A rare earth-based hydrogen storage alloy for hydrogen storage and a method for preparing the same

Abstract

The application discloses a rare earth hydrogen storage alloy for tritium storage and a preparation method thereof. The chemical formula of the alloy is R 1‑ a Mg a Co x N y wherein R is one or more of rare earth elements containing Y, N is one or more of Zr, V and Ti elements, 0.15<=a<0.3, 1.9<=x<=2.4, 0<=y<=0.1; the alloy has AB2 type and AB3 type mixed phases. The rare earth alloy for tritium storage has good hydrogen absorption kinetics, and the maximum hydrogen absorption can reach above 170ml / g under the conditions of 25 DEG C and 0.1MPa hydrogen pressure, and the hydrogen release platform pressure is below 1000Pa, so the rare earth alloy for tritium storage has high hydrogen (tritium) storage capacity, low platform pressure and good kinetics.

Description

Technical Field

[0001] This invention relates to a rare earth-based hydrogen storage alloy for tritium storage and its preparation method, belonging to the field of hydrogen storage alloys. Background Technology

[0002] Tritium is a crucial fuel for fusion energy and is radioactive. During the actual operation of a fusion reactor, deuterium-tritium gas needs to be rapidly supplied to the fuel loading system within a limited timeframe, depending on the plasma's operational requirements, to ensure smooth reactor operation and avoid the radioactive hazards and resource waste associated with tritium. Therefore, the safe handling, storage, and transportation of tritium require hydrogen (tritium) storage materials that, in addition to having high hydrogen (tritium) storage capacity, also exhibit the lowest possible hydrogen absorption / desorption pressure at room temperature. This ensures efficient absorption of radioactive tritium and prevents it from entering the environment during transport.

[0003] U, as one of the earliest used tritium storage materials, exhibits excellent hydrogen (tritium) storage and release performance, fast kinetic reaction, and a low dissociation plateau pressure (10) at room temperature. -3 While hydrogen storage alloys can reversibly absorb and release hydrogen isotopes (Pa), they suffer from problems such as radioactivity, poisoning resistance, and poor helium solidification performance. In contrast, hydrogen storage alloys offer advantages such as high hydrogen storage capacity, fast reaction speed, and good safety, making them a research hotspot in recent years. ZrCo alloys possess excellent low-pressure hydrogen isotope absorption capacity and relatively mild hydrogen release conditions. However, during high-temperature, high-pressure hydrogen absorption and release in closed systems, they easily disproportionate to form a non-hydrogen-absorbing ZrCo2 phase and a non-hydrogen-releasing ZrH2 phase, leading to a decrease in the alloy's hydrogen absorption capacity and a shortened cycle life. Furthermore, the helium solidification performance of materials is one of the most important indicators for tritium treatment materials, directly affecting the service life of the tritide bed, storage life, and the purity of tritium during absorption and release. However, the long-term tritium-helium solidification characteristics of Zr-Co based alloys still lack systematic research, and the long-term helium solidification mechanism remains unclear.

[0004] Rare-earth-based hydrogen storage alloys possess excellent tritium and helium storage properties. LaNi5 alloys, by replacing Ni with Al, can continuously and effectively reduce the hydrogen absorption and desorption plateau pressure of the LaNi5 alloy, meeting the requirements for tritium storage applications. For example, research at the Savannah River Nuclear Power Plant (SRS) in the United States has found that LaNi... 4.25 Al 0.75 Eight years after tritium storage, 95%-99% of the 3He produced by helium decay remains in the alloy. However, due to the low theoretical capacity of the LaNi5 structure (only 160 ml / g) and the further decrease in hydrogen storage capacity to approximately 120 ml / g after Al substitution of Ni, developing rare-earth tritium storage materials with high capacity, low equilibrium dissociation pressure, and excellent helium-fixing performance is a pressing issue that needs to be addressed. Summary of the Invention

[0005] To address the aforementioned issues, the inventors, through repeated research, discovered a rare-earth-based hydrogen storage alloy for tritium storage that possesses high hydrogen storage capacity, a low hydrogen absorption / desorption plateau pressure, and excellent hydrogen absorption / desorption kinetics. Therefore, the objective of this invention is to provide a rare-earth-based hydrogen storage alloy for tritium storage that exhibits the effects described above.

