A method for preparing aluminum nitride powder at low cost by self-propagating synthesis

Abstract

The application relates to the field of ceramic materials and provides a method for preparing aluminum nitride powder by a self-propagating synthesis method at low cost, solves the problems of high oxygen content, coarse and uneven grains, high production cost, long production cycle and easy secondary oxidation in the material transfer process of the prior art self-propagating synthesis aluminum nitride powder, and comprises the following steps: S1, batching: 70%-90% fine aluminum powder is mixed with the remaining coarse aluminum powder to obtain a first mixture, and then the first mixture is mixed with a diluent, a mixing aid and an ammonium salt in proportion to obtain a second mixture; S2, the second mixture is heated, dried and mixed in a vacuum ball milling device; S3, the mixture is distributed in a cover-free square frame with carbon felt and an ignition line is arranged; S4, nitrogen is introduced into a high-pressure reaction kettle, and the mixture is induced to carry out a self-propagating combustion reaction through an igniter; S5, post-treatment is carried out to obtain aluminum nitride powder; wherein the mixing aid is Fe3O4@TiO2-BNNS-C with a core-shell structure.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials, and in particular to a low-cost method for preparing aluminum nitride powder by self-propagating combustion synthesis. Background Technology

[0002] Aluminum nitride (AlN), as a core representative of third-generation wide-bandgap semiconductor materials and high-performance ceramic materials, has become an indispensable key material in microelectronic packaging, power device heat dissipation, and other fields due to its unique comprehensive properties. Its core advantages are reflected in three aspects: high thermal conductivity (theoretical thermal conductivity up to 319 W / (m·K)), low dielectric constant (εr≈8.5) and low dielectric loss (tanδ<0.001), and a thermal expansion coefficient matching that of silicon (AlN≈4.9×10⁻⁶ / ℃, Si≈3.5×10⁻⁶ / ℃). Based on its excellent properties, aluminum nitride powder is widely used in the preparation of key components such as electronic circuit substrates, chip thermal fillers, and power module packaging shells. Low-cost manufacturing of high-quality aluminum nitride powder is key to its widespread application.

[0003] The commonly used industrial methods for preparing aluminum nitride powder are carbothermal reduction and direct nitriding. Carbothermal reduction uses carbon powder and Al₂O₃ powder as raw materials. The Al₂O₃ powder is reduced and nitrided at high temperature, followed by decarbonization. This method has a long synthesis time, requires the removal of residual carbon powder from the product, and necessitates continuous heating to maintain high temperatures, resulting in high production costs. Direct nitriding uses Al powder and nitrogen gas as raw materials. The Al powder is directly nitrided into aluminum nitride at high temperature, but this method has a low conversion rate and incomplete reaction.

[0004] Self-propagating combustion synthesis is a technology that uses the heat released by a chemical reaction to allow the reaction to proceed spontaneously and synthesize materials. Its core is "self-powered" synthesis, which does not require continuous heating and relies on the heat released by the reaction to maintain and promote the synthesis. It has potential cost and efficiency advantages.

[0005] With the increasing demand for aluminum nitride powder in fields such as electronic packaging, the number of related patent applications is on the rise, but patents related to the self-propagating combustion synthesis method for preparing aluminum nitride all have some limitations.

[0006] Chinese Patent Publication No. CN115038665A discloses a method for manufacturing aluminum nitride powder, aluminum nitride powder, and packaging. The method involves igniting a mixed powder under a nitrogen atmosphere. The mixed powder is obtained by mixing aluminum nitride powder with an average primary particle size of less than 3 μm as a diluent at a ratio of 150 to 400 parts by mass relative to 100 parts by mass of metallic aluminum powder. The average particle size of the metallic aluminum powder is greater than 1 μm and less than 10 μm. The metallic aluminum powder used in this patent is ultrafine aluminum powder, which is expensive and has a high cost, making it unfavorable for reducing production costs in large-scale production.

