Graphene fiber heat conduction enhanced high-temperature-resistant composite material as well as preparation method and application thereof

Abstract

According to the graphene fiber heat conduction enhanced high-temperature-resistant composite material and the preparation method thereof, graphene fibers are adopted as a substrate and can be violently activated in a high-temperature environment, a large number of nucleation sites are formed to grow a carbide coating on a surface layer, and the anchoring effect is very strong through covalent bonds between the nucleation sites and the substrate. Furthermore, the modulus of the graphene fiber is low, and in the rapid cooling process, huge thermal stress generated in the cooling process due to the fact that the thermal expansion coefficients of the fiber substrate and the carbide coating are not matched can be effectively dissipated, so that stable combination between the coating and the substrate can be guaranteed. The obtained composite material has stable interface bonding and extremely high thermal conductivity, and can be applied to a spaceflight thermal protection system.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials, and specifically relates to a graphene fiber thermally conductive enhanced high temperature resistant composite material and a preparation method and application thereof. Background Art

[0002] Future aerospace weapons and equipment represented by hypersonic vehicles are developing towards faster flight speeds, longer flight times, and more additional functions. In this process, a key issue that must be solved is to establish a reliable thermal protection system so that the equipment can maintain absolute safety and stability in the extreme high temperature environment caused by ultra-high speed and long-term flight. Traditional thermal protection materials have low thermal conductivity. When heated, heat accumulates and the temperature rises sharply, resulting in ablation damage and protection failure. The introduction of high thermal conductivity materials in the thermal protection system can reduce the temperature of local hot spots through timely and effective heat expansion, and "conduct" to help "protection", which can achieve the effect of improving the performance of the thermal protection system. This puts forward new requirements for carbon materials, the core material of the thermal protection system, to achieve high thermal conductivity on the basis of meeting the requirements of traditional structural mechanics. However, the existing commonly used carbon materials, such as domestic asphalt-based carbon fibers, have a thermal conductivity of only 600W / mK, and poor flexibility, and cannot adapt to fine woven structures with small curvatures. These problems make the existing carbon fiber materials unable to meet the significant demand for high thermal conductivity carbon materials in the field of high-temperature thermal protection.

[0003] Carbon / ceramic composite materials are based on carbon fibers and covered with high-temperature resistant ceramics. The application of carbon / ceramic composite materials in the field of thermal protection is crucial. It combines the high strength of carbon fibers and the high thermal stability of ceramic materials to form a lightweight and high-temperature resistant protective layer. This material can maintain structural integrity in extremely high-temperature environments, effectively isolate heat, and protect the safety of spacecraft when re-entering the atmosphere. It also plays a protective role in high-temperature industrial equipment such as aircraft engines and gas turbines, which not only improves the reliability and work efficiency of the equipment, but also extends its service life. It is of great significance to promote the development of aerospace and high-temperature industrial technologies.

[0004] The carbon substrate used to prepare carbon / ceramic composite materials in the prior art is generally polyacrylonitrile-based carbon fiber. The performance of this carbon fiber will be significantly reduced when it is in a high-temperature environment for growing ceramics for a long time, which is extremely unfavorable in the actual application of the composite material in the later stage. At the same time, the carbon / ceramic composite material will experience drastic temperature changes during the preparation process. Due to the different thermal expansion coefficients of ceramic materials and carbon materials, the composite material with polyacrylonitrile-based carbon fiber as the matrix will experience breakage, delamination and other phenomena, which will seriously affect the ablation resistance of the final product. Graphene fiber has ultra-high thermal conductivity, and its unique surface wrinkle structure and good flexibility have significant advantages in improving the thermal conductivity and interface stability of composite materials. Summary of the invention

[0005] In view of the problem in the prior art that carbon fiber is easy to delaminate from the surface ceramic material, the present invention provides a graphene fiber thermally conductive reinforced high temperature resistant composite material and its preparation method and application. The present invention uses graphene fiber as a substrate, which is violently activated in a high temperature environment to form a large number of nucleation sites to grow a carbide coating on the surface, and the covalent bonds between the nucleation sites and the matrix make the anchoring effect very strong. Furthermore, the modulus of graphene fiber is low, and in the process of rapid cooling, it can effectively dissipate the huge thermal stress generated during the cooling process due to the mismatch of the thermal expansion coefficients of the fiber substrate and the carbide coating, thereby ensuring a stable bond between the coating and the matrix.

