A method for preparing molybdenum aluminum nitride based on interface whisker growth

Abstract

This invention belongs to the field of powder processing technology and discloses a method for preparing aluminum nitride with graphene based on interfacial whisker growth. The method involves pre-treating aluminum nitride powder in a chemical vapor deposition process to introduce an Fe source. The Fe source acts as a catalytic active site, catalyzing the formation of nanoparticles on the aluminum nitride surface. This induces the Al and N atoms on the aluminum nitride surface to combine with oxygen from the iron source, catalyzing the directional growth of high aspect ratio Al-Fe-O or AlN nanofibers on the aluminum nitride surface. Graphene coating is then applied, simultaneously completing the interweaving and entanglement with the whiskers to form a three-dimensional interlocked stable structure. Defects are eliminated through low-temperature vacuum annealing, further strengthening the interfacial bonding. This method is highly operable, better suited for downstream product processes, fully utilizing the structural combination function, and improving the strength and impact resistance of downstream composite materials.

Description

Technical Field

[0001] This invention belongs to the field of powder processing technology, specifically a method for preparing montmorillonite aluminum nitride based on interface whisker growth. Background Technology

[0002] Aluminum nitride (AlN) is an excellent inorganic non-metallic material, possessing both high thermal conductivity (theoretical value ~320 W / m²) and high thermal conductivity. -1 K -1 Aluminum nitride (AN) powder, with its low dielectric constant, thermal expansion coefficient matching that of silicon, and excellent high-temperature stability, has irreplaceable application value in fields such as electronic packaging, power device heat dissipation, and high-temperature structural materials. Coating AN powder with graphene (graphene-coated AN) not only solves its susceptibility to hydrolysis but also further enhances its thermal and electrical conductivity, expanding its application scenarios. However, AN powder itself has significant limitations, particularly its susceptibility to hydrolysis in humid environments, leading to performance degradation and limiting its application in a wider range of scenarios. In-situ growth or coating of AN powder with graphene using chemical vapor deposition can overcome the hydrolysis problem. The graphene layer not only acts as a dense physical barrier to prevent water molecule contact but also utilizes its inherent high electrical and thermal conductivity to further synergistically improve the overall performance of the composite material.

[0003] Patent CN120210761A discloses a graphene-coated inorganic non-metallic powder composite material and its preparation method. This method uses chemical vapor deposition to fix a metal catalyst (Fe) (foam / foam) or a mixed large-particle-size non-metallic porous catalyst in the low-temperature region of the reactor, thereby achieving in-situ growth of graphene. However, the graphene is only bonded to the aluminum nitride matrix through van der Waals forces and does not form any mechanical interlocking or strong chemical bonding structure. The interfacial bonding force is insufficient, and the sintering process is prone to separation, resulting in a significant decrease in the mechanical properties and thermal conductivity of the composite material. This technology has many problems and cannot be widely used.

[0004] In summary, while there are indeed technologies for coating inorganic non-metallic powders with graphene in the field of powder processing, there are still problems such as insufficient interfacial bonding, easy separation during sintering, and difficulty in bonding the coating layer due to its low surface energy. Therefore, it is of great significance to develop a graphene-coated aluminum nitride preparation technology with strong interfacial bonding and interface strengthening designed for the surface characteristics of aluminum nitride. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing aluminum nitride with graphene based on interfacial whisker growth. The method involves pretreating aluminum nitride powder with an Fe source during chemical vapor deposition (CVD). The Fe source acts as a catalytic active site, catalyzing the formation of nanoparticles on the aluminum nitride surface. This induces the Al and N atoms on the aluminum nitride surface to combine with oxygen from the iron source, catalyzing the directional growth of high aspect ratio Al-Fe-O or AlN nanofibers on the aluminum nitride surface. Graphene is then applied, simultaneously completing the interweaving and entanglement with the whiskers to form a three-dimensional interlocked stable structure. Finally, low-temperature vacuum annealing eliminates defects and further strengthens the interfacial bonding.

[0006] The objective of this invention is achieved through the following solution: A method for preparing montmorillonite aluminum nitride based on interface whisker growth includes the following steps: S1, iron source and aluminum nitride powder are dissolved in anhydrous ethanol, ultrasonically dispersed and rotary evaporated to obtain iron source-loaded aluminum nitride powder, placed in a fluidized bed reactor and argon gas is introduced, and the iron source is reduced by introducing an Ar / H2 mixed atmosphere to catalyze the growth of nano whiskers. S2, Maintain an argon atmosphere, increase the temperature and introduce a mixed gas of carbon source and hydrogen to grow and coat graphene. S3, stop the supply of carbon source and hydrogen, keep argon purging to lower the temperature, transfer to high temperature furnace, vacuum anneal, and cool to obtain montmorillonite aluminum nitride.

[0007] Preferably, the specific steps of S1 are as follows: dissolve the iron source and aluminum nitride powder in anhydrous ethanol, ultrasonically disperse for 15-30 min, remove the solvent by rotary evaporation at 60-85℃ to obtain iron source-loaded aluminum nitride powder, place the iron source-loaded aluminum nitride powder in a fluidized bed reactor, purge with argon gas for 30 min, raise the temperature to 300-500℃, introduce an Ar / H2 mixed atmosphere, and keep at this temperature for 0.5-2 h to reduce the iron source and catalyze the growth of nanocrystals.

