A method for synthesizing aluminum nitride powder by combustion
By introducing a stirring and cooling structure into the combustion synthesis equipment, combined with slightly positive pressure nitrogen and self-propagating combustion reaction, the deficiencies of diluents and solid nitriding agents in the existing technology are solved, and the efficient production of high-purity and easily broken aluminum nitride powder is achieved.
Patent Information
- Application Number
- CN202310813911.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-07-05
- Publication Date
- 2025-09-30
- Estimated Expiration
- 2043-07-05
AI Technical Summary
The existing combustion synthesis process requires the addition of diluents and solid nitriding agents, resulting in problems such as low output, high gas consumption, introduction of impurities, and equipment corrosion. It is difficult to control the reaction temperature and rate, resulting in sintering and incomplete synthesis products.
The combustion synthesis equipment with stirring and cooling structure is used. Through high-speed stirring and slightly positive pressure nitrogen replacing air, combined with spiral tungsten wire to induce self-propagating combustion reaction, the reaction temperature and rate are controlled, and the use of diluent and solid nitriding agent is avoided.
The method realizes efficient production of high-purity aluminum nitride powder, avoids the introduction of impurities by diluents, reduces production costs, improves output and reaction control capabilities, and the prepared aluminum nitride powder is easy to break and has high purity.
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Figure CN116553493B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of nitride ceramics, in particular to a method for synthesizing aluminum nitride powder by combustion. Background Art
[0002] Existing combustion synthesis processes generally use combustion synthesis kettles, fluidized beds or vertical combustion synthesis reactors. However, the material distribution method for combustion synthesis using a combustion synthesis kettle adopts flat distribution, which will lead to dense accumulation of synthetic raw materials. It is difficult to control the reaction temperature during combustion synthesis, resulting in severe sintering of the synthetic product, which is in a hardened state and difficult to break into fine particles. Therefore, it is necessary to add additional inert diluents to the synthetic raw materials to absorb the heat of combustion synthesis and isolate the reaction raw materials, so as to control the combustion synthesis temperature and rate. Taking the combustion synthesis of nitrides as an example, the dense accumulation of synthetic raw materials will also lead to the raw materials not being able to fully contact nitrogen, resulting in incomplete reaction and difficulty in obtaining high-purity nitrides. Therefore, it is necessary to add additional easily decomposable solid nitriding agents, such as ammonium chloride, ammonium fluoride, sodium azide, etc., to the synthetic raw materials. The decomposition of the solid nitriding agent generates gas to generate small holes in the accumulated synthetic raw materials, so that nitrogen can penetrate, so that the reaction raw materials can fully contact nitrogen and the reaction is complete. The disadvantages are:
[0003] 1) A diluent needs to be added, and the proportion is large, and the yield of one synthesis is small;
[0004] 2) Solid nitriding agent needs to be added, which will introduce impurities, some of which, such as chlorine, will corrode the equipment.
[0005] Combustion synthesis using a fluidized bed requires continuous introduction of a large amount of gas to suspend solid particles in the air to form a dilute phase, which then flows into the combustion synthesis zone for synthesis reaction. Taking nitrides as an example, the fluidized bed combustion synthesis process can disperse the reaction raw materials to a certain extent, allowing the reaction raw materials to fully contact nitrogen and complete the reaction. However, although the synthetic raw materials are diluted into a dilute phase by the airflow, the raw material particles can still contact each other, causing sintering during combustion synthesis. Moreover, when the particles are suspended in the air, there is no other energy absorption means around them except the airflow, making it difficult to control the heat generated by combustion synthesis, which can easily lead to severe sintering of the product. Its disadvantages are:
[0006] 1) A large amount of gas needs to be continuously introduced, resulting in high gas consumption;
[0007] 2) If no diluent is added, there is no means to control the heat during the combustion synthesis process, making it difficult to control the combustion synthesis rate, resulting in product hardening;
[0008] 3) If diluent is added, the combustion synthesis output will be smaller, and the amount of diluent used in continuous synthesis will be large.
[0009] The disadvantages of using a vertical combustion synthesis reactor for combustion synthesis are: additional diluent needs to be added, the combustion synthesis output is small, and the amount of diluent used is large during continuous synthesis. Summary of the Invention
[0010] The technical problem to be solved by the present invention is to provide a method for combustion synthesis of aluminum nitride powder with reasonable design, no need for additional diluent and high production efficiency, in view of the shortcomings of the existing technology.