[0007] Chinese Patent Publication No. CN121085227A discloses a method for preparing silicon nitride and aluminum nitride powders. The method involves mixing aluminum powder and aluminum nitride raw powder to obtain a first mixture; mixing silicon powder, silicon nitride raw powder, and ammonium salt to obtain a second mixture; placing the first and second mixtures in a material frame lined with carbon felt, using the carbon felt to separate the first and second mixtures; placing the material frame in a self-propagating reactor, evacuating it, and then introducing nitrogen gas to ignite the first mixture, inducing a combustion synthesis reaction in the second mixture; after the combustion synthesis reaction, cooling to room temperature, releasing the pressure inside the self-propagating reactor, removing the synthesized product, and grinding the synthesized product to obtain silicon nitride powder and aluminum nitride powder. However, this self-propagating synthesis process involves mostly dispersion processes for raw material mixing and drying, resulting in long production cycles and easy secondary oxidation during material transfer, leading to unstable product performance and difficulty in further reducing production costs. Summary of the Invention

[0008] Therefore, in view of the above problems, the present invention provides a low-cost method for preparing aluminum nitride powder by self-propagation synthesis, which solves the problems of high oxygen content, large and uneven grain size, high production cost, long production cycle and easy secondary oxidation during material transfer in the prior art of self-propagation synthesized aluminum nitride powder.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A method for low-cost preparation of aluminum nitride powder via self-propagating combustion synthesis includes the following steps: S1. Ingredients: By weight percentage, 70%-90% of fine aluminum powder and the remainder of coarse aluminum powder are mixed to obtain a first mixture; by weight percentage, the first mixture, diluent, mixing aid, and ammonium salt are mixed to obtain a second mixture; wherein, the first mixture accounts for 60%-70% of the total weight of the second mixture, the diluent accounts for 30%-40% of the total weight of the second mixture, the mixing aid accounts for 0.5%-1.5% of the total weight of the second mixture, and the ammonium salt accounts for 3%-6% of the total weight of the second mixture, and the sum of the weights of the first mixture, diluent, mixing aid, and ammonium salt is 100%; S2, One-step mixing and drying: The second mixture obtained in step S1 is added to a vacuum ball mill, which is equipped with a heating device. Under the conditions of vacuum degree -0.05 to -0.1 MPa, temperature 80-90℃, and rotation speed 120-160 r / min, the ball mill is dried for 1-2 hours, and mixing and drying are achieved simultaneously under vacuum conditions. S3, Fabric: The second mixture after mixing and drying in step S2 is evenly spread on an uncovered square frame. The bottom and sides of the uncovered square frame are covered with carbon felt. An ignition wire is placed at one end of the uncovered square frame and an ignition agent is added. S4. Combustion reaction: The uncovered square obtained in step S3 is placed in a high-pressure reactor. After two gas washings, high-purity nitrogen is injected. The nitrogen pressure in the high-pressure reactor is controlled at 1-2 MPa. Then, an electric current is passed through to make the igniter react, releasing heat and inducing the second mixture to undergo a self-propagating combustion synthesis reaction. During the reaction and cooling, the high-pressure reactor is circulated with cooling water. S5. Post-processing: After the reaction is completed and cooled to room temperature, the high-pressure gas in the high-pressure reactor is released. After washing the gas twice, the product is taken out to obtain loose blocky aluminum nitride, which is then finely ground to obtain aluminum nitride powder. The mixing aid is Fe3O4@TiO2-BNNS-C with a core-shell structure, the core layer being Fe3O4 nanoparticles with oxygen defects, the middle layer being a TiO2 coating layer deposited by atomic layer deposition, and the outer layer being carbon-coated boron nitride nanosheets.

[0010] Fe3O4 nanoparticles with oxygen-containing defects in the core layer effectively adsorb and fix free oxygen atoms in the reaction system during the reaction process, suppressing the formation of oxygen-containing impurities such as Al2O3 from the source. Combined with the chemical stability of the TiO2 interlayer, the oxygen content of the final aluminum nitride powder can be ≤1%, improving the purity and sintering activity of the product.

[0011] The outer carbon-coated boron nitride nanosheets (BNNS-C) possess a unique two-dimensional layered structure. In the high-temperature field of the self-propagating reaction, they provide physical guidance for the growth of AlN grains, directing them to preferentially grow along specific crystal planes and effectively suppressing abnormal grain growth and agglomeration. Simultaneously, the excellent thermal conductivity of BNNS-C improves the temperature field distribution of the reaction system, avoiding localized overheating, ultimately yielding high-quality aluminum nitride powder with an average grain size (D50) ≤1μm and uniform particle size distribution.

