Graphene aerogels, composites thereof, and applications thereof

Abstract

This invention provides graphene aerogel, its composite materials, and applications. The graphene aerogel comprises several graphene layers, which are stacked along the thickness direction to form a multilayer structure, with any two adjacent graphene layers being surface-to-surface bonded together. Each graphene layer includes several graphene sublayers stacked along the thickness direction and pores distributed between any two graphene sublayers; the thickness direction is perpendicular to the plane containing the graphene layers. Based on the graphene aerogel of this invention, the problem of significant performance differences in graphene aerogel materials in different directions in the prior art is solved.

Description

Technical Field

[0001] This invention relates to the field of aerogel technology, and more specifically, to a graphene aerogel, its composite materials, and their applications. Background Technology

[0002] With the rapid development of modern electronic technology, the power density of electronic devices is constantly increasing, and heat dissipation has become one of the key factors restricting their performance improvement and service life. Graphene aerogel, as a novel lightweight porous material, has advantages such as high specific surface area, low density, and good chemical stability, showing potential application prospects in the field of heat dissipation. Currently, isotropic graphene aerogels have randomly arranged graphene sheets, which hinders heat conduction in all directions, resulting in relatively low thermal conductivity. In practical heat dissipation requirements, such as in the heat dissipation process of high-power electronic chips, heat is difficult to transfer quickly and efficiently in aerogel materials, failing to meet the requirements of efficient heat dissipation. In contrast, anisotropic graphene aerogels have unique advantages. Analogous to carbon fiber silicone pads, when anisotropic graphene aerogels are used as a framework to fill polymers, the directional arrangement of graphene sheets provides directional conduction channels for heat, giving the composite material high thermal conductivity. This characteristic makes anisotropic graphene aerogels extremely promising for solving heat dissipation problems, and they are expected to significantly improve heat dissipation efficiency, meeting the urgent need for high-efficiency heat dissipation materials in modern electronic devices. However, existing anisotropic graphene aerogels suffer from poor heat dissipation performance and poor product stability. Summary of the Invention

[0003] The main objective of this invention is to provide a graphene aerogel and its composite materials and applications, in order to solve the problem that the performance of graphene aerogel materials varies significantly in different directions in the prior art.

[0004] This invention provides a graphene aerogel, which includes a plurality of graphene layers, each graphene layer being stacked along the thickness direction to form a multilayer structure, and any two adjacent graphene layers being surface-to-surface bonded together; each graphene layer includes a plurality of graphene sublayers stacked along the thickness direction and pores distributed between any two graphene sublayers; the thickness direction is perpendicular to the plane in which the graphene layers are located.

[0005] Furthermore, the horizontal thermal conductivity of the graphene aerogel along a first straight line parallel to the plane containing the graphene layer is greater than or equal to 30 W / m·K, and the vertical thermal conductivity of the graphene aerogel along a second straight line parallel to the plane containing the graphene layer and perpendicular to the first straight line direction is greater than or equal to 30 W / m·K.

[0006] Furthermore, after placing the graphene aerogel on a 100℃ constant temperature heating platform for 30 minutes, the temperature difference between any two points on any straight line parallel to the plane containing the graphene layer inside the graphene aerogel is ≤5℃.

[0007] Furthermore, by volume percentage, the proportion of macropores with a pore size of 100 μm to 200 μm in the graphene aerogel is greater than or equal to 50% and less than or equal to 80%.

[0008] Furthermore, by volume percentage, the proportion of pores with a diameter of 50 μm or less is greater than or equal to 1% and less than or equal to 15%.

[0009] Furthermore, the average pore size of the graphene aerogel ranges from 1 μm to 200 μm.

[0010] Furthermore, the density of the graphene aerogel is 0.01 g / cm³. 3 Up to 0.3 g / cm 3 .

[0011] Furthermore, the porosity of graphene aerogel is 75% to 90%.

[0012] Furthermore, the specific surface area of ​​graphene aerogel is 500 m². 2 / g to 1000m 2 / g.

[0013] Furthermore, the pore volume of the graphene aerogel is 2 cm³. 3 / g to 4cm 3 / g.

[0014] Furthermore, by weight percentage, the carbon content in the graphene aerogel is greater than or equal to 99%.

[0015] Furthermore, the graphene aerogel has a graphitization degree of ≥95%.

[0016] Furthermore, the Raman spectrum of the graphene aerogel has D peaks and G peaks, and the area ratio of D peak to G peak, ID / IG, is less than 0.01.

[0017] Furthermore, the thickness of the graphene layer is 10 nm to 100 nm.

[0018] Furthermore, the electrical conductivity of the graphene aerogel along the plane parallel to the graphene layer is greater than or equal to 300 S / m.

[0019] Furthermore, the electromagnetic shielding effectiveness of graphene aerogel along the thickness direction is greater than or equal to 100dB.

[0020] According to another aspect of the present invention, a composite material is provided, comprising a polymeric material and the graphene aerogel as described above, wherein the polymeric material is distributed in the pores of the graphene aerogel.

[0021] Furthermore, a vacuum-assisted impregnation method was used to penetrate the polymer material into the pores of the graphene aerogel, and the composite material was obtained after curing.

[0022] Furthermore, the polymer material is selected from one or more of liquid silicone, acrylic resin, epoxy resin, polyurethane, polyester, and phenolic resin.

[0023] Furthermore, by volume percentage, the polymer material fills 40% to 80% of the pores in the graphene aerogel material.

[0024] Furthermore, the horizontal thermal conductivity of the composite material along the third straight line direction parallel to the plane where the graphene layer is located is greater than or equal to 20 W / m·K, and the vertical thermal conductivity of the composite material along the fourth straight line direction parallel to the plane where the graphene layer is located and perpendicular to the third straight line direction is greater than or equal to 30 W / m·K.

[0025] According to another aspect of the invention, the above-described graphene aerogel or the above-described composite material is provided for use as a thermally conductive material in a thermal management system.

[0026] By applying the technical solution of this invention, graphene aerogel forms a continuous three-dimensional network structure through the stacking of graphene layers along the thickness direction and the surface-to-surface bonding of graphene layers. This continuous three-dimensional network structure retains the excellent electrical and thermal conductivity of graphene, significantly reducing the thermal resistance and electrical resistance of the graphene aerogel. This results in excellent thermal and electrical conductivity in all directions parallel to the graphene layers. Furthermore, the tightly connected graphene layers give the aerogel high structural stability. Moreover, the stacked graphene sublayers and the pores distributed between any two graphene sublayers preserve the resilience of the graphene aerogel. Attached Figure Description

[0027] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0028] Figure 1 The image shows a cross-section of the reduced graphene oxide aerogel in Example 1 after being cut along a plane parallel to the thickness direction.

[0029] Figure 2 The image shows a SEM image of the first cross-section of the graphene aerogel prepared in Example 1 after being cut along a first plane parallel to the thickness direction.

[0030] Figure 3 This image shows a SEM image of the second cross-section of the graphene aerogel prepared in Example 1, cut along a second plane parallel to the thickness direction, wherein the second cross-section is perpendicular to... Figure 2 The first cross section in;

[0031] Figure 4 The Raman spectrum of the graphene aerogel prepared in Example 1 is shown.

[0032] Figure 5 The XRD pattern of the graphene aerogel prepared in Example 1 is shown.

[0033] Figure 6 The electromagnetic shielding effectiveness of the graphene aerogel prepared in Example 1 is shown in the diagram.

[0034] Specific implementation party

[0035] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0036] As described in the background art, there is a problem in the prior art that graphene aerogels exhibit significant differences in performance in different directions. In order to solve the above problem, according to one aspect of the present invention, a graphene aerogel is provided, the graphene aerogel comprising a plurality of graphene layers, each graphene layer being stacked along the thickness direction to form a multilayer structure, and any two adjacent graphene layers being surface-to-surface bonded together; each graphene layer comprising a plurality of graphene sublayers stacked along the thickness direction and pores distributed between any two graphene sublayers; the thickness direction is perpendicular to the plane in which the graphene layers are located.

[0037] The graphene aerogel provided by this invention forms a continuous three-dimensional network structure through the stacking of graphene layers along the thickness direction and the surface-to-surface bonding of the graphene layers. This continuous three-dimensional network structure retains the excellent electrical and thermal conductivity of graphene material, significantly reducing the thermal resistance and electrical resistance of the graphene aerogel. This results in excellent thermal and electrical conductivity in all directions parallel to the graphene layers. Furthermore, the tightly connected graphene layers give the aerogel high structural stability. Moreover, the stacked graphene sublayers and the pores distributed between any two graphene sublayers preserve the resilience of the graphene aerogel.

