Graphene / aluminum nitride composite powder material and preparation method thereof

Abstract

The invention discloses a graphene / aluminum nitride composite powder material and a preparation method thereof. The composite powder material is formed by sequentially coating the surface of aluminum nitride powder with horizontal graphene and vertical graphene. The composite powder material solves the problems that aluminum nitride is low in heat conductivity, easy to hydrolyze, easy to oxidize and easy to carry static electricity.

Description

Technical Field

[0001] The present invention belongs to the field of graphene composite material preparation, and particularly relates to a graphene / aluminum nitride composite powder material and a preparation method thereof. Background Art

[0002] For a long time, Al2O3 and BeO ceramics have been the primary substrate materials for most high-power hybrid integrated circuits. However, Al2O3 substrates have low thermal conductivity and a thermal expansion coefficient that is poorly matched to silicon. While BeO offers excellent overall performance, its high production cost and high toxicity have limited its widespread application. Therefore, considering performance, cost, and environmental factors, these two materials no longer meet the needs of modern electronic power devices and their development. AlN ceramics, with their excellent comprehensive properties, have recently attracted widespread attention as a new generation of advanced ceramics with broad application prospects. In particular, their high thermal conductivity, low dielectric constant, low dielectric loss, excellent electrical insulation, a thermal expansion coefficient that matches silicon, and their non-toxicity make them ideal materials for high-density, high-power, and high-speed integrated circuit substrates and packaging. However, the highly active surface of AlN powder, a high-end heat dissipation material, often results in impurities and defects within the powder, resulting in the thermal conductivity of aluminum nitride products falling far short of the theoretical value of 320 W / (m·k).

[0003] Effective heat dissipation in electronic devices is crucial to ensuring their long-term reliability, as excessively high operating temperatures can lead to performance degradation, shortened lifespan, and even system failures in electronic components. As key components in thermal interface materials (TIMs), aluminum nitride (AlN) and graphene play a vital role in the field of heat dissipation in electronic devices due to their unique thermophysical properties, and have significant research significance. Aluminum nitride has an extremely high thermal conductivity. In practical applications, its thermal conductivity is usually between 180 and 210 W / (m·K), and can even reach 275 W / (m·K) in a single crystal state, making it an ideal heat conduction medium. Adding aluminum nitride filler to thermal interface materials can significantly improve the overall thermal conductivity of the material, quickly transfer the heat generated inside the electronic device to the radiator or the external environment, and effectively reduce the operating temperature of key components. However, traditional aluminum nitride thermal conductive fillers are prone to hydrolysis in humid environments, which not only produces aluminum hydroxide with very low thermal conductivity (0.4-0.5W / (m·K)), which interrupts the thermal conduction path and reduces heat dissipation performance; but also produces highly toxic ammonia in the process, which corrodes peripheral equipment and poses a health hazard.

[0004] Graphene's single-layer two-dimensional structure gives it a unique heat transfer mechanism, with an in-plane thermal conductivity of up to 5300 W / (m·K), which is several times higher than that of traditional high-thermal-conductivity metals, including silver. Even adding a small amount of graphene can significantly improve the overall thermal conductivity efficiency, making it particularly suitable for efficient heat dissipation in high-power density, compact electronic devices. This excellent thermal conductivity stems from the strong covalent bonding between atoms in the graphene lattice and its near-perfect planar structure, which enables phonons to propagate at high speed within the graphene layer with almost no scattering, thereby achieving extraordinary heat diffusion efficiency. Therefore, whether in electronic devices that require rapid heat dissipation, high-performance composite materials, or as a key component of thermal management systems such as thermal interface materials and nanoscale heat transfer devices, graphene has demonstrated irreplaceable application value. Graphene, a single-layer carbon atom crystal, has a low-dimensional structure that significantly reduces boundary scattering of phonons at grain boundaries and endows it with unique phonon modes, exhibiting excellent thermal conductivity. Graphene relies on these special phonon modes for heat transfer. Phonons are quanta of energy in the normal modes of lattice vibrations, which transfer heat in a ballistic-diffusive manner. Graphene's two-dimensional layered structure gives it an extremely short phonon mean free path, enabling rapid heat dissipation from hot spots to a large area, helping to quickly homogenize the temperature distribution and prevent localized overheating. Graphene's extremely low density, combined with excellent flexibility and mechanical strength, allows thermal interface materials containing graphene to adapt to the heat dissipation requirements of various complex shapes and curved surfaces while maintaining efficient heat dissipation. This presents unique advantages in flexible electronic devices and microelectronic packaging. Graphene also has a lubricating effect, which can increase the loading of thermally conductive fillers. However, single-use thermally conductive fillers made of graphene also suffer from the problems of easy agglomeration, difficulty in dispersion, rapid increase in precursor viscosity, poor processability, and significantly reduced mechanical properties of the resulting composites.