[0006] To achieve the above objectives, the present invention adopts the following technical solution.

[0007] A rare-earth hydrogen storage alloy for tritium storage, characterized in that the chemical formula of the hydrogen storage alloy is R 1-a Mg a Co x N y Where R is one or more rare earth elements containing Y, N is one or more of Zr, V, and Ti, and 0.15≤a<0.3, 1.9≤x≤2.4, 0≤y≤0.1, its maximum hydrogen absorption capacity is ≥170ml / g at 25℃ and 0.1MPa hydrogen pressure, and its hydrogen release plateau pressure is <1000Pa.

[0008] In the aforementioned rare-earth hydrogen storage alloys for tritium storage, R 1-a Mg a Co x N y One preferred scheme is 0.18≤a≤0.28, 1.9≤x≤2.3, 0≤y≤0.1.

[0009] A rare earth-based hydrogen storage alloy for tritium storage is characterized by comprising a (R,Mg,N)(Co,N)2 phase with space group F-43m and a (R,Mg,N)(Co,N)3 phase with space group R-3m.

[0010] The preferred element for R is Y or Y and Ce.

[0011] A method for preparing a rare-earth-based hydrogen storage alloy for tritium storage, wherein the chemical formula of the rare-earth-based hydrogen storage alloy is R. 1-a Mg a Co x N y Wherein, R is one or more rare earth elements containing Y, N is one or more of Zr, V, and Ti, and 0.15≤a<0.3, 1.9≤x≤2.4, 0≤y≤0.1, its maximum hydrogen absorption capacity is ≥170ml / g at 25℃ and 0.1MPa hydrogen pressure, and its hydrogen release plateau pressure is <1000Pa.

[0012] The preparation method includes the following steps:

[0013] (1) The rare earth, Co and N metal raw materials with a purity greater than 99.95% are mixed according to the above chemical formula composition ratio, and melted in a plasma arc melting furnace to prepare cast alloy ingots.

[0014] (2) The cast alloy ingot was activated by vacuuming at 400°C for one hour, and hydrogen was absorbed at 10MPa at room temperature until saturation. Then, vacuuming was performed to obtain cast alloy powder.

[0015] (3) Mix the as-cast alloy powder and Mg powder with a mesh size of less than 200 in an argon atmosphere according to the above chemical formula composition ratio, add 5wt.%-10wt.% of the Mg powder as burn-off, and cold press the uniformly mixed metal powder into an alloy sheet under a pressure of 5MPa-10MPa.

[0016] (4) The pressed alloy sheet is placed in a metal sealed container and then sintered in a muffle furnace to obtain the rare earth hydrogen storage alloy.

[0017] In step (1) above, plasma arc melting uses a mixture of H2 and Ar gas, wherein the mass percentage of H2 is 5 wt.% to 20 wt.%.

[0018] In step (4) above, the sintering procedure is as follows: first, the temperature is raised from room temperature to 700℃-800℃ and held for 6-12 hours; then the temperature is lowered to 500℃-600℃ and held for 40-60 hours, and then cooled to room temperature with the furnace.

[0019] Typically, the vacuum level of an electric arc melting furnace is 10. -3 Pa, pressure is 0.08 MPa.

[0020] The advantages of this invention are:

[0021] To improve the capacity of rare-earth-based hydrogen storage alloys, this invention employs Mg to partially replace rare-earth elements to prepare an alloy with both a C15-type Laves phase AB2 structure (theoretical hydrogen storage capacity >2.0 wt%) and a superlattice AB3 phase structure (theoretical hydrogen storage capacity 1.5–2.0 wt%), exhibiting high theoretical hydrogen storage capacity. Furthermore, due to the interaction between Co and the outer electrons of the A-side elements, a high hydrogen absorption / desorption capacity can be maintained while effectively reducing the hydrogen absorption / desorption plateau pressure. Through synergistic regulation of the Mg content on the A-side and the Co content on the B-side, the alloy achieves a hydrogen absorption plateau pressure below 1 kPa at room temperature, meeting the application requirements for tritium storage. Attached image description:

[0022] Figure 1 XRD patterns of Example 1 and Comparative Examples 1 and 2

[0023] Figure 2The hydrogen absorption kinetics curves for Examples 1 and 2 and Comparative Examples 1 and 2 at a hydrogen pressure of 0.1 MPa are shown.

