A TaF5-catalyzed high-capacity RE-Mg-Ni-Cu-Be-based Mg 24 Y5-type hydrogen storage alloy and method for producing the same

Abstract

The present invention relates to a TaF5-catalyzed high-capacity RE-Mg-Ni-Cu-Be-based Mg z Y5-type hydrogen storage alloy and its preparation method, belonging to the technical field of solid-state hydrogen storage alloy materials, and solving the problems in the prior art such as the high thermal stability of alloy hydrides and the poor thermodynamic and kinetic properties of alloy hydrogen absorption and desorption. A TaF5-catalyzed high-capacity RE-Mg-Ni-Cu-Be-based Mg 24 Y5-type hydrogen storage alloy, the chemical formula composition of the hydrogen storage alloy is: Mg 25 Y 5‑x Ce x Ni 2‑y‑z Cu y Be z +m wt.%TaF5, where x, y, z are atomic ratios, 0 < x ≤ 2, 0 < y ≤ 1, 0 < z ≤ 0.5, m is the percentage of TaF5 in Mg 25 Y 5‑x Ce x Ni 2‑y‑ z Cu y Be z alloy, 3 ≤ m ≤ 10. The thermal stability of the alloy hydride is reduced, and the thermodynamic and kinetic properties of alloy hydrogen absorption and desorption are improved.

Description

Technical Field

[0001] This invention relates to the field of solid-state hydrogen storage alloy materials technology, and particularly to a high-capacity RE-Mg-Ni-Cu-Be based Mg catalyst catalyzed by TaF5. 24 Y5 type hydrogen storage alloy and its preparation method. Background Technology

[0002] In recent decades, hydrogen has attracted worldwide interest as a clean energy source, the most abundant element in the universe, the lightest fuel, and the ideal energy carrier with the highest energy density per unit mass. Safe and efficient hydrogen storage methods are key technologies for advancing hydrogen and fuel cell power technologies in transportation, stationary, and portable applications. Traditional physical methods, such as compression or liquefaction, inherently suffer from low volumetric energy density, high economic costs, and poor safety. Another option is chemical hydrogen storage in hydrogen-rich liquids and solids, which may achieve high energy storage densities. Examples of such solid materials and liquids include boron-based compounds such as LiBH4, NaBH4, and NH3BH3, and organic liquids such as cyclohexane and decahydronaphthalene. However, the irreversible nature of these hydrogen storage methods means they are not feasible. Physical hydrogen storage using carbon materials such as activated carbon, carbon nanotubes, graphene, and carbon nanofibers is also an active research area. However, the hydrogen storage capacity of these carbon materials is entirely dependent on the external hydrogen pressure and temperature.

[0003] Metal hydrides are considered promising hydrogen storage materials due to their high energy density and safety. It is a solid-state hydrogen storage method that allows for the reversible absorption of hydrogen in atomic form without the need for high pressure (typically below 3 MPa), chemically compressing hydrogen to achieve high storage densities. For example, a typical LaNi5-based hydride can reversibly absorb and release approximately 0.9 wt.% hydrogen at 100 °C. TiFe alloys exhibit high hydrogen storage capacity (approximately 2 wt.%); however, their activation process is demanding, and their absorption / desorption kinetics are poor. MgH2 has the highest energy density among all reversible metal hydrides that can be used for hydrogen storage. MgH2 meets many technical requirements, such as being lightweight, low-cost, and having a considerable weight-based hydrogen storage capacity (7.6 wt.%). However, its hydrogenation / dehydrogenation kinetics are slow and the reaction temperature is high, which cannot meet the requirements of on-board hydrogen supply equipment. Although its performance has been optimized through alloying with transition metals and the addition of rare earth elements and nickel, the reaction temperature is still high, the reversible hydrogen capacity needs to be further improved, the hydrogenation / dehydrogenation kinetics are still not ideal under certain conditions, and some improvement methods may lead to problems such as increased costs or decreased material stability. Summary of the Invention

[0004] Based on the above analysis, the embodiments of the present invention aim to provide a TaF5-catalyzed high-capacity RE-Mg-Ni-Cu-Be-based Mg24 Y5-Type Hydrogen Storage Alloy and Its Preparation Method, which is used to solve at least one of the problems such as the high thermal stability of existing alloy hydrides and the poor thermodynamic and kinetic properties of alloy hydrogen absorption and desorption.

[0005] On the one hand, an embodiment of the present invention provides a TaF5-catalyzed high-capacity RE-Mg-Ni-Cu-Be-based Mg 24 Y5-Type Hydrogen Storage Alloy, and the chemical formula composition of the hydrogen storage alloy is: Mg 25 Y 5-x Ce x Ni 2-y-z Cu y Be z +m wt.%TaF5, where x, y, z are atomic ratios, 0 < x ≤ 2, 0 < y ≤ 1, 0 < z ≤ 0.5, and m is the percentage of TaF5 in Mg 25 Y 5-x Ce x Ni 2-y-z Cu y Be z alloy, 3 ≤ m ≤ 10.

