A high vertical thermal conductivity graphene frame, composite material and preparation method thereof

Abstract

The present invention provides a high vertical thermal conductivity graphene framework, composite material and preparation method thereof, by making the vertically oriented graphene aerogel of graphitization treatment and the graphene aerogel surface layer of the second component such as silica precursor solution, paraffin or phase change alloy collapse and internal bending at a specific temperature and a specific pressure, after solidification, a high vertical thermal conductivity graphene framework and corresponding composite material consisting of a vertically oriented graphene main layer and a parallel oriented graphene cortex are obtained, and the interlayer Π-Π interaction produced by the collapse of the cortex graphene during hot pressing and the inter-sheet intercalated structure produced by the bending of the main layer graphene can improve the thermal stability of the graphene framework and the composite compression and bending process. In addition, the calendering effect produced on the second component during the compression of the cortex can effectively thin the surface thickness of the low thermal conductivity component, reduce the composite material interface contact thermal resistance, enhance the interface heat conduction effect, and the resulting graphene framework and composite material can meet the thermal management requirements of high-power components of electronic equipment such as electronic base stations, communication radars, new energy vehicles and aerospace.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal management materials, and in particular relates to a high vertical thermal conductivity graphene frame, a composite material and a preparation method thereof. Background Art

[0002] As electronic components become increasingly miniaturized, integrated, and high-frequency, the power density of microprocessors has increased significantly, and heat dissipation has gradually become a key factor restricting the further development of the modern electronics industry. When the heat generated in electronic products cannot be directed to the outside world in a timely manner and gradually accumulates, it will cause the operating temperature of electronic components to rise and have an adverse effect on their performance, reliability, and service life. The thermal interface material or phase change heat storage material filled between the heat source and the heat spreader and between the heat spreader and the heat sink can quickly transfer the heat generated by the heat source to the heat sink or convert it into phase change latent heat for storage and then dissipate heat to avoid local high temperatures. Commercially, traditional thermal interface materials or phase change heat storage materials are mainly composed of a polymer or phase change material matrix and a thermally conductive filler, and have a low thermal conductivity (5 to 10 W m -1 K -1 ), it is difficult to meet the heat dissipation needs of rapidly developing high-power electronic devices. Although vertically oriented graphene frameworks are believed to be useful for preparing thermal interfaces and phase-change heat storage materials with high out-of-plane thermal conductivity, their thermally conductive skeletons only rely on graphene edge contact when in contact with electronic components, resulting in a small contact area, a large compression modulus, and a high interface thermal resistance. In addition, vertically oriented graphene frameworks and their composite materials also have the problems of weak interaction between graphene sheets, easy tearing under compression and bending, and poor thermal stability under complex deformation conditions. How to prepare high vertical thermal conductive graphene frameworks and their composite materials with high out-of-plane thermal conductivity, low interface thermal resistance, and excellent physical and mechanical properties still faces huge challenges. Summary of the Invention

[0003] The present invention aims to provide a high vertical thermal conductivity graphene framework, composite material, and preparation method thereof. A vertically oriented graphene oxide aerogel is prepared by stacking graphene oxide foam layers using a graphene oxide solution as a binder and then directionally cutting them. High-temperature graphitization restores in-plane defects in the graphene, significantly improving the intrinsic thermal conductivity of the graphene thermal conductive unit. The vertically oriented graphene aerogel and an aerogel composite containing a second functional component are subjected to surface collapse and internal bending at specific temperatures and pressures, followed by curing and shaping to produce a high vertical thermal conductivity graphene framework and corresponding composite material consisting of a vertically oriented graphene main layer and a parallel-oriented graphene cortex. The highly horizontally oriented graphene cortex produced during compression and its calendering effect on the low thermal conductivity component in the composite material reduces the surface thickness of the low thermal conductivity component, increases the contact area between the thermal conductive network in the graphene framework and composite material and electronic components, and reduces interfacial thermal resistance. The incompletely compressed high vertically oriented graphene main layer provides a fast transmission path for thermal phonons, thereby improving the thermal conductivity of the material. The tear resistance of the bonding interface of the graphene framework and its composite material is improved through the π-π interaction generated by the collapse of the cortical graphene and the inter-sheet mosaic structure generated by the incomplete compression of the main layer graphene.

