A device for producing nanoscale powders using microwave plasma

Abstract

This utility model relates to a device for preparing nanoscale powder using microwave plasma, comprising a plasma generating mechanism and a reaction vessel. 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. A powder receiving container is provided at the bottom of the reaction vessel, and a feeding port is located at the center of its top. The lower end of the quartz tube is partially disposed inside the reaction vessel through the feeding port, or connected to the feeding port. A high-temperature plasma region is formed in the upper part of the cavity of the reaction vessel. A vacuum mechanism is also directly or indirectly connected to the side wall of the reaction vessel, which can adjust the vacuum level inside the reaction vessel cavity, so that the length of the microwave plasma torch blown out from the lower end of the quartz tube is adjustable in the high-temperature plasma region. A spheroidized region is also formed in the lower part of the cavity of the reaction vessel, which can cause the molten powder to solidify when falling.

Description

Technical Field

[0001] This utility model relates to the field of powder metallurgy technology, and in particular to the field of spheroidizing and refining powders using microwave plasma technology. Background Technology

[0002] Powder preparation technology based on powder metallurgy has a history of several decades. In recent years, with the rise of new energy technologies, the market demand for positive and negative electrode powder materials and various oxide powder materials has been increasing. At the same time, the demand for spherical powders is growing, and the quality requirements for powders are becoming increasingly stringent, especially the requirements for powder particle size, which have gradually increased from the micrometer level to the submicrometer and nanometer levels. 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, the development has progressed from metal powders to ceramic powders, with significant demand across a melting point range from several hundred degrees to three thousand degrees. The finer the powder particle size and the higher the sphericity, the higher its value.

[0003] Currently, ball milling is commonly used for the preparation of ultrafine powders. However, this method has the following problems: 1. Long processing time: The ball milling process may require a long processing time, affecting production efficiency; 2. Thermal effect: Prolonged grinding can cause the material to overheat, which may affect product performance or lead to sintering; 3. High equipment investment: The investment cost of mills and related accessories is relatively high, which may impose 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, the preparation of high-melting-point powders in the market usually adopts chemical methods, such as evaporation. However, this method has disadvantages such as difficulty in collection and long reaction time, which are not conducive to large-scale production.

[0005] In addition to the above, microwave plasma spheroidization is another process currently available for powder spheroidization. Microwave plasma technology has advantages such as no electrode pollution, environmental friendliness, good temperature field consistency, and a wide operating range. However, this microwave plasma process equipment has the following shortcomings: 1. The required melting process conditions vary depending on the material of the metal and non-metal powders, as well as the particle size of the powder. Existing equipment cannot be adjusted to meet different process requirements, resulting in poor adaptability; 2. Powders, especially metal powders, tend to adhere to the quartz tube wall after melting, which not only affects their service life but also reflects microwave transmission, greatly reducing the energy density of the microwave plasma, decreasing the spheroidization rate, and preventing continuous and stable production.

[0006] Therefore, there is still a significant gap in the existing technology for the preparation of ultrafine and high-melting-point powders. Based on the above, this paper designs a device for spheroidizing and refining powders using microwave plasma technology, which can simultaneously achieve the preparation of spheroidized and refined powders. Its purpose is to prepare nanoscale powder materials for use in various fields. Utility Model Content

[0007] The purpose of this utility model embodiment is to address the shortcomings of the existing technology structure by proposing a device for preparing nanoscale powders using microwave plasma, thereby solving the defects in the existing technology.

[0008] To achieve the aforementioned objectives, the present invention provides a device for preparing nanoscale powders using microwave plasma, implemented through the following technical solution:

[0009] A device for preparing nanoscale powder using microwave plasma includes a plasma generating mechanism and a reaction vessel. 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. A powder receiving container is provided at the bottom of the reaction vessel, and a discharge port is located at the center of its top. The lower end of the quartz tube is partially disposed inside the reaction vessel through the discharge port, or connected to the discharge port. The device is characterized in that a high-temperature plasma region is formed in the upper part of the cavity of the reaction vessel; a vacuum mechanism is also directly or indirectly connected to the side wall of the reaction vessel, which can adjust the vacuum level inside the reaction vessel cavity, making the length of the microwave plasma torch blown out from the lower end of the quartz tube adjustable within the high-temperature plasma region; and a spheroidized region is also formed in the lower part of the cavity of the reaction vessel, which allows the molten powder to solidify upon falling.

