Device and method for preparing nano powder through microwave plasma

Abstract

The invention relates to equipment and a method for preparing nano powder through microwave plasma. Comprising a conductor tube, the conductor tube comprises a quartz tube and a powder feeding tube arranged in the quartz tube, the quartz tube vertically penetrates through a plasma conveying pipeline, the two ends of the quartz tube are open, a gas channel is formed in the interval between the powder feeding tube and the quartz tube, and the powder feeding tube comprises a powder feeding layer, a liquid inlet layer and a liquid outlet layer which are sequentially arranged from the center to the outside; the liquid inlet layer and the liquid outlet layer are communicated at the position close to the bottom of the powder feeding pipe; the vaporizing chamber is arranged below the quartz tube, the lower end of the quartz tube and the lower end of the powder feeding tube are both located in the vaporizing chamber, the vaporizing chamber comprises a reaction chamber and a first liquid cooling layer which are sequentially arranged from inside to outside, and the reaction chamber comprises a first conical tube, a first round tube, a second conical tube and a second round tube which are sequentially connected from top to bottom. By designing the powder feeding pipe of the three-layer structure, the vaporizing chamber of the first-expansion and second-aggregation structure and the quenching chamber comprising the delay layer, the second liquid cooling layer and the gas cooling layer, the powder manufacturing efficiency can be improved.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of additive manufacturing technology, and more particularly to a device and method for preparing nanopowder by microwave plasma. Background Art

[0002] Nanopowder refers to powder with a diameter in the range of 1-100nm. At this scale, the physical and chemical properties of powder particles are completely different from those at the macroscopic scale, which makes them have characteristics such as surface effect, volume effect, quantum size effect, etc. Nanopowder has broad application prospects in many fields such as chemical catalysts, microporous materials and conductive slurries. Microwave plasma uses microwaves as the heat source to generate plasma. Compared with DC and high-frequency plasma, the use of microwaves has many unique advantages: (1) High energy efficiency. Microwave energy is directly coupled to gas molecules, with high energy utilization and rapid heating. (2) No electrode pollution. There is no internal electrode during microwave discharge, which avoids electrode material contamination and is suitable for the preparation and treatment of high-purity materials. (3) Mild reaction conditions. The electron temperature is high and the gas temperature is low, and it can work at a lower gas pressure. (4) High safety. There is no high-voltage electrode, which is safer. (5) Wide range of applications. It is not limited by electrode materials and frequencies and is suitable for a variety of gases and reaction conditions. Based on the above advantages, microwave plasma has great potential and industrial application value in the application of material preparation, and has therefore become a hot topic of research at home and abroad.

[0003] In the related art, in the process of preparing nano-powder by microwave plasma, the powder outlet of the powder feeding tube is too high. When the raw material powder enters the vaporization chamber from the powder feeding tube, it is easy to melt at the powder outlet of the powder feeding tube and block the powder outlet. Moreover, after the raw material powder enters the vaporization chamber, the unreasonable structural design of the vaporization chamber makes the powder not fully vaporized. After the powder is gasified, the vaporized powder is not cooled thoroughly enough, which affects the efficiency of preparing nano-powder.

[0004] Therefore, it is necessary to improve one or more problems existing in the above-mentioned related technical solutions.

[0005] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present application, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0006] The purpose of the embodiments of the present application is to provide an apparatus and method for preparing nanopowder by microwave plasma, which can overcome one or more problems caused by the limitations and defects of the relevant technology to a certain extent.

[0007] According to a first aspect of an embodiment of the present application, there is provided a device for preparing nanopowder by microwave plasma, comprising: A plasma delivery pipeline, one end of which is open and the other end is blocked; The conductor tube comprises a quartz tube and a powder delivery tube arranged in the quartz tube, the quartz tube vertically passes through the plasma delivery pipeline, both ends of the quartz tube are open, the interval between the powder delivery tube and the quartz tube forms a gas channel, the powder delivery tube comprises a powder delivery layer, a liquid inlet layer and a liquid outlet layer arranged in sequence from the center to the outside, the liquid inlet layer and the liquid outlet layer are connected at a position close to the bottom of the powder delivery tube; wherein a plurality of powder outlets are evenly arranged on the bottom of the powder delivery tube, and each of the powder outlets is connected to the powder delivery layer; A gasification chamber is arranged below the quartz tube, and the lower end of the quartz tube and the lower end of the powder feeding tube are both located in the gasification chamber, the gasification chamber includes a reaction chamber and a first liquid cooling layer arranged sequentially from the inside to the outside, and the reaction chamber includes a first conical tube, a first round tube, a second conical tube and a second round tube connected sequentially from top to bottom; wherein the central axis of the first conical tube, the central axis of the first round tube, the central axis of the second conical tube and the central axis of the second round tube are collinear, and the diameter of the first round tube is greater than the diameter of the second round tube; A quenching chamber is arranged below the gasification chamber, the quenching chamber is communicated with the gasification chamber, the quenching chamber comprises a first cooling layer and a second cooling layer arranged in sequence from outside to inside, the second cooling layer comprises a delay layer, a second liquid cooling layer and an air cooling layer connected in sequence from top to bottom; The separation collector is arranged below the quenching chamber and communicated with the quenching chamber.

[0008] In one embodiment of the present application, the bottom of the powder delivery tube is a spherical curved surface, and the opening direction of the powder outlet is consistent with the radius direction of the spherical curved surface.

[0009] In one embodiment of the present application, the angle between the conical surface of the first conical tube and its central axis, and the angle between the conical surface of the second conical tube and its central axis are both 90±2°.

[0010] In one embodiment of the present application, the ratio of the diameter of the second circular tube to the diameter of the first circular tube is 2 / 7-1 / 3.

