Carbon / carbon composite material and preparation method and application thereof

Abstract

The invention provides a carbon / carbon composite material. The carbon / carbon composite material comprises two graphene layers, at least one spiral carbon fiber layer is arranged between every two graphene layers; the spiral carbon fiber layer is composed of hollow spiral carbon fibers laid in parallel, and the spiral directions of the adjacent hollow spiral carbon fibers are opposite; a gap formed between the hollow spiral carbon fibers laid in parallel and the graphene layer is filled with mesophase pitch pre-oxidized fibers; the shafts of the hollow spiral carbon fibers in the adjacent spiral carbon fiber layers are not parallel; the graphene layer is fixedly connected with the spiral carbon fiber layer; the adjacent spiral carbon fiber layers are fixedly connected; the adjacent hollow spiral carbon fibers are fixedly connected; the hollow spiral carbon fiber is obtained by spirally winding a twisted CNT film on the surface of an organic core material and then removing the organic core material. The invention also provides a preparation method and application of the carbon / carbon composite material.

Description

Technical Field

[0001] The present invention relates to a novel composite material, in particular to a carbon / carbon composite material with high thermal conductivity and high compression resilience. The present invention also relates to a method for preparing the carbon-based composite material. The present invention also relates to the application of the carbon-based composite material in the field of thermal management materials, high-end electronic products and new energy batteries. Background Art

[0002] With the increase in power density of electronic devices and the growing demand for lightweight and efficient thermal management materials in aerospace, automotive and other fields, composite materials with excellent thermal conductivity and stable structure have attracted widespread attention. Carbon-based materials are considered to be ideal thermal management solutions due to their low density, high thermal conductivity, excellent mechanical properties and high temperature resistance. However, due to the natural anisotropy of carbon materials, how to effectively improve their thermal conductivity in the z direction (thickness direction) becomes a key challenge. In some key application scenarios, such as thermal interface materials (TIMs) in electronic devices and aerospace thermal protection systems, higher requirements are placed on the thermal conductivity and mechanical properties of materials. These applications require materials to maintain excellent compression resilience when subjected to dynamic loads and have efficient thermal conductivity in the z direction. Currently, the main methods for achieving high thermal conductivity composite material design include filling with high thermal conductivity particles (such as graphite, carbon nanotubes) or fiber materials. However, these methods have the following significant limitations: (1) Compatibility between thermal conductivity and mechanical properties: Traditional fillers often reduce the mechanical properties of composite materials, such as compression resilience, while improving thermal conductivity. This reduces the reliability of the material in actual applications under dynamic loads. (2) Limitations caused by complex processes: High thermal conductivity materials usually require strict alignment techniques to arrange thermally conductive fillers in a specific direction, such as through electric fields, magnetic fields or heat treatment. However, these processes are complex, energy-intensive, and difficult to achieve large-scale production. (3) Design challenges caused by anisotropy: Carbon-based fillers such as carbon fibers and carbon nanotubes have significant thermal conductivity anisotropy. The thermal conductivity is high in the xy direction (in-plane), but relatively low in the z direction (thickness direction), which limits its application in scenarios with multi-directional heat dissipation requirements.

[0003] Carbon nanotubes (CNTs) are ideal candidates for enhancing the performance of composite materials due to their excellent in-plane thermal conductivity and mechanical properties. However, the application of CNT's two-dimensional film-like structure in the field of three-dimensional thermal conductivity is limited, and it is urgent to realize its three-dimensional thermal conductivity potential through structural innovation. In addition, in recent years, graphene has become an effective means to enhance the performance of composite materials due to its high thermal conductivity and adjustable surface chemical properties. However, the interface bonding between graphene and the matrix material and the control of its orientation and distribution in the composite material are still facing challenges. Therefore, how to utilize the high thermal conductivity of CNT films and graphene to prepare all-carbon-based composite materials with high z-direction thermal conductivity and excellent compression rebound performance through innovative structural design has become the key to solving the above problems. The Chinese invention patent application with publication number CN118459224A uses graphene and carbon nanotube films as the main materials. Although they have high thermal conductivity, they are costly. In addition, its preparation method involves horizontal spreading into a film and then cross-cutting, and obtaining a longitudinal high thermal conductivity after turning 90 degrees. The thickness of the film is the horizontal area of ​​the interface material. The preparation process is cumbersome and is not conducive to large-scale production.

