Graphene heat-conducting composite material, preparation method and application thereof

Abstract

The application belongs to the technical field of heat-conducting composite materials, and particularly relates to a graphene heat-conducting composite material and a preparation method and application thereof. First, a roller, a permanent magnet, an adhesive tape and a motor are assembled into a reaction device; then, a graphene and polymer mixed solution is transferred into the reaction device to obtain a graphene heat-conducting composite material with a highly aligned and stretched structure under the joint action of a magnetic field, a gravitational field and a surface tension field. The preparation method provided by the application has simple equipment, a short production cycle, and the graphene in the composite material has a highly aligned and stretched structure, high heat conductivity and high flexibility, and is suitable for heat management applications in the new era.

Description

Technical Field

[0001] This invention belongs to the field of thermally conductive composite materials technology, specifically relating to a graphene thermally conductive composite material, its preparation method, and its application. Background Technology

[0002] With the development of technologies such as energy, semiconductors, and 5G, electronic devices are evolving towards lighter weight, higher efficiency, greater integration, and more multifunctionality. This has led to a rapid increase in the energy density of electronic devices, resulting in the accumulation of significant amounts of heat during operation. This heat accumulation not only reduces the operating efficiency of electronic devices but also affects their safety and lifespan. Therefore, heat conduction and dissipation in electronic devices have become critical issues in the field of thermal management.

[0003] Thermally conductive composite materials, formed by combining highly thermally conductive fillers with highly flexible polymers, can be used to create thermal interface materials, thereby meeting the heat dissipation requirements of electronic devices. Currently, traditional thermally conductive composite materials are produced using a blending process to combine thermally conductive fillers with polymers. However, the disordered distribution of the thermally conductive fillers within the polymer makes it difficult to form efficient thermally conductive pathways and networks, resulting in the thermal conductivity of the prepared composite material failing to meet the heat dissipation requirements of electronic devices.

[0004] Although reports have shown that graphene can be oriented in thermally conductive composite materials—for example, patent CN118183715A discloses a method for preparing a three-dimensional graphene oxide framework using rotational centripetal force and foaming technology, followed by high-temperature reduction and silicone oil filling to prepare the thermally conductive composite material—the framework preparation process is time-consuming and requires complex low-temperature drying equipment, resulting in high costs and significant production difficulties.

[0005] The patent with publication number CN202410117415A discloses a method for preparing thermally conductive composite materials by using porous polymers as templates, and then compressing, reducing at high temperature, and filling with resin after adsorbing graphene. However, the preparation process of this method is lengthy and complex, and the multi-stage high-temperature treatment process increases the preparation cost and consumes energy.

[0006] Patent CN 113416420 A discloses a method for preparing a highly oriented graphene sheet thermal interface material. The method involves adding non-redox graphene sheets to a polymer matrix and mechanically stirring to obtain a dispersion; adding a curing agent and a catalyst to the dispersion and mechanically stirring to obtain a mixture; transferring the mixture to a magnetic field, where it changes from a liquid to a solid state, and then removing it from the magnetic field; further heating and curing the solid mixture to obtain the highly oriented graphene thermal interface material. However, this method cannot avoid the wrinkling problem of graphene during the drying and curing process, making it difficult to obtain a highly aligned and highly stretched structure when molding composite materials, thus affecting its thermal conductivity. Summary of the Invention

[0007] The purpose of this invention is to provide a graphene thermally conductive composite material, its preparation method, and its application. Compared with traditional blending processes, the graphene filler is oriented in the polymer, constructing oriented thermally conductive pathways or networks within the composite material. This avoids the wrinkling problem of graphene composite thermally conductive materials during curing, and improves the extensibility and high thermal conductivity of graphene in graphene composite materials.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0009] In a first aspect, embodiments of the present invention provide a graphene thermally conductive composite material comprising graphene and a polymer matrix, wherein the graphene is a single layer or multiple layers of graphene with a particle size of 5 μm-100 μm.

