Two-stage process for preparing AlON powder by taking Al powder and Al2O3 powder as raw materials

Abstract

The invention relates to a two-stage process for preparing AlON powder by taking Al powder and Al2O3 powder as raw materials, and belongs to the field of inorganic chemistry. According to the method, aluminum powder and aluminum oxide powder are used as raw materials, a first-stage target product aluminum nitride and aluminum oxide mixture can be generated through a low-pressure reaction under a certain condition in nitrogen, the first-stage target product is subjected to ball-milling mixing and second-stage high-temperature treatment under normal pressure after ball-milling to generate a target product AlON powder, the product is subjected to ball-milling treatment, and then drying and sieving are performed to obtain the aluminum nitride / aluminum oxide composite material. The high-purity AlON ceramic powder is obtained. Compared with other methods, the novel method for synthesizing the AlON ceramic powder has the advantages that the aluminum powder and the aluminum oxide powder are used as raw materials, the cost is low, the mixing uniformity is improved through ball milling of a first-stage target product, the purity of a reaction product is high, and the requirement for industrial production conditions is low.

Description

Technical Field

[0001] This invention belongs to the field of ceramic preparation technology, specifically relating to a two-stage process for preparing AlON powder using Al powder and Al2O3 powder as raw materials. Background Technology

[0002] AlON is a spinel-structured phase in the Al2O3-AlN system. AlON transparent ceramics have attracted widespread attention for their excellent optical properties. They have high light transmittance from near-ultraviolet (0.2μm) to mid-infrared (6.0μm), with a theoretical transmittance of up to 85.2%. In addition, AlON ceramics also have good mechanical properties, including high strength, high hardness, and chemical corrosion resistance. Their strength and hardness are as high as 380MPa and 17.7GPa, respectively. Currently, they are widely used in transparent armor, mid-infrared windows, fairings and other fields.

[0003] Currently, the main methods for preparing AlON ceramic powder include high-temperature solid-state synthesis, carbothermal reduction, and direct nitriding. Zhang Shuwei (Zhang Shuwei. Preparation and performance study of high-temperature resistant infrared-transmitting AlON raw material powder and ceramic materials [D]. Hunan: National University of Defense Technology, 2016) used alumina sol as the aluminum source, glucose as the carbon source, and urea as the catalyst to prepare AlON powder in one step via precursor conversion. After heat treatment at 1750℃ for 2 h, cubic γ-AlON with good crystallinity was prepared. However, the carbon content in the AlON powder was 2.6%, and after decarbonization at 700℃ for 5 h, the carbon content was still 2.1%. Moreover, the powder particles had irregular morphology, uneven grain size, large average particle size, and wide particle size distribution. Wu Qi et al. (Wu Qi, Wang Siqing, Zhang Changrui, et al. Study on the process and mechanism of solid-state reaction synthesis of AlON powder [C] / / Proceedings of the 11th National Conference on Engineering Ceramics. 2013:40-40) used nano-sized high-purity alumina and aluminum nitride powders as raw materials, and synthesized pure phase AlON by extending the holding time at 1800℃ through a high-temperature solid-state synthesis method, so that a small amount of residual aluminum nitride could be completely dissolved into the AlON lattice. Zhang Yiming (Zhang Yiming. Preparation, sintering and performance study of transparent aluminum oxynitride ceramic powder [D]. Beijing: Beijing University of Science and Technology, 2023) prepared AlON powder with an average particle size of 1.2-1.6μm by reacting at 1700℃ for 1h using a high-temperature solid-state reaction method. The high-temperature solid-state synthesis method uses aluminum nitride as raw material, which has high production cost, and aluminum nitride and alumina are difficult to mix evenly, which will affect the purity of the product. Xu Caiyi (Xu Caiyi. The Influence of Carbon Powder on the Synthesis and Sintering Properties of AlON Powder [D]. Heilongjiang: Harbin Engineering University, 2023) used γ-Al2O3 and VXC72 carbon powder as raw materials to synthesize AlON powder with high purity and uniform and fine particle size distribution through a two-step carbothermic reduction nitridation method, which was heated at 1550℃ for 1 h and then heated to 1750℃ for 5 h. Due to the introduction of carbon, the carbothermic reduction method requires a carbon removal process at the end of the process, which increases the synthesis steps. Moreover, the carbon is not easy to remove completely, and the residual carbon will affect the optical properties of the ceramic.