[0004] The present invention adopts the following technical solution: a highly vertical thermal conductive graphene frame, which is composed of a combination of thermal conductive sheets, wherein the thermal conductive sheets are composed of one or more layers of graphene sheets overlapped with each other; the central area of ​​the thermal conductive sheet is oriented along a near-vertical direction, and the upper and lower ends are oriented along a near-planar direction; the central area of ​​the thermal conductive sheet constitutes the main layer of the frame, and the upper and lower ends of the thermal conductive sheet respectively constitute the cortex located on the upper and lower sides of the main layer; the near-vertical direction is: an angle of 0 to 15 degrees with the thickness direction; the near-planar direction is: an angle of 0 to 10 degrees with the frame surface.

[0005] As is common knowledge in the art, graphene sheets have good thermal conductivity. Generally speaking, graphene sheets with an oxygen content of less than 1% and an Id / Ig ratio of less than 0.02 in the Raman spectrum are suitable for this application. Furthermore, graphene sheets with an oxygen content of less than 1% and an Id / Ig ratio of less than 0.02 in the Raman spectrum can be obtained by conventional thermal reduction methods at the thermal reduction temperature required by this application. The Id / Ig ratio is the ratio of the D peak to the G peak in the graphene Raman spectrum.

[0006] Furthermore, the thickness ratio of the main layer to the skin layer is 40 to 200:1.

[0007] Furthermore, the heat conducting sheet has folds, and two adjacent heat conducting sheets form a nested structure through the folds.

[0008] The present invention also provides a high vertical thermal conductivity graphene frame composite material, which consists of a high vertical thermal conductivity graphene frame and functional components filled in the frame.

[0009] Furthermore, the functional component is one of silica gel, paraffin and phase change alloy.

[0010] A method for preparing a high vertical thermal conductivity graphene framework, characterized by comprising the following steps:

[0011] (1) The concentration is 5-20 mg mL -1 The graphene oxide solution is coated with a knife to form a film, and after drying, it is placed in a hydrazine hydrate solution with a volume fraction of 5-85% for foaming for 15-300 minutes. The hydrazine hydrate solution is replaced with ethanol and then placed in an oven at 40-60°C to dry to obtain a graphene oxide foam film. The foaming temperature is 20-90°C.

[0012] (2) With a concentration of 1 to 5 mg mL -1 The graphene oxide solution is used as a binder, and the graphene oxide foam film obtained in step (1) is stacked layer by layer, and a pressure of 10 to 100 psi is applied during the stacking process, and the mixture is heated to 60 to 80° C. to obtain a graphene oxide foam block;

[0013] (3) cutting the graphene oxide foam block obtained in step (2) at an angle of 75 to 90° between the cutting direction and the graphene sheet, at a cutting speed of 0.1 to 5 mm / min, and at a cutting spacing of 100 μm to 10 mm to obtain oriented graphene oxide slices;

[0014] (4) placing the oriented graphene oxide slice obtained in step (3) in an argon atmosphere for high-temperature heat treatment. The heat treatment temperature is 2200-3200° C., and the heat treatment time is 1-3 hours to obtain a highly graphitized oriented graphene aerogel slice;

[0015] (5) Compressing and shaping the oriented graphene oxide slices obtained in step (4) along the thickness direction, with a compression rate of 5 to 50% and a shaping time of 30 minutes to 6 hours to obtain a high vertical thermal conductivity graphene frame.

[0016] The obtained high vertical thermal conductivity graphene framework has an applicable temperature range of -200 to 3200°C, a volatile component of <0.01%, a compression rate of >50% under a pressure of 10-50 psi, and a vertical thermal conductivity range of 46.7 to 79.1 W m -1 K -1 When the thickness is 0.1 to 5 mm and the applied pressure is 10 psi, the thermal impedance range is 0.003 to 0.21 K cm 2 W -1 .