[0010] The polymer matrix includes one or more of the following: high-temperature resistant silicone rubber, PDMS, polyvinyl alcohol, polyvinylpyrrolidone, or epoxy resin;

[0011] Graphene is arranged in a highly aligned manner parallel to the magnetic field direction within the polymer matrix through the combined action of the rotating roller motion and the magnetic field, forming heat-conducting channels.

[0012] The graphene used in this invention possesses excellent in-plane thermal conductivity (theoretically reaching 5300 W / mK) and is considered one of the most promising thermally conductive fillers. In composite materials, graphene exhibits a highly extended and aligned arrangement and is compounded with the polymer matrix, effectively leveraging its high in-plane thermal conductivity.

[0013] Secondly, embodiments of the present invention provide an apparatus for preparing the graphene thermally conductive composite material described in the first aspect, comprising a roller, a permanent magnet, a tape, a heating element, and a motor; the tape is provided on the outer wall of the roller, the permanent magnet is fixed inside the roller and the permanent magnet coincides with the axis of the roller; a heating element is provided above the roller, and the roller is connected to the motor.

[0014] The preparation apparatus of this invention is simple to assemble. A mixture of graphene and polymer is placed in the apparatus, and under the combined action of a magnetic field, a gravitational field, and a surface tension field, a highly aligned and stretched graphene thermally conductive composite material is obtained. Compared to the apparatus used in the prior art, the apparatus of this invention can achieve a higher degree of directional alignment of graphene, and the directional alignment of graphene is carried out simultaneously with polymer molding, eliminating the high-temperature preparation process of the graphene framework in the prior art, thus reducing the preparation difficulty and process cost. Furthermore, during the rotation of the drum, the heating element dries the mixture adhering to the drum, achieving layer-by-layer drying of graphene. This effectively suppresses wrinkling problems in the graphene composite material during the drying and curing process, improving the stretchability of graphene in the graphene thermally conductive composite material.

[0015] Thirdly, embodiments of the present invention provide a method for preparing a graphene thermally conductive composite material, comprising the following steps:

[0016] (a) Graphene and polymer are dissolved in a solvent, ultrasonically dispersed and mechanically stirred, and then a curing agent is added to form a uniform mixture;

[0017] (b) The mixture is placed in a rotating support device with tape. The graphene is oriented along the direction of the magnetic field under the action of the magnetic field, and the graphene is uniformly lifted by the continuous rotation of the rotating support device.

[0018] While the rotating support device rotates, the heating element dries the mixture, keeping the graphene oriented before curing.

[0019] (c) Further heating and curing dissolves the tape to obtain a graphene thermally conductive composite material with highly ordered thermally conductive channels.

[0020] This invention directly places a mixture of graphene and polymer into a rotating support device with an adhesive tape. The height of the mixture is precisely tangent to the roller, creating a thin liquid bridge between the roller and the mixture surface. Under the influence of a magnetic field, the graphene aligns parallel to the magnetic field lines within the dispersion. This alignment facilitates the roller's ability to lift the graphene from the solution surface. The roller's lifting action on the graphene allows it to achieve a highly aligned and stretched structure under the combined influence of a magnetic field, a gravitational field, and a surface tension field. This multi-field-induced graphene alignment method achieves a higher degree of alignment, effectively utilizing the graphene's high in-plane thermal conductivity.

[0021] Fourthly, embodiments of the present invention provide the application of the graphene thermally conductive composite material described in the first aspect in the thermal management of electronic devices; preferably, the graphene thermally conductive composite material is suitable for thermal interface materials, thermally conductive device substrates or housings.

[0022] The beneficial effects of the above embodiments of the present invention are as follows:

[0023] (1) In the graphene composite thermal conductive material prepared by the present invention, the graphene is a planar high thermal conductivity graphene with a single-layer structure. Its single-layer structure endows it with a high anisotropic magnetic susceptibility, which is sufficient to provide a magnetic torque for deflection in a low magnetic field.

[0024] (2) In the graphene composite thermal conductive material of the present invention, the oriented arrangement of graphene not only gives full play to the thermal conductivity of the two-dimensional thermal conductive filler in the advantageous direction, but also constructs oriented thermal conductive pathways or networks inside the composite material, thereby achieving high thermal conductivity of the composite material.

