Method for removing carbon in production of high-quality aluminum nitride powder

Abstract

The invention discloses a carbon removal method for producing high-quality aluminum nitride powder, which belongs to the field of aluminum nitride synthesis, and comprises the following steps: pretreatment: introducing mixed gas of nitrogen and oxygen into a reaction system at a cooling stage after the nitridation reaction of the aluminum nitride powder, and controlling the oxygen content in the mixed gas in different cooling temperature intervals, a passivation layer is formed on the surface of the aluminum nitride powder, and meanwhile, violent oxidative combustion of a residual carbon source is inhibited; and decarburization treatment: carrying out decarburization heat treatment on the pretreated aluminum nitride powder in an oxygen-containing atmosphere so as to remove a residual carbon source. According to the method, in the cooling stage at the end of nitridation, the oxygen content of the mixed gas is regulated and controlled by different temperature sections, so that the surface of the micron-sized aluminum nitride powder is uniformly passivated, hydrolysis during subsequent carbon removal can be effectively prevented, and powder peroxidation caused by heat release due to excessive combustion of carbon is inhibited, so that the operability and stability of aluminum nitride powder production are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of aluminum nitride synthesis technology, and in particular to a method for removing carbon from high-quality aluminum nitride powder. Background Technology

[0002] Aluminum nitride (AlN) ceramics, due to their excellent thermal conductivity, good electrical insulation, and thermal expansion coefficient matching that of silicon, have become key materials in high-performance electronic packaging and heat dissipation. The performance of ceramic products largely depends on the quality of the initial powder; therefore, obtaining high-quality aluminum nitride powder is a prerequisite for preparing high-performance AlN ceramics. Among numerous preparation methods, the carbothermic reduction method has become the mainstream technology for industrial production of aluminum nitride powder due to its advantages such as low cost, stable process, ease of large-scale production, and high purity, controllable particle size distribution, and good sintering activity. This method uses alumina (AlN) as the starting material. Using carbon source as raw material, AlN is generated through carbothermic reduction nitridation reaction under high temperature nitrogen atmosphere.

[0003] In the actual production of carbothermal reduction, an excess of carbon source is usually added to the feedstock to ensure complete nitridation of alumina. After the reaction, the excess carbon remaining in the product must be removed, as it severely hinders the subsequent densification sintering of the ceramic. Therefore, "carbon removal" is an indispensable and critical post-processing step in the carbothermal reduction process. Currently, industrially, residual carbon is mainly removed by controlled oxidative combustion in an oxygen-containing atmosphere (such as air).

[0004] To overcome the shortcomings of traditional static decarbonization methods, existing technologies have proposed several improvements. For example, Chinese invention patent CN113956051A discloses a decarbonization method for preparing aluminum nitride powder using carbothermal reduction. This method separates excess carbon powder through cyclone separation, aiming to avoid localized over-oxidation of the aluminum nitride powder caused by concentrated combustion heat in carbon-rich areas. Additionally, Chinese invention patent CN116534810A discloses a continuous and efficient decarbonization method and equipment for aluminum nitride powder. This method uses a rotating horizontal chamber to heat and oxidize the powder during movement, thereby achieving continuous production and aiming to improve processing efficiency and large-scale production capacity.

[0005] Although the above-mentioned technical solutions each have their own focus, significant limitations and challenges remain in achieving stable industrial production of high-quality aluminum nitride powder:

[0006] (1) The effectiveness of the commonly used static decarburization process is greatly affected by the thickness of the powder accumulation layer. When the layer is too thick, the heat and oxygen transfer is uneven, making it extremely sensitive to the process temperature: if the temperature is too low, the decarburization is incomplete and the residual carbon content in the powder is high; if the temperature is slightly high, the violent oxidation reaction of excess carbon will release a large amount of heat, which can easily cause a sudden rise in local temperature, resulting in severe oxidation of the aluminum nitride powder itself, leading to an increase in the oxygen impurity content. Oxygen impurities mainly refer to oxygen-containing compounds that are formed, adsorbed or combined on the surface or inside of the aluminum nitride powder during carbothermal reduction and subsequent decarburization processes; and oxygen impurities are the key factor that significantly degrades the thermal conductivity of AlN ceramics.