[0017] A method for preparing a high vertical thermal conductivity graphene frame composite material, characterized by comprising the following steps:

[0018] (1) The concentration is 5-20 mg mL -1 The graphene oxide solution is coated with a knife to form a film, and after drying, it is placed in a hydrazine hydrate solution with a volume fraction of 5-85% for foaming for 15-300 minutes. The hydrazine hydrate solution is replaced with ethanol and then placed in an oven at 40-60°C to dry to obtain a graphene oxide foam film. The foaming temperature is 20-90°C.

[0019] (2) With a concentration of 1 to 5 mg mL -1 The graphene oxide solution is used as a binder, and the graphene oxide foam film obtained in step (1) is stacked layer by layer, and a pressure of 10 to 100 psi is applied during the stacking process, and the mixture is heated to 60 to 80° C. to obtain a graphene oxide foam block;

[0020] (3) cutting the graphene oxide foam block obtained in step (2) at an angle of 75 to 90° between the cutting direction and the graphene sheet, at a cutting speed of 0.1 to 5 mm / min, and at a cutting spacing of 100 μm to 10 mm to obtain oriented graphene oxide slices;

[0021] (4) placing the oriented graphene oxide slice obtained in step (3) in an argon atmosphere for high-temperature heat treatment. The heat treatment temperature is 2200-3200° C., and the heat treatment time is 1-3 hours to obtain a highly graphitized oriented graphene aerogel slice;

[0022] (5) Infusing a silica gel precursor solution, molten paraffin or phase change alloy into the high vertical thermal conductivity graphene framework obtained in step (4), and hot pressing it along the thickness direction, with a compression rate of 5 to 50%, a hot pressing time of 30 minutes to 6 hours, and a hot pressing temperature of 80 to 200° C., and obtaining a high vertical thermal conductivity graphene framework composite after curing and shaping.

[0023] Furthermore, the solidification and setting in step (5) includes chemical reaction cross-linking of polymer precursor solutions such as silica gel, and phase changes occurring when the molten phase change heat storage material is cooled.

[0024] The obtained high vertical thermal conductivity graphene frame composite material has a vertical surface thermal conductivity range of 83.3 to 151.2 W m -1 K -1 , and has one of the elastic or phase change heat storage properties.

[0025] The beneficial effects of the present invention are:

[0026] (1) Compared to conventional graphene materials such as graphene films and single-oriented graphene aerogels, the skin-core structured oriented graphene framework of the present invention forms graphene skin layers and main layers with different orientations in situ within the material through limited-height compression and heat setting. The collapsed graphene skin layer is used to increase the contact area between the aerogel and the electronic components, enhance the gap filling effect, and reduce the interfacial thermal resistance. The incompletely compressed, highly vertically oriented graphene main layer is used to construct a fast transmission channel for thermal phonons, thereby improving the thermal conductivity of the material itself. This achieves the effective combination of graphene with different orientations and different functions in the same material.

[0027] (2) The interlayer π-π interaction generated by the collapse of the cortical graphene during hot pressing and the inter-sheet intercalation structure generated by the incomplete compression of the main graphene layer improve the bending and tearing strength of the graphene framework and its composite material, helping to maintain the structural integrity of the thermal conductivity path under deformation and increasing the thermal stability under complex deformation conditions. In addition, the high elasticity of the second component can ensure that the thermal conductivity performance does not decay after cyclic compression and rebound, making it suitable for use as an elastic thermal gasket.

[0028] (3) By combining with silicone precursor solution, molten paraffin or phase change alloy and then hot pressing, the calendering effect on the second component during the compression process can reduce the thickness of the low thermal conductivity component on the surface of the composite material, shorten the heat transfer distance of the skin, enhance the interface thermal conductivity, and form an insulating layer on the surface of the entire material, which is conducive to its application in thermal conductive elements of electronic components.

[0029] (3) The high thermal conductivity graphene aerogel composite material of the present invention organically combines the thermal conductivity of graphene with the second functional component. When compounded with silica gel, it can be used to prepare a highly elastic and highly thermally conductive interface material. When compounded with paraffin wax or phase change alloys, it can be used to prepare a highly thermally conductive phase change energy storage material, thereby meeting the application requirements of elastic components and phase change energy storage in the field of high thermal conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a scanning electron microscope photograph of the high vertical thermal conductivity graphene frame of Example 1.

