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; 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 through graphene; the adjacent spiral carbon fiber layers are fixedly connected through graphene; the adjacent hollow spiral carbon fibers are fixedly connected through graphene; 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) have become ideal candidates for enhancing the properties of composite materials due to their excellent in-plane thermal conductivity and mechanical properties. However, the two-dimensional film structure of CNTs is limited in applications in the field of three-dimensional heat conduction, and it is urgent to realize its three-dimensional heat conduction potential through structural innovation. In addition, in recent years, graphene has become an effective means of enhancing the properties of composite materials due to its high thermal conductivity and adjustable surface chemical properties. However, challenges still remain in the interfacial bonding between graphene and matrix materials and the control of its orientation and distribution in composite materials. Therefore, how to utilize the high thermal conductivity characteristics of CNT films and graphene to prepare all-carbon-based composite materials with both high z-directional thermal conductivity and excellent compression and rebound properties through innovative structural design has become the key to solving the above problems.

[0004] The Chinese patent application with the publication number CN118459224A uses graphene and carbon nanotube films as the main materials. Although it has high thermal conductivity performance, the cost is relatively high. In addition, its preparation method involves horizontally spreading into a film and then cross-cutting, and after turning 90 degrees, high thermal conductivity in the longitudinal direction is obtained. The thickness of the film is the horizontal area of this interfacial material, and the preparation process is cumbersome, which is not conducive to large-scale production.

[0005] The present invention aims to provide an all-carbon-based composite material with both high z-directional thermal conductivity and excellent compression and rebound properties. Through the three-dimensional interconnected structure of a unique hollow spiral carbon fiber layer and a graphene layer, it breaks through the bottleneck of the existing materials in terms of thermal conductivity and mechanical properties, and provides an innovative solution to the thermal management problems in the fields of high-end electronic devices and new energy. Summary of the Invention

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

[0007] The second object of the present invention is to provide a preparation method of the carbon / carbon composite material.

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

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

[0010] A carbon / carbon composite material includes two graphene layers;

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

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

[0013] When there are two or more layers of spiral carbon fiber layers 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 helical carbon fiber layer through graphene;

[0015] Adjacent helical carbon fiber layers are fixedly connected through graphene;

[0016] Adjacent hollow helical carbon fibers are fixedly connected through graphene;

[0017] The hollow helical carbon fiber is obtained by removing the organic core material after the CNT film after twisting is helically wound on the surface of the organic core material.

[0018] The thickness of the graphene layer is 15 - 30 μm;

[0019] The diameter of the twisted CNT straight fiber is 350 μm;

[0020] The twist of the twisted CNT straight fiber is 135;

[0021] The width of the CNT film is 10 mm;

[0022] The twist of the hollow helical carbon fiber is 200 - 450;

[0023] The inner diameter of the hollow helical carbon fiber is 0.2 - 0.6 mm;

[0024] The outer diameter of the hollow helical carbon fiber is 0.5 - 1.5 mm;

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

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

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

[0028] The preparation method of the carbon / carbon composite material includes the following steps:

[0029] S1 Twist the CNT film to obtain a twisted CNT straight fiber, and wind the twisted CNT straight fiber on the surface of the organic core material to obtain a core - carrying helical carbon fiber;

[0030] S2 Immerse the core-spiral carbon fiber in the GO solution, and then perform drying I to obtain a core-spiral carbon fiber coated with a GO sheath; S3 Arrange the core-spiral carbon fiber coated with a GO sheath in a single layer or multiple layers in parallel to obtain a single-layer or multi-layer spiral carbon fiber layer; S4 Brush the GO slurry on the upper and lower surfaces of the single-layer or multi-layer spiral carbon fiber layer, and then perform drying II to form a GO slurry layer; then perform hot pressing to obtain an untreated carbon-based composite material;

[0031] S5 Perform heat treatment on the untreated carbon-based composite material to obtain the product.

[0032] The core material includes nylon thread;

[0033] The diameter of the core material is 0.2 - 0.6 mm;

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

[0035] The heat source used for drying I includes an infrared heat source;

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

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

[0038] The concentration of the GO slurry is 15 mg / mL;

[0039] The temperature of drying II is 70 °C.

