A low-density three-dimensional graphene thermal conductive pad and its preparation method
By constructing a combination of thermally conductive filler/three-dimensional graphene framework and low-viscosity thermally conductive polymer, the problems of complex preparation and insufficient thermal conductivity of three-dimensional graphene thermally conductive pads in the prior art have been solved, achieving high efficiency, low density, improved thermal conductivity, and large-scale production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHANGZHOU XINDAFANG INNOVATIVE MATERIALS TECH CO LTD
- Filing Date
- 2024-12-31
- Publication Date
- 2026-06-30
AI Technical Summary
The existing three-dimensional graphene thermal pads have complex manufacturing processes, insufficient thermal conductivity, and cannot be mass-produced. Furthermore, their three-dimensional network structure is incomplete.
A thermally conductive filler/three-dimensional graphene framework was constructed using a freeze-drying method. Combined with the infusion of a low-viscosity thermally conductive polymer, the continuity between the thermally conductive filler and the polymer was improved by a modifier, forming stable C-C chemical bonds and enriching the thermal conduction channels.
A three-dimensional graphene thermal pad with high thermal conductivity has been developed, with an in-plane thermal conductivity of up to 30.2 W/(m·K) and a vertical thermal conductivity of 7.9 W/(m·K). The density is less than 1.6 g/cm3, making it suitable for lightweight electronic devices. The fabrication process is simple and can be mass-produced.
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Figure CN122302562A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of thermal interface materials, specifically to a low-density three-dimensional graphene thermal conductive pad and its preparation method. Background Technology
[0002] Thermal interface materials are primarily used to fill the space between device surfaces and heat sinks, eliminating air from interface pores and improving heat dissipation efficiency. Thermal interface materials are mainly categorized into thermally conductive gels, thermally conductive pads, thermally conductive silicone grease, and thermally conductive phase change materials. Thermally conductive pads are a relatively new type of thermal interface material that has emerged in recent years. Compared to thermally conductive silicone grease and thermally conductive gels, thermally conductive pads do not produce silicone oil precipitation, have lower thermal resistance, and can be infinitely compressed to fill gaps of various shapes, thereby maximizing the effective heat conduction area. Furthermore, high thermal conductivity pads are mainly represented by products from companies such as Deelink and Sekisui Chemicals in Japan. The directional alignment technology of high thermal conductivity carbon fibers yields longitudinally high thermal conductivity pads with thermal conductivity reaching 15~50 W / (m·K). Since the production technology of high thermal conductivity carbon fibers is mainly controlled by a few companies in the United States and Japan, companies like Deelink have made significant investments in intellectual property rights. Domestic companies are still in the catch-up stage in the field of high thermal conductivity carbon fiber pads, and it is difficult to achieve breakthroughs in raw materials and intellectual property rights in the short term.
[0003] Currently, an existing patent discloses a three-dimensional graphene thermally conductive and microwave-absorbing material and its preparation method, patent publication number: CN116261317 A, which includes the following steps: Step 1: Preparation of thermally conductive and microwave-absorbing material; Step 2: Using PDMS / three-dimensional graphene, PDMS / three-dimensional graphene composite material, and PDMS / three-dimensional graphene composite material II as thermally conductive and microwave-absorbing fillers, mixing with vinyl silicone oil, hydrogen-containing silicone oil, catalyst, and inhibitor in a stirrer to obtain a mixture; Step 3: Calendering the mixture in Step 2 into a sheet using a calender and then curing it to obtain a thermally conductive and microwave-absorbing gasket. In this technical solution, the network skeleton structure of three-dimensional graphene leverages the high thermal conductivity of graphene, giving the gasket good thermal conductivity. However, the existing technical solution has at least the following technical problems: First, the overall preparation process is complex, with high energy consumption and low yield in the solvothermal reaction, making large-scale preparation impossible; second, after the three-dimensional graphene is mixed in a stirrer, it only forms a local three-dimensional network structure in the pad, without forming an overall thermally conductive network structure, thus the thermal conductivity of the thermal pad needs to be improved. Therefore, there is an urgent need for a graphene thermal pad with a simple preparation process and high thermal conductivity. Summary of the Invention
[0004] The main objective of this invention is to provide a low-density, high-thermal-conductivity three-dimensional graphene thermal pad and its preparation method, so as to overcome the shortcomings of the prior art.
