CN115028459A - Method and device for preparing high-purity superfine aluminum nitride powder body by using plasma - Google Patents
Method and device for preparing high-purity superfine aluminum nitride powder body by using plasma Download PDFInfo
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Abstract
The invention discloses a method and a device for preparing high-purity superfine aluminum nitride powder by plasma, wherein discharge gas is sent into a plasma generator, ionized under the action of a power supply to form high-temperature argon/nitrogen mixed gas thermal plasma jet or nitrogen thermal plasma jet, and flows into a plasma high-temperature reactor; quantitatively feeding the simple substance aluminum powder into a plasma high-temperature reactor through a powder feeder, quickly liquefying and gasifying the simple substance aluminum powder, and reacting liquefied aluminum and/or gasified aluminum with high-temperature nitrogen in the plasma high-temperature reactor to generate an aluminum nitride powder precursor; the aluminum nitride powder precursor enters an aluminum nitride powder purity improving chamber to further improve the purity; then the mixture enters an aluminum nitride powder particle size sieving chamber, and is cooled and condensed to form superfine aluminum nitride powder; the superfine aluminum nitride powder enters a gas-solid separator for separation, and the superfine aluminum nitride powder obtained in each region of the aluminum nitride powder particle size sieving chamber and the gas-solid separator is respectively collected, and has the advantages of uniform particle size and high purity.
Description
Technical Field
The invention relates to the field of preparation of metal ceramic materials, in particular to a method and a device for preparing high-purity superfine aluminum nitride powder by using argon/nitrogen or nitrogen plasma.
Background
With the vigorous development of microelectronics and semiconductor technologies, chips, electronic components and motors gradually enter the micro, lightweight, high energy density and high power era. This results in a significant increase in the internal heat generation density of the chip, electronic component or high power IGBT. In order to keep the electronic equipment operating stably, this heat needs to be quickly removed.
The aluminum nitride ceramic as a typical representative of the third generation semiconductor material has the characteristics of high thermal conductivity, high temperature resistance, thermal expansion coefficient close to that of silicon, high mechanical strength, good chemical stability, environmental protection, no toxicity, small dielectric constant and the like, and is considered as an ideal material for packaging a new generation heat dissipation substrate and an electronic device.
The production of aluminum nitride ceramic devices mainly comprises two processes. Firstly, preparing aluminum nitride powder, and secondly, forming and sintering the aluminum nitride powder into an aluminum nitride ceramic device. Of the two, the preparation of the aluminum nitride powder is the most critical. At present, the traditional production methods of aluminum nitride powder mainly comprise the following steps:
1. direct nitriding method
The direct nitriding method uses metal aluminum powder to directly react with nitrogen at high temperature to synthesize aluminum nitride powder, and the reaction formula is as follows:
2Al+N 2 →2AlN；
2. carbothermic process
The carbothermic method is characterized in that alumina powder and carbon powder react with nitrogen at high temperature to generate aluminum nitride powder, and the reaction formula is as follows:
Al 2 O 3 +3C+N 2 →3CO+2AlN；
3. self-propagating high-temperature synthesis method
The reaction of the aluminum and the nitrogen is a strong exothermic reaction, no other heat source is needed once the reaction is ignited, and the combustion speed is high; the self-propagating high-temperature synthesis method utilizes the heat released by the nitrogen-aluminum reaction to initiate the self-sustaining reaction of aluminum and nitrogen, and is similar to a direct nitriding method, and the reaction formula is as follows:
2Al+N 2 →2AlN；
4. chemical vapor deposition method
Chemical Vapor Deposition (CVD) is a process in which a vapor phase compound of aluminum and a nitrogen-containing gas are reacted under a high temperature gaseous condition to produce aluminum nitride powder, the reaction formula is as follows:
AlCl 3 +NH 3 →AlN+3HCl。
in addition to the above conventional preparation method, the hydrogen thermal plasma method can also be used to prepare high purity nano aluminum nitride powder, such as CN108059134A, which is prepared in a plasma generator, nitrogen and hydrogen are used as discharge gas, the discharge gas is introduced into the plasma generator, the discharge gas generates plasma jet under high temperature condition, then the plasma jet is introduced into a straight tube reactor and reacts with vaporized high purity aluminum powder, thereby obtaining aluminum nitride powder, wherein the yield of the aluminum nitride powder can reach up to 70%, the purity can reach 99.02%, the average particle diameter is about 300-400 meshes, and the diameter of most particles is 50-200 nm.