[0006] Preferably, x:y:z = 1:0.5:0.3 and m = 8.

[0007] On the other hand, an embodiment of the present invention also provides a preparation method of a TaF5-catalyzed high-capacity RE-Mg-Ni-Cu-Be-based Mg 24 Y5-Type Hydrogen Storage Alloy, which is used for the preparation of the hydrogen storage alloy, and includes the following steps:

[0008] S1. Weigh the raw materials according to the preset chemical formula composition, and increase a certain proportion of burn loss when weighing Mg and rare earths Y and Ce;

[0009] S2. Place the prepared raw materials in a magnesia crucible in sequence, evacuate and then fill with a protective gas and heat to obtain a molten liquid master alloy;

[0010] S3. After maintaining the liquid master alloy prepared in S2 in a protective gas atmosphere for 3 - 5 minutes, inject it into a tundish with a BN nozzle embedded at the bottom, and the liquid alloy continuously sprays onto the smooth surface of a rotating water-cooled copper roller through the slit of the BN nozzle at the bottom of the tundish to obtain a rapidly quenched alloy ribbon;

[0011] S(4. Mechanically crush the rapidly quenched alloy ribbon and sieve it to obtain alloy powder. Put the sieved alloy powder, a certain amount of TaF5 catalyst and stainless steel grinding balls into a stainless steel ball milling tank, evacuate and then fill with high-purity argon, and ball mill in an all-round planetary high-energy ball mill to obtain ball-milled alloy powder, that is, the hydrogen storage alloy.

[0012] Specifically, the mass percentage of Mg lost during ignition in S1 is 8%-10%, and the mass percentage of rare earth elements Y and Ce lost during ignition is 5%-7%.

[0013] Furthermore, the specific process and parameters in S2 are as follows: evacuate to 1×10⁻⁶. -2 ~5×10 -5 Pa, introduce high-purity helium gas at 0.01-0.1 MPa or a helium-argon mixture with a volume ratio of 1:1 as a protective gas, and heat to 1450-1600℃.

[0014] Preferably, the slit width of the NB nozzle in S3 is 0.295-0.305mm, and the linear speed of the water-cooled copper roller is 2-30m / s.

[0015] Specifically, the thickness of the fast-quenched alloy strip described in S3 is between 100-450 μm.

[0016] For example, the fast-quenched alloy strip has a nanocrystalline structure with a grain size of 10-100 nm.

[0017] Furthermore, the specific parameters for the ball milling process in S4 are: ball-to-material ratio 20:1, ball mill speed 350 rpm, and ball milling time 2 to 7 hours.

[0018] Specifically, the ratio of nanocrystalline to amorphous phase in the ball-milled alloy powder obtained by S4 ranges from 76:1 to 83:1.

[0019] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0020] 1. This invention reduces the stability of Mg-based hydrides and improves their hydrogen absorption and desorption kinetics by adding multiple rare earth elements Y and Ce, as well as transition metal elements Ni, Cu and Be.

[0021] On the one hand, the addition of metallic elements Ni, Cu, and Be promotes hydrogen dissociation and reduces the bonding strength of Mg-H bonds; on the other hand, the addition of small amounts of multi-element rare earth elements Y and Ce, along with small amounts of metallic elements Ni, Cu, and Be for alloying, allows Mg and Y to form the main phase of the alloy, Mg. 24 Y5, Ce can form CeMg with Mg 12 In Mg-based alloys, Mg and Ni can form the Mg₂Ni phase, and Cu and Be can form the CuBe phase, among other intermetallic compounds. Mg₂Ni itself is a hydrogen-absorbing phase, while CuBe, although not hydrogen-absorbing, plays a positive role in the hydrogen absorption and desorption of Mg-based alloys. Rare earth elements Y and Ce, as well as metallic Be, can form highly stable YH₂ / YH₃ and CeH₂ phases with hydrogen. 2.73The presence of BeH2 hydrides significantly reduces the stability of magnesium hydrides. Furthermore, these hydrides are dispersed in the alloy matrix, serving as the nucleation sites for magnesium hydrides and exhibiting a significant catalytic effect on the hydrogen absorption and desorption processes of Mg-based alloys.

