Aluminum nitride ceramic powder and preparation method thereof

Abstract

The invention belongs to the technical field of aluminum nitride ceramic materials, and particularly relates to aluminum nitride ceramic powder and a preparation method thereof. Comprising the following steps: taking aluminum oxide powder as an aluminum source, taking silicon nitride powder as a nitrogen source, and mixing the aluminum source and the nitrogen source to obtain mixed powder; the preparation method comprises the following steps: mixing silicon nitride with aluminum oxide to obtain a mixture powder, pressing the mixture powder into a precast block, carrying out a high-temperature sintering reaction in a protective atmosphere, combining Si generated by silicon nitride decomposition with O in the aluminum oxide to form SiO, and inhibiting solid solution of oxygen in aluminum nitride crystal lattices by the SiO in a gas form to obtain the aluminum nitride ceramic powder with the oxygen content lower than 0.36 wt%. According to the invention, the aluminum nitride ceramic powder is prepared by utilizing a nitride thermal reduction method, and low-cost and high-efficiency preparation of the aluminum nitride ceramic powder is realized by optimizing the raw material combination and the reaction path.

Description

Technical Field

[0001] This invention belongs to the technical field of aluminum nitride ceramic materials, specifically relating to an aluminum nitride ceramic powder and its preparation method. Background Technology

[0002] Aluminum nitride (AlN) has become a highly sought-after material in the electronics field due to its outstanding thermal conductivity and coefficient of thermal expansion matching that of silicon. Aluminum nitride is a hexagonal wurtzite-type covalent compound with a series of excellent properties, including excellent thermal conductivity, reliable electrical insulation, low dielectric constant and dielectric loss, non-toxicity, and a coefficient of thermal expansion matching that of silicon. It is an ideal material for next-generation heat dissipation substrates and electronic device packaging, and can also be used in heat exchangers, piezoelectric ceramics and thin films, thermally conductive fillers, etc., showing broad application prospects. The crystal structure of AlN determines its excellent thermal conductivity and insulation properties.

[0003] Currently, the main methods for preparing aluminum nitride ceramic powder include carbothermic reduction nitriding and direct nitriding. Among them, carbothermic reduction is prone to the problem of residual carbon or carbides in the product, and its decarburization and impurity control processes are outdated. Direct nitriding is prone to the problem of residual alumina, metallic aluminum and other impurities in the product due to aluminum powder oxidation or incomplete reaction. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides an aluminum nitride ceramic powder and its preparation method.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing aluminum nitride ceramic powder includes the following steps: Using alumina (Al2O3) powder as the aluminum source and silicon nitride (Si3N4) powder as the nitrogen source, the aluminum source and nitrogen source are mixed to obtain a mixed powder. The mixed powder is pressed into preforms, and then sintered at high temperature under a protective atmosphere. The Si produced by the decomposition of silicon nitride combines with the O in alumina to form SiO. SiO inhibits the solid dissolution of oxygen in the aluminum nitride lattice in gaseous form, thus obtaining aluminum nitride ceramic powder with an oxygen content of less than 0.36 wt%.

[0006] This invention provides a method for preparing high-purity aluminum nitride ceramic powder based on the nitride thermal reduction method. The raw materials used are alumina and silicon nitride powders. After thorough mixing, the raw materials undergo a high-temperature sintering reaction. The reaction equation is: Al₂O₃ + Si₃N₄ = 2AlN + 3SiO↑ + N₂↑. Through high-temperature conditions (>1600℃), the atoms at the interface between Al₂O₃ and Si₃N₄ particles are activated, lattice vibrations are intensified, and atomic diffusion is promoted. Specifically, Si₃N₄ decomposes at high temperature, releasing active nitrogen (N) and active silicon (Si); Al₂O₃ contains Al₂N₄. 3+ The reaction reacts with active nitrogen (N) to form AlN, releasing oxygen (O). Simultaneously, the Si produced by the decomposition of Si3N4 combines with the oxygen (O) released from Al2O3 to form gaseous SiO. The oxygen exists in the form of SiO gas, reducing the solid solubility of oxygen in the aluminum nitride lattice. Excess active nitrogen atoms combine to form N2 gas, which escapes from the system. The products generated by the reaction in this invention are divided into three categories: solid AlN, gaseous SiO, and N2. The gaseous SiO and N2 can be directly separated by the exhaust device of the reaction system without the need for complex subsequent impurity removal steps. The oxygen exists in the form of SiO gas, reducing the solid solubility of oxygen in the aluminum nitride lattice. The remaining solid product is mainly AlN, and high-purity aluminum nitride ceramic powder can be obtained with simple screening.