The electronic grade aluminum nitride powder requires controllable particle size distribution and high purity of aluminum nitride, the use requirement of the aluminum nitride powder with D50 (median diameter) of 1-1.5 μm and purity of more than 99.2% (w/w) is increased, and the problem that the particle size and purity are difficult to control exists in the existing domestic aluminum nitride powder preparation process.
Disclosure of Invention
Aiming at the problems of harsh process conditions, difficult control of particle size and purity and the like of the traditional aluminum nitride powder preparation, the invention provides a novel preparation method with controllable particle size and high purity of aluminum nitride powder and a device for implementing the method.
In order to solve the technical problem, one embodiment of the present invention adopts the following technical solutions:
a device for preparing high-purity superfine aluminum nitride powder by using plasma structurally comprises: a plasma generator, a powder feeder, a plasma high-temperature reactor, an aluminum nitride powder purity improving chamber, an aluminum nitride powder particle size sieving chamber and a gas-solid separator. The components are organically combined and each is responsible for jointly completing the production of the high-purity superfine aluminum nitride powder body. The powder feeder is a powder feeder with controllable powder feeding amount.
The lower end of the plasma generator is connected with the powder feeder, the lower end of the powder feeder is connected with the plasma high-temperature reactor, one side of the plasma high-temperature reactor is connected with the aluminum nitride powder purity improving chamber, one side of the aluminum nitride powder purity improving chamber is connected with the aluminum nitride powder particle size sieving chamber, and the tail end of the aluminum nitride powder particle size sieving chamber is connected with the gas-solid separator.
The water chilling unit is arranged on the outer surface of the device for preparing the high-purity superfine aluminum nitride powder by the plasma, and the whole device or part of the device can be water-chilled. The water chilling unit can adopt a water chilling jacket.
The plasma generator can be driven by a direct current, high frequency (MHz) and microwave (GHz) power supply, and the fed argon and/or nitrogen is subjected to ionization breakdown to form argon-nitrogen plasma jet or nitrogen plasma jet with the central temperature of ten thousand K and the average temperature of more than 3000 ℃. At this temperature, nitrogen is broken down into highly reactive nitrogen atoms and flows into the plasma high temperature reactor. The input power and input gas flow of the plasma generator are adjustable.
The powder feeder with controllable powder feeding amount uses nitrogen, argon or ammonia as carrier gas to feed high-purity aluminum powder into the reactor in a fluidization mode. The particle size of the aluminum powder which can be conveyed by the powder feeder is 1-100 micrometers, including but not limited to 1 micrometer, 5 micrometers, 10 micrometers, 15 micrometers, 20 micrometers, 30 micrometers, 40 micrometers, 50 micrometers, 60 micrometers, 70 micrometers, 80 micrometers, 90 micrometers, 100 micrometers or the aluminum powder enters the powder feeder according to a certain particle size distribution range. The high-purity aluminum powder is powder with an aluminum content of 99% (w/w) or more.
The plasma high-temperature reactor continuously receives high-temperature argon nitrogen plasma jet (or high-temperature nitrogen plasma jet) from a plasma generator and aluminum powder from a powder feeder at the same time. The aluminum powder can be liquefied, gasified and nitrided in a plasma high-temperature reactor to generate a precursor capable of condensing aluminum nitride powder. The plasma high-temperature reactor is a hot wall channel space with an inner wall made of high-temperature resistant (more than 3000 ℃) materials.
The aluminum nitride powder purity improving chamber is equivalent to a subsequent reactor. The aluminum nitride powder purity improving chamber uses high-temperature resistant materials as a hot wall channel space of an inner wall, and keeps the average temperature above 3000 ℃ through heat preservation (using materials resistant to high temperature above 3000 ℃ as the inner wall) and reheating measures (plasma high-temperature reaction), so that the aluminum powder which is possibly not reacted in the precursor continues to react in the flow.