[0038] In some embodiments, the horizontal thermal conductivity of the graphene aerogel along a first straight direction parallel to the plane where the graphene layer is located is greater than or equal to 30 W / m·K, and the vertical thermal conductivity of the graphene aerogel along a second straight direction parallel to the plane where the graphene layer is located and perpendicular to the first straight direction is greater than or equal to 30 W / m·K. The thermal conductivity of graphene aerogels along a straight line parallel to the graphene layers is closely related to the thickness of the graphene layers, the tightness of the stacking of the graphene layers along the thickness direction, and the continuity between the layered structures. It is also affected by the structural properties such as the graphitization degree and porosity of the graphene sublayers. Graphene aerogels with thermal conductivity within the above range have graphene layers that are tightly stacked along the thickness direction and form a highly continuous layered structure. This results in high thermal conductivity along any straight line parallel to the graphene layers. The thermal conductivity in the plane parallel to the graphene layers is significant, enabling rapid and uniform heat transfer from hot spots to the entire cold spot area, effectively avoiding local overheating and improving the thermal management efficiency of graphene aerogels. They are particularly suitable for the development of thermal management, thermally conductive composite materials, and efficient heat dissipation solutions. For example, in the field of electronic packaging, graphene aerogels with high thermal conductivity can serve as thermal interface materials to rapidly conduct heat from heat-generating components such as chips to heat sinks. In the field of battery technology, the high thermal conductivity and uniform thermal conduction capabilities of graphene aerogels can effectively improve the heat dissipation performance of battery packs, reduce the risk of overheating, and improve battery safety and efficiency. Specifically, the horizontal thermal conductivity of graphene aerogels can be 30 W / mK, 31 W / mK, 32 W / mK, 33 W / mK, 34 W / mK, 35 W / mK, 36 W / mK, 37 W / mK, 38 W / mK, 39 W / mK, 40 W / mK, 41 W / mK, 42 W / mK, 43 W / mK, 44 W / mK, 45 W / mK, 50 W / mK, and 60 W / mK. The vertical thermal conductivity of graphene aerogels... The specific thermal conductivity can be 30 W / mK, 31 W / mK, 32 W / mK, 33 W / mK, 34 W / mK, 35 W / mK, 36 W / mK, 37 W / mK, 38 W / mK, 39 W / mK, 40 W / mK, 41 W / mK, 42 W / mK, 43 W / mK, 44 W / mK, 45 W / mK, 50 W / mK, or 60 W / mK. Other values ​​within the above range are also possible and are not limited here. The preferred horizontal and vertical thermal conductivity is between 35 W / mK and 50 W / mK. Within this preferred range, graphene aerogel exhibits high thermal conductivity, high compression resilience, and high compressibility.

[0039] In some embodiments, after placing the graphene aerogel on a 100°C constant-temperature heating platform for 30 minutes, the temperature difference between any two points on any straight line parallel to the plane containing the graphene layers within the graphene aerogel is ≤5°C. This ≤5°C temperature difference indicates that the graphene layers are tightly stacked along their thickness direction, forming a highly continuous layered structure. This allows heat energy to diffuse uniformly along any straight line parallel to the graphene layers, effectively avoiding hot or cold spots during heat conduction. This is crucial for applications requiring uniform heat conduction in three-dimensional space.

[0040] In some embodiments, by volume percentage, the proportion of macropores with a pore size of 100 μm to 200 μm in the graphene aerogel is greater than or equal to 50% and less than or equal to 80%. Specifically, the macropore proportion can be 50%, 55%, 60%, 65%, 70%, 75%, or 80%, or other values ​​within the above range, which are not limited here. Graphene composite aerogels within the above range have a high macropore proportion and a relatively concentrated pore size distribution, resulting in high porosity and lightweight properties.

[0041] In some embodiments, by volume percentage, the proportion of pores with a pore size of 50 μm or less in the graphene aerogel is greater than or equal to 1% and less than or equal to 20%. Specifically, the proportion of pores can be 1%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 15%, 16%, 18%, or 20%, or other values ​​within the above range, which are not limited here. Graphene composite aerogels within the above range help enhance the contact, interaction, and connectivity between graphene sublayers, facilitate the formation of a continuous thermally conductive network in the graphene aerogel, and improve the structural stability and mechanical strength of the graphene aerogel, thus better achieving a balance between the structural stability and thermal conductivity of the graphene aerogel.

[0042] In some embodiments, the average pore size of the graphene aerogel is from 1 μm to 200 μm. Specifically, the average pore size can be 1 μm, 5 μm, 10 μm, 20 μm, 50 μm, 100 μm, 120 μm, 150 μm, 180 μm, or 200 μm, or other values ​​within the above range, which are not limited here. The average pore size is preferably from 120 μm to 170 μm. An average pore size within this range is beneficial for the graphene aerogel to conduct heat quickly and uniformly, while simultaneously maintaining high mechanical strength and lightweight properties.

[0043] In some embodiments, the density of the graphene aerogel is 0.01 g / cm³. 3 Up to 0.3 g / cm 3 The density can be specifically 0.01 g / cm³.3 0.05g / cm 3 0.1g / cm 3 0.12g / cm 3 0.15g / cm 3 0.18g / cm 3 0.2g / cm 3 0.25g / cm 3 0.3g / cm 3 Of course, other values ​​within the above range are also possible and are not limited here. Graphene aerogel with a density within the above range not only maintains the lightweight properties of graphene aerogel but also enables the construction of a highly efficient thermally conductive network structure. This results in the graphene aerogel exhibiting high thermal and electrical conductivity along any straight line parallel to the graphene layers, meeting the high requirements of high-performance electronic devices, thermal interface materials, and thermally conductive composite materials, while also possessing high mechanical strength.

[0044] In some embodiments, the porosity of the graphene aerogel is 75% to 90%, specifically 75%, 76%, 78%, 80%, 82%, 84%, 85%, 88%, and 90%, or other values ​​within the above range, which are not limited herein. Graphene aerogels with porosity within the above range possess the characteristics of being lightweight and having a high specific surface area, which helps to improve the thermal conductivity of graphene aerogels and achieves a balance between structural stability and thermal conductivity.

[0045] In some embodiments, the specific surface area of ​​the graphene aerogel is 500 m². 2 / g to 1000m 2 / g, specifically 500m 2 / g、550m 2 / g、600m 2 / g、650m 2 / g、680m 2 / g、700m 2 / g、720m 2 / g、750m 2 / g、780m 2 / g、800m 2 / g、820m 2 / g、850m 2 / g、900m 2 / g、950m 2 / g, 1000m 2 / g, and of course, other values ​​within the above range are also possible, and are not limited here. The high specific surface area of ​​graphene aerogel is conducive to rapid heat conduction. With a specific surface area within the above range, the numerous graphene sublayer contact points and pore channels provide abundant heat conduction paths, reducing the interfacial thermal resistance between fillers and helping to improve heat conduction efficiency. At the same time, the aforementioned high specific surface area also promotes the improvement of the electrical conductivity and electromagnetic shielding effectiveness of graphene aerogel, making it suitable for fields that require both high conductivity and electromagnetic protection.

[0046] In some embodiments, the pore volume of the graphene aerogel is 2 cm³. 3 / g to 4cm 3 / g, specifically 2cm 3 / g, 2.2cm 3 / g, 2.5cm 3 / g, 2.8cm 3 / g, 3.0cm 3 / g, 3.2cm 3 / g, 3.5cm 3 / g, 3.8cm 3 / g, 4.0cm 3 / g, and of course, other values ​​within the above range are also possible, and are not limited here. The pore volume of graphene aerogel is within the above range, which is beneficial for the rapid heat conduction and efficient electromagnetic shielding of graphene aerogel.

[0047] In some embodiments, the carbon content in the graphene aerogel is greater than or equal to 99% by weight. With this high carbon content, the graphene aerogel exhibits high lattice integrity, and the hexagonal network structure of carbon atoms in the graphene sublayers provides efficient electronic and thermal conduction pathways, thus resulting in high thermal and electrical conductivity.

[0048] In some embodiments, the graphene aerogel has a graphitization degree of ≥95%. When the graphitization degree reaches or exceeds 95%, the highly ordered graphite structure reduces lattice defects in the heat conduction process, lowers interfacial thermal resistance, and enables heat to be transferred more efficiently within the material. Furthermore, the high conductivity of graphite originates from its continuous π-electron system within its plane. As the graphitization degree increases, the electron conduction paths between graphene sublayers become more continuous, reducing resistance and improving the overall electrical conductivity of the material. The highly ordered graphite structure can increase the electrical conductivity of the graphene aerogel, and highly graphitized graphene aerogels have a more stable structure, exhibiting higher thermal stability and mechanical strength.

[0049] In some embodiments, the Raman spectrum of graphene aerogel exhibits D and G peaks, with the area ratio of D to G peaks (ID / IG) being less than 0.01. An ID / IG ratio less than 0.01 indicates that the graphene aerogel has few defects, high graphitization, and excellent thermal and electrical conductivity.

[0050] In some embodiments, the thickness of the graphene layer is from 10 nm to 100 nm, specifically 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, and 100 nm, or other values ​​within the above range, which are not limited here. A graphene layer thickness within the above range is beneficial for the rapid heat transfer of the graphene aerogel.

[0051] In some embodiments, the electrical conductivity of the graphene aerogel along the direction parallel to the plane containing the graphene layer is greater than or equal to 300 S / m, specifically 320 S / m, 340 S / m, 360 S / m, 380 S / m, 400 S / m, 420 S / m, 440 S / m, 460 S / m, 480 S / m, 500 S / m, 550 S / m, and 6000 S / m. Other values ​​within the above range are also possible and are not limited thereto. With electrical conductivity within the above range, the graphene aerogel exhibits excellent electrical conductivity and enables rapid electron migration, playing an important role in electronic devices, conductive pads, electromagnetic shielding materials, and other fields.

