Lanthanum oxide catalyzed high-capacity hydrogen storage alloy and preparation method thereof

Abstract

The invention relates to a lanthanum oxide catalyzed high-capacity hydrogen storage alloy and a preparation method thereof, the hydrogen storage alloy comprises the following components: Mg < 85-x > Zr < x > Sm < 12-y > Nd < y > N < i < 5-z-m > Cu < z > Zn < m + n > wt.% La2O3, in the formula, x, y, z and m are atomic ratios, and 0 lt; x is less than or equal to 5, 0lt; y < = 3, 0lt; z < = 2, 0lt; m is less than or equal to 2, n is the percentage of La2O3 in the alloy, and n is more than or equal to 4 and less than or equal to 12. Preferably, the atomic ratio x: y: z: m is 3: 2: 1: 1, and n is equal to 7. The preparation method comprises the following steps: smelting by induction heating under the protection of inert gas, pouring a liquid alloy into a tundish, and continuously spraying the liquid alloy on the surface of a rotating water-cooled copper roller through a BN nozzle at the bottom of the tundish to obtain a rapidly quenched alloy with a nanocrystalline structure; and the rapidly quenched alloy is mechanically crushed and sieved, the sieved alloy powder and a certain amount of catalyst La2O3 are subjected to ball milling in an all-dimensional planetary high-energy ball mill under the protection of protective gas, and alloy powder with ultra-fine grains (nanoscale) is obtained. Through component design, microstructure regulation and control and addition of a catalyst, the thermal stability of alloy hydride is reduced, and the hydrogen absorption and desorption thermodynamic and dynamic performance of the alloy is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state hydrogen storage alloy materials. Specifically, it relates to a lanthanum oxide-catalyzed high-capacity hydrogen storage alloy and a preparation method thereof. Background Art

[0002] Mg-based hydrogen storage alloys have advantages such as high capacity, low density, easy activation, and non-toxicity. They are one of the most promising hydrogen storage materials in recent years and also play a crucial role in the field of automotive energy. However, the slow hydrogen absorption kinetics and high reaction temperature of MgH2 are the main obstacles to practical applications. To solve these problems, methods such as alloying, catalysts, and nano-confinement have been widely used. Research results show that in-situ rare earth hydrides (REH x ) can significantly improve the hydrogen storage performance. Some researchers have prepared alloys with fast hydrogen absorption / desorption and low decomposition temperature (Mg 95 Y3Zn2), which is due to the uniformly distributed YH2 / YH3 "hydrogen pump". In-situ nano REH x provides many diffusion channels, making the Mg grains refined, thus shortening the diffusion length.

[0003] Recently, some researchers have found that REH x acts as an active site to catalyze the dissociation of H2 and the nucleation of Mg, reducing the hydrogen desorption activation energy of the Mg 98 Ni 1.67 La 0.33 alloy to 107.26 kJ / mol. Although alloying has greatly improved the hydrogen storage performance of the alloy, due to the large amount of energy required for H2 cracking and the need to remove the "blocking effect" of MgH2 on the particle surface, its surface modification still needs to be further improved. Summary of the Invention

[0004] The purpose of the present invention is to prepare a lanthanum oxide-catalyzed high-capacity hydrogen storage alloy, which is a multi-element RE-Mg-Zr-Ni-Cu-Zn-based Mg 41 Sm5-type hydrogen storage alloy for high-capacity fuel cells. Through the present invention, the hydrogen storage performance of the alloy is greatly improved, thereby providing a Mg 41 Sm5-type hydrogen storage alloy with high hydrogen storage capacity and good kinetic performance and the corresponding preparation process.

[0005] Based on Mg-based alloys, the present invention adds a small amount of Y, Al, and Sn in the composition design to reduce the thermal stability of the hydride through the composition design. The alloy is prepared by vacuum rapid quenching technology, reducing the grain size of the alloy to the nanoscale, further reducing the thermal stability of the alloy and improving its hydrogen absorption and desorption kinetic properties. On this basis, a certain amount of La2O3 catalyst is added to the rapidly quenched alloy, and after short-time ball milling, the catalyst is uniformly mixed with the alloy, and a highly active interface is formed between the catalyst and the alloy particles, thereby obtaining a composite hydrogen storage material with excellent hydrogen absorption and desorption kinetic properties.

