An automated control feeding system for plasma powder preparation and its implementation method

Abstract

An automated control feeding system and method for plasma powder preparation belongs to the technical field of submicron / nano powder material preparation equipment. The feeding system includes an automatic feeding device and a plasma reaction chamber connected to the automatic feeding device. The automatic feeding device includes a conveying sealed top cover, a primary feeding bin, a gate valve, a secondary feeding bin, a sensor, and a conveying cylinder unit. The plasma reaction chamber includes a reaction chamber, a cathode operating rod vertically arranged within the reaction chamber, a cathode at the bottom of the cathode operating rod, a crucible below the cathode, and an anode copper seat. Automatic replenishment and supply of metal raw materials are achieved by monitoring the voltage change between the cathode and the molten metal surface of the anode. This invention automatically controls the opening and closing of the feeding system based on voltage feedback signals, ensuring long-term stable operation of the equipment and meeting the concentration requirements of the growth material inside the reaction chamber. The overall detachable structural unit can be replaced with a reduction gear unit of different structures to meet the feeding operation of raw materials with different morphologies.

Description

Technical Field

[0001] This invention belongs to the technical field of submicron / nano powder material preparation equipment. Specifically, it relates to an automatic control feeding system and its implementation method in the process of preparing powder materials using DC arc plasma evaporation, and particularly to the application of automatic control of the feeding system based on the voltage signal between the arc cathode and the molten liquid surface in related technical fields. Background Technology

[0002] Metal nanoparticles possess excellent mechanical, thermal, acoustic, optical, and electromagnetic properties, and are widely used in fields such as machinery, powder metallurgy, electronics, chemical industry, aerospace, and environmental protection, including electronic pastes, electrode materials, magnetic liquids, chemical catalysts, coatings, and electromagnetic wave shielding materials.

[0003] Currently, methods for industrial mass production of metal nanoparticles include ball milling, chemical reduction, and physical vapor-phase condensation. Among these, the DC arc plasma method melts and evaporates the anode target into gaseous atoms using high-temperature plasma, which then undergoes nucleation and growth processes to ultimately form nano / micron-sized powder materials. This method is simple to implement, highly efficient, environmentally friendly, allows for controllable particle size, size distribution, and microstructure, enables continuous powder production over extended periods, and is easy to operate, making it the preferred method for large-scale industrial production of metal powder materials. A complete DC arc plasma method for producing metal nanoparticles typically includes a reaction chamber, condensation chamber, collection chamber, vacuum system, cooling system, automatic feeding system, and operating system. The automatic feeding system is crucial for ensuring continuous operation of the equipment and providing sufficient raw materials for growth. Patents CN216863033U and CN 104907575A disclose a feeding machine that takes into account the feeding method and device for elemental metals and alloy raw materials. It can achieve uniform quantitative feeding under the same atmosphere or pressure conditions as the connected production equipment. This method ensures continuous feeding at a fixed feeding rate. However, it does not fully consider the real-time situation in the production equipment connected to the feeding device and cannot automatically adjust the feeding start and feeding rate according to the real-time situation. Summary of the Invention

[0004] This invention addresses the shortcomings of existing automatic feeding devices in physical vapor phase (PVP) powder preparation equipment, specifically the DC arc plasma method. It provides a device and method for controlling the opening and closing of the feeding system using the voltage signal between the arc cathode and the molten metal surface (anode), thereby achieving automatic feeding based on the real-time situation inside the powder generation reaction chamber. The principle lies in the fact that during the preparation of powder materials using high-temperature plasma, the voltage between the electrodes of the DC arc changes with their distance. Specifically, the distance between the cathode and the molten metal surface determines the magnitude of the voltage signal; a larger distance results in a larger voltage signal amplitude, and vice versa. Based on this, this invention feeds back the real-time monitored arc voltage signal to the servo motor of the feeding system, controlling its opening and closing, thus achieving automatic control of the feeding system's operation.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] An automatic control feeding system for plasma powder preparation, the feeding system comprising an automatic feeding device and a plasma reaction chamber connected to the automatic feeding device.

