Ti-Fe-RE-Mn-Zr-Bi-based hydrogen storage alloy and preparation method thereof

Abstract

This invention relates to a Ti-Fe-RE-Mn-Zr-Bi based hydrogen storage alloy and its preparation method, belonging to the technical field of hydrogen storage alloy materials. It solves one of the problems of high activation conditions, long activation cycles, and poor hydrogen absorption / desorption performance in existing TiFe hydrogen storage alloys. This invention discloses a Ti-Fe-RE-Mn-Zr-Bi based hydrogen storage alloy, wherein the alloy's specific composition is Ti... 1.15‑x‑ y Y x Pr y Fe 0.75 Mn 0.35‑z‑m Zr z Bi m Where x, y, z, and m are atomic ratios, 0.01≤x≤0.04, 0.01≤y≤0.04, 0.05≤z≤0.20, and 0.01≤m≤0.04. The Ti-Fe-RE-Mn-Zr-Bi-based hydrogen storage alloy provided by this invention exhibits excellent activation and hydrogen absorption / desorption properties. Furthermore, it retains its activation properties even after prolonged exposure to air, making it suitable for widespread application as a solid-state hydrogen storage material in scenarios such as hydrogen fuel cells.

Description

Technical Field

[0001] This invention relates to the field of hydrogen storage alloy materials technology, and to a Ti-Fe-RE-Mn-Zr-Bi based hydrogen storage alloy and its preparation method, particularly to a high-capacity, easily activated Ti-Fe-RE-Mn-Zr-Bi based hydrogen storage alloy and its preparation method. Background Technology

[0002] In recent years, fuel cell vehicles (FCVs) fueled by hydrogen have been considered a feasible technology for addressing the environmental and energy problems caused by the excessive consumption of fossil fuels. Currently, lightweight high-pressure hydrogen storage tanks (35 MPa) are one of the main technologies for on-board hydrogen storage in fuel cell vehicles. On the other hand, hydrogen fuel cells require high-purity hydrogen. Therefore, developing efficient hydrogen purification and compression technologies is of great significance. It is well known that hydrogen storage alloys have the dual functions of purifying and compressing hydrogen. Therefore, metal hydride hydrogen compressors (MHHCs) have many advantages compared to traditional compressors. For example, they integrate compression and purification functions, cover a wide pressure range, allow quiet operating conditions, and promote the utilization of low-grade energy. For metal hydride hydrogen compressors, it is desirable for the hydrogen storage alloy to have a large hydrogen storage capacity, good pressure plateau characteristics, and good activation and kinetic characteristics. Most of the hydrogen storage alloys reported in the literature use AB5 type alloys.

[0003] Among all solid-state hydrogen storage materials, TiFe alloys possess advantages such as high capacity, ability to absorb and desorb hydrogen at room temperature, low cost, and abundant resources, making them the most attractive and promising candidate material for hydrogen storage. Therefore, numerous researchers both domestically and internationally have conducted systematic studies on their hydrogen absorption performance.

[0004] To date, existing TiFe hydrogen storage alloys generally suffer from problems such as high activation requirements (i.e., difficulty in activation at room temperature), long activation cycles, and poor hydrogen absorption and desorption performance. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a Ti-Fe-RE-Mn-Zr-Bi based hydrogen storage alloy and its preparation method, particularly a high-capacity, easily activated Ti-Fe-RE-Mn-Zr-Bi based hydrogen storage alloy and its preparation method, to solve at least one of the problems of existing TiFe hydrogen storage alloys, namely, high activation conditions (i.e., difficult to activate at room temperature), long activation cycle, and poor hydrogen absorption and desorption performance.

[0006] This invention discloses a Ti-Fe-RE-Mn-Zr-Bi based hydrogen storage alloy, wherein the alloy is specifically composed of Ti 1.15-x- y Y x Pr y Fe0.75 Mn 0.35-z-m Zr z Bi m Where x, y, z, and m are atomic ratios, 0.01≤x≤0.04, 0.01≤y≤0.04, 0.05≤z≤0.20, and 0.01≤m≤0.04.