[0007] The aforementioned nitride thermal reduction method for preparing aluminum nitride ceramic powder does not require prolonged heat treatment, thus reducing costs, and the resulting aluminum nitride ceramic powder has an oxygen content of <0.36wt%. During the reaction, SiO exists in gaseous form, reducing the solid solution of oxygen in the aluminum nitride lattice. Furthermore, compared to the carbothermic reduction method, it eliminates the need for a decarburization process, reducing the impact of other impurities on the aluminum nitride ceramic powder. By optimizing the raw material combination and reaction pathway, the nitride thermal reduction method for preparing aluminum nitride ceramic powder achieves low-cost, high-efficiency preparation, providing guidance for the mass production of aluminum nitride ceramics.

[0008] Furthermore, the molar ratio of alumina powder to silicon nitride powder is 1:0.8–1.5. Too little silicon nitride will lead to incomplete reaction, while too much will result in residual silicon nitride powder.

[0009] Furthermore, the mixing is carried out at a rotation speed of 14 to 15 rpm for 8 to 10 hours. Under these conditions, the powder is fully mixed evenly.

[0010] Furthermore, the pressing pressure is 5MPa to 10MPa, and the holding time is 10s to 15s. By using specific pressure and time to press the powder into preforms, the contact area of ​​the powder is increased, thus promoting the reaction.

[0011] Furthermore, the high-temperature sintering reaction is carried out at a temperature of 1600℃~1800℃ for 30min~60min. High-purity aluminum nitride ceramic powder is obtained by holding the powder at this high temperature for a sufficient time.

[0012] Furthermore, the specific procedure for the high-temperature sintering reaction is as follows: first, the temperature is increased to 1000℃~1100℃ at a rate of 10℃ / min~15℃ / min, then increased to 1400℃~1500℃ at a rate of 8℃ / min~10℃ / min, and then increased to 1600℃~1800℃ at a rate of 5℃ / min~10℃ / min.

[0013] Furthermore, the alumina powder has a purity >99% and a particle size of 500 nm to 2 μm; the silicon nitride powder has a purity >99% and a particle size of 1 μm to 5 μm.

[0014] The aluminum nitride ceramic powder prepared by the above method has a purity >98%, an oxygen content of 0.248wt% to 0.358wt%, and an average particle size of 0.8μm to 0.9μm.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention employs a nitride thermal reduction technique, using alumina powder as the aluminum source and silicon nitride powder as the nitrogen source. By optimizing the raw material combination and reaction mechanism, it utilizes the active Si generated during high-temperature sintering from the decomposition of silicon nitride to combine with O in alumina to generate gaseous SiO. This avoids oxygen solidification in the aluminum nitride lattice and aluminum oxide residue, while simultaneously reducing the Al content in the alumina. 3+ Aluminum nitride is formed by combining with active nitrogen generated from the decomposition of silicon nitride. In the above preparation method, alumina and silicon nitride powders are used as raw materials, and no carbon source is introduced throughout the process, fundamentally avoiding the problem of carbon or carbide residues in carbothermic reduction methods, and eliminating the need for outdated decarburization processes. Furthermore, this invention uses stable alumina powder as the aluminum source, replacing metallic aluminum powder in direct nitriding methods, thus avoiding the problem of easy oxidation of aluminum powder. Simultaneously, SiO escapes from the reaction system in gaseous form, effectively removing oxygen and ensuring that the oxygen content of the final product is below 0.36 wt%, avoiding the formation of alumina residues from the combination of oxygen and aluminum. Moreover, the solid product generated by the reaction is mainly aluminum nitride, with no risk of metallic aluminum residue. This invention obtains high-purity aluminum nitride ceramic powder through specific raw materials and processes, solving the problem of impurity residues in traditional preparation methods. Attached Figure Description

[0016] 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 The image shows the XRD pattern of the aluminum nitride ceramic powder prepared in Example 1.