[0012] In step S2, the core-shell structured mixing agent utilizes the combined effect of the outer layer BNNS-C's layered structure and the magnetic properties of the core Fe3O4. This prevents the agglomeration of fine and coarse aluminum powders through steric hindrance and promotes dispersion among the components through electrostatic interaction. This results in more uniform mixing of the reactants at the microscale, ensuring a rapid, stable, and complete self-propagating combustion reaction, thereby improving the conversion rate of the raw materials.

[0013] Furthermore, the fine aluminum powder has a D50 of 55 μm and a purity of ≥99.9%.

[0014] Furthermore, the coarse aluminum powder has a D50 of 80 μm and a purity of ≥99.9%.

[0015] Furthermore, the diluent is aluminum nitride powder with an oxygen content ≤1% and an average particle size range of 1-2 μm.

[0016] Furthermore, the ammonium salt is ammonium chloride.

[0017] Furthermore, the preparation process of the Fe3O4@TiO2-BNNS-C with the core-shell structure is as follows: I. Core preparation: Oxygen-deficient Fe3O4 nanoparticles were synthesized via a hydrothermal method; II. Deposition of intermediate layer: A TiO2 layer is coated on the surface of Fe3O4 nanoparticles using atomic layer deposition technology; III. Assembling the outer layer: Carbon-coated boron nitride nanosheets are coated onto the surface of the TiO2 layer using an electrostatic self-assembly method to form Fe3O4@TiO2-BNNS-C with a core-shell structure.

[0018] Furthermore, in step III, the carbon-coated boron nitride nanosheets are prepared by mixing boron nitride nanosheets with a glucose solution and then carbonizing them at 180°C under an inert atmosphere.

[0019] In step S3, the ignition wire is a spiral tungsten wire.

[0020] In step S3, the igniter is a mixture of aluminum powder and aluminum nitride powder, with a mass ratio of 1:1.

[0021] In step S4, the ignition current is 15-30A and the energizing time is 5-10s.

[0022] In steps S4 and S5, the gas washing process involves turning on the vacuum pump to reduce the pressure inside the high-pressure reactor to -0.1 MPa, and then filling it with 0.1 MPa of nitrogen gas.

[0023] By adopting the aforementioned technical solution, the beneficial effects of the present invention are as follows: 1. By using mixed aluminum powders with different particle sizes, production costs can be significantly reduced compared to using a single fine aluminum powder.

[0024] 2. By adjusting the proportion of aluminum powder with different particle sizes, the particle size of the prepared aluminum nitride powder can be precisely adjusted.

[0025] 3. The mixing, drying and dispersion processes are integrated into a one-step process, which shortens the production cycle, greatly improves production efficiency, and the process is simple, reliable and stable, making it easy to achieve large-scale production.

[0026] 4. The mixing, drying and dispersion processes are integrated into a one-step process, which effectively reduces secondary oxidation of materials during the transfer process between multiple processes and improves the stability of product performance.

[0027] 5. The reaction pressure is low and the equipment requirements are low during the self-propagating combustion synthesis process.

[0028] 6. In the self-propagating combustion synthesis process, only a small amount of energy is used to ignite the combustion reaction in a short time. The materials rely on the heat released by the reactants themselves to maintain the synthesis process, without the need for continuous energy supply, thus saving energy.

[0029] 7. This invention improves upon the problems of excessively high temperature, excessively fast speed, and difficulty in controlling the reaction in traditional combustion synthesis reactions, making the self-propagating combustion reaction process controllable and stable. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the fabric in an embodiment of the present invention; Figure 2 This is a scanning electron microscope (SEM) image of the aluminum nitride powder synthesized in Example 1 of the present invention. Detailed Implementation Example 1

