Carbon-based heat conduction film and preparation method thereof

Abstract

The invention discloses a carbon-based heat conduction film and a preparation method thereof, and the carbon-based heat conduction film comprises a first structure layer which is prepared from graphene oxide in a first sheet diameter range; the second structural layer is made of a carbon-based material within a second sheet diameter range; the first structure layer and the second structure layer are at least partially stacked; the minimum value of the first sheet diameter range is greater than the maximum value of the second sheet diameter range; the microcosmic fold density of the first structural layer is greater than that of the second structural layer. The carbon-based heat-conducting film and the preparation method thereof have the beneficial effects that the carbon-based heat-conducting film with balanced heat-conducting property and bending resistance is obtained by adopting a film layer compounding mode, and the preparation method of the carbon-based heat-conducting film is provided.

Description

Technical Field

[0001] This application belongs to the field of thermal conductive materials technology, and in particular relates to a carbon-based thermal conductive film and its preparation method. Background Technology

[0002] With the advancement of modern technology, especially in fields such as microelectronics, semiconductors, and new energy, the problem of high heat flux density is becoming increasingly prominent. To effectively address heat dissipation issues in these fields, graphene thermal conductive films are widely used due to their superior thermal conductivity. As a key application material, graphene thermal conductive films are constructed through the self-assembly of graphene oxide sheets, creating a tightly structured thermally conductive film. This film exhibits excellent thermal conductivity and good electrical conductivity in the horizontal direction. With the continuous expansion of graphene thermal conductive film applications, especially in products prone to heat accumulation such as foldable screen phones, wearable electronic devices, and flexible sensors, it is often necessary to transfer this heat through hinges or bends to effectively prevent excessively high local temperatures. This requires the placement of flexible, highly thermally conductive materials in the hinge or bend areas. However, traditional graphite films or graphene thermal conductive films have limitations in terms of bending durability.

[0003] In some related technologies, graphene oxide is used as a raw material to prepare thermally conductive films with good flexibility (such as resistance to bending cycles). However, because such thermally conductive films require the microscopic wrinkles of graphene oxide to achieve sheet slippage properties, they sacrifice thermal conductivity while achieving high flexibility. Summary of the Invention

[0004] In view of this, this application provides a carbon-based thermally conductive film and its preparation method, aiming to solve the aforementioned technical problems.

[0005] According to a first aspect of this application, a carbon-based thermally conductive film is provided, comprising: a first structural layer made of a carbon-based material with a first sheet diameter range; a second structural layer made of a carbon-based material with a second sheet diameter range; the first structural layer and the second structural layer are at least partially stacked; the minimum value of the first sheet diameter range is greater than the maximum value of the second sheet diameter range; and the micro-fold density of the first structural layer is greater than the micro-fold density of the second structural layer.

[0006] Optionally, in some embodiments of this application, the ratio of the thickness of the second structural layer to the thickness of the first structural layer ranges from 0.25 to 4.

[0007] Optionally, in some embodiments of this application, the density of the carbon-based thermally conductive film ranges from 2.1 g / cm³. 3 Up to 2.3 g / cm 3; and / or, the thickness of the carbon-based thermally conductive film ranges from 20 μm to 100 μm; and / or, the thermal diffusivity of the carbon-based thermally conductive film ranges from 900 mm. 2 / s to 1100mm 2 / s; and / or, the thermal conductivity of the carbon-based thermal conductive film ranges from 1600 W / (m·K) to 2150 W / (m·K); and / or, the elongation at break of the carbon-based thermal conductive film ranges from 15% to 23%; and / or, the number of flexural cycles of the carbon-based thermal conductive film ranges from 600,000 to 1,000,000.

[0008] Optionally, in some embodiments of this application, the first film diameter range is from 100 μm to 300 μm; and / or, the second film diameter range is from 0.2 μm to 2 μm.

[0009] Optionally, in some embodiments of this application, the first structural layer is bonded to the second structural layer by means of a slurry coating.

[0010] According to a second aspect of this application, a method for preparing a carbon-based thermally conductive film is provided, comprising: providing a first film layer for constituting a first structural layer; providing a second film layer for constituting a second structural layer; combining the first film layer with the second film layer to obtain the carbon-based thermally conductive film; wherein the first structural layer is made of a carbon-based material with a first sheet diameter range; the second structural layer is made of a carbon-based material with a second sheet diameter range; the first structural layer and the second structural layer are at least partially stacked; the minimum value of the first sheet diameter range is greater than the maximum value of the second sheet diameter range; and the micro-fold density of the first structural layer is greater than the micro-fold density of the second structural layer.