[0005] Another object of the present invention is to provide the application of the aforementioned low-density, high-thermal-conductivity three-dimensional graphene thermal pad.
[0006] To achieve the aforementioned objectives, the technical solution adopted by this invention includes: This invention provides a method for preparing a low-density three-dimensional graphene thermal conductive pad, comprising: S1: Formation of graphene oxide dispersion; S2: Construction of thermally conductive filler / three-dimensional graphene framework: The spherical thermally conductive filler precursor is dispersed in the graphene oxide dispersion. After dispersion, it is freeze-dried and self-assembled to obtain the thermally conductive filler precursor / three-dimensional graphene oxide framework. The graphene oxide is reduced and the spherical thermally conductive filler is formed by high-temperature heat treatment under an inert atmosphere to obtain the thermally conductive filler / three-dimensional graphene framework. S3: Preparation of thermally conductive polymer: Low-dimensional thermally conductive filler and modifier are added to low-viscosity polymer and mixed evenly to obtain thermally conductive polymer; S4: Preparation of thermally conductive pads: The thermally conductive polymer is injected into the thermally conductive filler / three-dimensional graphene framework and cured by heating at 80~100 ℃ to obtain low-density thermally conductive pads.
[0007] In one aspect of the present invention, in step S1, graphene oxide is dispersed in deionized water to prepare a graphene oxide suspension with a mass concentration of 1-20 g / L. The graphene oxide suspension is then exfoliated by high-speed stirring at a speed of 1000-3000 rpm / min for 1-10 h to achieve a uniform and stable monolayer exfoliated graphene oxide dispersion; and / or, the size of the graphene oxide is 10-20 μm.
[0008] In one aspect of the present invention, in S2, the mass ratio of the spherical thermally conductive filler precursor to the graphene oxide is (1~5):1, the dispersion speed is 3000~6000 rpm / min, the high-temperature heat treatment temperature is 800~1200 ℃, and the heat treatment time is 2~6 h.
[0009] In one aspect of the present invention, the inert atmosphere during high-temperature heat treatment includes an argon atmosphere and / or a helium atmosphere.
[0010] In one aspect of the present invention, the spherical thermally conductive filler precursor is one of aluminum sol, nano-silicon, and zinc chloride.
[0011] In one aspect of the present invention, in S3, the mass ratio of the low-dimensional thermally conductive filler to the polymer is (0.5~1):1, and the mass ratio of the modifier to the low-dimensional thermally conductive filler is (0.01~0.03):1.
[0012] In one aspect of the present invention, the low-dimensional thermally conductive filler is one of one-dimensional silicon carbide whiskers, one-dimensional aluminum nitride whiskers, two-dimensional boron nitride, and two-dimensional aluminum nitride; and / or, the size of the low-dimensional thermally conductive filler is 1~5 μm.
[0013] In one aspect of the present invention, the modifier is CH2=CH(CH2). n SiX3, wherein n is 0~10, and X is one of methoxy, ethoxy, or methoxy / ethoxy; the polymer is one of silicone gel, polyurethane gel, and acrylic gel, and the viscosity of the polymer is 100~1000 mPa·s.
[0014] In one aspect of the present invention, in S4, the mass ratio of thermally conductive filler / three-dimensional graphene framework to thermally conductive polymer is (0.2-0.3):1.
[0015] A low-density three-dimensional graphene thermal conductive pad is prepared according to the above method.
[0016] The present invention also provides the application of the above-mentioned low-density three-dimensional graphene thermal conductive pad as a thermal interface material in the electronic field.
