Carbon-coated Mg-Ni-Nd alloy and preparation method and application thereof

Abstract

The invention discloses a carbon-coated Mg-Ni-Nd alloy which is characterized in that after activation and carbonization treatment, the phase composition of the alloy is an Mg phase, an Mg2Ni phase, an NdH2.61 phase and a C phase; the content of Mg is 85-90 wt.%, the content of Ni is 12-18 wt.%, the content of Nd is 15-20 wt.%, and the content of the CMC polymer is 1-5 wt.%. The preparation method comprises the following steps: 1, preparing a CMC (Carboxy Methylated Cellulose) coated Mg-Ni-Nd alloy precursor MNN / CMC; and 2, preparing the carbon-coated Mg-Ni-Nd alloy MNN / C, wherein the step 2 comprises activation and carbonization treatment. When the alloy is used as a hydrogen storage alloy, the maximum hydrogen absorption amount is greater than 4.0 wt.%; and the maximum hydrogen desorption amount is greater than 4.0 wt.%. The invention relates to a simulated poisoning treatment method of a hydrogen storage alloy, which comprises the following steps: firstly, carrying out a hydrogen absorption test on MNN / C under a poisoning atmosphere condition; then, under the vacuum condition, hydrogen desorption testing is carried out, and one-time simulated poisoning treatment is completed. Under the P-1% atmosphere condition, the maximum hydrogen absorption amount is larger than 4.0 wt.%; and the maximum hydrogen desorption amount is greater than 3.5 wt.%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrogen storage materials, in particular to a carbon-coated Mg-Ni-Nd alloy and a preparation method and application thereof. BACKGROUND

[0002] Magnesium-based hydrogen storage materials have a theoretical hydrogen storage capacity of up to 7.6wt.% and a relatively low cost, but in practical applications, they are easily poisoned by impurity gases CO2, O2, H2O and CO, resulting in a sharp decline in cycle stability. The poisoning mechanism mainly includes two aspects: first, impurity gases occupy the surface hydrogen dissociation active sites, inhibiting the adsorption and dissociation of hydrogen molecules; second, oxidation / carbonization reactions occur on the alloy surface to form a dense passivation layer, reducing the hydrogen storage phase content of the alloy. For example, existing document 1 (The storage of industrially pure hydrogen in magnesium. International Journal of Hydrogen Energy, 1993, 18(4): 297-300.), MgH2 completely loses its hydrogen absorption capacity in a H2 atmosphere containing 2% CO2, fully demonstrating its high sensitivity to impurity gases. In order to improve the CO2 poisoning resistance of magnesium-based hydrogen storage materials, there are two main methods: alloying modification and surface coating protection.

[0003] The basic principle of the alloying modification method is to introduce specific alloying elements to regulate the surface properties of the material to alleviate the poisoning effect. For example, the present inventors' previous research results, existing document 1 (Li Qian, Li Jie, Hu Bin, et al. A Mg-Ni-Nd hydrogen storage alloy with anti-poisoning and regeneration properties and its application and regeneration method: CN120210618A[P]2025-04-09.) obtained a Mg-Ni-Nd alloy with anti-poisoning and regeneration capabilities through alloying. This technical solution can enable magnesium-based hydrogen storage materials to have regeneration properties, but since the anti-poisoning mechanism only uses alloying modification, the CO2 poisoning resistance can be further improved by the method based on surface coating protection.

[0004] The basic principle of the surface coating protection method is to protect the alloy substrate through physical barrier action. According to the different coating materials, it can be divided into three categories: metal coating, carbon coating and polymer coating. Among them, metal coating can improve the anti-poisoning performance, but it has the problems of high cost and easy cracking and falling off of the coating, which is not suitable for long-term anti-poisoning requirements of hydrogen storage materials.

[0005] The carbon coating has the advantages of high temperature stability, simple process and low cost. For example, the existing document 2 (Improving oxygen resistance of hydrogen storage alloys with graphite or nickel coating International Journal of Hydrogen Energy, 2025, 103, 228-238) prepares a graphite-coated AB2 alloy by a ball milling method, which realizes the anti-poisoning performance in air exposure conditions. However, the loss of hydrogen storage capacity is still up to 25% even in weak poisoning conditions. The reason is that the graphite layer as a protective coating has the problems of poor combination and incomplete coverage with the alloy matrix, so that a dense isolation layer cannot be formed, resulting in the invasion of toxic gas.

[0006] The common method to solve the above problem of not forming a dense carbon coating is to use different carbon sources to prepare carbon coatings to achieve different anti-poisoning effects. For example, the existing document 3 (Carbon coating with different carbon sources on rare earth hydrogen storage alloy International Journal of Hydrogen Energy, 2025, 104, 30868-30876) uses different carbon-containing small molecules, specifically sucrose, glucose, pitch and chitosan as carbon sources, to prepare carbon coatings on the surface of hydrogen storage alloys to improve the anti-poisoning performance of the alloys. However, the capacity retention rate of the uncoated alloy is about 63% after 500 cycles, and the capacity retention rate of the alloy with the best carbon coating effect is only about 68% after 500 cycles, and the cycle stability improvement effect is only 5%. The reason is that such carbon coatings formed based on small molecule organic or amorphous carbon materials are also simple layered structures or amorphous structures, i.e. they cannot form a dense carbon coating with a specific micro-morphology. Therefore, such technical solutions based on small molecule organic or amorphous carbon materials to form carbon coatings in-situ effectively improve the anti-poisoning performance.

