System for preparing nanoscale powder through microwave plasma spheroidizing and refining

Abstract

The invention relates to a system for preparing nanoscale powder through microwave plasma spheroidizing and refining. The system comprises a powder feeder, an atomizing mechanism, a plasma generating mechanism, a vacuumizing assembly and a reaction tank. The plasma generating mechanism comprises a magnetron, a waveguide structure and a quartz tube, and the magnetron is coupled with the quartz tube through the waveguide structure to generate microwave plasma; the atomization mechanism is connected to the upper end of the quartz tube; the powder feeder is connected with and used for conveying powder to be spheroidized to the atomizing mechanism; a feed opening is formed in the center of the top of the reaction tank, and the lower end of the quartz tube is partially arranged in the reaction tank through the feed opening or is connected to the feed opening; a plasma high-temperature area is formed at the upper part of the cavity of the reaction tank; the vacuumizing assembly is connected with the reaction tank through the filter and the cyclone separator in sequence and can adjust the vacuum degree in a cavity of the reaction tank, so that the length of a microwave plasma torch blown out of the lower end of the quartz tube in the plasma high-temperature area is adjustable.

Description

Technical Field

[0001] The present invention relates to the technical field of powder metallurgy, and in particular to the field of spheroidizing and refining powders by utilizing microwave plasma technology. Background Art

[0002] Powder preparation technology based on powder metallurgy has a decades-long history. In recent years, with the rise of new energy technologies, market demand for positive and negative electrode powder materials and various oxide powder materials has increased. Simultaneously, demand for spherical powders has also increased, placing increasing demands on powder quality, particularly particle size, which has gradually increased from micrometers to submicrometers and nanometers. The smaller the powder particle size, the higher the requirements for preparation technology, and the higher the value of the powder. In terms of powder types, from the initial metal powders to ceramic powders, there is a significant demand for powders with melting points ranging from a few hundred degrees to three thousand degrees. The finer the powder particle size and the higher the sphericity, the higher the value.

[0003] Currently, ball milling is commonly used in the preparation of ultrafine powders on the market. This method has the following problems: 1. Time-consuming: The ball milling process may require a long processing time, affecting production efficiency; 2. Thermal effect problem: Prolonged grinding will cause the material to overheat, which may affect product performance or cause sintering; 3. High equipment investment: The investment cost of the mill and related accessories is relatively high, which may cause a certain burden on small and medium-sized enterprises; 4. Wear problem: Grinding balls and grinding jars are prone to wear after long-term use and need to be replaced regularly, increasing maintenance costs.

[0004] Currently, chemical methods, such as evaporation, are commonly used to prepare high-melting-point powders on the market. However, this method has disadvantages such as difficulty in collection and long reaction time, which is not conducive to large-scale production.

[0005] In addition, there is a process for powder spheroidization preparation on the market that uses microwave plasma to spheroidize powder. Microwave plasma technology has the characteristics of no electrode pollution, environmental friendliness, good temperature field consistency and a wide working range. However, this microwave plasma process equipment has the following shortcomings: 1. The melting process conditions required for metal and non-metal powders of different materials and different powder particle sizes are different, and the existing equipment cannot be adjusted in terms of process according to different process requirements, so its adaptability is poor; 2. Powders, especially metal powders, are easy to stick to the wall of the quartz tube after melting, which not only affects its service life, but also reflects the microwave transmission, greatly reducing the energy density of the microwave plasma and the spheroidization rate, resulting in the inability to achieve continuous and stable production for a long time.

[0006] Therefore, there is still a large gap in the existing technology for the preparation of ultrafine and high melting point powders. Based on the above situation, this paper designs a device that uses microwave plasma technology to spheroidize and refine powders, which can simultaneously realize the spheroidization and refinement of powders. Its purpose is to prepare nano-scale powder materials for use in various fields. Summary of the Invention

[0007] The purpose of the embodiments of the present invention is to address the structural shortcomings of the prior art and to propose a system for preparing nano-scale powders by using microwave plasma spheroidization and refinement, so as to solve the defects in the prior art.