[0005] Invention patent application CN114395254A proposes using aluminum nitride of four different particle sizes to form a thermally conductive filler, then nickel-plating the surface. This process involves reacting graphene oxide to form a charged, modified graphene composite with the aluminum nitride thermally conductive filler. However, this invention fails to effectively prevent the hydrolysis of aluminum nitride powder in thermal grease and fails to fully utilize the excellent thermal conductivity of graphene. Summary of the Invention

[0006] In order to solve the defects in the prior art, the purpose of the present invention is to provide a graphene / aluminum nitride composite powder material, wherein the composite powder material is an aluminum nitride powder surface coated with horizontal graphene and vertical graphene in sequence.

[0007] According to a specific embodiment of the present invention, the composite powder material is measured by Raman spectroscopy, and the peak ratio of the D band to the G band is I D / I G0.1 to 1.2, preferably 0.1 to 0.5;

[0008] Among them, the D band refers to the wave number at 1350cm -1 The G band refers to the wave number at 1600cm -1 band.

[0009] According to a specific embodiment of the present invention, the particle size of the composite powder material is 50 nm to 100 μm.

[0010] According to a specific embodiment of the present invention, the aluminum nitride powder has a particle size ranging from 50 nm to 100 μm and a spherical or quasi-spherical shape.

[0011] According to a specific embodiment of the present invention, the number of layers of the horizontal graphene is 1 to 10 layers.

[0012] According to a specific embodiment of the present invention, the height of the vertical graphene sheets is 5 nm to 500 nm, the thickness is 0.03 nm to 2 nm, and the spacing between the vertical graphene sheets is 1 nm to 100 nm.

[0013] According to a specific embodiment of the present invention, the mass percentage of the sum of the horizontal graphene and the vertical graphene in the composite powder material is 0.01 wt% to 0.5 wt%.

[0014] Another object of the present invention is to provide a method for preparing the composite powder material, comprising:

[0015] S1, growing the horizontal graphene on the surface of the aluminum nitride powder;

[0016] S2. Growing the vertical graphene on the surface of the horizontal graphene to obtain the composite powder material.

[0017] According to a specific embodiment of the present invention, step S1 and step S2 are performed in a rotary kiln reactor.

[0018] According to a specific embodiment of the present invention, in the step S1, the horizontal graphene is grown by chemical vapor deposition, the flow ratio of the carbon source to hydrogen in the chemical vapor deposition is 1:(1-100), the reaction time is 30min-300min, and the reaction temperature is 600℃-1600℃.

[0019] According to a specific embodiment of the present invention, the vertical graphene is grown by plasma enhanced chemical vapor deposition, the radio frequency power of the plasma enhanced chemical vapor deposition is 20W to 1000W, the reaction time is 30min to 300min, and the temperature is 400°C to 1100°C.

[0020] This invention innovatively develops a hydrolysis-resistant, highly thermally conductive aluminum nitride powder. This not only improves the thermal conductivity of traditional thermally conductive fillers, but also utilizes graphene as a coating layer, providing a lubricating effect. This not only improves the thermal conductivity of thermal interface materials at the same addition level, but also increases the maximum addition level of the thermally conductive filler, resulting in even better thermal performance. This composite powder can be mass-produced without the need for complex post-processing steps, making its preparation simple and convenient.

[0021] Specifically, the present invention first grows horizontal graphene on the surface of aluminum nitride powder to achieve full coverage of the surface of the aluminum nitride powder to prevent it from hydrolyzing during use, while dissipating the heat from local heat concentration points in the horizontal direction; then, vertical graphene is grown on its surface to convert the horizontal heat into a direction perpendicular to the surface of the thermal interface material, and the excellent in-plane thermal conductivity of graphene is used to achieve efficient heat dissipation.

