A combined device and method for a standby auxiliary heat source based on physical vapor phase micro / nano powder.

Abstract

A combined device and method for auxiliary heat source in physical vapor phase (PVP) micro / nano powder preparation belongs to the field of micro / nano powder material preparation. It includes an induction heating crucible system and a dual-flow DC arc plasma gun, which are housed within a vacuum chamber as part of the evaporation heat source. The induction heating crucible system consists of two induction heating coils arranged on an insulating ceramic crucible. The two coils have the same current magnitude but opposite directions, uniformly heating the material. The DC arc plasma gun comprises a cathode, a closed-loop cooling system, and dual-flow channels. This invention, based on the existing transfer arc heat source, promotes the coupling of the electric field and the induced magnetic field through auxiliary induction heating, improving heat source efficiency. The finely adjustable gas path design in the plasma gun increases the irradiation area of ​​the plasma flame and the stability of the molten pool within the crucible, accelerating material evaporation. This allows for efficient preparation of high-purity powder with uniform particle size while effectively preventing electrode contamination and wear.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano powder preparation technology, and relates to a combination device and method for auxiliary heat source in physical vapor phase micro-nano powder preparation, particularly to an auxiliary device and process implementation method for preparing micro-nano powder by DC arc plasma method, and particularly to improving the material heating, arc action area and preparation process stability in a physical vapor phase forming chamber by coupling auxiliary induction heating with DC arc plasma and dual airflow synergistic regulation. Background Technology

[0002] DC arc plasma method, with its outstanding advantages such as high temperature (up to 10000K or above), high enthalpy, high reactivity, high product purity, and relatively simple preparation process, has become one of the mainstream technologies for the industrial preparation of nano-metals (such as nickel, copper, and titanium), ceramics (such as alumina and zirconium oxide), and composite micro / nano powders. The core principle of this method is to use the high-temperature plasma jet generated by a DC arc to melt and evaporate bulk raw materials. The evaporated raw material vapor is then rapidly condensed in a vacuum or inert atmosphere to form micro / nano-scale powder particles. Currently, with the increasing demand for high-performance micro / nano powders in fields such as MLCCs, conductive powders, and microwave absorbing materials, higher requirements are being placed on the preparation efficiency, purity, and particle size uniformity of powders. However, existing DC arc plasma preparation devices and processes still have many technical bottlenecks, which seriously restrict the preparation efficiency, product quality, and equipment stability. Specifically, this manifests as: 1. Prominent electrode contamination problem: The material melts and evaporates rapidly under the action of high-temperature plasma, generating a large number of molten droplets. These droplets are prone to splashing, and some droplets adhere to the tip of the cathode tungsten electrode of the plasma gun. As adhering materials accumulate, the tungsten electrode surface oxidizes and wears down faster, leading to decreased arc discharge stability and phenomena such as arc vibration and deviation. In severe cases, this can cause electrode short circuits and torch burnout, not only shortening the lifespan of the tungsten electrode and increasing equipment maintenance costs, but also affecting the uniformity of powder particle size distribution. 2. The plasma action area is relatively concentrated: Conventional DC arc plasma jets are concentrated, with limited radial diffusion range and a small contact area with the bulk material in the crucible. This results in a small and shallow molten pool on the material surface, affecting the continuous melting and evaporation process and failing to meet the capacity requirements of industrial production. 3. There is room for improvement in the single plasma arc heating method: In the process of preparing micro and nano powders using the DC arc plasma method, the plasma arc mainly acts on a local area of ​​the material surface. The transfer of arc heat to the interior of the material requires a certain process, and the overall heating and melting process of the bulk material is limited by the arc action range. Especially when processing bulk materials that are large in volume or have slow thermal conductivity, relying solely on plasma arc heating results in a long time required for the material to form a stable molten pool, and the continuity of the material's continuous melting and evaporation process needs to be improved.

