1 The Mg prepared in Example 1 99.6 Nd 0.4 Microstructure diagram of hydrogen storage alloy; Figure 2 The Mg prepared in Example 2 99.2 Nd 0.8 Microstructure diagram of hydrogen storage alloy; Figure 3 The Mg prepared in Example 3 98.4 Nd 1.6 Microstructure diagram of hydrogen storage alloy; Figure 4 Mg 99.6 Nd 0.4 Mg 99.2 Nd 0.8 and Mg 98.4 Nd 1.6 XRD pattern of hydrogen storage alloy; Figure 5 For high-capacity, fast dehydrogenation of Mg 99.6 Nd 0.4 Mg 99.2 Nd 0.8 and Mg 98.4 Nd 1.6 Hydrogen absorption performance curves of hydrogen storage alloy under conditions of 375℃ and 3MPa; Figure 6 For high-capacity, fast dehydrogenation of Mg 99.6 Nd 0.4 Mg 99.2 Nd 0.8 and Mg 98.4 Nd 1.6 Hydrogen desorption performance curves of hydrogen storage alloy under conditions of 375℃ and normal pressure. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] This invention discloses an Nd-Mg-based hydrogen storage alloy with microstructure controlled by an electromagnetic-current composite field, wherein the Nd-Mg-based hydrogen storage alloy is composed of Mg and Nd, and the atomic percentage formula of the Nd-Mg-based hydrogen storage alloy is Mg 100-x Nd x The value of x ranges from 0.4 to 1.6. The low content of rare earth Nd doping in this magnesium-based hydrogen storage alloy improves the hydrogen storage capacity, maintaining it above 6.7 wt.%, while simultaneously enhancing hydrogen absorption and desorption kinetics and increasing the rate of dehydrogenation. This method utilizes electromagnetic stirring, electric field-assisted solidification, and the rational selection of low rare earth Nd content to form Mg3Nd and Mg... 12 The fine and uniform second phase of Nd provides a rapid diffusion path, featuring a uniform and refined microstructure, high hydrogen storage capacity, and low cost. It solves the problems of reduced hydrogen storage capacity and poor kinetic performance caused by excessive alloying elements and uneven melting microstructure.

[0020] A method for preparing the above-mentioned Nd-Mg-based hydrogen storage alloy based on electromagnetic-current composite field-controlled microstructure includes the following steps: S1: According to the above Mg 100-x Nd x Weigh and mix the raw materials according to the atomic percentage ratio to obtain the raw materials; S2: The raw materials from step S1 are completely melted in a protective atmosphere at 750-850℃. During the melting process, a low-turn induction coil coated with MgO is used to perform electromagnetic stirring in the melt for 2-3 seconds to obtain a homogeneous melt. S3: The melt obtained in step S2 is then cast into a boron nitride mold containing a pair of Ni electrode plates, and current stimulation is applied during solidification to obtain a cast alloy. S4: Grind the as-cast alloy obtained in step S3 to remove oxide scale and mechanically crush it to obtain alloy particles; S5: The alloy particles obtained in step S4 are mechanically ball-milled to obtain Mg. 100-x Nd x Hydrogen storage alloy ball milled powder.

[0021] This design employs an electromagnetic-current composite field control process, introducing electromagnetic stirring during resistance melting to avoid the introduction of impurities by mechanical stirring. This ensures atomic-level uniform distribution of Nd in the alloy, guaranteeing consistent overall material properties and compositional homogeneity. The use of an MgO coating prevents reaction between the coil metal and the molten magnesium, ensuring melt purity, reducing oxide inclusions, and further improving the material's effective hydrogen storage capacity. Furthermore, the electric field stimulation during solidification breaks down coarse dendrites, resulting in an ultrafine equiaxed crystal structure rich in high-density lattice defects. Nd doping is achieved through the formation of Mg3Nd and Mg... 12 Nd and in-situ NdH x The catalytic phase effectively inhibits grain coarsening and provides dispersed active sites, significantly reducing the energy barrier for dehydrogenation reactions. The resulting alloy combines high capacity with excellent kinetic properties, successfully solving the problem of balancing high capacity and fast dehydrogenation rate in traditional magnesium-based alloys.

[0022] In step S1 of this invention, the raw materials consist of pure Mg with a purity higher than 99.9 wt.% and Mg-30 wt.% Nd master alloy; by adjusting the proportions of pure Mg and Mg-30 wt.% Nd master alloy, the final prepared Mg... 100-x Nd x In hydrogen storage alloys, the atomic percentage of Mg is 98.4-99.6%, and the atomic percentage of Nd is 0.4-1.6%.

