A carbon-based composite material and its preparation method and application

Abstract

The present invention provides a carbon-based composite material, comprising two graphene layers; at least one spiral carbon fiber layer is provided between the two graphene layers; the spiral carbon fiber layer is composed of hollow spiral carbon fibers laid in parallel, and the twisting directions of adjacent hollow spiral carbon fibers are opposite; when two or more spiral carbon fiber layers are provided between the graphene layers, the axes of the hollow spiral carbon fibers in adjacent spiral carbon fiber layers are not parallel; the graphene layer is fixedly connected to the spiral carbon fiber layer; adjacent spiral carbon fiber layers are fixedly connected; adjacent hollow spiral carbon fibers are fixedly connected. The present invention also provides a preparation method and application of the carbon-based composite material.

Description

Technical Field

[0001] The present invention relates to a novel composite material, in particular to a carbon-based composite material with high thermal conductivity and high compression rebound performance. The material can be manufactured by a specific preparation method and can be used in the field of thermal management materials to meet the development needs of applications such as high-end electronic products and new energy batteries. Background Art

[0002] With the continuous improvement of the integration and power density of electronic devices, thermal management issues have become a key bottleneck restricting their performance and reliability. Taking new energy vehicle batteries as an example, if the heat generated during the charging and discharging process cannot be dissipated in time, it will lead to battery life decay, reduced safety, and even thermal runaway risks. For 5G base stations, high-performance computers and other equipment, the need for heat dissipation under high heat flux density is equally urgent. Existing thermal management materials are difficult to achieve a balance of performance. Although polymer materials have a certain degree of flexibility, their thermal conductivity is generally lower than 1 W / (m·K), and they are prone to aging and failure after long-term use, making it difficult to meet the heat dissipation needs of high-power equipment. Although metal materials have high thermal conductivity, they have high density and are prone to electrochemical corrosion in humid or corrosive environments, which limits their application in lightweight and high-reliability scenarios. Graphite materials have high in-plane thermal conductivity, but low interlayer thermal conductivity and high brittleness, making it difficult to adapt to complex stress environments.

[0003] Carbon fiber is a high-performance fiber material with many unique functions and structural characteristics. From a functional point of view, carbon fiber has high strength and high modulus, lightweight, corrosion resistance, high temperature resistance, and good electrical and thermal conductivity. In terms of structure, carbon fiber has the characteristics of fibrous structure, high specific surface area, and high crystallinity. Especially in terms of thermal conductivity, carbon fiber has high thermal conductivity in the axial direction, but in the radial direction, due to the scattering of phonon layers, the thermal conductivity is relatively low, resulting in significant anisotropy in the in-plane thermal conductivity direction of traditional carbon fiber composites. Therefore, in the process of using carbon fiber to prepare high thermal conductivity interface materials, magnetic fields, electric fields or flow fields are often used to induce the directional arrangement of carbon fibers, but this type of method is complex and energy-intensive, and it is difficult to achieve the construction of a three-dimensional thermal conductive network, and it is not easy to mass-produce on a large scale.

[0004] In addition, the existing thermal management materials are also difficult to meet the requirements of high-end applications in terms of mechanical properties. For example, automotive batteries need to withstand repeated impacts in a vibrating environment, requiring materials to have both high elastic modulus and compression rebound properties; wearable devices require materials to maintain stable thermal conductivity after bending and deformation. Traditional materials are prone to permanent deformation due to insufficient rigidity, or the interface contact thermal resistance increases due to excessively high elastic modulus, and both cannot achieve the coordinated optimization of thermal conductivity and mechanical properties.

[0005] The present invention aims to provide a carbon-based composite material that has high thermal conductivity, light weight, high compression rebound performance, high temperature resistance and corrosion resistance. Through the unique three-dimensional interconnected structure of hollow spiral carbon fiber layers and graphene layers, it breaks through the bottleneck of thermal conductivity and mechanical properties of existing materials and provides innovative solutions to thermal management problems in high-end electronic equipment and new energy fields. Summary of the invention

[0006] The first object of the present invention is to provide a carbon-based composite material with high thermal conductivity, light weight and high resilience.

[0007] The present invention and the second object is to provide a method for preparing the carbon-based composite material.

[0008] The third object of the present invention is to provide an application of the carbon-based composite material.

[0009] The present invention is achieved through the following technical solutions:

[0010] A carbon-based composite material comprising two graphene layers;

[0011] At least one spiral carbon fiber layer is provided between the two graphene layers;

[0012] The spiral carbon fiber layer is composed of hollow spiral carbon fibers laid in parallel, and the twisting directions of adjacent hollow spiral carbon fibers are opposite;

[0013] When two or more spiral carbon fiber layers are provided between the graphene layers, the axes of the hollow spiral carbon fibers in adjacent spiral carbon fiber layers are not parallel;

[0014] The graphene layer is fixedly connected to the spiral carbon fiber layer;

[0015] Adjacent spiral carbon fiber layers are fixedly connected;

[0016] Adjacent hollow spiral carbon fibers are fixedly connected.