[0008] Iron source is reduced to Fe / Fe3O4 nanoparticles under a reducing atmosphere. The nanoparticles serve as catalytic active sites, inducing Al and N atoms on the surface of aluminum nitride to combine with oxygen in the iron source, catalyzing the directional growth of aluminum nitride surface to form nanowhiskers. One end of the whisker is firmly bonded to the aluminum nitride matrix, while the other end is exposed on the powder surface.

[0009] In Fe / Fe3O4 composite nanoparticles, Fe provides high catalytic activity and affinity for Al, weakening the adjacent Al-N bonds and making the surface Al atoms more active, easier to migrate and react. The lattice oxygen in Fe3O4 provides an oxygen source, which combines with the activated Al atoms at the interface to form Al-O bonds. The nanoparticles are uniformly attached to the surface of aluminum nitride and are activated in a reducing atmosphere to a high-energy state. The interfacial reaction forms an Al-O supersaturated region at the contact point between the catalyst particles and AlN. Al-Fe-O compounds or AlN precipitate in solid form, forming the initial nuclei of whiskers. The released Al atoms diffuse along the surface of the catalyst particles to the growth front of the crystal nuclei. Due to the anisotropy of the growing crystal itself, the growth of the crystal nuclei is restricted to one direction, thereby obtaining a high aspect ratio. Finally, the roots are chemically bonded to the AlN matrix, and the other end is exposed.

[0010] Preferably, the specific steps of S2 are as follows: maintain an inert argon atmosphere in the fluidized bed, adjust the temperature to 700~850℃, introduce a mixed gas of carbon source and hydrogen, keep warm for 10~30 min, and grow coated graphene.

[0011] If the temperature is too low, the carbon source will not be fully decomposed, and amorphous carbon or carbon black will easily be generated, resulting in poor graphene crystal quality. If the temperature is too high, the aluminum nitride surface will be unstable, the iron catalyst will be deactivated by sintering too quickly, and the number of graphene layers will be difficult to control. The carbon source decomposes at the Fe catalytic sites and on the surface of the nanocrystals, producing active carbon atoms and hydrogen atoms. When the carbon in the catalyst reaches supersaturation, it begins to precipitate at the catalyst-whisker interface and grow laterally. During the growth process, the two-dimensional graphene sheet covers the surface of the aluminum nitride matrix, wraps and bridges adjacent whiskers, and is connected by covalent bonds to form a three-dimensional interlocking graphene network.

[0012] Preferably, the specific steps of S3 are as follows: stop the supply of carbon source and hydrogen, maintain argon purging, cool to room temperature, stop argon purging, remove the material and transfer it to a high-temperature furnace, and set the vacuum degree inside the furnace to 10. -3 ~10 -5 Pa, heat to 300~500℃, hold for 2~3 h for vacuum annealing, cool to room temperature after completion, and collect the material to obtain montmorillonite aluminum nitride.

[0013] Low-temperature vacuum annealing eliminates impurity molecules and interface defects in the graphite layer, fills vacancies, and promotes the formation of covalent bonds such as CO-Al and C-Fe between graphene and nanocrystals and aluminum nitride surfaces, further strengthening the interfacial bonding force.

[0014] Preferably, the iron source in step S1 is one or more of ferric nitrate, ferric chloride, or ferric acetylacetone, and the mass of the iron source is 0.05-1% of the mass of the aluminum nitride powder.

[0015] Preferably, the aluminum nitride powder has a mass of 90-110g and a powder size of 5-100 μm.

[0016] Fe has a good affinity with Al and can form iron-aluminum oxides, providing a crystal template. However, metals such as Ni and Co have a weak ability to catalyze the reaction of AlN and O to form aluminum oxide whiskers. They have poor affinity and are not easy to form stable eutectics or compounds to guide the directional assembly of Al-O bonds.

[0017] Preferably, in step S1, the total flow rate of the Ar / H2 mixed atmosphere is 16 L / min, and the volume ratio of Ar to H2 is 1:(5-10).

[0018] H2 acts as a reducing agent, reducing the AlN nanoparticles to Fe / Fe3O4. Diluting H2 prevents excessive reduction, which could lead to rapid agglomeration of the nanoparticles, excessive denitrification of the AlN surface, or even reduction to metallic aluminum, thus damaging the surface structure and making it impossible to controllably grow whiskers.

[0019] Preferably, the nanocrystals in step S1 are Al-Fe-O or AlN nanocrystals with an aspect ratio of 10-50.

[0020] In the catalyst particles, lattice oxygen combines with activated Al atoms at the Fe catalyst interface to form Al-O bonds. Neighboring Al atoms are added to the reaction interface through surface diffusion. Under the action of H2, N rearrangement occurs on the surface, forming an Al-rich region. Activated Al atoms, guided by the Fe catalyst, precipitate and grow directionally in the form of AlN. The extracted Al-O-Fe or Al-N units reach supersaturation at the catalyst / matrix interface and undergo heterogeneous nucleation on the specific crystal plane with the lowest energy. The whisker roots form strong chemical bonds with the AlN matrix.

[0021] Preferably, in step S2, the total flow rate of the mixed gas of carbon source and hydrogen is 22 L / min; the carbon source is one of methane, acetylene or ethylene, and the flow rate ratio of carbon source to hydrogen is 1:(5~20).

