Plasma aluminum nitride powder preparation device

Abstract

The invention discloses a plasma aluminum nitride powder preparation device, and relates to the technical field of plasma material preparation, the plasma aluminum nitride powder preparation device comprises a laminar plasma generation subsystem, a reaction subsystem, a cooling subsystem, a circulation subsystem and a powder return subsystem, the bottom end of the plasma generator is connected with the top of the powder return cylinder; the reaction subsystem comprises a main reaction cylinder, the top of the main reaction cylinder is connected with the bottom of the powder return cylinder, an inner reaction sleeve is arranged on the inner side of the main reaction cylinder, and a reaction cooling assembly is mounted on the main reaction cylinder; the top of the cooling subsystem is connected with the bottom of the main reaction cylinder, the bottom of the cooling subsystem is connected with one end of the circulation subsystem, and the other end of the circulation subsystem is connected with the middle of the side face of the powder return cylinder. The powder return subsystem is connected with the side face of the circulation subsystem. According to the plasma aluminum nitride powder preparation device, it is guaranteed that fed aluminum powder can fully react, and the purity of the prepared aluminum nitride powder can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of plasma material preparation, and specifically relates to a device for preparing plasma aluminum nitride powder. Background Art

[0002] Aluminum nitride material is a ceramic material with excellent properties. It has high thermal conductivity (theoretically up to 320 W / (m·K)), low thermal expansion coefficient (the theoretical value is 4×10 -6 K), good electrical insulation, strong mechanical properties, corrosion resistance, environmental protection and non-toxicity, etc. It is an essential basic material and key material for promoting the development of communication technology and new energy technology.

[0003] At present, the methods for preparing aluminum nitride include direct nitridation method, carbothermal reduction method, self-propagating high-temperature synthesis method, and chemical vapor synthesis method. Compared with the aforementioned preparation methods, the DC arc plasma method has the characteristics of high-active atmosphere, high-temperature environment, precise control of product size, environmental protection and non-toxicity, wide applicability, etc., and is an advanced process method for preparing aluminum nitride powder. The three key elements for preparing aluminum nitride powder are to solve the nitrogen source, aluminum source and heat source required in the preparation process. The principle of the plasma synthesis method is to send aluminum powder into the plasma reactor, and the aluminum powder reacts with high-energy nitrogen ions in the high-temperature plasma environment to generate aluminum nitride powder.

[0004] However, the existing equipment for synthesizing aluminum nitride powder by laminar plasma has the problem that the aluminum powder cannot fully react, resulting in low product purity. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the existing defects, and provide a device for preparing plasma aluminum nitride powder, which is provided with a new reaction subsystem and a circulation subsystem to ensure that the fed aluminum powder can fully react, which is beneficial to improving the purity of the prepared aluminum nitride powder, and can effectively solve the problems in the background art.

[0006] To achieve the above object, the present invention provides the following technical solution: A device for preparing plasma aluminum nitride powder, comprising: A laminar plasma generation subsystem, including a plasma generator and a powder return cylinder, the bottom end of the plasma generator is connected to the top of the powder return cylinder; A reaction subsystem, including a main reaction cylinder, an inner reaction sleeve and a reaction cooling component, the top of the main reaction cylinder is connected to the bottom of the powder return cylinder, the inner reaction sleeve is arranged inside the main reaction cylinder, and a reaction cooling component is installed on the main reaction cylinder; A cooling subsystem, the top of which is connected to the bottom of the main reaction cylinder, and the bottom of the cooling subsystem is connected to one end of the circulation subsystem, and the other end of the circulation subsystem is connected to the middle part of the side of the powder return cylinder; The powder return system is connected to the side of the circulation subsystem.

[0007] The plasma generator in the laminar flow plasma generation subsystem provides a heat source and a nitrogen source. The nitrogen source forms a highly reactive nitrogen source inside the plasma generator and forms a laminar flow plasma jet. Aluminum powder is fed into the plasma generator. The aluminum powder is mixed with the highly reactive nitrogen source, passes through the powder return cylinder, and then enters the interior of the main reaction cylinder and the inner reaction sleeve. The aluminum powder and the highly reactive nitrogen source react inside the main reaction cylinder and the inner reaction sleeve to generate aluminum nitride powder. The reaction cooling assembly is used to cool down the main reaction cylinder and the inner reaction sleeve, and the cooling subsystem is also used to quickly cool the prepared aluminum nitride powder. The cooled aluminum nitride powder and unreacted aluminum powder mixture reach the circulation subsystem under the action of the laminar flow plasma jet. The aluminum nitride powder and unreacted aluminum powder mixture in the circulation subsystem enter the powder return subsystem. The aluminum nitride powder is separated, and the unreacted aluminum powder re-enters the circulation subsystem and then flows back into the powder return cylinder along with the laminar flow plasma jet, enters the interior of the main reaction cylinder and the inner reaction sleeve again, and participates in the reaction with the highly reactive nitrogen source again, realizing the recycling of the unreacted aluminum powder, reducing the content of aluminum powder in the aluminum nitride powder, and effectively improving the purity of the prepared aluminum nitride powder.