[0022] When the composite powder material of the present invention is used as a thermal interface material, it can transform the point contact of traditional thermal conductive fillers into line contact between vertical graphene nanosheets, increase the heat conduction network channel, and at the same time make the thermal interface material have a certain flexibility, fully fill the gap between the heat source and the radiator, and improve the heat conduction and heat dissipation capabilities. When the composite powder material of the present invention is used as a thermal interface material for electronic devices, it is directly applied to components that need heat dissipation. By being in close contact with the heat source of the electronic device, the vertical graphene can quickly transfer heat, reduce thermal resistance, and improve heat dissipation efficiency. At the same time, due to the extremely high thermal conductivity of graphene, the heat dissipation effect of the vertical graphene is better than that of traditional heat dissipation materials, which can effectively reduce the temperature of electronic devices and improve their stability and reliability. At the same time, the horizontally coated graphene layer can block the contact between the core layer aluminum nitride powder and moisture, avoiding the interruption of the phonon transmission path due to the production of aluminum hydroxide due to hydrolysis. Moreover, through reasonable particle size control, morphology design, dispersion technology and other means, the dispersion state of aluminum nitride and graphene in the thermal interface material can be optimized, the interface thermal resistance can be reduced, and the overall heat dissipation efficiency can be improved. It is suitable for large-scale production and compatible with existing electronic manufacturing processes, meeting the electronics industry's requirements for green and sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1A This is a field emission scanning electron microscope (FESEM) photograph of the graphene / aluminum nitride composite powder material prepared in Example 1; the left picture is a powder coated with horizontal graphene, and the right picture is a powder coated with horizontal graphene and then vertical graphene.

[0024] Figure 1B yes Figure 1A Transmission electron microscopy (TEM) image of the powder shown on the left.

[0025] Figure 2This is the Raman spectrum curve of the graphene / aluminum nitride composite powder material prepared in Example 1.

[0026] Figure 3 This is the TG-FTIR curve of the graphene / aluminum nitride composite powder material prepared in Example 1 when heated to 1000° C. in an air atmosphere.

[0027] Figure 4 Phase analysis of aluminum nitride powder and graphene / aluminum nitride composite powder materials prepared in Example 1 and Comparative Examples 1-2 after moisture absorption.

[0028] Figure 5 is the thermal conductivity of the powder before and after graphene growth.

[0029] Figure 6 is the powder resistivity before and after graphene growth. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below with reference to specific embodiments.

[0031] The aluminum nitride thermal conductive filler in the prior art has the following technical problems: (1) Traditional aluminum nitride thermal conductive fillers are prone to hydrolysis in a humid environment, which not only produces aluminum hydroxide with very low thermal conductivity (0.4-0.5W / (m·K)), which interrupts the heat conduction path and reduces the heat dissipation performance. In addition, this process produces highly toxic ammonia gas, which corrodes peripheral equipment and poses a health hazard. In addition, the thermal conductivity of aluminum nitride thermal conductive fillers is limited when actually used in thermal interface materials; (2) Due to the insulating properties of aluminum nitride, in some electronic material applications, static electricity may cause functional loss, which limits its application. The present invention can reduce the loss caused by static electricity by coating with graphene.

[0032] The present invention provides a graphene / aluminum nitride composite powder material. The composite powder material is aluminum nitride powder whose surface is sequentially coated with horizontal graphene and vertical graphene.

[0033] An innovative composite material fabrication method involves first coating the surface of a non-metallic thermally conductive filler with graphene horizontally, then growing a layer of vertical graphene on top. This method aims to create a high-performance thermally conductive filler with a three-dimensional thermally conductive network. The advantage of this composite structure lies primarily in the construction of a three-dimensional thermally conductive network. The horizontal graphene layer, acting as the first coating layer, provides a highly efficient two-dimensional heat transfer channel with its extremely high in-plane thermal conductivity, enhancing the inherent thermal conductivity of the non-metallic filler. The vertically grown graphene layer acts as a "bridge" for the thermal conductivity, creating a vertical heat flow path above the horizontal layer. This significantly increases the rate and directional diversity of heat diffusion within the filler within the three-dimensional space. This structure overcomes the limitations of traditional filler thermal transport, allowing heat to rapidly transfer from the filler in all directions, particularly vertically upward to the heat dissipation interface, significantly reducing thermal resistance. The combination of horizontal and vertical graphene layers creates a continuous thermal path with multiple points of contact throughout the filler particles, effectively avoiding the bottleneck of unidirectional heat flow and further reducing the interfacial thermal resistance of the entire composite system.