[0007] Another type of polymer coating, such as carboxymethyl cellulose CMC, polystyrene PS and polymethyl methacrylate PMMA, has the advantages of good coating and lower preparation cost, and can also improve the anti-CO2 poisoning performance of magnesium-based hydrogen storage materials. For example, the existing document 4 (Hydrogen storage materials protected by a polymer shell Journal of Materials Chemistry, 2010, 20, 1452-1456) uses a solvent evaporation method to construct polystyrene-coated NaBH4, which realizes the air stability protection of NaBH4 hydrogen storage material. However, the mass of the coated NaBH4 still increases by 37.6% in the air, that is, it reacts to NaB(OH)4 in the air. The basic principle of the above-mentioned polystyrene coating is to block the water vapor in the air through the PS barrier material, but due to the multiple process and material property limitations in the preparation process, the PS cannot completely coat the NaBH4, resulting in the problem that the NaBH4 still exists partially reacts and decomposes. In addition, the technical scheme also has the problem of complex process flow, which is embodied in that the whole process flow needs 5 steps, specifically, dissolution, emulsification, precipitation separation, drying, so it is not conducive to large-scale application.

[0008] Similarly, the existing document 5 (Air-stable magnesium nanocomposites providerapid and high-capacity hydrogen storage without using heavy-metal catalysts Nature Communications, 2011, 10, 286-290) prepared Mg / PMMA composite material by solution reduction method. Through the film-forming property and barrier property of PMMA polymer coating, the material realizes efficient hydrogen storage and air stability under specific conditions, specifically obtains 5.97wt.% hydrogen storage capacity at 200℃, and the oxidation degree is low after 3 days of exposure in air. However, the technical scheme also has the problem of complex process flow, which is embodied in that the preparation process of PMMA coating needs to go through the complex procedures of raw material dissolution, solution preparation, reduction reaction, washing and purification, and drying.

[0009] As can be seen from existing references 4 and 5, while this solution-based method for preparing polymer coatings solves the problem of protective layer formation to some extent, it still cannot solve the problem of complex process flow. Therefore, the complexity of the polymer coating preparation process can be solved by solid-state methods. For example, existing reference 6 (Preparation of a Mg-Based alloy with a high hydrogen-storage capacity by adding a polymer CMC via milling in a hydrogen atmosphere, 2019, 44, 3779-3789) prepared a CMC-modified magnesium-based hydrogen storage alloy by ball milling carboxymethyl cellulose (CMC) with a magnesium-based hydrogen storage material. Although this technical solution simplifies the preparation process and improves the initial hydrogen absorption rate of the magnesium-based hydrogen storage material, the resulting hydrogen storage alloy does not possess anti-poisoning properties.

[0010] Similar work, such as existing literature 7 (Enhancing antioxidant properties of hydrogen storage alloys using PMMA coating), *International Journal of Hydrogen Energy*, 2023, 48, 4339-4348, describes the preparation of PMMA-coated Mg2Ni hydrogen storage alloys via a coating process. The goal of this technique is to simplify the process and improve the material's resistance to poisoning. However, experimental results from this technique show that after 168 hours of air exposure, the hydrogen absorption capacity of PMMA-coated Mg2Ni only slightly increased from 2.75 wt.% to 2.85 wt.%, indicating negligible air stability. Furthermore, the resulting hydrogen storage alloy lacks resistance to the complex hydrogen environment containing impurities. The reasons for these technical problems are that, due to the much larger microparticle size of polymers compared to carbon materials, the coating process cannot form a dense, intact protective layer with strong adhesion to the substrate on the alloy surface. In addition, PMMA itself suffers from low thermal stability and mechanical strength, leading to the inability to maintain the long-term stability of the coating layer under hydrogen storage cycling conditions.

[0011] The analysis of existing literature above shows that while carbon material coatings have the advantage of high stability, they also suffer from poor adhesion and uneven coverage. Polymer coatings, on the other hand, can achieve a relatively dense and effective protective layer, but the process is complicated. Simpler processes, however, cannot form a dense and stable protective layer. Summary of the Invention

[0012] The purpose of this invention is to overcome the susceptibility to poisoning of Mg-based hydrogen storage materials by providing a carbon-coated Mg-Ni-Nd alloy, its preparation method, and its applications.

[0013] The basic technical principle of this invention is as follows: Polymers have the advantages of good film-forming properties and easy processing, and are used as precursors for carbonization to make up for the problems of poor adhesion and uneven coverage in traditional carbon coatings; at the same time, the process of converting polymer coatings into carbon coatings can obtain the advantages of high temperature resistance, chemical inertness and high thermal stability, which can solve the technical problems of traditional polymer coatings.

[0014] To achieve the above objectives, the present invention adopts the following technical solution:

[0015] A carbon-coated Mg-Ni-Nd alloy, after activation and carbonization treatment, has a phase composition of Mg phase, Mg2Ni phase, and NdH phase. 2.61 Phase C;

[0016] The content of Mg is 85-90 wt.%, the content of Ni is 12-18 wt.%, the content of Nd is 15-20 wt.%, and the content of CMC polymer is 1-5 wt.%.

