Method for preparing aluminum nitride by indirect nitrogen nitridation of primary aluminum

Abstract

The invention discloses a method for preparing aluminum nitride by indirect nitrogen nitridation of primary aluminum, which comprises the following steps of: chlorinating the primary aluminum at high temperature by adopting AlCl3, converting aluminum in the primary aluminum into gas-phase AlCl, reacting the gas-phase AlCl with nitrogen in a heat exchange fluidized bed filled with an aluminum nitride bed material to generate aluminum nitride and gas-phase AlCl3, and performing multi-stage condensation recovery, gasification and heat exchange circulation on the gas-phase AlCl3 for chlorinating the primary aluminum. According to the method, the aluminum nitride powder is prepared by taking the primary aluminum as the aluminum source, the AlCl3 as the chlorinating agent and the nitrogen as the nitrogen source through high-temperature chlorination-cooling nitridation, the gas-gas nitridation reaction is high in efficiency and sufficient in reaction, the process is easy to adjust and control, heat generated by the nitridation reaction can be effectively removed, the production cost is low, and the product is convenient to collect, high in purity and good in quality. Meanwhile, the system is high in material cyclic utilization rate and high in energy utilization rate, large-scale efficient preparation of aluminum nitride can be achieved, and good economic benefits and social benefits are achieved.

Description

Technical Field

[0001] The invention relates to the fields of chemical industry and metallurgy, and in particular to a method for preparing aluminum nitride by indirect nitrogen nitriding of raw aluminum. Background Art

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

[0003] At present, the main preparation methods of AlN powder include direct nitridation, self-propagating high-temperature synthesis, carbon thermal reduction, chemical vapor deposition, high-energy physical assisted method and mechanochemical method. Among them, the direct nitridation method usually uses metal aluminum powder to directly react with nitrogen at high temperature to synthesize AlN. The powder does not need special treatment. This method has simple reaction, short process and low energy consumption. However, since the direct nitridation reaction of aluminum powder is a strong exothermic reaction, the gas-liquid reaction process is difficult to control, and the AlN layer formed on the surface of aluminum powder nitridation will hinder the reaction. As a result, the direct nitridation method has problems such as low reaction conversion rate, easy agglomeration of powder, irregular particles, and wide particle size distribution, which greatly limits the further development and application of this method.

[0004] Therefore, in order to address the problems existing in the current method of directly nitriding aluminum powder to prepare aluminum nitride, the key to achieving large-scale application of nitrogen nitriding of aluminum powder to prepare aluminum nitride is to strengthen the reaction process, improve reaction efficiency, and promptly remove the heat generated by the reaction through process and technological innovation. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention aims to provide a method for preparing aluminum nitride by indirect nitrogen nitridation of raw aluminum.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

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

[0008] S1. High temperature chlorination: using gas phase AlCl3 and argon to chlorinate the original aluminum at high temperature to obtain a mixed gas of gas phase AlCl3 and argon;

[0009] S2, cooling nitridation: nitrogen and the mixed gas of gaseous AlCl3 and argon obtained in step S1 are introduced into the nitridation reaction system, and the gaseous AlCl3 is nitrided by nitrogen to finally obtain a mixed gas of nitrogen, argon and gaseous AlCl3 and amorphous aluminum nitride. The nitrogen, argon and gaseous AlCl3 are fed into the multi-stage condensation process of step S3, and the amorphous aluminum nitride is fed into the crystallization process of step S6;

[0010] During the nitriding process, another gaseous AlCl3 and argon mixed gas is used to perform indirect heat exchange with the nitriding reaction system to absorb the heat generated during the nitriding process to obtain a high-temperature gaseous AlCl3 and argon mixed gas, which is fed into the high-temperature chlorination process of 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 of step S4, the solid AlCl3 is sent to the gasification process of step S5, and the nitrogen is sent to the cooling nitridation process of step S2;

[0012] S4, vaporization: vaporize the liquid argon obtained in step S3 at room temperature to obtain argon gas and feed it into the vaporization process in step S5;

[0013] S5, gasification: using argon as carrier gas, the solid phase AlCl3 is gasified to obtain a mixed gas of gas phase AlCl3 and argon, and the mixed gas of gas phase AlCl3 and argon is sent to the cooling nitriding process of step S2 for indirect heat exchange with the nitriding reaction system.

[0014] S6, crystallization: crystallize the amorphous aluminum nitride obtained in step S2 to obtain an aluminum nitride product.

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

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

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

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

[0019] Furthermore, in step S5, the gasification temperature is ≥ 190°C.

