Carbon material and preparation method thereof, display screen and electronic equipment

Abstract

The embodiment of the invention provides a carbon material and a preparation method thereof, a display screen and electronic equipment, the carbon material comprises a plurality of stacked carbon atom layers, the in-plane thermal diffusion coefficient of the carbon material is larger than or equal to 800 mm < 2 > / s, the Young modulus of the carbon material is 1000-6000 Mpa, the surface roughness Ra of the carbon material is smaller than or equal to 800 nm, and the elongation at break of the carbon material is larger than or equal to 2%. The carbon material has ultrahigh thermal diffusion coefficient, high modulus, low surface roughness and relatively high elongation at break, and can be used in appearance devices such as a flexible display module, so that the devices have good bendability and appearance delicacy while having high thermal conductivity.

Description

Technical Field

[0001] This application relates to the field of thermally conductive materials technology, and in particular to a carbon material and its preparation method, a display screen, and electronic devices. Background Technology

[0002] Currently, the power consumption and heat generation of 5G and AI electronic products are increasing dramatically. Furthermore, the pursuit of ultra-thin and lightweight designs in these products places higher demands on the performance of heat dissipation devices to achieve high power consumption within ultra-thin thicknesses. Using thermally conductive carbon materials as heat dissipation devices in electronic products to transfer heat from areas of high heat concentration to cooler areas, thereby reducing the temperature of hot zones and achieving efficient and flexible heat dissipation, is a common industry solution. However, current thermally conductive carbon materials used in flexible displays and other external components struggle to achieve both high heat dissipation performance and good bendability and aesthetic refinement. This can easily lead to problems such as particles, film marks, orange peel texture, and peeling upon bending in flexible displays. Figure 1 As shown, Figure 1 These are photos of displays that use existing thermally conductive carbon materials. Figure 1 It is evident that the display screen suffers from issues such as graininess, film marks, and orange peel texture, which affect its overall quality. Summary of the Invention

[0003] In view of this, embodiments of this application provide a carbon material and its preparation method, a display screen and an electronic device. The carbon material has ultra-high thermal diffusivity, high modulus, low surface roughness and high elongation at break, and can be used in appearance devices such as flexible display modules, so that the device has both high thermal conductivity and good bendability and exquisite appearance.

[0004] In a first aspect, embodiments of this application provide a carbon material comprising multiple stacked layers of carbon atoms, wherein the in-plane thermal diffusivity of the carbon material is ≥800 mm. 2 / s, the Young's modulus of the carbon material is 1000Mpa-6000Mpa, the surface roughness Ra of the carbon material is ≤800nm, and the elongation at break of the carbon material is ≥2%.

[0005] The carbon material 100 provided in this application embodiment has an ultra-high thermal diffusivity, high modulus, low surface roughness and high elongation at break, and is thin. It can be used in appearance devices such as flexible display modules, so that the device has both thinness and high thermal conductivity, as well as good bendability and appearance refinement. This can solve the problems of heat dissipation and appearance refinement of display modules at the same time, and also meet the requirements of foldability.

[0006] In this embodiment of the application, the grain size of the carbon material is L in crystallography. c The size is greater than or equal to 50 nm. The grain size L of the carbon material in this application... cThe larger size allows for the production of carbon materials with native film properties over a wider thickness range. This enables the direct use of single-piece carbon materials with the required thickness in scenarios with high heat dissipation and heat dissipation requirements, avoiding the need for multi-layer adhesive bonding to achieve the required thickness. This better meets the heat dissipation needs of high-power devices.

[0007] In this embodiment of the application, the degree of graphitization of the carbon material is greater than or equal to 0.97. The degree of graphitization is an indicator of the extent to which carbon atoms form a close-packed hexagonal graphite crystal structure; the closer the lattice size is to the lattice constant of ideal graphite, the higher the degree of graphitization.

[0008] In this embodiment, the interlayer spacing of the multilayer stacked carbon atoms is 0.3 nm to 0.5 nm. Smaller interlayer spacing is beneficial for improving the in-plane thermal diffusion performance of the carbon material.

[0009] In this embodiment, the carbon material has native film characteristics within a thickness range of ≤2mm. That is, carbon materials within a thickness range of 2mm do not require adhesive bonding, thereby improving the thermal diffusion performance and structural stability of the carbon material.

[0010] In this embodiment, the carbon material is bendable. The bendability of the carbon material better meets the needs of applications requiring bending.

[0011] In this embodiment of the application, the carbon material includes carbon film, carbon sheet, or carbon plate.

[0012] The second aspect of this application provides a method for preparing a carbon material, comprising:

[0013] A graphene oxide dispersion is mixed with an additive to obtain a slurry. The slurry is coated onto a substrate, dried to form a graphene oxide film, and then peeled off from the substrate. The additive includes one or more of transition metal compounds, boron-containing materials, nitrogen-containing materials, and phosphorus-containing materials.

[0014] Under air-isolated conditions, the graphene oxide film is heat-treated to cause the graphene oxide to undergo a pyrolysis reaction to generate graphene, thereby obtaining the heat-treated film material; the heat treatment includes heating to 250℃-400℃ at a first heating rate and holding at that temperature for a first time, then heating to 1000℃-1200℃ and holding at that temperature for a second time, and then heating to 2900℃-3300℃ at a second heating rate and holding at that temperature for a third time.

[0015] The heat-treated film is calendered to obtain carbon material of the required thickness.

[0016] The carbon material preparation method of this application embodiment is feasible for mass production and can achieve large-scale production.

[0017] In the embodiments of this application, the transition metal compound includes one or more of transition metal oxides, transition metal carbides, and transition metal halides.

[0018] In this embodiment, the transition metal compound includes one or more of Fe2O3, Fe5C2, FeCl3, Fe2(SO4)3, TiC, TiCl4, NiO, Ni(NO3)2, NiSO4, NiCl2, CoCl2, and CoO; the boron-containing material includes elemental boron and / or boron-containing compounds, wherein the boron-containing compound includes one or more of boric acid, triphenylboron, trimethyl borate, and neopentyl glycol diboronate; the nitrogen-containing material includes one or more of urea, ammonia, trimethylamine, nitromethane, and melamine; and the phosphorus-containing material includes one or more of tripoly(methoxyphosphoric acid) and tetrapoly(methoxyphosphoric acid).

[0019] In this embodiment, the graphene oxide dispersion and the additive are mixed at a mass ratio of graphene oxide to additive of 99.95:0.05-90:10. The addition of suitable additives helps to reduce the content of oxygen, hydrogen, etc., during heat treatment, while also catalyzing the repair of graphene defects, thereby preparing a graphene film with fewer impurities and fewer defects.

[0020] In this embodiment of the application, the first heating rate is 5℃ / min-20℃ / min; the first time is 10h-60h; the second time is 20h-80h; the second heating rate is 0.2℃ / min-5℃ / min; and the third time is 15h-200h.

[0021] In this embodiment of the application, during the heat treatment process, pressure treatment is performed while heating to 1000℃-1200℃, with a pressure of 0.1 MPa-10 MPa. Pressure treatment is beneficial for improving the quality of the obtained graphene.

[0022] In this embodiment, the graphene oxide film is sandwiched between two thermally conductive media during the heat treatment process, such that each graphene oxide film is sandwiched between two thermally conductive media. The thermal conductivity of the thermally conductive media is ≥100W / m*K. Using a high-thermal-conductivity thermally conductive media to sandwich the graphene oxide film creates a more uniform high-temperature thermal field around the film, which is beneficial for efficient and uniform heating of the graphene oxide film during heat treatment. This accelerates the growth and orderly stacking of graphene film grains, improves the quality of the graphene film generated by the reaction, and yields a more ordered and flat graphene film.

[0023] In this embodiment, the substrate comprises an organic polymer film or a metal foil; the drying temperature is 25℃-150℃. A suitable drying temperature facilitates the orderly arrangement of the mixed slurry to achieve highly oriented self-assembly, forming a more flat and ordered graphene oxide film.

[0024] In this embodiment of the application, the pressure used for the calendering process is 0.1 MPa-120 MPa.

[0025] A third aspect of this application provides a thermally conductive composite material, comprising at least one layer of carbon material and at least two additional layers stacked together, each of the carbon material layers being disposed between two additional layers; each additional layer is independently selected from a metal layer, a polymer layer, or a carbon fiber reinforced resin layer; the carbon material includes the carbon material described in the first aspect of this application or the carbon material prepared by the preparation method described in the second aspect. The additional layers can effectively protect the carbon material and prevent delamination, powder shedding, etc.

[0026] In this embodiment, the metal layer is selected from copper, nickel, stainless steel, or magnesium-aluminum alloy. The metal layer can better protect the carbon material, improve the surface smoothness of the thermally conductive composite material, and has a relatively high modulus, which is beneficial for the use of the thermally conductive composite material in scenarios requiring high modulus.

[0027] In this embodiment, the polymer layer comprises a flexible polymer material, including one or more of polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyimide (PI), thermoplastic polyurethane elastomer (TPU), polyamide (PA), parylene (parylene), and optical adhesive (OCA). The polymer layer can effectively protect the carbon material, improve the surface smoothness of the thermally conductive composite material, and exhibits excellent flexibility.

[0028] In this embodiment, the compression ratio of the flexible polymer material is 0-20%. The relatively small compression ratio of the flexible polymer material is beneficial for reducing surface variations.

[0029] In this embodiment, the thickness difference of the same polymer layer is ≤10%. A smaller thickness difference in the polymer layer helps improve the overall flatness of the thermally conductive composite material and enhances its appearance.

[0030] In this embodiment of the application, the carbon material and the additional layer are directly pressed together or connected by an adhesive layer.

[0031] In this embodiment of the application, the adhesive layer includes one or more of acrylic resin, silicone, epoxy resin, and optical adhesive.