[0004] The present invention aims to provide a full-carbon-based composite material with high z-direction thermal conductivity, excellent compression rebound performance and high structural stability. By introducing intermediate phase asphalt pre-oxidized fibers to fill the gaps in the spiral carbon fiber layer, the bottleneck of existing materials in thermal conductivity and mechanical properties is broken through, providing innovative solutions to thermal management problems in high-end electronic equipment and new energy fields. Summary of the invention

[0005] The first object of the present invention is to provide a carbon / carbon composite material with high thermal conductivity and high resilience.

[0006] The second object of the present invention is to provide a method for preparing a carbon / carbon composite material.

[0007] The third object of the present invention is to provide an application of a carbon / carbon composite material.

[0008] The present invention is achieved through the following technical solutions:

[0009] A carbon / carbon composite material comprising two graphene layers;

[0010] At least one spiral carbon fiber layer is provided between every two graphene layers;

[0011] The spiral carbon fiber layer is composed of hollow spiral carbon fibers laid in parallel, and the spiral directions of adjacent hollow spiral carbon fibers are opposite; and the hollow spiral carbon fibers laid in parallel and between the hollow spiral carbon fibers laid in parallel and the graphene layer are filled with mesophase pitch pre-oxidized fibers;

[0012] 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;

[0013] The graphene layer and the spiral carbon fiber layer are fixedly connected via graphene;

[0014] Adjacent spiral carbon fiber layers are fixedly connected via graphene;

[0015] Adjacent hollow spiral carbon fibers are fixedly connected by graphene;

[0016] The hollow spiral carbon fiber is obtained by spirally winding a twisted CNT film on the surface of an organic core material and then removing the organic core material.

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

[0018] The diameter of the twisted CNT straight fiber is 350 μm;

[0019] The twist of the twisted CNT straight fiber is 135

[0020] The width of the CNT film is 10 mm;

[0021] The twist of the hollow spiral carbon fiber is

[0022] The inner diameter of the hollow spiral carbon fiber is 0.2 to 0.6 mm;

[0023] The outer diameter of the hollow spiral carbon fiber is 0.5 to 1.5 mm;

[0024] The diameter of the mesophase pitch pre-oxidized fiber is 10-20 μm.

[0025] The angle between the axes of the hollow spiral carbon fibers in adjacent spiral carbon fiber layers is 30-90 degrees; or

[0026] The angle between the axes of the hollow spiral carbon fibers in adjacent spiral carbon fiber layers is 75-90 degrees; or

[0027] The angle between the axes of the hollow spiral carbon fibers in adjacent spiral carbon fiber layers is 90 degrees.

[0028] The method for preparing the carbon / carbon composite material comprises the following steps:

[0029] S1 twists the CNT film to obtain twisted CNT straight fibers, and winds the twisted CNT straight fibers on the surface of the organic core material to obtain a cored spiral carbon fiber;

[0030] S2 immerses the cored spiral carbon fiber in a GO solution, and then dries I to obtain a cored spiral carbon fiber coated with a GO sheath; S3 lays out a single layer or multiple layers of the cored spiral carbon fiber coated with a GO sheath in parallel to obtain a single layer or multiple layers of spiral carbon fiber layers; and during the laying, fills the gaps formed between the cored spiral carbon fibers with intermediate phase pitch pre-oxidized fibers;

[0031] 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; and then hot presses to obtain a carbon-based composite material that has not been heat-treated;

[0032] S5: graphitizing the unheat-treated carbon-based composite material to obtain the obtained carbon-based composite material.

[0033] The core material includes nylon thread;

[0034] The diameter of the core material is 0.2-0.6 mm;

[0035] The twist number of the twisting is 200-450.

[0036] The concentration of the GO solution is 5 mg / mL;

[0037] The heat source used in the drying I includes an infrared heat source;

[0038] The power of the infrared heat source is 2000W.