[0006] One of the technical solutions of the present invention is to provide a method for preparing a graphene fiber thermally conductive reinforced high temperature resistant composite material, comprising the following steps: 1) Mix the metal powder and salt in a mass ratio of 1: (2-10), grind to obtain a mixed powder with a particle size not greater than 300 mesh, and dry at 120-150°C for 1-3 hours; 2) completely embedding the graphite-treated graphene fiber material with the mixed powder; 3) Heat to 1000-1200°C in an argon atmosphere o C, keep warm for 10min-4h and then transfer to room temperature for cooling; compared with the sp3 / sp2 mixed structure of carbon fiber, it has a low degree of graphitization, small crystal size, high surface modulus and smooth surface; graphene fiber is a complete sp2 structure with a large number of wrinkled structures on the surface, and has the characteristics of low reaction energy barrier and high activity under high temperature conditions.

[0007] These properties enable graphene fibers to quickly generate carbides when reacting with metals, and the abundant wrinkles on their surface provide a large number of nucleation sites, accelerating the formation of carbide crystals. In addition, these nucleation sites not only promote rapid reactions in the early stages, but also play a key anchoring role in the subsequent epitaxial growth of crystals, ensuring the stability and orientation of the growth process.

[0008] Ultimately, through this mechanism, precise control of carbide coating thickness in the range of 30 nanometers to 5 micrometers can be achieved.

[0009] 4) Repeatedly boil the sample in deionized water to remove residual reactants, with each boiling time not less than 3 minutes; 5) Drying the obtained composite material in an oven at 60°C-80°C to obtain a graphene fiber / transition metal carbide composite material.

[0010] Furthermore, the metal powder is a transition metal powder, including transition metals such as titanium, chromium, zirconium, hafnium, rubidium, and thallium.

[0011] Furthermore, the salt is one or more of lithium fluoride, lithium chloride, sodium fluoride, sodium chloride, potassium fluoride, and potassium chloride.

[0012] Furthermore, the graphitization treatment is carried out at 2000° C.-3000° C. for 60-90 minutes under the protection of an inert gas; the inert gas is nitrogen or argon.

[0013] The second technical solution of the present invention is to provide a graphene fiber thermally conductive reinforced high temperature resistant composite material prepared by the above preparation method. The composite material is composed of graphene fiber and metal carbide loaded on the surface of the graphene fiber.

[0014] The surface modulus of graphene fiber is low. During the rapid cooling process, it can effectively dissipate the huge thermal stress generated during the cooling process due to the mismatch in thermal expansion coefficients between the fiber substrate and the carbide coating. The perfect crystal structure on the surface of graphene fiber provides a sufficient environment for the crystal growth of carbides, which is conducive to the growth of carbide crystals. At the interface between graphene and carbide, the two adapt to the lattice mismatch of the two substances through lattice distortion, achieving seamless integration at the atomic scale and having extremely high stability.

[0015] Furthermore, the coating composed of metal carbides has a thickness of 30 nm-5 μm.