[0008] In order to achieve the above-mentioned object of the invention, the system for preparing nano-scale powder by using microwave plasma spheroidization and refinement is implemented by the following technical solutions:

[0009] A system for preparing nano-scale powder by using microwave plasma spheroidization and refinement, characterized in that: the system includes a powder feeder, an atomizing mechanism, a plasma generating mechanism, a vacuum assembly and a reaction tank; the plasma generating mechanism includes a quartz tube that is through-through and is used to form microwave plasma inside the tube; the atomizing mechanism is connected to the upper end of the quartz tube and is used to provide an atomized material mixed with a carrier gas and the powder to be spheroidized into the quartz tube; the powder feeder is connected and is used to transport the powder to be spheroidized to the atomizing mechanism; the center of the top of the reaction tank has a feed opening, and the quartz tube has a feed opening. The lower end is partially arranged in the reaction tank through the discharge port, or is connected to the discharge port; a plasma high-temperature area is formed on the upper part of the cavity of the reaction tank; the vacuum pumping component is connected to the reaction tank through the filter and the cyclone separator in sequence, and can adjust the vacuum degree in the cavity of the reaction tank, so that the microwave plasma torch blown out from the lower end of the quartz tube can be adjusted in length within the plasma high-temperature area, and the lower part of the cavity of the reaction tank also forms a spheroidization area that can solidify the molten powder when falling; the filter, cyclone separator and the bottom of the reaction tank are all provided with a powder collecting tank.

[0010] The atomization mechanism includes a cylindrical main body, the upper end opening of the main body forms an inlet for the powder to be spheroidized, the lower end opening of the main body is connected to the upper end of the quartz tube, and a plurality of first air inlets are formed on the side wall of the main body. The air inlet direction of the first air inlets is configured to be along the tangent direction of the inner cavity of the circular cross-section of the main body, so that the carrier gas forms a cyclone in the inner cavity of the main body; the first air inlets form a carrier gas inlet joint on the outside of the main body.

[0011] A plurality of second air inlets are also formed on the side wall of the main body, and the second air inlets form a carrier gas inlet connector on the outside of the main body. The inner wall of the main body is also surrounded by an annular partition to form an annular cavity. The second air inlet is arranged in the annular cavity, and the first air inlet is arranged outside the annular cavity; the annular cavity is also provided with a plurality of air outlet holes opening in the direction of the lower end of the main body.

[0012] The annular partition is arranged at the upper end of the main body, and it at least includes an annular side wall for forming a central passage of the main body, and a bottom surface opening toward the lower end of the main body; the multiple air outlets are evenly distributed on the bottom surface; the first air inlet is located below the second air inlet.

[0013] The number of the first air inlets and the second air inlets are four, and the first air inlets are axially located on the same main body cross-section and evenly distributed along it; the air intake direction of the second air inlets is configured to be along the tangent direction of the inner cavity of the main body cross-section, and the second air inlets are axially located on the same main body cross-section and evenly distributed along it.

[0014] The powder feeder includes a vibrating plate that is driven by a vibration mechanism to vibrate. The vibrating plate is an inverted frustum-shaped hollow structure. A feed port is provided at the center of the top plate of the upper portion thereof. A powder conveying trough extending in a conical spiral shape is formed along the side wall of the inner cavity thereof. The lower end of the powder conveying trough extends to the bottom of the vibrating plate. A drop hole penetrating the vibrating plate is provided on the upper portion thereof on the conveying path. The outer end of the drop hole is connected to the inlet of the powder to be spheroidized of the atomizing mechanism through a conveying pipeline.

[0015] Along the conveying path of the powder conveying trough, the powder conveying trough is also provided with a notch behind the blanking hole, and the top plate of the vibration disk is provided with a high-pressure dispersion gas inlet corresponding to the notch. The notch is configured so that when the high-pressure gas blown into the high-pressure dispersion gas inlet rebounds through the notch, it can be blown toward the inside of the top plate.

