A method for preparing single-walled carbon nanotubes

Abstract

The application relates to the technical field of rice processing, and discloses a single-walled carbon nanotube preparation method, which comprises the following steps: providing a stirring device in a reactor to provide a uniform dispersion environment, applying an electric field to realize directional control, changing the temperature periodically according to a preset program to experience a thermal shock-stabilization-gradual cooling cycle process, and generating a hydrodynamic pulse to form a transient stress induction effect by changing the stirring mode at a specific time point. The application realizes accurate regulation of the spatial configuration, crystallinity and orientation of the single-walled carbon nanotube through the synergistic effect of multiple physical fields, and prepares a single-walled carbon nanotube product with a special curvature structure, high crystallinity and highly oriented arrangement, so that the application requirements of high-end electronic devices, super capacitors and the like can be met.

Description

Technical Field

[0001] This invention relates to the field of carbon nanotube preparation technology, and more specifically, to a method for preparing single-walled carbon nanotubes. Background Technology

[0002] Single-walled carbon nanotubes (SUVs) have broad application prospects in many high-tech fields due to their excellent mechanical, electrical, and thermal properties. However, existing methods for preparing SUVs suffer from the following major technical problems: First, the spatial configuration of the prepared SUVs is difficult to control precisely, especially for obtaining SUVs with specific curvature structures (such as Y-shaped, Z-shaped, or helical structures); second, the products have low crystallinity and numerous defects, affecting their mechanical and electrical properties; third, it is difficult to achieve precise control over the growth orientation of SUVs, resulting in disordered product arrangement and affecting their reinforcing effect in composite materials and other applications. Although existing technologies employ various preparation methods, such as chemical vapor deposition, arc discharge, and laser ablation, these methods often focus only on the effect of a single physical field and lack a systematic approach to the synergistic control of multiple physical fields, thus making it difficult to simultaneously solve the aforementioned technical problems. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a method for preparing single-walled carbon nanotubes.

[0004] A method for preparing single-walled carbon nanotubes includes the following steps:

[0005] Establish a mixing system, including a mixing device that can switch between mechanical mixing and pulse mixing modes;

[0006] Establish an electric field system, including an electrode device and a programmable DC power supply to form a uniform electric field in the reactor;

[0007] Establish a temperature cycle change system to realize the temperature cycle change of thermal shock-stabilization-slow cooling;

[0008] A transient stress-inducing system was established, which generates fluid dynamic pulses by changing the stirring mode, thereby creating transient mechanical stress on the growing carbon nanotubes;

[0009] By using a computer control unit to coordinate the synergistic effect of the above physical fields according to a preset timing sequence, precise control of the structure and properties of single-walled carbon nanotubes can be achieved.

[0010] Preparation of single-walled carbon nanotubes.

[0011] Preferably, the establishment of the stirring system includes:

[0012] Construct a variable-mode mixing device, including a mixing paddle, a variable-speed motor, and a control unit;

[0013] Determine the stirring parameters: in mechanical stirring mode, the speed is 200-600 rpm; in pulse stirring mode, the speed is increased from the normal speed to 800-1200 rpm within 0.1-0.5 seconds.

[0014] Arrange the stirring mode sequence, including the initial uniform dispersion stage, the middle stable growth stage, and the pulse impact stage at a predetermined time point.

[0015] Preferred: The establishment of the electric field system includes:

[0016] Parallel plate electrodes are installed in the reactor to form a uniform electric field, and the electrodes are connected to a programmable DC power supply.

[0017] Determine the electric field parameters: in the liquid phase reaction system, the electric field strength is 50-500 V / cm; in the gas phase reaction system, the electric field strength is 500-2000 V / cm.

[0018] A pulsed electric field is applied to adjust the electric field strength and direction at different stages of temperature change.

[0019] Preferred: The establishment of a temperature periodic change system includes:

[0020] Use a temperature control system that includes a heating element, a temperature sensor, and a temperature controller;

[0021] The temperature cycle is defined as having three phases: a thermal shock phase, in which the temperature is raised from room temperature to 600-900℃ within 30-60 seconds; a stabilization phase, in which the temperature is maintained at 600-900℃ for 10-30 minutes; and a slow cooling phase, in which the temperature is cooled to 400-600℃ at a rate of 1-5℃ / minute.

[0022] By configuring heating elements and using control algorithms, the temperature distribution within the reaction area is ensured to be uniform, with a temperature gradient of <10℃ / cm.

[0023] Preferred: The establishment of the transient stress-inducing system includes:

[0024] By rapidly changing the stirring mode, fluid dynamic pulses are generated, forming a transient shear force field;

[0025] The transient stress induction method is determined based on the type of carbon nanotube curvature structure to be prepared;

[0026] This allows for precise coordination between the timing of transient stress induction and the temperature cycle and electric field application.

[0027] Preferred methods for inducing transient stress include:

[0028] For the Y-type structure: In the middle of the stable phase of the temperature cycle, apply a single strong pulse stirring impact, with the impact direction at an angle of 60-90 degrees to the electric field direction;

[0029] For the Z-shaped structure: During the middle and late stages of the stable phase of the temperature cycle, two pulse stirring impacts of similar intensity are applied respectively, with the two impacts being opposite or nearly opposite in direction;

[0030] For spiral structures: During the stable phase of the temperature cycle, apply multiple (3-5) medium-intensity pulse stirring impacts at equal time intervals, with each impact direction at a 45-60 degree angle to the previous one.