[0003] To address the problems of electrode contamination risk, relatively concentrated plasma interaction area, and uneven overall heating of materials in existing DC arc plasma preparation processes, this invention proposes an auxiliary device and method integrating dual airflow synergistic control and induction coil-assisted heating. This device uses a first airflow to provide gas curtain protection to the cathode tip, a second airflow to guide and control the plasma interaction area, and an induction heating coil to assist heating of the material in the crucible. This improves electrode protection, material heating conditions, and process stability, making it suitable for continuous or large-scale preparation processes of physical vapor phase micro / nano powders. Summary of the Invention

[0004] The core objective of this invention is to address the problems of electrode contamination risk, relatively concentrated plasma action area, and uneven overall material heating in existing DC arc plasma preparation of micro / nano powders. It provides a simple and convenient auxiliary device and method suitable for continuous or large-scale preparation of micro / nano powders, meeting the application needs of MLCCs, conductive powders, and microwave absorbing materials. To address the shortcomings of existing technologies, the core technical problems to be solved by this invention are as follows: 1) Solving the problem of electrode contamination caused by molten material droplet splashing, which is beneficial for improving arc continuity, extending electrode life, and reducing maintenance costs; 2) Solving the problem of concentrated plasma jet and small action area, expanding the molten pool area, which is beneficial for expanding the material evaporation area; 3) Solving the problems of high energy consumption, uneven heating, slow material melting rate, and high load of single arc heating.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A combined device and method for preparing a backup auxiliary heat source for physical vapor phase micro / nano powder preparation is disclosed. The auxiliary device achieves efficient preparation of micro / nano powder through a combination of dual airflow coordinated control and induction coil auxiliary heating. The auxiliary device is installed in a vacuum chamber and includes a plasma gun body 1, a plasma arc 2, a ceramic crucible 3, an anode seat 4, a metal block material 5, an induction heating coil 6, a conductive plug 7, a lifting shaft 12, a water-cooled inlet channel 13, a water-cooled outlet channel 14, a cathode tip 15, a first airflow channel 16, a second airflow channel 17, and a condensate channel 18.

[0006] The plasma gun body 1 is a vertical columnar structure, located at the top of the auxiliary device, directly above the ceramic crucible 3, and coaxially aligned with it. The upper sidewall of the plasma gun body 1 has two airflow inlets 8 and a first airflow inlet 9, with the second airflow inlet 8 located above the first airflow inlet 9. These two inlets are independent and connect to the second airflow nozzle 11 and the first airflow nozzle 10 at the bottom of the plasma gun body 1, respectively. The first airflow inlet 9 and the first airflow nozzle 10 connect to the first airflow channel 16, through which the first airflow passes. The second airflow inlet 8 and the second airflow nozzle 11 connect to the second airflow channel 17, through which the second airflow passes.

[0007] The condensate inlet 13 and condensate outlet 14 are respectively connected to the condensate channel 18, which is a coaxial nested structure inside the plasma gun body 1. The two are arranged around the cathode assembly inside the gun body to form a closed-loop cooling water channel. Deionized water is introduced into the water channel to cool and protect the electrodes and the gun body.

[0008] The cathode tip 15 is made of tungsten material and is installed at the center of the bottom of the plasma gun body 1. It extends vertically downwards from the gun body, with the tip pointing towards the center area of ​​the ceramic crucible 3 directly below, and is coaxially opposite to the ceramic crucible 3.

[0009] The metal block material 5 is placed in the center of the ceramic crucible 3, directly below the cathode tip 15.

[0010] The induction heating coil 6 is coaxially wrapped around the ceramic crucible 3. The induction heating coil 6 is connected to a high-frequency induction power supply, and the plasma gun body 1 is connected to a DC arc power supply.

[0011] The conductive plug 7 is located at the center of the bottom of the ceramic crucible 3. Its upper end forms a conductive contact with the material 5 or the surface of the molten liquid inside the ceramic crucible 3, and its lower end is fixedly connected to the anode seat 4, so that the material 5, the conductive plug 7 and the anode seat 4 form an anode conductive path.

[0012] The shape-controllable plasma arc or plasma 2 is formed between the cathode tip 15 and the metal block material 5, and is distributed along the vertical central axis of the device. The lifting shaft 12 is located at the center of the top of the plasma gun body 1 and is coaxially fixedly connected to the plasma gun body 1. It can drive the plasma gun body 1 to move up and down in the vertical direction to adjust the distance between the cathode at the end of the plasma gun body 1 and the ceramic crucible 3, that is, to adjust the arc spacing between the cathode tip 15 and the metal block material 5.

[0013] Furthermore, the induction heating coil 6 is a coaxial ring structure, arranged concentrically with the ceramic crucible 3. The induction heating coil 6 includes a first induction heating coil 6-1 and a second induction heating coil 6-2, which are wound in opposite directions. They generate a first induced magnetic field 19 and a second induced magnetic field 20 of equal magnitude and opposite direction, respectively, by Ampere's law. The two sets of induced magnetic fields cancel each other out.

