Carbon-coated nickel-based hydrogen storage alloy and batch preparation method

Abstract

According to the carbon-coated nickel-based hydrogen storage alloy and the batch preparation method, nickel serves as a base material, rare earth elements are introduced to optimize the grain structure and inhibit the hydrogen embrittlement phenomenon, transition metal is combined to regulate and control the hydrogen storage dynamic performance, meanwhile, trace metal elements are added to enhance the oxidation resistance, nickel-based alloy components are precisely regulated and controlled through suspension smelting, and the carbon-coated nickel-based hydrogen storage alloy is obtained. Smelting under the protection of argon; the method comprises the following steps: converting molten alloy into micron-sized particles by adopting a high-pressure gas atomization process, introducing an olefin-containing mixed atmosphere into an atomization tower, cracking olefin at a high temperature by utilizing the catalytic activity of a nickel surface, and generating a graphitized carbon coating layer in situ in an atomization flight process; and the carbon layer structure is optimized through multi-stage annealing and trace oxygen passivation treatment subsequently, the carbon-coated nickel-based hydrogen storage alloy with high thermal conductivity and excellent cycle stability is finally obtained, the single-time treatment capacity reaches the hundred-kilogram level, and low-cost batch preparation is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen storage material preparation, and relates to a carbon-coated nickel-based hydrogen storage alloy and a batch preparation method. Background Art

[0002] With the rapid development of hydrogen energy technology, hydrogen storage alloys have attracted widespread attention as solid-state hydrogen storage materials due to their high safety and reversibility. Among them, nickel-based hydrogen storage alloys have shown great application potential in nickel-hydrogen batteries, fuel cells, and other fields due to their high hydrogen storage capacity, good kinetic properties, and excellent cycling stability. However, nickel-based hydrogen storage alloys still face two key challenges in practical applications: First, the alloys experience significant thermal effects during hydrogen absorption and desorption, and the material's inherent poor thermal conductivity leads to low heat transfer efficiency, severely restricting their hydrogen absorption and desorption kinetics. Second, during repeated hydrogen absorption and desorption cycles, alloy particles are prone to pulverization and structural collapse, resulting in a decrease in hydrogen storage capacity and cycle life. Research has shown that carbon coating technology can effectively improve the performance of nickel-based hydrogen storage alloys: carbon materials have excellent thermal conductivity and chemical stability. The coating not only serves as an efficient heat conduction channel, significantly improving the alloy's thermal transfer performance, but also acts as a physical barrier to inhibit pulverization and structural degradation of alloy particles during cycling, thereby enhancing its cycling stability. However, existing carbon coating methods (such as chemical vapor deposition and mechanical ball milling) generally have problems such as complex processes, high costs, difficulty in controlling the uniformity of the coating layer, and difficulty in achieving large-scale production, which seriously limit the practical application of carbon-coated nickel-based hydrogen storage alloys. Therefore, developing a method for preparing carbon-coated nickel-based hydrogen storage alloys with simple processes, low costs, and easy large-scale production has important scientific significance and engineering value for promoting the commercial application of high-performance hydrogen storage materials. Summary of the Invention

[0003] In response to the problems existing in the prior art, the present invention provides a carbon-coated nickel-based hydrogen storage alloy and a batch preparation method to solve the problems of traditional carbon coating process being complex, costly, and difficult to scale up.

[0004] The present invention is achieved through the following technical solutions:

[0005] A batch preparation method of carbon-coated nickel-based hydrogen storage alloy, comprising:

[0006] Under the protection of inert gas, nickel, rare earth elements, transition metal elements and doping elements are melted and mixed using suspension melting technology, and electromagnetic stirring is used to eliminate component segregation to obtain a molten alloy;

[0007] The molten alloy is atomized by high-pressure inert gas to break it into alloy droplets, and then a mixed atmosphere containing olefins is introduced to induce the alloy droplets to undergo carbon source gas cracking, forming amorphous carbon cores on the alloy surface;

[0008] The alloy with amorphous carbon core formed on the surface is subjected to a carbon layer graphitization transformation treatment, and an oxidizing gas is introduced to control the pore structure to obtain a carbon-coated powder alloy;

[0009] The carbon-coated nickel-based hydrogen storage alloy is obtained by annealing and surface passivation treatment of the carbon-coated powder alloy in an inert atmosphere.

[0010] Preferably, the content of rare earth elements in the molten alloy is 15wt%-25wt%, the content of transition metal elements is 8wt%-20wt%, the content of doping elements is 0.1wt%-1wt%, and the content of nickel is 60wt%-75wt%.

[0011] Preferably, the rare earth element is one or more of La, Ce and Pr; the transition metal element is one or more of Co, Mn, Al and Fe; and the doping element is one or more of Ti, Zr and V.

[0012] Preferably, the specific conditions of the suspension smelting technology are: using a vacuum suspension smelting furnace, the ultimate vacuum degree ≤ 10 - 3 Pa, oxygen content ≤10ppm, melting temperature is 1500℃-1700℃; the frequency of electromagnetic stirring is 50-100Hz, and the stirring time is 30-90min.

[0013] Preferably, the inert gas in the high-pressure inert gas atomization is nitrogen or argon, the atomization pressure is 2-5 MPa, the gas flow rate is 10-30 m / s, and the particle size of the alloy droplets is 20-100 μm; the high-pressure inert gas atomization is carried out in an atomization tower with a height of 3-6 m, the residence time of the alloy droplets in the atomization tower is 0.1-0.5 s, and 5-10 nm amorphous carbon cores are formed on the alloy surface.