[0022] 3. This invention uses mechanical crushing of rapidly quenched alloy sheets, adds a small amount of catalyst TaF5 and applies mechanical ball milling for an appropriate time. While maintaining the nanocrystalline microstructure of the rapidly quenched alloy, it can promote the introduction of high-density crystal defects and improve the surface activity of the ball milled particles, thereby improving the hydrogen storage performance of the target alloy and further improving the thermodynamics and kinetics of hydrogen absorption and desorption of the alloy.

[0023] On the one hand, the catalytic effect of TaF5 lies in its high hardness, which has a significant cutting effect on alloy particles during ball milling, improving ball milling efficiency and making the ball-milled alloy particles finer. On the other hand, after ball milling, the addition of a highly stable catalyst allows the catalyst to be evenly distributed between alloy particles, forming a large number of active interfaces between the alloy and the catalyst. These interfaces provide excellent nucleation sites for the formation and decomposition of hydrides.

[0024] 4. By adding a catalyst and selecting an appropriate ball milling time, the present invention obtains ball-milled alloy particles that are approximately spherical, ensuring that there are no excessive amorphous phases in the ball-milled alloy and that the alloy powder has good dispersion without serious agglomeration, thereby ensuring that the hydrogen absorption capacity of the alloy does not decrease significantly.

[0025] 5. The hydrogen storage alloy powder prepared by this invention possesses excellent hydrogen absorption and desorption capacity and good thermodynamic and kinetic properties. Its saturated hydrogen absorption capacity at an initial hydrogen pressure of 3 MPa and 200°C is ≥5.29%, its hydrogen absorption capacity within 5 minutes at an initial hydrogen pressure of 3 MPa and 200°C is ≥5.17%, and its hydrogen absorption capacity at an initial pressure of 1×10⁻⁶ MPa is ≥5.17%. -4 With a hydrogen release rate of ≥4.79% within 20 minutes at MPa and 270℃, the alloy demonstrates extremely high application potential in the field of hydrogen fuel cell hydrogen supply carriers; moreover, the alloy preparation process is simple and easy to operate, and can fully meet the requirements of large-scale preparation.

[0026] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this 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 this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0027] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0028] Figure 1 SEM morphologies of the as-cast alloys of Examples 1-6 of the present invention;

[0029] Fig. 2(a) is a physical photo of the rapidly quenched alloy ribbon of Example 1 of the present invention;

[0030] Fig. 2(b) is the HRTEM morphology of the microstructure of the rapidly quenched alloy ribbon of Example 1 of the present invention;

[0031] Figure 3 SEM morphologies of the ball-milled alloys of Examples 1-6 of the present invention;

[0032] Figure 4 XRD diffraction patterns of the ball-milled powders of Examples 1-6 of the present invention;

[0033] Figure 5 HRTEM morphologies of the ball-milled powders of Examples 1-6 of the present invention. Detailed implementation manners

[0034] The preferred embodiments of the present invention will be specifically described below with reference to the accompanying drawings. The accompanying drawings form a part of this application and are used together with the embodiments of the present invention to explain the principle of the present invention, and are not used to limit the scope of the present invention.

[0035] On the one hand, a specific embodiment of the present invention discloses a TaF5-catalyzed high-capacity RE-Mg-Ni-Cu-Be-based Mg 24 Y5-type hydrogen storage alloy, whose chemical formula composition is: Mg 25 Y 5-x Ce x Ni 2-y-z Cu y Be z +m wt. % TaF5, where x, y, z are atomic ratios, 0 < x ≤ 2, 0 < y ≤ 1, 0 < z ≤ 0.5, and m is the percentage of TaF5 in Mg 25 Y 5-x Ce x Ni 2-y-z Cu y Be z alloy, 3 ≤ m ≤ 10.

[0036] It should be noted that the preparation method of the TaF5-catalyzed high-capacity RE-Mg-Ni-Cu-Be-based Mg 24 Y5-type hydrogen storage alloy is:配料 according to the preset chemical formula, heating and melting into a master alloy under gas protection, using the rapid quenching method to prepare into a ribbon, mechanically crushing and sieving to obtain alloy powder, and then ball-milling with TaF5 catalyst and stainless steel grinding balls for 2- 7 hours under argon protection to finally obtain the ball-milled hydrogen storage alloy.

[0037] Preferably, x:y:z = 1:0.5:0.3, m = 8.

[0038] The composition of the hydrogen storage alloy is optimized to fully utilize the combined properties of rare earth and ferromagnetic elements, thereby improving the hydrogen storage performance of the alloy. The amount of catalyst added is controlled to prevent agglomeration during subsequent ball milling, which would negatively impact the alloy's hydrogen storage performance. Specific effects are as follows:

[0039] Alloying is achieved by adding small amounts of rare earth elements Y and Ce, along with small amounts of metallic elements Ni, Cu, and Be. Mg and Y can form the main phase of the alloy, Mg. 24 Y5, Ce can form CeMg with Mg 12 In Mg-based alloys, Mg and Ni can form the Mg2Ni phase, and Cu and Be can form the CuBe phase, among other intermetallic compounds. Mg2Ni itself is a hydrogen-absorbing phase, while CuBe, although it cannot absorb hydrogen, plays a positive role in the hydrogen absorption and desorption of Mg-based alloys.

