Manufacturing method of aluminum nitride powder

Abstract

To provide a method for producing aluminum nitride powder, which is different from a general method for producing aluminum nitride powder by direct nitriding of aluminum powder. [Solution] The manufacturing method is a method in which aluminum powder, a nitrogen source, a carbon source, and a halide are uniformly mixed to form a mixed powder, the mixed powder is directly nitrided in a high-temperature nitrogen-containing gas atmosphere to form a fully nitrided aluminum nitride powder, and finally, the mixed powder is decarburized in the atmosphere to form a high-purity aluminum nitride powder. By mixing a carbon source with the aluminum powder to use it as an isolating material, the problem of fusion and agglomeration of the aluminum powder particles can be avoided. In addition, by mixing a nitrogen source with the aluminum powder, when the nitrogen source is thermally decomposed and generates gas to escape to the outside, countless pores can be formed in the mixed powder, and the external nitrogen-containing gas atmosphere can easily enter the mixed powder and react with aluminum, improving the nitriding efficiency of the aluminum powder.

Description

[Technical field]

[0001] The present invention relates to a method for producing aluminum nitride powder, and in particular to a method for producing aluminum nitride powder using aluminum metal powder as a raw material. [Background technology]

[0002] Aluminum nitride (AlN) is a new electronic ceramic material, which is currently one of the most popular advanced materials due to its excellent thermal conductivity and electrical insulation properties. Its special physical properties include high thermal conductivity coefficient, high electrical resistivity, low dielectric constant, low thermal expansion coefficient, excellent heat resistance, excellent mechanical strength, high chemical stability, and non-toxicity, making it applicable in a wide range of applications such as electronic ceramic substrates, electronic component mounting materials, corrosion-resistant components, and high heat conductive additives.

[0003] Aluminum nitride has a hexagonal wurtzite structure, and its atoms are bonded by strong covalent bonds in a tetrahedral arrangement, giving it a high melting point and excellent thermal conductivity. It is one of the few nonmetallic solids with high thermal conductivity, and has a theoretical density of 3.26 g / cm. 3 This is because it satisfies four general rules: (1) low atomic weight, (2) strong atomic bonds, (3) simple crystal structure, and (4) high lattice vibration harmony. Its theoretical thermal conductivity coefficient can reach 320 W / mK, and the thermal conductivity coefficient of commercially available aluminum nitride products is in the range of 170 to 230 W / mK. High-purity aluminum nitride is colorless and has the ability to transmit light, but its characteristics are very susceptible to the influence of chemical purity and density. Since aluminum nitride has a strong affinity for oxygen atoms, some oxygen dissolves into the crystal lattice of aluminum nitride during the manufacturing process and forms impurity defects, which deteriorates the thermal conductivity performance. This is because the defects in the crystal lattice that cause impurities cause phonon scattering, resulting in an obvious decrease in thermal conductivity. Aluminum nitride with low density also has a low thermal conductivity coefficient.

