A method for preparing aluminum nitride by indirect nitrogen nitriding of primary aluminum

Abstract

This invention discloses a method for preparing aluminum nitride by indirect nitrogen nitridation of primary aluminum. The method involves chlorinating primary aluminum with AlCl3 at high temperature, converting the aluminum in the primary aluminum into gaseous AlCl3. The gaseous AlCl3 reacts with nitrogen in a heat-exchange fluidized bed containing aluminum nitride material to generate aluminum nitride and gaseous AlCl3. The gaseous AlCl3 is then recycled through multi-stage condensation, gasification, and heat exchange for further chlorination of the primary aluminum. This invention uses primary aluminum as the aluminum source, AlCl3 as the chlorinating agent, and nitrogen as the nitrogen source to prepare aluminum nitride powder through high-temperature chlorination-cooling nitridation. The gas-to-gas nitridation reaction is highly efficient and complete, the process is easy to adjust and control, and the heat generated by the nitridation reaction can be effectively removed. This results in low production costs and products that are easy to collect, have high purity, and are of good quality. Simultaneously, the system has a high material recycling rate and high energy utilization rate, enabling large-scale and efficient preparation of aluminum nitride, with significant economic and social benefits.

Description

Technical Field

[0001] This invention relates to the fields of chemical engineering and metallurgy, and specifically to a method for preparing aluminum nitride by indirect nitrogen nitriding of primary aluminum. Background Technology

[0002] Aluminum nitride (AlN) has high thermal conductivity (theoretically up to 320 W·m). -1 ·K -1 It exhibits good insulation (>10¹⁴ Ω·cm), low dielectric constant (8.0 under 1MHz testing conditions), and low dielectric loss (dielectric loss angle tanδ=10). -4 ), and its coefficient of thermal expansion matches that of silicon (3.2 × 10⁻⁶). -6 K -1 With its excellent chemical stability and non-toxicity, it has been widely used in semiconductors, vacuum electronics and other fields, and is also a key material for electronic components used in automotive electronics, aerospace and military defense.

[0003] Currently, the main methods for preparing AlN powder include direct nitriding, self-propagating high-temperature synthesis, carbothermal reduction, chemical vapor deposition, high-energy physics-assisted synthesis, and mechanochemical methods. Among these, direct nitriding typically involves reacting metallic aluminum powder directly with nitrogen at high temperatures to synthesize AlN. No special powder treatment is required, and this method is simple, has a short process, and low energy consumption. However, because the direct nitriding reaction of aluminum powder is a strongly exothermic reaction, the gas-liquid reaction process is difficult to control, and the AlN layer formed on the nitrided surface of the aluminum powder hinders the reaction. This leads to problems such as low reaction conversion rate, easy powder agglomeration, irregular particles, and wide particle size distribution in the direct nitriding method, which greatly limits its further development and application.

[0004] Therefore, addressing the problems existing in the current method of directly nitriding aluminum powder to prepare aluminum nitride, the key to realizing the large-scale application of aluminum powder to prepare aluminum nitride lies in strengthening the reaction process, improving reaction efficiency, and timely removing the heat generated by the reaction through process and technological innovation. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to provide a method for preparing aluminum nitride by indirect nitrogen nitriding of primary aluminum.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing aluminum nitride by indirect nitrogen nitriding of primary aluminum includes the following steps:

[0008] S1. High-temperature chlorination: Primary aluminum is chlorinated at high temperature using gaseous AlCl3 and argon to obtain a mixed gas of gaseous AlCl3 and argon.

[0009] S2, Cooling and Nitriding: Nitrogen gas and a mixture of gaseous AlCl and argon obtained in step S1 are introduced into the nitriding reaction system. The gaseous AlCl is nitrided by nitrogen gas, and finally a mixture of nitrogen gas, argon gas and gaseous AlCl3 and amorphous aluminum nitride are obtained. Nitrogen gas, argon gas and gaseous AlCl3 are sent to the multi-stage condensation process in step S3, and amorphous aluminum nitride is sent to the crystallization process in step S6.

[0010] During the nitriding process, a mixture of gaseous AlCl3 and argon is used to indirectly exchange heat with the nitriding reaction system to absorb the heat generated during the nitriding process, resulting in a high-temperature mixture of gaseous AlCl3 and argon. This high-temperature mixture of gaseous AlCl3 and argon is then fed into the high-temperature chlorination process in step S1.

