Post-treatment method and application for significantly improving the performance of carbon nanotube films

Abstract

The post-treatment method includes the following steps: immersing the raw state carbon nanotube film in chlorosulfonic acid and allowing it to stand, then leaving it in the air to allow the chlorosulfonic acid molecules inside the carbon nanotube film to react with water molecules in the air, then generating sulfuric acid molecules inside the carbon nanotube film, promoting the introduction of water molecules into the carbon nanotube film, then placing it back in chlorosulfonic acid to chemically react with water molecules to generate hydrogen chloride gas, then expanding the carbon nanotube film, then stretching, immersing it again in the chlorosulfonic acid solution, and finally performing high-temperature vacuum annealing heat treatment. The tensile strength of the carbon nanotube film prepared according to this application is in the order of GPa, and its conductivity is 10 6 It is at the S / m level, has higher surface flatness, and facilitates compounding with other materials.

Description

[Technical Field]

[0001] (Related applications) This application claims priority based on the Chinese patent application filed on March 24, 2023, application number 202310293493.1, application title "Post-treatment method and application for significantly improving the performance of carbon nanotube films."

[0002] (Technical field) This application relates to a post-treatment method for significantly improving the mechanical and electrical performance of carbon nanotube films, and belongs to the technical field of carbon nanotube post-treatment. [Background technology]

[0003] Carbon nanotubes have an extremely long mean free path of electrons, and research data shows that this value can exceed 30 μm (copper: 40 nm). This very long mean free path is what gives carbon nanotubes their excellent electrical conductivity (theoretical value is 10 μm). 8 It exhibits a conductivity of S / m, achieving a numerical improvement of an order of magnitude compared to copper. At the same time, carbon nanotubes possess properties such as low density, chemical stability, excellent thermal conductivity, and high tensile strength. Therefore, carbon nanotubes are one of the most promising highly conductive materials.

[0004] However, the process of constructing carbon nanotube aggregates on a macroscale inevitably introduces various defects, such as the creation of numerous voids within the structure, limited contact area between individual nanotubes, and insufficient orientation. As a result, the electrical properties of the carbon nanotube aggregates actually obtained deviate significantly from theoretical values. According to the data, the electrical conductivity of carbon nanotube films produced by suspended catalytic chemical vapor deposition is approximately 8 × 10⁻⁶. 4 With a density of approximately S / m and a tensile strength of only about 100 MPa, it has not yet reached the level of mechanical and electrical performance required for practical application.

[0005] To address the problem of the low mechanical and electrical properties of carbon nanotube films, treatments such as stretching in air, roll rolling, thermocompression bonding, or high-temperature graphitization are currently being applied to carbon nanotube films obtained by the floating catalyst method to improve their mechanical and electrical performance. However, the improvement effect of these methods is limited. Regarding electrical performance, its electrical conductivity is 10 5 The strength is at the S / m level, and in terms of mechanical performance, only a portion of the film reaches the GPa order after processing. Existing stretch strengthening methods for carbon nanotube films have a low success rate due to the non-uniformity of the microstructure of the carbon nanotube film itself, and the distribution of electrical and mechanical properties on the carbon nanotube surface is not uniform. Some regions obtain high tensile strength, but the overall mechanical performance of the carbon nanotube film is poor. Similarly, with roll rolling and thermocompression strengthening, the non-uniformity of the carbon nanotube film makes it prone to fracture during the pressurizing process, negatively impacting the success rate of experiments. The surface of the carbon nanotube film obtained under pressurization generally has many depressions and fractures, resulting in poor film flatness, which is likely to negatively affect the interface structure and interface performance when the carbon nanotube film is later composited with other materials.

[0006] Recently, researchers have developed a chlorosulfonic acid treatment process for carbon nanotube films. This post-treatment process promotes densification of the microstructure of the carbon nanotube films, resulting in a significant improvement in their mechanical and electrical properties. The electrical properties of the prepared carbon nanotube films are good, reaching 1 × 10⁻⁶. 6 Although it reached S / m, its tensile mechanical strength was still low at approximately 250 MPa, far from the GPa order. The mechanical and electrical performance of the prepared carbon nanotube film was still poor and did not meet the overall performance requirements of carbon nanotube films under actual application conditions. [Overview of the project] [Problems that the invention aims to solve]

[0007] The main objective of this application is to overcome the shortcomings of the prior art and provide a post-treatment method that significantly improves the mechanical and electrical performance of carbon nanotube films. [Means for solving the problem]

[0008] To achieve the objectives of the above application, this application employs the following technical solutions.

