Method and device for preparing aluminum nitride powder by centrifugal screening

Abstract

The present application relates to the technical field of inorganic material preparation, in particular to a method and device for preparing aluminum nitride powder by centrifugal screening. The method breaks the bubbles of nitrogen gas wrapped by the generated aluminum nitride film by continuously stirring during the reaction of aluminum liquid and nitrogen gas, so that the aluminum nitride film is broken into powder and suspended in the aluminum liquid to rise and gather on the surface of the aluminum liquid. This not only ensures that the particle size of the aluminum nitride powder is smaller, which can reach the nanometer level, and improves the product quality, but also releases the nitrogen gas to continue to form more bubbles of nitrogen gas wrapped by the aluminum nitride film, thereby improving the utilization rate of nitrogen gas. Then, part of the material in the reactor is transferred to a liquid-solid separator, and argon gas is sprayed by rotating the centrifugal collector, so that the aluminum liquid and the aluminum nitride powder are separated. After cooling and gas-solid separation, the aluminum nitride powder with small particle size, high purity and low oxygen content is obtained. The raw material utilization rate of the present application is high, the process is less and the production is continuous, which is suitable for industrial application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of inorganic material preparation, and particularly relates to a method and device for preparing aluminum nitride powder by centrifugal screening. BACKGROUND

[0002] Aluminum nitride (AlN) is a covalent compound with a hexagonal wurtzite structure, and its lattice parameters are a=3.114 and c=4.986. In normal state, aluminum nitride usually appears gray or off-white. Aluminum nitride is often used to make ceramic electronic substrates and packaging materials due to its excellent heat conduction performance, high volume resistivity, high insulation voltage, small thermal expansion coefficient, good matching with silicon and other characteristics, and is mainly used in heat dissipation substrates, heat exchange, functional materials, filling materials and other fields. In addition, the excellent high-temperature corrosion resistance, high-temperature stability, high strength and hardness make aluminum nitride also have great potential in high-temperature structural materials.

[0003] Aluminum nitride powder is difficult to prepare, and its easy hydrolysis also makes it difficult to store. The purity, particle size, oxygen content and other impurity content of aluminum nitride powder have important influences on the thermal conductivity of the prepared aluminum nitride ceramic and the subsequent sintering and forming processes. Generally, in order to obtain an aluminum nitride ceramic material with excellent performance, it is necessary to first prepare an aluminum nitride powder with high purity, fine particle size, narrow particle size distribution and stable performance. There are currently five main methods for synthesizing aluminum nitride powder: carbothermal reduction method, direct nitriding method, self-propagating high-temperature sintering method, chemical vapor method and plasma method. These preparation methods have problems such as high cost, many processes, inability to produce continuously, low product purity and poor product consistency to varying degrees, resulting in high prices of aluminum nitride powder, especially high-purity submicron and nanoscale aluminum nitride powder, which seriously restricts the market application and development of aluminum nitride.

[0004] In terms of market supply and demand, there are not many manufacturers that master the production technology of high-performance aluminum nitride powder, mainly in Japan, Germany and the United States. China's aluminum nitride industry started late, and aluminum nitride products have been mainly low-end products, with insufficient production capacity of high-end products and great dependence on imports. Therefore, it is necessary to develop a new method for preparing aluminum nitride powder to achieve the goals of low cost, continuous production and high quality (low oxygen content). SUMMARY

[0005] Therefore, the present application provides a method for preparing aluminum nitride powder by centrifugal screening to solve the problems of high cost, many processes, inability to produce continuously, low product purity and poor product consistency of the prior art.

[0006] In a first aspect, the present application provides a method for preparing aluminum nitride powder by centrifugal screening, comprising the following steps:

[0007] (1) nitrogen gas is introduced into the aluminum liquid in the reactor to react and form aluminum nitride film wrapped bubbles of nitrogen gas, which are broken under constant stirring to obtain a liquid-solid mixture; wherein the temperature of the aluminum liquid is 900-1300℃, and the amount of nitrogen gas introduced is 10-100L / min;

[0008] (2) after the reactor operates for a first time, nitrogen introduction and stirring are stopped, and the reactor is left to stand for a second time, after which part of the liquid-solid mixture in the reactor is transferred to a liquid-solid separator, an argon sparger and a centrifugal collector are arranged in the liquid-solid separator, a plurality of through holes are arranged on the side wall of the centrifugal collector, and the outlet of the argon sparger faces the inner wall of the centrifugal collector;

[0009] The centrifugal collector is immersed in the liquid-solid mixture in the liquid-solid separator, and then the centrifugal collector is lifted above the liquid surface and rotated, while argon is sparged into the centrifugal collector, and the above immersion-lifting-rotation-sparging operation is repeated.

[0010] (3) aluminum nitride powder dispersed in the space above the liquid surface in the liquid-solid separator is transported to a cooler for cooling, and then sent to a gas-solid separator for gas-solid separation to collect aluminum nitride powder.

[0011] In an alternative embodiment, the rotation speed of the stirring in step (1) is 100-600rpm.

[0012] In an alternative embodiment, the space above the liquid surface in the reactor is evacuated of air and filled with nitrogen gas.

[0013] In an alternative embodiment, the purity of the aluminum liquid is above 99.9%.

[0014] In an alternative embodiment, the purity of the nitrogen gas is above 99.99%.

[0015] In an alternative embodiment, the thickness of the aluminum nitride film on the periphery of the bubbles is 0.01-0.5μm.

[0016] In an alternative embodiment, the inside of the side wall of the centrifugal collector is provided with a plurality of fins, and the through holes are arranged in the projection range of each fin on the side wall of the centrifugal collector.

[0017] In an alternative embodiment, the angle between the fin and the side wall of the centrifugal collector is 30-60°.

[0018] In an alternative embodiment, the opening rate of the through holes is 30-50% based on the area of the side wall of the centrifugal collector.

[0019] In an alternative embodiment, the angle between the outlet of the argon blower and the horizontal direction is 10°-45°.

[0020] In an alternative embodiment, the minimum distance between the outlet of the argon blower and the inner wall of the centrifugal collector is 10cm-30cm.

[0021] In an alternative embodiment, the flow rate of the argon blower in step (2) is 100L-1000L / min.

[0022] In an alternative embodiment, the first time is 0.5h-3h.

[0023] In an alternative embodiment, the second time is 0min-30min.

[0024] In an alternative embodiment, the rotating speed in step (2) is 100rpm-600rpm.

[0025] In an alternative embodiment, step (2) further comprises the step of blowing argon into the liquid-solid separator from the bottom during the operation of the centrifugal collector.

[0026] In an alternative embodiment, the flow rate of the argon blowing from the bottom is 10L-100L / min.

[0027] In an alternative embodiment, step (2) is repeated for 3-10 times.