[0024] Figure 3 PCT curves at different temperatures in Example 1

[0025] Figure 4 PCT curves at different temperatures in Example 2

[0026] Figure 5 To compare the PCT curves of Example 1 at different temperatures

[0027] Figure 6 To compare the PCT curve of Example 2 at 293K Detailed implementation method:

[0028] The present invention will be further illustrated by the following embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0029] Example 1

[0030] Metal raw materials with a purity greater than 99.95% are classified according to their chemical composition Y. 0.72 Co 1.9 The ingredients are prepared, placed into a crucible, and smelted in a plasma arc melting furnace. A vacuum of 1000 elapsed beforehand is applied. -3 The furnace chamber was cleaned 1-2 times with high-purity argon gas, followed by the introduction of a mixed gas of H2 and Ar (H2 content 10 wt.%). High-purity titanium was used as a smelting purifying agent to further purify the atmosphere. Then, alloy smelting was performed to ensure complete melting and mixing of the metallic elements. After smelting, the smelting atmosphere in the furnace was evacuated, and high-purity argon gas was introduced for cooling. The smelting process was repeated 2-3 times to ensure uniform alloy composition, resulting in a cast alloy ingot. The cast alloy ingot was activated under vacuum at 400℃ for one hour, then subjected to hydrogen absorption at 10 MPa at room temperature until saturation, followed by vacuum to obtain cast alloy powder. The cast alloy powder and Mg powder (5% excess, i.e., 5% Mg powder burn-off) were mixed in an argon atmosphere at a ratio of Y... 0.72 Mg 0.28 Co 1.9 The metal powders were mixed and then cold-pressed into alloy sheets under a pressure of 10 MPa. The pressed alloy sheets were placed in a metal sealed container and sintered in a muffle furnace. The temperature was raised from room temperature to 800°C and held for 12 hours; then the temperature was lowered to 600°C and held for 60 hours, and then cooled to room temperature in the furnace to obtain a rare earth hydrogen storage alloy.

[0031] The preparation conditions are the same in all the following examples.

[0032] Comparative Example 1

[0033] Metal raw materials with a purity greater than 99.95% are selected according to the molecular formula LaNi. 4.25 Al 0.75 The ingredients are prepared, placed into a crucible, and smelted in a plasma arc melting furnace. A vacuum of 1000 elapsed beforehand is applied. -3 The furnace chamber is purged 1-2 times with high-purity argon gas, followed by the introduction of a mixture of H2 and Ar (H2 content 10 wt.%). High-purity titanium is used as a smelting purifying agent to further purify the atmosphere. Then, alloy smelting is performed to ensure complete melting and mixing of the metallic elements. After smelting, the smelting atmosphere is evacuated, and high-purity argon gas is introduced for cooling. The smelting process is repeated 2-3 times to ensure uniform alloy composition.

[0034] Comparative Example 2

[0035] Metal raw materials with a purity greater than 99.95% are classified according to the molecular formula Y. 0.7 Co 1.8 Ni 0.1 The ingredients are prepared, placed into a crucible, and smelted in a plasma arc melting furnace. A vacuum of 1000 elapsed beforehand is applied. -3 The furnace chamber was cleaned 1-2 times with high-purity argon gas, followed by the introduction of a mixture of H2 and Ar (H2 content 10 wt.%). The atmosphere was further purified using a smelting purifying agent (high-purity titanium), and then alloy smelting was performed to ensure complete melting and mixing of the metallic elements. After smelting, the smelting atmosphere in the furnace was evacuated, and high-purity argon gas was introduced for cooling. The smelting process was repeated 2-3 times to ensure uniform alloy composition. The as-cast alloy ingot was activated at 400℃ for one hour and then subjected to hydrogen absorption at 10 MPa at room temperature until saturation, yielding as-cast alloy powder. The as-cast alloy powder and Mg powder (5% excess, less than 200 mesh) were mixed in an argon atmosphere according to a specific ratio (Y). 0.7 Mg 0.3 Co 1.8 Ni 0.1 The metal powders were mixed and cold-pressed into alloy sheets under a pressure of 10 MPa. The pressed alloy sheets were placed in a metal sealed container and sintered in a muffle furnace. The temperature was raised from room temperature to 800°C and held for 12 hours. Then the temperature was lowered to 600°C and held for 60 hours. Finally, the temperature was cooled to room temperature in the furnace to obtain the hydrogen storage alloy.