[0052] In some embodiments, the electromagnetic shielding effectiveness of graphene aerogel along its thickness direction is greater than or equal to 100 dB, specifically 100 dB, 102 dB, 105 dB, 108 dB, 110 dB, 112 dB, 114 dB, 116 dB, 118 dB, 120 dB, and 130 dB, or other values ​​within the above range, which are not limited here. The electromagnetic shielding effectiveness of graphene aerogel along its thickness direction is greater than or equal to 100 dB, which can effectively prevent the penetration of electromagnetic waves and is suitable for applications requiring high electromagnetic shielding effectiveness, such as electromagnetic interference (EMI) shielding for military equipment, aerospace vehicles, medical equipment, and high-performance electronic products.

[0053] According to another aspect of the present invention, a composite material is provided, comprising a polymeric material and the graphene aerogel as described above, wherein the polymeric material is distributed within the pores of the graphene aerogel. By combining the polymeric material with the graphene aerogel, the composite material combines the high thermal conductivity of the graphene aerogel with the mechanical properties of the polymeric material, thereby enhancing the mechanical strength and toughness of the composite material. This results in the composite material exhibiting excellent thermal and electrical conductivity in all directions parallel to the graphene layer, while maintaining structural integrity under high stress conditions. This makes it suitable for manufacturing thermal interface materials and structural materials for high-load applications. Furthermore, by adjusting the type and filling rate of the polymeric material, the thermal conductivity, electrical conductivity, and electromagnetic shielding properties of the composite material, as well as its mechanical strength and processing properties, can be customized to meet the needs of different application fields. For example, a liquid silicone-filled composite material maintains high thermal conductivity while exhibiting good elasticity and crack resistance, making it suitable for electronic packaging and thermal interface materials; while an epoxy resin-filled composite material exhibits higher mechanical strength and stability, making it suitable for manufacturing thermally conductive pads for structural support.

[0054] In some embodiments, a vacuum-assisted impregnation method is used to permeate molten polymer material into the pores of the graphene aerogel, and the resulting composite material is obtained after solidification. The vacuum-assisted impregnation method (VACIMP) utilizes the pressure difference generated in a vacuum environment to accelerate the penetration of molten polymer material into the pores of the graphene aerogel. Under vacuum conditions, the gas inside the graphene aerogel is extracted, creating a negative pressure that promotes a more uniform and deeper distribution of the polymer material within the porous structure of the graphene aerogel during the impregnation process. This method can significantly improve the uniformity of the composite material and the filling efficiency of the polymer material in the aerogel.

[0055] In some embodiments, the polymer material is selected from one or more of liquid silicone, acrylic resin, epoxy resin, polyurethane, polyester, and phenolic resin. By selecting different types of polymer materials, the properties of the composite material can be customized to meet the needs of specific application areas. For example, liquid silicone can be selected for applications requiring high thermal conductivity and good elasticity; epoxy resin or acrylic resin is a better choice for applications requiring high mechanical strength and good adhesion; and polyester or phenolic resin is more suitable for composite materials requiring chemical resistance and high temperature resistance, making the properties of composite aerogel materials highly customizable and flexible.

[0056] In some embodiments, the polymer material filling rate in the pores of the graphene aerogel material is 40% to 80% by volume percentage, specifically 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, 65%, 70%, 75%, and 80%, or other values ​​within the above range, which are not limited herein. Composite materials with a polymer material filling rate within the above range exhibit high thermal conductivity, high mechanical strength, and good elasticity in the thickness direction.

[0057] In some embodiments, the horizontal thermal conductivity of the composite material along a third straight direction parallel to the plane containing the graphene layer is greater than or equal to 20 W / m·K, and the vertical thermal conductivity of the composite material along a fourth straight direction parallel to the plane containing the graphene layer and perpendicular to the third straight direction is greater than or equal to 30 W / m·K. The horizontal thermal conductivity of the composite material can specifically be 20 W / m·K, 23 W / m·K, 25 W / m·K, 27 W / m·K, 28 W / m·K, 30 W / m·K, 32 W / m·K, 34 W / m·K, 36 W / m·K, or 40 W / m·K. The vertical thermal conductivity of the composite material can also specifically be 20 W / m·K, 23 W / m·K, 25 W / m·K, 27 W / m·K, 28 W / m·K, 30 W / m·K, 32 W / m·K, 34 W / m·K, 36 W / m·K, or 40 W / m·K. Of course, other values ​​within the above ranges are also possible and are not limited here. The composite material uses graphene aerogel, which has excellent thermal conductivity, as a framework, resulting in a composite material with excellent thermal conductivity.

[0058] In some embodiments, the impregnation temperature in the vacuum-assisted impregnation method is 25°C to 35°C. By performing vacuum-assisted impregnation within the above temperature range, the process cost is low.

[0059] In some embodiments, the vacuum-assisted impregnation method uses a vacuum pressure of 50 Pa to 2000 Pa, specifically 50 Pa, 100 Pa, 200 Pa, 500 Pa, 600 Pa, 800 Pa, 1000 Pa, 1200 Pa, 2500 Pa, or 2000 Pa. Other values ​​within this range are also acceptable and are not limited here. This pressure range helps reduce pressure loss in the graphene aerogel and facilitates the entry of liquid polymer materials into the pores of the graphene aerogel.

[0060] In some embodiments, the vacuum-assisted impregnation method is vacuum cyclic impregnation, with a single impregnation time of 5 to 20 minutes. After reaching the specified vacuum level and impregnation time, the gas valve is opened to restore the internal pressure of the vacuum drying oven to the standard atmospheric pressure. Then, the operation steps are repeated, and the number of vacuum cyclic impregnations is 5 to 20.

[0061] In some embodiments, the curing temperature is 60°C to 180°C, and the curing time is 1 hour to 5 hours. Specifically, the curing temperature can be 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, or 180°C, or other values ​​within the above range, which are not limited here. The curing time can be 1 hour, 2 hours, 3 hours, 4 hours, or 5 hours, or other values ​​within the above range, which are not limited here.

[0062] According to another aspect of the invention, the above-described graphene aerogel or the above-described composite material is provided for use as a thermally conductive material in a thermal management system.

[0063] Currently, the mainstream preparation processes for anisotropic graphene aerogels face numerous challenges. Existing preparation methods are often complex, making it difficult to control the uniformity of different batches and resulting in poor product quality stability. This hinders large-scale production and limits the widespread application of anisotropic graphene aerogels in industrial fields. Therefore, developing anisotropic graphene aerogels and their composite materials with controllable processes and adjustable macroscopic dimensions is of paramount importance, as it will help promote their large-scale application and development in fields such as heat dissipation and electromagnetic shielding.

[0064] To address the aforementioned problems, according to another aspect of the present invention, a method for preparing graphene aerogel is provided, comprising the following steps:

[0065] Step S1: Coat the slurry containing graphene oxide sheets to obtain a wet film, and dry the wet film to obtain a graphene oxide film.

[0066] Step S2: The graphene oxide film is chemically reduced and foamed using a reducing foaming agent aqueous solution to obtain reduced graphene oxide aerogel.

[0067] Step S3: Immerse the reduced graphene oxide aerogel in an aqueous solution of a functional compound to obtain a functionalized reduced graphene oxide aerogel; the functional compound includes one or more of plasticizers, crosslinking agents, and surfactants;

[0068] Step S4: The functionalized reduced graphene oxide aerogel is stacked layer by layer along the thickness direction and a first calendering process is performed along the thickness direction during the stacking process to obtain the functionalized reduced graphene oxide aerogel stacked structure.

[0069] Step S5: Under the second calendering treatment along the thickness direction of the functionalized reduced graphene oxide aerogel stacked structure, the functionalized reduced graphene oxide aerogel stacked structure is subjected to low-temperature drying, carbonization treatment and graphitization treatment in sequence to obtain graphitized graphene aerogel.

[0070] Step S6: The graphite-based graphene aerogel is subjected to a third calendering process along the thickness direction to compress the graphite-based graphene aerogel, thereby obtaining graphene aerogel.

[0071] The present invention first prepares a graphene oxide film, then introduces a large number of pore structures between the graphene oxide sheets through chemical reduction foaming to obtain a reduced graphene oxide aerogel with a porous network structure. The reduced graphene oxide aerogel is then immersed in an aqueous solution of a functional compound, which helps to enhance the bonding force between the reduced graphene oxide sheets and the adhesion strength between the functionalized reduced graphene oxide aerogels during stacking assembly, so as to form a dense stacked structure and a continuous three-dimensional network structure, and ensure that the overall structure remains unlayered during subsequent processing. Subsequently, layer-by-layer stacking assembly is performed, and calendering is carried out during the layer-by-layer stacking assembly process to obtain a three-dimensional functionalized reduced graphene oxide aerogel stacked structure with tightly bonded functionalized reduced graphene oxide aerogels. Then, under calendering, low-temperature drying, carbonization, and graphitization are performed sequentially to form a graphitized graphene aerogel with a continuous and dense three-dimensional network structure. Finally, further calendering is performed to compress the graphitized graphene aerogel, reducing the porosity, resulting in a graphene aerogel with a continuous and dense three-dimensional network structure. The graphene oxide film undergoes chemical reduction foaming, functionalization, calendering (first, second, and third calendering), and heat treatment (low-temperature drying, carbonization, and graphitization) to form a graphene layer. This graphene layer comprises several graphene sublayers stacked along the thickness direction and pores distributed between any two sublayers. The functionalization, calendering, and heat treatments ensure a tight surface-to-surface bonding between adjacent graphene sublayers, resulting in excellent thermal and electrical conductivity in all directions parallel to the graphene layers. Furthermore, this continuous, dense three-dimensional network structure of graphene aerogel significantly enhances compressive strength, deformation resistance, and thermal stability. Moreover, the graphene aerogel preparation method of this invention is simple, allows for controllable macroscopic dimensions, and is suitable for mass production of graphene aerogels.