[0028] In an alternative embodiment, the aluminum liquid in the liquid-solid separator, after the operation of step (2) is completed, is returned to the reactor for further use.

[0029] In an alternative embodiment, the temperature of the cooled gas-solid mixture in step (3) is within 350℃.

[0030] In an alternative embodiment, the argon gas obtained from the gas-solid separation in step (3) is returned to the liquid-solid separator for further use.

[0031] In a second aspect, the present application further provides an aluminum nitride powder prepared by the method of the first aspect of the present application.

[0032] In an alternative embodiment, the aluminum nitride powder has a particle size of 0.01μm-1μm, an oxygen content of less than 0.1wt.%, and a purity of more than 99.99%.

[0033] In a third aspect, the present application further provides a device for preparing aluminum nitride powder by centrifugal screening, comprising a reactor, a liquid-solid separator, a cooler and a gas-solid separator which are sequentially connected.

[0034] The reactor is provided with a stirrer, and the bottom of the reactor is provided with an air inlet for introducing nitrogen into the reactor.

[0035] The liquid-solid separator is provided with an argon sparger and a centrifugal collector which can move up and down and rotate, the sidewall of the centrifugal collector is provided with a plurality of through holes, and the outlet of the argon sparger faces the inner wall of the centrifugal collector; the upper part of the liquid-solid separator is provided with a discharge port for conveying aluminum nitride powder escaping from the space above the liquid surface in the liquid-solid separator into the cooler.

[0036] In an alternative embodiment, the upper part of the reactor is in communication with the upper part of the liquid-solid separator through a first pipeline, and the first pipeline is provided with a valve.

[0037] In an alternative embodiment, the lower part of the reactor is in communication with the lower part of the liquid-solid separator through a second pipeline, and the second pipeline is provided with a delivery pump.

[0038] In an alternative embodiment, the bottom of the reactor is provided with 1-100 air inlets, and the diameter or equivalent diameter of each air inlet is 1-10 mm.

[0039] In an alternative embodiment, the upper part of the reactor is further provided with an aluminum liquid inlet for supplementing aluminum liquid into the reactor.

[0040] In an alternative embodiment, the reactor is a cylindrical or cubic cylindrical closed container.

[0041] In an alternative embodiment, the liquid-solid separator is a cylindrical or cubic cylindrical closed container.

[0042] In an alternative embodiment, the bottom of the liquid-solid separator is provided with an argon vent.

[0043] In an alternative embodiment, the number of argon vents is 1-100, and the diameter or equivalent diameter of each argon vent is 1-10 mm.

[0044] In an alternative embodiment, the inner side of the sidewall of the centrifugal collector is provided with a plurality of fins, and the through holes are arranged in the projection range of each fin on the sidewall of the centrifugal collector.

[0045] In an alternative embodiment, the angle between the fin and the centrifugal collector side wall is 30-60 degrees.

[0046] In an alternative embodiment, the opening rate of the through hole is 30-50% in terms of the area of the centrifugal collector side wall.

[0047] In an alternative embodiment, the angle between the outlet of the argon blower and the horizontal direction is 10-45 degrees.

[0048] In an alternative embodiment, the minimum distance between the outlet of the argon blower and the centrifugal collector inner wall is 10-30 cm.

[0049] In an alternative embodiment, the gas outlet of the gas-solid separator is connected to the gas inlet of the liquid-solid separator.

[0050] Compared with the prior art, the technical scheme of the present application has the following beneficial effects:

[0051] The method for preparing aluminum nitride powder by centrifugal screening provided by the present application can break the bubbles of nitrogen gas wrapped by the generated aluminum nitride film in time by continuously stirring during the reaction of aluminum liquid and nitrogen gas, so that the broken aluminum nitride film is suspended and rises in the aluminum liquid and is collected at the liquid surface of the aluminum liquid. This can not only ensure that the particle size of the aluminum nitride powder is smaller, can reach submicron and nanometer levels, and improve the product quality, but also can release the nitrogen gas to continue to form more bubbles of nitrogen gas wrapped by the aluminum nitride film, and improve the utilization rate of nitrogen gas. The unbroken bubbles of nitrogen gas wrapped by the aluminum nitride film rise to the liquid surface of the aluminum liquid and break, and the generated aluminum nitride powder floats on the surface of the aluminum liquid and / or escapes above the liquid surface. Then, part of the material (liquid-solid mixture) in the reactor is transferred to the liquid-solid separator. Since the aluminum nitride powder is not wetted by the aluminum liquid, the aluminum liquid can be thrown out by the rotation of the centrifugal collector, and most of the aluminum nitride powder adheres to the inner wall of the centrifugal collector. Argon is sprayed into the centrifugal collector to make the aluminum nitride powder adhering to the inner wall of the centrifugal collector escape into the cavity above the liquid surface, so as to realize the liquid-solid separation of the aluminum liquid and the aluminum nitride powder. After cooling and gas-solid separation, the aluminum nitride powder can be obtained. The production process of the preparation method is closed, no external oxygen is brought in, the purity of the prepared aluminum nitride powder is high, and the quality is good. The present application can prepare high-quality aluminum nitride powder at one time, without secondary processing such as grinding and impurity removal, the process is less, and the product consistency is good. The present application can use industrial aluminum ingots or aluminum particles as raw materials, without the need for high-purity and ultra-fine aluminum raw materials, and the raw material cost is low. Therefore, the preparation method has the advantages of low cost, less process, continuous production, high product purity, and good product consistency. BRIEF DESCRIPTION OF DRAWINGS

[0052] In order to more clearly illustrate the technical solutions in the specific embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or the prior art description. Obviously, the drawings described below are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0053] Figure 1 is the device for preparing aluminum nitride powder by centrifugal screening provided by the embodiment 1 of the present application;

[0054] The reference signs are explained as follows:

[0055] 1, reactor; 2, aluminum liquid supplement pipeline; 3, first driving motor; 4, stirrer; 5, gas inlet; 6, nitrogen gas inlet pipeline; 7, valve; 8, delivery pump; 9, liquid-solid separator; 10, nitrogen gas blowing pipeline; 11, second driving motor; 12, aluminum nitride powder pneumatic output pipeline; 13, centrifugal collector; 14, argon gas inlet pipeline; 15, argon gas inlet. DETAILED DESCRIPTION

[0056] The following embodiments are provided in order to better further understand the present application, and are not limited to the best embodiments, and do not constitute a limitation on the content and protection scope of the present application. Any person under the inspiration of the present application or the combination of the present application with other prior art features can obtain any product same or similar to the present application, which falls within the protection scope of the present application.

[0057] The specific experimental steps or conditions not mentioned in the embodiments can be performed according to the conventional experimental steps or conditions described in the literature in the art. The reagents or instruments not mentioned by the manufacturer are conventional reagent products that can be obtained by market purchase.