[0036] Example 2

[0037] Metal raw materials with a purity greater than 99.95% are classified according to the molecular formula Y. 0.74 Co 2.0 The ingredients are prepared, placed into a crucible, and smelted in a plasma arc melting furnace. A vacuum of 1000 elapsed beforehand is applied. -3The furnace chamber was cleaned 1-2 times with high-purity argon gas, followed by the introduction of a mixed gas of H2 and Ar (H2 content 10 wt.%). High-purity titanium was used as a smelting purifying agent to further purify the atmosphere. Then, alloy smelting was performed to ensure complete melting and mixing of the metallic elements. After smelting, the smelting atmosphere in the furnace was evacuated, and high-purity argon gas was introduced for cooling. The smelting process was repeated 2-3 times to ensure uniform alloy composition. The as-cast alloy ingot was activated at 400℃ for one hour and then subjected to hydrogen absorption to saturation at 10 MPa at room temperature to obtain as-cast alloy powder. The as-cast alloy powder and Mg powder (5% excess, less than 200 mesh) were mixed in an argon atmosphere according to a specific ratio (Y). 0.74 Mg 0.26 Co 2.0 The metal powders were mixed and then cold-pressed into alloy sheets under a pressure of 10 MPa. The pressed alloy sheets were placed in a metal sealed container and sintered in a muffle furnace. The temperature was raised from room temperature to 800°C and held for 12 hours; then the temperature was lowered to 600°C and held for 60 hours, and then cooled to room temperature in the furnace to obtain a rare earth hydrogen storage alloy.

[0038] After removing the oxide scale from the obtained hydrogen storage alloy block, it was mechanically crushed. Powder with a mesh size of less than 400 was selected for X-ray powder diffraction test. Cu Kα rays were used with a power of 40kV×150mA, step scanning, a step size of 0.02°, and a 2θ range of 10°~90°. Figure 1 The XRD patterns of Example 1 and Comparative Examples 1 and 2 are shown in the figures. As can be seen from the figures, Example 1 is mainly a mixed phase of (Y,Mg)Co2 with space group F-43m and (Y,Mg)Co3 with space group R-3m, Comparative Example 2 is mainly a mixed phase of (Y,Mg)(Ni,Co)2 with space group F-43m and (Y,Mg)(Ni,Co)3 with space group R-3m, and Comparative Example 1 is a pure LaNi5 phase.

[0039] The gaseous hydrogen storage performance of hydrogen storage alloys can be represented by the pressure-composition-temperature (PCT) characteristic curve of the alloy. The reversible hydrogen absorption / desorption capacity of the metal hydride and the hydrogen absorption / desorption plateau pressure at different temperatures can be obtained from the PCT curve. The PCT curve of the material was determined at a constant temperature using a Sievels apparatus. The test method was as follows: approximately 2g of alloy powder with a particle size less than 80 mesh was taken, vacuumed at 400℃ for 1–2 hours, and after cooling to room temperature, hydrogen was absorbed by charging at 25℃ with 5MPa pressure hydrogen gas. This process was repeated 2–3 times to fully activate the alloy. Hydrogen absorption was then performed by charging at 25℃ with 0.1MPa pressure hydrogen gas, and the hydrogen absorption kinetic curve was obtained. After hydrogen absorption reached saturation, the amount of hydrogen absorbed at this point was recorded. Figure 2 As shown. Then, PCT curve tests were performed at different temperatures, as shown. Figure 3-6 As shown.

