Aluminum nitride powder and method for producing the same

Abstract

The application relates to a preparation method of aluminum nitride powder, which uses commercial aluminum nitride powder as raw material, realizes carbon thermal reduction reaction of the surface oxidation film of particles through high-temperature step-by-step and different atmosphere treatment, and effectively removes the amorphous oxidation layer and residual carbon on the surface of the aluminum nitride powder. The oxygen content of the high-purity aluminum nitride powder prepared by the application is less than or equal to 0.40 wt%, the carbon content is less than or equal to 300 ppm, and the powder can be used to prepare hot-pressed aluminum nitride ceramics without sintering aids, which has a thermal conductivity of greater than or equal to 130 W.m- 1 ·K- 1 This is much higher than that of hot-pressed aluminum nitride ceramics prepared by using commercial raw materials.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of aluminum nitride materials, and particularly relates to an aluminum nitride powder and a preparation method thereof. BACKGROUND

[0002] In recent years, with the rapid development of strategic emerging industries such as microelectronic technology, 5G communication, semiconductors and new energy vehicles, higher and higher requirements are put forward for the performance of power electronic components. Power components are rapidly developing towards small size, high integration and high speed, however, this also leads to a sharp increase in the heat generated per unit area of the power components, posing a severe challenge to the thermal management of the power components, and the heat dissipation material is the core technology of the thermal management of the power components.

[0003] Aluminum nitride (AlN) has high thermal conductivity, excellent insulation performance, low dielectric constant, good mechanical properties and high corrosion resistance, and is an ideal heat dissipation material. The oxygen and carbon contents in the aluminum nitride powder raw material are the key to affecting the thermal conductivity of the aluminum nitride ceramic. At present, the oxygen content of the commercially available aluminum nitride powder is ≤0.90wt%, and the carbon content is ≤600ppm. The thermal conductivity of the hot-pressed aluminum nitride ceramic prepared from the powder is only 75-90W·m -1 ·K -1 . The industry usually introduces rare earth sintering aids (Y2O3, etc.) into the aluminum nitride ceramic, which can significantly reduce the influence of oxygen and carbon impurities, and the thermal conductivity of the aluminum nitride ceramic can reach 170W·m -1 ·K -1 , but this also causes the purity of the aluminum nitride ceramic to decrease and the mechanical properties to be insufficient, which cannot be applied to the strategic emerging industry field with high requirements for the purity and strength of the aluminum nitride, thereby limiting the application range of the aluminum nitride ceramic. SUMMARY

[0004] The application aims to overcome the problem of high oxygen and carbon contents in the existing aluminum nitride powder raw material, and provides an aluminum nitride powder and a preparation method thereof.

[0005] The specific scheme is as follows:

[0006] A preparation method of an aluminum nitride powder, comprising the following steps:

[0007] Step one: commercially available aluminum nitride powder and an infiltration solution are loaded into a nylon ball mill jar; the infiltration solution is composed of a coated carbon source and anhydrous ethanol, and the coated carbon source is at least one of polyvinyl butyral, polydopamine, citric acid and polyvinyl pyrrolidone;

[0008] Step two: alumina grinding balls are added for ball milling to form an infiltration slurry;

[0009] Step three: the infiltration slurry is subjected to spray drying treatment to obtain pre-coated aluminum nitride powder;

[0010] Step four: put the pre-coated aluminum nitride powder into a high temperature furnace to calcine and form carbon-coated aluminum nitride powder;

[0011] Step five: put the carbon-coated aluminum nitride powder into a high temperature furnace to reduce oxygen at high temperature, in a nitrogen atmosphere, at a temperature of 1600-1800℃, and after the end, cool down with the furnace;

[0012] Step six: after cooling, remove carbon at low temperature, use a vacuum pump to vacuumize, then introduce oxygen, and heat treat at 600-750℃; after the end, cool down with the furnace, take out and sieve, and obtain aluminum nitride powder.

[0013] Further, the mass ratio of the commercially available aluminum nitride powder to the infiltration solution is 0.5-1.5:1.

[0014] Further, the spray drying parameters are: drying temperature is 80-95℃, and nitrogen pressure is 1.5-2.0kPa.

[0015] Further, the calcination parameters are: the whole process is carried out under nitrogen atmosphere, temperature is 600-800℃, calcination time is 1-3h, and nitrogen gas pressure is kept above 2.5kPa.

