Preparation method of aluminum nitride powder with low lattice oxygen content and application thereof

Abstract

This invention relates to a method for preparing aluminum nitride powder with low lattice oxygen content and its application, belonging to the field of aluminum nitride technology. The invention involves pretreating aluminum nitride powder with a coupling agent, then coating it with a nitrogen-containing resin precursor through in-situ polymerization and low-temperature pyrolysis to obtain aluminum nitride powder with low lattice oxygen content. This powder is then mixed with a ternary eutectic nitride additive composed of silicon nitride, boron nitride, and germanium nitride, and subjected to low-temperature reduction, high-temperature densification, and annealing to obtain aluminum nitride material with low lattice oxygen content. Through the synergistic effect of carbothermic reduction deoxidation, lattice oxygen replacement, and nitrogen vacancy repair, extremely low lattice oxygen content is controlled, simultaneously inhibiting oxygen re-dissolution and reducing phonon scattering, significantly improving the thermal conductivity and resistance to damp heat aging of aluminum nitride ceramics. The aluminum nitride powder prepared by this invention exhibits low lattice oxygen content, excellent thermal conductivity, and resistance to damp heat aging.

Description

Technical Field

[0001] This invention relates to the field of aluminum nitride technology, specifically to a method for preparing aluminum nitride powder with low lattice oxygen content and its application. Background Technology

[0002] Aluminum nitride ceramics possess high thermal conductivity, high insulation, low dielectric constant, and a thermal expansion coefficient that matches that of silicon, making them a core material for high-end electronic packaging fields such as 5G communication, high-power semiconductor devices, and new energy vehicle electronic control modules.

[0003] However, aluminum nitride powder has high surface activity and is easily hydrolyzed and oxidized to form aluminum oxide. During sintering, oxygen easily enters the crystal lattice, forming Al-ON point defects, which severely exacerbates phonon scattering and leads to a significant decrease in the material's thermal conductivity. Existing modification technologies cannot simultaneously achieve deep deoxidation and densification during the sintering process, and cannot effectively suppress oxygen lattice re-dissolution, resulting in persistently high lattice oxygen content in the product, poor resistance to damp heat aging, and difficulty in meeting the stringent requirements for long-term service of high-power devices. At the same time, existing processes mostly rely on high-temperature, long-time sintering, which can easily cause abnormal grain growth, further deteriorating the overall performance of the material and limiting its large-scale application in high-end packaging fields. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing aluminum nitride powder with low lattice oxygen content and its application, so as to solve the problems existing in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing aluminum nitride powder with low lattice oxygen content and its application, comprising the following steps: (1) Aluminum nitride powder pretreated with silane coupling agent, resorcinol, melamine, 37% formaldehyde aqueous solution and 70wt% ethanol aqueous solution are mixed in a mass ratio of 9~11:0.04~0.06:0.1~0.2:0.1~0.2:20. Under nitrogen atmosphere, the pH is adjusted to 8.5 and stirred at 25~35℃ for 5~7h. After filtration, the mixture is vacuum dried at 50℃ for 12h. Under nitrogen atmosphere, the temperature is raised to 600℃ at a heating rate of 2℃ / min and held for 2h. The mixture is then cooled with the furnace to obtain aluminum nitride powder with surface coating. (2) Silicon nitride, boron nitride, germanium nitride, isopropanol and dispersant are mixed in a mass ratio of 5~7:2~4:1:10:0.1, with a ball-to-material ratio of 5:1. The mixture is then ball-milled for 2 hours to obtain an additive slurry. The aluminum nitride powder coated on the surface is added to the additive slurry, so that the total amount of the ternary additive is 2~5wt% of the mass of the aluminum nitride powder. The mixture is then ball-milled for 4 hours with a ball-to-material ratio of 8:1. After vacuum drying at 60℃ for 12 hours, the mixture is passed through a 200-mesh sieve to obtain a composite aluminum nitride powder with low lattice oxygen content.

[0006] Furthermore, the silane coupling agent in step (1) is: vinyltrimethoxysilane coupling agent.

[0007] Furthermore, the aluminum nitride powder in step (1) is aluminum nitride powder with a particle size of 1 μm.

[0008] Furthermore, the dispersant in step (2) is a polyetheramine dispersant with a molecular weight of 2000.

[0009] Furthermore, the application of an aluminum nitride powder with low lattice oxygen content includes the following steps: (1) Add composite aluminum nitride powder with low lattice oxygen content to a mixed solvent to make its solid content reach 50~60wt%. Then add 2~4wt% of the powder mass of binder, 1~2wt% of plasticizer and 0.5wt% of polyetheramine dispersant. Stir in a double planetary vacuum for 4h and vacuum degas for 30min to obtain casting slurry. Cast the slurry with a doctor blade gap of 0.3mm and a casting speed of 0.8m / min. Dry to obtain green body and punch to obtain green body sample. (2) The green sample was heated from room temperature to 1300℃ at a rate of 5℃ / min, mixed gas A was introduced at a rate of 2L / min, and the temperature was maintained for 2h; then the temperature was increased to 1500℃ at a rate of 3℃ / min and the temperature was maintained for 4h; finally, the temperature was decreased to 1000℃ at a rate of 2℃ / min, mixed gas B was introduced at a rate of 2L / min and the temperature was maintained for 1h; the furnace was naturally cooled to room temperature, and the sintered substrate was ground on both sides to remove the surface oxide layer, thus obtaining aluminum nitride material with low lattice oxygen content.

[0010] Furthermore, the mixed solvent is prepared by mixing xylene and anhydrous ethanol in a volume ratio of 1:1.