[0007] (2) For continuous dynamic decarbonization processes that pursue efficiency, although the throughput is increased, the inherent physicochemical sensitivity of aluminum nitride powder is often not fully taken into account. Micron-sized AlN powder that has just completed the nitridation reaction is chemically active and is very easy to hydrolyze with water vapor in the environment, resulting in an increase in oxygen content. If the exposure time of the powder during the feeding, conveying and waiting stages in the continuous process is not properly controlled, significant hydrolytic pollution will be introduced.

[0008] (3) Physical carbon removal methods such as cyclone separation, although theoretically avoiding the risk of combustion oxidation, in actual operation, because the powder needs to undergo a long processing and exposure time, it is also difficult to completely avoid the oxidation and hydrolysis problems caused by contact with air, which may eventually lead to the powder oxygen content exceeding the standard.

[0009] In summary, existing carbon removal technologies struggle to simultaneously address the three core challenges of "thorough carbon removal," "prevention of process oxidation," and "avoidance of hydrolysis risks" within a framework of efficient, stable, and large-scale industrial production. Therefore, developing a novel carbon removal method and process that comprehensively solves these problems is of urgent technical necessity and significant practical importance for obtaining high-quality aluminum nitride powder with low oxygen and carbon content, and thereby promoting the industrial application of high-end aluminum nitride ceramics. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide a method for decarbonizing high-quality aluminum nitride powder. The method involves pretreating the aluminum nitride powder that has just completed the nitriding reaction to form a dense and uniform aluminum oxide film with a thickness of 2-5 nm on its surface. The aluminum oxide film can effectively isolate air and prevent powder hydrolysis, and can also serve as a protective layer in the subsequent decarbonization process to avoid powder over-oxidation caused by the exothermic oxidation of residual carbon.

[0011] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0012] A method for decarbonizing high-quality aluminum nitride powder includes the following steps:

[0013] Step 1, Pretreatment: During the cooling stage after the aluminum nitride powder completes the nitriding reaction, a mixture of nitrogen and oxygen is introduced into the reaction system, and the oxygen content in the mixture is controlled in different cooling temperature ranges to form a passivation layer on the surface of the aluminum nitride powder, while inhibiting the violent oxidation and combustion of residual carbon sources.

[0014] Step 2, Decarburization treatment: The pretreated aluminum nitride powder is subjected to decarburization heat treatment in an oxygen-containing atmosphere to remove residual carbon sources.

[0015] A further improvement of the technical solution of the present invention is that: in step 1, the cooling stage specifically refers to: after the nitriding reaction is completed, controlled cooling is carried out starting from 450°C or below.

[0016] A further improvement of the technical solution of the present invention is that the controlled cooling is divided into multiple continuous temperature ranges.

[0017] A further improvement of the technical solution of the present invention is that: the plurality of continuous temperature ranges include a first range, a second range, a third range and a fourth range; the first range is 450℃-400℃; the second range is 400℃-350℃; the third range is 350℃-300℃; and the fourth range is 300℃-200℃.

[0018] A further improvement of the technical solution of the present invention is that: in the first interval, the oxygen content in the mixed gas is controlled to be 20-25%; in the second interval, the oxygen content in the mixed gas is controlled to be 30-40%; in the third interval, the oxygen content in the mixed gas is controlled to be 50-70%; and in the fourth interval, the oxygen content in the mixed gas is controlled to be 100%.

[0019] A further improvement of the technical solution of the present invention is that the ratio of the total amount of oxygen to the weight of the aluminum nitride powder in the mixed gas introduced into each temperature range is as follows: 4%-8% in the first range; 8-15% in the second range; 15-20% in the third range; and 20-25% in the fourth range.

[0020] A further improvement of the technical solution of the present invention is that: in step 1, it further includes: when the temperature drops below 200°C, switching to the introduction of pure nitrogen gas for atmosphere replacement and protection.

[0021] A further improvement of the technical solution of the present invention is that: in step 2, the decarbonization process adopts a static decarbonization method, in which the powder is placed in a large loading furnace for one-time processing.

[0022] A further improvement of the technical solution of the present invention is that: in step 2, the decarbonization process adopts a dynamic continuous decarbonization method, in which the powder is placed in a rotary kiln for continuous processing.

[0023] A further improvement of the technical solution of the present invention is that the residual carbon source includes graphite and / or carbon black.