[0017] The present invention has the following beneficial effects: (1) This invention utilizes a mild freeze-drying method to directly dry the mixture of thermally conductive filler precursor and graphene oxide, maintaining the three-dimensional network structure of the thermally conductive filler precursor / graphene oxide; then, under an inert atmosphere, high-temperature thermal reduction is used to reduce graphene oxide and form spherical thermally conductive fillers; finally, a low-viscosity thermally conductive polymer is injected into the thermally conductive filler / three-dimensional graphene framework. The low viscosity can better fill the void structure of the thermally conductive filler / three-dimensional graphene framework. After curing, the thermally conductive polymer effectively supports the three-dimensional network structure, so that the three-dimensional graphene thermally conductive pad has excellent thermal conductivity in both the in-plane and vertical directions. (2) This invention modifies the low-dimensional thermally conductive filler by using a long-chain vinylsiloxane as the modifier. The long-chain vinylsiloxane hydrolyzes to produce hydroxyl groups, which form hydrogen bonds with the oxygen in the low-dimensional thermally conductive filler and uniformly coat the surface of the low-dimensional thermally conductive filler. The vinyl unsaturated bonds of the long-chain vinylsiloxane are exposed on the surface and, under the action of a catalyst, undergo a cross-linking reaction with the polymer and form stable CC chemical bonds, which effectively improves the continuity between the low-dimensional thermally conductive filler and the polymer and enhances the overall thermal conductivity.
[0018] (3) This invention adds low-dimensional thermally conductive filler to a low-viscosity polymer and then casts it into a thermally conductive filler / three-dimensional graphene framework. The low-dimensional thermally conductive filler is further integrated into the three-dimensional graphene network, which enriches the thermal conductive channels in the thermally conductive pad. The low-dimensional thermally conductive filler also has a high theoretical thermal conductivity, which can effectively improve the thermal conductivity of the thermally conductive pad, reduce the interfacial thermal resistance, and meet the practical application requirements. The in-plane thermal conductivity of the obtained three-dimensional graphene thermally conductive pad can reach up to 30.2 W / (m•K), and the vertical thermal conductivity reaches 7.9 W / (m•K). (4) In this invention, the three-dimensional graphene framework is a carbon material with a low mass density, and the density of the obtained three-dimensional graphene thermal conductive pad is only 1.4-1.6 g / cm³. 3 This can meet the demand for lightweight electronic devices; (5) The three-dimensional graphene thermal pad obtained by the present invention overcomes the key problems of complex preparation process of graphene pad in the prior art and only local three-dimensional thermal conduction channels in the structure. The preparation process is simpler and more efficient, and can be mass-produced. Attached Figure Description
[0019] Figure 1 Image of the three-dimensional graphene thermal conductive pad obtained in Example 1 of this invention.
[0020] Figure 2 The in-plane thermal conductivity of the low-density three-dimensional graphene thermal pads obtained in Examples 1-5 and Comparative Examples 1-4 of this invention.
[0021] Figure 3 The vertical thermal conductivity of the low-density three-dimensional graphene thermal pads obtained in Examples 1-5 and Comparative Examples 1-4 of this invention. Detailed Implementation
[0022] The present invention will be described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely illustrative examples of implementation of the present invention and are not intended to limit the scope of the present invention.
[0023] The graphite oxide used in the following embodiments of the present invention was purchased from Changzhou Sixth Element Materials Technology Co., Ltd., with the product number SE2430W.
[0024] The one-dimensional silicon carbide whiskers used in the following embodiments of the present invention were purchased from Aladdin Chemical Reagents website, catalog number S196604.
[0025] The one-dimensional aluminum nitride whiskers used in the following embodiments of the present invention were purchased from Aladdin Chemical Reagents website, catalog number A109772.
[0026] The two-dimensional boron nitride used in the following embodiments of the present invention was purchased from Aladdin Chemical Reagents website, catalog number B106033.