[0040] The temperature of the hot pressing is 300 °C;

[0041] The pressure of the hot pressing is 1 - 1.5 MPa;

[0042] The pressure holding time of the hot pressing is 30 min;

[0043] The temperature of the graphitization is 2900 - 3100 °C.

[0044] The application of the carbon / carbon composite material is used for preparing a thermal management system; or

[0045] Used for preparing a battery system.

[0046] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0047] The carbon / carbon composite material provided by the present invention uses the twisted CNT film to prepare spiral fibers as elastic components, improving the resilience performance of the carbon / carbon composite material. At the same time, the introduction of the graphene layer can provide a stress-bearing surface. Therefore, the carbon / carbon composite material provided by the present invention is a fully carbon sandwich-shaped composite material with both high z-direction thermal conductivity and excellent mechanical properties, and can be widely applied in the fields of high-efficiency thermal management and structural applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 Shows a schematic diagram of the z-direction deformation of the hollow spiral carbon fiber when the carbon-based composite material provided by the present invention is stressed in the z-direction.

[0049] Figure 2 Shows a schematic diagram of the x-direction deformation of the hollow spiral carbon fiber when the carbon-based composite material provided by the present invention is stressed in the z-direction.

[0050] Figure 3 Shows a schematic diagram of the structure of the CNT spiral fiber.

[0051] Figure 4 Shows a schematic diagram of the layer structure of the sandwich carbon / carbon composite plate.

[0052] Figure 5 Shows a process flow chart. DETAILED DESCRIPTION OF THE INVENTION

[0053] The present invention provides a carbon / carbon composite material, whose basic structure is a sandwich structure composed of two graphene layers and at least one layer of hollow spiral carbon fiber layer. This structure is a kind of micro-spring-like structure with both high thermal conductivity and high resilience performance. As Figure 1 shown, different from ordinary springs, when the graphene layer is stressed, 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 compressive deformation perpendicular to their axial direction (ordinary springs produce a compressive deformation parallel to their axial direction), which makes the carbon-based composite material have good resilience performance. At the same time, as Figure 2 shown, since the twisting directions of adjacent hollow spiral carbon fibers in the spiral carbon fiber layer are opposite, and adjacent hollow spiral carbon fibers are fixedly connected to each other, an interlocking structure is formed between adjacent hollow spiral carbon fibers. When the graphene layer is stressed, it is difficult for the hollow spiral carbon fibers to undergo tilting deformation and instead undergo bending deformation, which also makes the sandwich structure have good resilience performance. This structure can also improve the load-bearing capacity of the carbon / carbon composite material.

[0054] Furthermore, the hollow spiral carbon fiber is obtained by helically winding a twisted CNT film on the surface of an organic core material and then removing the organic core material. This endows the hollow spiral carbon fiber with strong elasticity. The CNT film is a nano-scale film. After heat treatment, it will interleave and spread out after being twisted and heat-treated, 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 is a structure-functional integrated material with good three-dimensional heat conduction performance and good resilience performance. The graphene layer and the spiral carbon fiber layer are fixedly connected, preferably by graphene. Therefore, when stressed, 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 graphene layers, and spiral carbon fiber layers can be provided between each two graphene layers. This carbon-based composite material with multiple graphene layers can be regarded as being stacked by carbon-based composite materials composed of two graphene layers. The more the number of graphene layers, the better the resilience performance. Multiple spiral carbon fiber layers can also be provided between each two graphene layers. When there are two or more spiral carbon fiber layers 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 not parallel can effectively prevent slippage between adjacent spiral carbon fiber layers when the carbon-based composite material is stressed. Obviously, the composite material with multiple graphene layers can also be a stack of the above basic structures. The composite board provided by the present invention has a fully 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 its application more extensive.

[0055] The thickness of the graphene layer is 15 - 30 μm; this is because, if the thickness is too thin, it is easy to cause incomplete infiltration and coverage of the graphene, resulting in the exposure of the spiral carbon fiber layer, thereby affecting the heat conduction performance; if the thickness is too large, the graphene layer is prone to brittle fracture during the operation.

[0056] The twist of the hollow spiral carbon fiber is 200 - 450;

[0057] The width of the CNT film is 10 mm;

[0058] The inner diameter of the hollow spiral carbon fiber is 0.2 - 0.6 mm;

[0059] The outer diameter of the hollow spiral carbon fiber is 0.5 - 1.5 mm.