[0022] The carbon source provides carbon atoms for graphene growth; hydrogen works synergistically with the carbon source to react on the catalyst surface, promoting the breaking of carbon-hydrogen bonds and generating active carbon species. Hydrogen etches the amorphous carbon and defective graphene formed during the growth process, promoting the growth of high-quality graphene and maintaining the iron catalyst in a reduced state of metallic activity, preventing it from being oxidized and deactivated.

[0023] Preferably, the coating rate of the aluminum nitride before mechanical polishing is 98.5-99.2%, and the coating rate after mechanical polishing is 94.2-98.8%.

[0024] The beneficial effects of this invention are as follows: (1) Through in-situ catalytic growth, a three-dimensional interlocked structure of nano-whiskers chemically bonded to the matrix was constructed on the surface of aluminum nitride, which improved the combination of graphene and aluminum nitride in the graphene aluminum nitride from the traditional van der Waals force combination to mechanical interlocking and chemical synergistic combination. (2) The high strength and whisker toughening effect of graphene in the aluminum nitride prepared by this method are highly operable and can better match the downstream product process application, giving full play to the combination function of the structure and improving the strength and impact resistance of the downstream product composite material. Attached Figure Description

[0025] Figure 1 Example 1: SEM image before grinding.

[0026] Figure 2 Example 1: SEM image after grinding.

[0027] Figure 3 Example 1: EDS image of the covered area.

[0028] Figure 4 Example 1: EDS image of the exposed area.

[0029] Figure 5 Comparative Example 1: SEM image before grinding.

[0030] Figure 6 Comparative Example 1: SEM image after grinding. Detailed Implementation

[0031] Example 1: This embodiment provides a method for preparing aluminum montmorillonite nitride based on interface whisker growth, specifically including the following steps: S1. Weigh 100 g of aluminum nitride powder with a particle size D50 of 20 μm. Select analytical grade ferric nitrate hexahydrate as the iron source. Weigh 0.2 g (0.2 wt% of the aluminum nitride powder mass) and dissolve it in 50 mL of anhydrous ethanol. Stir until completely dissolved. Pour the iron source ethanol solution into the aluminum nitride powder and ultrasonically disperse it in an ultrasonic cleaner for 25 min. Then transfer it to a rotary evaporator and rotary evaporate it at 75℃ and a vacuum of 0.08 MPa for 30 min to remove the anhydrous ethanol, obtaining iron source-loaded aluminum nitride powder. Load the iron source-loaded aluminum nitride powder into a fluidized bed reactor and purge it with argon gas at a flow rate of 2 L / min for 30 min to remove air. Start the heating program to raise the temperature to 400℃ and switch to an Ar / H2 mixed atmosphere with a volume ratio of 1:7 (total flow rate 16 L / min). The temperature was maintained at L / min for 1 h to reduce ferric nitrate to Fe nanoparticles, which catalyzed the growth of Al-Fe-O nanocrystals with an aspect ratio of about 35 on the surface of aluminum nitride. S2, maintain an argon atmosphere, raise the reactor temperature to 780℃, adjust the gas flow ratio to a C2H2 / H2 mixed gas with a flow rate of 1:10 (total flow rate 22 L / min), and keep it at this temperature for 20 min to allow the carbon source to decompose at the Fe catalytic sites and on the surface of the nanocrystals and grow graphene in situ, forming a three-dimensional interlocked structure of "aluminum nitride-nanocrystals-graphene". S3, stop the C2H2 / H2 mixed gas flow, continue purging with argon gas until it cools naturally to room temperature, remove the powder and transfer it to a vacuum high-temperature furnace, start the vacuum system to achieve a vacuum degree of 5×10⁻⁶. -4 Pa was heated to 420℃ and held for 2.5 h for low-temperature vacuum annealing. After cooling, graphene-coated aluminum nitride powder was collected.

[0032] Example 2: This embodiment provides a method for preparing aluminum montmorillonite nitride based on interface whisker growth, specifically including the following steps: S1. Weigh 100 g of aluminum nitride powder with a particle size D50 of 20 μm. Select analytical grade ferric nitrate hexahydrate as the iron source. Weigh 0.05 g (0.05 wt% of the aluminum nitride powder mass) and dissolve it in 50 mL of anhydrous ethanol. Stir until completely dissolved. Pour the iron source ethanol solution into the aluminum nitride powder and ultrasonically disperse it in an ultrasonic cleaner for 25 min. Then transfer it to a rotary evaporator and rotary evaporate it at 75℃ and a vacuum of 0.08 MPa for 30 min to remove the anhydrous ethanol, obtaining iron source-loaded aluminum nitride powder. Load the iron source-loaded aluminum nitride powder into a fluidized bed reactor and purge it with argon gas at a flow rate of 2 L / min for 30 min to remove air. Start the heating program to raise the temperature to 400℃ and switch to an Ar / H2 mixed atmosphere with a volume ratio of 1:7 (total flow rate 16 L / min). The temperature was maintained at L / min for 1 h to reduce ferric nitrate to Fe nanoparticles, which catalyzed the growth of Al-Fe-O nanocrystals with an aspect ratio of about 35 on the surface of aluminum nitride. S2, maintain an argon atmosphere, raise the reactor temperature to 780℃, adjust the gas flow ratio to a C2H2 / H2 mixed gas with a flow rate of 1:10 (total flow rate 22 L / min), and keep it at this temperature for 20 min to allow the carbon source to decompose at the Fe catalytic sites and on the surface of the nanocrystals and grow graphene in situ, forming a three-dimensional interlocked structure of "aluminum nitride-nanocrystals-graphene". S3, stop the C2H2 / H2 mixed gas flow, continue purging with argon gas until it cools naturally to room temperature, remove the powder and transfer it to a vacuum high-temperature furnace, start the vacuum system to achieve a vacuum degree of 5×10⁻⁶. -4 Pa was heated to 420℃ and held for 2.5 h for low-temperature vacuum annealing. After cooling, graphene-coated aluminum nitride powder was collected.