[0018] Figure 2 The images shown are SEM images and EDS elemental distribution maps of the aluminum nitride ceramic powder prepared in Example 2. In the images, a is the SEM image of the aluminum nitride ceramic powder prepared in Example 2, b is the EDS elemental distribution map, c is the Al elemental distribution map, d is the N elemental distribution map, e is the Si elemental distribution map, and f is the O elemental distribution map.

[0019] Figure 3 The image shows the XRD pattern of the aluminum nitride ceramic powder prepared in Example 3. Detailed Implementation

[0020] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific 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. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods, and the materials and reagents used in the following embodiments are commercially available unless otherwise specified.

[0021] A method for preparing high-purity aluminum nitride ceramic powder based on nitride thermal reduction includes the following steps: S1. Ingredients: Weigh each component raw material according to the molar ratio of Al2O3:Si3N4 = 1:0.8~1.5 to form the first mixture; S2. Mixing: Add 99.9% pure anhydrous ethanol to the first mixed powder, then add zirconia balls with a particle size of 1mm to obtain a mixed liquid; place the mixed liquid on a two-dimensional mixer and mix at a speed of 14r / min to 15r / min for 8h to 10h. Then filter it through a 100-mesh sieve, place the filtered slurry in a forced-air drying oven for drying, grind it, and then pass it through a 60-mesh sieve to obtain the mixed powder. S3. Pre-forming: In order to improve heat conduction efficiency, increase contact area and promote reaction, the mixed powder is pressed into loose cylindrical pieces with a mass of 3g to 5g using a circular mold with a diameter of 15mm. The pre-forming pressure is 5MPa to 10MPa and the holding time is 10s to 15s. S4. Synthesis of aluminum nitride ceramic powder: The pre-made loose cylindrical pieces are placed into a pressureless sintering furnace, and Ar is introduced as a protective gas. The pressureless sintering furnace is heated to 1600℃~1800℃ for synthesis reaction, and the holding time is 30~60min to obtain single-phase aluminum nitride ceramic powder.

[0022] S5. Powder post-processing: Take out the single-phase aluminum nitride ceramic powder obtained by pressureless sintering, grind it in a mortar, and then pass it through a 60-mesh sieve to obtain aluminum nitride ceramic powder.

[0023] In step S1, the alumina powder has a purity >99% and a particle size of 500 nm to 2 μm; the silicon nitride powder has a purity >99% and a particle size of 1 μm to 5 μm. In step S2, the ball-to-powder ratio is 3 to 5:1, and the first mixture in the mixture accounts for 40% to 70% of the total mass of the first mixture and anhydrous ethanol. In step S4, the pressureless sintering process is as follows: the temperature is increased to 1000°C to 1100°C at a rate of 10°C / min to 15°C / min, then increased to 1400°C to 1500°C at a rate of 8°C / min to 10°C / min, then increased to 1600°C to 1800°C at a rate of 5°C / min to 10°C / min; after the heating process, the temperature is held for 30 to 60 minutes, and then cooled with the furnace after the temperature drops to 1000°C.

[0024] The method for preparing high-purity aluminum nitride ceramic powder provided by this invention involves a sintering temperature below 1800℃, the absence of other impurity phases, and a purity >98% for the resulting aluminum nitride ceramic powder. The oxygen content is <0.36wt%, with a minimum oxygen content of 0.248wt%. The powder exhibits uniform distribution and regular morphology. The average particle size distribution ranges from 0.8μm to 0.9μm.