[0027] The two-dimensional aluminum nitride used in the following embodiments of the present invention was purchased from Aladdin Chemical Reagents website, catalog number A109772. Example 1
[0028] (1) Formation of graphene oxide dispersion: Graphite oxide was dispersed in deionized water to prepare a graphite oxide suspension with a mass concentration of 20 g / L. The graphite oxide suspension was exfoliated by high-speed stirring and dispersed at 3000 rpm / min for 10 h to achieve single-layer exfoliation and obtain a uniform and stable graphene oxide dispersion with a size of 10 μm. (2) Construction of thermally conductive filler / three-dimensional graphene framework: 5 g of nano-silicon was dispersed in 100 mL of 20 g / L graphene oxide dispersion. After uniform dispersion at 3000 rpm / min, it was freeze-dried and self-assembled to obtain a thermally conductive filler precursor / three-dimensional graphene oxide framework. Under an inert atmosphere, the graphene oxide was reduced and spherical thermally conductive filler was formed at 1200 ℃ for 2 h to obtain nano-silicon / three-dimensional graphene framework. (3) Preparation of thermally conductive polymers: 1 g of one-dimensional silicon carbide with a size of 1 μm and 0.02 g of vinyltrimethoxysiloxane were added to 1 g of 100 mPa·S silica gel and mixed evenly to obtain thermally conductive silica gel. (4) Preparation of thermal pads: 1 g of thermally conductive silicone gel was infused into a 0.2 g nano-silicon / 3D graphene framework and cured by heating at 80 °C to obtain a low-density 3D graphene thermally conductive pad.
[0029] Tests showed that the low-density three-dimensional graphene thermally conductive pad obtained in Example 1 had an in-plane thermal conductivity of 23.6 W / (m·K), a vertical thermal conductivity of 6.5 W / (m·K), and a density of 1.5 g / cm³. 3 In-plane thermal conductivity was tested using the laser method (test standard ASTM E1461), and vertical thermal conductivity was tested using the steady-state heat flow method (test standard ASTM D5470).
[0030] The low-density three-dimensional graphene thermal conductive pad obtained in Example 1 is as follows: Figure 1 As shown, this thermal pad has excellent thermal conductivity and flexibility. Example 2
[0031] (1) Formation of graphene oxide dispersion: Graphite oxide was dispersed in deionized water to prepare a graphite oxide suspension with a mass concentration of 10 g / L. The graphite oxide suspension was exfoliated by high-speed stirring and dispersed at 2000 rpm / min for 1 h to achieve single-layer exfoliation and obtain a uniform and stable graphene oxide dispersion with a size of 18 μm. (2) Construction of thermally conductive filler / three-dimensional graphene framework: 10 g of aluminum sol was dispersed in 200 mL of 10 g / L graphene oxide dispersion. After uniform dispersion at 3000 rpm / min, the dispersion was freeze-dried and self-assembled to obtain a thermally conductive filler precursor / three-dimensional graphene oxide framework. Under an inert atmosphere, the graphene oxide was reduced and spherical thermally conductive filler was formed at 800 ℃ for 6 h to obtain an alumina / three-dimensional graphene framework. (3) Preparation of thermally conductive polymers: 2 g of one-dimensional aluminum nitride with a size of 5 μm and 0.06 g of propylenetrimethoxysiloxane were added to 4 g of 1000 mPa·S polyurethane gel and mixed evenly to obtain thermally conductive polyurethane gel. (4) Preparation of thermal pads: 2 g of thermally conductive polyurethane gel was infused into a 0.6 g alumina / 3D graphene framework and cured at 100 °C to obtain a low-density 3D graphene thermally conductive pad.
[0032] Tests showed that the low-density three-dimensional graphene thermally conductive pad obtained in Example 2 had an in-plane thermal conductivity of 20.3 W / (m·K), a vertical thermal conductivity of 6.1 W / (m·K), and a density of 1.6 g / cm³. 3 In-plane thermal conductivity was tested using the laser method (test standard ASTM E1461), and vertical thermal conductivity was tested using the steady-state heat flow method (test standard ASTM D5470). Example 3
[0033] (1) Formation of graphene oxide dispersion: Graphite oxide was dispersed in deionized water to prepare a graphite oxide suspension with a mass concentration of 1 g / L. The graphite oxide suspension was exfoliated by high-speed stirring at 1000 rpm / min for 2 h to achieve single-layer exfoliation and obtain a uniform and stable graphene oxide dispersion with a size of 16 μm.