[0031] refer to Figures 1 to 2 A method for low-cost preparation of aluminum nitride powder via self-propagating combustion synthesis includes the following steps: S1. Ingredients: By weight percentage, 90% fine aluminum powder and 10% coarse aluminum powder are mixed to obtain a first mixture; by weight percentage, the first mixture, diluent, mixing aid, and ammonium salt are mixed to obtain a second mixture; wherein, the first mixture accounts for 63% of the total weight of the second mixture, the diluent accounts for 30% of the total weight of the second mixture, the mixing aid accounts for 1% of the total weight of the second mixture, and the ammonium salt accounts for 6% of the total weight of the second mixture; S2, One-step mixing and drying: The second mixture obtained in step S1 is added to a vacuum ball mill, which is equipped with a heating device. The ball mill is dried for 2 hours under vacuum conditions of -0.1MPa, 80℃, and 120r / min, so that mixing and drying are achieved simultaneously under vacuum conditions. S3. Fabric: The second mixture, after being mixed and dried in step S2, is evenly spread on an uncovered frame. Carbon felt is laid on the bottom and sides of the uncovered frame. An ignition wire is placed at one end of the uncovered frame, and ignition agent is added. A schematic diagram of the fabric is shown below. Figure 1 As shown; the ignition wire is a spiral tungsten wire; the igniter is a mixture of aluminum powder and aluminum nitride powder, with a mass ratio of 1:1. S4. Combustion Reaction: The uncovered rectangular box obtained in step S3 is placed in a high-pressure reactor. After two gas washes, high-purity nitrogen is injected. The nitrogen pressure in the high-pressure reactor is controlled at 1 MPa. Then, an electric current is applied to ignite the reaction agent, releasing heat and inducing the second mixture to undergo a self-propagating combustion synthesis reaction. During the reaction and cooling, the high-pressure reactor is circulated with cooling water. The ignition current is 20 A, and the energizing time is 5 s. Gas washes are performed by turning on the vacuum pump to reduce the pressure in the high-pressure reactor to -0.1 MPa, and then 0.1 MPa of nitrogen is introduced. S5. Post-processing: After the reaction is complete and cooled to room temperature, the high-pressure gas in the high-pressure reactor is released. After two gas washings, the product is taken out. The product is loose and white, yielding loose blocky aluminum nitride. After fine grinding, aluminum nitride powder is obtained; purity ≥99%, oxygen content <1%; scanning electron microscopy analysis image as shown below. Figure 2 As shown; the gas washing process involves turning on the vacuum pump to reduce the pressure inside the high-pressure reactor to -0.1 MPa, followed by charging with 0.1 MPa of nitrogen gas; The mixing aid is Fe3O4@TiO2-BNNS-C with a core-shell structure, the core layer being Fe3O4 nanoparticles with oxygen defects, the middle layer being a TiO2 coating layer deposited by atomic layer deposition, and the outer layer being carbon-coated boron nitride nanosheets.

[0032] The fine aluminum powder has a D50 of 55 μm and a purity of ≥99.9%; the coarse aluminum powder has a D50 of 80 μm and a purity of ≥99.9%; the diluent is aluminum nitride powder with an oxygen content of ≤1% and an average particle size range of 2 μm; the ammonium salt is ammonium chloride.

[0033] The preparation process of the Fe3O4@TiO2-BNNS-C with the core-shell structure is as follows: I. Preparation of the core: oxygen-deficient Fe3O4 nanoparticles were synthesized by hydrothermal method; ferric nitrate nonahydrate, urea and polyvinylpyrrolidone were dissolved in deionized water, and after hydrothermal reaction at 180℃ for 12 hours, the mixture was washed and dried, and then calcined at 300℃ for 2 hours under argon atmosphere to obtain oxygen-deficient Fe3O4 nanoparticles. II. Deposition of intermediate layer: A TiO2 layer is coated on the surface of Fe3O4 nanoparticles using atomic layer deposition technology; TiO2 layer is deposited on the surface of Fe3O4 nanoparticles using tetrakis(dimethylamino)titanium and water as precursors. III. Assembling the outer layer: Carbon-coated boron nitride nanosheets are coated onto the surface of the TiO2 layer using an electrostatic self-assembly method to form Fe3O4@TiO2-BNNS-C with a core-shell structure. First, the boron nitride nanosheets are mixed with a glucose solution and then carbonized at 180℃ to obtain carbon-coated boron nitride nanosheets. Then, the carbon-coated boron nitride nanosheets are coated onto the surface of the TiO2 layer using an electrostatic self-assembly method.