[0016] The beneficial effect of the present invention is that a carbide coating is grown on the surface of graphene through high temperature treatment, which effectively solves the problem of ceramic layer shedding that occurs during the preparation of traditional carbon and ceramic composite materials, and ensures stable bonding between the coating and the substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is the X-ray diffraction spectrum of the graphene / chromium carbide composite fiber in Example 1; Figure 2 This is an electron microscope image of the graphene / chromium carbide fiber surface in Example 1; Figure 3 This is an electron microscope image of the cross section of the graphene / chromium carbide fiber in Example 1; Figure 4 is the X-ray diffraction spectrum of the graphene / titanium carbide composite fiber bundle in Example 2; Figure 5 This is an electron microscope photo of the graphene / titanium carbide composite fiber bundle in Example 2; Figure 6 This is a photo of the graphene / chromium carbide composite fiber fabric in Example 3; Figure 7 This is a photo of the graphene / titanium carbide composite fiber fabric in Example 4; Figure 8 This is an electron microscope image of the graphene / titanium carbide composite fiber fabric in Example 4; Fig. 9 This is a picture of the helical graphene / titanium carbide fiber bundle in Example 5; Fig.10 This is an electron microscope image of the carbon fiber / titanium carbide composite fiber bundle in Comparative Example 1. DETAILED DESCRIPTION

[0018] The following examples are used to further illustrate the present invention, and their purpose is to illustrate the present invention and should not be construed as limiting the scope of the present invention. Unless otherwise specified, all parts by weight and weight percentages are used below.

[0019] The raw materials used in the present invention, unless otherwise specified, are conventional commercially available products; the methods used in the present invention, unless otherwise specified, are conventional methods in the art.

[0020] The embodiments of the present invention are further described below with reference to a plurality of embodiments.

[0021] It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0022] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0023] Example 1 (1) Grind 0.5 g of chromium metal powder and 2.5 g of potassium chloride powder and dry them in a forced air oven at 120°C for 1 hour; (2) Cut the graphene fibers after graphitization at 2800°C for 60 minutes into 0.5 cm lengths, place them in an alumina crucible, and completely embed the fiber bundles with the dried mixed powder; (3) Place the crucible in a tube furnace and pass argon as a protective gas. Raise the temperature from room temperature to 1000°C at a rate of 7°C / min, keep it at that temperature for 2 hours, and then naturally cool it down to room temperature. (4) Wash the reactants three times with deionized water. (5) Drying in a 60°C forced air oven for 12 hours to obtain graphene / chromium carbide composite fibers.

[0024] The obtained graphene / chromium carbide composite fiber, Figure 1The X-ray diffraction results of the sample show that compared with the spectrum of graphene fiber, the spectrum of graphene / chromium carbide composite fiber shows a significant characteristic peak of Cr7C3, proving that the reaction successfully obtained carbide. Figure 2 As shown, the cross-sectional structure is Figure 3 As shown in the figure, it can be seen that a layer of chromium carbide grows evenly on the fiber surface, with a perfect and dense structure. The thickness of the chromium carbide coating is about 5 microns, which is tightly bonded to the fiber without obvious delamination. The thermal conductivity of the fiber single wire is 500W / mK.

[0025] Example 2 (1) Mix 1.5 g titanium metal powder and 3 g potassium fluoride powder and dry them in a 150°C forced air oven for 1 hour; (2) Cut the 3K graphene fiber bundle after graphitization at 2000°C for 90 minutes into a size of 4 cm, place it in an alumina crucible, and completely embed the fiber bundle with the dried mixed powder; (3) Place the crucible in a tube furnace and pass argon as a protective gas. Heating the temperature from room temperature to 1200°C at a rate of 10°C / min, keeping the temperature for 10 min, and then cooling it naturally to room temperature; (4) Wash the reactants three times with deionized water. (5) Drying in a forced air oven at 80°C for 12 hours to obtain a graphene / titanium carbide composite fiber bundle.

[0026] The obtained graphene / titanium carbide composite fiber bundle, Figure 4 The X-ray diffraction results of the sample show that compared with the spectrum of graphene fiber, the spectrum of graphene / chromium carbide composite fiber shows a significant characteristic peak of TiC, proving that the reaction successfully obtained carbide. Its microstructure is as follows Figure 5 As shown in the figure, it can be seen that a layer of chromium carbide grows evenly on the fiber surface, with a perfect and dense structure. The thickness of the chromium carbide coating is about 1.3 microns, which is tightly bonded to the fiber without obvious delamination. The thermal conductivity of the fiber single wire is 325W / mK.