[0014] Preferably, the temperature of the medium-high temperature zone of the atomizing tower is 800-1000°C, located 0.5-1m below the nozzle, to promote the cracking of the carbon source; the temperature of the medium-temperature zone of the atomizing tower is 500-700°C, located 1-3m in the middle of the tower body, to control the growth rate of the carbon layer; the temperature of the low temperature zone of the atomizing tower is 200-400°C, which is the collection area at the bottom of the tower to inhibit excessive graphitization of the carbon layer.

[0015] Preferably, the olefin-containing mixed atmosphere comprises Ar / H2 mixed gas, carbon source gas and auxiliary gas;

[0016] The H2 content in the Ar / H2 gas mixture is 5-20 vol%;

[0017] The carbon source gas is one or more of C2H4, C3H6 or CH4, with a concentration of 5-15 vol%;

[0018] The auxiliary gas is CO2 with a concentration of 0.1-1 vol%.

[0019] Preferably, the oxidizing gas is a doping gas and a C2H4 / H2 mixed gas, the C2H4 concentration in the C2H4 / H2 mixed gas is 10-15 vol%, the doping gas is CO2, and the concentration is 0.1-0.5 vol%; the pore structure has a pore size of 2-5 nm and a porosity of 10-30%;

[0020] The graphitization transformation treatment time of the carbon layer is 30-120 minutes.

[0021] During the graphitization transformation of the carbon layer, the thickness of the carbon layer increases to 20-50 nm, and the degree of graphitization is controlled at 0.1-1.2.

[0022] Preferably, the specific conditions of the annealing treatment are: under argon atmosphere protection, temperature is 300-500°C, heating rate is 5-10°C / min, and holding time is 1-3h;

[0023] The surface passivation treatment is specifically as follows: in an O2 / Ar mixed gas atmosphere with an O2 concentration of 0.1-0.5 vol%, heat preservation is performed for 10-30 minutes, and a 2-5 nm NiO transition layer is generated on the alloy surface.

[0024] A carbon-coated nickel-based hydrogen storage alloy is prepared based on the batch preparation method of the carbon-coated nickel-based hydrogen storage alloy.

[0025] Compared with the prior art, the present invention has the following beneficial technical effects:

[0026] The present invention provides a carbon-coated nickel-based hydrogen storage alloy and a method for mass production. The alloy uses nickel as the matrix material, introduces rare earth elements to optimize the grain structure and suppress hydrogen embrittlement, combines with transition metals to regulate hydrogen storage kinetics, and adds trace metal elements to enhance oxidation resistance. Under inert gas protection, a suspension smelting technique is used to achieve efficient and uniform mixing of the alloy components, and electromagnetic stirring is used to eliminate component segregation. The molten alloy is atomized by high-pressure inert gas and crushed into micron-sized particles. Simultaneously, an olefin-containing mixed atmosphere is introduced into the atomization tower. The catalytically active sites on the surface of the nickel-based alloy are utilized to induce the cracking of the carbon source gas, achieving in-situ growth of the carbon layer during the flight of the atomized droplets, and rapidly cracking the carbon source to form amorphous carbon cores. The reaction time is then extended in a collection device to promote graphitization of the carbon layer, and the pore structure is regulated by introducing trace amounts of oxidizing gas. Through the synergistic effect of multi-stage temperature and atmosphere, precise matching of the carbon layer thickness, degree of graphitization, and porosity is achieved, balancing the requirements for enhanced thermal conductivity and hydrogen storage capacity. The coated powder is annealed in an inert atmosphere to eliminate internal stress and strengthen the interface bonding between the carbon layer and the alloy. Subsequently, the surface is passivated in an atmosphere with controlled oxygen content to generate a nano-scale oxidation transition layer on the alloy surface, and the adhesion and oxidation resistance of the carbon layer are improved through chemical bonding. Finally, a carbon-coated hydrogen storage alloy with high thermal conductivity, long cycle life and resistance to environmental aging is obtained. This method optimizes the alloy composition design, regulates the atomization process and catalytic cracking reaction conditions, and completes the alloy smelting, powder preparation and carbon layer coating in one step, solving the problems of traditional carbon coating processes that are complex, costly and difficult to scale up. The single processing volume reaches hundreds of kilograms, realizing low-cost batch preparation.

[0027] Furthermore, the present invention adopts an integrated continuous production process, integrating the three key processes of alloy smelting, atomization powder making and carbon coating into the same equipment system. This not only eliminates the risk of intermediate contamination in traditional multi-step processes, but also significantly reduces energy consumption and production costs, and significantly improves process energy efficiency.

[0028] Furthermore, the present invention innovatively utilizes the dynamic temperature gradient changes of atomized droplets during flight, combined with the unique catalytic active sites on the surface of nickel-based alloys, to achieve in-situ uniform growth of a carbon layer on the surface of alloy particles. By precisely controlling the process parameters, the thickness of the carbon layer and the degree of graphitization can be precisely controlled.

[0029] Furthermore, the present invention achieves synergistic optimization of the carbon layer microstructure during the multi-stage cracking process by introducing specific doping gases. On the one hand, a microporous structure conducive to hydrogen storage is constructed, significantly improving the hydrogen storage capacity; on the other hand, the graphitization transformation of the carbon layer is promoted, greatly improving the thermal conductivity and enhancing the material's antioxidant properties.