[0023] In step S2 of this invention, the protective atmosphere is a mixture of CO2 and SF6, and the electromagnetic stirring current is 20-25A.

[0024] In step S3 of this invention, the boron nitride mold is a square boron nitride crucible, and nickel electrode plates are placed on the left and right sides inside the square boron nitride crucible, respectively. The preheating and drying temperature of the crucible and electrode plates is 300°C. The current-composite field control process of this application uses a square boron nitride mold to ensure the high purity of the melt. An electric field is introduced during solidification, and a current is instantaneously applied through the Ni plate electrode. The Joule heating effect and electromagnetic pressure generated by the current change the supercooling of the melt, increasing the nucleation rate. The current stimulation can break up coarse dendrites to refine the grains, further shortening the hydrogen diffusion distance. The large number of lattice defects introduced by the current become heterogeneous nucleation sites for hydrides, significantly improving the dehydrogenation rate and reducing the activation energy of the dehydrogenation reaction.

[0025] In step S3 of this invention, the current is 100-120 mA, and the cooling rate is controlled at 10-50 K / s. The current-composite-field control process of this application introduces an electric field during solidification and applies current instantaneously. The Joule heating effect and electromagnetic pressure generated by the current change the supercooling of the melt, increasing the nucleation rate. The current stimulation can break up coarse dendrites, obtaining extremely fine equiaxed crystal structures, further shortening the hydrogen diffusion distance. The numerous lattice defects introduced by the current become heterogeneous nucleation sites for hydrides, significantly increasing the dehydrogenation rate and reducing the activation energy of the dehydrogenation reaction.

[0026] In step S5 of this invention, a planetary ball mill is used for mechanical ball milling, and the ball mill jar is filled with argon gas of 99.999% purity. Dry ice is fixed on top of the ball mill jar during the ball milling process to prevent the temperature of the jar from rising. The ball milling process of this application uses dry ice fixed on top of the ball mill jar for cooling during the ball milling process. The low-temperature environment provided by the dry ice effectively counteracts the heat generated by the conversion of mechanical energy, maintaining the reaction at a lower temperature. The finer the grains, the shorter the diffusion path during hydrogen release, and the better the kinetic performance. This solves the chain reaction problem of "heating-grain growth-powder sticking to the jar" in magnesium alloy ball milling, thereby preparing Mg-Nd hydrogen storage alloy powder with extremely fine grains, abundant defects, and high chemical activity. In step S5 of the present invention, the ball-to-material ratio of the ball mill is 20:1, and the milling is carried out in stages. First, the milling is carried out at a speed of 100-110 rpm for 1-1.5 hours, and then at a speed of 160-170 rpm for 1-1.5 hours. The total milling time is 2-3 hours, and the mesh size of the hydrogen storage alloy ball mill powder after milling is <200 mesh.

[0027] Example 1

[0028] A Mg microstructure based on electromagnetic-current composite field modulation 99.6 Nd 0.4 Hydrogen storage alloy and its preparation method, including the following steps: S1: The raw materials are prepared using pure Mg and Mg-30wt.% Nd master alloys with a purity higher than 99.9wt.%, and are formulated with 99.6% Mg and 0.4% Nd by atomic percentage. To account for volatilization and burn-off during the smelting process, an additional 2.5wt.% Mg is added to compensate for these losses. To ensure easier melting and uniform diffusion of the pure Mg and Mg-Nd master alloys, all master alloy particles with a diameter of 4-8 mm are used.

[0029] S2: Mg 99.6 Nd 0.4The alloy was smelted in an electric resistance furnace. First, Mg-Nd master alloy particles were placed in a ceramic crucible. The furnace temperature was set to 750℃, and a protective gas mixture of CO2 and SF6 was introduced. Once the Mg-Nd master alloy particles reached a molten state, pure Mg ingots were added to the melt and smelted until fully molten. To ensure uniform alloy melting, a low-turn induction coil coated with MgO was used to electromagnetically stir the melt for 2-3 seconds during the smelting process, resulting in a homogeneous melt.

[0030] S3: The melt was then poured into a square boron nitride mold preheated to 300°C and fitted with a pair of Ni electrode plates. During solidification, a 100mA current was applied to obtain the as-cast alloy; Mg was obtained. 99.6 Nd 0.4 Alloy ingot.

[0031] S4: Mg obtained by polishing with 200-grit sandpaper 99.6 Nd 0.4 The alloy ingots are mechanically crushed after the surface oxide scale is removed, and the ingots are crushed into particles smaller than 2mm.