[0007] The automatic feeding device includes a conveying sealed top cover 1, a primary feeding bin 2, an automatic / manual control gate valve 4, a secondary feeding bin 5, a sensor 6, and a conveying cylinder unit. Specifically:

[0008] The primary feeding hopper 2 is equipped with a conveying and sealing top cover 1, which is used to hold the metal raw material 3. It has an extraction port 11 and an inflation port 12 on its side, allowing for separate vacuuming and gas filling to maintain the automatic feeding device and the connected plasma reaction chamber at the same pressure. The secondary feeding hopper 5 is located below the primary feeding hopper 2, and a sensor-controlled gate valve 4 connects them. The gate valve 4 controls the release of the metal raw material 3 from the primary feeding hopper 2 to the secondary feeding hopper 5. A sensor 6 is installed between the secondary feeding hopper 5 and the conveying cylinder 10 to monitor the presence of the metal raw material 3 in the secondary feeding hopper 5. The secondary feeding hopper 5 is connected to the plasma reaction chamber via the lower conveying cylinder unit. The feeding cylinder unit includes a feeding cylinder 10, a feeding rotating rod 8 inside the feeding cylinder 10, feeding blades 9 on the feeding rotating rod 8, and a servo motor 7 at the top of the feeding cylinder 10. The feeding cylinder 10 is arranged at an angle, with its bottom extending through the side wall of the reaction chamber 13 and above the crucible 17. The secondary feeding bin 5 is connected to the top of the feeding cylinder 10. The servo motor 7 drives the feeding rotating rod 8 to rotate, which in turn drives the feeding blades 9 to rotate, thus slowing down the metal raw material falling from the secondary feeding bin 5 and controlling the amount of raw material conveyed. This not only avoids splashing of molten liquid caused by rapid falling of raw material, but also avoids excessively dense falling of raw material.

[0009] The plasma reaction chamber includes a reaction chamber 13, a cathode operating rod 14 vertically arranged within the reaction chamber 13, a cathode 15 at the bottom of the cathode operating rod 14, a crucible 17 below the cathode 15, and an anode copper seat 19 below the crucible 17. During powder production, the metal raw material 3 located in the crucible 17 is first converted into a molten state by plasma 16, then continues to evaporate into an atomic gaseous state, and finally undergoes nucleation and growth to obtain powder particles. The magnitude of the voltage signal 20 between the cathode 15 and the molten metal surface 18 of the anode is proportional to the distance between the cathode 15 and the molten metal surface 18, serving as the electrical signal basis for judging the amount of material in the crucible.

[0010] Furthermore, the servo motor 7 has a motor rotation frequency of no more than 50Hz, corresponding to a rotation speed of no more than 12rpm / min.

[0011] Furthermore, the conveying blade 9 is a fan-shaped baffle connected to the conveying rotating rod 8, which gradually changes from its front end (at the outlet of the secondary feeding hopper) to its end (inside the reaction chamber). The size of its central angle gradually increases, and the arrangement distance between the baffles changes from sparse to dense, forming a blade group to decelerate the falling raw material and control the amount of raw material conveyed.

[0012] Furthermore, the automatic / manual control gate valve 4 is used to isolate the primary feeding hopper connected to the outside and the secondary feeding hopper connected to the reaction chamber. The opening of the gate valve can be automatically controlled by a voltage change signal, or it can be opened manually.

[0013] Furthermore, the conveying cylinder 10 has a diameter of 60 mm, a wall thickness of 3 mm, and forms a 30° angle with the horizontal plane.

[0014] A method for implementing an automated feeding system for plasma powder preparation involves monitoring the voltage change between the cathode 15 and the molten metal surface 18 of the anode to automatically replenish and supply the metal raw material 3. Specifically, the method automatically controls the opening and closing of the feeding system based on voltage feedback signals, ensuring long-term stable operation of the equipment and meeting the concentration requirements of the growth material inside the reaction chamber. The method includes the following steps:

[0015] The first step, before preparing the powder, is to add sufficient metal raw material 3 to crucible 17, ensuring that the raw material 3 remains sufficient even after complete melting into molten metal. Generally, the preferred addition amount is 2 / 3 of the crucible's capacity. Sufficient raw material is then added to the primary feeding chamber 2 as the subsequent automatic feeding material; the addition amount should not exceed 4 / 5 of the chamber's volume. The entire system (primary and secondary feeding chambers, reaction chamber, and the entire circulation system) is evacuated and filled with working gas. The working current is set, the arc is ignited, and the cathode movement is controlled to form a stable plasma, allowing the raw material 3 in crucible 17 to completely melt into a molten state. The cathode 15 is adjusted to an appropriate position. At this point, the voltage between the cathode and anode remains at a stable value, serving as the predetermined value for the feedback voltage signal. Typically, within a certain timeframe, generally 5-10 minutes, the molten liquid level does not drop significantly, and the voltage signal value remains basically stable, with possible voltage signal fluctuations within ±2V.

[0016] The second step involves setting the automatic / manual control mode of the gate valve to "automatic" on the control panel. This means that the opening and closing of the gate valve 4 is automatically controlled by the motor driven by the excitation signal. The amplitude of the voltage signal 20 for the automatic feeding response is set, the opening time of the gate valve 4 for each feeding cycle is set, and the rotation frequency of the servo motor 7 is set. Subsequently, the feeding control system monitors the changes in the electrode voltage signal 20 in real time, awaiting the automatic feeding signal. Furthermore, the voltage-feeding response system eliminates the possibility of slight, instantaneous voltage signal changes due to accidental factors; that is, instantaneous voltage changes (below ±2V amplitude) will not trigger an automatic feeding system response, ensuring stable system operation.

[0017] Thirdly, after a period of time, as the molten metal surface 18 drops to a certain height due to material evaporation, the voltage rises. When the control system detects that the voltage rise has reached the set change amplitude (usually set to a voltage signal increase of 5V or more above the initial value and remain unchanged for at least 10 seconds), the automatic feeding system responds: the servo motor 7 starts, and after 5 seconds, the gate valve 4 automatically opens, dropping a certain amount of metal raw material 3 before automatically closing (due to the rapid falling speed of the raw material, the gate valve is usually set to open for 1-3 seconds at a time). The metal raw material 3 passes through the conveyor cylinder 10, is buffered and controlled by the conveyor blades 9, and finally falls slowly into the crucible 17. After the metal raw material 3 falls to the molten metal surface 18, the molten metal surface 18 rises, and the voltage signal 20 decreases accordingly to close to the predetermined voltage value from the first step. Once the voltage signal 20 decreases to the point where it no longer changes, indicating that the metal raw material 3 in the conveyor cylinder has completely fallen, the servo motor 7 shuts off, completing one automatic feeding operation. Typically, one feeding operation (from the start of the feeding response to the servo motor shutting off) takes 60-90 seconds. Throughout the entire automatic feeding process, the plasma operates normally, evaporating the molten liquid surface 18. When the metal raw material 3 falls into the crucible, it will not affect the normal operation of the plasma.

[0018] In the fourth step, after one automatic feeding cycle, the molten liquid level 18 in crucible 17 rises due to the addition of raw material 3, the distance between cathode 15 and molten liquid level 18 decreases, and the voltage drops. After a short period of time, the voltage stabilizes, and the system automatically compares the current stable voltage value with the stable voltage value before automatic feeding. If the difference is greater than -2V, it is determined that the automatic feeding amount is appropriate, and the system is in a non-feeding state; conversely, if the difference is less than -2V, it is determined that the feeding amount is insufficient, and the automatic feeding system responds a second time to continue feeding until the feeding amount reaches the appropriate level. During the series of processes such as automatic feeding, reaching the appropriate feeding amount, and restarting feeding, the raw material sensor 6 is used to monitor the falling of raw material 3 in the primary feeding bin and maintains consistency with the automatic feeding operation. Once the automatic feeding response guides the gate valve 4 to open, but the sensor 6 does not detect any metal raw material 3 falling, the system will alarm, indicating that the spare metal raw material 3 in the primary feeding bin 2 is exhausted. At this time, it is necessary to open the conveying sealing top cover 1 to replenish the raw material. Before replenishing raw materials, the automatic feeding system and gate valve 4 should be turned off. After the metal raw material 3 is replenished, the primary feeding hopper 2 should be evacuated and working gas should be added to reach the working gas pressure value of the entire system.