[0004] At present, the manufacturing methods of aluminum nitride powder can be mainly divided into three types: direct nitridation, combustion synthesis, and carbothermal reduction. 1. The direct nitriding method is explained below. In the direct nitriding method, aluminum powder is heated in nitrogen gas and the aluminum powder is directly subjected to a nitriding reaction to produce aluminum nitride powder. The reaction formula is as follows: 2Al (s) +N 2(g) →2AlN (s) Aluminum and nitrogen start to react at 500℃, and at temperatures of 500-600℃, the oxide film on the surface of aluminum granules is removed by generating volatile low-value oxides through the reaction. However, the nitride film gradually generated on the surface of the granules makes it more difficult for nitrogen gas to penetrate, slowing down the nitriding rate. Therefore, in order to improve the nitriding efficiency, it is necessary to perform secondary nitriding, that is, the primary nitriding is performed by keeping at 800℃ for 1 hour, and the product of the primary nitriding is passed through a ball mill and then the secondary nitriding is performed at 1200℃, so that a uniform aluminum nitride powder can be produced. 2. Combustion synthesis is described below. After the aluminum powder is ignited by an external heat source under high pressure, the high chemical reaction heat generated by the reaction between Al and N continues to sustain the reaction until the aluminum powder is completely converted into aluminum nitride. The combustion synthesis method for producing aluminum powder is still essentially direct nitridation. Thus, the reaction equation is as follows: 2Al (s) +N 2(g) → 2AlN (s) The aluminum nitride powder produced by this method does not need to be nitrided at temperatures above 1000°C for a long time as in the direct nitridation method, and no external heat source is required other than ignition, so energy consumption is small, costs are low, and production efficiency is good. However, in the combustion synthesis process, as in the direct nitridation method, the melting point of aluminum is low, so the combustion synthesis reaction is high temperature and the molten aluminum is prone to agglomeration, which prevents nitrogen gas from penetrating into the powder, making it difficult for the aluminum powder to be completely nitrided. Therefore, multiple grinding and nitriding processes are required to improve the nitridation degree of the reaction product. 3. The carbothermal reduction method is explained below. Ultrafine aluminum oxide powder and high-purity carbon black are used as starting materials, and after mixing in a ball mill, the aluminum oxide is reduced using carbon black at 1400-1800°C in a flowing nitrogen gas atmosphere. The reduced aluminum and nitrogen gas react to produce aluminum nitride in a flowing state. The reaction equation is as follows: AlO 3(s) +3C (s) +N 2(g) → 2AlN (s) +3CO The carbothermal reduction reaction requires a molar ratio of aluminum oxide to carbon of 1:3, and more carbon is required to complete the conversion of aluminum oxide. If an excess amount of carbon is added appropriately, the reaction rate can be increased and the conversion efficiency of aluminum oxide powder can be improved, so that aluminum nitride powder with uniform particle size can be obtained. However, this method also has a drawback, that is, the excess carbon must be removed in dry air at 600-900°C after the reaction is complete. This method requires secondary carbon removal, which is expensive, but by omitting the subsequent grinding and polishing step, the carbothermal reduction method can produce aluminum nitride powder with higher purity.

[0005] Patent application CN1544306A discloses a method for producing high-performance aluminum nitride powder by combustion synthesis, which involves mixing aluminum powder and aluminum nitride diluent in a weight ratio of (1-3):(1-7), adding 0.5-2.5 wt% of NHF or NH4Cl additive in anhydrous ethanol, ball milling for 10-12 hours, and then drying. The dried powder is placed in a synthesis reaction vessel, which is evacuated and filled with nitrogen gas up to 8-10 MPa. An ignition agent is then ignited to induce the self-combustion reaction of the aluminum powder, thereby synthesizing the aluminum nitride powder. Patent application CN102531611B discloses a method for producing aluminum nitride, which comprises uniformly mixing aluminum powder and a surface modifier to form a reactant, the surface modifier being one selected from the group consisting of aluminum hydroxide, aluminum nitrate, magnesium hydroxide, and calcium hydroxide, the surface modifier being 0.1-30% of the total weight of the reactant, placing the reactant in a container, and exposing the reactant in the container to a nitrogen-containing gas (gas pressure of 0.1-30 atmospheres) and heating to a temperature of 660°C or higher to combust the reactant, during the heating process, the surface modifier and the aluminum powder react to form a ceramic layer on the surface of the aluminum powder, so that the aluminum powder is prevented from agglomerating due to high temperature melting, and the aluminum powder is combusted to undergo a combustion synthesis reaction with the nitrogen-containing gas to form aluminum nitride.

[0006] Patent application CN106744740A discloses a method for producing aluminum nitride, which comprises thoroughly mixing aluminum powder with 2%-20% aluminum nitride additive, and then placing the mixture in a sintering furnace, increasing the temperature to 500-800°C at a rate of 3-5°C / min in a mixed atmosphere of N2 and H2, maintaining the temperature for 2-6 hours, then lowering the temperature to 300°C at a rate of 3-7°C / min, and then naturally cooling to room temperature to obtain a primary sintered product; the primary sintered product is then pulverized, and flux is added to the mixture, which is then placed in a sintering furnace, increasing the temperature to 800-1100°C at a rate of 5-10°C / min in a mixed atmosphere of N2 and H2, maintaining the temperature for 6-9 hours, then lowering the temperature to 300°C at a rate of 3-7°C / min, and then naturally cooling to room temperature to obtain a secondary sintered product; the secondary sintered product is then pulverized and classified to obtain aluminum nitride powder. The flux is a mixture of NH4HCO3 and AlCl3, the mass ratio of the two being 1:2, and the amount of the flux added is 1 / 2 to 1 / 4 of the amount of the aluminum nitride additive.