[0058] In order to solve the problems existing in the above related technologies, according to the first aspect of the present application, a method for preparing aluminum nitride powder by centrifugal screening is provided, comprising the following steps:

[0059] (1) nitrogen gas is introduced into the aluminum liquid in the reactor to react, forming aluminum nitride film wrapped gas bubbles, and under continuous stirring, the bubbles are broken to obtain a liquid-solid mixture; wherein the temperature of the aluminum liquid is 900-1300℃, and the amount of nitrogen gas introduced is 10-100L / min;

[0060] (2) after the reactor runs for a first time, stop the nitrogen feeding and stirring, and stand for a second time, then transfer part of the liquid-solid mixture in the reactor to a liquid-solid separator, an argon sparger and a centrifugal collector are arranged in the liquid-solid separator, the centrifugal collector is provided with a plurality of through holes on the side wall, and the outlet of the argon sparger faces the inner wall of the centrifugal collector;

[0061] submerge the centrifugal collector in the liquid-solid mixture in the liquid-solid separator, then lift the centrifugal collector above the liquid surface and rotate, and spray argon into the centrifugal collector, and repeat the submerging-lifting-rotating-spraying operation.

[0062] (3) the aluminum nitride powder diffused in the space above the liquid surface in the liquid-solid separator is transported to a cooler for cooling, then is sent to a gas-solid separator for gas-solid separation, and the aluminum nitride powder is collected.

[0063] The preparation method of the present application can break the bubbles of the aluminum nitride film wrapped with nitrogen gas in time by continuously stirring during the reaction of the aluminum liquid and the nitrogen gas, so that the aluminum nitride film is broken into powder and suspended in the aluminum liquid and gathered on the liquid surface of the aluminum liquid, which not only ensures that the particle size of the aluminum nitride powder is smaller, can reach submicron and nanometer level, and improves the product quality, but also releases the nitrogen gas to continue to form more bubbles of the aluminum nitride film wrapped with nitrogen gas, and improves the utilization rate of the nitrogen gas, and the unbroken bubbles of the aluminum nitride film wrapped with nitrogen gas rise to the liquid surface of the aluminum liquid and break, and the generated aluminum nitride powder floats on the surface of the aluminum liquid and / or diffuses above the liquid surface; then, part of the material (liquid-solid mixture) in the reactor is transferred to a liquid-solid separator, since the aluminum nitride powder is not wetted by the aluminum liquid, the aluminum liquid can be thrown out by the rotation of the centrifugal collector, and most of the aluminum nitride powder adheres to the inner wall of the centrifugal collector, then nitrogen gas is sprayed into the centrifugal collector, so that the aluminum nitride powder adhering to the inner wall of the centrifugal collector diffuses into the cavity above the liquid surface, thereby realizing the liquid-solid separation of the aluminum liquid and the aluminum nitride powder; then, after cooling and gas-solid separation, the aluminum nitride powder can be obtained.

[0064] The preparation method of the present application produces a whole process in a closed manner, and no external oxygen is brought in, so that the prepared aluminum nitride powder has high purity and good quality; the present application can prepare high-quality aluminum nitride powder at one time, without secondary processing such as grinding and impurity removal, and has fewer processes, and can continuously produce, not batch production, which eliminates the inconsistency of specifications and parameters of different batches of products, and has good product consistency; the present application can use industrial aluminum ingots or aluminum particles as raw materials, without the need for high-purity and ultra-fine aluminum raw materials, and the raw material cost is low. Therefore, the preparation method of the present application has the advantages of low cost, fewer processes, continuous production, high product purity, and good product consistency.

[0065] In one optional embodiment, the stirring speed in step (1) is 100-600 rpm. The inventors have found that if the speed is too low, it will not be effective in breaking up the nitrogen bubbles encapsulated in the aluminum nitride film in time, while if the speed is too high, it will not provide substantial help in actual production and will also cause excessive wear on the spiral blades of the stirrer at high temperatures. Therefore, the present invention selects a speed range of 100-600 rpm, which can balance timely breaking of bubbles and extending the service life of the stirrer.

[0066] In one optional embodiment, the space above the liquid surface within the reactor is purged of air and filled with nitrogen. This ensures that the reaction products are unique, thereby improving product purity.

[0067] In one alternative embodiment, the molten aluminum has a purity of 99.9% or higher. Using high-purity reaction materials helps to obtain a high-purity product.

[0068] In one alternative embodiment, the nitrogen gas has a purity of 99.99% or higher. Using high-purity reaction raw materials helps to obtain high-purity products.

[0069] In one optional embodiment, the thickness of the aluminum nitride film surrounding the bubble is 0.01 μm to 0.5 μm. This particle size range reaches the submicron and nanometer scales, resulting in small particle size and high-quality powder.

[0070] In an optional embodiment, step (2) further includes bottom-blowing argon gas into the liquid-solid separator during the operation of the centrifugal collector. Argon bottom-blowing in the liquid-solid separator helps aluminum nitride powder particles in the molten aluminum float to near the liquid surface, facilitating collection by the centrifugal collector and thus improving centrifugal separation efficiency. In particular, controlling the argon gas flow rate to 10-100 L / min further promotes the aggregation of aluminum nitride powder at the surface of the molten aluminum.

[0071] In one optional embodiment, the inner side wall of the centrifugal collector is provided with a plurality of fins, and the through holes are opened within the projection range of each fin on the side wall of the centrifugal collector. This creates a certain resistance when the centrifugal collector rotates and throws out the molten aluminum, thus helping to achieve liquid-solid separation.

[0072] In one alternative embodiment, the angle between the fins and the sidewall of the centrifugal collector is 30°-60°.

[0073] In an alternative embodiment, the open porosity of the through holes is 30%-50% of the area of the side wall of the centrifugal collector. The inventors have found that too much open porosity will affect the mechanical strength of the centrifugal collector, while too little open porosity will affect the separation efficiency, and therefore the open porosity is preferably in the range of 30%-50%.

[0074] In an alternative embodiment, the angle between the outlet of the argon blower and the horizontal direction is 10°-45°, so that the blowing gas flow forms a cyclone in the centrifugal collector, which is conducive to carrying out the aluminum nitride powder.

[0075] In an alternative embodiment, the minimum distance between the outlet of the argon blower and the inner wall of the centrifugal collector is 10cm-30cm, and a suitable blowing distance is conducive to the blowing gas flow carrying out the aluminum nitride powder.

[0076] In an alternative embodiment, the blowing flow of the argon blower in step (2) is 100L-1000L / min, and the specific blowing amount of argon is determined according to the volume of the cavity and the required pressure.

[0077] In an alternative embodiment, the first time is 0.5h-3h, which can ensure sufficient reaction and prevent too much powder in the aluminum liquid from affecting the subsequent separation efficiency, and therefore the reaction time is controlled in the range of 0.5h-3h.

