An apparatus and method for preparing submicron powder with core-shell structure by thermal-insulated plasma arc-spray coating composite

Abstract

The present invention relates to the technical field of metal soft magnetic powder preparation, and relates to an apparatus and method for preparing core-shell structured submicron powder by heat-insulated plasma arc-spray coating composite. The apparatus includes a heat-insulated plasma arc system, a spray coating system, and a circulation system connected in sequence. The apparatus of the present invention combines the two processes of preparing submicron powder and spray coating into one. By controlling the size and temperature of the heating zone, the collision and further growth of molten nanoclusters are promoted to prepare submicron metal soft magnetic particles. The submicron powder is kept in a dispersed suspension state by the circulating air flow combined with the stirring air flow to avoid particle agglomeration, and the processes of coating, hydrolysis, and drying are completed instantaneously to obtain spherical submicron metal soft magnetic particles coated with SiO2.

Description

Technical Field

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

[0002] With the rise and continuous progress of new fields such as 5G communication and AI intelligence, electronic devices have developed rapidly towards high frequency, miniaturization and high integration. At present, the operating frequency of inductors has lagged behind the development requirements of electronic devices and has become an obstacle to the high-frequency development of electronic devices. The biggest reason is that it is difficult to increase the operating frequency of soft magnetic materials, which are the core of inductors, to dozens 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, the soft magnetic material needs to have a high resistivity to reduce the influence of eddy currents; 2) Miniaturization: In order to increase the atomic magnetic moment per unit volume, the soft magnetic material needs to have a high saturation magnetization intensity so as to achieve a higher magnetic field intensity in a smaller space; 3) High power: The soft magnetic material needs to have good anti-saturation ability to meet the requirements of high-power applications. In the range of dozens of MHz or even hundreds of MHz, the total loss of the inductor will increase significantly, affecting the operating efficiency and performance stability of the inductor, and even causing the inductor to fail. Among them, the eddy current loss is proportional to the square of the frequency and accounts for the main part of the total loss. By reducing the size of the soft magnetic powder, the resistance of the soft magnetic powder increases rapidly as the powder particle size decreases, reducing the eddy current in the particles and thus weakening the eddy current loss. 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 per unit volume, and are the preferred soft magnetic materials for inductor miniaturization. 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 of the inductor. Considering the above factors, submicron spherical magnetic metal powders with a scale in the range of 100 nm to 1 μm are strong candidate electromagnetic materials for inductor applications in the range of dozens 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 an insulating material to block the eddy current between powders can effectively reduce the total loss. At present, for the insulation coating process of metal powder, after obtaining the metal powder, subsequent insulation coating treatment is carried out in a solution. However, when the magnetic metal powder is at the sub-micron scale, it has a large specific surface area and high surface energy, and is prone to phenomena such as mutual adsorption and agglomeration, with poor fluidity, resulting in the surface of the magnetic powder being unable to fully contact and react with the insulating passivator, leading to disadvantages such as uneven thickness, irregular shape, and insufficient coating of the insulation coating layer, making it difficult to play a role in suppressing the eddy current loss between particles and deteriorating the high-frequency loss of the magnetic powder. A fluidized bed is a device that uses gas to make solid particles move in a suspended state through the powder. Generally, 3 or more nozzles are used, aiming at the same center. The agglomerated sub-micron powder is instantaneously accelerated, and the powders accelerated by airflows in different directions collide in the central area of the nozzle to complete the depolymerization of the sub-micron powder. The whole process of depolymerization is the collision of the sub-micron powder itself, without the generation of impurities. The spray coating technology developed based on the fluidized bed equipment suspends the material particles in the airflow and evenly covers the powder surface with the coating material by spraying, thereby forming a nano-level coating layer, and the drying process is completed instantaneously in a suspended state. However, this coating process not only increases the complexity of the production process, but also the transfer between processes involves an increase in the total process time and the replacement of different equipment, which undoubtedly leads to the oxidation of the sub-micron 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 carried away during the exhaust process, resulting in excessive consumption of raw materials. In addition, considering the existence of static magnetic force between sub-micron metal magnetic powders, the depolymerization effect is not obvious, and the quality stability of the obtained powder is low. Therefore, it is of great significance to study a new and efficient insulation coating process to improve the insulation coating quality of sub-micron magnetic powder.