[0008] Furthermore, the reaction cooling assembly includes a water cooling inlet and a transfer outlet. The inner reaction sleeve is in the shape of a Laval nozzle, and both ends of the inner reaction sleeve are connected to the inner wall of the main reaction cylinder. There is an inner cooling cavity between the outer side of the inner reaction sleeve and the inner side of the main reaction cylinder. The water cooling inlet is arranged at the position corresponding to the bottom of the inner cooling cavity on the side of the main reaction cylinder, and the transfer outlet is arranged at the position corresponding to the top of the inner cooling cavity on the side of the main reaction cylinder. The shape of the inner reaction sleeve is conducive to accelerating the laminar flow plasma jet. The main reaction cylinder provides a space for the reaction of the highly reactive nitrogen source and aluminum powder. Cold water is fed into the inner cooling cavity through the water cooling inlet, and the cold water is discharged through the transfer outlet. With the help of the cold water, the inner reaction sleeve and the aluminum nitride powder generated inside the inner reaction sleeve can be cooled down. Cold water is fed from the bottom of the inner cooling cavity and drained from the top of the inner cooling cavity to ensure that the interior of the inner cooling cavity is always filled with water and avoid the formation of an air chamber at the top of the inner cooling cavity affecting the cooling effect.

[0009] Furthermore, the reaction cooling assembly further includes a cooling outer cylinder, a transfer pipe, a transfer inlet, and a water cooling outlet. A cooling outer cylinder is sleeved outside the main reaction cylinder. An outer cooling cavity is left between the inner side of the cooling outer cylinder and the outer side of the main reaction cylinder. The ends of the water cooling inlet and the transfer outlet both pass through the side wall of the cooling outer cylinder and extend to the outside of the cooling outer cylinder. A transfer inlet is arranged on the side surface of the cooling outer cylinder corresponding to the bottom of the outer cooling cavity. One end of the transfer pipe is connected to the transfer inlet, and the other end of the transfer pipe is connected to the transfer outlet. A water cooling outlet is arranged on the side surface of the cooling outer cylinder corresponding to the top of the outer cooling cavity. The water discharged from the transfer outlet enters the outer cooling cavity through the transfer pipe and the transfer inlet, and then is discharged from the water cooling outlet after passing through the entire outer cooling cavity, making full use of the cooling water. When the cold water passes through the outer cooling cavity, it takes away the heat of the main reaction cylinder and the inside of the main reaction cylinder, cooling and lowering the temperature of the aluminum nitride powder in the main reaction cylinder, and having a good cooling effect on the aluminum nitride powder. Water is fed from the bottom of the outer cooling cavity and drained from the top of the outer cooling cavity, avoiding the formation of an air chamber at the top inside the outer cooling cavity and affecting the cooling effect.

[0010] Furthermore, the reaction cooling assembly further includes a spiral partition plate. A spiral partition plate is arranged between the inner side of the cooling outer cylinder and the outer side of the main reaction cylinder. The spiral partition plate divides the outer cooling cavity into a spiral cooling channel. The spiral partition plate divides the inside of the outer cooling cavity into a one-way spiral channel. The cooling water flows spirally upward along the spiral cooling channel, extending the path of the cooling water flowing through the outer cooling cavity. At the same time, it avoids the emergence of low-speed flow areas inside the outer cooling cavity where heat is not easily carried away, improving the cooling effect.

[0011] Furthermore, the cooling subsystem includes a cooling cavity and a spiral water cooling pipe. The cooling cavity is frustum-shaped. The top of the cooling cavity is connected to the bottom end of the main reaction cylinder. A spiral water cooling pipe is arranged inside the cooling cavity. The two ends of the spiral water cooling pipe respectively pass through the side wall of the cooling cavity and extend to the outside of the cooling cavity. Cold water is fed from the bottom of the spiral water cooling pipe. When the cold water flows through the spiral water cooling pipe, it can absorb the heat of the powder passing through the cooling cavity, facilitating the rapid cooling of the prepared aluminum nitride powder and facilitating the subsequent separation of the aluminum nitride powder.

[0012] Furthermore, the circulation subsystem includes a deposition horizontal pipe, a powder return vertical pipe, a discharge interface, a return material interface, a powder return pipe, and a powder return nozzle. The bottom of the cooling cavity is connected to one end of the deposition horizontal pipe. The other end of the deposition horizontal pipe is connected to the bottom end of the powder return vertical pipe. The top of the powder return vertical pipe is connected to one end of the powder return nozzle through the powder return pipe. A powder return side sleeve is arranged on the bottom side surface of the powder return cylinder. The powder return nozzle passes through the powder return side sleeve and extends to the inside of the powder return cylinder. A return material interface is arranged on the bottom side surface of the powder return vertical pipe, and a discharge interface is arranged on the top side surface of the powder return vertical pipe.

[0013] The cooled aluminum nitride powder reaches the interior of the deposition horizontal tube under the action of the laminar plasma jet, and sends the mixture of aluminum nitride powder and aluminum powder to the powder return vertical tube. The mixed powder enters the powder return subsystem through the discharge interface. The aluminum nitride powder is separated through the powder return subsystem, and the unreacted aluminum powder re-enters the powder return vertical tube through the return interface. Due to the action of the laminar plasma jet, it enters the powder return nozzle through the powder return pipe and then enters the powder return cylinder through the powder return nozzle. The port of the powder return nozzle is bent downward to ensure that the returned aluminum powder will not interfere with the downward laminar plasma jet generated by the plasma generator. The returned aluminum powder undergoes nitridation reaction again with the high-activity nitrogen source in the laminar plasma jet. After separation, the unreacted aluminum powder can participate in the preparation reaction again, reducing the content of aluminum powder in the aluminum nitride powder, which is beneficial to improving the purity of the aluminum nitride powder.

