A method for preparing a graphene-based composite thermal interface material

Abstract

The application belongs to the technical field of composite materials, and discloses a preparation method of a graphene-based composite thermal interface material. The method comprises the following steps: S1, obtaining a graphene dispersion liquid with a two-dimensional sheet structure; S2, obtaining a CuNPs / GNPs composite material; S3, preparing a dispersion liquid of the CuNPs / GNPs composite material obtained in step S2, adding 3-(methacryloyloxy)propyl trimethoxysilane to the dispersion liquid for surface modification, and obtaining a modified CuNPs / GNPs composite material dispersion liquid; and S4, adding a silver nanowire dispersion liquid to the modified CuNPs / GNPs composite material dispersion liquid obtained in step S3, and preparing the graphene-based composite thermal interface material. By loading metal nanoparticles between graphene layers and introducing a nanowire three-dimensional network, a high-efficiency longitudinal heat conduction channel is constructed, the transverse heat conduction capacity is simultaneously enhanced, and the overall heat dissipation performance of the composite material is improved.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, specifically relating to a method for preparing a graphene-based composite thermal interface material. Background Technology

[0002] As electronic devices continue to evolve towards miniaturization and high integration, their internal heat flux density is increasing exponentially, posing a serious threat to the operational stability and service life of these devices. Therefore, developing novel thermal interface materials that combine efficient heat dissipation with reliable service performance has become a research hotspot in the field of thermal management. However, currently available commercial thermal interface materials still have significant limitations; the out-of-plane thermal conductivity of typical thermal pads is only about 5 W·m. -1 ·K -1 Furthermore, its long-term stability is poor, making it difficult to meet the increasingly stringent heat dissipation requirements of high-power electronic devices. Graphene, with its unique two-dimensional crystal structure, excellent processability, and outstanding phonon transport properties, is considered to have broad application prospects in the field of thermal interface materials. However, it is worth noting that graphene exhibits significant thermal anisotropy, with a huge difference between its in-plane and out-of-plane (longitudinal) thermal conductivity. The heat dissipation bottleneck of modern microelectronic devices is precisely concentrated on the longitudinal heat conduction path perpendicular to the device surface, which poses a serious challenge to the direct application of graphene. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a method for preparing graphene-based composite thermal interface materials. By loading metal nanoparticles between graphene layers and introducing a three-dimensional network of nanowires, a highly efficient longitudinal thermal conduction channel is constructed while simultaneously enhancing the lateral thermal conduction capacity, thereby improving the overall heat dissipation performance of the composite material.

[0004] The objective of this invention is achieved through the following technical solution: This invention provides a method for preparing a graphene-based composite thermal interface material, comprising the following steps: S1, to obtain a graphene dispersion with a two-dimensional sheet structure; S2, NaOH solution, CuCl2 and hydrazine hydrate are added to the graphene dispersion obtained in step S1 to react and allow copper nanoparticles to grow in situ and be distributed on the surface of the graphene substrate, so as to obtain CuNPs / GNPs composite material, wherein the particle size of the copper nanoparticles is 10-100 nm. S3, the CuNPs / GNPs composite material obtained in step S2 is made into a dispersion, and 3-(methacryloyloxy)propyltrimethoxysilane and ammonia are added to it for surface modification to obtain the modified CuNPs / GNPs composite material dispersion. S4. Add silver nanowire dispersion to the modified CuNPs / GNPs composite material dispersion obtained in step S3, and perform mixing and assembly treatment so that the silver nanowires are arranged in a crisscross pattern on the surface of the graphene substrate and / or interspersed between the copper nanoparticles. The diameter of the silver nanowires is 20-150 nm, and the graphene-based composite thermal interface material is obtained.

[0005] In some embodiments, in step S1, the mass fraction of graphene in the graphene dispersion is 0.1 wt%-1.5 wt%.

[0006] In some embodiments, in step S2, the amount of CuCl2 added is 5 wt%-25 wt% of the mass of graphene, based on the mass of Cu element therein.

[0007] In some embodiments, in step S3, the CuNPs / GNPs composite material dispersion is obtained by adding the CuNPs / GNPs composite material obtained in step S2 to a mixture of anhydrous ethanol and deionized water, then adding PVP dispersant to the mixture, and finally ultrasonically treating the mixture to obtain the CuNPs / GNPs composite material dispersion.

[0008] In some embodiments, in step S3, the mass fraction of CuNPs / GNPs composite material in the CuNPs / GNPs composite material dispersion is 0.1 wt%-2 wt%.

[0009] In some embodiments, in step S3, the amount of 3-(methacryloyloxy)propyltrimethoxysilane added is 20-80 μL.

[0010] In some embodiments, in step S4, the mass fraction of silver nanowires in the silver nanowire dispersion is 0.1 wt%-1 wt%.

[0011] In some embodiments, in step S4, the amount of silver nanowire dispersion added is based on the mass of silver nanowires, and the mass percentage of silver nanowires relative to the CuNPs / GNPs composite material is 5 wt%-25 wt%.

[0012] In some embodiments, in step S4, the processing method is to ultrasonically stir the mixed liquid in the dark, and then wash, separate, and dry it in the dark.

[0013] Compared with the prior art, the beneficial technical effects of the present invention are as follows: This invention improves the overall heat dissipation performance of the composite material by loading metal nanoparticles between graphene layers and introducing a three-dimensional network of nanowires to construct efficient longitudinal heat conduction channels while simultaneously enhancing lateral heat conduction.

