Graphene-carbon nanotube continuous composite fiber and preparation method thereof

Abstract

The application discloses a preparation method of graphene-carbon nanotube continuous composite fibers. The preparation method of the graphene-carbon nanotube composite fibers is based on a floating catalytic chemical vapor deposition process, graphene is in-situ assembled and compounded in the process of carbon nanotube growth, the interface bonding force of graphene and the carbon nanotube is strong, the fiber structure is dense, the composite fiber can realize kilometer-level continuous preparation, and the mechanical performance and the electrical performance are better than those of the carbon nanotube fiber.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon material preparation, and in particular relates to a graphene-carbon nanotube continuous composite fiber and a preparation method thereof. Background Art

[0002] Carbon nanotubes, as one-dimensional carbon nanomaterials with a high aspect ratio, possess excellent mechanical properties. For example, they theoretically possess a Young's modulus of up to 1 TPa and a tensile strength exceeding 100 GPa. In recent years, macroscopic continuous carbon nanotube fibers composed of carbon nanotubes have been continuously developed, generally using three methods: liquid-phase spinning, array spinning, and floating catalytic chemical vapor deposition. Macroscopic continuous carbon nanotube fibers produced by floating catalytic chemical vapor deposition offer the greatest potential for industrial mass production, due to their excellent mechanical properties, low cost, ease of operation, and high yield.

[0003] However, the tensile strength of current continuous macroscopic carbon nanotube fibers is mostly reported to be 0.5-5 GPa, with the highest reaching ~9 GPa. The main reasons why macroscopic fibers are far from achieving the theoretical mechanical strength advantages of carbon nanotubes are: 1. The carbon nanotubes within the carbon nanotube fiber are loosely distributed, connected primarily by van der Waals forces, which cannot fully utilize the high strength advantages of individual carbon nanotubes; 2. The large number of carbon nanotubes within the fiber are not perfectly oriented along the fiber axis, resulting in uneven stress on the carbon nanotubes within the fiber; and 3. The fiber microstructure is very loose, with numerous voids and defects, resulting in a small contact area between the carbon nanotubes, which cannot fully utilize the van der Waals forces between the carbon nanotubes.

[0004] Graphene has an sp2 molecular structure similar to that of carbon nanotubes and a unique two-dimensional structure with a theoretical Young's modulus of up to 1.0 TPa. Filling the gaps within carbon nanotube fibers with graphene can make the fiber structure more compact, increase sp2 interfacial contact and van der Waals forces, and thus improve the mechanical properties of the fibers. CN111394833A discloses a method for preparing graphene-carbon nanotube composite fibers, in which graphene oxide is blended with carboxylated carbon nanotubes and the composite fibers are prepared using a liquid phase spinning process. CN107988656A discloses a method for preparing composite fibers using a graphene solution after preparing carbon nanotube aggregates by floating catalytic chemical vapor deposition. However, the graphene and carbon nanotubes in the above methods are simply physically combined as raw materials. There is no molecular bonding between the graphene and carbon nanotubes, and the microstructure is relatively loose, so that only a slight improvement in the mechanical strength of the fibers is achieved.

[0005] Therefore, developing a graphene-carbon nanotube composite fiber with dense structure and high tensile strength is an important research hotspot at present. Summary of the Invention

[0006] The present invention aims to address the shortcomings of existing technologies and provide a method for preparing continuous graphene-carbon nanotube composite fibers. This method utilizes a floating catalytic chemical vapor deposition process, where graphene is assembled and composited in situ during the growth of carbon nanotubes. This method results in strong interfacial bonding between the graphene and carbon nanotubes, resulting in a dense fiber structure. The composite fibers can be continuously produced at the kilometer level, and exhibit superior mechanical and electrical properties compared to carbon nanotube fibers.