[0031] Preferred method: The process for preparing single-walled carbon nanotubes includes the following stages:

[0032] Dispersion and activation stage: Start conventional stirring to uniformly disperse the catalyst at a speed of 200-300 rpm, and at the same time enter the thermal shock stage and apply a strong electric field;

[0033] Directional growth stage: Entering the stable stage of the temperature cycle, the electric field strength is adjusted to a medium level, and a carbon source is introduced to start the growth of carbon nanotubes;

[0034] Curvature control phase: At a predetermined point in the temperature cycle stabilization phase, transient stress-induced operation is performed, while the electric field parameters are adjusted simultaneously;

[0035] Structural refinement stage: Entering the slow cooling stage of the temperature cycle, the electric field strength is gradually reduced while maintaining low-speed conventional stirring;

[0036] Post-processing stage: Collect the product and perform washing, drying and purification.

[0037] Preferably, the catalyst is selected from metal salts containing iron group elements, and the carbon source is selected from carbon-containing gaseous or liquid carbon sources.

[0038] Preferred: When the carbon source is a liquid carbon source, the carbon source / catalyst mass ratio is 50-200:1; when the carbon source is a carbon-containing gas, the carbon source flow rate is 50-200 ml / min, and the catalyst loading is 0.5-2 wt%.

[0039] Preferred: Single-walled carbon nanotubes have the following characteristics:

[0040] The branching angle of Y-shaped carbon nanotubes is controlled within the range of 30-45 degrees, with a deviation of <5 degrees;

[0041] The turning angle of Z-shaped carbon nanotubes is controlled within the range of 100-140 degrees, with a deviation of <10 degrees;

[0042] The pitch of the helical carbon nanotubes is controlled within the range of 20-100 nm, and the uniformity deviation of the helical structure per unit length is <15%.

[0043] The intensity ratio (IG / ID) of the G peak to the D peak of carbon nanotubes is 8-12, and the orientation degree reaches 85-95%.

[0044] The beneficial effects of this invention are as follows: By leveraging the synergistic effect of electric field orientation and transient stress induction, this invention achieves precise control over the curvature structure of carbon nanotubes. Depending on the transient stress induction scheme, Y-type, Z-type, or helical single-walled carbon nanotubes can be selectively prepared. Specifically, the branching angle of Y-type carbon nanotubes can be controlled within the range of 30-45 degrees, with a deviation of <5 degrees; the turning angle of Z-type carbon nanotubes can be controlled within the range of 100-140 degrees, with a deviation of <10 degrees; and the pitch of helical carbon nanotubes can be controlled within the range of 20-100 nm, with a uniformity deviation of <15% per unit length of the helical structure.

[0045] The crystallinity of carbon nanotubes was significantly improved through the synergistic effect of temperature cycle changes and electric field, especially the structural repair process during the slow cooling stage. Raman spectroscopy characterization showed that the intensity ratio of the G peak to the D peak (IG / ID) increased to 8-12, which is significantly higher than that of carbon nanotubes prepared by conventional methods (IG / ID is usually 3-5), indicating a substantial reduction in structural defects in the carbon nanotubes.

[0046] By combining the directional effect of the electric field with the stirring system, a highly oriented arrangement of carbon nanotubes was achieved during the growth process. The orientation degree of the product (measured by polarizing microscope or X-ray diffraction) reached 85-95%, which is far higher than that of randomly arranged carbon nanotubes prepared by traditional methods.

[0047] Due to precise structural control and high crystallinity, the single-walled carbon nanotubes prepared by this method exhibit excellent comprehensive properties. Electrical conductivity is increased by 30-50%, thermal conductivity by 40-60%, and mechanical strength by 20-40%, demonstrating a significant improvement in overall performance compared to similar products prepared by traditional methods.

[0048] This method, by adjusting various physical field parameters and temporal relationships, can customize the preparation of single-walled carbon nanotubes with different structural characteristics to meet different application needs, and has broad adaptability and scalability. Attached Figure Description

[0049] Figure 1 The preparation effects of various curvature structures of single-walled carbon nanotubes in this invention are shown.

[0050] Figure 2 This is a comparison of the crystallinity of single-walled carbon nanotubes prepared by different experimental groups in this invention;

[0051] Figure 3 This is a comparison of the orientation degree of single-walled carbon nanotubes prepared by different experimental groups in this invention;

[0052] Figure 4 These are performance comparison data of two sets of samples in this invention;

[0053] Figure 5 These are the performance test results of the nanocomposite materials in this invention;

[0054] Figure 6 This relates to the adaptability of different catalysts in this invention to the multi-physics field synergistic preparation method;

[0055] Figure 7 This relates to the adaptability of different carbon sources to the multi-physics field synergistic preparation method in this invention;

[0056] Figure 8 This relates to the impact of key process parameters in this invention on product characteristics;

[0057] Figure 9 This is the customized preparation result for different applications in this invention. Detailed Implementation

[0058] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, some features described in the examples may be combined in other examples.

[0059] At least one embodiment of the present invention discloses a method for preparing single-walled carbon nanotubes, comprising the following steps:

[0060] Select catalysts and carbon source materials.

[0061] In this embodiment, the catalyst is selected from metal salts containing iron group elements (iron, cobalt, nickel, or combinations thereof), and the carbon source is selected from carbon-containing gaseous materials (methane, acetylene, or carbon monoxide) or liquid carbon sources (ethanol, benzene, or toluene). The catalyst precursor is dissolved in a solvent to prepare a catalyst solution or suspension.

[0062] 1. Establishment of the mixing system

[0063] Construction of the stirring device: A variable-mode stirring device is constructed, capable of switching between conventional mechanical stirring and pulse stirring modes based on a control signal. The stirring device includes a stirring paddle, a variable-speed motor, and a control unit. The variable-speed motor achieves rapid speed changes within a short time (<0.5 seconds), and the control unit controls the switching of stirring modes according to a program.

[0064] Stirring parameters are determined based on the viscosity, density, and catalyst properties of the reaction system. In conventional stirring mode, the stirring speed is fixed at 200, 400, or 600 rpm to ensure uniform dispersion of the reactants. In pulse stirring mode, the speed is increased from the conventional speed to 800, 1000, or 1200 rpm within 0.1, 0.3, or 0.5 seconds, then returned to the conventional speed, creating a pulse stirring impact.