[0011] Optionally, in some embodiments of this application, providing the first film layer as the first structural layer includes: providing a first aqueous slurry of graphene oxide to set the graphene oxide sheet diameter in the aqueous slurry within the first sheet diameter range; coating the first aqueous slurry onto the second film layer and then performing a first drying treatment to obtain the first film layer; combining the first film layer with the second film layer to obtain the carbon-based thermally conductive film includes: performing carbonization treatment, graphitization treatment and / or calendering treatment on the first film layer and the second film layer.

[0012] Optionally, in some embodiments of this application, the first sheet diameter range is from 100 μm to 300 μm; and / or, the pH value of the first aqueous slurry is from 6 to 7; and / or, the mass percentage of graphene oxide in the first aqueous slurry is from 0.5 to 5; and / or, the drying temperature of the first drying treatment is from 60°C to 100°C.

[0013] Optionally, in some embodiments of this application, providing the second film layer for constituting the second structural layer includes: providing a second aqueous slurry of graphene oxide; homogenizing the second aqueous slurry to reduce the diameter of the graphene oxide flakes in the aqueous slurry to within the range of the second flake diameter; and subjecting the homogenized aqueous slurry to a second coating process and a second drying process to obtain the second film layer.

[0014] Optionally, in some embodiments of this application, the second flake diameter range is from 0.2 μm to 2 μm; and / or, the pH value of the second aqueous slurry is from 6 to 7; and / or, the mass percentage of graphene oxide in the second aqueous slurry is from 0.5 to 5; and / or, the flake diameter of graphene oxide in the second aqueous slurry before homogenization is from 10 μm to 50 μm; and / or, the temperature of the second drying treatment is from 60°C to 100°C.

[0015] The beneficial effects of this application are: to provide a carbon-based thermally conductive film with balanced thermal conductivity and bending resistance obtained by means of film layer composite and the preparation method thereof. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 These are SEM images of carbon-based thermally conductive films provided in some embodiments of this application;

[0018] Figure 2 This is a schematic diagram of the main steps of the preparation method of carbon-based thermal conductive film provided in some embodiments of this application;

[0019] Figure 3 These are fitting curves showing the bending resistance and thermal conductivity of carbon-based thermally conductive films according to some embodiments of this application as a function of the thickness ratio of the second structural layer to the first structural layer.

[0020] Meaning of the reference numerals in the attached figures:

[0021] 101. First structural layer; 102. Second structural layer. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Furthermore, it should be understood that the specific embodiments described herein are only for illustration and explanation of this application and are not intended to limit this application.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0024] In this application, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in its actual use or operating state, specifically the drawing directions in the accompanying drawings; while "inner" and "outer" refer to the outline of the device. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". The terms first, second, third, etc., are used merely as illustrative purposes and do not impose numerical requirements or establish a numerical order.

[0025] 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. A and B can be singular or plural.

[0026] In this application, "at least one" means one or more, and "more than one" means two or more. "One 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.

[0027] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0028] Reference Figure 1 As shown, according to a first aspect of this application, this application provides a carbon-based thermal conductive film, which mainly includes: a first structural layer made of a carbon-based material with a first sheet diameter range; a second structural layer made of a carbon-based material with a second sheet diameter range; the first structural layer and the second structural layer are at least partially stacked; the minimum value of the first sheet diameter range is greater than the maximum value of the second sheet diameter range; and the micro-fold density of the first structural layer is greater than the micro-fold density of the second structural layer.

[0029] It should be noted that the micro-fold density in this application refers to the total length of micro-folds within a unit area at the micro level.

[0030] In some embodiments of this application, the ratio of the thickness of the second structural layer to the thickness of the first structural layer ranges from 0.25 to 4.

[0031] In some embodiments of this application, the density of the carbon-based thermally conductive film ranges from 2.1 g / cm³. 3 Up to 2.3 g / cm 3 .

[0032] As a specific approach, the thickness of the carbon-based thermal conductive film ranges from 20 μm to 100 μm.

[0033] As a specific solution, the thermal diffusivity of the carbon-based thermal conductive film ranges from 900 mm. 2 / s to 1100mm 2 / s;

[0034] As a specific solution, the thermal conductivity of the carbon-based thermal conductive film ranges from 1600 W / (m·K) to 2150 W / (m·K).