[0025] This invention uses alumina powder as the aluminum source and silicon nitride powder as the nitrogen source. The aluminum and nitrogen sources are mixed to obtain a mixed powder. The mixed powder is then sintered at high temperature under a protective atmosphere, causing the silicon nitride to decompose into active nitrogen and silicon, and the Al in the alumina to be released. 3+Aluminum nitride ceramic powder is generated by combining with active nitrogen. The products generated by the above reaction are divided into three categories: solid AlN, gaseous SiO, and N2. The gaseous SiO and N2 can be directly separated by the exhaust device of the reaction system without complicated subsequent impurity removal steps. Oxygen exists in the form of SiO gas, reducing the solid solubility of oxygen in the aluminum nitride lattice. The remaining solid product is mainly AlN, and high-purity aluminum nitride ceramic powder can be obtained with simple screening. This avoids the problems of residual carbon or carbides in the carbothermic reduction method and the problems of residual alumina, metallic aluminum, and other impurities in the products of the direct nitriding method. No toxic gases such as carbon monoxide are generated during the reaction process of this invention, and the generated N2 can be used as a protective gas to reduce the contamination of the product by external impurities. At the same time, it avoids the safety hazards of flammable aluminum powder in the direct nitriding method, and the process stability is stronger.

[0026] This invention discloses a method for preparing high-purity aluminum nitride ceramic powder based on the thermal reduction of nitrides. The two core raw materials used in this method, Al₂O₃ and Si₃N₄, are both common industrial-grade powders. Alumina is widely available, inexpensive, and its purity is easily controlled; while silicon nitride, although more expensive than basic chemical raw materials, can have its costs reduced through industrial by-product recovery or large-scale production. Overall, the raw material cost is lower than that of the direct nitriding method, which relies on high-purity aluminum powder. The combination of the two significantly reduces raw material costs, making it suitable for mass production. The highest temperature for synthesizing aluminum nitride ceramic powder in this invention is 1800℃, reducing energy consumption and equipment requirements. The by-products produced by this invention are SiO and N₂, eliminating the need for complex gas protection and carbon separation steps, simplifying post-processing and aligning with green manufacturing trends. This invention achieves low-cost, low-pollution, and high-efficiency preparation of aluminum nitride ceramic powder through the use of alumina and silicon nitride.

[0027] Example 1 A method for preparing high-purity aluminum nitride ceramic powder based on nitride thermal reduction, the method comprising the following steps: S1. Ingredients: Weigh each raw material according to the molar ratio of Al2O3:Si3N4 = 1:1, with a total mass of 40g. Mix the raw materials in a mixing bottle to obtain the first mixture. Al2O3 is used as the aluminum source, and Si3N4 is used as the nitrogen source.

[0028] S2. Mixing: Based on the first mixture, add zirconia grinding balls with a particle size of 1 mm and anhydrous ethanol with a purity of 99.9% to the mixing bottle to obtain a mixture. The mass ratio of the first mixture to anhydrous ethanol is 1:1, and the ball-to-material ratio (the ratio of the total mass of the zirconia grinding balls to the total mass of the first mixture) is 5:1. Then, place the mixing bottle on a two-dimensional mixer with a speed of 14 r / min and mix for 8 hours. Separate the slurry from the grinding balls through a 100-mesh sieve. Place the separated slurry into an evaporating dish and then dry it in a constant temperature drying oven at 100℃. Grind the dried powder with an agate mortar for 6 hours and then pass it through a 60-mesh sieve to obtain the mixed powder. This mixing process ensures that the powder is fully mixed and uniform, increasing the contact area.

[0029] S3. Pre-forming: The mixed powder is pressed into loose cylindrical blocks with a mass of 3g using a circular mold with a diameter of 15mm. The pre-forming pressure is 5MPa and the holding time is 10s. This pre-forming process can increase the contact area of ​​the powder and promote the reaction.

[0030] S4. Synthesis of aluminum nitride ceramic powder: The pre-made loose cylindrical pieces are placed into a pressureless sintering furnace. The pressureless sintering furnace is first evacuated to a vacuum state, and then Ar is introduced as a protective gas to make the furnace pressure reach 10 MPa. Then the pressureless sintering furnace is heated to 1700℃ to carry out the synthesis reaction and obtain single-phase aluminum nitride ceramic powder.