[0030] Furthermore, the present invention adopts optimized high-pressure gas atomization technology to achieve large-scale production capacity, significantly improves production efficiency compared with traditional processes, greatly reduces unit costs, and provides reliable technical support for the industrial application of hydrogen storage alloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 Schematic diagram of a method for batch preparation of carbon-coated nickel-based hydrogen storage alloys. DETAILED DESCRIPTION

[0033] The technical solution of the present invention will be described clearly and completely below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0034] This method optimizes the alloy composition design, regulates the atomization process and catalytic cracking reaction conditions, and completes alloy smelting, powder preparation and carbon layer coating in one step, solving the problems of traditional carbon coating process being complicated, costly and difficult to scale up. Specifically, the process route of the present invention is: accurately regulating the nickel-based alloy composition through suspension smelting, and smelting under argon protection; using a high-pressure gas atomization process to convert the molten alloy into micron-sized particles, while introducing a mixed atmosphere containing olefins into the atomizing tower, utilizing the catalytic activity of the nickel surface to crack olefins at high temperature, and generating a graphitized carbon coating layer in situ during the atomization flight process; subsequently, the carbon layer structure is optimized through multi-stage annealing and trace oxygen passivation treatment, and finally a carbon-coated nickel-based hydrogen storage alloy with high thermal conductivity and excellent cyclic stability is obtained, with a single processing capacity of hundreds of kilograms, realizing low-cost batch preparation.

[0035] Process such as Figure 1 As shown, it includes the following steps:

[0036] Step 1: Using nickel as the matrix material, rare earth elements are introduced to optimize the grain structure and inhibit hydrogen embrittlement. Transition metals are combined to regulate hydrogen storage kinetics, while trace metal elements are added to enhance oxidation resistance. Under inert gas protection, suspension melting technology is used to achieve efficient and uniform mixing of the alloy components, while electromagnetic stirring is used to eliminate component segregation.

[0037] Step 2: The molten alloy is atomized into micron-sized particles using high-pressure inert gas. Simultaneously, an olefin-containing mixed atmosphere is introduced into the atomization tower. The catalytically active sites on the nickel-based alloy surface induce the cracking of the carbon source gas, enabling in-situ growth of a carbon layer during the flight of the atomized droplets, rapidly cracking the carbon source to form amorphous carbon cores.

[0038] Step 3: The reaction time is then extended in the collection device to promote graphitization of the carbon layer, and the pore structure is regulated by introducing a trace amount of oxidizing gas. Through the synergistic effect of multiple temperature and atmosphere levels, the carbon layer thickness, graphitization degree, and porosity are precisely matched, balancing the requirements of enhanced thermal conductivity and hydrogen storage capacity.

[0039] Step 4: The coated powder undergoes an inert atmosphere annealing treatment to eliminate internal stress and strengthen the interface between the carbon layer and the alloy. Surface passivation is then performed in an atmosphere with controlled oxygen content to form a nanoscale oxide transition layer on the alloy surface. This chemical bonding enhances the carbon layer's adhesion and oxidation resistance. The result is a carbon-coated hydrogen storage alloy with high thermal conductivity, long cycle life, and resistance to environmental aging.

[0040] In step 1, the Ni content in the alloy is 60-75wt%; the rare earth element is one or more of La, Ce, and Pr, with a content of 15-25wt%, which is used to refine the grains, inhibit hydrogen embrittlement, and enhance the catalytic activity of the alloy surface; the transition metal element is one or more of Co, Mn, Al, and Fe, with a content of 8-20wt%, which regulates the hydrogen absorption and desorption platform pressure and cycle stability; the doping element is one or more of Ti, Zr, and V, with a content of 0.1-1wt%, which enhances the oxidation resistance of the alloy and the interface bonding strength of the carbon layer.

[0041] The ultimate vacuum degree of the vacuum suspension melting furnace in step 1 is ≤10 -3 Pa, oxygen content ≤ 10ppm;

[0042] In the raw material pretreatment in step 1, the metal raw material needs to be pickled with a 5-20% HNO3 solution for 30-120 minutes to remove surface oxides;

[0043] The melting temperature in step 1 is 1500-1700°C, which can be adjusted according to the liquidus temperature of the alloy, and the superheat must be ≥100°C; the electromagnetic stirring frequency is 50-100 Hz, and the stirring time is 30-90 minutes to ensure uniform composition;

[0044] In step 2, the high-pressure gas atomization carrier gas is nitrogen or argon with a purity of ≥99.999%; the atomization pressure is 2-5 MPa, the gas flow rate is 10-30 m / s, and the powder particle size (D50) is controlled to be 20-100 μm; the atomization tower height is 3-6 m, ensuring that the droplet flight time is ≥0.5 s to complete the initial deposition of the carbon layer;

[0045] Among them, in step 2, the temperature of the high temperature zone in the atomizing tower temperature zone is 800-1000 ° C, located 0.5-1m below the nozzle, to promote the cracking of the carbon source; the temperature of the medium temperature zone is 500-700 ° C, located 1-3m in the middle of the tower body, to control the growth rate of the carbon layer; the temperature of the low temperature zone is 200-400 ° C, the collection area at the bottom of the tower, to inhibit excessive graphitization of the carbon layer;