[0014] Furthermore, the powder return subsystem includes a cyclone separator and a discharge pipe, the discharge interface is connected to one end of the discharge pipe, the other end of the discharge pipe is connected to the cyclone separator, and the top center of the cyclone separator is connected to the aluminum nitride powder collection system. The mixture of aluminum nitride powder and aluminum powder enters the cyclone separator through the discharge interface and the discharge pipe, the cyclone separator separates the mixture of aluminum nitride powder and aluminum powder, and the aluminum nitride powder enters the aluminum nitride powder collection system to be collected.

[0015] Furthermore, the powder return subsystem also includes an ash hopper, an air supply pipe, a return material air supply device, a return material connecting pipe and an arc air collecting plate. The bottom of the cyclone separator is connected to the top of the ash hopper, an arc air collecting plate is arranged on one side of the bottom of the ash hopper, and the middle circular hole of the arc air collecting plate is connected to one end of the return material connecting pipe, and the other end of the return material connecting pipe passes through the side wall of the ash hopper and is connected to the return material interface. The other side of the bottom of the ash hopper is connected to one end of the air supply pipe, and the air supply pipe is arranged corresponding to the middle circular hole of the arc air collecting plate, and the other end of the air supply pipe is connected to the air outlet of the return material air supply device. The aluminum powder moves downward in the cyclone separator and falls into the ash hopper. The return air supply device adopts an air pump. The blown air flow enters the ash hopper through the air supply pipe, and blows the aluminum powder falling into the ash hopper to the arc wind collecting plate. The arc wind collecting plate collects the aluminum powder and the air flow, and then re-enters the return powder vertical pipe through the return material pipe and the return material interface to complete the separation and reflux of the aluminum powder. The aluminum powder moves with the laminar plasma jet, returns to the return powder cylinder through the return powder pipe and the return powder nozzle, and re-participates in the nitriding reaction.

[0016] Further, it further includes a powder feeding system. The powder feeding system includes a supply hopper, a supply elbow pipe, a motor bracket, a feeding motor, a feeding shaft, and a feeding spiral blade. The bottom side of the plasma generator is fixedly connected to the horizontal part of the supply elbow pipe. The top of the vertical part of the supply elbow pipe is connected to the bottom end of the supply hopper. A feeding shaft is rotatably connected to the bent part of the supply elbow pipe. A feeding spiral blade is arranged on the outer side of the shaft section of the feeding shaft located inside the horizontal part of the supply elbow pipe. One end of the feeding shaft located outside the supply elbow pipe is fixedly connected to the output shaft of the feeding motor. The feeding motor is installed on the outer side of the supply elbow pipe through the motor bracket. Aluminum powder is placed in the supply hopper. Due to gravity, the aluminum powder enters the end of the horizontal part through the vertical part of the supply elbow pipe. The feeding motor works to drive the feeding shaft and the feeding spiral blade to rotate. The rotation of the feeding spiral blade conveys the aluminum powder to the inner bottom of the plasma generator. By controlling the rotation speed of the feeding motor, the powder feeding speed can be controlled. The powder feeding method of the feeding spiral blade can prevent the aluminum powder from caking, allowing the aluminum powder to be dispersed into the plasma generator, which is beneficial to enhancing the full nitriding reaction of the aluminum powder.

[0017] Further, the powder feeding system further includes a connecting frame and a spherical dispersion feeding shell. One end of the feeding shaft located inside the plasma generator is connected to a spherical dispersion feeding shell through the connecting frame. The feeding circular opening on the side of the spherical dispersion feeding shell is correspondingly arranged with the end of the supply elbow pipe. The spherical dispersion feeding shell is evenly provided with feeding holes. The connecting frame is used to install the spherical dispersion feeding shell at the end of the feeding shaft. The aluminum powder fed into the plasma generator falls into the inside of the spherical dispersion feeding shell. As the spherical dispersion feeding shell rotates, the aluminum powder in the spherical dispersion feeding shell evenly enters the inner bottom of the plasma generator through the feeding holes. When the aluminum powder enters the plasma generator, it is more dispersed, and the reaction with the highly active nitrogen source is more sufficient, which is beneficial to improving the preparation efficiency.

[0018] Compared with the prior art, the beneficial effects of this plasma aluminum nitride powder preparation device are: 1. The plasma generator in the laminar plasma generation subsystem provides heat source and nitrogen source. The nitrogen source forms a highly active nitrogen source in the plasma generator and forms a laminar plasma jet. Aluminum powder is fed into the plasma generator. The aluminum powder and the highly active nitrogen source are mixed, and after passing through the powder return cylinder, they enter the inside of the main reaction cylinder and the inner reaction sleeve. The aluminum powder and the highly active nitrogen source react inside the main reaction cylinder and the inner reaction sleeve to generate aluminum nitride powder.

[0019] 2. The mixture of cooled aluminum nitride powder and unreacted aluminum powder reaches the inside of the circulation subsystem under the action of the laminar plasma jet. The mixture of aluminum nitride powder and unreacted aluminum powder in the circulation subsystem enters the powder return subsystem, where the aluminum nitride powder is separated, and the unreacted aluminum powder re-enters the circulation subsystem. Then, it flows back into the powder return cylinder with the laminar plasma jet and enters the inside of the main reaction cylinder and the inner reaction sleeve again to participate in the reaction with the highly active nitrogen source again, realizing the recycling of the unreacted aluminum powder, reducing the content of aluminum powder in the aluminum nitride powder, and effectively improving the purity of the prepared aluminum nitride powder.