[0035] As a specific embodiment, the elongation at break of the carbon-based thermal conductive film ranges from 15% to 23%. As a specific embodiment, the number of flexural cycles of the carbon-based thermal conductive film ranges from 600,000 to 1,000,000.

[0036] In some embodiments of this application, the first film diameter range is from 100 μm to 300 μm. Specifically, the second film diameter range is from 0.2 μm to 2 μm.

[0037] In some embodiments of this application, the first structural layer is bonded to the second structural layer by means of a slurry coating.

[0038] Reference Figure 2 As shown, according to a second aspect of this application, this application provides a method for preparing a carbon-based thermally conductive film, which mainly includes the following steps:

[0039] S100: Provides a first film layer for constituting the first structural layer.

[0040] S200: Provides a second film layer for constituting the second structural layer.

[0041] S300: The first film layer is combined with the second film layer to obtain a carbon-based thermal conductive film.

[0042] Specifically, the first structural layer is made of a carbon-based material with a first sheet diameter range; the second structural layer is made of a carbon-based material with a second sheet diameter range; the first structural layer and the second structural layer are at least partially stacked; the minimum value of the first sheet diameter range is greater than the maximum value of the second sheet diameter range; and the micro-fold density of the first structural layer is greater than the micro-fold density of the second structural layer.

[0043] In some embodiments of this application, step S100 specifically includes the following steps:

[0044] S101: Provide a first aqueous slurry of graphene oxide to set the graphene oxide sheet diameter in the aqueous slurry within a first sheet diameter range.

[0045] S102: After coating the first aqueous slurry onto the second film layer, perform a first drying process to obtain the first film layer.

[0046] In some embodiments of this application, step S300 specifically includes the following steps:

[0047] S301: Carbonization, graphitization and / or calendering treatments are performed on the first and second film layers.

[0048] In some embodiments of this application, the first diameter range is from 100 μm to 300 μm.

[0049] Specifically, the pH value of the first aqueous slurry ranges from 6 to 7.

[0050] Specifically, the mass percentage of graphene oxide in the first aqueous slurry ranges from 0.5 to 5%.

[0051] Specifically, the drying temperature of the first drying process ranges from 60℃ to 100℃.

[0052] In some embodiments of this application, step S200 specifically includes:

[0053] S101: Provides a second aqueous slurry for graphene oxide;

[0054] S102: Homogenize the second aqueous slurry to reduce the graphene oxide sheet size in the aqueous slurry to within the second sheet size range; then perform a second coating process and a second drying process on the homogenized aqueous slurry to obtain a second film layer.

[0055] In some embodiments of this application, the second aperture range is from 0.2 μm to 2 μm.

[0056] Specifically, the pH value of the second aqueous slurry ranges from 6 to 7.

[0057] Specifically, the mass percentage of graphene oxide in the second aqueous slurry ranges from 0.5 to 5%.

[0058] Specifically, the graphene oxide flake size in the second aqueous slurry before homogenization ranges from 10 μm to 50 μm. Specifically, the temperature range for the second drying process is 60°C to 100°C.

[0059] As a specific embodiment, the preparation method of this application is detailed below:

[0060] Graphene oxide powder can be purchased or made in-house. High-purity natural graphite raw materials (carbon content > 99.9%) with a mesh size of 150 to 300 can be used to prepare graphene oxide through a modified Hummer method. The graphene oxide filter cake is obtained by pressure filtration and water washing purification.

[0061] The relevant indicators for graphene oxide are as follows: filter cake solid content ≥40%, oxygen content ≥40%, carbon content ≥40%, sulfur content ≤2%, chlorine content <1.5%, and sheet diameter D50 between 10μm and 50μm.

[0062] Graphene oxide is prepared into an aqueous slurry of 0.5% to 5%. The pH of the slurry is adjusted to between 6 and 7 with ammonia. The slurry is then homogenized 3 to 10 times to ensure uniformity. Simultaneously, homogenization can peel the graphene oxide sheets to a diameter between 0.5 μm and 2 μm. The second film layer is obtained by coating with a coating machine and drying in a 60°C oven. The thickness of the second film layer can be adjusted according to the coating thickness.

[0063] Graphene oxide can be purchased or made in-house. High-purity natural graphite raw materials (carbon content > 99.9%) with a mesh size of 50 to 80 can be used to prepare large-diameter graphene oxide through a modified Hummer method. The graphene oxide filter cake is obtained by pressure filtration and water washing purification.