[0007] Patent application TW1496736B discloses a method for producing spherical aluminum nitride powder, in which a mixture of 100 parts by mass of aluminum oxide or aluminum hydroxide, 0.5 to 30 parts by mass of a rare earth metal compound, and 38 to 46 parts by mass of carbon powder is subjected to nitriding reduction at a temperature of 1620 to 1900°C for 2 hours or more in a nitrogen-containing atmosphere, and then decarburization is performed with an oxidizing gas, preferably air, at a decarburization temperature of 500 to 900°C, thereby producing spherical aluminum nitride powder.

[0008] Patent application CN1435371A discloses a method for producing ultrafine aluminum powder by low-temperature carbothermal reduction, as follows. Aluminum nitrate, an inorganic aluminum salt, is used as the aluminum source, and water-soluble organic matter such as glucose, sucrose, citric acid, and soluble starch is used as the carbon source, and urea is added. In addition, the production process involves preparing a mixed solution of aluminum nitrate, urea, and a water-soluble organic carbon source in a certain ratio, and drying and heating the solution within a temperature range of 100 to 400°C to obtain a bulky powder as a precursor mixture. In addition, the precursor is subjected to a reduction-nitridation reaction in a nitrogen gas atmosphere at a temperature range of 1200 to 1600°C for 1 to 24 hours. In an oxygen-containing atmosphere, the reduction-nitridation reaction product is calcined at a temperature range of 600 to 700°C for 1 to 7 hours to obtain aluminum nitride powder with an average particle size of less than 0.2 μm.

[0009] Patent application CN109437919B discloses a method for preparing ceramic powder of aluminum nitride based on urea / melamine nitrogen source as follows: The method includes the steps of (1) preparing raw materials, (2) dissolving aluminum nitrate nonahydrate in water, adding coupling agent and polyethylene glycol, and mixing uniformly, (3) adding precipitant, mixing until gel is formed, and filtering the gel after alcohol washing, (4) immersing the gel in anhydrous ethanol, adding phenolic resin under stirring conditions, stirring to form a paste, drying, calcining, and grinding to obtain precursor powder, (5) mixing with nitrogen source and grinding, placing in a heating furnace, raising the temperature to 950-1500°C under the condition that the pressure in the heating furnace is higher than atmospheric pressure, carrying out nitriding synthesis, and (6) grinding to obtain coarse powder while cooling the furnace, and (7) heating to 550-650°C for decarbonization. This invention uses highly active urea / melamine as a nitrogen source instead of nitrogen gas, and uses surface modification dispersion technology to uniformly mix the aluminum source and carbon source by atomic or molecular class, thereby lowering the temperature of the carbothermal reduction reaction.

[0010] At present, the main methods for synthesizing aluminum nitride powder are direct nitridation, combustion synthesis, and carbothermal reduction. The advantages of direct nitridation of aluminum powder are low cost, easy availability of raw materials, low equipment cost, and simple manufacturing steps. However, the nitridation reaction is difficult to control, the product quality is not stable, and the product is prone to agglomeration when produced, so that the grinding and crushing steps must be added, which may extend the production cycle, increasing the production cost, and impurities are easily mixed in during the grinding and crushing process, which affects the purity of the aluminum nitride powder. In the combustion synthesis method, the reaction is spontaneously carried out without an external heat source due to the high chemical reaction heat generated by the reaction of aluminum and nitrogen gas, so energy consumption is low and production efficiency is high, but the method must be carried out under high pressure, which places high demands on equipment performance and makes it difficult to control the spontaneous reaction process. At the same time, the molten aluminum is prone to agglomeration under the high temperature of the combustion synthesis reaction, so the product also needs to be ground and crushed, which is extremely disadvantageous to the management of the production cost cycle and the synthesis purity of the aluminum nitride powder. The carbothermal reduction method has the advantages of easy availability of starting materials, high purity of the synthesized powder, stable performance, uniform particle size distribution of the powder, and resistance to agglomeration, making it an ideal method for the industrial production of aluminum nitride powder. However, this method has high requirements for the quality of the raw materials aluminum oxide and carbon black, and it is difficult to mix the raw materials uniformly, the reaction temperature is high, the synthesis time is long, and at the same time, the excessive carbon needs to be removed after the reaction, resulting in complicated steps.