[0020] 3. The feeding motor operates to drive the feeding shaft and the feeding spiral blade to rotate. The rotation of the feeding spiral blade conveys the aluminum powder to the bottom inside the plasma generator. By controlling the rotation speed of the feeding motor, the powder feeding speed can be controlled. The powder feeding method of the feeding spiral blade can prevent the aluminum powder from caking and allow the aluminum powder to disperse into the plasma generator, which is beneficial to promoting the full nitridation reaction of the aluminum powder.

[0021] 4. The aluminum powder fed into the plasma generator falls into the inside of the spherical dispersion feeding shell. With the rotation of the spherical dispersion feeding shell, the aluminum powder in the spherical dispersion feeding shell uniformly enters the bottom inside the plasma generator through the feeding holes. When the aluminum powder enters the plasma generator, it is more dispersed, and the reaction with the highly active nitrogen source is more sufficient, which is beneficial to improving the preparation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic structural diagram of the plasma aluminum nitride powder preparation device of the present invention; Figure 2 is a schematic rear-side structural diagram of the plasma aluminum nitride powder preparation device of the present invention; Figure 3 is a schematic sectional structural diagram of the plasma aluminum nitride powder preparation device of the present invention Figure 1 ; Figure 4 is the plasma aluminum nitride powder preparation device of the present invention Figure 3 is a schematic structural diagram of a partial laminar plasma generation subsystem and a powder feeding subsystem in the plasma aluminum nitride powder preparation device of the present invention; Figure 5 is the plasma aluminum nitride powder preparation device of the present invention Figure 3 is a schematic structural diagram of a partial laminar plasma generation subsystem and a partial circulation subsystem in the plasma aluminum nitride powder preparation device of the present invention; Figure 6 is the plasma aluminum nitride powder preparation device of the present invention Figure 3 is a schematic structural diagram of the reaction subsystem in the plasma aluminum nitride powder preparation device of the present invention; Figure 7 is the plasma aluminum nitride powder preparation device of the present invention Figure 3 is a schematic structural diagram of the cooling subsystem in the plasma aluminum nitride powder preparation device of the present invention; Figure 8Schematic cross-sectional structure of the device for preparing plasma aluminum nitride powder of the present invention Figure 2 ; In the figure: 100 laminar plasma generation subsystem, 101 plasma generator, 102 nitrogen source inlet, 103 powder return cylinder, 104 powder return side sleeve, 200 reaction subsystem, 201 main reaction cylinder, 202 inner reaction sleeve, 203 cooling outer cylinder, 204 spiral partition plate, 205 water cooling inlet, 206 transfer outlet, 207 transfer pipe, 208 transfer inlet, 209 water cooling outlet, 300 cooling subsystem, 301 cooling cavity, 302 spiral water cooling pipe, 400 circulation subsystem, 401 deposition horizontal pipe, 402 powder return vertical pipe, 403 discharge interface, 404 return material interface, 405 powder return pipe, 406 powder return nozzle, 500 powder return subsystem, 501 cyclone separator, 502 discharge connecting pipe, 503 ash hopper, 504 gas supply pipe, 505 return material gas supply device, 506 return material connecting pipe, 507 detachable bottom cover, 508 arc air collecting plate, 600 aluminum nitride powder collection system, 601 collection pipe, 602 collection box, 603 collection hopper, 604 collection bottle, 700 powder feeding subsystem, 701 supply hopper, 702 supply elbow pipe, 703 motor frame, 704 feeding motor, 705 feeding shaft, 706 feeding spiral blade, 707 connecting frame, 708 spherical dispersion feeding shell, 709 hopper cover. Specific embodiments

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0024] Embodiment 1. Please refer to Figures 1 to 8 , this embodiment provides a technical solution: a device for preparing plasma aluminum nitride powder, including a laminar plasma generation subsystem 100, a reaction subsystem 200, a cooling subsystem 300, a circulation subsystem 400 and a powder return subsystem 500; The laminar plasma generation subsystem 100 includes a plasma generator 101 and a powder return cylinder 103. The bottom end of the plasma generator 101 is connected to the top of the powder return cylinder 103.

[0025] The laminar plasma generation subsystem 100 further includes a nitrogen source inlet 102. The nitrogen source inlet 102 is provided at the center of the top of the plasma generator 101, and nitrogen is fed into the plasma generator 101 through the nitrogen source inlet 102.

[0026] The reaction subsystem 200 includes a main reaction cylinder 201, an inner reaction sleeve 202 and a reaction cooling assembly. The top of the main reaction cylinder 201 is connected to the bottom of the powder return cylinder 103. An inner reaction sleeve 202 is arranged inside the main reaction cylinder 201, and a reaction cooling assembly is installed on the main reaction cylinder 201.

[0027] The reaction cooling assembly includes a water-cooling inlet 205 and a transfer outlet 206. The inner reaction sleeve 202 is in the shape of a Laval nozzle. The two ends of the inner reaction sleeve 202 are respectively connected to the inner wall of the main reaction cylinder 201. An inner cooling cavity is left between the outer side of the inner reaction sleeve 202 and the inner side of the main reaction cylinder 201. A water-cooling inlet 205 is arranged at the position of the side surface of the main reaction cylinder 201 corresponding to the bottom of the inner cooling cavity, and a transfer outlet 206 is arranged at the position of the side surface of the main reaction cylinder 201 corresponding to the top of the inner cooling cavity. The shape of the inner reaction sleeve 202 is conducive to accelerating the laminar plasma jet. The main reaction cylinder 201 provides a space for the reaction of the high-activity nitrogen source and aluminum powder. Cold water is sent into the inner cooling cavity through the water-cooling inlet 205, and the cold water is discharged through the transfer outlet 206. With the help of the cold water, the inner reaction sleeve 202 and the aluminum nitride powder generated by the reaction inside the inner reaction sleeve 202 can be cooled. Cold water is sent from the bottom of the inner cooling cavity and drained from the top of the inner cooling cavity to ensure that the inside of the inner cooling cavity is always filled with water and to avoid the formation of an air chamber at the top of the inner cooling cavity, which affects the cooling effect.