[0032] S5: Mg after mechanical crushing 99.6 Nd 0.4 Alloy particles were loaded into the grinding jar of a planetary ball mill and filled with 99.999% pure argon gas. The ball-to-particle ratio was 20:1. The milling was carried out at 100 rpm for 1 hour, followed by 170 rpm for 1 hour, for a total milling time of 2 hours. The alloy particles were then crushed to a mesh size below 200 to obtain Mg. 99.6 Nd 0.4 Magnesium-based hydrogen storage alloy.

[0033] pass Figure 1 Mg 99.6 Nd 0.4 Scanning electron microscopy (SEM) images of the hydrogen storage alloy reveal that it consists of two phases: the bright areas represent the Mg3Nd phase, distributed in short rod-like shapes, while the dark areas represent the Mg phase with uniformly distributed Nd elements. Figure 4 It can be seen that Mg 99.6 Nd 0.4 The hydrogen storage alloy consists of two phases: a Mg phase and a Mg3Nd phase. Through... Figure 5 It can be seen that under conditions of 375℃ and 3MPa, the alloy absorbs 6.69wt.% hydrogen gas within 60 minutes. Figure 6 It can be seen that under conditions of 375℃ and normal pressure, the alloy completely releases 6.69 wt.% of hydrogen gas within 13 minutes. The Nd element in the Mg3Nd phase acts as an active site during hydrogen absorption, preferentially absorbing hydrogen to form NdH. xThis process improves the hydrogen storage capacity of magnesium-based alloys, while allowing for complete hydrogen release within 13 minutes. In summary, this example demonstrates the melting of Mg alloys using electromagnetic stirring, electric field-assisted solidification, ball milling, and dry ice cooling. 99.6 Nd 0.4 The hydrogen storage alloy exhibits novel microstructure, high hydrogen storage capacity, and rapid dehydrogenation capability, with a hydrogen storage capacity of 6.69 wt.%.

[0034] Example 2

[0035] A Mg microstructure based on electromagnetic-current composite field modulation 99.2 Nd 0.8 Hydrogen storage alloy and its preparation method, including the following steps: S1: Pure Mg and Mg-30wt.% Nd master alloys with a purity higher than 99.9wt.% are used. The raw materials are prepared by mixing 99.2% Mg and 0.8% Nd according to atomic percentage. Considering the volatilization and burn-off during the melting process, an additional 2.5wt.% Mg is added to compensate for burn-off and volatilization. To facilitate melting and uniform diffusion of the pure Mg and Mg-Nd master alloys, the master alloys used are all alloy particles with a small particle size of 4-8mm.

[0036] S2: Mg 99.2 Nd 0.8 The alloy was smelted in an electric resistance furnace. First, Mg-Nd master alloy particles were placed in a ceramic crucible. The furnace temperature was set to 800℃, and a protective gas mixture of CO2 and SF6 was introduced. Once the Mg-Nd master alloy particles reached a molten state, pure Mg ingots were added to the melt and smelted until fully molten. To ensure uniform alloy melting, a low-turn induction coil coated with MgO was used to electromagnetically stir the melt for 2-3 seconds during the smelting process, resulting in a homogeneous melt.

[0037] S3: The melt was then poured into a square boron nitride mold preheated to 300°C and fitted with a pair of Ni electrode plates. During solidification, a 100mA current was applied to obtain the as-cast alloy; Mg was obtained. 99.2 Nd 0.8 Alloy ingot.

[0038] S4: Mg obtained by polishing with 200-grit sandpaper 99.2 Nd 0.8 The alloy ingots are mechanically crushed after the surface oxide scale is removed, and the ingots are crushed into particles smaller than 2mm.

[0039] S5: Mg after mechanical crushing 99.2 Nd 0.8Alloy particles were loaded into the grinding jar of a planetary ball mill and filled with 99.999% pure argon gas. The ball-to-particle ratio was 20:1. The milling was carried out at 100 rpm for 1 hour, followed by 170 rpm for 1 hour, for a total milling time of 2 hours. The alloy particles were then crushed to a mesh size below 200 to obtain Mg. 99.2 Nd 0.8 Magnesium-based hydrogen storage alloy.