[0024] The technological advancements achieved by this invention due to the adoption of the above technical solutions are as follows:

[0025] 1. This invention systematically solves the contradiction between carbon removal and oxygen control in carbothermal reduction powder production through a two-step process of "pretreatment" followed by "carbon removal treatment." This method first constructs a protective layer during the cooling stage when the powder is most reactive, effectively isolating direct contact between oxygen and the powder body during subsequent high-temperature carbon removal. This fundamentally inhibits powder over-oxidation during the carbon removal process, laying the technological foundation for achieving low oxygen content.

[0026] 2. This invention sets the starting point for atmosphere control at the cooling stage below 450°C after nitriding, effectively avoiding the problem of excessively rapid oxidation rate on the surface of aluminum nitride powder at higher temperatures. It avoids the defects of excessively rapid, thick, and uneven alumina growth caused by introducing oxygen too early or at too high temperatures, ensuring controllable quality of the initial passivation layer.

[0027] 3. This invention divides controlled cooling into multiple continuous temperature ranges for refined atmosphere management, enabling the introduction of oxygen to precisely match the reactivity of the powder at different temperatures. This overcomes the drawback of a single atmosphere condition being unable to adapt to the entire cooling process, providing a precise process path for achieving a uniform and controllable passivation reaction.

[0028] 4. This invention specifically defines four cooling zones from 450℃ to 200℃ (450-400℃, 400-350℃, 350-300℃, and 300-200℃), providing a clear temperature framework for the gradient increase of oxygen content. This design allows the passivation reaction to proceed gradually and uniformly as the temperature decreases slowly, preventing stress or non-density issues in the passivation layer structure caused by abrupt temperature changes or unreasonable temperature ranges.

[0029] 5. This invention precisely controls the oxygen content in the mixed gas within each temperature range (gradually increasing from 20-25% to 100%), achieving precise regulation of passivation kinetics. Using a lower oxygen content in the lower temperature range effectively suppresses violent combustion of the carbon source and excessive oxidation of the powder; gradually increasing the oxygen content in the higher temperature range ensures the full progress of the passivation reaction. This gradient oxygenation mode is key to forming a uniform, dense alumina film.

[0030] 6. This invention further limits the total amount of oxygen introduced in each temperature range (gradually increasing from 4%-8% of the powder weight to 20%-25%), achieving precise control of the reactant quantity. This quantitative supply method ensures sufficient oxygen for the formation of a complete passivation layer, while completely avoiding uncontrollable exothermic reactions (such as violent carbon combustion) and powder over-oxidation caused by excessive oxygen, thus guaranteeing the safety and repeatability of the process.

[0031] 7. The present invention switches to pure nitrogen for protection and atmosphere replacement after the temperature drops below 200℃, which has two benefits: first, it completely terminates the oxidation reaction and locks in the passivation layer state; second, it replaces the residual oxygen in the furnace, providing an inert protective environment for the powder, preventing it from being oxidized or hydrolyzed by contact with air before exiting the furnace, thus ensuring the stability of the pretreatment effect.

[0032] 8. After the passivation pretreatment described above, the oxidation resistance of the powder is significantly enhanced, greatly reducing the sensitivity to material layer thickness and temperature uniformity when using static decarbonization methods (such as large loading furnaces). This allows for large-scale processing in a single operation, increasing single-furnace capacity while still ensuring thorough decarbonization without localized over-oxidation, simplifying operation and reducing energy consumption.

[0033] 9. Similarly, the improved hydrolysis resistance of the pretreated powder makes the risk of brief exposure during feeding and conveying controllable when using dynamic continuous decarbonization methods (such as rotary kilns). This removes obstacles to continuous and automated production, greatly improving production efficiency and process stability while ensuring low oxygen content in the powder, making it more suitable for large-scale industrial applications.

[0034] 10. This invention clarifies that the method is applicable to systems with graphite and / or carbon black as residual carbon sources, demonstrating strong specificity. This passivation-decarbonization synergistic process can effectively suppress the violent combustion tendency of these common carbon sources at high temperatures, thereby protecting the powder and extending the life of graphite components in the furnace body, exhibiting broad industrial applicability and economic efficiency. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a flowchart of a method for decarbonizing high-quality aluminum nitride powder provided by the present invention.

[0037] Figure 2Metallographic image of the amorphous oxide layer formed on the surface of aluminum nitride powder after pretreatment in this invention. Detailed Implementation

[0038] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products or devices.

