Graphene composite heat-conducting gasket and preparation method thereof

Abstract

The invention discloses a graphene composite heat-conducting gasket and a preparation method thereof. The gasket comprises 30-45 parts of a three-dimensional graphene heat-conducting foam film skeleton, 40-60 parts of a modified heat-conducting filler, 2-5 parts of an interface bridging agent, 25-35 parts of a two-component adhesive, 8-15 parts of a curing agent and 1-3 parts of an auxiliary agent. Wherein the three-dimensional graphene heat-conducting foam film is subjected to laser drilling treatment, the aperture is 0.5-2 mm, and the porosity is 60-75%; the modified heat-conducting filler is boron nitride and / or aluminum oxide with the surface coated with a core-shell oxide layer, the core layer is TiO2 with the thickness of 5-10 nm, and the shell layer is a silane coupling agent derivative with the grafting rate of 2.5-3.0%; the interface bridging agent is a Ti < 3 > C < 2 > T < X > nanosheet; the two-component adhesive is composed of organic silicon resin and epoxy resin according to the weight ratio of 1: (0.3-0.8). The technical problems that an existing heat-conducting gasket is insufficient in heat-conducting property and large in interface contact thermal resistance are solved, and the heat-conducting gasket is mainly used for heat conduction and heat dissipation of electronic devices.

Description

Technical Field

[0001] This invention relates to the field of thermally conductive materials, specifically to a graphene composite thermally conductive pad and its preparation method. Background Technology

[0002] With the continuous increase in power density of electronic devices and increasingly stringent heat dissipation requirements, thermal interface materials, as key components of thermal management systems, directly affect the operational stability and lifespan of electronic devices. Graphene, due to its excellent intrinsic thermal conductivity (theoretical thermal conductivity up to 5300 W / (m·K)), has become an ideal material for preparing high-performance thermal pads.

[0003] Currently, the main technologies for preparing graphene thermal pads include graphene film lamination, graphene filler blending, and three-dimensional graphene network construction. Chinese patent CN108913104A discloses a thermal pad and its preparation method, employing a three-dimensional film-like graphene network structure. An ordered graphene framework is prepared using a template method, followed by filling with insulating thermally conductive fillers and a silicone matrix. Chinese patent CN112375392A discloses a method for preparing a graphene thermally conductive interface material, utilizing graphene oxide composite thermally conductive fillers combined with a silicone oil system, and improving thermal conductivity through reduction treatment. Chinese patent CN112341819B proposes a method for preparing an insulating graphene thermal pad, using electrostatic self-assembly technology to combine modified insulating fillers with graphene oxide to form a hybrid thermally conductive filler. Chinese patent CN115092920B describes a graphene thermal pad and its preparation method, which involves laminating and bonding a graphene composite film and a thermally conductive filler composite layer, then cutting it into thin sheets along the lamination direction. Chinese patent CN114148044B discloses a graphene composite thermally conductive pad and its preparation method. The method involves laser-drilling a graphene thermally conductive foam film and preparing the composite pad by impregnation with an adhesive and stacking layers.

[0004] However, existing graphene thermal pad technology still suffers from several technical shortcomings: First, the significant difference in surface energy between graphene and the polymer matrix leads to poor interfacial bonding, resulting in high interfacial thermal resistance and severe phonon scattering during transmission, which severely restricts the overall thermal conductivity of the composite material. Second, the high interlayer contact thermal resistance of graphene sheets makes it difficult to form a continuous and effective three-dimensional thermal conductive network, resulting in incomplete thermal pathways and failing to fully utilize the intrinsic thermal conductivity advantages of graphene. Third, pure graphene films are brittle, while simple blended pads suffer from insufficient compression resilience, making it difficult to meet the mechanical properties required for practical applications. Furthermore, high filler content leads to a sharp increase in resin viscosity, poor process compatibility, and difficulty in achieving sufficient impregnation, affecting product quality stability. Existing products generally have thermal conductivity limited to the range of 80-150 W / (m·K), and the interfacial modification methods are limited, making it difficult to simultaneously meet the dual requirements of ultra-high thermal conductivity and excellent mechanical properties. Therefore, new technical solutions are urgently needed to address these issues. Summary of the Invention

[0005] To address the technical challenges of existing graphene thermal pads, such as high interfacial thermal resistance, discontinuous thermal conductivity pathways, poor mechanical properties, and poor process compatibility, and to achieve ultra-high thermal conductivity, extremely low interfacial thermal resistance, excellent mechanical properties, process feasibility, and long-term stability, a graphene composite thermal pad is proposed.

[0006] The objective of this invention is achieved through the following technical solution: a graphene composite thermal conductive pad, comprising the following raw materials in parts by weight: 30-45 parts of three-dimensional graphene thermal conductive foam film skeleton, 40-60 parts of modified thermal conductive filler, 2-5 parts of interface bridging agent, 25-35 parts of two-component adhesive, 8-15 parts of curing agent, and 1-3 parts of additives. The three-dimensional graphene thermally conductive foam film is laser-drilled to have a pore size of 0.5-2 mm and a porosity of 60-75%. The modified thermally conductive filler is boron nitride and / or aluminum oxide with a core-shell oxide layer on the surface. The core layer is 5-10 nm thick TiO2, and the shell layer is a silane coupling agent derivative with a grafting rate of 2.5-3.0%.

[0007] Preferably, the interface bridging agent is Ti3C2T. X Nanosheets, 2-5 nm thick, 0.5-2 μm lateral dimension, with a surface zeta potential of -30 to -40 mV.

[0008] Preferably, the interface bridging agent is prepared by the following method: Ti3AlC2MAX phase raw material and ZnCl2 are mixed at a molar ratio of 1:1.5-1.8, calcined at 600-650℃ for 4-6h under an argon atmosphere, ZnCl2 is removed by ultrasonic washing with 0.1-0.2mol / L hydrochloric acid for 30-45min, and washed with deionized water until pH=6-7; then 8-12mL of tetrabutylammonium hydroxide and 8-12mL of tetramethylammonium hydroxide are added per 0.2g of crude product, and the mixture is stirred at 40±2℃ for 12-16h for intercalation treatment; then diluted with deionized water at a volume ratio of 1:400-500, ultrasonically exfoliated at 300-400W for 6-8h under ice bath conditions at ≤15℃, vacuum filtered, and vacuum dried at 50±5℃ for 12h to obtain layered MXenes nanosheets.

[0009] Preferably, the two-component adhesive is composed of silicone resin and epoxy resin in a weight ratio of 1:0.3-0.8; the silicone resin is vinyl-terminated polydimethylsiloxane with a viscosity of 5000-8000 mPa·s; and the epoxy resin is bisphenol A type epoxy resin E-44 or E-51 with an epoxy value of 0.41-0.53 eq / 100g.