[0011] S3, Multi-stage condensation: The mixed gas of nitrogen, argon and gaseous AlCl3 obtained in step S2 is subjected to multi-stage condensation to obtain nitrogen, solid AlCl3 and liquid argon. The liquid argon is sent to the vaporization process in step S4, the solid AlCl3 is sent to the vaporization process in step S5, and the nitrogen is sent to the cooling nitriding process in step S2.

[0012] S4. Vaporization: The liquid argon obtained in step S3 is vaporized at room temperature to obtain argon gas, which is then sent to the vaporization process in step S5.

[0013] S5. Gasification: Using argon as the carrier gas, solid AlCl3 is vaporized to obtain a mixture of gaseous AlCl3 and argon. The mixture of gaseous AlCl3 and argon is sent to the cooling nitriding process in step S2 for indirect heat exchange with the nitriding reaction system.

[0014] S6. Crystallization: The amorphous aluminum nitride obtained in step S2 is crystallized to obtain the aluminum nitride product.

[0015] Furthermore, in step S1, the main element contained in the primary aluminum is aluminum, and the other elements contained are one or more combinations of iron, silicon, and copper.

[0016] Furthermore, in step S1, the chlorination temperature is 1050-1250℃.

[0017] Further, in step S2, the temperature of the nitriding reaction is 670-900℃; the nitriding reaction system is a fluidized bed reactor, the fluidized bed reactor is provided with bed material, the bed material is aluminum nitride with a particle size of 0.5-2mm; the fluidized bed reactor is provided with an indirect heat exchange device.

[0018] Further, in step S3, the mixed gas of nitrogen, argon and gaseous AlCl3 obtained in step S2 is first condensed at -180℃ to 170℃ to obtain solid AlCl3, and then condensed at -195℃ to -187℃ to obtain liquid argon and nitrogen.

[0019] Furthermore, in step S5, the vaporization temperature is ≥190℃.

[0020] Furthermore, in step S6, the crystallization temperature is 1300-1500℃, and the crystallization time is 0.5-5h.

[0021] The beneficial effects of this invention are as follows:

[0022] 1. This invention uses primary aluminum as the aluminum source, AlCl3 as the chlorinating agent, and nitrogen as the nitrogen source to prepare aluminum nitride powder through high-temperature chlorination-cooling nitridation. Compared with the one-step direct nitridation method of aluminum liquid and nitrogen, the process is easier to adjust and control, has strong operability, and the obtained product has good quality.

[0023] 2. This invention employs a fluidized bed reactor with an aluminum nitride bed for the nitridation reaction of gaseous AlCl with nitrogen. The gas-to-gas nitridation reaction is highly efficient and complete. The fluidized bed reactor exhibits rapid interphase mass and heat transfer, effectively removing the heat generated during the reaction. Simultaneously, the aluminum nitride bed provides nucleation sites and a matrix for the nitridation reaction, promoting its occurrence. The resulting product is easy to collect and has high purity.

[0024] 3. In this invention, AlCl3 is consumed as a chlorinating agent in the chlorination reaction and regenerated in equal amounts as a byproduct in the nitriding reaction, which can be recycled within the system and effectively reduce production costs.

[0025] 4. By setting an indirect heat exchange device in the fluidized bed of nitriding reaction, the heat released by the reaction of gaseous AlCl with nitrogen can be removed in time through heat exchange cooling, which can effectively avoid a large amount of sintering of the product, and the resulting product has fine particle size and narrow distribution.

[0026] 5. This invention utilizes an indirect heat exchange device to preheat the chlorination reaction gas with the heat released from the nitriding reaction, effectively improving the overall thermal efficiency of the process system;

[0027] 6. This invention can efficiently convert aluminum resources in primary aluminum into high-value-added aluminum nitride, resulting in significant economic and social benefits. Attached Figure Description

[0028] Figure 1 The following are flowcharts of the methods in various embodiments of the present invention;

[0029] Figure 2 This is a scanning electron microscope (SEM) image of the solid aluminum nitride product obtained by the method in Example 1 of this invention.

[0030] Figure 3 This is a scanning electron microscope image of the solid aluminum nitride product obtained by the method in Example 2 of this invention;

[0031] Figure 4 This is a scanning electron microscope (SEM) image of the solid aluminum nitride product obtained by the method in Example 3 of this invention.

[0032] Figure 5 This is a scanning electron microscope image of the solid aluminum nitride product obtained by the method in Example 4 of the present invention. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings. It should be noted that this embodiment is based on the present technical solution and provides detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to this embodiment.