[0046] In the catalytic cracking atmosphere of step 2, the main atmosphere is an Ar / H2 mixed gas, in which H2 accounts for 5-20 vol%, which is used to reduce the oxides on the surface of the alloy; the carbon source gas is one or more of C2H4, C3H6 or CH4, with a concentration of 5-15 vol%, which is precisely controlled by a mass flow meter; the auxiliary gas is CO2, with a concentration of 0.1-1 vol%, which is used to adjust the porosity of the carbon layer;

[0047] In step 2, the alloy droplets reside in the atomization tower for 0.1-0.5 seconds, and 5-10 nm amorphous carbon nuclei are formed on the alloy surface;

[0048] In step 3, after the alloy powder enters the collection device, a C2H4 / H2 mixed gas at 700-800°C is introduced, wherein the C2H4 concentration is 10-15 vol%, the carbon layer graphitization transformation treatment time is 30-120 min, the carbon layer thickness increases to 20-50 nm during the carbon layer graphitization transformation, and the degree of graphitization (ID / IG) is controlled at 0.1-1.2; the doping gas is CO2 with a concentration of 0.1-0.5 vol% to introduce micropores in the carbon layer, the pore diameter of which is 2-5 nm and the porosity is 10-30%;

[0049] Wherein, in step 4, the annealing treatment is carried out in a tubular furnace under argon protection, with an oxygen content of ≤10ppm, a temperature of 300-500°C, a heating rate of 5-10°C / min, and a holding time of 1-3h;

[0050] Among them, in step 4, surface passivation, an O2 / Ar mixed gas is introduced in the late annealing stage, wherein the O2 concentration is 0.1-0.5 vol%, and the heat preservation is 10-30 minutes. A 2-5 nm NiO transition layer is generated on the alloy surface, and the adhesion of the carbon layer is improved through NiO-C chemical bonding.

[0051] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0052] Example 1: High thermal conductivity carbon-coated Ni-La-Co-Mn-Al alloy

[0053] Step 1: Ni (64.5wt%), La (17wt%), Co (6wt%), Mn (6wt%), Al (6wt%) and Zr (0.5wt%) are mixed in proportion. The metal raw materials are pre-picked with a 10% HNO3 solution for 60 minutes to remove surface oxides.

[0054] In the vacuum suspension melting furnace, the ultimate vacuum degree is controlled at 5×10 -4 Pa, oxygen content ≤ 5ppm, heated to 1650℃ for melting, superheated to 120℃, and electromagnetic stirring at 80Hz for 45min to ensure uniform alloy composition;

[0055] Step 2: The molten alloy is atomized and crushed by high-pressure argon gas, with an atomization pressure of 4MPa and a gas flow rate of 20m / s, and the powder particle size D50 is controlled to be 45μm. The atomization tower is equipped with a high-temperature zone (located 0.8m below the nozzle, with a temperature of 950℃), a medium-temperature zone (located 2m in the middle of the tower body, with a temperature of 600℃) and a low-temperature zone (3m in the bottom collection area, with a temperature of 300℃). Ar / H2 (H2 accounts for 15vol%) mixed gas is introduced as a carrier gas, and C2H4 (8vol%) and CO2 (0.3vol%) are introduced for catalytic cracking. The alloy droplets stay in the atomization tower for 0.3s, and 8nm amorphous carbon cores are formed on the surface.

[0056] Step 3: The atomized powder is further processed in the collection device, and a C2H4 / H2 (C2H4 concentration 12 vol%) / CO2 (0.3 vol%) mixture at 750°C is introduced and kept warm for 60 minutes to increase the carbon layer thickness to 35 nm, the degree of graphitization ID / IG = 0.95, and form a microporous structure with a porosity of 20% and a pore size of 2-5 nm;

[0057] Step 4: Annealing treatment is performed under argon protection at a temperature of 450°C, a heating rate of 5°C / min, and a time of 2 hours, with an oxygen content of ≤5ppm. At the end of the annealing, an O2 / Ar mixed gas (O2 concentration of 0.3 vol%) is introduced for passivation for 20 minutes to form a 3nm NiO transition layer on the alloy surface, enhancing the adhesion of the carbon layer, thereby preparing a carbon-coated nickel-based hydrogen storage alloy, namely a high thermal conductivity carbon-coated Ni-La-Co-Mn-Al alloy;

[0058] Performance characterization:

[0059] The thermal conductivity of the carbon-coated Ni-La-Co-Mn-Al alloy is 26.3 W / (m·K), a 190% increase compared to the uncoated alloy. The capacity retention rate is 90% after 200 hydrogen absorption and desorption cycles, and the capacity loss is 2.5% after exposure to air for 24 hours.

[0060] Example 2: High Capacity Carbon-Coated Ni-Ce-Mn-Al-Ti Alloy

[0061] Step 1: Ni (60 wt%), Ce (23.2 wt%), Mn (8 wt%), Al (8 wt%), Ti (0.6 wt%) and V (0.2 wt%) were mixed in proportion. The metal raw materials were pre-picked with 15% HNO3 solution for 90 min to remove surface oxides.

[0062] In the vacuum suspension melting furnace, the ultimate vacuum degree is controlled at 8×10 -4 Pa, oxygen content ≤ 5ppm, heated to 1600℃ for melting, superheated to 100℃, and electromagnetic stirring at 100Hz for 60min to ensure uniform alloy composition.