[0017] A method for preparing a carbon-coated Mg-Ni-Nd alloy includes the following steps:

[0018] Step 1, Preparation of CMC-coated Mg-Ni-Nd alloy precursor: First, carboxymethyl cellulose polymer (CMC) powder and Mg-Ni-Nd alloy are mixed. Then, the mixture is ball-milled using a gap ball milling method to obtain the CMC-coated Mg-Ni-Nd alloy precursor, abbreviated as MNN / CMC.

[0019] In step 1, CMC accounts for 1-5 wt.% of the total mass;

[0020] In step 1, the ball milling conditions are as follows: under argon atmosphere, using zirconia balls as milling beads, with a ball-to-material ratio of 40:1 and a milling speed of 400 rpm.

[0021] In step 1, the conditions for intermittent ball milling are as follows: the ball milling is performed in both forward and reverse directions, with a single forward ball milling time of 10 minutes and a pause time of 10 minutes. After that, the ball milling is performed in reverse direction for 10 minutes, and the total ball milling time is 1200 minutes.

[0022] Step 2, preparation of carbon-coated Mg-Ni-Nd alloy, involves activation and carbonization treatment under hydrogen conditions, simultaneously achieving carbonization and activation, to obtain carbon-coated Mg-Ni-Nd alloy MNN / C, abbreviated as MNN / C;

[0023] In step 2, the activation carbonization treatment method is to perform hydrogen absorption activation and hydrogen release activation in sequence, and the activation carbonization treatment is performed 3-5 times.

[0024] In the activated carbonization treatment, the specific conditions for hydrogen absorption activation are: hydrogen absorption temperature of 300℃, hydrogen absorption pressure of 3MPa, and hydrogen absorption time of 0.5-2h.

[0025] In the activated carbonization process, the specific conditions for hydrogen desorption activation are: hydrogen desorption temperature of 300℃, hydrogen desorption pressure of 0.001MPa, and hydrogen desorption time of 0.2-1h.

[0026] A simulated poisoning treatment method for a hydrogen storage alloy involves first conducting a hydrogen absorption test on MNN / C under a poisoning atmosphere; then, conducting a hydrogen release test under vacuum conditions, thus completing one simulated poisoning treatment.

[0027] The poisoning atmosphere is a mixture of CO2 and H2, and the volume fraction of CO2 is 1-5%.

[0028] The conditions for the hydrogen absorption test are: hydrogen absorption temperature of 300℃, hydrogen absorption pressure of 3MPa, and hydrogen absorption time of 30-120min.

[0029] The conditions for the hydrogen release test are: hydrogen release temperature of 300℃ and hydrogen release time of 20-60 min.

[0030] When carbon-coated Mg-Ni-Nd alloy is used as a hydrogen storage alloy, under hydrogen conditions, with a hydrogen absorption temperature of 300℃, a hydrogen absorption pressure of 3MPa, and a hydrogen absorption time of 10min, the maximum hydrogen absorption is greater than 4.0wt.%; with a hydrogen release temperature of 300℃, a hydrogen release pressure of 0.01MPa, and a hydrogen release time of 10min, the maximum hydrogen release is greater than 4.0wt.%.

[0031] Under P-1% atmosphere conditions, with a hydrogen absorption temperature of 300℃, a hydrogen absorption pressure of 3MPa, and a hydrogen absorption time of 10min, the maximum hydrogen absorption of MNN / C-5-P-1% is greater than 4.0 wt.%; with a hydrogen release temperature of 300℃, a hydrogen release pressure of 0.001MPa, and a hydrogen release time of 10min, the maximum hydrogen release is greater than 3.5 wt.%.

[0032] The technical effects of this invention have been tested and confirmed to be:

[0033] XRD analysis revealed that...

[0034] The phase composition of MNN / CMC is Mg, Mg2Ni, Nd4Mg 80 Ni8 phase; after activation and carbonization treatment;

[0035] The phase composition of carbon-coated Mg-Ni-Nd alloy consists of Mg phase, Mg2Ni phase, and NdH phase. 2.61 Phase C;

[0036] After simulated poisoning treatment, the phase composition of the alloy is Mg phase, Mg2Ni phase, and NdH phase. 2.61 Phases: C phase, Nd₂O₃ phase, and MgO phase;

[0037] XRD test results show that only a small amount of Mg phase and NdH are exposed on the alloy surface. 2.61 The phase is oxidized by CO2, while the internal Mg phase, Mg2Ni phase and NdH phase are oxidized. 2.61 Both phases are effectively protected.

[0038] According to EDS testing,

[0039] After activation and carbonization treatment, the alloy contains Mg, Ni, Nd and C elements;

[0040] After simulated poisoning treatment, the alloy contains Mg, Ni, Nd, C, and O elements, with each element maintaining a uniform distribution.

[0041] Test results show that the simulated poisoning treatment did not induce segregation of alloying elements.

[0042] SEM analysis revealed that...

[0043] After activation and carbonization treatment, the average particle size of the alloy is 10-50 μm, which is the same as the average particle size before activation and carbonization treatment.