[0040] Figure 2 The hydrogen absorption kinetics curves are for Examples 1 and 2 and Comparative Examples 1 and 2. Figures 3-6 The PCT curves are for Examples 1 and 2 and Comparative Examples 1 and 2, respectively. From... Figure 2 The hydrogen absorption kinetics curves show that the hydrogen absorption capacities of the four alloys with different compositions at a hydrogen pressure of 0.1 MPa are 188.0 ml / g, 182.3 ml / g, 136.1 ml / g, and 123.1 ml / g, respectively. Comparative Example 1, due to its LaNi5 structure, has the lowest hydrogen storage capacity. Examples 1 and 2, with their mixed AB2 and AB3 structures, exhibit significantly increased capacity due to the ability to accommodate more H atoms, resulting in hydrogen absorption capacities >180 ml / g. Because the hydrogen desorption plateau pressures of the alloys in Examples 1, 2, and Comparative Example 1 are too low, and complete PCT curves cannot be obtained due to the limitations of the testing equipment's range, the testing temperature was increased to above 100°C. PCT curves for hydrogen absorption and desorption at 100°C, 120°C, 140°C, and 160°C were tested. Extrapolated to room temperature (25°C), the hydrogen desorption plateau pressures were obtained as 406 Pa, 620 Pa, and 3900 Pa, respectively. Comparative Example 2 had a hydrogen desorption plateau pressure of 50600 Pa at 25°C. Due to the excessively high plateau pressure, although it also had a mixed structure of AB2 and AB3, its hydrogen absorption capacity at 0.1 MPa was only 136.1 ml / g, which was too low and could not meet the application requirements.

[0041] Example 3

[0042] Metal raw materials with a purity greater than 99.95% are classified according to the molecular formula Y. 0.75 Co 2.0 Zr 0.1 The ingredients are prepared, placed into a crucible, and smelted in a plasma arc melting furnace. A vacuum of 1000 elapsed beforehand is applied. -3 The furnace chamber was cleaned 1-2 times with high-purity argon gas, followed by the introduction of a mixture of H2 and Ar (H2 content 5 wt.%). High-purity titanium was used as a smelting purifying agent to further purify the atmosphere. Then, alloy smelting was performed to ensure complete melting and mixing of the metallic elements. After smelting, the smelting atmosphere in the furnace was evacuated, and high-purity argon gas was introduced for cooling. The smelting process was repeated 2-3 times to ensure uniform alloy composition. The as-cast alloy ingot was activated at 400℃ for one hour and then subjected to hydrogen absorption at 10 MPa at room temperature until saturation, yielding as-cast alloy powder. The as-cast alloy powder and Mg powder (10% excess, less than 200 mesh) were mixed in an argon atmosphere according to a specific ratio (Y). 0.75 Mg 0.25 Co 2.0 Zr 0.1The metal powders were mixed and then cold-pressed into alloy sheets under a pressure of 10 MPa. The pressed metal sheets were placed in a sealed metal container and sintered in a muffle furnace. The temperature was raised from room temperature to 800°C and held for 12 hours; then the temperature was lowered to 600°C and held for 60 hours, and then cooled to room temperature in the furnace to obtain a rare earth hydrogen storage alloy.

[0043] XRD and hydrogen storage performance tests showed that the alloy has a mixed phase of (Y,Mg,Zr)Co2 and (Y,Mg,Zr)Co3. The hydrogen absorption capacity at 0.1 MPa hydrogen pressure is 178 ml / g. Through PCT tests at different temperatures and extrapolation, the hydrogen release pressure at room temperature is 756 Pa.

