Unidirectional graphene fiber carbon / carbon composite material and preparation method and application thereof

Abstract

The invention discloses a unidirectional graphene fiber carbon / carbon composite material as well as a preparation method and application thereof, and belongs to the technical field of carbon / carbon composite materials. The preparation method comprises the following steps: adding phenolic resin powder into absolute ethyl alcohol to prepare a phenolic resin dipping solution; adding the graphene fiber bundle into a phenolic resin impregnation solution for impregnation under the conditions of normal temperature and normal pressure to prepare a pre-impregnated graphene fiber bundle; carrying out stepped heating curing on the pre-impregnated graphene fiber bundle, and then carrying out carbonization to prepare a pre-treated graphene fiber bundle; the pretreated graphene fiber bundles are arranged in parallel and stacked in the thickness direction, pressure is applied for fastening, and a one-way prefabricated body is obtained; and carrying out heat treatment on the unidirectional preform, densifying by adopting an isothermal chemical vapor infiltration process, and then carrying out graphitization treatment to obtain the unidirectional graphene fiber carbon / carbon composite material. The graphene fiber is pretreated to fill pores of the graphene fiber, so that the densification efficiency of the graphene fiber preform is improved, and finally, the heat conduction and mechanical properties of the composite material are enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon / carbon composites, and particularly relates to a unidirectional graphene fiber carbon / carbon composite material, a preparation method thereof, and an application thereof. Background Art

[0002] Carbon / carbon (C / C) composites have the characteristics of low density, high thermal conductivity, and good mechanical properties, and are indispensable materials for spacecraft thermal management. The heat dissipation of high-power satellite system levels and the local heat dissipation of high-power-consuming electronic devices have become challenges for spacecraft thermal management. High-thermal-conductivity structural materials and lightweight and efficient thermal management structures are required to meet the heat dissipation requirements, which also pose higher requirements for the comprehensive performance of C / C composites.

[0003] One of the factors affecting the performance of C / C composites is the type of reinforcing carbon fiber. C / C composites reinforced with polyacrylonitrile-based (PAN) carbon fibers have excellent mechanical properties and low thermal expansion coefficients, but poor thermal conductivity and are difficult to meet high heat dissipation requirements. C / C composites reinforced with mesophase pitch (MP)-based carbon fibers are the most widely used high-thermal-conductivity materials at present, with higher axial thermal conductivity (400 - 1100 W / m·K) and higher modulus, and have great application value in efficient thermal management. However, due to the high graphitization structure and relatively high degree of crystallization inside the mesophase pitch-based fibers, the fibers are prone to brittle fracture, resulting in a significant reduction in their weaving ability. Graphene fiber (GF) is a newly emerged high-thermal-conductivity carbonaceous fiber composed of graphene sheets arranged neatly along the fiber axis, with a tensile strength of 1.4 GPa, a density of 1.93 g / cm 3 and an electrical conductivity of 4.1×10 5 S / m and a thermal conductivity of 1204 W / m·K, and can still maintain a certain flexibility at high temperatures (Shi H, Wang B, Wang L, et al. Large-scale preparation of thermally conductive graphene fiber filaments[J]. Carbon, 2024, 221), and has excellent weaving performance, which is beneficial to the weaving and forming of complex preform structures. However, the graphene fiber has more internal pores and a larger A / V ratio, which will cause larger pore structures and surface crusting phenomena to remain in the C / C composite material during the subsequent densification process due to difficult deposition, greatly preventing the improvement of its thermal and mechanical properties. Summary of the Invention

[0004] In order to overcome the drawback of porous interior in graphene fibers in the above-mentioned existing technologies, the object of the present invention is to provide a unidirectional graphene fiber carbon / carbon composite material, its preparation method and application. By pre-treating the graphene fibers to fill their own pores, the densification efficiency of the graphene fiber preform is improved, and finally the thermal conductivity and mechanical properties of the composite material are enhanced.

[0005] To achieve the above object, the present invention is implemented by the following technical solutions: On the one hand, the present invention provides a preparation method of a unidirectional graphene fiber carbon / carbon composite material, including the following steps: Adding phenolic resin powder into absolute ethanol to prepare a phenolic resin impregnation solution; under normal temperature and pressure conditions, adding a graphene fiber bundle into the phenolic resin impregnation solution for impregnation to obtain a pre-impregnated graphene fiber bundle; subjecting the pre-impregnated graphene fiber bundle to stepwise temperature-rising curing and then carbonization to obtain a pre-treated graphene fiber bundle; Arranging the pre-treated graphene fiber bundles in parallel and stacking them along the thickness direction, and applying pressure to fasten to obtain a unidirectional preform; Performing heat treatment on the unidirectional preform and then using the isothermal chemical vapor infiltration process for densification, and then performing graphitization treatment to obtain a unidirectional graphene fiber carbon / carbon composite material.

[0006] In an embodiment, the mass ratio of the phenolic resin powder to absolute ethanol is 2-5:10-40.

