Carbon fiber / carbon nanotube fiber composite carbon-based material and preparation method and application thereof

Abstract

This invention discloses a carbon fiber / carbon nanotube fiber composite carbon-based material, its preparation method, and its application. The method involves sequentially and alternately layering carbon cloth, matrix carbon, and carbon nanotube films to form a green embryo. Under vacuum conditions, the green embryo is subjected to hot pressing, sintering heat treatment, and programmed cooling to obtain the carbon fiber / carbon nanotube fiber composite carbon-based material. This method directly combines carbon cloth and carbon nanotube films, avoiding the technical problem of poor carbon nanotube growth due to the inertness of the material surface during in-situ growth, which leads to poor reinforcement and toughening effects on the carbon cloth. Furthermore, the matrix phase of matrix carbon is directly added during the preparation process. The composite carbon-based material is obtained after a single hot pressing, sintering heat treatment, and programmed cooling step. The preparation method is simple and has a short preparation cycle.

Description

Technical Field

[0001] This invention belongs to the field of ultra-high temperature carbon / ceramic matrix composite material development technology, and relates to a carbon fiber / carbon nanotube fiber composite carbon-based material, its preparation method and application. Background Technology

[0002] Carbon / carbon (C / C) composites are multiphase materials composed of carbon fibers reinforced with a carbon matrix. They are composed of a single carbon element and possess a disordered graphite structure. They have a low density (<2.0 g / cm³). 3 With a strength only 1 / 4 that of nickel-based superalloys and 1 / 2 that of ceramic materials, C / C composites possess a series of unique and superior properties, including a low coefficient of thermal expansion, high specific strength / specific modulus, ablation resistance, thermal shock resistance, and excellent high-temperature mechanical properties. These properties make them widely used in photovoltaic thermal fields, vacuum high-temperature furnaces, aerospace, and other fields. Currently, C / C composites are mainly produced by densifying preforms formed by needle-punching carbon fiber bundles or preforms formed by laminating carbon fiber prepregs. Needle-punched preforms contain many pores of varying sizes. During densification, the surface pores are often filled first, while the smaller internal pores remain difficult to fill completely, resulting in poor density uniformity in the finished product and affecting the composite material's performance. The latter type of preform produces a material with higher tensile strength but poor interlayer bonding, making it prone to delamination during use.

[0003] With the emergence of novel carbon materials such as carbon nanotubes (CNTs) and graphene, their unique performance advantages have made them a potential choice for high-quality nano-reinforcement in carbon-based composites. However, the scale effect makes it difficult for CNTs to disperse uniformly, causing agglomeration within the composite material and leading to stress concentration, which in turn reduces the composite's performance. The emergence of carbon nanotube fibers (CNTFs) is considered the most effective means to solve these problems. CNTFs are quasi-one-dimensional macroscopic continuous combinations of CNTs, bound together by van der Waals interactions and entanglement, thus expected to have performance comparable to individual CNTs without being limited by length. Therefore, CNTFs can be assembled into microfiber yarns that can be easily laid between carbon fiber layers. More importantly, CNTF yarns have an unusual multi-level structure, with an accessible surface area several orders of magnitude higher than that of traditional fibers. Combined with the excellent mechanical properties of CNTFs themselves, weak interlayer bonding areas can be toughened by CNTFs to form tight "bridges," thereby improving the interlayer performance of the composite material.

[0004] Patent CN 113636854 A discloses a method for depositing carbon nanotubes on the surface of carbon fiber cloth using chemical vapor deposition (CVD), which significantly improves the mechanical properties of C / C composites, but the preparation cycle is relatively long. Patent CN116536597A discloses a method for in-situ generation of carbon nanotubes on porous short carbon fibers with pyrolytic carbon using CVD, which improves the electrical and thermal conductivity, mechanical properties, wear resistance, and self-lubricating properties of the composite material. However, due to the strong inertness of the carbon fiber surface, it is difficult to load a sufficient amount of catalyst onto the carbon fiber surface using traditional loading methods, thus affecting the effectiveness of carbon nanotube growth by CVD. Furthermore, the size effect of carbon nanotubes makes it difficult for them to exert an effective toughening effect. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a carbon fiber / carbon nanotube fiber composite carbon-based material, its preparation method, and its application. This solves the problems encountered in the prior art when preparing carbon fiber / nanotube reinforced carbon materials using in-situ growth methods. These methods suffer from the high inertness of the carbon fiber surface, limited catalyst loading capacity, and inability to effectively grow carbon nanotubes on the carbon fiber surface to obtain composite materials. Furthermore, the existing methods require additional processes to combine the matrix phase with the reinforcement, resulting in complex composite material preparation processes.