[0031] Figure 2 This is a scanning electron microscope photograph of the high vertical thermal conductivity graphene frame / silicone composite thermal interface material of Example 6.

[0032] Figure 3 This is the stress-strain curve of the high vertical thermal conductivity graphene frame / silicone composite thermal interface material of Example 6 during 1000 cycles of compression-rebound process. DETAILED DESCRIPTION

[0033] The present invention is described in detail below through examples. These examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art may make some non-essential changes and adjustments based on the contents of the above invention, which all fall within the scope of protection of the present invention.

[0034] Example 1:

[0035] (1) The concentration is 5 mg mL -1 The graphene oxide solution was coated to form a film, and after drying, it was placed in a 5% volume fraction hydrazine hydrate solution for foaming for 15 minutes. The hydrazine hydrate solution was replaced with ethanol and then placed in a 40°C oven to dry to obtain a graphene oxide foam film. The foaming temperature was 20°C.

[0036] (2) At a concentration of 1 mg mL -1 The graphene oxide solution is used as a binder, and the graphene oxide foam film obtained in step (1) is stacked layer by layer. During the stacking process, a pressure of 10 psi is applied and the mixture is heated to 60° C. to obtain a graphene oxide foam block;

[0037] (3) cutting the graphene oxide foam block obtained in step (2) at an angle of 90° between the cutting direction and the graphene sheet, at a cutting speed of 0.1 mm / min, and at a cutting spacing of 500 μm to obtain oriented graphene oxide slices;

[0038] (4) placing the oriented graphene oxide slice obtained in step (3) in an argon atmosphere for high-temperature heat treatment. The heat treatment temperature is 2800° C. and the heat treatment time is 1 hour to obtain a highly graphitized oriented graphene aerogel slice;

[0039] (5) The oriented graphene slices obtained in step (4) are compressed and shaped with a compression rate of 40% and a shaping time of 30 minutes to obtain a high vertical thermal conductivity graphene frame.

[0040] The obtained high vertical thermal conductivity graphene framework has a thickness of 300 μm and a density of 80 mg / cm 3 Its microstructure is as follows Figure 1 As shown in the figure, it can be found that the graphene in the main layer is generally oriented vertically, but it has a wrinkled structure at the microscopic level, with a mosaic structure of sheets between the wrinkles. From the surface of the cortex, the graphene sheets are basically distributed horizontally. This is because the graphene sheets at both ends are crushed during compression to form a horizontal orientation. The thickness ratio of the main layer to the cortex is 50:1. The out-of-plane thermal conductivity measured using the transient laser flash method is 54.3Wm -1 K -1 The steady-state heat flow meter method was used to measure the compressibility at 10 psi to be 80% and the thermal impedance to be 0.011 K cm 2 W-1 .

[0041] Example 2:

[0042] Steps (1) to (3) are the same as in Example 1, and steps (4) and (5) are:

[0043] (4) placing the oriented graphene oxide slice obtained in step (3) in an argon atmosphere for high-temperature heat treatment. The heat treatment temperature is 3200° C. and the heat treatment time is 3 hours to obtain a highly graphitized oriented graphene aerogel slice;

[0044] (5) The oriented graphene slices obtained in step (4) are compressed and shaped with a compression rate of 50% and a shaping time of 6 hours to obtain a high vertical thermal conductivity graphene frame.

[0045] The obtained high vertical thermal conductivity graphene framework has a thickness of 250 μm and a density of 97 mg / cm 3 The ratio of the main layer to the skin layer thickness is 40:1. The compression rate is 77% under 10 psi pressure, and the out-of-plane thermal conductivity is 72.5 Wm-2 measured using the transient laser flash method. -1 K -1 The thermal impedance was measured at 10 psi using a steady-state heat flow meter method and was 0.008 K cm 2 W -1 .