[0006] The inventors found in their work that adding an appropriate amount of rare earth oxide catalyst can significantly destabilize the Mg-H bond and accelerate the dehydrogenation reaction rate. La7Sm3Mg 80 Ni 10 +5wt% La2O3 takes 301 seconds to desorb 3wt.% H2 at 593K. In addition, rare earth oxides are very stable during the hydrogen absorption and desorption cycle and do not react with H2 to form REH x . In addition, its uniform distribution on the particle surface effectively promotes the hydrogen absorption and desorption performance of the alloy. The catalytic performance of different concentrations of CeO2 on Mg 90 Ni 10 Zn5 alloy was studied. It was found that the hydrogen desorption activation energy of the sample with 4wt.% CeO2 catalyst added decreased from 109.83 to 82.93 kJ / mol. The oxygen vacancy defects on the Ce6O 11 surface can capture H2 molecules during the hydrogen absorption process. It was thus recognized that a series of light rare earth oxides have excellent catalytic performance, while heavy rare earth oxides have not been systematically studied in current research. Some researchers prepared a Mg-In-F system, and the dehydrogenation activation energy and enthalpy change were 127.7 kJ / mol and 69.2 kJ / mol H2 respectively. Therefore, the key problems that need to be solved for hydrogen storage materials are the dual regulation of thermodynamics and kinetics.

[0007] Based on Mg-based alloys, the present invention adds a small amount of Y, Al, and Sn in the composition design to reduce the thermal stability of the hydride through the composition design. The alloy is prepared by vacuum rapid quenching technology, reducing the grain size of the alloy to the nanoscale, further reducing the thermal stability of the alloy and improving its hydrogen absorption and desorption kinetic properties. On this basis, a certain amount of La2O3 catalyst is added to the rapidly quenched alloy, and after short-time ball milling, the catalyst is uniformly mixed with the alloy, and a highly active interface is formed between the catalyst and the alloy particles, thereby obtaining a composite hydrogen storage material with excellent hydrogen absorption and desorption kinetic properties.

[0008] Previous work on the present invention has confirmed that the combination of different rare earth metals will be more effective than single rare earth metals in improving the hydrogen storage performance of Mg-based alloys. In the present invention, by adding multiple rare earth elements Sm and Nd, as well as metal elements Zr, Ni, Cu, and Zn, it is expected to reduce the stability of Mg-based hydrides and improve their hydrogen absorption and desorption kinetic properties. By adding a small amount of catalyst La2O3 and subjecting it to mechanical ball milling for an appropriate time, a microstructure with nanocrystals is obtained, greatly improving the hydrogen storage performance of the target alloy. On the one hand, the addition of rare earth elements Sm and Nd and metal elements Zr, Ni, Cu, and Zn promotes the dissociation of hydrogen and reduces the binding strength of the Mg-H bond; on the other hand, the catalyst La2O3 can not only improve the ball milling efficiency, but also promote the introduction of high-density crystal defects and the improvement of the surface activity of the ball-milled particles. The particle and grain refinement caused by ball milling greatly shortens the diffusion distance of hydrogen atoms, thus greatly increasing the rate of hydrogen absorption and desorption.

[0009] A high-capacity hydrogen storage alloy catalyzed by lanthanum oxide provided by the present invention is characterized in that the alloy contains multiple rare earth elements Sm and Nd, as well as metal elements Zr, Ni, Cu, and Zn, and a catalyst La2O3 is added, and its composition is: Mg 85-x Zr x Sm 12- y Nd y Ni 5-z-m Cu z Zn m +n wt.%La2O3, where x, y, z, m are atomic ratios, and 0 < x ≤ 5, 0 < y ≤ 3, 0 < z ≤ 2, 0 < m ≤ 2, n is the percentage of La2O3 in the alloy, and 4 ≤ n ≤ 12. The preferred atomic ratio x:y:z:m = 3:2:1:1, n = 7.