[0009] The embodiments of this application provide a post-treatment method for significantly improving the mechanical and electrical properties of carbon nanotube films, and include the following steps: (1) A primitive carbon nanotube film is thoroughly immersed in chlorosulfonic acid and left to stand, allowing chlorosulfonic acid molecules to be introduced into the carbon nanotube film. (2) The carbon nanotube film, which has been thoroughly immersed in the chlorosulfonic acid obtained in step (1), is placed in the air to allow the chlorosulfonic acid molecules inside the carbon nanotube film to react thoroughly with water molecules in the air, thereby generating sulfuric acid molecules inside the carbon nanotube film and introducing water molecules into the carbon nanotube film. (3) The carbon nanotube film obtained in step (2) is placed again in chlorosulfonic acid, and the chlorosulfonic acid reacts with water molecules to produce hydrogen chloride gas, causing the carbon nanotube film to expand. The expansion factor is 500 or more. (4) The expanded carbon nanotube film obtained in step (3) is stretched to a stretch ratio of 50% to 500%. (5) Repeat step (1) multiple times on the carbon nanotube film after stretching. (6) The carbon nanotube film obtained in step (5) is subjected to annealing heat treatment under high temperature and vacuum to prepare a high-strength, high-conductivity carbon nanotube film. The temperature of the high-temperature vacuum annealing heat treatment is 300°C or lower, and the vacuum level is 10°C. -2It is less than or equal to Pa. The aforementioned high-strength, high-conductivity carbon nanotube film has a tensile strength on the order of GPa and a conductivity of 10 6 It's at the S / m level.

[0010] The embodiments of this application provide a high-strength, high-electricity carbon nanotube film manufactured by the method described above.

[0011] The embodiments of this application further provide applications in the preparation of composites of high-performance carbon nanotube films obtained by a post-treatment method that significantly improves the mechanical and electrical properties of the carbon nanotube film, and other materials.

[0012] Furthermore, embodiments of this application further provide a high-performance carbon nanotube film composite material, which is formed by compounding a high-strength, high-conductivity carbon nanotube film manufactured by a post-treatment method that significantly improves the performance of the carbon nanotube film with a high-performance material, wherein the high-performance material includes at least one of the following materials: graphene, Mxene, etc. [Effects of the Invention]

[0013] Compared to prior art, this application offers the following beneficial effects.

[0014] 1) The post-processing method provided in this application can improve the mechanical performance of floating carbon nanotube films, currently mass-produced on the largest scale, to a maximum of 2 GPa (this mechanical performance is currently state-of-the-art in the world), eliminating the need for high-performance carbon nanotube films to rely on array growth or stretch-growth floating growth methods. As a result, production costs will be significantly reduced and the feasibility of industrial-scale production will be improved.

[0015] 2) The high-strength and high-conductivity carbon nanotube film prepared in this application has higher surface flatness, making it easier to composite with other materials. A composite interface with higher bonding strength can be constructed, leading to a significant improvement in the final mechanical and electrical properties of the composite material. (The carbon nanotube film requires higher surface flatness. After the fibers are densified, a serrated structure is formed on the surface.) Furthermore, the thickness of the prepared high-strength and high-conductivity carbon nanotube film is close to the level of several hundred nanometers. The number of defects associated with the increase in the film size is reduced, which is beneficial for the manifestation of the excellent mechanical and electrical properties inherent in carbon nanotubes.

Brief Description of Drawings

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the attached drawings necessary for use in the description of the embodiments or the prior art will be briefly described below. Obviously, the attached drawings described below are only some embodiments of this application. A person skilled in the art can obtain other drawings based on these attached drawings without creative labor.

[0017] [Figure 1] It is an image diagram of the process of densifying and stretching the carbon nanotube film in a typical embodiment of this application. [Figure 2a] It is a microstructure diagram of the pristine carbon nanotube film. [Figure 2b] It is a microstructure diagram of the densified + 0% stretched carbon nanotube film in a typical embodiment of this application. [Figure 2c] It is a microstructure diagram of the densified + 50% stretched carbon nanotube film in a typical embodiment of this application. [Figure 2d] It is a microstructure diagram of the densified + 200% stretched carbon nanotube film in a typical embodiment of this application. [Figure 3a]This is a schematic diagram illustrating the effect of dense stretching on the tensile mechanical properties of a carbon nanotube film in a typical embodiment of this application. [Figure 3b] This is a schematic diagram illustrating the effect of dense stretching on the electrical performance of a carbon nanotube film in a typical embodiment of this application. [Figure 4a] This is a microscopic fracture cross-sectional view of a primitive carbon nanotube film. [Figure 4b] This is a microscopic fracture cross-sectional view of a densified +0% stretched carbon nanotube film in a typical embodiment of this application. [Figure 4c] This is a microscopic fracture cross-sectional view of a densified +50% stretched carbon nanotube film in a typical embodiment of this application. [Figure 4d] This is a microscopic fracture cross-sectional view of a densified +200% stretched carbon nanotube film in a typical embodiment of this application. [Figure 5] This is a photograph of the thickness of the carbon nanotube film after stretching and densification in a typical example of this application. [Modes for carrying out the invention]

