A post-processing method for significantly improving the performance of carbon nanotube films and its application

Abstract

The present invention discloses a post-treatment method and application for greatly improving the performance of carbon nanotube films. The post-treatment method comprises: soaking the original carbon nanotube film in chlorosulfonic acid and letting it stand, then placing it in air, so that the chlorosulfonic acid molecules inside the carbon nanotube film can react with water molecules in the air, and then generating sulfuric acid molecules inside the carbon nanotube film, prompting water molecules to enter the carbon nanotube film; then placing it in chlorosulfonic acid again, so that it reacts chemically with water molecules to generate hydrogen chloride gas, causing the carbon nanotube film to expand; after stretching treatment, soaking it in chlorosulfonic acid solution again, and finally performing high-temperature vacuum annealing heat treatment. The tensile strength of the carbon nanotube film prepared by the present invention is in the GPa order, and the electrical conductivity is in the order of 10 6 S / m level and higher surface flatness, which is conducive to its composite with other materials, building a composite interface with stronger bonding force, and thus conducive to a significant improvement in the final mechanical and electrical properties of the composite material.

Description

Technical Field

[0001] The invention relates to a post-processing method for greatly improving the mechanical and electrical properties of a carbon nanotube film, and belongs to the technical field of carbon nanotube post-processing. Background Art

[0002] Carbon nanotubes have an extremely long electron mean free path. Research data shows that the longest electron mean free path can exceed 30μm (copper: 40nm). The large electron mean free path gives carbon nanotubes excellent electrical conductivity (theoretical value can reach 10 8 S / m), an order of magnitude improvement compared to copper. Furthermore, carbon nanotubes also possess excellent properties such as low density, chemical stability, excellent thermal conductivity, and high tensile strength, making them an important candidate for high-conductivity materials.

[0003] However, during the assembly process of carbon nanotube macrostructures, various types of defects are inevitably introduced, such as a large number of pores within the microstructure of the macrostructure, a small contact area between carbon nanotubes, and poor carbon nanotube orientation distribution; ultimately, the electrical properties of the carbon nanotube macrostructures are significantly different from the theoretical values. Data show that the electrical conductivity of carbon nanotube films produced by the floating catalytic method is generally around 8×10 4 S / m, and the tensile mechanical strength is only about 100MPa, which is far from the force and electrical performance level of practical applications.

[0004] In order to solve the problem of low mechanical and electrical properties of carbon nanotube films, the existing methods are to stretch, roll, hot press and high-temperature graphitize the carbon nanotube films prepared by the floating catalytic method in air to improve the mechanical and electrical properties of carbon nanotube films. However, the improvement effect of such methods is limited. In terms of electrical properties, the order of magnitude is 10 5 S / m level; in terms of mechanical properties, only local areas of the film can reach the GPa level after treatment. Existing stretching reinforcement methods for carbon nanotube films have a low success rate due to the heterogeneity of the microstructure of the carbon nanotube film itself. Furthermore, the electrical and mechanical properties of the carbon nanotube surface are unevenly distributed. Although high tensile strength can be achieved locally, the overall mechanical properties of the carbon nanotube film are poor. In terms of rolling and hot pressing reinforcement, the heterogeneity of the carbon nanotube film also makes it easy for the carbon nanotube film to break during the extrusion process, seriously affecting the success rate of the experiment. Furthermore, the surface of the extruded carbon nanotube film often has many pits and fractures, resulting in poor film flatness, which seriously affects the interface structure and performance when the carbon nanotube film is subsequently composited with other materials.

[0005] Recently, researchers have developed a chlorosulfonic acid treatment process for carbon nanotube films. Through this post-treatment process, the microstructure of the carbon nanotube film is densified, thereby significantly improving its mechanical and electrical properties. Although the electrical properties of the prepared carbon nanotube film are good, it can be improved to 1×10 6 S / m, but its tensile mechanical strength is still very low, at about 250MPa, far below the GPa level. The mechanical and electrical comprehensive properties of the prepared carbon nanotube film are poor and cannot meet the requirements of actual working conditions for the mechanical properties of the carbon nanotube film. Summary of the Invention

[0006] The main purpose of the present invention is to provide a post-processing method for significantly improving the mechanical and electrical properties of carbon nanotube films, so as to overcome the deficiencies in the prior art.