[0032] In this embodiment of the application, the carbon material and the additional layer are connected by a plurality of adhesive pillars.

[0033] In this embodiment of the application, the material of the adhesive column includes one or more of acrylic resin, silicone, epoxy resin, and optical adhesive.

[0034] In this embodiment of the application, each of the adhesive posts is simultaneously embedded in the adjacent carbon material and the additional layer, so that the adjacent carbon material and the additional layer form a riveted connection.

[0035] In this embodiment, the thickness of the additional layer is 4μm-200μm. A suitable additional layer thickness can better protect the carbon material, while also improving the appearance of the thermally conductive composite material while maintaining good thermal conductivity.

[0036] In this embodiment, the thickness ratio of the additional layer to the carbon material is greater than 0.5:1. This arrangement helps to make the surface of the thermally conductive composite material smoother and improves its appearance.

[0037] In this embodiment, each of the additional layers is a polymer layer, and the Young's modulus of the thermally conductive composite material is 2 GPa-20 GPa; or at least one of the additional layers is a metal layer or a carbon fiber resin reinforcement layer, and the Young's modulus of the thermally conductive composite material is 50 GPa-150 GPa.

[0038] In this embodiment, the pull-out force of the thermally conductive composite material is ≥0.05 MPa. A high pull-out force indicates a high bonding strength between the layers of the thermally conductive composite material, which reduces the risk of delamination during bending and improves the reliability of the thermally conductive composite material in bending scenarios.

[0039] In this embodiment, the elongation at break of the thermally conductive composite material is ≥3%. The thermally conductive composite material has a high elongation at break and is bendable, thus meeting the application requirements in bending scenarios.

[0040] In this embodiment, the surface roughness Ra of the thermally conductive composite material is ≤500nm. The low surface roughness of the thermally conductive composite material is beneficial for improving its appearance and refinement.

[0041] In this embodiment, the difference in surface area between the carbon material and the additional layer is ≤1μm. A smaller difference in surface area between the carbon material and the additional layer helps reduce film printing and improves the appearance finish.

[0042] This application also provides a display screen, which includes a display layer and a heat dissipation layer stacked on the backlight side of the display layer. The heat dissipation layer includes the carbon material described in the first aspect of this application, the carbon material prepared by the preparation method in the second aspect of this application, or the thermally conductive composite material described in the third aspect of this application.

[0043] This application also provides an electronic device, which includes a housing and a display screen mounted on the housing. The housing and / or the display screen include the carbon material described in the first aspect of this application, the carbon material prepared by the preparation method in the second aspect of this application, or the thermally conductive composite material described in the third aspect of this application. Attached Figure Description

[0044] Figure 1 It is a photo of a display screen that uses existing thermally conductive carbon materials;

[0045] Figure 2 This is a schematic diagram of the structure of the carbon material 100 provided in one embodiment of this application;

[0046] Figure 3a and Figure 3b This is a schematic diagram of selecting sampling points on carbon materials when performing parameter characterization on carbon materials.

[0047] Figure 4 These are images showing nitrogen-containing compounds repairing defects in the carbon atom layer during heat treatment;

[0048] Figure 5 This is a schematic diagram of the laminated structure of the thermally conductive composite material 200 provided in one embodiment of this application;

[0049] Figure 6 This is a schematic diagram of the laminated structure of the thermally conductive composite material 200 provided in another embodiment of this application;

[0050] Figure 7 This is a schematic diagram of the laminated structure of the thermally conductive composite material 200 provided in another embodiment of this application;

[0051] Figure 8 This is a schematic diagram of the laminated structure of the thermally conductive composite material 200 provided in another embodiment of this application;

[0052] Figure 9 This is a schematic diagram of the laminated structure of the thermally conductive composite material 200 provided in another embodiment of this application;

[0053] Figure 10 This is a schematic diagram showing the connection between carbon material 100 and additional layer 202 via adhesive layer 204;

[0054] Figure 11a , Figure 11b , Figure 11c , Figure 11d and Figure 11e This is a schematic diagram showing the connection between carbon material 100 and additional layer 202 via adhesive pillar 205;

[0055] Figure 12 This is a schematic diagram of the stacked structure of a display screen 300 provided in one embodiment of this application;

[0056] Figure 13 This is a schematic diagram of the stacked structure of the display screen 300 provided in another embodiment of this application;

[0057] Figure 14 This is a schematic diagram of the stacked structure of the display screen 300 provided in another embodiment of this application;

[0058] Figure 15 This is a schematic diagram of the stacked structure of the display screen 300 provided in another embodiment of this application;

[0059] Figure 16 This is a photograph of the display screen 300 in one embodiment of this application;

[0060] Figure 17 This is a schematic diagram of the structure of an electronic device 400 provided in an embodiment of this application. Detailed Implementation

[0061] The embodiments of this application will now be described in conjunction with the accompanying drawings.

[0062] This application provides a carbon material and its preparation method, a display screen, and an electronic device. The carbon material has ultra-high thermal diffusivity, high modulus, low surface roughness, and high elongation at break, and can be used in flexible display modules and other appearance devices, so that the devices have high thermal conductivity while also having good bendability and exquisite appearance.

[0063] See Figure 2 This application provides a carbon material 100, which comprises multiple stacked carbon atom layers, and the in-plane thermal diffusivity of the carbon material is ≥800 mm. 2 / s, the Young's modulus of the carbon material is 1000Mpa-6000Mpa, the surface roughness Ra of the carbon material is ≤800nm, and the elongation at break of the carbon material is ≥2%.

[0064] The carbon material 100 provided in this application embodiment has an ultra-high thermal diffusivity, high modulus, low surface roughness and high elongation at break, and is thin. It can be used in appearance devices such as flexible display modules, so that the device has both thinness and high thermal conductivity, as well as good bendability and appearance refinement. This can solve the problems of heat dissipation and appearance refinement of display modules at the same time, and also meet the requirements of foldability.

[0065] In this embodiment, the in-plane thermal diffusivity of the carbon material 100 is ≥800 mm. 2 / s, meaning the thermal diffusivity of carbon material 100 in the XY plane is ≥800mm. 2 / s, the XY plane direction is parallel to the plane direction of the carbon atom layer, and the XY plane direction is perpendicular to the Z direction of the carbon material, i.e., the thickness direction. Thermal diffusivity is a measure of the rate at which a temperature disturbance at one point in an object is transferred to another point. Taking the case of an object heating up as an example, in the unsteady-state heat conduction process of an object heating up, the heat entering the object is continuously absorbed along the way, causing the local temperature to rise. This process continues until the temperature at all points inside the object is the same. Materials with a higher thermal diffusivity allow the human body to more clearly feel the temperature quickly transferred from one end of the material to the other. In some embodiments of this application, the in-plane thermal diffusivity of the carbon material 100 is ≥850 mm. 2 / s; In some embodiments, the in-plane thermal diffusivity of the carbon material 100 is ≥900mm. 2 / s; In some embodiments, the in-plane thermal diffusivity of the carbon material 100 is ≥1000mm. 2 / s; In some embodiments, the in-plane thermal diffusivity of the carbon material 100 is ≥1100mm. 2 / s; In some embodiments, the in-plane thermal diffusivity of the carbon material 100 is ≥1200mm. 2 / s. For example, the in-plane thermal diffusivity of the carbon material 100 can be 800 mm. 2 / s, 820mm 2 / s, 850mm 2 / s, 870mm 2 / s, 900mm 2 / s, 920mm 2 / s, 950mm 2 / s, 970mm 2 / s, 1000mm 2 / s, 1020mm 2 / s, 1050mm 2 / s, 1080mm 2 / s, 1100mm 2 / s, 1120mm 2 / s, 1150mm 2 / s, 1180mm 2 / s, 1200mm 2 / s. The carbon material 100 of this application embodiment has a very high thermal diffusivity in the XY plane direction, which enables rapid thermal diffusion in the XY plane direction. It can be applied in the form of a large-area film, sheet or plate in devices with high heat dissipation requirements to improve the heat dissipation performance of the device, thereby improving its service life and safety.

[0066] In this embodiment, the carbon material 100 is a material with anisotropic thermal conductivity, and the thermal diffusivity of the carbon material 100 in the XY plane is ≥800 mm. 2 / s, while carbon material 100 has an extremely low thermal diffusivity in the Z direction, i.e., the thickness direction, for example, possibly within 10mm. 2 / s or less, in some embodiments, the thermal diffusivity in the Z direction is 5mm. 2 With a thermal diffusion coefficient of / s or less, the in-plane thermal diffusion coefficient can be up to 100 times that of the Z-direction thermal diffusion coefficient, which can better facilitate the in-plane diffusion of heat and meet the thermal diffusion requirements of electronic devices such as mobile phones.

[0067] In this embodiment, the thermal diffusivity of the carbon material 100 can be measured according to GB / T 22588-2008 "Measurement of Thermal Diffusivity or Thermal Conductivity by Flash Method". Specifically, the carbon material can be cut into a thin film with a diameter of 2 inches, and then the corresponding thermal diffusivity can be measured by a laser thermal conductivity meter.

[0068] In this embodiment, the Young's modulus of the carbon material 100 is 1000 MPa-6000 MPa. Young's modulus describes the ability of a solid material to resist deformation within its elastic limit; it is defined as the ratio of normal stress to normal strain experienced by the material during elastic deformation. A higher Young's modulus means the material is less prone to deformation under external force. Compared to existing thermally conductive carbon materials (with a Young's modulus of around 600 MPa), the carbon material 100 in this embodiment has a higher suitable Young's modulus. Using it directly for heat dissipation or combining it with other materials for heat dissipation in flexible display modules and other appearance devices can reduce wrinkles, improve device flatness, and alleviate appearance defects such as orange peel texture, thus improving the aesthetics and user experience. It also allows the carbon material 100 to have better bendability. For example, the Young's modulus of carbon material 100 can be 1000 MPa, 1100 MPa, 1200 MPa, 1300 MPa, 1400 MPa, 1500 MPa, 1600 MPa, 1700 MPa, 1800 MPa, 1900 MPa, 2000 MPa, 2500 MPa, 3000 MPa, 3500 MPa, 4000 MPa, 4500 MPa, 5000 MPa, 5500 MPa, or 6000 MPa.