[0064] The relevant indicators for graphene oxide are as follows: filter cake solid content ≥40%, oxygen content ≥40%, carbon content ≥40%, sulfur content ≤2%, chlorine content <1.5%, and sheet diameter D50 between 100 and 300 μm.

[0065] Graphene oxide is prepared into an aqueous slurry of 0.5% to 5%. The pH of the slurry is adjusted to between 6 and 7 with ammonia. The slurry does not require homogenization and maintains its large sheet size. The slurry is then uniformly coated onto one or both sides of the second film layer using a coating machine and dried in a 60°C oven to obtain a carbon-based thermally conductive film. The thickness of the first original film component can be adjusted according to the coating thickness.

[0066] The carbon-based thermally conductive film is heat-treated in a protective gas atmosphere at 200°C to 400°C, then carbonized in a protective gas atmosphere at 900°C to 1200°C, and finally graphitized in a protective gas atmosphere (argon, nitrogen, or other inert gases) at 2800°C to 3100°C.

[0067] The graphitized carbon-based thermally conductive film is statically cold-pressed on a membrane press at pressures ranging from 2000 kN to 3000 kN, increasing the density of the graphene composite thermally conductive film to ≥2.1 g / cm³. 3 A high thermal conductivity and high flexibility graphene composite thermal conductive film was obtained. The thickness of the composite thermal conductive film is 20μm to 100μm, the thermal diffusivity is in the range of 900mm / s to 1100mm / s, the thermal conductivity is in the range of 1600W / (m·K) to 2150W / (m·K), the elongation at break is 15% to 23%, and the bending resistance is 600,000 to 1,000,000 cycles.

[0068] The above-described scheme enables the carbon-based thermally conductive film to possess both highly oriented and highly wrinkled structural characteristics, while also exhibiting ultra-high in-plane thermal conductivity and excellent flexibility. This allows for the uniform transfer of heat from a point heat source to a large surface area, where heat is then dissipated through large-area convection and radiation. This characteristic enables the flexible thermally conductive film to more effectively disperse and dissipate heat in electronic devices, preventing localized overheating and thus extending the device's lifespan.

[0069] Furthermore, the aforementioned carbon-based thermal conductive film can adapt to complex spatial structures, closely adhere to various parts of the equipment, ensure that heat can be uniformly conducted, and avoid the heat dissipation blind spots of traditional heat dissipation materials in complex structures.

[0070] Furthermore, carbon-based thermal conductive films possess strong bending resistance and ultra-high thermal conductivity, making them particularly effective in heat dissipation applications for foldable screen phones.

[0071] Furthermore, this approach can achieve the mixing of two internal microstructures (highly oriented structure and highly wrinkled structure) in the same graphene film material without introducing other impurities. The intrinsic material properties of the two structures are consistent, enabling efficient heat transfer while ensuring that the film has high flexibility.

[0072] From a production perspective, the raw material particle size and coating thickness of the aforementioned carbon-based thermal conductive film can achieve the ratio control of two structures: a highly oriented microstructure and a highly wrinkled microstructure. This method is convenient, efficient, and mass-producible.

[0073] The present application will be further described below with reference to specific embodiments.

[0074] Example 1 (R = 0.25)

[0075] Graphene oxide was prepared using 300-mesh high-purity (99.93% carbon content) natural graphite raw material through a modified Hummer method, and purified by pressure filtration and water washing to obtain graphene oxide filter cake.

[0076] The relevant indicators of graphene oxide are as follows: filter cake solid content 40.5%, oxygen content 42.5%, carbon content 42.7%, sulfur content 1.95%, chlorine content 1.05%, and sheet diameter D50 of 32μm.

[0077] Take 98.8g of graphene oxide filter cake, 3673.7g of pure water and 10g of ammonia water, place them in a planetary mixer and stir to prepare an aqueous slurry containing 1% graphene oxide. The pH of the slurry was measured to be 6.5. The slurry was then homogenized three times to ensure uniformity, with homogenization pressures of 750 bar, 850 bar and 850 bar respectively.

[0078] The homogenized graphene oxide sheet diameter was characterized to be 2.0 μm. The sheet was coated with a coating machine to a thickness of 0.4 mm. The coated original film was then dried in a forced-air drying oven at 60 °C for 8 h to obtain a dried graphene oxide second film with a thickness of 8 μm.