[0014] Furthermore, the condensate channel 18 is located at the center of the plasma gun, the first airflow channel 16 is located outside the condensate channel 18, and the second airflow channel 17 is located outside the first airflow channel 16. The condensate channel 18, the first airflow channel 16, and the second airflow channel 17 are coaxially arranged along the plasma gun axis. Specifically: The first airflow nozzle 10 is a small-diameter circular nozzle, with three nozzles evenly distributed around the cathode tip 15 as the center, and the airflow direction is vertically downward. The second airflow nozzle 11 is a large-diameter adjustable-angle nozzle, with three nozzles located outside the first airflow nozzle 10, and the airflow direction is obliquely downward and outward, arranged at an angle to the gun body axis. The nozzle angle is adjusted according to the actual working conditions.

[0015] The first gas flow nozzle 10 is evenly distributed around the cathode tip 15, forming a complete annular gas curtain barrier. The second gas flow nozzle 11 is an angle-adjustable nozzle, which adjusts the gas output direction and diffusion angle according to the operating conditions to expand the plasma interaction area.

[0016] Furthermore, the water-cooled inlet channel 13 and the water-cooled outlet channel 14 are independent of each other, forming a closed-loop cooling structure. Deionized water is introduced into the water circuit to achieve cooling protection for the cathode tip 15 and the plasma gun body 1.

[0017] Furthermore, the anode holder 4 is made of copper. The conductive plug 7 is made of graphite, and the conductive plug 7 enables a conductive connection between the ceramic crucible 3 and the anode holder 4. The ceramic crucible 3 is an open-top, high-temperature resistant, insulating container structure, located directly below the plasma gun body 1. The plasma gun body 1 is a DC plasma gun body.

[0018] Furthermore, the anode seat 4 is located at the bottom of the device, directly below the ceramic crucible 3. Its upper surface is fixedly connected to the lower end of the conductive plug 7 and supports the ceramic crucible 3. That is, the anode seat 4, the conductive plug 7, and the ceramic crucible 3 are coaxially assembled from top to bottom, serving as the load-bearing base of the device. The plasma gun body 1, cathode tip 15, ceramic crucible 3, metal block material 5, conductive plug 7, and anode seat 4 are all located on the same vertical central axis, maintaining a strictly coaxial arrangement.

[0019] A method for preparing physical vapor phase micro / nano powders, based on the aforementioned auxiliary device, includes the following steps: Step 1, Material Pretreatment and Equipment Assembly: Place material 5 into the ceramic crucible 3 and lay it flat; fix the ceramic crucible 3 onto the anode seat 4. Connect the gas line and cooling water line, and check the sealing to ensure there is no air or water leakage.

[0020] The second step is to adjust the vacuum and protective atmosphere: start the vacuum pump to remove the air from the cavity in which this auxiliary device is placed until the vacuum level reaches below 1 Pa; turn off the vacuum pump and fill the cavity with nitrogen until the pressure is 40~80 kPa to maintain a stable protective atmosphere.

[0021] The third step is to start the cooling water circulation system, and the induction heating coil 6 will start simultaneously with the electric arc, while activating dual airflow control. Specifically: Turn on the cooling circulating water system with a flow rate of 80~160L / min and an inlet water temperature ≤25℃; turn on the high-frequency induction power supply to heat the material in the ceramic crucible 3 through the induction heating coil 6, and simultaneously start the DC arc power supply connected to the plasma gun and adjust the current to 50~200A and the voltage to 20~80V to ignite the arc, forming a high-temperature nitrogen plasma between the cathode tip 15 and the material. The material is heated and melts, forming a molten liquid surface in the ceramic crucible 3, and the liquid surface evaporates and vaporizes simultaneously; adjust the cathode position through the lifting shaft 12, controlling the linear distance of the lifting and lowering to 5~10cm, until the arc between the cathode and the molten liquid surface remains stable; at the same time, turn on the first airflow and the second airflow. The first airflow adjusts the nitrogen flow rate to 5~15L / min to purge the cathode tip, and the second airflow adjusts the nitrogen flow rate to 10~30L / min and the nozzle deflection angle to 5~30° to expand the plasma action area and form a stable molten pool, so that the material continues to melt and evaporate.