[0046] Example 3:

[0047] Steps (1) to (3) are the same as in Example 1, and steps (4) and (5) are:

[0048] (4) placing the oriented graphene oxide slice obtained in step (3) in an argon atmosphere for high-temperature heat treatment. The heat treatment temperature is 2200° C. and the heat treatment time is 1 hour to obtain a graphitized oriented graphene aerogel slice;

[0049] (5) The oriented graphene slices obtained in step (4) are compressed and shaped with a compression rate of 40% and a shaping time of 30 minutes to obtain a high vertical thermal conductivity graphene frame.

[0050] The obtained high vertical thermal conductivity graphene framework has a thickness of 300 μm and a density of 92 mg / cm 3 The ratio of the main layer to the skin layer thickness is 50:1. The compression rate is 72% under 10 psi pressure, and the out-of-plane thermal conductivity is 46.7 Wm-2 measured using the transient laser flash method. -1 K -1 The thermal impedance was measured at 10 psi using a steady-state heat flow meter method and was 0.018 K cm 2 W -1 .

[0051] Example 4:

[0052] (1) The concentration is 20 mg mL -1 The graphene oxide solution was coated with a knife to form a film, and after drying, it was placed in a hydrazine hydrate solution with a volume fraction of 85% to foam for 300 minutes. The hydrazine hydrate solution was replaced with ethanol and then dried in a 60°C oven to obtain a graphene oxide foam film. The foaming temperature was 90°C.

[0053] (2) At a concentration of 5 mg mL -1 The graphene oxide solution is used as a binder, and the graphene oxide foam film obtained in step (1) is stacked layer by layer. During the stacking process, a pressure of 100 psi is applied and the mixture is heated to 80° C. to obtain a graphene oxide foam block;

[0054] (3) cutting the graphene oxide foam block obtained in step (2) at an angle of 75° between the cutting direction and the graphene sheet, at a cutting speed of 5 mm / min, and at a cutting spacing of 10 mm to obtain oriented graphene oxide slices;

[0055] (4) placing the oriented graphene oxide slice obtained in step (3) in an argon atmosphere for high-temperature heat treatment. The heat treatment temperature is 2800° C. and the heat treatment time is 1 hour to obtain a highly graphitized oriented graphene aerogel slice;

[0056] (5) The oriented graphene oxide slices obtained in step (4) are compressed and shaped with a compression rate of 50% and a shaping time of 30 minutes to obtain a high vertical thermal conductivity graphene frame.

[0057] The obtained high vertical thermal conductivity graphene frame has a thickness of 5 mm and a density of 137 mg / cm 3 The ratio of the main layer to the skin layer thickness is 200:1. The compression rate is 67% under 10 psi pressure, and the out-of-plane thermal conductivity is 79.1 Wm-2 measured using the transient laser flash method. -1 K -1 The thermal impedance was measured at 10 psi using a steady-state heat flow meter method and was 0.21 K cm 2 W -1 .

[0058] Example 5:

[0059] (1) The concentration is 15 mg mL -1 The graphene oxide solution was scraped to form a film, and after drying, it was placed in a 25% volume fraction hydrazine hydrate solution for foaming for 30 minutes. The hydrazine hydrate solution was replaced with ethanol and then placed in a 50°C oven to dry to obtain a graphene oxide foam film. The foaming temperature was 50°C.

[0060] (2) At a concentration of 2 mg mL -1 The graphene oxide solution is used as a binder, and the graphene oxide foam film obtained in step (1) is stacked layer by layer. A pressure of 50 psi is applied during the stacking process, and the mixture is heated to 70° C. to obtain a graphene oxide foam block;

[0061] (3) cutting the graphene oxide foam block obtained in step (2) at an angle of 85° between the cutting direction and the graphene sheet, at a cutting speed of 2 mm / min, and at a cutting spacing of 100 μm to obtain oriented graphene oxide slices;

[0062] (4) placing the oriented graphene oxide slice obtained in step (3) in an argon atmosphere for high-temperature heat treatment. The heat treatment temperature is 2800° C. and the heat treatment time is 1.5 h to obtain a highly graphitized oriented graphene aerogel slice;

[0063] (5) The oriented graphene oxide slices obtained in step (4) are compressed and shaped with a compression rate of 5% and a shaping time of 45 minutes to obtain a high vertical thermal conductivity graphene frame.