[0007] In an embodiment, the graphene fiber bundle is a 1k graphene fiber bundle with a width of 5-7 mm, and the diameter of a single graphene fiber in the graphene fiber bundle is 13-14 μm; The impregnation time is 20 min-40 min.

[0008] In an embodiment, the process of stepwise temperature-rising curing is as follows: first, raise the temperature at a rate of 3-5 °C / min to 120 °C, keep it constant for 20 min, then raise the temperature at a rate of 2-4 °C / min to 150 °C, keep it warm for 20 min, and continue to raise the temperature at a rate of 2-4 °C / min to 180 °C, and keep it warm for 1-2 h.

[0009] In an embodiment, the process of carbonization is as follows: under the protective atmosphere of argon, carbonize the graphene fiber bundle after stepwise temperature-rising curing, raise the temperature at a rate of 4-5 °C / min to 500 °C, keep it constant for 1 h, and then raise the temperature at a rate of 3-4 °C / min to 950 °C, and keep it warm for 2 h.

[0010] In one embodiment, the process of obtaining the unidirectional preform is as follows: The pretreated graphene fiber bundles are uniformly arranged in parallel and stacked 8 to 9 layers in the thickness direction, and are pressed tightly in the thickness direction with a clamping force of 40 to 50 kPa to obtain the unidirectional preform; The process of the heat treatment is as follows: In an argon environment of a protective atmosphere, the unidirectional preform is heat-treated at 1500 to 1600 °C for 2 to 4 h.

[0011] In one embodiment, the process parameters of the densification are as follows: The deposition temperature is 1000 to 1100 °C, the pressure is 2 to 10 kPa, the flow rate of methane is 15 to 18 L / min, and the deposition time is 150 to 170 h; The process parameters of the graphitization treatment are as follows: In an argon environment of a protective atmosphere, graphitization treatment is carried out at a treatment temperature of 2400 to 2500 °C, and the holding time is 2 to 4 h.

[0012] The present invention also provides a unidirectional graphene fiber carbon / carbon composite material prepared by the above preparation method. The resin carbon, graphene fiber and pyrolytic carbon in the unidirectional graphene fiber carbon / carbon composite material form a soft-hard carbon inlaid structure; the resin carbon is filled as hard carbon inside the graphene fiber, the graphene fiber is used as soft carbon in the middle, and the pyrolytic carbon is tightly wrapped as hard carbon outside the graphene fiber.

[0013] In one embodiment, the density of the unidirectional graphene fiber carbon / carbon composite material is 1.58 to 1.65 g / cm 3 , and the thickness is 1.5 to 1.6 mm; the thermal conductivity of the unidirectional graphene fiber carbon / carbon composite material along the axial direction is 600 to 654 W·m -1 ·K -1 ; the flexural strength of the unidirectional graphene fiber carbon / carbon composite material along the axial direction is 100 to 150 MPa, and the tensile strength along the axial direction is 219 to 300 MPa.

[0014] The present invention also provides an application of the unidirectional graphene fiber carbon / carbon composite material prepared by the above preparation method in spacecraft thermal management.

[0015] Compared with the prior art, the present invention has the following beneficial effects: A preparation method of a unidirectional graphene fiber carbon / carbon composite provided by the present invention seals pores by impregnating phenolic resin in a unidirectional graphene fiber bundle. The phenolic resin is used to fill the pores of the graphene fiber bundle, enabling the phenolic resin to fully fill the pores inside the graphene fiber bundle and within individual fibers. Since the thermal resistance of the pores is relatively large, filling the phenolic resin can prevent the pores at these positions where it is difficult to deposit pyrolytic carbon during subsequent overall densification from being difficult to fill, which affects the densification efficiency and overall performance of the graphene fiber carbon / carbon composite, playing a role in compensating for weaknesses; after impregnating the phenolic resin, the ICVI process is used to deposit pyrolytic carbon to construct a soft-hard carbon inlaid structure. The resin carbon serves as hard carbon and fills inside the graphene fibers, while the graphene fibers serve as soft carbon in the middle, and the pyrolytic carbon serves as hard carbon and tightly wraps around the outside of the graphene fibers; the highly textured pyrolytic carbon has high thermal conductivity and can act as a heat transfer channel, and the resin carbon has high hardness, which can improve the mechanical properties while maintaining the original morphology of the graphene fibers. The two work together to achieve the preparation of a high thermal conductivity-high load-bearing composite material. A phenolic resin solution with a relatively low concentration has good fluidity during impregnation, better wettability with the fibers, and can effectively fill micron-sized pores; the present invention uses graphene fibers to prepare a unidirectional preform. The graphene fibers have good thermal conductivity and can construct a heat conduction channel, and can effectively improve the thermal conductivity of the carbon / carbon composite after subsequent high-temperature heat treatment, enabling heat to be directionally conducted within the composite material and improving the heat conduction efficiency; moreover, the graphene fibers also have excellent tensile properties and electrical conductivity. Therefore, the graphene fiber carbon / carbon composite prepared by the method combining pre-impregnation pore sealing and chemical vapor infiltration process has high density, high thermal conductivity, and load-bearing capacity.

