Preparation method and application of quasi-parallel arrangement graphene heat conduction network

Abstract

The invention belongs to the field of preparation of heat conduction materials or heat management materials, and particularly relates to a preparation method and application of a quasi-parallel arrangement graphene heat conduction network. The preparation method comprises the following steps: taking a graphene oxide aqueous dispersion and an additive as raw materials, preparing a graphene oxide film through a centrifugal casting method by mixing the graphene oxide aqueous dispersion or the graphene oxide aqueous dispersion and the additive, and reducing to obtain a quasi-parallel arrangement reduced graphene oxide network; the quasi-parallel arrangement graphene heat conduction network can be independently used or can be compounded with other materials to form a heat conduction assembly for use. The obtained heat-conducting network and the composite material thereof have excellent heat conductivity in the horizontal and vertical directions, and can be applied to multiple aspects such as a thermal interface material, a phase change heat storage material and a heat expansion device.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of thermal conductive materials or thermal management materials, and specifically relates to a preparation method of a quasi-parallel arranged graphene thermal conductive network and its application. Background Art

[0002] With the advent of the 5G era, the development of smartphones requires smaller and more transistors in their processors, further improving core computing and image processing capabilities. At the same time, the problem of waste heat generation and accumulation has become more serious, affecting the performance and lifespan of electronic devices. It is crucial to conduct waste heat to the outside of electronic products and dissipate or collect it. Efficient heat conduction requires the use of highly thermally conductive materials to establish an efficient thermal network. However, existing thermal networks often suffer from problems such as low thermal conductivity of thermally conductive fillers, lack of directional arrangement, and poor contact between fillers. The resulting thermal conductivity of the resulting thermally conductive components, such as thermal interface materials and phase change thermal storage materials, is often less than 15W / (m·K), which can no longer meet today's heat dissipation and heat storage needs. Graphene, with its extremely high in-plane thermal conductivity (3000-5000W / mK) and good cross-plane thermal conductivity (5-10W / mK), is a highly promising thermal conductive material. If graphene is vertically connected to two components that require heat exchange, its high heat transfer performance can be maximized and the heat transfer thermal resistance can be reduced, but at the same time, the large thermal resistance generated by the contact between graphene sheets in the network needs to be solved. Summary of the Invention

[0003] In response to the defects existing in existing thermal conductive networks, the purpose of the present invention is to provide a method for preparing a quasi-parallel arranged graphene thermal conductive network and its application, which solves the problem of low overall thermal conductivity of the network caused by poor contact of graphene thermal conductive fillers, as well as the problem of preparing high thermal conductivity and highly oriented graphene networks.

[0004] The technical solution of the present invention is:

[0005] A method for preparing a quasi-parallel arranged graphene thermal conductive network comprises the following steps: the raw materials are a graphene oxide aqueous dispersion and an additive, the graphene oxide aqueous dispersion or the graphene oxide aqueous dispersion and the additive are mixed, and a graphene oxide film is prepared by centrifugal casting, and then reduced to obtain a quasi-parallel arranged reduced graphene oxide network, and then high-temperature graphitization is performed to obtain a quasi-parallel arranged graphene thermal conductive network.

[0006] The preparation method of the quasi-parallel arranged graphene thermal conductive network, the preparation method of graphene oxide includes but is not limited to strong oxidant oxidation method or electrochemical oxidation method, the sheet diameter of graphene oxide is 200nm~100μm, and the concentration of graphene oxide aqueous dispersion is 0.01wt%~4wt%.

[0007] The method for preparing the quasi-parallel arranged graphene thermal conductive network, the additives include but are not limited to one or a combination of two or more dispersants, foaming agents, templates, and pore-forming agents, and the amount of additives added is 0.001wt% to 10wt%; wherein the dispersant includes but is not limited to sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, polyvinyl pyrrolidone or polyvinyl alcohol, the foaming agent includes but is not limited to sodium bicarbonate or low-boiling point alkanes, the template agent includes but is not limited to polystyrene beads, molecular sieves, silica microspheres or metal organic frameworks, and the pore-forming agent includes but is not limited to metal oxide particles.

[0008] The preparation method of the quasi-parallel arrangement graphene thermal conductive network is as follows: when the graphene oxide film is prepared by centrifugal casting, the diameter of the centrifugal casting drum is 5cm to 3m, the speed of the centrifugal casting is 200 to 2000rpm, and the membrane area of ​​the graphene oxide film is 1 to 100000cm 2 The thickness of each layer of graphene oxide film is 10 nm to 10 μm, and the total thickness of the graphene oxide film is 1 to 10000 μm.