[0018] To solve the above problems, the applicant of this application has conducted extensive research and numerous practical applications over a long period and submitted the technical solution described herein. This solution primarily concerns a post-treatment method that significantly improves the mechanical and electrical properties of carbon nanotube films simultaneously, based on the protonation effect of chlorosulfonic acid on carbon nanotubes, the expansion effect of chlorosulfonic acid on carbon nanotube films, and the orientation force effect of electric dipoles. The specific method includes techniques for thoroughly immersing the carbon nanotube film in chlorosulfonic acid to significantly expand the film, significant stretching of the carbon nanotube film, and an annealing process. Ultimately, through densification and significant stretching of the carbon nanotube film, it achieves a tensile strength in the GPa order and an electrical conductivity of 10⁻¹⁰. 6This enables the preparation of high-performance carbon nanotube films with a density of around S / m.

[0019] The following provides a further interpretation and explanation of this technical solution, its implementation process, and its principles.

[0020] One example of the embodiments of this application provides a post-treatment method that significantly improves the performance of a carbon nanotube film, and this method includes the following steps. (1) A primitive carbon nanotube film is thoroughly immersed in chlorosulfonic acid and left to stand, allowing chlorosulfonic acid molecules to be introduced into the carbon nanotube film. (2) The carbon nanotube film, which has been thoroughly immersed in the chlorosulfonic acid obtained in step (1), is placed in the air to allow the chlorosulfonic acid molecules inside the carbon nanotube film to react thoroughly with water molecules in the air, thereby generating sulfuric acid molecules inside the carbon nanotube film and introducing water molecules into the carbon nanotube film. (3) The carbon nanotube film obtained in step (2) is placed in chlorosulfonic acid again, and the chlorosulfonic acid reacts with water molecules to produce hydrogen chloride gas, causing the carbon nanotube film to expand. (4) The expanded carbon nanotube film obtained in step (3) is stretched to a stretch ratio of 50% to 500%. (5) Repeat step (1) multiple times on the carbon nanotube film after stretching. (6) The carbon nanotube film obtained in step (5) is subjected to high-temperature vacuum annealing heat treatment to prepare a high-strength, high-conductivity carbon nanotube film, the temperature of the high-temperature vacuum annealing heat treatment being 300°C or lower and the vacuum level being 10 -2 It is below Pa.

[0021] The reaction mechanism of this application is as follows: Based on the protonation effect of chlorosulfonic acid on carbon nanotubes, the expansion effect of chlorosulfonic acid on carbon nanotube films, and the orientation force of electric dipoles, the carbon nanotube film is thoroughly immersed in a chlorosulfonic acid solution to sufficiently fill the inside of the carbon nanotube film with chlorosulfonic acid molecules. Subsequently, a large amount of hydrogen chloride gas is generated by the reaction process between chlorosulfonic acid molecules and water, thereby achieving rapid expansion of the carbon nanotube film. Based on the expansion of the carbon nanotube film due to the above chemical reaction, a significant orientation of carbon nanotubes inside the film is achieved through stress relaxation stretching. A significant densification of the microstructure of the carbon nanotube film is achieved through high-temperature vacuum heat treatment and the orientation force of electric dipoles. Finally, a significant improvement in the mechanical and electrical performance of the suspended catalyst carbon nanotube film is achieved through an improvement in the degree of carbon nanotube orientation inside the film and an improvement in the density inside the carbon nanotube film.

[0022] In some embodiments, step (1) of the post-treatment method specifically includes thoroughly immersing a raw state carbon nanotube film in a chlorosulfonic acid solution, allowing it to stand for 12 hours or more, and introducing chlorosulfonic acid molecules into the carbon nanotube film until the carbon nanotube film becomes flexible. This application relates to the immersion of carbon nanotube films in chlorosulfonic acid, and experiments have shown that stretching a carbon nanotube film in any protonated acid improves its density, resulting in improved mechanical, electrical, and ultimately thermal performance.

[0023] In some embodiments, step (2) of the post-treatment method specifically includes placing the carbon nanotube film, after being thoroughly immersed in chlorosulfonic acid, into moist air to allow the chlorosulfonic acid molecules inside the carbon nanotube film to react sufficiently with water molecules in the air, generating sulfuric acid molecules inside the carbon nanotube film, and introducing water molecules into the carbon nanotube film until no more white mist of hydrogen chloride is generated from the surface of the carbon nanotube film.