[0060] The included angle between the axes of the hollow spiral carbon fibers in adjacent spiral carbon fiber layers is 30 - 90 degrees; setting this angle can effectively avoid slippage between adjacent spiral carbon fiber layers.

[0061] Further preferably, the included angle between the axes of the hollow spiral carbon fibers in adjacent spiral carbon fiber layers is 75 - 90 degrees. More preferably, when the included angle between the axes of the hollow spiral carbon fibers in adjacent spiral carbon fiber layers is 90 degrees, it is difficult for slippage to occur between adjacent spiral carbon fiber layers.

[0062] The present invention also provides a method for preparing the carbon / carbon composite material, comprising the following steps:

[0063] 1) Preparation of CNT straight fibers Using a CNT film as a raw material, cut it into long strips. One end of the CNT strip is fixed on the central axis of a 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 continuously twist to transform the CNT film into straight fibers.

[0064] 2) Preparation of CNT spiral fibers

[0065] Using the CNT straight fibers as raw materials. Through a winding machine, fix the core material on the synchronous motors at both ends, fix one end of the CNT straight fiber on a spool, and connect the other end to the surface of an electric slider through a thread guide. Under the coordinated action of the synchronous motor and the slider, tightly wind the CNT straight fibers on the surface of the core material to form core - containing CNT spiral fibers.

[0066] 3) Preparation of GO@CNT spiral fibers

[0067] Pass the CNT spiral fibers continuously through a diluted GO solution, and then dry to make GO sheets adhere to the surface of the spiral fibers and form a sheath layer. Control the thickness of the GO layer through multiple roller impregnations.

[0068] 4) Preparation of sandwich - type carbon / carbon composite plates

[0069] Lay the GO@CNT spiral fibers parallel in a mold. Spray GO slurry on the upper and lower surfaces. Dry the laid - out fiber sheets, and repeat the brushing and drying steps 5 - 10 times. Put them into the mold for hot pressing. Finally, the material is subjected to carbonization treatment and graphitization treatment to obtain a sandwich - structured carbon / carbon composite plate. The core material includes nylon thread, polyester fiber, polyethylene fiber, polypropylene fiber or polyurethane fiber; the above - mentioned fibers have certain mechanical strength for easy operation, and have low residual carbon during high - temperature heat treatment, which is beneficial to the formation of hollow cavities.

[0070] The diameter of the core material is 0.2 - 0.6 mm;

[0071] The number of twists of the twisting is 200 to 450. The higher the twist degree means the more turns of the fiber rotating within the unit length. Since the modulus of carbon fiber itself is relatively high, it is impossible to achieve a higher number of twists. If the number of twists is too low, the helix is insufficient, which will affect both the heat conduction and the resilience effect in the vertical direction.

[0072] The concentration of the GO solution is 5 mg / mL; if the concentration is too low, the number of impregnation times will increase significantly. The heat source used for the first drying includes an infrared heat source; if the concentration increases further, the viscosity of the solution will increase significantly, which is not convenient for the operation of the spiral fiber to quickly immerse and leach from the GO solution.

[0073] The heat source used for the first drying includes an infrared heat source; the power of the infrared heat source is 2000 W. Using an infrared heat source can achieve drying in the form of thermal radiation (non-contact). The power of the infrared heat source is 2000 W.

[0074] The thickness of the GO sheath is 5 to 10 μm.

[0075] The concentration of the GO slurry is 15 mg / mL;

[0076] The temperature of the second drying is 70 °C.

[0077] The temperature of the hot pressing is 300 °C;

[0078] The pressure of the hot pressing is 1 to 1.5 MPa;

[0079] The holding time of the hot pressing is 30 min;

[0080] The temperature of the graphitization is 2900 - 3100 °C.

[0081] Since the carbon-based composite material has both three-dimensional heat conduction and high resilience, it can be applied to the preparation of a thermal management system; moreover, it is particularly suitable for the preparation of a system that requires heat dissipation and shock absorption at the same time, such as a vehicle-mounted battery system. Since the carbon-based composite material has properties such as durability, chemical corrosion resistance, and flame retardancy, it is particularly suitable for the preparation of a vehicle-mounted new energy battery system.

[0082] The present invention will be further described below in conjunction with specific embodiments.