[0040] pass Figure 2 Mg 99.2 Nd 0.8 Scanning electron microscopy (SEM) images of the hydrogen storage alloy show that it consists of two phases: the bright areas are Mg3Nd phases, exhibiting a discontinuous network distribution, while the dark areas are Mg phases with uniformly distributed Nd elements. Figure 4 It can be seen that Mg 99.2 Nd 0.8 The hydrogen storage alloy consists of two phases: a Mg phase and a Mg3Nd phase. Through... Figure 5 It can be seen that under conditions of 375℃ and 3MPa, the alloy absorbs 6.68wt.% hydrogen gas within 60 minutes. Figure 6 It can be seen that under conditions of 375℃ and normal pressure, the alloy releases 6.68 wt.% hydrogen gas within 13 minutes. The Nd element in the Mg3Nd phase acts as an active site during hydrogen absorption, preferentially absorbing hydrogen to form NdH. x This process improves the hydrogen storage capacity of magnesium-based alloys, while allowing for complete hydrogen release within 13 minutes. In summary, this example demonstrates the melting of Mg alloys using electromagnetic stirring, electric field-assisted solidification, ball milling, and dry ice cooling. 99.2 Nd 0.8 The hydrogen storage alloy exhibits novel microstructure, high hydrogen storage capacity, and rapid dehydrogenation capability, with a hydrogen storage capacity of 6.68 wt.%.

[0041] Example 3

[0042] A Mg microstructure based on electromagnetic-current composite field modulation 98.4 Nd 1.6 Hydrogen storage alloy and its preparation method, including the following steps: S1: The raw materials are prepared using pure Mg and Mg-30wt.% Nd master alloys with a purity exceeding 99.9wt.%, and are formulated with 98.4% Mg and 1.6% Nd by atomic percentage. To account for volatilization and burn-off during the smelting process, an additional 2.5wt.% Mg is added to compensate for these losses. To ensure easier melting and uniform diffusion of the pure Mg and Mg-Nd master alloys, the master alloys used are all alloy particles with a small diameter of 4-8mm.

[0043] S2: Mg 98.4 Nd 1.6The alloy was smelted in an electric resistance furnace. First, Mg-Nd master alloy particles were placed in a ceramic crucible. The furnace temperature was set to 850℃, and a protective gas mixture of CO2 and SF6 was introduced. Once the Mg-Nd master alloy particles reached a molten state, pure Mg ingots were added to the melt and smelted until fully molten. To ensure uniform alloy melting, a low-turn induction coil coated with MgO was used to electromagnetically stir the melt for 2-3 seconds during the smelting process, resulting in a homogeneous melt.

[0044] S3: The melt was then poured into a square boron nitride mold preheated to 300°C and fitted with a pair of Ni electrode plates. During solidification, a 100mA current was applied to obtain the as-cast alloy; Mg was obtained. 98.4 Nd 1.6 Alloy ingot.

[0045] S4: Mg obtained by polishing with 200-grit sandpaper 98.4 Nd 1.6 The alloy ingots are mechanically crushed after the surface oxide scale is removed, and the ingots are crushed into particles smaller than 2mm.

[0046] S5: Mg after mechanical crushing 98.4 Nd 1.6 Alloy particles were loaded into the grinding jar of a planetary ball mill and filled with 99.999% pure argon gas. The ball-to-particle ratio was 20:1. The milling was carried out at 100 rpm for 1 hour, followed by 170 rpm for 1 hour, for a total milling time of 2 hours. The alloy particles were then crushed to a mesh size below 200 to obtain Mg. 98.4 Nd 1.6 Magnesium-based hydrogen storage alloy.

[0047] pass Figure 3 Mg 98.4 Nd 1.6 The scanning electron microscope (SEM) microstructure of the hydrogen storage alloy shows that it consists of two phases, with the bright area being Mg. 12 The Nd phase is distributed in a continuous network, while the dark areas are Mg phase, with Nd elements uniformly distributed. (Through...) Figure 4 It can be seen that Mg 98.4 Nd 1.6 Hydrogen storage alloys consist of Mg phase and Mg 12 The Nd phase is composed of two phases. (Through...) Figure 5 It can be seen that under conditions of 375℃ and 3MPa, the alloy absorbs 6.73wt.% hydrogen gas within 60 minutes. Figure 6 It can be seen that under conditions of 375℃ and normal pressure, the alloy releases 6.73 wt.% hydrogen gas within 8 minutes. Mg 12 In the Nd phase, the Nd element acts as an active site during hydrogen absorption, preferentially absorbing hydrogen to form NdH.x This process improves the hydrogen storage capacity of magnesium-based alloys, enabling complete hydrogen release within 8 minutes, significantly increasing the rate. In summary, this example demonstrates the melting of Mg alloys using electromagnetic stirring, electric field-assisted solidification, ball milling, and dry ice cooling. 98.4 Nd 1.6 The hydrogen storage alloy exhibits novel microstructure, high hydrogen storage capacity, and rapid dehydrogenation capability, with a hydrogen storage capacity of 6.73 wt.%.