[0034] In step III, the carbon-coated boron nitride nanosheets are prepared by mixing boron nitride nanosheets with glucose solution and then carbonizing them at 180°C under an inert atmosphere. Example 2

[0035] A method for low-cost preparation of aluminum nitride powder via self-propagating combustion synthesis includes the following steps: S1. Ingredients: By weight percentage, 80% fine aluminum powder and 20% coarse aluminum powder are mixed to obtain a first mixture; by weight percentage, the first mixture, diluent, mixing aid, and ammonium salt are mixed to obtain a second mixture; wherein, the first mixture accounts for 62% of the total weight of the second mixture, the diluent accounts for 32.5% of the total weight of the second mixture, the mixing aid accounts for 0.5% of the total weight of the second mixture, and the ammonium salt accounts for 5% of the total weight of the second mixture, and the sum of the weights of the first mixture, diluent, mixing aid, and ammonium salt is 100%; S2, One-step mixing and drying: The second mixture obtained in step S1 is added to a vacuum ball mill, which is equipped with a heating device. The ball mill is dried for 1.5 hours under vacuum conditions of -0.08 MPa, 85°C, and 140 r / min, achieving simultaneous mixing and drying under vacuum conditions. S3, Fabric: The second mixture after mixing and drying in step S2 is evenly spread on an uncovered square frame. The bottom and sides of the uncovered square frame are covered with carbon felt. An ignition wire is placed at one end of the uncovered square frame and an ignition agent is added. The ignition wire is a spiral tungsten wire. The ignition agent is a mixed powder of aluminum powder and aluminum nitride powder, with a mass ratio of aluminum powder to aluminum nitride powder of 1:1. S4. Combustion Reaction: The uncovered rectangular box obtained in step S3 is placed in a high-pressure reactor. After two gas washes, high-purity nitrogen is injected. The nitrogen pressure in the high-pressure reactor is controlled at 1.5 MPa. Then, an electric current is applied to ignite the reaction agent, releasing heat and inducing the second mixture to undergo a self-propagating combustion synthesis reaction. During the reaction and cooling, the high-pressure reactor is circulated with cooling water. The ignition current is 20 A, and the energizing time is 5 s. Gas washing involves turning on the vacuum pump to reduce the pressure in the high-pressure reactor to -0.1 MPa, and then filling it with 0.1 MPa of nitrogen. S5. Post-processing: After the reaction is completed and cooled to room temperature, the high-pressure gas in the high-pressure reactor is released. After two gas washings, the product is taken out. The product is loose and white, and loose blocky aluminum nitride is obtained. After fine grinding, aluminum nitride powder is obtained; the purity is ≥99% and the oxygen content is <1%; the gas washing is to turn on the vacuum pump to reduce the pressure in the high-pressure reactor to -0.1MPa, and then fill it with 0.1MPa of nitrogen. The mixing aid is Fe3O4@TiO2-BNNS-C with a core-shell structure, the core layer being Fe3O4 nanoparticles with oxygen defects, the middle layer being a TiO2 coating layer deposited by atomic layer deposition, and the outer layer being carbon-coated boron nitride nanosheets.

[0036] The fine aluminum powder has a D50 of 55 μm and a purity of ≥99.9%; the coarse aluminum powder has a D50 of 80 μm and a purity of ≥99.9%; the diluent is aluminum nitride powder with an oxygen content of ≤1% and an average particle size range of 2 μm; the ammonium salt is ammonium chloride.

[0037] The preparation process of the Fe3O4@TiO2-BNNS-C with the core-shell structure is as follows: I. Core preparation: Oxygen-deficient Fe3O4 nanoparticles were synthesized via a hydrothermal method; II. Deposition of intermediate layer: A TiO2 layer is coated on the surface of Fe3O4 nanoparticles using atomic layer deposition technology; III. Assembling the outer layer: Carbon-coated boron nitride nanosheets are coated onto the surface of the TiO2 layer using an electrostatic self-assembly method to form Fe3O4@TiO2-BNNS-C with a core-shell structure.