[0078] In an alternative embodiment, the second time is 0min-30min. The standing time is to make most of the powder float on the upper part of the aluminum liquid, but it cannot be too long to affect the production efficiency, and therefore the standing time is controlled in the range of 0min-30min.

[0079] In an alternative embodiment, the rotating speed in step (2) is 100r-600r / min to adapt to the solid-liquid separation.

[0080] In an alternative embodiment, the operation in step (2) is repeated 3-10 times to ensure that most of the powder is separated out, while not affecting the production efficiency.

[0081] In an alternative embodiment, the aluminum liquid in the liquid-solid separator that has completed the operation in step (2) is returned to the reactor for continuous use, thereby improving the utilization rate of raw materials.

[0082] In an alternative embodiment, the temperature of the gas-solid mixture after cooling in step (3) is within 350℃.

[0083] In an optional implementation, the argon obtained from the gas-solid separation in step (3) is returned to the liquid-solid separator for continued use, thereby improving the utilization rate of argon.

[0084] According to a second aspect of the present invention, an aluminum nitride powder is provided, which is prepared by the method described in the first aspect of the present invention.

[0085] In one optional embodiment, the aluminum nitride powder has a particle size of 0.01 μm-1 μm, an oxygen content of less than 0.1 wt.%, and a purity of more than 99.99%.

[0086] According to a third aspect of the present invention, the present invention also provides an apparatus for preparing aluminum nitride powder by centrifugal sieving, comprising a reactor, a liquid-solid separator, a cooler, and a gas-solid separator connected in sequence, wherein:

[0087] The reactor is equipped with a stirrer, and an air inlet is provided at the bottom of the reactor for introducing nitrogen into the reactor.

[0088] The liquid-solid separator is equipped with an argon gas injector and a centrifugal collector that can move up and down and rotate. The side wall of the centrifugal collector is provided with several through holes, and the outlet of the argon gas injector faces the inner wall of the centrifugal collector. The upper part of the liquid-solid separator is provided with a discharge port for conveying aluminum nitride powder that has escaped into the space above the liquid surface in the liquid-solid separator to the cooler.

[0089] The device of the present application can break the bubbles of the aluminum nitride film wrapped with nitrogen gas generated by the reaction of the molten aluminum and nitrogen gas in time, so that the aluminum nitride film is broken into powder and suspended in the molten aluminum and gathered on the surface of the molten aluminum. Thus, the particle size of the aluminum nitride powder can be smaller, reaching submicron and nanometer level, and the product quality is improved. Moreover, the nitrogen gas can be released to form more bubbles of the aluminum nitride film wrapped with nitrogen gas, improving the utilization rate of nitrogen gas. The unbroken bubbles of the aluminum nitride film wrapped with nitrogen gas rise to the surface of the molten aluminum and break, and the generated aluminum nitride powder floats on the surface of the molten aluminum and / or escapes above the surface of the molten aluminum. Then, part of the material (liquid-solid mixture) in the reactor enters the liquid-solid separator. The centrifugal collector is first immersed in the liquid-solid mixture, and then slowly lifted above the surface of the liquid-solid mixture and rotated. Since the aluminum nitride powder is not wetted by the molten aluminum, the molten aluminum can be thrown out of the centrifugal collector by the rotation of the centrifugal collector, and most of the aluminum nitride powder adheres to the inner wall of the centrifugal collector. Then, the argon gas sprayer sprays argon gas into the centrifugal collector, so that the aluminum nitride powder adhering to the inner wall of the centrifugal collector escapes into the cavity above the surface of the molten aluminum, thereby realizing the liquid-solid separation of the molten aluminum and the aluminum nitride powder. After cooling by the cooler and gas-solid separation by the gas-solid separator, the aluminum nitride powder can be obtained. Moreover, the device of the present application has the characteristics of simple structure and easy operation, so that the investment and operating cost of the device of the present application are low.

[0090] In an alternative embodiment, the upper part of the reactor is in communication with the upper part of the liquid-solid separator through a first pipeline, and a valve is arranged on the first pipeline. When the valve is opened, part of the material (liquid-solid mixture) in the reactor can automatically flow into the liquid-solid separator based on the principle of communicating vessels, and the valve is closed when the liquid surface in the reactor is below the first pipeline port, so that the automatic transfer of the material can be realized, which is beneficial to reduce the investment and operating cost of the device.

[0091] In an alternative embodiment, the lower part of the reactor is in communication with the lower part of the liquid-solid separator through a second pipeline, and a delivery pump is arranged on the second pipeline. The delivery pump is used to send the molten aluminum separated from the solid back to the reactor to continue the preparation of the aluminum nitride product, thereby improving the utilization rate of raw materials and reducing the production cost.

[0092] In an alternative embodiment, 1-100 gas inlets are arranged on the bottom of the reactor, and the diameter or equivalent diameter of each gas inlet is 1-10 mm.

[0093] In an alternative embodiment, an aluminum liquid inlet is further arranged on the upper part of the reactor, which is used to supplement the molten aluminum into the reactor. After part of the material (liquid-solid mixture) in the reactor is transferred to the liquid-solid separator, the molten aluminum is supplemented into the reactor through the aluminum liquid inlet to continue the reaction, so that the continuous production of the aluminum nitride can be realized.

[0094] In an alternative embodiment, the reactor is a cylindrical or cuboid closed container.

[0095] In an alternative embodiment, the inner lining of the reactor is made of high-temperature-resistant material, such as alumina ceramic, graphite, etc.; the outer wall of the reactor is provided with a heating assembly, which can be an electric heating wire or an electric arc heating. In this way, the reactor is both high-temperature-resistant and can be heated and insulated, which is conducive to the smooth progress of the reaction.

[0096] In an alternative embodiment, the liquid-solid separator is a cylindrical or cuboid closed container.

[0097] In an alternative embodiment, the inner lining of the liquid-solid separator is made of high-temperature-resistant material, such as alumina ceramic, graphite, etc.; the outer wall of the liquid-solid separator is provided with a heating assembly, which can be an electric heating wire or an electric arc heating. In this way, the liquid-solid separator is both high-temperature-resistant and can be heated and insulated, which is conducive to the smooth separation of the high-temperature aluminum liquid and the aluminum nitride powder.

[0098] In an alternative embodiment, the liquid-solid separator is provided with an argon gas vent at the bottom, which is used to blow argon gas into the bottom of the liquid-solid separator when the centrifugal collector is working, so as to facilitate the collection of the aluminum nitride powder at the surface of the aluminum liquid. The number of the argon gas vents is 1-100, and the diameter or equivalent diameter of each argon gas vent is 1-10 mm.

[0099] In an alternative embodiment, the inner side of the side wall of the centrifugal collector is provided with a plurality of fins, and the through holes are arranged in the projection range of each fin on the side wall of the centrifugal collector.