[0063] Step 2: The molten alloy is crushed by high-pressure argon atomization, with an atomization pressure of 5 MPa and a gas flow rate of 25 m / s, and the powder particle size D50 is controlled to be 30 μm. The atomization tower is equipped with a high-temperature zone (located 1 m below the nozzle, with a temperature of 1000 ° C), a medium-temperature zone (located 2 m in the middle of the tower body, with a temperature of 650 ° C) and a low-temperature zone (3 m in the bottom collection area, with a temperature of 350 ° C). Ar / H2 (15 vol%) mixed gas is introduced as a carrier gas, and C3H6 (10 vol%) and CO2 (0.5 vol%) are introduced for catalytic cracking. The alloy droplets stay in the atomization tower for 0.2 s, and 10 nm amorphous carbon cores are formed on the surface.

[0064] Step 3: The atomized powder is further processed in the collection device, and a C3H6 (15 vol%) / CO2 (0.5 vol%) mixed gas at 780°C is introduced and kept warm for 90 minutes to increase the carbon layer thickness to 45 nm, the degree of graphitization ID / IG = 1.10, and a microporous structure with a porosity of 25% is formed.

[0065] Step 4: Annealing treatment is performed under argon protection at a temperature of 400°C, a heating rate of 8°C / min, and a time of 3 hours, with an oxygen content of ≤5ppm. At the end of the annealing, an O2 / Ar mixed gas (O2 concentration of 0.5 vol%) is introduced for passivation for 30 minutes to form a 4nm NiO transition layer on the alloy surface, enhancing the adhesion of the carbon layer, thereby preparing a carbon-coated nickel-based hydrogen storage alloy, namely a high-capacity carbon-coated Ni-Ce-Mn-Al-Ti alloy.

[0066] Performance characterization:

[0067] The high-capacity carbon-coated Ni-Ce-Mn-Al-Ti alloy has a hydrogen storage capacity of 1.85wt%, a 15% increase over the uncoated alloy; the capacity retention rate is 88% after 250 hydrogen absorption and desorption cycles; and the capacity loss after exposure to air for 24 hours is ≤3%.

[0068] Example 3: High Stability Carbon-Coated Ni-Pr-Fe-Al-Zr Alloy

[0069] Step 1: Ni (69.2 wt%), Pr (15 wt%), Fe (10 wt%), Al (5 wt%) and Zr (0.8 wt%) were mixed in proportion. The metal raw materials were pre-washed with 12% HNO3 solution for 75 minutes to remove surface oxides. In a vacuum suspension melting furnace, the ultimate vacuum was controlled at 1×10- 3 Pa, oxygen content ≤ 5ppm, heated to 1700℃ for melting, superheated to 150℃, and electromagnetic stirring at 90Hz for 50min to ensure uniform alloy composition.

[0070] Step 2: The molten alloy was atomized and crushed by high-pressure argon gas at an atomization pressure of 3.5 MPa and a gas flow rate of 22 m / s, with the powder particle size D50 controlled at 50 μm. The atomization tower was equipped with a high-temperature zone (located 0.9 m below the nozzle, with a temperature of 980°C), a medium-temperature zone (located 2 m in the middle of the tower body, with a temperature of 620°C), and a low-temperature zone (3 m in the tower bottom collection area, with a temperature of 320°C). Ar / H2 (12 vol%) mixed gas was introduced as a carrier gas, and CH4 (12 vol%) and CO2 (0.4 vol%) were introduced for catalytic cracking. The alloy droplets stayed in the atomization tower for 0.25 s, and 7 nm amorphous carbon cores were formed on the surface.

[0071] Step 3: The atomized powder is further processed in a collection device by introducing a 700°C CH4 (12 vol%) / CO2 (0.4 vol%) mixed gas and keeping the temperature for 120 minutes to increase the carbon layer thickness to 25 nm, the degree of graphitization ID / IG = 0.85, and form a microporous structure with a porosity of 15%.

[0072] Step 4: Annealing treatment was performed under argon protection at a temperature of 500°C, a heating rate of 10°C / min, and a time of 1 hour, with an oxygen content of ≤5 ppm. At the end of the annealing, an O2 / Ar mixed gas (O2 0.4 vol%) was introduced for passivation for 15 minutes, forming a 3.5 nm NiO transition layer on the alloy surface to enhance the adhesion of the carbon layer, thereby preparing a carbon-coated nickel-based hydrogen storage alloy, namely a high-stability carbon-coated Ni-Pr-Fe-Al-Zr alloy.

[0073] Performance Characterization

[0074] The high-stability carbon-coated Ni-Pr-Fe-Al-Zr alloy has a thermal conductivity of 23.8W / (mK), which is 180% higher than that of the uncoated alloy. The capacity retention rate is 95% after 500 hydrogen absorption and desorption cycles. It has excellent anti-pulverization performance and the particle integrity is well maintained after cycles.

[0075] Example 4: Oxidation-resistant carbon-coated Ni-La-Fe-V alloy

[0076] Step 1: Ni (67.5 wt%), La (18 wt%), Fe (14 wt%), and V (0.5 wt%) were mixed in proportion. The metal raw materials were pre-washed with 10% HNO3 solution for 80 min to remove surface oxides. In a vacuum suspension melting furnace, the ultimate vacuum was controlled at 5 × 10 -4 Pa, oxygen content ≤ 5ppm, heated to 1620℃ for melting, superheated to 120℃, and electromagnetic stirring at 85Hz for 55min to ensure uniform alloy composition.

