Preparation method of core-shell structure powder

Abstract

The invention provides a core-shell structure powder preparation method which comprises the following steps: in a reaction chamber in an inert gas atmosphere, melting a metal raw material by using plasma jet, and crushing the molten metal raw material into metal powder which is a metal core of a core-shell structure. And meanwhile, precursor gas is introduced into the reaction chamber, so that the precursor gas is cracked under the combined action of high-energy plasma, high temperature, metal surface catalysis and the like and is recombined into a deposition layer on the surface of the metal core, and the core-shell structure powder with the metal core inside and the deposition layer outside is obtained at the moment. According to the core-shell structure powder preparation method provided by the invention, the gas is used as a precursor material, and under the combined action of the high-energy plasma and the high-temperature metal, the precursor gas can immediately complete cracking deposition of the shell material while melting and crushing the metal raw material through plasma jet, so that the deposition efficiency is high; and in addition, the gaseous precursor is relatively high in purity, so that the metal powder can be effectively prevented from being oxidized.

Description

Technical Field

[0001] This invention relates to the field of materials science and technology, and in particular to a method for preparing core-shell structured powder. Background Technology

[0002] Core-shell structured metal composite powders, as a class of advanced materials with unique core-shell configurations, achieve complementary performance advantages by combining cores and shells of different compositions, demonstrating significant potential in multiple high-tech fields such as aerospace, electronic packaging, biomedicine, and energy catalysis. For example, W@Cu core-shell powder retains the high melting point of tungsten while possessing the excellent conductivity of copper, making it an ideal choice for high-performance electronic contact materials; while Ti@Al core-shell powder combines the strength of titanium with the lightweight properties of aluminum, making it highly valuable for aerospace structural components; graphene@copper core-shell powder, which combines the advantages of graphene and copper, has broad application prospects in 3D printing, conductive pastes, and high-strength, high-conductivity composite materials.

[0003] However, existing preparation processes still have significant shortcomings in terms of efficiency, consistency, and cost control, making it difficult to meet the increasingly demanding market requirements. For example, fluidized bed chemical vapor deposition (FCVD), although widely used, is limited by non-continuous batch production methods, resulting in long single-processing cycles, low capacity, and a narrow applicable range of powder particle sizes, making it difficult to achieve large-scale, efficient production. On the other hand, while liquid precursor-assisted plasma atomization (LPPA) can achieve continuous production, its coating uniformity and integrity are severely constrained by the atomization quality of the precursor and the droplet-metal contact efficiency, making process control quite difficult. In addition, the placement of the liquid carbon source far from the atomization zone further contributes to the problem of low precursor mass transfer efficiency. Moreover, this technology has extremely high requirements for equipment atmosphere control—insufficient system vacuum or inadequate purity of inert gas can easily cause oxidation of the metal powder surface, which in turn seriously affects the final quality and performance of the core-shell structure powder. Summary of the Invention

[0004] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention provides a method for preparing core-shell structure powder, aiming to address the problems in related technologies where, when preparing core-shell structures using liquid precursor-assisted plasma atomization processes, insufficient precursor atomization quality and droplet-metal contact efficiency lead to poor coating uniformity and low integrity; the placement of the liquid carbon source far from the atomization zone results in low precursor mass transfer efficiency; and stringent requirements for equipment atmosphere control easily lead to powder oxidation.

[0005] This invention provides a method for preparing core-shell structured powder. In a reaction chamber under an inert gas atmosphere, a metal raw material is melted and broken into metal powder using a plasma jet. At the same time, a precursor gas is introduced into the reaction chamber. Under the combined action of plasma, high temperature, and catalysis on the surface of the metal powder, the precursor gas is decomposed and reorganized on the surface of the metal powder to form a deposition layer, resulting in a core-shell structured powder with a metal core inside and a deposition layer on the outside.

[0006] According to the core-shell structure powder preparation method provided by the present invention, the precursor gas and the plasma jet have the same outlet position in the reaction chamber; And / or, the precursor gas and the metal raw material have the same outlet position in the reaction chamber; And / or, the precursor gas enters the reaction chamber through a gas channel that is directly connected to the reaction chamber.