[0007] Preferably, the ratio of x, y, z, m is x:y:z:m = 0.02:0.02:0.10:0.02.

[0008] Specifically, the hydrogen storage alloy has a nanocrystalline structure with an average grain size of 40-60 nm, high defect density, and a large number of grain boundary and phase boundary defects.

[0009] Specifically, the hydrogen storage alloy has a multiphase structure containing TiFe phase and ZrMn2 phase.

[0010] This invention also discloses a method for preparing the hydrogen storage alloy, specifically comprising the following steps:

[0011] S1: The dosage is calculated according to the chemical formula composition and the ingredients are prepared, with appropriate amounts of Mn, Bi, Y and Pr added for loss on ignition;

[0012] S2: Place the prepared raw materials in a zirconia crucible, cover the furnace, heat the raw materials to a molten state and keep them at that temperature for a period of time, then pour the liquid alloy into a copper casting mold to obtain a master alloy ingot.

[0013] S3: The master alloy ingot is mechanically crushed and sieved. The sieved alloy powder is then ball-milled to obtain the finished hydrogen storage alloy powder.

[0014] Specifically, in step S1, the amount of Mn, Bi, Y, and Pr added is 4% to 6% of the calculated dosage.

[0015] Specifically, the order and operation of placing each raw material in step S2 are as follows: pure iron rods are placed vertically along the crucible wall, blocky rare earth Y and Pr are placed at the bottom of the crucible, sponge titanium and Zr are placed above rare earth Y and Pr, electrolytic manganese is placed above sponge titanium and Zr, and finally metallic Bi is added.

[0016] Specifically, the specific operation for melting the raw materials in step S2 is as follows: vacuuming to 1×10⁻⁶. -2 ~5×10 -5 After Pa, pure argon gas at a pressure of 0.01–0.1 MPa is introduced as a protective gas, and the melting temperature is 1500–1650℃ and held for 3–5 minutes.

[0017] Specifically, the sieving operation in step S3 involves passing the mechanically crushed alloy fragments through a 200-mesh sieve to obtain alloy powder with a diameter ≤75μm, followed by ball milling.

[0018] Specifically, the ball milling operation in step S3 is as follows: the alloy powder and stainless steel grinding balls are loaded into a stainless steel ball milling jar, vacuumed and then filled with high-purity argon gas, and ball milled in an all-round planetary high-energy ball mill for 0.5 to 2 hours, with a ball-to-material ratio of 1:15 to 25 and a rotation speed of 300 to 400 rpm.

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

[0020] 1. The Ti-Fe-RE-Mn-Zr-Bi-based hydrogen storage alloy provided by this invention has low activation conditions and a short activation cycle. This invention adds Y, Pr, Mn, Zr, and Bi elements to the TiFe alloy, with an excess of Ti, giving the alloy a polycrystalline structure and generating numerous grain boundaries and phase boundaries, providing a rapid pathway for hydrogen diffusion. The excess Ti has a particularly significant effect on improving the alloy's activation performance because Ti reacts with hydrogen before the TiFe phase during activation, forming the TiH2 phase. This leads to cracks in the Ti-Fe alloy, making it easier for hydrogen to enter the interior, effectively reducing activation conditions and shortening the activation cycle. Experimental data shows that the Ti-Fe-RE-Mn-Zr-Bi-based hydrogen storage alloy provided by this invention can be activated in a single activation treatment at 30℃ and 3MPa hydrogen pressure.

[0021] 2. The Ti-Fe-RE-Mn-Zr-Bi-based hydrogen storage alloy provided by this invention exhibits excellent hydrogen absorption and desorption performance at room temperature. This is attributed to the alloy's unique compositional design; the excess Ti and the polycrystalline structure formed by multiple elements result in a high defect density in the alloy, providing a rapid pathway for hydrogen diffusion and reducing the conditions required for hydrogen absorption and desorption reactions.

[0022] 3. The Ti-Fe-RE-Mn-Zr-Bi-based hydrogen storage alloy provided by this invention can maintain its activation ability even after prolonged exposure to air. The alloy powder was activated at 30℃ and 3MPa hydrogen pressure, and then exposed to air for 30 days. No significant changes were observed in the activation performance and hydrogen absorption / desorption performance of the alloy powder during this period.