[0011] Furthermore, the adhesive is an acrylic adhesive.

[0012] Furthermore, the plasticizer is: dibutyl phthalate plasticizer.

[0013] Furthermore, the mixed gas A is composed of nitrogen and hydrogen in a mass ratio of 95:5.

[0014] Furthermore, the mixed gas B is composed of nitrogen and ammonia in a mass ratio of 95:5. Compared with the prior art, the beneficial effects achieved by the present invention are: This invention combines surface-modified aluminum nitride powder with ternary eutectic nitride additives and then processes them through multiple steps to achieve low lattice oxygen content, excellent thermal conductivity, and resistance to damp heat aging.

[0015] This invention involves pre-treating aluminum nitride powder with a coupling agent, then coating it in situ with a nitrogen-containing resin precursor via in-situ polymerization. The resulting powder is then subjected to low-temperature pyrolysis to obtain surface-modified aluminum nitride powder with low lattice oxygen content. This powder is then compounded with a ternary eutectic nitride additive formed from silicon nitride, boron nitride, and germanium nitride in a specific ratio. After low-temperature reduction, high-temperature densification, and annealing, a low-lattice oxygen content aluminum nitride material is obtained. The surface of the modified aluminum nitride powder has a surface coating layer that isolates it from air and moisture, preventing secondary oxidation. Simultaneously, during the low-temperature reduction stage, the active carbon atoms in the coating layer undergo a carbothermic reduction nitridation reaction with the aluminum oxide on the aluminum nitride surface. Simultaneously, trace amounts of oxygen in the hydrogen-assisted reducing atmosphere generate carbon monoxide and water. The vapor can be completely discharged through the billet. In the high-temperature stage, the ternary additives form a eutectic liquid phase. The germanium atoms in the liquid phase undergo a lattice oxygen replacement reaction with the oxygen in the aluminum nitride lattice to form a stable Ge-Si-ON grain boundary phase, preventing the lattice re-dissolution of oxygen and achieving simultaneous densification and deoxidation. In the annealing stage, the formed Si-ON passivation layer completely seals the oxygen in the grain boundary. The above stages work together to achieve a low lattice oxygen content, significantly improving the resistance to damp heat aging. The doped nitrogen atoms in the coating layer replenish the nitrogen vacancies generated by oxygen removal in situ, repairing the lattice distortion. At the same time, the germanium atoms replace the lattice oxygen, eliminating Al-ON point defects. Together with the densified grain boundary layer, they reduce phonon scattering and further improve the thermal conductivity of aluminum nitride. Detailed Implementation

[0016] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0017] To more clearly illustrate the method provided by the present invention, the following embodiments are provided in detail. The testing methods for various indicators of the aluminum nitride powder prepared in the following embodiments are as follows: Lattice oxygen content test: The aluminum nitride materials prepared in Examples 1-5 and Comparative Examples 1-6 were ground into fine powder and passed through a 200-mesh sieve. They were then placed in a graphite crucible and heated to melt. The lattice oxygen content was measured using an oxygen, nitrogen and hydrogen analyzer. Thermal conductivity test: The specific heat capacity and thermal diffusivity of the samples prepared in Examples 1-5 and Comparative Examples 1-6 were tested at room temperature using the laser flash method, referring to ASTM E1461 standard, and the thermal conductivity was calculated based on the sample density. Moisture and heat aging test: The aluminum nitride materials prepared in Examples 1-5 and Comparative Examples 1-6 were placed at a temperature of 130°C and a relative humidity of 85%RH for 500 hours. The insulation resistance before and after aging was tested, and the insulation resistance decay rate was calculated. Example 1