[0014] Other features and beneficial effects of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other beneficial effects of the invention can be realized and obtained by means of the structures particularly pointed out in the description, claims and drawings. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 The images shown are electron microscope images of the materials obtained and used in Example 1, including (a) surface SEM images of silver nanowires, (b) and (c) surface SEM images of the (CuNPs-AgNWs) / GNPs composite material, (d) and (e) cross-sectional SEM images of the (CuNPs-AgNWs) / GNPs composite material, and (f) TEM image of the (CuNPs-AgNWs) / GNPs composite material. Figure 2 The images show (a) surface SEM images and (b) elemental mapping distributions of Cu and Ag for the material obtained in Example 1. Figure 3 The X-ray diffraction patterns of the materials obtained in Example 1, Comparative Examples 1, 4, and 5 are shown below. Figure 4 The X-ray photoelectron spectra of the materials obtained in Example 1, Comparative Examples 1, 4, and 5 are shown below. Figure 5 The infrared spectra of the materials obtained in Example 1, Comparative Examples 1, 4, and 5 are shown below. Figure 6 The Raman spectra of the materials obtained in Example 1 and Comparative Examples 1-5 are shown below. Figure 7 The graph shows the relationship between (a) longitudinal thermal diffusivity and (b) longitudinal thermal conductivity as a function of temperature for the materials obtained in Comparative Examples 1, 2, 3, and 5. Figure 8 The graphs show the relationship between (a) longitudinal thermal diffusivity and (b) longitudinal thermal conductivity as a function of temperature for the materials obtained in Example 1, Comparative Examples 1, 4, and 5. Figure 9 Thermogravimetric analysis (TGA) diagrams of the materials obtained in Example 1 and Comparative Example 5 are shown. Figure 10 The sheet resistance values ​​of the materials obtained in Example 1 and Comparative Examples 1-5 are shown in the diagram. Figure 11 For comparative examples 1, 2, 3, and 5, when the materials are used as heat sinks, (a) the temperature change of the LED beads over time and (b) the actual infrared thermal image; Figure 12 The images show (a) the temperature change of the LED beads over time and (b) the actual infrared thermal image when the materials obtained in Example 1, Comparative Examples 1, 4, and 5 are used as heat sinks. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The technical features designed in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0018] This invention provides a method for preparing a graphene-based composite thermal interface material, comprising the following steps: S1, to obtain a graphene dispersion with a two-dimensional sheet structure; S2, NaOH solution, CuCl2 and hydrazine hydrate are added to the graphene dispersion obtained in step S1 to react and allow copper nanoparticles to grow in situ and be distributed on the surface of the graphene substrate, so as to obtain CuNPs / GNPs composite material, wherein the particle size of the copper nanoparticles is 10-100 nm. S3, the CuNPs / GNPs composite material obtained in step S2 is made into a dispersion, and 3-(methacryloyloxy)propyltrimethoxysilane and ammonia are added to it for surface modification to obtain the modified CuNPs / GNPs composite material dispersion. S4. Add silver nanowire dispersion to the modified CuNPs / GNPs composite material dispersion obtained in step S3, and perform mixing and assembly treatment so that the silver nanowires are arranged in a crisscross pattern on the surface of the graphene substrate and / or interspersed between the copper nanoparticles. The diameter of the silver nanowires is 20-150 nm, and the graphene-based composite thermal interface material is obtained.

[0019] For step S1, the two-dimensional sheet-like graphene was prepared using the supercritical carbon dioxide method. The specific preparation process is as follows: 0.5 g of expanded graphite was weighed and added to an ultrasonic reactor. The apparatus was installed and its airtightness was checked. High-purity carbon dioxide was first introduced for a period of time to purge the air from the apparatus. The exhaust port was then closed, and the pressure inside the reactor was increased to 12 MPa, while the temperature was raised to 40 °C to ensure that the carbon dioxide inside the reactor reached a supercritical state. The pressure and temperature were then maintained constant for ultrasonication for 90 minutes. After ultrasonication, the venturi-like valve between the reactor and the receiving tank was opened. Under the rapid expansion of the supercritical carbon dioxide, the graphite was mechanically exfoliated into graphene. Finally, the gas inside the device was vented, and the obtained graphene nanosheets (GNPs) were collected.

[0020] The graphene dispersion was obtained by adding a certain amount of GNPs to 100 mL of anhydrous ethanol and adding 0.01 g of polyvinylpyrrolidone (PVP) to aid dispersion. The mixture was then subjected to ultrasonic treatment for 15 min to obtain the GNPs dispersion. The mass fraction of graphene in the graphene dispersion was 0.1 wt%-1.5 wt%.

[0021] For step S2, the NaOH solution had a concentration of 1 M and a volume of 1 mL. CuCl2 and hydrazine hydrate were added to the mixture at a molar ratio of 1:1.2. The amount of CuCl2 added, based on the mass of Cu element, was 5 wt%-25 wt% of the graphene mass. The reaction process was as follows: the reaction was carried out in an oil bath at 50 ℃ for 30 min, followed by washing and filtration with anhydrous ethanol and deionized water. The filter paper and filter cake were then placed together in a vacuum drying oven and dried overnight at 60 ℃ to obtain the CuNPs / GNPs composite material.

[0022] It's important to note that there's an optimal range for controlling the particle size of copper nanoparticles. If the particle size is too small (<10 nm), the number of particles increases significantly with the same amount of copper added, but the contact area between each particle and the graphene sheet decreases accordingly, leading to an increase in the proportion of interfacial thermal resistance and thus weakening thermal conductivity. However, smaller nanoparticles are generally more conducive to achieving uniform coverage on the graphene surface and passivating defect sites; this advantage cannot be ignored, but smaller particle size is not always better. Conversely, if the particle size is too large (>100 nm), the number of particles decreases significantly, making it difficult to form uniformly distributed heat conduction nodes between graphene sheets, and the connectivity of the thermal conduction network will be greatly reduced. Therefore, a comprehensive balance must be struck between the gains in coverage and passivation of small particles and the risk of increasing interfacial thermal resistance, controlling the particle size within a moderate range to fully utilize the role of copper nanoparticles as thermal interface fillers.

[0023] For step S3, the CuNPs / GNPs composite material dispersion is obtained as follows: the CuNPs / GNPs composite material obtained in step S2 is added to a mixture of anhydrous ethanol and deionized water, then PVP dispersant is added to the mixture, and finally the mixture is ultrasonically treated to obtain the CuNPs / GNPs composite material dispersion. The mass fraction of CuNPs / GNPs composite material in the CuNPs / GNPs composite material dispersion is 0.1 wt%-2 wt%. The amount of 3-(methacryloyloxy)propyltrimethoxysilane (MPS) added is 20-80 μL.

[0024] It should be noted that the purpose of adding 3-(methacryloyloxy)propyltrimethoxysilane (MPS) is to protect the Cu nanoparticles already loaded on the graphene surface and to modify the graphene surface to facilitate the subsequent loading of Ag nanowires.