[0010] Preferably, the additives are thixotropic agents and leveling agents.

[0011] Preferably, the modified thermally conductive filler is prepared by the following method: S1.1 Pretreatment of thermally conductive fillers: Spherical alumina (particle size 20-50μm, purity ≥99.5%) and / or hexagonal boron nitride (particle size 10-30μm, purity ≥99%) are vacuum dried at 120℃ for 4-6h to remove surface adsorbed moisture; S1.2, TiO2 core coating: The dried thermally conductive filler was dispersed in a mixed solution of anhydrous ethanol and deionized water at a volume ratio of 2:1 and a solid-liquid ratio of 1g:15-20mL. The mixture was ultrasonically dispersed for 30-40min at a stirring speed of 300-400rpm. Subsequently, an ethanol solution of tetrabutyl titanate (Ti(OC4H9)4) was added dropwise. The amount of Ti(OC4H9)4 was 8-12% of the mass of the thermally conductive filler, and the dropping rate was 2-3mL / min. Simultaneously, 25% ammonia solution was added dropwise. The pH of the system was adjusted to 8.8-9.2, the reaction temperature was controlled at 60±2℃, and the reaction was continuously stirred for 2-3 hours to allow tetrabutyl titanate to hydrolyze and condense to form TiO2 sol and coat the surface of the filler. After the reaction, the suspension was placed in a dialysis bag with a molecular weight cutoff of 1000-1200 and dialyzed with deionized water for 48-72 hours until the conductivity of the dialysate was <5μS / cm to remove residual ions. The obtained product was vacuum dried at 80℃ for 12 hours and calcined at 500℃ for 2 hours to obtain a core-layer modified filler with a TiO2 coating thickness of 5-10nm. S1.3, Hydrophobic modification of the core layer: The core-modified filler was dispersed in anhydrous ethanol at a solid-liquid ratio of 1g:10mL. Zinc stearate was added for surface hydrophobic modification. The amount of zinc stearate was 10-15% of the mass of the TiO2 core layer. The reaction was carried out under reflux in an oil bath at 80℃ for 4h with a stirring speed of 200-300rpm. After the reaction, the product was centrifuged and washed three times with a mixture of ethanol and deionized water in a volume ratio of 1:1, with a centrifugation speed of 4000-5000rpm for 10min each time. The washed product was vacuum dried at 80℃ for 6h and then calcined in a muffle furnace at 500℃ for 3h to obtain the hydrophobic core-modified filler. S1.4, Organosiloxane shell grafting: The hydrophobic core-layer modified filler was dispersed in isopropanol at a solid-liquid ratio of 1g:20mL, and ultrasonically dispersed for 30min at a frequency of 35-45kHz and a power of 400-450W; methacryloyloxypropyltrimethoxysilane (KH-570) was added as a silane coupling agent, with the amount of KH-570 being 6-9% of the mass of the core-layer modified filler; the mixture was stirred at room temperature for 30min to ensure complete hydrolysis; subsequently, an isopropanol solution of aluminum isopropoxide was added dropwise. The concentration is 0.2 mol / L, the amount is 3-5% of the mass of the core-shell modified filler, the dropping rate is 1-2 mL / min, the temperature is raised to 70-80℃, and the reaction is continuously stirred for 5-6 h to allow the silane coupling agent to condense on the surface of the filler to form a siloxane network; after the reaction is completed, the filler is filtered under reduced pressure, washed twice with isopropanol, and dried under vacuum at 60℃ for 12 h to obtain the core-shell structure modified thermally conductive filler, wherein the organosiloxane shell grafting rate is 2.5-3.0 wt%, and the shell thickness is 5-10 nm; The surface energy of the core-shell structure modified thermally conductive filler gradually transitions from 480-520 mJ / m² of TiO2 in the core layer to 20-30 mJ / m² of organosiloxane in the shell layer, achieving surface energy matching with the two-component adhesive, and reducing the interfacial contact angle from 85-90° in the unmodified layer to 10-15°.

[0012] Preferably, the modified thermally conductive filler and the interfacial bridging agent form a composite filler through electrostatic self-assembly: S2.1 Surface charge modification of the modified thermally conductive filler: The modified thermally conductive filler is dispersed in a mixed solution of ethanol and deionized water, with a volume ratio of ethanol to deionized water of 1:1 and a solid-liquid ratio of 1g:80-120mL. The mixture is ultrasonically dispersed for 30-40min at a power of 200-300W and a frequency of 40kHz to obtain a filler suspension. KH550 is dissolved in deionized water, with the amount of KH550 being 2.5-4.0% of the mass of the modified thermally conductive filler, and the amount of deionized water being... Add 4-6 times the mass of 50 glacial acetic acid to adjust the pH to 3.5-4.0, and stir at room temperature for 15-20 min to fully hydrolyze KH550. Slowly add the hydrolyzed KH550 solution to the filler suspension at a rate of 3-5 mL / min, raise the temperature to 75-85℃, and continue stirring for 3.5-4.5 h. After the reaction is complete, filter under vacuum, wash 3-4 times with deionized water, and dry under vacuum at 80-90℃ for 8-12 h to obtain a modified filler with a positively charged surface. S2.2 Preparation of interfacial bridging agent dispersion: The interfacial bridging agent is dispersed in deionized water to prepare an aqueous dispersion of interfacial bridging agent with a concentration of 1.5-2.5 mg / mL. The dispersion is ultrasonically dispersed for 1-1.5 h at an ultrasonic power of 200-250 W and a temperature controlled at 10-15℃. Then, the dispersion is magnetically stirred for 2-3 h at a stirring speed of 300-400 rpm to obtain a stable dispersion of interfacial bridging agent. S2.3 Electrostatic Self-Assembly: Under room temperature conditions, the interfacial bridging agent dispersion obtained in step S2.2 is slowly added dropwise to the modified filler dispersion with positive surface charge obtained in step S2.1 at a dropping rate of 1-2 mL / min. The solid content of the modified filler dispersion is 15-25 mg / mL, and the mass ratio of the interfacial bridging agent to the modified thermally conductive filler is 1:12-20. During the dropwise addition, the mixture is continuously magnetically stirred at a speed of 280-350 rpm. After the dropwise addition is completed, stirring is continued for 4-6 hours, followed by standing for 30-45 minutes to allow sufficient electrostatic adsorption. The resulting suspension is vacuum filtered and vacuum dried at 50-60℃ for 10-14 hours to obtain the composite filler.