[0024] In some embodiments, in step (3), the expansion factor of the expanded carbon nanotube film is 500 times or more, preferably 500 to 1000 times, and the expansion range can reach a maximum thickness of 5 μm to 5000 μm. This application cleverly and comprehensively utilizes the protonation of the carbon nanotube film by chlorosulfonic acid and the expansion of the carbon nanotube microstructure by the reaction of chlorosulfonic acid with water. This achieves a significant improvement in the elongation of the carbon nanotube film.

[0025] In some embodiments, step (4) of the post-treatment method specifically includes stretching the expanded carbon nanotube film by 50% to 500%, preferably 200% to 400%, tensing the carbon nanotube film, allowing it to rest for 2 hours or more, then tensing and resting again, repeating the step three times until the carbon nanotube film is finally stretched. Any stretching amount within the 50% to 500% range can be selected according to experimental requirements. Due to the large macro size and macro force, it is necessary to supply additional large stretching force manually (or mechanically) during the stretching process.

[0026] In some embodiments, step (5) of the post-treatment method specifically includes immersing the stretched carbon nanotube film again in chlorosulfonic acid and leaving it for 12 hours or more. This application relates to the multiple expansion of the carbon nanotube film in chlorosulfonic acid, thereby achieving a stepwise improvement in the degree of stretching of the carbon nanotube film.

[0027] In some embodiments, step (6) of the post-treatment method specifically comprises placing the carbon nanotube film after being immersed in chlorosulfonic acid again into a vacuum annealing apparatus, evacuating the reaction chamber of the vacuum annealing apparatus, heating the vacuum annealing apparatus when the degree of vacuum reaches <10 -2 Pa, with a heating rate of less than 10 °C / min, a heating temperature of 300 °C or lower (between 100 °C and 300 °C), and a time of 3 h or longer, thereby completely removing the chlorosulfonic acid inside the carbon nanotube film.

[0028] Considering the optimization of experimental effects, the present application selects the temperature and degree of vacuum of the annealing heat treatment in the implementation process. When the temperature is high (exceeding 300 °C) and the degree of vacuum is low (>10 -2 [[ID=!1]]Pa), the degree of densification of the carbon nanotube film is low. When the temperature is low (300 °C or lower) and the degree of vacuum is high (<10<!000011>Pa, especially <10 -4 Pa), the degree of densification of the carbon nanotube film is high, and finally, the mechanical and electrical properties of the carbon nanotube film are significantly improved.

[0029] Also, in the process of high-temperature vacuum annealing heat treatment of the carbon nanotube film, it is necessary to keep the film surface flat and maintain the film form.

[0030] Another aspect of the embodiment of the present application further provides a high-strength and high-conductivity carbon nanotube film manufactured by the preparation method.

[0031] Furthermore, the tensile strength of the high-strength and high-conductivity carbon nanotube film is on the order of GPa, and the conductivity is at the level of 10 6 S / m.

[0032] Furthermore, the thickness of the high-strength and high-conductivity carbon nanotube film is at the level of several hundred nanometers or more.

[0033] As described above, the surface flatness of the high-strength, high-conductivity carbon nanotube film prepared in this application is higher (roll rolling, thermocompression bonding, and graphitization treatment tend to cause significant roughness on the film surface), which is advantageous for composite formation with other materials, enabling the construction of composite interfaces with higher bonding strength, and further contributing to a significant improvement in the final mechanical and electrical performance of the composite material.

[0034] This application relates to the multiple expansion and stretching of carbon nanotube films during the preparation stage of high-performance carbon nanotube films. This process provides favorable process conditions for the composite of densified carbon nanotubes with high-performance materials such as graphene and Mxene, enabling the preparation of carbon nanotube film composite materials with higher electrical performance and greater versatility, thereby significantly expanding the practical production and everyday application fields of carbon nanotubes.

[0035] Another aspect of the embodiments of this application further provides a post-treatment method for significantly improving the performance of the carbon nanotube film, or an application in the preparation of high-strength, high-conductivity carbon nanotube films, or high-performance carbon nanotube film composite materials.

[0036] The surface flatness of the carbon nanotube film described in this application reaches the single carbon nanotube scale level, making it possible to physically deposit a continuous metal film of approximately 10 nm onto the carbon nanotube film surface.

[0037] In response to this, another aspect of the embodiments of this application further provides a high-performance carbon nanotube film composite material. It is formed by compounding a high-strength, high-conductivity carbon nanotube film, manufactured by a post-treatment method that significantly improves the performance of the carbon nanotube film, with a high-performance material, the high-performance material including, but not limited to, at least one of the following materials: graphene, Mxene, etc.