[0025] (3) The preparation device of the present invention is simple to assemble. Under the combined action of a magnetic field, a gravitational field, and a surface tension field, it can achieve a higher degree of directional alignment of graphene. Moreover, the directional alignment of graphene is carried out simultaneously with polymer molding, eliminating the high-temperature preparation process of graphene framework in the prior art, and reducing the preparation difficulty and process cost. In addition, during the rotation of the drum, the heating element dries the mixture adhering to the drum, realizing the layer-by-layer drying of graphene. This effectively suppresses the wrinkling problem of graphene composite material during the drying and curing process and improves the degree of graphene expansion in the graphene thermally conductive composite material.

[0026] (4) The preparation method of the present invention is simple and convenient and easy to promote. Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, 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 improper limitation of the invention.

[0028] Figure 1 A photograph of the graphene thermally conductive composite material prepared in Example 1 of this invention;

[0029] Figure 2 A cross-sectional scanning electron microscope image of the graphene thermally conductive composite material prepared in Example 1 of this invention;

[0030] Figure 3 Here is a scanning electron microscope image of the surface of the graphene thermally conductive composite material prepared in Example 1 of this invention;

[0031] Figure 4 A cross-sectional scanning electron microscope image of the graphene thermally conductive composite material prepared in Example 2 of this invention;

[0032] Figure 5 This is a cross-sectional scanning electron microscope image of the graphene thermally conductive composite material prepared in Comparative Example 1 of this invention;

[0033] Figure 6This is a schematic diagram of the device used in Embodiment 1 of the present invention, wherein: (1) heating plate, (2) roller, (3) magnet, (4) mixed solution. Detailed Implementation

[0034] The raw materials and apparatus components used in the embodiments of the present invention are all known products, obtained by purchasing commercially available products.

[0035] Among them, the graphene is high-purity single-layer graphene produced by Shenzhen Huiheng Company, with a particle size between 5-8μm and a thickness of less than 1nm.

[0036] The permanent magnet is a commercially available neodymium iron boron permanent magnet with a diameter of 50mm and a height of 30mm;

[0037] Water-soluble tape is a double-sided adhesive composed of water-soluble acrylic adhesive and a non-woven fabric substrate.

[0038] The roller is a hollow cylinder made of resin material using 3D printing, and it is also designed with a coupling to connect to the motor.

[0039] In a first aspect, embodiments of the present invention provide a graphene thermally conductive composite material comprising graphene and a polymer matrix, wherein the graphene is a single layer or multiple layers of graphene with a particle size of 5 μm-100 μm.

[0040] The polymer matrix includes one or more of the following: high-temperature resistant silicone rubber, PDMS, polyvinyl alcohol, polyvinylpyrrolidone, or epoxy resin;

[0041] Graphene is arranged in a highly aligned manner parallel to the magnetic field direction within the polymer matrix through the combined action of the rotating roller motion and the magnetic field, forming heat-conducting channels.

[0042] Secondly, embodiments of the present invention provide a preparation apparatus for graphene thermally conductive composite materials, including a roller, a permanent magnet, a tape, a heating element, and a motor; the tape is provided on the outer wall of the roller, the permanent magnet is fixed inside the roller and the permanent magnet coincides with the axis of the roller; a heating element is provided above the roller, and the roller is connected to the motor.

[0043] In some other embodiments, the tape is a water-soluble tape. To further improve the solvent affinity of the water-soluble tape, the surface of the water-soluble tape is modified. The modification method used is one or more of coating modification, plasma modification, chemical grafting modification, or etching modification. Preferably, graphene is coated on the surface of the water-soluble tape.

[0044] The heating element is one or more of the following: infrared lamp, ceramic heating plate, silicone rubber heating plate, or alumina heating plate.

[0045] Thirdly, embodiments of the present invention provide a method for preparing a graphene thermally conductive composite material, comprising the following steps:

[0046] (a) Graphene and polymer are dissolved in a solvent, ultrasonically dispersed and mechanically stirred, and then a curing agent is added to form a uniform mixture;

[0047] (b) The mixture is placed in a rotating support device with adhesive tape. Under the action of a magnetic field, the graphene is oriented along the direction of the magnetic field, and the graphene is uniformly lifted by the continuous rotation of the rotating support device.