[0013] This invention also provides a method for preparing a graphene composite thermal conductive pad, comprising the following steps: S31. Pretreatment of three-dimensional graphene thermally conductive foam film: The graphene foam film prepared by chemical vapor deposition is cut into shape, and through holes are prepared by laser drilling technology. The pore diameter is 0.5-2 mm, the pore spacing is 3-5 mm, and the porosity is controlled at 60-75%. Then, the perforated foam film is immersed in an ethanol solution containing 4-6 wt% Ti(OC4H9)4 and hydrolyzed at 80℃ for 4 h to form a 5-8 nm TiO2 core layer on the surface of the graphene framework. Then, it is modified by reflux of 0.1 mol / L zinc stearate ethanol solution at 80℃ for 4-5 h. Finally, the shell layer is grafted with methacryloxypropyltrimethoxysilane to obtain the core-shell modified graphene foam framework. S32. Preparation of two-component adhesive: Mix silicone resin and epoxy resin at a weight ratio of 1:0.3-0.8, degas at 80℃ for 2 hours, add additives, and stir evenly. S33, Impregnation and Composite Molding: The three-dimensional graphene foam film pretreated in step S1 is placed in a mold, and a vacuum is drawn to -0.09 MPa. The adhesive and composite filler from step S32 are injected, with the composite filler filling amount being 60-75% of the adhesive mass. The impregnation time is 30-60 min. Subsequently, a curing agent is added. The curing agent is a composite curing system composed of polyetheramine and methyltetrahydrophthalic anhydride in a weight ratio of 2:1. S34. Hot pressing: The impregnated foam film is hot-pressed and cured for 1-3 hours under a pressure of 5-15MPa and a temperature of 80-120℃, followed by curing at 80-100℃ for 2-4 hours, and then cooled to room temperature. S35. Surface treatment: The molded pad is polished on both sides, with a surface roughness Ra≤0.8μm and a thickness tolerance controlled within ±0.05mm, thus obtaining the graphene composite thermal conductive pad.

[0014] Preferably, the diameter of the laser-drilled holes in step S31 is 0.8-1.2 mm, and they are distributed in a hexagonal array. The roughness of the hole walls is increased after plasma treatment to enhance the mechanical bonding with the adhesive.

[0015] Preferably, the impregnation process in step S33 adopts a vacuum-pressure cycle process: first, vacuum is applied to -0.095MPa and held for 30 minutes, then pressure of 0.3-0.5MPa is applied and held for 20 minutes, and the cycle is repeated 2-3 times to ensure that the adhesive fully fills the pores of the foam film.

[0016] The beneficial effects of this invention are as follows: through the synergistic effect of the three-dimensional graphene foam skeleton and the core-shell filler / MXenes composite system, the thermal conductivity can reach 120-205 W / (m·K), which is 10-20 times higher than that of traditional gaskets; multi-level interface engineering makes the total interface thermal resistance less than 8 mm·K / W, reducing the thermal resistance by 50-65%; the two-component matrix design makes the rebound rate ≥60% at a compression rate of 30%, and the hardness (Shore A) controlled at 30-50; laser drilling and vacuum-pressure cyclic impregnation process solve the impregnation problem under high filling rate (>70wt%); the core-shell structure isolates MXenes from direct contact with the environment, and the thermal conductivity retention rate is ≥92% after aging at 85℃ / 85%RH for 1000h, achieving an organic unity of ultra-high thermal conductivity and excellent mechanical properties. Detailed Implementation

[0017] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments. The content mentioned in the embodiments is not intended to limit the present invention.

[0018] Example 1 This embodiment provides a graphene composite thermally conductive pad, which includes 35 parts of a three-dimensional graphene thermally conductive foam film skeleton, 50 parts of modified thermally conductive filler, 4 parts of interface bridging agent, 30 parts of two-component adhesive, 12 parts of curing agent, and 2 parts of additives.

[0019] The three-dimensional graphene thermally conductive foam membrane skeleton was prepared using CVD method. The graphene foam membrane had a density of 0.05 g / cm³ and a thermal conductivity of 800 W / (m·K). It underwent laser perforation, resulting in 1 mm pores arranged in a hexagonal array with a 4 mm spacing, achieving a porosity of 65%. Laser perforation creates a regular channel structure within the graphene foam membrane, providing pathways for subsequent adhesive penetration and filling, while maintaining the excellent thermal conductivity of graphene.

[0020] The modified thermally conductive filler is boron nitride with a core-shell oxide layer coated on its surface. The boron nitride particle size is 30 μm, and the purity is ≥99%. The core layer is 8 nm thick TiO2, and the shell layer is a silane coupling agent derivative with a grafting rate of 2.8%. The modified thermally conductive filler is prepared by the following method: S1: Pretreatment of thermally conductive filler: Hexagonal boron nitride is vacuum dried at 120℃ for 5h to remove surface adsorbed moisture; S2: TiO2 Core Coating: Dried boron nitride was dispersed in a mixed solution of anhydrous ethanol and deionized water at a volume ratio of 2:1 and a solid-liquid ratio of 1g:18mL. The mixture was ultrasonically dispersed for 35min with a stirring speed of 350rpm. Subsequently, an ethanol solution of tetrabutyl titanate (Ti(OC4H9)4) was added dropwise. The amount of Ti(OC4H9)4 was 10% of the mass of the thermally conductive filler, and the dropping rate was 2.5mL / min. Simultaneously, 25% (by mass) of... The pH of the system was adjusted to 9.0 with ammonia, and the reaction temperature was controlled at 60℃. The reaction was stirred continuously for 2.5 h to allow tetrabutyl titanate to hydrolyze and condense to form TiO2 sol, which then coated the surface of the filler. After the reaction, the suspension was placed in a dialysis bag with a molecular weight cutoff of 1100 and dialyzed with deionized water for 72 h until the conductivity of the dialysate was <5 μS / cm to remove residual ions. The product was vacuum dried at 80℃ for 12 h and calcined at 500℃ for 2 h to obtain a core-layer modified filler with a TiO2 coating thickness of 8 nm. S3: Core layer hydrophobic modification: The core layer modified filler was dispersed in anhydrous ethanol at a solid-liquid ratio of 1g:10mL. Zinc stearate was added for surface hydrophobic modification. The amount of zinc stearate was 12% of the mass of the TiO2 core layer. The reaction was carried out under reflux in an oil bath at 80℃ for 4h with a stirring speed of 250rpm. After the reaction, the product was centrifuged and washed three times with a mixture of ethanol and deionized water at a volume ratio of 1:1, with a centrifugation speed of 4500rpm and a time of 10min each time. After washing, the product was vacuum dried at 80℃ for 6h and then calcined in a muffle furnace at 500℃ for 3h to obtain the hydrophobic core layer modified filler. S4: Organosiloxane shell grafting: The hydrophobic core-layer modified filler was dispersed in isopropanol at a solid-liquid ratio of 1 g: 20 mL, and ultrasonically dispersed for 30 min at a frequency of 40 kHz and a power of 425 W. Methacryloxypropyltrimethoxysilane (KH-570) was added as a silane coupling agent, with the amount of KH-570 being 8% of the mass of the core-layer modified filler. The mixture was stirred at room temperature for 30 min to ensure complete hydrolysis. Subsequently, an isopropanol solution of aluminum isopropoxide was added dropwise at a concentration of 0.2 mol / L, with the amount being 4% of the mass of the core-layer modified filler and a dropping rate of 1.5 mL / min. The temperature was raised to 75 °C, and the reaction was continuously stirred for 5.5 h to allow the silane coupling agent to condense on the filler surface to form a siloxane network. After the reaction was completed, the mixture was filtered under reduced pressure, washed twice with isopropanol, and vacuum dried at 60 °C for 12 h to obtain a core-shell structure modified thermally conductive filler with an organosiloxane shell grafting rate of 2.8 wt% and a shell thickness of 7 nm.