[0019] The specific working principle and innovation of this invention are as follows: The physical vapor phase method uses a high-temperature heat source (thermal plasma, high-energy laser, resistance heating, electromagnetic induction heating, etc.) to evaporate bulk raw materials and form a gaseous state. When the gas concentration reaches a supersaturated state and approaches the melting point of the raw material, nucleation centers begin to appear, forming solid-phase crystal nuclei that gradually grow into particles. In this process, the gas concentration of the growing material is a key factor in nucleation and growth. The innovation of this invention lies in automatically controlling the delivery of raw materials based on the working voltage of the plasma, i.e., the voltage signal between the arc electrodes, so that the formed gas concentration is continuously and stably maintained within the required range, thereby improving the quality of the powder product and meeting the requirements for particle size and distribution.

[0020] The beneficial effects of this invention are as follows:

[0021] (1) The present invention can accurately replenish the raw materials in the crucible of the reaction chamber in real time, which solves the problem that common feeding devices can only set a fixed feeding rate and cannot change the feeding rate as needed and make timely adjustments. It can achieve the gas phase concentration requirements in the long-term powdering process, thereby ensuring the quality of the powder product.

[0022] (2) The present invention relates to all parameters that can be set as needed, such as the stable change range of the feedback voltage signal, the opening and speed of the servo motor according to the voltage signal, the opening and duration of the gate valve, and the voltage signal judgment criteria of the feeding state, which can meet the needs of continuous automatic feeding in the preparation of various powder materials.

[0023] (3) In addition, the conveying rotary rod and conveying blades involved in this invention are integral detachable structural units that can be replaced with deceleration units of different structures (such as blade spacing and shape, or spiral auger structure) to meet the feeding operation of raw materials with different morphologies (spherical, sheet-like, irregular morphology). Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the automatic feeding control system of the present invention;

[0025] Figure 2 This is a schematic diagram of the internal structure of the feed cylinder unit of the present invention.

[0026] In the diagram: 1. Conveying sealing top cover, 2. Primary feeding bin, 3. Metal raw material, 4. Slide valve, 5. Secondary feeding bin, 6. Sensor, 7. Servo motor, 8. Conveying rotating rod, 9. Conveying blade, 10. Conveying cylinder, 11. Air extraction port, 12. Air filling port, 13. Reaction chamber, 14. Cathode operating rod, 15. Cathode, 16. Plasma, 17. Crucible, 18. Molten liquid surface, 19. Anode copper seat, 20. Voltage signal. Detailed Implementation

[0027] The above-described contents of the present invention will be further described in detail below with reference to specific embodiments, but the scope of the present invention is not limited to the following examples.

[0028] Specifically, this embodiment uses nickel spheres with a diameter of 5-15mm as the raw material. Figure 2 The conveying blade shown is used as a deceleration unit with a working current of 600A, working gas of N2, and gas pressure of 80kPa to prepare submicron (200nm) nickel powder.

[0029] An automatic control feeding system for plasma powder preparation, the feeding system comprising an automatic feeding device and a plasma reaction chamber connected to the automatic feeding device.

[0030] The automatic feeding device includes a conveying sealed top cover 1, a primary feeding bin 2, an automatic / manual control gate valve 4 for metal raw materials, a secondary feeding bin 5, a sensor 6, and a conveying cylinder unit. The primary feeding bin 2 has a conveying sealed top cover 1 on its top, which is used to hold metal raw materials 3. It has an exhaust port 11 and an inflation port 12 on its side. The secondary feeding bin 5 is located below the primary feeding bin 2, and the automatic / manual control gate valve 4 connects them. The metal raw materials 3 enter the primary feeding bin 2 from the outside and then enter the secondary feeding bin 5 through the automatic / manual control gate valve 4. The sensor 6 monitors the presence of metal raw materials 3 in the secondary feeding bin 5 and sends a signal back to the gate valve 4 to control its opening and closing. The secondary feeding bin 5 is connected to the plasma reaction chamber through the lower conveying cylinder unit. The feeding cylinder unit includes a feeding cylinder 10, a feeding rotating rod 8 inside the feeding cylinder 10, feeding blades 9 on the feeding rotating rod 8, and a servo motor 7 at the top of the feeding cylinder 10. The feeding cylinder 10 is arranged at an angle, with its bottom extending through the side wall of the reaction chamber 13 and above the crucible 17. The secondary feeding bin 5 is connected to the top of the feeding cylinder 10. The servo motor 7 drives the feeding rotating rod 8 to rotate, which in turn drives the feeding blades 9 to rotate.