[0023] 4. The Ti-Fe-RE-Mn-Zr-Bi-based hydrogen storage alloy preparation process provided by this invention is simple and suitable for large-scale production. The Ti-Fe-RE-Mn-Zr-Bi-based hydrogen storage alloy preparation method disclosed in this invention has a simple process flow, readily available raw materials and equipment, relatively mild process conditions, and low operation difficulty, making it suitable for large-scale production and widespread application.

[0024] 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

[0025] 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.

[0026] Figure 1 The XRD diffraction patterns of the as-cast alloys (master alloy ingots) in Examples 1-6 are shown below.

[0027] Figure 2 The SEM morphology of hydrogen storage alloy powders in Examples 1-6 is shown.

[0028] Figure 3 The XRD patterns of hydrogen storage alloy powders in Examples 1-6 are shown below.

[0029] Figure 4 The HRTEM morphology of hydrogen storage alloy powders in Examples 1-6 is shown.

[0030] Figure 5 This is a flowchart of the preparation process for hydrogen storage alloys. Detailed Implementation

[0031] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0032] This invention discloses a Ti-Fe-RE-Mn-Zr-Bi based hydrogen storage alloy, wherein the alloy is specifically composed of Ti 1.15-x- y Y x Pr y Fe 0.75 Mn 0.35-z-m Zr z Bi m Where x, y, z, and m are atomic ratios, 0.01≤x≤0.04, 0.01≤y≤0.04, 0.05≤z≤0.20, and 0.01≤m≤0.04.

[0033] Replacing Ti with Y and Pr in Ti-Fe alloys improves the hydrogen absorption and desorption rates. Adding excess Ti promotes the formation of the TiH2 phase during initial activation, leading to crack formation and improved activation performance. Experiments have shown that an atomic ratio of 1.15-xy is optimal.

[0034] Y and Pr: Adding Y and Pr in a near 1:1 ratio allows for a more uniform distribution of Y and Pr in the alloy, reducing rare earth element segregation. The rare earth hydrides generated during hydrogen absorption can be uniformly embedded in the alloy matrix, which is beneficial for improving the alloy's hydrogen absorption / desorption rate and activation performance. Experiments have verified that the optimal ratio is 0.01 ≤ x, y ≤ 0.04, with x and y being close to the optimal value.

[0035] Fe: The amount of Fe added is slightly less than that of Ti, which helps improve the activation performance of the alloy while ensuring its hydrogen storage capacity. Experiments have shown that an atomic ratio of 0.75 is most suitable.

[0036] Mn: Replacing some Mn with Zr and Bi not only increases the hydrogen storage capacity of the alloy but also improves its hydrogen absorption and desorption kinetics. Experiments have shown that an atomic ratio of 0.35-zm is most suitable.

[0037] Zr: Adding a portion of Zr can generate the ZrMn2 phase in the alloy, which undergoes a reversible reaction with ZrMn2H3 during hydrogen absorption and desorption, thus improving the alloy's hydrogen storage capacity and activation performance. Experiments have shown that an atomic ratio of 0.05 ≤ z ≤ 0.20 is most suitable.

[0038] Bi: Replacing part of the Mn in the alloy with Bi allows Bi to dissolve into Mn, which is beneficial for improving the activation performance of the alloy. Experiments have verified that an atomic ratio of 0.01 ≤ m ≤ 0.04 is most suitable.