[0010] The preparation method steps of the high-capacity hydrogen storage alloy catalyzed by lanthanum oxide provided by the present invention include:

[0011] 1. Batching: According to the chemical formula composition Mg 85-x Zr x Sm 12-y Nd y Ni 5-z-m Cu z Zn m for batching, where 0 < x ≤ 5, 0 < y ≤ 3, 0 < z ≤ 2, 0 < m ≤ 2. Among them, the Mg in the chemical formula composition increases by 8% during batching, and the rare earth Sm and Nd and the metal Zn increase by 5% during batching for the loss during melting. The metal purity of the raw materials ≥ 99.5%.

[0012] 2. Alloy melting and rapid quenching: The weighed raw materials are melted by conventional heating methods, such as arc melting, induction heating melting or other heating methods. The heating conditions are as follows: evacuate to 1×10 -2 -5×10 -5 Pa, introduce high-purity helium gas with a pressure of 0.01 - 0.1 MPa or a helium + argon mixed gas with a volume ratio of approximately 1:1 as the protective gas, heat at a temperature of 1650 - 1750 °C to obtain molten Mg 85-x Zr x Sm 12-y Nd y Ni 5-z-m Cu z Zn m liquid master alloy. After the molten alloy is kept in the protective gas atmosphere for about 5 minutes, the liquid master alloy is directly injected into a tundish with an NB nozzle embedded at the bottom. The liquid alloy continuously drops from the slit of the NB nozzle at the bottom of the tundish (the slit width is 0.3 mm) onto the surface of a water-cooled copper roller rotating at a linear speed of 5 - 30 m / s, obtaining a rapidly quenched alloy thin sheet with a thickness between 50 - 300 μm. It is necessary to determine an appropriate rapid quenching cooling rate to ensure that the rapidly quenched alloy ribbon has an almost completely nanocrystalline structure with a grain size between 10 - 100 nm.

[0013] 3. Mechanical ball milling: Mechanically crush the rapidly quenched Mg 85-x Zr x Sm 12-y Nd y Ni 5-z-m Cu z Zn m alloy ribbon and pass it through a 200-mesh sieve. Load the sieved alloy powder together with a certain amount of catalyst La2O3 and stainless steel grinding balls into a stainless steel ball milling tank. After evacuating, fill it with high-purity argon gas and ball mill in an all-round planetary high-energy ball mill for 2 - 10 hours, preferably 4.5 hours, with a ball-to-material ratio of 20:1 and a rotation speed of 350 revolutions per minute. During the ball milling process, the ball mill stops for 0.5 hour every 1 hour of continuous operation to prevent the temperature of the ball milling tank and the grinding material from being too high. Determining the ball milling time is crucial. If the ball milling time is too long, a large amount of amorphous phase will appear, resulting in a decline in the hydrogen storage performance of the alloy. The optimal ball milling time is to ensure that there is no excessive amorphous phase in the ball milled alloy and to ensure good dispersion of the alloy powder without serious agglomeration, thereby ensuring that the hydrogen absorption capacity of the alloy does not decrease significantly.

[0014] 4. Structural analysis and performance testing: The phase structures of as-cast and ball-milled powders were tested by XRD. The morphologies and microstructures of as-cast and ball-milled alloys were observed by high-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM), and the crystallinity of the alloys was determined by selected area electron diffraction (SAED). The hydrogen absorption activation performance, hydrogen storage capacity and hydrogen absorption / desorption kinetics of the alloy powders were tested using a semi-automatic Sieverts apparatus. The hydrogen absorption temperature was 200 °C and the initial hydrogen pressure was 3 MPa; the dehydrogenation temperature was 260 °C, and dehydrogenation was carried out under a pressure of 1×10 -4 MPa.