[0016] Further, the high temperature oxygen reduction parameters are: the whole process is carried out under nitrogen atmosphere, temperature is 1600-1800℃, holding time is 5-8h, and nitrogen gas pressure is kept above 2.5kPa.

[0017] Further, the low temperature carbon removal in step six includes the following steps: vacuumize using a vacuum pump to make the vacuum degree in the furnace ≤10Pa, introduce oxygen to make the vacuum degree rise and keep at 1.0-3.0kPa, after the vacuum degree reaches the requirement, hold at 500-650℃ for 1-2h; then start to increase the temperature, when the furnace temperature reaches 700-780℃, increase the oxygen introduction amount to make the vacuum degree in the furnace rise and keep at 30-50kPa, and hold at 700-800℃ for 5-8h.

[0018] An aluminum nitride powder prepared by the preparation method of the aluminum nitride powder.

[0019] Further, the oxygen content of the aluminum nitride powder is ≤0.4wt%, the carbon content is ≤300ppm, and the particle size is 0.8-2.3μm.

[0020] An aluminum nitride ceramic obtained by hot-pressing sintering of the aluminum nitride powder.

[0021] Further, the hot-pressing sintering is carried out at 1800-1900℃, 25-35MPa for 3-7h, and the thermal conductivity of the obtained aluminum nitride ceramic is ≥130W·m-1 ·K -1 .

[0022] Beneficial effects:

[0023] 1. This invention achieves the carbothermic reduction reaction of the oxide film on the particle surface through high-temperature stepwise treatment and different atmospheres, effectively removing the amorphous oxide layer and residual carbon on the surface of aluminum nitride powder.

[0024] 2. This invention utilizes a wetting solution of a carbon source and anhydrous ethanol to pre-coat aluminum nitride powder particles and combines it with high-temperature calcination to form a uniform and dense carbon coating layer on the particle surface. This carbon coating layer provides a carbon source for the carbothermic reduction reaction, promotes the nitridation removal of the oxide film on the particle surface, and effectively isolates the powder particles from contact, avoiding the sintering growth and uneven particle size of the powder particles during high-temperature treatment.

[0025] 3. This invention employs high-temperature oxygen reduction and negative-pressure carbon removal processes, which effectively avoids the increase in oxygen content caused by carbon removal, while simultaneously reducing the oxygen and carbon content.

[0026] 4. This invention can significantly reduce the oxygen and carbon content in aluminum nitride powder. The prepared high-purity aluminum nitride powder has an oxygen content ≤0.40wt% and a carbon content ≤300ppm. Using this powder, aluminum nitride powder with a thermal conductivity ≥130W·m can be prepared. -1 ·K -1 The hot-pressed aluminum nitride ceramics without sintering aids are far superior to those prepared using commercially available raw materials. Attached Figure Description

[0027] To more clearly illustrate the technical solution of the present invention, the accompanying drawings will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention.

[0028] Figure 1 These are SEM microscopic images of aluminum nitride powder provided in Example 1 of this invention;

[0029] Figure 2 This is the XRD diffraction pattern of aluminum nitride powder provided in Example 1 of the present invention;

[0030] Figure 3 This is a SEM microscopic image of the aluminum nitride powder provided in Comparative Example 1 of this invention. Detailed Implementation

[0031] The preferred embodiments of the present application will be described in more detail below. Although the preferred embodiments of the present application are described below, it is understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. If no specific technique or condition is specified in the examples, the technique or condition described in the literature in the art or according to the product manual is used. If no manufacturer of the reagent or instrument is specified, it is a conventional product that can be commercially available. In the following examples, unless otherwise specified, "%" refers to the percentage by weight.

[0032] The present embodiment provides a method for preparing aluminum nitride powder, comprising the following steps:

[0033] Step one: Put commercially available aluminum nitride powder and infiltration solution into a nylon ball mill tank, the infiltration solution is composed of a carbon source and anhydrous ethanol, the carbon source is at least one of polyvinyl butyral, polydopamine, citric acid and polyvinylpyrrolidone; the infiltration solution is used for pre-coating the aluminum nitride powder particles and forming a uniform and dense carbon coating layer on the particle surface through high temperature calcination, which on the one hand provides a carbon source for carbothermal reduction reaction and promotes the nitriding removal of the oxidation film on the particle surface, and on the other hand effectively isolates the contact between the powder particles, avoiding the sintering and growth of the powder particles and the uneven particle size phenomenon during high temperature treatment.

