A porous base hydrogen storage alloy and a method for preparing the same

Abstract

The application provides a porous base hydrogen storage alloy and a preparation method thereof, and belongs to the technical field of hydrogen storage alloy materials, and comprises components Ti, Mn, Zr, Cr, V4Fe, zirconium hydride powder and rare earth, and a chemical formula composition is Ti0.9Zr0.1Mn1.4Cr0.1(V4Fe)0.2+xwt%RE; and the method comprises the following steps: weighing high-purity raw materials and loading the raw materials into a nylon ball mill tank; adding anhydrous ethanol solvent, adding zirconium oxide grinding balls, and performing vacuumization to below 10 Pa, then performing wet ball milling and mixing materials; taking out the mixed raw material powder and placing the powder in a vacuum oven to perform drying; filling the dried mixed raw material powder into a mold and placing the mold in a hot-pressing sintering furnace to perform primary sintering and secondary sintering under a vacuum degree of below 10 Pa, and finally obtaining the porous base hydrogen storage alloy. ‑3 The preparation method of the hydrogen storage alloy can effectively reduce the alloy composition deviation and furnace wall pollution caused by the burning loss of low-melting-point elements, and increase the mass transfer and heat transfer performance of the hydrogen storage alloy.

Description

Technical Field

[0001] This invention relates to the field of hydrogen storage alloy materials technology, and specifically to a method for preparing a porous-based hydrogen storage alloy. Background Technology

[0002] Hydrogen energy is a clean secondary energy carrier that is easily converted into electricity and heat with high conversion efficiency and wide availability. It serves as a bridge between renewable energy and traditional fossil fuels and is a crucial component of the future energy system. Currently, hydrogen storage and transportation are key links in the large-scale application of hydrogen energy. Hydrogen storage methods are mainly divided into three categories: gaseous hydrogen storage, liquid hydrogen storage, and solid-state hydrogen storage. From a technological development perspective, high-pressure gaseous hydrogen storage technology is relatively mature, but it has low volumetric hydrogen storage density and poor safety performance. While liquid hydrogen storage solves the problem of low storage density, it has high energy consumption during the conversion process, high requirements for storage devices, and lower economic efficiency. Solid-state hydrogen storage combines high storage capacity and safety, and has the characteristics that most closely address the primary problems of hydrogen storage, making it a promising solution for future hydrogen energy storage and transportation.

[0003] Solid-state hydrogen storage technologies mainly include metal hydrides, coordination hydrides, carbon materials, metal-organic frameworks (MOFs), and hydrated hydrogen storage. Currently, metal hydrides are the mainstream technology for solid-state hydrogen storage, involving materials such as magnesium-based, titanium-based, vanadium-based, rare-earth-based, and composite hydrogen storage alloys. Among these, titanium-based hydrogen storage alloys are favored both domestically and internationally due to their high volumetric hydrogen storage density and good environmental adaptability. Titanium-based hydrogen storage alloys mainly include Ti-Fe, Ti-Mn, Ti-Cr, and Ti-Zr, with Ti-Fe and Ti-Mn alloys being representative. They offer advantages such as low cost, simple preparation, hydrogen absorption and desorption at room temperature, and fast reaction rates, with a maximum hydrogen storage capacity of approximately 2.0 wt%, making them suitable for large-scale industrial production applications.

[0004] Currently, Ti-Mn-based hydrogen storage alloys are commonly prepared using vacuum melting. This involves repeatedly melting the constituent elemental metals in a high-temperature furnace in predetermined proportions to ensure compositional homogeneity. During this process, an additional 3-5% by mass is added to minimize the loss of low-melting-point Mn. To further improve the performance of Ti-Mn-based hydrogen storage alloys, in addition to replacing elements such as Zr, Cr, V, and Fe, additional low-melting-point elements, such as rare earth elements, are added to enhance the activation properties of the hydrogen storage alloy. However, during high-temperature melting, the addition of low-melting-point elements not only makes it difficult to control the alloy composition but also contaminates the inner wall of the melting furnace.