[0017] The thickness of the graphene layer is 15-30 μm;

[0018] The hollow spiral carbon fiber is obtained by twisting PAN-based carbon fiber;

[0019] The diameter of the PAN-based carbon fiber is 6-8 μm.

[0020] The inner diameter of the hollow spiral carbon fiber is 0.2-0.6 mm;

[0021] The outer diameter of the hollow spiral carbon fiber is 0.5-1.5 mm;

[0022] The angle between the axes of the hollow spiral carbon fibers in adjacent spiral carbon fiber layers is 30-90 degrees; or,

[0023] The angle between the axes of the hollow spiral carbon fibers in adjacent spiral carbon fiber layers is 75-90 degrees; or,

[0024] The angle between the axes of the hollow spiral carbon fibers in adjacent spiral carbon fiber layers is 90 degrees.

[0025] A method for preparing the carbon-based composite material comprises the following steps:

[0026] S1 twists the PAN-based carbon fiber so that it is wound on the surface of the core material to obtain a core-belted spiral carbon fiber;

[0027] S2 immerses the cored helical carbon fiber in a GO solution and then dries it I to obtain a cored helical carbon fiber coated with a GO sheath;

[0028] S3: arranging a single layer or multiple layers of core spiral carbon fiber coated with GO sheath in parallel to obtain a single layer or multiple layers of spiral carbon fiber layer;

[0029] S4 brushes GO slurry on the upper and lower surfaces of the single-layer or multi-layer spiral carbon fiber layer, and then dries Ⅱ to form a GO slurry layer; then immerses it in a phenolic resin-ethanol solution, vacuum impregnates and dries Ⅲ, and hot presses to obtain a carbon-based composite material that has not been heat-treated;

[0030] S5: graphitizing the unheat-treated carbon-based composite material to carbonize the phenolic resin and convert GO into graphene.

[0031] The core material includes nylon thread;

[0032] The diameter of the core material is 0.2 mm;

[0033] The twisting degree of the twisting is 200-450;

[0034] The concentration of the GO solution is 5-10 mg / mL;

[0035] The pyrogen used in the drying I includes an infrared heat source;

[0036] The power of the infrared heat source is 2000W;

[0037] The thickness of the GO sheath is 5-10 μm;

[0038] The concentration of the GO slurry is 10-20 mg / mL;

[0039] The temperature of the drying II is 70-75°C;

[0040] The concentration of the phenolic resin-ethanol is 5-7wt%;

[0041] The temperature of the hot pressing is 120-125°C;

[0042] The hot pressing pressure is 1-1.5 MPa;

[0043] The holding temperature of the hot pressing is 180-200°C;

[0044] The holding time of the hot pressing is 30-40min;

[0045] The graphitization temperature is 2900-3100°C.

[0046] The carbon-based composite material is used to prepare a thermal management system; or

[0047] Used in preparing battery systems.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The carbon-based composite material provided by the present invention has a spiral structure. The fiber orientation of the structure can enhance the thermal conductivity of the carbon-based composite material. This is because the axial thermal conductivity of carbon fiber is much greater than the radial direction, and the spiral structure enables the fiber to obtain a diameter direction orientation, so the thermal conductivity of the carbon-based composite material is improved.

[0050] The carbon-based composite material provided by the present invention is provided with a hollow spiral carbon fiber layer. Since the hollow spiral carbon fiber is a hollow structure inside, it has a smaller mass than solid carbon fiber. This makes the hollow spiral carbon fiber advantageous in applications requiring light weight, such as aerospace and automobile manufacturing. Since the hollow spiral carbon fiber is a hollow structure inside the fiber, it can be regarded as a micro spring and has excellent compression rebound performance.

[0051] The carbon-based composite material provided by the present invention is a full-carbon structure, and thus has the characteristics of high temperature resistance, corrosion resistance, flame retardancy, and high and low temperature resistance.

[0052] The preparation method of the carbon-based composite material provided by the present invention is simple and has industrial prospects. With the rapid development of electronic technology, the integration and power density of electronic devices are constantly improving, and the requirements for heat dissipation materials are becoming increasingly stringent. This high thermal conductivity and high resilience material can effectively improve the reliability and service life of electronic products, while reducing energy consumption and the risk of heat accumulation. When impacted by external forces, it can restore its original shape and reduce the impact of vibration and impact on the equipment. This performance is particularly important in fields that require shock absorption, such as aerospace, automobile manufacturing, precision instruments, etc. In these fields, high resilience can ensure the stability and durability of the material in extreme environments.