[0021] The surface energy of the core-shell modified thermally conductive filler gradually transitions from 500 mJ / m² for the core TiO₂ layer to 25 mJ / m² for the shell organosiloxane layer, achieving surface energy matching with the two-component adhesive. This reduces the interfacial contact angle from 87° (unmodified) to 12°. This surface energy gradient design effectively improves the interfacial compatibility between the filler and the matrix, and reduces interfacial thermal resistance.

[0022] The interfacial bridging agent is Ti3C2TX nanosheets with a thickness of 3 nm, a lateral dimension of 1 μm, and a surface zeta potential of -38 mV. The interfacial bridging agent was prepared by the following method: Ti3AlC2MAX phase raw material was mixed with ZnCl2 at a molar ratio of 1:1.7 and calcined at 600 °C for 5 h under an argon atmosphere. ZnCl2 was removed by ultrasonic washing with 0.1 mol / L hydrochloric acid for 40 min, and the mixture was washed with deionized water until pH=6.5. Subsequently, 8 mL of tetrabutylammonium hydroxide (10 wt%) and 8 mL of tetramethylammonium hydroxide (5 wt%) were added per 0.2 g of crude product, and the mixture was stirred at 40 °C for 14 h for intercalation treatment. The mixture was then diluted with deionized water at a volume ratio of 1:500, ultrasonically exfoliated at 350 W for 7 h under an ice bath at 12 °C, vacuum filtered, and vacuum dried at 50 °C for 12 h to obtain layered MXenes nanosheets.

[0023] Modified thermally conductive fillers and interfacial bridging agents form composite fillers through electrostatic self-assembly: S1: Surface charge modification of the modified thermally conductive filler: The modified thermally conductive filler was dispersed in a mixed solution of ethanol and deionized water at a volume ratio of 1:1 and a solid-liquid ratio of 1g:100mL. The mixture was ultrasonically dispersed for 35min at a power of 250W and a frequency of 40kHz to obtain a filler suspension. KH550 was dissolved in deionized water at a concentration of 3.5% of the mass of the modified thermally conductive filler and 5 times the mass of the deionized water. The pH was adjusted to 3.8 by adding glacial acetic acid. The mixture was stirred at room temperature for 18min to allow for complete hydrolysis of KH550. The hydrolyzed KH550 solution was slowly added dropwise to the filler suspension at a rate of 4mL / min. The temperature was raised to 80℃ and the reaction was continuously stirred for 4h. After the reaction, the mixture was vacuum filtered, washed three times with deionized water, and vacuum dried at 85℃ for 10h to obtain a modified filler with a positively charged surface and a zeta potential of +32mV. S2: Preparation of interfacial bridging agent dispersion: The interfacial bridging agent was dispersed in deionized water to prepare an aqueous dispersion of interfacial bridging agent with a concentration of 2 mg / mL. The dispersion was ultrasonically dispersed for 1.2 h at an ultrasonic power of 225 W and a temperature controlled at 12 °C. Then, the dispersion was magnetically stirred for 2.5 h at a stirring speed of 350 rpm to obtain a stable dispersion of interfacial bridging agent. S3: Electrostatic self-assembly: Under room temperature conditions, the interfacial bridging agent dispersion obtained in step S2 was slowly added dropwise to the modified filler dispersion with positive surface charge obtained in step S1 at a dropping rate of 1.5 mL / min. The solid content of the modified filler dispersion was 20 mg / mL, and the mass ratio of the interfacial bridging agent to the modified thermally conductive filler was 1:15. During the dropwise addition, the mixture was continuously stirred with magnetic force at a speed of 315 rpm. After the dropwise addition was completed, stirring was continued for 5 h, followed by standing for 38 min to allow electrostatic adsorption to proceed fully. The suspension was then vacuum filtered and vacuum dried at 55 °C for 12 h to obtain the composite filler with a zeta potential of +2 mV.

[0024] The two-component adhesive consists of silicone resin and epoxy resin in a weight ratio of 1:0.6; the silicone resin is vinyl-terminated polydimethylsiloxane with a viscosity of 6500 mPa·s; the epoxy resin is bisphenol A type epoxy resin E-44 with an epoxy value of 0.47 eq / 100g. 20 parts of vinyl-terminated polydimethylsiloxane and 12 parts of E-44 epoxy resin were mixed and degassed at 80℃ for 2 hours.

[0025] In a preferred embodiment, the weight ratio of silicone resin to epoxy resin in the two-component adhesive can also be 1:0.4. In this case, the silicone component content is higher, which can further improve the flexibility and compression resilience of the gasket.

[0026] The additives include thixotropic agents and leveling agents. The thixotropic agent is 2.5 parts of fumed silica, and the leveling agent is 0.8 parts of BYK-300 leveling agent. The thixotropic agent can adjust the rheological properties of the adhesive and prevent filler sedimentation, while the leveling agent improves the surface tension of the adhesive and enhances its wettability.

[0027] The preparation process of the graphene composite thermal conductive pad is as follows: A modified three-dimensional graphene foam film is placed in a mold, and a vacuum is applied to -0.095 MPa. A mixture of adhesive and composite filler is injected, with the filler accounting for 68% of the adhesive mass. A vacuum-pressure cycling process is performed: vacuum for 30 minutes, followed by pressure application at 0.4 MPa for 20 minutes, repeated twice to ensure the adhesive fully penetrates the pores of the foam film. A composite curing agent of polyetheramine and methyltetrahydrophthalic anhydride is added at a weight ratio of 2:1, with the curing agent accounting for 30% of the adhesive mass. A segmented hot-pressing process is used for curing: 80℃ / 5MPa / 1h → 100℃ / 10MPa / 1h → 120℃ / 15MPa / 1h, followed by curing at 90℃ for 3h. Finally, double-sided polishing is performed to a thickness of 2.0±0.05 mm and a surface roughness Ra=0.6 μm.