[0005] In addition, hydrogen storage alloys prepared by smelting need to be crushed before use. The pulverization of hydrogen storage alloys and the mass and heat transfer problems of materials will limit the release of their performance.

[0006] Therefore, it is particularly important to address the issues of element loss due to high-temperature melting, contamination of the inner wall of the smelting furnace by low-melting-point elements, and the limitation on the release of performance caused by the need for crushing treatment before use. Summary of the Invention

[0007] In view of this, the objective of this invention is to provide a method for preparing porous hydrogen storage alloys, which can effectively reduce alloy composition deviations and furnace wall contamination caused by the burning loss of low-melting-point elements, and increase the mass and heat transfer performance of the hydrogen storage alloys.

[0008] To achieve the above objectives, the present invention provides a method for preparing a porous hydrogen storage alloy, comprising the following steps: Step 1: Weigh out the high-purity raw materials, including titanium powder, zirconium hydride powder, manganese powder, chromium powder, ferrovanadium alloy, and rare earth elements, and put them into a nylon ball mill jar; Step 2: In the nylon ball milling jar from Step 1, add anhydrous ethanol solvent, add zirconia milling balls, and evacuate to below 10 Pa before wet ball milling to mix the materials. Step 3: Take out the mixed raw material powder that has been thoroughly mixed in Step 2, place it in a vacuum oven, and dry it. Step 4: Fill the mold with the dried mixed raw material powder and place it in a hot press sintering furnace, under a vacuum degree of less than 10. -3 Under Pa, primary and secondary sintering are carried out while maintaining a constant vacuum during the sintering process, ultimately yielding a porous hydrogen storage alloy.

[0009] This method prepares hydrogen storage alloys through a combination of anhydrous ethanol wet ball milling, vacuum drying, continuous vacuum hot pressing sintering, and high vacuum conditions, avoiding the energy-intensive and high-loss high-temperature melting or vacuum melting methods. By utilizing the enclosed space of the mold during the hot pressing sintering process, this invention suppresses the loss of low-melting-point elements such as Mn and rare earth elements, effectively solving problems such as compositional deviations and equipment contamination in hydrogen storage alloys. Furthermore, by leveraging the accelerated diffusion rate of metal elements under ultra-high vacuum hot pressing conditions, it promotes the migration and alloying of various elements, lowers the preparation temperature of the hydrogen storage alloy, and further avoids the loss of low-melting-point elements.

[0010] The porosity of hydrogen storage alloys can be effectively controlled by continuous hot pressing sintering. This involves obtaining a high-porosity blank through initial hot pressing sintering and the decomposition of zirconium hydride, followed by further control of porosity through variations in pressing pressure and temperature during secondary hot pressing sintering, ultimately achieving a more ideal porosity. Appropriate porosity provides space for the hydrogen storage alloy to absorb hydrogen and expand, inhibiting alloy pulverization. Zirconium hydride, as a raw material, avoids zirconium powder oxidation and provides high porosity to the initial sintered blank through pyrolysis. Furthermore, continuous hot pressing sintering forms neck-like connections between particles, increasing the specific surface area of ​​the hydrogen storage alloy and improving its mass and heat transfer capabilities.

[0011] The method of this invention is not limited to the preparation of Ti-Mn based hydrogen storage alloys, but is also applicable to the preparation of other titanium-based, vanadium-based, rare earth-based, and other hydrogen storage alloys. It is especially significant for the preparation of hydrogen storage alloys that require modification with low-melting-point elements.

[0012] Preferably, in step four, the initial hot-pressing sintering temperature is 500-700℃, the pressing pressure is 30-100MPa, and the time is 20-60min; the secondary hot-pressing sintering temperature is 900-1300℃, the pressing pressure is 0-500MPa, and the time is 0.5-4h, and the sintering process maintains a constant vacuum.

[0013] By sintering twice and controlling the pressing pressure and temperature, it is easier to form a sintering neck, increase the contact area between hydrogen and hydrogen in the hydrogen storage alloy, improve mass and heat transfer performance, and better control the porosity, making it easier to directly fill and use in the later stage.