[0010] The device also includes an atomizing mechanism for supplying atomized material, consisting of a carrier gas and powder to be spheroidized, into the quartz tube.

[0011] The atomizing mechanism includes a cylindrical body with an opening at the upper end to form an inlet for the powder to be spheroidized, and an opening at the lower end of the body connected to the upper end of the quartz tube. Several first air inlets are also formed on the side wall of the 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 body, so that the carrier gas forms an air vortex in the inner cavity of the body. The first air inlets form a carrier gas inlet connector on the outside of the body.

[0012] The main body sidewall is also provided with several second air inlets, which form air inlet connectors 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 inlets are located in the annular cavity, and the first air inlet is located outside the annular cavity. The annular cavity is also provided with several air outlets facing the opening direction at the lower end of the main body.

[0013] The annular partition is located at the upper end of the main body and includes at least an annular sidewall for forming a central passage of the main body and a bottom surface that opens toward the lower end of the main body; the plurality of air outlets are evenly distributed on the bottom surface; the first air inlet is located below the second air inlet.

[0014] There are four first air inlets and four second air inlets, and the first air inlets are axially located on the same main body cross section and are evenly distributed thereal; 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 are evenly distributed thereal.

[0015] Several temperature sensors are evenly distributed on the high-temperature plasma region of the reaction vessel, and a transparent observation window is provided on the vessel wall to observe the high-temperature plasma region inside.

[0016] The vacuum assembly includes a water ring pump, a Roots pump, and a proportional valve. The Roots pump and the proportional valve are connected in parallel, with one end of each connected to the water ring pump and the other end directly or indirectly connected to the reaction vessel.

[0017] Compared with the prior art, the beneficial effects of this utility model are:

[0018] (1) Compared with the prior art, the present invention provides a device for preparing nanoscale powders using microwave plasma. Employing microwave plasma heating, it can melt raw materials with melting points below 3000 degrees Celsius, and is not limited to metal or non-metal powders, thus meeting common market demands. The system includes a powder feeder, an atomizing mechanism, a plasma generating mechanism, a vacuum assembly, and a reaction vessel. Therefore, the equipment is capable of producing powder under vacuum, offering advantages in controlling the oxygen content of the powder. Furthermore, by adjusting the vacuum level within the reaction vessel, the plasma arc length varies under different vacuum levels, allowing for process adjustments based on the requirements of different processes.

[0019] (2) The microwave plasma torch adopts a unique cyclone design and has multiple gas channels 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. Attached Figure Description

[0020] The above features and advantages of the present invention will become clearer and easier to understand from the following description of exemplary embodiments thereof in conjunction with the accompanying drawings.

[0021] Figure 1 This is an overall schematic diagram of the cabinet of the device for preparing nanoscale powder using microwave plasma, according to an embodiment of this utility model.

[0022] Figure 2 This is a front view of the device for preparing nanoscale powder using microwave plasma, according to an embodiment of this utility model.

[0023] Figure 3 This is a side view of the device for preparing nanoscale powder using microwave plasma, according to an embodiment of this utility model.

[0024] Figure 4 This is a three-dimensional schematic diagram of a device for preparing nanoscale powder using microwave plasma, according to an embodiment of this utility model.

[0025] Figure 5 This is a top view of the plasma generating mechanism, reaction vessel, and atomizer components according to an embodiment of the present invention;

[0026] Figure 6 for Figure 5 Sectional view along axis AA;

[0027] Figure 7 This is a cross-sectional view of the atomizer portion of an embodiment of the present utility model;

[0028] Figure 8 This is a three-dimensional schematic diagram of the atomizer according to an embodiment of the present utility model. Detailed Implementation

[0029] The following specific embodiments illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0030] The terms "front," "rear," "left," "right," "inner," and "outer" used in this specification are merely for clarity of description and are not intended to limit the scope of implementation of this utility model. Any changes or adjustments to their relative relationships, without substantially altering the technical content, shall also be considered within the scope of implementation of this utility model.