[0007] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0008] An embodiment of the present invention provides a post-processing method for significantly improving the mechanical and electrical properties of a carbon nanotube film, comprising:

[0009] (1) fully soaking the original carbon nanotube film in chlorosulfonic acid and allowing it to stand to allow the chlorosulfonic acid molecules to enter the interior of the carbon nanotube film;

[0010] (2) placing the carbon nanotube film obtained in step (1) and fully soaked with chlorosulfonic acid in air, so that the chlorosulfonic acid molecules inside the carbon nanotube film can fully react with water molecules in the air, and then generate sulfuric acid molecules inside the carbon nanotube film, and allow the water molecules to enter the interior of the carbon nanotube film;

[0011] (3) placing the carbon nanotube film obtained in step (2) in chlorosulfonic acid again, causing the chlorosulfonic acid to react with water molecules to produce hydrogen chloride gas, causing the carbon nanotube film to expand by a multiple of 500 or more;

[0012] (4) stretching the expanded carbon nanotube film obtained in step (3) at a stretching amplitude of 50% to 500%;

[0013] (5) repeating step (1) multiple times on the carbon nanotube film after the stretching treatment;

[0014] (6) subjecting the carbon nanotube film obtained in step (5) to a high-temperature vacuum annealing heat treatment to obtain a high-strength, high-conductivity carbon nanotube film, wherein the temperature of the high-temperature vacuum annealing heat treatment is below 300° C. and the vacuum degree is less than 10 -2 Pa;

[0015] The tensile strength of the high-strength and high-conductivity carbon nanotube film is in the GPa range, and the electrical conductivity is in the range of 106 S / m level.

[0016] The embodiment of the present invention also provides a high-strength and high-conductivity carbon nanotube film produced by the above method.

[0017] The embodiments of the present invention further provide the application of the aforementioned post-treatment method for significantly improving the mechanical and electrical properties of the carbon nanotube film in the preparation of a high-performance carbon nanotube film composite material.

[0018] Correspondingly, an embodiment of the present invention also provides a high-performance carbon nanotube film composite material, which is formed by combining a high-strength, high-conductivity carbon nanotube film obtained by the aforementioned post-treatment method for significantly improving the performance of the carbon nanotube film with a high-performance material, wherein the high-performance material includes at least any one of graphene, Mxene, and other materials.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1) The post-treatment method provided by the present invention can achieve the highest mechanical properties of the floating carbon nanotube film currently produced on a large scale, reaching 2 GPa (a mechanical property currently at the leading level in the world). This eliminates the reliance of high-performance films on array methods and stretch-grown floating carbon nanotube films, thereby significantly reducing production costs and improving the feasibility of industrial-scale production.

[0021] 2) The high-strength, high-conductivity carbon nanotube film prepared by the present invention has a higher surface flatness, which is conducive to the composite of the carbon nanotube film with other materials, constructing a composite interface with stronger bonding force, and thus facilitating a substantial improvement in the final mechanical and electrical properties of the composite material (the carbon nanotube film pursues a higher surface flatness, and after the fibers are densified, the surface has a serrated structure); moreover, the thickness of the prepared high-strength, high-conductivity carbon nanotube film is close to the hundred-nanometer level, thereby reducing the number of defects caused by the large size of the film, and is more conducive to the performance of the inherent excellent mechanical and electrical properties of the carbon nanotubes. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 is a schematic diagram of a process for densifying and stretching a carbon nanotube film in a typical embodiment of the present invention;

[0024] Figure 2aThis is a schematic diagram of the microstructure of the original carbon nanotube film;

[0025] Figure 2b is a microstructure diagram of a densified + 0% stretched carbon nanotube film in a typical embodiment of the present invention;

[0026] Figure 2c is a microstructure diagram of a densified + 50% drawn carbon nanotube film in a typical embodiment of the present invention;

[0027] Figure 2d is a microstructure diagram of a densified + 200% drawn carbon nanotube film in a typical embodiment of the present invention;

[0028] Figure 3a Schematic diagram of the effect of dense stretching on the tensile mechanical properties of a carbon nanotube film in a typical embodiment of the present invention;

[0029] Figure 3b Schematic diagram of the effect of dense stretching on the electrical properties of a carbon nanotube film in a typical embodiment of the present invention;

[0030] Figure 4a This is the micro-fracture morphology of the original carbon nanotube film;