[0044] Example 4

[0045] Metal raw materials with a purity greater than 99.95% are classified according to the molecular formula Y. 0.77 Co 2.1 The ingredients are prepared, placed into a crucible, and smelted in a plasma arc melting furnace. A vacuum of 1000 elapsed beforehand is applied. -3 The furnace chamber was cleaned 1-2 times with high-purity argon gas, followed by the introduction of a mixture of H2 and Ar (H2 content 10 wt.%). The atmosphere was further purified using a smelting purifying agent (high-purity titanium), and then alloy smelting was performed to ensure complete melting and mixing of the metallic elements. After smelting, the smelting atmosphere in the furnace was evacuated, and high-purity argon gas was introduced for cooling. The smelting process was repeated 2-3 times to ensure uniform alloy composition. The as-cast alloy ingot was activated at 400℃ for one hour and then subjected to hydrogen absorption at 10 MPa at room temperature until saturation, yielding as-cast alloy powder. The as-cast alloy powder and Mg powder (5% excess, less than 200 mesh) were mixed in an argon atmosphere according to a specific ratio (Y). 0.77 Mg 0.23 Co 2.1 The metal powders were mixed and then cold-pressed into sheets under a pressure of 10 MPa. The pressed metal sheets were placed in a sealed metal container and sintered in a muffle furnace. The temperature was raised from room temperature to 800°C and held for 12 hours; then the temperature was lowered to 600°C and held for 60 hours, and then cooled to room temperature in the furnace to obtain a rare earth hydrogen storage alloy.

[0046] XRD and hydrogen storage performance tests showed that the alloy has a mixed phase of (Y,Mg)Co2 and (Y,Mg)Co3. The hydrogen absorption capacity at 0.1 MPa hydrogen pressure is 182 ml / g. Through PCT tests at different temperatures and extrapolation, the hydrogen release pressure at room temperature is 796 Pa.

[0047] Example 5

[0048] Metal raw materials with a purity greater than 99.95% are classified according to the molecular formula Y. 0.80 Co 2.2 The ingredients are prepared, placed into a crucible, and smelted in a plasma arc melting furnace. A vacuum of 1000 elapsed beforehand is applied.-3 The furnace chamber was cleaned 1-2 times with high-purity argon gas, followed by the introduction of a mixed gas of H2 and Ar (H2 content 10 wt.%). High-purity titanium was used as a smelting purifying agent to further purify the atmosphere. Then, alloy smelting was performed to ensure complete melting and mixing of the metallic elements. After smelting, the smelting atmosphere in the furnace was evacuated, and high-purity argon gas was introduced for cooling. The smelting process was repeated 2-3 times to ensure uniform alloy composition. The as-cast alloy ingot was activated at 400℃ for one hour and then subjected to hydrogen absorption to saturation at 10 MPa at room temperature to obtain as-cast alloy powder. The as-cast alloy powder and Mg powder (5% excess, less than 200 mesh) were mixed in an argon atmosphere according to a specific ratio (Y). 0.80 Mg 0.20 Co 2.2 The metal powders were mixed and then cold-pressed into sheets under a pressure of 10 MPa. The pressed alloy sheets were placed in a sealed metal container and sintered in a muffle furnace. The temperature was raised from room temperature to 800°C and held for 12 hours; then the temperature was lowered to 600°C and held for 60 hours, and then cooled to room temperature in the furnace to obtain a rare earth hydrogen storage alloy.

[0049] XRD and hydrogen storage performance tests showed that the alloy has a mixed phase of (Y,Mg)Co2 and (Y,Mg)Co3, and the hydrogen absorption capacity at 0.1 MPa hydrogen pressure is 175 ml / g. The hydrogen release pressure at room temperature was obtained by extrapolation from PCT tests at different temperatures and is 805 Pa.

[0050] Example 6

[0051] Metal raw materials with a purity greater than 99.95% are classified according to the molecular formula Y. 0.82 Co 2.3 The ingredients are prepared, placed into a crucible, and smelted in a plasma arc melting furnace. A vacuum of 1000 elapsed beforehand is applied. -3 The furnace chamber was cleaned 1-2 times with high-purity argon gas, followed by the introduction of a mixed gas of H2 and Ar (H2 content 10 wt.%). High-purity titanium was used as a smelting purifying agent to further purify the atmosphere. Then, alloy smelting was performed to ensure complete melting and mixing of the metallic elements. After smelting, the smelting atmosphere in the furnace was evacuated, and high-purity argon gas was introduced for cooling. The smelting process was repeated 2-3 times to ensure uniform alloy composition. The as-cast alloy ingot was activated at 400℃ for one hour and then subjected to hydrogen absorption to saturation at 10 MPa at room temperature to obtain as-cast alloy powder. The as-cast alloy powder and Mg powder (5% excess, less than 200 mesh) were mixed in an argon atmosphere according to a specific ratio (Y). 0.82 Mg 0.18 Co 2.3 The metal powders were mixed and then cold-pressed into alloy sheets under a pressure of 5 MPa-10 MPa. The pressed metal sheets were placed in a sealed metal container and sintered in a muffle furnace. The temperature was raised from room temperature to 800°C and held for 12 hours; then the temperature was lowered to 600°C and held for 60 hours, and then cooled to room temperature in the furnace to obtain a rare earth hydrogen storage alloy.