[0044] After simulated poisoning treatment, the particle size of the alloy is 10-50μm, which is basically the same as the microstructure before simulated poisoning treatment.

[0045] Test results show that neither the activation carbonization process nor the simulated poisoning process affects the microstructure.

[0046] As can be seen from the hydrogen absorption and desorption kinetic performance tests,

[0047] The maximum hydrogen absorption capacity of carbon-coated Mg-Ni-Nd alloy is greater than 4.0 wt.% under hydrogen conditions, with a hydrogen absorption temperature of 300℃, a hydrogen absorption pressure of 3MPa, and a hydrogen absorption time of 10min.

[0048] Under hydrogen conditions, with a hydrogen release temperature of 300℃, a hydrogen release pressure of 0.001MPa, and a hydrogen release time of 10min, the maximum hydrogen release amount is greater than 4.0wt.%.

[0049] The carbon-coated Mg-Ni-Nd alloy, under a P-1% atmosphere, at a hydrogen absorption temperature of 300℃, a hydrogen absorption pressure of 3MPa, and a hydrogen absorption time of 10min, exhibits a hydrogen absorption capacity greater than 4.0 wt.%.

[0050] Under the conditions of hydrogen release temperature of 300℃, hydrogen release pressure of 0.001MPa, and hydrogen release time of 10min, the hydrogen release amount is greater than 3.5wt.%.

[0051] Therefore, performance tests show that carbon-coated Mg-Ni-Nd alloys still possess hydrogen absorption and desorption properties under poisoning atmosphere conditions, with the reduction in hydrogen absorption capacity being less than 5.0% of the initial hydrogen absorption capacity. This demonstrates that carbon-coated Mg-Ni-Nd alloys exhibit excellent resistance to poisoning.

[0052] Compared with the prior art, the present invention has the following advantages:

[0053] 1. The process is simple and easy to scale up. Specifically, this invention uses a one-step ball milling method to achieve uniform composite of CMC and alloy, and then directly forms a protective layer through in-situ activation carbonization. The process is simple and the reaction conditions are mild, thus solving the problem of complex process of traditional polymer coatings, as well as the high cost and high energy consumption of vapor deposition.

[0054] 2. Furthermore, the raw material cost is low and the environment is environmentally friendly. Specifically, the raw material CMC is a commercially available polymer with wide availability and low price. Moreover, the entire preparation process does not require the use of toxic organic solvents.

[0055] 3. Possesses high resistance to poisoning under complex gaseous environments. Attached Figure Description

[0056] Figure 1 This is the XRD pattern of MNN / CMC in Embodiment 1 of the present invention;

[0057] Figure 2 This is the EDS image of MNN / CMC in Embodiment 1 of the present invention;

[0058] Figure 3 This is the SEM image of MNN / CMC in Embodiment 1 of the present invention;

[0059] Figure 4 This refers to the XPS results of MNN / CMC in Embodiment 1 of this invention;

[0060] Figure 5 This is the activation curve of MNN / CMC in Example 1 of the present invention;

[0061] Figure 6 This is the XRD pattern of MNN / C-5 in Embodiment 1 of the present invention;

[0062] Figure 7 This is the EDS image of MNN / C-5 in Embodiment 1 of the present invention;

[0063] Figure 8 This is the XPS result of MNN / C-5 in Embodiment 1 of the present invention;

[0064] Figure 9 This is the SEM image of MNN / C-5 in Embodiment 1 of the present invention;

[0065] Figure 10 This is the hydrogen absorption / desorption curve of MNN / C-5 in Example 1 of this invention;

[0066] Figure 11 This is the XRD pattern of MNN / C-5-P-1% in Embodiment 1 of the present invention;

[0067] Figure 12 It is the EDS image of MNN / C-5-P-1% in Embodiment 1 of the present invention;

[0068] Figure 13 It is the SEM image of MNN / C-5-P-1% in Embodiment 1 of the present invention;

[0069] Figure 14 This is the hydrogen absorption / desorption curve of MNN in Comparative Example 1 of this invention;

[0070] Figure 15 This is the hydrogen absorption / desorption curve of MNN / C-PVP in Comparative Example 2 of this invention. Detailed Implementation

[0071] The present invention will be further described in detail through embodiments and with reference to the accompanying drawings, but this is not intended to limit the scope of the invention.

[0072] Example 1

[0073] A method for preparing a carbon-coated Mg-Ni-Nd alloy includes the following steps:

[0074] Step 1, Preparation of CMC-coated Mg-Ni-Nd alloy precursor: First, CMC polymer powder and Mg-Ni-Nd alloy are mixed with CMC, which accounts for 5 wt.% of the total mass. Then, under argon conditions, the mixture is ball-milled using zirconia balls as milling beads at a ball-to-material ratio of 40:1 and a milling speed of 400 rpm using an intermittent ball milling method to obtain the CMC-coated Mg-Ni-Nd alloy precursor, abbreviated as MNN / CMC.

[0075] In the Mg-Ni-Nd alloy, the Mg content is 80-85%, the Mg2Ni phase content is 6-8%, and the Nd phase content is 2-5%.

[0076] The specific conditions for the intermittent ball milling are as follows: the ball milling is carried out in both forward and reverse directions, the ball milling time in one forward direction is 10 minutes, the pause time is 10 minutes, and then the ball milling in one reverse direction is 10 minutes, with a total ball milling time of 1200 minutes.