[0011] In order to solve the above problems, the applicant of the present application has provided a method for producing aluminum nitride powder in consideration of the shortcomings of the prior art. The method uses aluminum powder as a starting material, and by referring to the concept of carbothermal reduction, improves the technology of the direct nitrogen method, adding a carbon source as an insulating material to the starting material of aluminum powder, thereby avoiding the problem of high-temperature melting and agglomeration of aluminum powder, and omitting the subsequent grinding and crushing operation. At the same time, by mixing a nitrogen source with aluminum powder, the nitrogen source undergoes thermal decomposition to generate gas to escape to the outside, and can form countless pores in the mixed powder, so that the external nitrogen-containing gas atmosphere can easily enter the mixed powder and react with aluminum, thereby improving the nitriding efficiency of the aluminum powder. In addition, by adding a halide to the starting material of aluminum powder, the nitriding reaction of aluminum can be accelerated, improving the nitriding effect, which is useful for synthesizing high-purity aluminum nitride powder. The outline of the present application is described below. Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention relates to a method for producing aluminum nitride powder, and more particularly to a method for producing aluminum nitride powder using aluminum metal powder as a raw material. By using steps such as producing a precursor mixture of aluminum powder, nitriding at high temperature, and removing carbon in the atmosphere, the present invention is different from a general method for producing aluminum nitride powder by directly nitriding aluminum powder, and effectively improves the efficiency of aluminum powder nitriding, and can not only omit the subsequent grinding and crushing step caused by the molten agglomeration of aluminum powder, but also reduce the inclusion of unnecessary impurities, thereby improving the purity of the produced aluminum nitride powder.

[0013] According to the concept of the present invention, there is provided a method for producing aluminum nitride powder, the method including: (A) providing aluminum metal powder, a nitrogen source, a carbon source and a halide, and uniformly mixing the aluminum metal powder with the nitrogen source, the carbon source and the halide to form a mixed powder; (B) subjecting the mixed powder to a high-temperature direct nitriding reaction in a nitrogen-containing gas atmosphere to form fully nitrided aluminum nitride powder; and (C) decarburizing the fully nitrided aluminum nitride powder in the atmosphere to form high-purity aluminum nitride powder.

[0014] The aluminum metal powder in step (A) has a purity of 99% or more and an average particle size of 10 to 100 μm, the nitrogen source is one selected from the group consisting of urea, melamine, ammonium carbonate, ammonium hydrogen carbonate, ammonium nitrate, ammonium formate, and ammonium acetate, has a purity of 99% or more, and an average particle size of 10 to 100 μm, the halide is one selected from the group consisting of aluminum chloride, iron chloride, aluminum bromide, sodium fluoride, calcium fluoride, and polytetrafluoroethylene, has a purity of 99% or more, and an average particle size of 10 to 100 μm, and the carbon source is one selected from the group consisting of graphite, carbon black, and activated carbon, has a purity of 99% or more, an average particle size less than 30 μm, and a BET specific surface area of ​​0.1 to 500 m 2 / g.

[0015] The mixing method in step (A) is either a dry mixing method or a wet method. In the wet mixing method, a mixed powder can be obtained by a drying step. The mixing weight ratio of the aluminum metal powder, the nitrogen source, the carbon source and the halide is 1:0.5 to 1:0.3 to 1:0.01 to 0.1.

[0016] The temperature of the high-temperature direct nitriding reaction in step (B) is 1200° C. to 1800° C., and the reaction time is 1 to 10 hours.

[0017] The nitrogen-containing gas atmosphere in step (B) is one selected from the group consisting of ammonia gas, nitrogen gas, air, and a nitrogen-hydrogen mixed gas.

[0018] The decarburization temperature in step (C) is 500° C. to 900° C., and the decarburization time is 1 to 20 hours.

[0019] The present invention uses aluminum powder as a starting material, and improves the technology of the direct nitriding method by referring to the concept of carbothermal reduction. By adding a carbon source to the starting material of aluminum powder as an insulating material, the problem of high-temperature melting and agglomeration of aluminum powder can be avoided and the subsequent grinding and crushing operation can be omitted. At the same time, by mixing a nitrogen source with aluminum powder, the nitrogen source undergoes thermal decomposition to generate gas to escape to the outside, and countless pores can be formed in the mixed powder, so that the external nitrogen-containing gas atmosphere can easily enter the mixed powder and react with aluminum, thereby improving the nitriding efficiency of the aluminum powder. In addition, the addition of a halide can accelerate the nitriding reaction of aluminum and improve the nitriding effect, which is useful for synthesizing high-purity aluminum nitride powder.