[0034] (2) Construction of thermally conductive filler / three-dimensional graphene framework: 2 g of zinc chloride was dispersed in 1 L of 1 g / L graphene oxide dispersion. After uniform dispersion at 3000 rpm / min, the dispersion was freeze-dried and self-assembled to obtain a thermally conductive filler precursor / three-dimensional graphene oxide framework. Under an inert atmosphere, the graphene oxide was reduced and spherical thermally conductive filler was formed at 1000 ℃ for 4 h to obtain the zinc oxide / three-dimensional graphene framework.
[0035] (3) Preparation of thermally conductive polymers: Two-dimensional boron nitride with a size of 3 μm and 0.04 g of decenyltriethoxysilane siloxane were added to 2 g of 500 mPa·S acrylic gel and mixed evenly to obtain thermally conductive acrylic gel. (4) Preparation of thermal pads: 2 g of thermally conductive acrylic gel was infused into a 0.4 g zinc oxide / 3D graphene framework and cured at 100 °C to obtain a low-density 3D graphene thermally conductive pad.
[0036] Tests showed that the low-density three-dimensional graphene thermally conductive pad obtained in Example 3 had an in-plane thermal conductivity of 26.6 W / (m·K), a vertical thermal conductivity of 7.3 W / (m·K), and a density of 1.6 g / cm³. 3 In-plane thermal conductivity was tested using the laser method (test standard ASTM E1461), and vertical thermal conductivity was tested using the steady-state heat flow method (test standard ASTM D5470). Example 4
[0037] (1) Formation of graphene oxide dispersion: Graphite oxide was dispersed in deionized water to prepare a graphite oxide suspension with a mass concentration of 5 g / L. The graphite oxide suspension was exfoliated by high-speed stirring at 2000 rpm / min for 5 h to achieve single-layer exfoliation and obtain a uniform and stable graphene oxide dispersion with a size of 15 μm.
[0038] (2) Construction of thermally conductive filler / three-dimensional graphene framework: 5 g of nano-silicon was dispersed in 200 mL of 5 g / L graphene oxide dispersion. After uniform dispersion at 5000 rpm / min, it was freeze-dried and self-assembled to obtain a thermally conductive filler precursor / three-dimensional graphene oxide framework. Under an inert atmosphere, the graphene oxide was reduced and spherical thermally conductive filler was formed at 900 ℃ for 6 h to obtain nano-silicon / three-dimensional graphene framework.
[0039] (3) Preparation of thermally conductive polymers: 5 g of two-dimensional aluminum nitride with a size of 5 μm and 0.2 g of dodecenyltriethoxysiloxane were added to 10 g of 1000 mPa·S acrylic gel and mixed evenly to obtain thermally conductive acrylic gel. (4) Preparation of thermal pads: 10 g of thermally conductive acrylic gel was infused into a 2 g nano-silicon / 3D graphene framework and cured at 100 °C to obtain a low-density 3D graphene thermally conductive pad.
[0040] Tests showed that the low-density three-dimensional graphene thermally conductive pad obtained in Example 4 had an in-plane thermal conductivity of 23.1 W / (m·K), a vertical thermal conductivity of 6.8 W / (m·K), and a density of 1.5 g / cm³. 3 In-plane thermal conductivity was tested using the laser method (test standard ASTM E1461), and vertical thermal conductivity was tested using the steady-state heat flow method (test standard ASTM D5470). Example 5
[0041] (1) Formation of graphene oxide dispersion: Graphite oxide was dispersed in deionized water to prepare a graphite oxide suspension with a mass concentration of 20 g / L. The graphite oxide suspension was exfoliated by high-speed stirring at 1500 rpm / min for 2 h to achieve single-layer exfoliation and obtain a uniform and stable graphene oxide dispersion with a size of 15 μm.
[0042] (2) Construction of thermally conductive filler / three-dimensional graphene framework: 5 g of nano-silicon was dispersed in 300 mL of 5 g / L graphene oxide dispersion. After uniform dispersion at 6000 rpm / min, it was freeze-dried and self-assembled to obtain a thermally conductive filler precursor / three-dimensional graphene oxide framework. Under an inert atmosphere, the graphene oxide was reduced and spherical thermally conductive filler was formed at 1000 ℃ for 3 h to obtain nano-silicon / three-dimensional graphene framework.