[0039] The thickness of the GO sheath is 5 to 10 μm.

[0040] The concentration of the GO slurry is 15 mg / mL;

[0041] The temperature of the drying II is 70°C.

[0042] The temperature of the hot pressing is 300°C;

[0043] The hot pressing pressure is 1 to 1.5 MPa;

[0044] The holding time of the hot pressing is 30 minutes;

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

[0046] The carbon / carbon 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 / carbon composite material provided by the present invention utilizes twisted CNT film to prepare spiral fibers as elastic components, thereby improving the resilience of the carbon / carbon composite material. At the same time, the introduction of the graphene layer can provide a force-bearing surface. The mesophase asphalt pre-oxidized fibers filled between the spiral fibers have the property of being graphitizable, so they can increase the resilience of the carbon / carbon composite material and also improve the thermal conductivity of the carbon / carbon composite material. Therefore, the carbon / carbon composite material provided by the present invention is a full-carbon sandwich composite material having both high z-thermal conductivity and excellent mechanical properties, which can be widely used in the fields of efficient thermal management and structural applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] 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.

[0051] Figure 2 The diagram shows the x-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.

[0052] Figure 3 The diagram shows the z-direction deformation of the carbon / carbon composite plate when the carbon-based composite material provided by the present invention is subjected to force in the z-direction.

[0053] Figure 4 A schematic diagram of the structure of CNT helical fibers is shown.

[0054] Figure 5 A schematic diagram of the layer structure of a sandwich carbon / carbon composite sheet is shown.

[0055] Figure 6 A preparation process flow chart is shown. DETAILED DESCRIPTION

[0056] The present invention provides a carbon / carbon 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, so that the hollow spiral carbon fibers produce a compression deformation perpendicular to their axial direction (common springs produce a 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 stressed, the hollow spiral carbon fibers are difficult to bend and deform, and instead bend and deform, which also makes the sandwich structure have good resilience. Moreover, the hollow spiral carbon fibers laid in parallel and the hollow spiral carbon fibers laid in parallel and the graphene layer are filled with mesophase pitch pre-oxidized fibers, which can be graphitized, thereby providing an axial heat conduction channel and improving the thermal conductivity of the carbon / carbon composite material. At the same time, the mesophase pitch pre-oxidized fibers will also be connected to each other and connected to the hollow spiral carbon fibers after high temperature treatment, which makes the mesophase pitch pre-oxidized fibers also form a micro spring, thereby contributing to the resilience of the carbon / carbon composite material. The thermoplasticity and graphitization characteristics of the mesophase pitch pre-oxidized fibers can also effectively fill the fiber gaps to form high-quality graphite sheets. This structure can also improve the load-bearing capacity of the carbon / carbon composite material.

[0057] Furthermore, the hollow spiral carbon fiber is obtained by spirally winding the twisted CNT straight fiber on the surface of the organic core material and then removing the organic core material. This makes the hollow spiral carbon fiber have strong elasticity. The CNT film is a nano-scale film. After heat treatment, it will be staggered and spread after twisting and heat treatment, and the CNTs are interconnected to have strong elasticity. The hollow spiral carbon fiber can also provide a heat conduction channel in the z direction. Therefore, 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 and the spiral carbon fiber layer are fixedly connected, preferably fixedly connected by graphene. Therefore, when subjected to force, no slippage will occur between the graphene layer and the spiral carbon fiber layer, which will improve the structural stability of the material. The carbon-based composite material can be provided with multiple layers of graphene layers, and spiral carbon fiber layers can be provided between each layer of graphene layers. 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 graphene layers there are, 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 the adjacent spiral carbon fiber layers from slipping when the carbon-based composite material is subjected to force. Obviously, the composite material with multiple graphene layers can also be a stack of the above basic structures. The composite sheet provided by the present invention is a full carbon structure, so it has excellent high temperature resistance and can meet the requirements of high temperature thermal management. At the same time, it also has corrosion resistance, flame retardancy and high and low temperature resistance, which makes it more widely used.