[0038] The technical solutions of this application will be described in more detail below with reference to several preferred embodiments and accompanying drawings, but obviously the embodiments described are only a selection of embodiments of this application, not all embodiments. Any other embodiments that can be obtained by a person skilled in the art without creative work based on the embodiments of this application are all included in the scope of protection of this application. Experimental methods in the following embodiments where specific conditions are not explicitly described are usually carried out under general conditions or conditions recommended by the manufacturer.

[0039] (Example 1) As shown in Figure 1, the specific technical steps of the post-treatment method that significantly improves the performance of the carbon nanotube film in this embodiment are as follows.

[0040] 1. Immerse the carbon nanotube film thoroughly in chlorosulfonic acid solution.

[0041] A carbon nanotube film of a certain length and width (e.g., 1 cm to 50 cm, or any length and width greater than 1 cm) is taken, fixed to a jig, and the stretched state of the carbon nanotube film is maintained. Then the carbon nanotube film is left in a chlorosulfonic acid solution, ensuring that the carbon nanotube film is fully immersed in the chlorosulfonic acid solution, and then left to stand for 12 hours or more until the carbon nanotube film becomes completely flexible.

[0042] In this step of the experimental process, it is necessary to fix the carbon nanotube film with a jig to prevent the film from crimping, and to maintain the carbon nanotubes in their film form throughout the experimental process.

[0043] 2. Expansion process technology and stretching treatment of carbon nanotube films

[0044] After thoroughly immersing the carbon nanotube film in chlorosulfonic acid, it is placed in humid air to allow the chlorosulfonic acid molecules inside the carbon nanotube film to react sufficiently with the moisture in the air. Subsequently, sulfuric acid molecules are generated inside the carbon nanotube film, and then, utilizing the strong water absorption properties of sulfuric acid molecules, water molecules are gradually introduced into the carbon nanotube film until no more white mist of hydrogen chloride is generated on the carbon nanotube surface.

[0045] Based on the above, a carbon nanotube film is placed in a chlorosulfonic acid solution, and hydrogen chloride gas is generated by a chemical reaction between chlorosulfonic acid and water molecules, causing the carbon nanotube film to expand significantly. Then, the expanded carbon nanotube film is stretched by a certain amount (an arbitrary amount of stretching from 50% to 500%, as long as the film is kept taut at all times, and this can be determined experimentally), and after the film is taut, it is left to stand for 2 hours or more. After that, the stretching and standing process is repeated again, and the above process is repeated three or more times until the carbon nanotube film reaches a significant stretch (final maximum stretch). After that, the carbon nanotube film is left in chlorosulfonic acid for 12 hours or more. In this example, the reason for repeating the process multiple times is that if the film is stretched significantly in one go, it is prone to breaking.

[0046] 3. High-temperature vacuum annealing treatment of carbon nanotube films

[0047] The carbon nanotube film, after being immersed in a chlorosulfonic acid solution, is left in a vacuum annealing furnace, and the furnace tube space where the sample is placed is evacuated to a vacuum level of <10. -2 When Pa is reached, the tubular furnace is heated. The heating rate is less than 10°C / min, the heating temperature is 300°C (100°C to 300°C) or less, and the time is 3 hours or more, ultimately completely removing the chlorosulfonic acid from inside the carbon nanotube film.

[0048] The applicant of this application performed the following various evaluations and tests on the carbon nanotube film that was ultimately obtained.

[0049] (1) Effects on the microstructure of carbon nanotube films

[0050] Figures 2a to 2d show the effect of stretching and densification on the microstructure of carbon nanotubes. Here, Figure 2a is the microstructure diagram of a raw state carbon nanotube film, Figure 2b is the microstructure diagram of a densified + 0% stretched carbon nanotube film, Figure 2c is the microstructure diagram of a densified + 50% stretched carbon nanotube film, and Figure 2d is the microstructure diagram of a densified + 200% stretched carbon nanotube film. As can be seen from the results, the microstructure inside the raw state carbon nanotube film is relatively porosity, the carbon nanotubes are distributed disorderly, there are many pores between the carbon nanotubes, most of the carbon nanotubes appear to be floating, and the flatness of the carbon nanotube surface is low. When a carbon nanotube film is subjected to densification treatment without any stretching treatment (by immersing the carbon nanotube film in chlorosulfonic acid and then directly performing high-temperature vacuum annealing treatment), i.e., stretched to 0%, the pores on the surface of the carbon nanotubes are largely removed, the obvious porosity of the microstructure is eliminated, and a clear densification of the microstructure of the carbon nanotube film is achieved. However, a certain number of depressions still exist on the surface of the carbon nanotube film, and the distribution of these carbon nanotubes remains disordered.