[0016] The present invention heat-treats the unidirectional preform before depositing pyrolytic carbon at 1500 - 1600 °C for 2 - 4 h. The purpose is to release stress and avoid the resin carbon generating huge stress and shrinking during subsequent deposition and graphitization processes, which may cause secondary damage to the fiber structure. The graphene fibers have a certain flexibility and can release stress through free deformation.

[0017] The unidirectional graphene fiber carbon / carbon composite of the present invention is graphitized at 2400 - 2500 °C for 2 - 4 h, which promotes the graphite lamellae to be more regular, reduces defects, and also avoids reducing the interfiber bonding force during long-time high-temperature heat treatment and affecting its mechanical properties.

[0018] In summary, the unidirectional graphene fibers used in the present invention improve the comprehensive performance of C / C composites to a certain extent. Description of the Drawings

[0019] Figure 1 is the SEM photograph of the graphene fibers in the present invention; Figure 2 is the SEM photograph of the graphene fiber C / C composite without impregnation treatment in the present invention; Figure 3 SEM photograph of the graphene fiber C / C composite material after impregnation treatment in the present invention; Figure 4 SEM photograph of the pretreated graphene fiber in Example 1 provided by the present invention; Figure 5 SEM photograph of the pretreated graphene fiber in Example 2 provided by the present invention; Figure 6 SEM photograph of the pretreated graphene fiber in Example 3 provided by the present invention; Figure 7 SEM photograph of the pretreated graphene fiber in Comparative Example 1 provided by the present invention; Figure 8 SEM photograph of the pretreated graphene fiber in Comparative Example 2 provided by the present invention; Figure 9 SEM photograph of the pretreated graphene fiber in Comparative Example 3 provided by the present invention. Detailed implementation manners

[0020] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meaning understood by those skilled in the art for the present invention. In case of conflict, the definition in this specification shall prevail.

[0021] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall not limit the scope of the present invention in any way, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0022] In this article, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0023] In this article, unless otherwise specified, the terms "comprise", "include", "contain", "have" or similar terms cover the meanings of "consist of" and "consist essentially of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A consists only of a".

[0024] In this text, for the sake of brevity in description, all possible combinations of all technical features in each implementation or embodiment are not described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation or embodiment can be combined arbitrarily, and all possible combinations should be considered as the scope described in this specification.

[0025] The present invention provides a unidirectional graphene fiber carbon / carbon composite material, its preparation method and application. Through the pretreatment of graphene fiber bundles, the present invention obtains a C / C composite material with integrated lightweight, high thermal conductivity and load-bearing properties.

[0026] The present invention mainly uses graphene fibers (GF), see Figure 1 As shown, the graphene fiber is composed of graphene sheets arranged neatly along the fiber axis, with light weight, high mechanical strength and high thermal conductivity, and can also maintain a certain flexibility at high temperatures. However, there are many pores inside the graphene fiber, which will affect the subsequent densification process, see Figure 2 As shown, and the thermal resistance of the pores is very large, which will also affect the overall thermal conductivity of the material. The present invention prepares a unidirectional graphene fiber carbon / carbon composite material through the pre-impregnation treatment of graphene fibers, realizing the integration of high thermal conductivity, lightweight and load-bearing properties, and laying a theoretical foundation for promoting the application of graphene fibers in the field of high-power spacecraft thermal management.

[0027] The preparation method of a unidirectional graphene fiber carbon / carbon composite material provided by the present invention is as follows: Step 1: Add 2 - 5 parts of phenolic resin powder into 10 - 40 parts of absolute ethanol, and ultrasonically disperse for 30 min - 1 h until there is no obvious precipitation phenomenon to obtain a phenolic resin impregnation solution. Subsequently, add the porous graphene fiber bundle into the phenolic resin impregnation solution and impregnate for 20 min - 40 min under normal temperature and pressure conditions to obtain a pre-impregnated graphene fiber bundle. Put the pre-impregnated graphene fiber bundle into an oven for curing. First, heat it up to 120°C at a rate of 3 - 5°C / min, keep it at a constant temperature for 20 min, then heat it up to 150°C at a rate of 2 - 4°C / min, keep it warm for 20 min, and continue to heat it up to 180°C at a rate of 2 - 4°C / min, keep it warm for 1 - 2 h. Then cool it naturally to room temperature. The cured graphene fiber is transferred to a heat treatment furnace, and under the protective atmosphere of argon gas, the impregnated and cured graphene fiber is carbonized, heated up to 500°C at a rate of 4 - 5°C / min, kept at a constant temperature for 1 h, and then heated up to 950°C at a rate of 3 - 4°C / min, kept warm for 2 h to obtain a pretreated graphene fiber bundle.

