Device and method for preparing submicron powder with core-shell structure by compounding heat preservation type plasma arc-spray coating

Abstract

The invention relates to the technical field of metal soft magnetic powder preparation, in particular to a device and a method for preparing submicron powder with a core-shell structure by compounding heat preservation type plasma arc-spray coating, and the device comprises a heat preservation type plasma arc system, a spray coating system and a circulating system which are connected in sequence. According to the device disclosed by the invention, two processes of submicron powder preparation and spray coating are combined into a whole, and molten nanoclusters are promoted to collide and further grow by controlling the size and temperature of a heating area, so that the submicron metal soft magnetic particles are prepared. And the submicron powder is kept in a dispersed suspension state through the combination of circulating airflow and stirring airflow, particle aggregation is avoided, the coating, hydrolysis and drying processes are completed instantly, and the SiO2-coated spherical submicron metal soft magnetic particles are obtained.

Description

Technical Field

[0001] The invention relates to the technical field of metal soft magnetic powder preparation, and in particular to a device and method for preparing core-shell structure submicron powder by heat-insulating plasma arc-spray coating composite. Background Art

[0002] With the rise and continuous progress of new fields such as 5G communications and AI intelligence, electronic devices are rapidly developing towards high frequency, miniaturization and high integration. At present, the operating frequency of inductors has lagged behind the development needs of electronic devices, becoming an obstacle to the high frequency of electronic devices. The biggest reason is that the operating frequency of soft magnetic materials as the core of inductors is difficult to increase to tens of MHz or even hundreds of MHz. The high-frequency development direction puts forward corresponding requirements for supporting soft magnetic materials: 1) High frequency: In order to reduce eddy current loss, soft magnetic materials need to have high resistivity to reduce the influence of eddy current; 2) Miniaturization: In order to increase the atomic magnetic moment per unit volume, soft magnetic materials need to have high saturation magnetization intensity, so as to achieve higher magnetic field intensity in a smaller space; 3) High power: Soft magnetic materials need to have good anti-saturation ability to meet the needs of high-power applications. In the range of tens of MHz or even hundreds of MHz, the total loss of the inductor will increase significantly, affecting the working efficiency and performance stability of the inductor, and even causing the inductor to fail. Among them, eddy current loss is proportional to the square of the frequency and occupies the main part of the total loss. Reduce high-frequency eddy current losses. By reducing the size of soft magnetic powder, the resistance of soft magnetic powder increases rapidly as the powder particle size decreases, reducing the eddy current in the particles, thereby weakening the eddy current losses. Compared with amorphous materials and ferrite materials containing non-magnetic elements, magnetic metals Fe, Ni or FeNi alloys have the largest atomic magnetic moment at room temperature and the largest saturation magnetization intensity within the volume of a single body, making them the preferred soft magnetic materials for miniaturization of inductors. The sphericity of soft magnetic powder is an important factor affecting its performance. The higher the sphericity, the more regular the particle shape, which will enhance the anti-saturation resistance of the inductor. Considering the above factors, submicron spherical magnetic metal powders with a scale ranging from 100 nm to 1 μm are strong candidate electromagnetic materials for inductors used in tens of MHz or even hundreds of MHz.

[0003] The insulation coating of magnetic metal powder is an important process to reduce the eddy current loss between particles. Coating the surface of magnetic metal powder with insulating material to block the eddy current between powders can effectively reduce the total loss. At present, the insulation coating process of metal powder is to carry out subsequent insulation coating treatment in solution after obtaining the metal powder. However, when the magnetic metal powder is at the submicron scale, the specific surface area is large, the surface energy is high, and it is easy to adsorb and agglomerate each other. The fluidity is poor, which causes the surface of the magnetic powder to be unable to fully contact and react with the insulating passivator, resulting in the shortcomings of uneven thickness, irregular shape, and insufficient coating of the insulating coating layer. It is difficult to play the role of suppressing the eddy current loss between particles, and worsens the high-frequency loss of the magnetic powder. The fluidized bed is a device that uses gas to pass through the powder to suspend the solid particles in motion. Generally, 3 or more nozzles are used, aimed at the same center, and the agglomerated submicron powder is instantly accelerated. The powder accelerated by airflows in different directions collides in the central area of ​​the nozzle to complete the deagglomeration of the submicron powder. The entire deagglomeration process is a collision of the submicron powder itself, and no impurities are generated. The spray coating technology developed based on fluidized bed equipment is to suspend the material particles in the air flow, and evenly cover the coating material on the powder surface by spraying, thereby forming a nano-level coating layer. The drying process is completed instantly in the suspended state. However, this coating process not only increases the complexity of the production process, but also the process transfer involves the increase of the total process time and the replacement of different equipment, which undoubtedly leads to the oxidation of submicron powder. At the same time, the spray coating technology based on the fluidized bed requires continuous exhaust of the coating chamber, and a large amount of powder will be taken away during the exhaust process, resulting in excessive consumption of raw materials. In addition, considering the static magnetic force between submicron metal magnetic powders, the deagglomeration effect is not obvious, and the quality stability of the obtained powder is low. Therefore, in order to improve the insulation coating quality of submicron magnetic powder, it is of great significance to study a new and efficient insulation coating process.