[0031] In the description of the following embodiments, unless otherwise expressly specified and limited, the term "connection" and other such terms should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an indirect connection through an intermediate medium; it can be the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0032] See Figure 1-8 As shown in the figure, this utility model embodiment proposes a device for preparing nanoscale powders using microwave plasma. The device mainly includes an atomizing mechanism 2, a plasma generating mechanism 3, a reaction vessel 4, and a vacuum pumping assembly 7. Wherein:

[0033] Atomizing mechanism 2

[0034] See Figure 1-8 As shown, the atomizing mechanism 2 mainly includes a main body 21 that runs vertically through the body. The upper end of the main body has an opening to form an inlet for the powder to be spheroidized. The aforementioned conveying pipe 18 is connected to the inlet for the powder to be spheroidized in the main body.

[0035] Several first air inlets 22 and second air inlets 23 are provided on the side wall of the main body.

[0036] The air intake direction of the first air inlet 22 is configured along the tangent direction of the inner cavity of the main body cross section, so that the carrier gas forms an air vortex in the inner cavity of the main body. The first air inlet 22 forms a carrier gas inlet connector 24 on the outer side of the main body. In addition, a flow regulating valve is connected to the carrier gas inlet connector 24, which can regulate the gas flow of the four first air inlets 22.

[0037] The second air inlet 23 also forms a carrier air 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 located inside the annular cavity 27, and the first air inlet 22 is located outside the annular cavity 27. The annular cavity 27 is also provided with several air outlets facing the lower end opening direction of the main body 21. Specifically, the annular partition 26 is located in the upper part of the main body 21, and it includes an annular sidewall 261 for forming the central passage of the main body, and a bottom surface 262 opening towards the lower end of the main body, and surrounds the annular cavity 27 with the main body 21. The air outlets are evenly distributed on the bottom surface 262. The air intake 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 these second air inlets 23 are axially located on the same cross section of the main body and are evenly distributed along it.

[0038] In a preferred embodiment, the first air inlet 22 is located below the second air inlet 23. The main body 21 has four first air inlets 22 and four second air inlets 23, axially located on the cross-section of the main body. Each of the four first air inlets 22 can introduce four gases, such as air, argon, and nitrogen, depending on different process requirements. The four first air inlets 22 serve as the central gas, forming a central vortex to generate microwave plasma. The four second air inlets 23 serve as the side gas, 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.

[0039] Plasma Generator 3

[0040] The plasma generating mechanism 3 is a conventional plasma generator, including a waveguide structure 31, a magnetron 32, and a microwave power supply connected to the magnetron 32. The waveguide structure 31 includes a straight waveguide and a tapered microwave cavity. One end of the straight waveguide is connected to the microwave emission port of the magnetron, and the other end is connected to the small end of the tapered microwave cavity. A through quartz tube 33 is installed inside the tapered microwave cavity. The lower opening of the main body of the atomizing mechanism 2 is connected to the upper end of the quartz tube of the plasma generating mechanism 3.

[0041] Vacuum assembly 7

[0042] The vacuum assembly 7 includes a water ring pump 71, a Roots pump 72, and a proportional valve 73. The Roots pump 72 and the proportional valve 73 are connected in parallel, with one end connected to the water ring pump 71 and the other end connected to the filter 6, and then connected to the reaction vessel 4 via a cyclone separator 5. In addition, a vacuum valve 74 is also installed on the pipeline of the Roots pump 72.

[0043] The reason for using a combination of Roots pump 72 and water ring pump 71 in the above scheme is that some powder will still enter the vacuum assembly 7 through filter 6 during equipment operation. Water ring pump 71 can operate in dusty environments, but it cannot achieve extremely high vacuum conditions. Roots pump 72 can achieve high vacuum, but it cannot operate in dusty environments.