[0006] This invention is achieved through the following technical solution:

[0007] A method for preparing a carbon fiber / carbon nanotube fiber composite carbon-based material includes the following steps:

[0008] S1: Carbon cloth, carbon matrix, and carbon nanotube film are sequentially and alternately stacked to form a green embryo;

[0009] S2: Under vacuum conditions, the green embryo is subjected to hot pressing, sintering heat treatment and programmed cooling treatment in sequence to obtain the carbon fiber / carbon nanotube fiber composite carbon-based material.

[0010] Preferably, before preparing the green embryo using the matrix carbon, a pretreatment is performed, wherein the matrix carbon is ball-milled and sieved, and after ball milling, the size of the matrix carbon is 300-800 mesh.

[0011] Preferably, in step S1, the thickness of the embryo is 10-80 cm.

[0012] Preferably, the matrix carbon is resin or asphalt.

[0013] Preferably, in step S2, the vacuum degree of the vacuum condition is 3 to 5 kPa.

[0014] Preferably, in step S2, during the hot pressing process, the pressure is 5-40 MPa, the temperature is 200-500°C, the time is 1-5 h, and the heating rate is 10-15°C / min.

[0015] Preferably, in step S2, during the sintering heat treatment process, the temperature is 1200-1600℃, the holding time is 3-10h, and the heating rate is 5-10℃ / min.

[0016] Preferably, in step S2, the programmed cooling process specifically involves the hot-pressed product undergoing a first cooling process, a second cooling process, and a third cooling process in sequence.

[0017] The first cooling step specifically involves cooling the sample to 900–1100°C, and the cooling time for the first cooling step is 2–8 hours.

[0018] The secondary cooling specifically involves cooling the product that has undergone the first cooling to 400–600°C, with the cooling time for the second cooling being 2–5 hours.

[0019] The three cooling steps specifically involve allowing the product, which has undergone two cooling steps, to naturally cool down to room temperature.

[0020] A carbon fiber / carbon nanotube fiber composite carbon-based material is prepared by the above method.

[0021] The above-mentioned carbon fiber / carbon nanotube fiber composite carbon-based material has applications in photovoltaic thermal fields, vacuum high-temperature furnaces, and aerospace fields.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects:

[0023] This invention discloses a method for preparing carbon fiber / carbon nanotube fiber composite carbon-based materials. The method involves alternately layering carbon cloth, matrix carbon, and carbon nanotube films to form a green embryo. This method directly combines the carbon cloth and carbon nanotube film, effectively avoiding the problem of poor direct growth of carbon nanotubes on the carbon cloth surface in traditional methods. The direct addition of matrix carbon during the preparation process allows for more direct and flexible control over the matrix composition and its content. This method provides more possibilities for the designability of composite materials, allowing for optimization of the composite material's structure and properties according to different usage environments and application requirements. Then, under vacuum conditions, the green embryo undergoes programmed temperature rise hot pressing followed by programmed temperature drop to obtain the carbon fiber / carbon nanotube fiber composite carbon-based material. Programmed temperature rise hot pressing under vacuum conditions ensures that the material is not contaminated by oxygen during heating, maintaining its purity and performance. Programmed temperature rise and drop treatments help control the material's microstructure and properties; especially at high temperatures, the bonding between carbon nanotubes and carbon cloth becomes tighter, forming a more stable composite material. This one-step hot pressing and sintering heat treatment shortens the preparation cycle and improves production efficiency. This method directly combines carbon cloth with carbon nanotube films, avoiding the technical problem of poor carbon nanotube growth caused by the inertness of the material surface during in-situ growth, which leads to inadequate reinforcement and toughening of the carbon cloth. Furthermore, the method directly incorporates matrix carbon into the preparation process, followed by a one-step hot-pressing treatment, sintering heat treatment, and programmed cooling to obtain the composite carbon-based material. The preparation method is simple and has a short cycle time. This method not only shortens the preparation cycle of carbon-based composite materials but also achieves controllable regulation of the matrix composition and its content, exhibiting good designability. This provides more ideas for the subsequent structural design of composite materials for different usage environments and application requirements.