[0004] Chinese patent CN111554894A discloses a method for synthesizing metal oxide-coated heterogeneous metal "core / shell" nanoparticles. The method uses hydrogen plasma evaporation to use micron-sized metal and heterogeneous oxide ceramic powders, uniformly mix and press them into targets. The target is evaporated in an inert and active atmosphere through a gas-liquid-solid phase transition mechanism to synthesize nanocomposite powders with a special "core / shell" structure in situ. Chinese patent CN200910010232.4 discloses a method for preparing zinc oxide-coated nickel nano-wave absorbing materials. In argon and hydrogen gases, arc discharge between cathodes and anodes generates plasma. Under the action of high-temperature plasma, the anode target of the nickel and zinc mixture is evaporated. The difference in melting and boiling points between nickel and zinc is used. When away from the high-temperature plasma zone, nickel solidifies first, and zinc vapor is adsorbed on the surface of the nickel nanoparticles to form a thin zinc layer. During the passivation process, the zinc layer is oxidized into zinc oxide due to the high surface energy. The above-mentioned method for preparing core-shell structured nanoparticles based on plasma technology mainly utilizes collision in a high-temperature plasma arc zone for agglomeration and reaction. Although this method can form a complete insulating layer coating on the surface of the nanoparticles, the prepared nanoparticles are less than 100 nm, and once the coating layer is formed, it is difficult for the nanoparticles to grow further.

[0005] Therefore, in order to solve the problem of insufficient coating of submicron magnetic powder, it is urgent to carry out research on submicron powder production equipment integrating powder making and coating processes. Summary of the invention

[0006] In order to achieve the above objectives, the present invention adopts the following technical solution: In order to overcome the problems existing in the above-mentioned prior art, the present invention provides a device for preparing submicron powder with core-shell structure by combining the two processes of powder making and spray coating into one.

[0007] The present invention also provides a method for preparing core-shell structure submicron powder using the above device, which saves energy consumption, reduces costs, and can achieve large-scale industrial preparation of submicron (100 nm~1 μm) SiO2 insulating coating layer thickness of 10~50 nm and uniform distribution of metal magnetic powder.

[0008] A heat-insulating plasma arc-spray coating composite preparation device for core-shell structure submicron powder, comprising a heat-insulating plasma arc system (I), a spray coating system (II) and a circulation system (III) connected in sequence; the heat-insulating plasma arc system (I) comprises a vacuum chamber (1), wherein an electrode gun (5), a feeding device (7) and a heating jacket (8) are arranged in the vacuum chamber (1); the vacuum chamber (1) is connected to a spray coating chamber (11) via a transmission pipeline (10); the spray coating system (II) comprises, from top to bottom, a spray coating chamber (11), a cooling chamber (12), a collecting chamber (13) and a cooling chamber (14). ); a stirrer (15) and an atomizing nozzle (16) for atomizing and spraying a silane coupling agent solution are provided in the spray coating chamber (11); the circulation system (III) comprises a filter chamber (19) and a circulation air pipe (20); the top of the spray coating chamber (11) is connected to the filter chamber (19), the filter chamber (19) is connected to one end of the circulation air pipe (20), and the other end of the circulation air pipe (20) is connected to the vacuum chamber (1); a blower (21) is connected to the circulation air pipe (20) for driving the air flow in the circulation air pipe (20) to flow from the spray coating chamber (11) to the vacuum chamber (1).

