Method for manufacturing aluminum nitride powder

Abstract

To provide a method for manufacturing aluminum nitride powder that is different from a general method for manufacturing aluminum nitride powder by direct nitridation of aluminum powder.SOLUTION: The manufacturing method comprises forming a mixed powder by uniformly mixing aluminum powder, a nitrogen source, a carbon source, and a halide; subjecting the mixed powder to a direct nitridation reaction in a high-temperature nitrogen-containing gas atmosphere to form completely nitrided aluminum nitride powder; and finally, decarburizing in air to form high-purity aluminum nitride powder. By mixing the carbon source with the aluminum powder to serve as a separation material, it is possible to avoid the problem of fused lump formation among the aluminum powders. Furthermore, by mixing the nitrogen source with the aluminum powder, when the nitrogen source undergoes thermal decomposition and generates gas to escape outside, a large number of pores can be formed within the mixed powder, making it easier for the external nitrogen-containing gas atmosphere to enter the mixed powder and react with the aluminum, thereby improving the nitridation efficiency of the aluminum powder.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] 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.

Background Art

[0002] Aluminum nitride (AlN) is a novel electronic ceramic material, and due to its excellent thermal conductivity and electrical insulation properties, it has currently become one of the most popular advanced materials. 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, non-toxicity, etc., and it can be applied to various application fields such as electronic ceramic substrates, mounting materials for electronic components, corrosion-resistant parts, and high heat transfer additives.

[0003] Aluminum nitride has a hexagonal wurtzite structure, and the atoms are bonded by strong covalent bonds in a tetrahedral arrangement, so it has a high melting point and excellent thermal conduction performance. It is one of the few non-metallic solids with a high thermal conductivity, and its theoretical density value is 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 harmonicity of lattice vibrations. The theoretical value of its 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 - 230 W / mK. And high-purity aluminum nitride is colorless and has the performance of transmitting light, but its properties are very susceptible to the influence of chemical purity and density. Since aluminum nitride has a strong affinity for oxygen atoms, in the manufacturing process, some oxygen dissolves into the crystal lattice of aluminum nitride, forming impurity defects, so the thermal conduction performance deteriorates. This is because the defects in the crystal lattice that exist as impurities cause phonon scattering, resulting in a significant decrease in thermal conductivity. And aluminum nitride with low density also has a low thermal conductivity coefficient.

[0004] Currently, the manufacturing methods of aluminum nitride powder are mainly divided into three types: the direct nitridation method, the combustion synthesis method, and the carbon thermal reduction method. 1. The direct nitridation method will be described below. The direct nitridation method heats aluminum powder in nitrogen gas and directly subjects the aluminum powder to a nitridation 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 °C. At a temperature of 500 - 600 °C, the oxide film on the surface of the aluminum particles is removed by generating a low-volatile oxide through the reaction. However, on the particle surface, the nitride film gradually formed makes it more difficult for nitrogen gas to penetrate, thus slowing down the nitridation rate. Therefore, in order to increase the nitridation efficiency, it is necessary to perform secondary nitridation. That is, after primary nitridation by holding at 800 °C for 1 hour, and after the product of primary nitridation passes through a ball mill, secondary nitridation is performed at 1200 °C, and in this way, uniform aluminum nitride powder can be produced. 2. The combustion synthesis method will be described below. After igniting aluminum powder with an external heat source under high pressure, the high chemical reaction heat generated by the reaction between Al and N continues to maintain the reaction itself until the aluminum powder is completely converted into aluminum nitride. The combustion synthesis method for manufacturing aluminum powder is still essentially direct nitridation. Therefore, the reaction formula 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 a temperature of 1000 °C or higher for a long time like the direct nitridation method. Except for ignition, no external heat source is required, so the energy consumption is low, the cost is low, and the production efficiency is good. However, in the combustion synthesis process, like the direct nitridation method, since the melting point of aluminum is low, the combustion synthesis reaction is at a high temperature, and the molten aluminum is likely to cause agglomeration, preventing nitrogen gas from penetrating into the powder, making it difficult for the aluminum powder to be completely nitrided. Therefore, to improve the nitridation degree of the reaction product, multiple grinding and nitridation treatments are required. 3. The carbon thermal reduction method will be described below. Using ultrafine aluminum oxide powder and high-purity carbon black as starting materials, after ball milling and mixing, 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. Al2O 3(s) + 3C (s) + N 2(g) → 2AlN (s) + 3CO The carbon thermal reduction reaction requires that the molar ratio of aluminum oxide to carbon is 1:3. To achieve complete conversion of aluminum oxide, more carbon is required. Appropriately adding an excessive amount of carbon can increase the reaction rate and improve the conversion efficiency of the aluminum oxide powder, so that aluminum nitride powder with uniform particle size can be obtained. However, this method also has disadvantages, that is, after the reaction is complete, the excessive carbon must be subjected to a carbon removal treatment in dry air at 600 - 900 °C. This method requires secondary carbon removal and has a high cost. However, by omitting the subsequent grinding and polishing steps, the carbon thermal reduction method can produce aluminum nitride powder with higher purity.