[0025] For step S4, the silver nanowire dispersion was obtained as follows: (1) 20 mL of ethylene glycol (EG) was mixed with 5.2 mmol PVP and stirred at 120 °C until the solution was clear and free of precipitate. (2) 0.6 mL of 0.01 M NaCl solution was added and the temperature was raised to 175 °C. After the temperature stabilized, 3.5 mmol AgNO3 was added and the reaction was carried out in the dark for 18 min. (3) After the reaction was completed, the mixture was quickly cooled in an ice bath and kept in the dark. After cooling, the mixture was washed three times by centrifugation with anhydrous ethanol at a speed of 3000 r / min and a time of 5 min. The mixture was then dispersed in anhydrous ethanol and stored in a brown vial for later use to obtain the Ag nanowire dispersion. The mass fraction of silver nanowires in the silver nanowire dispersion was 0.1 wt%-1 wt%. The amount of silver nanowire dispersion added was based on the mass of silver nanowires, and the mass percentage of silver nanowires relative to the CuNPs / GNPs composite material was 5 wt%-25 wt%. The processing method involves ultrasonically stirring the mixed liquid in the dark, followed by washing, separation, and drying in the dark.

[0026] It should be noted that the primary purpose of pre-depositing copper nanoparticles on graphene nanosheets (GNPs) is to reduce the defect density on the graphene surface. Loading silver nanowires on this basis helps to construct a well-ordered thermally conductive network. If silver nanowires are directly loaded onto the GNP surface without copper nanoparticle pretreatment, the uneven surface of graphene makes it difficult to form ordered thermally conductive pathways. Furthermore, loading silver nanowires first and then depositing copper nanoparticles also presents significant problems: the preparation of silver nanowires introduces a large amount of surfactant, and even after cleaning, some residue is unavoidable. This weakens the adhesion between the subsequent copper nanoparticles and the substrate, resulting in weak deposition and easy detachment. Therefore, adopting a "copper first, silver later" deposition sequence is both a necessity for structural optimization and a choice based on process feasibility.

[0027] It should be noted that after obtaining CuNPs / GNPs by loading Cu nanoparticles onto graphene, further loading Ag nanowires provides more interfacial contact points compared to Ag nanoparticles. This results in more substantial bridging between graphene layers in the longitudinal direction, further enhancing longitudinal thermal conductivity. By connecting phonons on both sides through Ag nanowires, the nanowires fill more space between graphene layers, structurally reducing phonon scattering at the interface. This further reduces phonon mode mismatch, lowers interfacial thermal resistance, and enhances interfacial heat transfer characteristics. As the temperature rises, phonons within the graphene layers become more active, transferring heat longitudinally to the Ag nanowires and activating electrons within the Ag nanowires. Heat is primarily transferred in two directions. Laterally, it travels along the Ag nanowires. The crisscrossing network of Ag nanowires creates numerous connection points, increasing the pathways for heat transfer and facilitating further heat transfer by electrons. These additional contact points also effectively reduce the thermal resistance between different Ag nanowires. Vertically, electrons within the Ag nanowires transfer heat to another graphene layer, activating internal phonons and completing the vertical heat transfer. Compared to Ag nanoparticles, Ag nanowires provide more vertical heat conduction channels. While the former can transfer heat through these vertical channels, lateral heat transfer is limited to the graphene interfaces between each layer. Ag nanowires, however, can more quickly transfer heat laterally through the network and then vertically to another graphene layer, resulting in a stronger overall heat transfer capability and enabling timely heat dissipation through heat sinks.

[0028] The present invention will be further described in detail below with reference to specific embodiments. These embodiments will enable those skilled in the art to gain a more comprehensive understanding of the invention, but do not limit the invention in any way. Where techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0029] In the description of this invention, it should be noted that all terms used in this invention (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and should not be construed as limiting the invention; it should be further understood that the terms used in this invention should be understood to have the same meaning as those in the context of this specification and in the relevant field, and should not be understood in an idealized or overly formal sense, except as expressly defined in this invention.

[0030] Example 1: This embodiment provides a method for preparing a graphene-based composite thermal interface material, including the following steps: (1) Weigh 0.5 g of expanded graphite and add it to the ultrasonic reactor. Install the instrument and check its airtightness. First, introduce high-purity carbon dioxide for a period of time to purge the air in the instrument. Then, close the exhaust port and pressurize the reactor to 12 MPa. At the same time, raise the temperature to 40 °C to ensure that the carbon dioxide in the reactor reaches the supercritical state. Then, maintain the pressure and temperature unchanged and sonicate for 90 min. After the sonication is completed, open the venturi-like valve between the reactor and the receiving tank. The graphite is mechanically exfoliated into graphene under the rapid expansion of supercritical carbon dioxide. Finally, purge the gas in the device to collect the obtained graphene nanosheets (GNPs). Take 0.1 g of the obtained GNPs and add it to 100 mL of anhydrous ethanol. At the same time, add 0.01 g of polyvinylpyrrolidone (PVP) to aid dispersion. Sonicate the mixture for 15 min to obtain the GNPs dispersion.

[0031] (2) Add 1 mL of 1M NaOH solution to the GNPs dispersion. Add CuCl2 and hydrazine hydrate at a molar ratio of 1:1.2 to the mixture, with an amount of CuCl2 of 0.212 g. Transfer the mixture to a 50 ℃ oil bath and react for 30 min. After the reaction, wash and filter the mixture with anhydrous ethanol and deionized water. Place the filter paper and filter cake together in a vacuum drying oven and dry overnight at 60 ℃ to obtain the CuNPs / GNPs composite material.

[0032] (3) 0.1 g of dried CuNPs / GNPs was added to a mixture of 70 mL anhydrous ethanol and 30 mL deionized water, and 0.02 g of PVP was added to aid dispersion. The mixture was then sonicated for 30 min. 40 μL of 3-(methacryloyloxy)propyltrimethoxysilane (MPS) and 200 μL of ammonia were added to the ultrasonically dispersed mixture. An appropriate amount of Ag nanowire dispersion was added to make the final Ag nanowire mass fraction of the mixture 40 wt%. The mixture was sonicated for 2 min and then stirred in the dark at 25 ℃ for 2 h. Finally, the mixture was washed with anhydrous ethanol, filtered, and the filter paper and filter cake were placed together in a vacuum drying oven and dried overnight at 60 ℃ in the dark to obtain the (CuNPs-AgNWs) / GNPs composite material.

[0033] The preparation steps of the Ag nanowire dispersion are as follows: (1) Measure 20 mL of ethylene glycol (EG) and mix it with 5.2 mmol of PVP. Stir at 120 °C until the solution is clear and free of precipitate.