[0033] Example 3: This embodiment provides a method for preparing aluminum montmorillonite nitride based on interface whisker growth, specifically including the following steps: S1. Weigh 100 g of aluminum nitride powder with a particle size D50 of 20 μm. Select analytical grade ferric nitrate hexahydrate as the iron source. Weigh 1 g (1 wt% of the aluminum nitride powder mass) and dissolve it in 50 mL of anhydrous ethanol. Stir until completely dissolved. Pour the iron source ethanol solution into the aluminum nitride powder. Place it in an ultrasonic cleaner and ultrasonically disperse for 25 min. Then transfer it to a rotary evaporator and rotary evaporate at 75℃ and a vacuum of 0.08 MPa for 30 min to remove the anhydrous ethanol, obtaining iron source-loaded aluminum nitride powder. Load the iron source-loaded aluminum nitride powder into a fluidized bed reactor. Purge with argon gas at a flow rate of 2 L / min for 30 min to remove air. Start the heating program to raise the temperature to 400℃. Switch to a mixed atmosphere of Ar / H2 with a volume ratio of 1:7 (total flow rate 16 L / min) and keep it at this temperature for 1 h to reduce ferric nitrate to Fe nanoparticles. This catalyzes the growth of Al-Fe-O nanocrystals with an aspect ratio of about 35 on the surface of aluminum nitride. S2, maintain an argon atmosphere, raise the reactor temperature to 780℃, adjust the gas flow ratio to a C2H2 / H2 mixed gas with a flow rate of 1:10 (total flow rate 22 L / min), and keep it at this temperature for 20 min to allow the carbon source to decompose at the Fe catalytic sites and on the surface of the nanocrystals and grow graphene in situ, forming a three-dimensional interlocked structure of "aluminum nitride-nanocrystals-graphene". S3, stop the C2H2 / H2 mixed gas flow, continue purging with argon gas until it cools naturally to room temperature, remove the powder and transfer it to a vacuum high-temperature furnace, start the vacuum system to achieve a vacuum degree of 5×10⁻⁶. -4 Pa was heated to 420℃ and held for 2.5 h for low-temperature vacuum annealing. After cooling, graphene-coated aluminum nitride powder was collected.

[0034] Example 4: This embodiment provides a method for preparing aluminum montmorillonite nitride based on interface whisker growth, specifically including the following steps: S1. Weigh 100 g of aluminum nitride powder with a particle size D50 of 20 μm. Select analytical grade ferric nitrate hexahydrate as the iron source. Weigh 0.2 g (0.2 wt% of the aluminum nitride powder mass) and dissolve it in 50 mL of anhydrous ethanol. Stir until completely dissolved. Pour the iron source ethanol solution into the aluminum nitride powder and ultrasonically disperse it in an ultrasonic cleaner for 25 min. Then transfer it to a rotary evaporator and rotary evaporate it at 75℃ and a vacuum of 0.08 MPa for 30 min to remove the anhydrous ethanol, obtaining iron source-loaded aluminum nitride powder. Load the iron source-loaded aluminum nitride powder into a fluidized bed reactor and purge it with argon gas at a flow rate of 2 L / min for 30 min to remove air. Start the heating program to raise the temperature to 400℃ and switch to an Ar / H2 mixed atmosphere with a volume ratio of 1:5 (total flow rate 16 L / min). The temperature was maintained at L / min for 1 h to reduce ferric nitrate to Fe nanoparticles, which catalyzed the growth of Al-Fe-O nanocrystals with an aspect ratio of about 35 on the surface of aluminum nitride. S2, maintain an argon atmosphere, raise the reactor temperature to 780℃, adjust the gas flow ratio to a C2H2 / H2 mixed gas with a flow rate of 1:10 (total flow rate 22 L / min), and keep it at this temperature for 20 min to allow the carbon source to decompose at the Fe catalytic sites and on the surface of the nanocrystals and grow graphene in situ, forming a three-dimensional interlocked structure of "aluminum nitride-nanocrystals-graphene". S3, stop the C2H2 / H2 mixed gas flow, continue purging with argon gas until it cools naturally to room temperature, remove the powder and transfer it to a vacuum high-temperature furnace, start the vacuum system to achieve a vacuum degree of 5×10⁻⁶. -4 Pa was heated to 420℃ and held for 2.5 h for low-temperature vacuum annealing. After cooling, graphene-coated aluminum nitride powder was collected.