[0100] In an alternative embodiment, the angle between the fin and the side wall of the centrifugal collector is 30°-60°.

[0101] In an alternative embodiment, the opening rate of the through holes is 30%-50% based on the area of the side wall of the centrifugal collector.

[0102] In an alternative embodiment, the centrifugal collector is a cylindrical structure with an open top and is connected to the top of the liquid-solid separator through a screw rod, and the material of the centrifugal collector can be alumina ceramic, graphite, etc.

[0103] In an alternative embodiment, the angle between the outlet of the argon gas sparger and the horizontal direction is 10°-45°.

[0104] In an alternative embodiment, the minimum distance between the outlet of the argon gas sparger and the inner wall of the centrifugal collector is 10-30 cm.

[0105] In one alternative embodiment, the gas outlet of the gas-solid separator is connected to the inlet of the liquid-solid separator. This allows the argon gas obtained from the gas-solid separation to be recycled.

[0106] The present invention will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed by the present invention.

[0107] Example 1

[0108] like Figure 1 As shown, this embodiment provides an apparatus for preparing aluminum nitride powder using centrifugal sieving, comprising a reactor 1, a liquid-solid separator 9, a cooler (not shown in the figure), and a gas-solid separator (not shown in the figure) connected in sequence, wherein:

[0109] The reactor 1 is a cylindrical or cuboid closed container, and the production process is completely closed to avoid affecting the purity of the product due to the entry of air. The inner lining of the reactor 1 is made of high-temperature-resistant materials, such as alumina ceramic, graphite, etc. The outer wall of the reactor 1 is provided with heating components such as electric heating wires or electric arc heating, so that the reactor 1 is resistant to high temperature and can be heated and insulated, which is conducive to the smooth progress of the reaction. The reactor 1 is provided with a stirrer 4, which is composed of a screw and a blade. In use, the blade is located in the aluminum liquid, and the screw is connected to the first driving motor 3 outside the reactor 1. Under the driving action of the first driving motor 3, the screw rotates and drives the blade to rotate, thereby playing a stirring role. The bottom of the reactor 1 is provided with an air inlet 5, which is connected to a nitrogen inlet pipeline 6 for introducing nitrogen into the reactor 1. The number of air inlets 5 is any integer between 1 and 100. In order to ensure the uniformity of the gas distribution, 5 groups of air inlets can be arranged at the bottom of the reactor 1, each group being circular or linearly arranged. Each air inlet is a circular hole or a square hole, and the diameter of the circular hole or the equivalent diameter of the square hole is 1-10 mm, which can be determined according to the actual amount of material used in the reaction. The upper part of the reactor 1 is connected to the upper part of the liquid-solid separator 9 through a first pipeline, and a valve 7 is arranged on the first pipeline. When the valve 7 is opened, part of the material (liquid-solid mixture) in the reactor 1 can automatically flow into the liquid-solid reactor 9 based on the principle of communicating vessels, and the valve 7 is closed when the liquid level in the reactor 1 is lower than the first pipeline port. Thus, automatic transfer of the material can be realized, which is conducive to reducing equipment investment and operating costs. The lower part of the reactor 1 is connected to the lower part of the liquid-solid separator 9 through a second pipeline, and a delivery pump 8 is arranged on the second pipeline. The delivery pump 8 is used to send the aluminum liquid separated from the solid-liquid mixture back to the reactor 1 for continuous preparation of aluminum nitride products, which can improve the utilization rate of raw materials and reduce production costs. The upper part of the reactor 1 is also provided with an aluminum liquid inlet for supplementing the aluminum liquid in the reactor 1 through an aluminum liquid supplementing pipeline 2. After part of the material (liquid-solid mixture) in the reactor 1 is transferred to the liquid-solid separator 9, the aluminum liquid is supplemented to the reactor 1 through the aluminum liquid inlet to continue the reaction, thereby realizing continuous production of aluminum nitride.

[0110] The liquid-solid separator 9 is a cylindrical or cuboid closed container, and the production process is completely closed to avoid affecting the purity of the product due to the entry of air. The inner lining of the liquid-solid separator 9 is made of high-temperature-resistant materials, such as alumina ceramic, graphite, etc. The outer wall of the liquid-solid separator 9 is provided with heating components such as electric heating wires or electric arc heating. In this way, the liquid-solid separator 9 is resistant to high temperature and can be heated and insulated, which is beneficial to the smooth separation of high-temperature aluminum liquid and aluminum nitride powder. The liquid-solid separator 9 is provided with a centrifugal collector 13 that can move up and down and rotate. The centrifugal collector 13 is a cylindrical structure with an open top, and is connected to the second driving motor 11 at the top of the liquid-solid separator through a screw rod. Under the driving action of the second driving motor 11, the screw rod rotates and drives the centrifugal collector 13 to rotate, thereby achieving the effect of liquid-solid separation. The material of the centrifugal collector 13 can be alumina ceramic, graphite, etc. The inner side of the side wall of the centrifugal collector 13 is provided with a plurality of fins, and the included angle between the fin and the side wall of the centrifugal collector is 30°-60°. Each fin is provided with a through hole in the projection range on the side wall of the centrifugal collector. The opening rate of the through hole is 30%-50% based on the area of the side wall of the centrifugal collector. The liquid-solid separator 9 is also provided with an argon sparger connected to a nitrogen gas storage tank (not shown in the figure) through a nitrogen gas blowing pipe 10. The outlet of the argon sparger faces the inner wall of the centrifugal collector 13 and has an included angle of 10°-45° with the horizontal direction. The minimum distance between the outlet of the argon sparger and the inner wall of the centrifugal collector 13 is 10cm-30cm. The upper part of the liquid-solid separator 9 is provided with a discharge port connected to a vacuum pump through an aluminum nitride powder pneumatic output pipe 12, which is used to transport the aluminum nitride powder dispersed in the space above the liquid surface in the liquid-solid separator 9 to a cooler. The bottom of the liquid-solid separator 9 is provided with an argon gas vent 15 connected to an argon gas inlet pipe 14, which is used to introduce argon gas into the liquid-solid separator 9. The number of argon gas vents 15 is any integer between 1 and 100. To ensure uniformity of gas distribution, 5 groups of argon gas vents can be arranged at the bottom of the liquid-solid separator 9. Each group of argon gas vents is arranged in a circular or linear manner. Each argon gas vent is a circular hole or a square hole. The diameter of the circular hole or the equivalent diameter of the square hole is 1mm-10mm. The specific value can be determined according to the actual amount of material used in the reaction.

[0111] The gas outlet of the gas-solid separator is connected to the gas inlet of the liquid-solid separator, which can be the argon gas vent 15 or the nitrogen gas blowing pipe 10. In this way, the argon gas obtained by gas-solid separation can be recycled.