[0009] The method for preparing the quasi-parallel arranged graphene thermal conductive network includes, but is not limited to, thermal reduction or reducing agent reduction of the graphene oxide film, wherein: during thermal reduction, the thermal reduction temperature is room temperature to 1000°C, and the heating rate is 0.1 to 10°C / min; during reducing agent reduction, the reducing agent includes but is not limited to hydrazine hydrate, vitamin C solution or HI solution, and the reducing agent concentration is 0.1 to 20wt%. The graphene oxide film is immersed in the reducing agent and kept at 30 to 80°C for 1 to 40 hours, and then the residue is washed with ethanol or acetone.

[0010] In the method for preparing the quasi-parallel arranged graphene thermal conductive network, the expansion value of the reduced graphene oxide network is 1 to 500, and the expansion degree is the ratio of the thickness after reduction to the thickness before reduction. The expansion degree is controlled by using a mold to limit the expansion space during the thermal reduction process. The material of the mold includes but is not limited to graphite, stainless steel, aluminum, copper or organic polymer.

[0011] The method for preparing the quasi-parallel arranged graphene thermal conductive network comprises reducing the graphene oxide network and subjecting it to high-temperature graphitization to obtain the graphene thermal conductive network. The high-temperature graphitization temperature is 2500-3200°C, the heating rate is 1-20°C / min, and the holding time is 0.1-100h. The heating method for the high-temperature graphitization includes but is not limited to radiation heating or Joule heat self-heating. During the high-temperature graphitization process, a mold is used to control the increase, decrease or maintenance of the expansion degree. The material of the mold is but is not limited to graphite.

[0012] The preparation method of the quasi-parallel arranged graphene thermal conductive network is described. The internal structure of the graphene thermal conductive network is that ultra-thin layered graphene films are arranged in approximately parallel, the thickness of each layer of ultra-thin graphene film is 5nm to 5μm, and the thickness of the graphene thermal conductive network is 20μm to 20cm.

[0013] The application of the quasi-parallel arranged graphene thermal conductive network is that the graphene thermal conductive network is used independently or composited with other materials to form a thermal conductive component. The base material of the thermal conductive component includes but is not limited to one or a combination of two or more of polymers, phase change materials, and metals. In the thermal conductive component, the mass fraction of the graphene thermal conductive network is between 1% and 100%. The composite method includes but is not limited to blending, vacuum impregnation or surface coating. The graphene thermal conductive network is directly composited or two or more networks are superimposed and then composited.

[0014] In the application of the quasi-parallel arranged graphene thermal conductive network, the polymer substrate is natural latex, silicone rubber or polymer fiber, and the phase change material substrate is paraffin, fatty alcohol or fatty acid.

[0015] The technical principle of the present invention is:

[0016] The graphene oxide film prepared by the centrifugal casting method in the present invention has a thickness of 10 nm to 10 μm per layer, and the total thickness of the film is increased by cyclic preparation. However, the interfacial bonding force formed during the preparation process is relatively weak, and it is easy to expand and peel off each assembled single layer during heat treatment to form a parallel layered network. This layered network only undergoes interlayer peeling, and the bonding between the graphene within the layer is not destroyed. Therefore, after graphitization, it will be restored to high-quality crystallization and have extremely high thermal conductivity. The quasi-parallel arrangement of the structure has extremely high orientation and a short heat transfer path, which can form a very efficient heat transfer network. The composite material prepared on this basis can obtain a good thermal conductivity gain.

[0017] Advantages and beneficial effects of the present invention:

[0018] The present invention expands a centrifugally cast graphene oxide film during thermal reduction and then undergoes high-temperature graphitization to repair the crystal structure, forming a highly thermally conductive network of quasi-parallel (laminated) graphene. The expanded graphene film is porous and fluffy internally, yet retains an ordered layered structure. The graphene crystals within each layer are of high quality, with excellent contact between the graphene sheets. Each layer is 5nm to 5μm thick. This composite material can be combined with other materials to produce a thermal conductivity of up to 200W / mK, suitable for applications such as thermal interface materials and phase-change thermal storage materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a cross-sectional scanning electron microscope image of a typical quasi-parallel graphene thermal conductive network.

[0020] Figure 2 This is a photograph of the quasi-parallel arranged graphene thermal conductive network prepared according to Example 1.

[0021] Figure 3 This is a photo of the quasi-parallel arranged graphene thermal conductive network and silicone rubber composite material prepared according to Example 2.

[0022] Figure 4 This is a photograph of the quasi-parallel arranged graphene thermal conductive network and paraffin wax composite material prepared according to Example 3. DETAILED DESCRIPTION

[0023] The accompanying drawings and embodiments of the present invention are used to further describe the specific implementation methods of the present invention in detail. The following three embodiments are used to illustrate the present invention but cannot be used to limit the scope of the present invention.