[0007] The present invention aims to provide a method for preparing a graphene-carbon nanotube continuous composite fiber, which is characterized by comprising the following steps:

[0008] S1, preparing graphene solution;

[0009] S2, mixing the graphene solution, carbon source, catalyst, and accelerator to prepare a mixed spinning solution;

[0010] S3, injecting the spinning solution into a CVD reactor, introducing a carrier gas, and producing a cylindrical graphene-carbon nanotube aggregate;

[0011] S4. The graphene-carbon nanotube aggregates are subjected to water densification treatment and continuously collected by a winding collector in sequence to prepare several thousand meter-level graphene-carbon nanotube composite fibers.

[0012] Graphene is assembled and composited in situ during the growth of carbon nanotubes. The interface bonding between graphene and carbon nanotubes is strong, the fiber structure is dense, and the composite fibers can be prepared continuously at the kilometer level.

[0013] According to a specific embodiment of the present invention, step S1 includes dispersing graphene material powder in a solvent to prepare a graphene solution. Preferably, the solvent is one or more of water, ethanol, acetone, an alkane solvent, and a benzene solvent; more preferably, water.

[0014] According to a specific embodiment of the present invention: the graphene material includes one or more of pure graphene, hybrid graphene, graphene oxide, reduced graphene oxide, and graphene quantum dots.

[0015] According to one embodiment of the present invention, the graphene material has a flake size between 1 nm and 200 μm. Graphene within this size range is easier to disperse in a solvent. Flakes larger than 200 μm tend to aggregate in the graphene dispersion, affecting spinning performance.

[0016] According to a specific embodiment of the present invention, the concentration of the graphene material in the mixed spinning solution is between 0.01 mg / mL and 10 mg / mL. The concentration of the graphene material in the mixed spinning solution is controlled. A concentration exceeding 10 mg / mL substantially loses fluidity and cannot be injected into the reactor. A concentration below 0.01 mg / mL is too low and produces poor results.

[0017] According to a specific embodiment of the present invention: in step S2, the carbon source is a liquid carbon source, preferably one or more of alcohols, ketones, cyclohexane, and benzene; more preferably ethanol and / or acetone.

[0018] According to a specific embodiment of the present invention: in step S2, the catalyst is one or more of ferrocene, nickelocene, and cobaltocene; preferably ferrocene.

[0019] According to a specific embodiment of the present invention: in step S2, the accelerator is one or more of thiophene, elemental sulfur, and carbon disulfide; preferably thiophene.

[0020] According to a specific embodiment of the present invention: in step S3, the carrier gas is a mixture of hydrogen and an inert gas; preferably, the inert gas is one or more of argon and nitrogen.

[0021] According to a specific embodiment of the present invention: in step S3, the reaction temperature is 1000-1500° C., preferably 1300° C.; and the reaction time is 1 second to 20 seconds.

[0022] According to a specific embodiment of the present invention: step S4 includes: the graphene-carbon nanotube aggregates are subjected to water densification treatment in a water tank; then the aggregates subjected to water densification treatment are continuously collected by a winding collector outside the water tank to obtain several kilometers of continuous graphene-carbon nanotube composite fibers.

[0023] Another object of the present invention is to provide graphene-carbon nanotube composite fibers prepared by the above-mentioned preparation method.

[0024] Beneficial effects:

[0025] The present invention provides a method for preparing graphene-carbon nanotube composite fibers. Compared with the prior art, the method can effectively increase the dispersion of graphene between carbon nanotubes, tightly combine the graphene and carbon nanotubes in the fibers, highly orient the carbon nanotubes, and achieve a dense fiber structure. The resulting graphene-carbon nanotube continuous composite fibers have higher tensile strength and better conductivity than pure carbon nanotube fibers.

[0026] The preparation method of the graphene-carbon nanotube continuous composite fiber is simple, easy to implement, low in cost, high in yield, and suitable for industrial-scale application. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the device for preparing graphene-carbon nanotube composite fibers of the present invention.

[0028] Figure 2A This is a scanning electron microscope image of the graphene-carbon nanotube composite fiber in Example 1.

[0029] Figure 2B This is a scanning electron microscope image of another position of the graphene-carbon nanotube composite fiber in Example 1.