[0022] Step 4, powder collection: Continue preparation for 20-50 minutes, during which time all parameters are monitored in real time to ensure stability; after preparation is completed, turn off each device in sequence, wait for the chamber to cool to room temperature, remove the collection device, and obtain nanoparticles.

[0023] The working principle and innovations of this invention: The basic process of preparing submicron / nano-scale powders using the physical vapor phase method is as follows: a high-temperature heat source is used to evaporate bulk raw materials to form a gas phase. When the gaseous concentration of the component elements reaches supersaturation and is close to the melting point, nucleation occurs, and the powder particles gradually grow. This invention uses plasma and induction coils to construct a composite heat source. An innovative design uses a reverse-winding double-strand induction coil to achieve magnetic field cancellation and prevent magnetic interference. Simultaneously, eddy currents achieve uniform heating of the material across its entire surface. Combined with a dual-path independent airflow synergistic structure, an air curtain protection electrode, and deflection nozzles to expand the plasma action area, this reduces the heating load of a single electric arc, making it suitable for the large-scale preparation of micro / nano powders.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) It helps reduce the risk of electrode contamination. The first gas flow nozzle 10 is arranged circumferentially along the cathode tip 15. During operation, the first gas flow forms an annular gas curtain around the cathode tip 15. This gas curtain can block the molten droplets to a certain extent, thereby reducing the possibility of molten droplets splashing and adhering to the cathode tip 15. This helps reduce the risk of contamination and ablation of the cathode tip 15 and helps maintain the continuous combustion state of the plasma arc 2.

[0025] 2) It helps to expand the heating area of ​​the material. The second airflow nozzle 11 is located outside the first airflow nozzle 10 and is sprayed obliquely towards the surface area of ​​the material 5 inside the ceramic crucible 3. The second airflow can guide and diffuse the outer edge of the plasma arc 2, so that the plasma action area extends to the outer side of the material 5 surface, thereby increasing the molten pool area and improving the continuity of the heating, melting and evaporation process of the material 5.

[0026] 3) It helps reduce the heating load of a single electric arc. The induction heating coil 6 is coaxially arranged around the ceramic crucible 3, which can provide auxiliary heating for the material 5 inside the ceramic crucible 3, so that the material 5 can be heated as a whole before or during the action of the plasma arc 2. This composite heating method helps to reduce the problem of local heat concentration when relying solely on the plasma arc 2 for heating, and helps to improve the heating uniformity of the material 5.

[0027] 4) It helps to reduce the interference of the induced magnetic field on the electric arc and magnetic materials. The first induction heating coil 6-1 and the second induction heating coil 6-2 are wound in opposite directions, so that the magnetic field components generated by the two sets of coils near the plasma arc 2 cancel each other out or weaken each other, thereby reducing the magnetic field interference of the induced magnetic field on the plasma arc 2 and magnetic materials; at the same time, an alternating electromagnetic field for induction heating is still formed in the area where the ceramic crucible 3 and the material 5 are located, so that the material 5 can generate eddy currents and heat up.

[0028] 5) It helps improve the stability of the powder preparation process. By using a first airflow to provide gas curtain protection for the cathode tip 15, a second airflow to regulate the plasma action area, and an induction heating coil 6 to provide auxiliary heating for the material 5, this invention can achieve synergistic cooperation of electrode protection, heating assistance, and arc expansion in its structure, thereby helping to improve the continuity of the arc, the continuity of material evaporation, and the stability of powder formation in the micro-nano powder preparation process. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the overall operation of a physical vapor phase micro / nano powder system backup auxiliary heat source combination device according to the present invention. Figure 2 This is a schematic diagram of the composite heating system of the device described in this invention; Figure 3This is a detailed schematic diagram of the airflow nozzle at the cathode tip of the DC arc plasma gun described in this invention.

[0030] In the diagram: 1 DC arc plasma gun, 2 shape-controllable plasma arc or plasma, 3 ceramic crucible, 4 anode seat, 5 material, 6 induction heating coil; 7 conductive plug, 8 second gas flow inlet, 9 first gas flow inlet, 10 first gas flow nozzle, 11 second gas flow nozzle, 12 lifting shaft, 13 condensate inlet, 14 condensate outlet, 15 cathode tip, 16 first gas flow channel, 17 second gas flow channel, 18 condensate channel, 19 first induction magnetic field, 20 second induction magnetic field; 6-1 First induction heating coil, 6-2 Second induction heating coil. Detailed Implementation

[0031] To make the objectives, technical solutions, and features of the present invention clearer, a detailed description will be given below in conjunction with the embodiments of the present invention. However, the scope of the present invention is not limited to the following examples.