[0039] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0040] like Figure 1 As shown, a method for decarbonizing high-quality aluminum nitride powder includes the following steps:

[0041] Step 1, Pretreatment: During the cooling stage after the aluminum nitride powder completes the nitriding reaction, a mixture of nitrogen and oxygen is introduced into the reaction system. The oxygen content in the mixture is controlled within different cooling temperature ranges to form a passivation layer on the surface of the aluminum nitride powder (e.g., ...). Figure 2 The amorphous oxide layer shown in the figure simultaneously suppresses the violent oxidation and combustion of residual carbon sources; when the temperature drops below 200°C, it switches to pure nitrogen gas for atmosphere replacement and protection.

[0042] The cooling phase is as follows: after the nitriding reaction is completed, controlled cooling is carried out starting from 450℃ or below; the controlled cooling is divided into multiple consecutive temperature ranges; the multiple consecutive temperature ranges include the first range, the second range, the third range and the fourth range; the first range is 450℃-400℃; the second range is 400℃-350℃; the third range is 350℃-300℃; the fourth range is 300℃-200℃.

[0043] In the first interval, the oxygen content in the mixed gas is controlled at 20-25%; in the second interval, the oxygen content in the mixed gas is controlled at 30-40%; in the third interval, the oxygen content in the mixed gas is controlled at 50-70%; and in the fourth interval, the oxygen content in the mixed gas is controlled at 100%.

[0044] The ratio of total oxygen to aluminum nitride powder weight in the mixed gas introduced into each temperature range is as follows: 4%-8% in the first range; 8-15% in the second range; 15-20% in the third range; and 20-25% in the fourth range.

[0045] Step 2, Decarburization treatment: The pretreated aluminum nitride powder is subjected to decarburization heat treatment in an oxygen-containing atmosphere to remove residual carbon sources (including graphite and / or carbon black).

[0046] When static decarbonization is used, the powder is placed in a large loading furnace for one-time processing.

[0047] When a dynamic continuous decarbonization method is used, the powder is placed in a rotary kiln for continuous processing.

[0048] Example 1

[0049] A method for decarbonizing high-quality aluminum nitride powder includes the following steps:

[0050] (1) Preparation of nitrided powder: Take 1 kg of alumina powder and 0.5 kg of carbon black and mix them evenly in a rolling ball mill jar. After drying and granulating the slurry, place it in a nitriding furnace. The nitriding process is 1600℃ / 3h, and nitrogen gas is introduced for 3m. 3 / h. After the nitriding furnace process is completed, allow it to cool naturally to 450℃. Then, introduce a mixture of oxygen and nitrogen gas.

[0051] (2) Pretreatment: When the temperature drops to 450℃, adjust the oxygen content of the mixed gas introduced into the furnace, where 450-400℃, 20%; 400-350℃, 30%; 350-300℃, 50%; 300-200℃, 100%; the total amount of oxygen introduced is 8%; 15%; 20%; 25% of the mass of aluminum nitride powder.

[0052] (3) Decarbonization treatment: The aluminum nitride powder after pretreatment is decarbonized. The ambient humidity is 53% when it is taken out of the furnace, the decarbonization temperature is set to 680℃, and the air atmosphere is used.

[0053] (4) After carbon removal, determine the oxygen content and carbon content.

[0054] Example 2

[0055] A method for decarbonizing high-quality aluminum nitride powder includes the following steps:

[0056] (1) Preparation of nitrided powder: Take 1 kg of alumina powder and 0.5 kg of carbon black and mix them evenly in a rolling ball mill jar. After drying and granulating the slurry, place it in a nitriding furnace. The nitriding process is 1600℃ / 3h, and nitrogen gas is introduced for 3m. 3 / h. After the nitriding furnace process is completed, allow it to cool naturally to 450℃. Then, introduce a mixture of oxygen and nitrogen gas.

[0057] (2) Pretreatment: When the temperature drops to 450℃, adjust the oxygen content of the mixed gas introduced into the furnace, where 450-400℃, 25%; 400-350℃, 40%; 350-300℃, 70%; 300-200℃, 100%; the total amount of oxygen introduced is 4%; 8%; 15%; 20% of the mass of aluminum nitride powder.

[0058] (3) Decarbonization treatment: The aluminum nitride powder after pretreatment is decarbonized. The ambient humidity is 28% when it is taken out of the furnace, the decarbonization temperature is set to 680℃, and the air atmosphere is used.

[0059] (4) After carbon removal, determine the oxygen content and carbon content.