[0072] In some embodiments, graphene oxide raw materials are dispersed in water to form a graphene oxide dispersion. The graphene oxide dispersion is then subjected to high-pressure homogenization and degassing treatments to obtain a slurry containing graphene oxide sheets. High-pressure homogenization breaks down, refines, and exfoliates the graphene oxide raw materials in the dispersion to form graphene oxide sheets. Degassing then forms a stable slurry system, allowing the graphene oxide sheets to self-assemble and form a uniform graphene oxide layer during subsequent coating and drying processes. This ultimately yields a stable and uniform graphene oxide film, providing a stable and uniform graphene oxide film foundation for subsequent chemical reduction foaming treatments.

[0073] In some embodiments, the average particle size of the graphene oxide raw material is 30 μm to 50 μm.

[0074] In some embodiments, the atomic ratio of carbon atoms to oxygen atoms in the graphene oxide sheet is (1.0–1.5):1. Using graphene oxide raw materials containing the aforementioned high oxygen-to-carbon ratio, the high content of oxygen-containing functional groups on the surface of the graphene oxide sheet provides more reduction sites to generate more and denser pores. During the foaming stage to form a porous network structure, the resulting sample has high porosity, giving the graphene aerogel high porosity and lightweight properties, which is beneficial for rapid heat conduction and dissipation.

[0075] In some embodiments, the graphene oxide sheet has oxygen-containing functional groups, which include at least one of epoxy, hydroxyl, and carboxyl functional groups, including but not limited to the above-mentioned oxygen-containing functional groups. Other oxygen-containing functional groups that can undergo a reduction reaction with a reducing foaming agent aqueous solution and can generate gas are also applicable to the present invention.

[0076] In some embodiments, the solid content in the mixed dispersion is 2% to 10%, specifically 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 7%, 8%, 9%, 10%, or other values ​​within the above range, which are not limited here.

[0077] In some embodiments, a planetary mixer is used to prepare the mixed dispersion. The mixing speed is 30 rpm to 50 rpm, specifically 30 rpm, 35 rpm, 40 rpm, 45 rpm, or 50 rpm, or other mixing conditions within the above range. The dispersion speed is 500 rpm to 5000 rpm, specifically 500 rpm, 1000 rpm, 1500 rpm, 2000 rpm, 3000 rpm, or 5000 rpm, or other dispersion conditions within the above range. The running time is 5 min to 120 min. Specific process combinations can include stirring speed of 30 rpm, dispersion speed of 1000 rpm, and running time of 30 min; stirring speed of 40 rpm, dispersion speed of 2000 rpm, and running time of 60 min; stirring speed of 45 rpm, dispersion speed of 4000 rpm, and running time of 60 min; or stirring speed of 50 rpm, dispersion speed of 5000 rpm, and running time of 90 min. Of course, it can also be one or more processes within the above range, and they can be operated in the set order. There are no restrictions here.

[0078] In some embodiments, the high-pressure homogenization process is carried out at a pressure of 500 bar to 1250 bar, at a temperature of 10°C to 25°C, and for 2 to 4 cycles. High-pressure homogenization further disperses the mixed dispersion, bringing the slurry to a suitable viscosity to facilitate the subsequent self-assembly of graphene oxide sheets into a uniform graphene oxide film.

[0079] In some embodiments, degassing is performed using a vacuum degassing method at a vacuum pressure of -10 kPa to -200 kPa, a processing temperature of 15°C to 25°C, a rotation speed of 500 rpm to 2000 rpm, and a degassing time of 30 s to 10 min. Specifically, it can be degassing at 500 rpm for 10 min, at 800 rpm for 6 min, at 1000 rpm for 3 min, at 1200 rpm for 2 min, at 1400 rpm for 1.5 min, at 1500 rpm for 1 min, and at 2000 rpm for 30 s. Alternatively, a process can be repeated. Of course, other values ​​within the above range are also possible and are not limited here.

[0080] In some embodiments, the viscosity of the slurry containing graphene oxide sheets is between 30,000 cps and 60,000 cps, specifically 30,000 cps, 35,000 cps, 40,000 cps, 42,000 cps, 45,000 cps, 48,000 cps, 50,000 cps, 52,000 cps, 55,000 cps, 58,000 cps, and 60,000 cps. Other values ​​within the above range are also possible and are not limited herein. Slurries within the above viscosity range are beneficial for forming a more uniform wet film.

[0081] In some embodiments, the pH value of the slurry containing graphene oxide sheets is 6 to 9, specifically 6, 6.5, 6.8, 7, 7.2, 7.3, 7.5, 7.8, 8, 8.5, or 9. Of course, other values ​​within the above range are also possible and are not limited here. Within the above pH range, it is beneficial for the graphene oxide sheets to disperse and form a stable slurry so that the graphene oxide sheets can subsequently self-assemble into a uniform film.

[0082] In some embodiments, during the drying process of the wet film, the drying temperature is 60°C to 80°C, and the drying time is 2 hours to 6 hours. Specifically, it can be drying at 60°C for 6 hours, 62°C for 5.5 hours, 65°C for 5 hours, 68°C for 4.5 hours, 70°C for 4 hours, 72°C for 3.5 hours, 75°C for 3 hours, 78°C for 2.5 hours, and 80°C for 2 hours. Of course, other values ​​within the above range are also possible and are not limited here. The drying temperature affects the rate of water evaporation, thereby affecting the appearance and quality of the film. Under the above drying temperature and drying time, it is beneficial for the assembly of graphene oxide sheets to form a uniform and compact graphene oxide film, so as to facilitate the subsequent foaming to form a reduced graphene oxide aerogel with high mechanical strength.

[0083] In some embodiments, the thickness of the graphene oxide film is from 100 μm to 300 μm. Specifically, it can be 100 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 210 μm, 220 μm, 240 μm, 260 μm, 280 μm, or 300 μm, or other values ​​within the above range, which are not limited here. Graphene oxide films within the above thickness range have multiple layers of graphene oxide sheets, which is beneficial for subsequent foaming to form reduced graphene oxide aerogels with high porosity and mechanical strength.

[0084] The graphene oxide film is chemically reduced and foamed using an aqueous solution of a reducing foaming agent. During this process, the oxygen-containing functional groups on the graphene oxide sheets are reduced, and gas is generated inside the graphene oxide film, causing the graphene oxide sheets to expand, creating pores between the graphene oxide sheets, and causing the graphene oxide sheets to rearrange, ultimately forming a stable reduced graphene oxide aerogel with a porous network structure.

[0085] In some embodiments, the reducing foaming agent aqueous solution includes a reactive reducing agent, and further includes an auxiliary reducing agent and NH4. + One or two of the source compounds are used; among them, reactive reducing agents are mainly used to reduce oxygen-containing functional groups in graphene oxide to achieve the reduction of graphene oxide film; auxiliary reducing agents are used to regulate the rate of the foaming reaction, making it more stable and controllable, and reducing the occurrence of uneven bubbles or structural instability caused by excessively fast foaming reactions. NH4 is introduced into the chemical reduction foaming system. + NH4 + It can act as a pH buffer, preventing drastic pH changes within the system and maintaining a relatively stable reaction environment, which is beneficial for the stable progress of the chemical reduction foaming reaction. In addition, NH4... + This process can improve the dispersibility of graphene oxide films. Specifically, ammonia ions can adsorb onto the surface of graphene oxide, giving it a charge. This creates electrostatic repulsion between the graphene oxide sheets, which helps the graphene oxide disperse better in solution. Higher graphene oxide dispersibility facilitates sufficient contact between hydrazine hydrate and the graphene oxide sheets, ensuring a uniform, stable, and complete reduction reaction, resulting in high-quality reduced graphene oxide aerogel. Using the above-mentioned reducing foaming agent in an aqueous solution helps form more uniform and finer bubbles during the foaming process, thereby improving the porosity, uniformity, and structural stability of the graphene aerogel.

[0086] In some embodiments, the reactive reducing agent is selected from one or more of hydrazine hydrate and borohydride.

[0087] In some embodiments, the auxiliary reducing agent is selected from ascorbic acid, citric acid or more, and the auxiliary reducing agent can reduce the intensity of the reactive reducing agent reaction, making it more stable and controllable.

[0088] In some embodiments, NH4 + The source compound is selected from one or more of NH3·H2O, ammonium chloride, ammonium acetate, and amino acid salts.

[0089] In some embodiments, the reactive reducing agent content in the reducing foaming agent aqueous solution is 1% to 30% by weight, specifically 1%, 2%, 5%, 15%, 20%, 25%, or 30%, or other values ​​within the above range, which are not limited here. Using a reactive reducing agent within the above concentration range is beneficial for the stable conduct of the chemical reduction foaming reaction to obtain a more structurally stable graphene aerogel.

[0090] In some embodiments, the content of the auxiliary reducing agent in the reducing foaming agent aqueous solution is 1% to 10% by weight, specifically 1%, 2%, 3%, 6%, 8%, or 10%, or other values ​​within the above range, which are not limited here. Using an auxiliary reducing agent within the above concentration range is beneficial for regulating the chemical reduction foaming reaction to proceed stably and obtaining a more structurally stable graphene aerogel.