[0030] Figure 2C This is a transmission electron microscope image of the graphene-carbon nanotube composite fiber in Example 1.

[0031] Figure 2D This is the Raman spectrum of the graphene-carbon nanotube composite fiber in Example 1.

[0032] Figure 2E This is the tensile stress-strain curve of the graphene-carbon nanotube composite fiber in Example 1.

[0033] Figure 3A This is a scanning electron microscope image of the graphene-carbon nanotube composite fiber in Example 2.

[0034] Figure 3B This is the tensile stress-strain curve of the graphene-carbon nanotube composite fiber in Example 2.

[0035] Figure 4A This is a scanning electron microscope image of the graphene-carbon nanotube composite fiber in Example 3.

[0036] Figure 4B This is the tensile stress-strain curve of the graphene-carbon nanotube composite fiber in Example 3.

[0037] Figure 5 This is a scanning electron microscope image of the carbon nanotube fiber in Comparative Example 1.

[0038] Figure 6 This is a scanning electron microscope image of the graphene-carbon nanotube composite fiber prepared in Example 1 after being torn along the axial direction.

[0039] Ultrasonic atomization device 1, reaction furnace 2, reaction tube 3, cylindrical aggregate 4, water tank 5, fiber winding collector 6 DETAILED DESCRIPTION

[0040] In order to make the technical problems and technical solutions solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0041] Example 1

[0042] This embodiment provides a method for preparing graphene-carbon nanotube continuous composite fibers

[0043] (1) Graphene oxide powder with a flake size of ∼200 nm was dispersed in water to prepare a 10 mg / mL graphene solution, which was then ultrasonically dispersed to form a uniform solution. The graphene solution, acetone, ferrocene, and thiophene were prepared into a mixed spinning solution at mass ratios of 10.8%, 87.0%, 0.5%, and 1.7%, respectively, and ultrasonically dispersed to form a uniform solution. Acetone, ferrocene, and thiophene were used as a carbon source, catalyst, and accelerator, respectively, for preparing carbon nanotube fibers.

[0044] (2) See Figure 1 The mixed spinning solution is injected into an ultrasonic sprayer 1 and then into the furnace tube 3 of a 1300°C reactor 2. A mixed carrier gas of argon and hydrogen at a flow rate of 2 L / min and 3 L / min is introduced into the furnace tube 3, thereby growing cylindrical graphene-carbon nanotube aggregates 4. The graphene-carbon nanotube aggregates 4 are then compacted by water in a water tank 5 to form graphene-carbon nanotube composite fibers. The fibers are then collected by a winding collector 6 outside the water tank 5, enabling the continuous production of graphene-carbon nanotube composite fibers at the kilometer level.

[0045] (3) The scanning electron microscope image of the obtained graphene-carbon nanotube continuous composite fiber is as follows Figure 2A and Figure 2B As shown in the transmission electron microscope image Figure 2C As shown, the Raman spectrum is Figure 2D The stress-strain curve of the fiber is shown in Figure 2EAs shown. From the scanning electron microscope image, it can be seen that the structure of the prepared graphene-carbon nanotube composite fiber is dense. From the transmission electron microscope image, it can be seen that the graphene-carbon nanotubes in the prepared graphene-carbon nanotube composite fiber are tightly bound. From the Raman spectrum, it can be seen that the ratio of the D peak intensity to the G peak intensity of the graphene-carbon nanotube composite fiber is lower than that of the carbon nanotube fiber, indicating that the composite fiber has fewer intrinsic defects. From the stress-strain curve of the fiber, it can be seen that the graphene-carbon nanotube composite fiber has a higher strength of 3 to 3.5 GPa than the carbon nanotube fiber, with a maximum of 3.8 GPa. The conductivity of the carbon nanotube fiber tested by the four-probe method is 1.2×10 6 The mechanical strength and electrical conductivity of the composite fibers are significantly higher than those of carbon nanotube fibers. Figure 6 This is a scanning electron microscope image of the graphene-carbon nanotube composite fiber prepared in Example 1 after being torn along the axial direction. It can be seen from the figure that a graphene-wrapped carbon nanotube structure can be prepared by this method.