[0020] The technology of the present invention improves on the disadvantages of the direct nitridation method while retaining the advantages of the carbothermal reduction method, and thus, unlike general methods for producing aluminum nitride powder by direct nitridation of aluminum powder, it is possible to avoid the problem of molten agglomeration of aluminum powder by the direct nitridation method. Furthermore, compared to the direct nitridation method of aluminum powder, the present invention introduces the steps of mixing and decarburizing the raw materials, but the subsequent polishing and grinding step can be omitted, so that the advantage of the carbothermal reduction method, that is, the high purity of the aluminum nitride powder produced, can be retained while avoiding the introduction of unnecessary impurities.

[0021] The above general description and the following detailed description and drawings are all intended to explain the method, means and advantages of the present invention for achieving the desired objects. Other objects and advantages of the present invention will be set forth in the subsequent description and drawings. [Brief description of the drawings]

[0022] [Figure 1] 1 is a flowchart of a method for producing aluminum nitride powder according to the present invention. [Diagram 2] 1 shows X-ray diffraction patterns of aluminum nitride powders after direct nitriding at high temperature and decarburization in air for different formulations of starting powder in the present invention. [Diagram 3] 1 is a photograph showing the aluminum nitride powder produced after direct nitriding at high temperature and decarburization in air in an embodiment of the present invention. [Figure 4] 1 is a SEM photograph of aluminum nitride powder after direct nitriding at high temperature and decarburization in air in an embodiment of the present invention. [Diagram 5] 1 is an EDS composition and particle size analysis table of aluminum nitride powder after direct nitriding at high temperature and decarburization in air in an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The following is provided to illustrate the embodiments of the present invention through certain specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention based on the disclosure herein.

[0024] Please refer to Fig. 1. Fig. 1 is a flow chart of a method for producing aluminum nitride powder according to the present invention. In step S101, aluminum metal powder, a nitrogen source, a carbon source, and a halide are provided, and the aluminum metal powder, the nitrogen source, the carbon source, and the halide are uniformly mixed to form a mixed powder. In step S102, the mixed powder is directly nitrided in a high-temperature nitrogen-containing gas atmosphere to form a fully nitrided aluminum nitride powder. In step S103, the fully nitrided aluminum nitride powder is decarbonized in the atmosphere to form a high-purity aluminum nitride powder.

[0025] In this embodiment, the aluminum metal powder in step S101 is preferably a granulated aluminum powder having a purity of 99% or more and an average particle size of 30 to 80 μm, and the carbon source in step S101 is preferably carbon black having an average particle size of less than 30 μm and a BET specific surface area of ​​0.1 to 500 m. 2 It is preferred that the molecular weight is / g.

[0026] In this embodiment, the nitrogen source in step S101 is preferably melamine, has a purity of 99% or more, and has an average particle size of 50 μm. In this embodiment, the halide in step S101 is preferably polytetrafluoroethylene, has a purity of 99% or more, and has an average particle size of 20 to 60 μm.

[0027] Regarding the mixed powder in step S101, a suitable mixing weight ratio in this embodiment is aluminum powder:melamine:carbon black:polytetrafluoroethylene=1:0.5-1:0.3-0.5:0.01-0.05.

[0028] If the amount of carbon source used in the mixed powder is excessive, the aluminum source may be present in the mixture in a disintegrated state, and therefore, when heat treatment nitriding is performed, the aluminum nitride particles may not grow sufficiently, which may affect the crystallinity. If too much carbon source is used, the subsequent decarburization step becomes more difficult. On the other hand, if the amount of carbon source used is too small, the aluminum powder will aggregate severely, and the resulting aluminum nitride powder will contain a large number of coarse particles and lumps, and will need to be subjected to a grinding and crushing process.

[0029] In this embodiment, the temperature of the high-temperature direct nitriding reaction in step S102 is preferably 1400 to 1600° C., the reaction time is preferably 4 to 8 hours, and the nitrogen-containing gas in S103 is preferably nitrogen gas.