[0060] Example 3

[0061] A method for decarbonizing high-quality aluminum nitride powder includes the following steps:

[0062] (1) Preparation of nitrided powder: Take 1 kg of alumina powder and 0.5 kg of carbon black and mix them evenly in a rolling ball mill jar. After drying and granulating the slurry, place it in a nitriding furnace. The nitriding process is 1600℃ / 3h, and nitrogen gas is introduced for 3m. 3 / h. After the nitriding furnace process is completed, allow it to cool naturally to 450℃. Then, introduce a mixture of oxygen and nitrogen gas.

[0063] (2) Pretreatment: When the temperature drops to 450℃, adjust the oxygen content of the mixed gas introduced into the furnace, where 450-400℃, 23%; 400-350℃, 35%; 350-300℃, 60%; 300-200℃, 100%; the total amount of oxygen introduced is 6%; 12%; 18%; 23% of the mass of aluminum nitride powder.

[0064] (3) Decarbonization treatment: The aluminum nitride powder after pretreatment is decarbonized. The ambient humidity is 28% when it is taken out of the furnace, the decarbonization temperature is set to 650℃, and the air atmosphere is used.

[0065] (4) After carbon removal, determine the oxygen content and carbon content.

[0066] Comparative Example 1

[0067] Compared with Example 1, Comparative Example 1 did not undergo pretreatment, but all other process conditions were the same.

[0068] Nitriding powder preparation: 1 kg of alumina powder and 0.5 kg of carbon black were mixed evenly in a rolling ball mill jar. After drying and granulating the slurry, it was placed in a nitriding furnace. The nitriding process was carried out at 1600℃ for 3 hours, with nitrogen gas introduced at 3 m³ / h. 3 / h. After the nitriding furnace process is completed, allow it to cool naturally to room temperature. Then, decarburize the aluminum nitride powder. The ambient humidity at the time of exiting the furnace is 53%, the decarburization temperature is set to 680℃, and the atmosphere is air.

[0069] After carbon removal, the oxygen and carbon content are measured.

[0070] Comparative Example 2

[0071] Compared with Example 2, Comparative Example 2 did not undergo pretreatment, but all other process conditions were the same.

[0072] Nitriding powder preparation: 1 kg of alumina powder and 0.5 kg of carbon black were mixed evenly in a rolling ball mill jar. After drying and granulating the slurry, it was placed in a nitriding furnace. The nitriding process was carried out at 1600℃ for 3 hours, with nitrogen gas introduced at 3 m³ / h. 3 / h. After the nitriding furnace process is completed, allow it to cool naturally to room temperature, then decarburize the aluminum nitride powder. The ambient humidity at the time of exiting the furnace is 28%, the decarburization temperature is set to 680℃, and the atmosphere is air.

[0073] After carbon removal, the oxygen and carbon content are measured.

[0074] Comparative Example 3

[0075] Compared with Example 3, Comparative Example 3 did not undergo any pretreatment, but all other process conditions were the same.

[0076] Nitriding powder preparation: 1 kg of alumina powder and 0.5 kg of carbon black were mixed evenly in a rolling ball mill jar. After drying and granulating the slurry, it was placed in a nitriding furnace. The nitriding process was carried out at 1600℃ for 3 hours, with nitrogen gas introduced at 3 m³ / h. 3 / h. After the nitriding furnace process is completed, allow it to cool naturally to room temperature, then decarburize the aluminum nitride powder. The ambient humidity at the time of exiting the furnace is 28%, the decarburization temperature is set to 650℃, and the atmosphere is air.

[0077] After carbon removal, the oxygen and carbon content are measured.

[0078] Table 1. Results of oxygen and carbon content determination for each example and comparative example.

[0079] Ambient humidity Decarbonization temperature Oxygen content Carbon content Example 1 53% 680℃ 0.56% 287ppm Example 2 28% 680℃ 0.55% 298ppm Example 3 28% 650℃ 0.54% 456ppm Comparative Example 1 53% 680℃ 0.98% 293ppm Comparative Example 2 28% 680℃ 0.81% 303ppm Comparative Example 3 28% 650℃ 0.65% 443ppm

[0080] As shown in Table 1 above, the aluminum nitride powders prepared by the present invention after pretreatment and decarbonization under the same nitriding process (Examples 1-3) have lower oxygen and carbon contents. Specifically, even under high ambient humidity (53%), the oxygen content remained low (0.56%), indicating that the aluminum nitride powder did not undergo hydrolysis during the subsequent decarbonization process. Moreover, aluminum nitride powder with low carbon content could be prepared while maintaining a low oxygen content, indicating that the dense oxide layer formed on the surface of the aluminum nitride powder after pretreatment has antioxidant capacity. Therefore, the decarbonization temperature can be appropriately increased during the decarbonization process to reduce the carbon content (it should be noted that the carbon content is slightly higher at 650℃). This fully demonstrates the effectiveness of the pretreatment process provided by the present invention, which can reduce the oxygen and carbon content of aluminum nitride powder and improve the quality of aluminum nitride powder.