[0069] The Young's modulus of carbon material 100 can be obtained by testing the stress-strain curve of the carbon material specimen according to GB / T 1040.3, and then calculating the elastic modulus of the carbon material according to GB / T 1040.1.

[0070] In this embodiment, the surface roughness Ra of the carbon material 100 is less than or equal to 800 nm. The carbon material in this embodiment has high surface flatness, few wrinkles, and low surface roughness. Low surface roughness is beneficial for phonon conduction, resulting in a better effect on improving the thermal conductivity of the carbon material. Low surface roughness also helps improve the flatness and appearance of the device when the carbon material is used for heat dissipation in flexible display modules and other appearance devices. In some embodiments of this application, the surface roughness of the carbon material 100 can be, for example, 800 nm, 750 nm, 700 nm, 650 nm, 600 nm, 550 nm, 500 nm, etc. The surface roughness of the carbon material 100 refers, for example, to the surface roughness of a carbon film, carbon sheet, or carbon plate. Surface roughness can be detected using atomic force microscopy (AFM), white light interferometer, or laser confocal microscopy.

[0071] In this embodiment, the elongation at break of the carbon material 100 is ≥2%. Elongation at break is the ratio of the elongated length before and after tensile testing to the initial length before tensile testing, i.e., the ratio of the elongated length at break to the initial length, expressed as a percentage. Elongation at break characterizes the softness and elasticity of the carbon material. In some embodiments of this application, the elongation at break of the carbon material 100 is 2%-15%. Specifically, for example, it can be 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%. The elongation at break of the carbon material 100 can be obtained by testing with a mechanical testing machine according to GB 13022-91 (Test Method for Tensile Properties of Plastics-Films). Specifically, the carbon material can be cut into standard samples, and stress-strain curves can be obtained using a mechanical testing machine. The elongation at break can then be determined by analyzing the stress-strain curves.

[0072] In this embodiment, the graphitization degree of carbon material 100 is greater than or equal to 0.97. Graphitization degree is an indicator of the extent to which carbon atoms form a close-packed hexagonal graphite crystal structure; the closer the lattice size is to the lattice constant of ideal graphite, the higher the graphitization degree. A higher graphitization degree results in better thermal conductivity of carbon material 100. In some embodiments, the graphitization degree of carbon material 100 is greater than or equal to 0.98. In some embodiments, the graphitization degree of carbon material 100 is greater than or equal to 0.99. The graphitization degree of carbon material 100 can be measured using methods such as Raman spectroscopy, X-ray diffraction, and transmission electron microscopy.

[0073] In the embodiments of this application, the grain size of the carbon material 100 is L in crystallography. c The length in the C-axis is greater than or equal to 50 nm. In some embodiments of this application, the grain size of the carbon material 100 is L in crystallography. c The size is greater than or equal to 60 nm; in some embodiments of this application, the grain size of carbon material 100 is L in crystallography.c The size is greater than or equal to 65 nm; in some embodiments, the grain size of carbon material 100 is L in crystallography. c The size is greater than or equal to 70 nm. The grain size L of the carbon material 100 in this application... c The larger size allows for the production of carbon materials with native film properties over a wider thickness range. This enables the direct use of single-piece carbon materials with the required thickness in scenarios with high heat dissipation and heat dissipation requirements, avoiding the need for multi-layer adhesive bonding to achieve the required thickness. This better meets the heat dissipation needs of high-power devices.

[0074] In the embodiments of this application, the grain size of the carbon material 100 is L in crystallography. a The size is greater than or equal to 10 μm. In some embodiments, the grains of carbon material 100 have a crystallographic L... a The grain size ranges from 10 μm to 100 μm (including the two endpoints). Specifically, the L-shaped grain size of carbon material 100 in crystallography... a The dimensions can be, for example, 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, or 100μm. The carbon material 100 of this application has a large single-crystal L... a The size of the grains will allow for a larger phonon free path, thereby improving the thermal conductivity of carbon materials and achieving a higher thermal diffusivity. The La size of the grains can be measured according to GB / T 40069-2021 "Nanotechnology Graphene Related Two-Dimensional Materials Layer Number Measurement Raman Spectroscopy Method", specifically by observing the Raman signal on the carbon material surface: test wavelength 1200 cm⁻¹. -1 ~2800cm -1 Focus on 1200cm -1 ~1800cm -1 The wavelength band, with a signal-to-noise ratio greater than 20, can be used to test multiple sampling points on the carbon material. The laser wavelength used for testing can be a 638nm laser. In this application, the D peak (~1270cm⁻¹) in the Raman spectrum of carbon material 100 is shown. -1 G peak (~1580cm) -1 The ratio of intensities can be I D / I G <0.01, I D / I G The peak ratio of the D band to the G band in the Raman spectrum.

[0075] In this embodiment, the carbon atom layers are bonded to each other by van der Waals forces. The interlayer spacing of the multilayer stacked carbon atom layers can be 0.3 nm to 0.5 nm. Smaller carbon layer spacing is beneficial to improving the in-plane thermal diffusion performance of the carbon material. In some embodiments, the interlayer spacing of the multilayer stacked carbon atom layers can be 0.335 nm to 0.5 nm.

[0076] Among them, the L of the grain c The size and interlayer spacing of carbon atoms can be measured using X-ray powder diffraction (XRD) to observe the signal on the carbon surface: the test angle is 10° to 60°, with a focus on 20° to 30°, i.e., the information on the (001) crystal plane. Multiple sampling points can be taken on the carbon material for testing, and a wavelength of [wavelength missing] can be used. The excitation wavelength was determined using a Copper K-α light source. Based on information such as peak intensity, peak position, and full width at half maximum (FWHM), the interlayer distance of carbon atoms and the L-axis of the grain were calculated. c size.

[0077] The above parameters can be represented as follows Figure 3a and Figure 3b The sampling points are selected as shown in the figure. Figure 3a As shown, for regularly shaped carbon films, carbon sheets, or carbon plates, five sampling points can be taken; for example... Figure 3b As shown, for irregularly shaped carbon films, carbon sheets, or carbon plates, seven sampling points can be taken; each sampling point is at the geometric center of the relative area, and each sampling point can be tested three times, with the test results of ≥50% of the samples being used as the standard, excluding local defects and anomalies.

[0078] In this embodiment, the carbon material 100 exhibits high cohesion and possesses native film characteristics within a thickness range of ≤2mm. In existing technologies, to obtain a 2mm thick carbon material, multiple layers of native films need to be bonded together using adhesive. The disadvantages of multi-layer bonding are structural instability, easy delamination, and inferior heat dissipation performance compared to native films. However, the carbon material 100 of this application possesses native film characteristics within a thickness range of ≤2mm, meaning that carbon material 100 within a 2mm thickness range does not require adhesive bonding, thereby improving the thermal diffusion performance and structural stability of the carbon material. The carbon material 100 can be prepared to the required thickness as needed. The thickness of the carbon material 100 can be 1μm-2mm, specifically 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2mm, etc. In some embodiments, if a thicker heat-dissipating carbon material greater than 2mm is required, it can be bonded using adhesive.

[0079] In this embodiment, the carbon material 100 is flexible and bendable. Because the carbon material 100 is bendable, it can better meet the needs of application scenarios requiring bending, such as foldable screen terminal devices. When used in foldable screen terminal devices, the carbon material can be used across two or more screens.

[0080] In this application embodiment, the fracture strength of carbon material 100 is ≥30MPa. Fracture strength refers to the maximum tensile stress recorded when the tensile specimen breaks. Fracture strength can characterize the tensile strength of carbon material. The carbon material in this application embodiment has a high fracture strength, indicating that it has good softness and elasticity, good tensile strength, and can be well applied in application scenarios with bending requirements. In some embodiments of this application, the fracture strength of carbon material 100 is ≥40MPa. In some embodiments of this application, the fracture strength of carbon material 100 is 40MPa-80MPa. Specifically, for example, it can be 40MPa, 50MPa, 51MPa, 60MPa, 65MPa, 70MPa, 75MPa, or 80MPa. The fracture strength of carbon material 100 can be obtained by testing with a mechanical testing machine in accordance with GB 13022-91 (Test Method for Tensile Properties of Plastics-Films). Specifically, the carbon material can be cut into national standard samples, and the stress-strain curve can be obtained by mechanical testing machine. The fracture strength can be obtained by analyzing the stress-strain curve.

[0081] The carbon material 100 in this application embodiment can be a hybrid crystal structure, that is, it simultaneously contains single crystals and polycrystalline materials.

[0082] In this embodiment of the application, the carbon material 100 can be in the form of a film, sheet, or plate, that is, the carbon material 100 can be a carbon film, carbon sheet, or carbon plate.

[0083] The carbon material 100 provided in this application embodiment is a graphene material with a high thermal diffusivity, good bendability, high modulus, and low surface roughness. It can be used in flexible display modules and other appearance devices, enabling the devices to possess both high thermal conductivity and good bendability and aesthetic refinement. The carbon material 100 in this application embodiment has a high thermal diffusivity and can be applied to various heat dissipation scenarios. For example, it can be used for heat dissipation of power devices or modules on circuit boards, or for heat dissipation of heat-generating chips inside semiconductor chips or packaging modules. Furthermore, the carbon material 100 is lightweight. Compared to traditional aluminum or copper plate heat dissipation, using the carbon material 100 for heat dissipation can effectively reduce the weight of the equipment, resulting in significant weight reduction benefits. The carbon material 100 of this application can be used alone as a pure film or plate, or it can be processed into sheets, films or specific three-dimensional shapes for use; or its adhesion can be increased by means of adhesive backing, brushing, etc., and it can be used in the form of a bonding; or it can be welded with metal structural parts to form a heat dissipation structural module; or it can be combined with polymer materials, metals, fiber-reinforced resins, etc. to form a thermally conductive composite material.