[0031] The sintering procedure in the pressureless sintering furnace is as follows: the temperature is increased from room temperature to 1000℃ at a rate of 10℃ / min, then to 1400℃ at a rate of 8℃ / min, and then to 1700℃ at a rate of 5℃ / min; after reaching 1700℃, the temperature is held for 30 minutes, and then allowed to naturally decrease to 1000℃ before cooling down with the furnace. During the synthesis process, if the temperature is too low, the reaction will be incomplete and silane powder will be generated; if the temperature is too high, silicon nitride powder will decompose, resulting in a loss of nitrogen source and increasing costs.

[0032] S5. Powder post-processing: Take out the single-phase aluminum nitride ceramic powder obtained in step S4, grind it in a mortar for 6 hours, and then pass it through a 60-mesh sieve to obtain aluminum nitride ceramic powder.

[0033] The aluminum nitride ceramic powder prepared in this embodiment has a purity of 98.7%, an oxygen content of 0.297 wt%, and an average particle size of 0.89 μm.

[0034] Example 2 A method for preparing high-purity aluminum nitride ceramic powder based on nitride thermal reduction, the method comprising the following steps: S1. Ingredients: Weigh each raw material according to the molar ratio of Al2O3:Si3N4=1:1.2. The total mass of the raw materials is 40g. Mix the raw materials in a mixing bottle to obtain the first mixture.

[0035] S2. Mixing: Based on the first mixture, add zirconia grinding balls with a particle size of 1 mm and anhydrous ethanol with a purity of 99.9% to the mixing bottle to obtain a mixture. The mass ratio of the first mixture to anhydrous ethanol is 6:4, and the ball-to-material ratio is 3:1. Then, place the mixing bottle on a two-dimensional mixer with a speed of 14.5 r / min and mix for 10 hours. Separate the slurry from the grinding balls through a 100-mesh sieve. Place the separated slurry into an evaporating dish and then dry it in a constant temperature drying oven at 100℃. Grind the dried powder with an agate mortar and pestle and then pass it through a 60-mesh sieve to obtain the mixed powder.

[0036] S3. Pre-forming: The mixed powder is pressed into loose cylindrical blocks with a mass of 3.5g using a circular mold with a diameter of 15mm. The pre-forming pressure is 8MPa and the holding time is 12s.

[0037] S4. Synthesis of aluminum nitride ceramic powder: The pre-made loose cylindrical pieces are placed into a pressureless sintering furnace. The pressureless sintering furnace is first evacuated, and then Ar is introduced as a protective gas to achieve a furnace pressure of 10 MPa. Then the pressureless sintering furnace is heated to 1750℃ to carry out the synthesis reaction and obtain single-phase aluminum nitride ceramic powder.

[0038] The sintering process in the pressureless sintering furnace is as follows: the temperature is raised to 1100℃ at a rate of 15℃ / min, then raised to 1450℃ at a rate of 10℃ / min, and then raised to 1750℃ at a rate of 8℃ / min; after the temperature is raised to 1750℃, it is held for 50 minutes, and then the temperature is naturally lowered to 1000℃ before being cooled down with the furnace.

[0039] S5. Powder post-processing: Take out the single-phase aluminum nitride ceramic powder obtained in step S4, grind it in a mortar, and then pass it through a 60-mesh sieve to obtain aluminum nitride ceramic powder.

[0040] The aluminum nitride ceramic powder prepared in this embodiment has a purity of 98.86%, an oxygen content of 0.308 wt%, and an average particle size of 0.9 μm.

[0041] Example 3 A method for preparing high-purity aluminum nitride ceramic powder based on nitride thermal reduction, the method comprising the following steps: S1. Ingredients: Weigh each raw material according to the molar ratio of Al2O3:Si3N4=1:1.5. The total mass of the raw materials is 40g. Mix the raw materials in a mixing bottle to obtain the first mixture.