[0016] The bottom of the vibrating plate is arched from the edge to the center, and the lower end of the powder conveying trough extends to the outer edge of the bottom of the vibrating plate; in addition, a feed pipe is provided on the upper part of the vibrating plate, and the feed port is formed on the upper part of the feed pipe, and the lower end thereof extends into the vibrating plate cavity and is located directly above the bottom of the vibrating plate.

[0017] A plurality of temperature sensors are evenly distributed on the plasma high-temperature area of ​​the reaction tank, and a transparent observation window for observing the plasma high-temperature area therein is opened on the tank wall of the reaction tank.

[0018] The vacuum pump assembly includes a water ring pump, a Roots pump and a proportional valve. The Roots pump and the proportional valve are connected in parallel, and one end of the Roots pump and the proportional valve are connected to the water ring pump, and the other end is connected to the filter.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) Compared with the prior art, the present invention provides a system for preparing nano-scale powders by using microwave plasma spheroidization and refinement. The system adopts microwave plasma heating and can melt any raw material with a melting point below 3000 degrees, not limited to metal or non-metal powders, and can meet common market needs. The system includes a powder feeder, an atomizing mechanism, a plasma generating mechanism, a vacuum pumping component and a reaction tank. Therefore, the equipment has the conditions for powder preparation under vacuum and has advantages in controlling the oxygen content of the powder. At the same time, by adjusting the vacuum degree in the reaction tank, the plasma arc length under different vacuum degrees is different, and the process can be adjusted according to the requirements of different processes.

[0021] (2) A special powder feeder is used to disperse irregular powder raw materials using high-frequency vibration + high-pressure gas dispersion, especially for powders with high viscosity and easy to agglomerate.

[0022] (3) The microwave plasma torch adopts a unique cyclone design with multiple gases set inside, including plasma center gas and side gas. The center gas generates high-temperature plasma, and the side gas is set on the inner wall of the quartz tube to prevent powder from adhering to the quartz tube wall.

[0023] (4) The equipment adopts full closed-loop control, which can achieve stable control of microwave power, vacuum degree, and pressure inside the equipment to ensure the stability of equipment operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above features and advantages of the present invention will become more clear and easily understood through the following description of exemplary embodiments thereof in conjunction with the accompanying drawings.

[0025] Figure 1 This is an overall schematic diagram of a system with a cabinet for preparing nano-scale powder according to an embodiment of the present invention;

[0026] Figure 2 A front view of a system for preparing nano-scale powder according to an embodiment of the present invention;

[0027] Figure 3 A side view of a system for preparing nanoscale powder according to an embodiment of the present invention;

[0028] Figure 4 A schematic three-dimensional diagram of a system for preparing nano-scale powder according to an embodiment of the present invention;

[0029] Figure 5 This is a three-dimensional schematic diagram of a powder feeder according to an embodiment of the present invention;

[0030] Figure 6 This is an exploded view of a powder feeder according to an embodiment of the present invention;

[0031] Figure 7 A top view of the plasma generating mechanism, reaction tank, and atomizer of an embodiment of the present invention;

[0032] Figure 8 for Figure 7 AA sectional view;

[0033] Figure 9 is a cross-sectional view of the atomizer portion of an embodiment of the present invention;

[0034] Figure 10 A three-dimensional schematic diagram of an atomizer according to an embodiment of the present invention

[0035] Figure 11 is a cross-sectional view of a cyclone separator according to an embodiment of the present invention;

[0036] Figure 12 2 is a cross-sectional view of a filter according to an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The following describes the implementation of the present invention using specific embodiments. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. Obviously, the embodiments described are only a portion of the present invention, not all of it. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0038] The terms "front", "back", "left", "right", "inside", and "outside" used in this specification are for the purpose of clarification only and are not intended to limit the scope of the present invention. Any changes or adjustments to their relative relationships, without substantially changing the technical content, should be considered within the scope of the present invention.