[0030] The decarburization treatment in step S103 is for removing carbon by oxidation, and is carried out using an oxidizing gas. Any gas capable of removing carbon, such as air or oxygen, can be used as the oxidizing gas without any restrictions. However, in consideration of economy and the oxygen concentration of the aluminum nitride produced, it is preferable to use air (atmospheric atmosphere) as the oxidizing gas in this embodiment. In addition, in consideration of the efficiency of decarburization and excessive oxidation of the aluminum nitride surface, the decarburization temperature is preferably 600 to 750°C, and the decarburization time is preferably 1 to 10 hours in this embodiment.

[0031] Please refer to FIG. 2. FIG. 2 shows the X-ray diffraction patterns of aluminum nitride powders after direct nitriding at high temperature and decarburization in air for different starting powders in the embodiment of the present invention. In this embodiment, A+N represents the starting powder as aluminum powder+melamine (1:1 weight ratio). A+N+F represents the starting powder as aluminum powder+melamine+polytetrafluoroethylene (1:1:0.03 weight ratio). A+N+F+C represents the starting powder as aluminum powder+melamine+polytetrafluoroethylene+carbon black (1:1:0.03:0.5 weight ratio). By comparing the X-ray diffraction patterns of the powders produced after 5 hours of reaction time by direct nitriding at a high temperature of 1600°C using the above-mentioned various starting powders, as shown in FIG. 2, when the direct nitriding reaction is carried out at high temperature using only aluminum powder+melamine as the starting powder, as can be seen from FIG. 2(a), although an aluminum nitride phase is formed, the diffraction peak of aluminum metal still remains. In addition, when aluminum powder + melamine + polytetrafluoroethylene is used as the starting powder to carry out the direct nitridation reaction at high temperature, as can be seen from Figure 2 (b), the intensity of the diffraction peak of the remaining aluminum metal is obviously reduced, indicating that the addition of polytetrafluoroethylene helps to promote the nitridation reaction of aluminum metal and improves the nitridation efficiency of aluminum powder. When aluminum powder + melamine + polytetrafluoroethylene + carbon black is used as the starting powder to carry out the direct nitridation reaction at high temperature and completes the decarburization, as can be seen from Figure 2 (c), the produced powder has already completed the formation of the aluminum nitride phase, the diffraction peak of the aluminum metal has disappeared, there is no remaining starting aluminum powder and carbon black, and high purity aluminum nitride powder is formed.

[0032] Please refer to Fig. 3. Fig. 3 is a photograph of aluminum nitride powder produced after direct nitriding at high temperature and decarburization in air in an embodiment of the present invention. Aluminum powder, melamine, carbon black, and polytetrafluoroethylene were mixed in a dry ball mill based on a weight ratio of 1:1:0.5:0.03, and this uniformly mixed precursor was used as the starting powder to perform direct nitriding at a high temperature of 1600°C, with a reaction time of 5 hours. In the photograph, the aluminum nitride produced in the embodiment of the present invention is in powder form, and no melting and agglomeration of the aluminum powder occurs. As can be seen from this, unlike the general direct nitriding method of aluminum powder, the present invention can directly produce powdered aluminum nitride without the subsequent polishing step, thereby reducing the probability of impurities being mixed in.

[0033] Please refer to Figure 4. Figure 4 is an SEM photograph of aluminum nitride powder after direct nitriding at high temperature and decarburization in air in an embodiment of the present invention. A+N+F+C, where the starting powder is represented as aluminum powder+melamine+polytetrafluoroethylene+carbon black (weight ratio of 1:1:0.03:0.5). After direct nitriding at high temperature and decarburization are completed for the starting powder, as can be seen from the SEM in Figure 4, the produced powder crystals are generally hexagonal columnar, which is a typical expression of the hexagonal crystal structure of aluminum nitride, and the size of the crystal grains can be large or small, with the large crystal grains reaching 2-3 μm or more and the small crystal grains being about 100-200 nm.