[0031] Figure 4b is a micro-fracture morphology of a densified + 0% stretched carbon nanotube film in a typical embodiment of the present invention;

[0032] Figure 4c is a micro-fracture morphology of a densified + 50% drawn carbon nanotube film in a typical embodiment of the present invention;

[0033] Figure 4d is a micro-fracture morphology of a densified + 200% drawn carbon nanotube film in a typical embodiment of the present invention;

[0034] Figure 5 Schematic diagram of the thickness of the carbon nanotube film after stretching and densification in a typical embodiment of the present invention. DETAILED DESCRIPTION

[0035] To address the above-mentioned issues, the inventors of this case, after long-term research and extensive practice, have come up with the technical solution of the present invention. This solution is primarily based on the protonation of carbon nanotubes by chlorosulfonic acid, the expansion of carbon nanotube films by chlorosulfonic acid, and the oriented force of electric dipoles. This method has resulted in a post-processing method that significantly improves both the mechanical and electrical properties of carbon nanotube films. This method includes fully soaking the carbon nanotube film in chlorosulfonic acid, significantly puffing up the carbon nanotube film, significantly stretching the carbon nanotube film, and annealing the carbon nanotube film. Through the densification and significant stretching of the carbon nanotube film, tensile strengths in the GPa range and electrical conductivity of 10 6Preparation of high-performance carbon nanotube films with S / m of about 1.

[0036] The technical solution, its implementation process and principles are further explained below.

[0037] One aspect of an embodiment of the present invention provides a post-processing method for significantly improving the performance of a carbon nanotube film, comprising:

[0038] (1) fully soaking the original carbon nanotube film in chlorosulfonic acid and allowing it to stand to allow the chlorosulfonic acid molecules to enter the interior of the carbon nanotube film;

[0039] (2) placing the carbon nanotube film obtained in step (1) and fully soaked with chlorosulfonic acid in air, so that the chlorosulfonic acid molecules inside the carbon nanotube film can fully react with water molecules in the air, and then generate sulfuric acid molecules inside the carbon nanotube film, and allow the water molecules to enter the interior of the carbon nanotube film;

[0040] (3) placing the carbon nanotube film obtained in step (2) in chlorosulfonic acid again, so that the chlorosulfonic acid reacts with water molecules to produce hydrogen chloride gas, causing the carbon nanotube film to expand;

[0041] (4) stretching the expanded carbon nanotube film obtained in step (3) at a stretching amplitude of 50% to 500%;

[0042] (5) repeating step (1) multiple times on the carbon nanotube film after the stretching treatment;

[0043] (6) subjecting the carbon nanotube film obtained in step (5) to a high-temperature vacuum annealing heat treatment to obtain a high-strength, high-conductivity carbon nanotube film, wherein the temperature of the high-temperature vacuum annealing heat treatment is below 300° C. and the vacuum degree is less than 10 -2 Pa.

[0044] The reaction mechanism of the present invention is as follows: based on the protonation of carbon nanotubes by chlorosulfonic acid, the expansion of the carbon nanotube film by chlorosulfonic acid, and the orienting force of the electric dipole, the carbon nanotube film is fully filled with chlorosulfonic acid molecules by the chlorosulfonic acid solution. Subsequently, the carbon nanotube film rapidly expands due to the large amount of hydrogen chloride gas generated during the reaction of the chlorosulfonic acid molecules with water. Based on the expansion effect of the carbon nanotube film by the above chemical reaction, the carbon nanotubes in the film are significantly oriented by relaxation stretching. The microstructure of the carbon nanotube film is significantly densified by high-temperature vacuum heat treatment and the orienting force of the electric dipole. Ultimately, by improving the degree of orientation and densification of the carbon nanotubes in the film, the mechanical and electrical properties of the floating catalytic carbon nanotube film are significantly improved.

[0045] In some embodiments, step (1) of the post-treatment method specifically includes: fully soaking the original carbon nanotube film in a chlorosulfonic acid solution and allowing it to stand for more than 12 hours to allow the chlorosulfonic acid molecules to enter the carbon nanotube film until the carbon nanotube film is in a soft state. The present invention relates to soaking the carbon nanotube film in chlorosulfonic acid. Experiments have shown that stretching the carbon nanotube film in any protonated acid will improve its densification, thereby improving its mechanical, electrical, and even thermal properties.