[0028] The reaction cooling assembly further includes a cooling outer cylinder 203, a transfer pipe 207, a transfer inlet 208 and a water-cooling outlet 209. A cooling outer cylinder 203 is sleeved outside the main reaction cylinder 201. An outer cooling cavity is left between the inner side of the cooling outer cylinder 203 and the outer side of the main reaction cylinder 201. The ends of the water-cooling inlet 205 and the transfer outlet 206 both pass through the side wall of the cooling outer cylinder 203 and extend to the outside of the cooling outer cylinder 203. A transfer inlet 208 is arranged at the position of the side surface of the cooling outer cylinder 203 corresponding to the bottom of the outer cooling cavity. One end of the transfer pipe 207 is connected to the transfer inlet 208, and the other end of the transfer pipe 207 is connected to the transfer outlet 206. A water-cooling outlet 209 is arranged at the position of the side surface of the cooling outer cylinder 203 corresponding to the top of the outer cooling cavity. The water discharged from the transfer outlet 206 enters the outer cooling cavity through the transfer pipe 207 and the transfer inlet 208, and then is discharged from the water-cooling outlet 209 after passing through the entire outer cooling cavity. The cooling water is fully utilized. When the cold water passes through the outer cooling cavity, it takes away the heat of the main reaction cylinder 201 and the inside of the main reaction cylinder 201, cools the aluminum nitride powder inside the main reaction cylinder 201, and has a good cooling effect on the aluminum nitride powder. Water is sent from the bottom of the outer cooling cavity and drained from the top of the outer cooling cavity to avoid the formation of an air chamber at the top of the outer cooling cavity, which affects the cooling effect.

[0029] The reaction cooling assembly further includes a spiral partition plate 204. A spiral partition plate 204 is disposed between the inner side of the cooling outer cylinder 203 and the outer side of the main reaction cylinder 201. The spiral partition plate 204 divides the outer cooling cavity into a spiral cooling channel. The spiral partition plate 204 divides the outer cooling cavity into a one-way spiral channel. The cooling water flows spirally upward along the spiral cooling channel, extending the path of the cooling water flowing through the outer cooling cavity. At the same time, it avoids the emergence of a low-speed flow area in the outer cooling cavity where heat is not easily carried away, thus enhancing the cooling effect.

[0030] The top of the cooling subsystem 300 is connected to the bottom of the main reaction cylinder 201, and the bottom of the cooling subsystem 300 is connected to one end of the circulation subsystem 400. The other end of the circulation subsystem 400 is connected to the middle part of the side surface of the powder return cylinder 103.

[0031] The cooling subsystem 300 includes a cooling cavity 301 and a spiral water-cooled pipe 302. The cooling cavity 301 is frustum-shaped, and the diameter of the top of the cooling cavity 301 is larger than that of the bottom. The top of the cooling cavity 301 is connected to the bottom end of the main reaction cylinder 201, and a spiral water-cooled pipe 302 is disposed inside the cooling cavity 301. Both ends of the spiral water-cooled pipe 302 pass through the side wall of the cooling cavity 301 and extend to the outside of the cooling cavity 301. Cold water is fed into the bottom of the spiral water-cooled pipe 302. When the cold water flows through the spiral water-cooled pipe 302, it can absorb the heat of the powder passing through the cooling cavity 301, which is beneficial to quickly cooling the formed aluminum nitride powder and facilitating the subsequent separation of the aluminum nitride powder.

[0032] The circulation subsystem 400 includes a deposition horizontal pipe 401, a powder return vertical pipe 402, a discharge interface 403, a return material interface 404, a powder return pipe 405, and a powder return nozzle 406. One end of the deposition horizontal pipe 401 is connected to the bottom of the cooling cavity 301, and the other end of the deposition horizontal pipe 401 is connected to the bottom end of the powder return vertical pipe 402. The top of the powder return vertical pipe 402 is a conical structure, and the diameter of the top of the powder return vertical pipe 402 gradually decreases until it is the same as the diameter of the powder return pipe 405. The top of the powder return vertical pipe 402 is connected to one end of the powder return nozzle 406 through the powder return pipe 405. A powder return side sleeve 104 is provided on the bottom side of the powder return cylinder 103. The powder return nozzle 406 passes through the powder return side sleeve 104 and extends into the interior of the powder return cylinder 103. The angle between the axis of the end of the powder return nozzle 406 located inside the powder return cylinder 103 and the axis of the powder return cylinder 103 is an acute angle. For details, refer to Figure 5 , the left end of the powder return nozzle 406 is bent downward to the left. A return material interface 404 is provided on the bottom side of the powder return vertical pipe 402, and a discharge interface 403 is provided on the top side of the powder return vertical pipe 402.