[0035] Example 5: This embodiment provides a method for preparing aluminum montmorillonite nitride based on interface whisker growth, specifically including the following steps: S1. Weigh 100 g of aluminum nitride powder with a particle size D50 of 20 μm. Select analytical grade ferric nitrate hexahydrate as the iron source. Weigh 0.2 g (0.2 wt% of the aluminum nitride powder mass) and dissolve it in 50 mL of anhydrous ethanol. Stir until completely dissolved. Pour the iron source ethanol solution into the aluminum nitride powder and ultrasonically disperse it in an ultrasonic cleaner for 25 min. Then transfer it to a rotary evaporator and rotary evaporate it at 75℃ and a vacuum of 0.08 MPa for 30 min to remove the anhydrous ethanol, obtaining iron source-loaded aluminum nitride powder. Load the iron source-loaded aluminum nitride powder into a fluidized bed reactor and purge it with argon gas at a flow rate of 2 L / min for 30 min to remove air. Start the heating program to raise the temperature to 400℃, switch to an Ar / H2 mixed atmosphere with a volume ratio of 1:20 (total flow rate 16 L / min), and maintain the temperature for 1 minute. h, which reduces ferric nitrate to Fe nanoparticles, and catalyzes the growth of Al-Fe-O nanocrystals with an aspect ratio of about 35 on the surface of aluminum nitride; S2, maintain an argon atmosphere, raise the reactor temperature to 780℃, adjust the gas flow ratio to a C2H2 / H2 mixed gas with a flow rate of 1:10 (total flow rate 22 L / min), and keep it at this temperature for 20 min to allow the carbon source to decompose at the Fe catalytic sites and on the surface of the nanocrystals and grow graphene in situ, forming a three-dimensional interlocked structure of "aluminum nitride-nanocrystals-graphene". S3, stop the C2H2 / H2 mixed gas flow, continue purging with argon gas until it cools naturally to room temperature, remove the powder and transfer it to a vacuum high-temperature furnace, start the vacuum system to achieve a vacuum degree of 5×10⁻⁶. -4 Pa was heated to 420℃ and held for 2.5 h for low-temperature vacuum annealing. After cooling, graphene-coated aluminum nitride powder was collected.

[0036] Example 6: This embodiment provides a method for preparing aluminum montmorillonite nitride based on interface whisker growth, specifically including the following steps: S1. Weigh 100 g of aluminum nitride powder with a particle size D50 of 20 μm. Select analytical grade ferric nitrate hexahydrate as the iron source. Weigh 0.2 g (0.2 wt% of the aluminum nitride powder mass) and dissolve it in 50 mL of anhydrous ethanol. Stir until completely dissolved. Pour the iron source ethanol solution into the aluminum nitride powder and ultrasonically disperse it in an ultrasonic cleaner for 25 min. Then transfer it to a rotary evaporator and rotary evaporate it at 75℃ and a vacuum of 0.08 MPa for 30 min to remove the anhydrous ethanol, obtaining iron source-loaded aluminum nitride powder. Load the iron source-loaded aluminum nitride powder into a fluidized bed reactor and purge it with argon gas at a flow rate of 2 L / min for 30 min to remove air. Start the heating program to raise the temperature to 400℃ and switch to an Ar / H2 mixed atmosphere with a volume ratio of 1:7 (total flow rate 16 L / min). The temperature was maintained at L / min for 1 h to reduce ferric nitrate to Fe nanoparticles, which catalyzed the growth of Al-Fe-O nanocrystals with an aspect ratio of about 35 on the surface of aluminum nitride. S2, maintain an argon atmosphere, raise the reactor temperature to 780℃, adjust the gas flow rate to a 1:5 C2H2 / H2 mixed gas (total flow rate 22 L / min), and keep it at this temperature for 20 min to allow the carbon source to decompose at the Fe catalytic sites and on the surface of the nanocrystals and grow graphene in situ, forming a three-dimensional interlocked structure of "aluminum nitride-nanocrystals-graphene". S3, stop the C2H2 / H2 mixed gas flow, continue purging with argon gas until it cools naturally to room temperature, remove the powder and transfer it to a vacuum high-temperature furnace, start the vacuum system to achieve a vacuum degree of 5×10⁻⁶. -4 Pa was heated to 420℃ and held for 2.5 h for low-temperature vacuum annealing. After cooling, graphene-coated aluminum nitride powder was collected.