[0028] Step 2: Uniformly arrange the pre-treated graphene fiber bundles in parallel in a graphite mold, stack 8 - 9 layers in the thickness direction, then fasten with bolts and apply pressure for fastening, with the clamping force being 40 - 50 kPa, to obtain a unidirectional preform.

[0029] Step 3: Heat-treat the unidirectional preform prepared in Step 2 at 1500 - 1600 °C for a holding time of 2 - 4 h, with the protective atmosphere being argon.

[0030] Step 4: Place the unidirectional preform after heat-treatment in Step 3 into a pyrolytic carbon deposition furnace and densify it using the ICVI process. The deposition temperature is 1000 - 1100 °C, the pressure is 2 - 10 kPa, the flow rate of methane is 15 - 18 L / min, and the deposition time is 150 - 170 h. The density of the deposited graphene fiber carbon / carbon composite is 1.58 - 1.65 g / cm 3 , and the texture type of the pyrolytic carbon matrix is high texture, with the extinction angle being 20° ≤ Ae ≤ 24°.

[0031] Step 5: Graphitize the graphene fiber carbon / carbon composite prepared in Step 4 at a treatment temperature of 2400 - 2500 °C for a holding time of 2 - 4 h, with the protective atmosphere being argon, to obtain a unidirectional graphene fiber carbon / carbon composite.

[0032] In the specific implementation process, the fiber uses graphene fiber bundles, and the graphene fiber bundles use 1k graphene fiber bundles with a width of 5 - 7 mm. The diameter of a single graphene fiber in the graphene fiber bundle is 13 - 14 μm.

[0033] A preparation method of a unidirectional graphene fiber carbon / carbon composite provided by the present invention. In the present invention, phenolic resin is impregnated in graphene fibers for hole sealing, so that the phenolic resin fully fills the pores inside the graphene fiber bundle and inside single fibers. Since the thermal resistance of the pores is relatively large, filling the phenolic resin can avoid the difficulty in filling the pores at positions where it is difficult to deposit pyrolytic carbon during the subsequent overall densification process, which affects the densification efficiency and overall performance of the graphene fiber carbon / carbon composite, playing a role in compensating for weaknesses; after impregnating with phenolic resin, the ICVI process is adopted, which can achieve the coexistence of hard and soft carbon, and improve the mechanical properties while maintaining the original morphology of the graphene fibers; the phenolic resin solution with a relatively low concentration has good fluidity during the impregnation process, better wettability with the fibers, and can effectively fill the micron-sized pores; the present invention uses graphene fibers to prepare a unidirectional preform. The graphene fibers have good thermal conductivity and can build a heat conduction channel, and can effectively improve the thermal conductivity of the carbon / carbon composite after subsequent graphitization treatment, enabling heat to be directionally conducted within the composite and improving the heat conduction efficiency; moreover, the graphene fibers also have excellent flexibility and can release the stress generated by the resin carbon through free deformation. Therefore, the graphene fiber carbon / carbon composite prepared by the method combining pre-impregnation hole sealing and chemical vapor infiltration process has the characteristics of light weight, high thermal conductivity and load-bearing capacity.

[0034] The unidirectional graphene fibers used in the present invention improve the comprehensive performance of the C / C composite to a certain extent. A partial photograph of the prepared graphene fiber carbon / carbon composite is as Figure 3 shown. It can be seen from Figure 3 that the inside of the graphene fiber carbon / carbon composite is relatively dense, with a density of 1.58 - 1.65 g / cm 3 , and the thickness is 1.5 - 1.6 mm. The thermal conductivity of the composite along the axial direction is 600 - 654 W·m -1 ·K -1 ; the flexural strength along the axial direction is 100 - 150 MPa, and the tensile strength along the axial direction is 219 - 300 MPa.

[0035] The unidirectional graphene fiber carbon / carbon composite prepared by the present invention is applicable to spacecraft thermal management.

[0036] The following further elaborates the present invention in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0037] In the following examples, conventional instruments and equipment in the art are used. For the experimental methods without specific conditions noted in the following examples, they are generally carried out under conventional conditions or according to the conditions recommended by the manufacturers. In the following examples, various raw materials are used. Unless otherwise specified, commercially available products are used, and their specifications are the conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratio represents weight ratio.

[0038] Example 1 This example provides a method for preparing a unidirectional graphene fiber carbon / carbon composite, and the steps are as follows: 1. Add 2 parts of phenolic resin powder to 40 parts of absolute ethanol, and ultrasonically disperse for 30 min until there is no obvious precipitation phenomenon to obtain a phenolic resin impregnation solution; then add a porous graphene fiber bundle to the phenolic resin impregnation solution, and soak it at normal temperature and pressure for 20 min to obtain a pre-impregnated graphene fiber bundle; put the pre-impregnated graphene fiber bundle into an oven for curing; first heat it at a rate of 3 °C / min to 120 °C, keep it at a constant temperature for 20 min, then heat it at a rate of 3 °C / min to 150 °C, keep it warm for 20 min, continue to heat it at a rate of 2 °C / min to 180 °C, and keep it warm for 1 h; then naturally cool it to room temperature. The cured graphene fiber is transferred to a heat treatment furnace, and under the protective atmosphere of argon, the impregnated and cured fiber is carbonized, heated at a rate of 4 °C / min to 500 °C, kept at a constant temperature for 1 h, then heated at a rate of 3 °C / min to 950 °C, and kept warm for 2 h to obtain a pre-treated graphene fiber bundle; the photo of the pre-treated graphene fiber bundle is as Figure 4 shown, and it can be seen from Figure 4 that the graphene fiber is not completely sealed, and there is some resin carbon.