[0005] The patent application CN1544306A discloses a method for manufacturing high-performance aluminum nitride powder using a combustion synthesis method. The method involves mixing aluminum powder and an aluminum nitride diluent based on a weight ratio of (1 to 3):(1 to 7), adding an additive of 0.5 to 2.5 wt% of NH4F or NH4Cl using absolute ethanol as a medium, performing ball milling mixing for 10 to 12 hours, then carrying out a drying step. After drying, the powder is placed in a synthesis reaction kettle, evacuated, filled with nitrogen gas up to 8 to 10 MPa, and then an ignition agent is ignited to induce the self-combustion reaction of the aluminum powder, thereby synthesizing aluminum nitride powder. The patent application CN102531611B discloses a method for manufacturing aluminum nitride. The method involves uniformly mixing aluminum powder and a surface modifier to form a reactant. The surface modifier is one of the group selected from aluminum hydroxide, aluminum nitrate, magnesium hydroxide, and calcium hydroxide. The surface modifier accounts for 0.1 to 30% of the total weight of the reactant. The reactant is placed in a container and exposed to a nitrogen-containing gas (gas pressure of 0.1 to 30 atmospheres) in the container, and heated to a temperature of 660 °C or higher to burn 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. Therefore, the aluminum powder prevents the occurrence of agglomeration due to high-temperature melting, and the aluminum powder undergoes a combustion synthesis reaction with the nitrogen-containing gas due to combustion to form aluminum nitride.

[0006] The patent application CN106744740A discloses a method for manufacturing aluminum nitride. The method involves thoroughly mixing aluminum powder with 2% - 20% aluminum nitride additive, putting it into a sintering furnace, raising the temperature to 500 - 800°C at a rate of 3 - 5°C / min in a mixed atmosphere of N2 and H2, then maintaining the temperature for 2 - 6 hours, after that, 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. Further, after pulverizing the primary sintered product, adding a flux, putting it into a sintering furnace, raising the temperature to 800 - 1100°C at a rate of 5 - 10°C / min in a mixed atmosphere of N2 and H2, then maintaining the temperature for 6 - 9 hours, after that, the temperature drops to 300°C at a rate of 3 - 7°C / min, and then naturally cools to room temperature to obtain a secondary sintered product. After pulverizing and classifying the secondary sintered product, aluminum nitride powder can be obtained. The flux is a mixture of NH4HCO3 and AlCl3, the mass ratio of the two is 1:2, and the addition amount of the flux is 1 / 2 - 1 / 4 of the aluminum nitride additive.

[0007] The patent application TW1496736B discloses a method for manufacturing spherical aluminum nitride powder. The method involves performing nitridation reduction on a mixture of 100 parts by mass of aluminum oxide or aluminum hydroxide, 0.5 - 30 parts by mass of rare earth metal compound, and 38 - 46 parts by mass of carbon powder at a temperature of 1620 - 1900°C for 2 hours or more in a nitrogen-containing atmosphere, and then performing decarburization with an oxidizing gas. It is preferably that the oxidizing gas is air, and the decarburization treatment temperature is 500 - 900°C. Thereby, spherical aluminum nitride powder can be manufactured.