[0112] Example 2

[0113] The method for preparing aluminum nitride powder using the device provided in Example 1 includes the following steps:

[0114] (1) Add aluminum liquid (purity 99.9%) into the reactor, evacuate the space above the aluminum liquid surface and fill it with nitrogen, heat the reactor to ensure the aluminum liquid temperature is 900°C, and introduce nitrogen (purity 99.99%, nitrogen flow rate is 55 L / min) into the aluminum liquid to form aluminum nitride film (thickness is 0.01 μm) wrapped bubbles of nitrogen, and break the bubbles under the constant stirring of the stirrer (rotation speed is 600 rpm) to obtain a liquid-solid mixture.

[0115] (2) After the reactor runs for 2 h, stop the nitrogen introduction and stirring, and stand for 10 min, then open the valve on the first pipeline to transfer the liquid-solid mixture in the reactor above the liquid surface of the first pipeline to the liquid-solid separator, and open the aluminum liquid inlet to supplement the aluminum liquid in the reactor.

[0116] At the same time of introducing argon (purity 99.99%, argon flow rate is 55 L / min), first immerse the centrifugal collector in the liquid-solid mixture, then lift the centrifugal collector above the liquid surface and rotate (rotation speed is 200 rpm), and at the same time, spray argon into the centrifugal collector, and the spraying flow rate is 100 L / min; repeat the above immersion-lifting-rotation-spraying operation for 3 times. In the operation, the angle between the fins on the centrifugal collector and the side wall thereof is 30°, the opening rate of the through holes is 30%, the angle between the outlet of the argon sprayer and the horizontal direction is 10°, and the minimum distance between the outlet of the argon sprayer and the inner wall of the centrifugal collector is 10 cm.

[0117] (3) Start the delivery pump to return the aluminum liquid in the liquid-solid separator, which has completed the above operation, to the reactor for continuous use, use the vacuum pump to transport the aluminum nitride powder escaping in the space above the liquid surface in the liquid-solid separator to the cooler to cool to below 350°C, then send it into the gas-solid separator for gas-solid separation, and collect the aluminum nitride powder and argon respectively, and return the collected argon to the liquid-solid separator for continuous use.

[0118] Example 3

[0119] The method for preparing aluminum nitride powder by using the device provided in Example 1 comprises the following steps:

[0120] (1) Add aluminum liquid (purity 99.9%) into the reactor, evacuate the space above the aluminum liquid surface and fill it with nitrogen, heat the reactor to ensure the aluminum liquid temperature is 1000°C, and introduce nitrogen (purity 99.99%, nitrogen flow rate is 80 L / min) into the aluminum liquid to form aluminum nitride film (thickness is 0.05 μm) wrapped bubbles of nitrogen, and break the bubbles under the constant stirring of the stirrer (rotation speed is 350 rpm) to obtain a liquid-solid mixture.

[0121] (2) After the reactor runs for 0.5 h, stop the nitrogen feeding and stirring, and stand for 20 min. Then open the valve on the first pipe to transfer the liquid-solid mixture in the reactor above the liquid level of the first pipe to the liquid-solid separator, and open the inlet of the aluminum liquid to supplement the aluminum liquid in the reactor.

[0122] While argon gas (purity 99.99%, flow rate 80 L / min) is fed, first immerse the centrifugal collector in the liquid-solid mixture, then lift the centrifugal collector above the liquid level and rotate (speed 100 rpm), while spraying argon gas into the centrifugal collector, the flow rate of the spraying being 200 L / min; repeat the above immersion-lifting-rotation-spraying operation 5 times. In the operation, the angle between the fins on the centrifugal collector and the side wall thereof is 40°, the opening rate of the through holes is 35%, the angle between the outlet of the argon gas sprayer and the horizontal direction is 20°, and the minimum distance between the outlet of the argon gas sprayer and the inner wall of the centrifugal collector is 15 cm.

[0123] (3) Start the delivery pump to return the aluminum liquid in the liquid-solid separator, which has completed the above operation, to the reactor for continuous use, use the vacuum pump to transport the aluminum nitride powder dispersed in the space above the liquid level in the liquid-solid separator to the cooler to cool to below 350°C, and then send it to the gas-solid separator for gas-solid separation, and collect the aluminum nitride powder and argon gas respectively, and return the collected argon gas to the liquid-solid separator for continuous use.

[0124] Example 4

[0125] The method for preparing aluminum nitride powder using the device provided in Example 1 comprises the following steps:

[0126] (1) Add aluminum liquid (purity 99.9%) into the reactor, evacuate the space above the aluminum liquid and fill it with nitrogen gas, heat the reactor to ensure that the temperature of the aluminum liquid is 1100°C, and feed nitrogen gas (purity 99.99%, nitrogen feeding amount 30 L / min) into the aluminum liquid to generate a reaction, form an aluminum nitride film (thickness 0.1 μm) wrapped around the gas bubbles of nitrogen, and break the gas bubbles under the continuous stirring of the stirrer (speed 100 rpm) to obtain a liquid-solid mixture.

[0127] (2) After the reactor runs for 2.5 h, stop the nitrogen feeding and stirring, and then open the valve on the first pipe to transfer the liquid-solid mixture in the reactor above the liquid level of the first pipe to the liquid-solid separator, and open the inlet of the aluminum liquid to supplement the aluminum liquid in the reactor.

[0128] The centrifugal collector is first immersed in the liquid-solid mixture while argon gas (purity 99.99%, flow rate 30 L / min) is being introduced, then the centrifugal collector is lifted above the liquid surface and rotated (400 rpm), while argon gas is being sprayed into the centrifugal collector, the flow rate of the argon gas being 300 L / min; the above-mentioned immersing-lifting-rotating-spraying operation is repeated 10 times. The angle between the fins on the centrifugal collector and the side wall thereof is 50°, the open rate of the through holes is 40%, the angle between the outlet of the argon gas sprayer and the horizontal direction is 35°, and the minimum distance between the outlet of the argon gas sprayer and the inner wall of the centrifugal collector is 20 cm.

[0129] (3) The transport pump is started to return the aluminum liquid in the liquid-solid separator, which has completed the above-mentioned operation, to the reactor for continuous use, the vacuum pump is used to transport the aluminum nitride powder, which has escaped into the space above the liquid surface in the liquid-solid separator, to the cooler for cooling to below 350°C, and then the aluminum nitride powder is sent into the gas-solid separator for gas-solid separation, and the collected aluminum nitride powder and argon gas are collected and returned to the liquid-solid separator for continuous use.