[0015] The characteristics of the present invention are reflected in the following aspects: In terms of the composition design of the alloy, multiple rare earths Sm and Nd were added, and at the same time, a small amount of metal elements Zr, Ni, Cu and Zn were added for alloying. Mg and Sm can form the main phase Mg 41 Sm5, Nd and Mg can form Mg 41 Nd5 phase, Zr and Ni can form Zr2Ni phase, and Mg can form a variety of intermetallic compounds such as MgCu2 and MgZn2 with Cu and Zn. Some of these intermetallic compounds are hydrogen-absorbing phases themselves, and some, although not hydrogen-absorbing, have a positive effect on the hydrogen absorption and desorption of Mg-based alloys. At the same time, rare earths Sm and Nd can form Sm3H7 and NdH3 hydrides with hydrogen. These hydrides are distributed as dispersed particles in the alloy matrix and are the nuclei for the nucleation of magnesium hydrides themselves, and have an obvious catalytic effect on the hydrogen absorption and desorption process of Mg-based alloys. By rapid quenching treatment, a nanocrystalline structure was obtained, and the grain boundaries provided good channels for the diffusion of hydrogen atoms, which was particularly beneficial to improving the hydrogen absorption and desorption kinetics of Mg-based alloys. On this basis, the rapidly quenched alloy flakes were mechanically pulverized, and a small amount of catalyst La2O3 was added and then ball-milled for a short time. While maintaining the microstructure of the rapidly quenched alloy, the surface state of the rapidly quenched alloy was improved, and the hydrogen absorption and desorption thermodynamics and kinetics of the alloy were further improved. The hydrogen storage alloy powder prepared in this way not only has good hydrogen absorption and desorption capacity and excellent hydrogen absorption and desorption kinetics, but also is very promising to be a hydrogen supply carrier for hydrogen fuel cells. In addition, the preparation process of the alloy is simple and easy to operate, and can fully meet the requirements of large-scale preparation. Description of the Drawings

[0016] The accompanying drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0017] Figure 1 are the SEM morphologies of the as-cast alloys of Examples 1-6. It can be found that the as-cast alloys have a multiphase structure, including Mg 41 Sm5 main phase, Mg 41The Nd5 phase, Zr2Ni phase, MgCu2 and MgZn2 phases. It is the emergence of these intermetallic compounds that significantly changes the hydrogen absorption and desorption properties of the RE-Mg-Zr-Ni-Cu-Zn-based Mg 41 Sm5-type alloy.

[0018] Figure 2 Figure 1 is a physical photograph of the rapidly quenched alloy ribbon and the HRTEM morphology of the microstructure for Example 1. It can be seen that after appropriate rapid quenching treatment, a microstructure with almost all nanocrystalline structure is obtained, and the average grain size is about 34 nm

[0019] Figure 3 Figure 2 is the SEM morphology of the ball-milled alloy powders for Examples 1-6. It can be found that the ball-milled alloy particles are approximately spherical, and the dispersibility between the particles is good, without serious aggregation, which is obviously related to the role of the catalyst and the selection of the ball-milling time.

[0020] Figure 4 Figure 3 is the XRD diffraction pattern of the ball-milled powders for Examples 1-6. It can be found that ball milling significantly broadens the diffraction peaks of the alloy, which is obviously the result of grain refinement and increased lattice internal stress caused by ball milling.

[0021] Figure 5 Figure 4 is the HRTEM morphology of the ball-milled powders for Examples 1-6. The results show that the ball-milled powders have a microstructure mainly composed of nanocrystals. Detailed implementation manners

[0022] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0023] Combined with the drawings, comparative examples and embodiments, the design concept and mechanism of the present invention are further described in detail to make the technical solution of the present invention clearer.

[0024] The present invention discovers through research that in terms of alloy composition design, element substitution can reduce the thermal stability of Mg-based alloy hydrides and improve their hydrogen absorption and desorption kinetic properties. In particular, adding rare earth elements Sm and Nd can significantly reduce the stability of magnesium hydride. Since rare earth Sm and Nd can form Sm3H7 and NdH3 with high stability during hydrogen absorption, Zr and Ni can form Zr2Ni, and Cu and Zn can form MgCu2 and MgZn2 phases with Mg. These intermetallic compounds also have a good effect on improving the hydrogen storage performance of Mg-based alloys.

[0025] In terms of the preparation process, the melt spinning treatment can be used to obtain a precursor with ultrafine grains (nanoscale), and the rapidly quenched structure contains a high density of crystal defects, including dislocations, stacking faults, twins, a large number of grain boundaries, etc. This microstructure is extremely beneficial for improving the thermodynamic and kinetic properties of the alloy. Different from ball milling, the ultrafine structure and crystal defects obtained by rapid quenching have high stability, and the grains are not easy to aggregate and grow after multiple hydrogen absorption and desorption cycles. In terms of hydrogen absorption and desorption performance, it not only has excellent hydrogen absorption and desorption kinetics, but also has good cycle stability.