[0004] Chinese Patent CN111554894A discloses a method for synthesizing metal oxide-coated heterogeneous metal "core / shell" type nanoparticles. Using the hydrogen plasma evaporation method, micron-sized metal and heterogeneous oxide ceramic powders are uniformly mixed and pressed into a target. Through the gas-liquid-solid phase transition mechanism, the target is evaporated in an inert or reactive atmosphere to in-situ synthesize nanocomposite powders with a special "core / shell" structure. Chinese Patent CN200910010232.4 discloses a method for preparing zinc oxide-coated nickel nano-wave-absorbing materials. In an argon and hydrogen gas atmosphere, an arc discharge occurs between the anode and cathode to generate plasma. Under the action of the high-temperature plasma, the nickel and zinc mixture anode target is evaporated. Due to the difference in melting and boiling points between nickel and zinc, when away from the high-temperature plasma region, nickel solidifies first, and zinc vapor adsorbs on the surface of nickel nanoparticles to form a thin zinc layer. During the passivation process, due to the high surface energy, the zinc layer is oxidized to zinc oxide. The above methods for preparing core-shell structured nanoparticles based on plasma technology mainly utilize agglomeration and reaction through collisions in the high-temperature plasma arc region. Although this method can form a complete insulating layer coating on the surface of nanoparticles, the prepared nanoparticles are less than 100 nm, and once the coating layer is formed, it is difficult to further grow the nanoparticles.

[0005] Therefore, in view of problems such as insufficient coating of submicron magnetic powder, it is urgent to carry out research on the device for integrating the powder preparation and coating processes to produce submicron powder. Summary of the Invention

[0006] To achieve the above object, the present invention adopts the following technical solutions: In order to overcome the problems existing in the above-mentioned prior art, the present invention provides a device for preparing core-shell structured submicron powder that combines the two processes of powder preparation and spray coating into one.

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

[0008] A device for preparing core-shell structured submicron powder by thermal insulation type plasma arc-spray coating composite, comprising a thermal insulation type plasma arc system (I), a spray coating system (II) and a circulation system (III) which are connected in sequence; the thermal insulation type plasma arc system (I) includes a vacuum chamber (1), and an electrode gun (5), a feeding device (7) and a heating sleeve (8) are arranged in the vacuum chamber (1); the vacuum chamber (1) is connected to a spray coating chamber (11) through a transmission pipeline (10); the spray coating system (II) sequentially includes a spray coating chamber (11), a cooling chamber (12) and a collection chamber (13) from top to bottom; a stirrer (15) and an atomizing nozzle (16) for atomizing and spraying a silane coupling agent solution are arranged in the spray coating chamber (11); the circulation system (III) includes a filtration chamber (19) and a circulation gas pipe (20); the top of the spray coating chamber (11) is connected to the filtration chamber (19), one end of the filtration chamber (19) is connected to the circulation gas pipe (20), and the other end of the circulation gas pipe (20) is connected to the vacuum chamber (1); a blower (21) is connected to the circulation gas pipe (20) for driving the air flow in the circulation gas pipe (20) to flow from the spray coating chamber (11) to the vacuum chamber (1).

[0009] Preferably, the vacuum chamber (1) is further connected with a vacuum pumping system (2), an atmosphere gas path (3), cooling water (4), and an observation window (9); a heat insulation sleeve (14) is arranged on the outer wall of the spray coating chamber (11); the atomizing nozzle (16) is connected with a pressure pump (17) and a solution tank (18) for storing the 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; the stirring blades of the stirrer (15) are made of stainless steel or titanium.

[0011] Preferably, the feeding device includes two oppositely arranged discharging ports, and the electrode gun (5) is located 3 to 10 mm directly above the center of the two discharging ports of the feeding device (7); the two discharging ports are 10 to 20 mm apart.