[0065] In this embodiment, the stirring speed is kept constant at 400 rpm under normal stirring mode to ensure uniform dispersion of the reactants; under pulse stirring mode, the stirring speed is increased from the normal speed to 1000 rpm within 0.3 seconds.

[0066] The stirring mode timing arrangement is as follows: The stirring process is divided into multiple stages, including the initial uniform dispersion stage, the intermediate stable growth stage, and the pulse impact stage at a predetermined time point. A stirring mode control program is developed to coordinate with the timing of temperature changes and electric field application, achieving multi-physics field timing synergy.

[0067] 2. Establishment of the electric field system

[0068] Electric field generation device: Electrodes are installed in the reactor. The electrode materials are conductive materials with high temperature resistance and good chemical stability, such as graphite, stainless steel, or platinum. The electrodes are arranged in parallel plates to form a uniform electric field. The electrodes are connected to a programmable DC power supply to achieve programmed control of the electric field strength and application time.

[0069] Electric field parameters are determined by analyzing the dielectric properties of the reaction medium and the response characteristics of the catalyst. In a liquid-phase reaction system, the electric field strength is 50, 300, or 500 V / cm; in a gas-phase reaction system, the electric field strength is 500, 1200, or 2000 V / cm.

[0070] In this embodiment, the electric field strength is 300V / cm; in the gas phase reaction system, the electric field strength is 1200V / cm.

[0071] Electric field application method: A pulsed electric field application method is adopted, and the electric field strength and direction are adjusted at different stages of temperature change. A strong electric field (close to the upper limit of the set range) is applied during the thermal shock stage to promote the directional alignment of catalytic active sites; a medium-intensity electric field is maintained during the stable growth stage to guide the carbon nanotubes to grow along the direction of the electric field; the electric field strength is gradually reduced during the slow cooling stage to reduce interference with carbon atom rearrangement and facilitate the repair of structural defects.

[0072] 3. Establishment of a temperature cycle variation system

[0073] Temperature control device: A temperature control system is used, including a heating element, a temperature sensor, and a temperature controller. The heating element achieves rapid heating and temperature maintenance, while the temperature controller regulates the temperature change process according to a program.

[0074] Temperature cycle determination: Establish a temperature cycle model of thermal shock-stabilization-slow cooling, with a complete cycle consisting of three phases:

[0075] Thermal shock phase: The temperature is raised from room temperature to 600, 750 or 900°C within 30, 45 or 60 seconds, with a heating rate ≥10°C / second.

[0076] Stabilization phase: Maintain a constant temperature for 10, 20, or 30 minutes at a high temperature of 600, 750, or 900°C.

[0077] Slow cooling phase: Cool to 400, 500, or 600°C at a cooling rate of 1 or 3°C / min, then allow to cool naturally to room temperature.

[0078] In this embodiment, the following thermal shock stage is adopted: the temperature is raised from room temperature to 750°C within 45 seconds, and the heating rate is ≥10°C / second.

[0079] Stabilization phase: Maintain a constant temperature at 750℃ for 20 minutes.

[0080] Slow cooling phase: Cool to 500°C at a cooling rate of 3°C / minute, then allow to cool naturally to room temperature.

[0081] Temperature uniformity: Through the configuration and control algorithm of heating elements, the temperature distribution within the reaction area is made uniform, with a temperature gradient of <10℃ / cm. Combined with a stirring system, fluid circulation is used to enhance heat transfer and improve the uniformity of the temperature field.

[0082] 4. Establishment of the transient stress induction system

[0083] The principle of transient stress-induced effect: During the critical stage of single-walled carbon nanotube growth, a rapid change in stirring mode generates a hydrodynamic pulse, forming a transient shear force field that applies directional mechanical stress to the growing carbon nanotubes. This transient stress affects the arrangement of carbon atoms, inducing the formation of a curved structure in the carbon nanotubes.

[0084] Transient stress induction method: A transient stress induction method is formulated based on the type of carbon nanotube curvature structure to be prepared (Y-type, Z-type, or helical type).

[0085] For Y-type structures: In the middle of the stable phase of the temperature cycle (after the initial stage of growth is completed), apply a single strong pulse stirring impact, with the impact direction at an angle of 60, 75, or 90 degrees to the electric field direction.

[0086] In this embodiment, the impact direction is at a 75-degree angle to the electric field direction.

[0087] For the Z-shaped structure: During the middle and late stages of the temperature cycle's stabilization phase, two pulse stirring impacts of similar intensity are applied, with the two impacts occurring in opposite or nearly opposite directions.

[0088] For the spiral structure: during the stable phase of the temperature cycle, apply 3, 4, or 5 medium-intensity pulse stirring impacts at equal time intervals, with each impact direction at an angle of 45, 52, or 60 degrees to the previous one; in this embodiment, apply 4 medium-intensity pulse stirring impacts at equal time intervals, with each impact direction at an angle of 52 degrees to the previous one.

[0089] Synergy between transient stress induction and other physical fields: The timing of transient stress induction is precisely coordinated with the temperature period and the application of the electric field. Adjusting the electric field strength and direction while applying transient stress enhances control over the growth direction of carbon nanotubes. This synergistic effect of multiple physical fields is key to the fabrication of curved single-walled carbon nanotubes.

[0090] 5. Multi-field synergistic preparation process

[0091] Preparation process integration: The above-mentioned physical field systems are integrated into a single reaction apparatus, including a stirring device, an electric field generation system, a temperature control system, and a computer control unit. The computer control unit controls the intensity, direction, and temporal changes of all physical fields according to a preset program.

[0092] Reactor feed: The catalyst solution or suspension and the carbon source raw material are added to the reactor in a determined ratio.

[0093] When the carbon source is a liquid carbon source, it is referred to as a liquid phase system. The mass ratio of carbon source to catalyst in the liquid phase system is 50, 100, 150, or 200:1. In this embodiment, the mass ratio of carbon source to catalyst in the liquid phase system is 150:1.