[0040] Rare earth elements Y and Ce, along with metallic Be, can form thermally stable YH2 / YH3 and CeH with hydrogen. 2.73 The BeH2 hydride nanocrystalline phase, along with numerous stable nanocrystalline phases, acts as a pinning agent during hydrogen absorption and desorption, leading to nanostructuring of the magnesium matrix and introducing more nanocrystalline interfaces, thus providing more channels for hydrogen diffusion. Furthermore, these hydrides are dispersed throughout the alloy matrix, serving as nucleation sites for hydrogen absorption and desorption reactions, and exhibiting a significant catalytic effect on the hydrogen absorption and desorption processes of Mg-based alloys.

[0041] On the other hand, a specific embodiment of the present invention also discloses a TaF5-catalyzed high-capacity RE-Mg-Ni-Cu-Be-based Mg 24 The preparation method of Y5 type hydrogen storage alloy includes the following steps:

[0042] S1. Prepare the ingredients according to the preset chemical formula, and increase the burn-off amount by a certain proportion when weighing Mg and rare earth Y and Ce.

[0043] S2. Place the prepared raw materials in the magnesium oxide crucible in sequence, evacuate the vacuum, fill with protective gas and heat to obtain molten liquid master alloy.

[0044] S3. After the liquid master alloy prepared in S2 is kept in a protective gas atmosphere for 3 to 5 minutes, it is injected into the tundish with BN nozzles embedded at the bottom. The liquid alloy is continuously sprayed onto the smooth surface of the rotating water-cooled copper roller through the slit of the BN nozzle at the bottom of the tundish, to obtain a fast-quenched alloy strip with a thickness between 100-450 μm.

[0045] S4. The rapidly quenched alloy strip is mechanically crushed and sieved to obtain alloy powder. The sieved alloy powder, a certain amount of TaF5 catalyst and stainless steel grinding balls are loaded into a stainless steel ball mill jar, vacuumed and filled with high-purity argon gas, and ball-milled in an all-around planetary high-energy ball mill to obtain ball-milled alloy powder, namely the hydrogen storage alloy.

[0046] Rapid quenching of liquid master alloys can yield precursors with ultrafine grains (nanoscale). The rapidly quenched alloys have a columnar crystalline structure, which is a uniform nanocrystalline structure. Its grain boundaries provide good channels for the diffusion of hydrogen atoms, which is particularly beneficial for improving the hydrogen absorption and desorption kinetics of Mg-based alloys. In addition, the rapidly quenched alloy structure contains a high density of crystal defects, including dislocations, stacking faults, twins, and a large number of grain boundaries. This microstructure is extremely beneficial for improving the thermodynamic and kinetic properties of the alloy. Unlike the crystal defects formed by mechanically ball milling the cast master alloy ingot, the ultrafine structure and crystal defects obtained by rapid quenching have high stability. After multiple hydrogen absorption and desorption cycles, the grains are not easy to aggregate and grow. In terms of hydrogen absorption and desorption performance, it not only has excellent hydrogen absorption and desorption kinetic performance, but also has good cycle stability.

[0047] Mechanical crushing of rapidly quenched alloy flakes, followed by the addition of the catalyst TaF5 and short-term ball milling, improved the surface condition of the alloy while maintaining its microstructure in the rapidly quenched state, leveraging the advantages of both preparation processes. During ball milling, the catalyst is uniformly distributed within the alloy matrix, maximizing its catalytic effect and thus enhancing the thermodynamics and kinetics of hydrogen absorption and desorption. On one hand, the high hardness of TaF5 provides significant cutting action on the alloy particles during ball milling, resulting in finer particles. On the other hand, the addition of a highly stable catalyst allows for uniform distribution among the alloy particles after ball milling, forming numerous active interfaces between the alloy and catalyst. These interfaces provide excellent nucleation sites for hydride formation and decomposition. It is precisely this combination of rapid quenching, ball milling, and catalyst addition that significantly improves the thermodynamics and kinetics of hydrogen absorption and desorption in the alloy.

[0048] Preferably, the mass percentage of Mg loss during burning in S1 is 8%-10%, and the mass percentage of rare earth Y and Ce loss during burning is 5%-7%. Mg and rare earth Y and Ce are easily volatilized and will be lost during the batching and heating melting process, so a certain amount of loss during burning needs to be added.