[0058] The thickness of the graphene layer is 15 to 30 μm. This is because if the thickness is too thin, it is easy to cause incomplete graphene infiltration and coverage, resulting in 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.

[0059] The twist of the hollow spiral carbon fiber is 200 to 450;

[0060] The width of the CNT film is 10 mm;

[0061] The inner diameter of the hollow spiral carbon fiber is 0.2 to 0.6 mm;

[0062] The outer diameter of the hollow spiral carbon fiber is 0.5-1.5 mm.

[0063] 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.

[0064] Preferably, the angle between the axes of the hollow spiral carbon fibers in adjacent spiral carbon fiber layers is 75-90 degrees. 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 adjacent spiral carbon fiber layers to slip.

[0065] The present invention also provides a method for preparing the carbon / carbon composite material, comprising the following steps:

[0066] 1) Preparation of CNT straight fibers CNT film is used as raw material and cut into long strips. One end of the CNT strip is fixed to the central axis of the DC motor, and the other end is connected to a metal block that can move freely on a smooth platform. Turn on the motor and continue to twist the CNT film to transform it into straight fibers.

[0067] 2) Preparation of CNT helical fibers

[0068] CNT straight fiber is used as raw material. Through the winding machine, the core material is fixed on the synchronous motors at both ends. One end of the CNT straight fiber is fixed on the bobbin, and the other end is connected to the surface of the electric slider through the wire guide. Under the synergistic effect of the synchronous motor and the slider, the CNT straight fiber is tightly wound on the surface of the core material to form a cored CNT spiral fiber.

[0069] 3) Preparation of GO@CNT helical fibers

[0070] The CNT helical fibers were continuously passed through a diluted GO solution and then dried, so that GO sheets adhered to the surface of the helical fibers and formed a sheath layer. The thickness of the GO layer was controlled by multiple roller immersion.

[0071] 4) Preparation of sandwich carbon / carbon composite sheets

[0072] The GO@CNT spiral fibers are laid out in parallel in the mold. Due to the circular cross-section of the spiral fibers, triangular gaps are formed between the fibers. The gaps are filled with pre-oxidized fibers of the intermediate phase pitch, and GO slurry is sprayed on the upper and lower surfaces. The laid fiber sheets are dried, and the brushing and drying steps are repeated 5 to 10 times. Place them in the mold and hot press them. Finally, the material is carbonized and graphitized to obtain a sandwich structure carbon / carbon composite sheet.

[0073] 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.

[0074] The diameter of the core material is 0.2 to 0.6 mm;

[0075] The twist number of the twisting is 200 to 450. The higher the twist, 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.

[0076] The concentration of the GO solution is 5 mg / mL. If the concentration is too low, the number of immersions required will increase significantly. The heat source used in the drying I includes an infrared heat source. If the concentration is further increased, the viscosity of the solution will increase significantly, which will not facilitate the operation of quickly immersing the spiral fiber in and out of the GO solution.

[0077] The pyrogen used in the drying I includes an infrared pyrogen; the power of the infrared pyrogen is 2000W. The infrared heat source can be used to achieve drying in a heat radiation manner (non-contact). The power of the infrared heat source is 2000W.

[0078] The thickness of the GO sheath is 5-10 μm.

[0079] The concentration of the GO slurry is 15 mg / mL;

[0080] The temperature of the drying II is 70°C.

[0081] The temperature of the hot pressing is 300°C;

[0082] The hot pressing pressure is 1 to 1.5 MPa;

[0083] The holding time of the hot pressing is 30 minutes;

[0084] The temperature of the heat treatment is 2900-3100°C.

[0085] 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.

[0086] The present invention is further described below in conjunction with specific embodiments.

[0087] Example 1

[0088] Preparation of CNT straight fibers

[0089] Using CNT film as raw material, it is cut into 10mm wide strips. One end of the CNT strip is fixed to the central axis of the DC motor, and the other end is connected to a metal block that can move freely on a smooth platform. The motor speed is set to 140r / min and twisted for 15 minutes to transform the CNT film into straight fibers.