[0018] (1) Add aluminum nitride powder with a particle size of 1 μm to a 95 wt% ethanol aqueous solution to make its solid content reach 30 wt%. Then add vinyltrimethoxysilane coupling agent with a mass of 0.01 times the powder and adjust the pH to 4.5 with 1M acetic acid. Stir and reflux at 65℃ and 800 rpm for 3 h. Filter and wash three times with anhydrous ethanol. Dry at 50℃ and vacuum degree -0.09 MPa for 12 h to obtain pretreated aluminum nitride. (2) Pretreated aluminum nitride, resorcinol, melamine, 37% formaldehyde aqueous solution and 70wt% ethanol aqueous solution were mixed in a mass ratio of 9:0.04:0.1:0.1:20. Under a nitrogen atmosphere, the pH was adjusted to 8.5 with 0.2M ammonia water. The mixture was stirred at 25℃ and 300rpm for 5h to form a uniform resin coating layer on the surface of the aluminum nitride powder. After filtration, the mixture was dried at 50℃ and vacuum degree -0.09MPa for 12h. Then, under a high-purity nitrogen atmosphere, the temperature was raised to 600℃ at a heating rate of 2℃ / min and held for 2h. The mixture was then cooled with the furnace to obtain the surface-coated aluminum nitride powder. (3) Silicon nitride, boron nitride, germanium nitride, isopropanol and polyetheramine dispersant were mixed in a mass ratio of 5:2:1:10:0.1 and ball-milled for 2 hours at a ball-to-material ratio of 5:1 and a rotation speed of 300 rpm to obtain a uniformly dispersed additive slurry, thus avoiding agglomeration of nanoparticles; aluminum nitride powder coated on the surface was added to the additive slurry so that the total amount of ternary additives added was 2wt% of the mass of aluminum nitride powder, ball-milled for 4 hours at a ball-to-material ratio of 8:1 and a rotation speed of 280 rpm, and dried for 12 hours at 60℃ and vacuum degree of -0.09MPa before passing through a 200-mesh sieve to obtain composite aluminum nitride powder with low lattice oxygen content; (4) The composite aluminum nitride powder with low lattice oxygen content was added to a mixed solvent. The mixed solvent was prepared by mixing xylene and anhydrous ethanol in a volume ratio of 1:1 to make its solid content reach 50wt%. 2wt% of the powder mass of acrylic binder, 1wt% of dibutyl phthalate plasticizer, and 0.5wt% of polyetheramine dispersant were added in sequence. The mixture was stirred under double planetary vacuum for 4h and vacuum degassing for 30min to obtain a casting slurry with a viscosity of 15000mPa·s. The slurry was cast on a PET carrier with a doctor blade gap of 0.3mm and a casting speed of 0.8m / min. The drying temperature was controlled in segments of 60℃, 80℃, 100℃, and 120℃ to obtain a green body with a thickness of 0.1mm. The green body sample was obtained by stamping. (5) The green sample was heated from room temperature to 1300℃ at a rate of 5℃ / min. A mixed gas A consisting of nitrogen and hydrogen in a mass ratio of 95:5 was introduced at a rate of 2L / min and kept at this temperature for 2h. This temperature is lower than the eutectic point of the ternary additive, and no liquid phase is generated. The green body remains porous. The active C / N atoms in the coating layer undergo a carbothermic reduction nitridation reaction with the aluminum oxide on the surface of the aluminum nitride powder. The trace oxygen in the hydrogen-assisted reducing atmosphere reacts with the residual oxide layer of the powder. The carbon monoxide and water vapor generated by the reaction are completely discharged from the system through the porous green body, thus achieving surface oxygen removal. At the same time, the doped N atoms are in situ. The N vacancies generated by reduction are replenished to avoid lattice defects. Then, the temperature is increased to 1500℃ at a rate of 3℃ / min and held for 4 hours. This temperature is higher than the eutectic point of the ternary additive, and the additive forms a uniform non-oxygen eutectic liquid phase, which fills the pores of the green body and achieves rapid densification at low temperature. At the same time, Ge atoms in the liquid phase rapidly diffuse into the aluminum nitride lattice and form strong Ge-O bonds with interstitial oxygen and replaced oxygen in the lattice. This quantitatively replaces oxygen from the aluminum nitride lattice and fixes it at the grain boundary to form a stable Ge-Si-ON grain boundary phase, preventing the lattice re-dissolution of oxygen and achieving simultaneous densification and deep removal of lattice oxygen. (6) Finally, the temperature is lowered to 1000℃ at a rate of 2℃ / min, and a mixed gas B composed of nitrogen and ammonia in a mass ratio of 95:5 is introduced at a rate of 2L / min. The temperature is maintained for 1h. During the cooling process, the active N atoms decomposed by ammonia repair the N vacancies at the grain boundaries. The Si element in the additive reacts with the trace oxygen at the grain boundaries to form a dense Si-ON passivation layer at the grain boundaries, which prevents oxygen from diffusing into the lattice during long-term use. The furnace is naturally cooled to room temperature, and the sintered substrate is ground on both sides to remove the surface oxide layer, resulting in aluminum nitride material with low lattice oxygen content. Example 2