[0008] The patent application CN1435371A discloses a method for producing ultrafine aluminum powder by a low-temperature carbon thermal reduction method as follows. Using aluminum nitrate, an inorganic aluminum salt, as the aluminum source, and water-soluble organic substances such as glucose, sucrose, citric acid, and soluble starch as the carbon source, and adding urea. Also, in the manufacturing process, an aluminum nitrate, urea, and water-soluble organic carbon source are mixed in a certain ratio to prepare a mixed solution, and the above solution is dried and heated within a temperature range of 100 to 400 °C to obtain a bulky powder as a precursor mixture. Further, within a temperature range of 1200 to 1600 °C, the precursor is subjected to a reduction nitridation reaction in a nitrogen gas atmosphere for a time of 1 to 24 hours. By calcining the reduction nitridation reaction product in an oxygen-containing atmosphere within a temperature range of 600 to 700 °C for 1 to 7 hours, aluminum nitride powder with an average particle size of less than 0.2 μm can be obtained.

[0009] The patent application CN109437919B discloses a method for producing ceramic powder of aluminum nitride based on a urea / melamine nitrogen source as follows. The method includes step (1) of preparing raw materials, step (2) of dissolving aluminum nitrate nonahydrate in water, adding a coupling agent and polyethylene glycol, and mixing uniformly, step (3) of adding a precipitating agent, mixing until a gel is formed, and filtering the obtained gel after alcohol washing, step (4) of immersing the gel in absolute ethanol, adding phenol resin under stirring conditions to form a paste-like body by stirring, and obtaining a precursor powder by drying, calcining, and polishing, step (5) of mixing with a nitrogen source and polishing, placing it in a heating furnace, raising the temperature to 950 to 1500 °C with the pressure in the heating furnace higher than atmospheric pressure to perform nitridation synthesis, and obtaining a coarse powder by polishing while cooling the furnace, and step (6) of heating to 550 to 650 °C to remove carbon, which are carried out in sequence. This invention uses highly active urea / melamine as the nitrogen source instead of nitrogen gas, and by using a surface modification and dispersion technology, it can uniformly mix at the atomic or molecular level between the aluminum source and the carbon source, and can lower the temperature of the carbon thermal reduction reaction.

[0010] At present, the synthesis methods of aluminum nitride powder mainly include direct nitridation method, combustion synthesis method, and carbon thermal reduction method. The advantages of the direct nitridation method of aluminum powder are low cost, easy availability of raw materials, low equipment cost, and simple manufacturing steps. However, its nitridation reaction is difficult to control, the stability of product quality is poor, and the product is prone to agglomeration after being produced, so it is necessary to increase the polishing and grinding steps. In this way, the manufacturing cycle may be extended, resulting in increased production costs. Moreover, during the polishing and grinding process, impurities are likely to be mixed in, which affects the purity of aluminum nitride powder. The combustion synthesis method is such that the reaction occurs spontaneously without an external heat source due to the high chemical reaction heat generated by the reaction between aluminum and nitrogen gas, so the energy consumption is low and the production efficiency is high. However, this method needs to be carried out at a high pressure, so the requirements for equipment performance are high, and the spontaneous reaction process is difficult to control. At the same time, at the high temperature of the combustion synthesis reaction, the molten aluminum is prone to agglomeration, so the product also requires polishing and grinding treatment, which is extremely disadvantageous for the management of the production cost cycle and the synthesis purity of aluminum nitride powder. The advantages of the carbon thermal reduction method are easy availability of starting materials, high purity of the synthesized powder, stable performance, uniform particle size distribution of the powder, and difficulty in agglomeration, etc., which is 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, it is difficult to mix the raw materials uniformly, the reaction temperature is high, the synthesis time is long, and at the same time, after the excessive carbon reacts, it is necessary to carry out a treatment to remove the carbon, so the steps become complicated.

[0011] To solve the above problems, in view of the drawbacks of the prior art, the applicant of the present application provides a method for manufacturing aluminum nitride powder. This uses aluminum powder as the starting material and, referring to the concept of carbon thermal reduction, improves the technology of the manufacturing steps of the direct nitrogen method. As an isolation material, a carbon source is added to the starting material of aluminum powder to avoid the problem of high-temperature melting and agglomeration of aluminum powder and can omit the subsequent polishing and grinding operations. At the same time, by mixing a nitrogen source into the aluminum powder, when the nitrogen source undergoes thermal decomposition and generates gas to escape, innumerable pores can be formed within the mixed powder material. Thus, the atmosphere of the external nitrogen-containing gas can easily enter the mixed powder material and react with aluminum, improving the nitriding efficiency of the aluminum powder. Additionally, by adding a halide to the starting material of aluminum powder, the nitriding effect can be improved to accelerate the nitriding reaction of aluminum, which is useful for the synthesis of high-purity aluminum nitride powder. The following is an explanation of the outline of the present application.