[0053] The carbon-based composite material provided by the present invention is a structural and functional integrated material. Due to its good thermal conductivity and high resilience, it can be applied to technical fields that require both heat dissipation and shock absorption, such as the battery field, thermal management field, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 The diagram shows the z-direction deformation of the hollow spiral carbon fiber when the carbon-based composite material provided by the present invention is subjected to force in the z-direction.

[0055] Figure 2 The diagram shows the deformation of the hollow spiral carbon fiber in the x direction when the carbon-based composite material provided by the present invention is subjected to force in the z direction.

[0056] Figure 3 A schematic diagram of the preparation process of carbon-based composite materials is shown.

[0057] Figure 4 (a) shows the SEM image of PAN-based carbon fibers provided in Example 1.

[0058] Figure 4 (b) shows a photo of the spiral carbon fiber production device provided in Example 1.

[0059] Figure 4 (c) shows the SEM image of the helical carbon fiber provided in Example 1.

[0060] Figure 4 (d) shows the SEM image of the graphene oxide (GO) coated helical carbon fiber provided in Example 1.

[0061] Figure 5 The XY plane SEM image of the carbon-based composite material provided in Example 1 is shown.

[0062] Figure 6 The Z-plane SEM image of the carbon-based composite material provided in Example 1 is shown. DETAILED DESCRIPTION

[0063] The present invention provides a carbon-based composite material, the basic structure of which is a sandwich structure consisting of two graphene layers and at least one hollow spiral carbon fiber layer. The structure is a micro-spring-like structure with both high thermal conductivity and high resilience. Figure 1 As shown, unlike ordinary springs, when the graphene layer is subjected to force, the force will be transferred to the hollow spiral carbon fibers in the hollow spiral carbon fiber layer, causing the hollow spiral carbon fibers to produce a compression deformation perpendicular to their axial direction (common springs produce compression deformation parallel to their axial direction), which makes the carbon-based composite material have good rebound performance. Figure 2As shown, since the twisting directions of the adjacent hollow spiral carbon fibers in the spiral carbon fiber layer are opposite, and the adjacent hollow spiral carbon fibers are fixedly connected, an interlocking structure is formed between the adjacent hollow spiral carbon fibers. When the graphene layer is subjected to force, the hollow spiral carbon fiber is difficult to bend and deform, and instead bends and deforms, which also makes the sandwich structure have good resilience. Further, since the hollow spiral carbon fiber can provide a heat conduction channel in the z direction, the carbon-based composite material provided by the present invention has a structural functional integrated material with good three-dimensional thermal conductivity and good resilience. The graphene layer is fixedly connected to the spiral carbon fiber layer. Therefore, when subjected to force, no slippage occurs between the graphene layer and the spiral carbon fiber layer, which improves the structural stability of the material. The carbon-based composite material can be provided with multiple layers of graphene layers, and a spiral carbon fiber layer can be provided between each layer of graphene layer. This carbon-based composite material with multiple layers of graphene layers can be regarded as a carbon-based composite material composed of two layers of graphene layers superimposed. The more layers of graphene layers, the better its resilience. Multiple spiral carbon fiber layers may also be arranged between every two graphene layers. When two or more spiral carbon fiber layers are arranged between the graphene layers, the axes of the hollow spiral carbon fibers in adjacent spiral carbon fiber layers are not parallel, and the adjacent spiral carbon fiber layers are fixedly connected. Setting the axes of the hollow spiral carbon fibers in adjacent spiral carbon fiber layers to be non-parallel can effectively prevent slippage between adjacent spiral carbon fiber layers when the carbon-based composite material is subjected to force. Obviously, the carbon-based composite material may also be a stack of the above basic structures.

[0064] The thickness of the graphene layer is 5-15 μm. This is because if the thickness is too thin, it is easy to cause incomplete graphene infiltration and coverage, resulting in the exposure of the spiral carbon fiber layer, thereby affecting the thermal conductivity; if the thickness is too large, the graphene layer is prone to brittle fracture during operation.

[0065] The hollow spiral carbon fiber is obtained by twisting PAN-based carbon fibers; PAN-based carbon fibers have a relatively small modulus and a relatively high strength among carbon fibers, and are relatively difficult to break during the twisting operation.

[0066] The diameter of the PAN-based carbon fiber is 6-8 μm.