The aluminum nitride powder particle size screening chamber adopts a dust separation principle. The precursor of the aluminum nitride powder after the reaction is cooled, grown and condensed, and then passes through a channel embedded with a plurality of sedimentation lattices at a certain flow speed. And settling the agglomerated powder with larger grain diameter into the first grid, and repeating the steps to realize the screening control of the grain diameter of the product.
The gas-solid separator is a terminal end of the apparatus. The powder which is not settled after being sieved by the particle size of the powder is completely collected, and the collection mode is bag vacuum or electrostatic adsorption.
The whole system can adopt PLC control or manual control from the plasma generator, the powder feeder, the plasma high-temperature reactor to pressure feedback, and the intelligent degree of the reaction device is high.
In addition, the invention also provides a method for preparing high-purity superfine aluminum nitride powder by using the plasma, which comprises the following steps: argon and nitrogen are used as discharge gas, or nitrogen is used as discharge gas, the discharge gas is sent into the plasma generator, ionization is carried out under the action of a power supply, and argon/nitrogen mixed gas thermal plasma jet or nitrogen thermal plasma jet with high temperature (the average temperature is more than 3000 ℃) is formed and flows into the plasma high-temperature reactor; the simple substance aluminum powder is quantitatively fed into a plasma high-temperature reactor (2000-; the aluminum nitride powder precursor enters an aluminum nitride powder purity improving chamber to further improve the purity; then the powder enters a particle size sieving chamber of the aluminum nitride powder, and is cooled (finally cooled to the room temperature below the condensation temperature) to be condensed into the ultrafine aluminum nitride powder; the superfine aluminum nitride powder enters a gas-solid separator for separation, and the superfine aluminum nitride powder obtained in each region of the aluminum nitride powder particle size sieving chamber and the gas-solid separator is respectively collected, and has the advantages of uniform particle size (narrow distribution) and high purity.
When argon and nitrogen are used as discharge gas, the volume flow ratio of argon to nitrogen is 1: 2-10.
The temperature and flow rate of the plasma jet entering the lower plasma high-temperature reactor can be controlled by adjusting the discharge power of the plasma generator and the flow of the discharge gas. Preferably, the output power of the plasma generator is 30-200kW, and the discharge gas flow rate is 5-20m 3 In terms of hours. The output power is 30-200kW, including but not limited to 30kW, 40kW, 50kW, 60kW, 70kW, 80kW, 90kW, 100kW, 120kW, 150kW, 160kW, 180kW, 200 kW. The discharge gas has a flow rate of 5-20m 3 Hour, including but not limited to 5m 3 Hour, 7m 3 Hour, 9m 3 Hour, 12m 3 Hour, 15m 3 Hour, 18m 3 Hour, 20m 3 In terms of hours.
The powder feeder takes nitrogen or argon or ammonia as carrier gas, and feeds high-purity aluminum powder into the plasma high-temperature reactor in a fluidization mode. The carrier gas flow and the aluminum powder particle size are matched, and the mass of the aluminum powder fed into the reactor in unit time can be freely adjusted. Preferably, the aluminum powder has a particle size of 10-100 microns and a carrier gas flow of 0.5-5m 3 The aluminum powder carrying capacity is 200-. The particle size of the aluminum powder is 10-100 micrometers, including but not limited to 10, 30, 50, 80 and 100 micrometers; the carrier gas flow is 0.5-5m 3 H, including but not limited to 0.5, 1, 2, 3, 4, 5m 3 H; the carrying amount of the aluminum powder is 200-3000g/h, including but not limited to 200, 500, 800, 1200, 1800, 2300, 2700 and 3000 g/h.
The plasma high-temperature reactor is a hot wall channel space with an inner wall made of high-temperature resistant materials, the temperature of the inner space of the plasma high-temperature reactor is kept at 2000-4000 ℃, and the plasma high-temperature reactor can simultaneously receive high-temperature argon nitrogen plasma jet (or nitrogen plasma jet) from a plasma generator and continuous aluminum powder from a powder feeder. The diameter and the length of the matching channel can adjust the retention time of the aluminum powder in the reactor, ensure that the aluminum powder finishes the processes of liquefaction, gasification and nitridation, and improve the reaction rate. Preferably, the temperature of the inner space of the plasma high-temperature reactor is kept above 3000 ℃, the diameter is 2-8cm, and the length is 10-50 cm. Sufficient residence time to generate a precursor capable of condensing the aluminum nitride powder.