[0011] In one embodiment of the present application, the delay layer includes a graphite ring, a circle of first air holes is arranged inside the graphite ring along the radial direction of the graphite ring, an annular channel is arranged on the peripheral wall of the graphite ring along the axial direction of the graphite ring, and a plurality of first air inlet holes are evenly arranged on the first cooling layer; wherein the central axis of the graphite ring is collinear with the central axis of the second circular tube, each of the first air holes is connected to the annular channel, each of the first air holes is connected to the second circular tube, and the annular channel is connected to each of the first air inlet holes; The second liquid cooling layer comprises a guide water jacket, the upper surface of which is a conical surface; wherein the ratio of the diameter of the upper end of the upper surface of the guide water jacket to the diameter of the lower end of the upper surface of the guide water jacket is 1 / 3-1 / 2, and the ratio of the distance between the upper end of the upper surface of the guide water jacket and the lower end of the upper surface of the guide water jacket to the diameter of the upper end of the upper surface of the guide water jacket is greater than or equal to 1 / 2; The air cooling layer comprises an air dividing ring, on which a plurality of second air holes are evenly arranged, and the first cooling layer is evenly provided with a plurality of second air inlet holes, each of which is connected to the second air hole.

[0012] In one embodiment of the present application, the angle between the guide water jacket and the horizontal direction is 80±1°.

[0013] In one embodiment of the present application, the diameter of the second pore is 2-3 mm.

[0014] In one embodiment of the present application, a plurality of third air inlet holes are provided on the plasma delivery pipeline, and a plurality of air outlet holes are provided on the plasma delivery pipeline, and the diameter of the third air inlet holes and the diameter of the air outlet holes are both less than 4 mm.

[0015] In one embodiment of the present application, the separation collector includes a separation chamber, a powder barrel and a vacuum system, the upper end of the separation chamber is connected to the quenching chamber, the lower end of the separation chamber is connected to the powder barrel, and the separation chamber is connected to the vacuum system.

[0016] According to a second aspect of an embodiment of the present application, a method for preparing nanopowder by microwave plasma is provided, comprising: The plasma delivery pipeline conducts the microwave to the quartz tube of the conductor tube, and after being excited, it couples with the powder delivery tube in the quartz tube, forms a microwave torch at the bottom of the powder delivery tube, and the microwave torch is sprayed into the gasification chamber through the rotating gas in the gas channel; The airflow carries the raw material powder into the powder delivery layer, and cools the powder outlet position at the bottom of the powder delivery pipe through the liquid inlet layer and the liquid outlet layer, so that the raw material powder can be smoothly ejected from the powder outlet and enter the gasification chamber; When the raw material powder enters the gasification chamber, under the cooperation of the first conical tube in the reaction chamber and the powder outlet, the raw material powder fills the first conical tube and the first round tube with a diffusion trend, so that the raw material powder is fully gasified under the action of the microwave torch, and then the gasified powder is gathered under the action of the second conical tube and sent to the second round tube in a centralized manner; wherein the first liquid cooling layer cools the reaction chamber; Afterwards, the vaporized powder in the second round tube is sent to a quenching chamber, and the vaporized powder is acted on by the delaying layer in the quenching chamber to delay the falling of the vaporized powder, and then the vaporized powder is pre-cooled by the second liquid cooling layer, and then sent to the air cooling layer for rapid cooling, so that the vaporized powder is solidified to form a nano powder; wherein, during the process of the delaying layer acting on the vaporized powder and the process of the second liquid cooling layer pre-cooling the vaporized powder, the first cooling layer simultaneously performs full cooling on the vaporized powder entering the quenching chamber; The nano powder is collected by a separation collector to obtain the nano powder with different particle sizes.

[0017] The technical solution provided by the embodiments of the present application may have the following beneficial effects: In the embodiment of the present application, through the above-mentioned equipment, the raw material powder enters the powder feeding layer through the designed three-layer powder feeding tube, and the powder outlet position at the bottom of the powder feeding tube is cooled through the liquid inlet layer and the liquid outlet layer, which can avoid the raw material powder from melting at the powder outlet position due to the excessive temperature at the powder outlet position, causing the powder outlet to be blocked, thereby ensuring the smooth progress of powder feeding; through the designed reaction chamber with a structure of first expansion and then concentration, when the raw material powder enters the gasification chamber, under the cooperation of the first conical tube and the powder outlet, the raw material powder fills the first conical tube and the first circular tube with a diffusion trend , so that the raw material powder is fully vaporized under the action of the microwave torch, and then the vaporized powder is gathered under the action of the second conical tube and sent to the second circular tube to facilitate entering the quenching chamber for rapid quenching; through the quenching chamber including the delay layer, the second liquid cooling layer and the air cooling layer, when the vaporized powder enters the quenching chamber, the delay layer in the quenching chamber acts on the vaporized powder to delay the fall of the vaporized powder, and then the vaporized powder is pre-cooled by the second liquid cooling layer, and then sent to the air cooling layer for rapid cooling, so that the vaporized powder solidifies to form nano powder. The present application can improve the powder making efficiency by designing a three-layer powder delivery pipe, a vaporization chamber with a structure of first expansion and then gathering, and a quenching chamber including a delay layer, a second liquid cooling layer and an air cooling layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present application, and together with the specification are used to explain the principles of the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 A schematic structural diagram of a device for preparing nanopowder by microwave plasma in an exemplary embodiment of the present application is shown; Figure 2A schematic diagram showing the angle between the horizontal component of the rotating gas and the tangent direction of the tube wall in an exemplary embodiment of the present application; Figure 3 A flowchart showing a method for preparing nanopowder by microwave plasma in an exemplary embodiment of the present application; Figure 4 Shown is a transmission electron microscope image of nano copper powder; Figure 5 Shown is a transmission electron microscope image of nano-silicon powder.