[0033] The cooled aluminum nitride powder reaches the inside of the deposition horizontal pipe 401 under the action of the laminar plasma jet, and the mixture of aluminum nitride powder and aluminum powder is sent into the powder return vertical pipe 402. The mixed powder enters the powder return subsystem 500 through the discharge interface 403. The aluminum nitride powder is separated by the powder return subsystem 500, and the unreacted aluminum powder re-enters the powder return vertical pipe 402 through the return material interface 404. Due to the action of the laminar plasma jet, it enters the powder return nozzle 406 through the powder return pipe 405, and then enters the powder return cylinder 103 through the powder return nozzle 406. The port of the powder return nozzle 406 bends downward to ensure that the returned aluminum powder does not interfere with the downward laminar plasma jet generated by the plasma generator 101. The returned aluminum powder reacts with the highly active nitrogen source in the laminar plasma jet again. After separation, the unreacted aluminum powder can participate in the preparation reaction again, reducing the content of aluminum powder in the aluminum nitride powder and facilitating the improvement of the purity of the aluminum nitride powder.

[0034] The powder return subsystem 500 is connected to the side of the circulation subsystem 400.

[0035] The powder return subsystem 500 includes a cyclone separator 501 and a discharge connection pipe 502. One end of the discharge connection pipe 502 is connected to the discharge interface 403, and the other end of the discharge connection pipe 502 is connected to the cyclone separator 501. The top center of the cyclone separator 501 is connected to the aluminum nitride powder collection system 600. The mixture of aluminum nitride powder and aluminum powder enters the cyclone separator 501 through the discharge interface 403 and the discharge connection pipe 502. The cyclone separator 501 separates the mixture of aluminum nitride powder and aluminum powder, and the aluminum nitride powder enters the aluminum nitride powder collection system 600 to be collected.

[0036] The powder return system 500 further includes a hopper 503, a gas supply pipe 504, a return material gas supply device 505, a return material connection pipe 506, and an arc-shaped air collecting plate 508. The bottom of the cyclone separator 501 is threadedly connected to the top of the hopper 503. An arc-shaped air collecting plate 508 is provided on one side of the inner bottom of the hopper 503, and the middle circular hole of the arc-shaped air collecting plate 508 is connected to one end of the return material connection pipe 506. The other end of the return material connection pipe 506 passes through the side wall of the hopper 503 and is connected to the return material interface 404. The other side of the bottom of the hopper 503 is connected to one end of the gas supply pipe 504. The gas supply pipe 504 is correspondingly arranged with the middle circular hole of the arc-shaped air collecting plate 508, and the other end of the gas supply pipe 504 is connected to the air outlet of the return material gas supply device 505. The aluminum powder moves downward in the cyclone separator 501 and falls into the hopper 503. The return material gas supply device 505 uses an air pump, and the blown air flow enters the hopper 503 through the gas supply pipe 504, blowing the aluminum powder falling into the hopper 503 towards the arc-shaped air collecting plate 508. The arc-shaped air collecting plate 508 collects the aluminum powder and the air flow, and then re-enters the powder return vertical pipe 402 through the return material connection pipe 506 and the return material interface 404, completing the separation and return of the aluminum powder. The aluminum powder moves along with the laminar plasma jet, returns to the powder return cylinder 103 through the powder return pipe 405 and the powder return nozzle 406, and participates in the nitriding reaction again.

[0037] The powder return system 500 further includes a detachable bottom cover 507. There is a round opening at the bottom of the hopper 503, and the round opening at the bottom of the hopper 503 is threadedly connected with the detachable bottom cover 507. The detachable bottom cover 507 can be opened to install the arc-shaped air collecting plate 508 in the hopper 503 and also facilitate the cleaning of the aluminum powder inside the hopper 503.

[0038] During use, the plasma generator 101 in the laminar flow plasma generation subsystem 100 provides a heat source and a nitrogen source. The nitrogen source forms a highly active nitrogen source within the plasma generator 101 and forms a laminar flow plasma jet. Aluminum powder is fed into the plasma generator 101. The aluminum powder is mixed with the highly active nitrogen source, passes through the powder return cylinder 103, and then enters the interior of the main reaction cylinder 201 and the inner reaction sleeve 202. The aluminum powder and the highly active nitrogen source react inside the main reaction cylinder 201 and the inner reaction sleeve 202 to generate aluminum nitride powder. The reaction cooling assembly is used to cool down the main reaction cylinder 201 and the inner reaction sleeve 202. The cooling subsystem 300 is also used to rapidly cool the prepared aluminum nitride powder. The cooled aluminum nitride powder and unreacted aluminum powder mixture reach the recycling subsystem 400 under the action of the laminar flow plasma jet. The aluminum nitride powder and unreacted aluminum powder mixture in the recycling subsystem 400 enter the powder return subsystem 500. The aluminum nitride powder is separated, and the unreacted aluminum powder re-enters the recycling subsystem 400, then flows back into the powder return cylinder 103 along with the laminar flow plasma jet, and re-enters the interior of the main reaction cylinder 201 and the inner reaction sleeve 202 to participate in the reaction with the highly active nitrogen source again, realizing the recycling of unreacted aluminum powder, reducing the content of aluminum powder in the aluminum nitride powder, and effectively improving the purity of the prepared aluminum nitride powder.