[0091] In some embodiments, NH4, by weight percentage + The content of the source compound is 0.5% to 3%, but other values ​​within the above range are also acceptable and are not limited here. NH4 is used within the above concentration range. + The source compound is beneficial to the dispersion of graphene oxide aerogel and the stable progress of the chemical reduction foaming reaction to obtain a more structurally stable graphene aerogel.

[0092] In some embodiments, the chemical reduction foaming process includes multiple foaming processes and multiple washing processes, with the foaming and washing processes performed alternately. Through multiple foaming and washing cycles, the formation and stability of the pore structure can be effectively controlled, ensuring that the aerogel has a high porosity while possessing a uniform structure and excellent mechanical strength.

[0093] In some embodiments, the temperature of the chemical reduction foaming treatment is from 30°C to 90°C, specifically 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, or 90°C. Of course, other values ​​within the above range are also possible and are not limited here.

[0094] In some embodiments, the time for each foaming process is 1 min to 5 min.

[0095] In some embodiments, the time for each water washing process is 1 min to 10 min.

[0096] In some embodiments, the chemical reduction foaming treatment includes two foaming treatments and two washing treatments. After the first foaming treatment, a first washing is performed, followed by a second foaming treatment and a second washing treatment. The reducing foaming agent aqueous solution in the first foaming treatment includes a reactive reducing agent and an auxiliary reducing agent, wherein the weight percentage of the reactive reducing agent in the reducing foaming agent aqueous solution is 5% to 15%, and the weight percentage of the auxiliary reducing agent is 1% to 3%. The reducing foaming agent aqueous solution in the second foaming treatment includes a reactive reducing agent and NH4. + The source compound, and in the aqueous solution of the reducing foaming agent, the weight percentage of the reactive reducing agent is 3% to 7%, NH4 + The source compound comprises 0.5% to 1.5% by weight. In the first foaming process, oxygen-containing functional groups within the graphene oxide film are partially reduced, and the generated gas accumulates inside the film, driving the graphene oxide sheet to expand and form pores. The first water wash removes residual foaming agent and reaction byproducts, helping to prevent residual chemicals from affecting the subsequent foaming effect and ensuring the purity of the aerogel. The second foaming process further promotes the expansion of the graphene oxide sheet and the formation of pores, making the pore structure more uniform and stable. The second water wash removes residual foaming agent, ensuring that the final graphene aerogel has good structural purity and performance.

[0097] In some embodiments, the volume of the reduced graphene oxide aerogel is 4 to 10 times that of the graphene oxide film, preferably 5 to 6 times.

[0098] In some embodiments, the thickness of the reduced graphene oxide aerogel is 400 μm to 2000 μm, preferably 900 μm to 1000 μm;

[0099] Plasticizers, by penetrating into the pores of reduced graphene oxide aerogels, can increase the flexibility and plasticity of the reduced graphene oxide aerogels, reduce the brittleness between reduced graphene oxide aerogels, promote closer stacking, and help form a dense and non-layered structure during subsequent heat treatment processes such as drying. In some embodiments, the plasticizer is selected from one or more of glycerol, ethylene glycol, and propylene glycol, including but not limited to the above components. Other plasticizers that can achieve the purpose of this invention are also applicable to this invention.

[0100] Crosslinking agents can form chemical bonds between membranes, enhancing the interaction forces between reduced graphene oxide aerogels. This not only improves the overall mechanical strength of the structure but also prevents layer-to-layer separation in the stacked structure, contributing to the formation of a more stable and durable graphene aerogel structure. In some embodiments, the crosslinking agent is selected from one or more of glutaraldehyde and epoxide compounds, including but not limited to the above components. Other crosslinking agents capable of achieving the objectives of this invention are also applicable to this invention.

[0101] Surfactants can improve the wettability and surface tension of reduced graphene oxide aerogels, promote uniform contact between the reduced graphene oxide aerogels, thereby reducing interlayer voids, enhancing interlayer bonding, and facilitating the formation of a non-layered monolithic structure after drying. In some embodiments, the surfactant is selected from one or more of polyvinyl alcohol, polyethylene glycol, and polyvinylpyrrolidone, including but not limited to the above components. Other surfactants that can achieve the objectives of this invention are also applicable to this invention.

[0102] In some embodiments, the soaking time is 1 min to 5 min, specifically 1 min, 2 min, 3 min, 4 min, or 5 min, so as to fully wet the functional compound solution with the reduced graphene oxide aerogel and improve production efficiency.

[0103] In some embodiments, the content of the functional compound in the aqueous solution of the functional compound is 10% to 30% by weight, so that the reduced graphene oxide aerogel is fully wetted by the functional compound solution, which is beneficial to enhance the bonding force between the reduced graphene oxide sheets and enhance the bonding strength between the functionalized reduced graphene oxide aerogels during the stacking assembly process, thereby reducing the risk of delamination and cracking during subsequent stacking and drying processes.

[0104] On the one hand, during the stacking assembly process, van der Waals forces exist between adjacent layers of functionalized reduced graphene oxide aerogel. Although this intermolecular force is relatively weak, it can still act as an attraction within a certain distance, allowing adjacent layers of functionalized reduced graphene oxide aerogel to approach each other and stack together. Calendering further strengthens the contact and bonding between the two layers, and can induce structural adjustments within the functionalized reduced graphene oxide aerogel, reducing porosity and structural defects, resulting in a more ordered pore structure and thus improving stacking stability. On the other hand, the layer-by-layer stacking and the calendering process during stacking... The functionalized reduced graphene oxide aerogel layers are in close contact to form a continuous three-dimensional network structure, ultimately forming a graphene oxide aerogel with close contact between graphene layers. The close contact between each layer helps to reduce obstacles in heat conduction, thereby improving the thermal conductivity of the material. Furthermore, through layer-by-layer stacking, calendering during the stacking process, subsequent heat treatment, calendering during heat treatment, and final calendering and compression treatment, the number and thickness of graphene layers in the graphene aerogel can be precisely controlled, and its overall morphology, porosity, and density can be adjusted to improve the mechanical strength, structural stability, and skeleton density of the aerogel, thereby enhancing the overall performance of the graphene aerogel.

[0105] Applying appropriate pressure during the layer-by-layer stacking process helps to enhance the interlayer bonding force, reduce porosity and defects, thereby ensuring the stability and thickness uniformity of the entire functionalized reduced graphene oxide aerogel stacked structure. In some embodiments, the functionalized reduced graphene oxide aerogel is stacked layer by layer to a number of layers of 2n1. During the layer-by-layer stacking process, a pressure treatment is performed along the thickness direction every time the k-th layer is stacked; where n1 is an integer from 5 to 200, k = 10n2, and n2 is an integer from 1 to 40. Specifically, the pressure treatment can be performed by using several ceramic plates with the same length and width as the functionalized reduced graphene oxide aerogel for pressure treatment. The pressure of the pressure treatment is positively correlated with the product of the number of stacked layers and the weight of the ceramic plates. For example, in a specific embodiment of the present invention, the pressure P1 (in MPa) of the pressurization process satisfies the relationship P1=k / 5×p1, where k is the number of stacked layers during the pressurization process, p1 is the pressure applied to a single ceramic plate, the value is 90, and the unit is MPa. Each ceramic plate has the same dimensions as the functionalized reduced graphene oxide aerogel along the horizontal plane (i.e., the plane direction perpendicular to the thickness direction).

[0106] In some embodiments, the thickness of the functionalized reduced graphene oxide aerogel stacked structure is from 20 mm to 500 mm, specifically 20 mm, 100 mm, 200 mm, 300 mm, 400 mm, and 500 mm, or other values ​​within the above range, which are not limited here. Functionalized reduced graphene oxide aerogel stacked structures within this thickness range are advantageous for subsequent calendering and graphitization post-processing to obtain high-density and widely applicable graphitized aerogel products.

[0107] In some embodiments, during the layer-by-layer stacking process, each layer of functionalized reduced graphene oxide aerogel is precisely aligned to ensure good contact and uniform adhesion between layers, thereby preparing a graphene aerogel with stable structure and excellent electrical and thermal conductivity.

[0108] In some embodiments, a graphite plate is used for the second calendering process. The pressure P2 (in MPa) of the second calendering process is positively correlated with the total number of layers stacked in step S4. For example, in a specific embodiment of the present invention, P2 satisfies the relationship P2 = k t / 10×p2;k t p2 represents the total number of layers stacked layer by layer, and p2 represents the pressure applied to a single graphite plate, with a value of 350 MPa. Each graphite plate has the same dimensions as the functionalized reduced graphene oxide aerogel stacked structure along the horizontal plane (i.e., the plane perpendicular to the thickness direction).

[0109] The low-temperature drying process helps control the evaporation rate of moisture, allowing the moisture inside the aerogel to evaporate evenly and reducing stress concentration caused by rapid moisture evaporation, thereby ensuring the stability of the functionalized reduced graphene oxide aerogel stacked structure. In one embodiment, the low-temperature drying temperature is 50°C to 100°C, and the time is 2 hours to 10 hours. Specifically, it can be 50°C for 10 hours, 60°C for 8 hours, 90°C for 6 hours, and 100°C for 2 hours, or other values ​​within the above range, which are not limited here.

[0110] During the carbonization process, a certain degree of thermal reduction and structural adjustment occurs, and some oxygen-containing functional groups are removed. This enhances the interlayer interactions in the stacked structure of the functionalized reduced graphene oxide aerogel, laying the foundation for subsequent graphitization. In one embodiment, the carbonization temperature is 800℃ to 1200℃, the time is 2h to 10h, and the heating rate is ≤3℃ / min. Specifically, it can be 800℃ for 10h, 1000℃ for 5h, and 1200℃ for 2h, or other values ​​within the above range, which are not limited here. The heating rate can be 1℃ / min, 2℃ / min, or 3℃ / min, or other values ​​within the above range, which are not limited here.