[0042] S2. Mixing: Based on the first mixture, add zirconia grinding balls with a particle size of 1 mm and anhydrous ethanol with a purity of 99.9% to the mixing bottle to obtain a mixture. The mass ratio of the first mixture to anhydrous ethanol is 7:3, and the ball-to-material ratio is 3:1. Then, place the mixing bottle on a two-dimensional mixer with a speed of 15 r / min and mix for 10 hours. Separate the slurry from the grinding balls through a 100-mesh sieve. Place the separated slurry into an evaporating dish and then dry it in a constant temperature drying oven at 100℃. Grind the dried powder with an agate mortar and pestle and then pass it through a 60-mesh sieve to obtain the mixed powder.

[0043] S3. Pre-forming: The dried mixture powder is pressed into loose cylindrical blocks with a mass of 4g using a circular mold with a diameter of 15mm. The pre-forming pressure is 10MPa and the holding time is 15s.

[0044] S4. Synthesis of aluminum nitride ceramic powder: The pre-made loose cylindrical pieces are placed into a pressureless sintering furnace. The pressureless sintering furnace is first evacuated to a vacuum state, and then Ar is introduced as a protective gas. The pressure inside the furnace reaches 10 MPa. Then the pressureless sintering furnace is heated to 1800℃ to carry out the synthesis reaction and obtain single-phase aluminum nitride ceramic powder.

[0045] The sintering process in the pressureless sintering furnace is as follows: the temperature is increased to 1100℃ at a rate of 10℃ / min, then increased to 1500℃ at a rate of 10℃ / min, and then increased to 1800℃ at a rate of 10℃ / min; after the temperature is increased to 1800℃, it is held for 60 minutes, and then the temperature is naturally reduced to 1000℃ before being cooled down with the furnace.

[0046] S5. Powder post-processing: Take out the single-phase aluminum nitride ceramic powder obtained in step S4, grind it in a mortar, and then pass it through a 60-mesh sieve to obtain aluminum nitride ceramic powder.

[0047] The aluminum nitride ceramic powder prepared in this embodiment has a purity of 98.8%, an oxygen content of 0.248 wt%, and an average particle size of 0.87 μm.

[0048] Example 4 A method for preparing high-purity aluminum nitride ceramic powder based on nitride thermal reduction, the method comprising the following steps: S1. Ingredients: Weigh each raw material according to the molar ratio of Al2O3:Si3N4=1:0.8. The total mass of the raw materials is 40g. Mix the raw materials in a mixing bottle to obtain the first mixture.

[0049] S2. Mixing: Based on the first mixture, add zirconia grinding balls with a particle size of 1 mm and anhydrous ethanol with a purity of 99.9% to the mixing bottle to obtain a mixture. The mass ratio of the first mixture to anhydrous ethanol is 7:3, and the ball-to-material ratio is 3:1. Then, place the mixing bottle on a two-dimensional mixer with a speed of 15 r / min and mix for 10 hours. Separate the slurry from the grinding balls through a 100-mesh sieve. Place the separated slurry into an evaporating dish and then dry it in a constant temperature drying oven at 100℃. Grind the dried powder with an agate mortar and pestle and then pass it through a 60-mesh sieve to obtain the mixed powder.

[0050] S3. Pre-forming: The dried mixture powder is pressed into loose cylindrical blocks with a mass of 4g using a circular mold with a diameter of 15mm. The pre-forming pressure is 10MPa and the holding time is 15s.

[0051] S4. Synthesis of aluminum nitride ceramic powder: The pre-made loose cylindrical pieces are placed into a pressureless sintering furnace. The pressureless sintering furnace is first evacuated to a vacuum state, and then Ar is introduced as a protective gas. The pressure inside the furnace reaches 10 MPa. Then the pressureless sintering furnace is heated to 1600℃ to carry out the synthesis reaction and obtain single-phase aluminum nitride ceramic powder.

[0052] The sintering process in the pressureless sintering furnace is as follows: the temperature is raised to 1100℃ at a rate of 10℃ / min, then raised to 1400℃ at a rate of 8℃ / min, and then raised to 1600℃ at a rate of 5℃ / min; after the temperature is raised to 1600℃, it is held for 60 minutes, and then the temperature is naturally lowered to 1000℃ before being cooled down with the furnace.