[0019] (1) Add aluminum nitride powder with a particle size of 1 μm to a 95 wt% ethanol aqueous solution to make its solid content reach 30 wt%. Then add vinyltrimethoxysilane coupling agent with a mass of 0.01 times the powder and adjust the pH to 4.5 with 1M acetic acid. Stir and reflux at 65℃ and 800 rpm for 3 h. Filter and wash three times with anhydrous ethanol. Dry at 50℃ and vacuum degree -0.09 MPa for 12 h to obtain pretreated aluminum nitride. (2) Pretreated aluminum nitride, resorcinol, melamine, 37% formaldehyde aqueous solution and 70wt% ethanol aqueous solution were mixed in a mass ratio of 9.5:0.045:0.12:0.13:20. Under a nitrogen atmosphere, the pH was adjusted to 8.5 with 0.2M ammonia water. The mixture was stirred at 28℃ and 300rpm for 5.5h to form a uniform resin coating layer on the surface of the aluminum nitride powder. After filtration, the mixture was dried at 50℃ and vacuum degree -0.09MPa for 12h. Then, under a high-purity nitrogen atmosphere, the temperature was raised to 600℃ at a heating rate of 2℃ / min and held for 2h. The mixture was then cooled with the furnace to obtain the surface-coated aluminum nitride powder. (3) Silicon nitride, boron nitride, germanium nitride, isopropanol and polyetheramine dispersant were mixed in a mass ratio of 5.5:2.5:1:10:0.1 and ball-milled for 2 hours at a ball-to-material ratio of 5:1 and a rotation speed of 300 rpm to obtain a uniformly dispersed additive slurry, thus avoiding agglomeration of nanoparticles; aluminum nitride powder coated on the surface was added to the additive slurry so that the total amount of ternary additives added was 2.5 wt% of the mass of aluminum nitride powder, ball-milled for 4 hours at a ball-to-material ratio of 8:1 and a rotation speed of 280 rpm, and dried for 12 hours at 60℃ and vacuum degree of -0.09 MPa before passing through a 200-mesh sieve to obtain composite aluminum nitride powder with low lattice oxygen content; (4) The composite aluminum nitride powder with low lattice oxygen content was added to the mixed solvent, which was prepared by mixing xylene and anhydrous ethanol in a volume ratio of 1:1 to make its solid content reach 52wt%. 2.5wt% of acrylic binder, 1.2wt% of dibutyl phthalate plasticizer and 0.5wt% of polyetheramine dispersant were added sequentially. The mixture was stirred under double planetary vacuum for 4h and vacuum degassing for 30min to obtain a casting slurry with a viscosity of 15000mPa·s. The slurry was cast on a PET carrier with a doctor blade gap of 0.3mm and a casting speed of 0.8m / min. The drying temperature was controlled in stages at 60℃, 80℃, 100℃ and 120℃ to obtain a green body with a thickness of 0.15mm. The green body sample was obtained by stamping. (5) The green sample was heated from room temperature to 1300℃ at a rate of 5℃ / min. A mixed gas A consisting of nitrogen and hydrogen in a mass ratio of 95:5 was introduced at a rate of 2L / min and kept at this temperature for 2h. This temperature is lower than the eutectic point of the ternary additive, and no liquid phase is generated. The green body remains porous. The active C / N atoms in the coating layer undergo a carbothermic reduction nitridation reaction with the aluminum oxide on the surface of the aluminum nitride powder. The trace oxygen in the hydrogen-assisted reducing atmosphere reacts with the residual oxide layer of the powder. The carbon monoxide and water vapor generated by the reaction are completely discharged from the system through the porous green body, thus achieving surface oxygen removal. At the same time, the doped N atoms are in situ. The N vacancies generated by reduction are replenished to avoid lattice defects. Then, the temperature is increased to 1500℃ at a rate of 3℃ / min and held for 4 hours. This temperature is higher than the eutectic point of the ternary additive, and the additive forms a uniform non-oxygen eutectic liquid phase, which fills the pores of the green body and achieves rapid densification at low temperature. At the same time, Ge atoms in the liquid phase rapidly diffuse into the aluminum nitride lattice and form strong Ge-O bonds with interstitial oxygen and replaced oxygen in the lattice. This quantitatively replaces oxygen from the aluminum nitride lattice and fixes it at the grain boundary to form a stable Ge-Si-ON grain boundary phase, preventing the lattice re-dissolution of oxygen and achieving simultaneous densification and deep removal of lattice oxygen. (6) Finally, the temperature is lowered to 1000℃ at a rate of 2℃ / min, and a mixed gas B composed of nitrogen and ammonia in a mass ratio of 95:5 is introduced at a rate of 2L / min. The temperature is maintained for 1h. During the cooling process, the active N atoms decomposed by ammonia repair the N vacancies at the grain boundaries. The Si element in the additive reacts with the trace oxygen at the grain boundaries to form a dense Si-ON passivation layer at the grain boundaries, which prevents oxygen from diffusing into the lattice during long-term use. The furnace is naturally cooled to room temperature, and the sintered substrate is ground on both sides to remove the surface oxide layer, resulting in aluminum nitride material with low lattice oxygen content. Example 3

[0020] (1) Add aluminum nitride powder with a particle size of 1 μm to a 95 wt% ethanol aqueous solution to make its solid content reach 30 wt%. Then add vinyltrimethoxysilane coupling agent with a mass of 0.01 times the powder and adjust the pH to 4.5 with 1M acetic acid. Stir and reflux at 65℃ and 800 rpm for 3 h. Filter and wash three times with anhydrous ethanol. Dry at 50℃ and vacuum degree -0.09 MPa for 12 h to obtain pretreated aluminum nitride. (2) Pretreated aluminum nitride, resorcinol, melamine, 37% formaldehyde aqueous solution and 70wt% ethanol aqueous solution were mixed in a mass ratio of 10:0.05:0.15:0.16:20. Under a nitrogen atmosphere, the pH was adjusted to 8.5 with 0.2M ammonia water. The mixture was stirred at 30℃ and 300rpm for 6h to form a uniform resin coating layer on the surface of the aluminum nitride powder. After filtration, the mixture was dried at 50℃ and vacuum degree -0.09MPa for 12h. Then, under a high-purity nitrogen atmosphere, the temperature was raised to 600℃ at a heating rate of 2℃ / min and held for 2h. The mixture was then cooled with the furnace to obtain the surface-coated aluminum nitride powder. (3) Silicon nitride, boron nitride, germanium nitride, isopropanol and polyetheramine dispersant were mixed in a mass ratio of 6:3:1:10:0.1 and ball-milled for 2 hours at a ball-to-material ratio of 5:1 at a speed of 300 rpm to obtain a uniformly dispersed additive slurry, thus avoiding agglomeration of nanoparticles; aluminum nitride powder coated on the surface was added to the additive slurry so that the total amount of ternary additives added was 3.5 wt% of the mass of aluminum nitride powder, ball-milled for 4 hours at a ball-to-material ratio of 8:1 at a speed of 280 rpm, and dried for 12 hours at 60℃ and vacuum degree of -0.09 MPa before passing through a 200-mesh sieve to obtain composite aluminum nitride powder with low lattice oxygen content; (4) The composite aluminum nitride powder with low lattice oxygen content was added to the mixed solvent, which was prepared by mixing xylene and anhydrous ethanol in a volume ratio of 1:1 to make its solid content reach 55wt%. 3wt% of the powder mass of acrylic binder, 1.5wt% of dibutyl phthalate plasticizer and 0.5wt% of polyetheramine dispersant were added in sequence. The mixture was stirred under double planetary vacuum for 4h and vacuum degassing for 30min to obtain a casting slurry with a viscosity of 15000mPa・s. The slurry was cast on a PET carrier with a doctor blade gap of 0.3mm and a casting speed of 0.8m / min. The drying temperature was controlled in segments of 60℃, 80℃, 100℃ and 120℃ to obtain a green body with a thickness of 0.2mm. The green body sample was obtained by stamping. (5) The green sample was heated from room temperature to 1300℃ at a rate of 5℃ / min. A mixed gas A consisting of nitrogen and hydrogen in a mass ratio of 95:5 was introduced at a rate of 2L / min and kept at this temperature for 2h. This temperature is lower than the eutectic point of the ternary additive, and no liquid phase is generated. The green body remains porous. The active C / N atoms in the coating layer undergo a carbothermic reduction nitridation reaction with the aluminum oxide on the surface of the aluminum nitride powder. The trace oxygen in the hydrogen-assisted reducing atmosphere reacts with the residual oxide layer of the powder. The carbon monoxide and water vapor generated by the reaction are completely discharged from the system through the porous green body, thus achieving surface oxygen removal. At the same time, the doped N atoms are in situ. The N vacancies generated by reduction are replenished to avoid lattice defects. Then, the temperature is increased to 1500℃ at a rate of 3℃ / min and held for 4 hours. This temperature is higher than the eutectic point of the ternary additive, and the additive forms a uniform non-oxygen eutectic liquid phase, which fills the pores of the green body and achieves rapid densification at low temperature. At the same time, Ge atoms in the liquid phase rapidly diffuse into the aluminum nitride lattice and form strong Ge-O bonds with interstitial oxygen and replaced oxygen in the lattice. This quantitatively replaces oxygen from the aluminum nitride lattice and fixes it at the grain boundary to form a stable Ge-Si-ON grain boundary phase, preventing the lattice re-dissolution of oxygen and achieving simultaneous densification and deep removal of lattice oxygen. (6) Finally, the temperature is lowered to 1000℃ at a rate of 2℃ / min, and a mixed gas B composed of nitrogen and ammonia in a mass ratio of 95:5 is introduced at a rate of 2L / min. The temperature is maintained for 1h. During the cooling process, the active N atoms decomposed by ammonia repair the N vacancies at the grain boundaries. The Si element in the additive reacts with the trace oxygen at the grain boundaries to form a dense Si-ON passivation layer at the grain boundaries, which prevents oxygen from diffusing into the lattice during long-term use. The furnace is naturally cooled to room temperature, and the sintered substrate is ground on both sides to remove the surface oxide layer, resulting in aluminum nitride material with low lattice oxygen content. Example 4