[0111] During graphitization, the aerogel framework transforms from a disordered structure to a highly ordered graphite structure. In this process, carbon atoms rearrange to form a regular six-membered ring structure, resulting in graphitized graphene aerogels with excellent properties. In one embodiment, the graphitization treatment temperature is 2800℃ to 3100℃, the time is 1h to 5h, and the heating rate is ≤5℃ / min. Specifically, this can be 2600℃ for 5h, 2800℃ for 4h, 2900℃ for 3h, 3000℃ for 2h, or 3020℃ for 1h, or other values ​​within the above range. The heating rate can be 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, or 5℃ / min, or other values ​​within the above range. Preferably, the graphitization treatment temperature is 2900℃ to 3100℃. The higher graphitization temperature results in higher crystallinity of the graphene sublayers in the obtained graphene aerogel and a more ordered arrangement of carbon atoms.

[0112] In one embodiment, the thickness of the graphitized graphene aerogel is from 10 mm to 500 mm, specifically 10 mm, 100 mm, 200 mm, 300 mm, 400 mm, or 500 mm, or other values ​​within the above range, which are not limited here. Graphitized graphene aerogels of this thickness facilitate subsequent calendering processing to obtain high-density and widely applicable graphitized aerogel products.

[0113] The graphene aerogel is subjected to a third calendering process along its thickness to compress it. This compression reduces the internal pores, leading to a decrease in pore space and thus an increase in overall density. Furthermore, the calendering process reduces the distance between graphene sublayers, resulting in a denser packing and increased material content per unit volume, further contributing to the overall density. Additionally, the calendering process promotes a more ordered alignment of the graphene layers in a specific direction, resulting in a more regular aerogel structure and reducing the space occupied by disordered structures, thus increasing density. Finally, during calendering, some pre-existing micropores and structural defects are filled or eliminated, further enhancing the density of the graphene aerogel. Ultimately, this process yields a graphene aerogel with a continuous, dense three-dimensional network structure. Moreover, it significantly enhances the material's compressive strength and deformation resistance, improving the overall performance of the graphene aerogel.

[0114] In one embodiment, a microcomputer-controlled servo pressure testing machine is used to perform a third calendering process along the thickness direction. The pressure accuracy of this equipment can reach 0.01 MPa, and the pressure can be precisely adjusted according to the size of the graphite graphene aerogel.

[0115] In one embodiment, the pressure of the third calendering process is from 0.01 MPa to 2 MPa, and the time is from 1 min to 60 min. Specifically, the pressure can be 0.01 MPa, 0.2 MPa, 0.5 MPa, 1 MPa, 1.5 MPa, 1.8 MPa, or 2 MPa, or other values ​​within the above range. The calendering process time can be 1 min, 10 min, 20 min, 30 min, 40 min, 50 min, or 60 min, or other values ​​within the above range.

[0116] In one embodiment, a gradient pressure increase and holding period is used for the third calendering process. For example, it can be divided into six stages: the first stage, holding at a pressure of 0.01 MPa to 0.05 MPa for 1 to 10 minutes; the second stage, holding at a pressure of 0.05 MPa to 0.1 MPa for 1 to 10 minutes; the third stage, holding at a pressure of 0.1 MPa to 0.5 MPa for 1 to 10 minutes; the fourth stage, holding at a pressure of 0.5 MPa to 1 MPa for 1 to 10 minutes; the fifth stage, holding at a pressure of 1 MPa to 1.5 MPa for 1 to 10 minutes; and the sixth stage, holding at a pressure of 1.5 MPa to 2 MPa for 1 to 10 minutes. Of course, any combination of two or more of these stages is also possible, and not all are listed here.

[0117] In one embodiment, the thickness of the graphene aerogel is from 5 mm to 300 mm, specifically 5 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, and 300 mm, or other values ​​within the above range, which are not limited here. Using the above-mentioned thickness of the graphene aerogel is beneficial for subsequent cutting to obtain widely applicable graphitized aerogel products.

[0118] In one embodiment, step S6 further includes cutting the compressed graphite-based graphene aerogel to obtain a three-dimensional graphene aerogel. By cutting to remove defective structures and processing it into specific sizes and shapes, the macroscopic size can be controlled and the internal structure optimized, thereby better constructing graphene aerogels with interconnected graphene sublayers and excellent thermal and electrical conductivity. The macroscopic size of the graphene aerogel obtained after cutting is controllable, and it can have better high electrical conductivity, thermal conductivity, and electromagnetic shielding performance in several specific directions.

[0119] In one embodiment, the cutting equipment is selected from laser cutting machines, CNC cutting machines, and waterjet cutting machines. Specifically, the appropriate cutting equipment can be selected based on the required thickness, shape complexity, production scale, and cutting precision.

[0120] In one embodiment, the cutting process includes cutting along the plane parallel to the plane containing the graphene layer of the compressed graphite graphene aerogel and along the thickness direction perpendicular to the plane containing the graphene layer.

[0121] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0122] Example 1

[0123] A graphene aerogel is prepared by the following steps:

[0124] Step 1, Preparation of graphene oxide film: Graphene oxide raw material (particle size 45 μm) with a carbon-to-oxygen atomic ratio of 1:1 was dispersed in water to prepare a mixed dispersion with a solid content of 4%. The preparation process of the mixed dispersion is as follows: A planetary mixer was used for stirring. First, a three-step dispersion was carried out at a stirring speed of 45 rpm: the first step was a dispersion at 1000 rpm for 10 min, the second step was a dispersion at 2000 rpm for 20 min, and the third step was a dispersion at 4000 rpm for 20 min; then, dispersion was carried out at a stirring speed of 50 rpm for 6000 rpm for 30 min.

[0125] The mixed dispersion was subjected to high-pressure homogenization at a pressure of 750 bar, twice, at a temperature of 14°C.

[0126] The homogenized system was degassed to obtain a slurry containing graphene oxide sheets. The viscosity of the slurry containing graphene oxide sheets was 30,000 cps and the pH value was 6.8. The degassed process was as follows: the degassed process was carried out in two steps, the first step was degassed at 1500 rpm for 1 min and the second step was degassed at 2000 rpm for 1 min, the vacuum pressure was -98 kPa and the treatment temperature was 25℃.

[0127] A wet film is obtained by coating a slurry containing graphene oxide sheets, and the wet film is dried at 60°C for 5 hours to obtain a graphene oxide film, which includes graphene oxide sheets and has a thickness of 190 μm.

[0128] Step 2, Preparation of Reduced Graphene Oxide Aerogel: The graphene oxide film is chemically reduced and foamed using a reducing foaming agent aqueous solution to obtain reduced graphene oxide aerogel. The chemical reduction foaming treatment includes two foaming processes and two washing processes. After the first foaming process, a first washing is performed, followed by a second foaming process and a second washing process. The reducing foaming agent aqueous solution in the first foaming process includes the reactive reducing agent hydrazine hydrate and the auxiliary reducing agent ascorbic acid, with hydrazine hydrate comprising 10% by weight and ascorbic acid comprising 2% by weight. The reducing foaming agent aqueous solution in the second foaming process includes the reactive reducing agent hydrazine hydrate and NH4+. + The source compound was NH3·H2O, and the weight percentage of hydrazine hydrate and NH3·H2O in the aqueous solution of the reducing foaming agent was 5% and 1% respectively. The first foaming treatment time was 3 min, the first water washing treatment time was 5 min, the second foaming treatment time was 2 min, and the second water washing treatment time was 3 min. The volume of the reduced graphene oxide aerogel after foaming was 5.5 times that of the graphene oxide film, and the thickness of the reduced graphene oxide aerogel was 950 μm. The temperature of both foaming treatments was 45℃.

[0129] Step 3, preparation of functionalized reduced graphene oxide aerogel: The reduced graphene oxide aerogel is immersed in a plasticizer solution to obtain functionalized reduced graphene oxide aerogel; the plasticizer solution is an aqueous glycerol solution, and the content of glycerol in the aqueous glycerol solution is 20% by weight, and the immersion time is 3 min;

[0130] Step 4, Functionalized Reduced Graphene Oxide Aerogel Stacking Structure: Functionalized reduced graphene oxide aerogels are stacked layer by layer along the thickness direction, and a first calendering process is performed along the thickness direction during the stacking process to obtain the functionalized reduced graphene oxide aerogel stacking structure. During the stacking process, each layer of functionalized reduced graphene oxide aerogel is precisely aligned. The total number of stacked layers is 200, and a pressurization process is required after every 10 layers. The pressure P1 (in MPa) of the pressurization process satisfies the relationship P1=k / 5×p1, where k is the number of stacked layers during the pressurization process, p1 is the pressure applied by a single ceramic plate, with a value of 90 and a unit of MPa. The dimensions of each ceramic plate are the same as those of the functionalized reduced graphene oxide aerogel along the horizontal plane (i.e., the plane perpendicular to the thickness direction).