[0048] While the rotating support device is rotating, the heating element dries the mixture, keeping the graphene oriented before curing.

[0049] (c) Further heating and curing dissolves the tape to obtain a graphene thermally conductive composite material with highly ordered thermally conductive channels.

[0050] In some other embodiments, in (a), the graphene is a single layer or multiple layers of graphene, and the particle size of the graphene is 5 μm-100 μm;

[0051] Preferably, the graphene is a single-layer graphene with a particle size of 8μm-12μm;

[0052] To further improve the dispersibility of graphene, a dispersant with a mass fraction of 1-5 wt.% is added to the graphene solution.

[0053] Alternatively, the polymer material may be one or more of silicone rubber, PDMS, polyvinyl alcohol, polyvinylpyrrolidone, or epoxy resin;

[0054] Alternatively, the solvent may be one or more of deionized water, ethanol, benzene, methanol, solvent oil, white oil, n-hexane, or petroleum ether.

[0055] Preferably, the solvent is n-hexane.

[0056] In some other embodiments, in (a), the mass ratio of graphene to solvent is 0.001-0.1; preferably, the mass ratio of graphene to solvent is 0.004-0.005.

[0057] Alternatively, the mass ratio of polymer to solvent is 0.002-0.2;

[0058] Preferably, the mass ratio of polymer to solvent is 0.009-0.01;

[0059] Alternatively, the curing agent may be 1-5 wt.% of the polymer mass.

[0060] The rotational speed of the rotating support device is 10-150° / s, preferably 24° / s; the rotation time of the rotating support device is 0.5-1h; and the temperature of the heating plate is 150-200℃.

[0061] The curing temperature is 60-80℃, and the tape is dissolved by immersing it in deionized water at room temperature for 4-6 hours.

[0062] In addition, the present invention also provides an application of graphene thermally conductive composite material in thermal interface materials, thermally conductive device substrates or housings.

[0063] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0064] Example 1

[0065] A method for preparing a graphene thermally conductive composite material specifically includes the following steps:

[0066] (1) Co-dispersion of graphene and polymer:

[0067] Weigh 6g of raw silicone rubber and mix it with 1L of n-hexane to form a solution. Then weigh 3g of single-layer graphene and 5wt% of graphene dispersant (commercial graphene dispersant produced by Jia Cai Technology: JCGRDS) and add them to the solution to form a dispersion. Disperse the dispersion in an ultrasonic bath for 40 minutes. Then add 5wt% of the silicone rubber curing agent (methyl hexahydrophthalic anhydride) and stir to disperse evenly.

[0068] (2) Construction of the roller device

[0069] The roller device used in this invention is as follows: Figure 6 As shown,

[0070] A layer of graphite is uniformly sprayed onto the surface of the water-soluble tape using graphite spray to obtain a surface-modified water-soluble tape. The surface-modified water-soluble tape is then adhered to the outer wall of the roller (2) with the graphite-coated surface facing outwards. The magnet (3) is fixed inside the roller (2), and the roller (2) is connected to a speed-regulating motor. A silicone rubber heating plate (1) is fixed above the roller (2). The mixed solution (4) is placed under the roller (2) with the height of the mixed solution tangent to the roller, so that the roller (2) and the liquid surface form a thin liquid bridge.

[0071] (3) Graphene film formation

[0072] Adjust the motor speed to 24° / s, and the graphene is lifted out of the solution surface by the roller. At the same time, under the action of gravity and surface tension, the graphene adheres to the water-soluble adhesive tape on the inner wall of the roller. After rotating for 1 hour, a mixture film with a thickness of about 100μm is adhered to the water-soluble adhesive tape.

[0073] (4) Composite material molding

[0074] The water-soluble tape was removed and placed in a 60°C oven for further curing. Then, the water-soluble tape was dissolved in deionized water to obtain a graphene thermally conductive composite material.