[0007] According to the core-shell structure powder preparation method provided by the present invention, the method for manufacturing the inert gas atmosphere includes: The reaction chamber is evacuated to reduce the pressure inside the reaction chamber to below a preset pressure value; An inert gas is introduced into the reaction chamber until atmospheric pressure is reached; The inert gas is continuously introduced, and the oxygen content in the reaction chamber is measured in real time until the oxygen content in the reaction chamber decreases to below a preset oxygen content value.

[0008] According to the core-shell structure powder preparation method provided by the present invention, the step of melting and crushing the metal raw material into micron-sized metal powder using plasma jets includes using multiple plasma jets to act on the same region of the metal raw material from different directions.

[0009] According to the core-shell structure powder preparation method provided by the present invention, the plasma jet is generated by a plasma torch, and the discharge mode of the plasma torch is a DC arc or radio frequency discharge.

[0010] According to the core-shell structure powder preparation method provided by the present invention, the power of the plasma torch is 1kW-150kW, and the operating current of the plasma torch is 10A-800A.

[0011] According to the core-shell structure powder preparation method provided by the present invention, the metal raw material is a metal wire provided by a wire feeding assembly, and the flame cores of multiple plasma jets converge at a point, and the metal wire passes through the convergence point.

[0012] According to the core-shell structure powder preparation method provided by the present invention, the diameter of the metal wire is 1mm-10mm, and the wire feeding rate of the metal wire is less than 100mm / s.

[0013] According to the core-shell structure powder preparation method provided by the present invention, the precursor gas enters the reaction chamber through the plasma torch and / or the wire feeding assembly and / or directly.

[0014] According to the core-shell structure powder preparation method provided by the present invention, the core-shell structure powder is a structure in which graphene or boron nitride is coated with a metal core, and the precursor gas includes at least one or more of methane, acetylene, ethylene, propylene, silane, boron oxide, sodium borohydride, and ammonia borane. During the process of the precursor gas being decomposed and reorganized on the surface of the metal powder, hydrogen gas is introduced into the reaction chamber to assist the decomposition and deposition process.

[0015] The present invention has the following advantages due to the adoption of the above technical solutions: The core-shell structure powder preparation method provided by this invention involves melting a metal raw material using a plasma jet in an inert gas atmosphere within a reaction chamber, and then breaking it down into micron-sized metal powder, which forms the metal core of the core-shell structure. Simultaneously, a precursor gas is introduced into the reaction chamber. Under the combined action of high temperature, high-energy plasma, and surface catalysis of the metal powder, the precursor gas is decomposed and recombined into a deposition layer that coats the outside of the metal core. This results in a core-shell structure powder with a metal core and an outer deposition layer. In this method, the plasma melts and breaks down the metal raw material into powder, and simultaneously acts on the precursor gas along with the high-temperature metal powder. This allows the precursor gas to simultaneously melt and break down the metal raw material with the plasma jet, while simultaneously completing the decomposition and deposition of the shell material. This significantly improves the decomposition and deposition efficiency of the precursor gas. Furthermore, the high purity of the gaseous precursor effectively prevents oxidation of the metal powder, effectively enhancing the coating efficiency and integrity of the deposition layer, thus making the large-scale industrialization of core-shell structure powder possible. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of a method for preparing core-shell structured powder according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the apparatus required for a core-shell structure powder preparation method according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of a plasma torch provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the wire feeding mechanism provided in an embodiment of the present invention; Figure 5 These are scanning electron micrographs of the microstructure of the graphene shell structure on the surface of 15μm-53μm copper powder provided in Embodiment 1 of the present invention. Figure 6 This is the Raman spectrum of graphene coated on the surface of 15μm-53μm copper powder provided in Embodiment 1 of the present invention (in the Raman spectrum of graphene coated on the surface of copper powder, the 2D peak is the characteristic peak of graphene, the D peak is the defect peak, and the G peak is the intrinsic peak of hybrid carbon material; the following...) Figure 8 , Figure 10 , Figure 11 and Figure 12 Same as above); Figure 7 These are scanning electron micrographs of the microstructure of the graphene shell structure on the surface of 60μm-100μm copper powder provided in Embodiment 2 of the present invention. Figure 8 This is the Raman spectrum of graphene coated on the surface of 60μm-100μm copper powder provided in Embodiment 2 of the present invention; Figure 9 These are scanning electron micrographs of the microstructure of the graphene shell structure on the surface of 1μm-10μm copper powder provided in Embodiment 3 of the present invention. Figure 10 This is the Raman spectrum of graphene coated on the surface of 1μm-10μm copper powder provided in Embodiment 3 of the present invention; Figure 11 This is the Raman spectrum of copper powder coated with graphene provided in Embodiment 4 of the present invention; Figure 12 This is the Raman spectrum of the surface graphene on the copper powder provided in Embodiment 5 of the present invention.