[0094] When the carbon source is a carbon-containing gas, it is referred to as a gas phase system. The carbon source flow rate of the gas phase system is 50, 150, or 200 ml / min, and the catalyst loading is 0.5, 1.2, or 2% by weight. In this embodiment, the carbon source flow rate of the gas phase system is 150 mL / min, and the catalyst loading is 1.2% by weight.

[0095] Preparation conditions verification: Before starting the program, verify all physical field parameters, including stirring mode and speed, electric field strength and direction, temperature cycle parameters, and transient stress induction time points. Ensure the control system operates normally and that all sensor data are read correctly.

[0096] Multi-field synergistic preparation of single-walled carbon nanotubes:

[0097] First stage (dispersion and activation stage): Start conventional stirring and uniformly disperse the catalyst under constant low-speed stirring (200-300 rpm). At the same time, start the temperature control system and enter the thermal shock stage, rapidly heating to 700℃±50℃, and applying an electric field with an intensity of 80-90% of the upper limit of the set range to promote catalyst activation and active site alignment.

[0098] The second stage (directed growth stage): Entering the stable phase of the temperature cycle, maintaining a constant temperature. Adjust the electric field strength to a medium level (50-70% of the set range) and maintain regular stirring. Add the carbon source to begin the carbon nanotube growth process.

[0099] The third stage (curvature control stage): At a predetermined time point during the temperature stabilization phase, corresponding transient stress-induced operations are performed according to the type of curvature structure to be prepared. Simultaneously, the electric field strength and direction are adjusted to synergistically control the curvature of the carbon nanotube growth.

[0100] The fourth stage (structural refinement stage): This involves a slow cooling phase during the temperature cycle, with a cooling rate of 1-5℃ / minute. The electric field strength is gradually reduced, eventually being shut off. Low-speed, conventional stirring (100-200 rpm) is maintained, which is beneficial for carbon atom rearrangement and structural defect repair.

[0101] Fifth stage (post-processing stage): After the temperature drops to room temperature, all physical fields are turned off. The product is collected, washed, dried, and purified to obtain the final single-walled carbon nanotube product.

[0102] To verify the technical effects of the present invention, experiments and tests were conducted, as follows:

[0103] Experiment 1: Verification of the curvature structure control effect

[0104] 1. Experimental Objective

[0105] To verify whether the synergistic effect of electric field orientation and transient stress induction can achieve precise control of the curvature structure of carbon nanotubes and whether Y-shaped, Z-shaped and helical single-walled carbon nanotubes can be effectively prepared.

[0106] 2. Experimental Materials

[0107] Catalyst: Ferric nitrate, cobalt nitrate, nickel nitrate (mass ratio 3:2:1);

[0108] Carbon source: Acetylene gas (99.9% purity);

[0109] Carrier gas: Argon (99.999% purity);

[0110] Reaction apparatus: A self-assembled multi-physics field coordinated control device, including a stirring system, an electric field system, a temperature control system, and a computer control unit.

[0111] 2. Experimental Procedure

[0112] Catalyst preparation: Ferric nitrate, cobalt nitrate, and nickel nitrate were mixed in a mass ratio of 3:2:1 and dissolved in deionized water to a concentration of 0.1 mol / L.

[0113] Reactor preparation: Add the catalyst solution to the reactor and set up an electric field system, a temperature control system, and a stirring system.

[0114] Preparation of Y-shaped carbon nanotubes:

[0115] The electric field strength is set to 1000 V / cm, and the direction is perpendicular to the bottom of the reactor;

[0116] Set the temperature cycle: heat up to 800°C in 40 seconds, hold for 20 minutes, and then cool down to 500°C at a rate of 2°C / minute;

[0117] Set transient stress-induced parameters: In the middle of the steady-state phase (about 10 minutes), apply a single strong pulse stirring impact (1000 rpm), with the impact direction at a 70-degree angle to the electric field direction.

[0118] Preparation of Z-type carbon nanotubes:

[0119] The electric field strength is set to 1200V / cm, and the direction is perpendicular to the bottom of the reactor;

[0120] Set the temperature cycle: heat up to 850°C in 40 seconds, hold for 25 minutes, and then cool down to 500°C at a rate of 2°C / minute;

[0121] Set transient stress-induced parameters: Apply two pulse stirring impacts of similar intensity (1100 rpm) in the middle (about 8 minutes) and later (about 20 minutes) of the steady-state phase, respectively, with the two impacts in opposite directions.

[0122] Preparation of helical carbon nanotubes:

[0123] The electric field strength is set to 800 V / cm, and the direction is perpendicular to the bottom of the reactor;

[0124] Set the temperature cycle: heat up to 750°C in 35 seconds, hold for 30 minutes, and then cool down to 500°C at a rate of 3°C / minute;

[0125] Set transient stress induction parameters: During the steady-state phase (minutes 5, 10, 15, 20, and 25), apply 5 medium-intensity pulse stirring impacts (900 rpm), with each impact direction at a 50-degree angle to the previous one;

[0126] Product collection and processing: After the reaction is completed, the reactor is cooled to room temperature, the product is collected and washed with hydrochloric acid (3 mol / L) to remove the catalyst, then washed three times with deionized water, and dried at 60°C for 12 hours.

[0127] Structural characterization: The morphology and structure of the carbon nanotube samples were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM).

[0128] 3. Experimental Results

[0129] See Figure 1 Preparation effects of single-walled carbon nanotubes with various curvature structures.

[0130] It can be seen that the carbon nanotubes prepared by the method of this invention have distinct curvature structural characteristics, and the formation ratio is much higher than that of traditional methods (the control group used conventional chemical vapor deposition, without the synergistic effect of multiple physics fields). The structural parameter measurement results show that the Y-shaped branch angle, Z-shaped turning angle, and helical pitch all meet the design goals, and the structural deviation is small, which proves the precise control capability of this invention over the curvature structure of carbon nanotubes.