[0046] In some embodiments, step (2) of the post-treatment method specifically includes: placing the carbon nanotube film that has been fully soaked with chlorosulfonic acid in humid air, so that the chlorosulfonic acid molecules inside the carbon nanotube film can fully react with water molecules in the air, thereby generating sulfuric acid molecules inside the carbon nanotube film, and allowing water molecules to enter the carbon nanotube film, until no white hydrogen chloride mist is generated on the surface of the carbon nanotube film.

[0047] In some embodiments, in step (3), the expansion ratio of the expanded carbon nanotube film is greater than 500 times, preferably 500 to 1000 times, and the expansion range is from 5 μm to 5000 μm in thickness. The present invention cleverly 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 and water. This significantly improves the stretchability of the carbon nanotube film.

[0048] In some embodiments, step (4) of the post-processing method specifically includes: stretching the expanded carbon nanotube film by 50% to 500%, preferably 200% to 400%, and after the carbon nanotube film is stretched, keeping it still for more than 2 hours; then stretching and keeping it still again, and repeating the above steps three or more times until the carbon nanotube film is finally stretched. Any stretching amount within the range of 50% to 500% can be selected according to experimental requirements. Due to the large macroscopic size and macroscopic force, the stretching process requires manual (or machine) additional large stretching force.

[0049] In some embodiments, step (5) of the post-treatment method specifically includes: re-immersing the stretched carbon nanotube film in chlorosulfonic acid for more than 12 hours. The present invention relates to multiple expansions of the carbon nanotube film in chlorosulfonic acid, thereby gradually increasing the stretching degree of the carbon nanotube film.

[0050] In some embodiments, step (6) of the post-treatment method specifically includes: placing the carbon nanotube film soaked in chlorosulfonic acid again in a vacuum annealing device, and evacuating the reaction chamber of the vacuum annealing device until the vacuum is less than 10 -2Pa, the vacuum annealing equipment is heated at a heating rate of less than 10°C / min, a heating temperature not higher than 300°C (between 100°C and 300°C), and a time of not less than 3 hours, so that all the chlorosulfonic acid inside the carbon nanotube film is removed.

[0051] Taking into account the optimization of the experimental effect, the present invention selects the temperature and vacuum degree of annealing heat treatment during the implementation process; when the temperature is high (higher than 300 ° C) and the vacuum degree is low (> 10 -2 Pa), the densification degree of carbon nanotube film is low. When the temperature is low (not higher than 300℃) and the vacuum degree is high (less than 10 -2 Pa, especially <10 -4 Pa), the densification degree of the carbon nanotube film is higher, and the mechanical, electrical and other properties of the carbon nanotube film are also greatly improved.

[0052] Furthermore, during the high-temperature vacuum annealing heat treatment of the carbon nanotube film, the film surface needs to be flattened to maintain the film morphology.

[0053] Another aspect of the embodiments of the present invention further provides a high-strength, high-conductivity carbon nanotube film produced by the aforementioned preparation method.

[0054] Furthermore, the tensile strength of the high-strength and high-conductivity carbon nanotube film is in the GPa range, and the electrical conductivity is in the range of 10 6 S / m level.

[0055] Furthermore, the thickness of the high-strength and high-conductivity carbon nanotube film is above 100 nanometers.

[0056] In summary, the high-strength, high-conductivity carbon nanotube film prepared by the present invention has a higher surface flatness (rolling, hot pressing and graphitization treatment will cause the film surface to be rough and uneven), which is conducive to the composite of carbon nanotube film and other materials to construct a composite interface with stronger bonding force, and thus is conducive to a significant improvement in the final mechanical, electrical and other properties of the composite material.

[0057] The present invention involves multiple expansion and stretching of the carbon nanotube film in the preparation of high-performance carbon nanotube films. This process provides good process conditions for the densification of carbon nanotubes and the composite of high-performance materials such as graphene and MXene, which is conducive to the preparation of carbon nanotube film composite materials with higher electrical properties and more functions, greatly improving the application of carbon nanotubes in actual production and life.

[0058] Another aspect of the embodiments of the present invention further provides the aforementioned post-treatment method for significantly improving the performance of carbon nanotube films or the use of high-strength, high-conductivity carbon nanotube films in preparing high-performance carbon nanotube film composite materials.