[0039] 2. Arrange the pre-treated graphene fiber bundles uniformly and parallelly in a graphite mold, stack 8 layers in the thickness direction, then clamp them with a customized perforated high-strength graphite mold and fasten them with bolts, the clamping force is 40 kPa, and then heat-treat the unidirectional preform at 1500 °C in an argon atmosphere for 2 h; use the ICVI process to densify the treated preform, the deposition temperature is 1000 °C, the pressure is 2 kPa, the flow rate of methane is 15 L / min, and the deposition time is 150 h. The density of the obtained graphene fiber carbon / carbon composite is 1.59 g / cm 3 , and the porosity is 4.98%.

[0040] 3. Carry out graphitization treatment on the prepared graphene fiber carbon / carbon composite at 2400 °C in an argon atmosphere for 2 h to obtain a unidirectional graphene fiber carbon / carbon composite. The thermal conductivity of the composite along the axial direction is 635 W·m -1 ·K-1 ; The bending strength along the axial direction is 124 MPa, and the tensile strength along the axial direction is 250 MPa.

[0041] Example 2 This example provides a method for preparing a unidirectional graphene fiber carbon / carbon composite, and the steps are as follows: 1. Add 3 parts of phenolic resin powder to 17 parts of absolute ethanol, and ultrasonically disperse for 45 min until there is no obvious precipitation phenomenon to obtain a phenolic resin impregnation solution; then add the porous graphene fiber bundle to the phenolic resin impregnation solution and soak it at normal temperature and pressure for 30 min to obtain a pre-impregnated graphene fiber bundle; put the pre-impregnated graphene fiber bundle into an oven for curing; first slowly heat it to 120 °C at a rate of 4 °C / min, keep it at a constant temperature for 20 min, then heat it to 150 °C at a rate of 2 °C / min, keep it warm for 20 min, and continue to heat it to 180 °C at a rate of 2 °C / min, keep it warm for 1 h; then naturally cool it to room temperature. The cured graphene fiber is transferred to a heat treatment furnace, and under the protective atmosphere of argon, the impregnated and cured graphene fiber is carbonized, slowly heated to 500 °C at a rate of 4 °C / min, kept at a constant temperature for 1 h, then heated to 950 °C at a rate of 3.75 °C / min, and kept warm for 2 h to obtain a pre-treated graphene fiber bundle; the photo of the pre-treated graphene fiber bundle is as Figure 5 shown, and it can be seen from Figure 5 that the graphene fiber bundle has been completely sealed, and the resin carbon is evenly distributed.

[0042] 2. Arrange the pre-treated graphene fiber bundles evenly and parallelly in a graphite mold, stack 9 layers in the thickness direction, then clamp them with a customized high-strength graphite mold with holes and fasten them with bolts. The clamping force is 45 kPa, and then heat-treat the unidirectional preform at 1600 °C in an argon atmosphere for 3 h; use the ICVI process to densify the preform. The deposition temperature is 1050 °C, the pressure is 6 kPa, the flow rate of methane is 16 L / min, and the deposition time is 160 h. The density of the obtained graphene fiber carbon / carbon composite is 1.65 g / cm 3 , and the porosity is 4.29%.

[0043] 3. Heat-treat the prepared graphene fiber carbon / carbon composite at 2450 °C in an argon atmosphere for 3 h to obtain a unidirectional graphene fiber carbon / carbon composite. The thermal conductivity of the composite along the axial direction is 654 W·m -1 ·K -1 ; The bending strength along the axial direction is 150 MPa, and the tensile strength along the axial direction is 300 MPa.