[0024] Furthermore, before preparing the green body using the matrix carbon, a pretreatment process is performed. This pretreatment involves ball milling and sieving the matrix carbon. After ball milling, the size of the matrix carbon is 300–800 mesh. Ball milling and sieving ensures that the particle size of the matrix carbon is uniformly 300–800 mesh, which helps to form a more uniform material structure during subsequent layup and hot pressing. Uniform particle distribution reduces the concentration of internal stress in the material, thereby improving the overall mechanical properties of the composite material. Smaller matrix carbon particles are more likely to clump together tightly during hot pressing, forming a denser material structure. Increased density helps to enhance the mechanical properties and durability of the material. Matrix carbon particles ball-milled to 300–800 mesh are more likely to bond tightly with carbon cloth and carbon nanotube films, forming good interfacial bonding. This good interfacial bonding helps to improve the overall performance of the material and reduce potential problems such as delamination or cracking during use. Fine carbon particles in the matrix can increase the heat conduction path inside the material and improve the heat conduction efficiency. This is especially important for composite materials that need to work in high-temperature environments, as it can ensure that they maintain good thermal stability and thermal conductivity during use.

[0025] Furthermore, in step S1, the thickness of the green preform is 10–80 cm. This wide thickness range allows for flexible adaptation to different application scenarios. Thinner green preforms are more suitable for lightweight applications and those with strict space constraints, such as in the aerospace field; while thicker green preforms may be more suitable for applications requiring higher strength or larger dimensions, such as photovoltaic thermal fields or vacuum high-temperature furnaces. The choice of green preform thickness affects the performance of the final composite material. Thinner green preforms mean fewer internal defects and higher density, resulting in better mechanical and thermal properties. Thicker green preforms require more precise hot pressing and sintering control to ensure the uniformity and stability of the internal structure.

[0026] Furthermore, the matrix carbon is resin or asphalt. Resin, as a binder in carbon fiber composites, can tightly bond with the reinforcing fibers through the interface, allowing the load to be transferred to the fibers via the interface, thus leveraging the excellent tensile properties of the fibers. Simultaneously, the resin matrix can also ensure uniform load distribution and protect the fibers from external damage. Selecting a resin matrix with good interfacial properties with carbon fibers can fully utilize the high modulus, high strength, and low density of carbon fibers. Asphalt, as a high-molecular-weight organic compound, contains various hydrocarbons and aromatic compounds, possessing good adhesion, corrosion resistance, and insulation properties. Adding asphalt to carbon-based materials can improve the mechanical, electrical, and corrosion resistance properties of the material, making it more suitable for various harsh environmental conditions. The processability of the resin matrix includes the miscibility of the resin components, the film-forming properties of the resin system, the viscosity and flowability at a certain temperature, and the wettability to fibers. These properties determine the molding process and product performance of the composite material. Selecting a suitable resin matrix can optimize the processing performance of the composite material and reduce production costs. Asphalt has good adhesion and flowability and can be used as an additive in carbon-based materials to improve their processing performance. Adding asphalt makes carbon-based materials easier to mold and process, reducing production costs. Asphalt contains a large number of aromatic compounds, which have good antioxidant properties. Adding asphalt to carbon-based materials can improve their antioxidant properties and extend their service life.

[0027] Furthermore, in step S2, the vacuum level is 3–5 kPa. Performing hot pressing under a vacuum of 3–5 kPa effectively reduces contamination of the material by oxygen, moisture, and other impurities in the air. These impurities may react chemically with the material, leading to decreased material performance or defects. Lowering the vacuum level significantly reduces these risks. Under a certain vacuum level, gases in the material are more easily expelled, reducing the formation of pores and bubbles. This helps to form a denser and more uniform material structure, improving the mechanical and thermal properties of the composite material. Hot pressing under vacuum ensures that the material is not contaminated by oxygen during heating, maintaining its purity and performance. In addition, the vacuum environment helps improve the uniformity and consistency of the material, thereby improving the overall quality of the composite material. Lower vacuum levels reduce external interference and contamination during the preparation process, thus improving the reliability and stability of the material. This is particularly important for applications requiring long-term stable operation.