[0004] Chinese patent document CN114455952B discloses an AlON powder and its direct nitridation high-pressure synthesis method, including the following steps: ① Mixing: Aluminum powder, alumina powder, and organic solvent are mixed evenly; ② Drying: The organic solvent in the mixture obtained in step ① is removed, and the mixture is dried and sieved to obtain a mixed powder; ③ Loading: The mixed powder obtained in step ② is placed in a pressure sintering furnace and pressurized with nitrogen; ④ Calcination: After loading, the mixed powder is calcined to obtain the AlON powder. This method completes the preparation of AlON in one step and can obtain AlON with a purity greater than 99.9%. However, in order to obtain AlON with the above purity, although the specification describes that the particle size of the raw materials can be below 80 μm, according to the description of the patent embodiment, the actual particle size of alumina is 0.5 μm and the particle size of aluminum powder is 2 μm, and the final purity only reaches 99.9%. It is evident that this method suffers from high costs due to the use of high-pressure equipment, and also has extremely high requirements for the particle size of the raw materials, ultimately achieving a product purity of only 99.9%. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a two-stage process for preparing AlON powder using Al powder and Al2O3 powder as raw materials, aiming to reduce production costs and improve product purity through a two-step method.

[0006] According to one aspect of the present invention, a two-stage process for preparing AlON powder using Al powder and Al2O3 powder as raw materials is provided, comprising the following steps:

[0007] 1) Aluminum powder and alumina powder are mixed according to the chemical reaction stoichiometric ratio to obtain a mixed raw material;

[0008] 2) Under a nitrogen atmosphere, the raw material obtained in step 1) is subjected to low-temperature nitriding calcination under low pressure to obtain a target product;

[0009] 3) After ball milling the first target product obtained in step 2), two raw materials are obtained;

[0010] 4) Under a nitrogen atmosphere, the two raw materials obtained in step 3) are calcined at high temperature to obtain high-purity AlON ceramics.

[0011] As a preferred embodiment of the two-stage process for preparing AlON powder using Al powder and Al2O3 powder as raw materials according to the present invention, the method further includes the steps of ball milling and drying after high-temperature calcination.

[0012] As a preferred embodiment of the two-stage process for preparing AlON powder using Al powder and Al2O3 powder as raw materials according to the present invention, in step 1), the molar ratio of aluminum powder to alumina powder is 1:4 to 8:17.

[0013] As a preferred embodiment of the two-stage process for preparing AlON powder using Al powder and Al2O3 powder as raw materials according to the present invention, in step 2), the low pressure is 0.03~0.06MPa and the low-temperature nitriding calcination is specifically held at 700~1200℃ for 2~10h.

[0014] As a preferred embodiment of the two-stage process for preparing AlON powder using Al powder and Al2O3 powder as raw materials according to the present invention, the ball milling is specifically performed by mixing at a speed of 200~300 r / min for 2-6 hours.

[0015] As a preferred embodiment of the two-stage process for preparing AlON powder using Al powder and Al2O3 powder as raw materials according to the present invention, in step 4), the high-temperature calcination specifically refers to holding at 1650~1850℃ for 1~4h under normal pressure.

[0016] As a preferred embodiment of the two-stage process for preparing AlON powder using Al powder and Al2O3 powder as raw materials according to the present invention, the particle size of the aluminum powder and the alumina powder is 10~20μm.

[0017] As another aspect of the present invention, a high-purity AlON ceramic is provided, which is prepared by any of the methods described above, and the purity of the high-purity AlON ceramic is ≥99.95%.

[0018] Based on the technical solution proposed in this invention, low-pressure conditions suppress the reaction rate, avoiding agglomeration caused by violent exothermic reactions, thus affecting the reaction rate. Furthermore, due to the plasticity of aluminum particles, it is difficult to achieve uniform mixing of aluminum powder and alumina alone. However, after low-temperature nitriding treatment, the aluminum nitride generated from the nitriding of aluminum powder is easily broken into finer particles, thereby achieving more uniform mixing with Al2O3 and finer AlON particle size. In this invention, because the ball milling process can refine the material particle size, there is no particular limitation on the selection of raw material particle size. For example, any two particle size ranges from 10μm, 12μm, 14μm, 15μm, 16μm, 18μm, and 20μm can be selected.