[0077] Step 2: The molten alloy was atomized and crushed by high-pressure argon gas at an atomization pressure of 4 MPa and a gas flow rate of 23 m / s, with a powder particle size D50 controlled at 40 μm. The atomization tower was equipped with a high-temperature zone (0.85 m, 970°C), a medium-temperature zone (2 m, 630°C), and a low-temperature zone (3 m, 330°C). An Ar / H2 (14 vol%) mixture was introduced as a carrier gas, and C2H4 (9 vol%) and CO2 (0.4 vol%) were introduced for catalytic cracking. The alloy droplets remained in the atomization tower for 0.22 s, forming 9 nm amorphous carbon cores on the surface.

[0078] Step 3: The atomized powder is further processed in a collection device, and a C2H4 (9 vol%) / CO2 (0.4 vol%) mixed gas at 720°C is introduced and kept warm for 90 minutes to increase the carbon layer thickness to 30 nm, the degree of graphitization ID / IG = 1.05, and form a microporous structure with a porosity of 18%.

[0079] Step 4: Annealing under argon protection at 420°C for 2.5 hours with an oxygen content of ≤5 ppm. During the final stages of annealing, an O2 / Ar mixture (0.4 vol% O2) was introduced for passivation for 25 minutes. This generated a 3.2 nm thick NiO transition layer on the alloy surface, enhancing the adhesion of the carbon layer. This resulted in a carbon-coated nickel-based hydrogen storage alloy, namely an oxidation-resistant carbon-coated Ni-La-Fe-V alloy.

[0080] Performance Characterization

[0081] The oxidation-resistant carbon-coated Ni-La-Fe-V alloy exhibits outstanding oxidation resistance, with a capacity loss of only 1.8% after 30 days of exposure to air. Its thermal conductivity is 24.5 W / (m·K), and its capacity retention rate after 300 cycles of hydrogen absorption and desorption is 92%.

[0082] Example 5: High Dynamic Performance Carbon-Coated Ni-Ce-Co-Ti Alloy

[0083] Step 1: Ni (62 wt%), Ce (15 wt%), Co (8 wt%), and Ti (0.8 wt%) were mixed in proportion. The metal raw materials were pre-washed with 12% HNO3 solution for 70 min to remove surface oxides. In a vacuum suspension melting furnace, the ultimate vacuum was controlled at 6 × 10 -4 Pa, oxygen content ≤ 5ppm, heated to 1680℃ for melting, superheated to 140℃, and electromagnetic stirring at 88Hz for 52min to ensure uniform alloy composition.

[0084] Step 2: The molten alloy was atomized and crushed by high-pressure argon gas at an atomization pressure of 4.5 MPa and a gas flow rate of 24 m / s, with the powder particle size D50 controlled at 35 μm. The atomization tower was equipped with a high-temperature zone (0.95 m, 990°C), a medium-temperature zone (2 m, 640°C), and a low-temperature zone (3 m, 340°C). An Ar / H2 (13 vol%) mixture was introduced as a carrier gas, and C3H6 (11 vol%) and CO2 (0.45 vol%) were introduced for catalytic cracking. The alloy droplets remained in the atomization tower for 0.23 s, and 8.5 nm amorphous carbon cores were formed on the surface.

[0085] Step 3: The atomized powder is further processed in a collection device by introducing a C3H6 (11 vol%) / CO2 (0.45 vol%) mixed gas at 740°C and keeping the temperature for 100 minutes to increase the carbon layer thickness to 28 nm, the degree of graphitization ID / IG = 0.92, and form a microporous structure with a porosity of 20%.

[0086] Step 4: Annealing under argon protection at 460°C for 1.8 hours with an oxygen content of ≤5 ppm. During the final stages of annealing, an O2 / Ar mixture (0.45 vol% O2) was introduced for passivation for 22 minutes. This generated a 3.8 nm NiO transition layer on the alloy surface, enhancing the adhesion of the carbon layer and producing a carbon-coated nickel-based hydrogen storage alloy, namely a highly stable carbon-coated Ni-Pr-Fe-Al-Zr alloy.

[0087] Performance Characterization

[0088] High kinetic performance The carbon-coated Ni-Ce-Co-Ti alloy has excellent hydrogen absorption kinetics, with the 90% saturation hydrogen absorption time being 60% shorter than that of the uncoated alloy; the thermal conductivity is 25.2W / (mK); and the capacity retention rate is 94% after 400 hydrogen absorption and desorption cycles.

[0089] Example 6: High Dynamic Performance Carbon-Coated Ni-Ce-Co-Ti Alloy

[0090] Step 1: Ni (64 wt%), Ce (25 wt%), Co (10 wt%), and Ti (1 wt%) were mixed in proportion. The metal raw materials were pre-picked with 5% HNO3 solution for 120 min to remove surface oxides.

[0091] In the vacuum suspension melting furnace, the ultimate vacuum degree is controlled at 9×10 -4 Pa, oxygen content ≤ 9ppm, heated to 1700℃ for melting, superheated to 100℃, and electromagnetic stirring at 50Hz for 90min to ensure uniform alloy composition.

[0092] Step 2: The molten alloy was atomized and crushed by high-pressure nitrogen gas at an atomization pressure of 5 MPa and a gas flow rate of 30 m / s, with the powder particle size D50 controlled at 20 μm. The atomization tower was equipped with a high-temperature zone (1 m below the nozzle, 1000°C), a medium-temperature zone (3 m in the middle of the tower body, 700°C), and a low-temperature zone (3 m in the bottom collection area, 400°C). An Ar / H2 (H2 concentration of 20 vol%) mixed gas was introduced as the carrier gas, and C3H6 (15 vol%) and CO2 (1 vol%) were introduced for catalytic cracking. The alloy droplets stayed in the atomization tower for 0.5 s, and 10 nm amorphous carbon cores formed on the surface.