[0012] Preferably, the transmission pipeline (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 pipeline (10); the stirrer (15) is 5 to 15 cm lower than the transmission pipeline (10); the central points of the stirrer (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 arc column diameter 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 arc column diameter between the electrode gun (5) and the feeding device (7).

[0014] A method for preparing core-shell structured submicron powder using the described device, comprising the following steps:

[0015] (1) Introduce argon and hydrogen into the vacuum chamber;

[0016] (2) Feed the raw material metal or alloy into the vacuum chamber using a feeding device, and discharge using an electrode gun to form a stable arc between the electrode gun and the raw material to prepare molten nanoparticle clusters;

[0017] (3) Keep the inner surface of the heating jacket constant at a preset temperature, so that the nanoparticle clusters remain in a molten state and further collide and grow under the heating of the heating jacket to obtain submicron particles; In this step, the metal raw material is first made into nanoscale metal particles through plasma technology, and then a heating zone composed of a heating jacket is applied outside the high-temperature arc zone to keep the nanoscale metal particles in a molten state. By adjusting the size and temperature of the heating zone, the collision chance of the molten nanoparticles is increased to form a melt cluster, reaching the required submicron size. After flying out of the heating zone, the temperature drops, and spherical submicron particles are formed under the action of surface tension and further cooled.

[0018] (4) Use the circulation system to transfer the submicron particles into the spray coating chamber through a transmission pipeline. At the same time, pressurize the silane coupling agent solution and add it to the spray coating chamber through an atomizing nozzle. Set the temperature of the spray coating chamber and the rotation speed of the stirrer to complete the coating and drying process in the spray coating chamber to form core-shell structured submicron magnetic powder. After cooling in the cooling chamber, it falls into the powder collection chamber.

[0019] Preferably, in step (1), before introducing argon and hydrogen, the vacuum degree of the vacuum chamber is not less than 1×10 —2 Pa; the pressure of the argon introduced into the vacuum chamber is 1.0x10 3 ~1.0x10 5 Pa, and the pressure of hydrogen is 1.0x10 2 ~5.0x10 4 Pa; in step (2), the voltage range of the discharge 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 pressurizing the silane coupling agent solution is 1~10 Kg, the temperature of the spray coating chamber is 150~450 o °C, and the rotation speed of the stirrer is 100 revolutions per minute to 1000 revolutions per minute; in step (4), the silane coupling agent is one or a mixture of amino silane, vinyl silane, epoxy silane, mercapto silane; the solvent is one or a combination of deionized water, ethanol, acetone, methylal.

[0020] Preferably, in step (4), the core-shell structured submicron powder has a particle size of 100-1 μm and has a core-shell structure, where SiO2 is the outer shell and the thickness of the outer shell is 5-50 nm.

[0021] The submicron magnetic powder prepared by the present invention is directly brought into the spray coating chamber by the circulating air flow from the heating jacket area. Under the action of the rotating air flow provided by the stirrer, the magnetic powder is kept in a dispersed suspension state in the coating chamber, thus creatively avoiding the problems of adsorption, agglomeration, and fluidization and redispersion during the cooling and collection process. The silane coupling agent solution forms micron-sized droplets through a high-pressure atomizing nozzle and adsorbs on the surface of the submicron metal magnetic powder with high surface energy. At a certain temperature, hydrolysis occurs 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 in the micron order, the drying of the submicron magnetic powder is also completed in a short time, thus avoiding the problems of secondary adsorption and agglomeration during the drying process of the traditional insulation coating process.

[0022] The present invention creatively combines the two processes of preparing submicron powder and spray coating into one. By expanding the heating area, the molten nanopowder collides and fuses in the heating area and further grows into submicron particles. The submicron particles are kept in a dispersed suspension state by the circulating air flow and the stirring air flow and enter the spray coating chamber, where the coating, hydrolysis, and drying processes are completed instantaneously, obtaining SiO2-coated spherical submicron metal soft magnetic particles.