[0011] In order to achieve the above object, the present invention adopts the following technical solutions:
[0012] A method for combustion synthesis of aluminum nitride powder is characterized in that the method comprises the following steps: placing Al powder or Al powder and AlN powder as reaction raw materials in a combustion synthesis device with a stirring structure and a cooling structure; introducing cooling water into the cooling structure to control the temperature in the combustion synthesis device at 2°C-20°C; starting the stirring structure and maintaining high-speed stirring to fully break up the reaction raw materials so that they are evenly dispersed in the combustion synthesis device; then introducing flowing nitrogen and maintaining a slightly positive pressure for more than 5 minutes; and after the air in the combustion synthesis device is fully replaced by nitrogen, electrifying a spiral tungsten filament to induce a self-propagating combustion reaction in the reaction raw materials to obtain aluminum nitride powder with a high nitrogen content, wherein the nitrogen content of the aluminum nitride powder with a high nitrogen content is between 31.0wt.% and 34.15wt.%.
[0013] The technical problem to be solved by the present invention can also be achieved by the following technical solution: in the reaction raw materials containing AlN powder, the weight ratio of the Al powder to the AlN powder is 100:1-20.
[0014] The technical problem to be solved by the present invention can also be achieved by the following technical solution: the charging amount of the reaction raw materials in the combustion synthesis equipment is in the range of 50%-80%, preferably 65%-75%.
[0015] The technical problem to be solved by the present invention can also be achieved by the following technical solution: before the combustion reaction, the temperature in the combustion synthesis equipment is maintained at 5°C-15°C.
[0016] The technical problem to be solved by the present invention can also be achieved through the following technical solution: the micro-positive pressure range in the combustion synthesis equipment is 0.1-0.5 MPa.
[0017] The technical problem to be solved by the present invention can also be achieved by the following technical solution: the average particle size of the Al powder is 1-30 μm, and the average particle size of the AlN powder is 1-10 μm.
[0018] The technical problem to be solved by the present invention can also be achieved by the following technical solution, wherein the stirring speed of the high-speed stirring is 1500 rpm-2500 rpm.
[0019] Compared with the prior art, the present invention has the following technical effects:
[0020] (1) Introducing a rotary stirring process into the combustion synthesis process, by fully breaking up and dispersing the reaction materials, replacing the role of the solid nitriding agent, allowing the aluminum powder to fully contact the nitrogen without introducing impurities, replacing the isolation role of the diluent, and reducing the bulk density of the reaction raw materials, thereby reducing the reaction rate of the combustion synthesis, and easily obtaining aluminum nitride powder with a low degree of sintering and easy to break;
[0021] (2) During the combustion synthesis process, the cooling structure attached to the stirring structure (cooling water is introduced) is combined with the stirring structure (AlN ceramic) with high thermal conductivity to quickly remove the heat generated by the combustion reaction, replacing the energy absorption effect of the diluent, making the reaction rate of the combustion synthesis easier to control;
[0022] (3) Through the cooling structure in the combustion synthesis equipment, the powder can be quickly cooled after the reaction is complete, which solves the problem of each batch of powder being difficult to cool quickly during intermittent production and the long waiting time between batches, further reducing production costs.
[0023] The aluminum nitride powder prepared by this method can be fully crushed after 30 minutes of ball milling, without the need for high-intensity crushing means such as a jaw crusher or a roller crusher; the aluminum nitride powder prepared by this method is completely nitrided, and after XRD testing, it is found that it does not contain impurities such as elemental Al. After nitrogen content testing, the mass number of nitrogen element is above 31%. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 Schematic diagram of the dispersion state of materials in the combustion synthesis process of the present invention. DETAILED DESCRIPTION
[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.
[0026] A method for combustion synthesis of aluminum nitride powder, comprising placing Al powder or Al powder and AlN powder as reaction materials in a combustion synthesis device with a stirring structure and a cooling structure, introducing cooling water into the cooling structure to control the temperature in the combustion synthesis device at 2°C-20°C, preferably 5°C-15°C, starting the stirring structure and maintaining high-speed stirring to fully break up the reaction materials and uniformly disperse them in the combustion synthesis device, such as Figure 1As shown, flowing nitrogen is then introduced to maintain a slightly positive pressure (0.1-0.5 MPa) in the combustion synthesis equipment for more than 5 minutes. After the air in the combustion synthesis equipment is fully replaced by nitrogen, a spiral tungsten wire is electrified to induce a self-propagating combustion reaction in the reaction raw materials to obtain aluminum nitride powder.