[0059] The surface flatness of the carbon nanotube film of the present invention reaches the level of a single carbon nanotube, and physical deposition of a continuous metal film of about 10 nm can be performed on the surface of the carbon nanotube film.

[0060] Correspondingly, another aspect of an embodiment of the present invention further provides a high-performance carbon nanotube film composite material, which is formed by combining a high-strength, high-conductivity carbon nanotube film obtained by the aforementioned post-treatment method for significantly improving the performance of the carbon nanotube film with a high-performance material, wherein the high-performance material includes at least any one of graphene, Mxene, and other materials, but is not limited thereto.

[0061] The technical solution of the present invention is further described in detail below in conjunction with several preferred embodiments and the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The experimental methods in the following examples where specific conditions are not specified are generally based on conventional conditions or the conditions recommended by the manufacturer.

[0062] Example 1

[0063] See also Figure 1 As shown, the specific technical steps of a post-processing method for significantly improving the performance of carbon nanotube films in this embodiment are:

[0064] 1. Fully infiltration of carbon nanotube film in chlorosulfonic acid liquid

[0065] Take a carbon nanotube film of a certain length and width (such as 1cm to 50cm, or any length and width not less than 1cm), fix it on a fixture, keep the carbon nanotube film in a stretched state, then place the carbon nanotube film in a chlorosulfonic acid solution to ensure that the carbon nanotube film is fully immersed in the chlorosulfonic acid solution, and then let it stand for more than 12 hours until the carbon nanotube film is completely in a soft state.

[0066] During the experiment of this step, a clamp is required to fix the carbon nanotube film to maintain the film shape during the experiment to prevent the film from curling.

[0067] 2. Expansion technology and stretching treatment of carbon nanotube films

[0068] The carbon nanotube film that has been fully soaked with chlorosulfonic acid is placed in humid air to allow the chlorosulfonic acid molecules inside the carbon nanotube film to fully react with the moisture in the air, and then sulfuric acid molecules are generated inside the carbon nanotube film. The strong water absorption of the sulfuric acid molecules is continuously utilized to allow water molecules to slowly enter the interior of the carbon nanotube film until no white hydrogen chloride mist is generated on the surface of the carbon nanotubes.

[0069] Building on the previous step, the carbon nanotube film is placed in a chlorosulfonic acid solution. The chemical reaction between the chlorosulfonic acid and water molecules generates hydrogen chloride gas, causing the carbon nanotube film to expand significantly. The expanded carbon nanotube film is then stretched to a certain amount (any amount, from 50% to 500%, as long as the film remains taut, determined experimentally). Once stretched, the film is allowed to rest for at least two hours. The stretching and resting steps are repeated three more times until the carbon nanotube film is significantly stretched (reaching the final maximum stretch). The carbon nanotube film is then placed in the chlorosulfonic acid solution for at least 12 hours. This embodiment involves multiple cycles because stretching the film significantly at once can easily cause it to break.

[0070] 3. High temperature vacuum annealing of carbon nanotube films

[0071] The carbon nanotube film soaked in chlorosulfonic acid solution was placed in a vacuum annealing furnace, and the furnace space where the sample was located was vacuumed. -2 Pa, the tubular furnace is heated at a heating rate of less than 10°C / min, the heating temperature cannot be higher than 300°C (100°C~300°C), and the time is not less than 3h, ultimately achieving complete removal of chlorosulfonic acid inside the carbon nanotube film.

[0072] The inventors of this case also conducted the following characterization and testing on the final carbon nanotube film:

[0073] (1) Influence of carbon nanotube film microstructure

[0074] Figure 2a-2d The figure shows the influence of stretching and densification on the microstructure of carbon nanotubes, among which, Figure 2a Schematic diagram of the microstructure of the original carbon nanotube film. Figure 2b The microstructure of the densified + 0% stretched carbon nanotube film. Figure 2c The microstructure of the densified + 50% drawn carbon nanotube film. Figure 2dThe microstructure of a densified + 200% drawn carbon nanotube film shows that the original carbon nanotube film has a relatively fluffy microstructure, with a disordered distribution of carbon nanotubes, numerous pores between the carbon nanotubes, and a majority of the carbon nanotubes suspended in the air. The carbon nanotube surface has poor surface smoothness. When the carbon nanotube film is subjected to only densification (after soaking the carbon nanotube film in chlorosulfonic acid and then directly annealing it in a high-temperature vacuum) without any drawing treatment, i.e., a 0% draw, the pores on the carbon nanotube surface are largely removed, eliminating the apparent fluffiness of the microstructure and achieving significant densification of the carbon nanotube film's microstructure. However, a certain number of pits still remain on the surface of the carbon nanotube film, and the distribution of these carbon nanotubes remains disordered.