The aluminum nitride powder purity improving chamber uses high temperature resistant material as the hot wall channel space of the inner wall, and keeps the temperature above 3000 ℃ by heat preservation and reheating measures, so that the aluminum powder which is not reacted continues to complete the reaction in the flowing process. The heat preservation method is the same as that of a plasma high-temperature reactor (high-temperature resistant materials are used as the inner wall), and the heating method is the same as that of a plasma generator. Preferably, the plasma discharge power is 15-100 kW.
The aluminum nitride powder particle size sieving chamber is internally embedded with a plurality of lattices which can selectively settle or block aluminum nitride powder with different particle sizes in a flow channel, an aluminum nitride powder precursor which is from a purity improving chamber and has completely reacted is cooled and grown and condensed in the flow channel, and then when the aluminum nitride powder precursor passes through the embedded channel (such as 3-5 conical powder stoppers which are connected in series) at a certain flow speed, the agglomerated powder with larger particle size is settled in the first lattice, and the like, thereby realizing the sieving control of the particle size of the product.
The gas-solid separator adopts a cloth bag or filter element type vacuumizing gas-solid separation mode. The air resistance generated by the two methods is gradually increased, and a pressure feedback type vacuum pump is used for maintaining the normal pressure of the whole system. Preferably, the normal absolute pressure of the whole system is 0.9 multiplied by 10 5 Pa-1.4×10 5 Pa。
Compared with the prior art, the invention has at least the following beneficial effects: can realize the rapid preparation of the ultrafine high-purity aluminum nitride powder with the particle size of 200-500nm, 500-800nm and 800-1500 nm. The yield of the aluminum nitride powder can be up to 100 percent, the purity of the product can reach 99.5 percent, and DN50 is between 800 and 1200nm, which is obviously higher than that of the product obtained by the traditional process method and has controllable particle size.
Compared with the existing plasma process, the process has no environmental pollution, the device is easy to enlarge, and the large-scale production is easier. The aluminum nitride powder prepared by the method can be applied to chips, high-power IGBT module substrates and packaging materials; the method can be applied to the fields of 5G base stations, new energy automobile electronics, high-speed rail electronics, aerospace, military communication and the like.
Drawings
FIG. 1 is a schematic diagram of an apparatus for preparing high-purity ultrafine aluminum nitride powder by using plasma.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
The schematic diagram of the device for preparing high-purity superfine aluminum nitride powder by using the plasma is shown in figure 1. The structure of the device comprises: the device comprises a plasma generator, a powder feeder, a plasma high-temperature reactor, an aluminum nitride powder purity improving chamber, an aluminum nitride powder particle size sieving chamber and a gas-solid separator. The components are organically combined and each undertakes the responsibility to jointly complete the production of the high-purity ultrafine aluminum nitride powder body. The powder feeder is a powder feeder with controllable powder feeding quality. The lower end of the plasma generator is connected with the powder feeder, the lower end of the powder feeder is connected with the plasma high-temperature reactor, one side of the plasma high-temperature reactor is connected with the aluminum nitride powder purity improving chamber, one side of the aluminum nitride powder purity improving chamber is connected with the aluminum nitride powder particle size sieving chamber, and the tail end of the aluminum nitride powder particle size sieving chamber is connected with the gas-solid separator.
The plasma generator is driven by a direct-current power supply, and the fed argon and nitrogen are subjected to ionization breakdown to form argon-nitrogen plasma jet flow with the central temperature of ten thousand K and the average temperature of 3000 ℃. At this temperature, nitrogen is broken down into highly reactive nitrogen atoms and flows into the plasma high temperature reactor. The powder feeder uses nitrogen as carrier gas and feeds high-purity aluminum powder into the reactor in a fluidized mode. The grain diameter of the aluminum powder which can be conveyed by the powder feeder is distributed between 1 and 100 microns. The high-purity aluminum powder refers to powder with an aluminum content of 99% (w/w).