[0077] To compare with the MNN / C obtained after subsequent activation carbonization treatment, i.e. to prove the effect of activation carbonization treatment, the MNN / CMC obtained in step 1 was subjected to XRD test, EDS test, SEM test and hydrogen absorption / desorption test.

[0078] XRD test results are as follows Figure 1 As shown, the phase composition of MNN / CMC is Mg, Mg2Ni, Nd4Mg. 80 Ni8 phase, no diffraction peaks belonging to CMC polymers were detected;

[0079] Therefore, further EDS testing was conducted, and the test results were as follows: Figure 2 As shown, MNN / CMC contains Mg, Ni, and Nd elements, as well as C element, and the elements are evenly distributed.

[0080] Based on the XRD and EDS test results, the CMC polymer is an amorphous structure.

[0081] SEM test results are as follows Figure 3 As shown, the average particle size of MNN / CMC is 10-50 μm.

[0082] To further demonstrate the phase composition of MNN / CMC, particularly the variation in the C component, XPS analysis was performed. The test results are as follows: Figure 4 As shown, the C element spectrum of MNN / CMC exhibits characteristic peaks for C and C groups, as well as the characteristic peak of the carboxyl functional group OC=O. The test results indicate that the characteristic peak of the carboxyl functional group OC=O signifies successful encapsulation of CMC.

[0083] Step 2, preparation of carbon-coated Mg-Ni-Nd alloy: under hydrogen conditions, activation and carbonization treatment is carried out under certain conditions to achieve carbonization and activation at the same time, so as to obtain carbon-coated Mg-Ni-Nd alloy MNN / C, abbreviated as MNN / C. In specific embodiment 1, because the amount of CMC added is 5wt.%, it is named MNN / C-5.

[0084] The activation carbonization treatment method is to perform hydrogen absorption activation and hydrogen release activation in sequence, and the activation carbonization treatment is performed 3 times.

[0085] In the activated carbonization treatment, the specific conditions for hydrogen absorption activation are: hydrogen absorption temperature of 300℃, hydrogen absorption pressure of 3MPa, and hydrogen absorption time of 1h.

[0086] In the activated carbonization process, the specific conditions for hydrogen desorption activation are: hydrogen desorption temperature of 300℃, hydrogen desorption pressure of 0.001MPa, and hydrogen desorption time of 0.5h.

[0087] To verify the phase composition of MNN / C, XRD tests were performed. The test results are as follows: Figure 6 As shown, the phase composition of MNN / C-5 is Mg phase, Mg2Ni phase, and NdH phase. 2.61 The C phase and the MNN / CMC test results from step 1 show that the activation carbonization treatment causes the amorphous CMC polymer to undergo pyrolysis and carbonization, forming a crystalline C phase. Simultaneously, it also introduces the Nd-containing component, namely Nd₄Mg. 80 Ni8 phase hydrogenation decomposition, converting to NdH 2.61 The specific process is as follows: Nd4Mg 80 During the hydrogen absorption activation process of the activated carbonization treatment, the Ni8 phase transforms into the MgH2 phase, Mg2NiH4 phase, and NdH. 2.61 During subsequent hydrogen desorption and activation processes, the MgH2 and Mg2NiH4 phases transform into the Mg and Mg2Ni phases, respectively, while NdH... 2.61 As a thermally stable phase, no transformation was observed during the hydrogen deactivation process.

[0088] Further EDS test results are as follows Figure 7 As shown, MNN / C-5 contains Mg, Ni, Nd, and C elements. However, while Mg, Ni, and Nd elements are uniformly distributed, C element shows enrichment. Comparison with the test results of MNN / CMC in step 1 shows that the CMC polymer undergoes pyrolysis and carbonization during the activation carbonization process, a conclusion consistent with the XRD test results.

[0089] To further verify the phase composition of MNN / C, particularly the changes in the C component, XPS analysis was performed. The test results are as follows: Figure 8 As shown, the C element spectrum of MNN / C-5 exhibits characteristic peaks for CC, C=C, oxygen-containing functional group CO, and carboxyl functional group OC=O. The characteristic peaks of CC and C=C indicate the presence of a carbonized C phase, while the carboxyl functional group OC=O indicates the presence of CMC. The test results show that CMC partially decomposes and carbonizes during the activation carbonization process.

[0090] The results of XRD, EDS and XPS tests show that a composite carbon layer consisting of C phase and undecomposed CMC was formed on the surface of the Mg-Ni-Nd alloy through activation carbonization treatment, thus successfully preparing carbon-coated Mg-Ni-Nd alloy.

[0091] To verify the microstructure of MNN / C, SEM testing was performed. The test results are as follows: Figure 9 As shown, the average particle size of MNN / C-5 is 10-50 μm, which is the same as the average particle size of MNN / CMC in step 1, meaning that the activation carbonization process does not affect the microstructure.

[0092] To demonstrate the hydrogen storage performance of MNN / C-5, hydrogen absorption / desorption tests were conducted.

[0093] Hydrogen absorption test results are as follows Figure 10 As shown, under hydrogen conditions, with a hydrogen absorption temperature of 300℃, a hydrogen absorption pressure of 3MPa, and a hydrogen absorption time of 10min, the maximum hydrogen absorption capacity of MNN / C-5 reached 4.33wt.%.