Summary of the Invention

Problems to be Solved by the Invention

[0012] The present invention relates to a method for manufacturing aluminum nitride powder, and particularly to a method for manufacturing aluminum nitride powder using aluminum metal powder as a raw material. By using steps such as manufacturing a precursor mixture of aluminum powder, nitriding at high temperature, and removing carbon in the atmosphere, the present invention is different from the general method for manufacturing aluminum nitride powder by direct nitriding of aluminum powder. It can effectively improve the efficiency of aluminum powder nitriding, not only can omit the subsequent polishing and grinding steps caused by the melting and agglomeration of aluminum powder, but also can reduce the incorporation of extra impurities, thereby improving the purity of the produced aluminum nitride powder.

[0013] Based on the concept of the present invention, there is provided an aluminum metal powder, a nitrogen source, a carbon source, and a halide. The steps include: (A) 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 nitridation reaction in a nitrogen-containing gas atmosphere to form a completely nitrided aluminum nitride powder; and (C) removing carbon from the completely nitrided aluminum nitride powder in the atmosphere to form a high-purity aluminum nitride powder. A method for manufacturing an aluminum nitride powder is provided.

[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 bicarbonate, ammonium nitrate, ammonium formate, and ammonium acetate, with 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, with a purity of 99% or more and an average particle size of 10 to 100 μm. The carbon source is one selected from the group consisting of graphite, carbon black, and activated carbon, with a purity of 99% or more, an average particle size smaller 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 mixing method. Wet mixing can obtain the mixed powder through a drying step. The mixing weight ratio of the aluminum metal powder, nitrogen source, carbon source, and halide is 1:0.5 to 1:0.3 to 1:0.01 to 0.1.

[0016] 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.

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

[0018] The decarburization temperature in the 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 nitridation method with reference to the concept of carbon thermal reduction. As an isolation material, by adding a carbon source to the starting material of aluminum powder, the problem of high-temperature melting and agglomeration of aluminum powder can be avoided, and the subsequent polishing and grinding operations can be omitted. At the same time, by mixing a nitrogen source into the aluminum powder, when the nitrogen source undergoes thermal decomposition and generates gas to escape, innumerable pores can be formed in the mixed powder material. Therefore, the atmosphere of the external nitrogen-containing gas can easily enter the mixed powder material and react with aluminum, improving the nitridation efficiency of the aluminum powder. In addition, by adding a halide, the nitridation reaction of aluminum can be accelerated, improving the nitridation effect, which is useful for the synthesis of high-purity aluminum nitride powder.

[0020] The technology of the present invention retains the advantages of the carbon thermal reduction method and improves the disadvantages of the direct nitridation method. Different from the general method for producing aluminum nitride powder by direct nitridation of aluminum powder, the problem of melting and agglomeration of aluminum powder by the direct nitridation method can be avoided. Also, compared with the direct nitridation method of aluminum powder, the present invention introduces the steps of raw material mixing and decarburization, but the subsequent polishing and grinding steps can be omitted. Therefore, while avoiding the mixing of extra impurities, the present invention can retain the advantage of the carbon thermal reduction method that the purity of the produced aluminum nitride powder is high.

[0021] The above overview, the following detailed description, and the drawings are all for explaining the methods, means, and effects adopted to achieve the required objectives of the present invention. Other objectives and advantages of the present invention will be described in the subsequent description and drawings.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0023] The following is for explaining the embodiments of the present invention by specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention based on the disclosure of this specification.