[0034] (2) Add 0.6 mL of 0.01 M NaCl solution and heat to 175 °C. After the temperature stabilizes, add 3.5 mmol AgNO3 and react in the dark for 18 min.

[0035] (3) After the reaction is completed, the mixture is cooled in an ice bath and kept away from light. After cooling, it is washed three times by centrifugation with anhydrous ethanol at a speed of 3000 r / min and a time of 5 min. Then it is dispersed in anhydrous ethanol and stored in a brown vial for later use to obtain Ag nanowire dispersion.

[0036] Comparative Example 1 (Graphene Nanosheets (GNPs)): This comparative example provides a method for preparing a graphene thermal interface material, comprising the following steps: Weigh 0.5 g of expanded graphite and add it to the ultrasonic reactor. Install the apparatus and check its airtightness. First, purge the air from the apparatus by introducing high-purity carbon dioxide for a period of time. Then, close the exhaust port and pressurize the reactor to 12 MPa while simultaneously raising the temperature to 40 °C to ensure that the carbon dioxide in the reactor reaches a supercritical state. Maintain constant pressure and temperature and sonicate for 90 minutes. After sonication, open the venturi-like valve between the reactor and the receiving tank. The graphite is mechanically exfoliated into graphene under the rapid expansion of supercritical carbon dioxide. Finally, vent the gas from the device to collect the obtained graphene nanosheets (GNPs).

[0037] Comparative Example 2 (CuNPs / GNPs): This comparative example provides a method for preparing a graphene-based composite thermal interface material, comprising the following steps: (1) GNPs were prepared according to the method in step (1) of Example 1. 0.1 g of the obtained GNPs were weighed and added to 100 mL of anhydrous ethanol, and 0.01 g of PVP was added as a dispersant. The mixture was sonicated for 15 min to obtain a GNPs dispersion.

[0038] (2) Add 1 mL of 1 mol / L NaOH solution to the above GNPs dispersion, and add CuCl2 and hydrazine hydrate at a molar ratio of 1:1.2, wherein the amount of CuCl2 added is 0.212 g. Then place the mixture in an oil bath at 50 ℃ and react for 30 min.

[0039] After the reaction was completed, the resulting mixture was washed and filtered with anhydrous ethanol and deionized water, and dried overnight under vacuum at 60 °C to obtain CuNPs / GNPs composite material.

[0040] Comparative Example 3 (AgNPs / GNPs): This comparative example provides a method for preparing a graphene-based composite thermal interface material, comprising the following steps: (1) Prepare GNPs according to the method of step (1) in Example 1. Weigh 0.1 g of the obtained GNPs and add them to a mixture of 70 mL of anhydrous ethanol and 30 mL of deionized water. Add 0.02 g of PVP and sonicate for 30 min to obtain a uniform GNPs dispersion.

[0041] (2) Add 40 μL of MPS and 200 μL of ammonia to the above GNPs dispersion and stir thoroughly at room temperature for 180 min.

[0042] (3) Add 0.1050 g AgNO3 and 0.0525 g trisodium citrate to the treated GNPs dispersion. The mass ratio of AgNO3 to trisodium citrate is 2:1. Then transfer the mixture to an 80 °C oil bath and react for 180 min.

[0043] After the reaction was completed, the mixture was washed and filtered with anhydrous ethanol and deionized water, and dried overnight under constant temperature vacuum at 60 °C to obtain AgNPs / GNPs composite material, wherein the theoretical mass fraction of Ag nanoparticles was 40 wt%.

[0044] Comparative Example 4 (AgNWs / GNPs): This comparative example provides a method for preparing a graphene-based composite thermal interface material, comprising the following steps: (1) Prepare GNPs according to the method of step (1) in Example 1. Weigh 0.1 g of the obtained GNPs and add them to a mixture of 70 mL of anhydrous ethanol and 30 mL of deionized water. At the same time, add 0.02 g of PVP and sonicate for 30 min.

[0045] (2) Add 40 μL of MPS to the ultrasonically dispersed GNPs dispersion for surface modification, and then add the Ag nanowire dispersion prepared according to the method described in Example 1, wherein the actual mass of the added Ag nanowires is 0.0667 g, so that the Ag nanowires account for 40 wt% of the total solid mass of the final composite material.

[0046] (3) The obtained mixture was ultrasonically treated for 2 min and stirred in the dark at 25 ℃ for 2 h. After the reaction was completed, it was washed and filtered with anhydrous ethanol and dried overnight in the dark at 60 ℃ under vacuum to obtain AgNWs / GNPs composite material.

[0047] Comparative Example 5 (CuNPs-AgNPs / GNPs): This comparative example provides a method for preparing a graphene-based composite thermal interface material, comprising the following steps: (1) Weigh 0.5 g of expanded graphite and add it to the ultrasonic reactor. Install the instrument and check its airtightness. First, introduce high-purity carbon dioxide for a period of time to purge the air in the instrument. Then, close the exhaust port and pressurize the reactor to 12 MPa. At the same time, raise the temperature to 40 °C to ensure that the carbon dioxide in the reactor reaches the supercritical state. Then, maintain the pressure and temperature unchanged and sonicate for 90 min. After the sonication is completed, open the venturi-like valve between the reactor and the receiving tank. The graphite is mechanically exfoliated into graphene under the rapid expansion of supercritical carbon dioxide. Finally, purge the gas in the device to collect the obtained graphene nanosheets (GNPs). Take 0.1 g of the obtained GNPs and add it to 100 mL of anhydrous ethanol. At the same time, add 0.01 g of polyvinylpyrrolidone (PVP) to aid dispersion. Sonicate the mixture for 15 min to obtain the GNPs dispersion.

[0048] (2) Add 1 mL of 1M NaOH solution to the GNPs dispersion. Add CuCl2 and hydrazine hydrate at a molar ratio of 1:1.2 to the mixture, with an amount of CuCl2 of 0.212 g. Transfer the mixture to a 50 ℃ oil bath and react for 30 min. After the reaction, wash and filter the mixture with anhydrous ethanol and deionized water. Place the filter paper and filter cake together in a vacuum drying oven and dry overnight at 60 ℃ to obtain the CuNPs / GNPs composite material.