[0039] In the following descriptions of the embodiments, unless otherwise specified or limited, the term "connection" and other terms should be understood in a broad sense. For example, "connection" can refer to a fixed connection, a detachable connection, or an integral connection; it can refer to a mechanical connection or an indirect connection through an intermediate medium; it can refer to internal communication between two components or an interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0040] See also Figure 1-12 As shown, the embodiment of the present invention proposes a system for preparing nano-scale powder by using microwave plasma spheroidization and refinement, which includes a powder feeder 1, an atomizing mechanism 2, a plasma generating mechanism 3, a reaction tank 4, a cyclone separator 5, a filter 6 and a vacuum assembly 7. Among them:

[0041] Powder feeder 1

[0042] Different types of powders often exhibit different agglomeration characteristics due to different materials, different microscopic properties and even different storage conditions. For example:

[0043] The smaller the particles, the larger the specific surface area, and the stronger the van der Waals force between particles. At the same time, the smaller the particles, the more contact points there are, and the particles are more likely to attract and adhere to each other.

[0044] Powders with strong hygroscopicity tend to clump, while hydrophobic powders (such as certain plastic powders and hydrophobically treated metal powders) are less likely to form liquid bridges and are therefore looser.

[0045] When powder particles rub against each other or the container walls, static charge is easily generated. If the powder is an insulating material (such as plastic or dry organic matter), the charge is not easily dissipated, and particles of opposite charges will attract each other, causing them to agglomerate. In contrast, the static charge generated by highly conductive powders (such as metal powders) is quickly dissipated, and static agglomeration is less noticeable.

[0046] When powders are stored in silos or packaging, the lower layer of powder bears the weight of the upper layer. Prolonged static pressure forces particles into close contact, increasing van der Waals forces or promoting the formation of liquid / solid bridges, leading to compaction and agglomeration.

[0047] The present embodiment aims to provide a device that can be widely used to prepare various types of nano-scale powder materials. Therefore, for powders in different situations, the powder feeder in the present embodiment needs to be able to destroy weak agglomerations, improve fluidity, and achieve a good dispersion effect.

[0048] To achieve the above purpose, the powder feeder 1 of this embodiment adopts the method of high frequency vibration + high pressure gas dispersion. Figure 1-6 As shown, the powder feeder 1 mainly includes a vibration plate and a vibration mechanism 19 for driving the vibration plate to perform periodic mechanical vibration.

[0049] The main body of the vibrating plate is an inverted frustum-shaped plate 11, enclosed by a lid 12 at the top, forming a cavity. A feed pipe 13 is inserted through the center of lid 12. This circular tube has an inlet port 131 at its top, and its diameter is significantly larger than that of the inlet port. The lower end of the tube extends into the plate 11 and is located directly above the bottom of the plate 11. This structure allows powder to freely fall through the inlet port 131 and the tube 13 to the center of the bottom of the plate 11.

[0050] Correspondingly, the bottom of the disk 11 arches from the edge toward the center, with a hole at its center bolted to the output end of the vibration mechanism 19 via mushroom-head bolts 14. A powder conveying trough 15 extending in a tapered, spiral shape is provided on the sidewall of the disk 11. The lower end of this powder conveying trough extends to the outer edge of the bottom of the disk 11, and a drop hole 16 is provided at its upper end, extending through the vibration disk. The outer end of this drop hole 16 is connected to a conveying pipeline 17.

[0051] Along the powder conveying path of the powder conveying trough 15, a notch 18 is provided behind the discharge hole 16. The cover 12 has a high-pressure dispersion gas inlet 121 corresponding to this notch. Notch 18 is roughly crescent-shaped, and is configured so that high-pressure gas blown into the inlet 121 bounces off the notch 18 and then blows toward the inside of the cover 12. The airflow reflected by the notch 18 prevents powder from accumulating at the top of the conveying trough and reduces interference with the powder flow within the vibrating plate.