[0027] The loading amount of the reaction raw materials in the combustion synthesis equipment is within the range of 50%-80%. If AlN powder is contained, its weight proportion accounts for 1-20%.
[0028] The average particle size of the Al powder is 1-30 μm, and the average particle size of the AlN powder is 1-10 μm. Example 1
[0029] A method for synthesizing aluminum nitride powder by combustion, comprising the following steps:
[0030] 150 kg of raw aluminum powder with a loading rate of 50% was placed in the combustion synthesis equipment, the stirring structure speed was set to 95%, cooling water was introduced to keep the temperature in the equipment at 5°C, high-purity nitrogen was introduced, and the pressure was maintained at 0.1 MPa for 5 minutes. Then, a spiral tungsten wire was energized and heated to induce a self-propagating combustion reaction in the reaction raw materials to obtain AlN powder.
[0031] The obtained AlN powder was ball-milled for 30 minutes and then subjected to XRD, SEM and nitrogen content testing. The structure showed that there was a small amount of Al impurity phase in the AlN powder, no obvious sintered blocks were found in the SEM, and the nitrogen content was 27.12wt%. Example 2
[0032] A method for synthesizing aluminum nitride powder by combustion, comprising the following steps:
[0033] 165 kg of raw aluminum powder with a loading rate of 55% was placed in a combustion synthesis device, the stirring structure speed was set to 95%, cooling water was introduced to keep the temperature in the device at 10°C, high-purity nitrogen was introduced, and the pressure was maintained at 0.2 MPa for 5 minutes. Then, a spiral tungsten wire was energized and heated to induce a self-propagating combustion reaction in the reaction raw materials to obtain AlN powder.
[0034] The obtained AlN powder was ball-milled for 30 minutes and then subjected to XRD, SEM and nitrogen content tests. The structure showed that there was no obvious impurity phase in the AlN powder, no obvious sintered blocks in SEM, and the nitrogen content was 31.56wt%. Example 3
[0035] A method for synthesizing aluminum nitride powder by combustion, comprising the following steps:
[0036] 180 kg of raw aluminum powder with a loading rate of 60% was placed in a combustion synthesis equipment, the stirring structure speed was set to 95%, cooling water was introduced to keep the temperature in the equipment at 15°C, high-purity nitrogen was introduced, and the pressure was maintained at 0.3 MPa for 5 minutes. Then, a spiral tungsten wire was energized and heated to induce a self-propagating combustion reaction in the reaction raw materials to obtain AlN powder.
[0037] The obtained AlN powder was ball-milled for 30 minutes and then subjected to XRD, SEM and nitrogen content testing. The structure showed that there was no impurity phase in the AlN powder, no obvious sintered blocks in SEM, and the nitrogen content was 32.56wt%. Example 4
[0038] A method for synthesizing aluminum nitride powder by combustion, comprising the following steps:
[0039] 195 kg of raw aluminum powder with a loading rate of 65% was placed in a combustion synthesis device, the stirring structure speed was set to 95%, cooling water was introduced to keep the temperature in the device at 10°C, high-purity nitrogen was introduced, and the pressure was maintained at 0.2 MPa for 5 minutes. Then, a spiral tungsten wire was energized and heated to induce a self-propagating combustion reaction in the reaction raw materials to obtain AlN powder.
[0040] The obtained AlN powder was ball-milled for 30 minutes and then subjected to XRD, SEM and nitrogen content tests. The structure showed that there was no impurity phase in the AlN powder, no obvious sintered blocks in the SEM, and the nitrogen content was 32.33wt%. Example 5
[0041] A method for synthesizing aluminum nitride powder by combustion, comprising the following steps:
[0042] 210 kg of raw aluminum powder with a loading rate of 70% was placed in a combustion synthesis equipment, the stirring structure speed was set to 95%, cooling water was introduced to keep the temperature in the equipment at 10°C, high-purity nitrogen was introduced, and the pressure was maintained at 0.5 MPa for 5 minutes. Then, a spiral tungsten wire was energized and heated to induce a self-propagating combustion reaction in the reaction raw materials to obtain AlN powder.
[0043] The obtained AlN powder was ball-milled for 30 minutes and then subjected to XRD, SEM and nitrogen content testing. The structure showed that there was no impurity phase in the AlN powder, no obvious sintered blocks in the SEM, and the nitrogen content was 32.27wt%. Example 6
[0044] A method for synthesizing aluminum nitride powder by combustion, comprising the following steps:
[0045] 225 kg of raw aluminum powder with a loading rate of 75% was placed in a combustion synthesis equipment, the stirring structure speed was set to 95%, cooling water was introduced to keep the temperature in the equipment at 10°C, high-purity nitrogen was introduced, and the pressure was maintained at 0.2 MPa for 5 minutes. Then, a spiral tungsten wire was energized and heated to induce a self-propagating combustion reaction in the reaction raw materials to obtain AlN powder.