[0024] Example 1

[0025] In this example, a graphene oxide aqueous dispersion with an average flake diameter of 500 nm and a concentration of 1 wt% was centrifugally cast to form a membrane. During centrifugal casting, the drum diameter was 250 mm and the drum speed was 800 rpm. Each layer of the graphene oxide membrane had a thickness of 400 nm, and the total thickness of the graphene oxide membrane was 12 μm. After membrane formation, oxygen-containing functional groups were eliminated by thermal reduction. The temperature was increased from room temperature to 1000°C at a rate of 1°C / min and held at that temperature for 30 minutes. During this time, a graphite mold was used to control the expansion ratio to 10 (the expansion ratio was calculated by comparing the thickness after reduction to the thickness before reduction). This yielded a reduced graphene oxide network. Graphitization was then performed in a medium-frequency induction graphitization furnace at 2900°C for 30 minutes at a rate of 5°C / min. The expansion ratio was controlled to 10 (the expansion ratio was calculated by comparing the thickness after graphitization to the thickness before graphitization). Finally, a quasi-parallel arrangement graphene thermal conductive network with a total thickness of 40 μm and a thickness of 200 nm for each layer of ultra-thin graphene film was obtained. The cross-sectional structure is as follows: Figure 1 As shown, the macroscopic morphology is Figure 2 In this embodiment, the vertical thermal conductivity of the graphene thermal conductive network is 6W / mK, and the total thermal resistance when used as a thermal interface material is 0.081cm 2 ·K / W.

[0026] Example 2

[0027] In this embodiment, a graphene oxide aqueous dispersion with an average sheet diameter of 3 μm and a concentration of 1.5 wt% was centrifugally cast to form a membrane. During centrifugal casting, the drum diameter was 400 mm, the drum speed was 600 rpm, the thickness of each layer of graphene oxide membrane was 600 nm, and the total thickness of the graphene oxide membrane was 900 μm. After the membrane was formed, it was reduced with a 5 wt% vitamin C solution for 10 hours at a reduction temperature of 80°C. During this period, the stainless steel mold was controlled to have an expansion degree of 15, thereby obtaining a reduced graphene oxide network. The residue was washed with ethanol, and then graphitized in a medium-frequency induction graphitization furnace at 2900°C for 30 minutes, with a heating rate of 5°C / min, during which the expansion degree was controlled to remain unchanged. Finally, a quasi-parallel arranged graphene thermal conductive network with a total thickness of 4.5 mm and a thickness of 250 nm per layer of ultra-thin graphene film was obtained. The graphene thermal conductive network is compounded with the silicone rubber solution, vacuum impregnated for 2 hours, and cured at 120°C for 3 hours to obtain a composite thermal conductive block. Figure 3 As shown, it can be used as a thermal interface material. In this embodiment, the thermal conductivity of the thermal interface material is 196W / mK and the total thermal resistance is 0.28cm 2 ·K / W.

[0028] Example 3

[0029] In this embodiment, a graphene oxide aqueous dispersion with an average sheet diameter of 5 μm and a concentration of 1.2 wt% was added, and 0.2% by mass of sodium dodecylbenzene sulfonate and 0.1% by mass of ferroferric oxide particles with a particle size of 200 nm were uniformly mixed and centrifuged to form a film. During centrifugal casting, the drum diameter was 850 mm, the drum speed was 600 rpm, the thickness of each layer of graphene oxide film was 1 μm, and the total thickness of the graphene oxide film was 1.5 mm. After film formation, oxygen-containing functional groups were eliminated by thermal reduction, and the temperature was increased from room temperature to 1000°C at a heating rate of 1°C / min and kept warm for 30 min. During this period, the expansion degree was controlled to 20 by a graphite mold to obtain a reduced graphene oxide network. Afterwards, a medium-frequency induction graphitization furnace was used for graphitization at 2800°C for 30 min, with a heating rate of 5°C / min, during which the expansion degree was controlled to remain unchanged. Finally, a quasi-parallel arrangement graphene thermal conductive network with a total thickness of 10 mm and a thickness of 400 nm for each layer of ultra-thin graphene film was obtained. The graphene thermal conductive network was compounded with a paraffin solution with a melting point of 56-58°C, vacuum impregnated for 1 hour, and cooled to room temperature to obtain a composite thermal conductive block, such as Figure 4 In this embodiment, the thermal conductivity of the thermal storage material is 67 W / mK, the melting enthalpy is 180 J / g, and the solidification enthalpy is 179 J / g.

[0030] The implementation results show that the thermal conductive network and its composite material obtained by the present invention have excellent horizontal and vertical thermal conductivity, and can be used in many aspects such as thermal interface materials, phase change thermal storage materials, and thermal expansion devices.

[0031] The above three examples are further explanations of the present invention. Any changes and improvements that do not depart from the technical principles of the present invention should also be considered as within the scope of protection of the present invention.