[0018] Figure label: 100: Reaction vessel; 200: Plasma torch; 300: Straightening assembly; 400: Wire guide device; 500: Cyclone separator; 600: Vacuum equipment; 700: First receiving tank; 800: Second receiving tank; 900: Gas channel; 1000: Wire material. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0020] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0021] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0022] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0023] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0024] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0025] The core-shell structure powder preparation method provided by this invention involves melting a metal raw material using a plasma jet in an inert gas atmosphere within a reaction chamber, and then breaking it down into micron-sized metal powder, which serves as the metal core of the core-shell structure. Simultaneously, a precursor gas is introduced into the reaction chamber. Under the combined action of plasma, high temperature, and catalysis on the metal powder surface, the precursor gas is decomposed and recombined into a deposition layer that coats the outside of the metal core. This results in a core-shell structure powder with a metal core and an outer deposition layer. In this method, plasma can both break down the metal powder and act on the precursor gas simultaneously with the high-temperature metal powder. This allows the precursor gas to immediately complete the decomposition and deposition of the shell material while the plasma jet melts and breaks down the metal raw material, significantly improving the decomposition and deposition efficiency of the precursor gas. Furthermore, the high purity of the gaseous precursor effectively prevents oxidation of the metal powder, effectively enhancing the coating efficiency and integrity of the deposition layer, thus making the large-scale industrialization of core-shell structure powder possible.

[0026] The following is combined Figures 1 to 12 The present invention describes a method for preparing core-shell structured powder.

[0027] The core-shell structure powder preparation method provided in the embodiments of the present invention involves melting metal raw materials using the high temperature of a plasma jet in a reaction chamber under an inert gas atmosphere, and then breaking the molten metal raw materials into micron-sized metal powder under the action of a high-speed jet. This metal powder is the metal core of the subsequently generated core-shell structure.

[0028] Simultaneously, a precursor gas is introduced into the reaction chamber. Under the combined effects of plasma, high temperature, and catalysis on the metal powder surface, the precursor gas decomposes and recombines on the metal powder surface to form a deposition layer, which coats the outside of the metal core. Ultimately, a core-shell structure is formed with a metal core inside and a deposition layer outside.

[0029] The core-shell structure powder preparation method provided by this invention utilizes plasma to break down metal powder and act on a precursor gas together with the high-temperature metal powder. This allows the precursor gas to immediately complete the pyrolysis and deposition of the shell material while the plasma jet melts and breaks down the metal raw material, greatly improving the pyrolysis and deposition efficiency of the precursor gas. In addition, the high purity of the gaseous precursor effectively avoids the oxidation of the metal powder, effectively improving the coating efficiency and integrity of the deposition layer, thus making the large-scale industrialization of core-shell structure powder possible.

[0030] In some embodiments, the precursor gas and the plasma jet exit at the same location in the reaction chamber; and / or, the precursor gas and the metal raw material exit at the same location in the reaction chamber; and / or, the precursor gas enters the reaction chamber through a gas channel that is directly connected to the reaction chamber.

[0031] With this setup, when the precursor gas and the plasma jet are at the same outlet position in the reaction chamber, the plasma can be used to melt metal raw materials at high temperature and to crack the precursor gas. After the metal raw materials are melted and broken into metal powder by the plasma at high temperature, the cracked products can be immediately reassembled on the surface of the metal powder to form a deposition layer, which greatly improves the cracking and deposition efficiency of the precursor gas.

[0032] Furthermore, by simultaneously setting the precursor gas to enter the reaction chamber through the outlet of the metal raw material and / or through the gas channel located on the reaction chamber, the unpyrolyzed precursor gas can continue to be pyrolyzed under the high temperature and catalytic action on the surface of the metal powder, effectively improving the coating integrity of the deposition layer.