[0084] Accordingly, this application provides a method for preparing a carbon material, comprising the following steps:

[0085] Step S101: Mix the graphene oxide dispersion with the additive to obtain a mixed slurry, coat the mixed slurry onto a substrate, dry it to form a graphene oxide film, and then peel it off from the substrate; the additive includes one or more of transition metal compounds, boron-containing materials, nitrogen-containing materials, and phosphorus-containing materials;

[0086] Step S102: Under air-isolated conditions, the graphene oxide film is heat-treated to cause the graphene oxide to undergo a pyrolysis reaction to generate graphene, thereby obtaining the heat-treated film material; the heat treatment includes heating to 250℃-400℃ at a first heating rate and holding at that temperature for a first time, then heating to 1000℃-1200℃ and holding at that temperature for a second time, and then heating to 2900℃-3300℃ at a second heating rate and holding at that temperature for a third time.

[0087] Step S103: The heat-treated film material is calendered to obtain carbon material of the required thickness.

[0088] In step S101, the graphene oxide dispersion can be an aqueous dispersion of graphene oxide. The mass concentration of graphene oxide in the aqueous dispersion can be 1%-10%. For example, the mass concentration of graphene oxide in the aqueous dispersion can be 1%, 2%, 3%, 5%, 6%, 8%, or 10%.

[0089] During graphene preparation, defects such as missing carbon atoms and carbon atom misalignment often occur. These defects lead to smaller graphene crystal planes, affecting properties such as thermal diffusivity, Young's modulus, and elongation at break. Impurities such as oxygen and hydrogen also exist on the graphene surface, affecting its surface smoothness. In this application, the addition of additives acts as a catalyst, reducing the activation energy during heat treatment, increasing active sites on the graphene surface, accelerating the growth and orderly stacking of graphene film grains, reducing internal defects in graphene obtained from graphene oxide reaction, reducing the oxygen content of graphene, improving the surface smoothness and thermal diffusivity of the carbon material, and maintaining a relatively high elongation. Nitrogen-containing compounds are particularly effective in reducing activation energy, repairing internal defects in the graphene structure, increasing the thermal diffusivity, increasing Lc (thermal density), and resulting in a smoother surface.

[0090] In this embodiment, the transition metal compound may be one or more selected from transition metal oxides, transition metal carbides, and transition metal halides. The transition metal element in the transition metal compound may be, but is not limited to, one or more selected from Fe, Ti, Ni, and Co. For example, the transition metal compound may be one or more selected from Fe2O3, Fe5C2, FeCl3, Fe2(SO4)3, TiC, TiCl4, NiO, Ni(NO3)2, NiSO4, NiCl2, CoCl2, and CoO.

[0091] In this application, the boron-containing material can be elemental boron and / or a boron-containing compound, which can be one or more of boric acid, triphenylboron, trimethyl borate, and neopentyl glycol diborate. The nitrogen-containing material includes a nitrogen-containing compound, which can be one or more of urea, ammonia, trimethylamine, nitromethane, and melamine. The phosphorus-containing material includes a nitrogen-containing compound, which can be one or more of tripoly(methoxyphosphoric acid) and tetrapoly(methoxyphosphoric acid).

[0092] In this embodiment, the graphene oxide dispersion and additives can be mixed at a mass ratio of graphene oxide to additives of 99.95:0.05-90:10. The total mass of graphene oxide and additives is 100. Exemplarily, the graphene oxide dispersion and additives are mixed at mass ratios of 99.95:0.05, 99:1, 98:2, 97:3, 96:4, 95:5, 94:6, 93:7, 92:8, 91:9, and 90:10. The addition of suitable additives helps to reduce the content of oxygen, hydrogen, etc., during heat treatment, and simultaneously catalyzes the repair of graphene defects, thereby preparing a graphene film with fewer impurities and lower defects.

[0093] Figure 4 This image shows nitrogen-containing compounds repairing defects in the carbon atom layer during heat treatment. In step S102, the addition of nitrogen helps reduce the oxygen content in graphene, thereby reducing foaming of the graphene film during the heat treatment stage and reducing defects and wrinkles caused by foaming. At the same time, the addition of nitrogen increases the active sites on the graphene surface during the high-temperature (above 1000℃) heat treatment stage, making the entire high-temperature thermal field more uniform and accelerating the growth and orderly stacking of graphene film grains.

[0094] The coating operation, which involves applying the mixed slurry to the substrate, can be any one or more of spraying, scraping, and spin coating. Spraying can be planar spraying, axial spraying, or electrostatic spraying; spin coating can be planar spin coating or axial spin coating. The coating process can be carried out under the assistance of external forces such as enhanced magnetic fields, electrostatic forces, or ultra-high pressure. The spraying pressure can be 0.1 MPa-50 MPa. The spin coating speed can be 50 r / min-300 r / min. The coating environment can be one or more of the following: normal pressure environment, external magnetic field 1T-20T, electrostatic high voltage 4KV-100KV, or high voltage 0.1 MPa-5 MPa.

[0095] In this embodiment, the substrate may be an organic polymer film or a metal foil. The organic polymer film may be, but is not limited to, any one of polyimide (PI), polyethylene terephthalate (PET), polyamide (PA), or thermoplastic polyurethane (TPU). The metal foil may be, but is not limited to, any one of Ni foil, Cu foil, Fe foil, CuNi alloy foil, or FeCu alloy foil.

[0096] In this embodiment, the drying temperature is 25℃-150℃. A suitable drying temperature facilitates the orderly arrangement of the mixed slurry, enabling highly oriented self-assembly and forming a more smooth and ordered graphene oxide film. Exemplarily, the drying temperature can be 25℃, 30℃, 35℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, or 150℃. Lower drying temperatures are more conducive to improving the smoothness of the film.

[0097] In step S102, an inert gas or hydrogen may be used to create an air-isolated environment. For example, the inert gas may be nitrogen, argon, etc.

[0098] In this embodiment, the heat treatment includes a first stage heat treatment: heating to 250℃-400℃ at a first heating rate and holding for a first time; a second stage heat treatment: continuing to heat to 1000℃-1200℃ at the first heating rate and holding for a second time; and a third stage heat treatment: heating to 2900℃-3200℃ at a second heating rate and holding for a third time. This multi-stage heat treatment with a specific heating program is beneficial for improving the graphitization degree of graphene, reducing internal defects in graphene, improving the quality of carbon materials, enhancing the thermal conductivity and Young's modulus of carbon materials, and reducing the surface roughness of carbon materials. Furthermore, this multi-stage heat treatment with a specific heating program is also beneficial for constructing carbon interconnect structures while simultaneously removing oxides, thus achieving the acquisition of large-area sheet-like graphene films.

[0099] For example, the first heat treatment may be heating to 250℃, 260℃, 280℃, 300℃, 320℃, 350℃, 360℃, 380℃, or 400℃. In the embodiments of this application, the first heating rate may be 5℃ / min-20℃ / min, for example, 5℃ / min, 5.5℃ / min, 6℃ / min, 8℃ / min, 10℃ / min, 12℃ / min, 15℃ / min, 16℃ / min, 18℃ / min, or 20℃ / min. The first time may be 10h-60h, for example, 10h, 20h, 30h, 40h, 50h, or 60h.

[0100] In some embodiments of this application, pressurization is performed during heating to 1000℃-1200℃, i.e., during the second stage of heat treatment, with a pressurization pressure of 0.1 MPa-10 MPa. Exemplarily, the pressurization pressure can be 0.1 MPa, 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, or 10 MPa. Pressurization is beneficial for improving the quality of the obtained graphene.

[0101] For example, the second heat treatment can be heating to 1000℃, 1050℃, 1100℃, 1150℃, or 1200℃. The second time can be 20h-80h, for example, 20h, 30h, 40h, 50h, 60h, 70h, or 80h.

[0102] For example, the third stage of heat treatment can be heating to 2900℃, 2950℃, 3000℃, 3050℃, 3100℃, 3150℃, 3200℃, 3250℃, or 3300℃. In this embodiment, the second heating rate can be 0.2℃ / min-5℃ / min, for example, 0.2℃ / min, 0.5℃ / min, 0.8℃ / min, 1℃ / min, 1.5℃ / min, 2℃ / min, 2.5℃ / min, 3℃ / min, 3.5℃ / min, 4℃ / min, 4.5℃ / min, or 5℃ / min. A smaller second heating rate is beneficial for the removal of bubbles during the heat treatment process, resulting in a more flat and ordered graphene film. The third time can be 15h-200h, for example 15h, 20h, 250h, 30h, 35h, 40h, 50h, 60h, 80h, 100h, 120h, 150h, 180h, 200h.

[0103] In some embodiments of this application, a thermally conductive medium is used to sandwich the graphene oxide film during the heat treatment process, so that each graphene oxide film is sandwiched between two thermally conductive media, and the thermal conductivity of the thermally conductive media is ≥100W / m*K. The thermally conductive media located on both sides of the graphene oxide film can completely cover both sides of the graphene oxide film. Using a thermally conductive medium with a high thermal conductivity to sandwich the graphene oxide film can form a more uniform high-temperature thermal field around the graphene oxide film, which is beneficial for the graphene oxide film to be heated efficiently and uniformly during the heat treatment process, accelerates the growth and orderly stacking of graphene film grains, improves the quality of the graphene film generated by the reaction of the graphene oxide film, and obtains a more ordered and flat graphene film. For example, the thermal conductivity of the heat-conducting medium is 100 W / m*K, 200 W / m*K, 300 W / m*K, 400 W / m*K, 500 W / m*K, 600 W / m*K, 700 W / m*K, 800 W / m*K, 900 W / m*K, 1000 W / m*K, 1100 W / m*K, 1200 W / m*K, 1300 W / m*K, or 1400 W / m*K. The heat-conducting medium can be, for example, highly thermally conductive carbon paper.