[0044] Example 3 This embodiment provides a method for preparing a unidirectional graphene fiber carbon / carbon composite, and the steps are as follows: 1. Add 4 parts of phenolic resin powder to 12 parts of absolute ethanol, and ultrasonically disperse for 1 h until there is no obvious precipitation phenomenon to obtain a phenolic resin impregnation solution; then add the porous graphene fiber bundle to the phenolic resin impregnation solution and soak at normal temperature and pressure for 40 min to obtain a pre-impregnated graphene fiber bundle; put the pre-impregnated graphene fiber bundle into an oven for curing; first slowly heat up to 120 °C at a rate of 5 °C / min, keep the temperature constant for 20 min, then heat up to 150 °C at a rate of 4 °C / min, keep the temperature for 20 min, continue to heat up to 180 °C at a rate of 2 °C / min, and keep the temperature for 1 h; then naturally cool to room temperature. Subsequently, transfer the cured fiber to a heat treatment furnace, and under the protective atmosphere of argon, carbonize the impregnated and cured graphene fiber bundle, slowly heat up to 500 °C at a rate of 5 °C / min, keep the temperature constant for 1 h, then heat up to 950 °C at a rate of 4 °C / min, and keep the temperature for 2 h to obtain a pre-treated graphene fiber bundle; the photo of the pre-treated graphene fiber bundle is as Figure 6 shown, and it can be seen from Figure 6 that the graphene fiber has been completely sealed, and there is more resin carbon on the surface.

[0045] 2. Arrange the pre-treated graphene fiber bundles uniformly and parallelly in a graphite mold, stack 8 layers in the thickness direction, then clamp them with a customized perforated high-strength graphite mold and fasten them with bolts, the clamping force is 50 kPa, and then heat-treat the unidirectional preform at 1550 °C for 4 h in an argon atmosphere; densify the preform by ICVI process, the deposition temperature is 1100 °C, the pressure is 10 kPa, the flow rate of methane is 18 L / min, and the deposition time is 170 h, and the density of the obtained graphene fiber carbon / carbon composite is 1.60 g / cm 3 , and the porosity is 4.41%.

[0046] 3. Heat-treat the prepared graphene fiber carbon / carbon composite at 2500 °C for 4 h in an argon atmosphere to obtain a unidirectional graphene fiber carbon / carbon composite. The thermal conductivity of the composite along the axial direction is 627 W·m -1 ·K -1 ; the flexural strength along the axial direction is 113 MPa, and the tensile strength along the axial direction is 220 MPa.

[0047] Comparative Example 1 This comparative example provides a method for preparing a unidirectional graphene fiber carbon / carbon composite, and the steps are as follows: 1. Add 3 parts of phenolic resin powder to 17 parts of absolute ethanol, and ultrasonically disperse for 45 min until there is no obvious precipitation phenomenon to obtain a phenolic resin impregnation solution. Subsequently, add the porous graphene fiber bundle to the phenolic resin impregnation solution and impregnate it for 30 min under vacuum conditions to obtain a pre-impregnated graphene fiber bundle. Place the pre-impregnated graphene fiber bundle in an oven for curing. First, slowly heat it to 120 °C at a rate of 4 °C / min, keep it at a constant temperature for 20 min, then heat it to 150 °C at a rate of 2 °C / min, keep it warm for 20 min, and continue to heat it to 180 °C at a rate of 2 °C / min, keep it warm for 1 h. Then cool it naturally to room temperature. Subsequently, transfer the cured graphene fiber bundle to a heat treatment furnace and carbonize the impregnated and cured fiber under a protective atmosphere of argon gas. Slowly heat it to 500 °C at a rate of 4 °C / min, keep it at a constant temperature for 1 h, then heat it to 950 °C at a rate of 3.5 °C / min, keep it warm for 2 h to obtain a pre-treated graphene fiber bundle; The photo of the pre-treated graphene fiber bundle is as shown in Figure 7 shown, and it can be seen from Figure 7 that the original structure of the graphene fiber is damaged and there is more resin carbon on the surface.

[0048] 2. Arrange the pre-treated graphene fiber bundles uniformly and parallelly in a graphite mold, stack 9 layers in the thickness direction, then clamp them with a customized perforated high-strength graphite mold and fasten them with bolts. The clamping force is 45 kPa. Subsequently, heat-treat the unidirectional preform at 1600 °C for 3 h in an argon atmosphere. Use the ICVI process to densify the preform. The deposition temperature is 1050 °C, the pressure is 6 kPa, the flow rate of methane is 16 L / min, and the deposition time is 160 h. The density of the obtained graphene fiber carbon / carbon composite material is 1.58 g / cm 3 , and the porosity is 5.77%.

[0049] 3. Heat-treat the prepared graphene fiber carbon / carbon composite material at 2450 °C for 4 h in an argon atmosphere. The thermal conductivity of the composite material along the axial direction is 623 W·m -1 ·K -1 ; the bending strength along the axial direction is 138 MPa, and the tensile strength along the axial direction is 264 MPa.

[0050] In the comparative example, phenolic resin solution was used to vacuumize and then pressurize to impregnate the graphene fiber bundle, and the performance of the graphene fiber carbon / carbon composite material was poor. The main reason is that there are micron-sized small holes inside the graphene fiber. When pressurizing and impregnating, the internal pore pressure and the external pressure are a balanced system, and when pressurizing, the residual air in the internal pores of the fiber will expand, and the expanded pores will damage the original structure of the graphene fiber after curing.