[0034] Step two: Add alumina grinding balls for ball milling to form an infiltration slurry;

[0035] Step three: Spray dry the infiltration slurry to obtain pre-coated aluminum nitride powder;

[0036] Step four: Put the pre-coated aluminum nitride powder into a high temperature furnace for calcination to form carbon-coated aluminum nitride powder;

[0037] Step five: Put the carbon-coated aluminum nitride powder into a high temperature furnace for high temperature oxygen reduction in a nitrogen atmosphere, the temperature is 1600-1800℃, and after the end, the furnace is cooled down;

[0038] Step six: Perform low temperature carbon removal on the cooled powder, vacuumize by using a vacuum pump, then introduce oxygen, and perform heat treatment at 600-750℃; after the end, the furnace is cooled down, and the powder is taken out and sieved, to obtain aluminum nitride powder.

[0039] In the present embodiment, the mass ratio of the commercially available aluminum nitride powder to the infiltration solution is 0.5-1.5:1.

[0040] In the present embodiment, the spray drying parameters are: drying temperature is 80-95℃, and nitrogen pressure is 1.5-2.0kPa.

[0041] In the present embodiment, the calcination parameters are as follows: the whole process is carried out under nitrogen atmosphere, the temperature is 600-800℃, the calcination time is 1-3h, and the nitrogen pressure is kept above 2.5kPa.

[0042] In the present embodiment, the high-temperature oxygen reduction parameters are as follows: the whole process is carried out under nitrogen atmosphere, the temperature is 1600-1800℃, the holding time is 5-8h, and the nitrogen pressure is kept above 2.5kPa. The high-temperature oxygen reduction effectively avoids the increase of oxygen content caused by carbon removal during the preparation of aluminum nitride powder.

[0043] In the present embodiment, the low-temperature carbon removal in step six includes the following steps: vacuumizing by using a vacuum pump to make the vacuum degree in the furnace ≤10Pa, introducing oxygen to make the vacuum degree rise and keep at 1.0-3.0kPa, and after the vacuum degree reaches the requirement, holding at 500-650℃ for 1-2h; then start heating, when the furnace temperature reaches 700-780℃, increase the oxygen flow to make the vacuum degree in the furnace rise and keep at 30-50kPa, and hold at 700-800℃ for 5-8h.

[0044] The present embodiment provides an aluminum nitride powder prepared by the preparation method of the aluminum nitride powder.

[0045] In the present embodiment, the oxygen content of the aluminum nitride powder is ≤0.4wt%, the carbon content is ≤300ppm, and the particle size is 0.8-2.3μm.

[0046] The present embodiment provides an aluminum nitride ceramic obtained by hot-pressing sintering of the aluminum nitride powder.

[0047] In the present embodiment, the hot-pressing sintering is carried out at 1800-1900℃, 25-35MPa for 3-7h, and the thermal conductivity of the obtained aluminum nitride ceramic is ≥130W·m -1 ·K -1 .

[0048] Example 1

[0049] 1000g of commercially available aluminum nitride powder and 1000g of infiltration solution were loaded into a nylon ball mill tank, and alumina grinding balls were added for ball milling for 2 hours to form an infiltration slurry, wherein 1000g of the infiltration solution was composed of 100g of polydopamine, 100g of citric acid and 800g of absolute ethanol. The infiltration slurry was subjected to spray drying treatment, the drying temperature was 85℃, the nitrogen pressure was 1.7kPa, and it was passed through a 200 mesh screen to obtain pre-coated aluminum nitride powder.

[0050] The pre-coated aluminum nitride powder is placed in a high-temperature furnace, calcined for 2 hours under a nitrogen atmosphere of 2.5 kPa or above and at a calcination temperature of 650°C to form carbon-coated aluminum nitride powder. After the calcination is completed, the carbon-coated aluminum nitride powder is placed in a high-temperature furnace, high-temperature deoxygenation is performed under a nitrogen atmosphere of 2.5 kPa or above and with the furnace temperature raised to 1650°C, and the temperature is maintained for 8 hours. After the temperature is lowered to 600°C, the nitrogen supply is stopped, vacuum is applied using a vacuum pump, and when the vacuum degree in the furnace is reduced to 10 Pa or below, oxygen is supplied to the furnace to increase the vacuum degree to 1.3 kPa and maintain it. After the vacuum degree reaches the required value, the temperature is maintained at 600°C for 1.5 hours. After the temperature is raised, when the furnace temperature reaches 750°C, the oxygen supply is increased to increase the vacuum degree in the furnace to 35 kPa and maintain it. After the vacuum degree reaches the required value, the temperature is maintained at 750°C for 6 hours. After the temperature is lowered to room temperature, the oxygen supply is stopped, and the aluminum nitride powder is obtained by passing it through a 200-mesh sieve. The obtained aluminum nitride powder is analyzed by scanning electron microscopy.