[0009] Preferably, the vacuum chamber (1) is also connected to a vacuum pumping system (2), an atmosphere gas path (3), cooling water (4), and an observation window (9); the outer wall of the spray coating chamber (11) is provided with a heat-insulating sleeve (14); and the atomizing nozzle (16) is connected to a pressure pump (17) and a solution tank (18) for storing a silane coupling agent solution.

[0010] Preferably, the material of the electrode gun (5) is any one of the following: tungsten, graphite and niobium; the material fed by the feeding device (7) is metal or alloy; and the stirring blades of the stirrer (15) are stainless steel or titanium.

[0011] Preferably, the feeding device comprises two discharge ports arranged opposite to each other, the electrode gun (5) is located 3 to 10 mm above the centre of the two discharge ports of the feeding device (7); and the two discharge ports are 10 to 20 mm apart.

[0012] Preferably, the transmission pipe (10) is higher than the upper end of the electrode gun (5), the atomizing nozzle (16) is 20 to 40 cm higher than the transmission pipe (10); the agitator (15) is 5 to 15 cm lower than the transmission pipe (10); and the center points of the agitator (15) and the atomizing nozzle (16) are on the same axis.

[0013] Preferably, the inner diameter of the heating sleeve (8) is 3 to 5 times the diameter of the arc column between the electrode gun (5) and the feeding device (7), and the height of the heating sleeve (8) is 1.5 to 2 times the diameter of the arc column between the electrode gun (5) and the feeding device (7).

[0014] A method for preparing submicron powder with a core-shell structure using the device comprises the following steps: (1) Pass argon and hydrogen into the vacuum chamber; (2) Using a feeding device to feed the raw material metal or alloy into a vacuum chamber, using an electrode gun to discharge, forming a stable arc between the electrode gun and the raw material, and preparing molten nanoparticle clusters; (3) Maintaining the inner surface of the heating sleeve at a constant preset temperature, the nanoclusters remain in a molten state and further collide and grow under the heating action of the heating sleeve to obtain submicron particles. In this step, the metal raw material is first made into nano-sized metal particles through plasma technology, and then a heating zone composed of a heating sleeve is applied outside the high-temperature arc zone to keep the nano-metal particles in a molten state. By adjusting the size and temperature of the heating zone, the collision opportunities of the molten nanoparticles are increased to form melt clusters to reach the desired submicron size. After flying out of the heating zone, the temperature drops and submicron spherical particles are formed under the action of surface tension, which are further cooled.

[0015] (4) Submicron particles are introduced into the spray coating chamber through a transmission pipe by means of a circulation system. Meanwhile, the silane coupling agent solution is pressurized and added into the spray coating chamber through an atomizing nozzle. The temperature of the spray coating chamber and the speed of the agitator are set to complete the coating and drying process in the spray coating chamber to form a core-shell structure submicron magnetic powder. After being cooled in a cooling chamber, the submicron magnetic powder falls into a powder collection chamber.

[0016] Preferably, in step (1), before the argon and hydrogen are introduced, the vacuum degree of the vacuum chamber is not less than 1×10 —2 Pa; the pressure of the argon gas introduced into the vacuum chamber is 1.0x10 3 ~1.0x10 5 Pa, the pressure of hydrogen is 1.0x10 2 ~5.0x10 4 Pa; in step (2), the discharge voltage range is 20~200 V; in step (3), the preset temperature of the inner surface of the heating sleeve is 400~1000 o C; in step (4), the pressure of the silane coupling agent solution is 1~10 Kg, and the temperature of the spray coating chamber is 150~450 o C, the stirrer speed is 100 rpm~1000 rpm; in step (4), the silane coupling agent is a mixture of one or more of aminosilane, vinylsilane, epoxysilane, and mercaptosilane; the solvent is a combination of one or more of deionized water, ethanol, acetone, and methylal.

[0017] Preferably, in step (4), the core-shell submicron powder has a particle size of 100-1 μm and a core-shell structure, wherein SiO2 is the outer shell and the thickness of the outer shell is 5-50 nm.

[0018] The submicron magnetic powder prepared by the present invention is directly brought into the spray coating chamber by the circulating airflow from the heating jacket area. Under the action of the rotating airflow provided by the agitator, the magnetic powder is kept in a dispersed suspension state in the coating chamber, thereby creatively avoiding the problems of adsorption and agglomeration and fluidization re-depolymerization during the cooling and collection process. The silane coupling agent solution passes through a high-pressure atomizing nozzle to form micron-sized droplets, which are adsorbed on the surface of the submicron metal magnetic powder with high surface energy. At a certain temperature, it is hydrolyzed to produce SiO2, thereby forming a dense SiO2 layer on the surface of the submicron metal magnetic powder. At the same time, since the droplet size is at the micron level, the drying of the submicron magnetic powder is also completed in a short time, thereby avoiding the secondary adsorption and agglomeration problems in the drying process of the traditional insulation coating process.