[0081] In contrast, Comparative Examples 1-3 showed difficulty in simultaneously maintaining low oxygen and carbon content, and the oxygen content even increased to some extent. This result further demonstrates that the present invention can inhibit aluminum nitride hydrolysis, improve the oxidation resistance of aluminum nitride powder, and thus reduce the oxygen and carbon content of alumina powder.

[0082] In summary, this invention, through an innovative process combining a series of interconnected "gradient oxygen content passivation pretreatment" and "enhanced decarbonization," not only directly obtains intermediate powder with excellent resistance to hydrolysis and oxidation, but more importantly, significantly relaxes the stringent conditions for the subsequent core decarbonization process. Ultimately, it stably obtains high-quality aluminum nitride powder with low oxygen and low carbon content, comprehensively solving the industry problems of incomplete decarbonization, easy peroxidation, easy hydrolysis, and difficulty in achieving large-scale production while maintaining quality in existing technologies.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for decarbonizing high-quality aluminum nitride powder, characterized in that, Includes the following steps: Step 1, Pretreatment: During the cooling stage after the aluminum nitride powder completes the nitriding reaction, a mixture of nitrogen and oxygen is introduced into the reaction system, and the oxygen content in the mixture is controlled in different cooling temperature ranges to form a passivation layer on the surface of the aluminum nitride powder, while inhibiting the violent oxidation and combustion of residual carbon sources. Step 2, Decarburization treatment: The pretreated aluminum nitride powder is subjected to decarburization heat treatment in an oxygen-containing atmosphere to remove residual carbon sources.

2. The method for decarbonizing high-quality aluminum nitride powder according to claim 1, characterized in that, In step 1, the cooling stage specifically involves controlled cooling starting at 450°C or below after the nitriding reaction is completed.

3. The method for decarbonizing high-quality aluminum nitride powder according to claim 2, characterized in that, The controlled cooling is divided into multiple continuous temperature ranges.

4. The method for decarbonizing high-quality aluminum nitride powder according to claim 3, characterized in that, The multiple consecutive temperature ranges include a first range, a second range, a third range, and a fourth range; the first range is 450℃-400℃; the second range is 400℃-350℃; the third range is 350℃-300℃; and the fourth range is 300℃-200℃.

5. The method for decarbonizing high-quality aluminum nitride powder according to claim 4, characterized in that, Within the first interval, the oxygen content in the mixed gas is controlled to be 20-25%; within the second interval, the oxygen content in the mixed gas is controlled to be 30-40%; within the third interval, the oxygen content in the mixed gas is controlled to be 50-70%; and within the fourth interval, the oxygen content in the mixed gas is controlled to be 100%.

6. The method for decarbonizing high-quality aluminum nitride powder according to claim 5, characterized in that, The ratio of total oxygen to the weight of aluminum nitride powder in the mixed gas introduced into each temperature range is as follows: 4%-8% in the first range; 8-15% in the second range; 15-20% in the third range; and 20-25% in the fourth range.

7. A method for decarbonizing high-quality aluminum nitride powder according to any one of claims 1-6, characterized in that, Step 1 also includes: when the temperature drops below 200°C, switching to pure nitrogen gas for atmosphere replacement and protection.

8. The method for decarbonizing high-quality aluminum nitride powder according to claim 1, characterized in that, In step 2, the decarbonization process adopts a static decarbonization method, in which the powder is placed in a large loading furnace for one-time processing.

9. The method for decarbonizing high-quality aluminum nitride powder according to claim 1, characterized in that, In step 2, the decarbonization process adopts a dynamic continuous decarbonization method, in which the powder is placed in a rotary kiln for continuous processing.

10. The method for decarbonizing high-quality aluminum nitride powder according to claim 1, characterized in that, The residual carbon source includes graphite and / or carbon black.

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