[0014] Preferably, the amount of anhydrous ethanol solution added accounts for 15-30% of the mass of the mixed raw material powder. Wet ball milling with anhydrous ethanol is used to protect the activity of the raw materials and facilitates their removal later.

[0015] Preferably, in step two, the ball mill speed is set to 100-200 r / min; the ball-to-material volume ratio is 2:1-4:1, the speed is 100-200 r / min, and the ball milling time is 2-8 hours.

[0016] Preferably, the vacuum drying temperature of the mixed raw material powder is 50-80℃, and the time is 4-12 hours. After wet ball milling, the moisture is removed by vacuum drying, and only the dried raw material powder can be subjected to stable continuous hot pressing.

[0017] Preferably, in step one, a series of high-purity raw materials are weighed according to atomic percentage, including titanium powder, zirconium hydride powder, manganese powder, chromium powder, ferrovanadium alloy, and rare earth alloy or elemental powder, wherein the rare earth alloy powder is obtained by crushing and screening, and then loaded into nylon ball mill jars respectively.

[0018] Preferably, the titanium powder and manganese powder have a particle size of 200-325 mesh; the zirconium hydride powder, chromium powder, ferrovanadium alloy, and rare earth alloy or elemental powder have a particle size of 400-500 mesh, in order to maintain the uniformity and fineness of the raw materials.

[0019] The second objective of this invention is to provide a porous hydrogen storage alloy that does not require crushing before use, which facilitates the release of its performance. The specific solution is as follows: A porous hydrogen storage alloy comprises Ti, Mn, Zr, Cr, V4Fe, zirconium hydride powder, and rare earth elements, and its chemical formula is as follows: Ti0.9Zr0.1Mn1.4Cr0.1(V4Fe)0.2+xwt% RE; The RE is one or more of LaNi5, Ce, and Y; 0 <x≤5; It was prepared using the above-mentioned method for preparing porous hydrogen storage alloys.

[0020] This alloy is mainly composed of Ti and Mn, with small amounts of Zr, Cr, and V added to improve its overall hydrogen storage performance. To reduce preparation costs, vanadium-iron alloy V4Fe is used instead of pure V. Since zirconium powder is easily oxidized in air, zirconium hydride powder is used instead of zirconium powder to prevent self-oxidation to zirconium oxide during mixing. Small amounts of rare earth alloys or elements are also added; the large atomic radius of rare earth elements effectively increases the cell volume of the Ti-Mn-based hydrogen storage alloy, thereby lowering the activation temperature. This composition and proportion of hydrogen storage alloy facilitates the preparation of stable Ti-Mn-based hydrogen storage alloys and reduces manufacturing costs.

[0021] Preferably, the rare earth element is a rare earth alloy LaNi5, and the mass percentage of LaNi5 is 2-5 wt%.

[0022] Preferably, the rare earth element is one of Ce or Y powder, and the mass percentage of Ce or Y is 0.2-2 wt%.

[0023] The above-described technical solution of the present invention has at least the following beneficial effects: 1. This invention does not require high-temperature melting, which can effectively reduce alloy composition deviation and furnace wall contamination caused by the burning loss of low-melting-point elements. At the same time, the hydrogen storage alloy significantly increases the contact area with hydrogen through sintering neck connection, thereby increasing mass and heat transfer performance.

[0024] 2. This invention can effectively control the porosity of hydrogen storage alloys, so that the prepared hydrogen storage alloys can maintain appropriate porosity, resist the expansion and contraction of the alloys during hydrogen absorption and desorption, increase the cycle stability of the hydrogen storage alloys, and thus improve their service life.

[0025] 3. The hydrogen storage material obtained by this invention can be directly filled into hydrogen storage bottles / tanks without additional crushing or pressing processes, saving operating procedures and labor costs. The production process is simple and controllable, which is of great significance to the development of Ti-Mn based hydrogen storage alloys. Attached Figure Description