[0038] In step III, the carbon-coated boron nitride nanosheets are prepared by mixing boron nitride nanosheets with glucose solution and then carbonizing them at 180°C under an inert atmosphere. Example 3

[0039] A method for low-cost preparation of aluminum nitride powder via self-propagating combustion synthesis includes the following steps: S1. Ingredients: By weight percentage, 70% fine aluminum powder and 30% coarse aluminum powder are mixed to obtain a first mixture; by weight percentage, the first mixture, diluent, mixing aid, and ammonium salt are mixed to obtain a second mixture; wherein, the first mixture accounts for 64.5% of the total weight of the second mixture, the diluent accounts for 30% of the total weight of the second mixture, the mixing aid accounts for 1.5% of the total weight of the second mixture, and the ammonium salt accounts for 4% of the total weight of the second mixture, and the sum of the weights of the first mixture, diluent, mixing aid, and ammonium salt is 100%; S2, One-step mixing and drying: The second mixture obtained in step S1 is added to a vacuum ball milling device equipped with a heating device. The ball milling device is used to dry the mixture for 1 hour under vacuum conditions of -0.05MPa, 90℃, and 140r / min. Mixing and drying are achieved simultaneously under vacuum conditions. S3, Fabric: The second mixture after mixing and drying in step S2 is evenly spread on an uncovered square frame. The bottom and sides of the uncovered square frame are covered with carbon felt. An ignition wire is placed at one end of the uncovered square frame and an ignition agent is added. The ignition wire is a spiral tungsten wire. The ignition agent is a mixed powder of aluminum powder and aluminum nitride powder, with a mass ratio of aluminum powder to aluminum nitride powder of 1:1. S4. Combustion Reaction: The uncovered rectangular box obtained in step S3 is placed in a high-pressure reactor. After two gas washes, high-purity nitrogen is injected. The nitrogen pressure in the high-pressure reactor is controlled at 2 MPa. Then, an electric current is applied to ignite the reaction agent, releasing heat and inducing the second mixture to undergo a self-propagating combustion synthesis reaction. During the reaction and cooling, the high-pressure reactor is circulated with cooling water. The ignition current is 20 A, and the energizing time is 5 s. Gas washing involves turning on the vacuum pump to reduce the pressure in the high-pressure reactor to -0.1 MPa, and then filling it with 0.1 MPa of nitrogen. S5. Post-processing: After the reaction is completed and cooled to room temperature, the high-pressure gas in the high-pressure reactor is released. After two gas washings, the product is taken out. The product is loose and white, and loose blocky aluminum nitride is obtained. After fine grinding, aluminum nitride powder is obtained; the purity is ≥99% and the oxygen content is <1%; the gas washing is to turn on the vacuum pump to reduce the pressure in the high-pressure reactor to -0.1MPa, and then fill it with 0.1MPa of nitrogen. The mixing aid is Fe3O4@TiO2-BNNS-C with a core-shell structure, the core layer being Fe3O4 nanoparticles with oxygen defects, the middle layer being a TiO2 coating layer deposited by atomic layer deposition, and the outer layer being carbon-coated boron nitride nanosheets.

[0040] The fine aluminum powder has a D50 of 55 μm and a purity of ≥99.9%; the coarse aluminum powder has a D50 of 80 μm and a purity of ≥99.9%; the diluent is aluminum nitride powder with an oxygen content of ≤1% and an average particle size range of 2 μm; the ammonium salt is ammonium chloride.

[0041] The preparation process of the Fe3O4@TiO2-BNNS-C with the core-shell structure is as follows: I. Core preparation: Oxygen-deficient Fe3O4 nanoparticles were synthesized via a hydrothermal method; II. Deposition of intermediate layer: A TiO2 layer is coated on the surface of Fe3O4 nanoparticles using atomic layer deposition technology; III. Assembling the outer layer: Carbon-coated boron nitride nanosheets are coated onto the surface of the TiO2 layer using an electrostatic self-assembly method to form Fe3O4@TiO2-BNNS-C with a core-shell structure.

[0042] In step III, the carbon-coated boron nitride nanosheets are prepared by mixing boron nitride nanosheets with glucose solution and then carbonizing them at 180°C under an inert atmosphere.