[0094] Hydrogen release test results as follows Figure 10 As shown, under hydrogen conditions, with a hydrogen release temperature of 300℃, a hydrogen release pressure of 0.01MPa, and a hydrogen release time of 10min, the maximum hydrogen release of MNN / C-5 reached 4.12wt.%.

[0095] To demonstrate the anti-poisoning properties of MNN / C-5, a simulated poisoning treatment was conducted, namely, hydrogen absorption / desorption tests were performed under poisoning atmosphere conditions.

[0096] The method for simulating poisoning treatment is as follows: First, under poisoning atmosphere conditions, the hydrogen absorption temperature is 300℃, the hydrogen absorption pressure is 3MPa, and the hydrogen absorption time is 30min, the MNN / C-5 is subjected to a hydrogen absorption test; then, under vacuum conditions, a hydrogen release test is conducted at a hydrogen release temperature of 300℃ and a hydrogen release time of 20min, thus completing one simulated poisoning treatment.

[0097] The poisoning atmosphere is a mixture of CO2 and H2, and the volume fraction of CO2 is 1%. Therefore, the poisoning atmosphere of Example 1 is simply referred to as P-1%, and the poisoned state of MNN / C-5 obtained in Specific Example 1 is simply referred to as MNN / C-5-P-1.

[0098] Hydrogen absorption test results are as follows Figure 10 As shown, under P-1% atmosphere conditions, with a hydrogen absorption temperature of 300℃, a hydrogen absorption pressure of 3MPa, and a hydrogen absorption time of 10min, the hydrogen absorption capacity of MNN / C-5-P-1% reached 4.14wt.%.

[0099] Hydrogen release test results as follows Figure 10 As shown, under P-1% atmosphere conditions, with a hydrogen release temperature of 300℃, a hydrogen release pressure of 0.001MPa, and a hydrogen release time of 10min, the hydrogen release amount of MNN / C-5-P-1% reaches 3.78wt.%.

[0100] Test results show that MNN / C-5 still has hydrogen absorption and desorption properties under P-1% atmosphere conditions, which proves that the MNN / C-5 composite hydrogen storage material has anti-poisoning properties.

[0101] Compared with the test results of MNN / C-5 in step 2, the hydrogen absorption capacity of MNN / C-5-P-1% decreased slightly, by only 3.62% of the initial hydrogen absorption capacity, i.e., the hydrogen absorption capacity of MNN / C-5; the hydrogen absorption rate also decreased slightly, by only 5.04% of the hydrogen storage capacity of the MNN / C-5 sample.

[0102] The slight decrease in performance is due to the following two factors:

[0103] 1. Despite the protection of the carbon layer, in a poisoning atmosphere, the active sites on the surface of MNN / C-5 form stable oxides / carbonates with CO2 gas molecules, causing irreversible deactivation of these active sites, which in turn causes a slight decrease in hydrogen absorption and desorption capacity and rate.

[0104] 2. The excellent anti-poisoning properties of MNN / C-5 come from the effective coverage of the carbon layer on the surface of MNN / C-5, which physically blocks most of the active sites of the alloy from direct contact with CO2 gas, thus achieving anti-poisoning properties.

[0105] To demonstrate the tissue structure of MNN / C-5-P-1%, i.e., to simulate the effect of poisoning treatment, XRD, EDS, SEM and hydrogen absorption tests were performed.

[0106] XRD test results are as follows Figure 11 As shown, the phase composition of MNN / C-5-P-1% is Mg phase, Mg2Ni phase, and NdH phase. 2.61 The phases include C, Nd2O3, and MgO. Comparison with the MNN / C-5 test results in step 2 shows that during the simulated poisoning treatment, the Mg and NdH phases... 2.61 The phases partially transform into MgO and Nd2O3 phases. Test results show that only a small amount of Mg and NdH phases are exposed on the MNN / C-5 surface. 2.61 The phase is oxidized by CO2, while the internal Mg phase, Mg2Ni phase and NdH phase are oxidized. 2.61 Both phases are effectively protected.

[0107] Further EDS test results are as follows Figure 12As shown, MNN / C-5-P-1% contains Mg, Ni, Nd, C, and O elements, with each element maintaining a uniform distribution. Comparison with the test results of MNN / C-5 in step 2 shows that no alloy element segregation was induced during the simulated poisoning treatment.

[0108] To verify the microstructure of MNN / C-5-P-1%, SEM testing was performed. The test results are as follows: Figure 13 As shown, MNN / C-5-P-1% has a particle size of 10-50 μm. This is the same as the average particle size of MNN / C-5 in step 2, meaning that the simulated poisoning process does not affect the microstructure.

[0109] To demonstrate the effect of MNN / C in improving anti-poisoning properties, Comparative Example 1 is provided, which is a conventional Mg-Ni-Nd alloy, i.e., a Mg-Ni-Nd alloy without carbon coating.

[0110] Comparative Example 1

[0111] A method for preparing a conventional Mg-Ni-Nd alloy, the steps of which are the same as those in Example 1 unless otherwise specified, are different in that: in step 1, CMC is not added, the resulting conventional Mg-Ni-Nd alloy is referred to as MNN, and the resulting poisoned Mg-Ni-Nd alloy is referred to as MNN-P-1.