[0064] The obtained high vertical thermal conductivity graphene framework has a thickness of 95 μm and a density of 71 mg / cm 3 The ratio of the main layer to the skin layer thickness is 45:1. The compression rate is 83% under 10 psi pressure, and the out-of-plane thermal conductivity is 51.1 Wm-2 measured using the transient laser flash method. -1 K -1 The thermal impedance was measured at 10 psi using a steady-state heat flow meter method and was 0.003 K cm 2 W -1 .

[0065] Example 6:

[0066] (1) The concentration is 5 mg mL -1 The graphene oxide solution was coated to form a film, and after drying, it was placed in a 5% volume fraction hydrazine hydrate solution for foaming for 15 minutes. The hydrazine hydrate solution was replaced with ethanol and then placed in a 40°C oven to dry to obtain a graphene oxide foam film. The foaming temperature was 20°C.

[0067] (2) At a concentration of 1 mg mL -1 The graphene oxide solution is used as a binder, and the graphene oxide foam film obtained in step (1) is stacked layer by layer. During the stacking process, a pressure of 10 psi is applied and the mixture is heated to 60° C. to obtain a graphene oxide foam block;

[0068] (3) cutting the graphene oxide foam block obtained in step (2) at an angle of 90° between the cutting direction and the graphene sheet, at a cutting speed of 0.1 mm / min, and at a cutting spacing of 500 μm to obtain oriented graphene oxide slices;

[0069] (4) placing the oriented graphene oxide slice obtained in step (3) in an argon atmosphere for high-temperature heat treatment. The heat treatment temperature is 2800° C. and the heat treatment time is 1 hour to obtain a highly graphitized oriented graphene aerogel slice;

[0070] (5) The silica gel precursor solution is poured into the high vertical thermal conductivity graphene frame obtained in step (4), and hot pressing is performed on it with a compression rate of 40%, a hot pressing time of 1 hour, and a hot pressing temperature of 100° C. After cross-linking and shaping, a high vertical thermal conductivity graphene frame / silicone composite thermal interface material is obtained.

[0071] The obtained high vertical thermal conductivity graphene frame / silicone composite thermal interface material has a thickness of 300 μm and a density of 810 mg / cm 3 Its microstructure is as follows Figure 2 As shown in the figure, similar to the pure graphene framework, the graphene in the main layer is oriented vertically as a whole, and the folds form a mosaic structure of sheets and sheets. The cured silicone fills the gaps between the graphene framework, while the graphene in the skin layer is basically distributed horizontally. The thickness ratio of the main layer to the skin layer is 50:1. The compression-rebound stress-strain curve of the above composite material is shown in the figure. Figure 3 As shown in Figure 1, the compression rate is 51% under a pressure of 10 psi, and the rebound rate is 93% after 1000 compression-rebound cycles. The out-of-plane thermal conductivity of the uncompressed composite thermal interface material is 98.3 W m-2 measured using the transient laser flash method. -1 K -1 After 1000 compression-rebound cycles, the external thermal conductivity can still maintain 90%. The thermal impedance of the uncompressed composite thermal interface material under 10 psi is measured using a steady-state heat flow meter method to be 0.015 K cm 2 W -1 .

[0072] Example 7:

[0073] (1) The concentration is 20 mg mL -1 The graphene oxide solution was coated with a knife to form a film, and after drying, it was placed in a hydrazine hydrate solution with a volume fraction of 85% to foam for 300 minutes. The hydrazine hydrate solution was replaced with ethanol and then dried in a 60°C oven to obtain a graphene oxide foam film. The foaming temperature was 90°C.