[0028] This graphene composite thermal pad exhibits excellent thermal conductivity, reaching 185 W / (m·K), with an interfacial thermal resistance of only 6.5 mm·K / W, a compression resilience of 68%, a hardness (Shore A) of 42, and a volume resistivity of 2.5 × 10¹³ Ω·cm. After aging at 85℃ / 85%RH for 1000 hours, the thermal conductivity remains at 172 W / (m·K), with a retention rate of 93%, demonstrating excellent long-term stability.

[0029] Example 2 This embodiment provides a method for preparing a graphene composite thermally conductive pad. The method uses core-shell modification of a three-dimensional graphene foam film, a two-component adhesive system, and electrostatic self-assembly technology of composite fillers to prepare a composite thermally conductive pad with excellent thermal conductivity and interfacial thermal resistance control capability.

[0030] S31: Pretreatment of the 3D graphene thermally conductive foam film: A graphene foam film with a density of 0.05 g / cm³ and a thermal conductivity of 800 W / (m·K) was prepared by chemical vapor deposition and cut into 50×50 mm sizes. Through-holes were created on the surface of the foam film using CO2 laser drilling technology. The pore diameter was set to 1 mm, and the pores were arranged in a hexagonal array with a spacing of 4 mm. By controlling the drilling density, the porosity reached 65%. Laser drilling technology can precisely control the pore diameter and spacing, ensuring that the foam film maintains structural integrity while having good adhesive permeability.

[0031] The perforated foam film was immersed in an ethanol solution containing 5 wt% Ti(OC4H9)4 and hydrolyzed at 80°C for 4 h. During the hydrolysis process, tetrabutyl titanate formed a uniform TiO2 precursor, which, after heat treatment, formed a 6 nm thick TiO2 core layer on the graphene framework surface. The formation of the TiO2 core layer provided active sites for subsequent surface modification and enhanced the mechanical strength of the graphene framework.

[0032] The foam film with the TiO2 core layer was then immersed in a 0.1 mol / L zinc stearate ethanol solution and refluxed at 80 °C for 4 h for modification. Zinc stearate forms stable coordination bonds by binding its zinc ions to the hydroxyl groups on the TiO2 surface, while the long stearic acid chains provide a hydrophobic surface, improving the compatibility between the graphene framework and the organic matrix.

[0033] Finally, shell grafting was performed using methacryloxypropyltrimethoxysilane, with the silane coupling agent amounting to 7 wt% of the foam film mass. The reaction was carried out at 70 °C for 6 h. The methoxy group in the methacryloxypropyltrimethoxysilane molecule underwent a condensation reaction with the hydroxyl groups on the TiO2 surface to form a stable Si-O-Ti bond, while the methacryloxy group provided an active site for chemical cross-linking with the organic matrix, ultimately yielding a core-shell modified graphene foam framework.

[0034] S32: Two-component adhesive formulation: 20 parts of vinyl-terminated polydimethylsiloxane and 12 parts of E-44 epoxy resin are mixed at a weight ratio of 1:0.6. The silicone resin provides excellent flexibility and temperature resistance, while the epoxy resin provides good adhesive strength and mechanical properties. Their synergistic effect ensures that the adhesive system has both sufficient adhesive strength and good elastic recovery. During mixing, 2.5 parts of fumed silica are added as a thixotropic agent, and 0.8 parts of BYK-300 leveling agent are added to improve flowability. Vacuum degassing is performed at 80°C for 2 hours, with the degassing pressure controlled at -0.09 MPa, to ensure no air bubbles remain in the adhesive.

[0035] S33: Impregnation and Composite Molding: First, composite fillers are prepared by electrostatic self-assembly of modified thermally conductive fillers and interfacial bridging agents. The modified thermally conductive filler uses core-shell boron nitride. 50 parts of boron nitride (30 μm particle size) are dispersed in an ethanol-water mixed solution with a volume ratio of ethanol to water of 2:1 and a solid-liquid ratio of 1 g:100 mL. A 0.15 mol / L Ti(OC4H9)4 solution is added, and the pH is adjusted to 9 with ammonia. The mixture is stirred at 60 °C for 2.5 h to form a TiO2 core layer. After dialysis for 72 h, 12 wt% zinc stearate is added, and the mixture is refluxed at 80 °C for 4 h, followed by calcination at 500 °C to form a stable core-shell structure.

[0036] The core-shell boron nitride was dispersed in isopropanol, and 8 wt% methacryloyloxypropyltrimethoxysilane was added and ultrasonically treated for 40 min. Then, 0.2 mol / L aluminum isopropoxide solution was added dropwise, and the mixture was hydrolyzed at 75 °C for 5.5 h to obtain a core-shell boron nitride filler with a shell grafting rate of 2.8%.

[0037] Surface charge modification of core-shell boron nitride was performed by dispersing it in an ethanol-water mixed solution, adding 3.5wt% KH550 silane coupling agent, and modifying it at 80℃ for 4h. After modification, the filler surface was positively charged with a zeta potential of +32mV.

[0038] The interfacial bridging agent used was MXenes nanosheets. Ti3AlC2 and ZnCl2 were mixed at a molar ratio of 1:1.7, calcined at 600℃ for 5 h under argon protection, and then ultrasonically washed with 0.1 mol / L hydrochloric acid for 40 min to remove byproducts. 8 mL of TBAOH (10 wt%) and 8 mL of TMAOH (5 wt%) were added per 0.2 g of product, and the mixture was stirred at 40℃ for 14 h to perform intercalation. Then, the mixture was diluted 1:500 and ultrasonically treated at 12℃ in an ice bath (350 W power) for 7 h to obtain MXenes nanosheets with a thickness of 3 nm, a lateral dimension of 1 μm, and a zeta potential of -38 mV.

[0039] The MXenes dispersion (concentration 2 mg / mL) was slowly added dropwise to the modified filler dispersion with a positively charged surface. The amount of MXenes used was 4% of the filler mass. The mixture was stirred continuously at room temperature for 5 h. The MXenes were uniformly distributed on the filler surface through electrostatic interaction, and the composite filler was finally obtained. The zeta potential was +2 mV, indicating that the electrostatic self-assembly process was successfully completed.