[0090] Preparation of CNT helical fibers

[0091] A nylon wire with a diameter of 0.2 mm is used as the core material, and CNT straight fiber is used as the raw material. The core material is fixed on the synchronous motors at both ends through a homemade winding machine. One end of the CNT straight fiber is fixed on the bobbin, and the other end is connected to the surface of the electric slider through a wire guide. Under the synergistic action of the synchronous motor and the slider, the CNT straight fiber is tightly wound on the surface of the core material to form a cored CNT spiral fiber. The spacing of the synchronous motor is 260 mm. The CNT straight fiber passes through the wire guide on the stepper motor and controls the slider speed to 200 mm / min. The speed of the synchronous motor is T = 1000L / d (T (rpm / min) is the speed of the synchronous motor, L (mm / min) is the slider movement speed, and d (μm) is the diameter of the CNT straight fiber.

[0092] Preparation of GO@CNT helical fibers

[0093] The CNT helical fiber was continuously passed through a diluted GO solution (concentration of 5 mg / ml) at a speed of 20 m / h, and then dried by an infrared radiation lamp to make the GO sheets adhere to the surface of the helical fiber and form a sheath layer. The thickness of the GO layer was controlled by 5 times of roller immersion.

[0094] Preparation of sandwich carbon / carbon composite sheet GO@CNT spiral fibers are laid out in parallel in a mold, and the spiral directions of adjacent hollow spiral carbon fibers are kept opposite during laying. Due to the circular cross-section of the spiral fibers, triangular gaps are formed between the fibers, and the gaps are filled with pre-oxidized fibers of intermediate phase pitch with a diameter of 10 μm, and GO slurry (concentration of 15 mg / ml) is brushed on the upper and lower surfaces. The laid fiber sheet is dried at 70°C for 30 minutes, and the brushing and drying steps are repeated 5 times. Then it is placed in a mold and hot pressed at 300°C and 1MPa for 30 minutes. Finally, the material is carbonized at 1600°C for 1 hour and graphitized at 3100°C for 1 hour to obtain a carbon / carbon composite material with a sandwich structure.

[0095] Example 2

[0096] The preparation of spiral fibers having two spiral fiber layers and two adjacent spiral fiber layers stacked orthogonally is different from that of Example 1 in that the two adjacent spiral fiber layers are stacked orthogonally. During the preparation of the sandwich carbon / carbon sheet, the GO@CNT spiral fibers are laid out in parallel in the mold, and the spiral directions of the adjacent hollow spiral carbon fibers are kept opposite during the laying. Due to the circular cross-section of the spiral fibers, triangular gaps are formed between the fibers, and the gaps are filled with pre-oxidized fibers with an intermediate phase pitch having a diameter of 10 μm, and GO slurry (concentration of 15 mg / ml) is brushed on the upper and lower surfaces. The laid fiber sheet was dried at 70°C for 30 minutes, and the brushing and drying steps were repeated 5 times. Then the second layer of GO@CNT spiral carbon fiber layer was laid out, and the two adjacent spiral fiber layers were stacked orthogonally, followed by a circular cross-section of the spiral fibers, and triangular gaps were formed between the fibers, and the gaps were further filled with pre-oxidized fibers with an intermediate phase pitch having a diameter of 10 μm, and then GO slurry (15 mg·mL -1 ), and put it into a blast drying oven at 70°C for 5 hours, and repeat the brushing and drying steps 5 times, so that the GO layer can fill 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 are consistent with Example 1.