[0052] The purpose of providing the high-pressure dispersion gas inlet 121 is to provide positive pressure for the powder feeder 1, so that the powder dispersed by vibration is sent into the conveying pipeline 17 through the air flow, avoiding blockage at the bending part and the inclined upward part of the conveying pipeline 17.

[0053] The purpose of providing the gap 18 is that, as the powder moves forward along the powder conveying trough 15, some powder may skip the drop-out hole 16 and continue to move backward along the powder conveying trough 15, thereby accumulating at the upper end of the powder conveying trough 15. The gap 18 is provided in conjunction with the high-pressure dispersion gas inlet 121, so that the airflow can blow the powder at the gap 18 down. In addition, after passing through the gap 18, the high-pressure gas is reflected and blown toward the inside of the cover 12, and then dispersed and blown downward. This makes the airflow from the high-pressure gas entering through the gap 18 gentle and does not disturb the vibration of the powder in the vibrating plate.

[0054] By adopting high-frequency vibration, the vibration plate disperses irregular powder raw materials and outputs them, especially for powders with high viscosity and easy to agglomerate, it has a better dispersion effect.

[0055] Atomization mechanism 2

[0056] See also Figure 7-10 As shown, the atomizing mechanism 2 mainly includes a main body 21 that is through-through from top to bottom. The upper end of the main body is opened to form an inlet for powder to be spheroidized. The above-mentioned conveying pipeline 18 is connected to the inlet of the powder to be spheroidized of the main body.

[0057] A plurality of first air inlets 22 and second air inlets 23 are formed on the side wall of the main body.

[0058] The first air inlet 22 is configured to flow tangentially along the inner cavity of the main body's cross-section, allowing the carrier gas to form a vortex within the main body's inner cavity. The first air inlet 22 forms a carrier gas inlet connector 24 on the outside of the main body. A flow control valve is also connected to the carrier gas inlet connector 24, which regulates the gas flow to the four first air inlets 22.

[0059] The second air inlet 23 also forms a carrier gas inlet connector 25 on the outside of the main body 21. The inner wall of the main body 21 is also surrounded by an annular partition 26 to form an annular cavity 27. The second air inlet 23 is arranged in the annular cavity 27, and the first air inlet 22 is arranged outside the annular cavity 27. The annular cavity 27 is also provided with a number of air outlet holes facing the opening direction of the lower end of the main body 21. Specifically, the annular partition 26 is provided in the upper part of the main body 21, which includes an annular side wall 261 for forming a central passage of the main body, and a bottom surface 262 opening toward the lower end of the main body, and encloses an annular cavity 27 with the main body 21. The air outlet holes are evenly distributed on the bottom surface 262. The air inlet direction of the second air inlet 23 is configured to be along the tangent direction of the inner cavity of the cross section of the main body 21, and the second air inlets 23 are axially located on the same cross section of the main body and are evenly distributed along it.

[0060] In a preferred embodiment, the first air inlet 22 is located below the second air inlet 23. There are four first air inlets 22 and four second air inlets 23 on the main body 21, which are axially located on the cross-section of the main body. The four first air inlets 22 can respectively introduce four gases, and air, argon, nitrogen, etc. can be introduced according to different process requirements. The four first air inlets 22 are central gases, and the carrier gas introduced by the first air inlet 22 forms a central cyclone for generating microwave plasma. The four second air inlets 23 are side gases, which are used to purge the inner wall from top to bottom, forming a protective layer along the inner wall of the quartz tube to prevent powder from adhering to the inner wall.

[0061] Plasma generating mechanism 3

[0062] The plasma generator 3 is a conventional plasma generator, comprising a waveguide structure 31, a magnetron 32, and a microwave power supply connected to the magnetron 32. The waveguide structure 31 comprises a straight waveguide and a tapered microwave cavity. One end of the straight waveguide interfaces with the microwave emission port of the magnetron, and the other end interfaces with the small end of the tapered microwave cavity. A quartz tube 33 is disposed within the tapered microwave cavity. The lower end opening of the main body of the atomization mechanism 2 is connected to the upper end of the quartz tube of the plasma generator 3.