[0075] After densification and 50% stretching of the carbon nanotube film, no micro-pits were observed on the film's surface, and the carbon nanotube distribution on the film's surface showed a high degree of orientation, significantly improving the film's surface smoothness. However, upon closer inspection, the cleaned carbon nanotube structure could still be observed on the film's surface, indicating that while the 50% stretching treatment improved the film's surface smoothness, it still had a certain degree of surface unevenness. After densification and 200% stretching of the carbon nanotube film, not only were there no nano-pits on the film's surface, but the tubular structure of most carbon nanotubes was almost invisible. These experimental results indicate that the densification of the carbon nanotube film's microstructure has been further significantly improved.

[0076] (2) Influence of mechanical and electrical properties of carbon nanotube films

[0077] Figure 3a-Figure 3b The figure shows the effect of densification + orientation stretching post-treatment on the mechanical and electrical properties of carbon nanotube films. Figure 3a As shown in the results, the mechanical strength of the original carbon nanotubes is about 100MPa. After densification treatment alone, the mechanical strength of the carbon nanotube film is increased to about 300MPa. After the film is densified and stretched by 50%, the strength of the film is increased to about 600MPa. When the stretching degree is further increased to 200%, the tensile strength of the carbon nanotube film reaches more than GPa. Based on the floating catalytic carbon nanotube film, the preparation of high-strength films of the GPa level is achieved. Figure 3b As shown in the results, the conductivity of the original carbon nanotube film is 0.8×10 5 S / m. After densification, the conductivity of carbon nanotube film reaches 1×10 6 S / m. Although the conductivity decreased slightly after drawing, it showed an upward trend when the drawing amount increased, and finally reached 0.8×10 6S / m, still maintaining a high level of conductivity. These results demonstrate that, based on the largest floating carbon nanotube film currently produced, densification followed by a 200% stretching post-processing has enabled the preparation of high-strength, highly conductive carbon nanotube films, with world-leading performance. This preparation technology has enormous social significance for the practical engineering applications of these films.

[0078] (3) Influence of carbon nanotube film fracture morphology

[0079] Figure 4a-4d The results show that after the original carbon nanotube film is broken, the length of the fracture wire is 20 to 30 μm, and the fracture morphology is fluffy, indicating that the original carbon nanotube film is mainly broken by the slippage between the carbon nanotubes. Figure 4a When the carbon nanotube film is only densified, the length of the wire at the fracture is about 10 μm after the film breaks, and the wire length is significantly reduced, as shown in Figure 2. Figure 4b As shown in the figure, it shows that the friction between the carbon nanotubes increases significantly, and some carbon nanotubes begin to break during the film fracture process, resulting in a weakening of the wire-drawing morphology of the fracture. When the carbon nanotube film is subjected to densification and stretching treatment at the same time, the wire-drawing phenomenon is basically not observed at the fracture of the film, and the fracture flatness is high, indicating that the friction between the carbon nanotubes is very strong at this time, and the fracture of the film is mainly caused by the fracture of the carbon nanotubes, as shown in the figure. Figure 4c and Figure 4d As shown, this further promotes the full manifestation of the intrinsic high-strength characteristics of carbon nanotubes in the macroscopic film and achieves a significant improvement in the final mechanical properties of the macroscopic film.

[0080] The thickness of the high-strength and high-conductivity carbon nanotube film prepared in this embodiment is close to the hundred-nanometer level. Figure 5 As shown, the thickness is 1500nm, which reduces the number of defects caused by the large size of the film and is more conducive to the excellent mechanical and electrical properties of carbon nanotubes.

[0081] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments using other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0082] Although the present invention has been described with reference to illustrative embodiments, it will be understood by those skilled in the art that various other changes, omissions, and / or additions may be made and that substantial equivalents may be substituted for elements of the described embodiments without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present invention without departing from the scope of the invention. Therefore, it is not intended that the present invention be limited to the specific embodiments disclosed for carrying out the invention, but rather that the invention will encompass all embodiments falling within the scope of the appended claims.