[0019] Based on the technical solution of this invention, the temperature of low-temperature nitriding calcination is particularly critical for the nitriding rate of aluminum powder. If the temperature is too low, the aluminum powder nitriding is incomplete, and ball milling in the intermediate stage still makes it difficult to completely and uniformly mix it with alumina and the generated aluminum nitride. If the temperature is too high, the exothermic reaction of aluminum powder during nitriding can easily cause sintering of the material layer, affecting the nitriding efficiency. Therefore, the suitable temperature should be controlled between 700 and 1200°C. Furthermore, the ball milling process also affects the mixing effect of aluminum powder and alumina powder. If the ball milling time is too short, the mixing is incomplete; if the ball milling time is too long, impurities are easily introduced. Based on the solution of this invention, the suitable ball milling time should be controlled between 2 and 6 hours. In addition, the reaction pressure needs to be controlled during the calcination process to suppress the reaction rate and avoid violent exothermic reactions that could lead to agglomeration. Based on the solution of this invention, the suitable reaction pressure should be controlled between 0.03 and 0.06 MPa.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. This invention uses aluminum powder as a raw material, which is lower in cost compared to using aluminum nitride powder as a raw material;

[0022] 2. This invention employs a two-stage process. The first stage involves low-pressure, low-temperature treatment, which, compared to a single-stage direct high-temperature heat treatment, suppresses the reaction rate of the first stage and avoids agglomeration caused by the intense exothermic reaction of aluminum powder during nitriding.

[0023] 3. This invention employs a two-stage processing method, in which the product of the first stage is ball-milled and mixed. Compared with a one-step direct high-temperature heat treatment, the raw materials are mixed more uniformly and the reaction product has higher purity.

[0024] 4. In addition to using aluminum powder and alumina powder as raw materials, this invention does not require the addition of other raw materials, resulting in a higher purity of the reaction product;

[0025] 5. The AlON purity obtained based on the scheme of the present invention is above 99.95%. Detailed Implementation

[0026] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1

[0028] A two-stage process for preparing AlON powder using Al powder and Al2O3 powder as raw materials includes the following steps:

[0029] 1) Aluminum powder with a particle size of 10μm and alumina powder with a particle size of 10μm are mixed according to the stoichiometric ratio of the chemical reaction to obtain a uniformly mixed raw material, wherein the molar percentage of aluminum powder in the raw material is 27%;

[0030] 2) Under a nitrogen atmosphere, the raw material obtained in step 1) was subjected to low-temperature nitriding calcination at 800℃ and 0.05MPa for 2 hours, and then cooled under a nitrogen atmosphere to obtain a target product.

[0031] 3) The first target product obtained in step 2) is mixed and ball-milled at a speed of 200 r / min for 4 h to obtain the second raw material;

[0032] 4) Under a nitrogen atmosphere, the two-stage raw materials obtained in step 3) are calcined at atmospheric pressure and 1700℃ for 2 hours;

[0033] 5) After cooling the two raw materials obtained in step 4) to room temperature under a nitrogen atmosphere, they are mixed and ball-milled at a speed of 200 r / min for 4 h. After drying, high-purity AlON ceramic powder is obtained.

[0034] The purity of the AlON ceramic powder obtained in this embodiment was determined to be 99.95%.

[0035] Example 2

[0036] A low-cost method for preparing high-purity AlON ceramics includes the following steps:

[0037] 1) Aluminum powder with a particle size of 12μm and alumina powder with a particle size of 12μm are mixed according to the stoichiometric ratio of the chemical reaction to obtain a uniformly mixed raw material, wherein the molar percentage of aluminum powder in the raw material is 28%;

[0038] 2) Under a nitrogen atmosphere, the raw material obtained in step 1) was subjected to low-temperature nitriding calcination at 900℃ and 0.05MPa for 3 hours, and then cooled under a nitrogen atmosphere to obtain a target product.