[0034] Example 1

[0035] This embodiment provides a method for preparing aluminum nitride by indirect nitrogen nitriding of primary aluminum, such as... Figure 1 As shown, it includes the following steps:

[0036] S1. High-Temperature Chlorination: Primary aluminum is chlorinated at 1050℃ using gaseous AlCl3 and argon, yielding a mixture of gaseous AlCl3 and argon. The primary aluminum contains aluminum as the main element, with other elements including iron, silicon, and copper. Sufficient temperature and heat are provided to the mixture of gaseous AlCl3 and argon through indirect heating via external fuel combustion. During the high-temperature chlorination process, the chlorination temperature is controlled and maintained by adjusting the amount of primary aluminum fed and the flow rate of the gaseous AlCl3 and argon mixture.

[0037] S2, Cooling Nitriding: Nitrogen gas and a mixture of gaseous AlCl and argon obtained in step S1 are introduced into the nitriding reaction system. The gaseous AlCl obtained in step S1 is nitrided using nitrogen gas to obtain a mixture of nitrogen, argon, and gaseous AlCl3, and amorphous aluminum nitride. The resulting mixture of nitrogen, argon, and gaseous AlCl3 is then fed into the multi-stage condensation process in step S3 to obtain amorphous aluminum nitride, which is then fed into the crystallization process in step S6. The nitriding temperature is 900℃. The nitriding reaction system is a fluidized bed reactor, which contains a bed material of aluminum nitride with a particle size of 0.5 mm. The fluidized bed reactor is equipped with an indirect heat exchange device.

[0038] Another mixture of gaseous AlCl3 and argon is passed into an indirect heat exchanger to cool the nitriding reaction system and absorb the heat released during the nitriding reaction, resulting in a high-temperature mixture of gaseous AlCl3 and argon. This high-temperature mixture of gaseous AlCl3 and argon is then fed into the high-temperature chlorination process in step S1.

[0039] The temperature required for the nitriding reaction is provided by the heat carried by the mixture of gaseous AlCl and argon. During the nitriding reaction, the nitriding temperature is controlled and maintained by controlling the amount of aluminum nitride fed into the bed, the amount of gaseous AlCl and argon mixed gas introduced, and the heat exchange.

[0040] S3. Multi-stage condensation: The mixture of nitrogen, argon, and gaseous AlCl3 obtained in step S2 undergoes multi-stage condensation. First, primary condensation is performed at -180℃ to obtain solid AlCl3. Then, secondary condensation is performed at -195℃ to obtain liquid argon and nitrogen. The liquid argon is fed into the vaporization process in step S4, the solid AlCl3 is fed into the vaporization process in step S5, and the nitrogen is fed into the cooling and nitriding process in step S2.

[0041] S4. Vaporization: The liquid argon obtained in step S3 is vaporized at room temperature to obtain argon gas, which is then fed into the vaporization process in step S5.

[0042] S5. Vaporization: Using argon as the carrier gas, solid AlCl3 is vaporized at a vaporization temperature of 190°C to obtain a mixture of gaseous AlCl3 and argon. The mixture of gaseous AlCl3 and argon is sent to the cooling nitriding process in step S2 to cool the nitriding reaction system.

[0043] S6. Crystallization: The amorphous aluminum nitride obtained in step S2 is crystallized at 1300℃ for 5 hours to obtain the aluminum nitride product. The morphology of the aluminum nitride product is as follows: Figure 2 As shown. From Figure 2 As can be seen, the aluminum nitride solid product prepared in this embodiment has a fine particle size and narrow distribution, with an average particle size of about 1.15 μm and a purity of over 99.5%.

[0044] Example 2

[0045] The method flow in this embodiment is basically the same as that in Embodiment 1, except that: in step S1, the chlorination reaction temperature is 1250℃; in step S2, the nitriding reaction temperature is 670℃, and the particle size of the aluminum nitride bed material is 2mm; in step S3, the primary condensation temperature is 170℃, and the secondary condensation temperature is -187℃; in step S5, the vaporization temperature is 260℃; and in step S6, the crystallization temperature is 1400℃, and the crystallization time is 2.5h. Figure 3As can be seen, the aluminum nitride solid product prepared in this embodiment has a fine particle size and narrow distribution, with an average particle size of about 0.85 μm and a purity of over 99.5%.