[0046] Example 2

[0047] This embodiment provides a method for preparing graphene-carbon nanotube continuous composite fibers

[0048] (1) Pure graphene powder with a flake size of 50 to 200 nm was dispersed in water to prepare a 1 mg / mL graphene solution, which was then ultrasonically dispersed to form a uniform solution. The graphene solution, acetone, ferrocene, and thiophene were prepared into a mixed spinning solution at a mass ratio of 10.8%, 87.0%, 0.5%, and 1.7%, respectively, and ultrasonically dispersed to form a uniform solution. Acetone, ferrocene, and thiophene were used as a carbon source, catalyst, and promoter, respectively, for preparing carbon nanotube fibers.

[0049] (2) See Figure 1 The mixed spinning solution is injected into an ultrasonic atomizer 1 and then into furnace tube 3 of a 1300°C reactor 2. A mixed carrier gas of 2 L / min argon and 3 L / min hydrogen is introduced into furnace tube 3, growing cylindrical graphene-carbon nanotube aggregates 4. The graphene-carbon nanotube aggregates 4 are then compacted by water in a water tank 5 to form graphene-carbon nanotube composite fibers. The fibers are then collected by a winding collector 6 outside the water tank 5, enabling the continuous production of thousands of meters of graphene-carbon nanotube composite fibers.

[0050] (3) From the scanning electron microscope images (such as Figure 3A ) It can be seen that the structure of the prepared graphene-carbon nanotube continuous composite fiber is dense, but it is easy to have more graphene agglomerates. From the stress-strain curve of the fiber (such as Figure 3B) It can be seen that the strength of graphene-carbon nanotube composite fibers and carbon nanotube fibers is as high as ~1.7GPa, which is similar to the tensile strength of carbon nanotube fibers. The conductivity of carbon nanotube fibers tested by the four-probe method is 5.7×10 5 S / m.

[0051] Example 3

[0052] This embodiment provides a method for preparing graphene-carbon nanotube continuous composite fibers

[0053] (1) Graphene oxide quantum dot powder with a flake size of 1 to 10 nm was dispersed in water to prepare a 5 mg / mL graphene solution, which was then ultrasonically dispersed to form a uniform solution. The graphene solution, acetone, ferrocene, and thiophene were prepared into a mixed spinning solution in a mass ratio of 10.8%, 87.0%, 0.5%, and 1.7%, respectively, and ultrasonically dispersed to form a uniform solution, wherein acetone, ferrocene, and thiophene were used as a carbon source, catalyst, and accelerator, respectively, for preparing carbon nanotube fibers.

[0054] (2) See Figure 1 The mixed spinning solution is injected into an ultrasonic sprayer 1 and then into a furnace tube 3 of a 1300°C reactor 2. A mixed carrier gas of argon and hydrogen at a flow rate of 2 L / min and 3 L / min is introduced into the furnace tube 3 to grow cylindrical graphene-carbon nanotube aggregates 4. These cylindrical graphene-carbon nanotube aggregates 4 are then compacted by water in a water tank 5 to form continuous graphene-carbon nanotube composite fibers. The fibers are then collected by a winding collector 6 outside the water tank 5, enabling the continuous production of thousands of meters of continuous graphene-carbon nanotube composite fibers.

[0055] (3) From the scanning electron microscope images (such as Figure 4A ) It can be seen that the structure of the prepared graphene-carbon nanotube continuous composite fiber is dense. From the stress-strain curve of the fiber (such as Figure 4B ) It can be seen that the strength of the graphene-carbon nanotube continuous composite fiber is as high as ~2.3GPa, slightly higher than the tensile strength of the carbon nanotube fiber. The conductivity of the carbon nanotube fiber tested by the four-probe method is 7.3×10 5 S / m.