[0034] In an optional embodiment, the composite powder material is measured by Raman spectroscopy, and the peak ratio of the D band to the G band is D / I G 0.1 to 1.2, preferably 0.1 to 0.5;

[0035] Among them, the D band refers to the wave number at 1350cm -1 The G band refers to the wave number at 1600cm -1 band.

[0036] After Raman spectroscopy measurement, the test results of aluminum nitride powder coated with graphene are D band (1350cm -1 ) and G band (1600cm -1 ) D / I G The range is 0.1 to 1.2, and most of them are between 0.1 and 0.5, which indicates that the coating quality of graphene on the aluminum nitride surface is high.

[0037] In an optional embodiment, the particle size of the composite powder material is 50 nm to 100 μm.

[0038] In an optional embodiment, the aluminum nitride powder has a particle size ranging from 50 nm to 100 μm and a spherical or quasi-spherical shape.

[0039] In an optional embodiment, the number of horizontal graphene layers is 1 to 10 layers.

[0040] In an optional embodiment, the height of the vertical graphene sheets is 5 nm to 500 nm, the thickness is 0.03 nm to 2 nm, and the spacing between the vertical graphene sheets is 1 nm to 100 nm.

[0041] In an optional embodiment, the mass percentage of the sum of the horizontal graphene and the vertical graphene in the composite powder material is 0.01 wt % to 0.5 wt %. The mass ratio of the horizontal graphene to the vertical graphene in the composite powder material can be appropriately selected based on the aforementioned roles of the horizontal graphene and the vertical graphene in the composite powder material and actual needs to meet different requirements.

[0042] Another object of the present invention is to provide a method for preparing the composite powder material, comprising:

[0043] S1, growing horizontal graphene on the surface of aluminum nitride powder;

[0044] S2. Growing vertical graphene on the horizontal graphene surface to obtain a composite powder material.

[0045] The present invention first grows horizontal graphene on the surface of aluminum nitride powder through an in-situ growth method to achieve full coverage of the aluminum nitride powder surface to prevent it from hydrolyzing during use, while dissipating the heat from local heat concentration points in the horizontal direction; then, vertical graphene is grown on its surface through plasma enhanced chemical vapor deposition technology to convert the horizontal heat into a direction perpendicular to the surface of the thermal interface material, and the excellent in-plane thermal conductivity of graphene is used to achieve efficient heat dissipation.

[0046] The composite powder material can be prepared in a controllable manner with respect to the number of graphene layers, defect density, and uniformity by adjusting growth parameters such as gas flow rate, growth time, and growth temperature.

[0047] In an optional embodiment, steps S1 and S2 can be performed in a rotary kiln reactor. Compared with the traditional plasma enhanced chemical vapor deposition device, the use of a rotary kiln reactor can effectively achieve all-round coating of graphene on the surface of the powder, and can achieve large-scale preparation of such graphene / aluminum nitride composite powders. The present invention adopts a rotary kiln device to increase the batch output from the milligram level to the hundred-gram level. The present invention innovatively applies the mature powder preparation rotary kiln process in industrial production to the preparation of new composite materials, and combines it with the chemical vapor deposition technology for growing high-quality graphene, thereby realizing the batch preparation of horizontal-vertical graphene / aluminum nitride powder composite materials. The rotary kiln process has been widely used in the industrial production of powders, and its mass transfer and heat transfer efficiency is high, the substrate and the precursor gas source are in more complete contact, and the graphene coating grows more uniformly, so it is easy to scale up from laboratory-level basic research to industrial-level batch production.

[0048] In an optional embodiment, in step S1, horizontal graphene is grown using chemical vapor deposition (CVD). The flow ratio of the carbon source to hydrogen in the CVD is 1:(1-100), the reaction time is 30-300 minutes, and the reaction temperature is 600°C-1600°C. Of course, other methods can also be used to grow horizontal graphene in this step.

[0049] In an optional embodiment, in step S2, the vertical graphene is grown by plasma enhanced chemical vapor deposition (PECVD), wherein the radio frequency power of the plasma enhanced chemical vapor deposition is 20W to 1000W, the reaction time is 30min to 300min, and the temperature is 400°C to 1100°C.