[0021] (1) Add aluminum nitride powder with a particle size of 1 μm to a 95 wt% ethanol aqueous solution to make its solid content reach 30 wt%. Then add vinyltrimethoxysilane coupling agent with a mass of 0.01 times the powder and adjust the pH to 4.5 with 1M acetic acid. Stir and reflux at 65℃ and 800 rpm for 3 h. Filter and wash three times with anhydrous ethanol. Dry at 50℃ and vacuum degree -0.09 MPa for 12 h to obtain pretreated aluminum nitride. (2) Pretreated aluminum nitride, resorcinol, melamine, 37% formaldehyde aqueous solution and 70wt% ethanol aqueous solution were mixed in a mass ratio of 10.5:0.055:0.18:0.18:20. Under a nitrogen atmosphere, the pH was adjusted to 8.5 with 0.2M ammonia water. The mixture was stirred at 32℃ and 300rpm for 6.5h to form a uniform resin coating layer on the surface of the aluminum nitride powder. After filtration, the mixture was dried at 50℃ and vacuum degree -0.09MPa for 12h. Then, under a high-purity nitrogen atmosphere, the temperature was raised to 600℃ at a heating rate of 2℃ / min and held for 2h. The mixture was then cooled with the furnace to obtain the surface-coated aluminum nitride powder. (3) Silicon nitride, boron nitride, germanium nitride, isopropanol and polyetheramine dispersant were mixed in a mass ratio of 6.5:3.5:1:10:0.1 and ball-milled for 2 hours at a ball-to-material ratio of 5:1 and a rotation speed of 300 rpm to obtain a uniformly dispersed additive slurry, thus avoiding agglomeration of nanoparticles; aluminum nitride powder coated on the surface was added to the additive slurry so that the total amount of ternary additives added was 4.5 wt% of the mass of aluminum nitride powder, ball-milled for 4 hours at a ball-to-material ratio of 8:1 and a rotation speed of 280 rpm, and dried for 12 hours at 60℃ and vacuum degree of -0.09 MPa before passing through a 200-mesh sieve to obtain composite aluminum nitride powder with low lattice oxygen content; (4) The composite aluminum nitride powder with low lattice oxygen content was added to the mixed solvent, which was prepared by mixing xylene and anhydrous ethanol in a volume ratio of 1:1 to make its solid content reach 58wt%. 3.5wt% of acrylic binder, 1.8wt% of dibutyl phthalate plasticizer and 0.5wt% of polyetheramine dispersant were added sequentially. The mixture was stirred under double planetary vacuum for 4h and vacuum degassing for 30min to obtain a casting slurry with a viscosity of 15000mPa·s. The slurry was cast on a PET carrier with a doctor blade gap of 0.3mm and a casting speed of 0.8m / min. The drying temperature was controlled in segments of 60℃, 80℃, 100℃ and 120℃ to obtain a green body with a thickness of 0.25mm. The green body sample was obtained by stamping. (5) The green sample was heated from room temperature to 1300℃ at a rate of 5℃ / min. A mixed gas A consisting of nitrogen and hydrogen in a mass ratio of 95:5 was introduced at a rate of 2L / min and kept at this temperature for 2h. This temperature is lower than the eutectic point of the ternary additive, and no liquid phase is generated. The green body remains porous. The active C / N atoms in the coating layer undergo a carbothermic reduction nitridation reaction with the aluminum oxide on the surface of the aluminum nitride powder. The trace oxygen in the hydrogen-assisted reducing atmosphere reacts with the residual oxide layer of the powder. The carbon monoxide and water vapor generated by the reaction are completely discharged from the system through the porous green body, thus achieving surface oxygen removal. At the same time, the doped N atoms are in situ. The N vacancies generated by reduction are replenished to avoid lattice defects. Then, the temperature is increased to 1500℃ at a rate of 3℃ / min and held for 4 hours. This temperature is higher than the eutectic point of the ternary additive, and the additive forms a uniform non-oxygen eutectic liquid phase, which fills the pores of the green body and achieves rapid densification at low temperature. At the same time, Ge atoms in the liquid phase rapidly diffuse into the aluminum nitride lattice and form strong Ge-O bonds with interstitial oxygen and replaced oxygen in the lattice. This quantitatively replaces oxygen from the aluminum nitride lattice and fixes it at the grain boundary to form a stable Ge-Si-ON grain boundary phase, preventing the lattice re-dissolution of oxygen and achieving simultaneous densification and deep removal of lattice oxygen. (6) Finally, the temperature is lowered to 1000℃ at a rate of 2℃ / min, and a mixed gas B composed of nitrogen and ammonia in a mass ratio of 95:5 is introduced at a rate of 2L / min. The temperature is maintained for 1h. During the cooling process, the active N atoms decomposed by ammonia repair the N vacancies at the grain boundaries. The Si element in the additive reacts with the trace oxygen at the grain boundaries to form a dense Si-ON passivation layer at the grain boundaries, which prevents oxygen from diffusing into the lattice during long-term use. The furnace is naturally cooled to room temperature, and the sintered substrate is ground on both sides to remove the surface oxide layer, resulting in aluminum nitride material with low lattice oxygen content. Example 5