[0051] As can be seen from the results of Example 1, the oxygen content of the aluminum nitride powder prepared in this example is 0.31%, the carbon content is 260 ppm, and the particle size is 1.3-1.6 μm. Compared with the original commercial powder, the oxygen and carbon contents are reduced by 63% and 57%, respectively. Figure 1 As can be seen from the results of Example 1, the aluminum nitride powder prepared in this example has uniform particles and does not exhibit sintering and bonding. Figure 2 As can be seen from the results of Example 1, the aluminum nitride is a pure phase with high crystallinity and does not contain other impurity phases.

[0052] Using the aluminum nitride powder of this example and a commercial aluminum nitride powder, aluminum nitride ceramics are prepared by hot-pressing sintering technology (1850°C / 5h, 30 MPa). The thermal conductivities of the aluminum nitride ceramics are 130 W·m -1 ·K -1 and 85 W·m -1 ·K -1 , respectively. The thermal conductivity of the aluminum nitride ceramics of this example is increased by 53% compared with the thermal conductivity of the aluminum nitride ceramics prepared using the commercial aluminum nitride powder.

[0053] Example 2

[0054] 1000 g of commercial aluminum nitride powder and 1000 g of infiltration solution are placed in a nylon ball mill jar, and alumina milling balls are added for ball milling for 2 hours to form an infiltration slurry. The 1000 g of infiltration solution is composed of 100 g of polyvinylpyrrolidone, 100 g of citric acid, and 800 g of absolute ethanol. The infiltration slurry is subjected to spray drying treatment at a drying temperature of 85°C and under a nitrogen pressure of 1.8 kPa, and is passed through a 200-mesh sieve to obtain pre-coated aluminum nitride powder.

[0055] The pre-coated aluminum nitride powder is placed in a high-temperature furnace, calcined at a calcination temperature of 700°C for 2 hours under a nitrogen atmosphere of 2.5 kPa or more, to form carbon-coated aluminum nitride powder. After the calcination is completed, the carbon-coated aluminum nitride powder is placed in a high-temperature furnace, high-temperature deoxygenation is performed at a furnace temperature of 1700°C under a nitrogen atmosphere of 2.5 kPa or more, and the temperature is maintained for 6 hours. After the temperature is lowered to 600°C, the nitrogen supply is stopped, vacuum pumping is performed using a vacuum pump, and when the vacuum degree in the furnace is reduced to 10 Pa or less, oxygen is supplied to the furnace to increase the vacuum degree to 1.3 kPa and maintain it. After the vacuum degree reaches the required value, the temperature is maintained at 600°C for 1.5 hours. After the temperature is raised to 750°C, the oxygen supply is increased to increase the vacuum degree in the furnace to 37 kPa and maintain it. After the vacuum degree reaches the required value, the temperature is maintained at 750°C for 6 hours. After the temperature is lowered to room temperature, the aluminum nitride powder is obtained by stopping the oxygen supply and passing it through a 200-mesh sieve.

[0056] The aluminum nitride powder prepared in this example has an oxygen content of 0.38%, a carbon content of 250 ppm, and a particle size of 1.6-2.0 μm. Compared with the original commercially available powder, the oxygen and carbon contents are reduced by 42%.

[0057] Example 3

[0058] 1000 g of commercially available aluminum nitride powder and 1000 g of infiltration solution are placed in a nylon ball mill tank, and alumina balls are added for ball milling for 2 hours to form an infiltration slurry, wherein the 1000 g of infiltration solution is composed of 100 g of polydopamine, 80 g of citric acid, 80 g of polyvinylpyrrolidone, and 740 g of absolute ethanol. The infiltration slurry is subjected to spray drying treatment at a drying temperature of 85°C and a nitrogen pressure of 1.9 kPa, and is passed through a 200-mesh sieve to obtain pre-coated aluminum nitride powder.