[0112] To demonstrate the hydrogen storage performance of MNN, hydrogen absorption / desorption tests were conducted.

[0113] Hydrogen absorption test results are as follows Figure 14 As shown, under hydrogen conditions, with a hydrogen absorption temperature of 300℃, a hydrogen absorption pressure of 3MPa, and a hydrogen absorption time of 10min, the maximum hydrogen absorption capacity of MNN reached 5.36wt.%.

[0114] Hydrogen release test results as follows Figure 14 As shown, under hydrogen conditions, with a hydrogen release temperature of 300℃, a hydrogen release pressure of 0.001MPa, and a hydrogen release time of 10min, the maximum hydrogen release of MNN reaches 5.26wt.%.

[0115] To demonstrate the anti-poisoning properties of MNN, a simulated poisoning treatment was performed.

[0116] Hydrogen absorption test results are as follows Figure 14 As shown, under P-1% atmosphere conditions, with a hydrogen absorption temperature of 300℃, a hydrogen absorption pressure of 3MPa, and a hydrogen absorption time of 10min, the maximum hydrogen absorption of MNN-P-1% is only 2.02wt.%, and the hydrogen absorption after poisoning is only 37.7%.

[0117] Meanwhile, compared with MNN, it can be seen that the hydrogen absorption rate of MNN-P-1% is significantly reduced, and the reduction is 63% of the initial hydrogen absorption rate, i.e., the hydrogen absorption rate of MNN-A.

[0118] Furthermore, compared with MNN / C-5-P-1%, the reduction in hydrogen absorption rate of MNN / C-5-P-1% is significantly lower than that of MNN-P-1%, meaning that the anti-poisoning performance of MNN / C-5-P-1% is significantly higher than that of MNN.

[0119] Hydrogen release test results as follows Figure 14 As shown, under P-1% atmosphere conditions, with a hydrogen release temperature of 300℃, a hydrogen release pressure of 0.001MPa, and a hydrogen release time of 10min, the maximum hydrogen release of MNN-P-1% is only 2.02wt.%, and the hydrogen release after poisoning is only 38.4%.

[0120] Meanwhile, compared with MNN, it can be seen that the hydrogen release rate of MNN-P-1% is significantly reduced, by 61.6% of the initial hydrogen release rate, i.e., the hydrogen release rate of MNN-A.

[0121] Examples 1 and 1 Comparative Example demonstrate that coating Mg-Ni-Nd alloys with a carbon layer introduced by CMC can significantly improve their resistance to poisoning.

[0122] To further demonstrate the effect of CMC on anti-poisoning performance, Comparative Example 2 is provided, a carbon-coated Mg-Ni-Nd alloy prepared based on PVP.

[0123] Comparative Example 2

[0124] A carbon-coated Mg-Ni-Nd alloy prepared based on PVP, wherein the steps are the same as those in Example 1 unless otherwise specified, except that in step 1, polyvinylpyrrolidone polymer PVP is added to replace CMC, and the resulting carbon-coated Mg-Ni-Nd alloy is referred to as MNN / C-PVP, and the resulting poisoned MNN / C-PVP is referred to as MNN / C-PVP-P-1.

[0125] To demonstrate the hydrogen storage performance of MNN / C-PVP, hydrogen absorption / desorption tests were conducted.

[0126] Hydrogen absorption test results are as follows Figure 15 As shown, under hydrogen conditions, with a hydrogen absorption temperature of 300℃, a hydrogen absorption pressure of 3MPa, and a hydrogen absorption time of 10min, the maximum hydrogen absorption capacity of MNN / C-PVP reached 4.30wt.%.

[0127] Hydrogen release test results as follows Figure 15As shown, under hydrogen conditions, with a hydrogen release temperature of 300℃, a hydrogen release pressure of 0.01MPa, and a hydrogen release time of 10min, the maximum hydrogen release of MNN / C-PVP reaches 3.83wt.%.

[0128] To demonstrate the anti-toxicity properties of MNN / C-PVP, simulated toxicity treatment was conducted.

[0129] Hydrogen absorption test results are as follows Figure 15 As shown, under P-1% atmosphere conditions, hydrogen absorption temperature of 300℃, hydrogen absorption pressure of 3MPa, and hydrogen absorption time of 10min, the maximum hydrogen absorption capacity of MNN / C-PVP reaches 2.57wt.%; after poisoning, the hydrogen absorption capacity is only 59.77%.

[0130] Hydrogen release test results as follows Figure 15 As shown, under P-1% atmosphere conditions, with a hydrogen release temperature of 300℃, a hydrogen release pressure of 0.01MPa, and a hydrogen release time of 10min, the maximum hydrogen release of MNN / C-PVP is only 0.03wt.%. The hydrogen release after poisoning is negligible.

[0131] Meanwhile, compared with MNN / C-5-P-1%, the hydrogen absorption rate of MNN / C-PVP-P-1% decreased more significantly than that of MNN / C-5-P-1%, meaning that the anti-toxicity performance of MNN / PVP is weaker than that of MNN / CMC.