[0046] The obtained AlN powder was ball-milled for 30 minutes and then subjected to XRD, SEM and nitrogen content testing. The structure showed that there was no impurity phase in the AlN powder, no obvious sintered blocks in the SEM, and the nitrogen content was 32.43wt%. Example 7
[0047] A method for synthesizing aluminum nitride powder by combustion, comprising the following steps:
[0048] 240 kg of raw aluminum powder with a loading rate of 80% was placed in the combustion synthesis equipment, the stirring structure speed was set to 95%, cooling water was introduced to keep the temperature in the equipment at 10°C, high-purity nitrogen was introduced, and the pressure was maintained at 0.2 MPa for 5 minutes. Then, a spiral tungsten wire was energized and heated to induce a self-propagating combustion reaction in the reaction raw materials to obtain AlN powder.
[0049] The obtained AlN powder was ball-milled for 30 minutes and then subjected to XRD, SEM and nitrogen content tests. The structure showed that there was no obvious impurity phase in the AlN powder, a small amount of sintered blocks were present in the SEM, and the nitrogen content was 31.18wt%. Example 8
[0050] A method for synthesizing aluminum nitride powder by combustion, comprising the following steps:
[0051] 240 kg of reaction raw materials with a charge of 80% were placed in a combustion synthesis device, where 10 wt% AlN powder was mixed into the reaction raw materials. The stirring structure speed was set to 95%, and cooling water was introduced to maintain the temperature in the device at 10°C. High-purity nitrogen was introduced and the pressure was maintained at 0.2 MPa for 5 minutes. Then, a spiral tungsten wire was energized and heated to induce a self-propagating combustion reaction in the reaction raw materials to obtain AlN powder.
[0052] The obtained AlN powder was ball-milled for 30 minutes and then subjected to XRD, SEM and nitrogen content testing. The structure showed that there was no impurity phase in the AlN powder, no obvious sintered blocks in SEM, and the nitrogen content was 32.39wt%.
[0053] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.
Claims
1. A method for synthesizing aluminum nitride powder by combustion, characterized in that: The method comprises the following steps: placing Al powder or Al powder and AlN powder as reaction raw materials in a combustion synthesis device with a stirring structure and a cooling structure, introducing cooling water into the cooling structure to control the temperature in the combustion synthesis device at 2°C-20°C, starting the stirring structure and maintaining high-speed stirring at a stirring speed of 1500 rpm-2500 rpm to fully break up the reaction raw materials so that they are evenly dispersed in the combustion synthesis device, then introducing flowing nitrogen and maintaining a slightly positive pressure for more than 5 minutes, and after the air in the combustion synthesis device is fully replaced by nitrogen, electrifying a spiral tungsten wire to induce a self-propagating combustion reaction in the reaction raw materials to obtain aluminum nitride powder with a high nitrogen content.
2. The method for combustion synthesis of aluminum nitride powder according to claim 1, characterized in that: In the reaction raw materials containing AlN powder, the weight ratio of the Al powder to the AlN powder is 100:1-20.
3. The method for combustion synthesis of aluminum nitride powder according to claim 1, characterized in that: The loading amount of the reaction raw materials in the combustion synthesis device is in the range of 50%-80%.
4. The method for combustion synthesis of aluminum nitride powder according to claim 3, characterized in that: The charging amount of the reaction raw materials in the combustion synthesis equipment is in the range of 65%-75%.
5. The method for combustion synthesis of aluminum nitride powder according to claim 1, characterized in that: Before the combustion reaction, the temperature in the combustion synthesis device is maintained at 5°C-15°C.
6. The method for combustion synthesis of aluminum nitride powder according to claim 1, characterized in that: The micro-positive pressure in the combustion synthesis equipment is in the range of 0.1-0.5 MPa.
7. The method for combustion synthesis of aluminum nitride powder according to claim 1, characterized in that: The average particle size of the Al powder is 1-30 μm, and the average particle size of the AlN powder is 1-10 μm.
8. The method for combustion synthesis of aluminum nitride powder according to claim 1, characterized in that: The nitrogen content of the high nitrogen content aluminum nitride powder is 31.0 wt.%-34.15 wt.%.