[0052] XRD and hydrogen storage performance tests showed that the alloy has a mixed phase of (Y,Mg)Co2 and (Y,Mg)Co3, and the hydrogen absorption capacity at 0.1 MPa hydrogen pressure is 180 ml / g. The hydrogen release pressure at room temperature was obtained by extrapolation from PCT tests at different temperatures and is 823 Pa.

[0053] Example 7

[0054] Metal raw materials with a purity greater than 99.95% are classified according to the molecular formula Y. 0.85 Co 2.4 The ingredients are prepared, placed into a crucible, and smelted in a plasma arc melting furnace. A vacuum of 1000 elapsed beforehand is applied. -3 The furnace chamber was cleaned 1-2 times with high-purity argon gas, followed by the introduction of a mixed gas of H2 and Ar (H2 content 10 wt.%). High-purity titanium was used as a smelting purifying agent to further purify the atmosphere. Then, alloy smelting was performed to ensure complete melting and mixing of the metallic elements. After smelting, the smelting atmosphere in the furnace was evacuated, and high-purity argon gas was introduced for cooling. The smelting process was repeated 2-3 times to ensure uniform alloy composition. The as-cast alloy ingot was activated at 400℃ for one hour and then subjected to hydrogen absorption to saturation at 10 MPa at room temperature to obtain as-cast alloy powder. The as-cast alloy powder and Mg powder (5% excess, less than 200 mesh) were mixed in an argon atmosphere according to a specific ratio (Y). 0.85 Mg 0.15 Co 2.4 The metal powders were mixed and then cold-pressed into alloy sheets under a pressure of 10 MPa. The pressed metal sheets were placed in a sealed metal container and sintered in a muffle furnace. The temperature was raised from room temperature to 800°C and held for 12 hours; then the temperature was lowered to 600°C and held for 60 hours, and then cooled to room temperature in the furnace to obtain a rare earth hydrogen storage alloy.

[0055] XRD and hydrogen storage performance tests showed that the alloy has a mixed phase of (Y,Mg)Co2 and (Y,Mg)Co3, and the hydrogen absorption capacity at 0.1 MPa hydrogen pressure is 173 ml / g. The hydrogen release pressure at room temperature was obtained by extrapolation from PCT tests at different temperatures and is 846 Pa.

[0056] Example 8

[0057] Metal raw materials with a purity greater than 99.95% are classified according to the molecular formula Y. 0.50 Ce 0.28 Co 1.9 The ingredients are prepared, placed into a crucible, and smelted in a plasma arc melting furnace. A vacuum of 1000 elapsed beforehand is applied. -3The furnace chamber was cleaned 1-2 times with high-purity argon gas, followed by the introduction of a mixed gas of H2 and Ar (H2 content 20 wt.%). High-purity titanium was used as the smelting purifying agent to further purify the atmosphere. Then, alloy smelting was performed to ensure complete melting and mixing of the metallic elements. After smelting, the smelting atmosphere in the furnace was evacuated, and high-purity argon gas was introduced for cooling. The smelting process was repeated 2-3 times to ensure uniform alloy composition. The as-cast alloy ingot was activated at 400℃ for one hour and then subjected to hydrogen absorption at 10 MPa at room temperature until saturation, yielding as-cast alloy powder. The as-cast alloy powder and Mg powder (5% excess, less than 200 mesh) were mixed in an argon atmosphere according to a specific ratio (Y). 0.50 Ce 0.28 Mg 0.22 Co 1.9 The metal powders were mixed and then cold-pressed into alloy sheets under a pressure of 5 MPa. The pressed metal sheets were placed in a sealed metal container and sintered in a muffle furnace. The temperature was raised from room temperature to 700°C and held for 6 hours; then the temperature was lowered to 500°C and held for 40 hours; finally, the furnace was cooled to room temperature to obtain a rare earth hydrogen storage alloy.