[0049] Specifically, the process and parameters in S2 are as follows: evacuate to 1×10⁻⁶. -2 ~5×10 -5Pa, introduce high-purity helium gas at 0.01-0.1 MPa or a helium-argon mixture with a volume ratio of 1:1 as a protective gas, and heat to 1450-1600℃. The heating method is electric arc melting or induction heating melting.

[0050] It is worth noting that the order in which the raw materials are placed in the magnesium oxide crucible in S2 is as follows: bulk rare earth elements Y and Ce are placed at the bottom of the crucible, electrolytic Ni is placed on top of the rare earth elements Y and Ce, metallic Cu and Be are placed on top of metallic Ni, and bulk metallic Mg is placed on top. This arrangement order is determined by the melting point and solid solubility of the metals, allowing the metals to melt sequentially in order of increasing melting point, effectively reducing the burn-off of elements such as Y and Ce, resulting in a more stable alloy composition and a more uniform element distribution.

[0051] For example, in S3, the slit width of the NB nozzle is set to 0.295-0.305mm, and the linear speed of the water-cooled copper roller is 2-30m / s, specifically 2m / s, 5m / s, 8m / s, 10m / s, 15m / s, 18m / s, 20m / s, 22m / s, 25m / s, 28m / s, and 30m / s. By controlling the rotation speed of the copper roller, a suitable rapid quenching rate is determined to ensure that the rapid quenching alloy strip has a nanocrystalline structure of more than 98.5% and a grain size of 10-100nm.

[0052] For rapid quenching of liquid master alloys, it is necessary to ensure that the rapidly quenched alloy strip 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 large number of microcrystalline structures will appear, which will weaken the hydrogen absorption and desorption kinetics of the alloy.

[0053] Preferably, the linear speed of the water-cooled copper roller is 20 m / s.

[0054] Preferably, after the rapid quenching alloy strip in S4 is mechanically crushed, a 200-mesh sieve is used for sieving; before the catalyst is added to the stainless steel ball mill jar, it is ground and then sieved through a 200-mesh sieve.

[0055] Specifically, the specific parameters of the ball milling process in S4 are: ball-to-material ratio 20:1, ball mill speed 350 rpm, and ball milling time 2 to 7 hours. Specifically, the ball milling time is 2, 3, 4, 5, 6, or 7 hours; preferably, the ball milling time is 6 hours.

[0056] During ball milling, the ball mill is stopped for 0.5 hours after every hour of continuous operation to prevent the temperature of the milling jar and abrasive from becoming too high. Determining the milling time is crucial, as it significantly affects the bonding between the alloy and the catalyst. On one hand, excessive milling time will result in a large amount of amorphous phase, reducing the alloy's hydrogen storage capacity. The optimal milling time ensures that too many amorphous phases do not appear in the milled alloy; the volume ratio of nanocrystalline to amorphous phases in the milled alloy powder ranges from 76:1 to 83:1, preferably 80:1. On the other hand, a suitable milling time ensures good dispersion of the alloy powder without severe agglomeration, thus preventing a significant decrease in the alloy's hydrogen absorption capacity. Excessive milling time will result in a large amount of amorphous phase in the microstructure, and agglomeration due to cold welding between particles will also reduce the alloy's hydrogen absorption and desorption performance.

[0057] In summary, this invention reduces the stability of Mg-based hydrides and improves their hydrogen absorption and desorption kinetics by adding multi-element rare earth elements Y and Ce, as well as transition metal elements Ni, Cu, and Be. Furthermore, the mechanical crushing of rapidly quenched alloy sheets, the addition of a small amount of catalyst TaF5, and appropriate mechanical ball milling further improve the thermodynamics and kinetics of hydrogen absorption and desorption. The hydrogen storage alloy powder prepared by this invention possesses excellent hydrogen absorption and desorption capacity and good thermodynamic and kinetic properties, demonstrating high application potential in the field of hydrogen fuel cell hydrogen supply carriers. Moreover, the alloy preparation process is simple and easy to operate, fully meeting the requirements for large-scale production.

[0058] The following specific examples illustrate the high-capacity RE-Mg-Ni-Cu-Be-based Mg catalyzed by TaF5 of the present invention. 24 The Y5 type hydrogen storage alloy and its preparation method are described.

[0059] Examples 1-6 all employed the following method to carry out high-capacity RE-Mg-Ni-Cu-Be-based Mg catalysis catalyzed by TaF5. 24 Preparation of Y5 type hydrogen storage alloy:

[0060] S1. Select bulk metal Mg, rare earth metals Y and Ce, electrolytic Ni, metal Cu and Be according to the chemical formula composition of each embodiment. The metal purity is required to be ≥99.5%. After grinding the selected bulk metal to remove the surface oxide layer, weigh it according to the chemical dosage ratio. Among them, metal Mg is increased by 8% and rare earth Y and Ce are increased by 5% to compensate for the burn-off during smelting.