[0039] Preferably, the ratio of x, y, z, and m is x:y:z:m = 0.02:0.02:0.10:0.02. At this ratio, Y and Pr are added to the alloy in a 1:1 ratio, which effectively reduces the segregation of rare earth elements, ensuring their uniform distribution on the alloy matrix. During hydrogen absorption, the rare earth hydrides generated are uniformly embedded in the alloy in the form of nanocrystals, becoming active sites for hydrogen absorption and desorption reactions and rapid channels for hydrogen diffusion. Adding trace amounts of Bi can dissolve in Mn, which is beneficial for improving the alloy's activation performance. The added Zr element can form the ZrMn2 phase with Mn, increasing the alloy's hydrogen storage capacity and activation performance. When Zr is in excess, the ZrH2 phase can be generated during hydrogen absorption, increasing the alloy's defect density and improving its activation performance. When the ratio of x, y, z, m is x:y:z:m = 0.02:0.02:0.10:0.02, each element in the alloy can be evenly distributed in the matrix, so that the metal hydrides generated after hydrogen absorption are also evenly distributed, which is beneficial to improving the activation performance of the alloy.

[0040] Specifically, the hydrogen storage alloy has a nanocrystalline structure with an average grain size of 40–60 nm and a high defect density, containing numerous grain boundaries, phase boundaries, and other defects. The presence of numerous nanocrystals and crystal defects can effectively suppress grain growth during hydrogen absorption and desorption, provide a rapid channel for hydrogen diffusion, and provide nucleation sites for hydrogen absorption and desorption reactions, thereby improving the alloy's activation performance and hydrogen absorption and desorption kinetics.

[0041] Specifically, the hydrogen storage alloy has a multiphase structure containing a TiFe phase and a ZrMn2 phase, with a TiFe to ZrMn2 phase ratio of approximately 75:5 to 11. TiFe is the primary hydrogen-absorbing phase, undergoing a reversible reaction with the TiFeH2 phase. ZrMn2 and ZrMn2H3 undergo a reversible hydrogen absorption and desorption reaction, which not only increases the alloy's hydrogen storage capacity but also increases the defect density and improves the alloy's activation performance.

[0042] This invention also discloses a method for preparing the hydrogen storage alloy, specifically comprising the following steps:

[0043] S1: The dosage is calculated according to the chemical formula composition and the ingredients are prepared, with appropriate amounts of Mn, Bi, Y and Pr added for loss on ignition;

[0044] S2: Place the prepared raw materials in a zirconia crucible, cover the furnace, heat the raw materials to a molten state and keep them at that temperature for a period of time, then pour the liquid alloy into a copper casting mold to obtain a master alloy ingot.

[0045] S3: The master alloy ingot is mechanically crushed and sieved. The sieved alloy powder is then ball-milled to obtain the finished hydrogen storage alloy powder.

[0046] The Ti-Fe-RE-Mn-Zr-Bi-based hydrogen storage alloy and its preparation method provided by this invention achieve the corresponding technical effects through a combination of "composition design + mechanical ball milling". Scientific composition design combined with an appropriate ball milling process can obtain alloy powder with a special structure, enabling the alloy to maintain excellent activation performance in air for a long time. Mechanical ball milling significantly reduces the grain size of the alloy while greatly increasing the density of grain boundaries and defects. This provides diffusion channels for the rapid diffusion of hydrogen atoms within the alloy, thus significantly improving the hydrogen absorption / desorption kinetics of the alloy while improving activation performance.

[0047] Specifically, in step S1, the burn-off amount of Mn, Bi, Y, and Pr is 4% to 6% of the calculated addition amount. Since elements such as Mn, Bi, Y, and Pr are volatile, an appropriate burn-off amount needs to be added to ensure that the final alloy composition reaches the preset value. According to experimental verification, a burn-off amount of 4% to 6% of the calculated addition amount is preferable. Too little burn-off will result in insufficient content of this component in the alloy; too much will lead to material waste and excessive content.

[0048] Specifically, the order and operation of placing the raw materials in step S2 are as follows: Pure iron rods are placed vertically along the crucible wall; blocky rare earth elements Y and Pr are placed at the bottom of the crucible; sponge titanium and Zr are placed above rare earth elements Y and Pr; electrolytic manganese is placed above sponge titanium and Zr; and finally, metallic Bi is added. This order is determined by the melting point and solid solubility of the metals, allowing them to melt sequentially in the order of Fe, Y, Pr, Ti, Zr, Mn, and Bi. This effectively reduces the burn-off of elements such as Mn, Bi, Y, and Pr, resulting in a more stable alloy composition and a more uniform element distribution.