[0132] Examples 1 and 2 demonstrate that although the carbon source is also a polymer, the anti-poisoning properties of the carbon coating formed after carbonization differ significantly. The reason for this difference is that...

[0133] The CMC molecular chain is rich in carboxyl groups, which enable it to form a strong interaction with the alloy surface in solution and during heat treatment. Ultimately, it carbonizes to form a uniform, dense, and firmly bonded amorphous carbon layer. This carbon layer can effectively block poisonous gases, while selectively allowing hydrogen to pass through.

[0134] PVP has a fundamentally different molecular structure and carbonization characteristics from CMC. Specifically, its carbonization products have poor compatibility with the alloy interface, thus failing to form a continuous and dense carbon layer. Furthermore, due to structural defects or self-catalysis in the obtained carbon layer, there is an exacerbation of poisoning, which ultimately results in not only failing to provide effective protection but also significantly reducing the material's performance.

[0135] In short, the protective effect of forming a carbon layer using polymers as a carbon source depends on the structural characteristics of the polymer molecules themselves and their carbonization behavior.

Claims

1. A carbon-coated Mg-Ni-Nd alloy, characterized in that: After activation and carbonization treatment, the phase composition of the alloy is Mg phase, Mg2Ni phase, and NdH phase. 2.61 Phase C; The content of Mg is 85-90 wt.%, the content of Ni is 12-18 wt.%, the content of Nd is 15-20 wt.%, and the content of CMC polymer is 1-5 wt.%.

2. A method for preparing a carbon-coated Mg-Ni-Nd alloy, characterized in that... Includes the following steps: Step 1, Preparation of CMC-coated Mg-Ni-Nd alloy precursor: First, carboxymethyl cellulose polymer (CMC) powder and Mg-Ni-Nd alloy are mixed. Then, the mixture is ball-milled using a gap ball milling method to obtain the CMC-coated Mg-Ni-Nd alloy precursor, abbreviated as MNN / CMC. Step 2, preparation of carbon-coated Mg-Ni-Nd alloy: activation and carbonization treatment is carried out under hydrogen conditions to achieve both carbonization and activation, resulting in carbon-coated Mg-Ni-Nd alloy MNN / C, abbreviated as MNN / C.

3. The preparation method according to claim 2, characterized in that: In step 1, CMC accounts for 1-5 wt.% of the total mass; In step 1, the ball milling conditions are as follows: under argon atmosphere, using zirconia balls as milling beads, with a ball-to-material ratio of 40:1 and a milling speed of 400 rpm. In step 1, the conditions for intermittent ball milling are as follows: the ball milling is performed in both forward and reverse directions, with a single forward ball milling time of 10 minutes and a pause time of 10 minutes. After that, the ball milling is performed in reverse direction for 10 minutes, and the total ball milling time is 1200 minutes.

4. The preparation method according to claim 2, characterized in that: In step 2, the activation carbonization treatment method is to perform hydrogen absorption activation and hydrogen release activation in sequence, and the activation carbonization treatment is performed 3-5 times. In the activated carbonization treatment, the specific conditions for hydrogen absorption activation are: hydrogen absorption temperature of 300℃, hydrogen absorption pressure of 3MPa, and hydrogen absorption time of 0.5-2h. In the activated carbonization process, the specific conditions for hydrogen desorption activation are: hydrogen desorption temperature of 300℃, hydrogen desorption pressure of 0.001MPa, and hydrogen desorption time of 0.2-1h.

5. A method for simulating poisoning treatment of hydrogen storage alloys, characterized in that: First, under poisoning atmosphere conditions, MNN / C is subjected to hydrogen absorption test; then, under vacuum conditions, hydrogen release test is conducted, thus completing one simulated poisoning treatment.

6. The simulated poisoning treatment method according to claim 5, characterized in that: The poisoning atmosphere is a mixture of CO2 and H2, and the volume fraction of CO2 is 1-5%. The conditions for the hydrogen absorption test are: hydrogen absorption temperature of 300℃, hydrogen absorption pressure of 3MPa, and hydrogen absorption time of 30-120min. The conditions for the hydrogen release test are: hydrogen release temperature of 300℃ and hydrogen release time of 20-60 min.

7. The carbon-coated Mg-Ni-Nd alloy according to claim 1, characterized in that, When used as a hydrogen storage alloy, under hydrogen conditions, with a hydrogen absorption temperature of 300℃, a hydrogen absorption pressure of 3MPa, and a hydrogen absorption time of 10min, the maximum hydrogen absorption is greater than 4.0wt.%; with a hydrogen release temperature of 300℃, a hydrogen release pressure of 0.01MPa, and a hydrogen release time of 10min, the maximum hydrogen release is greater than 4.0wt.%.

8. The carbon-coated Mg-Ni-Nd alloy according to claim 1, characterized in that, When used as a poison-resistant hydrogen storage alloy, under P-1% atmosphere conditions, with a hydrogen absorption temperature of 300℃, a hydrogen absorption pressure of 3MPa, and a hydrogen absorption time of 10min, the maximum hydrogen absorption capacity of MNN / C-5-P-1% is greater than 4.0 wt.%; under hydrogen release conditions of 300℃, a hydrogen release pressure of 0.001MPa, and a hydrogen release time of 10min, the maximum hydrogen release capacity is greater than 3.5 wt.%.

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