[0020] In the figure: 100, plasma delivery pipeline; 110, blocking plate; 200, conductor tube; 210, quartz tube; 220, powder delivery tube; 221, powder delivery layer; 222, liquid inlet layer; 223, liquid outlet layer; 224, powder outlet; 300, gasification chamber; 310, reaction chamber; 311, first conical tube; 312, first round tube; 313, second conical tube; 314, second round tube; 320, first liquid cooling layer; 400, quenching chamber; 410, first cooling layer; 411, first air inlet; 412, second air inlet; 420, second cooling layer; 421, graphite ring; 422, annular channel; 423, first an air hole; 430, a guide water jacket; 440, an air cooling layer; 441, an air dividing ring; 442, a second air hole; 500, a separation collector; 510, a separation chamber; 520, a powder barrel; 530, a vacuum system; 600, a first flange; 700, a second flange; 800, a third flange; 900, a fourth flange; 1000, a fifth flange; 1100, a sixth flange; 1200, a seventh flange; 1300, an eighth flange; 1400, a ninth flange; 1500, a first sealing ring; 1600, a second sealing ring; 1700, a third sealing ring; 1800, a fourth sealing ring; 1900, a fifth sealing ring. DETAILED DESCRIPTION

[0021] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this application will be more comprehensive and complete and fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0022] In addition, the accompanying drawings are only schematic illustrations of the embodiments of the present application and are not necessarily drawn to scale. The same reference numerals in the drawings represent the same or similar parts, and their repeated descriptions will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0023] In this exemplary embodiment, a microwave plasma device for preparing nanopowder is first provided. Figure 1 As shown in, the device may include: a plasma delivery pipeline 100, a conductor tube 200, a vaporization chamber 300, a quenching chamber 400 and a separation collector 500. Among them, one end of the plasma delivery pipeline 100 is open and the other end is blocked; the conductor tube 200 includes a quartz tube 210 and a powder delivery tube 220 arranged in the quartz tube 210, the quartz tube 210 vertically passes through the plasma delivery pipeline 100, both ends of the quartz tube 210 are open, and the interval between the powder delivery tube 220 and the quartz tube 210 forms a gas channel, and the powder delivery tube 220 includes a powder delivery layer 221, a liquid inlet layer 222 arranged in sequence from the center to the outside. 22 and the liquid outlet layer 223, the liquid inlet layer 222 and the liquid outlet layer 223 are connected at a position close to the bottom of the powder feeding pipe 220; wherein, a plurality of powder outlets 224 are evenly arranged on the bottom of the powder feeding pipe 220, and each powder outlet 224 is connected to the powder feeding layer 221; the gasification chamber 300 is arranged below the quartz tube 210, and the lower end of the quartz tube 210 and the lower end of the powder feeding pipe 220 are both located in the gasification chamber 300, and the gasification chamber 300 includes from inside to outside A reaction chamber 310 and a first liquid cooling layer 320 are arranged in sequence, and the reaction chamber 310 includes a first conical tube 311, a first circular tube 312, a second conical tube 313 and a second circular tube 314 connected in sequence from top to bottom; wherein the central axis of the first conical tube 311, the central axis of the first circular tube 312, the central axis of the second conical tube 313 and the central axis of the second circular tube 314 are collinear, and the diameter of the first circular tube 312 is greater than the diameter of the second circular tube 314; a quenching chamber 400 is arranged below the gasification chamber 300, and the quenching chamber 400 is connected to the gasification chamber 300, and the quenching chamber 400 includes a first cooling layer 410 and a second cooling layer 420 arranged in sequence from outside to inside, and the second cooling layer 420 includes a delay layer, a second liquid cooling layer and an air cooling layer 440 connected in sequence from top to bottom; a separation collector 500 is arranged below the quenching chamber 400 and is connected to the quenching chamber 400.

[0024] It can be understood that the plasma delivery pipe 100 is a hollow cavity for the transmission of microwaves. One end of the plasma delivery pipe 100 is open, and a first flange 600 is welded to the open end. The other end of the plasma delivery pipe 100 is blocked, specifically by a plugging plate 110, which is connected to the other end of the plasma delivery pipe 100 through a second flange 700. The plugging plate 110 is used to limit the divergence direction of the microwaves. Among them, the first flange 600 and the second flange 700 are coaxially arranged relative to each other, and the inner holes are concentric and have equal inner diameters. Microwaves are generated by a plasma generator. The process of generating microwaves by a plasma generator can be understood with reference to the prior art, and this application will not elaborate on this.

[0025] The inner conduit is used to couple with the microwave to generate a microwave torch. Specifically, after the microwave is conducted to the quartz tube 210 of the conductor tube 200 through the plasma delivery pipe 100, it is excited and coupled with the powder delivery tube 220 in the quartz tube 210 to form a microwave torch at the bottom of the powder delivery tube 220, and the microwave torch is sprayed into the vaporization chamber 300 through the rotating gas in the gas channel. Among them, the gas channel is formed by the interval between the powder delivery tube 220 and the quartz tube 210. Three-way rotating gas cutting downward is arranged at the top of the gas channel, and the air inlets of the three-way rotating gas are evenly arranged on the circumference of the top of the quartz tube 210. The rotating gas makes a spiral motion from top to bottom along the arc surface of the tube wall, such as Figure 2 As shown, the rotating gas component in the horizontal direction has an angle with the tangent direction of the tube wall, and the angle can be 30-60°. By setting the angle within the range of 30-60°, the positive pressure in the quartz tube 210 can be maintained to prevent the gas turbulence backflow in the quartz tube 210. In addition to spraying the microwave torch into the vaporization chamber 300, the rotating gas can also cool the quartz tube 210 to prevent the temperature of the quartz tube 210 from being too high. In addition, the rotating gas can also form a gas wall to prevent the raw material powder from sticking to the wall and affecting the transmission of microwaves. It should be noted that the tube wall here refers to the tube wall of the quartz tube 210.