[0051] After densification and 50% stretching of a carbon nanotube film, the presence of fine depressions on the film surface is no longer observed, and the carbon nanotube distribution on the film surface shows high orientation. In this case, the flatness of the film surface is clearly improved, but upon careful observation, clear carbon nanotube structures can still be observed on the film surface, indicating that even with 50% stretching alone, although the flatness of the film surface is improved, a certain degree of unevenness remains on the surface. After densification and 200% stretching of the carbon nanotube film, not only is the presence of nano-sized depressions on the film surface no longer observed, but the tubular structure of most carbon nanotubes is also almost completely absent. The above experimental results indicate that the degree of densification of the microstructure of the carbon nanotube film has been further and significantly improved.

[0052] (2) Influence on the mechanical and electrical properties of carbon nanotube films

[0053] Figures 3a and 3b show the effects of densification and orientation stretching post-treatment on the mechanical and electrical properties of carbon nanotube films. As shown in Figure 3a, the mechanical strength of raw state carbon nanotubes is approximately 100 MPa. With densification treatment alone, the mechanical strength of the carbon nanotube film improves to approximately 300 MPa. After densification and 50% stretching of the film, the film strength improves to approximately 600 MPa. When the degree of stretching is further increased by 200%, the tensile strength of the carbon nanotube film reaches over GPa, enabling the preparation of GPa-order high-strength films using the floating catalyst method for carbon nanotube films. As shown in Figure 3b, the conductivity of raw state carbon nanotube film is approximately 0.8 × 10⁻⁶. 5 The density is S / m. With densification treatment alone, the conductivity of the carbon nanotube film is 1 × 10⁻⁶. 6 It reaches S / m, and the conductivity decreases slightly after stretching, but the conductivity tends to increase as the amount of stretching increases, and ultimately it reaches approximately 0.8 × 10⁻⁶. 6The conductivity level reaches S / m and remains high. As can be seen from the above results, in the floating carbon nanotube film currently being mass-produced on the largest scale, the preparation of a high-strength, high-conductivity carbon nanotube film through densification + 200% stretching post-treatment has been achieved, and its performance has reached the most advanced level in the world, demonstrating that this preparation technology has great social significance in the actual engineering applications of the film.

[0054] (3) Influence on fracture surface morphology of carbon nanotube film

[0055] Figures 4a to 4d show the effect of the densification + stretching post-treatment process on the fracture surface morphology of carbon nanotube films. As shown in Figure 4a, after the fracture of the primitive state carbon nanotube film, the fiber pull-out length at the fracture surface is 20-30 μm, and the fracture surface morphology is porosity, indicating that the primitive state carbon nanotube film is ultimately fractured mainly by sliding detachment between carbon nanotubes. When only densification treatment is performed on the carbon nanotube film, after the film fractures, the fiber pull-out length at the fracture surface is approximately 10 μm, which is clearly shorter, and as shown in Figure 4b, the frictional force between carbon nanotubes increases significantly. This indicates that some carbon nanotubes begin to fracture during the film fracture process, and the fiber pull-out morphology at the fracture surface weakens. When densification and stretching treatments are performed on the carbon nanotube film simultaneously, almost no fiber pull-out is observed at the fracture surface of the film, and the flatness of the fracture surface is high. At this time, the frictional force between carbon nanotubes is very strong, indicating that film rupture is mainly caused by the rupture of carbon nanotubes. As shown in Figures 4c and 4d, the inherent high-strength properties of carbon nanotubes are fully realized on the macrofilm, promoting a significant improvement in the final mechanical performance of the macrofilm.

[0056] The high-strength, high-conductivity carbon nanotube film prepared in this embodiment has a thickness of approximately several hundred nanometers, and as shown in Figure 5, the thickness is 1500 nm. This reduces the number of defects associated with large-sized films and is advantageous in that it allows carbon nanotubes to exhibit their inherently excellent mechanical and electrical properties.

[0057] Furthermore, the applicant of this application has conducted tests using other raw materials, process operations, and process conditions described herein, with reference to the above examples, and has obtained relatively ideal results in all cases.

[0058] While this application has been described with reference to exemplary embodiments, those skilled in the art can make various changes, omissions, and / or additions, and replace elements of the embodiments with substantial equivalents, without departing from the spirit and scope of this application. Furthermore, various modifications can be made to adapt the teachings of this application to specific circumstances or materials, without departing from the scope of this application. Accordingly, this specification does not limit this application to any specific embodiments disclosed herein, and this application includes all embodiments within the claims.