[0027] Example 3 (1) Mix 0.8 g of chromium metal powder and 4 g of potassium aluminide powder and dry them in a forced air oven at 120°C for 3 hours; (2) The 3K graphene fiber bundles that were graphitized at 3000°C for 60 min were woven into fabrics, placed in an alumina crucible, and the fiber bundles were completely embedded with the dried mixed powder; (3) Place the crucible in a tube furnace and pass argon as a protective gas. Raise the temperature from room temperature to 1100°C at a rate of 5°C / min, keep it at that temperature for 4 hours, and then cool it down to room temperature at a rate of 10°C / min. (4) Wash the reactants three times with deionized water. (5) Drying in a vacuum oven at 60°C for 12 hours obtains graphene / chromium carbide composite fiber fabric.

[0028] The obtained graphene / chromium carbide composite fiber fabric, Figure 6 It is a composite fiber fabric. You can see that the color of the fabric has changed to silvery white, indicating that a uniform chromium carbide coating has formed on the surface of the graphene fiber fabric. Example 4 (1) Mix 1 g of titanium metal powder and 10 g of potassium chloride powder and dry them in a 150°C forced air oven for 1 hour; (2) The 3K graphene fiber bundles that were graphitized at 3000°C for 60 min were woven into fabrics, placed in an alumina crucible, and the fiber bundles were completely embedded with the dried mixed powder; (3) Place the crucible in a tube furnace and pass argon as a protective gas. Raise the temperature from room temperature to 1200°C at a rate of 7°C / min, keep it at that temperature for 2 hours, and then naturally cool it down to room temperature. (4) Wash the reactants three times with deionized water. (5) Drying in a forced air oven at 80°C for 12 hours to obtain graphene / titanium carbide composite fiber fabric.

[0029] The obtained graphene / titanium carbide composite fiber fabric, the actual photo is as follows Figure 7 As shown in the electron microscope photos Figure 8 As shown. It can be seen that the metallic luster of the graphene fiber surface disappears, and the color of the fabric turns black. From the electron microscope image, it can be seen that the carbide coating grows uniformly on the surface of the fabric fiber, and the coating thickness is about 30nm. The thermal conductivity of the single fiber is about 720W / mK. The mass ablation rate is about 0.3mg / s when ablated with a 2200℃ flame for 210s, and the temperature difference between the front and back sides is always kept above 200℃.

[0030] Example 5 (1) Mix 1 g of titanium metal powder and 10 g of potassium chloride powder and dry them in a vacuum oven at 120 °C for 1.5 hours; (2) The 3K graphene fiber bundle that was graphitized at 3000°C for 60 min was wound on an alumina rod with a diameter of 2 mm, placed in an alumina crucible, and the fiber bundle was completely embedded with the dried mixed powder; (3) Place the crucible in a tube furnace and pass argon as a protective gas. Heating the temperature from room temperature to 1200°C at a rate of 7°C / min, keeping the temperature for 1 hour, and then naturally cooling it down to room temperature. (4) Remove the fiber bundle from the alumina rod and wash the reactants three times with deionized water; (5) Drying in a vacuum oven at 60°C for 12 hours yields the spiral graphene / titanium carbide composite fiber fabric.

[0031] The obtained spiral graphene / titanium carbide composite fiber fabric, the actual photo is as follows Fig. 9 As shown in the electron microscope photos Figure 8 As shown in the figure, it can be seen that the metallic luster on the surface of the graphene fiber bundle disappears, and the color of the fabric turns black, 600W / mK. The mass ablation rate is about 0.4mg / s when ablated with a 2200℃ flame for 150s.

[0032] Comparative Example 1 The difference from Example 1 is that polyacrylonitrile-based carbon fiber tow is used to replace graphene fiber, and the heating temperature is 800°C.