[0059] The pre-coated aluminum nitride powder is placed in a high-temperature furnace, calcined at a calcination temperature of 750°C for 1 hour under a nitrogen atmosphere of 2.5 kPa or more, to form carbon-coated aluminum nitride powder. After the calcination is completed, the carbon-coated aluminum nitride powder is placed in a high-temperature furnace, high-temperature deoxygenation is performed at a furnace temperature of 1750°C under a nitrogen atmosphere of 2.5 kPa or more, and the temperature is maintained for 5 hours. After the temperature is lowered to 600°C, the nitrogen supply is stopped, vacuum pumping is performed using a vacuum pump, and when the vacuum degree in the furnace is reduced to 10 Pa or less, oxygen is supplied to the furnace to increase the vacuum degree to 1.4 kPa and maintain it. After the vacuum degree reaches the required value, the temperature is maintained at 600°C for 1.5 hours. After the temperature is raised to 750°C, the oxygen supply is increased to increase the vacuum degree in the furnace to 40 kPa and maintain it. After the vacuum degree reaches the required value, the temperature is maintained at 750°C for 6 hours. After the temperature is lowered to room temperature, the aluminum nitride powder is obtained by stopping the oxygen supply and passing it through a 200-mesh sieve.

[0060] The aluminum nitride powder prepared in this example has an oxygen content of 0.40%, a carbon content of 280 ppm, and a particle size of 1.4-1.8 μm. Compared with the original commercial powder, the oxygen and carbon contents are reduced by 44% and 47%, respectively.

[0061] Comparative Example 1

[0062] A nylon ball mill tank was charged with 1000 g of commercial aluminum nitride powder, 20 g of carbon powder, and 1000 g of anhydrous ethanol, and alumina balls were added for ball milling for 2 hours to form an infiltration slurry. The infiltration slurry was subjected to spray drying at a drying temperature of 85°C and a nitrogen pressure of 1.8 kPa, and was passed through a 200 mesh screen to obtain a pre-coated aluminum nitride powder.

[0063] The pre-coated aluminum nitride powder was placed in a high temperature furnace and calcined at a calcination temperature of 650°C for 2 hours in a nitrogen atmosphere of 2.5 kPa or more to form a carbon-coated aluminum nitride powder. After the calcination was completed, the carbon-coated aluminum nitride powder was placed in a high temperature furnace and subjected to high temperature oxygen reduction at a furnace temperature of 1650°C in a nitrogen atmosphere of 2.5 kPa or more, and was held for 8 hours. After the holding was completed, the temperature was decreased. When the furnace temperature decreased to 600°C, the nitrogen gas was stopped, and a vacuum pump was used to perform vacuum pumping. When the vacuum degree in the furnace decreased to 10 Pa or less, oxygen was introduced into the furnace to increase the vacuum degree to 1.6 kPa, and was held at 600°C for 1.5 hours. After the holding was completed, the temperature was increased. When the furnace temperature reached 750°C, the oxygen flow was increased to increase the vacuum degree in the furnace to 38 kPa, and was held at 750°C for 6 hours. After the holding was completed, the oxygen flow was stopped, and the furnace was cooled to room temperature. The aluminum nitride powder was obtained by passing the powder through a 200 mesh screen. The obtained aluminum nitride powder was subjected to scanning electron microscope analysis.

[0064] As can be seen from the results of Comparative Example 1, the aluminum nitride powder prepared in this example has an oxygen content of 0.48%, a carbon content of 760 ppm, and a particle size of 1.5-3.8 μm. Compared with Example 1, the carbon content of the aluminum nitride powder prepared in this example is greatly increased, and the oxygen content is slightly increased. As can be seen from the results of Example 1 and Comparative Example 1, the carbon content of the aluminum nitride powder prepared in Example 1 is greatly reduced, and the oxygen content is also reduced. Figure 3 As can be seen from the results of Comparative Example 1, the aluminum nitride powder prepared in this example has an oxygen content of 0.48%, a carbon content of 760 ppm, and a particle size of 1.5-3.8 μm. Compared with Example 1, the carbon content of the aluminum nitride powder prepared in this example is greatly increased, and the oxygen content is slightly increased. As can be seen from the results of Example 1 and Comparative Example 1, the carbon content of the aluminum nitride powder prepared in Example 1 is greatly reduced, and the oxygen content is also reduced.

[0065] Comparative Example 2

[0066] 1000g of commercially available aluminum nitride powder and 1000g of infiltration solution were loaded into a nylon ball mill tank, and alumina grinding balls were added for ball milling for 2 hours to form an infiltration slurry, wherein the 1000g of infiltration solution was composed of 100g of polydopamine, 100g of citric acid and 800g of anhydrous ethanol. The infiltration slurry was subjected to spray drying treatment, the drying temperature was 85°C, the nitrogen pressure was 1.9kPa, and the powder was sieved through a 200 mesh screen to obtain pre-coated aluminum nitride powder.