[0131] Step 5, Preparation of graphitized graphene aerogel: The functionalized reduced graphene oxide aerogel stacked structure is subjected to a second calendering process along its thickness direction, followed by low-temperature drying, carbonization, and graphitization to obtain graphitized graphene aerogel. Throughout the entire heat treatment process, a graphite plate is used for the second calendering process, and the pressure P2 of the second calendering process satisfies the relationship P2 = k t / 10×p2;k t p2 represents the total number of layers stacked sequentially, and p2 represents the pressure applied to a single graphite plate, with a value of 350 MPa. Each graphite plate has the same dimensions as the functionalized reduced graphene oxide aerogel stacked structure along the horizontal plane (i.e., the plane perpendicular to the thickness direction). The low-temperature drying temperature is 80℃ for 25 hours; the carbonization temperature is 1200℃ for 5 hours with a heating rate of 2℃ / min; the graphitization temperature is 3100℃ for 2 hours with a heating rate of 3℃ / min; the thickness of the graphitized graphene aerogel is 95 mm.

[0132] Step 6: Using a servo pressure testing machine, the graphite-coated graphene aerogel is subjected to a third calendering process along its thickness direction to compress it, resulting in compressed graphite-coated graphene aerogel. Uneven edges are removed by trimming along both the plane parallel to the graphene layer and the thickness direction perpendicular to the plane of the graphene layer, thus obtaining graphene aerogel. The third calendering process employs a gradient pressure increase and holding pressure: first stage, holding pressure at 0.5 MPa for 10 min; second stage, holding pressure at 1 MPa for 5 min; third stage, holding pressure at 1.5 MPa for 5 min; fourth stage, holding pressure at 2 MPa for 2 min. The thickness of the compressed graphite-coated graphene aerogel is 38 mm; the dimensions of the graphene aerogel are 40 mm (length) × 50 mm (width) × 30 mm (thickness).

[0133] Figure 1 The SEM image of the cross-section of the reduced graphene oxide aerogel in Example 1 above, cut along a plane parallel to the thickness direction, shows a large number of pore structures. Figure 2 SEM image of the first cross-section of the graphene aerogel prepared in Example 1 after being cut along a first plane parallel to the thickness direction; Figure 3 The first cross-section of the graphene aerogel prepared in Example 1, cut along a first plane parallel to the thickness direction, is shown in the SEM image. The graphene layer structure can be observed. Each graphene layer includes several graphene sublayers stacked along the thickness direction and pores distributed between any two graphene sublayers. Figure 4The Raman spectrum of the graphene aerogel prepared in Example 1 shows a distinct D-peak defect peak (1350 cm⁻¹). -1 ) and the G peak (1580 cm⁻¹) related to the in-plane vibrations of sp² hybridized carbon atoms in graphene. -1 The low intensity of the D peak defect indicates that the prepared graphene aerogel has few defects. Figure 5 The image shows the XRD pattern of the graphene aerogel prepared in Example 1, where the graphene oxide was completely reduced. Figure 6 The image shows the electromagnetic shielding effectiveness of the graphene aerogel prepared in Example 1. The graphene aerogel obtained after cutting has a thickness of 30 mm and a density of 0.20 g / cm³. 3 It has an average pore size of 120 μm, a porosity of 78%, a horizontal thermal conductivity of 48 W / mK, a vertical thermal conductivity of 47 W / mK, an electrical conductivity of 450 S / m, and an electromagnetic shielding effectiveness of 118 dB.

[0134] Example 2

[0135] The only difference between it and Example 1 is that:

[0136] In step two, during the first foaming treatment, the weight percentage of hydrazine hydrate was 15% and the weight percentage of ascorbic acid was 5%; during the second foaming treatment, the weight percentage of hydrazine hydrate was 10% and the weight percentage of NH3·H2O was 2%; the volume of the reduced graphene oxide aerogel after foaming was 6.5 times that of the graphene oxide film, and the thickness of the reduced graphene oxide aerogel was 1350 μm.

[0137] In step five, the thickness of the graphite-based graphene aerogel is 135 mm.

[0138] In step six, the thickness of the compressed graphite graphene aerogel is 54 mm, and the dimensions of the graphene aerogel are 60 mm (length) × 60 mm (width) × 50 mm (thickness).

[0139] Example 3

[0140] The only difference between this and Example 1 is that the plasticizer solution in step 3 is replaced with a crosslinking agent solution; wherein the crosslinking agent is an aqueous solution of glutaraldehyde, and the content of glutaraldehyde in the aqueous solution of glutaraldehyde is 30% by weight, and the soaking time is 2 minutes.

[0141] Example 4

[0142] The only difference between this and Example 1 is that the plasticizer solution in step three is replaced with a surfactant solution; wherein the surfactant is an aqueous solution of polyvinyl alcohol.

[0143] Example 5

[0144] The only difference between this and Example 1 is that the gradient pressurization and pressure holding conditions in step six are as follows: in the first stage, the pressure is held at 0.05 MPa for 10 min; in the second stage, the pressure is held at 0.1 MPa for 5 min; in the third stage, the pressure is held at 0.5 MPa for 5 min; and in the fourth stage, the pressure is held at 1 MPa for 2 min.

[0145] Example 6

[0146] The only difference between it and Example 1 is that in step five, the carbonization temperature is 900℃, the heating rate is 1℃ / min, and the time is 4h.

[0147] Example 7

[0148] The only difference between it and Example 1 is that in step five, the temperature of the graphitization treatment is 2800℃, the heating rate is 3℃ / min, and the time is 2h.

[0149] Example 8

[0150] A composite material, comprising the following steps:

[0151] Using the graphene aerogel prepared in Example 1 as raw material, silica gel was permeated into the pores of the graphene aerogel by vacuum cyclic impregnation, and the composite material was obtained after curing. The impregnation temperature was 30°C, the vacuum pressure was 1000 Pa, the single vacuum impregnation time was 5 min, and the number of vacuum cyclic impregnations was 10. The curing temperature was 150°C and the curing time was 1 h.

[0152] Example 9

[0153] The only difference between it and Example 8 is that the composite material is prepared using the graphene aerogel prepared in Example 2 as the raw material.

[0154] Example 10

[0155] The only difference between it and Example 8 is that the composite material is prepared using the graphene aerogel prepared in Example 3 as the raw material.

[0156] Example 11

[0157] The only difference between it and Example 8 is that the composite material is prepared using the graphene aerogel prepared in Example 4 as the raw material.

[0158] Example 12

[0159] The only difference between it and Example 8 is that the composite material is prepared using the graphene aerogel prepared in Example 5 as the raw material.

[0160] Example 13

[0161] The only difference between it and Example 8 is that the composite material is prepared using the graphene aerogel prepared in Example 6 as the raw material.

[0162] Example 14

[0163] The only difference between it and Example 8 is that the composite material is prepared using the graphene aerogel prepared in Example 7 as the raw material.

[0164] Example 15

[0165] A composite material, comprising the following steps:

[0166] Using the graphene aerogel prepared in Example 1 as raw material, epoxy resin (weight average molecular weight of 500 g / mol) was impregnated into the pores of the graphene aerogel by vacuum cyclic impregnation, and the composite material was obtained after curing. The impregnation temperature was 30°C, the vacuum pressure was 1000 Pa, the single vacuum impregnation time was 5 min, the number of vacuum cyclic impregnations was 15, the curing temperature was 120°C, and the curing time was 1 h.

[0167] Comparative Example 1

[0168] The only difference between it and Example 1 is that step three is omitted, and the reduced graphene oxide aerogel prepared in step two is directly used in step four to prepare a functionalized reduced graphene oxide aerogel stacked structure.

[0169] Comparative Example 2

[0170] The only difference between it and Example 1 is that in step four, no first calendering process is performed during the process of stacking functionalized reduced graphene oxide aerogel layer by layer along the thickness direction.

[0171] Comparative Example 3

[0172] The only difference between it and Example 1 is that the third calendering process is not performed in step six.

[0173] Comparative Example 4

[0174] The only difference between it and Example 1 is that in step five, the second calendering process is not performed during the carbonization and graphitization processes.

[0175] Comparative Example 5

[0176] The only difference between it and Example 8 is that the composite material is prepared using the graphene aerogel prepared in Comparative Example 1 as the raw material.

[0177] Comparative Example 6

[0178] The only difference between it and Example 8 is that the composite material is prepared using the graphene aerogel prepared in Comparative Example 2 as the raw material.

[0179] Comparative Example 7

[0180] The only difference between it and Example 8 is that the composite material is prepared using the graphene aerogel prepared in Comparative Example 3 as the raw material.

[0181] Comparative Example 8

[0182] The only difference between it and Example 8 is that the composite material is prepared using the graphene aerogel prepared in Comparative Example 4 as the raw material.

[0183] Performance testing

[0184] (1) Electron microscopy test: SEM characterization was performed using a scanning electron microscope to determine the pore size and graphene layer thickness of the graphene aerogel, and ImageJ was used to statistically calculate the average pore size and the ratio of large and small pores.

[0185] (2) Carbon content test: Weigh a certain amount of sample, heat it to 950℃ in a muffle furnace and keep it warm. Weigh the percentage of the residue after combustion to calculate the carbon content (weight percentage).

[0186] (3)I D / I G Ratio: The defects and crystal structure of the sample were analyzed using Raman spectroscopy. The continuous scanning range was 100 cm⁻¹ to 4000 cm⁻¹ at room temperature, and the laser wavelength λ was 532 nm. The ID / IG ratio was calculated using the area ratio.

[0187] (4) Graphitization degree: The interlayer spacing d002 of the 002 peak of graphene aerogel was determined by XRD, and the graphitization degree G was calculated by the formula G=(0.3440-d002) / (0.3440-0.3354)×100%.