[0023] Therefore, the present invention also has the following beneficial effects:

[0024] (1) The device of the present invention combines the two processes of preparing submicron powder and atomizing coating into one. By expanding the heating area, the molten nanopowder collides and fuses in the heating area and further grows into submicron particles. The submicron particles are kept in a dispersed suspension state by the circulating air flow and the stirring air flow and enter the spray coating chamber, where the coating, hydrolysis, and drying processes are completed instantaneously, obtaining SiO2-coated spherical submicron metal soft magnetic particles.

[0025] (2) The present invention creatively avoids the problems of adsorption, agglomeration, and fluidization and redispersion during the cooling and collection process of the traditional device, effectively keeping the magnetic powder in a dispersed suspension state and promoting a good insulation coating effect. At the same time, it also avoids the problems of secondary adsorption and agglomeration during the drying process of the traditional insulation coating process.

[0026] (3) The present invention reduces the complexity of the production process, saves energy consumption, and reduces costs. It can realize the large-scale industrial preparation of powders with a submicron size (100 nm - 1 μm), a SiO2 outer shell thickness of 5 - 50 nm, and a uniform distribution. At the same time, this process can be carried out under closed, high-vacuum, and industrial conditions. Description of the Drawings

[0027] Figure 1 It is a schematic structural diagram of the heat-insulating plasma arc - spray coating composite powder-making device of Embodiment 1.

[0028] In the figure: Heat-insulating plasma arc system I: Vacuum chamber 1, vacuum pumping system 2, atmosphere gas path 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, heat-insulating jacket 14, stirrer 15, atomizing nozzle 16, pressure pump 17, solution tank 18, Circulation gas path system III: Filter chamber 19, circulation gas pipe 20, blower 21. Specific implementation manners

[0029] The technical solutions of the present invention will be further specifically described below through specific embodiments in conjunction with the accompanying drawings.

[0030] In the present invention, unless otherwise specified, all devices and raw materials can be purchased from the market or are commonly used in this industry. The methods in the following embodiments are conventional methods in this field unless otherwise specified. Embodiment

[0031] The Figure 1As shown in the figure, a device for preparing submicron powder by thermal insulation plasma arc - spray coating composite includes a thermal insulation plasma arc system (I), a spray coating system (II) and a circulation system (III) connected in sequence; the thermal insulation plasma arc system (I) includes a vacuum chamber (1), a vacuum pumping system (2), an atmosphere gas path (3), a cooling water (4), an electrode gun (5), a power supply (6), a feeding device (7), a heating jacket (8), an observation window (9), and a transmission pipeline (10) placed in the vacuum chamber. During the arc - starting 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 lower than atmospheric pressure during operation. Long - term use will cause the strength of the vacuum wall to decline, posing a safety hazard. Therefore, cooling water is needed to cool the vacuum chamber wall. The power supply of the electrode gun (5) is controlled by the power supply (6). The material of the electrode gun is tungsten, and the material fed by the feeding device is metal Fe. The electrode gun is located 3 - 10 mm directly above the center of the feeding device; the feeding device includes two oppositely arranged discharge ports. To maintain the stability of the arc and the output of the product, the two discharge ports feed materials simultaneously. The stability of the arc will affect the particle size of the produced nano - powder. The distance between the discharge ports of the feeding device is 10 - 20 mm. The relative distance between the raw material at the discharge port and the electrode gun is set within the above - mentioned range to maintain the stability of the arc. If the distance is set too far, the arc cannot be started stably; the inner diameter of the heating jacket is 3 times the diameter of the arc column between the electrode gun and the feeding device, and 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), a heat - insulating sleeve (14), a pressure pump (17), and a solution tank (18), as well as a stirrer (15) and an atomizing nozzle (16) placed in the spray coating chamber.

[0032] The atomizing nozzle should be 20 cm higher than the transmission pipeline, and the stirrer should be 5 cm 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 smoothly coated with a shell layer. The stirring blades of the stirrer are made of stainless steel. The central points of the stirrer and the atomizing nozzle are on the same axis.