[0049] Specifically, the specific operation for melting the raw materials in step S2 is as follows: vacuuming to 1×10⁻⁶. -2 ~5×10 -5 After Pa, pure argon gas at a pressure of 0.01–0.1 MPa is introduced as a protective gas, and the melting temperature is 1500–1650℃, held for 3–5 minutes. The vacuum degree, protective gas, and pressure are commonly used technical parameters. The melting temperature and holding time are determined based on the phase diagram. At these melting temperatures and holding times, the alloy can be kept in a molten state with minimal volatilization, thus saving costs and improving the stability of the alloy composition.

[0050] Specifically, the sieving operation in step S3 involves passing the mechanically crushed alloy fragments through a 200-mesh sieve to obtain alloy powder with a diameter ≤75μm, which is then ball-milled. Choosing this particle size ensures the ball-milling effect while reducing the cost of mechanical crushing.

[0051] Specifically, the ball milling operation in step S3 is as follows: the alloy powder and stainless steel grinding balls are loaded into a stainless steel ball milling jar, vacuumed and then filled with high-purity argon gas, and ball milled in an all-round planetary high-energy ball mill for 0.5 to 2 hours, with a ball-to-material ratio of 1:15 to 25 and a rotation speed of 300 to 400 rpm.

[0052] The ball milling parameters set here can ensure the ball milling effect while shortening the ball milling time and reducing the ball milling cost. If the ball milling time is extended, the ball-to-material ratio is increased, or the ball milling speed is increased, an excessive amount of amorphous phase will appear in the alloy, reducing the alloy's hydrogen storage capacity and hydrogen storage kinetics. If the ball milling time is shortened, the ball-to-material ratio is reduced, or the ball milling speed is decreased, the grain size in the alloy will increase and the defect density will decrease, impairing the alloy's hydrogen storage kinetics.

[0053] Based on the above preparation method, the specific components of the embodiments and comparative examples of the present invention are as follows:

[0054] Example 1: Ti 1.11 Y 0.02 Pr 0.02 Fe 0.75 Mn 0.18 Zr 0.15 Bi 0.02

[0055] Example 2: Ti 1.09 Y 0.03 Pr 0.03 Fe 0.75 Mn 0.18 Zr 0.15 Bi 0.02

[0056] Example 3: Ti 1.07 Y 0.04 Pr 0.04 Fe 0.75 Mn 0.18 Zr 0.15 Bi 0.02

[0057] Example 4: Ti 1.11 Y 0.02 Pr 0.02 Fe 0.75 Mn 0.23 Zr 0.1 Bi 0.02

[0058] Example 5: Ti 1.11 Y 0.02 Pr 0.02 Fe 0.75 Mn 0.28 Zr 0.05 Bi 0.02(30 days of air exposure)

[0059] Example 6: Ti 1.11 Y 0.02 Pr 0.02 Fe 0.75 Mn 0.16 Zr 0.15 Bi 0.04 (30 days of air exposure)

[0060] Comparative Example 1: Ti 1.2 Fe 0.8 Mn 0.2 (As-cast state)

[0061] Hydrogen storage alloy preparation process:

[0062] S1: Rare earth metals Y and Pr, sponge Ti and Zr, high-purity Fe, electrolytic Mn, and metallic Bi are selected according to the chemical formula composition of each embodiment. The surface oxide layer of the high-purity iron rod is removed by sandpaper polishing. The rare earth metals Y and Pr and electrolytic Mn and Bi are added with a 5wt.% burn-off amount during the preparation. The metal purity of the raw materials is ≥99.5%.

[0063] S2: Place the weighed bulk metal into the zirconia crucible of the medium-frequency induction furnace according to the designed process. Place the pure iron rod vertically along the crucible wall. Place the bulk rare earth elements Y and Pr at the bottom of the crucible, and the sponge Ti and Zr above the rare earth elements Y and Pr. Place the electrolytic Mn on top of the sponge Ti and Zr, and finally add Bi. The vacuum induction melting furnace is evacuated for approximately 30 minutes before heating to a vacuum degree of 5 × 10⁻⁶. -2 The pressure is above 100 Pa; then, 0.04 MPa of inert argon gas is introduced into the furnace as a protective gas; the heating temperature is adjusted to 1650℃; the liquid alloy is held at the molten state for 5 minutes; then, the uniformly mixed liquid metal is injected into a cylindrical copper mold with a diameter of 30 mm and a depth of 80 mm, cooled to room temperature in the furnace, and then removed to obtain the master alloy ingot.