[0188] (5) Porosity test: The equipment used was a MAY-12450 ceramic porosity tester. The dry sample was placed on the air-filled measuring stage, and after stabilization, the dry, empty weight of the sample was measured. The sample was then placed in a water cup for saturation treatment, and then placed on the water-filled measuring stage. After stabilization, the saturated water weight of the sample was measured. The sample was then removed and placed on a water-saturated nano-sponge. Excess water on the sample surface was wiped off, and after stabilization, the sample was saturated with air, and the porosity was then displayed.

[0189] (6) Horizontal and vertical thermal conductivity tests: The equipment used was an LFA-467 Hyper Flash. Referring to ASTM-E1461, "Standard Test Method for Determination of Fixed Thermal Conductivity by Flash Method," the sample was cut into small circular pieces with a thickness of 3 mm and a diameter of 25.4 mm. The thermal diffusivity was measured using in-plane and single-round supports. Thermal conductivity = thermal diffusivity × density × specific heat capacity. The thermal conductivity (i.e., thermal conductivity ratio) was calculated, and the unit of diffusivity is m. 2 / s, specific heat capacity is 0.85, unit is J / (kg·K), density is the density of graphene aerogel, unit is kg / m³ 3 Wherein, the horizontal thermal conductivity is the thermal conductivity of the graphene aerogel along the first straight line direction parallel to the plane where the graphene layer is located, and the vertical thermal conductivity is the thermal conductivity of the graphene aerogel along the second straight line direction parallel to the plane where the graphene layer is located and perpendicular to the first straight line direction.

[0190] (7) Thermal conductivity test: After placing the sample on a 100℃ constant temperature heating table and keeping it at that temperature for 30 minutes, the average temperature difference between the horizontal and vertical planes inside the graphene aerogel was measured using a FLIR-T420 infrared thermal imager. The horizontal plane is the third plane parallel to the thickness direction of the graphene aerogel, and the vertical plane is the fourth plane parallel to the thickness direction of the graphene aerogel and perpendicular to the horizontal plane.

[0191] (8) Cut the graphene aerogel into small pieces of uniform size, measure its mass m1, vacuum-assisted impregnation with polymer material, clean the residual polymer material on the surface, measure its mass m2 after curing, and calculate the filling rate of polymer material by using the formula (m2-m1) / m2.

[0192] (9) Conductivity test: The electrical conductivity of graphene aerogel was measured using a Keithley four-probe resistivity meter.

[0193] (10) Electromagnetic shielding effectiveness: The electromagnetic shielding effectiveness of graphene aerogel was analyzed using a vector network analyzer.

[0194] (11) Density test: The graphene aerogel was cut into small pieces of uniform size, and its thickness, area and mass were measured. The sample density was calculated by ρ = m / v.

[0195] (12) Specific surface area test: The specific surface area was tested using a pore size analyzer (TriStar 3000, USA).

[0196] (13) Pore volume test: The pore volume was tested using a fully automated mercury porosimetry pore size analyzer (AutoPore V, USA).

[0197] The performance test results of the graphene aerogels prepared in Examples 1-7 and Comparative Examples 1-4 are shown in Table 1.

[0198] The performance test results of the composite materials prepared in Examples 8-15 and Comparative Examples 5-8 are shown in Table 2.

[0199] Table 1

[0200]

[0201]

[0202] Note: " / " indicates that the graphene aerogel collapsed during the preparation process and no relevant measurements were taken.

[0203] Table 2

[0204]

[0205] Note: " / " indicates that the graphene aerogel collapsed during the preparation process and no relevant measurements were taken.

[0206] As shown in Tables 1 and 2, the graphene aerogels prepared in Examples 1-7 have excellent horizontal thermal conductivity (32 W / mK to 49 W / mK) and vertical thermal conductivity (30 W / mK to 47 W / mK), and the two are comparable. Although the thermal conductivity of the composite material prepared from it is reduced, it still has excellent horizontal thermal conductivity and vertical thermal conductivity, and the two are comparable.

[0207] Comparing Example 1 with Comparative Examples 1-4, it can be seen that Comparative Example 1 did not undergo soaking treatment with the aqueous solution of the functional compound; the reduced graphene oxide aerogel was directly used to prepare the functionalized reduced graphene oxide aerogel stacked structure, resulting in delamination during the stacking process. Comparative Example 2 did not undergo a first calendering process during the layer-by-layer stacking of functionalized reduced graphene oxide aerogels along the thickness direction, and delamination also occurred during stacking. Comparative Example 3 did not undergo a third calendering process; the resulting graphene aerogel showed a significant increase in density, porosity, specific surface area, pore volume, macropore ratio, and average pore size, while horizontal thermal conductivity, vertical thermal conductivity, electrical conductivity, and electromagnetic shielding effectiveness were all significantly reduced, and the average temperature difference between the horizontal and vertical planes increased. In Comparative Example 4, no second calendering process was performed during the carbonization and graphitization processes. The resulting graphene aerogel exhibited significantly increased density, porosity, specific surface area, pore volume, macropore ratio, and average pore size. However, the horizontal thermal conductivity, vertical thermal conductivity, electrical conductivity, and electromagnetic shielding effectiveness all decreased significantly, and the average temperature difference between the horizontal and vertical planes increased.

[0208] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A graphene aerogel, characterized in that, The graphene aerogel comprises a plurality of graphene layers, each graphene layer being stacked along the thickness direction to form a multilayer structure, and any two adjacent graphene layers being surface-to-surface bonded together; each graphene layer includes a plurality of graphene sublayers stacked along the thickness direction and pores distributed between any two graphene sublayers. The thickness direction is perpendicular to the plane containing the graphene layer.

2. The graphene aerogel according to claim 1, characterized in that, The graphene aerogel has at least one of the following characteristics: (1) The horizontal thermal conductivity of the graphene aerogel along the first straight line direction parallel to the plane where the graphene layer is located is greater than or equal to 30 W / m·K, and the vertical thermal conductivity of the graphene aerogel along the second straight line direction parallel to the plane where the graphene layer is located and perpendicular to the first straight line direction is greater than or equal to 30 W / m·K. (2) After placing the graphene aerogel on a 100℃ constant temperature heating table for 30 minutes, the temperature difference between any two points on any straight line parallel to the plane where the graphene layer is located in the graphene aerogel is ≤5℃.

3. The graphene aerogel according to claim 1 or 2, characterized in that, The graphene aerogel has at least one of the following characteristics: (1) In terms of volume percentage, the proportion of macropores with a pore size of 100 μm to 200 μm in the graphene aerogel is greater than or equal to 50% and less than or equal to 80%. (2) By volume percentage, the proportion of pores with a diameter of 50 μm or less is greater than or equal to 1% and less than or equal to 15%; (3) The average pore size of the graphene aerogel is 1 μm to 200 μm.

4. The graphene aerogel according to claim 1 or 2, characterized in that, The graphene aerogel has at least one of the following characteristics: (1) The density of the graphene aerogel is 0.01 g / cm³. 3 Up to 0.3 g / cm 3 ; (2) The porosity of the graphene aerogel is 75% to 90%; (3) The specific surface area of ​​the graphene aerogel is 500 m². 2 / g to 1000m 2 / g; (4) The pore volume of the graphene aerogel is 2 cm³. 3 / g to 4cm 3 / g.

5. The graphene aerogel according to claim 1 or 2, characterized in that, The graphene aerogel has at least one of the following characteristics: (1) The carbon content in the graphene aerogel is greater than or equal to 99% by weight percentage; (2) The graphene aerogel has a graphitization degree of ≥95%; (3) The Raman spectrum of the graphene aerogel has a D peak and a G peak, and the area ratio of the D peak and the G peak, ID / IG, is less than 0.01; (4) The thickness of the graphene layer is 10 nm to 100 nm.

6. The graphene aerogel according to claim 1 or 2, characterized in that, The graphene aerogel has at least one of the following characteristics: (1) The electrical conductivity of the graphene aerogel along the plane parallel to the graphene layer is greater than or equal to 300 S / m; (2) The electromagnetic shielding effectiveness of the graphene aerogel along the thickness direction is greater than or equal to 100dB.

7. A composite material, characterized in that, The invention includes a polymeric material and a graphene aerogel according to any one of claims 1 to 6, wherein the polymeric material is distributed in the pores of the graphene aerogel; Preferably, the polymer material is permeated into the pores of the graphene aerogel using a vacuum-assisted impregnation method, and the composite material is obtained after curing.

8. The composite material according to claim 7, characterized in that, The polymer material is selected from one or more of liquid silicone, acrylic resin, epoxy resin, polyurethane, polyester, and phenolic resin.

9. The composite material according to claim 7, characterized in that, The composite material has at least one of the following characteristics: (1) In terms of volume percentage, the filling rate of the polymer material in the pores of the graphene aerogel material is 40% to 80%; (2) The horizontal thermal conductivity of the composite material along the third straight direction parallel to the plane where the graphene layer is located is greater than or equal to 20 W / m·K, and the vertical thermal conductivity of the composite material along the fourth straight direction parallel to the plane where the graphene layer is located and perpendicular to the third straight direction is greater than or equal to 30 W / m·K.

10. The application of the graphene aerogel according to any one of claims 1 to 6 or the composite material according to any one of claims 7 to 9, characterized in that, It is used as a thermally conductive material in thermal management systems.

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