[0043] The chemical equations for the synthesis of the micron-sized aluminum nitride powder described in Examples 1 to 3 above are as follows:

[0044] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A low-cost method for preparing aluminum nitride powder via self-propagating combustion synthesis, characterized in that, Includes the following steps: S1. Ingredients: By weight percentage, 70%-90% of fine aluminum powder and the remainder of coarse aluminum powder are mixed to obtain a first mixture; by weight percentage, the first mixture, diluent, mixing aid, and ammonium salt are mixed to obtain a second mixture; wherein, the first mixture accounts for 60%-70% of the total weight of the second mixture, the diluent accounts for 30%-40% of the total weight of the second mixture, the mixing aid accounts for 0.5%-1.5% of the total weight of the second mixture, and the ammonium salt accounts for 3%-6% of the total weight of the second mixture, and the sum of the weights of the first mixture, diluent, mixing aid, and ammonium salt is 100%; S2, One-step mixing and drying: The second mixture obtained in step S1 is added to a vacuum ball mill, which is equipped with a heating device. Under the conditions of vacuum degree -0.05MPa to -0.1MPa, temperature 80℃ to 90℃, and rotation speed 120r / min to 160r / min, the ball mill is dried for 1h to 2h, and mixing and drying are achieved simultaneously under vacuum conditions. S3, Fabric: The second mixture after mixing and drying in step S2 is evenly spread on an uncovered square frame. The bottom and sides of the uncovered square frame are covered with carbon felt. An ignition wire is placed at one end of the uncovered square frame and an ignition agent is added. S4. Combustion reaction: The uncovered frame obtained in step S3 is placed in a high-pressure reactor. After two gas washings, high-purity nitrogen is injected. The nitrogen pressure in the high-pressure reactor is controlled at 1MPa-2MPa. Then, an electric current is passed through to make the igniter react, releasing heat and inducing the second mixture to undergo a self-propagating combustion synthesis reaction. During the reaction and cooling, the high-pressure reactor is circulated with cooling water. S5. Post-processing: After the reaction is completed and cooled to room temperature, the high-pressure gas in the high-pressure reactor is released. After washing the gas twice, the product is taken out to obtain loose blocky aluminum nitride, which is then finely ground to obtain aluminum nitride powder. The mixing aid is Fe3O4@TiO2-BNNS-C with a core-shell structure, the core layer being Fe3O4 nanoparticles with oxygen defects, the middle layer being a TiO2 coating layer deposited by atomic layer deposition, and the outer layer being carbon-coated boron nitride nanosheets.

2. The method for low-cost preparation of aluminum nitride powder by self-propagating combustion synthesis according to claim 1, characterized in that, The fine aluminum powder has a D50 of 55 μm and a purity of ≥99.9%.

3. The method for low-cost preparation of aluminum nitride powder by self-propagating combustion synthesis according to claim 1, characterized in that, The coarse aluminum powder has a D50 of 80 μm and a purity of ≥99.9%.

4. The method for low-cost preparation of aluminum nitride powder by self-propagating combustion synthesis according to claim 1, characterized in that, The diluent is aluminum nitride powder with an oxygen content ≤1% and an average particle size range of 1μm-2μm.

5. The method for low-cost preparation of aluminum nitride powder by self-propagating combustion synthesis according to claim 1, characterized in that, The ammonium salt is ammonium chloride.

6. The method for low-cost preparation of aluminum nitride powder by self-propagating combustion synthesis according to claim 1, characterized in that, The preparation process of the Fe3O4@TiO2-BNNS-C with the core-shell structure is as follows: I. Core preparation: Oxygen-deficient Fe3O4 nanoparticles were synthesized via a hydrothermal method; II. Deposition of intermediate layer: A TiO2 layer is coated on the surface of Fe3O4 nanoparticles using atomic layer deposition technology; III. Assembling the outer layer: Carbon-coated boron nitride nanosheets are coated onto the surface of the TiO2 layer using an electrostatic self-assembly method to form Fe3O4@TiO2-BNNS-C with a core-shell structure.

7. The method for low-cost preparation of aluminum nitride powder by self-propagating combustion synthesis according to claim 6, characterized in that, In step III, the carbon-coated boron nitride nanosheets are prepared by mixing boron nitride nanosheets with glucose solution and then carbonizing them at 180°C under an inert atmosphere.

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