[0046] Example 3

[0047] The method flow in this embodiment is basically the same as that in Embodiment 1, except that: in step S1, the chlorination reaction temperature is 1150℃; in step S2, the nitriding reaction temperature is 800℃, and the particle size of the aluminum nitride bed material is 1mm; in step S3, the primary condensation temperature is 0℃, and the secondary condensation temperature is -190℃; in step S5, the vaporization temperature is 200℃; and in step S6, the crystallization temperature is 1350℃, and the crystallization time is 3 hours. Figure 4 As can be seen, the aluminum nitride solid product prepared in this embodiment has a fine particle size and narrow distribution, with an average particle size of about 0.97 μm and a purity of over 99.5%.

[0048] Example 4

[0049] The method flow in this embodiment is basically the same as that in Embodiment 1, except that: in step S1, the chlorination reaction temperature is 1100℃; in step S2, the nitriding reaction temperature is 750℃, and the particle size of the aluminum nitride bed material is 0.8mm; in step S3, the primary condensation temperature is 20℃, and the secondary condensation temperature is -192℃; in step S5, the vaporization temperature is 230℃; and in step S6, the crystallization temperature is 1500℃, and the crystallization time is 0.5h. Figure 5 As can be seen, the aluminum nitride solid product prepared in this embodiment has a fine particle size and narrow distribution, with an average particle size of about 1.05 μm and a purity of over 99.5%.

[0050] For those skilled in the art, various corresponding changes and modifications can be made based on the above technical solutions and concepts, and all such changes and modifications should be included within the protection scope of the claims of this invention.

Claims

1. A method for producing aluminum nitride by indirect nitrogen nitridation of primary aluminum, characterized by, The method comprises the following steps: S1, high-temperature chlorination: high-temperature chlorination of raw aluminum by using gaseous AlCl3 and argon to obtain a mixed gas of gaseous AlCl3 and argon; S2, cooling nitridation: nitrogen and the mixed gas of gaseous AlCl3 and argon obtained in step S1 are introduced into a nitridation reaction system, and the gaseous AlCl3 is nitridated by using nitrogen to finally obtain a mixed gas of nitrogen, argon and gaseous AlCl3 and amorphous aluminum nitride, the mixed gas of nitrogen, argon and gaseous AlCl3 is sent to a multi-stage condensation process in step S3, and the amorphous aluminum nitride is sent to a crystallization process in step S6; In the nitridation process, the mixed gas of gaseous AlCl3 and argon is used to indirectly exchange heat with the nitridation reaction system to absorb the heat generated in the nitridation process, and a high-temperature mixed gas of gaseous AlCl3 and argon is obtained, which is sent to the high-temperature chlorination process in step S1; S3, multi-stage condensation: the mixed gas of nitrogen, argon and gaseous AlCl3 obtained in step S2 is subjected to multi-stage condensation to obtain nitrogen, solid-phase AlCl3 and liquid argon, the liquid argon is sent to a vaporization process in step S4, the solid-phase AlCl3 is sent to a gasification process in step S5, and the nitrogen is sent to the cooling nitridation process in step S2; S4, vaporization: the liquid argon obtained in step S3 is vaporized at room temperature to obtain argon which is sent to the gasification process in step S5; S5, gasification: the solid-phase AlCl3 is gasified by using argon as a carrier gas to obtain a mixed gas of gaseous AlCl3 and argon, which is sent to the cooling nitridation process in step S2 for indirectly exchanging heat with the nitridation reaction system; S6, crystallization: the amorphous aluminum nitride obtained in step S2 is crystallized to obtain an aluminum nitride product.

2. The method of claim 1, wherein, In step S1, the main element contained in the raw aluminum is aluminum, and the other elements contained in the raw aluminum are one or a combination of iron, silicon and copper.

3. The method of claim 1, wherein, In step S1, the temperature of chlorination is 1050-1250℃.

4. The method of claim 1, wherein, In step S2, the temperature of nitridation reaction is 670-900℃; the nitridation reaction system is a fluidized bed reactor, the fluidized bed reactor is provided with bed materials, and the bed materials are aluminum nitride with a particle size of 0.5-2mm; The fluidized bed reactor is provided with an indirect heat exchange device.

5. The method of claim 1, wherein, In step S3, the mixed gas of nitrogen, argon and gaseous AlCl3 obtained in step S2 is first subjected to primary condensation at-180℃ to 170℃ to obtain solid-phase AlCl3, and then subjected to secondary condensation at-195℃ to-187℃ to obtain liquid argon and nitrogen.

6. The method of claim 1, wherein, In step S5, the gasification temperature is ≥190℃.

7. The method of claim 1, wherein, In step S6, the temperature of crystallization is 1300-1500℃, and the crystallization time is 0.5-5h.

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