[0037] Example 7: This embodiment provides a method for preparing aluminum montmorillonite nitride based on interface whisker growth, specifically including the following steps: S1. Weigh 100 g of aluminum nitride powder with a particle size D50 of 20 μm. Select analytical grade ferric nitrate hexahydrate as the iron source. Weigh 0.2 g (0.2 wt% of the aluminum nitride powder mass) and dissolve it in 50 mL of anhydrous ethanol. Stir until completely dissolved. Pour the iron source ethanol solution into the aluminum nitride powder and ultrasonically disperse it in an ultrasonic cleaner for 25 min. Then transfer it to a rotary evaporator and rotary evaporate it at 75℃ and a vacuum of 0.08 MPa for 30 min to remove the anhydrous ethanol, obtaining iron source-loaded aluminum nitride powder. Load the iron source-loaded aluminum nitride powder into a fluidized bed reactor and purge it with argon gas at a flow rate of 2 L / min for 30 min to remove air. Start the heating program to raise the temperature to 400℃ and switch to an Ar / H2 mixed atmosphere with a volume ratio of 1:7 (total flow rate 16 L / min). The temperature was maintained at L / min for 1 h to reduce ferric nitrate to Fe nanoparticles, which catalyzed the growth of Al-Fe-O nanocrystals with an aspect ratio of about 35 on the surface of aluminum nitride. S2, maintain an argon atmosphere, raise the reactor temperature to 780℃, adjust the gas flow ratio to a C2H2 / H2 mixed gas with a flow rate of 1:20 (total flow rate 22 L / min), and keep it at this temperature for 20 min to allow the carbon source to decompose at the Fe catalytic sites and on the surface of the nanocrystals and grow graphene in situ, forming a three-dimensional interlocked structure of "aluminum nitride-nanocrystals-graphene". S3, stop the C2H2 / H2 mixed gas flow, continue purging with argon gas until it cools naturally to room temperature, remove the powder and transfer it to a vacuum high-temperature furnace, start the vacuum system to achieve a vacuum degree of 5×10⁻⁶. -4 Pa was heated to 420℃ and held for 2.5 h for low-temperature vacuum annealing. After cooling, graphene-coated aluminum nitride powder was collected.

[0038] Comparative Example 1: This embodiment provides a method for preparing aluminum montmorillonite nitride based on interface whisker growth, specifically including the following steps: S1. Weigh 100 g of aluminum nitride powder with a particle size D50 of 20 μm. Select analytical grade ferric nitrate hexahydrate as the iron source. Weigh 0.2 g (0.2 wt% of the aluminum nitride powder mass) and dissolve it in 50 mL of anhydrous ethanol. Stir until completely dissolved. Pour the iron source ethanol solution into the aluminum nitride powder. Place it in an ultrasonic cleaner and ultrasonically disperse for 25 min. Then transfer it to a rotary evaporator and rotary evaporate at 75℃ and 0.08 MPa for 30 min to remove the anhydrous ethanol, thus obtaining iron source-loaded aluminum nitride powder. S2, Maintain an argon atmosphere, raise the reactor temperature to 780℃, adjust the gas flow rate to a 1:10 C2H2 / H2 mixed gas (total flow rate 22 L / min), and hold for 20 min to allow the carbon source to decompose on the Fe catalytic site surface and grow graphene in situ. S3, stop the C2H2 / H2 mixed gas flow, continue purging with argon gas until it cools naturally to room temperature, remove the powder and transfer it to a vacuum high-temperature furnace, start the vacuum system to achieve a vacuum degree of 5×10⁻⁶. -4 Pa was heated to 420℃ and held for 2.5 h for low-temperature vacuum annealing. After cooling, graphene-coated aluminum nitride powder was collected.

[0039] Comparative Example 2: This embodiment provides a method for preparing aluminum montmorillonite nitride based on interface whisker growth, specifically including the following steps: S1. Weigh 100 g of aluminum nitride powder with a particle size D50 of 20 μm. Select analytical grade ferric nitrate hexahydrate as the iron source. Weigh 0.2 g (0.2 wt% of the aluminum nitride powder mass) and dissolve it in 50 mL of anhydrous ethanol. Stir until completely dissolved. Pour the iron source ethanol solution into the aluminum nitride powder and ultrasonically disperse it in an ultrasonic cleaner for 25 min. Then transfer it to a rotary evaporator and rotary evaporate it at 75℃ and a vacuum of 0.08 MPa for 30 min to remove the anhydrous ethanol, obtaining iron source-loaded aluminum nitride powder. Load the iron source-loaded aluminum nitride powder into a fluidized bed reactor and purge it with argon gas at a flow rate of 2 L / min for 30 min to remove air. Start the heating program to raise the temperature to 400℃ and switch to an Ar / H2 mixed atmosphere with a volume ratio of 1:7 (total flow rate 16 L / min). The temperature was maintained at L / min for 1 h to reduce ferric nitrate to Fe nanoparticles, which catalyzed the growth of Al-Fe-O nanocrystals with an aspect ratio of about 35 on the surface of aluminum nitride. S2, maintain an argon atmosphere, raise the reactor temperature to 780℃, adjust the gas flow ratio to a C2H2 / H2 mixed gas with a flow rate of 1:10 (total flow rate 22 L / min), and keep it at this temperature for 20 min to allow the carbon source to decompose at the Fe catalytic sites and on the surface of the nanocrystals and grow graphene in situ, forming a three-dimensional interlocked structure of "aluminum nitride-nanocrystals-graphene". S3, stop the C2H2 / H2 mixed gas flow, continue to purge with argon gas until it cools naturally to room temperature, and collect the graphene-coated aluminum nitride powder.