The plasma high-temperature reactor (adopting a graphite tube reactor) continuously receives the high-temperature argon nitrogen plasma jet flow from the plasma generator and the aluminum powder from the powder feeder at the same time. The aluminum powder can complete the processes of liquefaction, gasification and nitridation in the plasma high-temperature reactor to generate a precursor of the condensable aluminum nitride powder. The plasma high-temperature reactor is a hot wall channel space with an inner wall made of high-temperature resistant (more than 3000 ℃) materials.
The aluminum nitride powder purity improving chamber is equivalent to a subsequent reactor. The aluminum nitride powder purity improving chamber uses high-temperature resistant materials as a hot wall channel space of an inner wall, a plasma generator is used for heating, and the average temperature is kept above 3000 ℃ through heat preservation and reheating measures, so that the aluminum powder which is possibly not reacted in the precursor continues to complete the reaction in the flow.
The aluminum nitride powder particle size screening chamber adopts a dust separation principle. The reacted aluminum nitride powder precursor is cooled to grow and agglomerate and then passes through a channel embedded with three serially connected conical powder stoppers at a certain flow speed. And settling the agglomerated powder with larger grain diameter into the first grid, and repeating the steps to realize the screening control of the grain diameter of the product.
The gas-solid separator is a cloth bag vacuum pumping air-solid separator. The pressure feedback of the whole system from the plasma generator, the powder feeder, the plasma high-temperature reactor to the gas-solid separator can be controlled by a PLC automatic control system or manually, and the intelligent degree of the reaction device is high.
Taking the dc arc thermal plasma as an example, the working process of the device is as follows:
1. starting a water chilling unit to enable the outer layer of the whole device to be in a water-cooling state;
2. starting an air source, performing air replacement on the inside of the device by using nitrogen through a PLC automatic control system, and completely replacing the air in the device with the nitrogen;
3. controlling argon and nitrogen to be proportionally input into the plasma generator through a PLC automatic control system, and starting a plasma power supply and the generator to enable plasma discharge to be in a stable state;
4. starting the powder feeder through a PLC automatic control system, leading aluminum powder to enter the upper part of the graphite tube type reactor in a fluidization manner according to a set amount to be mixed with high-temperature plasma jet, and generating nitridation reaction under the action of nitrogen plasma in the graphite tube type reactor;
5. starting a plasma generator of the purity improving chamber through a PLC automatic control system, ensuring that incomplete reactants from a front-end plasma high-temperature reactor are further reacted, and then entering an aluminum nitride powder particle size screening chamber;
6. the sieving chamber is composed of three conical powder stoppers connected in series, and the powder stoppers can respectively stop the powder with different particle sizes, so that the particle size sieving is realized.
7. The gas passing through the sieving chamber also contains superfine aluminum nitride dust, and is finally collected by a cloth bag. When the cloth bag is collected, the rotation speed of the vacuum pump is regulated through the PLC to ensure that the pressure of the system is in a safe operation range;
8. and the aluminum nitride powder collected by the powder sieving chamber and the cloth bag is analyzed by adopting instruments such as a scanning electron microscope, a particle size analyzer and the like to obtain the particle size of the aluminum nitride.
Example 2
With the apparatus described in example 1, nano aluminum nitride powder was produced by the following process:
argon and nitrogen are used as discharge gas, and the flow rate of the discharge gas is 10m 3 The volume flow ratio of argon to nitrogen is 1: 5; the discharge gas is sent into a plasma generator, ionized under the action of a direct current power supply, the output power of the plasma generator is 100kW, and an argon/nitrogen mixed gas thermal plasma jet with high temperature (average temperature is 3000 ℃) is formed and flows into a plasma high-temperature reactor; the powder feeder uses nitrogen as carrier gas, high-purity aluminum powder (purity 99%) is fed into plasma high-temperature reactor in fluidization mode, the particle size of aluminum powder is distributed in 40-60 micrometers, and carrier gas flow rate is 2.5m 3 The aluminum powder carrying capacity is 1000 g/h. The temperature of the inner space of the plasma high-temperature reactor was maintained at 3000 ℃ and 6cm in diameter and 35cm in length. The aluminum powder is rapidly liquefied and gasified in the plasma high-temperature reactor, and the liquefied aluminum and/or the gasified aluminum react with high-temperature nitrogen in the plasma high-temperature reactor to generate an aluminum nitride powder precursor. Aluminum nitride powderThe precursor enters an aluminum nitride powder purity improving chamber (the internal temperature is 3000 ℃, and the output power of a plasma generator is 100kW) to further improve the purity; then the powder enters a particle size sieving chamber of the aluminum nitride powder, and is cooled (finally cooled to the room temperature below the condensation temperature, and is assisted by a water chilling unit) to be condensed into the ultrafine aluminum nitride powder; the superfine aluminum nitride powder enters a gas-solid separator for separation, and the normal absolute pressure of the whole system is 1.0 multiplied by 10 5 And Pa, respectively collecting the superfine aluminum nitride powder obtained in each region of the aluminum nitride powder particle size sieving chamber and the gas-solid separator.