[0130] Example 5

[0131] The method for preparing aluminum nitride powder by using the device provided in Example 1 comprises the following steps:

[0132] (1) The aluminum liquid (purity 99.9%) is added into the reactor, the space above the liquid surface of the aluminum liquid is evacuated and filled with nitrogen gas, the reactor is heated to ensure that the temperature of the aluminum liquid is 1200°C, and the nitrogen gas (purity 99.99%, flow rate 90 L / min) is introduced into the aluminum liquid to cause a reaction, forming an aluminum nitride film (thickness 0.3 μm) wrapped around the gas bubbles of nitrogen gas, and the gas bubbles are broken by the continuous stirring of the stirrer (500 rpm) to obtain a liquid-solid mixture.

[0133] (2) After the reactor is operated for 0.5 h, the nitrogen introduction and stirring are stopped, and the liquid-solid mixture in the reactor is transferred to the liquid-solid separator after 5 min, and the aluminum liquid inlet is opened to supplement the aluminum liquid in the reactor.

[0134] The centrifugal collector is first immersed in the liquid-solid mixture while argon gas (purity 99.99%, flow rate 90 L / min) is being introduced, then the centrifugal collector is lifted above the liquid surface and rotated (600 rpm), while argon gas is being sprayed into the centrifugal collector, the flow rate of the argon gas being 400 L / min; the above-mentioned immersing-lifting-rotating-spraying operation is repeated 4 times. The angle between the fins on the centrifugal collector and the side wall thereof is 50°, the open rate of the through holes is 45%, the angle between the outlet of the argon gas sprayer and the horizontal direction is 45°, and the minimum distance between the outlet of the argon gas sprayer and the inner wall of the centrifugal collector is 25 cm.

[0135] (3) Start the delivery pump to return the aluminum liquid in the liquid-solid separator, which has completed the above operation, to the reactor for continuous use. Use the vacuum pump to transport the aluminum nitride powder that has escaped from the space above the liquid level in the liquid-solid separator to the cooler to cool to within 350°C, and then send it to the gas-solid separator for gas-solid separation. Collect the aluminum nitride powder and argon gas separately, and return the collected argon gas to the liquid-solid separator for continuous use.

[0136] Example 6

[0137] The method for preparing aluminum nitride powder using the device provided in Example 1 includes the following steps:

[0138] (1) Add aluminum liquid (purity 99.9%) to the reactor, evacuate the space above the liquid level of the aluminum liquid and fill it with nitrogen, heat the reactor to ensure that the temperature of the aluminum liquid is 1300°C, and introduce nitrogen gas (purity 99.99%, nitrogen flow rate 100 L / min) into the aluminum liquid to form an aluminum nitride film (thickness 0.5 μm) wrapped around the gas bubbles of nitrogen. Under the continuous stirring of the stirrer (rotation speed 400 rpm), the gas bubbles are broken to obtain a liquid-solid mixture.

[0139] (2) After the reactor has been operated for 1 h, stop the nitrogen introduction and stirring, and stand for 30 min. Then open the valve on the first pipeline to transfer the liquid-solid mixture in the reactor, which is higher than the liquid level of the first pipeline, to the liquid-solid separator, and open the aluminum liquid inlet to supplement the aluminum liquid in the reactor.

[0140] At the same time as introducing argon gas (purity 99.99%, argon flow rate 100 L / min), first immerse the centrifugal collector in the liquid-solid mixture, then lift the centrifugal collector above the liquid level and rotate it (rotation speed 350 rpm), and at the same time spray argon gas into the centrifugal collector, with a spraying flow rate of 600 L / min. Repeat the above immersion-lifting-rotation-spraying operation 4 times. The angle between the fins on the centrifugal collector and the side wall thereof is 60°, the opening rate of the through holes is 50%, the angle between the outlet of the argon gas sprayer and the horizontal direction is 15°, and the minimum distance between the outlet of the argon gas sprayer and the inner wall of the centrifugal collector is 30 cm.

[0141] (3) Start the delivery pump to return the aluminum liquid in the liquid-solid separator, which has completed the above operation, to the reactor for continuous use. Use the vacuum pump to transport the aluminum nitride powder that has escaped from the space above the liquid level in the liquid-solid separator to the cooler to cool to within 350°C, and then send it to the gas-solid separator for gas-solid separation. Collect the aluminum nitride powder and argon gas separately, and return the collected argon gas to the liquid-solid separator for continuous use.

[0142] Comparative Example 1

[0143] The aluminum nitride powder is prepared by the same method as in Example 3 of the present application, except that in step (1) there is no stirring, and the nitrogen gas bubbles wrapped by the aluminum nitride film produced rise to the surface of the aluminum liquid and break, and the aluminum nitride powder produced floats on the surface of the aluminum liquid and / or escapes above the surface of the liquid.

[0144] Comparative Example 2

[0145] The method for preparing the aluminum nitride powder in this comparative example comprises the following steps:

[0146] An aluminum liquid (purity 99.9%) is added to the reactor, the space above the surface of the aluminum liquid is evacuated of air and filled with nitrogen, the reactor is heated to ensure that the temperature of the aluminum liquid is 1000°C, and nitrogen gas (purity 99.99%, amount of nitrogen gas introduced 80 L / min) is introduced into the aluminum liquid to cause a reaction, forming bubbles of nitrogen gas wrapped by an aluminum nitride film (thickness 0.05 μm), and the bubbles are broken up by the constant stirring of a stirrer (rotational speed 350 rpm). After the reactor has been operated for 0.5 h, the introduction of nitrogen gas and the stirring are stopped, and the reactor is allowed to stand for 20 min, after which a vacuum pump is used to transport the aluminum nitride powder that has escaped into the space above the surface of the liquid in the reactor to a cooler and cooled to below 350°C, after which it is sent to a gas-solid separator to be subjected to gas-solid separation, and the aluminum nitride powder and nitrogen gas are collected separately, and the collected nitrogen gas is returned to the reactor for continued use.

[0147] Experimental Example

[0148] The particle size, purity, oxygen content and other indicators of the aluminum nitride powder produced in Examples 2-6 of the present application and Comparative Examples 1-2 are tested respectively, and the results are shown in Table 1.

[0149] Table 1

[0150]

[0151]

[0152] In the table, wt.% represents weight percent content.

[0153] As can be seen from Table 1, the purity of the aluminum nitride powder produced in the present application is above 99.99%, and because a closed system is used, the oxygen content can be controlled to be below 0.1 wt.%. Because of differences in production processes such as reaction temperature, reaction time, and stirring speed, the D50 particle size of the aluminum nitride powder varies, and the particle size can be controlled to be in the range of 0.01-1 μm, and the particle size tends to increase as the reaction temperature increases, which is related to the fact that the higher the temperature, the more complete the reaction, and the thicker the aluminum nitride film formed.

[0154] Comparative Example 1 did not have stirring during the reaction, resulting in larger particle size of the product aluminum nitride powder and lower hourly yield (ratio of the weight of aluminum in the aluminum nitride powder produced per hour to the weight of the initial aluminum liquid). Comparative Example 2 did not have a liquid-solid separation step, resulting in very low hourly yield.