[0019] The present invention creatively combines the two processes of preparing submicron powder and spray coating into one. By expanding the heating zone, the molten nanopowder is allowed to collide and fuse in the heating zone and further grow into submicron particles. The submicron particles are kept in a dispersed suspended state by circulating airflow combined with stirring airflow to enter the spray coating chamber, and the coating, hydrolysis and drying processes are completed instantly to obtain SiO2-coated spherical submicron metal soft magnetic particles.

[0020] Therefore, the present invention also has the following beneficial effects: (1) The device of the present invention combines the two processes of preparing submicron powder and atomization coating into one. By expanding the heating zone, the molten nanopowder is allowed to collide and fuse in the heating zone and further grow into submicron particles. The submicron particles are kept in a dispersed suspended state by circulating airflow and stirring airflow to enter the spray coating chamber. The coating, hydrolysis and drying processes are completed instantly to obtain SiO2-coated spherical submicron metal soft magnetic particles.

[0021] (2) The present invention creatively avoids the problems of adsorption and agglomeration as well as fluidized re-deagglomeration during the cooling and collection process of the traditional device, so that the magnetic powder can be effectively kept in a dispersed and suspended state, promoting a good insulation coating effect. At the same time, it also avoids the secondary adsorption and agglomeration problems during the drying process of the traditional insulation coating process.

[0022] (3) The present invention reduces the complexity of the production process, saves energy consumption, and reduces costs. It can achieve large-scale industrial preparation of submicron (100nm~1μm) SiO2 shell thickness of 5~50nm and uniform distribution of powder. At the same time, the process can be realized under closed, high vacuum, industrial conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of the heat-insulating plasma arc-spray coating composite powder making device of Example 1.

[0024] In the figure: Insulated plasma arc system I: vacuum chamber 1, vacuum system 2, atmosphere gas circuit 3, cooling water 4, electrode gun 5, power supply 6, feeding device 7, heating jacket 8, observation window 9, transmission pipeline 10, spray coating system II: spray coating chamber 11, cooling chamber 12, collection chamber 13, insulation jacket 14, stirrer 15, atomizing nozzle 16, pressure pump 17, solution tank 18, circulation gas circuit system III: filter chamber 19, circulation gas pipe 20, blower 21. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings.

[0026] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments, unless otherwise specified, are conventional methods in the art. Example

[0027] Place Figure 1As shown, a heat-insulating plasma arc-spray coating composite preparation submicron powder device includes a heat-insulating plasma arc system (I), a spray coating system (II) and a circulation system (III) connected in sequence; the heat-insulating plasma arc system (I) includes a vacuum chamber (1), a vacuum pumping system (2) placed in the vacuum chamber, an atmosphere gas path (3), cooling water (4), an electrode gun (5), a power supply (6), a feeding device (7), a heating sleeve (8), an observation window (9), and a transmission pipeline (10). During the arcing process, the temperature is as high as several thousand degrees, which will cause the vacuum chamber wall to heat up rapidly. At the same time, the vacuum chamber is in a state below atmospheric pressure during operation. Long-term use will cause the vacuum wall strength to decrease, posing a safety hazard. Therefore, cooling water is required to cool the vacuum chamber wall. The power supply of the electrode gun (5) is controlled by a power supply (6). The material of the electrode gun is tungsten. The material fed by the feeding device is metal Fe. The electrode gun is located 3 to 10 mm above the center of the feeding device. The feeding device includes two discharge ports arranged opposite to each other. In order to maintain the stability of the electric arc and the output of the product, the discharge ports on both sides feed the material simultaneously. The stability of the electric arc will affect the particle size of the generated nano powder. The discharge ports of the feeding device are 10 to 20 mm apart. The relative distance between the raw material at the discharge port and the electrode gun is set according to the above distance range to maintain the stability of the electric arc. If the distance is set too far, the arc cannot be stably started. The inner diameter of the heating jacket is 3 times the diameter of the arc column between the electrode gun and the feeding device. The height of the heating jacket is 1.5 times the diameter of the arc column between the electrode gun and the feeding device. The transmission pipeline should be higher than the upper end of the electrode gun. The spray coating system (II) includes a spray coating chamber (11), a cooling chamber (12), a collection chamber (13), an insulation jacket (14), a pressure pump (17), a solution tank (18), an agitator (15) placed in the spray coating chamber, and an atomizing nozzle (16).