[0067] The inner diameter of the hollow spiral carbon fiber is consistent with the diameter range of the nylon fiber, which is 0.2-0.6 mm. If the inner diameter of the hollow spiral carbon fiber is too small, the deformation resilience of the final sandwich carbon / carbon sheet will be significantly reduced.

[0068] The outer diameter of the hollow spiral carbon fiber is 0.5-1.5 mm.

[0069] The angle between the axes of the hollow spiral carbon fibers in adjacent spiral carbon fiber layers is 30-90 degrees; this angle can effectively prevent slippage between adjacent spiral carbon fiber layers.

[0070] Further preferably, the angle between the axes of the hollow spiral carbon fibers in adjacent spiral carbon fiber layers is 75-90 degrees.

[0071] More preferably, when the angle between the axes of the hollow spiral carbon fibers in adjacent spiral carbon fiber layers is 90 degrees, it is difficult for the adjacent spiral carbon fiber layers to slip.

[0072] The present invention also provides a method for preparing the carbon-based composite material, in which PAN-based carbon fibers that are difficult to graphitize, phenolic resin, core materials and graphene oxide (GO) that can be graphitized are used as raw materials to prepare the carbon-based composite material.

[0073] Specifically, first, PAN-based carbon fiber is wound on the surface of the core material to obtain a cored spiral carbon fiber. PAN-based carbon fiber itself has a certain elasticity, so it can be wound. The core material is usually an organic material, and during the heat treatment process, elements such as oxygen and nitrogen will be converted into gas and volatilized, leaving only a small amount of carbon, so that after the heat treatment, the cored spiral carbon fiber will be transformed into a spiral carbon fiber.

[0074] The cored helical carbon fiber is then immersed in a GO solution and dried. This will coat the cored helical carbon fiber with a GO sheath. The reason for coating the cored helical carbon fiber with a GO sheath is that during the subsequent heat treatment, GO will be converted into graphene, during which adjacent helical carbon fibers will bond together to form a fixed connection.

[0075] Then, the cored spiral carbon fibers coated with GO sheaths were laid in parallel to obtain a spiral carbon fiber layer that had not been heat-treated.

[0076] After GO slurry is applied to the upper and lower surfaces of the unheat-treated spiral carbon fiber layer and dried, a GO slurry layer is formed on the unheat-treated spiral carbon fiber layer. During the heat treatment process, the GO slurry layer is converted into a graphene layer. At the same time, the GO sheath and the GO slurry layer are converted at the same time, thereby achieving a fixed connection between the spiral carbon fiber layer and the graphene layer.

[0077] The phenolic resin-ethanol solution is vacuum impregnated and dried to remove the ethanol. The purpose is to use the phenolic resin as a temporary adhesive to fix the position of the spiral carbon fiber with core in the ungraphitized carbon-based composite material and stabilize the structure of the board. This is because the phenolic resin softens during the hot pressing process, and after cooling, the phenolic resin will solidify. After high-temperature pyrolysis of the phenolic resin, pyrolysis carbon is formed. The pyrolysis carbon can not only enhance the thermal conductivity of the carbon-based composite material, but also strengthen the fixed connection of the interface layer in the carbon-based composite material.

[0078] Finally, the ungraphitized carbon-based composite material is heat-treated to carbonize the phenolic resin, graphitize the GO, and carbonize the core material to obtain a composite material.

[0079] The core material includes nylon thread, polyester fiber, polyethylene fiber, polypropylene fiber or polyurethane fiber; the above fibers have a certain mechanical strength for easy operation, and low carbon residue during high-temperature heat treatment is conducive to the formation of a hollow cavity.

[0080] The diameter of the core material is 0.2-0.6 mm;

[0081] The twisting degree of the twisting is 200 to 450. The higher the twist degree, the more turns the fiber rotates per unit length. Since the modulus of the carbon fiber itself is relatively high, a higher twist number cannot be achieved. If the twist number is too low, the spiral is insufficient, which affects the thermal conductivity and rebound effect in the vertical direction.

[0082] Specifically, the concentration of the GO solution is 5-10 mg / mL. If the concentration is too low, the number of immersions required will increase significantly.

[0083] Further increase in concentration will lead to a significant increase in the viscosity of the solution, making it difficult to quickly immerse the helical fibers in the GO solution.

[0084] The pyrogen used in the drying I includes an infrared pyrogen; the power of the infrared pyrogen is 2000 W. The use of an infrared heat source can achieve drying in a thermal radiation manner (non-contact).

[0085] The thickness of the GO sheath is 5-10 μm. The GO sheath is wrapped around the spiral fiber, and then converted into a graphene layer through a carbonization and graphitization process, which can generate interlayer van der Waals forces between the spiral fibers, attracting and fixing each other. If the GO sheath is too thin, it cannot wrap the spiral fiber and produce a flat surface interaction. If the GO sheath is too thick, it will greatly increase the process time and fail to provide further interaction force.