[0131] Experiment 2: Verification of the effect of improving crystallinity

[0132] 1. Experimental Objective

[0133] The study aimed to verify whether the synergistic effect of temperature cycle changes and electric field, especially the structural repair process during the slow cooling phase, could significantly improve the crystallinity of carbon nanotubes and reduce structural defects.

[0134] 2. Experimental Materials

[0135] Catalyst: Ferric nitrate (99.5% purity);

[0136] Carbon source: methane gas (99.9% purity);

[0137] Carrier gas: a mixture of hydrogen (99.999% purity) and argon (99.999% purity) (volume ratio 1:9);

[0138] Reaction apparatus: Same as Experiment 1

[0139] 2. Experimental Procedure

[0140] Catalyst preparation: Ferric nitrate was dissolved in anhydrous ethanol to a concentration of 0.05 mol / L.

[0141] Experimental group setup:

[0142] Experimental Group A (method of this invention): The temperature cycle change process is adopted, including a thermal shock stage (heating to 850°C within 45 seconds), a stabilization stage (maintaining 850°C for 20 minutes), and a slow cooling stage (cooling to 450°C at a rate of 3°C / minute), while applying an electric field of 200-400V / cm.

[0143] Experimental group B (control group 1): The conventional isothermal process was used, and the reaction was carried out directly at 850℃ for 20 minutes, followed by rapid cooling without applying an electric field;

[0144] Experimental group C (control group 2): The conventional isothermal process was used, and the reaction was carried out directly at 850℃ for 20 minutes, followed by rapid cooling and application of a constant electric field of 300V / cm.

[0145] Experimental group D (control group 3): The temperature periodic change process was used, and no electric field was applied.

[0146] 3. Experimental procedure:

[0147] The catalyst solution is added dropwise onto a silicon substrate and then placed in a reactor;

[0148] Based on the parameter settings of each experimental group, the temperature change process and the application of the electric field were controlled;

[0149] During the stabilization phase, a mixture of methane and carrier gas is introduced at a flow rate of 50 mL / min for methane and 150 mL / min for the mixed carrier gas.

[0150] After the reaction is complete, turn off the methane gas supply, continue to introduce carrier gas, and cool according to the set cooling method;

[0151] Product collection and processing: The silicon substrate was removed and ultrasonically cleaned with acetone and anhydrous ethanol to obtain carbon nanotube samples.

[0152] Crystallinity characterization:

[0153] Raman spectroscopy analysis: The intensity ratio (IG / ID) of the G peak (~1580 cm⁻¹) and the D peak (~1350 cm⁻¹) was measured using a Raman spectrometer with a 532 nm laser.

[0154] High-resolution transmission electron microscopy (HRTEM) observation: measuring the integrity and defect density of carbon nanotube walls;

[0155] X-ray diffraction (XRD) analysis: to determine the crystallinity of carbon nanotubes.

[0156] 4. Experimental Results

[0157] See Figure 2 Comparison of crystallinity of single-walled carbon nanotubes prepared in different experimental groups.

[0158] High-resolution TEM observation and defect site statistics showed that the carbon nanotubes prepared by the method of this invention (experimental group A) had fewer fractures, deformations, and vacancy defects in their tube wall structure. Raman spectroscopy analysis showed that the IG / ID ratio of experimental group A reached 10.8, which was much higher than that of the control group, indicating that it had higher crystallinity and fewer structural defects. XRD test results also confirmed that experimental group A had higher lattice integrity (95.7%).

[0159] The results analysis shows that the synergistic effect of temperature cycle variation and electric field (experimental group A) has a significant effect on improving the crystallinity of carbon nanotubes, with the slow cooling stage playing a key role in carbon atom rearrangement and structural defect repair. Control experiments show that temperature cycle variation alone (experimental group D) or electric field alone (experimental group C) can also improve crystallinity to some extent, but the synergistic effect (experimental group A) is the most significant, confirming the technical advantages of this invention.

[0160] Experiment 3: Verification of the effect of orientation alignment control

[0161] 1. Experimental Objective

[0162] To verify whether the synergistic effect of electric field orientation and stirring system can achieve highly oriented alignment of carbon nanotubes during growth, and to measure their degree of orientation.

[0163] 2. Experimental Materials

[0164] Catalyst: Cobalt nitrate (99.5% purity);

[0165] Carbon source: Acetylene gas (99.9% purity);

[0166] Carrier gas: Nitrogen (99.999% purity);

[0167] Reaction substrate: silicon substrate (100nm oxide layer);

[0168] Reaction apparatus: Same as Experiment 1, but equipped with a polarizing microscope and an X-ray diffractometer with an image acquisition system.

[0169] 3. Experimental Procedure

[0170] Catalyst preparation: Cobalt nitrate was dissolved in anhydrous ethanol to a concentration of 0.08 mol / L.

[0171] Substrate preparation: After cleaning the silicon substrate, the catalyst solution is uniformly coated on its surface by spin coating to form a catalyst film with a thickness of about 50 nm.

[0172] Experimental group setup:

[0173] Experimental group E (method of the present invention): An electric field of 350V / cm was applied, with the direction of the electric field parallel to the substrate surface, and a multi-physics field synergy was adopted (including temperature periodic changes and a stirring system).

[0174] Experimental group F (control group 1): An electric field of 350V / cm was applied, but without temperature periodic changes and a stirring system.

[0175] Experimental group G (control group 2): No electric field was applied, and conventional synthesis methods were used;

[0176] Experimental group H (control group 3): An electric field of 350V / cm was applied, and the temperature was changed periodically, but no stirring system was used.