[0074] (2) At a concentration of 5 mg mL -1The graphene oxide solution is used as a binder, and the graphene oxide foam film obtained in step (1) is stacked layer by layer. During the stacking process, a pressure of 100 psi is applied and the mixture is heated to 80° C. to obtain a graphene oxide foam block;

[0075] (3) cutting the graphene oxide foam block obtained in step (2) at an angle of 75° between the cutting direction and the graphene sheet, at a cutting speed of 5 mm / min, and at a cutting spacing of 100 μm to obtain oriented graphene oxide slices;

[0076] (4) placing the oriented graphene oxide slice obtained in step (3) in an argon atmosphere for high-temperature heat treatment. The heat treatment temperature is 2200° C. and the heat treatment time is 1 hour to obtain a highly graphitized oriented graphene aerogel slice;

[0077] (5) pouring molten bismuth into the high vertical thermal conductivity graphene framework obtained in step (4), hot pressing it and then cooling it to shape, with a compression rate of 50%, a hot pressing time of 30 minutes, and a hot pressing temperature of 80° C. After cooling and shaping, a high vertical thermal conductivity graphene framework / paraffin phase change energy storage material is obtained.

[0078] The obtained high vertical thermal conductivity graphene framework / paraffin phase change energy storage material has a thickness of 5 mm and a density of 760 mg / cm 3 The ratio of the main layer to the skin layer thickness is 200:1, and the out-of-plane thermal conductivity measured by the transient laser flash method is 83.3 Wm -1 K -1 , the phase change temperature is 42-45°C, and the phase change enthalpy is 170 J / g.

[0079] Example 8:

[0080] (1) The concentration is 20 mg mL -1 The graphene oxide solution was coated with a knife to form a film, and after drying, it was placed in a hydrazine hydrate solution with a volume fraction of 85% to foam for 300 minutes. The hydrazine hydrate solution was replaced with ethanol and then dried in a 60°C oven to obtain a graphene oxide foam film. The foaming temperature was 90°C.

[0081] (2) At a concentration of 5 mg mL -1 The graphene oxide solution is used as a binder, and the graphene oxide foam film obtained in step (1) is stacked layer by layer. During the stacking process, a pressure of 100 psi is applied and the mixture is heated to 80° C. to obtain a graphene oxide foam block;

[0082] (3) cutting the graphene oxide foam block obtained in step (2) at an angle of 75° between the cutting direction and the graphene sheet, at a cutting speed of 5 mm / min, and at a cutting spacing of 10 mm to obtain oriented graphene oxide slices;

[0083] (4) placing the oriented graphene oxide slice obtained in step (3) in an argon atmosphere for high-temperature heat treatment. The heat treatment temperature is 3200° C. and the heat treatment time is 3 hours to obtain a highly graphitized oriented graphene aerogel slice;

[0084] (5) The molten bismuth indium tin alloy is poured into the high vertical thermal conductivity graphene framework obtained in step (4), and the molten bismuth indium tin alloy is hot-pressed and then cooled to shape. The compression rate is 5%, the hot pressing time is 6 hours, and the hot pressing temperature is 200° C. After cooling and shaping, a high vertical thermal conductivity graphene framework / bismuth indium tin phase change energy storage material is obtained.

[0085] The obtained high vertical thermal conductivity graphene framework / paraffin phase change energy storage material has a thickness of 95 μm and a density of 8.1 g / cm 3 The ratio of the main layer to the skin layer thickness is 40:1, and the out-of-plane thermal conductivity measured by the transient laser flash method is 151.2 Wm -1 K -1 , the phase change temperature is 105-115℃, and the phase change enthalpy is 41.7J / g.

Claims

1. A high vertical thermal conductivity graphene frame, characterized in that: The thermal conductive sheet is composed of one or more overlapping graphene sheets; the middle area of ​​the thermal conductive sheet is oriented in a near vertical direction, and the upper and lower ends are oriented in a near planar direction; the middle area of ​​the thermal conductive sheet constitutes the main layer of the frame, and the upper and lower ends of the thermal conductive sheet respectively constitute the skin layers located on the upper and lower sides of the main layer; the near vertical direction is: an angle of 0-15 with the thickness direction o ; Near plane direction: Angle 0~10 with the frame surface o .

2. The graphene framework according to claim 1, characterized in that The thickness ratio of the main layer to the skin layer is 40-200:

1.