[0093] Step 3: The atomized alloy powder is further processed in a collection device by introducing a C2H4 / H2 mixture (C2H4 concentration is 10 vol%) / CO2 (0.5 vol%) mixture at 800°C and keeping the temperature for 120 minutes to increase the carbon layer thickness to 50 nm, the degree of graphitization ID / IG = 1.2, and form a microporous structure with a porosity of 30%.

[0094] Step 4: Annealing treatment was performed under argon protection at a temperature of 500°C, a heating rate of 10°C / min, and a time of 3 hours, with an oxygen content of ≤9 ppm. At the end of the annealing, an O2 / Ar mixed gas (O2 0.5 vol%) was introduced for passivation for 30 minutes, forming a 5 nm NiO transition layer on the alloy surface to enhance the adhesion of the carbon layer, thereby preparing a carbon-coated nickel-based hydrogen storage alloy, namely a high-stability carbon-coated Ni-Pr-Fe-Al-Zr alloy.

[0095] Performance Characterization

[0096] High kinetic performance The carbon-coated Ni-Ce-Co-Ti alloy has excellent hydrogen absorption kinetics, with the 90% saturation hydrogen absorption time being 58% shorter than that of the uncoated alloy; the thermal conductivity is 24.6W / (mK); and the capacity retention rate is 93% after 400 hydrogen absorption and desorption cycles.

[0097] Example 7: High Stability Carbon-Coated Ni-Pr-Fe-Al-Zr Alloy

[0098] Step 1: Ni (75 wt%), Pr (15.9 wt%), Fe (5 wt%), Al (4 wt%) and Zr (0.1 wt%) were mixed in proportion. The metal raw materials were pre-washed with 20% HNO3 solution for 30 min to remove surface oxides. In a vacuum suspension melting furnace, the ultimate vacuum was controlled at 1×10 - 3Pa, oxygen content ≤10ppm, heated to 1700℃ for melting, superheated to 150℃, and electromagnetic stirring at 100Hz for 30min to ensure uniform alloy composition.

[0099] Step 2: The molten alloy is atomized and crushed by high-pressure argon gas, with an atomization pressure of 2 MPa and a gas flow rate of 10 m / s, and the powder particle size D50 is controlled to be 100 μm. The atomization tower is equipped with a high-temperature zone (located 0.5 m below the nozzle, with a temperature of 800 ° C), a medium-temperature zone (located 1 m in the middle of the tower body, with a temperature of 500 ° C) and a low-temperature zone (2 m in the bottom collection area of the tower, with a temperature of 200 ° C). Ar / H2 (H2 accounts for 5 vol%) mixed gas is introduced as a carrier gas, and CH4 (5 vol%) and CO2 (0.1 vol%) are introduced for catalytic cracking. The alloy droplets stay in the atomization tower for 0.1 s, and 5 nm amorphous carbon cores are formed on the surface.

[0100] Step 3: The atomized powder is further processed in a collection device, and a CH4 (15 vol%) / CO2 (0.1 vol%) mixture at 700°C is introduced and kept warm for 30 minutes to increase the carbon layer thickness to 20 nm, the degree of graphitization ID / IG = 0.1, and a microporous structure with a porosity of 10% is formed.

[0101] Step 4: Annealing treatment was performed under argon protection at a temperature of 500°C, a heating rate of 10°C / min, and a time of 1 hour, with an oxygen content of ≤5 ppm. At the end of the annealing, an O2 / Ar mixed gas (O2 0.4 vol%) was introduced for passivation for 15 minutes, forming a 3.5 nm NiO transition layer on the alloy surface to enhance the adhesion of the carbon layer, thereby preparing a carbon-coated nickel-based hydrogen storage alloy, namely a high-stability carbon-coated Ni-Pr-Fe-Al-Zr alloy.

[0102] Performance Characterization

[0103] The high-stability carbon-coated Ni-Pr-Fe-Al-Zr alloy has a thermal conductivity of 23.3W / (mK), which is 168% higher than that of the uncoated alloy. The capacity retention rate is 92% after 500 hydrogen absorption and desorption cycles. It has excellent anti-pulverization performance and the particle integrity is well maintained after cycles.

[0104] In the present invention, unless otherwise specified, all the embodiments and preferred implementation methods mentioned herein can be combined with each other to form a new technical solution.

[0105] In the present invention, unless otherwise specified, all technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0106] In the present invention, unless otherwise specified, percentages (%) or parts refer to percentages by weight or parts by weight relative to the composition.

[0107] In the present invention, unless otherwise specified, the components involved or their preferred components can be combined with each other to form a new technical solution.

[0108] In this disclosure, unless otherwise specified, the numerical range "a-b" is an abbreviation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6-22" indicates that all real numbers between "6-22" are listed herein, and "6-22" is merely an abbreviation for these numerical combinations.

[0109] The "range" disclosed in the present invention is in the form of lower limit and upper limit, which can be one or more lower limits, and one or more upper limits respectively.

[0110] In the present invention, the term "and / or" used herein refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0111] In the present invention, unless otherwise specified, each reaction or operation step can be carried out sequentially or in accordance with the order. Preferably, the reaction method herein is carried out sequentially.