[0050] The advantages of using plasma-enhanced chemical vapor deposition for vertical graphene growth are as follows:

[0051] (1) Low deposition temperature: Since the high-energy particles in the plasma ionize the gas molecules and cause various excitations and chemical reactions, chemical reactions can be achieved at lower temperatures, which can reduce thermal stress, prevent substrate deformation, and allow deposition on temperature-sensitive substrates;

[0052] (2) Fast reaction speed: The high-energy particles in the plasma can provide a higher reaction speed, thereby achieving rapid deposition, which can improve production efficiency and reduce the impact of thermal diffusion on the film structure;

[0053] (3) High graphene quality: The high-energy particles and active species in the plasma can provide better chemical reaction conditions, thereby generating high-quality deposited films, which can improve the adhesion, density and corrosion resistance of the films;

[0054] (4) Uniform growth: The powder can fully contact with the carbon source gas in the rotary kiln, forming a uniform graphene coating on the surface of the aluminum nitride powder;

[0055] (5) Stable performance and good thermal conductivity: The hydrolysis resistance of aluminum nitride powder after graphene deposition is significantly improved, which is manifested in the ability to maintain good chemical stability and thermal conductivity even after long-term exposure to hot and humid conditions. This is undoubtedly an important technological advancement for high-temperature electronic packaging, thermal management components, and high-performance ceramics that rely on the excellent thermal properties and insulation characteristics of aluminum nitride, ensuring the long-term reliability and performance consistency of related materials and products.

[0056] Of course, other methods can also be used to grow vertical graphene in step S2. For example, hot filament chemical vapor deposition (HCVD), low-temperature chemical vapor deposition (LT-CVD), direct growth method (CVD), microwave-assisted chemical vapor deposition (MWCVD), etc. The appropriate growth method can be selected according to actual needs.

[0057] Preferably, in the preparation method of the present invention, step S1 and step S2 are carried out in a rotary kiln reactor, step S1 adopts traditional chemical vapor deposition, and step S2 adopts plasma enhanced chemical vapor deposition. This method only requires adding a rotary kiln-chemical vapor deposition process after the original production process of preparing thermally conductive powder, without the need for complicated post-processing steps, and the preparation is simple and convenient. The composite powder material obtained by this method improves the interfacial bonding force between graphene and thermally conductive powder. Through the rotary kiln chemical vapor deposition method, the in-situ growth of graphene on the surface of the thermally conductive powder can be achieved at high temperature, which enhances the interfacial bonding between graphene and the thermally conductive powder. Therefore, the method of the present invention can not only solve the problems of easy hydrolysis and easy generation of static electricity of traditional aluminum nitride, but also effectively improve the thermal conductivity and stability of the material.

[0058] The method for preparing composite powder materials using a rotary kiln reactor in combination with plasma enhanced chemical vapor deposition technology may specifically include, but is not limited to, the following steps:

[0059] (1) Aluminum nitride powder is added to the rotary kiln reactor. The particle size range is 50 nm to 100 μm, and the shape is spherical or quasi-spherical. The mass of the aluminum nitride powder added is determined according to the size of the reactor and the bulk density of the thermal conductive powder used to ensure that the material is evenly heated and deposited during the rotation process; for example, the aluminum nitride powder can be 10 g to 3000 g.

[0060] (2) After heating the reactor to a set temperature under an argon or nitrogen protective atmosphere, introduce protective gas alone or a mixture of protective gas and hydrogen, and keep warm for 5 minutes to 180 minutes to fully remove impurities and oxides adsorbed on the surface of the aluminum nitride powder, wherein the total gas flow rate is 1 to 50 L / min.

[0061] (3) When growing horizontal graphene: a mixture of a carbon source precursor and hydrogen is introduced, wherein the carbon source precursor is methane, acetylene, ethylene, propylene or methanol, and the flow ratio of the carbon source precursor to hydrogen in the mixture is 1:(1-100), the rotary kiln speed is 5-50 r / min, the reaction time is 30 min-300 min, and the reaction temperature is 600°C-1600°C.

[0062] (4) When growing vertical graphene: maintain the gas type and flow ratio and rotary kiln speed in step (3), turn on the plasma generator, set the RF power to 20W~1000W, the reaction time to 30min~300min, the temperature to 400℃~1100℃, and the starting gas to argon, nitrogen or ammonia, with a starting gas flow rate of 50~500sccm.

[0063] (5) Cooling to room temperature under a protective atmosphere to prepare a composite powder material.