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

[0021] The beneficial effects of the present invention are:

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

[0023] 2. The present invention uses a fluidized bed reactor equipped with aluminum nitride bed material to carry out the nitridation reaction of gas-phase AlCl and nitrogen. The gas-gas nitridation reaction has high efficiency and sufficient reaction. The fluidized bed reactor has fast interphase mass transfer and heat transfer rate, which can effectively remove the heat generated by the reaction. At the same time, the aluminum nitride bed material can provide nucleation sites and matrix for the nitridation reaction, promote the occurrence of the nitridation reaction, and the obtained product is easy to collect and has high purity;

[0024] 3. In the present invention, AlCl3 is consumed as a chlorinating agent in the chlorination reaction step, and is regenerated in equal amounts as a by-product in the nitridation reaction step, and can be recycled in the system, effectively reducing production costs;

[0025] 4. The present invention provides an indirect heat exchange device in the nitriding reaction fluidized bed, and can timely remove the heat released by the reaction of gas phase AlCl and nitrogen through heat exchange cooling, which can effectively avoid the large-scale sintering of the product, and the obtained product has fine particle size and narrow distribution;

[0026] 5. The present invention utilizes an indirect heat exchange device to use the heat released by the nitridation reaction to preheat the chlorination reaction gas, thereby effectively improving the thermal efficiency of the overall process system;

[0027] 6. The present invention can efficiently convert aluminum resources in raw aluminum into high-value-added aluminum nitride, with significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a method flow chart of each embodiment of the present invention;

[0029] Figure 2 This is an electron microscope scanning image of the aluminum nitride solid product obtained by the method of Example 1 of the present invention;

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

[0031] Figure 4 This is an electron microscope scanning image of the aluminum nitride solid product obtained by the method of Example 3 of the present invention;

[0032] Figure 5 This is an electron microscope scanning image of the aluminum nitride solid product obtained by the method of Example 4 of the present invention. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, 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 nitridation of primary aluminum, such as Figure 1 As shown, the following steps are included:

[0036] S1. High temperature chlorination: The raw aluminum is subjected to high temperature chlorination using gaseous AlCl3 and argon, and the chlorination temperature is 1050°C to obtain a mixed gas of gaseous AlCl3 and argon. The main element contained in the raw aluminum is aluminum, and the other elements contained are iron, silicon, copper, etc. The mixed gas of gaseous AlCl3 and argon is provided with sufficient temperature and heat by indirect heating by burning external fuel. During the high temperature chlorination process, the temperature of the high temperature chlorination is controlled and maintained by controlling the feeding amount of the raw aluminum and the introduction amount of the mixed gas of gaseous AlCl3 and argon.

[0037] S2, cooling nitridation: nitrogen and a mixed gas of gaseous AlCl3 and argon obtained in step S1 are introduced into the nitridation reaction system, and the gaseous AlCl3 obtained in step S1 is nitrided by nitrogen to obtain a mixed gas of nitrogen, argon and gaseous AlCl3 and amorphous aluminum nitride, and the obtained mixed gas of nitrogen, argon and gaseous AlCl3 is sent to the multi-stage condensation process of step S3, and the obtained amorphous aluminum nitride is sent to the crystallization process of step S6. The nitridation temperature is 900°C, and the nitridation reaction system is a fluidized bed reactor, in which a bed material is provided, and the bed material is aluminum nitride with a particle size of 0.5 mm, and an indirect heat exchange device is provided in the fluidized bed reactor.

[0038] The other gaseous AlCl3 and argon mixed gas is introduced into the indirect heat exchange device to perform heat exchange cooling on the nitridation reaction system, absorb the heat released in the nitridation reaction, and obtain a high-temperature gaseous AlCl3 and argon mixed gas. The high-temperature gaseous AlCl3 and argon mixed gas is sent to the high-temperature chlorination process of step S1.

[0039] The temperature conditions required for the nitriding reaction are provided by the heat brought by the mixed gas of gaseous AlCl and argon. During the nitriding reaction, the nitriding temperature is controlled and maintained by controlling the feeding amount of the aluminum nitride bed material, the feeding amount of the mixed gas of gaseous AlCl and argon, and the heat exchange amount.

[0040] S3, multi-stage condensation: The mixed gas of nitrogen, argon and gaseous AlCl3 obtained in step S2 is subjected to multi-stage condensation, firstly, a primary condensation is performed at -180°C to obtain solid AlCl3, and then a secondary condensation is performed at -195°C to obtain liquid argon and nitrogen. The liquid argon is fed to the vaporization process of step S4, the solid AlCl3 is fed to the vaporization process of step S5, and the nitrogen is fed to the cooling nitridation process of step S2.

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

[0042] S5, gasification: using argon as carrier gas, the solid phase AlCl3 is gasified at a gasification temperature of 190°C to obtain a mixed gas of gaseous phase AlCl3 and argon. The mixed gas of gaseous phase AlCl3 and argon is sent to the cooling nitriding process of step S2 to perform heat exchange cooling on the nitriding reaction system.

[0043] S6, crystallization: the amorphous aluminum nitride obtained in step S2 is crystallized at 1300°C for 5 hours to obtain an aluminum nitride product. The morphology of the aluminum nitride product is as follows: Figure 2 As shown. Figure 2 It can be seen that the aluminum nitride solid product obtained in this embodiment has a finer particle size and a narrower distribution, an average particle size of about 1.15 μm, and a purity higher than 99.5%.