[0040] The pretreated three-dimensional graphene foam film was placed in a mold, and a vacuum was drawn to -0.095 MPa. The mixture of adhesive and composite filler prepared in step S32 was then injected, with the composite filler accounting for 68% of the adhesive mass. A vacuum-pressure cyclic impregnation process was used: vacuum impregnation for 30 minutes, followed by pressurization to 0.4 MPa and holding for 20 minutes, repeated twice to ensure the adhesive fully penetrated the pore structure of the foam film. Subsequently, a curing agent was added. The curing agent was a composite curing system composed of polyetheramine and methyltetrahydrophthalic anhydride in a weight ratio of 2:1, and its dosage was 30% of the adhesive mass.

[0041] S34: Hot Press Molding: The impregnated foam film undergoes segmented hot press curing. The first stage involves holding the film at 80℃ and 5MPa for 1 hour to allow the adhesive to initially cure and remove residual solvent. The second stage involves raising the temperature to 100℃ and 10MPa for 1 hour to promote the cross-linking reaction. The third stage involves holding the film at 120℃ and 15MPa for 1 hour to complete the final curing. This segmented heating and pressurization process ensures complete curing of the adhesive and avoids stress concentration caused by excessive temperature gradients. After hot press curing, the film is post-cured at 90℃ for 3 hours to further refine the cross-linked network structure, and then naturally cooled to room temperature.

[0042] S35: Surface Treatment: The molded gasket undergoes double-sided polishing using progressively finer abrasives, achieving a final surface roughness Ra of 0.6 μm and a thickness controlled within the range of 2.0 ± 0.05 mm. This precise surface treatment ensures good contact between the gasket and the cooled device, reducing contact thermal resistance.

[0043] The graphene composite thermal pad obtained by the above preparation method has a thermal conductivity of 185 W / (m·K), an interfacial thermal resistance of 6.5 mm·K / W, a compression resilience of 68%, a Shore A hardness of 42, and a volume resistivity of 2.5 × 10¹³ Ω·cm. After aging at 85℃ / 85%RH for 1000 h, the thermal conductivity remains at 172 W / (m·K), with a retention rate of 93%, demonstrating excellent long-term stability.

[0044] In a preferred embodiment, the weight ratio of silicone resin to epoxy resin in the two-component adhesive can be adjusted to 1:0.4, the amount of MXenes can be adjusted to 3% of the filler mass, and alumina (40 μm particle size) can be used instead of boron nitride as the core-shell filler, while other process parameters remain unchanged. The resulting thermal pad exhibits a thermal conductivity of 142 W / (m·K), an interfacial thermal resistance of 8.2 mm·K / W, a compression resilience of 75%, and a Shore A hardness of 35, demonstrating excellent overall performance.

[0045] Example 3 This embodiment provides a method for preparing a graphene composite thermal conductive pad. Based on Embodiment 2, the laser drilling process in step S31 has been further optimized.

[0046] S31: Pretreatment of the three-dimensional graphene thermally conductive foam film: A graphene foam film prepared using the same chemical vapor deposition method as in Example 2, with a density of 0.05 g / cm³ and a thermal conductivity of 800 W / (m·K), was cut into 50×50 mm sizes. In the laser drilling process, the pore size was precisely controlled within the range of 0.8-1.2 mm. In this example, a pore size of 1.0 mm was selected, and a hexagonal array distribution was used for drilling with a pore spacing of 4 mm. By controlling the drilling density, the porosity reached 65%. After laser drilling, the pore walls were subjected to plasma treatment using argon plasma at a power of 150 W for 3 minutes, increasing the surface roughness of the pore walls from 0.2 μm to 1.5 μm. Plasma treatment, through high-energy particle bombardment of the pore wall surface, generates a micro-uneven structure, significantly enhancing the mechanical interlocking force between the pore walls and the adhesive, and improving the interfacial bonding strength.

[0047] The subsequent Ti(OC4H9)4 impregnation treatment, zinc stearate modification, and methacryloyloxypropyltrimethoxysilane grafting processes were exactly the same as in Example 2, ultimately yielding a core-shell modified graphene foam skeleton.

[0048] S32 to S35: The steps of two-component adhesive preparation, impregnation and composite molding, hot pressing molding and surface treatment are consistent with those in Example 2, including mixing silicone resin and epoxy resin at a weight ratio of 1:0.6, the composite filler filling amount is 68% of the adhesive mass, a composite curing system composed of polyetheramine and methyltetrahydrophthalic anhydride at a weight ratio of 2:1, and a segmented hot pressing curing process.

[0049] By optimizing the laser-drilled hole diameter to the range of 0.8-1.2 mm and employing plasma treatment to enhance the hole wall roughness, the prepared graphene composite thermal conductive pads achieved improved structural stability while maintaining excellent thermal conductivity. Test results show that the thermal conductivity reaches 188 W / (m·K), the interfacial thermal resistance is 6.2 mm·K / W, the compression resilience is 70%, the Shore A hardness is 43, and the volume resistivity is 2.3 × 10¹³ Ω·cm. After aging at 85℃ / 85%RH for 1000 h, the thermal conductivity remains at 175 W / (m·K), with a retention rate of 93.1%, demonstrating superior long-term stability and mechanical properties.

[0050] In a preferred embodiment, the laser drilling aperture can be selected as 0.8 mm or 1.2 mm, the plasma treatment power can be adjusted to 100 W or 200 W, and the treatment time can be adjusted accordingly to 2 min or 4 min. Other process parameters remain unchanged, and good overall performance can still be obtained.

[0051] Example 4 This embodiment provides a method for preparing a graphene composite thermal conductive pad, which further optimizes the impregnation process based on Embodiment 2.

[0052] S31: The pretreatment process of the three-dimensional graphene thermally conductive foam film is the same as that in Example 2. The graphene foam film prepared by chemical vapor deposition is cut and shaped, and through holes are prepared by laser drilling technology. The pore diameter is 1 mm, the pore spacing is 4 mm, and the porosity is controlled at 65%. After treatment by tetrabutyl titanate hydrolysis, zinc stearate modification and silane coupling agent grafting, a core-shell modified graphene foam skeleton is obtained.

[0053] S32: The preparation process of the two-component adhesive is the same as in Example 2. Vinyl-terminated polydimethylsiloxane and E-44 epoxy resin are mixed at a weight ratio of 1:0.6. Fumed silica is added as a thixotropic agent and BYK-300 leveling agent, and the mixture is vacuum degassed at 80°C for 2 hours.

[0054] S33: During the impregnation and composite molding process, the preparation of the composite filler is the same as in Example 2. MXene nanosheets are combined with core-shell boron nitride using electrostatic self-assembly technology to form the composite filler. The pretreated three-dimensional graphene foam film is placed in a mold, and a mixture of adhesive and composite filler is injected. The composite filler filling amount is 68% of the adhesive mass.