[0064] The preparation method of the present invention may further include other auxiliary steps, such as heating the reactor to a set temperature under a protective atmosphere, introducing a protective gas alone or a mixture of a protective gas and hydrogen, and maintaining the temperature for 5 to 180 minutes to fully remove impurities and oxides adsorbed on the surface of the aluminum nitride powder. The protective gas may be argon, nitrogen, or the like.

[0065] Example 1

[0066] 150g of aluminum nitride powder with an average particle size of 10μm was placed in a rotary kiln reactor. The reactor chamber was slowly heated to 1100°C under an argon atmosphere. The temperature was maintained for 10 minutes in an argon and hydrogen atmosphere. Graphene growth was initiated by introducing a mixture of hydrogen and methane at a 1:1 flow rate, with argon as the carrier gas. The rotary kiln reactor speed was set at 50 rpm, and the growth time was set for 30 minutes, resulting in a complete horizontal layer of graphene coating on the powder surface.

[0067] A layer of vertical graphene was then grown on the surface using plasma-assisted growth. The vacuum in the reaction chamber was maintained at 0.2 Torr, the plasma generator was turned on, the RF power was set to 200W, the rotary kiln speed was set at 50 rpm, and the growth time was 120 minutes. After growth was complete, the material was cooled to 500°C under an argon and hydrogen atmosphere, and then to room temperature under an argon atmosphere. The graphene / aluminum nitride composite powder was then removed.

[0068] The microscopic morphology of the graphene / aluminum nitride composite powder material prepared in Example 1 is as follows: Figure 1A and Figure 1B As shown. Figure 1A It can be seen from the field emission scanning electron microscope photos that graphene is evenly and tightly coated on the surface of the spherical aluminum nitride powder, maintaining the spherical morphology of aluminum nitride. The particle size of the prepared composite material is basically unchanged relative to the aluminum nitride powder. Figure 1A As can be seen from the right photo, the height of the vertical graphene is about 8nm, the thickness is about 0.05nm, and the spacing is about 5nm. Figure 1B It can be seen from the transmission electron microscope photo that the number of horizontal graphene layers is about 5.

[0069] Figure 2 The Raman spectra of the prepared graphene / aluminum nitride composite powder material at different locations are shown in Figure 2. From the Raman spectra, it can be seen that each curve has obvious graphene characteristic peaks, and the presence of D peak, G peak and 2D peak is observed. D / I G The value of is 0.31.

[0070] Figure 3This figure shows the thermal weight loss curve of the prepared graphene / aluminum nitride composite powder material heated to 1000°C in air. As can be seen from the figure, the weight percentage of graphene in the composite material is approximately 0.34%. Furthermore, the weight loss temperature of the composite filler exceeds 650°C, far exceeding the weight loss temperature of typical amorphous carbon in air, verifying the growth of high-quality graphene layers.

[0071] Comparative Example 1 (only horizontal graphene coating)

[0072] 150g of aluminum nitride powder with an average particle size of 10μm was placed in a rotary kiln, and the temperature of the reactor cavity was slowly raised to 1100℃ under an argon protective atmosphere. Keep warm for 10 minutes under an argon and hydrogen atmosphere. According to the flow ratio of hydrogen and methane of 1:1, argon was used as the carrier gas, and the mixed gas was introduced to start graphene growth. The speed of the rotary kiln reactor was set to 50r / min, and the growth time was 30min, so that a layer of horizontal graphene was completely coated on the surface of the powder. After the growth was completed, the temperature was lowered to 500℃ under an argon and hydrogen protective atmosphere, and then the graphene / aluminum nitride powder was taken out after being lowered to room temperature under an argon protective atmosphere. Using the above-mentioned rotary kiln-chemical vapor deposition method, a horizontal graphene / aluminum nitride powder composite material in which horizontal graphene was uniformly and completely coated on the surface of spherical aluminum nitride powder can be prepared, and its Raman spectrum shows I D / I G The value of is 0.49.