[0026] Figure 1 This is a process flow diagram of the present invention; Figure 2 The image shows a SEM image of the Ti0.9Zr0.1Mn1.4Cr0.1(V4Fe)0.2+5wt% LaNi5 hydrogen storage alloy obtained in Example 1 of this invention. Figure 3 The image shows a SEM image of the Ti0.9Zr0.1Mn1.4Cr0.1(V4Fe)0.2+1wt% Ce hydrogen storage alloy obtained in Example 3 of this invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0028] Example 1 Weigh out the following components of a hydrogen storage alloy: Ti0.9Zr0.1Mn1.4Cr0.1(V4Fe)0.2+5wt% LaNi5. These components include 325-mesh titanium powder, 400-mesh zirconium hydride powder, 325-mesh manganese powder, 400-mesh chromium powder, 400-mesh ferrovanadium alloy powder, and 400-mesh crushed and sieved LaNi5 hydrogen storage alloy powder. Then, load the mixture into a nylon ball mill jar. Add 25wt% anhydrous ethanol as a solvent and add zirconium oxide grinding balls at a ball-to-material volume ratio of 2:1. After evacuating to below 10 Pa, set the ball mill speed to 200 r / min and mill for 4 hours to mix the materials. Remove the mixed raw material powder and place it in a vacuum oven at 50℃ for 12 hours to dry. Fill a graphite mold with the dried mixed raw material powder and place it in a hot-press sintering furnace under a vacuum of below 10 Pa. -3 Under pressure of 100 MPa, the alloy was first sintered at 500 °C for 60 min, and then the pressure was adjusted to 15 MPa and sintered at 1300 °C for 2 h. The vacuum was kept constant during the sintering process to obtain Ti0.9Zr0.1Mn1.4Cr0.1(V4Fe)0.2+5wt% LaNi5 hydrogen storage alloy.

[0029] Example 2 Weigh the following components according to the composition of Ti0.9Zr0.1Mn1.4Cr0.1(V4Fe)0.2+2wt% Y hydrogen storage alloy: 200-mesh titanium powder, 500-mesh zirconium hydride powder, 200-mesh manganese powder, 500-mesh chromium powder, 500-mesh ferrovanadium alloy powder, and 500-mesh crushed and sieved LaNi5 hydrogen storage alloy powder. Then, load the mixture into a nylon ball mill jar. Add 30wt% anhydrous ethanol as a solvent and add zirconium oxide grinding balls at a ball-to-material volume ratio of 4:1. After evacuating to below 10 Pa, set the ball mill speed to 100 r / min and ball mill for 8 hours to mix the materials. Remove the mixed raw material powder and place it in a vacuum oven at 80℃ for 4 hours to dry. Fill a graphite mold with the dried mixed raw material powder and place it in a hot-press sintering furnace under a vacuum of below 10 Pa.-3 Under the pressure of 40 MPa, the alloy was first sintered at 700℃ for 20 min, and then the pressure was adjusted to 0.5 MPa and sintered at 900℃ for 2 h. The vacuum was kept constant during the sintering process to obtain Ti0.9Zr0.1Mn1.4Cr0.1(V4Fe)0.2+2wt% Y hydrogen storage alloy.

[0030] Example 3 Weigh out the following components according to the composition of a hydrogen storage alloy: Ti0.9Zr0.1Mn1.4Cr0.1(V4Fe)0.2+1 wt%Ce. These components include 300-mesh titanium powder, 450-mesh zirconium hydride powder, 300-mesh manganese powder, 450-mesh chromium powder, 450-mesh ferrovanadium alloy powder, and 450-mesh cerium powder. Then, load the mixture into a nylon ball mill jar. Add 20 wt% anhydrous ethanol as a solvent and add zirconium oxide grinding balls at a ball-to-material volume ratio of 2:1. Evacuate the jar to below 10 °C. -3 After Pa, the ball mill speed was set to 180 r / min, and ball milling was performed for 4 hours to mix the materials. The mixed raw material powder was then removed and placed in a vacuum oven at 50℃ for 10 hours to dry. The dried mixed raw material powder was then filled into a graphite mold and placed in a hot-pressing sintering furnace under a vacuum degree below 10℃. -3 Under the pressure of 30 MPa, the alloy was first sintered at 600℃ for 20 min, and then the pressure was adjusted to 0.1 MPa and sintered at 1000℃ for 1 h. The vacuum was kept constant during the sintering process to obtain Ti0.9Zr0.1Mn1.4Cr0.1(V4Fe)0.2+1wt% Ce hydrogen storage alloy.