[0083] Example 1

[0084] The preparation of CNT straight fibers uses a CNT film as the raw material, and it is cut into strips with a width of 10 mm. One end of the CNT strip is fixed on the central axis of a 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 140 r / min, and twisting is continued for 15 minutes to transform the CNT film into straight fibers.

[0085] Preparation of CNT Spiral Fibers

[0086] Using a nylon thread with a diameter of 0.2 mm as the core material and CNT straight fibers as the raw material. Through a self-made 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 spool, and the other end is connected to the surface of the electric slider through a thread guide. Under the coordinated action of the synchronous motor and the slider, the CNT straight fiber is tightly wound around the surface of the core material to form a core-containing CNT spiral fiber. The distance between the synchronous motors is 260 mm. The CNT straight fiber passes through the thread guide on the stepping motor and the slider speed is controlled at 200 mm / min. The rotational speed T of the synchronous motor is T = 1000L / d (T (rpm / min) is the rotational speed of the synchronous motor, L (mm / min) is the moving speed of the slider, and d (μm) is the diameter of the CNT straight fiber).

[0087] Preparation of GO@CNT Spiral Fibers

[0088] The CNT spiral fibers are 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, so that GO flakes are attached to the surface of the spiral fibers and form a sheath layer. The thickness of the GO layer is controlled by 5 times of roller dipping.

[0089] Preparation of Sandwich Carbon / Carbon Composite Plates

[0090] The GO@CNT spiral fibers are arranged in parallel in the mold, and when arranging, the spiral directions of adjacent hollow spiral carbon fibers are opposite. GO slurry (concentration of 15 mg / ml) is brushed on the upper and lower surfaces. The arranged fiber sheet is dried at 70 °C for 30 minutes, and the brushing and drying steps are repeated 5 times. Then it is put into the mold and hot-pressed at 300 °C and 1 MPa for 30 minutes. Finally, the material is subjected to carbonization treatment at 1600 °C for 1 hour and graphitization treatment at 3100 °C for 1 h to obtain a carbon / carbon composite material with a sandwich structure.

[0091] Example 2

[0092] The preparation of the carbon / carbon composite material with two layers of spiral fiber layers and the adjacent two layers of spiral fiber layers orthogonally stacked is different from that of Example 1 in that the adjacent two layers of spiral fiber layers are orthogonally stacked. In the process of preparing the sandwich carbon / carbon plate, the GO@CNT spiral fibers are arranged in parallel in the mold, and when arranging, the spiral directions of adjacent hollow spiral carbon fibers are opposite. GO slurry (concentration of 15 mg / ml) is brushed on the upper and lower surfaces. The arranged fiber sheet is dried at 70 °C for 30 minutes, and the brushing and drying steps are repeated 5 times. Then the second layer of GO@CNT spiral carbon fiber layer is arranged, and the adjacent two layers of spiral fiber layers are orthogonally stacked, and then GO slurry (15 mg·mL -1), and then placed in a forced-air drying oven at 70 °C for 30 minutes. Repeat the brushing and drying steps 5 times, so that the GO layer can fill the depressions between the fibers and form a tight and flat GO layer on the surface of the sheet. The remaining steps, parameters, and methods are the same as those in Example 1.

[0093] Example 3

[0094] The preparation of a carbon / carbon composite material with two layers of helical fiber layers and the adjacent two layers of helical fiber layers stacked at 75 degrees is different from that in Example 1 in that the adjacent two layers of helical fiber layers are stacked at 75 degrees. During the preparation of the sandwich carbon / carbon sheet, the GO@CNT helical fibers are arranged in parallel in the mold, and when arranging, the helical directions of the adjacent hollow helical carbon fibers are opposite. Brush the GO slurry (concentration: 15 mg / ml) on the upper and lower surfaces. Dry the arranged fiber sheet at 70 °C for 30 minutes, and repeat the brushing and drying steps 5 times. Then arrange the second layer of GO@CNT helical carbon fiber layer, and the adjacent two layers of helical fiber layers are stacked at 75 degrees. Then further brush the GO slurry (15 mg·mL -1 ), and then placed in a forced-air drying oven at 70 °C for 30 minutes. Repeat the brushing and drying steps 5 times, so that the GO layer can fill the depressions between the fibers and form a tight and flat GO layer on the surface of the sheet. The remaining steps, parameters, and methods are the same as those in Example 1.