[0034] Please refer to FIG. 5. FIG. 5 is an EDS composition and particle size analysis table of aluminum nitride powder after direct nitriding at high temperature and decarburization in air in the embodiment of the present invention. A+N+F+C represents the starting powder as aluminum powder+melamine+polytetrafluoroethylene+carbon black (1:1:0.03:0.5 weight ratio). After the starting powder is directly nitrided at high temperature and decarburization is completed, as can be seen from the EDS composition analysis data in FIG. 5, the average Al content of the produced powder is 64.79 wt%, the average N content is 33.78 wt%, and the average O content is 1.43 wt%. If the O content is excluded, the calculated molar percentage of AlN is about 2.40:2.41, which is close to the theoretical molar ratio of AlN of 1:1. The presence of O content may be caused by the oxygen in the air being adsorbed on the surface of the aluminum nitride powder. The particle size analysis results show that the D of the aluminum nitride powder in this embodiment is 0.001 to 0.001. 10 , D 50 , D 90 are 0.94 μm, 8.19 μm, and 38.12 μm, respectively, which indicates that the average particle size is approximately 7 to 8 μm.

[0035] Through the above description of the embodiments, the method for producing aluminum nitride powder of the present invention uses aluminum powder as a starting material, refers to the concept of carbothermal reduction, and improves the technology of the direct nitridation method, thereby adding and mixing a carbon source, a nitrogen source, and a halide to the starting material of aluminum powder, and directly nitriding the mixture at high temperature to produce a precursor mixture, which is then directly nitrided at high temperature and decarburized in air to form high-purity aluminum nitride powder. The present invention can effectively avoid the problem of fusion and agglomeration of aluminum powder at high temperature, and can omit the subsequent grinding and pulverizing operation, thereby reducing the probability of impurities being mixed in. In addition, the nitriding efficiency of aluminum powder can be improved, which is useful for synthesizing high-purity aluminum nitride powder. The present invention can produce aluminum nitride powder with high economic value using aluminum powder recycled by melting waste aluminum target material as a starting material, thereby strengthening the recycling application of waste material cycle and promoting the development of the circular economy industry.

[0036] The above embodiments are merely illustrative of the features and advantages of the present invention, and are not intended to limit the scope of the substantial technical content of the present invention. Those skilled in the art may modify and change the above embodiments without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention is as set forth in the claims. [Explanation of symbols]

[0037] S101- S103 Steps

Claims

1. (A) providing an aluminum metal powder, a nitrogen source, a carbon source, and a halide, and uniformly mixing the aluminum metal powder, the nitrogen source, the carbon source, and the halide to form a mixed powder; (B) directly nitriding the mixed powder in a high-temperature nitrogen-containing gas atmosphere to form a fully nitrided aluminum nitride powder; (C) decarburizing the fully nitrided aluminum nitride powder in air to form high purity aluminum nitride powder; a nitrogen source selected from the group consisting of urea, melamine, ammonium carbonate, ammonium bicarbonate, ammonium nitrate, ammonium formate, and ammonium acetate, having a purity of 99% or more and an average particle size of 10 to 100 μm; and a halide selected from the group consisting of aluminum chloride, iron chloride, aluminum bromide, sodium fluoride, calcium fluoride, and polytetrafluoroethylene, having a purity of 99% or more and an average particle size of 10 to 100 μm.

2. The aluminum metal powder in step (A) has a purity of 99% or more and an average particle size of 10 to 100 μm, and the carbon source in step (A) is one selected from the group consisting of graphite, carbon black, and activated carbon, has a purity of 99% or more, an average particle size of less than 30 μm, and a BET specific surface area of ​​0.1 to 500 m. ２ The method for producing aluminum nitride powder according to claim 1, characterized in that:

3. 2. The method for producing aluminum nitride powder according to claim 1, wherein the mixing method in step (A) is either a dry mixing method or a wet ball mill method.

4. 2. The method for producing aluminum nitride powder according to claim 1, wherein the mixing weight ratio of the aluminum metal powder, the nitrogen source, the carbon source and the halide in step (A) is 1:0.5 to 1:0.3 to 1:0.01 to 0.

1.

5. 2. The method for producing aluminum nitride powder according to claim 1, wherein the temperature of the high-temperature direct nitridation reaction in step (B) is 1200° C. to 1800° C., and the reaction time is 1 to 10 hours.

6. 2. The method for producing aluminum nitride powder according to claim 1, wherein the nitrogen-containing gas atmosphere in step (B) is one selected from the group consisting of ammonia gas, nitrogen gas, air, and nitrogen-hydrogen mixed gas.

7. 2. The method for producing aluminum nitride powder according to claim 1, wherein the decarburization temperature in step (C) is 500° C. to 900° C., and the decarburization time is 1 to 20 hours.

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