The detection result shows that the product has better dispersibility, and the average particle sizes of the three conical powder stoppers are respectively about 150-500nm, 500-1000nm and 1-1.5 μm. The particle size range collected by the cloth bag is 40-140 nm. The purity of the aluminum nitride is 99.5 percent. The powder D50 in three separate sieve chambers is 1.1 μm, and the yield of the aluminum nitride powder is 99%.
Example 3
With the apparatus described in example 1, nano aluminum nitride powder was produced by the following process:
argon and nitrogen are used as discharge gas, and the flow rate of the discharge gas is 15m 3 The volume flow ratio of argon to nitrogen is 1: 6; the discharge gas is sent into a plasma generator, ionized under the action of a direct current power supply, the output power of the plasma generator is 100kW, and an argon/nitrogen mixed gas thermal plasma jet with high temperature (average temperature is 3000 ℃) is formed and flows into a plasma high-temperature reactor; the powder feeder uses nitrogen as carrier gas, high-purity aluminum powder (purity 99%) is fed into plasma high-temperature reactor in fluidization mode, the particle size of aluminum powder is distributed in 30-50 micrometers, and carrier gas flow rate is 3m 3/ h, the carrying capacity of the aluminum powder is 800 g/h. The temperature of the inner space of the plasma high-temperature reactor was kept at 3200 deg.C, 6cm in diameter and 35cm in length. The aluminum powder is rapidly liquefied and gasified in the plasma high-temperature reactor, and the liquefied aluminum and/or the gasified aluminum react with high-temperature nitrogen in the plasma high-temperature reactor to generate an aluminum nitride powder precursor. The aluminum nitride powder precursor enters an aluminum nitride powder purity improving chamber (the internal temperature is 3000 ℃, and the output power of a plasma generator is 100kW) to further improve the purity; then enters the aluminum nitride powderThe particle size is divided into a sieve chamber, and the sieve chamber is cooled (finally cooled to the temperature below the condensation temperature to the room temperature, and assisted by a water chilling unit) to condense the aluminum nitride powder into superfine aluminum nitride powder; the superfine aluminum nitride powder enters a gas-solid separator for separation, and the normal absolute pressure of the whole system is 1.0 multiplied by 10 5 And Pa, respectively collecting the superfine aluminum nitride powder obtained in each area of the aluminum nitride powder particle size sieving chamber and the gas-solid separator.
The detection result shows that the dispersibility of the product is relatively good, and the average particle sizes of the powder of the three conical powder stoppers are respectively about 150-500nm, 500-800nm and 800-1.2 μm. The particle size range collected by the cloth bag is 40-140 nm. The purity of the aluminum nitride is 99.6%. The powder D50 in three sieve chambers is 1.0 μm, and the yield of aluminum nitride powder reaches 99.5%.
Although the invention has been described herein with reference to illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More specifically, various variations and modifications may be made to the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure herein. In addition to variations and modifications in the component parts and/or arrangements, other uses will also be apparent to those skilled in the art.
Claims (10)
1. The device for preparing high-purity superfine aluminum nitride powder by using plasma is characterized in that the structure of the device comprises: the device comprises a plasma generator, a powder feeder, a plasma high-temperature reactor, an aluminum nitride powder purity improving chamber, an aluminum nitride powder particle size sieving chamber and a gas-solid separator; the lower end of the plasma generator is connected with the powder feeder, the lower end of the powder feeder is connected with the plasma high-temperature reactor, one side of the plasma high-temperature reactor is connected with the aluminum nitride powder purity improving chamber, one side of the aluminum nitride powder purity improving chamber is connected with the aluminum nitride powder particle size screening chamber, and the tail end of the aluminum nitride powder particle size screening chamber is connected with the gas-solid separator.