[0112] Unless otherwise indicated, the professional and scientific terms used herein are the same as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the described content can also be applied to the present invention.

[0113] It will be understood that when used in this specification and the appended claims, the terms “comprises” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0114] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0115] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in this industry can smoothly implement the present invention as shown in the drawings and described above. However, any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the scope of the technical solution of the present invention using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of protection of the technical solution of the present invention.

Claims

1. A method for batch preparation of carbon-coated nickel-based hydrogen storage alloy, characterized in that: include, Under the protection of inert gas, nickel, rare earth elements, transition metal elements and doping elements are melted and mixed using suspension melting technology, and electromagnetic stirring is used to eliminate component segregation to obtain a molten alloy; The molten alloy is atomized by high-pressure inert gas to break it into alloy droplets, and then a mixed atmosphere containing olefins is introduced to induce the alloy droplets to undergo carbon source gas cracking, forming amorphous carbon cores on the alloy surface; The alloy with amorphous carbon core formed on the surface is subjected to a carbon layer graphitization transformation treatment, and an oxidizing gas is introduced to control the pore structure to obtain a carbon-coated powder alloy; The carbon-coated nickel-based hydrogen storage alloy is obtained by annealing and surface passivation treatment of the carbon-coated powder alloy in an inert atmosphere.

2. The method for batch preparation of carbon-coated nickel-based hydrogen storage alloy according to claim 1, characterized in that: The content of rare earth elements in the molten alloy is 15wt%-25wt%, the content of transition metal elements is 8wt%-20wt%, the content of doping elements is 0.1wt%-1wt%, and the content of nickel is 60wt%-75wt%.

3. The method for batch preparation of carbon-coated nickel-based hydrogen storage alloy according to claim 1, characterized in that: The rare earth element is one or more of La, Ce and Pr; the transition metal element is one or more of Co, Mn, Al and Fe; and the doping element is one or more of Ti, Zr and V.

4. The method for batch preparation of carbon-coated nickel-based hydrogen storage alloy according to claim 1, characterized in that: The specific conditions of the suspension melting technology are: using a vacuum suspension melting furnace, the ultimate vacuum degree ≤ 10 -3 Pa, oxygen content ≤10ppm, melting temperature is 1500℃-1700℃; the frequency of electromagnetic stirring is 50-100Hz, and the stirring time is 30-90min.

5. The method for batch preparation of carbon-coated nickel-based hydrogen storage alloy according to claim 1, characterized in that: The inert gas in the high-pressure inert gas atomization is nitrogen or argon, the atomization pressure is 2-5 MPa, the gas flow rate is 10-30 m / s, and the particle size of the alloy droplets is 20-100 μm; the high-pressure inert gas atomization is carried out in an atomization tower with a height of 3-6 m. The residence time of the alloy droplets in the atomization tower is 0.1-0.5 s, and 5-10 nm amorphous carbon nuclei are formed on the alloy surface.

6. The method for batch preparation of carbon-coated nickel-based hydrogen storage alloy according to claim 1, characterized in that: The temperature of the medium-high temperature zone of the atomizing tower is 800-1000°C, located 0.5-1m below the nozzle, to promote the cracking of the carbon source; the temperature of the medium-temperature zone of the atomizing tower is 500-700°C, located 1-3m in the middle of the tower body, to control the growth rate of the carbon layer; the temperature of the low temperature zone of the atomizing tower is 200-400°C, which is the collection area at the bottom of the tower and inhibits excessive graphitization of the carbon layer.

7. The method for batch preparation of carbon-coated nickel-based hydrogen storage alloy according to claim 1, characterized in that: The olefin-containing mixed atmosphere includes Ar / H2 mixed gas, carbon source gas and auxiliary gas; The H2 content in the Ar / H2 gas mixture is 5-20 vol%; The carbon source gas is one or more of C2H4, C3H6 or CH4, with a concentration of 5-15 vol%; The auxiliary gas is CO2 with a concentration of 0.1-1 vol%.

8. The method for batch preparation of carbon-coated nickel-based hydrogen storage alloy according to claim 1, characterized in that: The oxidizing gas is a doping gas and a C2H4 / H2 mixed gas, wherein the C2H4 concentration in the C2H4 / H2 mixed gas is 10-15 vol%, and the doping gas is CO2 with a concentration of 0.1-0.5 vol%. The pore structure has a pore size of 2-5 nm and a porosity of 10-30%. The graphitization transformation treatment time of the carbon layer is 30-120 minutes. During the graphitization transformation of the carbon layer, the thickness of the carbon layer increases to 20-50 nm, and the degree of graphitization is controlled at 0.1-1.

2.

9. The method for batch preparation of carbon-coated nickel-based hydrogen storage alloy according to claim 1, characterized in that: The specific conditions of the annealing treatment are: under argon atmosphere protection, temperature is 300-500°C, heating rate is 5-10°C / min, and holding time is 1-3h; The surface passivation treatment is specifically as follows: in an O2 / Ar mixed gas atmosphere with an O2 concentration of 0.1-0.5 vol%, heat preservation is performed for 10-30 minutes, and a 2-5 nm NiO transition layer is generated on the alloy surface.

10. A carbon-coated nickel-based hydrogen storage alloy, prepared based on the batch preparation method of a carbon-coated nickel-based hydrogen storage alloy according to any one of claims 1 to 9.

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