[0051] Comparative Example 2 This comparative example provides a method for preparing a unidirectional graphene fiber carbon / carbon composite, and the steps are as follows: 1. Add 4 parts of phenolic resin powder to 12 parts of absolute ethanol, and ultrasonically disperse for 1 h until there is no obvious precipitation phenomenon to obtain a phenolic resin impregnation solution; then add a porous graphene fiber bundle to the phenolic resin impregnation solution and impregnate it under vacuum conditions for 40 min to obtain a pre-impregnated graphene fiber bundle; put the pre-impregnated graphene fiber bundle into an oven for curing; first slowly heat it to 120 °C at a rate of 5 °C / min, keep it at a constant temperature for 20 min, then heat it to 150 °C at a rate of 4 °C / min, keep it warm for 20 min, continue to heat it to 180 °C at a rate of 4 °C / min, and keep it warm for 1 h; then naturally cool it to room temperature. The cured graphene fiber bundle is transferred to a heat treatment furnace, and in an argon gas protective atmosphere, the cured fiber is carbonized, slowly heated to 500 °C at a rate of 5 °C / min, kept at a constant temperature for 1 h, then heated to 950 °C at a rate of 4 °C / min, and kept warm for 2 h to obtain a pre-treated graphene fiber bundle; the photo of the pre-treated graphene fiber bundle is as Figure 8 shown, and it can be seen from Figure 8 that the graphene fibers do not completely seal the pores.

[0052] 2. Arrange the pre-treated graphene fiber bundles uniformly and parallel in a graphite mold, stack 8 layers in the thickness direction, then clamp them with a customized perforated high-strength graphite mold and fasten them with bolts. The clamping force is 50 kPa, and then heat-treat the unidirectional preform at 1550 °C for 4 h in an argon atmosphere; densify the preform by the ICVI process. The deposition temperature is 1100 °C, the pressure is 10 kPa, the flow rate of methane is 18 L / min, and the deposition time is 170 h. The density of the obtained graphene fiber carbon / carbon composite is 1.59 g / cm 3 , and the porosity is 5.28%.

[0053] 3. Heat-treat the prepared graphene fiber carbon / carbon composite at 2500 °C for 4 h in an argon atmosphere. The thermal conductivity of the composite along the axial direction is 612 W·m -1 ·K -1 ; the bending strength along the axial direction is 106 MPa, and the tensile strength along the axial direction is 227 MPa.

[0054] The comparative example uses a relatively fast curing and carbonization heating rate. If the heating rate is too fast during the curing process, phenomena such as swelling and bubbling will occur, damaging the original structure of the graphene fibers. If the heating rate is too fast during the carbonization process, more pores will appear, showing a honeycomb shape and presenting a relatively brittle macroscopic morphology.

[0055] Comparative Example 3 This comparative example provides a method for preparing a unidirectional graphene fiber carbon / carbon composite material, and the steps are as follows: 1. Add 5 parts of phenolic resin powder to 7 parts of absolute ethanol, and ultrasonically disperse for 30 min until there is no obvious precipitation phenomenon to obtain a phenolic resin impregnation solution; then add the porous graphene fiber bundle into the phenolic resin impregnation solution, and impregnate for 20 min under vacuum conditions to obtain a pre-impregnated graphene fiber bundle; put the pre-impregnated graphene fiber bundle into an oven for curing; first slowly heat it to 120 °C at a rate of 3 °C / min, keep it at a constant temperature for 20 min, then heat it to 150 °C at a rate of 2 °C / min, keep it warm for 20 min, continue to heat it to 180 °C at a rate of 2 °C / min, and keep it warm for 1 h; then naturally cool it to room temperature. The cured graphene fiber is transferred to a heat treatment furnace, and under the protective atmosphere of argon, the cured graphene fiber bundle is carbonized, slowly heated to 500 °C at a rate of 4 °C / min, kept at a constant temperature for 1 h, then heated to 950 °C at a rate of 3 °C / min, and kept warm for 2 h to obtain a pre-treated graphene fiber bundle; the photo of the pre-treated graphene fiber bundle is as Figure 9 shown, and it can be seen from Figure 9 that the graphene fiber does not completely seal the pores.

[0056] 2. Arrange the pre-treated graphene fiber bundles uniformly and parallelly in a graphite mold, stack 9 layers in the thickness direction, then clamp them with a customized perforated high-strength graphite mold and fasten them with bolts, the clamping force is 50 kPa, and then heat-treat the unidirectional preform at 1500 °C for 2 h in an argon atmosphere; densify the preform by the ICVI process, the deposition temperature is 1050 °C, the pressure is 10 kPa, the flow rate of methane is 18 L / min, and the deposition time is 170 h. The density of the obtained graphene fiber carbon / carbon composite material is 1.60 g / cm 3 , and the porosity is 5.62%.

[0057] 3. Heat-treat the prepared graphene fiber carbon / carbon composite material at 2400 °C for 4 h in an argon atmosphere. The thermal conductivity of the composite material along the axial direction is 600 W·m -1 ·K -1 ; the bending strength along the axial direction is 100 MPa, and the tensile strength along the axial direction is 219 MPa.