[0049] (3) 0.1 g of dried CuNPs / GNPs was added to a mixture of 70 mL anhydrous ethanol and 30 mL deionized water, and 0.02 g of PVP was added to aid dispersion. The mixture was then sonicated for 30 min. 40 μL of 3-(methacryloyloxy)propyltrimethoxysilane (MPS) and 200 μL of ammonia were added to the ultrasonically dispersed mixture, and the mixture was stirred thoroughly for 180 min. Then, 0.105 g of AgNO3 and 0.0525 g of trisodium citrate (mass ratio 2:1) were added. The mixture was then transferred to an 80 ℃ oil bath and reacted for 180 min. After the reaction, the mixture was washed with anhydrous ethanol and deionized water, filtered, and the filter paper and filter cake were placed together in a vacuum drying oven and dried overnight under constant temperature vacuum conditions at 60 ℃ to obtain the (CuNPs-AgNWs) / GNPs composite material.

[0050] The materials obtained in the examples and comparative examples were characterized in a series of ways: To understand the microstructure and approximate elemental distribution of (CuNPs-AgNWs) / GNPs composites and related materials, each composite material was analyzed using scanning electron microscopy (SEM, ZEISS Sigma, Germany), transmission electron microscopy (TEM, TALOS F200, FEI, USA), and energy dispersive electron spectroscopy. Figure 1 (a) The Ag nanowires prepared for the experiment clearly show a slender and uniform morphology, with very few byproduct Ag nanoparticles, indicating that most of the Ag nanoparticles at the beginning of the reaction have already extended into Ag nanowires, and the Ag nanowires are produced during the reaction. + The reduction and directional growth were effectively controlled, which also proved that Ag nanowires prepared by the polyol method have excellent morphological uniformity. Figure 1 (b) and (c) are surface images of the (CuNPs-AgNWs) / GNPs composite material. It can be seen that the crisscrossing silver nanowires are uniformly distributed on the surface of graphene, forming a three-dimensional thermally conductive network between the graphene layers. The magnified image shows small Cu nanoparticles uniformly distributed on the graphene surface. Figure 1 (d) and (e) are cross-sectional views of the (CuNPs-AgNWs) / GNPs composite material. Due to the external force during cross-section failure, the Ag nanowires on the cross-section exhibit some bending and interlacing, but still maintain structural integrity. The magnified view also shows abundant silver nanowires loaded between graphene layers, constructing lateral directional thermal conduction channels between the layers through the Ag nanowires. Numerous thermal conduction channels form a lateral thermal conduction network. Compared to Ag nanoparticles, Ag nanowires provide more interfacial contact points, further reducing interfacial thermal resistance and improving both lateral and longitudinal thermal conductivity of the graphene composite material. Figure 1(f) is a transmission electron microscope image of the (CuNPs-AgNWs) / GNPs composite material. It can also be seen that small Cu nanoparticles are uniformly distributed on the graphene surface, with an average particle diameter of about 20 nm and an average Ag nanowire diameter of about 80 nm.

[0051] The elemental distribution of the (CuNPs-AgNWs) / GNPs composite material was characterized and analyzed using scanning electron microscopy coupled with energy dispersive spectroscopy (EDS). The results are shown in Figure 2. Figure 2 The scanning electron microscope (SEM) images and corresponding elemental energy dispersive spectroscopy (EDS) diagrams of the (CuNPs-AgNWs) / GNPs composite materials (a)-(c) show that the graphene substrate maintains a complete two-dimensional sheet structure. Both Cu nanoparticles and Ag nanowires are successfully and uniformly loaded on its surface without significant agglomeration. The interlacing of the nanowires helps reduce interfacial thermal resistance. The interlaced Ag nanowires form a three-dimensional continuous thermally conductive network, and it can be seen that the Ag nanowires in the next graphene sheet also interlaced, forming a continuous thermally conductive network laterally.

[0052] To investigate the crystal structure of the (CuNPs-AgNWs) / GNPs composite material and its comparative sample, characterization analysis was performed using X-ray diffraction (XRD, Rigaku Corporation, Japan, Ultima-IV). Figure 3 It can be seen that the characteristic peak of pure graphene at 2θ = 26.5 ° still exists after loading Cu nanoparticles and Ag nanowires, indicating that the loading of both did not have a significant impact on the crystal structure of graphene. Compared with the (CuNPs-AgNPs) / GNPs composite material, the intensity of the graphene characteristic peak did not decrease significantly when loading Ag nanowires at a moderate temperature, indicating that the crystallinity did not decrease significantly. The appearance of characteristic peaks on the Ag(111), Ag(200), Ag(220), and Ag(311) crystal planes proves the successful loading of Ag nanowires. Since the prepared Ag nanowires mainly grow along the Ag(111) crystal plane under the action of PVP coating, this characteristic peak has the highest intensity among the characteristic peaks of Ag. The presence of characteristic peaks on the Cu(111) and Cu(220) crystal planes proves the successful loading of Cu nanoparticles. Because the reaction temperature is not high, the characteristic peaks on the Cu2O(111) crystal plane did not appear, indicating that the Cu nanoparticles were basically not oxidized or the oxidized part was very small, and the minimum intensity of the peak did not reach the target.

[0053] To determine the surface elemental composition of the (CuNPs-AgNWs) / GNPs composite material and its comparative sample, X-ray photoelectron spectroscopy (XPS, Physical Electronics, Quantum 2000, USA) was used for characterization. Figure 4It can be seen that the main characteristic peak of pure graphene is the C 1s absorption peak at 284 eV, and the O 1s absorption peak at 532 eV mainly originates from air exposure during storage and partial oxidation caused by water in the air. In the XPS spectrum of the (CuNPs-AgNWs) / GNPs composite material, the Cu 2p absorption peak and Cu LMN Auger peak prove the successful loading of Cu nanoparticles; the Ag 3d double absorption peak proves the successful loading of Ag nanowires, and the O 1s absorption peak mainly comes from the partial oxidation of Cu nanoparticles and graphene.

[0054] To analyze the main chemical bonds or functional groups present in the samples, the prepared graphene and its composites were characterized by Fourier transform infrared spectroscopy (FTIR, Nicolet 6700, Nicolet Corporation, USA). Figure 5 It can be seen that the main characteristic peaks of each sample are at 1383 cm⁻¹. -1 1633 cm -1 and 3419 cm -1 Location. 1383 cm -1 The peak at that point mainly comes from sp 3 The vibrations of hybrid carbon originate from some defects on the graphene surface. 1633 cm -1 The sharp peak at 3419 cm⁻¹ is a characteristic peak of graphene, mainly originating from the stretching vibrations of the C=C framework within graphene itself, proving that the supporting substrate is indeed graphene. -1 The broad peak at this point originates from the stretching vibration of the OH bonds in water molecules, primarily due to the small amount of water present in the sample itself. Comparison of the spectra of various samples also reveals that no significant new peaks were generated, indicating that the loading of Cu nanoparticles and Ag nanowires is merely physical loading, without any reaction to form new chemical bonds. The interlacing of Ag nanowires on the graphene surface causes some shielding of infrared light, resulting in a relatively weak overall peak intensity in the Ag nanowire-loaded composite material, which is normal.