[0059] (Note) (Note 1) (1) A step of thoroughly immersing a raw state carbon nanotube film in chlorosulfonic acid and letting it stand to introduce chlorosulfonic acid molecules into the carbon nanotube film, (2) The carbon nanotube film, after being thoroughly immersed in the chlorosulfonic acid obtained in step (1), is placed in the air to allow the chlorosulfonic acid molecules inside the carbon nanotube film to react thoroughly with water molecules in the air, and then sulfuric acid molecules are generated inside the carbon nanotube film, and water molecules are introduced into the carbon nanotube film. (3) The carbon nanotube film obtained in step (2) is again placed in chlorosulfonic acid, and the chlorosulfonic acid and water molecules are chemically reacted to generate hydrogen chloride gas, causing the carbon nanotube film to expand, with an expansion factor of 500 or more. (4) The expanded carbon nanotube film obtained in step (3) is stretched to a stretch ratio of 50% to 500%, (5) A step of repeating step (1) multiple times on the carbon nanotube film after stretching, (6) The carbon nanotube film obtained in step (5) is subjected to high-temperature vacuum annealing heat treatment to prepare a high-strength, high-conductivity carbon nanotube film, wherein the temperature of the high-temperature vacuum annealing heat treatment is 300°C or lower and the vacuum degree is <10 -2 The step includes Pa, The aforementioned high-strength, high-conductivity carbon nanotube film has a tensile strength on the order of GPa and a conductivity of 10 6 A post-treatment method that significantly improves the performance of carbon nanotube films, characterized by having an S / m level.

[0060] (Note 2) Step (1) is as follows: a post-treatment method for significantly improving the performance of a carbon nanotube film as described in Appendix 1, characterized by including thoroughly immersing a raw state carbon nanotube film in a chlorosulfonic acid solution, allowing it to stand for 12 hours or more, and introducing chlorosulfonic acid molecules into the carbon nanotube film until the carbon nanotube film becomes flexible.

[0061] (Note 3) Step (2) is as follows: a post-treatment method for significantly improving the performance of a carbon nanotube film as described in Appendix 1, characterized by including placing the carbon nanotube film, after being thoroughly immersed in chlorosulfonic acid, in humid air to allow the chlorosulfonic acid molecules inside the carbon nanotube film to react thoroughly with water molecules in the air to generate sulfuric acid molecules inside the carbon nanotube film, and introducing water molecules into the carbon nanotube film until no more white mist of hydrogen chloride is generated from the surface of the carbon nanotube film.

[0062] (Note 5) A post-treatment method for significantly improving the performance of a carbon nanotube film as described in Appendix 1, characterized in that, in step (3), the expansion factor of the carbon nanotube film after expansion is 500 to 1000 times.

[0063] (Note 5) Step (4) is as follows: The expanded carbon nanotube film is stretched by 50% to 500%, preferably 200% to 400%, the carbon nanotube film is stretched, then left to stand for 2 hours or more, and then stretched and left to stand again, and the above step is repeated three times until the stretching of the carbon nanotube film is finally achieved. This post-treatment method for significantly improving the performance of the carbon nanotube film as described in Appendix 1.

[0064] (Note 6) Step (5) is the following: a post-treatment method for significantly improving the performance of the carbon nanotube film described in Appendix 1, characterized by immersing the stretched carbon nanotube film again in chlorosulfonic acid and leaving it for 12 hours or more.

[0065] (Note 7) Step (6) is as follows: Place the carbon nanotube film, which has been immersed again in chlorosulfonic acid, into the vacuum annealing apparatus, and evacuate the reaction chamber of the vacuum annealing apparatus to a vacuum level of <10 -2 A post-treatment method for significantly improving the performance of a carbon nanotube film as described in Appendix 1, characterized by comprising: heating the vacuum annealing apparatus when Pa is reached, with a heating rate of less than 10°C / min, a heating temperature of less than 300°C, preferably 100°C to 300°C, and a duration of 3 hours or more, to completely remove chlorosulfonic acid from inside the carbon nanotube film.

[0066] (Note 8) A post-treatment method for significantly improving the performance of a carbon nanotube film according to any one of the appendices 1 to 7, characterized in that the thickness of the high-strength, high-conductivity carbon nanotube film is at the level of several hundred nanometers or more.

[0067] (Note 9) Application of a post-treatment method for significantly improving the performance of carbon nanotube films, as described in any one of Appendix 1 to 8, to the preparation of high-performance carbon nanotube film composite materials.

[0068] (Note 10) A high-performance carbon nanotube film composite material characterized by being formed by compounding a high-strength, high-conductivity carbon nanotube film prepared by a post-treatment method for significantly improving the performance of a carbon nanotube film as described in any one of Appendix 1 to 8 with a high-performance material, wherein the high-performance material includes at least one of graphene and Mxene material.