[0026] After adding the catalyst La2O3 and performing short-term ball milling, while maintaining the microstructure of the rapidly quenched alloy, the surface state of the alloy is improved, and the advantages of the two preparation processes are exerted. The catalyst is evenly distributed in the alloy matrix during ball milling, and its catalytic effect can be fully exerted, thereby improving the hydrogen absorption and desorption thermodynamics and kinetics of the alloy. The catalytic effect of La2O3 lies in its high hardness, which has an obvious cutting effect on the alloy particles during ball milling, making the particles of the ball-milled alloy finer. After adding a highly stable catalyst and performing ball milling, it can be evenly distributed between the alloy particles, and a large number of active interfaces between the alloy and the catalyst will inevitably be formed. These interfaces provide good nucleation sites for the formation and decomposition of hydrides. It is precisely due to the combination of rapid quenching, ball milling, and adding a catalyst that the hydrogen absorption and desorption thermodynamics and kinetics of the alloy are greatly improved.

[0027] The present invention further illustrates the composition and preparation method of the RE-Mg-Zr-Ni-Cu-Zn-based Mg 41 Sm5 type hydrogen storage alloy through the following examples.

[0028] The RE-Mg-Zr-Ni-Cu-Zn-based Mg 41 Sm5 type solid-state hydrogen storage alloy for fuel cells of the present invention has a chemical formula of: Mg 85-x Zr x Sm 12-y Nd y Ni 5-z-m Cu z Zn m +n wt.%La2O3, where x, y, z, m are atomic ratios, and 0 < x ≤ 5, 0 < y ≤ 3, 0 < z ≤ 2, 0 < m ≤ 2, n is the percentage of La2O3 in the alloy, 4 ≤ m ≤ 12. The preferred atomic ratio x:y:z:m = 3:2:1:1, n = 7

[0029] The preparation method of the high-capacity RE-Mg-Zr-Ni-Cu-Zn-based Mg 41 Sm5 type hydrogen storage alloy of the present invention includes the following steps:

[0030] A. Composed by chemical formula: Mg 85-x Zr x Sm 12-y Nd y Ni 5-z-m Cu z Zn m Perform batching. Since the melting points of Mg, Zn, and rare earths Sm and Nd are relatively low and they are prone to volatilization, therefore, during the proportioning, Mg is added by 8% more, and rare earths Sm and Nd and metal Zn are added by 5% more to make up for the loss by burning.

[0031] B. Place the prepared raw materials in a magnesia crucible in sequence. Blocky rare earths Sm and Nd are placed at the bottom of the crucible, sponge Zr is placed on top of rare earths Sm and Nd, electrolytic Ni is placed on top of sponge Zr, metal Cu is placed on top of electrolytic Ni, and metal Zn and Mg are placed on the top. After the materials are placed in sequence, cover the furnace lid, evacuate to 1×10 -2 -5×10 -5 Pa, and fill with high-purity helium gas at a pressure of 0.01 - 0.1 MPa as the protective gas. The melting temperature is 1650 - 1750 °C to obtain molten Mg 85- x Zr x Sm 12-y Nd y Ni 5-z-m Cu z Zn m Liquid master alloy.

[0032] C. Under the protection of an inert gas atmosphere, after the alloy is melted and held for about 5 minutes, directly inject the liquid master alloy into a tundish with an NB nozzle embedded at the bottom. The liquid alloy continuously sprays onto the smooth surface of a water-cooled copper roller rotating at 5 - 30 m / s through the nozzle slit of the NB nozzle. 18 m / s can be preferably selected to obtain a rapidly quenched alloy thin sheet with a thickness between 50 - 300 μm. This rapidly quenched alloy has a columnar crystal structure, and this structure is a uniform and consistent nanocrystalline structure; the requirement for rapid quenching is to ensure that the rapidly quenched alloy ribbon has as many nanocrystalline structures as possible. If the rapid quenching cooling rate is too fast, a considerable proportion of amorphous phase will appear in the structure, which will significantly reduce the hydrogen absorption capacity of the alloy. If the cooling rate is too slow, a relatively large number of microcrystalline structures will appear, weakening the hydrogen absorption and desorption kinetic performance of the alloy.