[0058] XRD and hydrogen storage performance tests showed that the alloy has a mixed phase of (Y,Ce,Mg)Co2 and (Y,Ce,Mg)Co3. The hydrogen absorption capacity at 0.1 MPa hydrogen pressure is 171 ml / g. The hydrogen release pressure at room temperature is 877 Pa, obtained by PCT tests at different temperatures and extrapolation.

[0059] As can be seen from the data above, due to the small atomic radius of Mg, increasing its content on side A reduces the unit cell volume, thereby decreasing the hydrogen storage capacity and increasing the plateau pressure. In Comparative Example 2, the high Mg content (greater than 0.3%) and the presence of Ni (smaller than Co atomic radius) result in a high plateau pressure at room temperature and a low capacity at low hydrogen pressure, failing to meet application requirements. However, as can be seen from the data and figures of Examples 1-8, when the magnesium content on side A is ≥0.15 and less than 0.3 (i.e., within the scope of this invention), the plateau pressure of the alloy can be effectively adjusted to <1 kPa by synergistically adjusting the Mg and Co contents on side B, resulting in an alloy with high capacity that meets application requirements.

[0060] Possibilities of the present invention

[0061] This invention provides a rare earth-based hydrogen storage alloy for tritium storage and its preparation method. It has good performance in terms of high hydrogen storage capacity, hydrogen absorption and desorption plateau pressure and hydrogen absorption and desorption kinetics, and has potential application prospects in the field of tritium storage.

[0062] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations 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. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A rare-earth-based hydrogen storage alloy for tritium storage, characterized in that, The chemical formula of this hydrogen storage alloy is R. 1-a Mg a Co x N y Wherein, R is one or more rare earth elements including Y, N is one or more of Zr, V, and Ti, and 0.15≤a<0.3, 1.9≤x≤2.4, 0≤y≤0.

1. Its maximum hydrogen absorption capacity is ≥170ml / g at 25℃ and 0.1MPa hydrogen pressure, and its hydrogen release plateau pressure is <1000Pa. The hydrogen storage alloy contains a (R, Mg, N)(Co, N)2 phase with space group F-43m and a (R, Mg, N)(Co, N)3 phase with space group R-3m.

2. The rare-earth-based hydrogen storage alloy for tritium storage as described in claim 1, characterized in that, The R element is either Y alone or a combination of Y and Ce.

3. A method for preparing a rare-earth-based hydrogen storage alloy for tritium storage, which is the method for preparing a rare-earth-based hydrogen storage alloy for tritium storage as described in claim 1 or 2, characterized in that, Includes the following steps: (1) The rare earth, Co and N metal raw materials with a purity greater than 99.95% are mixed in the proportion of the above chemical formulas and smelted in a plasma arc melting furnace to prepare cast alloy ingots. (2) The cast alloy ingot was activated by vacuuming at 400°C for one hour, and hydrogen was absorbed at 10MPa at room temperature until saturation. Then, vacuuming was performed to obtain cast alloy powder. (3) Mix the cast alloy powder and Mg powder with a mesh size of less than 200 in an inert atmosphere according to the proportion of the above chemical formula, add 5wt.%-10wt.% of the Mg powder as burn-off, and cold press the uniformly mixed metal powder into alloy sheets under a pressure of 5MPa-10MPa. (4) The pressed alloy sheet is placed in a metal sealed container and then sintered in a muffle furnace to obtain a rare earth hydrogen storage alloy for tritium storage. The sintering procedure is as follows: first, the temperature is raised from room temperature to 700℃-800℃ and held for 6-12 hours; then the temperature is lowered to 500℃-600℃ and held for 40-60 hours, and then cooled to room temperature with the furnace.

4. The preparation method of rare earth-based hydrogen storage alloy for tritium storage as described in claim 3, characterized in that, The plasma arc melting in step (1) uses a mixture of H2 and Ar gas, wherein the mass percentage of H2 is 5wt.%~20wt.%.

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