[0055] A vacuum-pressure cycling process is employed during the impregnation process: First, a vacuum is drawn to -0.095 MPa and maintained for 30 minutes to completely expel air from the pores of the foam film, creating favorable conditions for adhesive penetration. Then, a pressure of 0.4 MPa is applied and maintained for 20 minutes, forcing the adhesive into the microporous structure of the foam film under pressure. This cycle is repeated twice to ensure the adhesive fully fills the pores of the foam film and eliminates any potential air bubble defects. Compared to the traditional single vacuum impregnation method, this vacuum-pressure cycling process significantly improves the penetration depth and filling uniformity of the adhesive, avoiding a decrease in thermal conductivity due to incomplete filling. Subsequently, a composite curing agent consisting of polyetheramine and methyltetrahydrophthalic anhydride in a weight ratio of 2:1 is added, at a dosage of 30% of the adhesive mass.

[0056] S34: The hot pressing process is the same as in Example 2, using segmented hot pressing curing treatment, holding at 80℃ / 5MPa, 100℃ / 10MPa, and 120℃ / 15MPa for 1 hour each, followed by post-curing at 90℃ for 3 hours.

[0057] S35: The surface treatment process is the same as in Example 2. The molded gasket is polished on both sides to achieve a surface roughness of 0.6μm and a thickness controlled within the range of 2.0±0.05mm.

[0058] The graphene composite thermal pads prepared using a vacuum-pressure cyclic impregnation process achieved a 96% adhesive filling rate in the foam film, a significant improvement over the 85% filling rate achieved by conventional processes. The prepared thermal pads exhibited a thermal conductivity of 195 W / (m·K), a 5.4% increase compared to Example 2, a reduced interfacial thermal resistance of 5.8 mm·K / W, a compression resilience of 70%, a Shore A hardness of 44, and a volume resistivity of 2.8 × 10¹³ Ω·cm. After aging at 85°C / 85%RH for 1000 hours, the thermal conductivity remained at 184 W / (m·K), maintaining a retention rate of 94.4%, demonstrating excellent long-term stability and reliability.

[0059] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A graphene composite thermal conductive pad, characterized in that: The raw materials include the following parts by weight: 30-45 parts of three-dimensional graphene thermally conductive foam film skeleton, 40-60 parts of modified thermally conductive filler, 2-5 parts of interface bridging agent, 25-35 parts of two-component adhesive, 8-15 parts of curing agent, and 1-3 parts of additives. The three-dimensional graphene thermally conductive foam film is laser-drilled to have a pore size of 0.5-2 mm and a porosity of 60-75%. The modified thermally conductive filler is boron nitride and / or aluminum oxide with a core-shell oxide layer on the surface. The core layer is 5-10 nm thick TiO2, and the shell layer is a silane coupling agent derivative with a grafting rate of 2.5-3.0%.

2. The graphene composite thermal conductive pad according to claim 1, characterized in that: The interface bridger is Ti3C2T. X Nanosheets, 2-5 nm thick, 0.5-2 μm lateral dimension, with a surface zeta potential of -30 to -40 mV.

3. The graphene composite thermal conductive pad according to claim 2, characterized in that: The interface bridging agent was prepared by the following method: Ti3AlC2MAX phase raw material and ZnCl2 were mixed at a molar ratio of 1:1.5-1.8 and calcined at 600-650℃ for 4-6 h under an argon atmosphere. ZnCl2 was removed by ultrasonic washing with 0.1-0.2 mol / L hydrochloric acid for 30-45 min, and then washed with deionized water until pH=6-7. Subsequently, 8-12 mL of tetrabutylammonium hydroxide and 8-12 mL of tetramethylammonium hydroxide were added per 0.2 g of crude product, and the mixture was stirred at 40±2℃ for 12-16 h for intercalation treatment. Then, the mixture was diluted with deionized water at a volume ratio of 1:400-500, and ultrasonically exfoliated at 300-400 W for 6-8 h under ice bath conditions at ≤15℃. The mixture was then vacuum filtered and vacuum dried at 50±5℃ for 12 h to obtain layered MXenes nanosheets.

4. The graphene composite thermal conductive pad according to claim 1, characterized in that: The two-component adhesive is composed of silicone resin and epoxy resin in a weight ratio of 1:0.3-0.8; the silicone resin is vinyl-terminated polydimethylsiloxane with a viscosity of 5000-8000 mPa·s; the epoxy resin is bisphenol A type epoxy resin E-44 or E-51 with an epoxy value of 0.41-0.53 eq / 100g.

5. The graphene composite thermal conductive pad according to claim 1, characterized in that: The additives are thixotropic agents and leveling agents.

6. The graphene composite thermal conductive pad according to claim 1, characterized in that: The modified thermally conductive filler is prepared by the following method: S1.1, Pretreatment of thermally conductive fillers: Vacuum dry spherical alumina and / or hexagonal boron nitride at 120℃ for 4-6 hours to remove surface adsorbed moisture; S1.2, TiO2 core coating: The dried thermally conductive filler was dispersed in a mixed solution of anhydrous ethanol and deionized water at a volume ratio of 2:1 and a solid-liquid ratio of 1g:15-20mL. The mixture was ultrasonically dispersed for 30-40 minutes at a stirring speed of 300-400rpm. Subsequently, an ethanol solution of tetrabutyl titanate was added dropwise. The amount of tetrabutyl titanate was 8-12% of the mass of the thermally conductive filler, and the dropping rate was 2-3mL / min. Simultaneously, 25% ammonia solution was added dropwise to adjust the pH of the system to 8. .8-9.2, control the reaction temperature at 60±2℃, and continuously stir the reaction for 2-3 hours to allow tetrabutyl titanate to hydrolyze and condense to form TiO2 sol and coat the surface of the filler; after the reaction, the suspension is placed in a dialysis bag with a molecular weight cutoff of 1000-1200 and dialyzed with deionized water for 48-72 hours until the conductivity of the dialysate is <5μS / cm to remove residual ions; the obtained product is vacuum dried at 80℃ for 12 hours and calcined at 500℃ for 2 hours to obtain a core-layer modified filler with a TiO2 coating thickness of 5-10nm; S1.3, Hydrophobic modification of the core layer: The core-modified filler was dispersed in anhydrous ethanol at a solid-liquid ratio of 1g:10mL. Zinc stearate was added for surface hydrophobic modification. The amount of zinc stearate was 10-15% of the mass of the TiO2 core layer. The reaction was carried out under reflux in an oil bath at 80℃ for 4h with a stirring speed of 200-300rpm. After the reaction, the product was centrifuged and washed three times with a mixture of ethanol and deionized water in a volume ratio of 1:1, with a centrifugation speed of 4000-5000rpm for 10min each time. The washed product was vacuum dried at 80℃ for 6h and then calcined in a muffle furnace at 500℃ for 3h to obtain the hydrophobic core-modified filler. S1.4, Organosiloxane shell grafting: The hydrophobic core-layer modified filler was dispersed in isopropanol at a solid-liquid ratio of 1 g: 20 mL, and ultrasonically dispersed for 30 min at a frequency of 35-45 kHz and a power of 400-450 W. KH-570 was added as a silane coupling agent, with the amount of KH-570 being 6-9% of the mass of the core-layer modified filler. The mixture was stirred at room temperature for 30 min to ensure complete hydrolysis. Subsequently, an isopropanol solution of aluminum isopropoxide with a concentration of 0.2 mol was added dropwise. The dosage is 3-5% of the mass of the core-shell modified filler, with a dropping rate of 1-2 mL / min. The temperature is raised to 70-80℃, and the reaction is continuously stirred for 5-6 h to allow the silane coupling agent to condense on the filler surface to form a siloxane network. After the reaction is completed, the filler is filtered under reduced pressure, washed twice with isopropanol, and dried under vacuum at 60℃ for 12 h to obtain the core-shell structure modified thermally conductive filler, wherein the organosiloxane shell grafting rate is 2.5-3.0 wt%, and the shell thickness is 5-10 nm.