[0022] (1) Add aluminum nitride powder with a particle size of 1 μm to a 95 wt% ethanol aqueous solution to make its solid content reach 30 wt%. Then add vinyltrimethoxysilane coupling agent with a mass of 0.01 times the powder and adjust the pH to 4.5 with 1M acetic acid. Stir and reflux at 65℃ and 800 rpm for 3 h. Filter and wash three times with anhydrous ethanol. Dry at 50℃ and vacuum degree -0.09 MPa for 12 h to obtain pretreated aluminum nitride. (2) Pretreated aluminum nitride, resorcinol, melamine, 37% formaldehyde aqueous solution and 70wt% ethanol aqueous solution were mixed in a mass ratio of 11:0.06:0.2:0.2:20. Under a nitrogen atmosphere, the pH was adjusted to 8.5 with 0.2M ammonia water. The mixture was stirred at 35℃ and 300rpm for 7h to form a uniform resin coating layer on the surface of the aluminum nitride powder. After filtration, the mixture was dried at 50℃ and vacuum degree -0.09MPa for 12h. Then, under a high-purity nitrogen atmosphere, the temperature was raised to 600℃ at a heating rate of 2℃ / min and held for 2h. The mixture was then cooled with the furnace to obtain the surface-coated aluminum nitride powder. (3) Silicon nitride, boron nitride, germanium nitride, isopropanol and polyetheramine dispersant were mixed in a mass ratio of 7:4:1:10:0.1 and ball-milled for 2 hours at a ball-to-material ratio of 5:1 at a speed of 300 rpm to obtain a uniformly dispersed additive slurry, thus avoiding agglomeration of nanoparticles; aluminum nitride powder coated on the surface was added to the additive slurry so that the total amount of ternary additives added was 5 wt% of the mass of aluminum nitride powder, ball-milled for 4 hours at a ball-to-material ratio of 8:1 at a speed of 280 rpm, and dried for 12 hours at 60℃ and vacuum degree of -0.09 MPa before passing through a 200-mesh sieve to obtain composite aluminum nitride powder with low lattice oxygen content; (4) The composite aluminum nitride powder with low lattice oxygen content was added to the mixed solvent, which was prepared by mixing xylene and anhydrous ethanol in a volume ratio of 1:1 to make its solid content reach 60wt%. 4wt% of the powder mass of acrylic binder, 2wt% of dibutyl phthalate plasticizer, and 0.5wt% of polyetheramine dispersant were added in sequence. The mixture was stirred under double planetary vacuum for 4h and vacuum degassing for 30min to obtain a casting slurry with a viscosity of 15000mPa・s. The slurry was cast on a PET carrier with a doctor blade gap of 0.3mm and a casting speed of 0.8m / min. The drying temperature was controlled in segments of 60℃, 80℃, 100℃, and 120℃ to obtain a green body with a thickness of 0.3mm. The green body sample was obtained by stamping. (5) The green sample was heated from room temperature to 1300℃ at a rate of 5℃ / min. A mixed gas A consisting of nitrogen and hydrogen in a mass ratio of 95:5 was introduced at a rate of 2L / min and kept at this temperature for 2h. This temperature is lower than the eutectic point of the ternary additive, and no liquid phase is generated. The green body remains porous. The active C / N atoms in the coating layer undergo a carbothermic reduction nitridation reaction with the aluminum oxide on the surface of the aluminum nitride powder. The trace oxygen in the hydrogen-assisted reducing atmosphere reacts with the residual oxide layer of the powder. The carbon monoxide and water vapor generated by the reaction are completely discharged from the system through the porous green body, thus achieving surface oxygen removal. At the same time, the doped N atoms are in situ. The N vacancies generated by reduction are replenished to avoid lattice defects. Then, the temperature is increased to 1500℃ at a rate of 3℃ / min and held for 4 hours. This temperature is higher than the eutectic point of the ternary additive, and the additive forms a uniform non-oxygen eutectic liquid phase, which fills the pores of the green body and achieves rapid densification at low temperature. At the same time, Ge atoms in the liquid phase rapidly diffuse into the aluminum nitride lattice and form strong Ge-O bonds with interstitial oxygen and replaced oxygen in the lattice. This quantitatively replaces oxygen from the aluminum nitride lattice and fixes it at the grain boundary to form a stable Ge-Si-ON grain boundary phase, preventing the lattice re-dissolution of oxygen and achieving simultaneous densification and deep removal of lattice oxygen. (6) Finally, the temperature is lowered to 1000℃ at a rate of 2℃ / min, and a mixed gas B composed of nitrogen and ammonia in a mass ratio of 95:5 is introduced at a rate of 2L / min. The temperature is maintained for 1h. During the cooling process, the active N atoms decomposed by ammonia repair the N vacancies at the grain boundaries. The Si element in the additive reacts with the trace oxygen at the grain boundaries to form a dense Si-ON passivation layer at the grain boundaries, which prevents oxygen from diffusing into the lattice during long-term use. The furnace is naturally cooled to room temperature, and the sintered substrate is ground on both sides to remove the surface oxide layer, resulting in aluminum nitride material with low lattice oxygen content.