[0028] Furthermore, in step S2, during the hot-pressing process, the pressure is 5–40 MPa, the temperature is 200–500 °C, the time is 1–5 h, and the heating rate is 10–15 °C / min. Under a pressure of 5–40 MPa, the contact between the carbon cloth, the matrix carbon, and the carbon nanotube film is closer, which helps to form a more uniform and dense material structure. This structure helps to improve the mechanical and thermal properties of the composite material. The temperature range of 200–500 °C is suitable for hot-pressing most resin or asphalt matrices. Within this temperature range, the matrix material can flow fully and penetrate between the fibers to form a strong bond. At the same time, this temperature range also helps to remove volatiles and impurities from the material, improving the purity and performance of the material. The hot-pressing time of 1–5 h can be adjusted according to the specific characteristics and requirements of the material. Sufficient time ensures that the matrix material fully penetrates between the fibers and forms a good interfacial bond with the fibers. A moderate heating rate of 10–15 °C / min avoids excessive thermal stress during hot pressing, which can lead to internal cracks or deformation, affecting the material's performance and lifespan. A suitable heating rate helps ensure uniform and stable performance during hot pressing. Optimizing parameter settings during the hot pressing process can shorten the preparation cycle and improve production efficiency. This helps reduce production costs and meet market demand for high-performance composite materials.

[0029] Furthermore, in step S2, during the sintering heat treatment, the temperature is 1200–1600℃, the holding time is 3–10 hours, and the heating rate is 5–10℃ / min. At this high temperature of 1200–1600℃, sufficient diffusion, recrystallization, and welding processes can occur between the powder particles, ensuring a tight bond between the particles and forming a dense bulk material. This temperature range can be optimized for different material properties to achieve the best sintering effect. An appropriate sintering temperature helps improve the material's density, mechanical properties, and chemical stability. Sintering at high temperatures can make the bonding between particles within the material tighter, reducing porosity and defects, and improving the overall performance of the material. The heating rate of 5–10℃ / min ensures uniform heating of the material during the heating process, avoiding thermal stress concentration and crack formation caused by excessively rapid heating. A slower heating rate also facilitates the expulsion of gases from within the material, reducing the porosity after sintering. The holding time is 3–10 hours, ensuring sufficient internal diffusion and bonding of the material after reaching the sintering temperature. A longer holding time increases the degree of diffusion within the sintered body, resulting in a tighter bond between the components. However, excessively long holding times also increase production costs and energy consumption; therefore, a reasonable selection based on specific material and process requirements is necessary. By selecting appropriate sintering temperature, holding time, and heating rate, the production cycle can be shortened as much as possible while ensuring material performance, thereby improving production efficiency. Simultaneously, these parameter settings also help reduce energy consumption and production costs, improving economic benefits.

[0030] Further, in step S2, the programmed cooling process specifically involves the hot-pressed product undergoing a first cooling, a second cooling, and a third cooling process sequentially. The first cooling process involves cooling the sample to 900–1100°C for 2–8 hours. The second cooling process involves cooling the product after the first cooling to 400–600°C for 2–5 hours. The third cooling process involves allowing the product after the second cooling to naturally cool to room temperature.

[0031] High temperatures generate thermal stress within materials. Direct, rapid cooling can lead to stress concentration, even cracking or deformation. Staged cooling, particularly longer primary and secondary cooling periods, allows the internal temperature to decrease gradually, reducing thermal stress and protecting the material's integrity and performance. During cooling, a series of physical and chemical changes occur within the material, such as phase transitions and grain growth. Staged cooling ensures these changes occur under controlled conditions, avoiding structural inhomogeneities or defects caused by rapid cooling. The secondary cooling process, from 900–1100℃ to 400–600℃, particularly contributes to further optimization of the material's internal structure. Programmed cooling helps reduce residual stress and defects, improving mechanical properties and thermal stability. Furthermore, controlling the cooling rate and time can optimize the material's microstructure and properties, such as increasing hardness, wear resistance, and corrosion resistance. The tertiary cooling process, using natural cooling, avoids the thermal stress concentration and cracking that can occur with rapid cooling. During natural cooling, the internal temperature of the material gradually decreases, which helps to release internal stress and stabilize the structure. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic flowchart of a method for preparing carbon fiber / carbon nanotube fiber composite carbon-based materials according to the present invention.