[0095] Example 4

[0096] The preparation of a carbon / carbon composite material with two layers of helical fiber layers and the adjacent two layers of helical fiber layers stacked at 30 degrees is different from that in Example 1 in that the adjacent two layers of helical fiber layers are stacked at 30 degrees. During the preparation of the sandwich carbon / carbon sheet, the GO@CNT helical fibers are arranged in parallel in the mold, and when arranging, the helical directions of the adjacent hollow helical carbon fibers are opposite. Brush the GO slurry (concentration: 15 mg / ml) on the upper and lower surfaces. Dry the arranged fiber sheet at 70 °C for 30 minutes, and repeat the brushing and drying steps 5 times. Then arrange the second layer of GO@CNT helical carbon fiber layer, and the adjacent two layers of helical fiber layers are stacked at 30 degrees. Then further brush the GO slurry (15 mg·mL -1 ), and then placed in a forced-air drying oven at 70 °C for 30 minutes. Repeat the brushing and drying steps 5 times, so that the GO layer can fill the depressions between the fibers and form a tight and flat GO layer on the surface of the sheet. The remaining steps, parameters, and methods are the same as those in Example 1.

[0097] Example 5

[0098] 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 the same as those in Example 1.

[0099] Example 6 (repeatedly brushing GO slurry and drying step for 10 times)

[0100] The difference from Example 1 is that in the preparation process of the sandwich carbon / carbon plate, the steps of repeatedly brushing GO slurry and drying are carried out 10 times. The remaining steps, parameters, and methods are the same as those in Example 1.

[0101] Example 7

[0102] The difference from Example 1 is that in the preparation process of the sandwich carbon / carbon plate, the hot pressing pressure subsequently put into the mold is 1.5 MPa. The remaining steps, parameters, and methods are the same as those in Example 1.

[0103] Example 8

[0104] 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 the same as those in Example 1.

[0105] In the present invention, the samples prepared in Examples 1-8 can be tested by the following methods, and the results are listed in Table 1:

[0106] 1. Use an Elementar vario EL cube organic elemental analyzer to test the carbon content of the sample in CHNS mode.

[0107] 2. 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 0.0001 g; 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.

[0108] 4. The thermal conductivity of the all-carbon plate (sandwich carbon / carbon plate) is measured by a DRL-III type thermal conductivity meter. The DRL-III type 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 measured area of the specimen is 1.5 cm × 1.5 cm. Set the hot electrode temperature at 30 °C and the cold electrode temperature at 20 °C. Apply a layer of thermal conductive silicone grease evenly on the contact plane between the hot and cold electrodes and the specimen to reduce the influence of air on the thermal conductivity test. After the temperatures of the hot and cold electrodes are stable, measure the thermal conductivity of the sample when the pressure on the sample is 0.1 MPa and 1 MPa.

[0109] 4. The compression and rebound rate of the all-carbon plate (sandwich carbon / carbon plate) is measured by an electronic universal testing machine (AG-plus type). When testing the compression and rebound performance of the sample, it can apply an accurate compression force to the sample at a set rate. The measured area of the specimen is 1.5 cm ×1.5 cm. Record the initial thickness of the sample, and test the pressure on the sample at 0.1 MPa and 1 MPa. After unloading the pressure, record the thickness of the sample after compression and rebound, and calculate the compression and rebound rate of the sample. The calculation method is the thickness after compression and rebound / the initial thickness of the sample.

[0110] Table 1

[0111]

[0112] From the data of Examples 1-8, it can be seen that the carbon content of the sample provided by the present invention is as high as 99.9%, and it has a low bulk density. The bulk density of the examples is 0.23-0.32 g / cm 3 ; the thermal conductivity of the sample obtained by the present invention in the vertical direction increases with the increase of the applied pressure. When the pressure is 0.1 MPa, the thermal conductivity is 9.1-15.9 W / mK, and when the pressure is 1 MPa, the thermal conductivity is 10.9-19.2 W / mK; the deformation and rebound rate of the sample obtained by the present invention at 0.1 MPa is 72-96%, and the deformation and rebound rate at 1 MPa is 45-64%. Therefore, the sample obtained by the present invention is a all-carbon material with high thermal conductivity and high rebound rate, and can be used as an excellent thermal interface material.