[0032] This embodiment provides a backup auxiliary heat source combination device for physical vapor phase micro / nano powder preparation. The auxiliary device is installed entirely within a vacuum chamber and achieves efficient preparation of micro / nano powders through a combination of dual airflow coordinated control and induction coil auxiliary heating. The auxiliary device includes a DC arc plasma gun 1, a plasma arc 2, a ceramic crucible 3, an anode seat 4, material 5, an induction heating coil 6, a conductive plug 7, a second airflow inlet 8, a first airflow inlet 9, a first airflow nozzle 10, a second airflow nozzle 11, a lifting shaft 12, a water-cooled inlet 13, a water-cooled outlet 14, a cathode tip 15, a first airflow channel 16, a second airflow channel 17, a condensate channel 18, a first induction magnetic field 19, and a second induction magnetic field 20.

[0033] In this embodiment, the DC arc plasma gun 1 is a vertically oriented gun structure located at the top of the auxiliary device and directly above the ceramic crucible 3. The DC arc plasma gun 1 and the ceramic crucible 3 are arranged opposite each other along the same vertical central axis, so that the cathode tip 15 can be directly facing the central area of ​​the material 5 inside the ceramic crucible 3. The lifting shaft 12 is located at the center of the top of the DC arc plasma gun 1 and is connected to the DC arc plasma gun 1. It is used to drive the DC arc plasma gun 1 to move up and down in the vertical direction, thereby adjusting the distance between the cathode tip 15 and the material 5 or the molten liquid surface.

[0034] In this embodiment, the cathode tip 15 is installed at the lower center of the DC arc plasma gun 1. The cathode tip 15 is preferably made of tungsten material, with its tip facing directly downwards towards the ceramic crucible 3. The material 5 is placed at the center of the ceramic crucible 3, directly below the cathode tip 15. The ceramic crucible 3 is an open-topped, high-temperature resistant, insulating container used to hold the bulk material 5 to be evaporated and prepared into powder. A conductive plug 7 is installed at the center of the bottom of the ceramic crucible 3. The upper end of the conductive plug 7 is in conductive contact with the bottom of the ceramic crucible 3 and the material 5, and the lower end of the conductive plug 7 is fixedly connected to the anode seat 4. The anode seat 4 is located directly below the ceramic crucible 3, serving as a support base for the device and an anode conductive component. Thus, a DC arc discharge path is formed between the cathode tip 15, the material 5, the conductive plug 7, and the anode seat 4, enabling a stable plasma arc 2 to be formed between the cathode tip 15 and the material 5.

[0035] In this embodiment, the DC arc plasma gun 1 is provided with a condensate channel 18, a first airflow channel 16, and a second airflow channel 17. The condensate channel 18 is located inside the DC arc plasma gun 1 and is connected to the water-cooling inlet 13 and the water-cooling outlet 14, respectively. Cooling water enters the condensate channel 18 through the water-cooling inlet 13, cools and protects the DC arc plasma gun 1 and the area near the cathode tip 15, and then exits through the water-cooling outlet 14, thereby reducing the temperature rise of the gun body and the cathode tip 15 and improving the stability of continuous operation of the device.

[0036] The first airflow inlet 9 is connected to the first airflow channel 16, and the first airflow channel 16 is connected to the first airflow nozzle 10. The second airflow inlet 8 is connected to the second airflow channel 17, and the second airflow channel 17 is connected to the second airflow nozzle 11. The first airflow channel 16 and the second airflow channel 17 are independent of each other, allowing the first airflow and the second airflow to have their flow rate, pressure, and injection state adjusted separately. In this embodiment, the first airflow nozzle 10 is a small-diameter circular nozzle, preferably three in number. The three first airflow nozzles 10 are evenly distributed around the cathode tip 15 in the circumferential direction, with the jet direction facing the area below the cathode tip 15. During operation, the first airflow is ejected from the first airflow nozzle 10, forming an annular air curtain around the cathode tip 15 to prevent molten material droplets from splashing onto the cathode tip 15, reducing adhesion contamination and ablation of the cathode tip 15.