[0079] Graphene oxide was prepared using 50-mesh high-purity (99.93% carbon content) natural graphite raw material through a modified Hummer method, and then purified by pressure filtration and water washing to obtain graphene oxide filter cake.

[0080] The relevant indicators of graphene oxide are as follows: filter cake solid content 41.5%, oxygen content 42.3%, carbon content 42.5%, sulfur content 1.35%, chlorine content 0.85%, and sheet diameter D50 of 280μm.

[0081] 592.6g of graphene oxide filter cake, 1837g of pure water and 30g of ammonia were placed in a planetary mixer and stirred to prepare an aqueous slurry containing 6% graphene oxide. The pH of the slurry was measured to be 6.5. The slurry did not require homogenization to maintain its large sheet size. The slurry was then evenly coated on both sides of the second film layer using a coating machine to a thickness of 2.0mm. The film was then dried in an oven at 60℃ to obtain a dried carbon-based thermal conductive film with a thickness of 48μm.

[0082] The dried membrane was then placed in a muffle furnace for heat treatment at 400°C under a protective N2 atmosphere for 2 hours. After heat treatment, the membrane was placed in a carbonization furnace and carbonized at 900°C under a protective N2 atmosphere. The carbonized membrane was then vertically placed in a graphitization furnace for heat treatment at 2800°C under a protective N2 atmosphere for 1 hour.

[0083] The graphitized carbon-based thermally conductive film was statically cold-pressed on a membrane press using 7075 aerospace-grade aluminum plate as a fixture. The pressurization rate was 60 kN / s, the target pressure was 3200 kN, the pressure was held for 1 second, and the pressing cycle was 60 times. The final carbon-based thermally conductive film was obtained, with a thickness of 40 μm, a density of 2.18 g / cm³, a thermal diffusivity of 880 mm / s, a thermal conductivity of 1631 W / mK, an elongation at break of 23%, and a bending resistance of 1,100,000 cycles.

[0084] The ratio of the thickness of the second structure formed by the second film layer to the thickness of the first structure formed by the first film layer is defined as the interlayer ratio R. In Example 1, the interlayer ratio R is 0.25.

[0085] Example 2 (R = 0.33)

[0086] Except for the interlayer ratio R being 0.33, the rest is the same as in Example 1.

[0087] Example 3 (R = 0.5)

[0088] Except for the interlayer ratio R being 0.5, the rest is the same as in Example 1.

[0089] Example 4 (R = 0.75)

[0090] Except for the interlayer ratio R being 0.75, the rest is the same as in Example 1.

[0091] Example 5 (R=1)

[0092] Except for the interlayer ratio R being 1, everything else is the same as in Example 1.

[0093] Example 6 (R=1.5)

[0094] Except for the interlayer ratio R being 1.5, the rest is the same as in Example 1.

[0095] Example 7 (R=2.0)

[0096] Except for the interlayer ratio R being 2.0, the rest is the same as in Example 1.

[0097] Example 8 (R=3.0)

[0098] Except for the interlayer ratio R being 3.0, the rest is the same as in Example 1.

[0099] Example 9 (R = 4.0)

[0100] Except for the interlayer ratio R being 4, the rest is the same as in Example 1.

[0101] Example 10 (R = 5.0)

[0102] Except for the interlayer ratio R being 5, the rest is the same as in Example 1.

[0103] Comparative Example 1

[0104] Graphene oxide is prepared by purchasing or manufacturing it in-house using 300-mesh high-purity (99.93% carbon content) natural graphite raw materials through a modified Hummer method. The resulting graphene oxide filter cake is purified by pressure filtration and water washing. The relevant parameters of the graphene oxide are as follows: filter cake solids content 40.5%, oxygen content 42.5%, carbon content 42.7%, sulfur content 1.95%, chlorine content 1.05%, and sheet diameter D50 of 32 μm.

[0105] 296.3g of graphene oxide filter cake, 3673.7g of pure water, and 30g of ammonia were placed in a planetary mixer and stirred to prepare an aqueous slurry containing 3% graphene oxide. The pH of the slurry was measured to be 6.5. The slurry was homogenized three times using a homogenizer at pressures of 750 bar, 850 bar, and 850 bar, respectively. The diameter of the homogenized graphene oxide flakes was characterized to be 0.8 μm. The slurry was then coated with a coating machine to a thickness of 3 mm. The coated film was placed in a 60℃ forced-air drying oven for 8 hours to dry, resulting in a film thickness of 150μm. The dried film was then placed in a muffle furnace for heat treatment at 400℃ under a protective N2 atmosphere for 2 hours. After heat treatment, the film was placed in a carbonization furnace and carbonized at 900℃ under a protective N2 atmosphere. The carbonized film was then vertically placed in a graphitization furnace for heat treatment at 3000℃ under a protective N2 atmosphere for 1 hour.