[0026] It should also be noted that the plasma delivery pipe 100 controls the microwave torch to provide appropriate torch parameters (such as microwave torch diameter, microwave torch length, and microwave torch temperature) through the combined constraints of the quartz tube 210 and the rotating gas in the gas channel. The microwave torch diameter can be controlled by the quartz tube 210, and the microwave torch length can be adjusted by the flow rate and pressure of the rotating gas.

[0027] In the present application, the inner conduit includes a quartz tube 210 and a powder delivery tube 220 disposed in the quartz tube 210. The powder delivery tube 220 is a three-layer structure including a powder delivery layer 221, a liquid inlet layer 222, and a liquid outlet layer 223, which are sequentially arranged from the center to the outside. The powder delivery layer 221 is arranged in the middle position of the powder delivery tube 220 to ensure that the energy utilization of the microwave torch is maximized. The liquid inlet layer 222 and the liquid outlet layer 223 are connected near the bottom position of the powder delivery tube 220, which can better cool the powder outlet 224 of the powder delivery tube 220, and avoid the powder outlet 224 at the bottom of the powder delivery tube 220 from being too high in temperature, causing the raw material powder to melt at the powder outlet 224 and block the powder outlet 224. Among them, the number of powder outlets 224 can be set according to actual conditions, and this application does not limit this.

[0028] It should be noted that the specific connection relationship between the quartz tube 210 and the plasma delivery pipeline 100 is as follows: The upper end of the quartz tube 210 is connected to the plasma delivery pipe 100 through the third flange 800, and the lower end of the quartz tube 210 is connected to the plasma delivery pipe 100 through the fourth flange 900, so that the quartz tube 210 vertically passes through the plasma delivery pipe 100. The wall thickness of the quartz tube 210 is 4-6 mm, and the inner and outer surfaces of the quartz tube 210 are smooth. The inner diameter of the third flange 800 is equal to the inner diameter of the fourth flange 900, and the outer diameter of the quartz tube 210 is slightly smaller than the inner diameter of the third flange 800, so that the quartz tube 210 is easily connected to the plasma delivery pipe 100 through the third flange 800 and the fourth flange 900.

[0029] Further, in order to ensure the sealed connection between the quartz tube 210 and the plasma delivery pipe 100, the present application is also equipped with a first sealing ring 1500 when the upper end of the quartz tube 210 is connected to the plasma delivery pipe 100 through the third flange 800, so as to achieve the sealed connection between the upper end of the quartz tube 210 and the plasma delivery pipe 100. When the lower end of the quartz tube 210 is connected to the plasma delivery pipe 100 through the fourth flange 900, it is also equipped with a second sealing ring 1600 to achieve the sealed connection between the lower end of the quartz tube 210 and the plasma delivery pipe 100. Among them, the third flange 800 and the fourth flange 900 are both provided with a 45° inner chamfer for placing the corresponding sealing rings. The first sealing ring 1500 and the second sealing ring 1600 are both O-rings, and the materials of the first sealing ring 1500 and the second sealing ring 1600 are both rubber.

[0030] In the present application, the gasification chamber 300 is a double-layer structure, and the gasification chamber 300 includes a reaction chamber 310 and a first liquid cooling layer 320. The reaction chamber 310 is a structure that expands first and then gathers, and the reaction chamber 310 is used to fully gasify the raw material powder entering the reaction chamber 310. Specifically, when the raw material powder enters the reaction chamber 310, under the cooperation of the first conical tube 311 and the powder outlet 224, the diameter of the first round tube 312 is designed to be larger than the diameter of the second round tube 314, so that the raw material powder can be filled with the first conical tube 311 and the first round tube 312 with a diffusion trend, and fully gasified under the action of the microwave torch, and then the gasified powder is gathered under the action of the second conical tube 313, and concentrated to the second round tube 314, so as to enter the quenching chamber 400 for rapid quenching. Among them, the first liquid cooling layer 320 is used to cool the reaction chamber 310 to prevent the temperature in the reaction chamber 310 from being too high, which affects the gasification of the raw material powder.

[0031] It should be noted that the specific connection relationship between the vaporization chamber 300 and the quartz tube 210 is as follows: the lower end of the quartz tube 210 is located in the vaporization chamber 300, and the vaporization chamber 300 is connected to the quartz tube 210 through the fifth flange 1000. At the same time, the fifth flange 1000 and the fourth flange 900 are connected by screws. A sixth flange 1100 is provided at the lower end of the vaporization chamber 300. In order to ensure the sealed connection between the fifth flange 1000 and the fourth flange 900, a third sealing ring 1700 is also provided between the fifth flange 1000 and the fourth flange 900.

[0032] In the present application, the quenching chamber 400 is also a double-layer structure, including a first cooling layer 410 and a second cooling layer 420. The second cooling layer 420 includes a delay layer, a second liquid cooling layer and an air cooling layer 440 connected in sequence from top to bottom. Among them, the delay layer is used to act on the gasified powder so that the gasified powder delays falling, the second liquid cooling layer is used to pre-cool the gasified powder that delays falling, and the air cooling layer 440 is used to rapidly cool the pre-cooled gasified powder so that the gasified powder solidifies to form nano powder. The first cooling layer 410 cools the gasified powder entering the quenching chamber 400 throughout the process.