[0086] The concentration of the GO slurry is 15-20 mg / mL. Because this process is carried out by brushing, a high concentration of GO solution should be selected as much as possible under the premise of easy operation. A solid content of 15 mg / mL is more suitable for this process. The temperature of the drying II is 70°C.

[0087] The concentration of the phenolic resin-ethanol is 5wt%; the concentration is appropriate and easy to operate. If the concentration is too low, the solid content is low, and it is not conducive to the fixation effect after the ethanol evaporates; if the concentration is too high, it is not conducive to impregnation, and there will be too much subsequent pyrolysis carbon. The thermal conductivity of the pyrolysis carbon of the phenolic resin after high-temperature heat treatment is not as good as that of graphene and carbon fiber, so it should not account for too much. It is more appropriate to choose this concentration.

[0088] The temperature of the hot pressing is 120°C, the pressure of the hot pressing is 1MPa; the holding temperature of the hot pressing is 180°C; and the holding time of the hot pressing is 30min;

[0089] Specifically, the carbonization temperature is 1600°C; the graphitization temperature is 3000°C.

[0090] Since the carbon-based composite material has both three-dimensional thermal conductivity and high resilience, it can be used to prepare thermal management systems; moreover, it is particularly suitable for preparing systems that require both heat dissipation and shock absorption, such as vehicle-mounted battery systems. Since the carbon-based composite material has properties such as durability, chemical corrosion resistance and flame retardancy, it is particularly suitable for preparing vehicle-mounted new energy battery systems.

[0091] The present invention will be further described below in conjunction with specific embodiments.

[0092] Example 1

[0093] Preparation of Helical Polyacrylonitrile (PAN)-Based Carbon Fibers

[0094] With nylon wire of 0.2 mm in diameter as the core material and 1K T300 PAN-based carbon fiber (1000 fibers in each bundle, thermal conductivity ≈ 6 W / (m·K)) as the raw material, the cored spiral fiber was prepared by a winder.

[0095] The two ends of the nylon wire are fixed to the synchronous motors on both sides of the winding machine, and fixed to one end of the nylon core material through the wire guide on the electric slide rail. The specific parameters and twist number are controlled by the coordinated control of the motor speed and the forward speed of the slide, so that the carbon fiber is tightly wound on the core material, thereby obtaining a cored spiral carbon fiber. Among them, the forward speed of the slide is 200mm / min and the motor speed is 300rpm.

[0096] Preparation of graphene oxide (GO) coated helical carbon fibers

[0097] The coating device is assembled from a roller immersion assembly and an infrared (IR) heating lamp. Specifically, the cored spiral carbon fiber is continuously passed through a diluted GO solution (5 mg / mL) at a given speed of 20 m / h under the traction of a motor and the limiting action of a roller, and then dried under an infrared radiation lamp (2000 W, distance 20 cm). The GO solution adheres to the surface of the spiral fiber, and after removing the moisture, the GO sheets are assembled on the fiber surface to form a sheath layer. This step is repeated 10 times, and the thickness of the GO sheath layer can be adjusted by controlling the number of roller immersions. Adjusting the thickness can regulate the thickness of the graphene sheath layer that is finally converted from graphene oxide, thereby adjusting the thermal conductivity of the spiral carbon fiber.

[0098] Preparation of carbon-based composite materials with single-layer spiral fiber layers having a sandwich structure

[0099] After the cored spiral carbon fibers coated with GO sheaths were laid out in parallel, GO slurry (15 mg / mL) was brushed on the upper and lower surfaces of the fiber sheets, and then placed in a blast drying oven at 70°C for 5 hours. Repeating the brushing-drying process 20 times can fill the GO layer into the depressions between the fibers and form a tight and flat GO layer on the surface of the sheet. Then it was immersed in a 5wt% phenolic-ethanol solution, vacuum impregnated for 30 minutes, and then taken out and dried at 70°C in a blast drying oven for 5 hours. The dried cored spiral carbon fiber layer was placed in a square mold and placed in a hot press, heated to 120°C for 30 minutes to soften the phenolic, and then pressurized to 1MPa, and heated to 180°C for 30 minutes to solidify the phenolic. In this process, phenolic acts as a binder to fix the fiber position and stabilize the board structure. The hot-pressed fiberboard was heated in an argon atmosphere and kept at 1600°C for 30 minutes to carbonize the phenolic formaldehyde, and then further heated to 3000°C for high-temperature graphitization treatment for 30 minutes.