[0055] To analyze the surface defect level of graphene and its composites, Raman spectroscopy (Renishaw, UK, In Via) was used to characterize each sample. By comparing different characteristic peaks and peak area information, the defect level and structural information of the (CuNPs-AgNWs) / GNPs composites were obtained. Figure 6 The main characteristic peak of graphene materials is the D peak (~1350 cm⁻¹). -1 G peak (~1580 cm) -1 ) and 2D peak (2600 ~ 2700 cm⁻¹) -1 The D peak represents the sp peak of the carbon atom. 3Hybrid structure, G peak originates from in-plane stretching of CC, representing sp2 of carbon atoms. 2 The hybrid structure and 2D peaks reflect the intrinsic electronic structure and can appear without defects, serving as indicators of graphene quality. The ratio I of the peak areas of the D and G peaks in graphene composites is calculated. D / I G This can represent the degree of defect in graphene, I D / I G A lower value indicates a lower degree of defect. Figure 6 It can be seen that the I of pristine pure graphene D / I G The ID / IG value is only 0.037, indicating that the graphene prepared by the supercritical carbon dioxide method has extremely low defect levels. Unlike the AgNPs / GNPs composite material, which shows an increase in defect levels despite the presence of Cu nanoparticle agglomeration, the CuNPs / GNPs composite material exhibits a significantly lower defect level. This suggests that small-sized Cu nanoparticles can indeed reduce the defect level of graphene to some extent. Therefore, the ID / IG value of the (CuNPs-AgNPs) / GNPs composite material is only 0.026, lower than that of pure graphene. The main characteristic peak of graphene loaded with Ag nanowires is the D peak (~1350 cm⁻¹). -1 G peak (~1580 cm) -1 ) and 2D peak (2600 ~ 2700 cm⁻¹) -1 The ) still exists, without significantly disrupting its intrinsic structure. The I of the AgNWs / GNPs composite material D / I G The value increased from 0.037 for pure graphene to 0.056, mainly because the mechanical interaction between Ag nanowires and graphene during mixing and stirring created some new defects on the surface, leading to an increase in the overall defect level. Since CuNPs / GNPs loaded with small-sized Cu nanoparticles have even lower defect levels, although the overall defect level increased after loading Ag nanowires, it remained at an extremely low level. D / I G The value is only 0.040. This indicates that the simultaneous introduction of Cu nanoparticles and Ag nanowires did not significantly affect the main structure of graphene and did not alter its original crystal structure.

[0056] Figure 7 , 8 (a) and (b) show the longitudinal thermal diffusivity α of each composite material, measured at different temperatures using a laser flare analyzer (Netzsch, Germany, LFA447). ⊥ And calculation (the calculation formula is) k=α·C p ·ρ, In the formula,k Thermal conductivity can be classified according to the measurement method. k ⊥ and k ∥ W·m -1 ·K -1 ; α Thermal diffusivity, which can be classified according to the measurement method, is called thermal diffusivity. α ⊥ and α ∥ mm 2 ·s -1 ; C p For specific heat capacity, J·g -1 ·K -1 ; ρ Density, g·cm -3 The longitudinal thermal conductivity k obtained after ) ⊥ The "Through-Plane" mode is used when determining the longitudinal thermal diffusivity. Figure 7 (a) It can be seen that the longitudinal thermal diffusivity of the (CuNPs-AgNPs) / GNPs composite material decreases with increasing temperature, from 4.692 at 25 °C to 3.764 mm at 125 °C. 2 ·s -1 The longitudinal thermal diffusivity of other control samples all decreased with increasing temperature, with pure graphene decreasing from 3.413 mm. 2 ·s -1 The temperature decreased to 2.722 mm as the temperature increased. 2 ·s -1 CuNPs / GNPs composites from 2.394 mm 2 ·s -1 The temperature decreased to 2.01 mm as the temperature increased. 2 ·s -1 It is less affected by temperature; AgNPs / GNPs composites are 3.952 mm thick. 2 ·s -1 The temperature decreased to 3.205 mm as the temperature increased. 2 ·s -1 .Depend on Figure 7 (b) It can be seen that the longitudinal thermal conductivity of the (CuNPs-AgNPs) / GNPs composite material first increases and then decreases with temperature, from 7.763 W·m at 25 ℃. -1 ·K -1 The highest value was 9.587 W·m at 75 °C. -1 ·K -1 Although the longitudinal thermal conductivity decreased slightly as the temperature continued to rise, it still remained at a relatively high value of 8.970 W·m.-1 ·K -1 Furthermore, it is evident that the (CuNPs-AgNPs) / GNPs composite material outperforms other comparative samples in both longitudinal thermal diffusivity and longitudinal thermal conductivity, and is significantly superior to pure graphene, with a longitudinal thermal conductivity approximately 2.5 times that of pure graphene. The longitudinal thermal conductivity of pure graphene is relatively stable, increasing from 3.280 W·m with increasing temperature. -1 ·K -1 Increased to 3.567 W·m -1 ·K -1 The CuNPs / GNPs composite material has a slightly higher yield than pure graphene, increasing from 3.849 W·m⁻¹ with increasing temperature. -1 ·K -1 Increased to 4.526 W·m -1 ·K -1 AgNPs / GNPs composites, starting with 5.677 W·m at 25 °C. -1 ·K -1 The highest value was 6.428 W·m⁻¹ when the temperature was increased to 50 °C. -1 ·K -1 It then decreased to 5.746 W·m at 125 °C as the temperature rose. -1 ·K -1 .