3. The graphene framework according to claim 1, wherein The heat conducting sheet has folds, and two adjacent heat conducting sheets form a nested structure through the folds.

4. A high vertical thermal conductivity graphene frame composite material, characterized in that: The invention comprises the graphene framework according to any one of claims 1 to 3, and a functional component filled in a main layer of the graphene framework.

5. The high vertical thermal conductivity graphene frame composite material according to claim 4, characterized in that: The functional component is one of silica gel, paraffin wax and phase change alloy.

6. A method for preparing a high vertical thermal conductivity graphene framework, characterized in that: The following steps are involved: (1) The concentration is 5~20 mg mL -1 The graphene oxide solution was scraped to form a film, and after drying, it was placed in a hydrazine hydrate solution with a volume fraction of 5-85% to foam for 15-300 min, and the hydrazine hydrate solution was replaced with ethanol and placed in a 40-60 o C oven to obtain graphene oxide foam film; wherein the foaming temperature is 20~90 o C; (2) At a concentration of 1-5 mg mL -1 The graphene oxide solution is used as a binder, and the graphene oxide foam film obtained in step (1) is stacked layer by layer. During the stacking process, a pressure of 10 to 100 psi is applied and the temperature is heated to 60 to 80 o C, obtaining graphene oxide foam blocks; (3) Cut the graphene oxide foam block obtained in step (2) with the cutting direction and the angle between the graphene sheet and the graphene sheet being 75 to 90 degrees. o , the cutting speed is 0.1~5 mm / min, the cutting spacing is 100 μm~10 mm, and the oriented graphene oxide slices with a thickness of 100 μm~10 mm are obtained; (4) placing the oriented graphene oxide slice obtained in step (3) in an argon atmosphere for high-temperature heat treatment; wherein the heat treatment temperature is 2200~3200 o C, heat treatment time is 1~3 h, and highly graphitized oriented graphene aerogel slices are obtained; (5) The oriented graphene oxide slices obtained in step (4) are compressed and shaped along the thickness direction, with a compression rate of 5-50% and a shaping time of 30 min-6 h to obtain a high vertical thermal conductivity graphene frame.

7. A method for preparing a high vertical thermal conductivity graphene frame composite material, characterized in that: The following steps are involved: (1) The concentration is 5~20 mg mL -1 The graphene oxide solution was scraped to form a film, and after drying, it was placed in a hydrazine hydrate solution with a volume fraction of 5-85% to foam for 15-300 min, and the hydrazine hydrate solution was replaced with ethanol and placed in a 40-60 o C oven to obtain graphene oxide foam film; wherein the foaming temperature is 20~90 o C; (2) At a concentration of 1-5 mg mL -1 The graphene oxide solution is used as a binder, and the graphene oxide foam film obtained in step (1) is stacked layer by layer. During the stacking process, a pressure of 10 to 100 psi is applied and the temperature is heated to 60 to 80 o C, obtaining graphene oxide foam blocks; (3) Cut the graphene oxide foam block obtained in step (2) with the cutting direction and the angle between the graphene sheet and the graphene sheet being 75 to 90 degrees. o , the cutting speed is 0.1~5 mm / min, the cutting spacing is 100 μm~10 mm, and oriented graphene oxide slices are obtained; (4) placing the oriented graphene oxide slice obtained in step (3) in an argon atmosphere for high-temperature heat treatment; wherein the heat treatment temperature is 2200~3200 o C, heat treatment time is 1~3 h, and highly graphitized oriented graphene aerogel slices are obtained; (5) Pour the silica precursor solution, molten paraffin or phase change alloy into the high vertical thermal conductivity graphene frame obtained in step (4), and hot press it along the thickness direction, with a compression rate of 5-50%, a hot pressing time of 30 min-6 h, and a hot pressing temperature of 80-200 o C, after curing and shaping, a high vertical thermal conductivity graphene frame composite material is obtained.

8. The method according to claim 7, characterized in that The solidification in step (5) is a phase change caused by the chemical reaction cross-linking of the polymer precursor solution, or a phase change caused by the cooling of the molten phase change heat storage material.

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