[0033] In some embodiments, the equipment required to create an inert gas atmosphere within the reaction chamber includes a reaction vessel 100, a vacuum pump 600, and a water-oxygen meter. The reaction vessel 100 is hollow, forming a reaction chamber. The vacuum pump 600 is connected to the reaction chamber and is used to evacuate the reaction chamber. The water-oxygen meter is used to detect the oxygen content inside the reaction chamber.

[0034] The method for manufacturing an inert gas atmosphere based on the above-mentioned equipment includes the following steps: The reaction chamber is evacuated using a vacuum pump (600) until the pressure inside the chamber drops below a preset pressure value, which can be 100 Pa. The purpose of evacuation is to remove the air from the reaction chamber, or more specifically, to reduce the oxygen content within the chamber as much as possible.

[0035] Then, inert gas is introduced into the reaction chamber to bring the pressure inside the reaction chamber down to atmospheric pressure, i.e., 101 kPa.

[0036] Inert gas is continuously introduced into the reaction chamber, and the oxygen content inside the reaction chamber is measured in real time using a water-oxygen meter until the oxygen content inside the reaction chamber decreases to the preset oxygen content value.

[0037] At this point, the inert gas atmosphere is created. The purpose of creating the inert gas atmosphere is to use inert gas to replace the air in the reaction vessel 100 to prevent the metal powder from being oxidized.

[0038] In some embodiments, the inert gas used in the above process may be argon or nitrogen.

[0039] In some embodiments, the above-described method for melting and breaking down metal raw materials into micron-sized metal powder using a plasma jet includes the following steps: Multiple plasma jets are used to simultaneously melt the same area of ​​a metal raw material from different directions.

[0040] Specifically, multiple plasma jets can be provided simultaneously, distributed around the circumference of the metal raw material, and simultaneously sprayed onto the metal raw material and along the conveying direction of the metal raw material, so that multiple plasma jets are sprayed toward the same position, and the metal raw material will be instantly melted and broken when it passes through that position.

[0041] Furthermore, the aforementioned plasma jet can be generated by a plasma torch 200, and the discharge mode of the plasma torch 200 can be a DC arc or a radio frequency discharge.

[0042] Specifically, the top of the aforementioned reaction vessel 100 can be a frustum-shaped structure, with its smaller end facing upwards and its larger end facing downwards. Three plasma torches 200 can be installed, with their nozzles inserted into the inner side of the top of the reaction vessel 100 and perpendicular to the outer circumferential surface of the frustum-shaped structure. At this point, the plasma torches 200 spray direction is towards the axis of the frustum-shaped structure and extends downwards. The three plasma torches 200 have the same height, and ultimately, the plasma jets sprayed by the three plasma torches 200 converge at the same point on the axis of the frustum-shaped structure.

[0043] In some embodiments, the power of the plasma torch 200 can be 1kW-150kW, and the operating current can be 10A-800A, which can be adjusted within the above range according to experimental requirements.

[0044] In some embodiments, the metal raw material may be a metal wire 1000, which is conveyed to the reaction vessel 100 by a wire feeding assembly. The conveying path of the metal wire 1000 entering the reaction vessel 100 coincides with the axis of the frustum-shaped structure described above.

[0045] Specifically, the wire feeding assembly may include a straightening assembly 300 disposed on the top of the reaction vessel 100 and a wire guide device 400 disposed on the inner top of the reaction vessel 100. The straightening assembly 300 can straighten the neatly bundled curved wire 1000 and guide it into the reaction vessel 100 through the wire guide device 400, which is used to make the wire enter the reaction vessel 100 in a vertical direction.

[0046] The plasma jet of the plasma torch 200 converges at a point below the wire guide device 400. The wire guided by the wire guide device 400 passes through this convergence point and is instantly melted and shattered by the plasma jet at that point.

[0047] In some embodiments, the diameter of the metal wire 1000 is 1mm-10mm, and the wire feeding rate of the metal wire 1000 is less than 100mm / s. Appropriate parameters can be selected according to production requirements.

[0048] In some embodiments, the core-shell structure powder can be a graphene-coated metal core structure, in which case the precursor gas used can be at least one or more of methane, acetylene, ethylene, propylene, and silane. The core-shell structure powder can also be a boron nitride-coated metal core structure, in which case the precursor gas used can be at least one or more of boron oxide, sodium borohydride, and ammoniaborane. During the preparation of the graphene-coated metal core or boron nitride-coated metal core structure, hydrogen gas can also be simultaneously introduced into the reaction chamber during the precursor gas decomposition and recombination process to assist the decomposition and deposition process.