[0033] D. The rapidly quenched Mg 85-x Zr x Sm 12-y Nd y Ni 5-z-m Cu z Zn mAfter the alloy thin strip is mechanically crushed and passed through a 200-mesh sieve, it is mixed with a certain amount of catalyst La2O3 and stainless steel grinding balls and loaded into a stainless steel ball mill tank. After evacuating, high-purity argon is filled, and ball milling is carried out in an all-round planetary high-energy ball mill for 2 - 10 hours, preferably 4.5 hours; the ball-to-material ratio is 20:1, and the rotation speed is 350 revolutions per minute. During the ball milling process, the ball mill stops for 0.5 hours every 1 hour of continuous operation to prevent the temperature of the ball mill tank and the abrasive from being too high. Through the above preparation process, the multi-component RE-Mg-Zr-Ni-Cu-Zn-based Mg 41 Sm5-type hydrogen storage material is obtained. It should be noted that the ball milling process must be appropriate. An overly long ball milling time will result in more amorphous phases in the microstructure, and at the same time, due to cold welding between particles, agglomeration phenomena will occur, which will all lead to a decrease in the hydrogen absorption and desorption performance of the alloy.

[0034] E. The structure of the ball-milled powder is tested by XRD, and the morphology and microstructure of the alloy before and after ball milling are observed by high-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM), and the crystal state of the alloy is determined by selected area electron diffraction (SAED). The gaseous hydrogen storage capacity and hydrogen absorption and desorption kinetics of the alloy powder are tested by a fully automatic Sieverts device. The hydrogen absorption temperature is 200 °C, the initial hydrogen pressure for hydrogen absorption is 3 MPa, and desorption is carried out at 260 °C and 1×10 -4 MPa pressure.

[0035] The chemical composition and ratio of the specific embodiments of the present invention are selected as follows:

[0036] Example 1: Mg 82 Zr3Sm 10 Nd2Ni3Cu1Zn1 + 7 wt.% La2O3

[0037] Example 2: Mg 80 Zr5Sm 10 Nd2Ni3Cu1Zn1 + 4 wt.% La2O3

[0038] Example 3: Mg 82 Zr3Sm9Nd3Ni3Cu1Zn1 + 5 wt.% La2O3

[0039] Example 4: Mg 82 Zr3Sm 10 Nd2Ni2Cu2Zn1 + 8 wt.% La2O3

[0040] Example 5: Mg 82 Zr3Sm 10 Nd2Ni2Cu1Zn2 + 10 wt.% La2O3

[0041] Example 6: Mg 82Zr3Sm 10 Nd2Ni3Cu1Zn1 + 12 wt.% La2O3

[0042] Comparative Example 1: Mg 41 Sm5 (rapid quenching + ball milling)

[0043] Select bulk metals Mg, rare earth metals Sm and Nd, sponge Zr, electrolytic Ni and Cu, and metal Zn according to the chemical formula compositions of the respective examples. The metal purity requirement is ≥99.5%. After grinding the selected bulk metals to remove the surface oxide layer, weigh them according to the stoichiometric ratio. Among them, 8% is added to the metal Mg during the proportioning, and 5% is added to the rare earth Sm, Nd and metal Zn to make up for the loss during melting; during the preparation process, technical parameters at each stage are as follows: when induction heating, the vacuum is from 1×10 -2 -5×10 -4 Pa, and high-purity helium gas with a filling pressure of 0.01 - 0.1 MPa or a helium + argon mixed gas with a volume ratio of 1:1 is filled; the melting temperature is 1650 - 1750 °C; the surface linear velocity of the rapid quenching water-cooled copper roller is 5 - 30 m / s. After mechanically crushing the rapidly quenched thin slices and passing them through a 200-mesh sieve, mix them with the catalyst La2O3 and stainless steel grinding balls and load them into a stainless steel ball milling tank, and ball mill for 2 - 10 hours with a ball mill stopping for 0.5 hours every 1 hour of continuous operation. All process parameters can be appropriately selected within the above ranges to prepare the hydrogen storage alloy powder described in the patent. Therefore, although only one typical example is given in the present invention, this example is applicable to preparation methods with different parameters.