[0075] The prepared graphene thermally conductive composite material was tested by scanning electron microscopy, and the test results are as follows: Figure 2 , 3 As shown. Among them, Figure 2 The cross-sectional scanning electron microscope image of the prepared graphene thermally conductive composite material shows that the graphene exhibits a stretched and aligned arrangement structure inside the composite material. Figure 3 The surface scanning electron microscope image of the prepared graphene thermally conductive composite material shows that the parallel alignment of the graphene makes the surface of the composite material relatively smooth.

[0076] Example 2

[0077] Unlike Example 1, the mass of graphene in step (1) was changed to 4g, while the other process steps were the same as in Example 1.

[0078] The prepared graphene thermally conductive composite material was tested by scanning electron microscopy, and the test results are as follows: Figure 4 As shown, the graphene in the composite material no longer stretches out, but instead exhibits obvious bending.

[0079] Example 3

[0080] Unlike Example 1, the mass of graphene in step (1) was changed to 2g, while the other process steps were the same as in Example 1.

[0081] Example 4

[0082] Unlike Example 1, the mass of graphene in step (1) was changed to 1g, while the other process steps were the same as in Example 1.

[0083] Comparative Example 1

[0084] Unlike Example 1, the magnet in the drum is removed in step (2), while the other process steps are the same as in Example 1.

[0085] The prepared graphene thermally conductive composite material was tested by scanning electron microscopy, and the test results are as follows: Figure 5As can be seen, the alignment of graphene in the composite material is significantly reduced compared to Example 1.

[0086] In addition, the inventors discovered during the research process that the mechanical properties of the composite material prepared by removing the magnet from the drum, removing the heating plate, or not rotating the drum decreased significantly, failing to meet the sample preparation requirements for thermal conductivity testing, and thus making it impossible to test the thermal conductivity.

[0087] Experimental test:

[0088] The in-plane thermal conductivity of the graphene thermally conductive composite materials prepared in Examples 1-4 was tested using an LFA 427 laser thermal conductivity meter manufactured by Netzsch GmbH, Germany, according to ASTM 1461 standard and anisotropy module. The test results are shown in Table 1.

[0089] Table 1 Comparison of thermal conductivity of graphene thermally conductive composite materials

[0090]

[0091] As can be seen from Table 1, the graphene thermally conductive composite material prepared in Example 1 exhibits the best thermal conductivity. This is consistent with the alignment and spread of the graphene structure observed in the scanning electron microscopy test in Example 1, demonstrating that the highly spread and aligned structure of graphene results in a composite material with high thermal conductivity.

[0092] Compared to Example 1, Examples 3 and 4 used less graphene, resulting in less dense thermally conductive pathways formed by graphene in the composite material, thus reducing the thermal conductivity. Compared to Example 1, Example 2 used more graphene, causing the graphene to easily aggregate in the dispersion, disrupting the parallel alignment structure and hindering the high in-plane thermal conductivity of graphene, thus reducing the thermal conductivity. Comparative Example 1 lacked the directional effect of a magnetic field, and the graphene arrangement structure was also disrupted.

[0093] The above description is merely a preferred embodiment of the present invention and is not intended to limit the 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 thermally conductive composite material, characterized in that, It contains graphene and a polymer matrix, wherein the graphene is a single layer or multiple layers of graphene with a particle size of 5μm-100μm and a thickness of less than 1nm; The polymer matrix is ​​one or more of the following: high-temperature resistant silicone rubber, PDMS, polyvinyl alcohol, polyvinylpyrrolidone, or epoxy resin; The apparatus for preparing graphene thermally conductive composite materials includes a roller, a permanent magnet, a tape, a heating element, and a motor; the tape is provided on the outer wall of the roller, the permanent magnet is fixed inside the roller and the permanent magnet coincides with the axis of the roller; a heating element is provided above the roller, and the roller is connected to the motor; Graphene is arranged in a highly aligned manner parallel to the direction of the magnetic field in a polymer matrix through the combined action of the rotating motion of the drum and the magnetic field, forming heat conduction channels; The preparation method of graphene thermally conductive composite material includes the following steps: (a) Graphene and polymer are dissolved in a solvent, ultrasonically dispersed and mechanically stirred, and then a curing agent is added. The mass ratio of graphene to solvent is 0.001-0.1 to form a uniform mixture. (b) The mixture is placed in a rotating support device with tape. The mixture of graphene and polymer is placed directly in the rotating support device with tape. The height of the mixture is exactly tangent to the roller, so that the roller and the liquid surface of the mixture form a thin liquid bridge. The graphene is oriented along the direction of the magnetic field under the action of the magnetic field, and the graphene is uniformly lifted by the continuous rotation of the rotating support device. While the rotating support device rotates, the heating element dries the mixture, keeping the graphene oriented before curing. (c) Further heating and curing to dissolve the tape yields a graphene thermally conductive composite material with highly ordered thermally conductive channels. The thermal diffusivity of the graphene thermally conductive composite material is ≥ 94.14 mm. 2 ·s -1 Thermal conductivity ≥112.93 W·mK -1 .