[0024] Please refer to FIG. 1. FIG. 1 is a flowchart of a method for manufacturing aluminum nitride powder according to the present invention. Step S101 provides aluminum metal powder, a nitrogen source, a carbon source, and a halide, and uniformly mixes the aluminum metal powder and the nitrogen source, the carbon source, and the halide to form a mixed powder material. Also, step S102 directly causes a nitriding reaction of the mixed powder material in a high-temperature nitrogen-containing gas atmosphere to form a completely nitrided aluminum nitride powder. Also, step S103 decarburizes the completely nitrided aluminum nitride powder in air to form a high-purity aluminum nitride powder.

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

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

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

[0028] In the mixed powder, when the amount of the carbon source used is excessive, the aluminum source may exist in a loose state in the mixture. Therefore, when heat treatment nitridation is performed, the aluminum nitride particles may not grow sufficiently, which may affect the crystallinity. The excessive amount of the carbon source used increases the difficulty of the subsequent carbon removal step. On the other hand, when the amount of the carbon source used is excessively small, the aggregation of the aluminum powder becomes intense. Therefore, the obtained aluminum nitride powder contains a large number of coarse particles and lumps and needs to undergo a polishing and grinding process.

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

[0030] The decarburization treatment in step S103 oxidizes and removes carbon and is performed using an oxidizing gas. As this oxidizing gas, any gas that can remove carbon, such as air, oxygen, etc., can be adopted without any restrictions as long as it can remove carbon. However, considering the economy and the oxygen concentration of the produced aluminum nitride, it is preferable to use air (atmospheric atmosphere) as the oxidizing gas in this embodiment. Also, considering the decarburization efficiency and the 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 directly nitriding starting powder mixtures with different compositions at high temperature and decarburizing in air in the embodiments of the present invention. In this embodiment, A+N represents the starting powder mixture as aluminum powder + melamine (1:1 weight ratio). A+N+F represents the starting powder mixture as aluminum powder + melamine + polytetrafluoroethylene (1:1:0.03 weight ratio). A+N+F+C represents the starting powder mixture as aluminum powder + melamine + polytetrafluoroethylene + carbon black (1:1:0.03:0.5 weight ratio). When directly nitriding at a high temperature of 1600 °C using the above various starting powder mixtures and comparing the X-ray diffraction patterns of the powders produced with a reaction time of 5 hours, as shown in Fig. 2, when directly performing the nitriding reaction at high temperature using only aluminum powder + melamine as the starting powder mixture, as can be seen from Fig. 2(a), although the aluminum nitride phase is formed, the diffraction peak of aluminum metal still remains. Also, when directly performing the nitriding reaction at high temperature using aluminum powder + melamine + polytetrafluoroethylene as the starting powder mixture, as can be seen from Fig. 2(b), the intensity of the remaining diffraction peak of aluminum metal has significantly decreased, indicating that the addition of polytetrafluoroethylene helps to promote the nitriding reaction of aluminum metal and improves the nitriding efficiency of aluminum powder. When directly performing the nitriding reaction at high temperature using aluminum powder + melamine + polytetrafluoroethylene + carbon black as the starting powder mixture and completing decarburization, as can be seen from Fig. 2(c), the produced powder has already completed the formation of the aluminum nitride phase, the diffraction peak of aluminum metal has disappeared, there is no remaining of the starting aluminum powder and carbon black, and high-purity aluminum nitride powder is formed.

[0032] Please refer to FIG. 3. FIG. 3 is a physical photograph of aluminum nitride powder produced after direct nitridation at high temperature and decarburization in air in an embodiment of the present invention. Aluminum powder, melamine, carbon black, and polytetrafluoroethylene were subjected to dry ball milling mixing based on a weight ratio of 1:1:0.5:0.03, and this uniformly mixed precursor was used as the starting powder material for direct nitridation 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 there is no phenomenon of melting and agglomeration of the aluminum powder. As can be seen from this, different from the general direct nitridation method of aluminum powder, the present invention can directly produce powdery aluminum nitride by omitting the subsequent polishing step, so the probability of impurity mixing can be reduced.

[0033] Please refer to FIG. 4. FIG. 4 is an SEM photograph of aluminum nitride powder after direct nitridation at high temperature and decarburization in air in an embodiment of the present invention. Represent the starting powder material as aluminum powder + melamine + polytetrafluoroethylene + carbon black (1:1:0.03:0.5 weight ratio) with A+N+F+C. For the starting powder material, while performing direct nitridation at high temperature and after decarburization is completed, as can be seen from the SEM in FIG. 4, the produced powder crystals are generally hexagonal columnar, which is a typical representation of the hexagonal crystal structure of aluminum nitride. At the same time, the sizes of the crystal grains vary, with large crystal grains reaching 2 - 3 μm or more and small crystal grains being about 100 - 200 nm.