[0044] Process technical parameters of Example 1: According to the chemical formula Mg 82 Zr3Sm 10 Nd2Ni3Cu1Zn1, select bulk Mg and rare earth Sm and Nd, sponge Zr, electrolytic Ni and Cu, and metal Zn. The purity of these metals is 99.5%, weigh them according to the stoichiometric ratio, and charge 5 kg per furnace. Among them, bulk metal Mg is 2466.3 grams, rare earth Sm is 1808.9 grams, rare earth Nd is 347.1 grams, sponge Zr is 313.5 grams, electrolytic Ni is 201.7 grams, electrolytic Cu is 72.8 grams, and metal Zn is 78.7 grams. Place the weighed bulk metals in a magnesia crucible of an intermediate frequency induction furnace according to the designed process, place the bulk rare earth Sm and Nd at the bottom of the crucible, place the sponge Zr on the rare earth Sm and Nd, place the electrolytic Ni on the sponge Zr, place the electrolytic Cu on the electrolytic Ni, and place the metal Zn and Mg on the top. Then cover the furnace lid, evacuate to a vacuum of about 30 minutes to a vacuum degree of 5×10 -2Above Pa, then fill with high-purity helium protective gas until the pressure reaches 0.04 MPa, adjust the power to 5 kW, control the temperature at 650 °C to melt the metal Mg, and then adjust the power to 25 kW and control the temperature at 1750 °C to melt the remaining metals. After the molten alloy is kept in the protective gas atmosphere for 5 minutes, the liquid master alloy is directly injected into the tundish with an NB nozzle embedded at the bottom. The liquid alloy continuously drops from the gap of the NB nozzle at the bottom of the tundish (the nozzle gap width is 0.3 mm) onto the surface of a water-cooled copper roller rotating at a linear velocity of 18 m / s, obtaining a rapidly quenched alloy thin sheet with a thickness of about 135 μm and an average grain size of about 34 nm. The rapidly quenched Mg 82 Zr3Sm 10 The Nd2Ni3Cu1Zn1 alloy thin sheet is mechanically crushed and passed through a 200-mesh sieve. Weigh 20 grams of the sieved alloy powder, 1.4 grams of the catalyst La2O3, and 400 grams of stainless steel grinding balls and mix them together and load them into a 250-ml stainless steel ball mill jar. After evacuating and filling with high-purity argon, seal it. Ball mill in an all-round planetary high-energy ball mill for 4.5 hours. The ball mill stops for 0.5 hours every 1 hour of continuous operation.

[0045] Figure 1 For the SEM morphology of the as-cast alloys in Examples 1-6, the results show that after adding multiple rare earths and alloying with multiple metals, a variety of intermetallic compounds are formed. Among them, Mg and Sm form Mg 41 Sm5 main phase, Nd and Mg form Mg 41 Nd5 phase, Zr and Ni form Zr2Ni, and Cu and Zn and Mg form various intermetallic compounds such as MgCu2 and MgZn2 phases.

[0046] Figure 2 For the physical picture of the rapidly quenched alloy thin strip, the thickness of the tested thin strip is about 135 μm. It is found by HRTEM observation that the rapidly quenched alloy thin strip is almost a completely nanocrystalline structure with an average grain size of about 34 nm.

[0047] Figure 3 For the SEM morphology of the ball-milled powders in Examples 1-6, it is observed that the dispersion of the alloy particles after ball milling is very good and no obvious agglomeration phenomenon is formed.

[0048] Figure 4 For the XRD patterns of the ball-milled alloys in Examples 1-6, it is found that the ball-milled materials have the structural characteristics of nanocrystals and amorphous.

[0049] Figure 5 For the HRTEM morphology of the ball-milled alloys in Examples 1-6, it shows that the alloy has a nanocrystalline and a very small amount of amorphous structure.

[0050] The gaseous hydrogen absorption and desorption amounts and kinetics of the alloy powder were tested using a fully automatic Sieverts device, and the results are shown in Table 1.

[0051] Table 1 Hydrogen absorption and desorption kinetics of alloy powders with different compositions

[0052]

[0053]

[0054] C max — Saturation hydrogen absorption amount (wt.%) at an initial hydrogen pressure of 3 MPa and 200 °C; — Hydrogen absorption amount (wt.%) within 5 minutes at an initial hydrogen pressure of 3 MPa and 200 °C, — Desorption amount (wt.%) within 20 minutes at an initial pressure of 1×10 -4 MPa and 260 °C.