[0053] S5. Powder post-processing: Take out the single-phase aluminum nitride ceramic powder obtained in step S4, grind it in a mortar, and then pass it through a 60-mesh sieve to obtain aluminum nitride ceramic powder.

[0054] The aluminum nitride ceramic powder prepared in this embodiment has a purity of 98.26%, an oxygen content of 0.358 wt%, and an average particle size of 0.97 μm.

[0055] Comparative Example 1 Aluminum nitride ceramic powder was prepared using a direct nitriding method, the steps of which are as follows: S1. Raw material pretreatment: Select high-purity metallic Al powder (purity ≥99.9%, industrial grade commonly uses 99.95%), grind or sieve the powder to a suitable particle size (1μm~10μm), and dry it in a vacuum drying oven at 100℃ for 2 hours to remove the moisture adsorbed on the powder surface.

[0056] S2. Charging and Atmosphere Preparation: Select an alumina crucible, place the crucible containing the raw material into the tube furnace, and first evacuate to 10°C. -3Below Pa, introduce high-purity nitrogen (purity ≥ 99.999%) at a flow rate of 300 mL / min to maintain a slight positive pressure inside the furnace (0.01 MPa to 0.05 MPa). Repeat the vacuuming and N2-introduction operation 2 to 3 times to ensure that the O2 content inside the furnace is < 100 ppm.

[0057] S3. Heating Reaction: Slowly increase the temperature to 700℃ at a rate of 8℃ / min to avoid localized overheating and agglomeration or oxidation of the powder due to excessively rapid heating. Continue heating to 1500℃ and hold for 4 hours. During this stage, N2 is activated at high temperature, overcomes the surface energy barrier of the metal, and diffuses into the crystal lattice to form nitrides. Continuously replenish N2 during the reaction to maintain a stable nitrogen partial pressure within the furnace and prevent insufficient nitrogen content due to N2 consumption.

[0058] S4. Cooling Protection: After turning off the heating device, keep N2 continuously supplied and allow the furnace temperature to cool naturally to room temperature at a rate of 8℃ / min to avoid excessive temperature difference causing product cracking. After cooling to below 200℃, you can switch to an inert gas (such as Ar) to continue cooling, or take out the product under N2 atmosphere and transfer it directly to a desiccator for storage.

[0059] The aluminum nitride ceramic powder prepared in this comparative example has a purity of <98%, an oxygen content of >1.58wt%, an average particle size of >50μm, uneven particle size distribution, and low specific surface area, making it difficult to densify during subsequent forming (such as AlN ceramic sintering).

[0060] Performance testing The XRD image of the aluminum nitride ceramic powder obtained in Example 1 is as follows: Figure 1 As shown, the aluminum nitride ceramic powder prepared by this invention does not contain other impurities, has good crystallinity, and the oxygen content is controlled within 0.36 wt%.

[0061] The SEM image of the aluminum nitride ceramic powder obtained in Example 2 is shown below. Figure 2 As shown in Figure a, micron-sized agglomerates of aluminum nitride powder appear. The EDS of the aluminum nitride ceramic powder obtained in Example 2 is as follows. Figure 2 Figures b through f show the elemental distribution maps, where b is the EDS surface scan map, c is the Al elemental distribution map, d is the N elemental distribution map, e is the Si elemental distribution map, and f is the O elemental distribution map. It can be seen that Al and N elements are uniformly distributed, while Si and O elements are present in relatively small amounts in the aluminum nitride ceramic powder, and no other impurity elements are present.

[0062] The XRD image of the aluminum nitride ceramic powder obtained in Example 3 is as follows: Figure 3 As shown, the aluminum nitride ceramic powder prepared by this invention does not contain other impurities, has good crystallinity, and the oxygen content is controlled within 0.36 wt%.