[0028] The atomizing nozzle should be 20cm higher than the transmission pipeline, and the agitator should be 5cm lower than the transmission pipeline, so that the intermediate product output from the outlet of the transmission pipeline in the spray coating chamber can be coated with the shell layer smoothly. The stirring blades of the agitator are made of stainless steel. The center points of the agitator and the atomizing nozzle are on the same axis.

[0029] The circulation system (III) includes a filter chamber (19), a circulation air pipe (20), and a blower (21). The function of the filter chamber is to filter out the powder in the air flow, protect the blower, and reduce the loss of powder. The main purpose of the circulation air pipe is to form a circulating air flow therein to drive the powder from the vacuum chamber (1) to the spray coating chamber (11).

[0030] A method for preparing submicron magnetic powder with core-shell structure using the above device comprises the following steps: (1) Seal the vacuum chamber (1) and evacuate the entire device to a vacuum of 1×10 —2Pa; The main purpose of vacuuming is to remove oxygen from the equipment, because hydrogen will be introduced later. The presence of oxygen will cause safety hazards and also cause damage to the electrodes.

[0031] 1.0x10 3 Pa argon and 1.0x10 2 Pa hydrogen gas is introduced into the vacuum chamber (1) through the atmosphere gas path (3). The function of argon gas is to provide a plasma gas source, and the function of hydrogen gas is to promote the volatilization of metal and promote the increase of production; the gas pressure of argon gas and hydrogen gas is limited so that after the argon gas and hydrogen gas are filled, the gas pressure of the system is lower than one atmosphere, so that the whole system operates at a negative pressure to prevent the reactants from leaking into the environment.

[0032] (2) Using a feeding device (7) to feed metal Fe into a vacuum chamber (1), turning on a power source (6), striking an arc between a tungsten electrode gun (5) and the raw material, and controlling the voltage at 200 V to form a stable arc to prepare molten nanoparticle clusters; (3) Keep the inner surface of the heating jacket (8) constant at 1000 o C, keeping the nanoclusters in a molten state and further colliding and growing under the heating of the heating jacket to obtain submicron particles; (4) Under the action of the circulation system (III), the submicron Fe particles enter the spray coating chamber (11) through the transmission pipe (10). At the same time, the aminosilane ethanol solution in the solution tank (18) is applied with a pressure of 10 KG through the pressure pump (17) and enters the spray coating chamber (11) through the atomizing nozzle (16). The spray coating chamber is insulated by the insulation jacket (14) to keep the temperature of the spray coating chamber (11) at 400°C. o C, the agitator (15) rotates at a speed of 1000 rpm, and the complete coating and drying process is completed in the spray coating chamber (11) to form a core-shell structured submicron Fe powder with a particle size of 600 nm and a SiO2 shell thickness of 20 nm. Then, it passes through the cooling chamber (12) and falls into the powder collection chamber (13) at the lower end of the equipment. Example

[0033] The difference between the device for preparing core-shell submicron magnetic powder in Example 2 and Example 1 is that the material of the electrode gun is graphite, the material fed by the feeding device is metal Ni, the electrode gun is located 10 mm above the center of the feeding device, the feeding port of the feeding device is 20 mm apart, the inner diameter of the heating jacket is 5 times the diameter of the arc column between the electrode gun and the feeding device, and the height of the heating jacket is 2 times the diameter of the arc column between the electrode gun and the feeding device. The atomizing nozzle should be 40 cm higher than the transmission pipeline, and the stirrer should be 15 cm lower than the transmission pipeline. The stirring blade of the stirrer is titanium.