[0033] It should be noted that the specific connection relationship between the quenching chamber 400 and the gasification chamber 300 is as follows: The quenching chamber 400 is connected to the gasification chamber 300 via the seventh flange 1200. Meanwhile, the seventh flange 1200 is connected to the sixth flange 1100 via screws. In order to ensure the sealing connection between the seventh flange 1200 and the sixth flange 1100, a fourth sealing ring 1800 is further provided between the seventh flange 1200 and the sixth flange 1100.

[0034] In the present application, the separation collector 500 is located below the quench chamber 400 and is in communication with the quench chamber 400, and is used to collect the nano powder to obtain nano powders of different particle sizes.

[0035] It should be noted that the specific connection relationship between the separation collector 500 and the quench chamber 400 is as follows: The lower end of the quench chamber 400 is provided with an eighth flange 1300, and the separation collector 500 is connected to the quench chamber 400 through a ninth flange 1400. Meanwhile, the ninth flange 1400 and the eighth flange 1300 are connected by screws. In order to ensure the sealing connection between the ninth flange 1400 and the eighth flange 1300, a fifth sealing ring 1900 is further provided between the ninth flange 1400 and the eighth flange 1300.

[0036] In the embodiment of the present application, through the above-mentioned device, the raw material powder enters the powder delivery layer 221 through the designed three-layer structure of the powder delivery tube 220, and the powder outlet 224 at the bottom of the powder delivery tube 220 is cooled through the liquid inlet layer 222 and the liquid outlet layer 223, which can avoid the raw material powder from melting at the powder outlet 224 due to the excessive temperature at the powder outlet 224, causing the powder outlet 224 to be blocked, thereby ensuring the smooth progress of powder delivery; through the designed reaction chamber 310 of the first expansion and then gathering structure, when the raw material powder enters the gasification chamber 300, under the cooperation of the first conical tube 311 and the powder outlet 224, the raw material powder fills the first conical tube 311 with a diffusion trend. 1 and the first round tube 312, so that the raw material powder is fully gasified under the action of the microwave torch, and then the gasified powder is gathered under the action of the second conical tube 313, and sent to the second round tube 314, so as to enter the quenching chamber 400 for rapid quenching; through the quenching chamber 400 including the delay layer, the second liquid cooling layer and the air cooling layer 440, when the gasified powder enters the quenching chamber 400, the delay layer in the quenching chamber 400 acts on the gasified powder to delay the fall of the gasified powder, and then the gasified powder is pre-cooled by the second liquid cooling layer, and then sent to the air cooling layer 440 for rapid cooling, so that the gasified powder solidifies to form nano powder. The present application is designed to improve the powder making efficiency through the three-layer structure of the powder feeding tube 220, the gasification chamber 300 with the structure of expanding first and gathering later, and the quenching chamber 400 including the delay layer, the second liquid cooling layer and the air cooling layer 440.

[0037] Next, we will refer to Figure 1 The various parts of the above-mentioned microwave plasma nanopowder preparation device in this exemplary embodiment are described in more detail.

[0038] In one embodiment, the bottom of the powder delivery tube 220 is a spherical curved surface, and the opening direction of the powder outlet 224 is consistent with the radius direction of the spherical curved surface.

[0039] It can be understood that the opening direction of the powder outlet 224 is consistent with the radius direction of the spherical surface, which can achieve full dispersion of the raw material powder and rapid and synchronous powder delivery from multiple powder outlets 224 to maximize the use of microwave torch energy.

[0040] In one embodiment, the angle between the conical surface of the first conical tube 311 and its central axis and the angle between the conical surface of the second conical tube 313 and its central axis are both 90±2°.

[0041] It is understandable that if the angle between the conical surface of the first conical tube 311 and its central axis is too small, it is not conducive to the diffusion of the raw material powder. If the angle between the conical surface of the first conical tube 311 and its central axis is too large, it will weaken the pressure of the gas entering the reaction chamber 310 from the powder delivery tube 220, which is not conducive to the movement of the raw material powder to the middle first circular tube 312. Therefore, the present application sets the angle between the conical surface of the first conical tube 311 and its central axis to 90±2°, so that the gas and raw material powder coming out of the powder outlet 224 at the bottom of the powder delivery tube 220 can be quickly diffused for full gasification.

[0042] The angle between the conical surface of the second conical tube 313 and its central axis is 90±2°, which can quickly gather the gasified powder obtained after being fully gasified in the middle first circular tube 312, so as to facilitate the subsequent entry into the quenching chamber 400. If the angle between the conical surface of the second conical tube 313 and its central axis is too large, the gasified powder is likely to accumulate on the conical surface of the second conical tube 313.

[0043] In one embodiment, the ratio of the diameter of the second circular tube 314 to the diameter of the first circular tube 312 is 2 / 7-1 / 3.

[0044] It is understandable that the ratio of the diameter of the second circular tube 314 to the diameter of the first circular tube 312 is designed to be 2 / 7-1 / 3, which can ensure that the gas in the quenching chamber 400 does not flow back into the gasification chamber 300 .

[0045] In one embodiment, the delay layer includes a graphite ring 421, a circle of first air holes 423 is arranged inside the graphite ring 421 along the radial direction of the graphite ring 421, an annular channel 422 is arranged on the peripheral wall of the graphite ring 421 along the axial direction of the graphite ring 421, and a plurality of first air inlet holes 411 are evenly arranged on the first cooling layer 410; wherein the central axis of the graphite ring 421 is collinear with the central axis of the second circular tube 314, each first air hole 423 is connected to the annular channel 422, each first air hole 423 is connected to the second circular tube 314, and the annular channel 422 is connected to each first air inlet hole 411; The second liquid cooling layer includes a guide water jacket 430, the upper surface of which is a conical surface; wherein the ratio of the diameter of the upper end of the upper surface of the guide water jacket 430 to the diameter of the lower end of the upper surface of the guide water jacket 430 is 1 / 3-1 / 2, and the ratio of the distance between the upper end of the upper surface of the guide water jacket 430 and the lower end of the upper surface of the guide water jacket 430 to the diameter of the upper end of the upper surface of the guide water jacket 430 is greater than or equal to 1 / 2; The air cooling layer 440 includes an air dividing ring 441 , on which a plurality of second air holes 442 are evenly arranged. A plurality of second air inlet holes 412 are evenly arranged on the first cooling layer 410 , and each second air inlet hole 412 is connected to the second air hole 442 .