[0055] The above results show that the ball-milled alloy powder has a high hydrogen absorption and desorption capacity and excellent kinetic performance. In particular, the alloy has good hydrogen desorption performance at a relatively low temperature (260 °C), and the preparation process is simple and easy to operate, which is very suitable for large-scale preparation of this alloy. Obviously, the hydrogen absorption and desorption capacity of the alloy of the present invention can fully meet the hydrogen capacity requirements of the hydrogen supply system for fuel cells. Compared with similar alloys at home and abroad, the hydrogen absorption and desorption kinetics of the alloy of the present invention have been significantly improved, especially the hydrogen desorption temperature has been significantly reduced.

[0056] Although the preferred embodiments of the present invention have been described, it is obvious that those skilled in the art can adopt other embodiments. For example, by changing the composition content and the addition amount of the catalyst, various deformations and modifications can be made without departing from the design concept of the present invention, and these changes all fall within the protection scope of the present invention.

Claims

1. A lanthanum oxide-catalyzed high-capacity hydrogen storage alloy with a chemical formula composition of: Mg 85-x Zr x Sm 12-y Nd y Ni 5-z-m Cu z Zn m + n wt.% La2O3, where x, y, z, m are atomic ratios, and 0 < x ≤ 5, 0 < y ≤ 3, 0 < z ≤ 2, 0 < m ≤ 2, n is the percentage of La2O3 in the alloy, and 4 ≤ n ≤ 12.

2. The hydrogen storage alloy according to claim 1, characterized in that, The atomic ratio of the chemical formula composition is: x:y:z:m = 3:2:1:1, n = 7.

3. A preparation method of a lanthanum oxide-catalyzed high-capacity hydrogen storage alloy, characterized in that, The method steps include: Step (1) proportion materials according to the chemical formula Mg 85-x Zr x Sm 12-y Nd y Ni 5-z-m Cu z Zn m where x, y, z, m are atomic ratios, and 0 < x ≤ 5, 0 < y ≤ 3, 0 < z ≤ 2, 0 < m ≤ 2. Step (2) Add the weighed raw materials into the magnesia crucible in sequence, evacuate the vacuum to 1×10 -2 to 5×10 -5 Pa, then fill with a protective gas, and heat to 1650 - 1750 °C by induction heating method to obtain molten Mg 85-x Zr x Sm 12- y Nd y Ni 5-z-m Cu z Zn m liquid alloy. Step (3): Directly inject the liquid master alloy prepared in the above step (2) into the tundish with a BN nozzle embedded at the bottom. The liquid alloy continuously sprays onto the smooth surface of a copper roller rotating at a linear velocity of 5 - 30 m / s (preferably 18 m / s) through the slit of the BN nozzle at the bottom of the tundish, obtaining a rapidly quenched alloy ribbon with a thickness between 50 - 300 μm. The rapidly quenched ribbon should have a nanocrystalline structure with a grain size of about 10 - 100 nm. Step (4) Mechanically crush the as-quenched Mg 85-x Zr x Sm 12-y Nd y Ni 5-z-m Cu z Zn m Alloy is mechanically crushed and sieved through a 200-mesh sieve. The sieved alloy powder, a certain amount of La2O3 catalyst, and stainless steel grinding balls are loaded into a stainless steel ball milling tank together. After evacuating the air, high-purity argon is filled in, and ball milling is carried out in an all-round planetary high-energy ball mill for 2 - 10 hours.

4. The preparation method according to claim 3, characterized in that: In step (1), the atomic ratio x:y:z:m = 3:2:1:1, n = 7.

5. The preparation method according to claim 3, characterized in that: In step (2), after evacuation, the protective gas filled is high-purity helium at 0.01 to 0.1 MPa or helium + argon with a volume ratio of 1:

1.

6. The preparation method according to claim 3, characterized in that: In step (4), ball milling is carried out for 4.5 hours, the ball-to-material ratio is 20:1, and the rotation speed is 350 revolutions per minute. During the ball milling process, the ball mill stops for 0.5 hours every 1 hour of continuous operation to prevent the temperature of the ball milling tank and the abrasive from being too high.

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