[0033] The obtained carbon fiber / titanium carbide composite fiber bundle has an electron microscope image as shown below: Fig.10 As shown. It can be seen that under the same preparation conditions, the thickness of the carbide coating on the carbon fiber surface is only 0.3 microns, and the coating has a lot of cracking, peeling and poor growth uniformity. On the one hand, compared with graphene fibers, polyacrylonitrile-based carbon fibers have a smooth surface and low reaction activity, which cannot provide a large number of nucleation sites for carbides. At the same time, the surface crystal structure is not perfect, and there is no large enough crystal area to provide space for the growth of carbide crystals. On the other hand, because the thermal expansion coefficient of carbon fiber is too different from that of carbides, huge interfacial tensile stress will be generated during the cooling process after the high-temperature reaction. At the same time, the carbon fiber surface modulus is large and the morphology is smooth, which cannot dissipate stress in time and effectively and form a strong physical chelation effect with the carbide coating. It can be proved that compared with traditional carbon fibers, the growth of transition metal carbides on the surface of graphene fibers has significant advantages in growth rate and sample quality, which can effectively reduce production energy consumption and improve sample quality.

[0034] Comparative Example 2 The difference from Example 3 is that commercial polyacrylonitrile-based carbon fiber fabric is used to replace the graphitized 3K graphene fiber tow braid, and the heating temperature is 850°C.

[0035] The obtained carbon fiber / titanium carbide composite fiber fabric has a single-filament thermal conductivity of about 40W / mK, which is less than one-tenth of the graphene / titanium carbide composite fiber fabric prepared under the same conditions. It is ablated with a 2200℃ flame for 210s, and the mass ablation rate is about 0.6mg / s, which is twice that of the graphene / titanium carbide composite fiber fabric. The temperature difference between the front and back sides is always maintained at about 100℃, which is half of that of the graphene / titanium carbide composite fiber fabric. Compared with the graphene / titanium carbide composite fiber fabric, the ablation rate of the carbon fiber / titanium carbide composite fiber fabric has increased significantly, and the thermal insulation capacity has decreased. This is because compared with the graphene / titanium carbide composite fiber fabric, the thermal conductivity of the carbon fiber / titanium carbide composite fiber fabric is low, and the temperature cannot be quickly and effectively diffused in time, and the local heat of the material is accumulated, resulting in more obvious ablation of the material.

[0036] The above embodiments describe in detail the structure, features and effects of the present invention. The above are only preferred embodiments of the present invention. Any changes made in accordance with the concept of the present invention, or modifications to equivalent embodiments with equivalent changes, which do not exceed the scope covered by the specification, should be within the protection scope of the present invention.

Claims

1. A method for preparing a graphene fiber thermally conductive enhanced high temperature resistant composite material, characterized in that: The following steps are involved: 1) Mix metal powder and salt in a mass ratio of 1: (2-10), grind to obtain a mixed powder with a particle size not greater than 300 mesh, and dry at 120-150°C for 1-3 hours; 2) completely embedding the graphite-treated graphene fiber material with the mixed powder; 3) Heat to 1000-1200 degrees in an argon atmosphere, keep warm for 10min-4h, then transfer to room temperature for cooling; 4) Repeatedly boil and wash the sample in deionized water to remove residual reactants; 5) Drying the obtained composite material in an oven at 60°C-80°C to obtain a graphene fiber thermally conductive enhanced high temperature resistant composite material.

2. The preparation method according to claim 1, characterized in that: The metal powder is a transition metal powder.

3. The preparation method according to claim 1, characterized in that: The salt is one or more of lithium fluoride, lithium chloride, sodium fluoride, sodium chloride, potassium fluoride and potassium chloride.

4. The preparation method according to claim 1, characterized in that: The graphitization treatment is carried out at 2000° C.-3000° C. for 60-90 minutes under the protection of an inert gas; the inert gas is nitrogen or argon.

5. A graphene fiber thermally conductive enhanced high temperature resistant composite material prepared by the preparation method as claimed in claim 1.

6. The material according to claim 5, characterized in that It consists of graphene fibers and metal carbides on its surface.

7. The material according to claim 6, characterized in that The thickness of the coating composed of metal carbides is 30nm-5μm.

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