[0104] In step S103, the calendering process can remove the foam pores formed in the heat-treated film material due to the volatilization of lightweight components, resulting in a thinner and smoother graphene film. The pressure used for calendering can be 0.1 MPa to 120 MPa. For example, the calendering pressures are 0.1 MPa, 1 MPa, 5 MPa, 10 MPa, 20 MPa, 50 MPa, 60 MPa, 80 MPa, 100 MPa, and 120 MPa.

[0105] The carbon material preparation method of this application embodiment is feasible for mass production and can achieve large-scale production.

[0106] See Figure 5 , Figure 5 This is a schematic diagram of the laminated structure of the thermally conductive composite material 200 provided in one embodiment of this application. The thermally conductive composite material 200 includes at least one layer of carbon material 100 and at least two additional layers 202, each carbon material 100 being disposed between two additional layers 202. The at least one layer of carbon material 100 and the at least two additional layers 202 are laminated together. Each additional layer 202 is independently selected from a metal layer, a polymer layer, or a carbon fiber reinforced resin layer. The carbon material 100 is as described above. The additional layers 202 can effectively protect the carbon material 100, preventing delamination, powder shedding, etc.

[0107] In this embodiment, the thermally conductive composite material 200 includes at least one layer of carbon material 100. "At least one layer" means one or more layers, specifically one, two, or three layers. When the thermally conductive composite material 200 includes two or more layers of carbon material 100, each carbon material 100 is disposed between two additional layers 202, meaning each carbon material 100 is spaced apart by the additional layers 202. The two or more carbon material layers 100 can have the same thickness or different thicknesses.

[0108] In this embodiment, the thermally conductive composite material 200 includes at least two additional layers 202. "At least two layers" means two or more layers, specifically, two, three, four, or five layers. Each of the at least two additional layers 202 may be spaced apart by carbon material 100, forming an alternating layered structure of carbon material 100 and additional layers 202; alternatively, some additional layers 202 may be spaced apart by carbon material 100, while others may be stacked together in contact. These stacked additional layers 202 may be layers of the same material or layers of different materials. The at least two additional layers 202 may have the same thickness or different thicknesses.

[0109] In this embodiment, at least two additional layers 202 can be layers of the same material. For example, at least two additional layers 202 can be polymer layers, metal layers, or carbon fiber reinforced resin layers. At least two additional layers can also be layers of different materials. For example, some additional layers 202 can be polymer layers and others can be metal layers; or some additional layers 202 can be polymer layers and others can be carbon fiber reinforced resin layers; or some additional layers 202 can be metal layers and others can be carbon fiber reinforced resin layers; or some additional layers 202 can be metal layers, some additional layers 202 can be polymer layers, and some additional layers 202 can be carbon fiber reinforced resin layers.

[0110] In this embodiment, the thickness of the carbon material 100 and the thickness of the additional layer 202 can be the same or different. The thickness of the carbon material 100 can be greater than or less than the thickness of the additional layer 202.

[0111] In this embodiment, the thickness of the additional layer 202 can be between 4 μm and 200 μm. A suitable thickness of the additional layer 202 can effectively protect the carbon material 100, while simultaneously improving the appearance and sophistication of the thermally conductive composite material while maintaining good thermal conductivity. For example, the thickness of the additional layer 202 can be 4 μm, 5 μm, 8 μm, 10 μm, 20 μm, 30 μm, 50 μm, 80 μm, 100 μm, 120 μm, 130 μm, 150 μm, 160 μm, 180 μm, or 200 μm.

[0112] In some embodiments of this application, the thickness ratio of the additional layer 202 to the carbon material 100 is greater than 0.5:1. This arrangement facilitates a smoother surface on the thermally conductive composite material 200, improving its appearance. Exemplarily, the thickness ratio of the additional layer 202 to the carbon material 100 is 0.5:1, 0.8:1, 1:1, 1.1:1, 1.5:1, 2:1, or 3:1. In some embodiments, the thickness ratio of the additional layer 202 to the carbon material 100 is greater than 1. Since the carbon material 100 itself has a high thermal diffusivity and a high Young's modulus, setting the thickness of the additional layer 202 to be greater than the thickness of the carbon material 100 helps to achieve good thermal conductivity while improving the appearance of the thermally conductive composite material 200.

[0113] In one embodiment of this application, in order to balance the internal stress of the thermally conductive composite material 200 and improve its quality and performance, the thermally conductive composite material 200 has a symmetrical structure in its thickness direction, that is, the two sides along the centerline of its thickness direction are completely identical (including material and thickness).

[0114] In some embodiments of this application, such as Figure 5 As shown, the thermally conductive composite material 200 includes a layer of carbon material 100 and two additional layers 202 stacked together. The carbon material 100 is sandwiched between the two additional layers 202, forming a structure in which the carbon material 100 and the additional layers 202 are alternately stacked. In one embodiment, both additional layers 202 are polymer layers; in another embodiment, both additional layers 202 are metal layers; in another embodiment, both additional layers 202 are carbon fiber reinforced resin layers; in another embodiment, one of the two additional layers 202 is a polymer layer and the other is a metal layer; in yet another embodiment, one of the two additional layers 202 is a polymer layer and the other is a carbon fiber reinforced resin layer; in yet another embodiment, one of the two additional layers 202 is a metal layer and the other is a carbon fiber reinforced resin layer. The two additional layers 202 can have the same thickness or different thicknesses.

[0115] See Figure 6 , Figure 6 This is a schematic diagram of the laminated structure of a thermally conductive composite material 200 according to another embodiment of this application. In this embodiment, the thermally conductive composite material 200 includes two layers of carbon material 100 and three additional layers 202 stacked together. Each carbon material 100 is sandwiched between two additional layers 202, forming a structure in which the carbon material 100 and the additional layers 202 are alternately stacked. The three additional layers 202 can be layers of the same material or layers of different materials, and can have the same thickness or different thicknesses.

[0116] See Figure 7 , Figure 7 This is a schematic diagram of the laminated structure of a thermally conductive composite material 200 according to another embodiment of this application. In this embodiment, the thermally conductive composite material 200 includes a layer of carbon material 100 and four additional layers 202 stacked together. Two additional layers 202 are disposed on one side of the carbon material 100, and two additional layers 202 are disposed on the other side of the carbon material 100. The four additional layers 202 can be layers of the same material or layers of different materials, and can have the same thickness or different thicknesses. In some embodiments, the four additional layers 202 on both sides of the carbon material 100 are symmetrically arranged, that is, the two additional layers 202 on one side of the carbon material 100 and the two additional layers 202 on the other side of the carbon material 100 are exactly the same (including material and thickness). The symmetrical arrangement is beneficial to balancing the internal stress of the thermally conductive composite material 200 and improving the quality and performance of the thermally conductive composite material 200.

[0117] See Figure 8 , Figure 8 This is a schematic diagram of the laminated structure of a thermally conductive composite material 200 according to another embodiment of this application. In this embodiment, the thermally conductive composite material 200 includes a layer of carbon material 100 and three additional layers 202 stacked together. Two additional layers 202 are disposed on one side of the carbon material 100, and one additional layer 202 is disposed on the other side of the carbon material 100. The three additional layers 202 can be layers of the same material or layers of different materials, and can have the same thickness or different thicknesses.

[0118] In this embodiment, the additional layers 202 located on both sides of the carbon material 100 completely cover both sides of the carbon material 100. The additional layers 202 can either just cover the carbon material 100 or extend beyond the surface of the carbon material 100; that is, in the stacking direction of the carbon material 100 and the additional layers 202, they can be as follows: Figure 5 As shown: the edge of the additional layer 202 is flush with the edge of the carbon material 100, or it can be as follows: Figure 9As shown: the edge of the additional layer 202 extends beyond the edge of the carbon material 100. This extension of the edge of the additional layer 202 beyond the edge of the carbon material 100 helps to better protect the carbon material 100 and also helps to reduce the surface gradient of the composite material. In some embodiments of this application, such as... Figure 9 As shown, when the edge of the additional layer 202 extends beyond the edge of the carbon material 100, an adhesive 203 can be filled at the position where the carbon material 100 is recessed relative to the additional layer 202. The adhesive 203 can be an acrylic adhesive, silicone, or other adhesive with a certain compressibility. The addition of this adhesive 203 can improve the bonding reliability between the additional layer 202 and the carbon material 100.

[0119] In this embodiment, the metal layer can be selected from copper, nickel, stainless steel, or magnesium-aluminum alloy. When the thermally conductive composite material 200 includes multiple metal layers, the multiple metal layers can be of the same material or different materials.

[0120] In this embodiment, the polymer layer may include a flexible polymer material, which may include, but is not limited to, one or more of polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyimide (PI), thermoplastic polyurethane elastomer (TPU), polyamide (PA), parylene (parylene), and optical adhesive (OCA). When the thermally conductive composite material 200 includes multiple polymer layers, the multiple polymer layers may be made of the same material or different materials. The elongation at break of the polymer layer is greater than that of the carbon material 100, which is beneficial to improving the bendability of the thermally conductive composite material 200.

[0121] In this embodiment, the compression ratio of the flexible polymer material is 0-20%. Compression ratio refers to the percentage reduction in volume or size of a material when compressed. A relatively small compression ratio in flexible polymer materials is beneficial for reducing surface defects. Exemplarily, the compression ratios of the flexible polymer materials are 0%, 1%, 2%, 5%, 7%, 9%, 10%, 12%, 14%, 15%, 16%, 18%, and 20%.