[0023] Comparative Example 1 The difference between Comparative Example 1 and Example 3 is that step (1) is omitted, and step (2) is changed to: aluminum nitride with a particle size of 1 μm, resorcinol, melamine, 37% formaldehyde aqueous solution and 70wt% ethanol aqueous solution are mixed in a mass ratio of 10:0.05:0.15:0.16:20. Under a nitrogen atmosphere, the pH is adjusted to 8.5 with 0.2M ammonia water and stirred at 300 rpm for 6 h at 30 °C. A uniform resin coating layer is formed in situ on the surface of the aluminum nitride powder. After filtration, the powder is dried at 50 °C and vacuum degree -0.09 MPa for 12 h. Then, under a high-purity nitrogen atmosphere, the temperature is raised to 600 °C at a heating rate of 2 °C / min and held for 2 h. The powder is then cooled with the furnace to obtain the surface-coated aluminum nitride powder. The remaining steps are the same as in Example 3.

[0024] Comparative Example 2 The difference between Comparative Example 2 and Example 3 is that steps (1) and (2) are omitted, and step (3) is changed to: mixing silicon nitride, boron nitride, germanium nitride, isopropanol and polyetheramine dispersant in a mass ratio of 6:3:1:10:0.1, ball milling for 2 hours with a ball-to-material ratio of 5:1 and a rotation speed of 300 rpm to obtain a uniformly dispersed additive slurry, thus avoiding the agglomeration of nanoparticles; adding aluminum nitride powder with a particle size of 1 μm to the additive slurry so that the total amount of ternary additives added is 3.5 wt% of the mass of aluminum nitride powder, ball milling for 4 hours with a ball-to-material ratio of 8:1 and a rotation speed of 280 rpm, drying at 60°C and a vacuum degree of -0.09 MPa for 12 hours, and then passing through a 200-mesh sieve to obtain composite aluminum nitride powder with low lattice oxygen content. The remaining steps are the same as in Example 3.

[0025] Comparative Example 3 The difference between Comparative Example 3 and Example 3 is that steps (1), (2), and (3) are omitted, and step (4) is changed to: aluminum nitride powder with a particle size of 1 μm is added to a mixed solvent, which is prepared by mixing xylene and anhydrous ethanol at a volume ratio of 1:1 to make its solid content reach 55 wt%. 3 wt% of acrylic binder, 1.5 wt% of dibutyl phthalate plasticizer, and 0.5 wt% of polyetheramine dispersant are added sequentially. The mixture is stirred under double planetary vacuum for 4 h and vacuum degassed for 30 min to obtain a casting slurry with a viscosity of 15000 mPa·s. The slurry is cast on a PET carrier with a doctor blade gap of 0.3 mm and a casting speed of 0.8 m / min. The drying temperature is controlled in segments of 60℃, 80℃, 100℃, and 120℃ to obtain a green body with a thickness of 0.2 mm. The green body sample is obtained by stamping. The remaining steps are the same as in Example 3.

[0026] Comparative Example 4 The difference between Comparative Example 4 and Example 3 is that there is no annealing stage; the remaining steps are the same as in Example 3.

[0027] Comparative Example 5 The difference between Comparative Example 5 and Example 3 is that steps (5) and (6) are omitted, and the green sample is sintered in a conventional manner. The remaining steps are the same as in Example 3.

[0028] Comparative Example 6 The difference between Comparative Example 6 and Example 3 is that aluminum nitride powder with a particle size of 1 μm was used as a blank group and conventional sintering was performed.

[0029] Example of effect Table 1 below shows the performance analysis results of aluminum nitride powders from Examples 1 to 5 and Comparative Examples 1 to 6 of the present invention.