[0063] Vacuum component 7

[0064] The vacuum assembly 7 includes a water ring pump 71, a Roots pump 72, and a proportional valve 73. The Roots pump 72 and proportional valve 73 are connected in parallel, with one end connected to the water ring pump 71 and the other end to the filter 6. This is then connected to the reactor 4 via the cyclone separator 5. A vacuum valve 74 is also provided on the Roots pump 72 pipeline.

[0065] In the above solution, the Roots pump 72 and the water ring pump 71 are used together because, during operation, a certain amount of powder will still pass through the filter 6 and enter the vacuum assembly 7. The water ring pump 71 can operate in dusty environments, but it cannot achieve extremely high vacuum conditions. The Roots pump 72 can achieve a high vacuum degree, but it cannot operate in dusty environments.

[0066] During the initial startup of the equipment (before powder is fed in), the Roots pump 72 and the water ring pump 71 work simultaneously, working together to evacuate the interior of the equipment. During the spheroidization operation, the Roots pump 72 is shut down, and the water ring pump 71 is connected to the filter via a bypass with a proportional valve 73. The high vacuum environment inside the equipment is maintained through the water ring pump 71 and the proportional valve 73. The PID algorithm dynamically adjusts the opening of the proportional valve to balance the intake and exhaust flow rates, stabilizing the pressure within the set range, thereby regulating the vacuum degree in the reaction tank cavity.

[0067] Through the above structure, the vacuum degree of the equipment can reach within 1000Pa, and the negative pressure arc striking effect is significant.

[0068] Filter 6 and cyclone separator 5

[0069] See also Figure 8-9 As shown, filter 6 comprises a housing 61, within which is housed a filter element 62, and below which is a powder collecting tank 63. Cyclone separator 5 comprises a housing 51, with an air outlet connected to reaction tank 4 provided on the sidewall thereof, a cyclone separation mechanism 52 disposed within the housing, and a powder collecting tank 53 disposed below the housing. Both filter 6 and cyclone separator 5 are conventional equipment in the industry, and their specific structures are not further described here.

[0070] Reactor 4

[0071] The reactor 4 comprises a housing 41 with a discharge port at its top and a powder collecting tank 42 at its bottom. The lower end of the quartz tube 33 is connected to the reactor 4 via the discharge port. Accordingly, a high-temperature plasma region 43 is formed in the upper portion of the reactor 4 cavity. A spheroidization region 44 is also formed in the lower portion of the reactor 4 cavity, where the molten powder solidifies as it falls.

[0072] During the operation of this system, the pressure inside the reaction tank 4 gradually increases due to the continuous consumption of argon by the plasma generating mechanism 3. To ensure stable pressure within the tank, the vacuum pump assembly 7 remains in continuous operation. Unlike the fully open pipeline during vacuum pumping, a bypass is used during the powder production process. A proportional valve 73 is installed in the bypass to maintain stable exhaust flow. Through PID regulation, the inlet and outlet air flows within the sealed tank are essentially balanced. The outlet air flow can also be adjusted according to process requirements to ensure that the tank pressure fluctuates within a certain range. Controlling the vacuum pump assembly 7 can adjust the vacuum level of the reaction tank 4. At different vacuum levels, the length of the microwave plasma torch emitted from the lower end of the quartz tube 33 within the high-temperature plasma zone 43 is adjustable, which has a certain regulatory effect on the powder production process. Correspondingly, the spheroidization zone 44 should be configured so that even when the microwave plasma torch is at its maximum length, it can still ensure that the molten powder solidifies at the corresponding vacuum level as it falls.

