Technology for regulating and controlling hydrogenated LaNi5 rare earth hydrogen storage material in whole process

Abstract

The invention discloses a LaNi5 hydrogen storage material modification method based on a whole-process regulation and control hydrogenation technology and an obtained material, and belongs to the technical field of hydrogen storage material modification. In order to solve the problems that an existing LaNi5 alloy is poor in impact resistance, insufficient in cycling stability and high in safety risk, material strengthening is achieved through a staged hydrogenation process, generation of a nanoscale LaNi5H6 dispersed phase is induced through coordinated regulation and control of pulse pressure and temperature gradient, and a grain boundary structure is optimized. The impact strength of the obtained material is larger than or equal to 45 kJ / m (increased by 200% or above), the capacity fading rate after 100 cycles is smaller than or equal to 2%, the critical explosion pressure is larger than or equal to 80 MPa, the thermal runaway temperature is larger than or equal to 400 DEG C, and safety and stability are remarkably improved. According to the method, the process time is short (less than or equal to 8 hours), the energy consumption is reduced by 25%, and the method is adaptive to a vehicle-mounted hydrogen storage tank (70 MPa standard), a fuel cell hydrogen supply system and an aerospace hydrogen storage device, and has an efficient industrial application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen storage material modification, and specifically to a method for improving the impact stability of LaNi5 rare earth hydrogen storage alloy by regulating hydrogenation technology throughout the entire process, and its application. The method is suitable for on-board hydrogen storage devices, fuel cell hydrogen supply systems, and hydrogen energy storage. Background Art

[0002] LaNi5 alloy is widely used in hydrogen storage due to its excellent hydrogen absorption and desorption kinetics and low hysteresis coefficient. However, existing technologies have the following drawbacks: First, it suffers from poor impact resistance. When subjected to mechanical shock or temperature fluctuations, traditional LaNi5 materials experience brittle fracture of hydrides due to lattice stress concentration, which can easily lead to hydrogen leakage or even explosion. Second, modification technology is limited. While existing methods, such as element substitution, can adjust the plateau pressure, they increase the hysteresis coefficient and reduce compression efficiency.

[0003] In response to the above problems, the present invention proposes a full-process regulated hydrogenation technology, which significantly improves the impact stability of the material by regulating the alloy microstructure and hydride phase distribution. Summary of the Invention

[0004] A method for modifying LaNi5 hydrogen storage materials by regulating hydrogenation technology throughout the entire process comprises the following steps:

[0005] 1. Pretreatment and impurity removal: Place LaNi5 alloy powder (particle size ≤ 100 μm) in a vacuum reactor, evacuate to ≤ 1 Pa, and heat to 300-500 ° C to desorb impurity gases;

[0006] 2. Low-temperature pre-hydrogenation: Control the temperature at 50-100°C, introduce hydrogen with a purity of ≥99.999% into the reactor, increase the pressure to 10-20 MPa, and maintain for 1-2 hours;

[0007] 3. High temperature and high pressure stabilization: Maintain a system containing hydrogen with a purity of ≥99.999%, raise the temperature to 250-350°C, increase the pressure gradient to 50-150 MPa, and maintain constant pressure and temperature for 2-3 hours;

[0008] 4. Phase change control: During the hydrogenation process, the temperature is raised to 600-800°C at a rate of 2-5°C / min and maintained for 1-2 hours to promote uniform diffusion of hydrogen atoms and form a stable hydride phase (LaNi5H6);

[0009] 5. High temperature annealing: After high temperature and high pressure hydrogenation, maintain the temperature at 400°C for 0.5-1 hour;

[0010] 6. Post-processing: Slowly cool to room temperature, release the pressure and remove the alloy to obtain a highly stable hydrogen storage material.

[0011] Attached photos

[0012] Figure 1 The flow chart of hydrogenation technology for full process control. DETAILED DESCRIPTION

[0013] Example 1:

[0014] 1. Take 100g of LaNi5 alloy powder (particle size 80μm) and place it in a vacuum reactor. Evacuate to 0.8Pa, heat to 400℃ and hold for 2 hours to remove surface adsorbed gases and impurities. Cool to 80℃, introduce 99.999% pure hydrogen, and increase the pressure gradient to 15MPa. Maintain constant temperature and pressure for 1.5 hours to complete initial hydrogen adsorption. Raise the temperature to 300℃ at a rate of 5℃ / min, and simultaneously increase the hydrogen pressure to 100MPa. Maintain the pressure and temperature constant for 2 hours to promote hydrogen atomic lattice penetration. Continue to heat at a rate of 3℃ / min to 700℃ and hold for 1.5 hours. XRD analysis confirms the formation of LaNi5H6 phase (characteristic peaks 2θ = 35.2°, 41.5°). Cool to 400℃ and hold for 0.8 hour to eliminate lattice residual stress. The temperature was lowered to room temperature at a rate of 1°C / min, and the pressure was slowly released to normal pressure. The alloy powder was taken out and sieved to obtain the modified hydrogen storage material.

Claims

1. A LaNi5 hydrogen storage material modification method by regulating hydrogenation technology throughout the entire process, characterized in that The following steps are involved: a) Pretreatment: LaNi5 alloy powder (particle size ≤ 100 μm) is placed in a vacuum reactor, evacuated to ≤ 1 Pa, and heated to 300-500°C to desorb impurity gases; b) Low-temperature pre-hydrogenation: Control the temperature at 50-100°C, introduce hydrogen with a purity of ≥99.999%, increase the pressure to 10-20 MPa, and maintain for 1-2 hours; c) High temperature and high pressure stabilization: raise the temperature to 250-350°C, increase the hydrogen pressure to 50-150 MPa, and maintain constant pressure and temperature for 2-3 hours; d) Phase transition control: heating to 600-800°C at 2-5°C / min and maintaining for 1-2 hours to form the LaNi5H6 phase; e) High temperature annealing: cool to 400°C and hold for 0.5-1 hour; f) Post-processing: Cool down to room temperature and release the pressure to obtain a highly stable hydrogen storage material.

2. The method according to claim 1, wherein: The hydrogen pressure gradient rate of the low-temperature pre-hydrogenation in step b) is 0.5-2 MPa / min.

3. The method according to claim 1, wherein: In step c), the pressure and temperature of the high temperature and high pressure stabilization are increased simultaneously, with a heating rate of 3-8° C. / min and a pressure increase rate of 10-30 MPa / h.

4. The method according to claim 1, wherein: In the phase change control stage in step d), the formation of the hydride phase is monitored by in situ XRD, and the temperature increase is terminated when the LaNi5H6 phase accounts for ≥90%.

5. The method according to claim 1, wherein: In step e) high temperature annealing, an inert gas (argon or nitrogen) is introduced at a flow rate of 5-10 L / min.

6. A LaNi5 hydrogen storage material prepared by the method of any one of claims 1 to 5, characterized in that: (1) Impact strength ≥45 kJ / m²; (2) Capacity attenuation rate ≤ 2% after 100 cycles; (3) Critical explosion pressure ≥80 MPa, thermal runaway temperature ≥400℃.

7. The hydrogen storage material according to claim 6, characterized in that Its microstructure contains LaNi5H6 dispersed phase with a particle size of 20-100 nm and a grain boundary coverage of ≥85%.

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