[0043] (3) Preparation of thermally conductive polymers: 10 g of two-dimensional aluminum nitride with a size of 2 μm and 0.2 g of dodecenyltrimethoxysiloxane were added to 10 g of 1000 mPa·S silica gel and mixed evenly to obtain thermally conductive silica gel. (4) Preparation of thermal pads: 15 g of thermally conductive silicone gel was infused into a 4.5 g nano-silicon / 3D graphene framework and cured at 90 °C to obtain a low-density 3D graphene thermally conductive pad.
[0044] Tests showed that the low-density three-dimensional graphene thermal pad obtained in Example 5 had an in-plane thermal conductivity of 30.2 W / (m·K), a vertical thermal conductivity of 7.9 W / (m·K), and a density of 1.6 g / cm³. 3 In-plane thermal conductivity was tested using the laser method (test standard ASTM E1461), and vertical thermal conductivity was tested using the steady-state heat flow method (test standard ASTM D5470).
[0045] Comparative Example 1 is the same as Example 5, except that two-dimensional aluminum nitride and modifier were not added in step (3) of Comparative Example 1.
[0046] Tests showed that the low-density three-dimensional graphene thermally conductive pad obtained in Comparative Example 1 had an in-plane thermal conductivity of 19.3 W / (m·K), a perpendicular thermal conductivity of 4.9 W / (m·K), and a density of 1.4 g / cm³. 3 In-plane thermal conductivity was tested using the laser method (test standard ASTM E1461), and vertical thermal conductivity was tested using the steady-state heat flow method (test standard ASTM D5470).
[0047] The properties of the low-density three-dimensional graphene thermal pad prepared in Example 5 were compared with those of the low-density three-dimensional graphene thermal pad prepared in Comparative Example 1. The in-plane thermal conductivity of the pad prepared in Example 5 reached 30.2 W / (m·K), and the vertical thermal conductivity was 7.9 W / (m·K), which was much higher than the in-plane thermal conductivity of 19.3 W / (m·K) and the vertical thermal conductivity of 4.9 W / (m·K) of Comparative Example 1. The main difference between Comparative Example 1 and Example 5 is that two-dimensional aluminum nitride was not added. Two-dimensional aluminum nitride can form more thermal conduction paths with the three-dimensional graphene framework, and it also has a high theoretical thermal conductivity, which can improve the thermal conductivity of the thermal pad in the three-dimensional direction.
[0048] Comparative Example 2 is the same as Example 5, except that no modifier was added in step (3) of Comparative Example 2.
[0049] Tests showed that the low-density three-dimensional graphene thermal pad obtained in Comparative Example 2 had an in-plane thermal conductivity of 19.8 W / (m·K), a vertical thermal conductivity of 5.0 W / (m·K), and a density of 1.5 g / cm³. 3 In-plane thermal conductivity was tested using the laser method (test standard ASTM E1461), and vertical thermal conductivity was tested using the steady-state heat flow method (test standard ASTM D5470).
[0050] Comparative Example 3 is the same as Example 5, except that no thermally conductive filler precursor nano-silicon was added in step (2) of Comparative Example 3.
[0051] Tests showed that the low-density three-dimensional graphene thermal pad obtained in Comparative Example 3 had an in-plane thermal conductivity of 18.3 W / (m·K), a perpendicular thermal conductivity of 4.1 W / (m·K), and a density of 1.4 g / cm³. 3 In-plane thermal conductivity was tested using the laser method (test standard ASTM E1461), and vertical thermal conductivity was tested using the steady-state heat flow method (test standard ASTM D5470).
[0052] Comparative Example 4 is the same as Example 5, except that in step (2) of Comparative Example 4, a composite of vacuum-dried nano-silicon and graphene oxide dispersion is used.
[0053] Tests showed that the low-density three-dimensional graphene thermal pad obtained in Comparative Example 4 had an in-plane thermal conductivity of 10.1 W / (m·K), a perpendicular thermal conductivity of 2.3 W / (m·K), and a density of 1.6 g / cm³. 3 In-plane thermal conductivity was tested using the laser method (test standard ASTM E1461), and vertical thermal conductivity was tested using the steady-state heat flow method (test standard ASTM D5470).