Claims

1. A post-treatment method for significantly improving the performance of carbon nanotube films, characterized in that: include: (1) Fix the original carbon nanotube film on a fixture to keep it in a stretched state, then fully immerse it in chlorosulfonic acid and let it stand to allow the chlorosulfonic acid molecules to enter the interior of the carbon nanotube film; (2) placing the carbon nanotube film obtained in step (1) and fully soaked with chlorosulfonic acid in air, so that the chlorosulfonic acid molecules inside the carbon nanotube film can fully react with the water molecules in the air, and then generate sulfuric acid molecules inside the carbon nanotube film, and allow the water molecules to enter the interior of the carbon nanotube film; (3) placing the carbon nanotube film obtained in step (2) in chlorosulfonic acid again, causing the chlorosulfonic acid to react with water molecules to produce hydrogen chloride gas, causing the carbon nanotube film to expand by a multiple of 500 or more; (4) stretching the expanded carbon nanotube film obtained in step (3) at a stretching amplitude of 50% to 500%; after the carbon nanotube film is stretched, it is kept still for more than 2 hours; then it is stretched and left to stand again, and the above steps are repeated three or more times until the stretching of the carbon nanotube film is finally achieved; (5) Repeating step (1) multiple times on the carbon nanotube film after the stretching treatment; (6) The carbon nanotube film obtained in step (5) is subjected to high-temperature vacuum annealing heat treatment to obtain a high-strength and high-conductivity carbon nanotube film, wherein the temperature of the high-temperature vacuum annealing heat treatment is below 300°C and the vacuum degree is less than 10 -2 Pa; The high-strength and high-conductivity carbon nanotube film has a high surface smoothness, reaching the scale of a single carbon nanotube, a tensile strength of the GPa level, and an electrical conductivity of 10 6 S / m level.

2. The post-treatment method for significantly improving the performance of carbon nanotube films according to claim 1, characterized in that: Step (1) comprises: fully soaking the original carbon nanotube film in a chlorosulfonic acid solution and leaving it to stand for more than 12 hours, so that the chlorosulfonic acid molecules enter the interior of the carbon nanotube film until the carbon nanotube film is in a soft state.

3. The post-treatment method for significantly improving the performance of carbon nanotube films according to claim 1, characterized in that: Step (2) includes: placing the carbon nanotube film that has been fully soaked with chlorosulfonic acid in humid air, so that the chlorosulfonic acid molecules inside the carbon nanotube film can fully react with water molecules in the air, thereby generating sulfuric acid molecules inside the carbon nanotube film and allowing water molecules to enter the carbon nanotube film, until no white hydrogen chloride mist is generated on the surface of the carbon nanotube film.

4. The post-treatment method for significantly improving the performance of carbon nanotube films according to claim 1, characterized in that: In step (3), the expansion ratio of the expanded carbon nanotube film is 500 to 1000 times.

5. The post-treatment method for significantly improving the performance of carbon nanotube films according to claim 1, characterized in that: Step (4) includes: stretching the expanded carbon nanotube film by 200% to 400%.

6. The post-treatment method for significantly improving the performance of carbon nanotube films according to claim 1, wherein: Step (5) includes: soaking the stretched carbon nanotube film in chlorosulfonic acid again and leaving it for more than 12 hours.

7. The post-treatment method for significantly improving the performance of carbon nanotube films according to claim 1, wherein: Step (6) includes: placing the carbon nanotube film soaked in chlorosulfonic acid again in a vacuum annealing device, and evacuating the reaction chamber of the vacuum annealing device until the vacuum is less than 10 -2 Pa, the vacuum annealing equipment is heated at a heating rate of less than 10 °C / min, the heating temperature is 100 °C~300 °C, and the time is not less than 3 h, so that the chlorosulfonic acid inside the carbon nanotube film is completely removed.

8. The 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 and high-conductivity carbon nanotube film is above 100 nanometers.

9. Use 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 preparing a high-performance carbon nanotube film composite material.

10. A high-performance carbon nanotube film composite material, characterized in that: It is a composite of a high-strength, high-conductivity carbon nanotube film obtained by the post-treatment method for significantly improving the performance of the carbon nanotube film according to any one of claims 1-8 and a high-performance material, wherein the high-performance material is selected from at least one of graphene and Mxene materials.

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