[0039] Example 2. Please refer to Figures 1 to 8 , this example provides a technical solution: a plasma aluminum nitride powder preparation device. This example is a further explanatory description of the structure in Example 1: The aluminum nitride powder collection system 600 includes a collection pipe 601, a collection box 602, a collection hopper 603, and a collection bottle 604. One end of the collection pipe 601 is connected to the center of the top of the cyclone separator 501, and the other end of the collection pipe 601 is connected to the side of the collection box 602. A collection hopper 603 is provided at the bottom of the collection box 602. The bottom of the collection hopper 603 is threadedly connected to the collection bottle 604. After the aluminum nitride powder is separated by the cyclone separator 501, it enters the collection pipe 601, and then enters the collection box 602. The aluminum nitride powder in the collection box 602 is filtered by a filtering component, then converges into the collection hopper 603, and finally falls into the collection bottle 604. After the collection bottle 604 is filled with aluminum nitride powder, the collection bottle 604 can be removed and a new collection bottle 604 can be replaced. The filtering component in the collection box 602 separates the aluminum nitride powder from the air flow, and the filtering component can be selected as a filter screen or other structures according to actual needs.

[0040] Example 3. Please refer to Figures 1 to 8 , this example provides a technical solution: a plasma aluminum nitride powder preparation device. This example is substantially the same as the structure in Example 2, and the difference lies in: It also includes a powder feeding system 700. The powder feeding system 700 includes a supply hopper 701, a supply elbow 702, a motor bracket 703, a feeding motor 704, a feeding shaft 705, and a feeding spiral blade 706. The bottom side of the plasma generator 101 is fixedly connected to the horizontal part of the supply elbow 702. The top of the vertical part of the supply elbow 702 is connected to the bottom end of the supply hopper 701. A feeding shaft 705 is rotatably connected to the bent part of the supply elbow 702. A feeding spiral blade 706 is arranged outside the shaft section of the feeding shaft 705 located inside the horizontal part of the supply elbow 702. One end of the feeding shaft 705 located outside the supply elbow 702 is fixedly connected to the output shaft of the feeding motor 704. The feeding motor 704 is installed outside the supply elbow 702 through the motor bracket 703. Aluminum powder is placed in the supply hopper 701. Due to gravity, the aluminum powder enters the end of the horizontal part through the vertical part of the supply elbow 702. When the feeding motor 704 works, it drives the feeding shaft 705 and the feeding spiral blade 706 to rotate. The rotation of the feeding spiral blade 706 conveys the aluminum powder to the bottom inside the plasma generator 101. By controlling the rotation speed of the feeding motor 704, the powder feeding speed can be controlled. The powder feeding method of the feeding spiral blade 706 can prevent the aluminum powder from caking, allowing the aluminum powder to disperse and enter the plasma generator 101, which is beneficial to enhancing the full nitriding reaction of the aluminum powder.

[0041] The powder feeding system 700 also includes a hopper cover 709. The opening at the top of the supply hopper 701 is threadedly connected to the hopper cover 709. After adding sufficient aluminum powder into the supply hopper 701, the hopper cover 709 can be covered to seal the top of the supply hopper 701.

[0042] The powder feeding system 700 also includes a connecting frame 707 and a spherical dispersion feeding shell 708. One end of the feeding shaft 705 located inside the plasma generator 101 is connected to the spherical dispersion feeding shell 708 through the connecting frame 707. The feeding circular opening on the side of the spherical dispersion feeding shell 708 is correspondingly arranged with the end of the supply elbow 702, and the center of the spherical dispersion feeding shell 708 is located on the center line of the plasma generator 101. The spherical dispersion feeding shell 708 is evenly provided with feeding holes. The connecting frame 707 is used to install the spherical dispersion feeding shell 708 at the end of the feeding shaft 705. The aluminum powder fed into the plasma generator 101 falls into the inside of the spherical dispersion feeding shell 708. As the spherical dispersion feeding shell 708 rotates, the aluminum powder inside the spherical dispersion feeding shell 708 evenly enters the bottom inside the plasma generator 101 through the feeding holes. When the aluminum powder enters the plasma generator 101, it is more dispersed, and the reaction with the highly active nitrogen source is more sufficient, which is beneficial to improving the preparation efficiency.

[0043] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device.

[0044] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A plasma aluminum nitride powder preparation device, characterized in that: include: A laminar plasma generation subsystem (100) comprises a plasma generator (101) and a powder return cylinder (103), wherein the bottom end of the plasma generator (101) is connected to the top of the powder return cylinder (103); The reaction subsystem (200) comprises a main reaction cylinder (201), an inner reaction sleeve (202) and a reaction cooling assembly, wherein the top of the main reaction cylinder (201) is connected back to the bottom of the powder cylinder (103), the inner side of the main reaction cylinder (201) is provided with the inner reaction sleeve (202), and the reaction cooling assembly is installed on the main reaction cylinder (201); A cooling subsystem (300), the top of which is connected to the bottom of the main reaction cylinder (201), and the bottom of the cooling subsystem (300) is connected to one end of a circulation subsystem (400), and the other end of the circulation subsystem (400) is connected back to the middle of the side of the powder cylinder (103); The powder return subsystem (500) is connected to the side of the circulation subsystem (400).

2. The plasma aluminum nitride powder preparation device according to claim 1, characterized in that: The reaction cooling assembly comprises a water cooling inlet (205) and a transfer outlet (206); the inner reaction sleeve (202) is in the shape of a Laval nozzle, and both ends of the inner reaction sleeve (202) are respectively connected to the inner wall of the main reaction barrel (201), and an inner cooling cavity is left between the outer side of the inner reaction sleeve (202) and the inner side of the main reaction barrel (201); a water cooling inlet (205) is arranged on the side of the main reaction barrel (201) at a position corresponding to the bottom of the inner cooling cavity, and a transfer outlet (206) is arranged on the side of the main reaction barrel (201) at a position corresponding to the top of the inner cooling cavity.