[0049] Specifically, gas channels 900 can be provided on the plasma torch 200, the wire guide device 400, and the reaction vessel 100. Inert gas, precursor gas, and hydrogen gas used to create an inert gas atmosphere and assist in the pyrolysis and deposition process can all enter the reaction chamber through any of the above gas channels 900.

[0050] In a preferred embodiment, the precursor gas can enter the reaction chamber through the gas channel 900 provided on the plasma torch 200, hydrogen as an auxiliary gas can enter the reaction chamber through the gas channel 900 provided on the wire guide device 400, and inert gas can enter the reaction chamber through the gas channel 900 provided on the reaction container 100.

[0051] Using the gas intake method in this embodiment, the precursor gas can be ionized in the plasma torch and enter the reaction vessel in an ionized state. It is then directed towards the metal raw material along with the plasma jet. During this process, the plasma jet acts on the precursor gas to cause it to decompose. At the same time, after the plasma jet melts and breaks the metal raw material into metal powder, the decomposition products can be rapidly reassembled on the surface of the metal powder to form a deposition layer, thereby accelerating the decomposition and reassembly efficiency of the precursor gas and reducing the risk of oxidation of the metal powder.

[0052] In another preferred embodiment, the precursor gas can enter the reaction chamber through the gas channel 900 provided on the wire guide device 400, hydrogen as an auxiliary gas can enter the reaction chamber through the gas channel 900 provided on the plasma torch, and the inert gas can enter the reaction chamber through the gas channel 900 provided on the reaction container 100.

[0053] In the air intake method described in this embodiment, the precursor gas is wrapped around the outer layer of the metal raw material. When the plasma jet acts on the metal raw material, it will first act on the precursor gas to cause it to decompose. After the plasma jet melts and breaks the metal raw material into metal powder, the decomposition products can be quickly reassembled on the surface of the metal powder to form a deposition layer, thereby accelerating the decomposition and reassembly efficiency of the precursor gas and reducing the risk of the metal powder being oxidized.

[0054] In some embodiments, the prepared core-shell structured powder can be collected in stages. The core-shell structured powder with larger particle size can be directly collected in the first collection tank 700 at the bottom of the reaction vessel 100, while the core-shell structured powder with smaller particle size is sucked in by the cyclone separator 500 connected to one side of the reaction vessel 100 and then collected in the second collection tank 800 at the bottom of the cyclone separator 500.

[0055] It should be noted that the particle size of core-shell structured powder with a larger particle size can be greater than 10 μm, while the particle size of core-shell structured powder with a smaller particle size can be less than 10 μm.

[0056] The following will disclose several specific embodiments to illustrate the method for preparing core-shell structured powder provided by the present invention.

[0057] The plasma atomization preparation method of core-shell structured powder of the present invention includes the following steps: Example 1 A core-shell structure powder with a copper metal core and a graphene deposition layer was prepared by DC arc plasma jet, with the metal core particle size ranging from 15 μm to 53 μm.

[0058] Its preparation process is as follows: A copper wire with a diameter of 2mm is fed into the reaction chamber via a wire feeding assembly; The internal pressure of the reaction chamber was reduced to below 100 Pa. The reaction chamber was filled with inert gas to a pressure of 101 kPa, and the oxygen content in the reaction chamber was measured using a water-oxygen meter. Inert gas was continuously introduced until the oxygen content was below 300 ppm. Three plasma torches 200 were ignited sequentially, the current of the plasma torches 200 was increased to 300A, and the flow rate of ionized argon gas entering the plasma torches 200 was increased to 10.0m³. 3 / h.

[0059] The inert gas, precursor gas, and auxiliary gas are simultaneously introduced into the reaction vessel 100 through the gas channel 900 set on the plasma torch 200. The precursor gas can be methane or acetylene, the inert gas can be argon, and the auxiliary gas can be hydrogen. The inlet rate of the precursor gas is 15.0 LPM, and the inlet rate of the hydrogen is 1.0 LPM. The wire feeding rate is set to 20 mm / s, and the copper wire is continuously fed into the intersection of three plasma torches 200 jets for high-temperature melting and crushing. Graphene begins to grow on the surface of the copper powder generated by atomization under the action of inert gas, precursor gas and auxiliary gas; Copper powder flies in an atmosphere of inert gas, precursor gas and auxiliary gas, and graphene continues to grow on its surface during the flight until a core-shell structure is formed.