7. The graphene composite thermal conductive pad according to claim 2, characterized in that: The modified thermally conductive filler and the interfacial bridging agent form a composite filler through electrostatic self-assembly: S2.1 Surface charge modification of the modified thermally conductive filler: The modified thermally conductive filler is dispersed in a mixed solution of ethanol and deionized water, with a volume ratio of ethanol to deionized water of 1:1 and a solid-liquid ratio of 1g:80-120mL. The mixture is ultrasonically dispersed for 30-40min at a power of 200-300W and a frequency of 40kHz to obtain a filler suspension. KH550 is dissolved in deionized water, with the amount of KH550 being 2.5-4.0% of the mass of the modified thermally conductive filler, and the amount of deionized water being... Add 4-6 times the mass of 50 glacial acetic acid to adjust the pH to 3.5-4.0, and stir at room temperature for 15-20 min to fully hydrolyze KH550. Slowly add the hydrolyzed KH550 solution to the filler suspension at a rate of 3-5 mL / min, raise the temperature to 75-85℃, and continue stirring for 3.5-4.5 h. After the reaction is complete, filter under vacuum, wash 3-4 times with deionized water, and dry under vacuum at 80-90℃ for 8-12 h to obtain a modified filler with a positively charged surface. S2.2 Preparation of interfacial bridging agent dispersion: The interfacial bridging agent is dispersed in deionized water to prepare an aqueous dispersion of interfacial bridging agent with a concentration of 1.5-2.5 mg / mL. The dispersion is ultrasonically dispersed for 1-1.5 h at an ultrasonic power of 200-250 W and a temperature controlled at 10-15℃. Then, the dispersion is magnetically stirred for 2-3 h at a stirring speed of 300-400 rpm to obtain a stable dispersion of interfacial bridging agent. S2.3 Electrostatic Self-Assembly: Under room temperature conditions, the interfacial bridging agent dispersion obtained in step S2.2 is slowly added dropwise to the modified filler dispersion with positive surface charge obtained in step S2.1 at a dropping rate of 1-2 mL / min. The solid content of the modified filler dispersion is 15-25 mg / mL, and the mass ratio of the interfacial bridging agent to the modified thermally conductive filler is 1:12-20. During the dropwise addition, the mixture is continuously magnetically stirred at a speed of 280-350 rpm. After the dropwise addition is completed, stirring is continued for 4-6 hours, followed by standing for 30-45 minutes to allow sufficient electrostatic adsorption. The resulting suspension is vacuum filtered and vacuum dried at 50-60℃ for 10-14 hours to obtain the composite filler.

8. A method for preparing a graphene composite thermal conductive pad according to claim 7, characterized in that: Includes the following steps: S31. Pretreatment of three-dimensional graphene thermally conductive foam film: The graphene foam film prepared by chemical vapor deposition is cut into shape, and through holes are prepared by laser drilling technology. The pore diameter is 0.5-2 mm, the pore spacing is 3-5 mm, and the porosity is controlled at 60-75%. Then, the perforated foam film is immersed in an ethanol solution containing 4-6 wt% Ti(OC4H9)4 and hydrolyzed at 80℃ for 4 h to form a 5-8 nm TiO2 core layer on the surface of the graphene framework. Then, it is modified by reflux of 0.1 mol / L zinc stearate ethanol solution at 80℃ for 4-5 h. Finally, the shell layer is grafted with methacryloxypropyltrimethoxysilane to obtain the core-shell modified graphene foam framework. S32. Preparation of two-component adhesive: Mix silicone resin and epoxy resin at a weight ratio of 1:0.3-0.8, degas at 80℃ for 2 hours, add additives, and stir evenly. S33, Impregnation and Composite Molding: The three-dimensional graphene foam film pretreated in step S1 is placed in a mold, and a vacuum is drawn to -0.09 MPa. The adhesive and composite filler from step S32 are injected, with the composite filler filling amount being 60-75% of the adhesive mass. The impregnation time is 30-60 min. Subsequently, a curing agent is added. The curing agent is a composite curing system composed of polyetheramine and methyltetrahydrophthalic anhydride in a weight ratio of 2:

1. S34. Hot pressing: The impregnated foam film is hot-pressed and cured for 1-3 hours under a pressure of 5-15MPa and a temperature of 80-120℃, followed by curing at 80-100℃ for 2-4 hours, and then cooled to room temperature. S35. Surface treatment: The molded pad is polished on both sides, with a surface roughness Ra≤0.8μm and a thickness tolerance controlled within ±0.05mm, thus obtaining the graphene composite thermal conductive pad.

9. A graphene composite thermal conductive pad according to claim 8, characterized in that: In step S31, the diameter of the laser-drilled holes is 0.8-1.2 mm, and they are distributed in a hexagonal array. The roughness of the hole walls is increased after plasma treatment to enhance the mechanical bonding with the adhesive.

10. A graphene composite thermal conductive pad according to claim 8, characterized in that: The impregnation process described in step S33 adopts a vacuum-pressure cycle process: first, vacuum is drawn to -0.095MPa and held for 30 minutes, then 0.3-0.5MPa pressure is applied and held for 20 minutes, and the cycle is repeated 2-3 times to ensure that the adhesive fully fills the pores of the foam film.