[0034] Please refer to Fig. 5. Fig. 5 is an EDS component and particle size analysis table of aluminum nitride powder after direct nitridation at high temperature and decarburization in air in an embodiment of the present invention. It is represented by A+N+F+C, and the starting powder material is aluminum powder + melamine + polytetrafluoroethylene + carbon black (1:1:0.03:0.5 by weight). While performing direct nitridation on the starting powder material at high temperature and after the decarburization is completed, as can be seen from the EDS component 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, approaching the theoretical molar ratio of AlN of 1:1. Also, the presence of the O content may be due to the adsorption of oxygen in the air on the surface of the aluminum nitride powder. As a result of the particle size analysis, D 10 , D 50 , D 90 are 0.94 μm, 8.19 μm, and 38.12 μm respectively, indicating that the average particle size is about 7 - 8 μm.

[0035] Through the description of the above embodiments, the manufacturing method of the aluminum nitride powder of the present invention uses aluminum powder as the starting material, refers to the concept of carbon thermal reduction, and improves the technology of the manufacturing process of the direct nitridation method. By adding a carbon source, a nitrogen source, and a halide to the starting material of aluminum powder and mixing them, a precursor mixture directly nitrided at high temperature is manufactured. After direct nitridation at high temperature and decarburization in air, high-purity aluminum nitride powder can be formed. The present invention can effectively avoid the problem of melting and agglomeration of aluminum powder at high temperature, can omit the subsequent grinding and pulverization operations, and thus can reduce the probability of impurity mixing. Also, since the nitridation efficiency of aluminum powder can be improved, it is useful for the synthesis of high-purity aluminum nitride powder. The present invention can manufacture aluminum nitride powder with high economic value using the aluminum powder obtained by melting and recycling waste aluminum target materials as the starting material, thus strengthening the recycling application of waste materials and promoting the development of the circular economy industry.

[0036] The above embodiments only exemplarily explain the features and effects of the present invention, and do not limit the scope of the substantial technical content of the present invention. Those skilled in the art can make modifications and changes to the above embodiments without departing from the spirit and scope of the present invention. Therefore, the scope of the right protection of the present invention is as described in the claims.

Description of Reference Numerals

[0037] Steps S101 - S103

Claims

1. 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 material (Step A); Directly subjecting the mixed powder material to a nitriding reaction in a high-temperature nitrogen-containing gas atmosphere to form a completely nitrided aluminum nitride powder (Step B); And degassing the completely nitrided aluminum nitride powder in air to form a high-purity aluminum nitride powder (Step C). A method for manufacturing an aluminum nitride powder, characterized by comprising the above steps.

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

3. The nitrogen source in Step (A) is one selected from the group consisting of urea, melamine, ammonium carbonate, ammonium bicarbonate, ammonium nitrate, ammonium formate, and ammonium acetate, with a purity of 99% or more and an average particle size of 10 to 100 μm. The halide in Step (A) is one selected from the group consisting of aluminum chloride, iron chloride, aluminum bromide, sodium fluoride, calcium fluoride, and polytetrafluoroethylene, with a purity of 99% or more and an average particle size of 10 to 100 μm. The method for manufacturing an aluminum nitride powder according to Claim 1, characterized by the above.

4. The mixing method in Step (A) is either a dry mixing method or a wet ball mill method. The method for manufacturing an aluminum nitride powder according to Claim 1, characterized by the above.

5. The mixing weight ratio of the aluminum metal powder, nitrogen source, carbon source, and halide in Step (A) is 1:0.5 to 1:0.3 to 1:0.01 to 0.

1. The method for manufacturing an aluminum nitride powder according to Claim 1, characterized by the above.

6. 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. The method for manufacturing an aluminum nitride powder according to Claim 1, characterized by the above.

7. 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. The method for manufacturing an aluminum nitride powder according to Claim 1, characterized by the above.

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

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