[0034] A method for preparing submicron magnetic powder with core-shell structure using the above device comprises the following steps: (1) Seal the vacuum chamber (1) and evacuate the entire device to a vacuum of 1×10 —2 Pa, 1.0x10 4 Pa argon and 1.0x10 3 Pa hydrogen gas is introduced into the vacuum chamber (1) through the atmosphere gas path (3); (2) Using a feeding device (7) to feed metal Ni into a vacuum chamber (1), turning on a power source (6), striking an arc between a tungsten electrode gun (5) and the raw material, controlling the voltage at 20 V, forming a stable arc, and preparing molten nanoparticle clusters; (3) Keep the inner surface of the heating jacket (8) constant at 400 o C, keeping the nanoclusters in a molten state and further colliding and growing under the heating of the heating jacket to obtain submicron particles; (4) Under the action of the circulation system (III), the submicron Ni particles enter the spray coating chamber (11) through the transmission pipe (10). At the same time, the epoxysilane acetone solution in the solution tank (18) is applied with a pressure of 1 KG through the pressure pump (17) and enters the spray coating chamber (11) through the atomizing nozzle (16). The temperature of the spray coating chamber (11) is set to 300°C through the insulation jacket (14). o C and the agitator (15) rotate at a speed of 100 rpm, and the complete coating and drying process is completed in the spray coating chamber (11) to form a core-shell structured submicron Ni powder with a particle size of 400 nm and a SiO2 shell thickness of 10 nm. Then, it passes through the cooling chamber (12) and falls into the powder collection chamber (13) at the lower end of the equipment. Example

[0035] The difference between the device for preparing core-shell submicron magnetic powder in Example 3 and Example 1 is that the material of the electrode gun is niobium, the material fed by the feeding device is alloy FeNi, the electrode gun is located 8 mm above the center of the feeding device, the feeding port of the feeding device is 15 mm apart, the inner diameter of the heating jacket is 4 times the diameter of the arc column between the electrode gun and the feeding device, and the height of the heating jacket is 2 times the diameter of the arc column between the electrode gun and the feeding device. The atomizing nozzle should be 30 cm higher than the transmission pipeline, and the stirrer should be 10 cm lower than the transmission pipeline. The stirring blade of the stirrer is titanium.

[0036] A method for preparing submicron magnetic powder with core-shell structure using the above device comprises the following steps: (1) Seal the vacuum chamber (1) and evacuate the entire device to a vacuum of 1×10 —2 Pa, 1.0x10 5Pa argon and 1.0x10 3 Pa hydrogen gas is introduced into the vacuum chamber (1) through the atmosphere gas path (3); (2) Using a feeding device (7) to feed the FeNi alloy into a vacuum chamber (1), turning on a power source (6), striking an arc between a tungsten electrode gun (5) and the raw material, controlling the voltage at 100 V, forming a stable arc, and preparing molten nanoparticle clusters; (3) Keep the inner surface of the heating jacket (8) constant at 600 o C, keeping the nanoclusters in a molten state and further colliding and growing under the heating of the heating jacket to obtain submicron particles; (4) Under the action of the circulation system (III), the submicron FeNi particles enter the spray coating chamber (11) through the transmission pipe (10). At the same time, the vinyl silane methylal solution in the solution tank (18) is pressurized to 5 kg by the pressure pump (17) and enters the spray coating chamber (11) through the atomizing nozzle (16). The temperature of the spray coating chamber (11) is set to 400°C through the insulation jacket (14). o C and the agitator (15) rotate at a speed of 700 rpm, and the complete coating and drying process is completed in the spray coating chamber (11) to form a core-shell structure submicron FeNi powder with a particle size of 800 nm and a SiO2 shell thickness of 10 nm. Then, it passes through the cooling chamber (12) and falls into the powder collection chamber (13) at the lower end of the equipment.

Claims

1. A heat-insulating plasma arc-spray coating composite preparation device for core-shell structure submicron powder, characterized in that: It comprises a heat-insulating plasma arc system (I), a spray coating system (II) and a circulation system (III) which are connected in sequence; The heat-insulating plasma arc system (I) comprises a vacuum chamber (1), wherein an electrode gun (5) feeding device (7) and a heating jacket (8) are arranged in the vacuum chamber (1); the vacuum chamber (1) is connected to a spray coating chamber (11) via a transmission pipeline (10); The spray coating system (II) comprises, from top to bottom, a spray coating chamber (11), a cooling chamber (12), and a collecting chamber (13); a stirrer (15) and an atomizing nozzle (16) for atomizing and spraying a silane coupling agent solution are provided in the spray coating chamber (11); The circulation system (III) comprises a filter chamber (19) and a circulation air pipe (20); the top of the spray coating chamber (11) is connected to the filter chamber (19), the filter chamber (19) is connected to one end of the circulation air pipe (20), and the other end of the circulation air pipe (20) is connected to the vacuum chamber (1); the circulation air pipe (20) is connected to a blower (21) for driving the air flow in the circulation air pipe (20) to flow from the spray coating chamber (11) to the vacuum chamber (1).