[0122] In this embodiment, the thickness difference of the same polymer layer is ≤10%, meaning the percentage difference between the thickness Dm at any location of the polymer layer and the average thickness D of the polymer layer relative to the average thickness D of the polymer layer is ≤10%, i.e., (|Dm-D| / D)*100%≤10%. A small thickness difference in the polymer layer is beneficial for improving the overall flatness of the thermally conductive composite material and enhancing its appearance. In some embodiments, the thickness difference of the same polymer layer may be ≤9%, ≤8%, or ≤7%.

[0123] In this embodiment, the carbon fiber reinforced resin layer is a composite material layer formed with carbon fiber or carbon fiber fabric as the reinforcement and resin as the matrix.

[0124] In some embodiments of this application, such as Figure 5 As shown, carbon material 100 and additional layer 202 are directly pressed together, meaning that carbon material 100 and additional layer 202 are directly in contact and laminated together. Specifically, the bonding interface between carbon material 100 and additional layer 202 can be formed through hot pressing. The hot pressing temperature can be 80℃-200℃. Hot pressing composite allows carbon material 100 and additional layer 202 to be directly in contact and laminated, which is beneficial for obtaining a smaller thickness of thermally conductive composite material 200.

[0125] In some embodiments of this application, such as Figure 10 As shown, the carbon material 100 and the additional layer 202 are connected by an adhesive layer 204. The adhesive layer 204 is disposed between the carbon material 100 and the additional layer 202, bonding the carbon material 100 and the additional layer 202 together.

[0126] In this embodiment, the adhesive layer 204 may be one or more of acrylic resin, silicone, epoxy resin, and optical adhesive.

[0127] In some embodiments of this application, such as Figure 11a , Figure 11b , Figure 11c and Figure 11d As shown, the carbon material 100 and the additional layer 202 are connected by a plurality of adhesive posts 205. In this embodiment, each adhesive post 205 is simultaneously embedded in adjacent carbon materials 100 and additional layers 202, so that adjacent carbon materials 100 and additional layers 202 form a riveted connection.

[0128] In some embodiments, the adhesive column 205 is configured such that a portion of it is non-penetratingly embedded in the carbon material 100, and another portion is non-penetratingly embedded in the additional layer 202 (e.g., Figure 11a As shown), the adhesive column 205 extends into the carbon material 100 at one end and into the additional layer 202 adjacent to the carbon material 100 at the other end. In this case, the adhesive column 205 only connects the adjacent carbon material 100 and the additional layer 202, which is beneficial for in-plane heat dissipation of the carbon material 100.

[0129] In some embodiments, the adhesive column 205 is configured such that its middle portion, along the thickness direction of the thermally conductive composite material 200, is embedded through a layer of carbon material 100, while its two ends are non-penetratingly embedded in additional layers 202 on both sides of the carbon material 100, such as... Figure 11b As shown, in the thickness direction of the thermally conductive composite material 200, the adhesive column 205 is embedded in a layer of carbon material 100, and the two ends of the adhesive column 205 extend into the additional layers 202 on both sides of the carbon material 100. At this time, the adhesive column 205 connects the carbon material 100 and the additional layers 202 on both sides adjacent to the carbon material 100, which is beneficial to improving the bonding force between the multiple layers.

[0130] In some embodiments, the adhesive column 205 is configured such that its middle portion, along the thickness direction of the thermally conductive composite material 200, is embedded through the middle layer (all layers other than the outermost two sides) of the thermally conductive composite material 200, while its two ends are non-penetratingly embedded in the additional layers 202 of the outermost two sides of the thermally conductive composite material 200, which is beneficial to improving the bonding strength between multiple layers. In some embodiments, such as Figure 11b As shown, the middle layer is a layer of carbon material 100. In some embodiments, such as... Figure 11d As shown, the intermediate layer includes two carbon material layers 100 and an additional layer 202 sandwiched between the two carbon material layers 100.

[0131] In some implementations, such as Figure 11e As shown, the adhesive column 205 is configured such that one end of it is embedded through the middle layer (all layers other than the outermost layers on both sides) and the outermost layer on one side of the thermally conductive composite material 200 along the thickness direction, while the other end is embedded in the additional layer 202 of the outermost layer on the other side of the thermally conductive composite material 200 without penetrating. That is, the surface of one end of the adhesive column 205 is flush with the surface of the additional layer 202 of the outermost layer on one side of the thermally conductive composite material 200.

[0132] In this application embodiment, the arrangement of the multiple adhesive columns 205 can be the same or different. In some embodiments, such as Figure 11a As shown, each of the multiple adhesive pillars 205 is configured such that a portion is non-penetratingly embedded in the carbon material 100, and another portion is non-penetratingly embedded in the additional layer 202. In some embodiments, such as Figure 11b As shown, multiple adhesive pillars 205 are configured such that their central portions are embedded through a layer of carbon material 100, while their two ends are non-penetratingly embedded in additional layers 202 on both sides of the carbon material 100. In some embodiments, such as Figure 11c As shown, some of the multiple adhesive columns 205 are configured such that a portion of them are not penetrated and embedded in the carbon material 100, and another portion is not penetrated and embedded in the additional layer 202; another portion of the adhesive columns 205 are configured such that the middle portion is penetrated and embedded in a layer of carbon material 100, and the two ends are respectively not penetrated and embedded in the additional layers 202 on both sides of the carbon material 100.

[0133] In this embodiment, the multiple adhesive pillars 205 can be evenly spaced to improve the bonding force between the carbon material 100 and the additional layer 202.

[0134] In this embodiment, the material of the adhesive pillar 205 can be one or more of acrylic resin, silicone, epoxy resin, and optical adhesive. The adhesive pillar 205 can be formed by perforation and adhesive injection. In some embodiments, after the layers constituting the thermally conductive composite material 200 are stacked to form a laminate, holes are drilled into the interior of the laminate on its four sides, for example, along the X or Y direction of the corresponding carbon material 100. In some embodiments, after the layers constituting the thermally conductive composite material 200 are stacked to form a laminate, holes are drilled into the interior on both the upper and lower surfaces of the laminate, i.e., along the Z direction of the corresponding carbon material 100. The shape of the holes is not limited; the cross-sectional shape of the holes can be circular, square, elliptical, or zigzag. The depth of the holes is not limited, as long as it allows for strong bonding between the layers.

[0135] For the scheme in which the adhesive column 205 penetrates and embeds the carbon material 100 in the thickness direction (i.e., the Z direction) of the thermally conductive composite material 200, in order to enable the carbon material 100 to better exert its high in-plane thermal diffusion performance, the adhesive column 205 does not penetrate the carbon material 100 in the X and Y directions.

[0136] In some embodiments of this application, each additional layer 202 is a polymer layer, and the Young's modulus of the thermally conductive composite material 200 is 2 GPa-20 GPa. Exemplarily, the Young's modulus of the thermally conductive composite material 200 is 2 GPa, 5 GPa, 6 GPa, 10 GPa, 12 GPa, 15 GPa, 18 GPa, or 20 GPa.

[0137] In some embodiments of this application, at least one additional layer 202 is a metal layer or a carbon fiber resin reinforcement layer, and the Young's modulus of the thermally conductive composite material 200 is 50 GPa-150 GPa. In this case, some or all of the additional layers 202 may be metal layers or carbon fiber resin reinforcement layers. The thermally conductive composite material 200 has a high Young's modulus, which helps reduce the risk of deformation under external forces and is advantageous for applications requiring higher modulus, such as support structures and shell structures.

[0138] In this embodiment, the pull-out force of the thermally conductive composite material 200 is ≥0.05 MPa. A high pull-out force indicates a high bonding strength between the layers of the thermally conductive composite material 200, which reduces the risk of bending peeling and improves the reliability of the thermally conductive composite material 200 in bending scenarios. The pull-out force can be tested using the following vertical pull-out test: the entire sample is bonded to a steel plate, a steel block is bonded to the upper surface of the sample with double-sided adhesive, and the steel block is secured with cable ties; a tensile testing machine is used to pull the top of the cable ties.

[0139] In this embodiment, the elongation at break of the thermally conductive composite material 200 is ≥3%. The thermally conductive composite material 200 has a high elongation at break, is bendable, and can meet the application requirements in bending scenarios.

[0140] In this embodiment, the surface roughness Ra of the thermally conductive composite material 200 is ≤500nm. The low surface roughness of the thermally conductive composite material 200 is beneficial for improving its appearance and refinement.

[0141] In this embodiment, the surface difference between the carbon material 100 and the additional layer 202 is ≤1μm. A smaller surface difference between the carbon material 100 and the additional layer 202 helps reduce film printing and improves the appearance finish. For example, the surface difference between the carbon material 100 and the additional layer 202 is 1μm, 0.8μm, 0.6μm, 0.5μm, 0.3μm, 0.1μm, 0.08μm, or 0.05μm.

[0142] The thermally conductive composite material 200 of this application embodiment has high thermal conductivity and can be used in various scenarios with heat dissipation requirements. The thermally conductive composite material 200 also has good bendability and high peel strength, making it suitable for scenarios with bending requirements. Furthermore, the thermally conductive composite material 200 has good appearance refinement and high modulus, making it suitable for use in exterior parts. For example, the thermally conductive composite material 200 can be used as a heat dissipation layer or support layer in a display screen, or in the mid-frame, battery cover, plastic structural parts, or other structural parts of electronic devices.

[0143] See Figure 12 , Figure 13 , Figure 14 and Figure 15 , Figure 12 This is a schematic diagram of the stacked structure of the display screen 300 provided in one embodiment of this application. Figure 13 This is a schematic diagram of the stacked structure of the display screen 300 provided in another embodiment of this application. Figure 14 This is a schematic diagram of the stacked structure of the display screen 300 provided in another embodiment of this application. Figure 15 This is a schematic diagram of the stacked structure of a display screen 300 provided in another embodiment of this application. The display screen 300 in this embodiment includes a display layer 301 and a heat dissipation layer 302 stacked on the backlight side of the display layer 301. The heat dissipation layer 302 includes the carbon material 100 described in the embodiments of this application or the thermally conductive composite material 200 described in the embodiments of this application.