[0177] Carbon nanotube growth process:

[0178] Experimental group E adopted the method of the present invention, placed the substrate into the reactor, and set up an electric field system (350V / cm), a temperature cycle change system (heating to 800℃ within 45 seconds, holding for 15 minutes, and then cooling to 500℃ at 2℃ / min), and a stirring system (300rpm conventional stirring).

[0179] During the stabilization phase, acetylene gas (80 ml / min) and carrier gas (200 ml / min) are introduced.

[0180] Other experimental groups operated according to their respective parameter settings.

[0181] Orientation characterization:

[0182] Polarizing microscope observation: Observe the alignment direction of carbon nanotubes under polarized light and calculate the percentage of carbon nanotubes that are aligned with the main direction (deviation <15°);

[0183] X-ray diffraction (XRD) analysis: The orientation degree is determined by scanning the azimuth angle of the (002) diffraction peak;

[0184] Field emission scanning electron microscopy (FESEM) observation: Direct observation of the alignment and uniformity of carbon nanotubes.

[0185] 4. Experimental Results

[0186] See Figure 3 Comparison of orientation degree of single-walled carbon nanotubes prepared in different experimental groups.

[0187] FESEM image analysis showed that the carbon nanotubes prepared by experimental group E (using the method of this invention) exhibited a highly consistent alignment, with over 90% of the carbon nanotubes aligned along the main direction (electric field direction), forming a highly ordered parallel structure. Polarizing microscopy observation indicated that the orientation degree of experimental group E reached 92.3%, and XRD azimuth scanning analysis also confirmed that it had a high orientation degree of 90.6%.

[0188] The comparative results of the experimental groups show that applying an electric field alone (experimental group F) can achieve a certain degree of orientation control (orientation degree of approximately 65-68%), but compared with the synergistic effect of temperature periodic changes and a stirring system (experimental group E), both the orientation degree and uniformity are significantly lower than the method of this invention. Experimental group G, without an applied electric field, shows almost no orientation, with carbon nanotubes arranged randomly. Experimental group H, with a synergistic effect of electric field and temperature periodic changes but without stirring, has an orientation degree between experimental groups E and F, further demonstrating the importance of the synergistic effect of multiple physical fields in improving the orientation degree.

[0189] Experimental results confirm that the method of the present invention, through the synergistic effect of electric field orientation and stirring system, can effectively achieve highly oriented carbon nanotubes with an orientation degree of over 90%, which is far higher than that of traditional methods, providing an effective way to prepare highly oriented carbon nanotube materials.

[0190] Experiment 4: Verification of Overall Performance Improvement

[0191] 1. Experimental Objective

[0192] The method of this invention was used to verify the improvement effect of the single-walled carbon nanotubes prepared by this invention on the comprehensive properties such as electrical conductivity, thermal conductivity and mechanical strength.

[0193] 2. Experimental Materials

[0194] Single-walled carbon nanotube samples prepared by the method of this invention (Experimental Group I);

[0195] Single-walled carbon nanotube samples prepared by conventional chemical vapor deposition (control group J).

[0196] Testing equipment: Four-probe conductivity testing system, laser scintillation thermal conductivity analyzer, nanoindentation tester, tensile testing machine;

[0197] 3. Experimental Procedure

[0198] Sample preparation:

[0199] Experimental Group I: Single-walled carbon nanotubes were prepared using the method of this invention (synergistic effect of multiple physical fields). The specific conditions were: electric field strength of 300 V / cm, temperature cycle of heating to 800℃ within 40 seconds, holding for 20 minutes, then cooling to 500℃ at 2℃ / min, and stirring speed of 300 rpm.

[0200] Control group J: Single-walled carbon nanotubes were prepared by conventional chemical vapor deposition at a fixed temperature of 800℃ for 20 minutes.

[0201] Sample preparation: Both groups of samples underwent the same purification process, including acid washing, filtration and drying, to ensure that the sample purity was basically consistent.

[0202] Performance testing:

[0203] Conductivity testing: The conductivity of the two sets of samples was measured at room temperature using a four-probe conductivity testing system.

[0204] Thermal conductivity test: The thermal conductivity of the two sets of samples was measured using a laser scintillation thermal conductivity analyzer.

[0205] Mechanical property testing: Young's modulus was determined using a nanoindentation tester, and tensile strength was determined using a tensile testing machine;

[0206] Cyclic voltammetry test: The electrochemical performance of two groups of samples as electrode materials was determined using a three-electrode electrochemical workstation;

[0207] Preparation and testing of nanocomposite materials:

[0208] Two groups of carbon nanotube samples were mixed with epoxy resin in the same proportion (3wt%) to prepare nanocomposite materials.

[0209] The tensile strength, elastic modulus, and electrical conductivity of the composite material were tested.

[0210] 4. Experimental Results

[0211] See Figure 4 Performance comparison data of the two groups of samples;

[0212] See Figure 5 Performance test results of nanocomposite materials.

[0213] Experimental data analysis shows that the single-walled carbon nanotubes prepared by the method of this invention (experimental group I) are significantly superior to the products prepared by traditional methods (control group J) in all key performance indicators. The electrical conductivity is increased by 50.0%, the thermal conductivity is increased by 60.9%, and the mechanical properties (Young's modulus and tensile strength) are increased by more than 30%.

[0214] The nanocomposite materials prepared by combining the two groups of carbon nanotubes with epoxy resin also showed a similar trend. The composite material containing carbon nanotubes prepared by the method of this invention is significantly better than the composite material containing carbon nanotubes prepared by the traditional method in terms of mechanical properties and conductivity.

[0215] The significant improvement in overall performance is attributed to three key effects of the method described in this invention: higher crystallinity reduces structural defects and improves electron and phonon transport efficiency; precisely controlled curvature structure enhances the three-dimensional mechanical properties of carbon nanotubes; and highly oriented alignment improves the reinforcing effect and anisotropic conductivity in composite materials. These experimental results fully demonstrate the significant effect of this invention in improving the overall performance of carbon nanotubes.