[0073] In order to observe and monitor the microwave plasma torch state of the plasma high temperature area 43 in the reaction tank, a number of temperature sensors are evenly distributed on the plasma high temperature area 43, and a transparent observation window 45 is opened on the tank wall of the reaction tank 4 for observing the plasma operation state of the plasma high temperature area therein.

[0074] Compared with the prior art, the present invention has the following beneficial effects:

[0075] (1) Compared with the prior art, the present invention provides a system for preparing nano-scale powders by using microwave plasma spheroidization and refinement. The system adopts microwave plasma heating and can melt any raw material with a melting point below 3000 degrees, not limited to metal or non-metal powders, and can meet common market needs. The system includes a powder feeder, an atomizing mechanism, a plasma generating mechanism, a vacuum pumping component and a reaction tank. Therefore, the equipment has the conditions for powder preparation under vacuum and has advantages in controlling the oxygen content of the powder. At the same time, by adjusting the vacuum degree in the reaction tank, the plasma arc length under different vacuum degrees is different, and the process can be adjusted according to the requirements of different processes.

[0076] (2) A special powder feeder is used to disperse irregular powder raw materials using high-frequency vibration + high-pressure gas dispersion, especially for powders with high viscosity and easy to agglomerate.

[0077] (3) The microwave plasma torch adopts a unique cyclone design, with multiple gases set inside, including plasma center gas and side gas. The center gas generates high-temperature plasma, and the side gas is set on the inner wall of the quartz tube to prevent powder from adhering to the quartz tube wall.

[0078] (4) The equipment adopts full closed-loop control, which can achieve stable control of microwave power, vacuum degree, and pressure inside the equipment to ensure the stability of equipment operation.

[0079] The above embodiments describe in detail the inventive intent and implementation methods of the present invention. However, those skilled in the art will appreciate that the above embodiments are only preferred embodiments of the present invention. Due to space limitations, not all implementation methods are listed here. Any implementation that can embody the technical solutions of the claims of the present invention is within the scope of protection of the present invention.

[0080] It should be noted that the above content is a further detailed description of the present invention in combination with specific implementation methods, and it cannot be determined that the specific implementation methods of the present invention are limited to these. Under the guidance of the above embodiments, those skilled in the art can make various improvements and modifications on the basis of the above embodiments, and these improvements or modifications fall within the scope of protection of the present invention.

Claims

1. A system for preparing nano-scale powders by spheroidization and refinement using microwave plasma, characterized by: The system includes a powder feeder, an atomizing mechanism, a plasma generating mechanism, a vacuum assembly and a reaction tank; the plasma generating mechanism includes a magnetron, a waveguide structure and a quartz tube, the magnetron is coupled to the quartz tube through the waveguide structure to generate microwave plasma; the atomizing mechanism is connected to the upper end of the quartz tube and is used to provide an atomized material mixed with a carrier gas and a powder to be spheroidized into the quartz tube; the powder feeder is connected and used to convey the powder to be spheroidized to the atomizing mechanism; the center of the top of the reaction tank has a feed opening, and the lower end of the quartz tube is connected to the feed opening. The mouth part is arranged in the reaction tank, or connected to the discharge port; a plasma high-temperature area is formed on the upper part of the cavity of the reaction tank; the vacuum pumping component is connected to the reaction tank through the filter and the cyclone separator in sequence, and can adjust the vacuum degree in the cavity of the reaction tank, so that the microwave plasma torch blown out from the lower end of the quartz tube can be adjusted in length in the plasma high-temperature area, and the lower part of the cavity of the reaction tank also forms a spheroidization area that can solidify the molten powder when falling; the filter, cyclone separator and the bottom of the reaction tank are all provided with a powder collecting tank.

2. The system for preparing nano-scale powders by microwave plasma spheroidization and refinement according to claim 1, characterized in that: The atomization mechanism includes a cylindrical main body, the upper end opening of the main body forms an inlet for the powder to be spheroidized, the lower end opening of the main body is connected to the upper end of the quartz tube, and a plurality of first air inlets are formed on the side wall of the main body. The air inlet direction of the first air inlets is configured to be along the tangent direction of the inner cavity of the circular cross-section of the main body, so that the carrier gas forms a cyclone in the inner cavity of the main body; the first air inlets form a carrier gas inlet joint on the outside of the main body.