[0031] Example 4 Weigh out the following components of a hydrogen storage alloy: Ti0.9Zr0.1Mn1.4Cr0.1(V4Fe)0.2+3wt% LaNi5. These components include 250-mesh titanium powder, 460-mesh zirconium hydride powder, 250-mesh manganese powder, 460-mesh chromium powder, 460-mesh ferrovanadium alloy powder, and 460-mesh crushed and sieved LaNi5 hydrogen storage alloy powder. Then, load the mixture into a nylon ball mill jar. Add 15wt% anhydrous ethanol as a solvent and add zirconium oxide grinding balls at a ball-to-material volume ratio of 3:1. After evacuating to below 10 Pa, set the ball mill speed to 200 r / min and mill for 2 hours to mix the materials. Remove the mixed raw material powder and place it in a vacuum oven at 60℃ for 10 hours to dry. Fill a graphite mold with the dried mixed raw material powder and place it in a hot-press sintering furnace under a vacuum of below 10 Pa. -3 Under pressure of 30 MPa, the alloy was first sintered at 500 °C for 30 min, and then the pressure was adjusted to 500 MPa and sintered at 1300 °C for 0.5 h. The vacuum was kept constant during the sintering process to obtain Ti0.9Zr0.1Mn1.4Cr0.1(V4Fe)0.2+3wt% LaNi5 hydrogen storage alloy.

[0032] Comparative Example 1 Compared with Example 3, the only difference is that zirconium powder is used instead of zirconium hydride powder, while everything else remains the same, to obtain Ti0.9Zr0.1Mn1.4Cr0.1(V4Fe)0.2+1wt% Ce hydrogen storage alloy.

[0033] Comparative Example 2 Compared with Example 3, the only difference is that vacuum melting is used instead of vacuum hot pressing sintering. That is, in step four, the dried mixed raw material powder is placed in a vacuum melting furnace and repeatedly melted to achieve uniformity, finally obtaining Ti0.9Zr0.1Mn1.4Cr0.1(V4Fe)0.2+1wt% Ce hydrogen storage alloy.

[0034] Comparative Example 3 Compared with Example 3, the only difference is that in step four, the first sintering and the second sintering are carried out under a vacuum of 10 Pa. Everything else remains the same. In the end, the experiment failed and a uniform and stable hydrogen storage alloy material was not obtained.

[0035] This is because it requires continuous hot pressing and sintering under high vacuum conditions to prepare the porous hydrogen storage alloy; otherwise, it is impossible to prepare the porous hydrogen storage alloy by sintering under ordinary vacuum conditions.

[0036] Porosity and burn-off tests were conducted on the hydrogen storage alloys obtained in Examples 1-4 and Comparative Examples 1-2.

[0037] (a) Porosity testing The porosity of Examples 1-4 and Comparative Examples 1-2 was determined using the Archimedes' displacement method, and the results are shown in Table 1 and Appendix 2. Figure 2-3 As shown.

[0038] (ii) Burn-off test of low melting point rare earth and Mn elements The original rare earth and Mn content of each Example 1-4 and Comparative Example 1-2 was compared with the actual rare earth and Mn content of the final product to obtain the burn-off ratio of low melting point elements in the hydrogen storage alloy, as shown in Table 1 below.

[0039]

[0040] Based on the test results in Table 1 above, the burning loss ratio of rare earth and Mn elements was significantly reduced during the process of obtaining hydrogen storage alloys in Examples 1-4 of this invention. This effectively solved the problems of large deviations in the composition of hydrogen storage alloys and contamination of equipment cavities, laying the foundation for obtaining accurate ratios and high-performance hydrogen storage alloys.