[0056] Comparative Example 1

[0057] This comparative example provides a method for preparing continuous carbon nanotube fibers

[0058] (1) Water, acetone, ferrocene, and thiophene were prepared into a spinning solution in a mass ratio of 10.8%, 87.0%, 0.5%, and 1.7%, and ultrasonically dispersed into a uniform solution, wherein acetone, ferrocene, and thiophene were used as a carbon source, a catalyst, and a promoter, respectively, for preparing carbon nanotube fibers.

[0059] (2) See Figure 1 The mixed spinning solution is injected into an ultrasonic atomizer 1 and then into furnace tube 3 of a 1300°C reactor 2. A mixed carrier gas of argon and hydrogen at a flow rate of 2 L / min and 3 L / min is introduced into furnace tube 3 to grow cylindrical carbon nanotube aggregates 4. These cylindrical carbon nanotube aggregates 4 are then compacted by water in a water tank 5 to form continuous carbon nanotube fibers. The fibers are then collected by a winding collector 6 outside the water tank 5, enabling the continuous production of carbon nanotube fibers on the order of kilometers.

[0060] (3) From the scanning electron microscope images (such as Figure 5 ) It can be seen that the structure of the prepared carbon nanotube fibers is relatively dense. From the stress-strain curve of the fibers (such as Figure 2E ) It can be seen that the strength of carbon nanotube fibers is as high as ~1.7GPa. The conductivity of carbon nanotube fibers tested by four-probe method is 2.2×10 5 S / m.

Claims

1. A method for preparing graphene-carbon nanotube continuous composite fibers, characterized in that: The following steps are involved: S1, preparing graphene solution; S2, mixing the graphene solution, carbon source, catalyst, and accelerator to prepare a mixed spinning solution; S3, injecting the spinning solution into a CVD reactor, introducing a carrier gas, and producing graphene-carbon nanotube aggregates; S4. The graphene-carbon nanotube aggregates are subjected to water densification treatment and continuously collected by a winding collector in sequence to prepare several thousand meter-level graphene-carbon nanotube composite fibers.

2. The preparation method according to claim 1, characterized in that The step S1 includes: dispersing graphene material powder in a solvent to prepare a graphene solution.

3. The preparation method according to claim 2, characterized in that The solvent is one or more of water, ethanol, acetone, alkane solvent and benzene solvent.

4. The preparation method according to claim 2, characterized in that The graphene material includes one or more of pure graphene, hybrid graphene, graphene oxide, reduced graphene oxide, and graphene quantum dots.

5. The preparation method according to claim 1, characterized in that In step S2, the carbon source is a liquid carbon source.

6. The preparation method according to claim 5, characterized in that The liquid carbon source is one or more of alcohol, ketone, cyclohexane and benzene.

7. The preparation method according to claim 6, characterized in that The liquid carbon source is ethanol and / or acetone.

8. The preparation method according to claim 1, characterized in that In step S2, the catalyst is one or more of ferrocene, nickelocene, and cobaltocene.

9. The preparation method according to claim 1, characterized in that In step S2, the accelerator is one or more of thiophene, elemental sulfur, and carbon disulfide.

10. The preparation method according to claim 1, characterized in that In step S3, the carrier gas is a mixture of hydrogen and an inert gas.

11. The preparation method according to claim 10, characterized in that: The inert gas is one or more of argon and nitrogen.

12. The preparation method according to claim 1, characterized in that In step S3, the reaction temperature is 1000-1500° C.; and the reaction time is 1 second to 20 seconds.

13. The preparation method according to claim 12, characterized in that The reaction temperature is 1300°C.

14. The preparation method according to claim 1, characterized in that Step S4 includes: the graphene-carbon nanotube aggregates are subjected to water densification treatment in a water tank; then the aggregates subjected to water densification treatment are continuously collected by a winding collector outside the water tank to obtain several kilometers of continuous graphene-carbon nanotube composite fibers.

15. A graphene-carbon nanotube composite fiber prepared by the preparation method according to any one of claims 1 to 14.

Images