2. The apparatus for preparing high-purity ultrafine aluminum nitride powder according to claim 1, wherein the plasma generator is driven by a direct current, high-frequency or microwave power supply, and ionizes and breaks down the fed argon and/or nitrogen to form an argon-nitrogen plasma jet or a nitrogen plasma jet with a central temperature of ten thousand K and an average temperature of more than 3000 ℃.
3. The apparatus for preparing high purity ultrafine aluminum nitride powder according to claim 1, wherein the powder feeder feeds high purity aluminum powder into the reactor in a fluidized manner using nitrogen, argon or ammonia as a carrier gas.
4. The apparatus for preparing high-purity ultrafine aluminum nitride powder by using plasma according to claim 1, wherein the plasma high-temperature reactor continuously receives the high-temperature argon nitrogen plasma jet or the high-temperature nitrogen plasma jet from the plasma generator and the aluminum powder from the powder feeder at the same time; the plasma high-temperature reactor is a hot wall channel space with an inner wall made of a material resistant to more than 3000 ℃.
5. The apparatus for preparing high-purity ultrafine aluminum nitride powder by using plasma according to claim 1, wherein the aluminum nitride powder purity-improving chamber is heated by a plasma high-temperature reactor, and the hot wall channel space of the inner wall is made of a material resistant to a temperature of more than 3000 ℃.
6. The apparatus for preparing high-purity ultrafine aluminum nitride powder by using plasma according to claim 1, wherein the aluminum nitride powder particle size sieving chamber is provided with a channel embedded with a plurality of sedimentation lattices.
7. The apparatus for preparing high-purity ultrafine aluminum nitride powder by using plasma according to claim 1, wherein the aluminum nitride powder particle size sieving chamber is composed of 3-5 channels of serially connected conical powder stoppers.
8. The apparatus for preparing high-purity ultrafine aluminum nitride powder according to claim 1, wherein the gas-solid separator is a cloth bag vacuum-pumping or electrostatic adsorption type gas-solid separator.
9. A method for preparing high-purity ultrafine aluminum nitride powder by using plasma, which is implemented in the device of any one of claims 1 to 8, and comprises the following steps:
argon and nitrogen are used as discharge gas, or nitrogen is used as discharge gas, the discharge gas is sent into a plasma generator, and is ionized under the action of a power supply to form argon/nitrogen mixed gas thermal plasma jet or nitrogen thermal plasma jet with the average temperature of more than 3000 ℃, and the argon/nitrogen mixed gas thermal plasma jet or the nitrogen thermal plasma jet flows into a plasma high-temperature reactor;
quantitatively feeding the simple substance aluminum powder into a plasma high-temperature reactor with the internal temperature of 2000-4000 ℃ through a powder feeder, quickly liquefying and gasifying the simple substance aluminum powder, and reacting liquefied aluminum and/or gasified aluminum with high-temperature nitrogen in the plasma high-temperature reactor to generate an aluminum nitride powder precursor;
the aluminum nitride powder precursor enters an aluminum nitride powder purity improving chamber to further improve the purity; then the mixture enters an aluminum nitride powder particle size sieving chamber, and is cooled and condensed to form superfine aluminum nitride powder;
and the superfine aluminum nitride powder enters a gas-solid separator for separation, and the superfine aluminum nitride powder obtained in each region of the aluminum nitride powder particle size sieving chamber and the gas-solid separator is respectively collected.
10. The method of preparing high purity ultra fine aluminum nitride powder according to claim 9, wherein when argon and nitrogen are used as discharge gas, the volume flow ratio of argon to nitrogen is 1:2-10, and the discharge gas flow is 5-20m 3 Hour/hour; the output power of the plasma generator is 30-200 kW; the particle diameter of the aluminum powder is 10-100 microns, and the carrier gas flow is 0.5-5m 3 The aluminum powder carrying capacity is 200-.
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