[0037] The second airflow nozzle 11 is located outside the first airflow nozzle 10, and is preferably configured as a three-angle adjustable nozzle. The outlet direction of the second airflow nozzle 11 is obliquely downward and outward, and towards the surface area of ​​the material 5 inside the ceramic crucible 3. During operation, the second airflow is ejected from the second airflow nozzle 11, which guides and diffuses the outer edge of the plasma arc 2, thereby expanding the effective area of ​​the plasma arc 2, increasing the molten pool area on the surface of the material 5, and accelerating the evaporation of the material 5.

[0038] In this embodiment, the induction heating coil 6 is coaxially arranged around the outer periphery of the ceramic crucible 3 and connected to a high-frequency induction power supply. The induction heating coil 6 includes a first induction heating coil 6-1 and a second induction heating coil 6-2. The first induction heating coil 6-1 and the second induction heating coil 6-2 are wound in opposite directions. After being energized, the first induction heating coil 6-1 and the second induction heating coil 6-2 generate a first induced magnetic field 19 and a second induced magnetic field 20 in opposite directions, respectively, so that the two sets of induced magnetic fields cancel each other out or weaken each other near the plasma arc 2, thereby reducing the magnetic field interference of the induced magnetic field on the plasma arc 2 and the magnetic material. At the same time, the induction heating coil 6 can still provide auxiliary heating to the material 5 in the ceramic crucible 3 through electromagnetic induction, so that the material 5 is heated as a whole, and the melting rate of the material 5 is accelerated.

[0039] Specific procedures for powder preparation: First, material pretreatment and device assembly: Select nickel blocks (nickel balls with a diameter of about 1 cm) with a purity of 99.95%, and place the material flat in a ceramic crucible; fix the crucible on the anode holder. Connect the gas line and cooling water line, and check the sealing to ensure there is no air or water leakage.

[0040] Second, vacuum and protective atmosphere conditioning: Start the vacuum pump to remove the air inside the vacuum chamber until the vacuum level reaches 1 Pa; turn off the vacuum pump and fill the chamber with nitrogen until the pressure is 80 kPa to maintain a stable protective atmosphere.

[0041] Third, the induction coil auxiliary heating and the electric arc are activated simultaneously, and dual airflow control is initiated: the high-frequency induction power supply is turned on to heat the material, and the DC arc power supply is simultaneously activated and the current is adjusted to 100A and the voltage to 40V to ignite the arc, forming a high-temperature nitrogen plasma between the cathode tip and the material. The material is heated and melts, forming a molten liquid surface in the crucible, and the liquid surface evaporates and vaporizes simultaneously. The distance between the cathode and the molten liquid surface is adjusted up and down by the lifting shaft to keep the arc spacing within a suitable range, preferably controlled between 5cm and 10cm, so that the arc between the cathode and the molten liquid surface remains stable and the evaporation efficiency reaches the optimal level. At the same time, the first airflow and the second airflow are activated. The first airflow adjusts the nitrogen flow rate to 10L / min to purge the cathode tip, and the second airflow adjusts the nitrogen flow rate to 25L / min and the nozzle deflection angle to 15° to expand the plasma action area and form a stable molten pool, ensuring uniform melting and efficient evaporation of the material.

[0042] Fourth, powder collection: Continue preparation for 30 minutes, during which time all parameters are monitored in real time to ensure stability; after preparation is completed, turn off each device in sequence, wait for the chamber to cool to room temperature, remove the collection device, and obtain nickel nanopowder.

[0043] The above specific embodiments are merely one implementation of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make several changes without departing from the concept of the present invention, including but not limited to changing the type of raw materials, gas pressure, power supply, auxiliary heat source, carrier gas circulation rate, feeding method, etc., all of which fall within the protection scope of the present invention.