[0060] After being coated with graphene, the copper powder is cooled and falls directly into the first receiving tank 700 at the bottom of the reaction chamber for product collection.

[0061] Example 2 A core-shell structure powder with a copper metal core and a graphene deposition layer was prepared by DC arc plasma jet, with the metal core particle size ranging from 60 μm to 100 μm.

[0062] Unlike Example 1, the outer diameter of the copper wire is 8 mm, the oxygen content in the reaction chamber is less than 600 ppm, the current of the plasma torch 200 is 350 A, and the flow rate of the argon gas is 15.0 m / s². 3 The flow rate of the precursor gas is 30.0 LPM, the flow rate of hydrogen is 5.0 LPM, and the wire feed rate is 25 mm / s.

[0063] Example 3 A core-shell structure powder with a copper metal core and a graphene deposition layer was prepared by DC arc plasma jet, with the metal core particle size ranging from 1 μm to 10 μm.

[0064] Unlike Example 1, the outer diameter of the copper wire is 1 mm, the oxygen content in the reaction chamber is less than 200 ppm, the current of the plasma torch 200 is 100 A, and the flow rate of the argon gas is 3.0 m / s².3 The flow rate of the precursor gas is 1.0 LPM, the wire feeding rate is 1 mm / s, and the copper powder coated with graphene is cooled and then sucked into the cyclone separator 500 and falls into the second receiving tank 800.

[0065] Example 4 A core-shell structure powder with a copper metal core and a graphene deposition layer was prepared by DC arc plasma jet, with the metal core particle size ranging from 15 μm to 53 μm.

[0066] Unlike Embodiment 1, the gas intake method is as follows: inert gas and hydrogen enter the reaction vessel through the gas channel 900 provided on the plasma torch 200, and precursor gas enters the reaction chamber through the gas channel 900 provided on the wire guide device 400.

[0067] Example 5 A core-shell structure powder with a copper metal core and a graphene deposition layer was prepared by DC arc plasma jet, with the metal core particle size ranging from 15 μm to 53 μm.

[0068] Unlike Embodiment 1, the gas intake method is as follows: inert gas and hydrogen enter the reaction vessel through gas channel 900 provided on plasma torch 200, and precursor gas enters through gas channel 900 provided on reaction vessel 100.

[0069] In some other embodiments, a combined gas intake method can also be adopted. For example, the precursor gas can enter the reaction vessel 100 simultaneously through two or three of the gas channels 900 provided on the plasma torch 200, the wire guide device 400 and the reaction vessel 100. The inert gas and hydrogen can also enter the reaction vessel 100 by choosing one, two or three of the above three gas channels 900.

[0070] Compared to existing liquid carbon source-assisted plasma atomization or fluidized bed chemical vapor deposition (CVD) processes, the core-shell structure powder preparation method provided by this invention combines plasma atomization with CVD, offering significant advantages in terms of production capacity and continuity. Existing fluidized bed CVD processes operate on a non-continuous batch processing model, with single-batch processing times reaching 2-4 hours and a capacity of less than 50 g / h. Furthermore, a significant amount of time is wasted on non-production stages such as powder loading / unloading and system cleaning. While liquid carbon source-assisted plasma atomization achieves one-step continuous production, its capacity remains limited. This invention, by integrating raw material feeding, reaction synthesis, and finished product collection, achieves fully automated continuous production, with a target capacity exceeding 20 kg / h, reaching 5-10 times the level of existing technologies, laying a solid foundation for large-scale industrial applications.

[0071] Regarding product consistency and coating quality, fluidized bed CVD processes have strict requirements on powder particle size; ultrafine powders are prone to agglomeration, resulting in generally low coating integrity. Liquid carbon source-assisted plasma atomization processes, on the other hand, are highly dependent on the atomization quality and contact efficiency of the liquid carbon source, making it difficult to guarantee coating uniformity and integrity, and are susceptible to oxidation due to improper atmosphere control. The core-shell structure powder preparation method provided by this invention uses a gaseous precursor, which is naturally uniform and requires no atomization, thus eliminating the problem of insufficient atomization quality. Furthermore, the gaseous precursor has high purity, making it less likely to cause oxidation of the metal powder, significantly improving coating integrity and batch-to-batch stability, and ensuring the quality reliability and performance consistency of the core-shell powder.