[0034] Figure 2 The image shows a SEM image of the carbon fiber / carbon nanotube fiber composite carbon-based material in this invention, where (a) is the surface and (b) is the cross-section.

[0035] Figure 3 The density and porosity of the carbon fiber / carbon nanotube fiber composite carbon-based materials prepared in Examples 1-3 of this invention are shown. Detailed Implementation

[0036] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0037] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0038] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0039] In this article, unless otherwise specified, the terms “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of”. For example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a”.

[0040] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0041] like Figure 1 As shown, this invention provides a method for preparing carbon fiber / carbon nanotube fiber composite carbon-based materials, comprising the following steps:

[0042] S1: Carbon cloth, carbon matrix and carbon nanotube film are alternately stacked to form a green embryo with a thickness of 10-80cm;

[0043] Before preparing the green embryo using the matrix carbon, a pretreatment process is performed. This pretreatment involves ball milling the matrix carbon for 5–20 hours, followed by sieving. After ball milling, the size of the matrix carbon is 300–800 mesh. The matrix carbon is resin or pitch. The carbon cloth is a single-layer 2D carbon cloth woven from carbon fibers.

[0044] The carbon nanotube thin film is prepared by a spinnable array spinning method. The array uses a silicon wafer, quartz wafer, or stainless steel sheet as a substrate, and a spinnable carbon nanotube array is grown on the substrate surface, with the carbon nanotubes arranged vertically within the array. Subsequently, a dry spinning method is used to pull the carbon nanotubes from the substrate and twist them into carbon nanotube fibers.

[0045] The carbon cloth has the same dimensions as the carbon nanotube film. Furthermore, the amount of matrix carbon used per unit area of ​​the carbon cloth is 0.1–1 g / cm³. 2 .

[0046] The thickness of the aforementioned embryo can be further preferably 10-60 cm.

[0047] S2: Under vacuum conditions of 3-5 kPa, the green preform is subjected to hot pressing, sintering heat treatment and programmed cooling treatment in sequence to obtain the carbon fiber / carbon nanotube fiber composite carbon-based material.

[0048] During the hot pressing process, the pressure is 5-40 MPa, the temperature is 200-500℃, the time is 1-5 h, and the heating rate is 10-15℃ / min.

[0049] During the sintering heat treatment process, the temperature is 1200-1600℃, the holding time is 3-10h, and the heating rate is 5-10℃ / min.

[0050] The programmed cooling process specifically involves the hot-pressed product undergoing a first cooling, a second cooling, and a third cooling process. The first cooling process involves cooling the sample to 900–1100°C for 2–8 hours. The second cooling process involves cooling the product after the first cooling process to 400–600°C for 2–5 hours. The third cooling process involves allowing the product after the second cooling process to cool naturally to room temperature.

[0051] This invention boasts a short preparation cycle. Traditional CVI preparation processes take approximately two weeks, while this invention's cycle is only about two days, resulting in a significantly shorter preparation time. By employing carbon nanotube fiber-reinforced C / C composite materials, it avoids the problem of traditional loading methods failing to load sufficient catalysts onto the carbon fiber surface due to its high inertness, thus improving the toughening effect of carbon nanotubes. This invention achieves control over the matrix composition and component distribution of the composite material, exhibiting strong design flexibility. Compared to traditional methods, the matrix composition and its ratio can be adjusted according to actual conditions. Therefore, the coating composition and structure on the carbon cloth surface have strong design flexibility, allowing for structural design of the composite material to meet different usage environments and practical engineering needs.