[0048] Therefore, it can be concluded that the Mg in this application 100-x Nd x The alloy was prepared using a synergistic process of electromagnetic stirring and electromagnetic current-assisted solidification, achieving atomically uniform Nd distribution and obtaining an ultrafine equiaxed grain structure. Utilizing the solid solution strengthening and "hydrogen pump" catalytic effect of Nd, the hydrogen desorption temperature and reaction energy barrier of MgH₂ were significantly reduced, forming NdH₂ during the hydrogen absorption and desorption process. x Rare earth catalytic phases are formed and dispersed in situ within the alloy, providing more highly dispersed active sites for hydrogen diffusion. Mg 98.4 Nd 1.6 The alloy absorbs 6.73 wt.% H2 within 60 minutes and releases it completely within 8 minutes, significantly improving the high capacity and dehydrogenation rate of the magnesium-based hydrogen storage alloy. The alloy preparation method and process of this invention are simple, have a short cycle, and are low in cost. It is a magnesium-based hydrogen storage alloy with both high capacity and excellent kinetic performance.

[0049] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A Nd-Mg-based hydrogen storage alloy with microstructure controlled by an electromagnetic-current composite field, characterized in that, The Nd-Mg-based hydrogen storage alloy is composed of Mg and Nd, and the atomic percentage formula of the Nd-Mg-based hydrogen storage alloy is Mg 100-x Nd x , where x ranges from 0.4 to 1.

6.

2. A method for preparing an Nd-Mg-based hydrogen storage alloy with a microstructure controlled by an electromagnetic-current composite field as described in claim 1, characterized in that, Includes the following steps: S1: Mg as described in claim 1 100-x Nd x Weigh and mix the raw materials according to the atomic percentage ratio to obtain the raw materials; S2: The raw materials of step S1 are completely melted in a protective atmosphere at 750-850°C. During the melting process, a low-turn induction coil coated with MgO is used to perform electromagnetic stirring in the melt for 2-3 seconds to obtain a homogeneous melt. S3: The melt obtained in step S2 is poured into a boron nitride mold containing a pair of Ni electrode plates, and current stimulation is applied during solidification to obtain a cast alloy. S4: Grind the as-cast alloy obtained in step S3 to remove oxide scale and mechanically crush it to obtain alloy particles; S5: The alloy particles obtained in step S4 are mechanically ball-milled to obtain Mg. 100-x Nd x Hydrogen storage alloy ball milled powder.

3. The preparation method according to claim 2, characterized in that, In step S1, the raw materials consist of pure Mg with a purity higher than 99.9 wt.% and Mg-30 wt.% Nd master alloy; by adjusting the proportions of pure Mg and Mg-30 wt.% Nd master alloy, the final prepared Mg... 100-x Nd x In hydrogen storage alloys, the atomic percentage of Mg is 98.4-99.6%, and the atomic percentage of Nd is 0.4-1.6%.

4. The preparation method according to claim 2, characterized in that, In step S2, the protective atmosphere is a mixture of CO2 and SF6.

5. The preparation method according to claim 2, characterized in that, In step S2, the electromagnetic stirring current is 20-25A.

6. The preparation method according to claim 2, characterized in that, In step S3, the boron nitride mold is a square boron nitride crucible, and nickel electrode plates are placed on the left and right sides inside the square boron nitride crucible, respectively. The preheating and drying temperature of the crucible and electrode plates is 300°C.

7. The preparation method according to claim 2, characterized in that, In step S3, the current is 100-120mA, and the cooling rate is controlled at 10-50K / s.

8. The preparation method according to claim 2, characterized in that, In step S5, the mechanical ball milling adopts a planetary ball mill, the ball mill jar is filled with argon gas with a purity of 99.999%, and dry ice is fixed on the top of the ball mill jar during the ball milling process.

9. The preparation method according to claim 2, characterized in that, In step S5, the ball-to-material ratio of the ball mill is 20:1, and the milling is carried out in stages. First, the milling is carried out at a speed of 100-110 rpm for 1-1.5 hours, and then at a speed of 160-170 rpm for 1-1.5 hours. The total milling time is 2-3 hours. After milling, the mesh size of the hydrogen storage alloy ball mill powder is <200 mesh.

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