[0031] The plasma reaction chamber includes a reaction chamber 13, a cathode operating rod 14 vertically arranged within the reaction chamber 13, a cathode 15 at the bottom of the cathode operating rod 14, a crucible 17 below the cathode 15, and an anode copper seat 19 below the crucible 17. During powder preparation, the metal raw material 3 located in the crucible 17 is first converted into a molten state by plasma 16, then continues to evaporate into an atomic gaseous state, and finally moves to a low-temperature region to nucleate and grow into submicron / nano powder. The magnitude of the voltage signal 20 between the cathode 15 and the molten metal surface 18 of the anode is proportional to the distance between the cathode 15 and the molten metal surface 18.

[0032] The specific implementation steps are as follows:

[0033] 1. Add nickel ball raw material, accounting for 2 / 3 of the total capacity of crucible 17, into crucible 17. After installing electrode 15, close the top cover of the generation chamber. Add nickel ball raw material, accounting for 4 / 5 of the total capacity (30kg), into the primary feeding bin 2. Close the conveying sealing top cover 1. Evacuate the entire chamber, including the feeding bin, to below 1Pa and fill it with N2 at a pressure of 80kPa. Set the working current to 600A, start the arc, and move the cathode operating rod 14 to adjust the electrode spacing so that the nickel ball raw material in crucible 17 melts into a liquid state (this process lasts for 5-10 minutes). Maintain the distance between cathode 15 and the molten liquid surface 18 to 5cm. At this time, the arc voltage is maintained at a stable value of 45V, which is used as the predetermined value for the feedback voltage signal.

[0034] 2. On the control panel, set the automatic / manual control mode of the slide gate valve 4 to "automatic," set the amplitude of the voltage signal 20 for automatic feeding response to 6V (i.e., a voltage rise of 6V), set the servo motor frequency to 50Hz, and set the opening and closing time of the slide gate valve 4 to 3s. The control system will then monitor the changes in the equipment voltage signal 20 in real time, waiting for the voltage rise exceeding 6V due to the drop in the molten metal level 18 to serve as the trigger signal to activate the automatic feeding device (the monitoring system will ignore cases where the voltage changes instantaneously and then returns to its normal value).

[0035] III. The powder-making process after arc ignition lasts for 50 minutes. The molten liquid level 18 in crucible 17 drops, causing the working voltage to rise by 6V, reaching 51V or higher. After maintaining this voltage for more than 10 seconds, the automatic feeding device responds: the servo motor starts (50Hz), initiating raw material supply. Metallic nickel balls (typically weighing 2-4kg, falling within 3 seconds) are fed through the conveyor cylinder 10, decelerated by the conveyor blades 19, and finally fall into crucible 17. Once the voltage signal 20 drops back to approximately 45V and stabilizes, the servo motor 7 automatically shuts off, thus completing one automatic feeding operation. Taking nickel balls as an example, the feeding time—from the system's response to the raw material falling into the crucible—typically takes 60-100 seconds.

[0036] 4. After one automatic feeding is completed, the molten liquid level 18 in crucible 17 rises due to the addition of metal raw material 3, the distance between cathode 15 and the liquid surface decreases again, and the voltage signal 20 drops to close to 45V. The system automatically compares the stable voltage value at this time with the predetermined voltage value of 45V to determine whether the amount of automatic feeding is appropriate (for the nickel ball raw material preparation process in this embodiment, the amount of feeding when the gate valve 4 automatically opens for 3 seconds and then automatically closes is sufficient to meet the raw material supply). The system returns to the monitoring state and waits for the next feeding signal. The feeding operation is repeated to ensure a continuous and stable supply of raw materials, which accompanies the continuous powder production process.