[0052] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0053] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0054] Example 1

[0055] A method for preparing a carbon fiber / carbon nanotube fiber composite carbon-based material includes the following steps:

[0056] First, the asphalt is placed in a ball mill jar containing grinding beads and milled for 15 hours. Then, it is sieved through a 300-mesh screen to obtain the desired resin or asphalt powder. Single-layer 2D carbon cloth woven from carbon fibers and carbon nanotube fiber yarn are processed into 40cm square sheets. Subsequently, the carbon cloth, asphalt powder, and carbon nanotube fiber yarn are sequentially laid flat in a mold, with each layer of mesophase asphalt powder weighing approximately 3g. These layers are stacked alternately to form a 60cm thick green mold. The assembled graphite mold is then placed in a sintering furnace, and the pressure from a hot pressing device is applied. The pressure is drawn down to 3 kPa; the temperature is increased to 400℃ at a rate of 10-15℃ / min and held for 2 hours. The pressure is gradually applied to increase the pressure of the equipment to 5 MPa and is maintained. After the holding time, the temperature is increased to 1200℃ at a rate of 6℃ / min and held for 3 hours. After the holding time, the temperature is reduced from 1200℃ to 1100℃, which takes 2 hours. The temperature is then reduced from 1100℃ to 600℃, which takes 5 hours. The cooling program is then turned off and the furnace is cooled to obtain a carbon-based composite material with carbon fiber and carbon nanotube fiber mixed and enhanced.

[0057] Example 2

[0058] A method for preparing a carbon fiber / carbon nanotube fiber composite carbon-based material includes the following steps:

[0059] First, the asphalt is placed in a ball mill jar containing grinding beads and milled for 20 hours. Then, it is sieved through a 300-mesh screen to obtain the desired resin or asphalt powder. Single-layer 2D carbon cloth woven from carbon fibers and carbon nanotube fiber yarn are processed into 40cm square sheets. Subsequently, the carbon cloth, asphalt powder, and carbon nanotube fiber yarn are sequentially laid flat in a mold, with each layer of mesophase asphalt powder weighing approximately 5g. These layers are stacked alternately to form a green mold with a thickness of 60cm. The assembled graphite mold is then placed in a sintering furnace, and the pressure from a hot pressing device is applied. The pressure is pumped down to 5 kPa; the temperature is increased to 350°C at a rate of 10–15°C / min and held for 2 hours. Pressure is gradually applied to increase the pressure of the equipment to 8 MPa and is maintained. After the holding time, the temperature is increased to 1400°C at a rate of 6°C / min and held for 3 hours. After the holding time, the temperature is reduced from 1400°C to 1100°C, which takes 4 hours. The temperature is then reduced from 1100°C to 600°C, which takes 5 hours. The cooling program is then turned off and the furnace is cooled to obtain a carbon-based composite material with carbon fiber and carbon nanotube fiber mixed and enhanced.

[0060] Figure 2 The images show the surface and cross-sectional SEM images of the carbon-based composite material prepared in this embodiment. As can be seen from the images, the modified carbon-based composite material has a dense structure with no obvious defects. The carbon-based composite material block after sintering at 1400℃ has high density and flexural strength.

[0061] Example 3

[0062] A method for preparing a carbon fiber / carbon nanotube fiber composite carbon-based material includes the following steps:

[0063] First, the asphalt is placed in a ball mill jar containing grinding beads and milled for 10 hours. Then, it is sieved through a 300-mesh screen to obtain the desired resin or asphalt powder. Single-layer 2D carbon cloth woven from carbon fibers and carbon nanotube fiber yarn are processed into 40cm square sheets. Subsequently, the carbon cloth, asphalt powder, and carbon nanotube fiber yarn are sequentially laid flat in a mold, with each layer of mesophase asphalt powder weighing approximately 5g. These layers are stacked alternately to form a green mold with a thickness of 60cm. The assembled graphite mold is then placed in a sintering furnace, and the pressure from a hot pressing device is applied. The pressure is drawn down to 3 kPa; the temperature is increased to 350°C at a rate of 10–15°C / min and held for 2 hours. Pressure is gradually applied to increase the pressure of the equipment to 5 MPa and is maintained. After the holding time, the temperature is increased to 1600°C at a rate of 6°C / min and held for 3 hours. After the holding time, the temperature is reduced from 1600°C to 1100°C, which takes 5 hours. The temperature is then reduced from 1100°C to 600°C, which takes 5 hours. The cooling program is then turned off, and the furnace is cooled to obtain a carbon-based composite material with a mixture of carbon fiber and carbon nanotube fiber.

[0064] Figure 3The figures show the density and porosity of the carbon fiber / carbon nanotube fiber composite carbon-based materials prepared in Examples 1-3 of this invention. As can be seen from the figures, the density and porosity of the carbon fiber / carbon nanotube fiber composite carbon-based materials prepared in Examples 1-3 of this invention are 1.5-1.7 g / cm³. 3 With 5% to 10%, it has excellent performance.