[0044] Example 2

[0045] The method flow of this embodiment is basically the same as that of embodiment 1, except that: in step S1, the temperature of the chlorination reaction is 1250°C; in step S2, the temperature of the nitridation reaction is 670°C, and the particle size of the aluminum nitride bed material is 2 mm; in step S3, the temperature of the first condensation is 170°C, and the temperature of the second condensation is -187°C; in step S5, the temperature of the vaporization is 260°C; in step S6, the crystallization temperature is 1400°C, and the crystallization time is 2.5h. Figure 3It can be seen that the aluminum nitride solid product obtained in this embodiment has a finer particle size and a narrower distribution, with an average particle size of about 0.85 μm and a purity higher than 99.5%.

[0046] Example 3

[0047] The method flow of this embodiment is basically the same as that of embodiment 1, except that: in step S1, the temperature of the chlorination reaction is 1150°C; in step S2, the temperature of the nitridation reaction is 800°C, and the particle size of the aluminum nitride bed material is 1 mm; in step S3, the temperature of the first condensation is 0°C, and the temperature of the second condensation is -190°C; in step S5, the temperature of the vaporization is 200°C; in step S6, the crystallization temperature is 1350°C, and the crystallization time is 3h. Figure 4 It can be seen that the aluminum nitride solid product obtained in this embodiment has a finer particle size and a narrower distribution, with an average particle size of about 0.97 μm and a purity higher than 99.5%.

[0048] Example 4

[0049] The method flow of this embodiment is basically the same as that of embodiment 1, except that: in step S1, the temperature of the chlorination reaction is 1100°C; in step S2, the temperature of the nitridation reaction is 750°C, and the particle size of the aluminum nitride bed material is 0.8 mm; in step S3, the temperature of the first condensation is 20°C, and the temperature of the second condensation is -192°C; in step S5, the vaporization temperature is 230°C; in step S6, the crystallization temperature is 1500°C, and the crystallization time is 0.5h. Figure 5 It can be seen that the aluminum nitride solid product obtained in this embodiment has a finer particle size and a narrower distribution, with an average particle size of about 1.05 μm and a purity higher than 99.5%.

[0050] For those skilled in the art, various corresponding changes and modifications can be made according to the above technical solutions and concepts, and all of these changes and modifications should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing aluminum nitride by indirect nitrogen nitridation of primary aluminum, characterized in that: The following steps are involved: S1. High temperature chlorination: using gas phase AlCl3 and argon to chlorinate the original aluminum at high temperature to obtain a mixed gas of gas phase AlCl3 and argon; S2, cooling nitridation: nitrogen and the mixed gas of gaseous AlCl3 and argon obtained in step S1 are introduced into the nitridation reaction system, and the gaseous AlCl3 is nitrided by nitrogen to finally obtain a mixed gas of nitrogen, argon and gaseous AlCl3 and amorphous aluminum nitride. The nitrogen, argon and gaseous AlCl3 are fed into the multi-stage condensation process of step S3, and the amorphous aluminum nitride is fed into the crystallization process of step S6; During the nitriding process, another gaseous AlCl3 and argon mixed gas is used to perform indirect heat exchange with the nitriding reaction system to absorb the heat generated during the nitriding process to obtain a high-temperature gaseous AlCl3 and argon mixed gas, which is fed into the high-temperature chlorination process of 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 AlCl3 and liquid argon, the liquid argon is sent to the vaporization process of step S4, the solid AlCl3 is sent to the gasification process of step S5, and the nitrogen is sent to the cooling nitridation process of step S2; S4, vaporization: vaporize the liquid argon obtained in step S3 at room temperature to obtain argon gas and feed it into the vaporization process in step S5; S5, gasification: using argon as carrier gas, gasifying solid AlCl3 to obtain a mixed gas of gaseous AlCl3 and argon, and sending the mixed gas of gaseous AlCl3 and argon into the cooling nitriding process of step S2 for indirect heat exchange with the nitriding reaction system; S6, crystallization: crystallize the amorphous aluminum nitride obtained in step S2 to obtain an aluminum nitride product.

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

3. The method according to claim 1, characterized in that In step S1, the chlorination temperature is 1050-1250°C.

4. The method according to claim 1, characterized in that: In step S2, the temperature of the nitridation reaction is 670-900° C.; the nitridation reaction system is a fluidized bed reactor, and a bed material is provided in the fluidized bed reactor, and the bed material is aluminum nitride with a particle size of 0.5-2 mm; An indirect heat exchange device is provided in the fluidized bed reactor.

5. The method according to claim 1, characterized in that In step S3, the mixed gas of nitrogen, argon and gaseous AlCl3 obtained in step S2 is first condensed at -180°C to 170°C to obtain solid AlCl3, and then secondarily condensed at -195°C to -187°C to obtain liquid argon and nitrogen.

6. The method according to claim 1, characterized in that In step S5, the gasification temperature is ≥190°C.

7. The method according to claim 1, characterized in that In step S6, the crystallization temperature is 1300-1500° C., and the crystallization time is 0.5-5 h.

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