[0046] It can be understood that the inside of the graphite ring 421 is provided with a circle of first air holes 423 along the radial direction of the graphite ring 421, and the height position of the first air holes 423 is in the middle of the graphite ring 421. When preparing nano powder, an inert gas is introduced from the outside to the inside through the first air inlet 411 on the first cooling layer 410, and the inert gas enters the annular channel 422 and enters the second air holes 442 distributed along the radial direction to form a gas wall, which cooperates with the heat preservation effect of the graphite ring 421 to delay the fall of the gasified powder and enhance the gasification effect. The gasified powder enters the area where the guide water jacket 430 is located, and the guide water jacket 430 pre-cools the gasified powder. Among them, the inert gas is nitrogen or argon, and the number of the first air inlet 411 and the number of the second air holes 442 can be set according to actual conditions, and this application does not limit this.

[0047] Furthermore, the number of the first air inlet holes 411 may be four, and the four first air inlet holes 411 are evenly distributed along the peripheral wall of the first cooling layer 410, each first air inlet hole 411 is connected to the annular channel 422, and the inner diameter of the first air inlet hole 411 is 16 mm.

[0048] At the same time, since the upper surface of the guide water jacket 430 is a conical surface, and the ratio of the diameter of the upper end of the upper surface of the guide water jacket 430 to the diameter of the lower end of the upper surface of the guide water jacket 430 is 1 / 3-1 / 2, the ratio of the distance between the upper end of the upper surface of the guide water jacket 430 and the lower end of the upper surface of the guide water jacket 430 to the diameter of the upper end of the upper surface of the guide water jacket 430 is greater than or equal to 1 / 2. The guide water jacket 430 is designed in this way, so that the guide water jacket 430 can be constrained to reduce its diameter, which is convenient for better pre-cooling of the gasified powder.

[0049] After the pre-cooling is completed, the pre-cooled vaporized powder enters the gas dividing ring 441. At the same time, a large flow of cooling gas is introduced into the area where the gas dividing ring 441 is located through the second air inlet hole 412 and the second air holes 442 evenly distributed on the gas dividing ring 441 to rapidly cool the pre-cooled vaporized powder and solidify it to form nano powder.

[0050] In one embodiment, the angle between the guide water jacket 430 and the horizontal direction is 80±1°.

[0051] It can be understood that in order to constrain the diameter of the guide water jacket 430 to be reduced and to better pre-cool the gasified powder, the angle between the guide water jacket 430 and the horizontal direction is designed to be 80±1°.

[0052] In one embodiment, the diameter of the second air hole 442 is 2-3 mm.

[0053] It is understandable that the aperture of the second air hole 442 is designed to be 2-3 mm, which can facilitate the cooling gas to flow into the area where the gas dividing ring 441 is located. The aperture of the second air hole 442 can be 2 mm, 2.3 mm, 2.5 mm, 2.7 mm or 3 mm, etc., which can be set according to actual conditions, and this application does not limit this.

[0054] In one embodiment, a plurality of third air inlet holes are disposed on the plasma delivery pipe 100, and a plurality of air outlet holes are disposed on the plasma delivery pipe 100, and the diameter of the third air inlet holes and the diameter of the air outlet holes are both less than 4 mm.

[0055] It is understandable that the third air inlet is used to pass cooling gas to cool the plasma delivery pipe 100, and the air outlet is used to let out the cooling gas after cooling the plasma delivery pipe 100. Among them, because microwaves cannot pass through holes with a diameter less than 4 mm, in order to prevent microwave leakage while cooling the plasma delivery pipe 100, the diameter of the third air inlet and the diameter of the air outlet are designed to be less than 4 mm in this application. The number of the third air inlet and the number of the air outlet can be set according to actual conditions, and this application does not impose any restrictions on this.

[0056] In one embodiment, the separation collector 500 includes a separation chamber 510 , a powder barrel 520 and a vacuum system 530 , the upper end of the separation chamber 510 is connected to the quench chamber 400 , the lower end of the separation chamber 510 is connected to the powder barrel 520 , and the separation chamber 510 is connected to the vacuum system 530 .

[0057] It is understandable that the number of powder barrels 520 can be set according to actual conditions, and the present application does not impose any limitation thereto. The separation chamber 510 and the vacuum system 530 are used to collect nano powders of different particle sizes into corresponding powder barrels 520 .

[0058] This exemplary embodiment also provides a method for preparing nano powders with microwave plasma, using the device for preparing nano powders with microwave plasma in any of the above embodiments to prepare powders, referring to Figures 1 to 3 The method includes: step S101 to step S105.

[0059] Among them, step S101: the plasma delivery pipeline 100 transmits microwaves to the quartz tube 210 of the conductor tube 200, and after excitation and coupling with the powder delivery tube 220 in the quartz tube 210, a microwave torch is formed at the bottom of the powder delivery tube 220, and the microwave torch is sprayed into the gasification chamber 300 through the rotating gas in the gas channel.

[0060] Step S102: The airflow carries the raw material powder into the powder feeding layer 221 , and cools the powder outlet 224 at the bottom of the powder feeding tube 220 through the liquid inlet layer 222 and the liquid outlet layer 223 , so that the raw material powder can be smoothly ejected from the powder outlet 224 and enter the gasification chamber 300 .