[0100] Example 2

[0101] Preparation of carbon-based composite materials with double-layer orthogonally stacked spiral fiber layers with sandwich structure

[0102] The difference from Example 1 is that after the cored spiral carbon fibers coated with GO sheaths are laid out in parallel, GO slurry (15 mg / mL) is brushed on the upper and lower surfaces of the fiber sheets, and the sheets are placed in a blast drying oven at 70°C for 5 hours. Repeating the brushing-drying process 20 times allows the GO layer to fill the depressions between the fibers and form a tight and smooth GO layer on the surface of the sheet. Then lay out the second layer of spiral carbon fiber layers, and the adjacent two layers of spiral fiber layers are stacked orthogonally, and then GO slurry (15 mg / mL) is further brushed on the surface of the fiber sheet, and placed in a blast drying oven at 70°C for 5 hours. Repeating the brushing-drying process 20 times allows the GO layer to fill the depressions between the fibers and form a tight and smooth GO layer on the surface of the sheet. The remaining steps, parameters, and methods are consistent with Example 1.

[0103] Example 3

[0104] Preparation of carbon-based composite materials with double-layer 75-degree stacked spiral fiber layers with sandwich structure

[0105] The difference from Example 1 is that after the cored spiral carbon fibers coated with GO sheaths are laid out in parallel, GO slurry (15 mg / mL) is brushed on the upper and lower surfaces of the fiber sheets, and placed in a blast drying oven at 70°C for 5 hours. Repeating the brushing-drying process 20 times can fill the GO layer into the depressions between the fibers and form a tight and smooth GO layer on the surface of the sheet. Then lay out the second spiral carbon fiber layer, and the adjacent two spiral fiber layers are stacked at 75, and then further brush GO slurry (15 mg / mL) is brushed on the surface of the fiber sheet, and placed in a blast drying oven at 70°C for 5 hours. Repeating the brushing-drying process 20 times can fill the GO layer into the depressions between the fibers and form a tight and smooth GO layer on the surface of the sheet. The remaining steps, parameters, and methods are consistent with Example 1.

[0106] Example 4

[0107] Preparation of carbon-based composite materials with double-layer 30-degree stacked spiral fiber layers with sandwich structure

[0108] The difference from Example 1 is that after the cored spiral carbon fibers coated with GO sheaths are laid out in parallel, GO slurry (15 mg / mL) is brushed on the upper and lower surfaces of the fiber sheets, and placed in a blast drying oven at 70°C for 5 hours, and the brushing-drying process is repeated 20 times to fill the GO layer into the depressions between the fibers and form a tight and smooth GO layer on the surface of the sheet. Then the second spiral carbon fiber layer is laid out, and the adjacent two spiral fiber layers are stacked at 30, and then GO slurry (15 mg / mL) is further brushed on the surface of the fiber sheet, and placed in a blast drying oven at 70°C for 5 hours, and the brushing-drying process is repeated 20 times to fill the GO layer into the depressions between the fibers and form a tight and smooth GO layer on the surface of the sheet. The remaining steps, parameters, and methods are consistent with Example 1.

[0109] Example 5

[0110] Preparation of carbon-based composite materials with three adjacent two-layer spiral fiber layers orthogonally stacked in a sandwich structure

[0111] (Three layers of spiral fiber layers, and two adjacent layers of spiral fiber layers are orthogonally stacked)

[0112] The difference from Example 1 is that during the preparation of the sandwich carbon / carbon sheet, the cored spiral carbon fibers coated with GO sheaths are laid out in parallel, and GO slurry (15 mg / mL) is brushed on the upper and lower surfaces of the fiber sheets, and placed in a blast drying oven at 70°C for 5 hours. Repeating the brushing-drying process 20 times allows the GO layer to fill the recesses between the fibers and form a tight and smooth GO layer on the surface of the sheet. Then lay out the second layer of spiral carbon fiber layers, and the adjacent two layers of spiral fiber layers are stacked orthogonally, and then GO slurry (15 mg / mL) is further brushed on the surface of the fiber sheet, and placed in a blast drying oven at 70°C for 5 hours. Repeating the brushing-drying process 20 times allows the GO layer to fill the recesses between the fibers and form a tight and smooth GO layer on the surface of the sheet. Then, the third spiral carbon fiber layer was laid, and the adjacent two spiral fiber layers were stacked orthogonally, and then GO slurry (15 mg / mL) was further brushed on the surface of the fiber sheet, and placed in a forced air drying oven at 70°C for 5 hours. The brushing-drying process was repeated 20 times to fill the GO layer into the recesses between the fibers and form a tight and flat GO layer on the surface of the sheet. The remaining steps, parameters, and methods were consistent with Example 1.

