Method for preparing aluminum nitride by indirect nitridation of waste aluminum material

Abstract

The invention discloses a method for preparing aluminum nitride by indirect nitridation of waste aluminum materials, which comprises the following steps: S1, chlorination: chlorinating the waste aluminum materials by using gas-phase AlCl3 to obtain gas-phase AlCl; s2, nitriding: nitriding the gas-phase AlCl obtained in the step S1 by using nitrogen to obtain gas-phase AlCl3 and amorphous aluminum nitride; returning the gas phase AlCl3 to the chlorination process in the step S1; and S3, crystallization: performing high-temperature crystallization on the amorphous aluminum nitride obtained in the step S2 to obtain an aluminum nitride product. The aluminum nitride powder is prepared by taking the waste aluminum material as an aluminum source, AlCl3 as a chlorinating agent and nitrogen as a nitrogen source through a chlorination-nitridation two-step method, and compared with an aluminum liquid nitrogen one-step direct nitridation method, the process is easy to adjust and control, the operability is high, and the obtained product is good in quality.

Description

Technical Field

[0001] The invention relates to the technical field of ceramic powder preparation, and in particular to a method for preparing aluminum nitride by indirect nitridation of waste aluminum materials. 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. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention aims to provide a method for preparing aluminum nitride by indirect nitridation of waste aluminum.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A method for preparing aluminum nitride by indirect nitridation of waste aluminum material comprises the following steps:

[0007] S1, chlorination: using gas phase AlCl3 to chlorinate the waste aluminum material to obtain gas phase AlCl;

[0008] S2, nitridation: Nitriding the gas phase AlCl obtained in step S1 with nitrogen to obtain gas phase AlCl3 and amorphous aluminum nitride; the gas phase AlCl3 is returned to the chlorination process of step S1, and the amorphous aluminum nitride is sent to the crystallization process of step S3;

[0009] S3, crystallization: crystallize the amorphous aluminum nitride obtained in step S2 to obtain an aluminum nitride product.

[0010] Furthermore, in step S1, the scrap aluminum material is one or a combination of scrap aluminum and scrap aluminum alloy, the main element contained in the scrap aluminum and scrap aluminum alloy is aluminum, and the other elements contained are one or more of manganese, zinc, silicon and copper.

[0011] Furthermore, in step S1, the chlorination temperature is 1050-1250°C.

[0012] Furthermore, in step S2, the nitriding temperature is 670-900°C; the reactor used for nitriding 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.

[0013] Furthermore, in step S1, the gaseous AlCl3 is first heated by indirect heating through combustion of external fuel, and then the heated gaseous AlCl3 is used to chlorinate the waste aluminum material; during the chlorination process, the chlorination temperature is controlled and maintained by controlling the addition amount of the waste aluminum material and the introduction amount of gaseous AlCl3.

[0014] Furthermore, in step S2, before entering the chlorination process of step S1, the gaseous AlCl3 is first passed into the indirect heat exchange device for heat exchange to absorb the heat generated in the nitridation reaction. The gaseous AlCl3 after heat exchange directly enters the chlorination process of step S1 according to the specific temperature or enters the chlorination process of step S1 after indirect heating by combustion of external fuel.

[0015] Furthermore, in step S3, the crystallization temperature is 1300-1500° C., and the crystallization time is 0.5-5 h.

[0016] The beneficial effects of the present invention are:

[0017] 1. The present invention uses waste aluminum as an aluminum source, AlCl3 as a chlorinating agent, and nitrogen as a nitrogen source to prepare aluminum nitride powder through a two-step chlorination-nitridation method. 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;

[0018] 2. The present invention uses a fluidized bed 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 gas-solid fluidized bed has a fast 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;

[0019] 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 utilized in the system, effectively reducing production costs;

[0020] 4. The present invention provides an indirect heat exchange device in the nitriding reaction fluidized bed, which can timely remove the heat released by the reaction of gas phase AlCl and nitrogen through heat exchange, effectively avoiding a large amount of sintering of the product, and the obtained product has fine particle size and narrow distribution;

[0021] 5. The present invention can efficiently convert aluminum resources in waste aluminum into high-value-added aluminum nitride, with significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Flowchart of methods according to various embodiments of the present invention. DETAILED DESCRIPTION

[0023] 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.

[0024] Example 1

[0025] This embodiment provides a method for indirectly nitriding waste aluminum to prepare aluminum nitride, such as Figure 1 As shown, the following steps are included:

[0026] S1, chlorination: chlorination of waste aluminum material using gaseous AlCl3, the waste aluminum material is waste aluminum, the main element contained in the waste aluminum is aluminum, and contains various elements such as manganese, zinc, silicon, copper, etc. The temperature of the chlorination reaction is 1250°C to obtain gaseous AlCl. In this embodiment, the gaseous AlCl3 is first heated by indirect heating through combustion of external fuel, and then the heated gaseous AlCl3 is used to chlorinate the waste aluminum material to provide the required temperature conditions for chlorination. During the chlorination process, the chlorination temperature is controlled and maintained by controlling the amount of waste aluminum material added and the amount of gaseous AlCl3 introduced.