[0057] Depend on Figure 8 (a) It can be seen that the longitudinal thermal diffusivity of the (CuNPs-AgNWs) / GNPs composite material decreases with increasing temperature, from 5.245 at 25 °C to 4.122 mm at 125 °C. 2 ·s -1 The longitudinal thermal diffusivity of pure graphene also decreases with increasing temperature, from 3.413 mm at 25 °C. 2 ·s -1 2.722 mm at 125 °C 2 ·s -1 The longitudinal thermal diffusivity of the AgNWs / GNPs composite material increased from 4.567 mm at 25 °C. 2 ·s -1 3.774 mm at 125 °C 2 ·s -1 The longitudinal thermal diffusivity of the (CuNPs-AgNPs) / GNPs composite decreased from 4.692 at 25 °C to 3.764 mm at 125 °C. 2 ·s -1 The longitudinal thermal diffusivity and its variation trend are similar to those of AgNWs / GNPs composite materials.

[0058] Depend on Figure 8 (b) It can be seen that the longitudinal thermal conductivity of the (CuNPs-AgNWs) / GNPs composite material first increases with temperature and then decreases slightly, from 9.244 W·m at 25 ℃. -1 ·K -1 The highest value was 10.444 W·m at 50 °C. -1 ·K -1 It then remained relatively stable, averaging 10.163 W·m -1 ·K -1 The longitudinal thermal conductivity of the (CuNPs-AgNPs) / GNPs composite material fluctuates. It first increases and then decreases with temperature, from 7.763 W·m at 25 °C. -1 ·K -1 The highest value was 9.587 W·m at 75 °C. -1 ·K -1 After the temperature continued to rise, it decreased to 8.970 W·m at 125 ℃. -1 ·K -1 The longitudinal thermal conductivity of the AgNWs / GNPs composite material first increases and then decreases with temperature, from 7.681 W·m at 25 °C. -1 ·K -1 The highest value was 10.006 W·m at 50 °C. -1 ·K -1 It later decreased to 7.706 W·m at 125 °C. -1 ·K -1 The longitudinal thermal conductivity of pure graphene is relatively stable, decreasing from 3.280 W·m at 25 °C with increasing temperature. -1 ·K -1 3.567 W·m at 125 °C -1 ·K -1 Because Ag nanowires can provide more interfacial contact points than Ag nanoparticles, and the contact between Ag nanowires can also reduce interfacial thermal resistance, the longitudinal thermal conductivity of the (CuNPs-AgNWs) / GNPs composite material is further improved compared with that of the (CuNPs-AgNPs) / GNPs composite material.

[0059] The thermal stability of (CuNPs-AgNWs) / GNPs composites in air was investigated using a thermogravimetric analyzer (Netzsch TG209F1, Germany). The results are as follows: Figure 9As shown. According to the spectrum analysis, the pyrolysis of (CuNPs-AgNWs) / GNPs composite material in air is mainly divided into two processes: (1) When the heating temperature is 20 ~ 300 ℃, the main mass loss is caused by the decomposition and volatilization of the remaining water and internal residual reactants in the composite material. Since there is a small amount of PVP remaining on the surface of Ag nanowires, and small Cu nanoparticles will also be oxidized, the overall mass of the composite material will fluctuate at this stage. Even so, the mass loss before 300 ℃ does not exceed 1 wt%; (2) When the heating temperature is 550 ~ 800 ℃, the main mass loss is caused by the high-temperature decomposition or even oxidation and combustion of the carbon main body in the composite material, which changes from a large amount of solid to gas, resulting in a large degree of mass loss. In actual use, electronic components do not reach extremely high temperatures. Compared with (CuNPs-AgNPs) / GNPs composite materials, (CuNPs-AgNWs) / GNPs composite materials have stronger thermal stability, exhibiting larger fluctuations later and having a decomposition temperature that is about 50 °C higher. This ensures stable use of electronic devices over a wider temperature range, further improving overall heat resistance.

[0060] Since thermal interface materials are mainly encapsulated in various electronic products, and practical applications require a certain level of electrical insulation performance, the sheet resistance of different samples was tested using an RTS-8 four-probe tester (Guangzhou Four-Probe Technology Co., Ltd., RTS-8). Figure 10As shown, since graphene itself is a two-dimensional material with ultra-high electrical conductivity, the electron movement in pure graphene is less affected by scattering and has high electron mobility. Therefore, the measured sheet resistance is also very low, only 41.18 mΩ / sq. The doping of Cu and Ag nanoparticles introduces new free electrons, and the metal nanoparticles (such as Au, Ag, and Cu) form local barriers on the graphene surface. These particles also become scattering centers, causing collisions when electrons pass through, thus reducing electron mobility. According to the previous characterization analysis, the metal nanoparticles do not bond with graphene and disrupt the original π-π stacking and interlayer electron coupling. Furthermore, the metal nanoparticles are discrete and discontinuous, making it difficult to form a continuous conductive network on the graphene plane. In addition, larger nanoparticles (≥ 5 nm) also increase the probability of electron scattering. At the same time, the aggregation and surface oxidation of some metal nanoparticles can also form discontinuous conductive pathways, which will also have an adverse effect on the conductive network of graphene. All of these factors lead to an increase in the overall sheet resistance of the (CuNPs-AgNPs) / GNPs composite material. Due to their small size and relatively low loading, Cu nanoparticles resulted in a sheet resistance of 62.58 mΩ / sq for the CuNPs / GNPs composite material. In contrast, the larger Ag nanoparticles had a greater impact on the overall graphene structure after loading, leading to an even higher sheet resistance of 69.54 mΩ / sq for the AgNPs / GNPs composite material. In summary, by simultaneously loading Cu and Ag nanoparticles, the sheet resistance of the (CuNPs-AgNPs) / GNPs composite material ultimately increased to 72.26 mΩ / sq, 1.75 times that of pure graphene. This improved the overall insulation performance of pure graphene and is beneficial for its application in the field of thermal interface materials. The sheet resistance of AgNWs / GNPs composites increased to 62.14 mΩ / sq compared to pure graphene, while the sheet resistance of (CuNPs-AgNWs) / GNPs composites further increased to 83.40 mΩ / sq, which is 2.03 times that of pure graphene, thus further improving the insulation performance of graphene. The main reason for this is that the Ag nanowires, crisscrossing on the graphene surface and between layers, introduce a much richer array of free electrons, making them far more complex than uniformly distributed metal nanoparticles. The electron network between the Ag nanowires and the electronic system of graphene itself differs, further affecting the electron permeability of graphene. In addition, the Ag nanowires also introduce some new defects during loading, and residual PVP impurities on the nanowires also affect the resistance and scattering at the interface, leading to improved electrical insulation performance.