[0216] Experiment 5: Verification of the universality of controllable preparations

[0217] 1. Experimental Objective

[0218] To verify whether the method of the present invention has broad adaptability and scalability, and whether it can be customized to prepare single-walled carbon nanotubes with different structural characteristics for different application needs by adjusting various physical field parameters and time sequence relationships.

[0219] 2. Experimental Materials

[0220] Catalysts: Iron-based catalysts (ferric nitrate, ferric chloride), cobalt-based catalysts (cobalt nitrate, cobalt chloride), nickel-based catalysts (nickel nitrate, nickel chloride) and combinations thereof;

[0221] Carbon sources: different types of carbon sources such as methane, acetylene, ethanol, and benzene;

[0222] Reaction apparatus: Same as Experiment 1, but with a precisely controllable multi-physics field synergistic device.

[0223] 3. Experimental Procedure

[0224] Catalyst universality test:

[0225] Three different catalysts, namely iron-based, cobalt-based, and nickel-based catalysts, and their combinations, were used respectively;

[0226] For each catalyst, the multi-physics synergistic preparation method of the present invention is applied;

[0227] Keeping other conditions constant, record the effects of different catalysts on carbon nanotube growth.

[0228] Carbon source universality test:

[0229] Gaseous carbon sources (methane, acetylene) and liquid carbon sources (ethanol, benzene) were used respectively.

[0230] For each carbon source, the multi-physics field synergistic preparation method of the present invention is applied;

[0231] Keeping other conditions constant, record the effects of different carbon sources on carbon nanotube growth.

[0232] Parameter control experiment:

[0233] Electric field strength control: Set different electric field strengths (100-1500V / cm) and observe their effects on the structure and properties of carbon nanotubes;

[0234] Temperature cycle control: Set different thermal shock rates, stable temperatures, and cooling rates, and observe their impact on the product;

[0235] Transient stress-induced control: Set different stirring impact intensities, time points, and directions, and observe the effects on the curvature structure of the product.

[0236] Application-customized experiments:

[0237] Customized for electronic device applications: Adjusting process parameters to prepare carbon nanotubes with high electrical conductivity and high crystallinity;

[0238] Customized for supercapacitor applications: Adjusting process parameters to prepare carbon nanotubes with specific curvature structures (increasing specific surface area);

[0239] Customized for composite reinforcement applications: Adjusting process parameters to prepare highly oriented, high-strength carbon nanotubes.

[0240] 4. Experimental Results

[0241] See Figure 6 The adaptability of different catalysts to multi-physics synergistic preparation methods;

[0242] See Figure 7 The adaptability of different carbon sources to multi-physics synergistic preparation methods;

[0243] See Figure 8 The impact of key process parameters on product characteristics;

[0244] See Figure 9 Customized preparation results for different applications.

[0245] Experimental results show that the method of this invention has broad applicability: it exhibits good adaptability to different types of catalysts and carbon sources; by simply adjusting process parameters, various catalysts and carbon sources can be efficiently prepared using this method; by precisely controlling the electric field strength, temperature period parameters, and transient stress-induced parameters, the structural characteristics and performance indicators of the product can be specifically controlled; and single-walled carbon nanotube products that meet specific performance requirements can be customized according to the needs of different application fields, with all key performance indicators significantly superior to traditional methods.

[0246] These experimental results fully demonstrate the universality and scalability of the method of the present invention in terms of controllable preparation, and provide an effective technical path for the customized production of single-walled carbon nanotubes in a variety of high-end application fields.

[0247] Experiment Summary

[0248] Through the above five sets of systematic experiments, the key technical effects of the single-walled carbon nanotube preparation method of the present invention were comprehensively verified. Experimental results show that:

[0249] Curvature Structure Control Effect: The method of this invention achieves precise control over the curvature structure of carbon nanotubes through the synergistic effect of electric field orientation and transient stress induction. It can selectively prepare Y-shaped, Z-shaped, or helical single-walled carbon nanotubes with a formation rate of 78-86%, far exceeding the 2-5% of traditional methods. Structural parameters are precisely controlled; deviations in the branching angle of the Y-shape, the turning angle of the Z-shape, and the pitch of the helical shape are all within the design target range.

[0250] Crystallinity Enhancement: The synergistic effect of temperature cycle variation process and electric field significantly improved the crystallinity of carbon nanotubes, with an IG / ID ratio reaching 10.8, which is 1.5-2.5 times higher than that of traditional methods. Defect density was reduced by approximately 75%, lattice integrity was increased to 95.7%, and the structural integrity of the product was greatly improved.

[0251] Orientation alignment control effect: The synergistic effect of electric field orientation and stirring system achieved a high degree of orientation of carbon nanotubes, with an orientation degree of over 90%, which is about 25% higher than using an electric field alone and about 80% higher than traditional methods. Orientation uniformity was also greatly improved, providing a foundation for high-performance anisotropic materials.

[0252] Overall performance improvement: The single-walled carbon nanotubes prepared by this invention significantly outperform traditional methods in key performance indicators such as electrical conductivity, thermal conductivity, and mechanical strength, with improvements reaching 30-60%. When applied to nanocomposite materials, they also exhibit significant performance advantages, laying the foundation for high-performance material applications.

[0253] Universality of controllable preparation: The method of this invention has good adaptability to different types of catalysts and carbon sources. By adjusting the physical field parameters and timing relationships, it is possible to prepare single-walled carbon nanotubes with different structural characteristics according to different application requirements. The process versatility and product adaptability are both excellent.

[0254] In summary, the experimental results fully demonstrate the innovation and practicality of this invention in the field of single-walled carbon nanotube preparation. Through the synergistic effect of four physical fields—stirring, electric field, periodic temperature changes, and transient stress induction—precise control of the structure and properties of single-walled carbon nanotubes was achieved. This solves the technical problems of existing technologies in spatial configuration control, crystallinity improvement, and orientation alignment, providing a new technical solution for the preparation of high-performance single-walled carbon nanotube materials.