[0027] S2, nitridation: Nitriding the gas phase AlCl obtained in step S1 with nitrogen, the temperature of the nitridation reaction is 900°C, and obtaining gas phase AlCl3 and amorphous aluminum nitride. The amorphous aluminum nitride is sent to the crystallization process of step S3. The reactor for the nitridation reaction 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 mm, and the fluidized bed reactor is provided with an indirect heat exchange device.

[0028] Before entering the chlorination process of step S1, the gaseous AlCl3 can be first introduced into an indirect heat exchange device for heat exchange to absorb the heat generated in the nitridation reaction to obtain the gaseous AlCl3 after heat exchange. The gaseous AlCl3 after heat exchange can directly enter the chlorination process of step S1 according to the specific temperature or enter the chlorination process of step S1 after further indirect heating by combustion of external fuel, thereby making full use of the heat generated by the nitridation reaction, and can timely remove the heat released by the reaction of gaseous AlCl and nitrogen through heat exchange, which can effectively avoid large-scale sintering of the product.

[0029] S3, crystallization: the amorphous aluminum nitride obtained in step S2 is crystallized at 1500°C for 0.5h to obtain an aluminum nitride product with a purity higher than 99.8% and an average particle size of 1.05 μm.

[0030] Example 2

[0031] 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 1200°C; in step S1, the scrap aluminum material is a scrap aluminum alloy, the main element contained in the scrap aluminum alloy is aluminum, and it also contains various elements such as manganese, zinc, silicon, and copper; in step S2, the temperature of the nitridation reaction is 800°C, and the particle size of the aluminum nitride bed material is 2 mm; in step S3, the crystallization temperature is 1400°C, the crystallization time is 3 hours, and the purity of the obtained aluminum nitride product is higher than 99.8%, and the average particle size is 0.93 μm.

[0032] Example 3

[0033] 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 S1, the scrap aluminum material is a mixture of scrap aluminum and scrap aluminum alloy, and the main element contained in the mixture of scrap aluminum and scrap aluminum alloy is aluminum, and contains multiple elements such as manganese, zinc, silicon, and copper; in step S2, the temperature of the nitridation reaction is 700°C, and the particle size of the aluminum nitride bed material is 1 mm; in step S3, the crystallization temperature is 1350°C, and the crystallization time is 4.5 h. The purity of the obtained aluminum nitride product is higher than 99.8%, and the average particle size is 0.82 μm.

[0034] Example 4

[0035] 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 1050°C; in step S1, the scrap aluminum material is a mixture of scrap aluminum and scrap aluminum alloy, and the main element contained in the mixture of scrap aluminum and scrap aluminum alloy is aluminum, and contains multiple elements such as manganese, zinc, silicon, and copper; in step S2, the temperature of the nitridation reaction is 670°C, and the particle size of the aluminum nitride bed material is 0.8mm; in step S3, the crystallization temperature is 1300°C, the crystallization time is 5h, and the purity of the obtained aluminum nitride product is higher than 99.8%, and the average particle size is 0.75μm.

[0036] 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 nitridation of waste aluminum, characterized in that: The following steps are involved: S1, chlorination: using gas phase AlCl3 to chlorinate the waste aluminum material to obtain gas phase AlCl; S2, nitridation: Nitriding the gas phase AlCl obtained in step S1 with nitrogen to obtain gas phase AlCl3 and amorphous aluminum nitride; the gas phase AlCl3 is returned to the chlorination process of step S1, and the amorphous aluminum nitride is sent to the crystallization process of step S3; S3, 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 scrap aluminum material is one or a combination of scrap aluminum and scrap aluminum alloy, the main element contained in the scrap aluminum and scrap aluminum alloy is aluminum, and the other elements contained are one or more of manganese, zinc, 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 nitriding temperature is 670-900°C; the reactor used for nitriding 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.

5. The method according to claim 1, characterized in that In step S1, the gaseous AlCl3 is first heated by indirect heating through combustion of external fuel, and then the heated gaseous AlCl3 is used to chlorinate the waste aluminum material; during the chlorination process, the chlorination temperature is controlled and maintained by controlling the addition amount of the waste aluminum material and the introduction amount of gaseous AlCl3.

6. The method according to claim 4, characterized in that In step S2, before entering the chlorination process of step S1, the gaseous AlCl3 is first passed into the indirect heat exchange device for heat exchange to absorb the heat generated in the nitridation reaction. The gaseous AlCl3 after heat exchange directly enters the chlorination process of step S1 according to the specific temperature or enters the chlorination process of step S1 after indirect heating by burning external fuel.

7. The method according to claim 1, characterized in that In step S3, the crystallization temperature is 1300-1500° C., and the crystallization time is 0.5-5 h.

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