Claims

1. (1) A step of thoroughly immersing a raw state carbon nanotube film in chlorosulfonic acid and letting it stand to introduce chlorosulfonic acid molecules into the carbon nanotube film, (2) The carbon nanotube film, after being thoroughly immersed in the chlorosulfonic acid obtained in step (1), is placed in the air to allow the chlorosulfonic acid molecules inside the carbon nanotube film to react thoroughly with water molecules in the air, and then sulfuric acid molecules are generated inside the carbon nanotube film, and water molecules are introduced into the carbon nanotube film. (3) The carbon nanotube film obtained in step (2) is again placed in chlorosulfonic acid, and the chlorosulfonic acid and water molecules are chemically reacted to generate hydrogen chloride gas, causing the carbon nanotube film to expand, with an expansion factor of 500 or more. (4) The expanded carbon nanotube film obtained in step (3) is stretched to a stretch ratio of 50% to 500%, (5) A step of repeating step (1) multiple times on the carbon nanotube film after stretching, (6) The carbon nanotube film obtained in step (5) is subjected to high-temperature vacuum annealing heat treatment to prepare a high-strength, high-electrical conductivity carbon nanotube film, wherein the temperature of the high-temperature vacuum annealing heat treatment is 300°C or lower and the vacuum degree is <10 -２ The step is Pa, and includes The aforementioned high-strength, high-conductivity carbon nanotube film has a tensile strength on the order of GPa and an conductivity of 10 ６ A post-treatment method for carbon nanotube films that significantly improves performance, characterized by having an S / m level.

2. Step (1) is as follows: a post-treatment method for significantly improving the performance of a carbon nanotube film according to claim 1, characterized in that it includes thoroughly immersing a raw state carbon nanotube film in a chlorosulfonic acid solution, allowing it to stand for 12 hours or more, and introducing chlorosulfonic acid molecules into the carbon nanotube film until the carbon nanotube film becomes flexible.

3. Step (2) is as follows: a post-treatment method for significantly improving the performance of a carbon nanotube film according to claim 1, characterized in that it includes placing the carbon nanotube film, after being thoroughly immersed in chlorosulfonic acid, into moist air to allow the chlorosulfonic acid molecules inside the carbon nanotube film to react thoroughly with water molecules in the air to generate sulfuric acid molecules inside the carbon nanotube film, and introducing water molecules into the carbon nanotube film until no more white mist of hydrogen chloride is generated from the surface of the carbon nanotube film.

4. A post-treatment method for significantly improving the performance of a carbon nanotube film according to claim 1, characterized in that, in step (3), the expansion factor of the carbon nanotube film after expansion is 500 to 1000 times.

5. Step (4) is as follows: the expanded carbon nanotube film is stretched by 50% to 500%, preferably 200% to 400%, the carbon nanotube film is stretched, then left to stand for 2 hours or more, and then stretched and left to stand again, and the above step is repeated three times until the stretching of the carbon nanotube film is finally achieved, characterized in that the post-treatment method for significantly improving the performance of the carbon nanotube film according to claim 1.

6. Step (5) is as follows: a post-treatment method for significantly improving the performance of a carbon nanotube film according to claim 1, characterized in that the stretched carbon nanotube film is immersed again in chlorosulfonic acid and left for 12 hours or more.

7. Step (6) is as follows: Place the carbon nanotube film, which has been immersed again in chlorosulfonic acid, into the vacuum annealing apparatus, and evacuate the reaction chamber of the vacuum annealing apparatus to a vacuum level of < 10. -２ A post-treatment method for significantly improving the performance of a carbon nanotube film according to claim 1, characterized in that when Pa is reached, the vacuum annealing apparatus is heated, the heating rate is less than 10°C / min, the heating temperature is less than 300°C, preferably 100°C to 300°C, the time is 3 hours or more, and the chlorosulfonic acid inside the carbon nanotube film is completely removed.

8. A post-treatment method for significantly improving the performance of a carbon nanotube film according to any one of claims 1 to 7, characterized in that the thickness of the high-strength, high-conductivity carbon nanotube film is at the level of several hundred nanometers or more.

9. Application of the post-treatment method for significantly improving the performance of a carbon nanotube film according to any one of claims 1 to 8 in the preparation of a high-performance carbon nanotube film composite material.

10. A high-performance carbon nanotube film composite material characterized by being formed by compounding a high-strength, high-conductivity carbon nanotube film prepared by a post-treatment method for significantly improving the performance of a carbon nanotube film according to any one of claims 1 to 8 with a high-performance material, wherein the high-performance material includes at least one of graphene and Mxene material.

Images