[0065] Comparative Example

[0066] A method for preparing a carbon fiber / carbon nanotube fiber composite carbon-based material includes the following steps:

[0067] First, the asphalt is placed in a ball mill jar containing grinding beads and milled for 10 hours. Then, it is sieved through a 300-mesh screen to obtain the desired resin or asphalt powder. Single-layer 2D carbon cloth woven from carbon fibers and carbon nanotube fiber yarn are processed into 40cm square sheets. Subsequently, the carbon cloth, asphalt powder, and carbon nanotube fiber yarn are sequentially laid flat in a mold, with each layer of mesophase asphalt powder weighing approximately 5g. These layers are stacked alternately to form a 60cm thick green mold. The assembled graphite mold is then placed in a sintering furnace, and the pressure is applied using a hot pressing device. The pressure was increased to 3 kPa; the temperature was raised to 350°C at a rate of 10-15°C / min and held for 2 hours. The pressure was gradually increased to 5 MPa and maintained. After the holding time, the temperature was raised to 1400°C at a rate of 6°C / min and held for 3 hours. After the holding time, the temperature was lowered from 1400°C to 1100°C and cooled with the furnace to obtain a carbon-based composite material with carbon fiber and carbon nanotube fiber mixed. However, due to the lack of segmented cooling, the carbon-based composite material block also showed relatively wide macroscopic crack defects.

[0068] Example 5

[0069] This invention provides a method for preparing carbon fiber / carbon nanotube fiber composite carbon-based materials, comprising the following steps:

[0070] S1: After ball milling the matrix carbon for 5 hours, it is sieved. After ball milling, the matrix carbon has a mesh size of 300. Carbon cloth, pretreated matrix carbon, and carbon nanotube film are alternately layered to form a green body with a thickness of 60 cm. The carbon cloth and carbon nanotube film have the same size, and the amount of matrix carbon used per unit area of ​​carbon cloth is 0.1 g / cm³. 2 .

[0071] The pretreatment involves using resin or asphalt as the matrix carbon.

[0072] S2: Under vacuum conditions of 3 kPa, the green preform is subjected to hot pressing, sintering heat treatment and programmed cooling treatment in sequence to obtain the carbon fiber / carbon nanotube fiber composite carbon-based material.

[0073] During the hot pressing process, the pressure is 5 MPa, the temperature is 200℃, the time is 5 hours, and the heating rate is 10℃ / min. During the sintering heat treatment process, the temperature is 1200℃, the holding time is 10 hours, and the heating rate is 5℃ / min.

[0074] The cooling process specifically involves the hot-pressed product undergoing a first cooling, a second cooling, and a third cooling process. The first cooling process involves cooling the sample to 900°C for 2 hours. The second cooling process involves cooling the product to 400°C for 2 hours. The third cooling process involves allowing the product to cool naturally to room temperature.

[0075] Example 6

[0076] This invention provides a method for preparing carbon fiber / carbon nanotube fiber composite carbon-based materials, comprising the following steps:

[0077] S1: After ball milling the matrix carbon for 20 hours, it is sieved. After ball milling, the matrix carbon has a size of 800 mesh. Carbon cloth, pretreated matrix carbon, and carbon nanotube film are alternately layered to form a green body with a thickness of 80 cm. The carbon cloth and carbon nanotube film have the same size, and the amount of matrix carbon used per unit area of ​​carbon cloth is 1 g / cm. 2 .

[0078] The pretreatment involves using resin or asphalt as the matrix carbon.

[0079] S2: Under vacuum conditions of 5 kPa, the green embryo is subjected to hot pressing, sintering heat treatment and programmed cooling treatment in sequence to obtain the carbon fiber / carbon nanotube fiber composite carbon-based material.

[0080] During the hot pressing process, the pressure is 40 MPa, the temperature is 500℃, the time is 1 hour, and the heating rate is 15℃ / min. During the sintering heat treatment process, the temperature is 1600℃, the holding time is 3 hours, and the heating rate is 10℃ / min.

[0081] The cooling process specifically involves the hot-pressed product undergoing a first cooling, a second cooling, and a third cooling process. The first cooling process involves cooling the sample to 1100°C for 8 hours. The second cooling process involves cooling the product to 600°C for 5 hours. The third cooling process involves allowing the product to cool naturally to room temperature.