Claims

1. A method for preparing a quasi-parallel arranged graphene thermal conductive network, characterized in that: The raw materials are graphene oxide aqueous dispersion and additives. The graphene oxide aqueous dispersion or the graphene oxide aqueous dispersion and additives are mixed and prepared into a graphene oxide film by centrifugal casting. The quasi-parallel arranged reduced graphene oxide network is obtained after reduction, and then high-temperature graphitization is performed to obtain a quasi-parallel arranged graphene thermal conductive network.

2. The method for preparing the quasi-parallel arranged graphene thermal conductive network according to claim 1, characterized in that: The preparation method of graphene oxide includes but is not limited to a strong oxidant oxidation method or an electrochemical oxidation method. The diameter of the graphene oxide sheet is 200 nm to 100 μm, and the concentration of the graphene oxide aqueous dispersion is 0.01 wt% to 4 wt%.

3. The method for preparing the quasi-parallel arranged graphene thermal conductive network according to claim 1, characterized in that: The additives include but are not limited to one or a combination of two or more dispersants, foaming agents, templates, and pore-forming agents, and the amount of the additives added is 0.001wt% to 10wt%; wherein the dispersant includes but is not limited to sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, polyvinyl pyrrolidone or polyvinyl alcohol, the foaming agent includes but is not limited to sodium bicarbonate or low-boiling-point alkanes, the template agent includes but is not limited to polystyrene beads, molecular sieves, silica microspheres or metal organic frameworks, and the pore-forming agent includes but is not limited to metal oxide particles.

4. The method for preparing a quasi-parallel arranged graphene thermal conductive network according to claim 1, characterized in that: When the graphene oxide film is prepared by centrifugal casting, the diameter of the centrifugal casting drum is 5 cm to 3 m, the rotation speed of the centrifugal casting is 200 to 2000 rpm, and the membrane area of ​​the graphene oxide film is 1 to 100,000 cm 2 The thickness of each layer of graphene oxide film is 10 nm to 10 μm, and the total thickness of the graphene oxide film is 1 to 10000 μm.

5. The method for preparing the quasi-parallel arranged graphene thermal conductive network according to claim 1, characterized in that: The reduction method of the graphene oxide film includes but is not limited to thermal reduction or reducing agent reduction, wherein: during thermal reduction, the thermal reduction temperature is room temperature to 1000°C, and the heating rate is 0.1 to 10°C / min; during reducing agent reduction, the reducing agent includes but is not limited to hydrazine hydrate, vitamin C solution or HI solution, and the reducing agent concentration is 0.1 to 20wt%. The graphene oxide film is immersed in the reducing agent and kept warm at 30 to 80°C for 1 to 40 hours, and then the residue is washed with ethanol or acetone.

6. The method for preparing a quasi-parallel arranged graphene thermal conductive network according to claim 1, characterized in that: The expansion value of the reduced graphene oxide network is 1 to 500, and the expansion degree is the ratio of the thickness after reduction to the thickness before reduction. The expansion degree is controlled by using a mold to limit the expansion space during the thermal reduction process. The material of the mold includes but is not limited to graphite, stainless steel, aluminum, copper or organic polymer.

7. The method for preparing a quasi-parallel arranged graphene thermal conductive network according to claim 1, characterized in that: The reduced graphene oxide network is subjected to high-temperature graphitization to obtain a graphene thermal conductive network. The temperature of the high-temperature graphitization is 2500-3200°C, the heating rate is 1-20°C / min, and the holding time is 0.1-100h. The heating method of the high-temperature graphitization includes but is not limited to radiation heating or Joule heat self-heating. During the high-temperature graphitization process, a mold is used to control the increase, decrease or maintenance of the expansion degree. The material of the mold includes but is not limited to graphite.

8. The method for preparing a quasi-parallel arranged graphene thermal conductive network according to claim 1, characterized in that: The internal structure of the graphene thermal conductive network is that ultra-thin layered graphene films are arranged in approximately parallel patterns. The thickness of each layer of ultra-thin graphene film is 5nm to 5μm, and the thickness of the graphene thermal conductive network is 20μm to 20cm.

9. An application of the quasi-parallel arranged graphene thermal conductive network according to any one of claims 1 to 8, characterized in that: The graphene thermal conductive network is used independently or composited with other materials to form a thermal conductive component. The base material of the thermal conductive component includes but is not limited to one or a combination of two or more of polymers, phase change materials, and metals. In the thermal conductive component, the mass fraction of the graphene thermal conductive network is between 1% and 100%. The composite method includes but is not limited to blending, vacuum impregnation or surface coating. The graphene thermal conductive network is directly composited or two or more networks are superimposed and then composited.

10. The use of the quasi-parallel arranged graphene thermal conductive network according to claim 9, characterized in that: The polymer base material is natural latex, silicone rubber or polymer fiber, and the phase change material base material is paraffin, fatty alcohol or fatty acid.

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