[0039] 3) The first target product obtained in step 2) is mixed and ball-milled at a speed of 200 r / min for 6 h to obtain the second raw material;

[0040] 4) Under a nitrogen atmosphere, the two-stage raw materials obtained in step 3) are calcined at atmospheric pressure and 1750℃ for 2 hours;

[0041] 5) After cooling the two raw materials obtained in step 4) to room temperature under a nitrogen atmosphere, they are mixed and ball-milled at a speed of 200 r / min for 6 h. After drying, high-purity AlON ceramic powder is obtained.

[0042] The purity of the AlON ceramic powder obtained in this example was determined to be 99.96%.

[0043] Example 3

[0044] A low-cost method for preparing high-purity AlON ceramics includes the following steps:

[0045] 1) Aluminum powder with a particle size of 10μm and alumina powder with a particle size of 10μm are mixed according to the stoichiometric ratio of the chemical reaction to obtain a uniformly mixed raw material, wherein the molar percentage of aluminum powder in the raw material is 30%;

[0046] 2) Under a nitrogen atmosphere, the raw material obtained in step 1) was subjected to low-temperature nitriding calcination at 1000℃ and 0.06MPa for 2 hours, and then cooled under a nitrogen atmosphere to obtain a target product.

[0047] 3) The first target product obtained in step 2) is mixed and ball-milled at a speed of 200 r / min for 5 h to obtain the second raw material;

[0048] 4) Under a nitrogen atmosphere, the two-stage raw materials obtained in step 3) are calcined at atmospheric pressure and 1800℃ for 2 hours;

[0049] 5) After cooling the two raw materials obtained in step 4) to room temperature under a nitrogen atmosphere, they are mixed and ball-milled at a speed of 200 r / min for 6 h. After drying, high-purity AlON ceramic powder is obtained.

[0050] The purity of the AlON ceramic powder obtained in this example was determined to be 99.97%.

[0051] Comparative Example 1

[0052] A low-cost method for preparing high-purity AlON ceramics includes the following steps:

[0053] 1) Aluminum powder with a particle size of 10μm and alumina powder with a particle size of 10μm are mixed according to the stoichiometric ratio of the chemical reaction to obtain a uniformly mixed raw material, wherein the molar percentage of aluminum powder in the raw material is 30%;

[0054] 2) Under a nitrogen atmosphere, the raw material obtained in step 1) was subjected to low-temperature nitriding calcination at 1000℃ and 0.06MPa for 2 hours, and then cooled under a nitrogen atmosphere to obtain a target product.

[0055] 3) Under a nitrogen atmosphere, a section of the target product obtained in step 2) was calcined at 1800℃ under normal pressure for 2 hours;

[0056] 4) After cooling the two raw materials obtained in step 3) to room temperature under nitrogen atmosphere, they are mixed and ball-milled at a speed of 200 r / min for 6 h. After drying, high-purity AlON ceramic powder is obtained.

[0057] The purity of the AlON ceramic powder obtained in this comparative example was measured to be 98.78%. It can be seen that, compared with Example 3, the purity of the AlON ceramic powder in this comparative example was significantly reduced because the ball milling step was not performed after low-temperature nitriding calcination, resulting in uneven mixing of the two raw materials.

[0058] Comparative Example 2

[0059] A two-stage process for preparing AlON powder using Al powder and Al2O3 powder as raw materials includes the following steps:

[0060] 1) Aluminum powder with a particle size of 10μm and alumina powder with a particle size of 10μm are mixed according to the stoichiometric ratio of the chemical reaction to obtain a uniformly mixed raw material, wherein the molar percentage of aluminum powder in the raw material is 27%;

[0061] 2) Under a nitrogen atmosphere, the raw material obtained in step 1) was subjected to low-temperature nitriding roasting at 800°C and atmospheric pressure for 2 hours, and then cooled under a nitrogen atmosphere to obtain a target product.

[0062] 3) The first target product obtained in step 2) is mixed and ball-milled at a speed of 200 r / min for 4 h to obtain the second raw material;

[0063] 4) Under a nitrogen atmosphere, the two-stage raw materials obtained in step 3) are calcined at atmospheric pressure and 1700℃ for 2 hours;

[0064] 5) After cooling the two raw materials obtained in step 4) to room temperature under a nitrogen atmosphere, they are mixed and ball-milled at a speed of 200 r / min for 4 h. After drying, high-purity AlON ceramic powder is obtained.