[0030] Table 1

[0031] A comparison of experimental data on lattice oxygen content in the examples and comparative examples reveals that the present invention pre-treated aluminum nitride powder is coated with a nitrogen-containing resin precursor through in-situ polymerization, followed by low-temperature pyrolysis to obtain surface-modified aluminum nitride powder with low lattice oxygen content. This powder is then compounded with a ternary eutectic nitride additive formed by silicon nitride, boron nitride, and germanium nitride in a specific ratio. After low-temperature reduction, high-temperature densification, and annealing, aluminum nitride material with low lattice oxygen content is obtained. The surface of the coated aluminum nitride powder has a surface coating layer that isolates air and moisture, preventing secondary oxidation. Simultaneously, during the low-temperature reduction stage, the active carbon atoms in the coating layer undergo a carbothermic reduction nitridation reaction with the aluminum oxide on the aluminum nitride surface. The trace oxygen in the hydrogen-assisted reducing atmosphere, along with the generated carbon monoxide and moisture, can be completely discharged through the green body. During the high-temperature stage, the ternary... The additives form a eutectic liquid phase, in which germanium atoms undergo a lattice oxygen substitution reaction with oxygen in the aluminum nitride lattice, forming a stable Ge-Si-ON grain boundary phase. This prevents oxygen lattice re-dissolution, achieving simultaneous densification and deoxidation. During the annealing stage, the formed Si-ON passivation layer completely seals oxygen within the grain boundaries. These stages work synergistically to achieve a low lattice oxygen content. A comparison of the room temperature thermal conductivity experimental data from the examples and comparative examples reveals that the doped nitrogen atoms in the coating layer of this invention replenish nitrogen vacancies generated by oxygen removal in situ, repairing lattice distortion. Simultaneously, germanium atoms substitute lattice oxygen to eliminate Al-ON point defects, synergistically reducing phonon scattering with the densified grain boundary layer, further improving the thermal conductivity of aluminum nitride. A comparison of the damp heat aging resistance experimental data from the examples and comparative examples reveals that the components of this invention synergistically impart excellent damp heat aging resistance to the material.

[0032] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. An aluminum nitride powder having a low lattice oxygen content, characterized by Includes the following steps: (1) Aluminum nitride powder pretreated with silane coupling agent, resorcinol, melamine, 37% formaldehyde aqueous solution and 70wt% ethanol aqueous solution are mixed in a mass ratio of 9~11:0.04~0.06:0.1~0.2:0.1~0.2:

20. Under nitrogen atmosphere, the pH is adjusted to 8.5 and stirred at 25~35℃ for 5~7h. After filtration, the mixture is vacuum dried at 50℃ for 12h. Under nitrogen atmosphere, the temperature is raised to 600℃ at a heating rate of 2℃ / min and held for 2h. The mixture is then cooled with the furnace to obtain aluminum nitride powder with surface coating. (2) Silicon nitride, boron nitride, germanium nitride, isopropanol and dispersant are mixed in a mass ratio of 5~7:2~4:1:10:0.1, with a ball-to-material ratio of 5:

1. The mixture is then ball-milled for 2 hours to obtain an additive slurry. The aluminum nitride powder coated on the surface is added to the additive slurry, so that the total amount of the ternary additive is 2~5wt% of the mass of the aluminum nitride powder. The mixture is then ball-milled for 4 hours with a ball-to-material ratio of 8:

1. After vacuum drying at 60℃ for 12 hours, the mixture is passed through a 200-mesh sieve to obtain a composite aluminum nitride powder with low lattice oxygen content.

2. The aluminum nitride powder with low lattice oxygen content according to claim 1, characterized in that, The silane coupling agent in step (1) is: vinyltrimethoxysilane coupling agent.

3. The aluminum nitride powder with low lattice oxygen content according to claim 1, characterized in that, The aluminum nitride powder mentioned in step (1) is aluminum nitride powder with a particle size of 1 μm.

4. The aluminum nitride powder with low lattice oxygen content according to claim 1, characterized in that, The dispersant in step (2) is a polyetheramine dispersant with a molecular weight of 2000.

5. An application of an aluminum nitride powder with low lattice oxygen content, characterized in that, Includes the following steps: (1) Add composite aluminum nitride powder with low lattice oxygen content to a mixed solvent to make its solid content reach 50~60wt%. Then add 2~4wt% of the powder mass of binder, 1~2wt% of plasticizer and 0.5wt% of polyetheramine dispersant. Stir in a double planetary vacuum for 4h and vacuum degas for 30min to obtain casting slurry. Cast the slurry with a doctor blade gap of 0.3mm and a casting speed of 0.8m / min. Dry to obtain green body and punch to obtain green body sample. (2) The green sample was heated from room temperature to 1300℃ at a rate of 5℃ / min, and mixed gas A was introduced at a rate of 2L / min and kept at the temperature for 2h; then the temperature was increased to 1500℃ at a rate of 3℃ / min and kept at the temperature for 4h; finally, the temperature was decreased to 1000℃ at a rate of 2℃ / min, and mixed gas B was introduced at a rate of 2L / min and kept at the temperature for 1h. The substrate is naturally cooled to room temperature in the furnace, and then the sintered substrate is ground on both sides to remove the surface oxide layer, resulting in aluminum nitride material with low lattice oxygen content.

6. The application of the aluminum nitride powder with low lattice oxygen content according to claim 5, characterized in that, The mixed solvent in step (1) is prepared by mixing xylene and anhydrous ethanol in a volume ratio of 1:

1.

7. The application of the aluminum nitride powder with low lattice oxygen content according to claim 5, characterized in that, The adhesive used in step (1) is an acrylic adhesive.

8. The application of the aluminum nitride powder with low lattice oxygen content according to claim 5, characterized in that, The plasticizer mentioned in step (1) is dibutyl phthalate plasticizer.

9. The application of the aluminum nitride powder with low lattice oxygen content according to claim 5, characterized in that, The mixed gas A mentioned in step (2) is composed of nitrogen and hydrogen in a mass ratio of 95:

5.

10. The application of the aluminum nitride powder with low lattice oxygen content according to claim 5, characterized in that, The mixed gas B mentioned in step (2) is composed of nitrogen and ammonia in a mass ratio of 95:5.

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