Claims

1. A combined device and method for a backup auxiliary heat source in physical vapor phase micro / nano powder production, characterized in that, The auxiliary device improves the material heating, the arc action area and the stability of the preparation process by combining dual airflow coordinated regulation with induction coil auxiliary heating. It is installed in a vacuum chamber and includes a plasma gun body (1), a plasma arc (2), a ceramic crucible (3), an anode seat (4), a metal block material (5), an induction heating coil (6), a conductive plug (7), a lifting shaft (12), a cathode tip (15), a first airflow channel (16), a second airflow channel (17), and a condensate channel (18). The plasma gun body (1) is a vertical columnar structure, located at the top, and positioned directly above the ceramic crucible (3), coaxially opposite to the ceramic crucible (3). Its upper sidewalls are respectively provided with a second airflow inlet (8) and a first airflow inlet (9). The two interfaces are independent of each other and are respectively connected to the second airflow nozzle (11) and the first airflow nozzle (10) at the bottom of the plasma gun body (1). The first airflow inlet (9) and the first airflow nozzle (10) are connected to the first airflow channel (16), and the second airflow inlet (8) and the second airflow nozzle (11) are connected to the second airflow channel (17). The condensate channel (18) connects the condensate inlet (13) and the condensate outlet (14), and is a coaxial nested structure inside the plasma gun body (1). The two are arranged around the cathode inside the gun body to form a closed-loop cooling water path. The cathode tip (15) is installed at the bottom center of the plasma gun body (1), extends vertically downwards from the gun body, and the tip faces the metal block material (5) placed in the center area of ​​the ceramic crucible (3); The induction heating coil (6) is coaxially wrapped around the ceramic crucible (3), the induction heating coil (6) is connected to a high-frequency induction power supply, and the plasma gun body (1) is connected to a DC arc power supply. The conductive plug (7) is located at the center of the bottom of the ceramic crucible (3). Its upper end forms a conductive contact with the metal block material (5) or the molten liquid surface inside the ceramic crucible (3), and its lower end is connected to the anode seat (4), so that the metal block material (5), the conductive plug (7) and the anode seat (4) form an anode conductive path. The shape-controllable plasma arc or plasma 2 is formed between the cathode tip (15) and the metal block material (5), and is distributed along the vertical central axis of the device; the lifting shaft (12) adjusts the arc distance between the cathode tip (15) and the metal block material (5).

2. The physical vapor phase micro / nano powder system backup auxiliary heat source combination device according to claim 1, characterized in that, The induction heating coil (6) is a coaxial ring structure and is arranged concentrically with the ceramic crucible (3). The induction heating coil (6) includes a first induction heating coil (6-1) and a second induction heating coil (6-2). The two are wound in opposite directions, with the same current magnitude and opposite direction, that is, they generate a first induction magnetic field (19) and a second induction magnetic field (20) of equal magnitude and opposite direction, respectively. The two sets of induction magnetic fields are equal in magnitude and opposite in direction and cancel each other out.

3. The physical vapor phase micro / nano powder system backup auxiliary heat source combination device according to claim 1, characterized in that, The lifting shaft (12) is located at the center of the top of the plasma gun body (1) and is coaxially fixedly connected to the plasma gun body (1). It can drive the plasma gun body (1) to move up and down in the vertical direction to adjust the distance between the cathode at the end of the plasma gun body (1) and the ceramic crucible (3), that is, to adjust the arc distance between the cathode tip (15) and the metal block material (5).

4. The physical vapor phase micro / nano powder system backup auxiliary heat source combination device according to claim 1, characterized in that, The condensate channel (18) is located at the center of the plasma gun, the first airflow channel (16) is located outside the condensate channel (18), and the second airflow channel (17) is located outside the first airflow channel (16); the condensate channel (18), the first airflow channel (16) and the second airflow channel (17) are coaxially arranged along the plasma gun axis.

5. The combined device for backup auxiliary heat source of physical vapor phase micro / nano powder system according to claim 1, characterized in that, In the auxiliary device: The first airflow nozzle (10) is a small-diameter circular nozzle, with a total of 3 nozzles. They are evenly distributed around the cathode tip (15) to form a complete annular air curtain barrier, with the air outlet direction vertically downward. The second airflow nozzle (11) is an angle-adjustable nozzle, with a total of 3. It is located outside the first airflow nozzle (10), and the air outlet direction is obliquely downward and outward, arranged at an angle with the axis of the gun body. The air outlet direction and diffusion angle are adjusted according to the working conditions to expand the plasma action area. The second airflow inlet (8) is located above the first airflow inlet (9).

6. The physical vapor phase micro / nano powder system backup auxiliary heat source combination device according to claim 1, characterized in that, The water-cooled inlet channel (13) and the water-cooled outlet channel (14) are independent of each other, forming a closed-loop cooling structure. Deionized water is introduced into the water channel to achieve cooling protection for the cathode tip (15) and the plasma gun body (1).