[0058] In the comparative example, a phenolic resin solution with a higher concentration is used to impregnate the fiber under pressure. The resin with a higher concentration has a higher viscosity and poor fluidity during the impregnation process, cannot effectively fill some smaller pores, and will also damage the original structure of single fiber filaments. A large amount of phenolic resin adheres to the fiber surface, which is not conducive to the subsequent densification process.

[0059] The above content is only for explaining the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A preparation method of a unidirectional graphene fiber carbon / carbon composite material, characterized in that, It includes the following steps: Add phenolic resin powder into absolute ethanol to prepare a phenolic resin impregnating solution; under normal temperature and pressure conditions, add a graphene fiber bundle into the phenolic resin impregnating solution for impregnation to obtain a pre-impregnated graphene fiber bundle; perform stepwise temperature-rising curing on the pre-impregnated graphene fiber bundle and then carbonize it to obtain a pretreated graphene fiber bundle; Arrange the pretreated graphene fiber bundles in parallel and stack them along the thickness direction, and apply pressure to fasten to obtain a unidirectional preform; Perform heat treatment on the unidirectional preform and then densify it by an isothermal chemical vapor infiltration process, and then perform graphitization treatment to obtain a unidirectional graphene fiber carbon / carbon composite.

2. The preparation method of the unidirectional graphene fiber carbon / carbon composite material according to claim 1, characterized in that, The mass ratio of the phenolic resin powder to absolute ethanol is 2-5:10-40.

3. The preparation method of the unidirectional graphene fiber carbon / carbon composite material according to claim 1, characterized in that, The graphene fiber bundle is a 1k graphene fiber bundle with a width of 5-7 mm, and the diameter of a single graphene fiber in the graphene fiber bundle is 13-14 μm; The impregnation time is 20 min-40 min.

4. The preparation method of the unidirectional graphene fiber carbon / carbon composite material according to claim 1, wherein, The process of stepwise temperature-rising curing is as follows: first, heat up at a rate of 3-5 °C / min to 120 °C, keep the temperature constant for 20 min, then heat up to 150 °C at a rate of 2-4 °C / min, keep the temperature for 20 min, and continue to heat up to 180 °C at a rate of 2-4 °C / min, and keep the temperature for 1-2 h.

5. The preparation method of the unidirectional graphene fiber carbon / carbon composite material according to claim 1, wherein, The process of carbonization is as follows: Under the protective atmosphere of argon, carbonize the graphene fiber bundle after stepwise temperature-rising curing, heat up at a rate of 4-5 °C / min to 500 °C, keep the temperature constant for 1 h, then heat up to 950 °C at a rate of 3-4 °C / min, and keep the temperature for 2 h.

6. The preparation method of the unidirectional graphene fiber carbon / carbon composite material according to claim 1, characterized in that, The process of obtaining the unidirectional preform is as follows: The pretreated graphene fiber bundles are uniformly arranged in parallel and stacked 8-9 layers along the thickness direction, and are pressed tightly along the thickness direction, and the clamping force is 40-50 kPa to obtain a unidirectional preform; The process of heat treatment is as follows: Under the protective atmosphere of argon, perform heat treatment on the unidirectional preform at 1500-1600 °C for 2-4 h.

7. The preparation method of the unidirectional graphene fiber carbon / carbon composite material according to claim 1, wherein The process parameters of densification are as follows: the deposition temperature is 1000-1100 °C, the pressure is 2-10 kPa, the flow rate of methane is 15-18 L / min, and the deposition time is 150-170 h; The process parameters of graphitization treatment are as follows: under the protective atmosphere of argon, perform graphitization treatment at a treatment temperature of 2400-2500 °C, and the heat preservation time is 2-4 h.

8. A unidirectional graphene fiber carbon / carbon composite material prepared by the preparation method according to any one of claims 1-7, characterized in that, In the unidirectional graphene fiber carbon / carbon composite, the resin carbon, graphene fiber and pyrolytic carbon form a soft-hard carbon inlaid structure; the resin carbon is filled as hard carbon inside the graphene fiber, the graphene fiber is used as soft carbon in the middle, and the pyrolytic carbon tightly wraps the outside of the graphene fiber as hard carbon.

9. The unidirectional graphene fiber carbon / carbon composite material according to claim 8, characterized in that, The density of the unidirectional graphene fiber carbon / carbon composite material is 1.58~1.65 g / cm 3 , and the thickness is 1.5~1.6 mm; the thermal conductivity of the unidirectional graphene fiber carbon / carbon composite material along the axial direction is 600~654 W·m -1 ·K -1 ; the flexural strength of the unidirectional graphene fiber carbon / carbon composite material along the axial direction is 100~150 MPa, and the tensile strength along the axial direction is 219~300 MPa.

10. Application of a unidirectional graphene fiber carbon / carbon composite prepared by the preparation method according to any one of claims 1-7 in spacecraft thermal management.

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