[0061] To more intuitively demonstrate the heat dissipation effect of graphene and various composite materials, a 1W LED was selected as the heat source. The control system operated at a stable 3V voltage. Different materials were used as heat sinks, and an infrared thermal imager was used to record the temperature changes of the LED during heating and cooling in real time. The first 90 seconds represent the temperature rise of the LED during constant operation, and 90-180 seconds represent the cooling process after operation was stopped. A photograph was taken every 15 seconds. Figure 11 , 12 (a) is a summary graph showing the temperature changes of LED chips when different materials are used as heat sinks. Figure 11 , 12 (b) shows a portion of the actual infrared thermal images taken at the corresponding time. For example... Figure 11 As shown in (a), the surface temperature of the LED chip without a heat sink rapidly increases after power-on, reaching 62.2 °C in just 90 seconds. When pure graphene is used as the heat sink, the temperature decreases somewhat, reaching 54.6 °C after 90 seconds of power-on and 45 °C and 39.2 °C respectively after 30 seconds of power-off. This is mainly because while pure graphene has strong lateral thermal conductivity, its longitudinal thermal conductivity is relatively weak, resulting in a generally poor overall heat dissipation effect. When CuNPs / GNPs composite materials and AgNPs / GNPs composite materials are used as heat sinks, the temperatures after 90 seconds of power-on are 51.9 °C and 52.8 °C respectively, and the temperatures after 30 seconds of power-off are 37.1 °C and 33.9 °C respectively. When using the (CuNPs-AgNPs) / GNPs composite material as a heat sink, the temperature was only 43 °C after 90 seconds of power-on. At this temperature, most electronic components could operate well, which was 19.2 °C lower than when no heat sink was used and 11.6 °C lower than when pure graphene was used as a heat sink. After power was turned off, the temperature dropped to 29.4 °C in just 30 seconds and to 22.8 °C after 60 seconds, close to room temperature. The thermal conductivity was far superior to other comparative samples. This indicates that the modified graphene composite material effectively improved the overall thermal conductivity. Although the lateral thermal conductivity decreased slightly, the significant improvement in longitudinal thermal conductivity made it more suitable for various electronic components in practical applications. Figure 12As shown in (a), the surface temperature of the LED chip without a heat sink rises to 62.2℃ after 90 s of power-on. When pure graphene sheet is used as the heat sink, the temperature decreases to 54.6℃ after 90 s of power-on, and drops to 45.0℃ and 39.2℃ respectively after 30 s of power-off. When AgNWs / GNPs composite material and (CuNPs-AgNPs) / GNPs composite material are used as heat sinks, the chip temperatures are 50.9℃ and 43.0℃ after 90 s of power-on, respectively, and 36.3℃ and 29.4℃ respectively after 30 s of power-off. When using the (CuNPs-AgNWs) / GNPs composite material as a heat sink, the surface temperature of the LED chip was only 39.4 ℃ after 90 seconds of power-on, far lower than the 62.2 ℃ without a heat sink. This performance was also better than using pure graphene and the (CuNPs-AgNPs) / GNPs composite material as heat sinks, with temperatures 15.2 ℃ and 3.6 ℃ lower, respectively. After power-off, the temperature dropped to 25.2 ℃ in just 30 seconds, close to room temperature, which is 4.2 ℃ lower than the (CuNPs-AgNPs) / GNPs composite material. This indicates that while maintaining high longitudinal thermal conductivity, extending Ag nanoparticles into Ag nanowires, and constructing a lateral thermally conductive network through the Ag nanowires, facilitates faster heat transfer. Maintaining low anisotropy and synergistically improving both lateral and longitudinal thermal conductivity effectively enhances the overall thermal conductivity of the composite material, making it more suitable for various electronic components in practical applications.

[0062] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for preparing a graphene-based composite thermal interface material, characterized in that, Includes the following steps: S1, to obtain a graphene dispersion with a two-dimensional sheet structure; S2, NaOH solution, CuCl2 and hydrazine hydrate are added to the graphene dispersion obtained in step S1 to react and allow copper nanoparticles to grow in situ and be distributed on the surface of the graphene substrate, so as to obtain CuNPs / GNPs composite material, wherein the particle size of the copper nanoparticles is 10-100 nm. S3, the CuNPs / GNPs composite material obtained in step S2 is made into a dispersion, and 3-(methacryloyloxy)propyltrimethoxysilane and ammonia are added to it for surface modification to obtain the modified CuNPs / GNPs composite material dispersion. S4. Add silver nanowire dispersion to the modified CuNPs / GNPs composite material dispersion obtained in step S3, and perform mixing and assembly treatment so that the silver nanowires are arranged in a crisscross pattern on the surface of the graphene substrate and / or interspersed between the copper nanoparticles. The diameter of the silver nanowires is 20-150 nm, and the graphene-based composite thermal interface material is obtained.

2. The preparation method according to claim 1, characterized in that, In step S1, the mass fraction of graphene in the graphene dispersion is 0.1 wt%-1.5 wt%.

3. The preparation method according to claim 1, characterized in that, In step S2, the amount of CuCl2 added is 5 wt%-25 wt% of the mass of graphene, based on the mass of Cu element therein.

4. The preparation method according to claim 1, characterized in that, In step S3, the CuNPs / GNPs composite material dispersion is obtained by adding the CuNPs / GNPs composite material obtained in step S2 to a mixture of anhydrous ethanol and deionized water, then adding PVP dispersant to the mixture, and finally ultrasonically treating the mixture to obtain the CuNPs / GNPs composite material dispersion.

5. The preparation method according to claim 1, characterized in that, In step S3, the mass fraction of CuNPs / GNPs composite material in the CuNPs / GNPs composite material dispersion is 0.1 wt%-2 wt%.

6. The preparation method according to claim 1, characterized in that, In step S3, the amount of 3-(methacryloyloxy)propyltrimethoxysilane added is 20-80 μL.

7. The preparation method according to claim 1, characterized in that, In step S4, the mass fraction of silver nanowires in the silver nanowire dispersion is 0.1 wt%-1 wt%.

8. The preparation method according to claim 1, characterized in that, In step S4, the amount of silver nanowire dispersion added is based on the mass of silver nanowires, and the mass percentage of silver nanowires relative to CuNPs / GNPs composite material is 5 wt%-25 wt%.

9. The preparation method according to claim 1, characterized in that, In step S4, the processing method is to ultrasonically stir the mixed liquid in the dark, and then wash, separate, and dry it in the dark.

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