2. The device for preparing core-shell structure submicron powder by heat-insulating plasma arc-spray coating composite according to claim 1, characterized in that: The vacuum chamber (1) is also connected to a vacuum pumping system (2), an atmosphere gas path (3), cooling water (4), and an observation window (9); the outer wall of the spray coating chamber (11) is provided with a heat-insulating sleeve (14); and the atomizing nozzle (16) is connected to a pressure pump (17) and a solution tank (18) for storing a silane coupling agent solution.

3. The device for preparing core-shell structure submicron powder by heat-insulating plasma arc-spray coating composite according to claim 1, characterized in that: The material of the electrode gun (5) is any one of the following: tungsten, graphite and niobium; the material fed by the feeding device (7) is metal or alloy; and the stirring blades of the stirrer (15) are stainless steel or titanium.

4. The device for preparing core-shell structure submicron powder by heat-insulating plasma arc-spray coating composite according to claim 1, characterized in that: The feeding device comprises two discharge ports arranged opposite to each other, and the electrode gun (5) is located 3 to 10 mm above the centre of the two discharge ports of the feeding device (7); the two discharge ports are 10 to 20 mm apart.

5. The device for preparing core-shell structure submicron powder by heat-insulating plasma arc-spray coating composite according to claim 1, characterized in that: The transmission pipe (10) is higher than the upper end of the electrode gun (5); the atomizing nozzle (16) is 20 to 40 cm higher than the transmission pipe (10); the agitator (15) is 5 to 15 cm lower than the transmission pipe (10); and the center points of the agitator (15) and the atomizing nozzle (16) are on the same axis.

6. The device for preparing core-shell structure submicron powder by heat-insulating plasma arc-spray coating composite according to claim 1, characterized in that: The inner diameter of the heating sleeve (8) is 3 to 5 times the diameter of the arc column between the electrode gun (5) and the feeding device (7), and the height of the heating sleeve (8) is 1.5 to 2 times the diameter of the arc column between the electrode gun (5) and the feeding device (7).

7. A method for preparing submicron powder with a core-shell structure using the device according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) Pass argon and hydrogen into the vacuum chamber; (2) Using a feeding device to feed the raw material metal or alloy into a vacuum chamber, using an electrode gun to discharge, forming a stable arc between the electrode gun and the raw material, and preparing molten nanoparticle clusters; (3) Maintaining the inner surface of the heating jacket at a constant preset temperature, so that the nanoclusters remain in a molten state and further collide and grow under the heating action of the heating jacket to obtain submicron particles; (4) Submicron particles are introduced into the spray coating chamber through a transmission pipe by means of a circulation system. Meanwhile, the silane coupling agent solution is pressurized and added into the spray coating chamber through an atomizing nozzle. The temperature of the spray coating chamber and the speed of the agitator are set to complete the coating and drying process in the spray coating chamber to form a core-shell structure submicron magnetic powder. After being cooled in a cooling chamber, the submicron magnetic powder falls into a powder collection chamber.

8. The method for preparing submicron powder with core-shell structure according to claim 7, characterized in that: In step (1), before the argon and hydrogen are introduced, the vacuum degree of the vacuum chamber is not less than 1×10 —2 Pa; The pressure of the argon gas introduced into the vacuum chamber is 1.0x10 3 ~1.0x10 5 Pa, the pressure of hydrogen is 1.0x10 2 ~5.0x10 4 Pa In step (2), the discharge voltage range is 20-200 V; In step (3), the preset temperature of the inner surface of the heating jacket is 400-1000 o C; In step (4), the pressure of the silane coupling agent solution is 1-10 kg, and the temperature of the spray coating chamber is 150-450 o C, the agitator speed is 100 rpm to 1000 rpm; In step (4), the silane coupling agent is a mixture of one or more of aminosilane, vinylsilane, epoxysilane, and mercaptosilane; and the solvent is a combination of one or more of deionized water, ethanol, acetone, and methylal.

9. The method for preparing submicron powder with core-shell structure according to claim 7, characterized in that: In step (4), the core-shell submicron powder has a particle size of 100-1 μm and a core-shell structure, wherein SiO2 is the outer shell and the outer shell thickness is 5-50 nm.

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