[0061] S2. Place the prepared raw materials in the magnesium oxide crucible in sequence, evacuate the vacuum, fill with protective gas and induction heat to obtain molten liquid master alloy.

[0062] Heating process parameters: Vacuum is drawn to 1×10 during induction heating.-2 ~5×10 -4 Pa, filled with high-purity helium or a helium + argon mixture with a volume ratio of 1:1 at a pressure of 0.01 to 0.1 MPa; melting temperature is 1450-1600℃;

[0063] S3. After the liquid master alloy prepared in S2 is kept in a protective gas atmosphere for 3 to 5 minutes, it is injected into the tundish with BN nozzles embedded at the bottom. The liquid alloy is continuously sprayed onto the smooth surface of the rotating water-cooled copper roller through the slit of the BN nozzle at the bottom of the tundish. The surface linear velocity of the water-cooled copper roller is 2-30 m / s, and a fast-quenched alloy strip with a thickness between 100-450 μm is obtained.

[0064] S4. After mechanically crushing the rapid quenching sheet and passing it through a 200-mesh sieve, mix it with the catalyst TaF5 and stainless steel grinding balls and load it into a stainless steel ball mill jar. Use an all-around planetary ball mill to ball mill for 2 to 7 hours. Stop the ball mill for 0.5 hours every 1 hour of continuous operation to obtain ball-milled alloy powder, which is the hydrogen storage alloy.

[0065] S5. Structural analysis and performance testing: The phase structure of the cast and ball-milled powders was tested by XRD. The morphology and microstructure of the cast and ball-milled alloys were observed by high-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM). The crystal state of the alloy was determined by selected area electron diffraction (SAED).

[0066] The hydrogen absorption activation performance, hydrogen storage capacity, and hydrogen absorption / desorption kinetics of the alloy powder were tested using a semi-automatic Sieverts apparatus: the hydrogen absorption temperature was 200℃, the initial hydrogen pressure was 3 MPa; the hydrogen desorption temperature was 270℃, and the hydrogen desorption rate was 1×10⁻⁶ MPa. -4 The test was conducted at a pressure of MPa.

[0067] The chemical composition and proportions of specific embodiments of the present invention are selected as follows:

[0068] Example 1: Mg 25 Y4Ce1Ni 1.2 Cu 0.5 Be 0.3 +8wt.%TaF5

[0069] Example 2: Mg 25 Y3Ce2Ni 1.2 Cu 0.5 Be 0.3 +8wt.%TaF5

[0070] Example 3: Mg 25 Y4Ce1Ni 0.7 Cu1Be 0.3 +3wt.%TaF5

[0071] Example 4: Mg 25 Y4Ce1Ni1Cu 0.5 Be 0.5 +5wt.%TaF5

[0072] Example 5: Mg 25 Y4Ce1Ni 1.2 Cu 0.5 Be 0.3 +9wt.%TaF5

[0073] Example 6: Mg 25 Y4Ce1Ni 1.2 Cu 0.5 Be 0.3 +10wt.%TaF5

[0074] Comparative Example 1: Mg 24 Y5 (quick quenching + ball milling)

[0075] Comparative Example 2: Mg 25 Y4Ce1Ni 1.2 Cu 0.5 Be 0.3 (Quick quenching + ball milling)

[0076] Comparative Example 3: Mg 25 Y4Ce1Ni 1.2 Cu 0.5 Be 0.3 +3wt.% TaF5 (10 hours)

[0077] Comparative Example 4: Mg 25 Y4Ce1Ni 1.2 Cu 0.5 Be 0.3 +8wt.%TaF5 (10 hours)

[0078] Process parameters for Example 1:

[0079] S1, according to the chemical formula Mg 25 Y4Ce1Ni 1.2 Cu 0.5 Be 0.3 The raw materials are selected as follows: bulk Mg, rare earth Y and Ce, electrolytic Ni, and metallic Cu and Be. The metal purity is 99.5%. The raw materials are weighed according to the chemical dosage ratio, and each furnace is prepared with 5 kg of raw materials, including 2715.6 g of bulk Mg, 1545.2 g of rare earth Y, 608.8 g of rare earth Ce, 291.5 g of electrolytic Ni, 131.5 g of metallic Cu, and 11.2 g of metallic Be.