[0106] The graphitized RGO membrane was removed and subjected to static cold pressing on a membrane press using 7075 aerospace aluminum plates as fixtures. The pressurization rate was 60 kN / s, the target pressure was 3000 kN, the pressure was held for 1 second, and the pressing cycle was 60 times. The resulting RGO thermally conductive membrane had a thickness of 40 μm, a density of 2.28 g / cm³, a thermal diffusivity of 1065 mm / s, a thermal conductivity of 2064 W / mK, an elongation at break of 1.8%, and a bending resistance of 5814 cycles.

[0107] Comparative Example 2

[0108] Graphene oxide is prepared by purchasing or manufacturing it in-house using 80-mesh high-purity (99.93% carbon content) natural graphite raw materials through a modified Hummer process. The resulting graphene oxide filter cake is purified by pressure filtration and water washing. The relevant parameters of the graphene oxide are as follows: filter cake solids content 41.5%, oxygen content 42.3%, carbon content 42.5%, sulfur content 1.35%, chlorine content 0.85%, and sheet diameter D50 of 150 μm.

[0109] 296.3g of graphene oxide filter cake, 3673.7g of pure water, and 30g of ammonia were placed in a planetary stirrer and stirred to prepare an aqueous slurry containing 3% graphene oxide. The pH of the slurry was measured to be 6.5. The slurry was coated with a coating machine to a thickness of 3mm. The coated film was then dried in a 60℃ forced-air drying oven for 8 hours, resulting in a film thickness of 150μm. The dried film was then heat-treated in a muffle furnace at 400℃ under a protective N2 atmosphere for 2 hours. The heat-treated film was then placed in a carbonization furnace at 900℃ under a protective N2 atmosphere for carbonization. Finally, the carbonized film was vertically placed in a graphitization furnace for heat treatment at 3000℃ under a protective N2 atmosphere for 1 hour.

[0110] The graphitized RGO membrane was removed and subjected to static cold pressing on a membrane press using 7075 aerospace aluminum plates as fixtures. The pressurization rate was 60 kN / s, the target pressure was 3000 kN, the pressure was held for 1 second, and the pressing cycle was 60 times. The resulting RGO thermally conductive membrane had a thickness of 40 μm, a density of 2.19 g / cm³, a thermal diffusivity of 850.8 mm / s, a thermal conductivity of 1583.8 W / mK, an elongation at break of 24.2%, and a bending resistance of 1500134 cycles.

[0111] The performance of the above embodiments and comparative examples is shown in Table 1.

[0112] Table 1

[0113]

[0114]

[0115] Table 2

[0116] R value Thermal conductivity trend Bending resistance trend Typical applications ＞3 Approaching the maximum value of the pure second structural layer Approximately the minimum requirement Fixed high-power heat sink 0.75 to 3 Equilibrium range Commercial foldable screens meet standards Phone / Tablet hinge area ＜0.75 33% higher than the pure first structural layer industry top level Flexible wearable devices

[0117] Table 1 shows the R-values ​​and performance parameters for the examples and comparative examples; Table 2 shows the correspondence between R-values, bending resistance trends, and typical applications.

[0118] Refer to Table 1 and Figure 3 As can be seen, the thermal conductivity gradually decreases while the bending resistance gradually increases as the R value increases. This shows that increasing the thickness of the first structural layer improves the bending resistance, but the corresponding thermal conductivity is affected to some extent. Therefore, a suitable R value needs to be selected to simultaneously achieve the required thermal conductivity and bending resistance. Referring to Table 2, when the R value ranges from 0.75 to 3, the carbon-based thermal conductive film of this application is more suitable for applications such as foldable screens.

[0119] Especially when the R value is in the range of 1 to 2, the carbon-based thermal conductive film of this application exhibits a relatively balanced bending performance and thermal conductivity, maintaining a bending resistance of over 80W cycles while keeping the thermal conductivity close to 1800W / mK. Outside this range, the bending resistance decreases rapidly with increasing R value, while the improvement in thermal conductivity slows down. Therefore, from the perspective of overall performance balance and film thickness, this range has significant advantages.