[0155] Obviously, the above examples are merely illustrative in nature and are not intended to limit the scope of the embodiments. For ordinary skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, it is not necessary and also impossible to exhaust all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for preparing aluminum nitride powder using centrifugal sieving, characterized in that, Includes the following steps: (1) Nitrogen gas is introduced into the aluminum liquid in the reactor to react and form bubbles of nitrogen gas wrapped in aluminum nitride film. The bubbles are broken under continuous stirring to obtain a liquid-solid mixture; wherein the temperature of the aluminum liquid is 900℃-1300℃ and the nitrogen gas flow rate is 10L-100L / min. (2) After the reactor has been running for a first time, stop the nitrogen flow and stirring, let it stand for a second time, and then transfer part of the liquid-solid mixture in the reactor to a liquid-solid separator. An argon gas injector and a centrifugal collector are installed inside the liquid-solid separator. Several through holes are provided on the side wall of the centrifugal collector, and the outlet of the argon gas injector faces the inner wall of the centrifugal collector. The centrifugal collector is immersed in the liquid-solid mixture in the liquid-solid separator, then the centrifugal collector is raised above the liquid surface and rotated, while argon gas is blown into the centrifugal collector. The above immersion-raising-rotation-blowing operation is repeated. (3) The aluminum nitride powder that has escaped into the space above the liquid surface in the liquid-solid separator is transported to the cooler for cooling, and then sent to the gas-solid separator for gas-solid separation to collect the aluminum nitride powder.

2. The method for preparing aluminum nitride powder by centrifugal sieving according to claim 1, characterized in that, The stirring speed in step (1) is 100-600 rpm; And / or, the space above the liquid surface in the reactor has been emptied of air and filled with nitrogen; And / or, the purity of the molten aluminum is 99.9% or higher; And / or, the purity of the nitrogen gas is 99.99% or higher; And / or, the thickness of the aluminum nitride film surrounding the bubble is 0.01μm-0.5μm.

3. The method for preparing aluminum nitride powder by centrifugal sieving according to claim 1, characterized in that, The inner side wall of the centrifugal collector is provided with a number of fins, and the through holes are opened within the projection range of each fin on the side wall of the centrifugal collector.

4. The method for preparing aluminum nitride powder by centrifugal sieving according to claim 3, characterized in that, The angle between the fins and the sidewall of the centrifugal collector is 30°-60°; And / or, based on the area of ​​the sidewall of the centrifugal collector, the opening ratio of the through hole is 30%-50%.

5. The method for preparing aluminum nitride powder by centrifugal sieving according to claim 1, characterized in that, The angle between the outlet of the argon gas injector and the horizontal direction is 10°-45°; And / or, the minimum distance between the outlet of the argon gas injector and the inner wall of the centrifugal collector is 10cm-30cm; And / or, the argon gas injector has a flow rate of 100L-1000L / minute.

6. The method for preparing aluminum nitride powder by centrifugal sieving according to claim 1, characterized in that, The first time period is 0.5h-3h; And / or, the second time is 0 min-30 min; And / or, the rotation speed described in step (2) is 100-600 rpm; And / or, step (2) further includes the step of bottom-blowing argon gas into the liquid-solid separator during the operation of the centrifugal collector; And / or, the operation in step (2) is repeated 3-10 times; And / or, the molten aluminum that has completed the operation in step (2) in the liquid-solid separator is returned to the reactor for continued use.

7. The method for preparing aluminum nitride powder by centrifugal sieving according to claim 6, characterized in that, The bottom-blown argon gas flow rate is 10L-100L / minute.

8. The method for preparing aluminum nitride powder by centrifugal sieving according to claim 1, characterized in that, The temperature of the cooled gas-solid mixture in step (3) is below 350°C; And / or, in step (3), the argon gas obtained from the gas-solid separation is returned to the liquid-solid separator for continued use.

9. An aluminum nitride powder, characterized in that, It is prepared by the method described in any one of claims 1 to 8.

10. The aluminum nitride powder according to claim 9, characterized in that, The aluminum nitride powder has a particle size of 0.01μm-1μm, an oxygen content of less than 0.1wt.%, and a purity of more than 99.99%.

11. An apparatus for implementing the method for preparing aluminum nitride powder by centrifugal sieving according to any one of claims 1 to 8, characterized in that, It includes a reactor, a liquid-solid separator, a cooler, and a gas-solid separator connected in sequence, wherein: The reactor is equipped with a stirrer, and an air inlet is provided at the bottom of the reactor for introducing nitrogen into the reactor. The liquid-solid separator is equipped with an argon gas injector and a centrifugal collector that can move up and down and rotate. The side wall of the centrifugal collector is provided with several through holes, and the outlet of the argon gas injector faces the inner wall of the centrifugal collector. The upper part of the liquid-solid separator is provided with a discharge port for conveying aluminum nitride powder that has escaped into the space above the liquid surface in the liquid-solid separator to the cooler.

12. The apparatus for preparing aluminum nitride powder by centrifugal sieving according to claim 11, characterized in that, The upper part of the reactor is connected to the upper part of the liquid-solid separator through a first pipe, and a valve is installed on the first pipe; And / or, the lower part of the reactor is connected to the lower part of the liquid-solid separator through a second pipe, and a delivery pump is provided on the second pipe; And / or, the bottom of the reactor is provided with 1-100 air inlets, each air inlet having a diameter or equivalent diameter of 1mm-10mm; And / or, the upper part of the reactor is also provided with an aluminum liquid inlet for replenishing the reactor with aluminum liquid; And / or, the reactor is a cylindrical or cubical closed container; And / or, the liquid-solid separator is a cylindrical or cubic closed container; And / or, the liquid-solid separator is provided with an argon gas inlet at the bottom; And / or, the inner side wall of the centrifugal collector is provided with a plurality of fins, and the through holes are opened within the projection range of each fin on the side wall of the centrifugal collector; And / or, the angle between the outlet of the argon gas injector and the horizontal direction is 10°-45°; And / or, the minimum distance between the outlet of the argon gas injector and the inner wall of the centrifugal collector is 10cm-30cm; And / or, the gas outlet of the gas-solid separator is connected to the air inlet of the liquid-solid separator.

13. The apparatus for preparing aluminum nitride powder by centrifugal sieving according to claim 12, characterized in that, The number of argon gas inlets is 1-100, and the diameter or equivalent diameter of each argon gas inlet is 1mm-10mm.

14. The apparatus for preparing aluminum nitride powder by centrifugal sieving according to claim 12, characterized in that, The angle between the fins and the sidewall of the centrifugal collector is 30°-60°.

15. The apparatus for preparing aluminum nitride powder by centrifugal sieving according to claim 11, characterized in that, Based on the area of ​​the sidewall of the centrifugal collector, the opening ratio of the through hole is 30%-50%.

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