[0040] Comparative Example 3: This embodiment provides a method for preparing aluminum montmorillonite nitride based on interface whisker growth, specifically including the following steps: S1. Weigh 100 g of aluminum nitride powder with a particle size D50 of 20 μm. Select analytical grade ferric nitrate hexahydrate as the iron source. Weigh 0.2 g (0.2 wt% of the aluminum nitride powder mass) and dissolve it in 50 mL of anhydrous ethanol. Stir until completely dissolved. Pour the iron source ethanol solution into the aluminum nitride powder. Place it in an ultrasonic cleaner and ultrasonically disperse for 25 min. Then transfer it to a rotary evaporator and rotary evaporate at 75℃ and a vacuum of 0.08 MPa for 30 min to remove the anhydrous ethanol, obtaining iron source-loaded aluminum nitride powder. Purge the iron source-loaded aluminum nitride powder with argon gas at a flow rate of 2 L / min for 30 min to remove air. Raise the temperature to 400℃, switch to a mixed atmosphere of Ar / H2 with a volume ratio of 1:7 (total flow rate 16 L / min), and keep it at this temperature for 1 h. S2, maintain an argon atmosphere, raise the temperature to 780℃, adjust the gas flow ratio to a 1:10 C2H2 / H2 mixed gas (total flow rate 22 L / min), and hold for 20 min; S3, stop the C2H2 / H2 mixed gas flow, continue purging with argon gas until it cools naturally to room temperature, remove the powder and transfer it to a vacuum high-temperature furnace, start the vacuum system to achieve a vacuum degree of 5×10⁻⁶. -4 Pa was heated to 420℃ and held for 2.5 h for low-temperature vacuum annealing. After cooling, graphene-coated aluminum nitride powder was collected.

[0041] Test Example 1: This test example is to test the aspect ratio and coating rate before and after grinding of Examples 1-7 and Comparative Examples 1-3.

[0042] The graphene materials prepared in each example and comparative example were mechanically ground at 3000 r / min for 30 min, and the graphene coating effect on their surfaces was tested. The testing method followed the enterprise standard Q / BGI J011-2024. A focused electron beam with a certain energy was used to irradiate the sample surface using a scanning electron microscope, exciting secondary electrons from the sample surface. After collecting and processing the secondary electrons, a scanning image of the sample surface morphology could be obtained, allowing observation of the sample's microstructure. Then, the raw SEM image was analyzed using software, and the number of pixels in the graphene-coated area and the total number of pixels in all graphene powder particles were obtained based on the grayscale differences. Finally, the graphene coating rate was evaluated based on the number of pixels. The coating rate of the sample was obtained by statistically calculating the area of ​​the coated region. The specific steps are as follows: Randomly select a sample of no less than 10g. Fix the grid carrier to the sample stage using conductive adhesive. Dip a toothpick into a small amount of powder and gently shake it to ensure it falls evenly into the grid. Use a syringe to blow away any excess sample from the top layer, ensuring a uniform single-layer distribution of particles within the grid. Acquire images using a scanning electron microscope (SEM) (accelerating voltage: 5KV, electron beam spot / current: 3.0 / 28 pA, brightness: 45%, contrast: 80%). Each image should contain no less than 15 particles. Based on the contrast, use image processing software (ImageJ) to select the uncoated areas on the surface of the montmorillonite powder particles in the image and read the pixel count (PD) of that area. Additionally, select all powder particles in the entire image and read the pixel count (PT) (see...). Figure 1-4 The coating rate was calculated as (PT-PD) / PT*100%, and the experimental data are shown in Table 1.

[0043] Table 1: Aspect ratio and coating rate before and after grinding in Examples 1-7 and Comparative Examples 1-3 Effect of catalyst loading: In Example 2, with an aspect ratio of 20, the coating rate after grinding was 94.2%. The catalyst nanoparticles were insufficient in number and sparsely distributed, resulting in low whisker nucleation density and large spacing between whiskers. This led to larger whisker diameters or uneven growth, thus reducing the aspect ratio and creating a sparse three-dimensional framework. This resulted in fewer anchor points and nucleation sites for graphene, ultimately forming a weaker three-dimensional interlocking structure. During grinding, stress concentration made the graphene layer easier to peel off from the sparse anchor points, resulting in the worst grinding resistance. In Example 3, with an aspect ratio of 45, the coating rate after grinding was 98.8%. The catalyst particles were sufficient and uniform, forming high-density, high aspect ratio whiskers, providing a dense mechanical interlocking network with the most graphene nucleation sites. This promoted the formation of a denser and more complete coating layer, exhibiting the highest interfacial strength. The coating rate after grinding was close to 99%, demonstrating the strongest bonding force.

[0044] The effect of Ar / H2 ratio: The coating rates after grinding in Examples 4 and 5 were lower than those in Example 1. In Example 4, the hydrogen concentration was relatively low, the reducing power was weak, and the reduction driving force on the iron precursor was weak, which promoted the nucleation and growth of Al-Fe-O whiskers. The aspect ratio reached 40 in the experimental data, and the growth was good. However, due to the micro-inhomogeneity at the interface, the catalyst activity was slightly poor, which resulted in the subsequent graphene growth not being optimal. In Example 5, the hydrogen concentration was very high, the reducing power was extremely strong, which triggered the migration and aggregation of iron nanoparticles, resulting in slightly larger catalyst particle size and uneven distribution. The extremely high H2 partial pressure suppressed the equilibrium oxygen partial pressure of the system to a very low level. The Fe catalyst lacked an oxygen transfer medium, which resulted in slow reaction kinetics for extracting Al atoms from the AlN surface and assembling them into Al-Fe-O whiskers. The generated whisker array was not firmly bonded to the matrix, and the quality of the whisker skeleton itself decreased. The decrease in the quality of the whisker skeleton itself weakened the effect of forming a three-dimensional interlocking structure with graphene, resulting in the lowest coating rate after grinding.