3. The system for preparing nano-scale powders by microwave plasma spheroidization and refinement according to claim 2, characterized in that: A plurality of second air inlets are also formed on the side wall of the main body, and the second air inlets form a carrier gas inlet connector on the outside of the main body. The inner wall of the main body is also surrounded by an annular partition to form an annular cavity. The second air inlet is arranged in the annular cavity, and the first air inlet is arranged outside the annular cavity; the annular cavity is also provided with a plurality of air outlet holes opening in the direction of the lower end of the main body.

4. The system for preparing nano-scale powders by microwave plasma spheroidization and refinement according to claim 3, characterized in that: The annular partition is arranged at the upper end of the main body, and it at least includes an annular side wall for forming a central passage of the main body, and a bottom surface opening toward the lower end of the main body; the multiple air outlets are evenly distributed on the bottom surface; the first air inlet is located below the second air inlet.

5. The system for preparing nano-scale powders by microwave plasma spheroidization and refinement according to claim 4, characterized in that: The number of the first air inlets and the second air inlets are four, and the first air inlets are axially located on the same main body cross-section and evenly distributed along it; the air intake direction of the second air inlets is configured to be along the tangent direction of the inner cavity of the main body cross-section, and the second air inlets are axially located on the same main body cross-section and evenly distributed along it.

6. The system for preparing nano-scale powders by using microwave plasma spheroidization and refinement according to claim 1, characterized in that: The powder feeder includes a vibrating plate that is driven by a vibration mechanism to vibrate. The vibrating plate is an inverted frustum-shaped hollow structure. A feed port is provided at the center of the top plate of the upper portion thereof. A powder conveying trough extending in a conical spiral shape is formed along the side wall of the inner cavity thereof. The lower end of the powder conveying trough extends to the bottom of the vibrating plate. A drop hole penetrating the vibrating plate is provided on the upper portion thereof on the conveying path. The outer end of the drop hole is connected to the inlet of the powder to be spheroidized of the atomizing mechanism through a conveying pipeline.

7. The system for preparing nano-scale powders by using microwave plasma spheroidization and refinement according to claim 6, characterized in that: Along the conveying path of the powder conveying trough, the powder conveying trough is further provided with a notch downstream of the blanking hole, and the notch faces the inner side of the top plate; the top plate of the vibration disk is provided with a high-pressure dispersion gas inlet corresponding to the notch, and the notch is configured so that when the high-pressure gas blown into the high-pressure dispersion gas inlet rebounds through the notch, it can be blown toward the inner side of the top plate.

8. The system for preparing nano-scale powders by using microwave plasma spheroidization and refinement according to claim 7, characterized in that: The bottom of the vibrating plate is arched from the edge to the center, and the lower end of the powder conveying trough extends to the outer edge of the bottom of the vibrating plate; in addition, a feed pipe is provided on the upper part of the vibrating plate, and the feed port is formed on the upper part of the feed pipe, and the lower end thereof extends into the vibrating plate cavity and is located directly above the bottom of the vibrating plate.

9. The system for preparing nano-scale powders by using microwave plasma spheroidization and refinement according to claim 1, characterized in that: A plurality of temperature sensors are evenly distributed on the plasma high-temperature area of ​​the reaction tank, and a transparent observation window for observing the plasma high-temperature area therein is opened on the tank wall of the reaction tank.

10. A system for preparing nano-scale powders by using microwave plasma spheroidization and refinement according to any one of claims 1 to 9, characterized in that: The vacuum pump assembly includes a water ring pump, a Roots pump and a proportional valve. The Roots pump and the proportional valve are connected in parallel, and one end of the Roots pump and the other end of the proportional valve are connected to the water ring pump and the other end is connected to the filter.

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