[0073] Comparative Example 2 (only vertical graphene coating)

[0074] 150g of aluminum nitride powder with an average particle size of 10μm was placed in a rotary kiln, and the temperature of the reactor cavity was slowly raised to 1100℃ under an argon protective atmosphere. The plasma-assisted growth device was turned on to grow vertical graphene. The vacuum degree in the reaction chamber was 0.2torr, the radio frequency power was 200W, the speed of the rotary kiln reactor was set to 50r / min, and the growth time was 120min. After the growth was completed, the temperature was first lowered to 500℃ in a mixed atmosphere of argon and hydrogen, and then lowered to room temperature in a pure argon atmosphere. The obtained graphene / aluminum nitride composite powder material was taken out, which was a composite material in which vertical graphene was completely coated on the surface of spherical aluminum nitride powder. Its Raman spectrum showed I D / I G The value of is 0.58.

[0075] Figure 4 Phase analysis of aluminum nitride powder and graphene / aluminum nitride composite powder materials prepared in Example 1, Comparative Example 1 and Comparative Example 2 after moisture absorption. Figure 4It can be seen that the aluminum nitride powder forms a distinct Al(OH)3 phase after absorbing moisture, while the powders prepared in Example 1 and Comparative Example 1 remain in the AlN phase, without any Al(OH)3 phase. This indicates that after being coated with horizontal graphene, the aluminum nitride is protected from contact with water, thereby preventing hydrolysis.

[0076] Figure 5 The thermal conductivity of aluminum nitride powder and the composite powder material after coating is shown. As can be seen from the figure, the thermal conductivity of the composite powder is significantly improved after coating with graphene. The thermal conductivity of the composite powder material coated with horizontal and vertical graphene (Example 1) is better than that of the composite powder material coated with only horizontal graphene (Comparative Example 1) and the composite powder material coated with only vertical graphene (Comparative Example 2).

[0077] Figure 6 The resistivity of aluminum nitride powder and the composite powder material after coating is shown. As can be seen from the figure, the resistivity of the powder decreases significantly after graphene growth, which helps reduce the occurrence of static electricity, thereby improving the safety, stability and service life of electronic components.

[0078] Unless otherwise defined, the terms used in the present invention have the same meanings as those commonly understood by those skilled in the art.

[0079] The embodiments described in the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Those skilled in the art may make various other substitutions, changes and improvements within the scope of the present invention. Therefore, the present invention is not limited to the above-mentioned embodiments, but is only limited by the claims.

Claims

1. A graphene / aluminum nitride composite powder material, characterized in that: The composite powder material is aluminum nitride powder whose surface is sequentially coated with horizontal graphene and vertical graphene.

2. The composite powder material according to claim 1, characterized in that The composite powder material is measured by Raman spectroscopy, and the peak ratio of the D band to the G band is I D / I G 0.1 to 1.2, preferably 0.1 to 0.5; Among them, the D band refers to the wave number at 1350cm -1 The G band refers to the wave number at 1600cm -1 band.

3. The composite powder material according to claim 1, characterized in that The particle size of the composite powder material is 50nm-100μm.

4. The composite powder material according to claim 1, characterized in that The aluminum nitride powder has a particle size range of 50 nm to 100 μm and a spherical or quasi-spherical shape.

5. The composite powder material according to claim 1, characterized in that The number of layers of the horizontal graphene is 1 to 10.

6. The composite powder material according to claim 1, characterized in that The height of the vertical graphene sheets is 5nm to 500nm, the thickness is 0.03nm to 2nm, and the spacing between the vertical graphene sheets is 1nm to 100nm.

7. The composite powder material according to claim 1, characterized in that The mass percentage of the sum of the horizontal graphene and the vertical graphene in the composite powder material is 0.01 wt% to 0.5 wt%.

8. A method for preparing the composite powder material according to any one of claims 1 to 7, characterized in that: include: S1, growing the horizontal graphene on the surface of the aluminum nitride powder; S2. Growing the vertical graphene on the surface of the horizontal graphene to obtain the composite powder material.

9. The preparation method according to claim 8, characterized in that The steps S1 and S2 are carried out in a rotary kiln reactor.

10. The preparation method according to claim 8, characterized in that In the step S1, the horizontal graphene is grown by chemical vapor deposition, the flow ratio of the carbon source to hydrogen in the chemical vapor deposition is 1:(1-100), the reaction time is 30 min-300 min, and the reaction temperature is 600° C.-1600° C.; and / or, In the step S2, the vertical graphene is grown by plasma enhanced chemical vapor deposition, the radio frequency power of the plasma enhanced chemical vapor deposition is 20W to 1000W, the reaction time is 30min to 300min, and the temperature is 400°C to 1100°C.

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