[0080] S2. Place the weighed bulk metal into the magnesium oxide crucible of the medium-frequency induction furnace according to the designed process. Place the bulk rare earth Y and Ce at the bottom of the crucible, the electrolytic Ni on top of the rare earth Y and Ce, the metallic Cu and Be on top of the electrolytic Ni, and the bulk metal Mg on top. Then cover the furnace and evacuate for 30 minutes to a vacuum degree of 5×10⁻⁶. -2 Above Pa, high-purity helium protective gas is then introduced until the pressure reaches 0.04 MPa. The power is adjusted to 5 kW, and the temperature is controlled at 650℃ to melt the Mg metal. Then, the power is adjusted to 25 kW, and the temperature is controlled at 1600℃ to melt the remaining metals.

[0081] S3. After the molten alloy is held in a protective gas atmosphere for 5 minutes, the liquid master alloy is directly injected into the tundish with NB nozzles embedded at the bottom. The liquid alloy is continuously sprayed from the gap between the NB nozzles at the bottom of the tundish (the gap width is 0.3 mm) onto the surface of a water-cooled copper roller rotating at a linear speed of 20 m / s, to obtain a fast-quenched alloy sheet with a thickness of 130 μm and an average grain size of 32 nm.

[0082] S4, rapidly quenched Mg 25 Y4Ce1Ni 1.2 Cu 0.5 Be 0.3 The alloy flakes were mechanically crushed and passed through a 200-mesh sieve. 20 grams of the sieved alloy powder, 1.6 grams of TaF5 catalyst, and 400 grams of stainless steel grinding balls were weighed and mixed together, then placed into a 250 ml stainless steel ball mill jar. The jar was evacuated, filled with high-purity argon, and sealed. The mixture was then ball-milled for 6 hours in an omnidirectional planetary high-energy ball mill, with the mill stopped for 0.5 hours after every hour of continuous operation.

[0083] The raw materials in Examples 2-6 were weighed according to their chemical formulas, and other preparation process parameters were the same as in Example 1.

[0084] The raw materials of Comparative Examples 1 to 4 were weighed according to their chemical formulas. Other preparation process parameters were basically the same as those of Example 1. The difference was that no catalyst was added during ball milling in Comparative Examples 1 and 2, while a different amount of catalyst was added in Comparative Example 3. The ball milling time for Comparative Examples 3 and 4 was 10 hours.

[0085] Figure 1 The SEM images of the as-cast alloys in Examples 1-6 show that the addition of multi-element rare earth elements and alloying with various metals resulted in the formation of multiple intermetallic compounds, among which Mg and Y formed Mg 24 Y5 main phase, Ce reacts with Mg to form CeMg 12 In the intermetallic phase, Mg and Ni form Mg2Ni, and Cu and Be form CuBe, among other intermetallic compounds.

[0086] Figure 2(a) is a photograph of the rapidly quenched alloy strip, with a thickness of 130 μm. As shown in Figure 2(b), HRTEM observation revealed that the rapidly quenched alloy strip was almost entirely nanocrystalline, with an average grain size of 32 nm.

[0087] Figure 3 The SEM images of the ball-milled powders in Examples 1-6 show that the alloy particles were well dispersed after ball milling, and no obvious agglomeration was observed.

[0088] Figure 4 The XRD patterns of the ball-milled alloys in Examples 1-6 show that the ball-milled materials have nanocrystalline and amorphous structural characteristics. Ball milling significantly broadens the diffraction peaks of the alloys, which is a result of grain refinement and increased lattice stress caused by ball milling.

[0089] Figure 5 The HRTEM morphology of the ball-milled alloys in Examples 1-6 shows that the alloys have nanocrystalline and a very small amount of amorphous structure.

[0090] The hydrogen absorption and release capacity and kinetics of the alloy powders in the examples and comparative examples were tested using a fully automated Sieverts system. The results are shown in Table 1.

[0091] Table 1 Hydrogen absorption and desorption kinetics of alloy powders with different compositions

[0092]

[0093] C max —Saturated hydrogen absorption (wt.%) at an initial hydrogen pressure of 3 MPa and a temperature of 200 °C; —The amount of hydrogen absorbed (wt.%) within 5 minutes at an initial hydrogen pressure of 3 MPa and a temperature of 200°C. —At an initial pressure of 1×10 -4 Hydrogen release (wt.%) within 20 minutes at MPa and 270℃.

[0094] The above results indicate that the ball-milled alloy powder of the present invention has high hydrogen absorption and desorption capacity and excellent kinetic properties, especially the alloy has good hydrogen desorption performance at a relatively low temperature (270°C).

[0095] Compared with the examples, the alloy composition of Comparative Example 1 does not meet the requirements of the present invention, and no catalyst is added during the ball milling process. Its hydrogen storage capacity and hydrogen absorption and desorption kinetics are much lower than those of the examples. Compared with Example 1, Comparative Example 2 has the same alloy composition, but no catalyst is added during the ball milling process. Its hydrogen storage capacity and hydrogen absorption and desorption kinetics are both lower than those of Example 1.