[0054] The test performance data of the low-density three-dimensional graphene thermal conductive pads obtained in Examples 1-5 and Comparative Examples 1-4 of this invention are as follows: Figure 2 and Figure 3 As shown.
[0055] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.
Claims
1. A method for preparing a low-density three-dimensional graphene thermal conductive pad, characterized in that, include: S1: Formation of graphene oxide dispersion; S2: Construction of thermally conductive filler / three-dimensional graphene framework: The spherical thermally conductive filler precursor is dispersed in the graphene oxide dispersion. After dispersion, it is freeze-dried and self-assembled to obtain the thermally conductive filler precursor / three-dimensional graphene oxide framework. The graphene oxide is reduced and the spherical thermally conductive filler is formed by high-temperature heat treatment under an inert atmosphere to obtain the thermally conductive filler / three-dimensional graphene framework. S3: Preparation of thermally conductive polymer: Low-dimensional thermally conductive filler and modifier are added to low-viscosity polymer and mixed evenly to obtain thermally conductive polymer; S4: Preparation of thermally conductive pads: The thermally conductive polymer is injected into the thermally conductive filler / three-dimensional graphene framework and cured by heating at 80~100 ℃ to obtain low-density thermally conductive pads.
2. The method for preparing a low-density three-dimensional graphene thermal conductive pad according to claim 1, characterized in that, In step S1, graphene oxide is dispersed in deionized water to prepare a graphene oxide suspension with a mass concentration of 1~20 g / L. The graphene oxide suspension is exfoliated by high-speed stirring at a speed of 1000~3000 rpm / min for 1~10 h to achieve a uniform and stable monolayer exfoliated graphene oxide dispersion; and / or, the size of the graphene oxide is 10~20 μm.
3. The method for preparing a low-density three-dimensional graphene thermal conductive pad according to claim 1, characterized in that, In S2, the mass ratio of the spherical thermally conductive filler precursor to the graphene oxide is (1~5):1, the dispersion speed is 3000~6000 rpm / min, the high-temperature heat treatment temperature is 800~1200 ℃, and the heat treatment time is 2~6 h.
4. The method for preparing a low-density three-dimensional graphene thermal conductive pad according to claim 3, characterized in that, The spherical thermally conductive filler precursor is one of aluminum sol, nano-silicon, and zinc chloride.
5. The method for preparing a low-density three-dimensional graphene thermal conductive pad according to claim 1, characterized in that, In S3, the mass ratio of low-dimensional thermally conductive filler to polymer is (0.5~1):1, and the mass ratio of modifier to low-dimensional thermally conductive filler is (0.01~0.03):
1.
6. The method for preparing a low-density three-dimensional graphene thermal conductive pad according to claim 5, characterized in that, The low-dimensional thermally conductive filler is one of one-dimensional silicon carbide whiskers, one-dimensional aluminum nitride whiskers, two-dimensional boron nitride, and two-dimensional aluminum nitride; and / or, the size of the low-dimensional thermally conductive filler is 1~5 μm.
7. The method for preparing a low-density three-dimensional graphene thermal conductive pad according to claim 5, characterized in that, The modifier is CH2=CH(CH2). n SiX3, wherein n is 0~10, and X is one of methoxy, ethoxy, or methoxy / ethoxy; the polymer is one of silicone gel, polyurethane gel, and acrylic gel, and the viscosity of the polymer is 100~1000 mPa·s.
8. The method for preparing a low-density three-dimensional graphene thermal conductive pad according to claim 1, characterized in that, In S4, the mass ratio of thermally conductive filler / three-dimensional graphene framework to thermally conductive polymer is (0.2-0.3):
1.
9. A low-density three-dimensional graphene thermal pad, prepared by the method described in any one of claims 1-8.
10. The application of the low-density three-dimensional graphene thermal conductive pad as a thermal interface material according to claim 9 in the field of electronics.