[0044] During the initial startup phase (before powder is fed), Roots pump 72 and water ring pump 71 operate simultaneously, working together to create a vacuum inside the equipment. During spheroidizing operations, Roots pump 72 is shut off, and water ring pump 71 is connected to a filter via a bypass with a proportional valve 73. The high vacuum environment inside the equipment is maintained through water ring pump 71 and proportional valve 73, and the opening of the proportional valve is dynamically adjusted using a PID algorithm to balance the intake and extraction flow rates, stabilizing the pressure within the set range and thus regulating the vacuum level inside the reaction vessel.

[0045] Reaction vessel 4

[0046] The reaction vessel 4 has a shell 41, with a feed port at the top and a powder collection tank 42 connected to the bottom. The lower end of the quartz tube 33 is connected to the reaction vessel 4 via the feed port. Correspondingly, a high-temperature plasma region 43 is formed in the upper part of the cavity of the reaction vessel 4. A spheroidizing region 44 is also formed in the lower part of the cavity of the reaction vessel 4, which allows the molten powder to solidify as it falls.

[0047] During the operation of this system, the pressure inside the reaction vessel 4 gradually increases due to the continuous consumption of argon gas by the plasma generator 3. To ensure pressure stability within the vessel, the vacuum pumping component 7 remains continuously running. Unlike the fully open pipeline state during vacuuming, a bypass is used during powder preparation. A proportional valve 73 is installed in the bypass, which maintains a stable pumping flow rate. Through PID regulation, the inlet and outlet flow rates within the sealed vessel are kept in a basic balance. Furthermore, the outlet flow rate can be adjusted according to process requirements to ensure the vessel pressure fluctuates within a certain range. By controlling the vacuum pumping component 7, the vacuum level of the reaction vessel 4 can be adjusted. Under different vacuum levels, the length of the microwave plasma torch blown from the lower end of the quartz tube 33 within the high-temperature plasma region 43 is adjustable, providing a certain degree of regulation for the powder process. Correspondingly, the spheroidization region 44 should be set so that even when the microwave plasma torch is at its maximum length, the molten powder still solidifies at the corresponding vacuum level during its descent.

[0048] In order to observe and monitor the state of the microwave plasma torch in the high-temperature plasma region 43 of the reaction vessel, several temperature sensors are evenly distributed on the high-temperature plasma region 43, and a transparent observation window 45 is provided on the wall of the reaction vessel 4 to observe the plasma operation state of the high-temperature plasma region inside.

[0049] With the above structure, the vacuum level of the equipment can reach within 1000pa, and the negative pressure arc ignition effect is significant.

[0050] In conjunction with the above-described device structure, the system using paper cup powder also includes a powder feeder 1, a filter 6, and a cyclone separator 5.

[0051] The powder feeder 1 disperses irregular powder raw materials through high-frequency vibration and high-pressure airflow, and outputs them. It has a good dispersion effect, especially for powders with high viscosity and easy agglomeration.

[0052] Filter 6 has a housing containing a filter element, and a powder collection tank 61 is located at its lower part. Cyclone separator 5 has a housing with an outlet on its side wall that connects to reaction vessel 4, and a powder collection tank 51 is located at its lower part. Both filter 6 and cyclone separator 5 are standard equipment in the industry, and their specific structures will not be described in detail here.

[0053] Compared with the prior art, the beneficial effects of this utility model are:

[0054] (1) Compared with the prior art, the present invention provides a device for preparing nanoscale powders using microwave plasma. Employing microwave plasma heating, it can melt raw materials with melting points below 3000 degrees Celsius, and is not limited to metal or non-metal powders, thus meeting common market demands. The system includes a powder feeder, an atomizing mechanism, a plasma generating mechanism, a vacuum assembly, and a reaction vessel. Therefore, the equipment is capable of producing powder under vacuum, offering advantages in controlling the oxygen content of the powder. Furthermore, by adjusting the vacuum level within the reaction vessel, the plasma arc length varies under different vacuum levels, allowing for process adjustments based on the requirements of different processes.

[0055] (2) A special powder feeder is used, and high-frequency vibration + high-pressure gas dispersion is used to disperse irregular powder raw materials, especially for powders with high viscosity and easy to form agglomerates, which has a good dispersion effect.

[0056] (3) The microwave plasma torch adopts a unique cyclone design and has multiple gas channels inside, including plasma center gas and side gas. The center gas generates high-temperature plasma with high vibration mechanism 11, and the side gas is set on the inner wall of the quartz tube to prevent powder from adhering to the quartz tube wall.