[0033] The circulation system (III) includes a filtration chamber (19), a circulation gas pipe (20), and a blower (21). The role of the filtration chamber is to filter the powder in the air flow, which plays a protective role for the blower and can also reduce the powder loss generated. The main purpose of the circulation gas pipe is to form a circulating air flow therein to drive the powder from the vacuum chamber (1) to the spray coating chamber (11).

[0034] A method for preparing core - shell structured submicron magnetic powder using the above - mentioned device includes the following steps:

[0035] (1) Seal the vacuum chamber (1), and evacuate the entire device to 1×10—2 Pa; The main purpose of evacuation is to remove oxygen inside the equipment because hydrogen will be introduced later. The presence of oxygen will pose a safety hazard and also cause loss to the electrodes.

[0036] Introduce 1.0x10 3 Pa argon gas and 1.0x10 2 Pa hydrogen gas into the vacuum chamber (1) through the atmosphere gas path (3). The role of argon is to provide a plasma gas source, and the role of hydrogen is to promote the volatilization of metals and increase the yield. The limitation of the argon and hydrogen gas pressures is to make the pressure of the system lower than one atmosphere after filling with argon and hydrogen, so that the whole system operates under negative pressure to prevent the leakage of reactants to the environment.

[0037] (2) Use the feeding device (7) to send metallic Fe into the vacuum chamber (1), turn on the power supply (6), generate an arc between the tungsten electrode gun (5) and the raw material, control the voltage at 200 V to form a stable arc, and prepare molten nanoparticle clusters.

[0038] (3) Keep the inner surface of the heating jacket (8) constant at 1000 o °C, so that the nanoparticle clusters remain in a molten state and further collide and grow under the heating of the heating jacket to obtain submicron particles.

[0039] (4) Under the action of the circulation system (III), the submicron Fe particles enter the spray coating chamber (11) through the transfer pipeline (10). At the same time, the amino silane ethanol solution in the solution tank (18) is pressurized by 10 KG by the pressure pump (17) and enters the spray coating chamber (11) through the atomizing nozzle (16). The spray coating chamber is insulated by the heat preservation jacket (14) to keep the temperature of the spray coating chamber (11) at 400 o °C, the rotation speed of the stirrer (15) is 1000 revolutions per minute, and a complete coating and drying process is completed in the spray coating chamber (11) to form submicron Fe powder with a core-shell structure, the particle size is 600 nm, and the thickness of the SiO2 outer shell is 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

[0040] The difference between the device for preparing submicron magnetic powder with a core-shell structure in Example 2 and that in Example 1 is as follows: the material of the electrode gun is graphite, the material sent by the feeding device is metallic Ni, the electrode gun is 10 mm directly above the center of the feeding device, the distance between the discharge ports of the feeding device is 20 mm, 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 transfer pipeline, and the stirrer should be 15 cm lower than the transfer pipeline. The stirring blades of the stirrer are made of titanium.

[0041] A method for preparing core-shell structured submicron magnetic powder by using the above device, comprising the following steps:

[0042] (1) Seal the vacuum chamber (1), and evacuate the whole device to 1×10 —2 Pa through the vacuum pumping system (2), and introduce 1.0x10 4 Pa argon gas and 1.0x10 3 Pa hydrogen gas into the vacuum chamber (1) through the atmosphere gas path (3);

[0043] (2) Feed metallic Ni into the vacuum chamber (1) by the feeding device (7), turn on the power supply (6), generate an arc between the tungsten electrode gun (5) and the raw material, control the voltage at 20 V to form a stable arc, and prepare molten nanoparticle clusters;

[0044] (3) Keep the inner surface of the heating jacket (8) constant at 400 o °C, keep the nanoparticle clusters in a molten state, and further collide and grow under the heating of the heating jacket to obtain submicron particles;