[0255] The embodiments of the present invention have been described above. However, the embodiments are not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make more equivalent embodiments under the guidance of the present embodiments, and all of them are within the protection scope of the present embodiments.

Claims

1. A method for preparing single-walled carbon nanotubes, characterized by, Includes the following steps: Establish a mixing system, including a mixing device that can switch between mechanical mixing and pulse mixing modes; Establish an electric field system, including an electrode device and a programmable DC power supply to form a uniform electric field in the reactor; Establish a temperature cycle change system to realize the temperature cycle change of thermal shock-stabilization-slow cooling; A transient stress-inducing system was established, which generates fluid dynamic pulses by changing the stirring mode, thereby creating transient mechanical stress on the growing carbon nanotubes; The establishment of the transient stress-inducing system includes: By rapidly changing the stirring mode, fluid dynamic pulses are generated, forming a transient shear force field; The transient stress induction method is determined based on the type of carbon nanotube curvature structure to be prepared; To precisely coordinate the timing of transient stress induction with the temperature cycle and the application of the electric field; For the Y-type structure: In the middle of the stable phase of the temperature cycle, apply a single strong pulse stirring impact, with the impact direction at an angle of 60-90 degrees to the electric field direction; For the Z-shaped structure: During the middle and late stages of the stable phase of the temperature cycle, two pulse stirring impacts of similar intensity are applied respectively, with the two impacts being opposite or nearly opposite in direction; For spiral structures: During the stable phase of the temperature cycle, apply several medium-intensity pulse stirring impacts at equal time intervals, with each impact direction at a 45-60 degree angle to the previous one; Through a computer control unit, the synergistic effect of the above physical fields is coordinated according to a preset timing sequence: the timing of transient stress induction is precisely matched with the stable phase of the temperature cycle, and transient stress induction is applied at a predetermined time point in the stable phase of the temperature cycle; at the same time, the electric field strength is dynamically adjusted according to each phase of the temperature cycle: a strong electric field is applied during the thermal shock phase, a medium-intensity electric field is maintained during the stable growth phase, and the electric field strength is gradually reduced during the slow cooling phase; thus achieving precise control over the structure and properties of single-walled carbon nanotubes. Preparation of single-walled carbon nanotubes.

2. The method of claim 1, wherein, The establishment of the stirring system includes: Construct a variable-mode mixing device, including a mixing paddle, a variable-speed motor, and a control unit; Determine the stirring parameters: in mechanical stirring mode, the speed is 200-600 rpm; in pulse stirring mode, the speed is increased from the normal speed to 800-1200 rpm within 0.1-0.5 seconds. Arrange the stirring mode sequence, including the initial uniform dispersion stage, the middle stable growth stage, and the pulse impact stage at a predetermined time point.

3. The method according to claim 1, characterized in that, The establishment of the electric field system includes: Parallel plate electrodes are installed in the reactor to form a uniform electric field, and the electrodes are connected to a programmable DC power supply. Determine the electric field parameters: in the liquid phase reaction system, the electric field strength is 50-500 V / cm; in the gas phase reaction system, the electric field strength is 500-2000 V / cm. A pulsed electric field is applied to adjust the electric field strength and direction at different stages of temperature change.

4. The method according to claim 1, characterized in that, The establishment of the temperature periodic change system includes: Use a temperature control system that includes a heating element, a temperature sensor, and a temperature controller; The temperature cycle is defined as having three phases: a thermal shock phase, in which the temperature is raised from room temperature to 600-900℃ within 30-60 seconds; a stabilization phase, in which the temperature is maintained at 600-900℃ for 10-30 minutes; and a slow cooling phase, in which the temperature is cooled to 400-600℃ at a rate of 1-5℃ / minute. By configuring heating elements and using control algorithms, the temperature distribution within the reaction area is ensured to be uniform, with a temperature gradient of <10℃ / cm.

5. The method according to claim 1, characterized in that, The process for preparing single-walled carbon nanotubes includes the following stages: Dispersion and activation stage: Start conventional stirring to uniformly disperse the catalyst at a speed of 200-300 rpm, and at the same time enter the thermal shock stage and apply a strong electric field; Directional growth stage: Entering the stable stage of the temperature cycle, the electric field strength is adjusted to a medium level, and a carbon source is introduced to start the growth of carbon nanotubes; Curvature control phase: At a predetermined point in the temperature cycle stabilization phase, transient stress-induced operation is performed, while the electric field parameters are adjusted simultaneously; Structural refinement stage: Entering the slow cooling stage of the temperature cycle, the electric field strength is gradually reduced while maintaining low-speed conventional stirring; Post-processing stage: Collect the product and perform washing, drying and purification.

6. The method according to claim 5, characterized in that, The catalyst is selected from metal salts containing iron group elements, and the carbon source is selected from carbon-containing gaseous or liquid carbon sources.

7. The method according to claim 6, characterized in that, When the carbon source is a liquid carbon source, the carbon source / catalyst mass ratio is 50-200:1; when the carbon source is a carbon-containing gas, the carbon source flow rate is 50-200 ml / min, and the catalyst loading is 0.5-2 wt%.

8. The method according to claim 6, characterized in that, The prepared single-walled carbon nanotubes have the following characteristics: The branching angle of Y-shaped carbon nanotubes is controlled within the range of 30-45 degrees, with a deviation of <5 degrees; The turning angle of Z-shaped carbon nanotubes is controlled within the range of 100-140 degrees, with a deviation of <10 degrees; The pitch of the helical carbon nanotubes is controlled within the range of 20-100 nm, and the uniformity deviation of the helical structure per unit length is <15%. The intensity ratio (IG / ID) of the G peak to the D peak of carbon nanotubes is 8-12, and the orientation degree reaches 85-95%.

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