[0065] The purity of the AlON ceramic powder obtained in this comparative example was measured to be 97.58%. It can be seen that, compared with Example 1, the purity of the ceramic powder in this comparative example was affected by the fact that the low-temperature nitriding calcination was carried out at atmospheric pressure, which led to an excessively fast reaction rate and violent exothermic reaction, resulting in agglomeration.

[0066] Comparative Example 3

[0067] A two-stage process for preparing AlON powder using Al powder and Al2O3 powder as raw materials includes the following steps:

[0068] 1) Aluminum powder with a particle size of 10μm and alumina powder with a particle size of 10μm are mixed according to the stoichiometric ratio of the chemical reaction to obtain a uniformly mixed raw material, wherein the molar percentage of aluminum powder in the raw material is 27%;

[0069] 2) Under a nitrogen atmosphere, the raw material obtained in step 1) was subjected to low-temperature nitriding calcination at 500℃ and 0.05MPa for 2 hours, and then cooled under a nitrogen atmosphere to obtain a target product.

[0070] 3) The first target product obtained in step 2) is mixed and ball-milled at a speed of 200 r / min for 4 h to obtain the second raw material;

[0071] 4) Under a nitrogen atmosphere, the two-stage raw materials obtained in step 3) are calcined at atmospheric pressure and 1700℃ for 2 hours;

[0072] 5) After cooling the two raw materials obtained in step 4) to room temperature under a nitrogen atmosphere, they are mixed and ball-milled at a speed of 200 r / min for 4 h. After drying, high-purity AlON ceramic powder is obtained.

[0073] The purity of the AlON ceramic powder obtained in this example was measured to be 96.68%. It is evident that, compared to Example 1, the low-temperature nitriding process in this comparative example resulted in a low nitriding rate in one stage of the product, affecting the purity of the final product.

[0074] It should be noted that, based on the above embodiments of the present invention, those skilled in the art can fully realize the scope of the independent claims and dependent claims of the present invention, and the implementation process and methods are the same as those in the above embodiments; and the parts of the present invention not described in detail belong to the well-known technology in the art. However, the protection scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the protection scope of the present invention.

Claims

1. A two-stage process for preparing AlON powder using Al powder and Al2O3 powder as raw materials, characterized in that, Includes the following steps: 1) Aluminum powder and alumina powder are mixed according to the chemical reaction stoichiometric ratio to obtain a mixed raw material; 2) Under a nitrogen atmosphere, the raw material obtained in step 1) is subjected to low-temperature nitriding calcination under low pressure to obtain a target product; 3) After ball milling the first target product obtained in step 2), two raw materials are obtained; 4) Under a nitrogen atmosphere, the two raw materials obtained in step 3) are calcined at high temperature to obtain high-purity AlON ceramics.

2. The two-stage process as described in claim 1, characterized in that, The method also includes the steps of ball milling and drying after high-temperature calcination.

3. The two-stage process as described in claim 1 or 2, characterized in that, In step 1), the molar ratio of aluminum powder to alumina powder is 1:4 to 8:

17.

4. The two-stage process as described in claim 1 or 2, characterized in that, In step 2), the low pressure is 0.03~0.06MPa, and the low-temperature nitriding calcination is specifically held at 700~1200℃ for 2~10h.

5. The two-stage process as described in claim 1 or 2, characterized in that, The ball milling process specifically involves mixing at a speed of 200-300 r / min for 2-6 hours.

6. The two-stage process as described in claim 1 or 2, characterized in that, In step 4), the high-temperature calcination specifically refers to holding at 1650~1850℃ for 1~4 hours.

7. The two-stage process as described in claim 1 or 2, characterized in that, The aluminum powder and the alumina powder have a particle size of 10~20μm.

8. A high-purity AlON ceramic, wherein the high-purity AlON ceramic is prepared by a two-stage process as described in any one of claims 1 to 7, and the purity of the high-purity AlON ceramic is ≥99.95%.