[0045] Effect of carbon-hydrogen ratio: In Example 6, the carbon source ratio is high, the carbon supply is sufficient, and the growth rate is fast, but the hydrogen etching effect is relatively weak, resulting in a large number of graphene layers and the generation of a small amount of amorphous carbon or defects. These defects or thicker layered structures are more prone to interlayer slip or cracking under mechanical stress, resulting in a slightly larger decrease in coverage. In Example 7, the carbon source ratio is low, the hydrogen etching effect is extremely strong, the carbon supply is strictly limited, the graphene growth is very slow, and the etching effect is strong, resulting in some microscopic uncovered areas. During grinding, these weak areas fail first, leading to a decrease in coverage.

[0046] Nanocrystal-free growth steps: After grinding, the coating rate of Comparative Example 1 decreased to 84.5%. Without the effect of whiskers, graphene grows directly on the smooth AlN surface and is bound only by weak van der Waals forces. The interface is extremely fragile and a large amount of it is peeled off with slight grinding.

[0047] No low-temperature vacuum annealing step: After grinding, the coverage rate of Comparative Example 2 decreased to 90.2%. There was no annealing. There was residual thermal stress inside the material, defects in the graphene, insufficient relaxation of interface atoms, and stress concentration during grinding of the metastable structure, which led to interface failure.

[0048] Chemical vapor deposition process: Comparative Example 3 only grew whiskers without graphene coating, which clarified the integrity and purpose of the whisker + graphene montmorillonite structure.

Claims

1. A method for preparing montmorillonite aluminum nitride based on interface whisker growth, characterized in that, Includes the following steps: S1, iron source and aluminum nitride powder are dissolved in anhydrous ethanol, ultrasonically dispersed and rotary evaporated to obtain iron source-loaded aluminum nitride powder, placed in a fluidized bed reactor and argon gas is introduced, and the iron source is reduced by introducing an Ar / H2 mixed atmosphere to catalyze the growth of nano whiskers. S2, Maintain an argon atmosphere, increase the temperature and introduce a mixed gas of carbon source and hydrogen to grow and coat graphene. S3, stop the supply of carbon source and hydrogen, keep argon purging to lower the temperature, transfer to high temperature furnace, vacuum anneal, and cool to obtain montmorillonite aluminum nitride.

2. The method for preparing montmorillonite aluminum nitride based on interface whisker growth according to claim 1, characterized in that, The specific steps of S1 are as follows: dissolve the iron source and aluminum nitride powder in anhydrous ethanol, ultrasonically disperse for 15-30 min, remove the solvent by rotary evaporation at 60-85℃ to obtain iron source-loaded aluminum nitride powder, place the iron source-loaded aluminum nitride powder in a fluidized bed reactor, purge with argon gas for 30 min, raise the temperature to 300-500℃, introduce an Ar / H2 mixed atmosphere, keep warm for 0.5-2 h to reduce the iron source and catalyze the growth of nano whiskers.

3. The method for preparing montmorillonite aluminum nitride based on interface whisker growth according to claim 1, characterized in that, The specific steps of S2 are as follows: maintain an inert argon atmosphere in the fluidized bed, adjust the temperature to 700~850℃, introduce a mixed gas of carbon source and hydrogen, keep warm for 10~30 min, and grow coated graphene.

4. The method for preparing montmorillonite aluminum nitride based on interface whisker growth according to claim 1, characterized in that, The specific steps of S3 are as follows: stop the introduction of carbon source and H2, maintain argon purging, cool to room temperature, stop argon purging, remove the material and transfer it to a high-temperature furnace, and set the vacuum degree inside the furnace to 10. -3 ~10 -5 Pa, heat to 300~500 ℃, hold for 2~3 h for vacuum annealing, cool to room temperature after completion, and collect the material to obtain montmorillonite aluminum nitride.

5. The method for preparing montmorillonite aluminum nitride based on interface whisker growth according to claim 1 or 2, characterized in that, The iron source in step S1 is one or more of ferric nitrate, ferric chloride, or ferric acetylacetone, and the mass of the iron source is 0.05-1% of the mass of the aluminum nitride powder.

6. The method for preparing montmorillonite aluminum nitride based on interface whisker growth according to claim 5, characterized in that, The aluminum nitride powder has a mass of 90-110g and a powder size of 5-100 μm.

7. The method for preparing montmorillonite aluminum nitride based on interface whisker growth according to claim 1 or 2, characterized in that, In step S1, the total flow rate of the Ar / H2 mixed atmosphere is 16 L / min, and the volume ratio of Ar to H2 is 1:(5-10).

8. The method for preparing montmorillonite aluminum nitride based on interface whisker growth according to claim 1 or 2, characterized in that, The nanocrystals in step S1 are Al-Fe-O or AlN nanocrystals with an aspect ratio of 10-50.

9. The method for preparing montmorillonite aluminum nitride based on interface whisker growth according to claim 1 or 3, characterized in that, In step S2, the total flow rate of the mixed gas of carbon source and H2 is 22 L / min; the carbon source is one of methane, acetylene or ethylene, and the volume ratio of carbon source to H2 is 1:(5~20).

10. The method for preparing montmorillonite aluminum nitride based on interface whisker growth according to claim 1, characterized in that, The coating rate of the aluminum nitride before mechanical polishing was 98.5-99.2%, and the coating rate after mechanical polishing was 94.2-98.8%.

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