[0113] From the data of Examples 1-4, it can be seen that increasing the number of layers of spiral carbon fiber layers can improve the deformation and rebound rate, but the thermal conductivity will decrease; with the increase of the number of layers, that is, the number of hollow cavities increases in the Z-axis direction. When the sample is under a constant pressure, the deformable space increases, so more deformation can be obtained. This constant pressure does not damage the sample, and the deformation and rebound rate increases; increasing the number of layers of spiral carbon fiber layers increases the thermal interface, so the thermal conductivity decreases.

[0114] From the data of Example 1 and Example 5, it can be seen that reducing the graphitization temperature makes the crystallization degree of graphene, carbon fiber and pyrolytic carbon lower. Therefore, the thermal conductivity of the sample obtained in Example 5 is lower.

[0115] From the data of Example 1 and Example 6, it can be seen that increasing the number of times of repeatedly brushing GO slurry and drying steps makes the voids denser by graphene more fully, and at the same time the formed graphene layer is thicker. Therefore, the thermal conductivity is higher and the rebound rate is lower.

[0116] From the data of Example 1 and Example 7, it can be seen that increasing the molding pressure makes the bulk density of the obtained sample increase, the contact is more and closer, and the interface thermal resistance decreases. Therefore, the thermal conductivity is higher, but the rebound rate is lower.

[0117] From the data of Example 1 and Example 8, it can be seen that increasing the diameter of the nylon fiber, that is, increasing the inner diameter of the hollow spiral carbon fiber, leads to an increase in 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 the amount of deformation. Therefore, the deformation recovery rate is greater.

Claims

1. A carbon / carbon composite material, characterized in that: It includes two graphene layers; There is at least one layer of helical carbon fiber layer between every two graphene layers; The helical carbon fiber layer is composed of hollow helical carbon fibers laid parallel, and the helical directions of adjacent hollow helical carbon fibers are opposite; When there are two or more layers of helical carbon fiber layers between the graphene layers, the axes of the hollow helical carbon fibers in adjacent helical carbon fiber layers are not parallel; The graphene layer and the helical carbon fiber layer are fixedly connected by graphene; Adjacent helical carbon fiber layers are fixedly connected by graphene; Adjacent hollow helical carbon fibers are fixedly connected by graphene; The hollow helical carbon fiber is obtained by heat-treating and removing the organic core material after the twisted CNT film is helically wound on the surface of 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 - 30 μm; The diameter of the twisted CNT straight fiber is 350 μm; The twist of the twisted CNT is 135; The width of the CNT film is 10 mm; The twist of the hollow helical carbon fiber is 200 - 450 The inner diameter of the hollow helical carbon fiber is 0.2 - 0.6 mm; The outer diameter of the hollow helical carbon fiber is 0.5 - 1.5 mm.

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

4. The preparation method of the carbon / carbon composite material according to claim 1, characterized in that: It includes the following steps: S1 Twist the CNT film to obtain twisted CNT straight fibers, and wind the twisted CNT straight fibers on the surface of the organic core material to obtain core-containing helical carbon fibers; S2 Immerse the core-containing helical carbon fibers in the GO solution, and then dry I to obtain core-containing helical carbon fibers coated with a GO sheath; S3 Lay the core-containing helical carbon fibers coated with a GO sheath in a single layer or multiple layers in parallel to obtain a single layer or multiple layers of helical carbon fiber layers; S4 Brush the GO slurry on the upper and lower surfaces of the single layer or multiple layers of helical carbon fiber layers, and then dry II to form a GO slurry layer; then hot press to obtain an untreated carbon-based composite material; S5 Heat-treat the untreated carbon-based composite material to obtain the product.

5. The preparation method of the 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; The number of twists is 200 - 450.

6. The preparation method of the 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 for drying I includes an infrared heat source; The power of the infrared heat source is 2000 W.

7. The preparation method of the carbon / carbon composite material according to claim 1, characterized in that: The thickness of the GO sheath is 5-10 μm.

8. The preparation method of the 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 second drying is 70 °C.

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

10. The application of the carbon / carbon composite material according to claim 1, characterized in that: It is applied to prepare a thermal management system; or It is applied to prepare a battery system.

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