[0061] Step S103: When the raw material powder enters the gasification chamber 300, under the cooperation of the first conical tube 311 and the powder outlet 224 in the reaction chamber 310, the raw material powder fills the first conical tube 311 and the first circular tube 312 with a diffusion trend, so that the raw material powder is fully gasified under the action of the microwave torch, and then the gasified powder is gathered under the action of the second conical tube 313 and sent to the second circular tube 314; wherein, the first liquid cooling layer 320 cools the reaction chamber 310.

[0062] Step S104: Afterwards, the vaporized powder in the second circular tube 314 is sent to the quenching chamber 400, and the vaporized powder is acted on by the delay layer in the quenching chamber 400 to delay the falling of the vaporized powder, and then the vaporized powder is pre-cooled by the second liquid cooling layer, and then sent to the air cooling layer 440 for rapid cooling, so that the vaporized powder is solidified to form nano powder; wherein, during the process of the delay layer acting on the vaporized powder and the second liquid cooling layer pre-cooling the vaporized powder, the first cooling layer 410 simultaneously cools the vaporized powder entering the quenching chamber 400 throughout the entire process.

[0063] Step S105: collecting the nano powder through the separation collector 500 to obtain nano powders of different particle sizes.

[0064] It should be noted that the method for preparing nanopowder by microwave plasma of the present application has been described in the above-mentioned device for preparing nanopowder by microwave plasma, and the present application will not elaborate on it.

[0065] The present application is further described below through the following examples.

[0066] Example 1 Start the vacuum system 530 to evacuate the closed chamber composed of the reaction chamber 310, the quenching chamber 400, and the separation collector 500 to a vacuum of 1.0×10 -2 Pa, and then fill the closed chamber with high-purity nitrogen until the closed chamber pressure reaches 8×10 4 Pa; The power of the ion generator is set to 12 kW, a microwave torch is generated in the middle of the reaction chamber 310, the diameter of the microwave torch is set to 75-80 mm, and the length of the microwave torch is set to 300-330 mm; The three-way cut-wall at the top of the start-up gas channel rotates downward, the single-way gas flow is 200-300L / min, the inlet gas pressure is 4-5Bar, and the gas temperature is 10-15℃.

[0067] Irregular copper powder with a diameter of 20-30 μm is fed in, and 5 powder outlets 224 with a diameter of 3 mm are arranged at the bottom of the powder feeding tube 220 . The powder feeding amount of a single powder outlet 224 is 1-2 g / min.

[0068] The graphite ring 421 in the quench chamber 400 is started to form a gas wall with a gas volume diameter of 80 mm and a thickness of 2 mm, so that the gasified copper powder stays in the high temperature zone for 0.5-1.0 s.

[0069] The second air hole 442 of the air distribution ring 441 in the quenching chamber 400 is started, and the air intake volume of the cooling gas is controlled at 500-600 L / min.

[0070] Nano copper powder with a particle size of 10-50 nm is collected at the bottom of the powder barrel 520 .

[0071] Figure 4 This is a transmission electron microscope image of nano-copper powder, from which it can be seen that the spheroidization degree of the nano-copper powder is improved, the yield of the nano-copper powder is higher, and the particle size is smaller.

[0072] Example 2 Start the vacuum system 530 to evacuate the closed chamber composed of the reaction chamber 310, the quenching chamber 400, and the separation collector 500 to a vacuum of 1.0×10 -2 Pa, and then fill the closed chamber with high-purity nitrogen until the closed chamber pressure reaches 8×10 4 Pa; The power of the ion generator is set to 12 kW, a microwave torch is generated in the middle of the reaction chamber 310, the diameter of the microwave torch is set to 75-80 mm, and the length of the microwave torch is set to 350-400 mm; The three-way cut-wall at the top of the start-up gas channel rotates downward, the single-way gas flow is 300-350L / min, the inlet gas pressure is 4-5Bar, and the gas temperature is 10-15℃.

[0073] Irregular silicon powder with a diameter of 1-10 μm is fed in, and 7 powder outlets 224 with a diameter of 4 mm are arranged at the bottom of the powder feeding pipe 220. The powder feeding amount of a single powder outlet 224 is 0.5-1.0 g / min.

[0074] The graphite ring 421 in the quench chamber 400 is started to form a gas wall with a gas volume diameter of 80 mm and a thickness of 2 mm, so that the gasified silicon powder stays in the high temperature zone for 1-1.5 seconds.

[0075] The second air hole 442 of the air distribution ring 441 in the quenching chamber 400 is started, and the air intake volume of the cooling gas is controlled at 650-700 L / min.

[0076] Nano silicon powder with a particle size of 10-30 nm is collected at the bottom of the powder barrel 520 .

[0077] Figure 5 This is a transmission electron microscope image of nano-silicon powder, from which it can be seen that the spheroidization degree of nano-silicon powder is improved, the yield of nano-silicon powder is higher, and the particle size is smaller.

[0078] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

[0079] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the invention disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary technical means in the art that are not disclosed in the present application.