[0096] Compared with the examples, Comparative Examples 3 and 4 have alloy composition and catalyst addition amount that meet the requirements of the present invention, but the ball milling time is too long, which leads to a decrease in hydrogen absorption and desorption kinetics.

[0097] In summary, this invention reduces the stability of Mg-based hydrides and improves their hydrogen absorption and desorption kinetics by adding multi-element rare earth elements Y and Ce, as well as transition metal elements Ni, Cu, and Be. Furthermore, the use of mechanical pulverization of rapidly quenched alloy sheets, the addition of a small amount of catalyst TaF5, and appropriate mechanical ball milling further improve the thermodynamics and kinetics of hydrogen absorption and desorption. The hydrogen storage alloy powder prepared by this invention possesses excellent hydrogen absorption and desorption capacity and good thermodynamic and kinetic properties, demonstrating high application potential in the field of hydrogen fuel cell hydrogen supply carriers. Moreover, the alloy preparation process is simple and easy to operate, fully meeting the requirements for large-scale production.

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

Claims

1. A TaF5-catalyzed high-capacity RE-Mg-Ni-Cu-Be-based Mg 24 Y5 type hydrogen storage alloy, characterized in that... The chemical formula composition of the hydrogen storage alloy is: Mg 25 Y 5-x Ce x Ni 2-y-z Cu y Be z + mwt.% TaF5, where x, y, z are atomic ratios, 0 < x ≤ 2, 0 < y ≤ 1, 0 < z ≤ 0.5, and m is the percentage of TaF5 in the Mg 25 Y 5-x Ce x Ni 2-y-z Cu y Be z alloy, 3 ≤ m ≤ 10.

2. The hydrogen storage alloy according to claim 1, characterized in that, x:y:z = 1:0.5:0.3, m = 8.

3. A TaF5-catalyzed high-capacity RE-Mg-Ni-Cu-Be-based Mg 24 The preparation method of Y5 type hydrogen storage alloy is characterized by, The preparation of the hydrogen storage alloy according to claim 1 or 2 includes the following steps: S1. Prepare the ingredients according to the preset chemical formula, and increase the burn-off amount by a certain proportion when weighing Mg and rare earth Y and Ce. S2. Place the prepared raw materials in the magnesium oxide crucible in sequence, evacuate the vacuum, fill with protective gas and heat to obtain molten liquid master alloy. S3. After the liquid master alloy prepared in S2 is kept in a protective gas atmosphere for 3 to 5 minutes, it is injected into the tundish with BN nozzles embedded at the bottom. The liquid alloy is continuously sprayed onto the smooth surface of the rotating water-cooled copper roller through the slit of the BN nozzle at the bottom of the tundish to obtain a fast-quenched alloy strip. S4. The rapidly quenched alloy strip is mechanically crushed and sieved to obtain alloy powder. The sieved alloy powder, a certain amount of TaF5 catalyst and stainless steel grinding balls are loaded into a stainless steel ball mill jar, vacuumed and filled with high-purity argon gas, and ball-milled in an all-around planetary high-energy ball mill to obtain ball-milled alloy powder, namely the hydrogen storage alloy.

4. The preparation method according to claim 3, characterized in that, The mass percentage of Mg loss upon ignition in S1 is 8%-10%, and the mass percentage of rare earth elements Y and Ce loss upon ignition is 5%-7%.

5. The preparation method according to claim 3, characterized in that, The specific process and parameters in S2 are as follows: evacuate to 1×10⁻⁶. -2 ~5×10 -5 Pa, introduce high-purity helium gas at 0.01-0.1 MPa or a helium-argon mixture with a volume ratio of 1:1 as a protective gas, and heat to 1450-1600℃.

6. The preparation method according to claim 3, characterized in that, The nozzle slit width of the BN nozzle in S3 is 0.295-0.305mm, and the linear speed of the water-cooled copper roller is 2-30m / s.

7. The preparation method according to claim 3, characterized in that, The thickness of the fast-quenching alloy strip described in S3 is between 100-450 μm.

8. The preparation method according to claim 7, characterized in that, The fast-quenching alloy strip has a nanocrystalline structure with a grain size of 10-100 nm.

9. The preparation method according to claim 3, characterized in that, The specific parameters for the ball milling process in S4 are: ball-to-material ratio 20:1, ball mill speed 350 rpm, and ball milling time 2 to 7 hours.

10. The preparation method according to claim 3, characterized in that, The ratio of nanocrystalline to amorphous phase in the ball-milled alloy powder obtained by S4 ranges from 76:1 to 83:1.

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