[0097] Example 3

[0098] The preparation of spiral fibers having two spiral fiber layers, and the two adjacent spiral fiber layers are stacked at 75 degrees is different from that of Example 1 in that the two adjacent spiral fiber layers are stacked at 75 degrees. During the preparation of the sandwich carbon / carbon sheet, the GO@CNT spiral fibers are laid out in parallel in the mold, and the spiral directions of the adjacent hollow spiral carbon fibers are kept opposite during the laying. Due to the circular cross-section of the spiral fibers, triangular gaps are formed between the fibers, and the gaps are filled with pre-oxidized fibers with an intermediate phase pitch having a diameter of 10 μm, and GO slurry (concentration of 15 mg / ml) is brushed on the upper and lower surfaces. The laid fiber sheet was dried at 70°C for 30 minutes, and the brushing and drying steps were repeated 5 times. Then the second layer of GO@CNT spiral carbon fiber layer was laid out, and the two adjacent spiral fiber layers were stacked at 75 degrees. Subsequently, the circular cross-section of the spiral fibers formed triangular gaps between the fibers, and the gaps were further filled with pre-oxidized fibers with an intermediate phase pitch having a diameter of 10 μm, and then GO slurry (15 mg·mL -1 ), and put it into a blast drying oven at 70°C for 30 minutes, repeat the brushing and drying steps 5 times, so that the GO layer can fill 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 are consistent with Example 1.

[0099] Example 4

[0100] The preparation of spiral fibers having two spiral fiber layers, and the two adjacent spiral fiber layers are stacked at 30 degrees is different from that of Example 1 in that the two adjacent spiral fiber layers are stacked at 30 degrees. During the preparation of the sandwich carbon / carbon sheet, the GO@CNT spiral fibers are laid out in parallel in the mold, and the spiral directions of the adjacent hollow spiral carbon fibers are kept opposite during the laying. Due to the circular cross-section of the spiral fibers, triangular gaps are formed between the fibers, and the gaps are filled with pre-oxidized fibers with an intermediate phase asphalt having a diameter of 10 μm, and GO slurry (concentration of 15 mg / ml) is brushed on the upper and lower surfaces. The laid fiber sheet was dried at 70°C for 30 minutes, and the brushing and drying steps were repeated 5 times. Then the second layer of GO@CNT spiral carbon fiber layer is laid out, and the two adjacent spiral fiber layers are stacked at 30 degrees. Subsequently, the circular cross-section of the spiral fibers forms triangular gaps between the fibers, and the gaps are further filled with pre-oxidized fibers with an intermediate phase asphalt having a diameter of 10 μm, and then GO slurry (15 mg·mL -1 ), and put it into a blast drying oven at 70°C for 30 minutes, repeat the brushing and drying steps 5 times, so that the GO layer can fill 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 are consistent with Example 1.

[0101] Example 5

[0102] The difference from Example 1 is that during the preparation of the sandwich carbon / carbon sheet, the temperature of high-temperature graphitization is 2900° C. The remaining steps, parameters, and methods are consistent with those of Example 1.

[0103] Example 6

[0104] The difference from Example 1 is that in the preparation process of the sandwich carbon / carbon sheet, the mesophase pitch pre-oxidized fiber is 20 μm. The remaining steps, parameters, and methods are consistent with Example 1.

[0105] Example 7

[0106] The difference from Example 1 is that in the preparation process of the sandwich carbon / carbon sheet, the steps of brushing GO slurry and drying are repeated 10 times. The remaining steps, parameters, and methods are consistent with those of Example 1.

[0107] Example 8

[0108] The difference from Example 1 is that during the preparation of the sandwich carbon / carbon sheet, the hot pressing pressure in the mold is 1.5 MPa. The remaining steps, parameters, and methods are consistent with Example 1.

[0109] Example 9

[0110] The difference from Example 1 is that in the preparation process of the CNT spiral fiber, a nylon wire with a diameter of 0.6 mm is used as the core material. The remaining steps, parameters, and methods are consistent with those of Example 1.

[0111] 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:

[0112] 1. Use Elementar vario EL cube organic element analyzer to test the carbon content of the sample in CHNS mode.

[0113] 2. The bulk density of the sample is calculated by 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.

[0114] 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, test the thermal conductivity of the sample when the pressure on the sample is 0.1MPa and 1MPa.

[0115] 4. 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.

[0116] Table 1

[0117]

[0118] From the data of Examples 1-9, it can be seen that the carbon content of the samples provided by the present invention is as high as 99.9%, and has a relatively high bulk density. The bulk density of the examples is 0.33-0.49 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 12.5-23.1W / mK, and when the pressure is 1MPa, the thermal conductivity is 15.9-31.5W / mK; The deformation resilience of the sample obtained in the present invention is 56-78% when the pressure is 0.1MPa, and the deformation resilience is 28-47% 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.