[0072] In terms of material versatility and application flexibility, fluidized bed CVD technology struggles to handle high-melting-point metal shell coatings, while liquid carbon source-assisted plasma atomization is primarily suitable for specific systems such as graphene-coated copper powder, lacking versatility. The core-shell structure powder preparation method provided by this invention can be flexibly applied to various material combinations, including metal-metal, metal-ceramic, and even metal-polymer core-shell structures, greatly expanding the application scenarios of core-shell powders in aerospace, electronic packaging, energy catalysis, and other fields.

[0073] In terms of cost control and process simplification, fluidized bed CVD equipment requires high investment, has a complex process flow, and consumes a lot of energy, resulting in expensive core-shell powders. While liquid carbon source-assisted plasma atomization reduces reprocessing steps, it places extremely high demands on equipment atmosphere control, increasing operational difficulty and cost. The core-shell structure powder preparation method provided by this invention simplifies the production process through process innovation. It accelerates precursor decomposition by directly reacting gaseous precursors in the atomization zone, solving the problem of precursor mass transfer, reducing energy consumption and material loss, and controlling the overall production cost to less than half of existing technologies. At the same time, it reduces oxidation risk and quality fluctuations, improving overall economic efficiency and industrialization feasibility.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for preparing core-shell structured powder, characterized in that, In a reaction chamber under an inert gas atmosphere, a plasma jet is used to melt and break down the metal raw material into metal powder. At the same time, a precursor gas is introduced into the reaction chamber. Under the combined action of plasma, high temperature and catalysis on the surface of the metal powder, the precursor gas is decomposed and reorganized on the surface of the metal powder to form a deposition layer, resulting in a core-shell structure powder with a metal core inside and a deposition layer on the outside.

2. The method for preparing core-shell structured powder according to claim 1, characterized in that, The precursor gas and the plasma jet have the same outlet position in the reaction chamber; And / or, the precursor gas and the metal raw material have the same outlet position in the reaction chamber; And / or, the precursor gas enters the reaction chamber through a gas channel that is directly connected to the reaction chamber.

3. The method for preparing core-shell structured powder according to claim 1, characterized in that, The method for producing the inert gas atmosphere includes: The reaction chamber is evacuated to reduce the pressure inside the reaction chamber to below a preset pressure value; An inert gas is introduced into the reaction chamber until atmospheric pressure is reached; The inert gas is continuously introduced, and the oxygen content in the reaction chamber is measured in real time until the oxygen content in the reaction chamber decreases to below a preset oxygen content value.

4. The method for preparing core-shell structured powder according to claim 1, characterized in that, The method of melting and breaking down metal raw materials into micron-sized metal powder using plasma jets includes using multiple plasma jets to act on the same area of ​​the metal raw materials from different directions.

5. The method for preparing core-shell structured powder according to claim 4, characterized in that, The plasma jet is generated by a plasma torch (200), and the plasma torch (200) discharges via a direct current arc or a radio frequency discharge.

6. The method for preparing core-shell structured powder according to claim 5, characterized in that, The plasma torch (200) has a power of 1kW-150kW and an operating current of 10A-800A.

7. The method for preparing core-shell structured powder according to claim 5, characterized in that, The metal raw material is a metal wire (1000) provided by the wire feeding assembly. The flame cores of multiple plasma jets converge at a point, and the metal wire (1000) passes through the convergence point.

8. The method for preparing core-shell structured powder according to claim 7, characterized in that, The diameter of the metal wire (1000) is 1mm-10mm, and the wire feeding rate of the metal wire (1000) is less than 100mm / s.

9. The method for preparing core-shell structured powder according to claim 7, characterized in that, The precursor gas enters the reaction chamber through the plasma torch (200) and / or the wire feeding assembly and / or directly.

10. The method for preparing core-shell structured powder according to claim 1, characterized in that, The core-shell structured powder is a graphene or boron nitride-coated metal core structure. The precursor gas includes at least one or more of methane, acetylene, ethylene, propylene, silane, boron oxide, sodium borohydride, and ammonia borane. During the process of the precursor gas being cracked and recombined on the surface of the metal powder, hydrogen gas is introduced into the reaction chamber to assist the cracking and deposition process.

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