Claims

1. A device for preparing nano powder by microwave plasma, characterized in that: include: A plasma delivery pipeline, one end of which is open and the other end is blocked; The conductor tube comprises a quartz tube and a powder delivery tube arranged in the quartz tube, the quartz tube vertically passes through the plasma delivery pipeline, both ends of the quartz tube are open, the interval between the powder delivery tube and the quartz tube forms a gas channel, the powder delivery tube comprises a powder delivery layer, a liquid inlet layer and a liquid outlet layer arranged in sequence from the center to the outside, the liquid inlet layer and the liquid outlet layer are connected at a position close to the bottom of the powder delivery tube; wherein a plurality of powder outlets are evenly arranged on the bottom of the powder delivery tube, and each of the powder outlets is connected to the powder delivery layer; A gasification chamber is arranged below the quartz tube, and the lower end of the quartz tube and the lower end of the powder feeding tube are both located in the gasification chamber, the gasification chamber includes a reaction chamber and a first liquid cooling layer arranged sequentially from the inside to the outside, and the reaction chamber includes a first conical tube, a first round tube, a second conical tube and a second round tube connected sequentially from top to bottom; wherein the central axis of the first conical tube, the central axis of the first round tube, the central axis of the second conical tube and the central axis of the second round tube are collinear, and the diameter of the first round tube is greater than the diameter of the second round tube; A quenching chamber is arranged below the gasification chamber, the quenching chamber is communicated with the gasification chamber, the quenching chamber comprises a first cooling layer and a second cooling layer arranged in sequence from outside to inside, the second cooling layer comprises a delay layer, a second liquid cooling layer and an air cooling layer connected in sequence from top to bottom; The separation collector is arranged below the quenching chamber and communicated with the quenching chamber.

2. The device for preparing nano powder by microwave plasma according to claim 1, characterized in that: The bottom of the powder delivery pipe is a spherical curved surface, and the opening direction of the powder outlet is consistent with the radius direction of the spherical curved surface.

3. The device for preparing nano powder by microwave plasma according to claim 1, characterized in that: The included angle between the conical surface of the first conical tube and its central axis, and the included angle between the conical surface of the second conical tube and its central axis are both 90±2°.

4. The device for preparing nano powder by microwave plasma according to claim 1, characterized in that: The ratio of the diameter of the second circular tube to the diameter of the first circular tube is 2 / 7-1 / 3.

5. The device for preparing nano powder by microwave plasma according to claim 1, characterized in that: The delay layer comprises a graphite ring, a circle of first air holes is arranged inside the graphite ring along the radial direction of the graphite ring, an annular channel is arranged on the peripheral wall of the graphite ring along the axial direction of the graphite ring, and a plurality of first air inlet holes are evenly arranged on the first cooling layer; wherein the central axis of the graphite ring is collinear with the central axis of the second circular tube, each of the first air holes is communicated with the annular channel, each of the first air holes is communicated with the second circular tube, and the annular channel is communicated with each of the first air inlet holes; The second liquid cooling layer comprises a guide water jacket, the upper surface of which is a conical surface; wherein the ratio of the diameter of the upper end of the upper surface of the guide water jacket to the diameter of the lower end of the upper surface of the guide water jacket is 1 / 3-1 / 2, and the ratio of the distance between the upper end of the upper surface of the guide water jacket and the lower end of the upper surface of the guide water jacket to the diameter of the upper end of the upper surface of the guide water jacket is greater than or equal to 1 / 2; The air cooling layer comprises an air dividing ring, on which a plurality of second air holes are evenly arranged, and the first cooling layer is evenly provided with a plurality of second air inlet holes, each of which is connected to the second air hole.

6. The device for preparing nano powder by microwave plasma according to claim 5, characterized in that: The included angle between the guide water jacket and the horizontal direction is 80±1°.

7. The device for preparing nano powder by microwave plasma according to claim 6, characterized in that: The diameter of the second pores is 2-3 mm.

8. The device for preparing nano powder by microwave plasma according to claim 1, characterized in that: A plurality of third air inlet holes are arranged on the plasma delivery pipeline, and a plurality of air outlet holes are arranged on the plasma delivery pipeline. The diameter of the third air inlet holes and the diameter of the air outlet holes are both less than 4 mm.

9. The device for preparing nano powder by microwave plasma according to claim 1, characterized in that: The separation collector comprises a separation chamber, a powder barrel and a vacuum system. The upper end of the separation chamber is communicated with the quenching chamber, the lower end of the separation chamber is communicated with the powder barrel, and the separation chamber is communicated with the vacuum system.

10. A method for preparing nano powder by microwave plasma, characterized in that: The device for preparing nano powder by microwave plasma according to any one of claims 1 to 9 is used for powder preparation, comprising: The plasma delivery pipeline conducts the microwave to the quartz tube of the conductor tube, and after being excited, it couples with the powder delivery tube in the quartz tube, forms a microwave torch at the bottom of the powder delivery tube, and the microwave torch is sprayed into the gasification chamber through the rotating gas in the gas channel; The airflow carries the raw material powder into the powder delivery layer, and cools the powder outlet position at the bottom of the powder delivery pipe through the liquid inlet layer and the liquid outlet layer, so that the raw material powder can be smoothly ejected from the powder outlet and enter the gasification chamber; When the raw material powder enters the gasification chamber, under the cooperation of the first conical tube in the reaction chamber and the powder outlet, the raw material powder fills the first conical tube and the first round tube with a diffusion trend, so that the raw material powder is fully gasified under the action of the microwave torch, and then the gasified powder is gathered under the action of the second conical tube and sent to the second round tube in a centralized manner; wherein the first liquid cooling layer cools the reaction chamber; Afterwards, the vaporized powder in the second round tube is sent to a quenching chamber, and the vaporized powder is acted on by the delaying layer in the quenching chamber to delay the falling of the vaporized powder, and then the vaporized powder is pre-cooled by the second liquid cooling layer, and then sent to the air cooling layer for rapid cooling, so that the vaporized powder is solidified to form a nano powder; wherein, during the process of the delaying layer acting on the vaporized powder and the process of the second liquid cooling layer pre-cooling the vaporized powder, the first cooling layer simultaneously performs full cooling on the vaporized powder entering the quenching chamber; The nano powder is collected by a separation collector to obtain the nano powder with different particle sizes.

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