[0067] The pre-coated aluminum nitride powder was placed in a high-temperature furnace and calcined at a calcination temperature of 650°C for 2h under a nitrogen atmosphere of 2.5kPa or more to form carbon-coated aluminum nitride powder. After calcination, the carbon-coated aluminum nitride powder was placed in a high-temperature furnace and subjected to high-temperature oxygen reduction at a furnace temperature of 1650°C under a nitrogen atmosphere of 2.5kPa or more, and was kept at this temperature for 8h, and then was cooled to room temperature. The powder after high-temperature oxygen reduction was placed in a muffle furnace and kept at 750°C for 6h under atmospheric environment, and then was cooled to room temperature. After cooling, the powder was sieved through a 200 mesh screen to obtain aluminum nitride powder.

[0068] As can be seen from the results of Comparative Example 2, the oxygen content of the aluminum nitride powder prepared in this comparative example was 1.2%, the carbon content was 270ppm, and the particle size was 1.3-1.6μm. Compared with Example 1, it can be seen that the carbon content and particle size distribution of the powder changed little, but the oxygen content increased significantly.

[0069] The above describes the preferred embodiments of the present application, but the present application is not limited to the specific details in the above-described embodiments, and various simple modifications can be made to the technical solutions of the present application within the technical concept of the present application, and these simple modifications all belong to the protection scope of the present application.

[0070] In addition, it should be noted that each specific technical feature described in the above-described specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, various possible combinations are not described again in the present application.

[0071] In addition, various different embodiments of the present application can also be combined in any appropriate manner, as long as it does not deviate from the technical concept of the present application, and it should also be considered as disclosed in the present application.

Claims

1. A method for producing an aluminum nitride powder, characterized by comprising: The method comprises the following steps: ​ Step 1: 1000g of commercially available aluminum nitride powder and 1000g of infiltration solution are loaded into a nylon ball mill tank, wherein the 1000g of infiltration solution is composed of 100g of polydopamine, 100g of citric acid and 800g of anhydrous ethanol; Step 2: aluminum oxide grinding balls are added for ball milling to form an infiltration slurry; Step 3: the infiltration slurry is subjected to spray drying treatment to obtain pre-coated aluminum nitride powder; the spray drying parameters are: a drying temperature of 85℃ and a nitrogen pressure of 1.7 kPa; Step 4: the pre-coated aluminum nitride powder is placed in a high-temperature furnace for calcination to form carbon-coated aluminum nitride powder; the calcination parameters are: the whole process is carried out under a nitrogen atmosphere, the temperature is 650℃, the calcination time is 2h, and the nitrogen gas pressure is kept above 2.5 kPa; Step 5: the carbon-coated aluminum nitride powder is placed in a high-temperature furnace for high-temperature oxygen reduction, and after the end, the furnace is cooled down; the high-temperature oxygen reduction parameters are: the whole process is carried out under a nitrogen atmosphere, the temperature is 1650℃, the holding time is 8h, and the nitrogen gas pressure is kept above 2.5 kPa; Step 6: the powder after cooling is subjected to low-temperature carbon removal; after the end, the furnace is cooled down, and the powder is taken out and sieved, thereby obtaining aluminum nitride powder; The low-temperature carbon removal in Step 6 comprises the following steps: vacuumizing by using a vacuum pump to make the vacuum degree in the furnace ≤10Pa, introducing oxygen to make the vacuum degree rise and keep at 1.3kPa, after the vacuum degree reaches the requirement, keeping at 600℃ for 1.5h; then, increasing the temperature, when the furnace temperature reaches 750℃, increasing the oxygen introduction amount to make the vacuum degree in the furnace rise and keep at 35kPa, keeping at 750℃ for 6h.

2. The aluminum nitride powder prepared by the method of claim 1.

3. The aluminum nitride powder of claim 2, wherein: The oxygen content of the aluminum nitride powder is 0.31%, the carbon content is 260ppm, and the particle size is 1.3-1.6μm.

4. An aluminum nitride ceramic obtained by hot-pressing sintering of the aluminum nitride powder of claim 2 or 3.

5. The aluminum nitride ceramic of claim 4, wherein: The hot-press sintering is sintered at 1800-1900 DEG C, 25-35 MPa for 3-7 h, and the thermal conductivity of the obtained aluminum nitride ceramic is greater than or equal to 130 W m -1 K -1 .

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