[0113] Example 6

[0114] The difference from Example 1 is that, in the preparation process of spiral polyacrylonitrile (PAN)-based carbon fiber, a nylon wire with a diameter of 0.5 mm is used as the core material, and the other steps, parameters, and methods are consistent with Example 1.

[0115] Example 7

[0116] The difference from Example 1 is that in the preparation process of graphene oxide (GO) coated spiral carbon fiber, the thickness of the GO sheath layer is controlled by controlling the number of roller immersion to 20 times. The remaining steps, parameters, and methods are consistent with Example 1.

[0117] Example 8

[0118] The difference from Example 1 is that during the preparation of the sandwich carbon / carbon sheet, the temperature of high-temperature graphitization is 2800° C. The remaining steps, parameters, and methods are consistent with those of Example 1.

[0119] Example 9

[0120] The difference from Example 1 is that in the preparation process of spiral polyacrylonitrile (PAN)-based carbon fiber, 3KT800 PAN-based carbon fiber (3000 fibers in each bundle, thermal conductivity ≈7 W / (m·K)) is used as raw material, and the remaining steps, parameters, and methods are consistent with Example 1.

[0121] In the present invention, the samples prepared in Examples 1-9 can be tested by the following method, and the results are listed in Table 1:

[0122] 1. Observe the front view, cross-section and fiber morphology of the sample using a JSM-7610 scanning electron microscope.

[0123] 2. Use Elementar vario EL cube organic element analyzer to test the carbon content of the sample in CHNS mode.

[0124] 3. The bulk density of the sample is calculated from the ratio of the mass to the volume of the sample. The mass is directly weighed by a balance with an accuracy of 0.0001g. The length, width and height of the sample are measured by a micrometer, and the volume of the sample is the product of the length, width and height.

[0125] 4. The thermal conductivity of the full carbon plate (sandwich carbon / carbon plate) is tested by the DRL-III thermal conductivity meter. The DRL-III thermal conductivity meter is suitable for measuring the out-of-plane thermal conductivity of the sample, and can measure the thermal conductivity of the sample under a certain pressure by applying pressure to both sides of the sample. The test area of ​​the sample is 1.5cm × 1.5cm. Set the hot electrode temperature to 30℃ and the cold electrode temperature to 20℃, and evenly apply a layer of thermal conductive silicone grease on the contact plane between the hot electrode, the cold electrode and the sample to reduce the influence of air on the thermal conductivity test. After the hot and cold electrode temperatures are stable, load the motor to make the thermal conductivity of the sample when the pressure on the sample is 0.1MPa and 1MPa.

[0126] 5. The compression rebound rate of the full carbon plate (sandwich carbon / carbon plate) is measured by an electronic universal testing machine (AG-plus model). When testing the compression rebound performance of the sample, it can apply precise compression force to the sample at a set rate. The test area of ​​the sample is 1.5cm × 1.5cm. Record the initial thickness of the sample, and the pressure on the test sample is 0.1MPa and 1MPa. After unloading the pressure, record the thickness of the sample after compression and rebound, and calculate the compression rebound rate of the sample, which is calculated as the thickness after compression and rebound / initial thickness of the sample.

[0127] Table 1

[0128]

[0129] It can be seen from the data of Examples 1-9 that the carbon content of the samples provided by the present invention is as high as 99.9%, and has a relatively low bulk density. The bulk density of the examples is 0.25-0.35 g / cm 3; The thermal conductivity of the sample obtained in the present invention in the vertical direction increases with the increase of the applied pressure. When the pressure is 0.1MPa, the thermal conductivity is 1.83~3.21W / mK, and when the pressure is 1MPa, the thermal conductivity is 2.11~3.43W / mK; The deformation resilience of the sample obtained in the present invention is 59~63% when the pressure is 0.1MPa, and the deformation resilience is 27~41% when the pressure is 1MPa. Therefore, the sample obtained in the present invention is a full-carbon material with high thermal conductivity and high resilience, and can be used as an excellent thermal interface material.

[0130] It can be seen from the data of Examples 1 to 5 that increasing the number of spiral carbon fiber layers can increase the deformation rebound rate, but the thermal conductivity will decrease; as the number of layers increases, that is, the number of layers of the hollow cavity increases in the Z-axis direction, when the sample is subjected to a constant pressure, the deformable space increases, so more deformation can be obtained, and this constant pressure does not destroy the sample, and the deformation rebound rate increases; increasing the number of spiral carbon fiber layers increases the thermal interface, so the thermal conductivity decreases.