[0063] This invention provides a method for preparing high-purity aluminum nitride ceramic powder based on the nitride thermal reduction method. The method involves mixing alumina powder and silicon nitride powder as raw materials using a two-dimensional mixer. The mixture is then placed in a graphite mold and heat-treated with argon gas as a protective gas to obtain submicron-sized high-purity aluminum nitride powder. The aluminum nitride ceramic powder prepared by this invention has a purity >98%, an oxygen content <0.36 wt%, with a minimum oxygen content of only 0.248 wt%, uniform powder distribution, and regular powder morphology. The particle size distribution ranges from 0.8 μm to 0.9 μm.

[0064] This invention utilizes the nitride thermal reduction method to prepare aluminum nitride ceramic powder. Its core advantages lie in low raw material cost, high product purity, and superior environmental friendliness. Traditional methods, such as direct nitriding and carbothermic reduction, often rely on high-purity aluminum powder or alumina and expensive carbon sources (such as graphite), resulting in high raw material costs. Direct nitriding is prone to aluminum powder oxidation or incomplete reaction, leading to residual impurities such as alumina and metallic aluminum in the product, affecting the insulation and thermal conductivity of aluminum nitride. The nitride thermal reduction method has a more stable reaction system. The byproducts generated by the reaction of the reducing agent (such as silicon nitride) and the aluminum source (such as alumina) are gaseous SiO and N2, and the final product purity can easily reach over 98%, better meeting the requirements of high-end electronic packaging for high-purity aluminum nitride. In contrast, the carbothermic reduction method requires high temperatures (1500℃~1700℃) and produces harmful gases such as carbon monoxide, resulting in high energy consumption and environmental pollution.

[0065] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the inventive concept of the present invention, can make other changes and modifications to these embodiments, all of which fall within the scope of the present invention.

[0066] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. If such modifications and variations fall within the scope of equivalents of this invention, then this invention also intends to include these modifications and variations.

Claims

1. A method for producing an aluminum nitride ceramic powder, characterized by comprising the steps of: The method comprises the following steps: ​ The aluminum source and the nitrogen source are mixed to obtain mixed powder; The mixed powder is pressed into a preform, and then, under a protective atmosphere, through a sintering reaction, Si produced by the decomposition of silicon nitride combines with O in alumina to form SiO, which inhibits the solid solution of oxygen in the aluminum nitride lattice in the form of gas, and aluminum nitride ceramic powder with an oxygen content of less than 0.36wt% is obtained.

2. The method of producing an aluminum nitride ceramic powder according to claim 1, wherein The molar ratio of the alumina powder to the silicon nitride powder is 1:0.8-1.

5.

3. The method of producing an aluminum nitride ceramic powder according to claim 1, wherein The sintering reaction is performed at a temperature of 1600-1800°C for 30-60 minutes.

4. The method of producing an aluminum nitride ceramic powder according to claim 1, wherein The specific procedure of the high-temperature sintering reaction is as follows: first, the temperature is raised to 1000-1100°C at a rate of 10-15°C / min, then the temperature is raised to 1400-1500°C at a rate of 8°C / min, and then the temperature is raised to 1600-1800°C at a rate of 5°C / min.

5. The method of producing an aluminum nitride ceramic powder according to claim 1, wherein The mixing is performed at a rotation speed of 14-15 r / min for 8-10 hours.

6. The method of producing an aluminum nitride ceramic powder according to claim 1, wherein The pressure for pressing is 5-10 MPa, and the pressure holding time is 10-15 seconds.

7. The method of producing an aluminum nitride ceramic powder according to claim 1, wherein The purity of the alumina powder is greater than 99%, and the particle size is 500 nm-2 μm; the purity of the silicon nitride powder is greater than 99%, and the particle size is 1-5 μm.

8. An aluminum nitride ceramic powder, characterized by, The aluminum nitride ceramic powder is prepared by the method of any one of claims 1-7.

9. The aluminum nitride ceramic powder of claim 8, wherein, The oxygen content of the aluminum nitride ceramic powder is 0.248-0.358wt%.

10. The aluminum nitride ceramic powder of claim 8, wherein The average particle size of the aluminum nitride ceramic powder is 0.8-0.9 μm.

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