[0037] 5. After the nickel material in the primary feeding hopper is depleted and sensor 6 triggers an alarm, promptly shut down the automatic feeding system and gate valve 4, open the conveying sealing top cover 1 to replenish nickel material, and evacuate the primary feeding hopper 2 while replenishing working gas to reach the overall system's working pressure value. After replenishing the nickel material, reopen the automatic feeding system. The automatic control feeding system can ensure continuous and stable operation of the powder making equipment for 72 hours or more. This relies on the coordinated work of other components of the overall equipment. Any abnormality in any component will cause the equipment to stop or cease operation, such as if no operation is performed within ten minutes after the raw material sensor 6 triggers an alarm, or if the working conditions (air pressure, temperature, etc.) change drastically and trigger an alarm. Automatic feeding operation can only resume after the alarm is cleared.

[0038] 6. After the powder preparation time is completed, turn off the electric arc and keep the chiller running for more than 12 hours until the temperature inside the chamber is completely cooled to room temperature. Finally, collect the nickel powder obtained in this powder preparation process through a powder collection device, and classify the collected nickel powder to obtain submicron spherical nickel powder with a size of around 200 nm.

[0039] 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, the raw material conveying buffer and control structure unit, the amplitude and range of the feeding response voltage signal, and the time interval between opening and closing of the slide valve, etc., all of which fall within the protection scope of the present invention.

Claims

1. A kind of automatic control feeding system of plasma powder preparation, it is characterized in that, The feeding system comprises an automatic feeding device and a plasma reaction cavity connected with the automatic feeding device; The automatic feeding device comprises a feeding sealing top cover (1), a first-stage feeding bin (2), a second-stage feeding bin (5), a plug valve (4), a sensor (6) and a feeding cylinder unit; the first-stage feeding bin (2) is internally provided with metal raw materials (3), and is provided with an air exhaust port (11) and an air charging port (12) on the side surface, so that the automatic feeding device and the plasma reaction cavity are kept in the same air pressure condition; the second-stage feeding bin (5) is arranged below the first-stage feeding bin (2), and the plug valve (4) is arranged between the first-stage feeding bin (2) and the second-stage feeding bin (5); the sensor (6) is arranged between the second-stage feeding bin (5) and the feeding cylinder (10), and is used for monitoring the existence of the metal raw materials (3) in the second-stage feeding bin (5) and feeding a signal to the plug valve (4) to control the opening and closing of the plug valve (4); the second-stage feeding bin (5) is communicated with the plasma reaction cavity through the feeding cylinder unit below; the feeding cylinder unit comprises the feeding cylinder (10), a feeding rotating rod (8) in the feeding cylinder (10), feeding blades (9) on the feeding rotating rod (8) and a servo motor (7) on the top of the feeding cylinder (10); the feeding cylinder (10) is arranged in an inclined manner, and the bottom of the feeding cylinder (10) penetrates through the side wall of the reaction cavity (13) and extends into the upper portion of a crucible (17); the servo motor (7) drives the feeding blades (9) to rotate through the feeding rotating rod (8), so that the metal raw materials falling from the second-stage feeding bin (5) are decelerated, and the conveying amount of the raw materials is controlled; The plasma reaction cavity comprises a reaction cavity (13), a cathode operating rod (14) arranged in the reaction cavity (13) in a vertical manner, a cathode (15) at the bottom of the cathode operating rod (14), a crucible (17) below the cathode (15), and the crucible (17) arranged on an anode copper base (19); the metal raw materials (3) in the crucible (17) are converted into a molten state by plasma (16), continue to evaporate into an atomic gaseous state, and finally obtain powder particles through nucleation and growth; the size of a voltage signal (20) between the cathode (15) and the molten metal liquid surface of the anode is proportional to the spacing between the cathode (15) and the molten liquid surface (18); The opening and closing of the feeding system are automatically controlled by monitoring the voltage change between the cathode (15) and the molten metal liquid surface of the anode.

2. The automatic control feeding system for preparing plasma powder according to claim 1, wherein, The rotating frequency of the servo motor (7) is not greater than 50 Hz, and the corresponding rotating speed is not greater than 12 rpm / min.