[0064] S3: After mechanically crushing the cast alloy ingot, pass it through a 200-mesh sieve to obtain a particle size of 70-75μm. Place 20g of alloy powder and 400g of stainless steel grinding balls into a 250mL stainless steel ball mill jar and ball mill using an omnidirectional planetary ball mill for 50 minutes.

[0065] It is worth emphasizing that the specific parameters of all preparation processes can be appropriately selected within the corresponding ranges described above to prepare the hydrogen storage alloy powder of this invention. Therefore, although this invention only lists a set of typical examples of preparation processes, the selection of relevant parameters is not specific.

[0066] Performance testing:

[0067] The phase structure of the cast (master alloy ingot) and spherically milled alloy powders was tested by XRD. The morphology and microstructure of the spherically milled alloy particles 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). Specific results are as follows: Figures 1-4 As shown.

[0068] Figure 1 The XRD patterns of the as-cast alloys in Examples 1-6 show that alloying with rare earth elements Y and Pr, and metallic elements Mn, Zr, and Bi resulted in a multiphase structure, containing not only the main TiFe phase but also the intermetallic compound ZrMn2 phase. The peak height and area of ​​the XRD patterns can preliminarily characterize the content of the two phases. Figure 1 The ratio of TiFe to ZrMn2 phases is approximately 75:5 to 11.

[0069] Figure 2 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. This is because the ball milling time was reasonably controlled, which reduced the particle size of the powder and avoided agglomeration.

[0070] Figure 3 The XRD patterns of the ball-milled alloys in Examples 1-6 show that ball milling significantly broadens the diffraction peaks of the alloys, which is obviously attributed to the lattice stress and grain refinement generated after ball milling.

[0071] Figure 4 The HRTEM morphology of the ball-milled alloys in Examples 1-6 shows that the alloys have a nanocrystalline structure (e.g., Figure 4 (As shown in the dashed box), the average grain size is 40–60 nm (see details). Figure 4 (Scale bar / length bar), and a large number of defects such as grain boundaries and phase boundaries can be observed. Furthermore, according to... Figure 4 It can be seen that elements or intermetallic compounds such as TiFe, ZrMn2 and Pr are uniformly distributed in the matrix, so that the metal hydrides generated after hydrogen absorption are also uniformly distributed, which is beneficial to improving the activation performance of the alloy.

[0072] The hydrogen absorption activation performance, hydrogen storage capacity, and hydrogen absorption / desorption kinetics of the alloy powder were tested using a fully automated Sieverts system. The hydrogen absorption temperature was 30°C, and the initial hydrogen pressure was 3 MPa; the hydrogen desorption temperature was 30°C, and the hydrogen desorption rate was 1 × 10⁻⁶ MPa. -4 The test was conducted at a pressure of MPa, and the specific results are shown in Table 1.

[0073] Table 1 Solid-state hydrogen storage performance of alloys from different embodiments

[0074]

[0075] The above results show that the ball-milled alloy powders (hydrogen storage alloys) of Examples 1-6 have excellent activation performance and high hydrogen absorption capacity. Under the activation conditions of 30℃ and 3MPa, activation can be achieved in one activation treatment, which is significantly better than Comparative Example 1 (300℃, 5MPa, 8 activation treatments to achieve activation). The activation conditions are significantly reduced and the number of activations is greatly reduced. The hydrogen storage capacity of Examples 1-4 (under the conditions of 30℃ and 3MPa) is ≥1.78wt.%, the hydrogen absorption plateau is ≥0.41MPa, and the hydrogen release plateau is ≥0.28MPa. The hydrogen storage capacity and hydrogen absorption and release performance are significantly higher than those of Comparative Example 1.