3. The plasma aluminum nitride powder preparation device according to claim 2, characterized in that: The reaction cooling assembly further comprises a cooling outer cylinder (203), a transfer tube (207), a transfer inlet (208) and a water cooling outlet (209); the cooling outer cylinder (203) is sleeved on the outer side of the main reaction cylinder (201); an outer cooling cavity is left between the inner side of the cooling outer cylinder (203) and the outer side of the main reaction cylinder (201); ends of the water cooling inlet (205) and the transfer outlet (206) pass through the side wall of the cooling outer cylinder (203) and extend to the outer side of the cooling outer cylinder (203); a transfer inlet (208) is arranged on the side of the cooling outer cylinder (203) at a position corresponding to the bottom of the outer cooling cavity; the transfer inlet (208) is connected to one end of the transfer tube (207); the other end of the transfer tube (207) is connected to the transfer outlet (206); and a water cooling outlet (209) is arranged on the side of the cooling outer cylinder (203) at a position corresponding to the top of the outer cooling cavity.

4. The plasma aluminum nitride powder preparation device according to claim 3, characterized in that: The reaction cooling assembly further comprises a spiral partition plate (204), wherein the spiral partition plate (204) is arranged between the inner side of the cooling outer cylinder (203) and the outer side of the main reaction cylinder (201), and the spiral partition plate (204) divides the outer cooling cavity into spiral cooling channels.

5. The plasma aluminum nitride powder preparation device according to claim 1, characterized in that: The cooling subsystem (300) comprises a cooling cavity (301) and a spiral water-cooling pipe (302); the cooling cavity (301) is in the shape of a cone; the top of the cooling cavity (301) is connected to the bottom of the main reaction cylinder (201); and a spiral water-cooling pipe (302) is arranged in the cooling cavity (301); two ends of the spiral water-cooling pipe (302) respectively pass through the side wall of the cooling cavity (301) and extend to the outside of the cooling cavity (301).

6. The plasma aluminum nitride powder preparation device according to claim 5, characterized in that: The circulation subsystem (400) comprises a deposition transverse tube (401), a powder return vertical tube (402), a discharge interface (403), a return interface (404), a powder return tube (405) and a powder return nozzle (406); the bottom of the cooling chamber (301) is connected to one end of the deposition transverse tube (401); the other end of the deposition transverse tube (401) is connected to the bottom end of the powder return vertical tube (402); the top of the powder return vertical tube (402) is connected to one end of the powder return nozzle (406) through the powder return tube (405); a powder return side sleeve (104) is provided on the bottom side of the powder return cylinder (103); the powder return nozzle (406) passes through the powder return side sleeve (104) and extends to the inside of the powder return cylinder (103); a material return interface (404) is provided on the bottom side of the powder return vertical tube (402); and a discharge interface (403) is provided on the top side of the powder return vertical tube (402).

7. The plasma aluminum nitride powder preparation device according to claim 6, characterized in that: The powder return subsystem (500) comprises a cyclone separator (501) and a discharge pipe (502), the discharge interface (403) is connected to one end of the discharge pipe (502), the other end of the discharge pipe (502) is connected to the cyclone separator (501), and the top center of the cyclone separator (501) is connected to the aluminum nitride powder collection system (600).

8. The plasma aluminum nitride powder preparation device according to claim 7, characterized in that: The powder return subsystem (500) further comprises an ash hopper (503), an air supply pipe (504), a return material air supply device (505), a return material pipe (506) and an arc air collecting plate (508); the bottom of the cyclone separator (501) is connected to the top of the ash hopper (503); an arc air collecting plate (508) is arranged on one side of the bottom of the ash hopper (503); a central circular hole of the arc air collecting plate (508) is connected to one end of the return material pipe (506); the other end of the return material pipe (506) passes through the side wall of the ash hopper (503) and is connected to the return material interface (404); the other side of the bottom of the ash hopper (503) is connected to one end of the air supply pipe (504); the air supply pipe (504) and the central circular hole of the arc air collecting plate (508) are arranged correspondingly; and the other end of the air supply pipe (504) is connected to the air outlet of the return material air supply device (505).

9. The plasma aluminum nitride powder preparation device according to claim 1, characterized in that: The invention also comprises a powder feeding subsystem (700), wherein the powder feeding subsystem (700) comprises a supply hopper (701), a supply elbow (702), a motor frame (703), a supply motor (704), a supply shaft (705) and a supply spiral blade (706); the bottom side of the plasma generator (101) is fixedly connected to the horizontal part of the supply elbow (702); the top of the vertical part of the supply elbow (702) is connected to the bottom end of the supply hopper (701); the bent part of the supply elbow (702) is rotatably connected to the supply shaft (705); the supply spiral blade (706) is arranged on the outside of the shaft section of the supply shaft (705) located inside the horizontal part of the supply elbow (702); one end of the supply shaft (705) located outside the supply elbow (702) is fixedly connected to the output shaft of the supply motor (704); and the supply motor (704) is installed on the outside of the supply elbow (702) through the motor frame (703).

10. The plasma aluminum nitride powder preparation device according to claim 9, characterized in that: The powder feeding subsystem (700) further comprises a connecting frame (707) and a spherical dispersion feeding shell (708); one end of the feeding shaft (705) located inside the plasma generator (101) is connected to the spherical dispersion feeding shell (708) via the connecting frame (707); a feeding circular opening on the side of the spherical dispersion feeding shell (708) is arranged corresponding to the end of the supply elbow (702); and feeding holes are evenly opened on the spherical dispersion feeding shell (708).

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