[0082] Example 7

[0083] This invention provides a method for preparing carbon fiber / carbon nanotube fiber composite carbon-based materials, comprising the following steps:

[0084] S1: After ball milling the matrix carbon for 10 hours, it is sieved. After ball milling, the matrix carbon has a mesh size of 500. Carbon cloth, pretreated matrix carbon, and carbon nanotube film are alternately layered to form a green body with a thickness of 50 cm. The carbon cloth and carbon nanotube film have the same size, and the amount of matrix carbon used per unit area of ​​carbon cloth is 0.5 g / cm³. 2 .

[0085] The pretreatment involves using resin or asphalt as the matrix carbon.

[0086] S2: Under vacuum conditions of 2 kPa, the green preform is subjected to hot pressing, sintering heat treatment and programmed cooling treatment in sequence to obtain the carbon fiber / carbon nanotube fiber composite carbon-based material.

[0087] During the hot pressing process, the pressure is 20 MPa, the temperature is 300℃, the time is 3 hours, and the heating rate is 13℃ / min. During the sintering heat treatment process, the temperature is 1400℃, the holding time is 7 hours, and the heating rate is 7℃ / min.

[0088] The cooling process specifically involves the hot-pressed product undergoing a first cooling, a second cooling, and a third cooling process. The first cooling process involves cooling the sample to 1000°C for 5 hours. The second cooling process involves cooling the product to 500°C for 3 hours. The third cooling process involves allowing the product to cool naturally to room temperature.

[0089] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for producing a carbon fiber / carbon nanotube fiber composite carbon-based material, characterized by, Includes the following steps: S1: Carbon cloth, carbon matrix, and carbon nanotube film are sequentially and alternately stacked to form a green embryo; S2: Under vacuum conditions, the green embryo is subjected to hot pressing, sintering heat treatment and programmed cooling treatment in sequence to obtain the carbon fiber / carbon nanotube fiber composite carbon-based material. In step S2, the programmed cooling process specifically involves the hot-pressed product undergoing a first cooling process, a second cooling process, and a third cooling process in sequence. The first cooling step specifically involves cooling the sample to 900~1100℃, and the cooling time for the first cooling step is 2~8 hours. The secondary cooling specifically involves cooling the product that has undergone the first cooling to 400~600℃, and the cooling time for the secondary cooling is 2~5 hours. The three cooling steps specifically involve allowing the product, which has undergone two cooling steps, to naturally cool down to room temperature.

2. The method for preparing a carbon fiber / carbon nanotube fiber composite carbon-based material according to claim 1, characterized in that, Before preparing the green embryo using matrix carbon, a pretreatment is performed, which involves ball milling and sieving the matrix carbon. After ball milling, the size of the matrix carbon is 300-800 mesh.

3. The method for preparing a carbon fiber / carbon nanotube fiber composite carbon-based material according to claim 1, characterized in that, In step S1, the thickness of the embryo is 10~80 cm.

4. The method for preparing a carbon fiber / carbon nanotube fiber composite carbon-based material according to claim 1, characterized in that, The matrix carbon is resin or asphalt.

5. The method for preparing a carbon fiber / carbon nanotube fiber composite carbon-based material according to claim 1, characterized in that, In step S2, the vacuum level of the vacuum condition is 3~5 kPa.

6. The method for preparing a carbon fiber / carbon nanotube fiber composite carbon-based material according to claim 1, characterized in that, In step S2, during the hot pressing process, the pressure is 5~40 MPa, the temperature is 200~500℃, the time is 1~5 h, and the heating rate is 10~15℃ / min.

7. The method for preparing a carbon fiber / carbon nanotube fiber composite carbon-based material according to claim 1, characterized in that, In step S2, during the sintering heat treatment, the temperature is 1200~1600℃, the holding time is 3~10 h, and the heating rate is 5~10℃ / min.

8. A carbon fiber / carbon nanotube fiber composite carbon-based material, characterized in that, It is prepared by the method described in any one of claims 1 to 7.

9. The application of the carbon fiber / carbon nanotube fiber composite carbon-based material as described in claim 8 in the fields of photovoltaic thermal fields, vacuum high-temperature furnaces, and aerospace.

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