[0057] (4) The equipment adopts a fully closed-loop control, which can stably control the microwave power, vacuum degree and internal pressure of the equipment, ensuring the stability of the equipment operation.

[0058] The present invention has been described in detail above through embodiments. However, those skilled in the art will understand that the above embodiments are only one of the preferred embodiments of the present invention. Due to space limitations, not all embodiments can be listed here. Any implementation that can embody the technical solution of the claims of the present invention is within the protection scope of the present invention.

[0059] It should be noted that the above content is a further detailed description of the present utility model in conjunction with specific embodiments, and it should not be considered that the specific embodiments of the present utility model are limited to this. Under the guidance of the above embodiments, those skilled in the art can make various improvements and modifications based on the above embodiments, and these improvements or modifications fall within the protection scope of the present utility model.

Claims

1. A device for preparing nanoscale powder using microwave plasma, comprising a plasma generating mechanism and a reaction vessel, wherein the plasma generating mechanism includes a magnetron, a waveguide structure, and a quartz tube, the magnetron being coupled to the quartz tube through the waveguide structure to generate microwave plasma; a powder receiving container is provided at the bottom of the reaction vessel, and a discharge port is located at the center of its top; the lower end of the quartz tube is partially disposed inside the reaction vessel via the discharge port, or connected to the discharge port; characterized in that: The upper part of the cavity of the reaction vessel forms a high-temperature plasma region; the side wall of the reaction vessel is also directly or indirectly connected to a vacuum mechanism, which can adjust the vacuum level inside the reaction vessel cavity, so that the length of the microwave plasma torch blown out from the lower end of the quartz tube is adjustable in the high-temperature plasma region; the lower part of the cavity of the reaction vessel also forms a spheroidized region that can cause the molten powder to solidify when it falls.

2. The apparatus for producing nanoscale powders using microwave plasma according to claim 1, wherein: The device also includes an atomizing mechanism for supplying atomized material, consisting of a carrier gas and powder to be spheroidized, into the quartz tube.

3. The apparatus for producing nanoscale powders using microwave plasma according to claim 2, wherein: The atomizing mechanism includes a cylindrical body with an opening at the upper end to form an inlet for the powder to be spheroidized, and an opening at the lower end of the body connected to the upper end of the quartz tube. Several first air inlets are also formed on the side wall of the 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 body, so that the carrier gas forms an air vortex in the inner cavity of the body. The first air inlets form a carrier gas inlet connector on the outside of the body.

4. The apparatus for producing nanoscale powders using microwave plasma according to claim 3, wherein: The main body sidewall is also provided with several second air inlets, which form air inlet connectors 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 inlets are located in the annular cavity, and the first air inlet is located outside the annular cavity. The annular cavity is also provided with several air outlets facing the opening direction at the lower end of the main body.

5. The apparatus for producing nanoscale powders using microwave plasma according to claim 4, wherein: The annular partition is located at the upper end of the main body and includes at least an annular sidewall for forming a central passage of the main body and a bottom surface that opens toward the lower end of the main body; the plurality of air outlets are evenly distributed on the bottom surface; the first air inlet is located below the second air inlet.

6. The apparatus for producing nanoscale powders using microwave plasma as set forth in claim 5, wherein: There are four first air inlets and four second air inlets, and the first air inlets are axially located on the same main body cross section and are evenly distributed thereal; 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 are evenly distributed thereal.

7. The apparatus for producing nanoscale powders using microwave plasma as set forth in claim 1, wherein: Several temperature sensors are evenly distributed on the high-temperature plasma region of the reaction vessel, and a transparent observation window is provided on the vessel wall to observe the high-temperature plasma region inside.

8. The apparatus for producing nanoscale powders using microwave plasma as claimed in any one of claims 1 to 7, wherein: The vacuum mechanism is a vacuum pumping assembly, which includes a water ring pump, a Roots pump, and a proportional valve. The Roots pump and the proportional valve are connected in parallel, with one end of each connected to the water ring pump and the other end directly or indirectly connected to the reaction vessel.

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