[0045] (4) Under the action of the circulation system (III), the submicron Ni particles enter the spray coating chamber (11) through the transfer pipeline (10). Meanwhile, the epoxy group silane acetone solution in the solution tank (18) is pressurized to 1 KG by the pressure pump (17) and enters the spray coating chamber (11) through the atomizing nozzle (16). Set the temperature of the spray coating chamber (11) at 300 o °C and the rotation speed of the stirrer (15) at 100 revolutions per minute, and complete the complete coating and drying process in the spray coating chamber (11) to form core-shell structured submicron Ni powder with a particle size of 400 nm and a SiO2 shell thickness of 10 nm. Then, pass through the cooling chamber (12) and fall into the powder collection chamber (13) at the lower end of the device. Example

[0046] The differences between the device for preparing core-shell structured submicron magnetic powder in Example 3 and that in Example 1 are as follows: 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 directly above the center of the feeding device, the distance between the discharge ports of the feeding device is 15 mm, 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 transfer pipeline, and the stirrer should be 10 cm lower than the transfer pipeline. The stirring blades of the stirrer are made of titanium.

[0047] A method for preparing core-shell structured submicron magnetic powder by using the above device, comprising the following steps:

[0048] (1) Seal the vacuum chamber (1), and evacuate the entire device to 1×10 —2 Pa through the vacuum pumping system (2). Introduce 1.0x10 5 Pa argon gas and 1.0x10 3 Pa hydrogen gas into the vacuum chamber (1) through the atmosphere gas path (3);

[0049] (2) Use the feeding device (7) to send the alloy FeNi into the vacuum chamber (1), turn on the power supply (6), generate an arc between the tungsten electrode gun (5) and the raw material, control the voltage at 100 V to form a stable arc, and prepare molten nanoparticle clusters;

[0050] (3) Keep the inner surface of the heating jacket (8) constant at 600 o °C, so that the nanoparticle clusters remain in a molten state and further collide and grow under the heating of the heating jacket to obtain submicron particles;

[0051] (4) Under the action of the circulation system (III), the submicron FeNi particles enter the spray coating chamber (11) through the transfer pipeline (10). At the same time, the vinyl silane dimethyl acetal 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). Set the temperature of the spray coating chamber (11) at 400 o °C and the rotation speed of the stirrer (15) at 700 revolutions per minute. Complete the complete coating and drying process in the spray coating chamber (11) to form submicron FeNi powder with a core-shell structure, with a particle size of 800 nm and a SiO2 shell thickness of 10 nm. Then, pass through the cooling chamber (12) and fall into the powder collection chamber (13) at the lower end of the device.

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), 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), 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); The feeding device comprises two discharge ports arranged opposite to each other, the electrode gun (5) is located 3 to 10 mm above the center of the two discharge ports of the feeding device (7); the two discharge ports are 10 to 20 mm apart; 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); The inner surface temperature of the heating jacket (8) is kept constant at 400-1000°C; The size of the core-shell structured submicron powder is in the range of 100nm to 1μm.

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; 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 transmission pipe (10) is higher than the upper end of the electrode gun (5), and 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.

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 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 an alloy; and the stirring blades of the stirrer (15) are stainless steel or titanium.

6. A method for preparing core-shell structure submicron powder using the device as described in any one of claims 1 to 5, characterized in that: The following steps are involved: (1) passing argon and hydrogen into the vacuum chamber; (2) feeding the raw materials into the vacuum chamber using a feeding device, discharging using an electrode gun, forming a stable arc between the electrode gun and the raw materials, 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 using a circulation system. At the same time, 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, which falls into a powder collection chamber after being cooled in a cooling chamber.

7. The method for preparing submicron powder with core-shell structure according to claim 6, 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 1.0×10 3 ~1.0×10 5 Pa, the pressure of hydrogen is 1.0×10 2 ~5.0×10 4 Pa In step (2), the discharge voltage range is 20 to 200 V; In step (3), the preset temperature of the inner surface of the heating jacket is 400-1000° C.; In step (4), the pressure of the silane coupling agent solution is 1-10 kg, the temperature of the spray coating chamber is 150-450° C., and the speed of the agitator 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; and the solvent of the silane coupling agent solution is a combination of one or more of deionized water, ethanol, acetone, and methylal.

8. 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 100nm to 1μm and a core-shell structure, wherein SiO2 is the outer shell and the thickness of the outer shell is 5-50nm.

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