[0120] The technical solutions provided by the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A carbon-based thermally conductive film, characterized in that: The carbon-based thermally conductive film includes: The first structural layer is made of a carbon-based material within a first sheet diameter range; The second structural layer is made of carbon-based material within the second sheet diameter range; The first structural layer and the second structural layer are at least partially stacked; The minimum value of the first sheet diameter range is greater than the maximum value of the second sheet diameter range; the micro-fold density of the first structural layer is greater than the micro-fold density of the second structural layer.

2. The carbon-based thermally conductive film according to claim 1, characterized in that: The ratio of the thickness of the second structural layer to the thickness of the first structural layer ranges from 0.25 to 4.

3. The carbon-based thermally conductive film according to claim 1, characterized in that: in, The density of the carbon-based thermally conductive film ranges from 2.1 g / cm³. 3 Up to 2.3 g / cm 3 ; And / or, the thickness of the carbon-based thermally conductive film ranges from 20 μm to 100 μm; And / or, the thermal diffusivity of the carbon-based thermally conductive film ranges from 900 mm. 2 / s to 1100mm 2 / s; And / or, the thermal conductivity of the carbon-based thermal conductive film ranges from 1600 W / (m·K) to 2150 W / (m·K); And / or, the elongation at break of the carbon-based thermal conductive film ranges from 15% to 23%; And / or, the number of flexural cycles of the carbon-based thermal conductive film ranges from 600,000 to 1,000,000.

4. The carbon-based thermally conductive film according to claim 1, characterized in that: in, The first sheet diameter range is from 100 μm to 300 μm; And / or, the second sheet diameter range is from 0.2 μm to 2 μm.

5. The carbon-based thermally conductive film according to claim 1, characterized in that: The first structural layer is bonded to the second structural layer by means of a slurry coating.

6. A method for preparing a carbon-based thermally conductive film, characterized in that: The preparation method includes: A first film layer is provided to form the first structural layer; A second film layer is provided for constituting the second structural layer; The first film layer is combined with the second film layer to obtain the carbon-based thermal conductive film; Wherein, the first structural layer is made of a carbon-based material with a first sheet diameter range; the second structural layer is made of a carbon-based material with a second sheet diameter range; The first structural layer and the second structural layer are at least partially stacked; The minimum value of the first sheet diameter range is greater than the maximum value of the second sheet diameter range; the micro-fold density of the first structural layer is greater than the micro-fold density of the second structural layer.

7. The preparation method according to claim 6, Its features are: The first film layer provided as the first structural layer includes: A first aqueous slurry of graphene oxide is provided, wherein the graphene oxide sheet diameter in the aqueous slurry is set within the first sheet diameter range; The first aqueous slurry is coated onto the second film layer and then subjected to a first drying process to obtain the first film layer. The step of combining the first film layer with the second film layer to obtain the carbon-based thermally conductive film includes: The first film layer and the second film layer are subjected to carbonization, graphitization and / or calendering treatment.

8. The preparation method according to claim 7, characterized in that: in, The first sheet diameter range is from 100 μm to 300 μm; And / or, the pH value of the first aqueous slurry is in the range of 6 to 7; And / or, the mass percentage of graphene oxide in the first aqueous slurry ranges from 0.5 to 5; And / or, the drying temperature of the first drying process is in the range of 60°C to 100°C.

9. The preparation method according to claim 6, Its features are: The provision of the second film layer for constituting the second structural layer includes: Provides a second aqueous slurry for graphene oxide; The second aqueous slurry is homogenized to reduce the diameter of the graphene oxide sheets in the aqueous slurry to within the range of the second sheet diameter. The aqueous slurry that has undergone homogenization is subjected to a second coating process and a second drying process to obtain the second film layer.

10. The preparation method according to claim 9, characterized in that: in, The second sheet diameter range is from 0.2 μm to 2 μm; And / or, the pH value of the second aqueous slurry is in the range of 6 to 7; And / or, the mass percentage of graphene oxide in the second aqueous slurry ranges from 0.5 to 5; And / or, the graphene oxide in the second aqueous slurry has a sheet diameter ranging from 10 μm to 50 μm before the homogenization treatment; And / or, the temperature range for the second drying process is 60°C to 100°C.

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