3. The automatic control feeding system for preparing plasma powder according to claim 1, wherein, The feeding blades (9) are fan-shaped baffles connected to the feeding rotating rod (8) and gradually changing from the front end to the tail end, the central angles of the fan-shaped baffles gradually increase, the arrangement distances between the baffles change from sparse to dense, the baffles form a blade group, and the conveying amount of the raw materials is controlled.

4. The automatic control feeding system for preparing plasma powder according to claim 1, wherein, The diameter of the feeding cylinder (10) is 60 mm, the thickness of the cylinder wall is 3 mm, and the angle between the feeding cylinder (10) and the horizontal plane is 30°.

5. A method for implementing an automatic control feeding system for the production of plasma powders according to any one of claims 1 to 4, characterized in that, The automatic replenishment and provision of the metal raw materials (3) are realized by monitoring the voltage change between the cathode (15) and the molten metal liquid surface of the anode, and the method comprises the following steps: The first step, first add metal raw material (3) in the crucible (17), ensure that the metal raw material (3) in the crucible is still sufficient after completely melting into metal liquid; Add raw material in the first stage feeding bin (2) as subsequent automatic feeding raw material; The whole system is vacuumized and filled with working gas; Set the working current, arc ignition, control the cathode movement to form a stable plasma (16), so that the metal raw material (3) in the crucible (17) is completely melted into liquid, adjust the cathode (15) to the appropriate position, at this time the voltage between the cathode and the anode is kept at a stable value, which is the predetermined value of the feedback voltage signal; The second step, set the opening and closing of the plug valve (4) to be automatically controlled by the excitation signal driving motor, set the voltage signal (20) change amplitude of the automatic feeding response, set the plug valve (4) opening time for one time feeding, set the servo motor (7) rotation frequency; After that, the feeding control system monitors the change of the electrode voltage signal (20) in real time and waits for the automatic feeding signal; The third step, after the metal molten liquid surface (18) drops due to material evaporation, the voltage rises, and the control system monitors the voltage rise to reach the set change amplitude, and the automatic feeding system responds: the servo motor (7) starts, the plug valve (4) automatically opens, and automatically closes after the metal raw material (3) falls; The metal raw material (3) falls into the crucible (17) through the feeding cylinder (10) at low speed, and the voltage signal (20) decreases accordingly, and the feeding servo motor (7) automatically closes when the voltage signal (20) reaches the voltage stable amplitude of the first step, completing one automatic feeding operation; The fourth step, after one automatic feeding is completed, the molten liquid surface (18) in the crucible (17) moves up due to the addition of metal raw material (3), the distance between the cathode (15) and the molten liquid surface (18) becomes smaller, and the voltage decreases; After waiting for a short time for the voltage to reach a stable state, the system automatically compares the voltage stable value at this time with the voltage stable value before automatic feeding, if the difference between the two is greater than-2V, it is judged that the automatic feeding amount is appropriate, and the system is in non-feeding state; Otherwise, if the difference between the two is less than-2V, it is judged that the feeding amount is insufficient, and the automatic feeding system responds again, and continues to feed until the feeding amount reaches the appropriate state.

6. The method of claim 5, wherein the method comprises: In the whole process, the sensor (6) is used to monitor the falling of the metal raw material (3) in the first stage feeding bin, and to keep consistent with the automatic feeding operation, once the automatic feeding response leads to the opening of the plug valve (4), but the sensor (6) does not monitor the falling of the metal raw material (3), the system will alarm, indicating that the standby metal raw material (3) in the first stage feeding bin (2) is exhausted, at this time the raw material needs to be supplemented; Before supplementing the raw material, the automatic feeding system and the plug valve (4) are closed, and after the metal raw material (3) is supplemented, the first stage feeding bin (2) is vacuumized and the working gas is supplemented to reach the working gas pressure value of the whole system.

7. The method for implementing an automatic control feeding system for plasma powder preparation according to claim 5, characterized in that, In the first step, the metal raw material (3) added in the crucible (17) is 2 / 3 of the capacity of the crucible, and the amount of raw material added in the first stage feeding bin (2) cannot exceed 4 / 5 of the volume of the feeding bin.

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