[0144] In this embodiment of the application, the display screen 300 may include one or more (two or more) heat dissipation layers 302, and the multiple heat dissipation layers 302 may be stacked at intervals.

[0145] In some embodiments of this application, the display screen 300 further includes a support layer 303 disposed on the backlight side of the display layer 301. The support layer 303 may be one layer or multiple layers, and multiple support layers 303 may be stacked at intervals.

[0146] In some embodiments of this application, the display screen 300 includes at least one heat dissipation layer 302 and at least one support layer 303, with the heat dissipation layer 302 and the support layer 303 being stacked alternately.

[0147] In some embodiments of this application, such as Figure 12 As shown, the display screen 300 includes a heat dissipation layer 302 and a support layer 303, with the heat dissipation layer 302 disposed between the display layer 301 and the support layer 303.

[0148] In some embodiments of this application, such as Figure 13 As shown, the display screen 300 includes a heat dissipation layer 302 and a support layer 303. The heat dissipation layer 302 is disposed on the side of the support layer 303 away from the display layer 301, that is, the support layer 303 is disposed between the display layer 301 and the heat dissipation layer 302.

[0149] In some embodiments of this application, the display screen 300 includes at least one heat dissipation layer 302 and at least two support layers 303, with the heat dissipation layer 302 and support layers 303 alternately stacked. For example... Figure 14 As shown, the display screen 300 includes a heat dissipation layer 302 and two support layers 303; Figure 15 As shown, the display screen 300 includes two heat dissipation layers 302 and three support layers 303.

[0150] The aforementioned support layer 303 can be made of polymer or metal. The heat dissipation layer 302 and the support layer 303 can be bonded together using an optical adhesive layer. The heat dissipation layer 302 and the display layer 301, as well as the support layer 303 and the display layer 301, can also be bonded together using an optical adhesive layer.

[0151] In some embodiments of this application, the heat dissipation layer 302 can also directly serve as a support layer. In this case, the heat dissipation layer 302 includes the thermally conductive composite material 200 described in the embodiments of this application, and the outermost additional layers 202 on both sides of the thermally conductive composite material 200 are metal layers or carbon fiber reinforced resin layers. The Young's modulus of the thermally conductive composite material 200 can be greater than or equal to 90 GPa.

[0152] In some embodiments of this application, the display screen 300 further includes a protective layer 304 disposed on the light-emitting side of the display layer 301, the protective layer 304 being used to protect the display layer 301.

[0153] The display screen 300 of this application embodiment uses the thermally conductive composite material 200 provided in this application embodiment as the heat dissipation layer 302, which can improve bending reliability while obtaining good thermal conductivity. At the same time, it can improve the refinement problems of existing display screens such as particles, film imprints, and orange peel texture, and improve the appearance refinement of the display screen. When applied to cross-axis heat dissipation of foldable electronic devices, it can avoid light and shadow asymmetry in the cross-axis area of ​​carbon material and poor light and shadow problems such as local protrusions and bulges, thus ensuring the refinement of foldable electronic devices. Figure 16 This is a photograph of the display screen 300 in one embodiment of this application. (Comparison) Figure 1 As can be seen, the appearance and refinement of the display screen 300 in this application embodiment are significantly improved.

[0154] See Figure 17 , Figure 17 This is a schematic diagram of the structure of an electronic device 400 provided in one embodiment of this application. The electronic device 200 can be various electronic devices with heat dissipation requirements, such as mobile phones, tablets, laptops, wearable devices (e.g., glasses, watches, bracelets), display devices, AR devices, VR devices, AR / VR devices, televisions, adapters, routers, in-vehicle devices, in-vehicle displays, gateways, set-top boxes, charging bases, heat dissipation modules, battery systems, power devices, packaging modules, and other devices with heat dissipation requirements. In particular, the electronic device in this embodiment can be a foldable electronic device.

[0155] In some embodiments of this application, the electronic device 400 includes a housing 401 and a display screen 402 mounted on the housing 401. The housing 401 and / or the display screen 402 include the carbon material 100 described in the embodiments of this application or the thermally conductive composite material 200 described in the embodiments of this application.

[0156] In some embodiments of this application, the display screen 402 may include the aforementioned display screen 300.

[0157] In this embodiment, the housing 401 may include a mid-frame and a battery cover. The mid-frame supports the display screen 402, and the battery cover is located on the rear side of the electronic device 400, i.e., the side facing away from the display screen 402. In some embodiments, the mid-frame includes the carbon material 100 described in the embodiments of this application or the thermally conductive composite material 200 described in the embodiments of this application. In some embodiments, the battery cover includes the carbon material 100 described in the embodiments of this application or the thermally conductive composite material 200 described in the embodiments of this application. In some embodiments, both the mid-frame and the battery cover include the carbon material 100 described in the embodiments of this application or the thermally conductive composite material 200 described in the embodiments of this application.

[0158] The technical solution of this application will be further described below with reference to several embodiments.

[0159] Example 1

[0160] A method for preparing a carbon material includes the following steps:

[0161] Step S101: Mix the graphene oxide dispersion with a transition metal compound containing Fe and / or Ni to obtain a mixed slurry. Coat the mixed slurry onto a PI substrate, dry it at 20-60℃ to form a graphene oxide film, and then peel it off from the PI substrate. In the mixed slurry, the sum of the mass percentages of graphene oxide and the transition metal compound containing Fe and / or Ni is 5%, and the mass ratio of graphene oxide to the transition metal compound containing Fe and / or Ni is 99.9:0.1.

[0162] Step S102: Under air-isolated conditions, the graphene oxide film is subjected to the following heat treatment: first, it is heated to 300℃ at 10℃ / min and held for 40h, then heated to 1100℃ and held for 50h, and then heated to 3100℃ at 3℃ / min and held for 20h; so that the graphene oxide undergoes a pyrolysis reaction to generate graphene, and the heat-treated film material is obtained.

[0163] Step S103: The heat-treated film material is calendered under a pressure of 400 MPa to obtain a carbon material with a thickness of 40 μm.

[0164] Preparation of thermally conductive composite material A:

[0165] The carbon material prepared above is sandwiched between two 20μm thick polyimide (PI) layers, and a 5μm thick acrylic resin adhesive layer is placed between the carbon material and the polyimide (PI) layers. The mixture is then hot-pressed at 150°C to obtain thermally conductive composite material A.

[0166] Preparation of thermally conductive composite material B: The carbon material prepared above is sandwiched between two copper layers with a thickness of 20 μm, and an acrylic resin adhesive layer with a thickness of 5 μm is placed between the carbon material and the copper layers. The thermally conductive composite material B is obtained by hot pressing at 150℃.

[0167] Example 2

[0168] A method for preparing a carbon material includes the following steps:

[0169] Step S101: Mix the graphene oxide dispersion with a transition metal compound containing Fe and / or Ni to obtain a mixed slurry. Coat the mixed slurry onto a PI substrate, dry it at 20-60℃ to form a graphene oxide film, and then peel it off from the PI substrate. In the mixed slurry, the sum of the mass percentages of graphene oxide and the transition metal compound containing Fe and / or Ni is 5%, and the mass ratio of graphene oxide to the transition metal compound containing Fe and / or Ni is 99.7:0.3.

[0170] Step S102 is the same as in Example 1;

[0171] Step S103 is the same as in Example 1.

[0172] Preparation of thermally conductive composite material A: Same as in Example 1.

[0173] Preparation of thermally conductive composite material B: Same as in Example 1.

[0174] Example 3

[0175] A method for preparing a carbon material includes the following steps:

[0176] Step S101: Mix the graphene oxide dispersion with a nitrogen-containing compound to obtain a mixed slurry. Coat the mixed slurry onto a PI substrate, dry it at 25-60℃ to form a graphene oxide film, and then peel it off from the PI substrate. In the mixed slurry, the sum of the mass percentages of graphene oxide and nitrogen-containing compound is 5%, and the mass ratio of graphene oxide to nitrogen-containing compound is 99.7:0.3.

[0177] Step S102 is the same as in Example 1;

[0178] Step S103 is the same as in Example 1.

[0179] Preparation of thermally conductive composite material A: Same as in Example 1.

[0180] Preparation of thermally conductive composite material B: Same as in Example 1.

[0181] Example 4

[0182] A method for preparing a carbon material includes the following steps:

[0183] Step S101 is the same as in Example 3;

[0184] Step S102 differs from Example 1 in that a graphene oxide film is sandwiched between high thermal conductivity carbon paper (thermal conductivity 600-800W / m*K) during the heat treatment process.

[0185] Step S103 is the same as in Example 1.

[0186] Preparation of thermally conductive composite material A: Same as in Example 1.

[0187] Preparation of thermally conductive composite material B: Same as in Example 1.

[0188] Comparative Example 1

[0189] A method for preparing a carbon material includes the following steps:

[0190] Step S101: Coat a 5% (w / w) graphene oxide dispersion onto a PI substrate, dry at 25-60°C to form a graphene oxide film, and then peel it off from the PI substrate.

[0191] Step S102: Under air-isolated conditions, the graphene oxide film is subjected to the following heat treatment: first, it is heated to 300℃ at 10℃ / min and held for 40h, then heated to 1100℃ and held for 50h, and then heated to 2800℃ and held for 20h; so that the graphene oxide undergoes a pyrolysis reaction to generate graphene, and the heat-treated film material is obtained.

[0192] Step S103 is the same as in Example 1.

[0193] Preparation of thermally conductive composite material A: Same as in Example 1.

[0194] Preparation of thermally conductive composite material B: Same as in Example 1.

[0195] The carbon materials prepared in Examples 1 to 4 and Comparative Example 1 were characterized in terms of performance, and the results are shown in Table 1.