2. An apparatus for preparing the graphene thermally conductive composite material according to claim 1, characterized in that, It includes a roller, a permanent magnet, a tape, a heating element, and a motor; the outer wall of the roller is provided with a tape, the permanent magnet is fixed inside the roller and the permanent magnet coincides with the axis of the roller; a heating element is provided above the roller, and the roller is connected to the motor.

3. The preparation apparatus as described in claim 2, characterized in that, The tape is a water-soluble tape. Alternatively, the heating element may be one or more of an infrared lamp, a ceramic heating plate, a silicone rubber heating plate, or an alumina heating plate.

4. The preparation apparatus as described in claim 3, characterized in that, The water-soluble adhesive includes an adhesive layer and a surface layer.

5. A method for preparing the graphene thermally conductive composite material according to claim 1, characterized in that, Includes the following steps: (a) Graphene and polymer are dissolved in a solvent, ultrasonically dispersed and mechanically stirred, and then a curing agent is added to form a uniform mixture; (b) The mixture is placed in a rotating support device with tape. The mixture of graphene and polymer is placed directly in the rotating support device with tape. The height of the mixture is exactly tangent to the roller, so that the roller and the liquid surface of the mixture form a thin liquid bridge. The graphene is oriented along the direction of the magnetic field under the action of the magnetic field, and the graphene is uniformly lifted by the continuous rotation of the rotating support device. While the rotating support device rotates, the heating element dries the mixture, keeping the graphene oriented before curing. (c) Further heating and curing dissolves the tape to obtain a graphene thermally conductive composite material with highly ordered thermally conductive channels.

6. The preparation method according to claim 5, characterized in that, In (a), the graphene is a single layer or multiple layers of graphene, and the particle size of the graphene is 5μm-100μm; Alternatively, the polymer material may be one or more of silicone rubber, PDMS, polyvinyl alcohol, polyvinylpyrrolidone, or epoxy resin; Alternatively, the solvent may be one or more of deionized water, ethanol, benzene, methanol, solvent oil, white oil, n-hexane, or petroleum ether.

7. The preparation method according to claim 6, characterized in that, The graphene is a single-layer graphene with a particle size of 8μm-12μm; the solvent is n-hexane.

8. The preparation method according to claim 5, characterized in that, The mass ratio of graphene to solvent is 0.004-0.005; Alternatively, the mass ratio of polymer to solvent is 0.002-0.2; Alternatively, the curing agent is 1-5 wt.% of the polymer mass.

9. The preparation method according to claim 8, characterized in that, The mass ratio of polymer to solvent is 0.009-0.

01.

10. The preparation method according to claim 8, characterized in that, In (b), the rotational speed of the rotating support device is 10-150° / s; the rotation time of the rotating support device is 0.5-1h; and the heating temperature of the heating element is 150-200℃.

11. The preparation method according to claim 10, characterized in that, The rotational speed is 24° / s.

12. The preparation method according to claim 5, characterized in that, In (c), the curing temperature is 60-80℃, and the conditions for dissolving the tape are immersion in deionized water at room temperature for 4-6 hours.

13. The application of the graphene thermally conductive composite material according to claim 1 in the thermal management of electronic devices, characterized in that, The graphene thermally conductive composite material is suitable for thermal interface materials, thermally conductive equipment substrates, or housings.

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