[0041] Appendix Figure 2-3 These are SEM scans of the hydrogen storage alloys obtained in Examples 1 and 3 of this invention, respectively. Figure 3As can be seen from the above, the hydrogen storage alloy obtained in Example 3 of this invention has a very high porosity, with obvious and uniform pores, reaching as high as 20.3%. Figure 1 The porosity of the alloy was adjusted to a low level, with minimal porosity (only 1.2%). Combined with the porosity test results in Table 1, it is evident that the porosity of the hydrogen storage alloy obtained by this invention is not fixed and can be adjusted as needed. This allows for the acquisition of a hydrogen storage alloy with suitable porosity, increasing mass and heat transfer performance. It eliminates the need for destructive treatment during use and resists the expansion and contraction of the alloy during hydrogen absorption and desorption, thereby increasing the cycle stability and service life of the hydrogen storage alloy. In contrast, the cast alloy prepared using traditional smelting methods, such as Comparative Example 2, had a measured porosity of 0%, failing to yield a hydrogen storage alloy with suitable porosity.

[0042] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a porous hydrogen storage alloy, characterized in that, Includes the following steps: Step 1: Weigh high-purity raw materials including titanium powder, zirconium hydride powder, manganese powder, chromium powder, ferrovanadium alloy, and rare earth alloys or elemental powders, and load them into a nylon ball mill jar. Step 2: In the nylon ball milling jar from Step 1, add anhydrous ethanol and zirconium oxide grinding balls, and then evacuate to below 10 Pa before wet ball milling to mix the materials. Step 3: Take out the mixed raw material powder that has been thoroughly mixed in Step 2, place it in a vacuum oven, and dry it. Step 4: Fill the mold with the dried mixed raw material powder and place it in a hot press sintering furnace, under a vacuum degree of less than 10. -3 Under Pa, primary and secondary sintering were carried out, with the vacuum maintained throughout the sintering process, ultimately yielding a porous hydrogen storage alloy. In step four, the initial hot pressing sintering temperature is 500-700℃, the pressing pressure is 30-40MPa, and the time is 20-60min; the secondary hot pressing sintering temperature is 900-1300℃, the pressing pressure is 0-15MPa, and the time is 0.5-4h, and the sintering process is kept under vacuum.

2. The method for preparing a porous hydrogen storage alloy according to claim 1, characterized in that, The amount of anhydrous ethanol added is 15-30% of the mass of the mixed raw material powder.

3. The method for preparing a porous hydrogen storage alloy according to claim 1, characterized in that, In step two, the ball mill speed is set to 100-200 r / min; the ball-to-material volume ratio is 2:1-4:1, the speed is 100-200 r / min, and the ball milling time is 2-8 hours.

4. The method for preparing a porous hydrogen storage alloy according to claim 1, characterized in that, The mixed raw material powder is vacuum dried at a temperature of 50-80℃ for 4-12 hours.

5. The method for preparing a porous hydrogen storage alloy according to claim 1, characterized in that, In step one, a series of high-purity raw materials are weighed according to atomic percentage, including titanium powder, zirconium hydride powder, manganese powder, chromium powder, ferrovanadium alloy, and rare earth alloy or elemental powder. The rare earth alloy powder is obtained by crushing and screening, and then loaded into nylon ball mill jars respectively.

6. The method for preparing a porous hydrogen storage alloy according to claim 1, characterized in that, The titanium powder and manganese powder have a particle size of 200-325 mesh; the zirconium hydride powder, chromium powder, ferrovanadium alloy, and rare earth alloy or elemental powder have a particle size of 400-500 mesh.

7. A porous hydrogen storage alloy, characterized in that, It includes the components Ti, Mn, Zr, Cr, V4Fe, as well as zirconium hydride powder and rare earth elements, and its chemical formula is as follows: You 0.9 Zr 0.1 Mn 1.4 Cr 0.1 (V4Fe) 0.2 +xwt% RE; The RE is one or more of LaNi5, Ce, and Y; 0 <x≤5; It is prepared by any one of the porous hydrogen storage alloy preparation methods of claims 1-6.

8. The porous hydrogen storage alloy according to claim 7, characterized in that, The rare earth element is a rare earth alloy LaNi5, with a mass percentage of 2-5 wt%.

9. A porous hydrogen storage alloy according to claim 8, characterized in that, The rare earth element is one of Ce or Y powder, with Ce or Y accounting for 0.2-2 wt% of the total mass.

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