[0196] Table 1

[0197]

[0198] As shown in Table 1, compared to Comparative Example 1, the carbon materials prepared by adding specific additives and employing specific heat treatment processes in Examples 1 to 4 of this application can achieve larger Lc size, higher thermal diffusivity, higher modulus, lower surface roughness, and higher graphitization degree, while maintaining a large elongation at break. Comparing Examples 1 and 2, it is evident that appropriately increasing the amount of additives is beneficial for obtaining larger Lc size, higher thermal diffusivity, higher modulus, lower surface roughness, and higher graphitization degree in the carbon material. Comparing Examples 2 and 3, it is evident that using nitrogen-containing compounds is more beneficial than using transition metal compounds containing Fe and / or Ni for improving Lc size, thermal diffusivity, modulus, graphitization degree, and reducing surface roughness. Comparing Examples 3 and 4, it is evident that using high thermal conductivity carbon paper to sandwich the graphene oxide film during the heat treatment stage is beneficial for improving Lc size, thermal diffusivity, modulus, graphitization degree, and reducing surface roughness.

[0199] As can be seen from Table 1, compared with the thermally conductive composite material prepared in Comparative Example 1, the thermally conductive composite materials of Examples 1 to 4 of this application have a smaller step difference between the carbon material and the additional layer interface and a lower surface roughness.

[0200] The thermally conductive composite materials of Examples 1 to 4 and Comparative Example 1 of this application were used as heat dissipation layers to prepare display screens. The results showed that, compared with Comparative Example 1, Examples 1 to 4 significantly improved the refinement issues such as particles, film imprints, and orange peel texture, and the appearance refinement of the display screens was significantly improved.

[0201] It should be understood that the use of the terms "first," "second," and various numerical designations in this document is merely for descriptive convenience and is not intended to limit the scope of this application.

[0202] In this application, "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone, where A and B can be singular or plural. The character " / " generally indicates that the related objects before and after it are in an "or" relationship.

[0203] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0204] In this application, "-" indicates a range value, including the endpoint values ​​at both ends. For example, the value of a can be 0.5-15, meaning that the value of a can be between 0.5 and 15, and includes the endpoint values ​​of 0.5 and 15.

[0205] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

Claims

1. A carbon material, characterized in that, The carbon material comprises multiple stacked layers of carbon atoms, and the in-plane thermal diffusivity of the carbon material is ≥800 mm. 2 / s, the Young's modulus of the carbon material is 1000Mpa-6000Mpa, the surface roughness Ra of the carbon material is ≤800nm, and the elongation at break of the carbon material is ≥2%.

2. The carbon material according to claim 1, characterized in that, The crystallographic L of the carbon material c Size greater than or equal to 50nm.

3. The carbon material according to claim 1 or 2, characterized in that, The degree of graphitization of the carbon material is greater than or equal to 0.

97.

4. The carbon material according to any one of claims 1-3, characterized in that, The interlayer spacing of the multilayer stacked carbon atoms is 0.3nm-0.5nm.

5. The carbon material according to any one of claims 1-4, characterized in that, The carbon material has native film properties within a thickness range of ≤2mm.

6. The carbon material according to any one of claims 1-5, characterized in that, The carbon material is bendable.

7. The carbon material according to any one of claims 1-6, characterized in that, The carbon material includes carbon film, carbon sheet, or carbon plate.

8. A method for preparing a carbon material, characterized in that, include: A graphene oxide dispersion is mixed with an additive to obtain a slurry. The slurry is coated onto a substrate, dried to form a graphene oxide film, and then peeled off from the substrate. The additive includes one or more of transition metal compounds, boron-containing materials, nitrogen-containing materials, and phosphorus-containing materials. Under air-isolated conditions, the graphene oxide film is heat-treated to cause the graphene oxide to undergo a pyrolysis reaction to generate graphene, thereby obtaining the heat-treated film material; the heat treatment includes heating to 250℃-400℃ at a first heating rate and holding at that temperature for a first time, then heating to 1000℃-1200℃ and holding at that temperature for a second time, and then heating to 2900℃-3300℃ at a second heating rate and holding at that temperature for a third time. The heat-treated film is calendered to obtain carbon material of the required thickness.

9. The preparation method according to claim 8, characterized in that, The transition metal compounds include one or more of transition metal oxides, transition metal carbides, and transition metal halides.

10. The preparation method according to claim 8 or 9, characterized in that, The transition metal compound includes one or more of Fe2O3, Fe5C2, FeCl3, Fe2(SO4)3, TiC, TiCl4, NiO, Ni(NO3)2, NiSO4, NiCl2, CoCl2, and CoO; the boron-containing material includes elemental boron and / or boron-containing compounds, wherein the boron-containing compound includes one or more of boric acid, triphenylboron, trimethyl borate, and neopentyl glycol diboronate; the nitrogen-containing material includes one or more of urea, ammonia, trimethylamine, nitromethane, and melamine; and the phosphorus-containing material includes one or more of tripoly(methoxyphosphoric acid) and tetrapoly(methoxyphosphoric acid).

11. The preparation method according to any one of claims 8-10, characterized in that, The graphene oxide dispersion and the additive are mixed at a mass ratio of graphene oxide to additive of 99.95:0.05-90:

10.

12. The preparation method according to any one of claims 8-11, characterized in that, The first heating rate is 5℃ / min-20℃ / min; the first time is 10h-60h; the second time is 20h-80h; the second heating rate is 0.2℃ / min-5℃ / min; and the third time is 15h-200h.

13. The preparation method according to any one of claims 8-12, characterized in that, During the heat treatment process, the temperature is increased to 1000℃-1200℃ and then pressurized at a pressure of 0.1Mpa-10Mpa.

14. The preparation method according to any one of claims 8-13, characterized in that, During the heat treatment process, the graphene oxide film is sandwiched between two thermally conductive media, such that each graphene oxide film is sandwiched between two thermally conductive media, and the thermal conductivity of the thermally conductive media is ≥100W / m*K.

15. The preparation method according to any one of claims 8-14, characterized in that, The substrate includes an organic polymer film or a metal foil; the drying temperature is 25℃-150℃.

16. The preparation method according to any one of claims 8-15, characterized in that, The pressure used in the calendering process is 0.1 MPa-120 MPa.

17. A thermally conductive composite material, characterized in that, The thermally conductive composite material comprises at least one layer of carbon material and at least two additional layers stacked together, wherein each carbon material is disposed between two additional layers; each additional layer is independently selected from a metal layer, a polymer layer, or a carbon fiber reinforced resin layer; the carbon material comprises the carbon material according to any one of claims 1-7 or the carbon material prepared by any one of claims 8-16.

18. The thermally conductive composite material according to claim 17, characterized in that, The metal layer is selected from copper, nickel, stainless steel or magnesium-aluminum alloy.

19. The thermally conductive composite material according to claim 17 or 18, characterized in that, The polymer layer comprises a flexible polymer material, which includes one or more of polyethylene terephthalate, polytetrafluoroethylene, polyimide, thermoplastic polyurethane elastomer, polyamide, parylene, and optical adhesive.

20. The thermally conductive composite material according to claim 19, characterized in that, The compression ratio of the flexible polymer material is 0-20%.

21. The thermally conductive composite material according to any one of claims 17-20, characterized in that, The thickness difference of the same polymer layer is ≤10%.

22. The thermally conductive composite material according to any one of claims 17-21, characterized in that, The carbon material is directly pressed together with the additional layer, or connected by an adhesive layer.

23. The thermally conductive composite material according to claim 22, characterized in that, The adhesive layer includes one or more of acrylic resin, silicone, epoxy resin, and optical adhesive.

24. The thermally conductive composite material according to any one of claims 17-21, characterized in that, The carbon material and the additional layer are connected by multiple adhesive pillars.

25. The thermally conductive composite material according to claim 24, characterized in that, The material of the adhesive column includes one or more of acrylic resin, silicone, epoxy resin, and optical adhesive.

26. The thermally conductive composite material according to claim 24 or 25, characterized in that, Each of the adhesive posts is simultaneously embedded in the adjacent carbon material and the additional layer, so that the adjacent carbon material and the additional layer form a riveted connection.

27. The thermally conductive composite material according to any one of claims 17-26, characterized in that, The thickness of the additional layer is 4μm-200μm.

28. The thermally conductive composite material according to any one of claims 17-27, characterized in that, The thickness ratio of the additional layer to the carbon material is greater than 0.5:

1.

29. The thermally conductive composite material according to any one of claims 17-28, characterized in that, Each of the additional layers is a polymer layer, and the Young's modulus of the thermally conductive composite material is 2 GPa-20 GPa; or at least one of the additional layers is a metal layer or a carbon fiber resin reinforcement layer, and the Young's modulus of the thermally conductive composite material is 50 GPa-150 GPa.

30. The thermally conductive composite material according to any one of claims 17-29, characterized in that, The pull-out force of the thermally conductive composite material is ≥0.05 MPa; The thermally conductive composite material has an elongation at break of ≥3%.

31. The thermally conductive composite material according to any one of claims 17-30, characterized in that, The surface roughness Ra of the thermally conductive composite material is ≤500nm; the step difference between the bonding surfaces of the carbon material and the additional layer is ≤1μm.

32. A display screen, characterized in that, It includes a display layer and a heat dissipation layer stacked on the backlight side of the display layer, wherein the heat dissipation layer includes the carbon material according to any one of claims 1-7, or the carbon material prepared by any one of claims 8-16, or the thermally conductive composite material according to any one of claims 17-31.

33. An electronic device, characterized in that, The device includes a housing and a display screen mounted on the housing, wherein the housing and / or the display screen comprises the carbon material as described in any one of claims 1-7, or the carbon material prepared by any one of claims 8-16, or the thermally conductive composite material as described in any one of claims 17-31.

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