[0119] It can be seen from the data of Examples 1 to 4 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.

[0120] It can be seen from the data of Example 1 and Example 5 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 5 is lower.

[0121] It can be seen from the data of Example 1 and Example 6 that increasing the diameter of the mesophase pitch fiber can increase the density of the sample and reduce the contact thermal resistance between the fibers, so the thermal conductivity is higher but the rebound rate is lower.

[0122] It can be seen from the data of Example 1 and Example 7 that increasing the number of repeated brushing of GO slurry and drying steps 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.

[0123] It can be seen from the data of Example 1 and Example 8 that increasing the molding pressure increases the bulk density of the obtained sample, increases the contact and makes it closer, and reduces the interface thermal resistance, so the thermal conductivity is higher, but the rebound rate is lower.

[0124] It can be seen from the data of Example 1 and Example 9 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.

Claims

1. A carbon / carbon composite material, characterized in that: comprising two graphene layers; At least one spiral carbon fiber layer is provided between every two graphene layers; The spiral carbon fiber layer is composed of hollow spiral carbon fibers laid in parallel, and the spiral directions of adjacent hollow spiral carbon fibers are opposite; The gaps formed between the parallel-laid hollow spiral carbon fibers and the graphene layer are filled with mesophase pitch pre-oxidized fibers; When at least two layers of spiral carbon fiber layers are provided between every two layers of the graphene layers, the gaps formed between adjacent spiral carbon fibers are filled with mesophase pitch pre-oxidized fibers; 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 hollow spiral carbon fiber is obtained by spirally winding a twisted CNT film on the surface of an organic core material and then performing a heat treatment to remove the organic core material.

2. The carbon / carbon composite material according to claim 1, characterized in that: The thickness of the graphene layer is 15 to 30 μm; The diameter of the twisted CNT straight fiber is 350 μm; The twist of the twisted CNT straight fiber is 135; The width of the CNT film is 10 mm; The twist of the hollow spiral carbon fiber is 200 to 450; The inner diameter of the hollow spiral carbon fiber is 0.2 to 0.6 mm; The outer diameter of the hollow spiral carbon fiber is 0.5 to 1.5 mm; The diameter of the mesophase pitch pre-oxidized fiber is 10-20 μm.

3. The carbon / carbon 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 a carbon / carbon composite material according to claim 1, characterized in that: The steps include: S1 twists the CNT film to obtain twisted CNT straight fibers, and winds the twisted CNT straight fibers on the surface of the organic core material to obtain a cored spiral carbon fiber; S2 immerses the cored spiral carbon fiber in a GO solution, and then dries I to obtain a cored spiral carbon fiber coated with a GO sheath; S3 lays out a single layer or multiple layers of the cored spiral carbon fiber coated with a GO sheath in parallel to obtain a single layer or multiple layers of spiral carbon fiber layers; and during the laying, fills the gaps formed between the cored spiral carbon fibers with intermediate phase pitch pre-oxidized fibers; 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; and then 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 obtain the obtained carbon-based composite material.

5. The method for preparing a carbon / carbon composite material according to claim 1, characterized in that: The core material includes nylon thread; The diameter of the core material is 0.2-0.6 mm.

6. The method for preparing a carbon / carbon composite material according to claim 1, characterized in that: The concentration of the GO solution is 5 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 / carbon composite material according to claim 1, characterized in that: The thickness of the GO sheath is 5 to 10 μm.

8. The method for preparing a carbon / carbon composite material according to claim 1, characterized in that: The concentration of the GO slurry is 15 mg / mL; The temperature of the drying II is 70°C.

9. The method for preparing a carbon / carbon composite material according to claim 1, characterized in that: The temperature of the hot pressing is 300°C; The hot pressing pressure is 1 to 1.5 MPa; The holding time of the hot pressing is 30 minutes; The graphitization temperature is 2900-3100°C.

10. The use of the carbon / carbon 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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