[0076] In particular, the ability to maintain its activation capacity even after prolonged exposure to air is an advantage that other hydrogen storage alloys do not possess (Examples 5 and 6). As shown in Table 1, after activation, the hydrogen storage alloys in Examples 5 and 6, after being exposed to air for 30 days, still exhibited a hydrogen storage capacity ≥1.75 wt.%, a hydrogen absorption plateau ≥0.38 MPa, and a hydrogen release plateau ≥0.26 MPa. Their activation performance did not decrease significantly and was still superior to that of Comparative Example 1.

[0077] Clearly, the alloy preparation process of this invention is simple and easy to operate, fully suitable for large-scale production, and its performance meets the requirements of various applications for hydrogen storage materials. Compared with similar alloys at home and abroad, the hydrogen storage performance of the alloy of this invention is significantly improved, exhibiting obvious advantages.

[0078] 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 Ti-Fe-RE-Mn-Zr-Bi based hydrogen storage alloy, characterized in that: The alloy is specifically composed of Ti. 1.15-x- y Y x Pr y Fe 0.75 Mn 0.35-z-m Zr z Bi m Where x, y, z, and m are atomic ratios, 0.01≤x≤0.04, 0.01≤y≤0.04, 0.05≤z≤0.20, and 0.01≤m≤0.

04.

2. The hydrogen storage alloy according to claim 1, characterized in that: The ratio of x, y, z, m is x:y:z:m = 0.02:0.02:0.10:0.

02.

3. The hydrogen storage alloy according to claim 1, characterized in that: The hydrogen storage alloy has a nanocrystalline structure with an average grain size of 40–60 nm and contains grain boundary and phase boundary defects.

4. The hydrogen storage alloy according to claim 1, characterized in that: The hydrogen storage alloy has a multiphase structure containing TiFe phase and ZrMn2 phase.

5. A method for preparing the hydrogen storage alloy according to any one of claims 1 to 4, characterized in that, Specifically, the following steps are included: S1: The dosage is calculated according to the chemical formula composition and the ingredients are prepared, with appropriate amounts of Mn, Bi, Y and Pr added for loss on ignition; S2: Place the prepared raw materials in a zirconia crucible, cover the furnace, heat the raw materials to a molten state and keep them at that temperature for a period of time, then pour the liquid alloy into a copper casting mold to obtain a master alloy ingot. S3: The master alloy ingot is mechanically crushed and sieved. The sieved alloy powder is then ball-milled to obtain the finished hydrogen storage alloy powder.

6. The preparation method according to claim 5, characterized in that: In step S1, the amount of Mn, Bi, Y, and Pr added is 4% to 6% of the calculated dosage.

7. The preparation method according to claim 5, characterized in that: The order and specific operation of placing each raw material in step S2 are as follows: pure iron rods are placed vertically along the crucible wall, blocky rare earth Y and Pr are placed at the bottom of the crucible, sponge titanium and Zr are placed above rare earth Y and Pr, electrolytic manganese is placed above sponge titanium and Zr, and finally metallic Bi is added.

8. The preparation method according to claim 5, characterized in that: The specific operation for melting the raw materials in step S2 is as follows: evacuate to 1×10⁻⁶. -2 ~5×10 -5 After Pa, pure argon gas at a pressure of 0.01–0.1 MPa is introduced as a protective gas, and the melting temperature is 1500–1650℃ and held for 3–5 minutes.

9. The preparation method according to claim 5, characterized in that: The sieving operation in step S3 involves passing the mechanically crushed alloy fragments through a 200-mesh sieve to obtain alloy powder with a diameter ≤75μm, followed by ball milling.

10. The preparation method according to claim 5, characterized in that: The ball milling operation in step S3 is as follows: the alloy powder and stainless steel grinding balls are loaded into a stainless steel ball mill jar, vacuumed and then filled with high-purity argon gas, and ball milled in an all-round planetary high-energy ball mill for 0.5 to 2 hours, with a ball-to-material ratio of 1:15 to 25 and a rotation speed of 300 to 400 rpm.

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