7. The physical vapor phase micro / nano powder system backup auxiliary heat source combination device according to claim 1, characterized in that, In the auxiliary device: The anode holder (4) is made of copper; The conductive plug (7) is made of graphite and enables conductive connection between the ceramic crucible (3) and the anode seat (4). The cathode tip (15) is made of tungsten material; The ceramic crucible (3) is an open-top, high-temperature resistant, insulating container structure, located directly below the plasma gun body (1); The plasma gun body (1) is a DC plasma gun body.

8. The physical vapor phase micro / nano powder system backup auxiliary heat source combination device according to claim 1, characterized in that, The anode seat (4) is located at the bottom of the device, directly below the ceramic crucible (3). Its upper surface is fixedly connected to the lower end of the conductive plug (7) and supports the ceramic crucible (3). That is, the anode seat (4), the conductive plug (7), and the ceramic crucible (3) are coaxially assembled from top to bottom, serving as the load-bearing base of the device. The plasma gun body (1), the cathode tip (15), the ceramic crucible (3), the metal block material (5), the conductive plug (7), and the anode seat (4) are all located on the same vertical central axis, maintaining a coaxial arrangement.

9. A method for preparing physical vapor phase micro / nano powders with improved electrode protection, material thermal state, and preparation process stability, characterized in that, Based on the auxiliary device according to any one of claims 1-8, the implementation includes the following steps: Step 1, material pretreatment and device assembly: Put the metal block material (5) into the ceramic crucible (3) and place it flat; fix the ceramic crucible (3) on the anode seat (4); connect the gas line and cooling water line, check the sealing performance, and ensure that there is no air or water leakage; The second step is to adjust the vacuum and protective atmosphere: start the vacuum pump to remove the air from the cavity where the auxiliary device is located; turn off the vacuum pump and fill the cavity with nitrogen to maintain a stable protective atmosphere. The third step involves the induction heating coil (6) assisted in heating, which is simultaneously activated with the electric arc. Dual airflow control is also initiated at the same time. Specifically: Turn on the cooling circulating water system and the high-frequency induction power supply. Heat the metal block material (5) in the ceramic crucible (3) through the induction heating coil (6). Simultaneously start the DC arc power supply connected to the plasma gun and adjust the current and voltage to ignite the arc. An arc is formed between the cathode tip (15) and the metal block material (5) to form a high-temperature nitrogen plasma. The metal block material (5) is heated and melts and forms a molten liquid surface in the ceramic crucible (3). The liquid surface evaporates and vaporizes simultaneously. Adjust the cathode position by lifting shaft (12) until the electric arc between the cathode and the molten liquid surface remains stable; at the same time, start the first gas flow and the second gas flow to form a stable molten pool; Step 4, Powder Collection: The preparation process continues, with real-time monitoring of various parameters, including DC arc current, DC arc voltage, high-frequency induction power supply output power, vacuum chamber pressure, first gas flow rate, second gas flow rate, and cooling circulating water flow rate. The preparation is considered complete when the preset preparation time is reached, or when the amount of powder collected during continuous preparation reaches the preset value and the above process parameters remain stable. After preparation is completed, each device is turned off in sequence, and the chamber is allowed to cool to room temperature. The collection device is then removed to obtain nanopowder.

10. The method for preparing physical vapor phase micro / nano powders according to claim 9, characterized in that, In the auxiliary method: In the second step, until the vacuum level reaches below 1 Pa, the nitrogen pressure in the cavity is 40~80 kPa; In the third step, the current range is adjusted to 50~200A and the voltage range is adjusted to 20~80V, thereby igniting the electric arc; the lifting shaft (12) is adjusted to adjust the lifting linear distance to 5~10cm; the high-frequency induction power output power is 15~30kW, the first airflow adjustment nitrogen flow range is 5~15L / min, to purge the cathode tip, the second airflow adjustment nitrogen flow range is 10~30L / min, the nozzle deflection angle is 5~30°, the cooling circulating water flow is 80~160L / min, and the inlet water temperature is ≤25℃; In the fourth step, the parameters monitored in real time include: DC arc current, with fluctuation values ​​of 3-5% of the normal preset value; DC arc voltage, with fluctuation values ​​of ±1-5V of the preset value; high-frequency induction power supply output power of 15-30kW and vacuum chamber pressure, with fluctuation values ​​of ±2% of the preset value; first gas flow rate fluctuation value of ±5% of the preset value; second gas flow rate fluctuation value of ±5% of the preset value; cooling circulating water pressure of 0.25-0.3MPa; and circulating water outlet temperature of <50℃.

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