[0131] It can be seen from the data of Example 1 and Example 6 that increasing the diameter of the nylon fiber, that is, increasing the inner diameter of the hollow spiral carbon fiber, increases the thermal resistance. Therefore, the larger the diameter of the nylon fiber, the lower the thermal conductivity; however, the increase in the inner diameter of the hollow spiral carbon fiber provides space for the increase in deformation, so the deformation rebound rate is greater.

[0132] It can be seen from the data of Example 1 and Example 7 that increasing the number of roller immersion times makes the gaps more fully compacted by graphene, and at the same time the formed graphene layer is thicker, so the thermal conductivity is higher and the rebound rate is lower.

[0133] It can be seen from the data of Example 1 and Example 8 that lowering the graphitization temperature makes the degree of crystallization of graphene, carbon fiber and cracked carbon lower, so the thermal conductivity of the sample obtained in Example 8 is lower.

[0134] It can be seen from the data of Example 1 and Example 9 that, because the thermal conductivity of T800 is higher than that of T300, and the filament bundle of T800 used in the example is larger than that of T300, the thermal conductivity of the sample obtained in Example 9 is higher.

Claims

1. A carbon-based composite material, characterized in that: comprising two graphene layers; At least one spiral carbon fiber layer is provided between the two graphene layers; The spiral carbon fiber layer is composed of hollow spiral carbon fibers laid in parallel, and the twisting directions of adjacent hollow spiral carbon fibers are opposite; When two or more spiral carbon fiber layers are provided between the graphene layers, the axes of the hollow spiral carbon fibers in adjacent spiral carbon fiber layers are not parallel; The graphene layer is fixedly connected to the spiral carbon fiber layer; Adjacent spiral carbon fiber layers are fixedly connected; Adjacent hollow spiral carbon fibers are fixedly connected.

2. The carbon-based composite material according to claim 1, characterized in that: The thickness of the graphene layer is 15-30 μm; The hollow spiral carbon fiber is obtained by twisting PAN-based carbon fiber; The diameter of the PAN-based carbon fiber is 6-8 μm; The inner diameter of the hollow spiral carbon fiber is 0.2-0.6 mm; The outer diameter of the hollow spiral carbon fiber is 0.5-1.5 mm.

3. The carbon-based composite material according to claim 1, characterized in that: The angle between the axes of the hollow spiral carbon fibers in adjacent spiral carbon fiber layers is 30-90 degrees; or The angle between the axes of the hollow spiral carbon fibers in adjacent spiral carbon fiber layers is 75-90 degrees; or The angle between the axes of the hollow spiral carbon fibers in adjacent spiral carbon fiber layers is 90 degrees.

4. The method for preparing the carbon-based composite material according to claim 1, characterized in that: The steps include: S1 twists the PAN-based carbon fiber so that it is wound on the surface of the core material to obtain a core-belted spiral carbon fiber; S2 immerses the cored helical carbon fiber in a GO solution and then dries it I to obtain a cored helical carbon fiber coated with a GO sheath; S3: arranging a single layer or multiple layers of core spiral carbon fiber coated with GO sheath in parallel to obtain a single layer or multiple layers of spiral carbon fiber layer; S4 brushes GO slurry on the upper and lower surfaces of the single-layer or multi-layer spiral carbon fiber layer, and then dries Ⅱ to form a GO slurry layer; then immerses it in a phenolic resin-ethanol solution, vacuum impregnates and dries Ⅲ, and hot presses to obtain a carbon-based composite material that has not been heat-treated; S5: graphitizing the unheat-treated carbon-based composite material to carbonize the phenolic resin and convert GO into graphene.

5. The method for preparing the carbon-based composite material according to claim 4, characterized in that: The core material includes nylon thread; The diameter of the core material is 0.2-0.6 mm; The twist number of the twisting is 200-450.

6. The method for preparing the carbon-based composite material according to claim 4, characterized in that: The concentration of the GO solution is 5-10 mg / mL; The heat source used in the drying I includes an infrared heat source; The power of the infrared heat source is 2000W.

7. The method for preparing a carbon-based composite material according to claim 4, characterized in that: The thickness of the GO sheath is 5-10 μm.

8. The method for preparing a carbon-based composite material according to claim 4, characterized in that: The concentration of the GO slurry is 10-20 mg / mL; The temperature of the drying II is 70-75°C.

9. The method for preparing a carbon-based composite material according to claim 4, characterized in that: The concentration of the phenolic resin-ethanol is 5-7wt%; The temperature of the hot pressing is 120-125°C; The hot pressing pressure is 1-1.5 MPa; The holding temperature of the hot pressing is 180-200°C; The holding time of the hot pressing is 30-40min; The graphitization temperature is 2900-3100°C.

10. The use of the carbon-based composite material according to claim 1, characterized in that: Used in the preparation of thermal management systems; or Used in preparing battery systems.

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